Re: 자가포식 유도체 '스퍼미딘' DNA 메틸화를 통해 장수 유도 기전!! 2022

[문형철]

Cells

. 2022 Jan 4;11(1):164. doi: 10.3390/cells11010164

Overview of Polyamines as Nutrients for Human Healthy Long Life and Effect of Increased Polyamine Intake on DNA Methylation

Kuniyasu Soda 1

Editors: Gil Atzmon1, Michael Klutstein1, Yitzhak Reizel1

• Author information
• Article notes
• Copyright and License information

PMCID: PMC8750749  PMID: 35011727

Abstract

Polyamines, spermidine and spermine, are synthesized in every living cell and are therefore contained in foods, especially in those that are thought to contribute to health and longevity. They have many physiological activities similar to those of antioxidant and anti-inflammatory substances such as polyphenols. These include antioxidant and anti-inflammatory properties, cell and gene protection, and autophagy activation. We have first reported that increased polyamine intake (spermidine much more so than spermine) over a long period increased blood spermine levels and inhibited aging-associated pathologies and pro-inflammatory status in humans and mice and extended life span of mice. However, it is unlikely that the life-extending effect of polyamines is exerted by the same bioactivity as polyphenols because most studies using polyphenols and antioxidants have failed to demonstrate their life-extending effects. Recent investigations revealed that aging-associated pathologies and lifespan are closely associated with DNA methylation, a regulatory mechanism of gene expression‎. There is a close relationship between polyamine metabolism and DNA methylation. We have shown that the changes in polyamine metabolism affect the concentrations of substances and enzyme activities involved in DNA methylation. I consider that the increased capability of regulation of DNA methylation by spermine is a key of healthy long life of humans.

요약 

폴리아민, 스퍼미딘 및 스퍼민은 

모든 생체 세포에서 합성되므로 

식품, 특히 건강과 장수에 도움이 되는 식품에 함유되어 있습니다. 

폴리아민은 

폴리페놀과 같은 항산화 및 항염증 물질과 유사한 여러 가지 생리학적 활동을 합니다. 

이러한 활동에는 

항산화 및 항염증 특성, 

세포 및 유전자 보호, 

자가포식 활성화 등이 있습니다. 

우리는 

처음으로 장기간 폴리아민 섭취 증가(스퍼미딘이 스퍼민보다 훨씬 더 많이)가 

인간과 쥐에서 혈중 스퍼민 수치를 증가시키고 

노화 관련 질환 및 염증 상태를 억제하며 쥐의 수명을 연장한다는 사실을 보고했습니다. 

그러나 

폴리아민의 수명 연장 효과가 폴리페놀과 동일한 생물학적 활성으로 인해 발생한다는 것은 가능성이 낮습니다. 

대부분의 폴리페놀과 항산화 물질을 사용한 연구에서 

수명 연장 효과가 입증되지 않았기 때문입니다. 

최근 연구들은 

노화 관련 질환과 수명이 유전자 발현 조절 메커니즘인 

DNA 메틸화와 밀접하게 연관되어 있음을 밝혀냈습니다. 

폴리아민 대사 과정과 

DNA 메틸화 사이에는 밀접한 관계가 있습니다. 

우리는 

폴리아민 대사 변화가 DNA 메틸화에 관여하는 물질의 농도와 효소 활성에 

영향을 미친다는 것을 보여주었습니다. 

저는 

스퍼민이 DNA 메틸화 조절 능력을 향상시키는 것이 

인간의 건강한 장수의 핵심 요인이라고 생각합니다.

Keywords: polyamine, spermine, spermidine, methylation, DNA, lymphocyte function-associated antigen 1 (LFA-1), LFA-1 promoter (ITGAL), DNA methyltransferases (DNMT)

1. Introduction

Biological aging or senescence is associated with declines in physiological function and altered structural changes. The elderly become increasingly susceptibile to aging-associated pathologies such as sarcopenia, frailty, decreases in higher brain function such as decreased cognitive impairment, cardiovascular disease, metabolic diseases, neoplastic diseases, and neurodegenerative diseases. Epidemiological analyses and interventional trials have shown that, among many life-style factors, the differences in food preferences and dietary patterns contribute to the inhibition of aging-associated diseases and senescence. Among them, what has been carefully examined is that the relationship between increased consumption of soybeans and decreases in the incidence of cardiovascular diseases (CVDs) [1,2] and malignancies such as breast [3,4,5] and colon cancer [6,7,8,9], or a Mediterranean diet and increased vegetable intake are associated with a decreased incidence of lifestyle-related diseases, such as CVDs [10,11,12] and breast and colon cancer [13,14,15,16]. These findings indicate that ingredients contained in these foods play an important role in the inhibition of aging-associated pathologies.

Among these substances, antioxidant polyphenols were considered important candidates for extending healthy lifespans. Examples include isoflavones, found at high levels in soybeans, and resveratrol, which is preval‎ent in the Mediterranean diet. The molecules have many biological activities that counteract the pathogenesis of aging-associated pathologies. For example, they have antioxidant and anti-inflammatory properties [17,18,19,20,21,22], protect cells and genes from harmful stimuli [18,23], increase sirtuin expression‎, and induce autophagy [17,18,24,25,26,27,28,29,30,31]. Early animal experiments and research performed under specific conditions or in a particular animal demonstrated that the increased intake of polyphenols extended lifespans [32,33]. However, evidence from human intervention studies and recent animal experiments is inconsistent and inconclusive because many studies have failed to show any effects on the prevention of aging-associated pathologies and the extension of lifespan [27,34,35,36,37,38,39,40]. Similarly, vitamin E and β-carotene with potent antioxidant and autophagy-induction properties increased, rather than decreased, the incidence of CVDs and related mortality [41,42,43,44,45,46,47,48].

Based on these scientific facts, we considered that substances other than antioxidants contained in these foods are exerting their health and longevity effects. At that time, we found that natural polyamine synthesized in all cells from the lower primitive organisms to humans and contained abundantly in soybeans and the Mediterranean diet have strong anti-inflammatory properties [49]. Polyamines, spermine and spermidine, in food are absorbed from the intestinal tract, and these polyamines are considered one of the most important sources of polyamines in the body. We also examined the relationship between polyamine content and dietary patterns using the food supply database of 49 Western countries from the Food and Agriculture Organization of the United Nations, and we found that the Mediterranean diet is composed of many polyamine-rich food [50,51].

Simultaneously, we first showed that mouse lifespans were increased by the life-time consumption of chow containing synthetic polyamines with an overall polyamine concentration of about three times that in soybeans [52]. Moreover, when mice with no baseline-elevated risk of carcinogenesis or prior treatment with carcinogenic stimuli were reared on three types of chow with different polyamine concentrations and then multiple, moderate doses of a carcinogen were administered, mice that were fed high-polyamine chow had a significantly lower incidence of colon tumors (most of them were cancer) [53]. In addition, we further examined the biological background of life span extension by increased polyamine intake [53,54,55]. Simultaneously, an intervention trial in humans confirmed the same changes in biological markers observed in mouse models and in vitro studies [56]. The current review will introduce the polyamines in general that has been clarified by many previous papers and discuss the biological background of polyamine-induced life span extension of mammals including humans.

1. 서론

생물학적 노화 또는 노화는 생리적 기능의 저하와 구조적 변화와 연관되어 있습니다.

노인들은

사르코페니아, 허약증, 인지 기능 저하(인지 장애 감소), 심혈관 질환, 대사 질환, 종양성 질환, 신경퇴행성 질환 등

노화와 관련된 질환에 점점 더 취약해집니다.

역학 분석과 개입 연구는

많은 생활 방식 요인 중 식습관과 식이 패턴의 차이가

노화 관련 질환과 노화의 억제에 기여한다는 것을 보여주었습니다.

이 중 특히 주목받은 것은

대두 섭취 증가와 심혈관 질환(CVD) [1,2] 및 유방암 [3,4,5]과 대장암 [6,7,8,9]과 같은

악성 종양의 발생률 감소, 또는 지중해 식단과 채소 섭취 증가가

생활습관 관련 질환의 발생률 감소와 연관되어 있다는 점입니다.

예를 들어

CVDs [10,11,12]와 유방 및 대장암 [13,14,15,16] 등이 있습니다.

이러한 결과는

이러한 식품에 함유된 성분이 노화 관련 질환의 억제에 중요한 역할을 한다는 것을 시사합니다.

이 중 항산화 폴리페놀은

건강한 수명을 연장하는 중요한 후보 물질로 고려되었습니다.

예를 들어,

대두에 풍부하게 함유된 이소플라본과

지중해 식단에 널리 분포된 레스베라트롤이 있습니다.

이 분자들은

노화 관련 질환의 병리 과정을 억제하는

다양한 생물학적 활동을 가지고 있습니다.

예를 들어,

항산화 및 항염증 특성 [17,18,19,20,21,22],

유해한 자극으로부터 세포와 유전자를 보호 [18,23],

시르투인 발현을 증가시키고,

자가포식을 유도 [17,18,24,25,26,27,28,29,30,31] 등의 효과가 있습니다.

초기 동물 실험과 특정 조건 하에서 수행된 연구 또는 특정 동물 모델에서 폴리페놀 섭취 증가가 수명을 연장한다는 결과가 보고되었습니다 [32,33]. 그러나 인간 대상 연구와 최근 동물 실험의 증거는 일관되지 않고 결론적이지 않습니다. 많은 연구에서 노화 관련 질환 예방과 수명 연장 효과에 대한 증거를 보여주지 못했기 때문입니다 [27,34,35,36,37,38,39,40].

마찬가지로,

강력한 항산화 및 자가포식 유도 특성을 가진

비타민 E와 β-카로틴은 CVD의 발병률과 관련 사망률을 감소시키지 않고

오히려 증가시켰습니다 [41,42,43,44,45,46,47,48].

이러한 과학적 사실에 기반해,

우리는 이러한 식품에 포함된 항산화제 이외의 성분이

건강과 장수 효과를 발휘한다고 고려했습니다.

이때 우리는 원시적 생물체부터 인간까지

모든 세포에서 합성되며 대두와 지중해 식단에 풍부하게 포함된

천연 폴리아민이 강력한 항염증 효과를 갖는다는 사실을 발견했습니다 [49].

식품에 존재하는 폴리아민(스퍼민과 스퍼미딘)은

장관에서 흡수되며,

이 폴리아민은 신체 내 폴리아민의 가장 중요한 공급원 중 하나로 간주됩니다.

우리는 유엔 식량농업기구(FAO)의 49개 서구 국가 식품 공급 데이터베이스를 활용해

폴리아민 함량과 식이 패턴의 관계를 분석했으며,

지중해 식단이 폴리아민이 풍부한 식품으로 구성되어 있음을 확인했습니다 [50,51].

동시에, 우리는 합성 폴리아민을 함유한 사료를 평생 섭취한 쥐의 수명이 대두의 폴리아민 농도의 약 3배인 전체 폴리아민 농도를 가진 사료를 섭취한 경우 수명이 연장됨을 최초로 보여주었습니다 [52].

또한, 암 발생 위험이 높지 않거나 암 유발 자극을 사전 투여받지 않은 쥐를 폴리아민 농도가 다른 세 가지 사료로 사육한 후 암 유발 물질을 다중·중간 용량으로 투여한 결과, 고폴리아민 사료를 섭취한 쥐에서 대장 종양 발생률(대부분 암으로 진단됨)이 유의미하게 낮았습니다 [53].

또한 우리는 폴리아민 섭취 증가에 의한 수명 연장 현상의 생물학적 배경을 추가로 조사했습니다 [53,54,55]. 동시에 인간 대상 개입 연구에서도 쥐 모델과 체외 연구에서 관찰된 생물학적 지표의 동일한 변화가 확인되었습니다 [56]. 본 리뷰는 이전 연구에서 명확히 규명된 폴리아민의 일반적인 특성을 소개하고, 인간을 포함한 포유류의 폴리아민에 의한 수명 연장 현상의 생물학적 배경을 논의합니다.

2. Polyamine

The natural polyamines (spermine and spermidine) and their precursor, putrescine, are ubiquitous low-molecular-weight aliphatic amines, which contain multiple amino groups (-NH2). Spermine and spermidine have four and three amino groups, respectively, and molecular weights of approximately 140 and 200 g/mol, respectively. Putrescine, a precursor of polyamine, has two amines and is therefore referred to as a diamine. Polyamines are synthesized within all living cells. In eukaryotes, polyamine synthesis begins with ornithine, which is synthesized through the urea cycle from arginine. The decarboxylation of ornithine catalyzed by ornithine decarboxylase (ODC) is the rate-limiting step in polyamine synthesis. Spermidine and spermine are then synthesized by the sequential addition of aminopropyl groups donated from decarboxylated S-adenosylmethionine (dcSAM), which is converted from S-adenosylmethionine (SAM) by the enzymatic activities of adenosylmethionine decarboxylase (AdoMetDC) (Figure 1).

2. 폴리아민

자연계에 존재하는 폴리아민(스퍼민과 스퍼미딘)과

그 전구체인 푸트레신은

다중 아미노 그룹(-NH2)을 포함하는 저분자량 알리파틱 아민으로,

자연계에 널리 분포합니다.

ubiquitous low-molecular-weight

aliphatic amines

알리페틱 아민은 지방족 아민을 말해요. 지방족 아민은 탄소 사슬에 아미노기가 결합된 형태를 띠고 있습니다. 이들은 생체 내에서 다양한 생리활성 물질로 작용하며, 특히 DNA와 RNA의 안정화에 중요한 역할을 합니다.

알리파틱 아민은 지방족 탄화수소에 아미노기가 붙어 있는 형태이고, 

방향족 아민은 벤젠 고리 같은 방향족 탄화수소에 아미노기가 붙어 있는 형태예요. 

이 둘은 구조적인 차이 때문에 성질도 조금씩 다르답니다. 

알리파틱 아민은 주로 염기성을 띠고, 방향족 아민은 약한 염기성을 보여요. 

또, 알리파틱 아민은 물에 잘 녹지만, 방향족 아민은 잘 녹지 않는 경우가 많아요.

스퍼미딘은 수용성이라 식후에 꼭 먹어야 하는 건 아니지만, 

위장이 약한 분들은 식후에 드시는 게 좋아요. 

스퍼민과 스퍼미딘은 각각 4개와 3개의 아미노 그룹을 가지고 있으며,

분자량은 약 140 및 200 g/mol입니다.

폴리아민의 전구체인 푸트레신은

두 개의 아민을 포함하므로 다이아민으로 분류됩니다.

폴리아민은

모든 살아있는 세포 내에서 합성됩니다.

진핵생물에서 폴리아민 합성은

아르기닌으로부터 요산 순환을 통해 합성되는 오르니틴으로부터 시작됩니다.

오르니틴의 탈카복실화 반응은

오르니틴 탈카복실화 효소(ODC)에 의해 촉매되며,

이는 폴리아민 합성의 속도 제한 단계입니다.

스퍼미딘과 스퍼민은

S-아데노실메티오닌(SAM)에서 아데노실메티오닌 디카르복실라제(AdoMetDC)의 효소 활성에 의해

S-아데노실메티오닌 메틸(dcSAM)로 전환된 후,

dcSAM에서 기증된 아미노프로필 그룹이 순차적으로 추가되어 합성됩니다(그림 1).

Figure 1.

Polyamine biosynthesis, degradation, and transmembrane transport.

Spermidine/spermine N-(1)-acetyltransferase (SSAT) and N1-acetylpolyamine oxidase (APAO) degrade intracellular spermine and spermidine. SSAT, a highly inducible enzyme, catalyzes the transfer of acetyl groups from acetyl-coenzyme A to the terminal amines of spermine and spermidine. APAO preferentially catalyzes the oxidation of the N1-acetylspermine and N1-acetylspermidine produced by SSAT activity and yields spermidine and putrescine with the release of an aldehyde and hydrogen peroxide. Alternatively, spermine oxidase (SMO) directly convert spermine to spermidine and release an aldehyde and hydrogen peroxide. Additionally, the polyamine transporter located in the cell membrane can transport polyamines across the cell membrane. The cellular levels of polyamines are tightly regulated through their import, export, synthesis, and catabolism (Figure 1).

폴리아민 생합성, 분해 및 막을 통한 수송.

스퍼미딘/스퍼민 N-(1)-아세틸트랜스퍼레이즈 (SSAT)와 N1-아세틸폴리아민 산화효소 (APAO)는 세포 내 스퍼민과 스퍼미딘을 분해합니다. SSAT는 고도로 유도 가능한 효소로, 아세틸-코엔자임 A로부터 아세틸 그룹을 스퍼민과 스퍼미딘의 말단 아민으로 전이시키는 반응을 촉매합니다. APAO는 SSAT 활성에 의해 생성된 N1-아세틸스퍼민과 N1-아세틸스퍼미딘을 선택적으로 산화시켜 스퍼미딘과 푸트레신으로 전환하며, 이 과정에서 알데히드와 수소 과산화물을 방출합니다. 대안적으로, 스퍼민 산화효소(SMO)는 스퍼민을 직접 스퍼미딘으로 전환하며 알데히드와 수소 과산화물을 방출합니다.

또한 세포막에 위치한 폴리아민 운반체는

폴리아민을 세포막을 통해 운반합니다.

세포 내 폴리아민 수준은

수입, 수출, 합성, 분해(그림 1)를 통해 엄격히 조절됩니다.

Polyamines are universally prerequisite for cell growth and differentiation. However, each of them is of different importance to different organisms. In lower organisms such as bacteria and fungi, putrescine is essential for growth, whereas spermine is not present in the cell [57,58,59,60,61]. In yeasts and nematodes, the concentration of spermine is low and is nonessential for growth [62,63]. These indicate that the role of spermine in cell growth, differentiation, and cell function is insignificant in these lower primitive organisms. Spermine is considered more important in highly developed animals. In fact, a decrease in spermine levels due to a deficiency in spermine synthase have dreadful consequences in humans [64].

In addition to intracellular de novo synthesis, cells can take up polyamine from the extracellular space through a polyamine transporter in the cell membrane. The effects of extracellular polyamine on intracellular polyamine concentration are noticeable in cancer patients. Polyamine biosynthesis is upregulated in cancer cells, and therefore, polyamine concentrations are higher in cancer tissues than in normal surrounding tissues [65,66,67]. Circulating blood cells also take up polyamines synthesized in cancer cells; as a result, the blood cell concentrations and urinary excretion of polyamines, especially those of spermidine, are increased in cancer patients [65,67,68]. These levels decrease after tumor eradication and increase after relapse, indicating that polyamines synthesized in any part of the body, e.g., in cancer tissues, are transferred to blood cells [69].

폴리아민은

세포 성장과 분화에 필수적입니다.

그러나

각 폴리아민은 다양한 생물체에서 서로 다른 중요성을 가집니다.

세균과 곰팡이와 같은 저등생물에서는

푸트레신이 성장에 필수적이지만,

스퍼민은 세포 내에 존재하지 않습니다 [57,58,59,60,61].

효모와 선충에서는 스퍼민의 농도가 낮으며 성장에 필수적이지 않습니다 [62,63]. 이는 스퍼민이 이러한 저등한 원시적 생물체에서 세포 성장, 분화, 세포 기능에 미치는 역할이 미미함을 나타냅니다. 스퍼민은 고등 동물에서 더 중요하게 여겨집니다.

실제로

스퍼민 합성 효소 결핍으로 인한 스퍼민 수준 감소는

인간에서 심각한 결과를 초래합니다 [64].

https://pmc.ncbi.nlm.nih.gov/articles/PMC2822986/

세포 내 신생합성 외에도 세포는

세포막의 폴리아민 운반체를 통해

세포 외 공간에서 폴리아민을 흡수할 수 있습니다.

세포 외 폴리아민이

세포 내 폴리아민 농도에 미치는 영향은

암 환자에서 두드러집니다.

폴리아민 생합성은

암 세포에서 활성화되며,

따라서 암 조직의 폴리아민 농도는 정상 주변 조직보다 높습니다 [65,66,67].

순환 혈액 세포는 암 세포에서 합성된 폴리아민을 흡수하며,

결과적으로 암 환자의 혈액 세포 농도와 요중 배설량,

특히 스퍼미딘의 농도가 증가합니다 [65,67,68].

이 수준은 종양 제거 후 감소하고 재발 후 증가하며,

이는 신체 어느 부분에서든(예: 암 조직) 합성된 폴리아민이 혈액 세포로 이동함을 나타냅니다 [69].

The polyamines are synthesized from arginine. Arginase converts arginine to ornithine, and ornithine decarboxylase (ODC), a rate-limiting enzyme with a short half-life, catalyzes the decarboxylation of ornithine to form putrescine, a polyamine precursor containing two amine groups. ODC is inhibited by antizyme, and antizyme is inhibited by an antizyme inhibitor. S-adenosylmethionine decarboxylase (AdoMetDC) is the second rate-limiting enzyme in polyamine synthesis and is involved in the decarboxylation of s-adenosylmethionine (SAM). Spermidine synthetase and spermine synthase are constitutively expressed aminopropyl transferases that catalyze the transfer of the aminopropyl group from decarboxylated s-adenosylmethionine (dcSAM) to putrescine and spermidine to form spermidine and spermine, respectively. Polyamine catabolism is mediated by the back conversion pathway in which spermine or spermidine are first acetylated by spermine/spermidine N1-acetyltransferase (SSAT) and then oxidized by N1-acetylpolyamine oxidase (APAO) to yield spermidine or putrescine, respectively. Spermine can be directly converted to spermidine via the spermine oxidase (SMO) reaction. Polyamines are transported across the membrane by the polyamine transporter.

Black text indicates the substance name, while spermidine and spermine are shown in green and blue, respectively. Red letters indicate enzyme names. The solid black arrows indicate the metabolic pathway, and the dashed black arrows indicate the transfer of some material from the upstream material. Thick gray T-bars indicate inhibitory activity on the target.

ODC: Ornithine decarboxylase; SSAT: Spermidine/spermine N1-acetyltransferase; APAO: N1-acetylpolyamine oxidase; SMO: Spermine oxidase; SAM: S-adenosylmethionine; AdoMetDC: Adenosylmethionine decarboxylase; dcSAM: Decarboxylated S-adenosylmethionine.

폴리아민은 아르기닌에서 합성됩니다.

아르기나제는 아르기닌을 오르니틴으로 전환하며,

오르니틴 디카르복실라제(ODC)는 짧은 반감기를 가진 속도 제한 효소로,

오르니틴의 디카르복실화를 촉매하여 두 개의 아민 그룹을 포함한

폴리아민 전구체인 푸트레신(putrescine)을 형성합니다.

ODC는 안티자임에 의해 억제되며,

안티자임은 안티자임 억제제에 의해 억제됩니다.

S-아데노실메티오닌 탈카복실화효소(AdoMetDC)는

폴리아민 합성의 두 번째 속도 제한 효소로,

S-아데노실메티오닌(SAM)의 탈카복실화를 촉매합니다.

스퍼미딘 합성효소와 스퍼민 합성효소는

CONSTITUTIVE로 발현되는 아미노프로필 전이효소로,

탈카복실화된 S-아데노실메티오닌(dcSAM)의 아미노프로필 그룹을

푸트레신과 스퍼미딘으로 각각 전이시켜 스퍼미딘과 스퍼민을 형성합니다.

폴리아민 분해는 스퍼민 또는 스퍼민딘이 먼저 스퍼민/스퍼민딘 N1-아세틸트랜스퍼레이즈(SSAT)에 의해 아세틸화되고,

이후 N1-아세틸폴리아민 산화효소(APAO)에 의해 산화되어

각각 스퍼민딘 또는 푸트레신으로 전환되는 역전환 경로를 통해 매개됩니다.

스퍼민은

스퍼민 산화효소(SMO) 반응을 통해 직접 스퍼민딘으로 전환될 수 있습니다.

폴리아민은

폴리아민 운반체에 의해 막을 통해 운반됩니다.

3. Aging and Polyamine

The activity of ODC, the rate-limiting enzyme in polyamine synthesis, declines with age [70,71,72]. ODC has been well characterized and has had a short half-life and to be stimulated by various factors [71,73]. The properties of spermidine synthase and spermine synthase have not been fully clarified, however, they seem to lack a regulatory or rate-limiting role in polyamine synthesis. The administration of arginine or ornithine stimulates putrescine levels; however, the subsequent synthesis of polyamines is not necessarily stimulated in elderly people or aged animals [72,74,75,76]. These findings indicate that the activities of spermine and spermidine synthases decrease gradually with aging.

From these findings, it appears that the polyamine concentrations decrease with aging, and it has been reported that there is an age-associated decrease in polyamine concentrations. Madeo et al., citing mainly their own papers, stated that spermidine concentrations decline in an age-dependent manner [77]. However, their group did not show any data on aging-associated changes in polyamine concentrations in humans. The age-associated decline in polyamine concentrations described in the title and abstract in the papers indicate a decline during early life (fetal period or developmental period) [78]. This decrease slows down markedly in adulthood, and there is no significant decrease in healthy adult animals or humans. Nishimura et al. found that polyamine concentrations in various tissues and organs were significantly lower in 10- and 26-week-old mice than in 3-week-old mice, but no differences in spermine and spermidine concentrations were observed between 10- and 26-week-old mice, except the skin [79]. Morrison et al. measured polyamine levels in autopsied human brain, and they reported that no statistically significant influence of aging (from 1 day to 103 years old) on either putrescine or spermine levels, and spermidine levels increased markedly from birth, reaching maximal levels up to 40 years of age and maintained up to old age [80]. Similarly, an age-associated increase, but not decrease, in spermidine concentrations was also reported in a few organs and the semen of animals and humans in good health [81,82].

3. 노화와 폴리아민

폴리아민 합성의 속도 제한 효소인 ODC의 활성은

연령과 함께 감소합니다 [70,71,72].

ODC는 잘 caractérisé되어 있으며

짧은 반감기를 가지고 있으며 다양한 요인에 의해 자극됩니다 [71,73].

스퍼미딘 합성효소와 스퍼민 합성효소의 특성은 완전히 명확히 밝혀지지 않았지만,

폴리아민 합성에서 조절 또는 속도 제한 역할을 하지 않는 것으로 보입니다.

아르기닌 또는 오르니틴 투여는 푸트레신 농도를 증가시키지만,

노인이나 노화 동물에서 폴리아민 합성이 반드시 증가하지는 않습니다 [72,74,75,76].

이러한 결과는

스퍼민과 스퍼미딘 합성효소의 활성이

노화에 따라 점차 감소함을 시사합니다.

이러한 결과로부터 폴리아민 농도가 노화에 따라 감소한다는 것이 나타나며,

폴리아민 농도의 연령 관련 감소가 보고되었습니다.

Madeo 등(주로 자신의 논문을 인용하여)은 스퍼미딘 농도가 연령에 따라 감소한다고 밝혔습니다[77]. 그러나 그들의 연구 그룹은 인간에서 노화 관련 폴리아민 농도 변화에 대한 데이터를 제시하지 않았습니다. 논문 제목과 초록에 언급된 폴리아민 농도의 연령 관련 감소는 생애 초기(태아기 또는 발달기) 동안의 감소를 의미합니다[78]. 이 감소는 성인기에서 현저히 둔화되며, 건강한 성인 동물이나 인간에서는 유의미한 감소가 관찰되지 않습니다. 니시무라 등(Nishimura et al.)은 다양한 조직과 장기에서 폴리아민 농도가 10주령과 26주령 쥐에서 3주령 쥐보다 유의미하게 낮았지만, 스퍼민과 스퍼미딘 농도는 피부 제외 모든 조직에서 10주령과 26주령 쥐 사이에 차이를 보이지 않았다고 보고했습니다[79].

Morrison 등[80]은 부검된

인간 뇌의 폴리아민 수준을 측정했으며,

노화(1일에서 103세까지)가 푸트레신이나 스퍼민 수준에 통계적으로 유의미한 영향을 미치지 않았으며,

스퍼미딘 수준은 출생 후 급격히 증가해

40세까지 최대 수준에 도달한 후 노년까지 유지되었다고 보고했습니다.

유사하게,

동물과 건강한 인간의 몇 가지 장기 및 정액에서

스퍼미딘 농도의 연령 관련 증가(감소가 아닌)가 보고되었습니다 [81,82].

Polyamine concentrations in blood cells reflect polyamine levels in organs and tissues throughout the body. Elworthy and Hitchcock measured red blood cell polyamine concentrations in 117 patients (ranging from 0 to 80 years old) who were largely in good health but had various neurological problems known not to affect polyamine levels and reported no statistically significant age-dependent changes in spermine or spermidine concentrations [83]. Chaisiri et al. also showed no age-associated decline in plasma polyamine concentrations [84]. Our analyses of aging-associated changes in blood polyamine concentrations in human male volunteers showed no age-associated decline in polyamine concentrations [49,56].

Similarly, urinary polyamine excretion, which reflects blood polyamine concentrations, does not change with age during adulthood. van den Berg et al. measured urinary polyamine excretion in 51 healthy volunteers whose ages ranged from 4 days to 77 years and found an age-dependent decrease in urinary excretion of spermidine in terms of creatinine excretion. However, they clearly indicated that the overall age-dependent decline was merely due to the rapid decrease during the first year of life, and it did not occur during adulthood [85]. Yodfat et al. also examined urinary polyamine concentrations in 171 male and 166 female healthy volunteers whose ages ranged from 14 days to 84 years and demonstrated an age-dependent decrease in diamine levels in males but no age-dependent decrease of polyamines (either spermidine or spermine) in either gender [86]. Several reports have shown that the ratio of spermine/spermidine tends to decrease due to the absence of an age-related decrease in spermidine concentration and an age-related decreasing trend in spermine concentration [56,83,87].

혈액 세포의 폴리아민 농도는

신체 전체의 장기 및 조직 내 폴리아민 수준을 반영합니다.

Elworthy와 Hitchcock은 주로 건강 상태가 좋지만 폴리아민 수준에 영향을 주지 않는 것으로 알려진 다양한 신경학적 문제를 가진 117명(0세부터 80세까지)의 환자를 대상으로 적혈구 폴리아민 농도를 측정했으며, 스퍼민 또는 스퍼미딘 농도에 연령에 따른 통계적으로 유의미한 변화가 없었다고 보고했습니다 [83]. Chaisiri 등도 혈장 폴리아민 농도의 연령 관련 감소가 없음을 보여주었습니다 [84]. 인간 남성 자원자의 노화 관련 혈액 폴리아민 농도 변화를 분석한 우리 연구에서도 폴리아민 농도의 연령 관련 감소가 관찰되지 않았습니다 [49,56].

同様に, 혈중 폴리아민 농도를 반영하는 요중 폴리아민 배설량은 성인기 동안 연령에 따라 변화하지 않습니다. 반 덴 버그 등(van den Berg et al.)은 4일에서 77세 사이의 건강한 자원자 51명을 대상으로 요중 폴리아민 배설량을 측정했으며, 크레아티닌 배설량 대비 스퍼미딘 배설량이 연령에 따라 감소하는 것을 발견했습니다. 그러나 그들은 전체적인 연령에 따른 감소가 생후 첫 해의 급격한 감소에 기인하며, 성인기에는 발생하지 않았다고 명확히 밝혔습니다 [85]. Yodfat 등[86]은 14일에서 84세 사이의 건강한 남성 171명과 여성 166명을 대상으로 소변 폴리아민 농도를 조사했으며, 남성에서는 다이아민 농도가 연령에 따라 감소했지만, 양성 모두에서 폴리아민(스퍼미딘 또는 스퍼민)의 연령에 따른 감소는 관찰되지 않았습니다. 여러 보고서에 따르면, 스퍼민/스퍼미딘 비율은 스퍼미딘 농도의 연령 관련 감소가 없으며 스퍼민 농도의 연령 관련 감소 추세로 인해 감소하는 경향이 있습니다 [56,83,87].

While there is no age-associated decline in polyamine concentrations in tissues, organs, blood, and urine of animals and humans, it is pointed out that there are large inter-individual differences in blood polyamine concentrations [49,83]. The exact biological mechanisms underlying the large inter-individual differences in blood polyamine concentrations are not fully understood. However, these large individual differences in polyamine concentration are one aspect that makes the clinical application of polyamines difficult. In cancer patients, polyamine levels are elevated due to the active synthesis of polyamines in cancer cells, and attempts have been made to diagnose the presence of cancer using polyamine levels as an indicator. Due to this large individual difference, it has been difficult to apply polyamine blood levels and urinary polyamine excretion to the diagnosis of neoplastic diseases. These indicate that reports examining polyamine concentrations in few cases are unreliable. Note that due to the large difference in polyamine concentration, the analysis results vary greatly depending on the choice of cases. For example, Pekar et al. showed that impaired cognitive function is associated with low serum spermidine level [88]. In contrast, Sternberg et al. showed that impaired cognitive function is associated with high serum spermidine levels [89].

동물과 인간의 조직, 장기, 혈액, 소변에서 폴리아민 농도의 연령 관련 감소는 관찰되지 않았지만, 혈중 폴리아민 농도에 큰 개인 간 차이가 존재한다는 점이 지적되었습니다 [49,83]. 혈중 폴리아민 농도의 큰 개인 간 차이를 유발하는 정확한 생물학적 메커니즘은 완전히 이해되지 않았습니다. 그러나 이러한 폴리아민 농도의 큰 개인 간 차이는 폴리아민의 임상적 적용을 어렵게 만드는 요인 중 하나입니다.

암 환자의 경우

암 세포에서 폴리아민이 활발히 합성되어 폴리아민 수치가 상승하며,

폴리아민 수치를 지표로 암의 존재를 진단하려는 시도가 이루어져 왔습니다.

이러한 큰 개인 차이로 인해 폴리아민 혈중 수치와 요중 폴리아민 배설량을 종양 질환 진단에 적용하는 것이 어려웠습니다. 이는 소수의 사례를 대상으로 한 폴리아민 농도 연구 결과가 신뢰하기 어렵다는 것을 의미합니다. 폴리아민 농도의 큰 차이로 인해 사례 선택에 따라 분석 결과가 크게 달라질 수 있다는 점을 주의해야 합니다. 예를 들어, Pekar 등[88]은 인지 기능 저하가 혈청 스페르미딘 농도 저하와 연관되어 있음을 보여주었습니다. 반면 Sternberg 등[89]은 인지 기능 저하가 혈청 스페르미딘 농도 증가와 연관되어 있음을 보여주었습니다.

4. The Effect of Dietary Polyamines on the Body Polyamine

In healthy adult animals and humans, the major source of polyamines is thought to be in the digestive tract, i.e., polyamines in food and polyamines synthesized by the intestinal microbiota. Therefore, a factor to create wide inter-individual differences in polyamine concentrations is thought to be the difference in the polyamine amount supplied from the digestive tract. In fact, a decrease in polyamine intake due to a polyamine-deficient diet and a decrease in polyamine synthesis by intestinal bacteria due to the elimination of intestinal microbiota by antimicrobial agents will lead to a gradual decrease in blood polyamine levels [90,91,92]. Conversely, a long-term increase in the polyamine supply from food gradually increases blood polyamine concentrations, especially spermine concentrations, in humans and mice [52,56,93].

Polyamines exist in all living organisms, and thus, foods that comprise various types of organisms and their related substances contain polyamines, though at a wide variety of concentrations. Germ and bran, legumes such as soybeans, vegetables, and shellfish are foods with high polyamine concentrations per calorie, and spermidine is contained much more than spermine in food [79,94,95,96]. The polyamine concentration in a particular food differs depending on the part of the food examined [96,97]. For example, although fish and shellfish are lower in polyamines than beans and vegetables, higher concentrations of polyamines are found in the internal organs and roe of the fish and shellfish. Therefore, personal food preferences and regional dietary patterns affect polyamine intake from food and influence polyamine levels in the body.

4. 식이 폴리아민이 신체에 미치는 영향 폴리아민

건강한 성인 동물과 인간에서 폴리아민의 주요 공급원은

소화관, 즉 음식에 포함된 폴리아민과

장내 미생물에 의해 합성된 폴리아민으로 추정됩니다.

따라서

폴리아민 농도의 개인 간 차이를 유발하는 요인은

소화관에서 공급되는 폴리아민 양의 차이로 추정됩니다.

실제로 폴리아민 결핍 식이로 인한 폴리아민 섭취 감소와

항생제 투여로 인한 장내 미생물 제거로 인한 장내 세균의 폴리아민 합성 감소는

혈중 폴리아민 농도의 점진적 감소로 이어집니다 [90,91,92].

반면,

식품을 통해 폴리아민 공급이 장기적으로 증가하면 인

간과 쥐에서 혈중 폴리아민 농도,

특히 스퍼민 농도가 점차 증가합니다 [52,56,93].

폴리아민은 모든 생물체에 존재하며,

따라서 다양한 종류의 생물체와 그 관련 물질을 포함하는 식품에는 폴리아민이 함유되어 있지만,

농도는 매우 다양합니다.

곡물의 껍질과 씨앗, 콩류(예: 콩), 채소, 갑각류는 칼로리당 폴리아민 농도가 높은 식품이며,

식품에는 스퍼민보다 스퍼민딘이 훨씬 더 많이 함유되어 있습니다 [79,94,95,96].

특정 식품의 폴리아민 농도는 식품의 부위에 따라 다릅니다 [96,97].

예를 들어, 어류와 갑각류는

콩과 채소보다 폴리아민 함량이 낮지만,

어류와 갑각류의 내장 및 알에는 폴리아민 농도가 높게 나타납니다.

따라서

개인의 식품 선호도와 지역별 식습관은 식품으로부터의 폴리아민 섭취량에 영향을 미치며,

이는 체내 폴리아민 수치에도 영향을 미칩니다.

Because polyamine homeostasis maintains individual polyamine concentrations, short-term increases in polyamine supply do not change them [52,56,93,98,99].

폴리아민 균형은

개인의 폴리아민 농도를 유지하기 때문에

단기적인 폴리아민 공급 증가가 이를 변화시키지 않습니다 [52,56,93,98,99].

Schwarz et al. showed that 28 days of augmentation of spermidine supplementation in mice resulted in no change in blood polyamines in mice [99]. Brodal et al. also reported similar results. For 20 days of feeding with experimental chow with different polyamine concentrations, the levels of putrescine, spermine, and spermidine in rat blood remained remarkably constant irrespective of chow [98]. In our animal experiments using mice, chow containing synthetic polyamine of which concentrations are about 3 times higher than those of soybean failed to increase blood spermine and spermidine concentrations for at least 16 weeks [52,93]. Eisenberg et al. postulated that increased spermidine intake supply spermidine to tissues and organs and spermidine provokes biological activities. They showed using few mice that spermidine ingestion increases blood spermidine levels with large individual differences for 16 weeks, but they did not show a study of a large enough number of mice to be able to rule out the effect of large individual differences in blood spermidine levels [100]. We confirmed that spermine (but not spermidine) concentrations in whole blood of mice fed high-polyamine chow for 26 weeks increased significantly, after repeated attempts with more mice. Spermidine concentrations increased in some animals, however, there were no significant changes [53].

Schwarz 등[99]은 쥐에게 28일 동안 스퍼미딘 보충제를 투여한 결과 혈중 폴리아민 농도에 변화가 없음을 보여주었습니다. Brodal 등도 유사한 결과를 보고했습니다. 실험용 사료에 다양한 폴리아민 농도를 포함시켜 20일 동안 급여한 결과, 쥐의 혈중 푸트레신, 스퍼민, 스퍼미딘 농도는 사료 종류에 관계없이 놀랍게도 일정한 수준을 유지했습니다 [98]. 우리 연구에서 쥐를 대상으로 한 동물 실험에서, 대두의 폴리아민 농도보다 약 3배 높은 합성 폴리아민을 함유한 사료를 급여한 결과, 적어도 16주 동안 혈중 스퍼민과 스퍼미딘 농도가 증가하지 않았습니다 [52,93]. Eisenberg 등[100]은 스퍼미딘 섭취 증가가 조직과 기관에 스퍼미딘을 공급하며, 스퍼미딘이 생물학적 활동을 유발한다고 제안했습니다. 그들은 소수의 쥐를 대상으로 스퍼미딘 섭취가 16주 동안 혈중 스퍼미딘 농도를 증가시키지만, 혈중 스퍼미딘 농도의 큰 개인 차이를 배제할 수 있을 만큼 충분한 수의 쥐를 대상으로 한 연구를 제시하지 않았습니다. 우리는 고폴리아민 사료를 26주간 섭취한 쥐의 전혈에서 스퍼민(스퍼미딘은 아니지만) 농도가 유의미하게 증가함을 반복 실험을 통해 확인했습니다. 일부 동물에서는 스퍼미딘 농도가 증가했지만, 유의미한 변화는 관찰되지 않았습니다 [53].

Similar findings were observed in human interventional studies. Schwarz et al. showed that a human trial of 3-months of increased oral spermidine supplementation did not change blood spermidine levels at all [99]. A few intervention studies reported the favorable effects of increased spermidine intake on human memory function, however, they did not present individual data concerning the effect of increased spermidine intake on blood polyamine concentrations or a relationship between spermidine intake and changes in blood spermidine levels [101]. As they seemed to finish a large scale of intervention study [102], I am looking forward to the results of how spermidine consumption affected polyamine levels in humans. In our latest study, in which volunteers were asked to eat fermented soybeans containing high levels of polyamines, blood spermine levels gradually rose very slowly. During the first 8 months of the study, spermine levels slightly elevated in the high-polyamine diet group, however, there was no difference between the control group and the high-polyamine diet group. After 12 months of intervention, the blood spermine level in the high-polyamine group increased with a significant difference [56]. The lack of changes in blood polyamine concentration upon an increase in polyamine intake for a short period indicates that the intracellular polyamine concentration is strictly maintained by polyamine homeostasis. In addition, the findings that the concentration of spermine in blood cells increases only when polyamine intake is increased over a long period indicate that the presence of a long-lasting polyamine supply from the digestive tract can affect polyamine homeostasis and alter intracellular spermine concentrations. However, up to the present, it is unlikely that spermidine supplementation affects spermidine levels in the organs, tissues, or blood in animals and humans because of the lack of data from studies with sufficient populations for analysis.

In both our animal experiments and human interventional studies, increased polyamine intake increased blood spermine levels, while spermidine levels did not change, despite both animals and humans taking more spermidine than spermine [53,56]. Several studies indicate the importance of the composition of the intestinal microbiota for synthesis of intestinal polyamines [103]. Matsumoto et al. reported that probiotics administration increased spermine, but not spermidine, concentrations in feces in humans and animals, although probiotics and intestinal microbiota by themselves cannot synthesize spermine [104,105]. Considering these scientific facts, we can consider that the long-term and continuous increase in polyamine (spermidine > spermine) intake increases the supply of spermine, but not of spermidine, from the digestive tract. The role of intestinal environment and microbiota, especially in the composition of the intestinal microbiota, in polyamine synthesis in the intestinal lumen should be further examined.

In our intervention study using a high-polyamine diet, we found that the relationship between increases in polyamine intake and those in blood spermine levels seems not to be simply additive. The continuous intake of the high-polyamine diet increased blood spermine concentration of the subjects, but the increase in polyamine intake was not necessarily reflected in the increase in blood concentration [52,53,56]. The difference in the increase in blood polyamines in response to increased polyamine intake and wide inter-individual differences in blood polyamine concentration reflect differences in the intestinal environment.

인간 대상 개입 연구에서도 유사한 결과가 관찰되었습니다. Schwarz 등[99]은 3개월간의 경구 스퍼미딘 보충이 혈중 스퍼미딘 농도에 전혀 영향을 미치지 않았다는 것을 보여주었습니다. 몇 가지 개입 연구에서는 스퍼미딘 섭취 증가가 인간 기억 기능에 유익한 효과를 보였지만, 스퍼미딘 섭취 증가가 혈중 폴리아민 농도에 미치는 영향이나 스퍼미딘 섭취와 혈중 스퍼미딘 농도 변화 간의 관계에 대한 개인별 데이터를 제시하지 않았습니다[101]. 그들이 대규모 개입 연구를 완료한 것으로 보입니다 [102], 인간에서 스페르미딘 섭취가 폴리아민 농도에 미치는 영향에 대한 결과를 기대하고 있습니다. 우리 최신 연구에서, 고농도 폴리아민을 함유한 발효 콩을 섭취한 자원자들에게 혈중 스페르민 농도가 점차 매우 천천히 상승했습니다. 연구 초기 8개월 동안 고폴리아민 식이군에서 스퍼민 농도가 약간 상승했지만, 대조군과 고폴리아민 식이군 사이에 차이는 없었습니다. 12개월간의 개입 후, 고폴리아민 식이군의 혈중 스퍼민 농도는 유의미한 차이로 증가했습니다 [56]. 폴리아민 섭취량이 단기간 증가해도 혈중 폴리아민 농도가 변화하지 않는 것은 세포 내 폴리아민 농도가 폴리아민 항상성에 의해 엄격히 유지되기 때문입니다. 또한, 폴리아민 섭취량이 장기간 증가할 때만 혈액 세포 내 스퍼민 농도가 증가한다는 결과는 소화관에서 장기간 지속되는 폴리아민 공급이 폴리아민 항상성에 영향을 미치고 세포 내 스퍼민 농도를 변화시킬 수 있음을 시사합니다. 그러나 현재까지 동물과 인간에서 충분한 표본 규모를 가진 연구 데이터가 부족하기 때문에, 스퍼미딘 보충이 동물과 인간의 장기, 조직, 혈액 내 스퍼미딘 수준에 영향을 미친다는 것은 가능성이 낮습니다.

우리의 동물 실험과 인간 개입 연구 모두에서 폴리아민 섭취량이 증가하면 혈중 스퍼민 농도가 증가했지만, 스퍼미딘 농도는 변화하지 않았으며, 이는 동물과 인간 모두 스퍼민보다 스퍼미딘을 더 많이 섭취했음에도 불구하고였습니다 [53,56]. 여러 연구는 장내 미생물군집의 구성물이 장내 폴리아민 합성에 중요함을 보여줍니다 [103]. Matsumoto 등[104,105]은 프로바이오틱스 투여가 인간과 동물에서 분변 내 스퍼민 농도를 증가시켰지만, 스퍼미딘 농도는 증가시키지 않았다고 보고했습니다. 그러나 프로바이오틱스와 장내 미생물군집 자체는 스퍼민을 합성할 수 없습니다. 이러한 과학적 사실을 고려할 때, 폴리아민(스퍼미딘 > 스퍼민) 섭취의 장기적이고 지속적인 증가가 소화관에서 스퍼민 공급을 증가시키지만 스퍼미딘 공급은 증가시키지 않는다고 고려할 수 있습니다. 장 환경과 미생물군집, 특히 장내 미생물군집의 구성은 장 내강에서의 폴리아민 합성에 미치는 역할을 추가로 조사해야 합니다.

고폴리아민 식이를 사용한 우리 개입 연구에서, 폴리아민 섭취 증가와 혈중 스퍼민 농도 증가 사이의 관계가 단순히 가산적이지 않다는 것을 발견했습니다. 고폴리아민 식이의 지속적인 섭취는 대상자의 혈중 스퍼민 농도를 증가시켰지만, 폴리아민 섭취 증가가 반드시 혈중 농도 증가로 반영되지 않았습니다 [52,53,56]. 폴리아민 섭취 증가에 따른 혈중 폴리아민 농도의 증가 차이 및 개인 간 혈중 폴리아민 농도의 광범위한 차이는 장 환경의 차이를 반영합니다.

5. Polyamine Localization in the Body

Polyamines have a binding capacity to DNA, RNA, and various protein molecules, and are implicated in diverse cellular functions such as transcription, RNA modification, protein synthesis, and modulation of enzyme activities. It has been estimated that a high percentage of total polyamines is bound by ionic interactions to nucleic acids, proteins, and other negatively charged molecules in the cell, while the free intracellular concentration of each polyamine is much lower (7–15% of total for spermidine and 2–5% for spermine in tissues and organs) [106,107]. Therefore, most polyamines in circulating blood are present in blood cells. Copper et al. showed that spermidine and spermine concentrations in plasma account for only 1.0% (spermine) to 1.2% (spermidine) of whole blood [108]. When we measure serum or plasma polyamine concentration by HPLC, it is sometimes hard to detect the peak of spermine due to the low levels [109]. When the concentration of spermine is low, HPLC can only depict the peak of spermine as a shaking of the baseline. We consider that it is difficult to determine accurate polyamine concentrations using such unclear peak. It is also important to note that even if a small amount of hemolysis occurs in the blood sample, the polyamines present in the cells leak out and have a significant effect on the polyamine concentration. The reason for measuring whole blood polyamine levels is to accurately measure all the polyamines present or attached to blood cells.

Blood cells circulate in organs and tissues throughout the body. Polyamine concentrations are increased in cancer tissues due to active polyamine synthesis, and blood polyamine concentrations are increased in cancer patients. These indicate that blood polyamine levels reflect polyamine concentrations in some organs and tissues in the body. Conversely, polyamines in blood cells can be passed to cells in tissues and organs, affecting their concentration. The brain is a typical example of an organ where polyamines in the blood cannot be transferred. Polyamines are highly water-soluble and polar compounds and thus their passage across the intact blood–brain barrier (BBB) is poor [110,111]. Polyamines have been noxious to the BBB by several investigators in different pathological states of the brain, including cerebral ischemia [112,113,114,115]. In animal models, there have been reports of the collapse of the BBB, allowing polyamines to enter brain tissue. However, such disruption occurs only in critical situations such as following traumatic brain injury [116] and ischemic injury [117]. Similarly, BBB dysfunction is reported in 14 patients following traumatic brain injury [118]. Several studies have reported that polyamine aggravate structural defects and even lead to membrane and vascular dysfunction after several different pathological conditions [113,119]. Considering these reports, the BBB protects the brain from being damaged by polyamines entering the brain tissue in otherwise normal conditions, and disruption of the BBB indicates that vascular function and the brain tissue is affected by some serious pathology.

5. 폴리아민의 체내 분포

폴리아민은

DNA, RNA 및 다양한 단백질 분자와 결합하는 능력을 가지고 있으며,

전사, RNA 변형, 단백질 합성, 효소 활성 조절 등 다양한 세포 기능에 관여합니다.

전체 폴리아민 중 높은 비율이

세포 내 핵산, 단백질 및 기타 음전하를 띤 분자와 이온 결합으로 결합되어 있으며,

각 폴리아민의 자유 세포 내 농도는 훨씬 낮습니다

(조직 및 장기에서 스페르미딘은 전체의 7–15%, 스페르민은 2–5%) [106,107].

따라서

순환 혈액 내 대부분의 폴리아민은 혈액 세포에 존재합니다.

Copper 등[108]은

혈장 내 스퍼미딘과 스퍼민 농도가 전체 혈액의 1.0%(스퍼민)에서 1.2%(스퍼미딘)에 불과함을 보여주었습니다.

HPLC로 혈청 또는 혈장 폴리아민 농도를 측정할 때 스퍼민의 피크를 낮은 농도로 인해 탐지하기 어려운 경우가 있습니다[109]. 스퍼민 농도가 낮을 경우 HPLC는 스퍼민의 피크를 기저선 흔들림으로만 나타낼 수 있습니다. 이러한 불분명한 피크를 통해 정확한 폴리아민 농도를 결정하는 것은 어렵다고 판단됩니다. 또한 혈액 샘플에 작은 양의 용혈이 발생하더라도 세포 내 폴리아민이 유출되어 폴리아민 농도에 큰 영향을 미친다는 점도 중요합니다. 전혈 폴리아민 농도를 측정하는 이유는 혈액 세포에 존재하거나 결합된 모든 폴리아민을 정확히 측정하기 위함입니다.

혈액 세포는

신체 내 장기와 조직을 순환합니다.

폴리아민 합성이 활발히 이루어지는 암 조직에서는

폴리아민 농도가 증가하며,

암 환자의 혈중 폴리아민 농도도 증가합니다.

이는 혈중 폴리아민 농도가 신체 내 일부 장기와 조직의 폴리아민 농도를 반영함을 의미합니다. 반면, 혈액 세포 내의 폴리아민은 조직과 장기의 세포로 전달되어 그 농도에 영향을 미칠 수 있습니다. 뇌는 혈액 내 폴리아민이 전달되지 않는 대표적인 장기입니다. 폴리아민은 고도로 수용성이고 극성 화합물로, 따라서 완전한 혈액-뇌 장벽(BBB)을 통해의 이동이 불량합니다 [110,111]. 여러 연구자들은 뇌의 다양한 병리적 상태에서 폴리아민이 BBB에 유해한 영향을 미친다는 사실을 보고했습니다. 이는 뇌 허혈 [112,113,114,115]을 포함합니다. 동물 모델에서 BBB의 붕괴로 폴리아민이 뇌 조직으로 유입되는 사례가 보고되었습니다. 그러나 이러한 장애는 외상성 뇌 손상 [116]이나 허혈성 손상 [117]과 같은 극한 상황에서만 발생합니다. 유사하게, 외상성 뇌 손상 후 14명의 환자에서 BBB 기능 장애가 보고되었습니다 [118]. 여러 연구에서 폴리아민이 다양한 병리적 조건 후 구조적 결함을 악화시키고 심지어 세포막 및 혈관 기능 장애로 이어질 수 있음을 보고했습니다 [113,119]. 이러한 보고를 고려할 때, BBB는 정상 조건에서 폴리아민이 뇌 조직으로 침투하여 뇌를 손상시키는 것을 방지하며, BBB의 파괴는 혈관 기능과 뇌 조직이 심각한 병리학적 상태에 의해 영향을 받았음을 나타냅니다.

6. Biological Activities of Polyamines

The biological activities of putrescine differ from those of polyamines, spermine and spermidine. For example, whereas spermine and spermidine have strong anti-inflammatory activities and are absorbed quickly from the intestinal lumen [120,121], putrescine has little to no anti-inflammatory effect and is degraded in the intestinal lumen [121,122]. Both spermidine and spermine have superficially similar biological activities, however, experiments have shown that spermine has greater potency. In cells with normal homeostasis, the influx of polyamines from the extracellular space suppresses ODC activity. Yuan Q et al. showed that putrescine, spermidine, and spermine inhibited ODC activity stimulated by serum to 85, 46, and 0% of control, indicating spermine is the most, and putrescine the least, effective polyamine in regulating ODC activity [123]. The difference in the strength of the suppression of one of the polyamine synthetic enzymes, e.g., ODC, between spermine and spermidine is reflected in the difference in their ability to regulate DNA methylation and the resultant change in the amount of lymphocyte function-associated antigen 1 (LFA-1), a protein involved in immune function that we have noted. In in vitro studies, we and others found that increasing the spermine concentration to about 1.2 times the level that occurs in vivo resulted in significant biological activity [49,123]. However, intracellular concentrations of spermidine had to increase two- to three-fold in human mononuclear blood cells to elicit obvious biological activities, i.e., the suppression of LFA-1 expression‎, the production of proinflammatory cytokines, and autophagy induction [49,87,121]. A two- to three-fold change in spermidine concentration is rare, except for a few cases in cancer patients. The difference in activity between spermidine and spermine is also observed in the relationship between blood concentration and LFA-1 levels, one of the bioactive targets of polyamine. When the relationship between polyamine concentration and LFA-1 level was examined in healthy volunteers, blood spermine concentration was inversely correlated with LFA-1 expression‎, while blood spermidine concentration was not [49,56]. Similarly, Saiki et al. reported that spermine is three to four times more capable of inducing autophagy than spermidine, and that the activity of spermine can be confirmed at concentrations in the physiological range [87].

6. 폴리아민의 생물학적 활성

푸트레신(putrescine)의 생물학적 활성은 폴리아민, 스퍼민(spermine) 및 스퍼미딘(spermidine)과 다릅니다. 예를 들어, 스퍼민과 스퍼미딘은 강한 항염증 활동을 보이며 장 내강에서 빠르게 흡수됩니다 [120,121], 반면 푸트레신은 항염증 효과가 거의 없으며 장 내강에서 분해됩니다 [121,122]. 스퍼미딘과 스퍼민은 표면상 유사한 생물학적 활동을 보이지만, 실험 결과 스퍼민이 더 강력한 효과를 나타냅니다. 정상적인 항상성 상태의 세포에서 세포외 공간으로부터의 폴리아민 유입은 ODC 활성을 억제합니다. Yuan Q 등[123]은 푸트레신, 스퍼미딘, 스퍼민이 혈청에 의해 자극된 ODC 활성을 각각 대조군의 85%, 46%, 0%로 억제함을 보여주었으며, 이는 스퍼민이 ODC 활성 조절에 가장 효과적이며, 푸트레신이 가장 덜 효과적인 폴리아민임을 나타냅니다. 폴리아민 합성 효소 중 하나인 ODC의 억제 강도 차이는 스퍼민과 스퍼미딘의 DNA 메틸화 조절 능력 차이와, 우리가 관찰한 면역 기능에 관여하는 단백질인 림프구 기능 연관 항원 1(LFA-1)의 양 변화에 반영됩니다. 체외 연구에서 우리와 다른 연구자들은 스퍼민 농도를 체내 수준보다 약 1.2배로 증가시키면 유의미한 생물학적 활성이 관찰되었다고 보고했습니다 [49,123]. 그러나, 인간 단핵 혈액 세포에서 스퍼미딘의 세포 내 농도가 2~3배 증가해야만 LFA-1 발현 억제, 전염증성 사이토카인 생성, 자가포식 유도 등 뚜렷한 생물학적 활성이 나타났습니다 [49,87,121]. 스퍼미딘 농도가 2~3배 변화하는 경우는 암 환자 몇몇을 제외하고는 드문 일입니다. 스페르미딘과 스페르민의 활성 차이는 폴리아민의 생물학적 표적 중 하나인 LFA-1 수준과 혈중 농도 간의 관계에서도 관찰됩니다. 건강한 자원자를 대상으로 폴리아민 농도와 LFA-1 수준 간의 관계를 조사한 결과, 혈중 스페르민 농도는 LFA-1 발현과 역상관 관계를 보였지만, 혈중 스페르미딘 농도는 그렇지 않았습니다 [49,56]. 마찬가지로 Saiki 등도 스퍼민이 스퍼미딘보다 자가포식을 유도하는 능력이 3~4배 더 높고, 스퍼민의 활성은 생리학적 농도 범위에서도 확인할 수 있다고 보고했습니다 [87].

Polyamines have many biological activities that may counteract the pathogenesis of aging-associated pathologies. For instance, they exert anti-inflammatory [49,121,124,125,126,127,128] and antioxidant properties [129,130,131,132,133,134,135,136,137,138]; protect cells and genes from harmful stimuli such as radiation [139,140,141,142,143,144,145,146,147], ultraviolet rays [148,149,150], toxic chemicals [128,151,152,153,154], and other stresses [148,155,156,157]; and they promote autophagy [128,158,159]. Very interestingly, polyphenols and antioxidant vitamins, which are abundant in legumes such as soybeans and in the Mediterranean diet, also have the same bioactivity as polyamines. For example, they have anti-inflammatory and antioxidant properties [17,19,20,21,22], and they protect cells and genes from harmful stimuli [18,23] and activate autophagy [17,25,26,28,29,30,31]. These biological activities were considered to inhibit the development of age-related pathologies. However, despite the large number of research conducted with antioxidants, the majority failed to show any effects on the prevention of aging-associated pathologies and the extension of lifespan of mammals [27,34,35,36,37,39,40] (Figure 2).

폴리아민은

노화 관련 병리의 발병을 막는

여러 가지 생물학적 활성을 가지고 있습니다.

For instance, they exert anti-inflammatory [49,121,124,125,126,127,128]

and antioxidant properties [129,130,131,132,133,134,135,136,137,138];

유해 자극으로부터

세포와 유전자를 보호합니다.

예를 들어 방사선 [139,140,141,142,143,144,145,146,147], 자외선 [148,149,150],

독성 화학물질 [128,151,152,153,154], 및 기타 스트레스 [148,155,156,157]로부터 보호하고,

자가포식을 촉진합니다 [128,158,159].

매우 흥미롭게도,

콩과 같은 콩류와 지중해 식단에 풍부하게 함유된 폴리페놀과 항산화 비타민도

폴리아민과 동일한 생물학적 활성을 가지고 있습니다.

예를 들어,

항염증 및 항산화 특성이 있으며 [17,19,20,21,22],

유해한 자극으로부터 세포와 유전자를 보호하고 [18,23]

자가포식을 활성화합니다 [17,25,26,28,29,30,31].

이러한 생물학적 활동은 노화 관련 질환의 발병을 억제하는 것으로 여겨져 왔습니다. 그러나 항산화제를 대상으로 한 수많은 연구에도 불구하고, 대부분의 연구는 포유류의 노화 관련 질환 예방 및 수명 연장 효과에 대해 유의미한 결과를 보여주지 못했습니다 [27,34,35,36,37,39,40] (그림 2).

Figure 2.

Open in a new tab

Biological activities of polyamine and polyphenols.

Recently, a research group has highlighted the importance of autophagy-mediated bioactivity by spermidine on life span extension [77]. Autophagy is a natural regulatory mechanism within the cells to remove degenerated or dysfunctional components from the cell. If autophagy function is inhibited, these unwanted components accumulate in cells, inhibit cellular homeostasis, and provoke various pathological changes [160]. Animal experiments using organ-specific conditional autophagy-deficient mice have revealed a close relationship between decreased autophagy and aging-associated pathologies [161,162].

Given that the increases in the incidence of aging-associated diseases with aging, we can speculate that autophagy activity decreases with aging [163]. In addition, decreased autophagy with aging has been reported in various studies [161,164,165,166]. However, other investigators have demonstrated that autophagy does not necessarily decline with age [167,168]. Yamamoto et al. even demonstrated substantial upregulation of autophagy in the aged kidney, suggesting compensatory activation of basal autophagy in response to the increased number of unwanted components with aging-associated accumulation [169].

Experiments using several primitive organisms confirm‎ that inactivation of an autophagy gene suppressed the lifespan extension of long-lived mutant worms and slightly shortened the lifespan of wild-type worms [170,171,172,173,174,175,176]. However, the relationship between autophagy and longevity is not straightforward. Other investigators have shown that the inhibition of autophagy genes in several organisms does not always reduce normal lifespan [163,175,177]. Hashimoto et al. have systematically examined the effect of suppression of 14 autophagy genes on life span using RNAi. They reported that the suppression of autophagy genes can extend, but not shorten, the lifespan of Caenorhabditis elegans. These results indicate that autophagy activation is not necessarily beneficial for longevity and functions to shorten, or at least not extend, lifespan in several nematodes and flies [178]. Additionally, it has also been suggested that physiological levels of autophagy promote survival, while inadequate or excessive levels of autophagy promote death [179]. Because there is little scientific evidence indicating that autophagy activation helps extend the life span of mammals and aging is a complex process in highly developed mammals, the simple relationship between autophagy and aging observed in certain primitive organisms with short life spans is not straightforward in mammals, especially humans.

From these scientific facts, the biological activities described above are not enough to achieve the life span extension and inhibit the progression of senescence in mammals, especially humans, even if the mechanism and/or the pathway by which polyamines and polyphenols elicit these biological activities are different (Figure 2).

Both polyamines (spermidine and spermine) and antioxidants such as polyphenols and antioxidant vitamins have anti-inflammatory properties, antioxidant properties, and protect cells and genes from harmful stimuli and activate autophagy. Despite the vast amount of research on antioxidants, most of the studies have failed to show any benefit in preventing age-related conditions or extending lifespan. Therefore, the biological activities described in the figure are not enough to achieve life span extension and inhibition of the progression of senescence, especially of mammals, even if the mechanism and/or the pathway by which polyamines and polyphenols elicit these biological activities are different.

References for A circled: [17,18,19,20,21,22,23,25,26,28,29,30,31], References for B circled: [49,121,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159], References for “?”: [22,25,26,27,28,30,31].

폴리아민과 폴리페놀의 생물학적 활동.

최근 한 연구 그룹은 스퍼미딘이 수명 연장에 미치는 자가포식 매개 생물학적 활성의 중요성을 강조했습니다 [77]. 자가포식은 세포 내에서 퇴화되거나 기능 장애를 일으킨 성분을 제거하는 자연적인 조절 메커니즘입니다. 자가포식 기능이 억제되면 이러한 불필요한 성분이 세포에 축적되어 세포의 항상성을 저해하고 다양한 병리학적 변화를 유발합니다 [160]. 장기별 조건부 자가포식 결핍 마우스를 사용한 동물 실험을 통해 자가포식의 감소와 노화 관련 병리학 사이의 밀접한 관계가 밝혀졌습니다 [161,162].

노화와 함께 노화 관련 질병의 발병률이 증가한다는 점을 고려할 때, 자식 세포 사멸 활동은 노화와 함께 감소한다고 추측할 수 있습니다 [163]. 또한, 노화와 함께 자식 세포 사멸이 감소한다는 것이 여러 연구에서 보고되었습니다 [161,164,165,166]. 그러나 다른 연구자들은 자식 세포 사멸이 반드시 나이와 함께 감소하는 것은 아니라고 밝혔습니다 [167,168]. Yamamoto 등은 노화된 신장에서 자가포식이 상당히 증가함을 입증하여, 노화와 함께 축적되는 불필요한 성분의 수에 대응하여 기초적인 자가포식이 보상적으로 활성화된다는 것을 시사했습니다 [169].

여러 원시 유기체를 사용한 실험을 통해, 자가포식 유전자의 비활성화가 장수 돌연변이 벌레의 수명 연장을 억제하고 야생형 벌레의 수명을 약간 단축한다는 것이 확인되었습니다 [170,171,172,173,174,175,176]. 그러나, 자가포식과 장수의 관계는 간단하지 않습니다. 다른 연구자들은 여러 유기체에서 자가포식 유전자의 억제가 항상 정상적인 수명을 단축하는 것은 아니라는 것을 보여주었습니다 [163,175,177]. Hashimoto 등은 RNAi를 사용하여 14개의 자가포식 유전자의 억제가 수명에 미치는 영향을 체계적으로 조사했습니다. 그들은 자가포식 유전자의 억제가 Caenorhabditis elegans의 수명을 단축하지는 않지만 연장할 수 있다고 보고했습니다. 이러한 결과는 자가포식 활성화가 반드시 장수에 유익한 것은 아니며, 여러 선충류와 파리에서 수명을 단축하거나 적어도 연장하지는 않는 기능을 한다는 것을 나타냅니다 [178]. 또한, 생리학적 수준의 자가포식은 생존을 촉진하는 반면, 자가포식이 부족하거나 과도하면 사망을 촉진한다는 것도 제시되어 있습니다 [179]. 자가포식 활성화가 포유류의 수명 연장에 도움이 된다는 것을 나타내는 과학적 증거는 거의 없고, 고도로 발달한 포유류에서 노화는 복잡한 과정이기 때문에, 수명이 짧은 특정 원시 생물에서 관찰된 자가포식과 노화의 단순한 관계는 포유류, 특히 인간에서는 명확하지 않습니다.

이러한 과학적 사실로부터, 위에서 설명된 생물학적 활동만으로는 포유류, 특히 인간에서 수명 연장과 노화 진행 억제를 달성하기에 충분하지 않습니다. 이는 폴리아민과 폴리페놀이 이러한 생물학적 활동을 유발하는 메커니즘과/또는 경로가 다르더라도 마찬가지입니다(그림 2).

폴리아민(스퍼미딘 및 스퍼민)과 폴리페놀 및 항산화 비타민과 같은 항산화제는 항염증 및 항산화 특성을 가지고 있으며, 유해한 자극으로부터 세포와 유전자를 보호하고 자가포식을 활성화합니다. 항산화제에 대한 광범위한 연구에도 불구하고, 대부분의 연구는 노화 관련 질환 예방이나 수명 연장에 대한 이점을 보여주지 못했습니다. 따라서 그림에 설명된 생물학적 활동은 포리페놀과 폴리아민이 이러한 생물학적 활동을 유발하는 메커니즘과/또는 경로가 다르더라도, 특히 포유류에서 수명 연장 및 노화 진행 억제를 달성하기에 충분하지 않습니다.

참고문헌 (A 표시된 부분): [17,18,19,20,21,22,23,25,26,28,29,30,31], 참고문헌 (B 표시된 부분): [49,121,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159], References for “?”: [22,25,26,27,28,30,31].

7. Aging, Proinflammatory Status, and DNA Methylation

Mammals are composed of countless numbers of cells and are made up of a complex interplay of various tissues and organs (nervous system, endocrine function, respiratory system, digestive system, immune functions, etc.). In humans, aging is associated with increased susceptibility to numerous different kinds of pathological conditions such as anemia, decreased kidney function, physical function impairment, sarcopenia, metabolic syndrome, diabetes, impaired cognitive function, neurodegenerative diseases, cardiovascular diseases, and cancer. Therefore, the type of disease they suffer from, the organ where pathology develops, and the progression of the disease affect their lifespan.

When considering that aging is associated with an increased incidence of these various diseases, the changes in the body environment that develop with aging play an important role in triggering these various diseases. Among changes, the increased pro-inflammatory status is considered a typical change associated with aging and triggering aging-associated diseases because inflammation and the resulting increase in oxidative stress have been shown to be involved in many aging-associated diseases [180]. Chronic, low-level elevation of proinflammatory cytokines and chemokines, and the resulting increases in inflammatory biomarkers, are associated with age-related declines in function and increased risks of morbidity and mortality [181]. Although the biological background of aging-associated increase in pro-inflammatory status is not fully clarified, one of the typical changes associated with aging responsible for increased pro-inflammatory status is the aging-associated increase in LFA-1 expression‎ in immune cells. [182,183,184,185].

LFA-1 is an important protein involved in the induction of inflammation. The immune cells are activated when they recognize substances to be eliminated, and inflammation is generally the result of immune cell activation to eliminate harmful pathogens. The first step in this process is the binding of LFA-1 on immune cell membranes to intercellular adhesion molecules on endothelial cells lining the innermost layer of blood vessels. The increase in persistent inflammation associated with aging is likely the result of continuously weak stimulation by originally non-stimulatory degraded cells and substances and the increased response of aged immune cells with increased LFA-1 expression‎ [186]. The activation of immune cells results in the production of proinflammatory cytokines, and aging is accompanied by progressive increases in the blood levels of proinflammatory mediators, including tumor necrosis factor α, interleukin-1, and interleukin-6 [187,188,189,190]. All three of these cytokines inhibit erythropoiesis [191], accelerate muscle wasting [192], induce insulin resistance [193], promote vascular dysfunction [194], and the resulting chronic inflammation provoked by cytokine production has also been linked to neurodegenerative diseases such as Alzheimer’s disease [195] and carcinogenesis [196].

The amount of LFA-1 protein on immune cells’ membrane is regulated by two main mechanisms. One is the intracellular signaling pathways, which result in rapid redistribution of LFA-1 to the cell membrane, regulating LFA-1 levels [197]. Apart from that, the alteration of DNA methylation status of the responsible part of LFA-1 expression‎, called ITGAL, also regulate LFA-1 expression‎. DNA methylation is a mechanism to regulate gene expression‎ by modulating methylation in genomic regions that are either distal or proximal to the transcription start site of a gene. It has been reported that increases in LFA-1 protein levels in immune cells with aging are associated with enhanced demethylation of the ITGAL (LFA-1 promoter area) and increased LFA-1 protein levels [49,56,198,199].

A growing number of recent studies have shown a close relationship between aging and DNA methylation [198,200,201]. Aging is associated with enhanced demethylation of DNA in various organs and tissues in several animals and humans [202,203,204]. However, increased methylation (hypermethylation) associated with age has also been reported in other genes [205,206]. The condition in which demethylation and hypermethylation are present in various parts of the entire gene is called the aberrant DNA methylation. The progression of aberrant DNA methylation changes are key regulators of the aging process and contributors to the development of aging-associated diseases [207,208,209,210,211,212,213], including neoplastic growth [214,215,216,217,218] and senescence [219,220,221,222].

DNA methylation is susceptible to various lifestyle and living environments, such as environmental air pollution [223,224,225,226,227], smoking [218,228,229,230,231,232], and excessive alcohol consumption [233,234,235,236]. It has been reported that the changes observed on DNA methylation induced by these environmental factors with negative health effects have similarities to those associated with aging-associated diseases, such as malignant transformation [218,232,237], CVDs [231,238], and the acceleration of senescence [229,230,239]. Contrarily, lifestyle habits considered having favorable consequences for health, such as exercise [240,241,242,243] and dietary restriction for obesity [244], also alter DNA methylation status, which is the opposite of the changes observed during aging.

8. Polyamine, DNA Methylation, and LFA-1

Age-related genome-wide aberrant DNA methylation status [222,245], enhanced demethylation of the LFA-1 promoter area [199], and increases in LFA-1 protein levels [49,56,185,198] are accompanied by decreases in ODC [70,246,247] and DNA methyltransferases (DNMTs) activities [248,249,250,251]. There is a close relationship between ODC, a rate-limiting enzyme for polyamine synthesis, and DNMTs involved in DNA methylation. Ornithine and SAM are two crucial substrates for polyamine synthesis. Ornithine is converted to putrescine by ODC, and SAM is converted to dcSAM by AdoMetDC. Putrescine receives the aminopropyl group from dcSAM and is sequentially synthesized into spermidine and spermine. DNA methylation is the conversion of cytosine residues to 5-methylcytosine by the addition of the methyl group to a cytosine residue at the C-5 position. DNMTs regulate methylation of DNA in the presence of SAM, while dcSAM is a strong inhibitor of DNMTs [252]. The activity of DNMT is closely associated with the concentration of SAM [253] and dcSAM [254,255], and with the dcSAM to SAM ratio [252,255] (Figure 3).

Figure 3.

Open in a new tab

Polyamine metabolism and gene methylation.

The relationship between polyamine metabolism (left side) and gene methylation (right side) is indicated. S-adenosylmethionine (SAM), an amino acid, is a substrate for polyamine synthesis and a donor of methyl groups. During polyamine synthesis, spermidine and spermine synthase require an aminopropyl group from decarboxylated s-adenosylmethionine (dcSAM), which is converted from SAM by the enzymatic action of adenosylmethionine decarboxylase (AdoMetDC). DNA methyltransferases (DNMTs) regulate gene methylation status by receiving a supply of the methyl group from SAM. SAM is essential as a source of methyl groups in gene methylation reactions, and dcSAM is a strong inhibitor of DNMTs.

Black text indicates the substance name, while spermidine and spermine are shown in green and blue, respectively. Red letters indicate enzyme names. The solid black arrows indicate the metabolic pathway, and the dashed black arrows indicate the transfer of some material from the upstream material. The thick gray arrow indicates activity on the target, and thick gray T-bar indicates the inhibitory activity on target.

ODC: Ornithine decarboxylase; SAM: S-adenosylmethionine; AdoMetDC: Adenosylmethionine decarboxylase; dcSAM: Decarboxylated S-adenosylmethionine; DNMT: DNA methyltransferase.

Intracellular concentrations of dcSAM rise in cells when the addition of aminopropyl groups for polyamine synthesis is no longer necessary. This condition is observed when ODC activity is decreased due to the overexpression‎ of antizyme that degrade ODC or treatment with α-D,L-difluoromethylornithine hydrochloride (DFMO), which inhibits ODC activity [252,255,256,257]. An increase in dcSAM induced by inhibition of ODC activity decreases DNMT activity [254,255,258]. We also showed that ODC inhibition by DFMO increased dcSAM concentrations and the dcSAM/SAM ratio and decreased activities of DNMT 1, 3a, and 3b in Jurkat cells [55]. We initially speculated that decreased DNMT activity and decreased donation of methyl groups to cytosine residues would lead to progressive demethylation of the entire genome, but in fact, aberrant methylation of the entire genome was promoted. The decline in DNMT activity induced by the inhibition of polyamine synthesis both increased demethylation in certain areas and increased hypermethylation in other areas, resulting in genome-wide aberrant methylation status [53,259,260,261,262,263]. Simultaneously, polyamine-deprivation enhanced demethylation of ITGAL region and increased LFA-1 protein levels [54]. The changes in methylation status in the ITGAL region were similar to those observed in the entire genome, i.e., aberrant methylation. In other words, some sites in ITGAL were demethylated, some were hypermethylated, and sites important for LFA-1 expression‎ in immune cells were demethylated upon polyamine deprivation, increasing LFA-1 protein levels. The increase in LFA-1 expression‎ associated with aging has been reported in animals and humans [53,182,183,184,185]. In addition, the age-dependent increase in the LFA-1 expression‎ is associated with the age-dependent methylation changes in ITGAL region [53,198,264].

As we have shown in our animal experiments and human intervention studies, increased polyamine intake (spermidine content is much higher than spermine content) elevates blood spermine levels [52,53,56,93]. Many reports have shown that the biological activities of spermine are much stronger than those of spermidine [49,87,98,123]. Therefore, spermine was employed to study its effects on enzyme activities and substance concentrations involved in polyamine synthesis and DNA methylation. In cells with or without suppressed ODC activity by DFMO, spermine supplementation inhibited AdoMetDC activity and decreased dcSAM concentrations with a decreased dcSAM/SAM ratio. Decreasing dcSAM concentration or decreasing dcSAM/SAM ratio by spermine supplementation weakened the inhibitory effect of dcSAM on DNMT3a and 3b and activated these two enzymes (Figure 4), but did not reactivate DNMT1, which was inhibited by polyamine deprivation by DFMO [55]. Similarly, it has been reported that the presence or absence of methyl donors affects the expression‎ of DNMT3a and 3b by other researchers [253]. DNMT3a and 3b are involved in de novo methylation and DNMT1 is involved in the maintenance of gene methylation status. Spermine supplementation reversed the changes in methylation status, i.e., a reversal of increased demethylation, in ITGAL induced by polyamine deprivation, resulting in decreased LFA-1 protein levels [54] (Figure 4).

Figure 4.

Open in a new tab

The effects of increased polyamine intake on enzyme activities and substance levels related to polyamine metabolism and gene methylation.

Increased polyamine intake elevates blood spermine levels and inhibits ODC activity. Increased spermine concentration strongly suppresses AdoMetDC activity, resulting in an increased amount of SAM and reduced amount of dcSAM. Since SAM is a methyl group donor for DNA methylation and dcSAM inhibits the activity of DNMTs, DNMTs are activated. As a result, enhanced aberrant methylation of entire genome and increased demethylation of ITGAL are reversed and regulated.

Black text indicates the substance name, while spermidine and spermine are shown in green and blue, respectively. Red letters indicate enzyme names. The solid black arrows indicate the metabolic pathway, and the dashed black arrows indicate the transfer of the methyl group from SAM. The brown arrows indicate the conditions of enzymatic activities (upward and downward arrows). Upward arrows indicate activation of the enzyme, and downward arrows indicate the inhibition of enzyme activity. Green arrows indicate the change in material quantity and enzymatic activity. The thick gray arrows indicate the stimulus given to the target by the upstream enzyme activity, and the thick gray T-bars indicate the inhibitory activities on the target.

The right figures show the condition and changes in DNA methylation status. The length of the line of black circles with bars indicates the progression of demethylation and hyper-methylation. The upward line indicates the progression of demethylation, and the downward lines indicate the progression of hyper-methylation.

ODC: ornithine decarboxylase; SSAT: Spermidine/spermine N1-acetyltransferase; APAO: N1-acetylpolyamine oxidase; SAM: S-adenosylmethionine; AdoMetDC: Adenosylmethionine decarboxylase; dcSAM: Decarboxylated S-adenosylmethionine; DNMT: DNA methyltransferase; ITGAL: gene promoter area that is responsible for the LFA-1 expression‎.

Spermine can reverse the methylation status of ITGAL in several cells. However, spermine seems not to be able to reverse all the methylation changes associated with aging. In our earlier report, we noticed that the effects of spermine on LFA-1 expression‎ are different from those of aging [49]. And, in our latest intervention study, we observed that the group of cells in which LFA-1 expression‎ increases with age is different from the group of cells in which LFA-1 expression‎ decreases by spermine supplementation, suggesting that the sites and cells in which spermine alters methylation status are different from those affected with aging [56]. Additionally, both abnormal genome-wide methylation and elevated LFA-1 protein levels observed in aged mice fed a normal chow were significantly suppressed, though not completely restored, in mice fed a high-polyamine diet [53]. Based on these results, spermine does not necessarily have effects on chronologically induced methylation changes. However, the regulation of DNA methylation by spermine may inhibit the onset and progression of various pathological changes and lifestyle-related diseases and consequently to slowing down the progression of senescence.

9. Possible Role of Polyamine in Cognitive Function

The role of polyamines in cancer progression is well known. Polyamine accelerates neoplastic growth and enhance metastatic spread [69]. However, it is controversial whether polyamines act as an initiator of carcinogenesis in normal cells that do not have existing carcinogenic elements (genetic abnormalities leading to carcinogenesis, exposure to preceding carcinogens and carcinogenic stimuli, etc.). There are several reports suggesting that increased polyamine intake does not increase carcinogenesis but has a suppressive effect on carcinogenesis in healthy individuals [53,265,266]. I have discussed the issues in my previous review [267].

In this section, I will discuss the possible role of polyamine in the inhibition of cognitive decline or the improvement of cognitive function. One of the major risk factors for poor health and shortened life expectancy among the elderly is the incidence and progression of diseases associated with cognitive decline and impaired cognitive function [268,269,270]. Individuals with cognitive impairment with or without definite neurodegenerative diseases have a higher mortality risk than healthy controls [270,271,272,273,274]. Therefore, it would make sense to investigate the possible role of increased polyamine intake, which extends the lifespan, in these aging-associated changes.

The possibility that spermidine is involved in memory function through a mechanism involving a novel memory-related molecule has been reported in insects such as Drosophila [275]. It cannot be completely ruled out the possibility of these mechanisms to function in the learning memory of higher animals such as mammals including humans. However, differences in basic biological background between insect memory and human memory are not known in detail, and the biological activities of spermidine in insects are not similar to its role in humans (described in Section 2. Polyamine). Additionally, because polyamines cannot cross the BBB under otherwise normal conditions, it is not expected that spermidine or spermine supplied from the intestinal lumen enters brain cells and exert their biological activities. Moreover, the role of autophagy activation in memory function and life span extension of mammals, especially humans, is not known (described in Section 6. Biological activities of polyamine). Therefore, I think it is difficult to believe that the effects on cognitive functions confirmed in some insects can be demonstrated in humans.

While polyamines cannot cross the BBB under normal conditions, reports have indicated that BBB dysfunction is associated with the pathogenesis of various neurodegenerative disorders such as Alzheimer’s disease [276,277], Parkinson’s disease [278,279], multiple sclerosis [280,281,282], and amyotrophic lateral sclerosis [283,284], in addition to typical cerebrovascular disorders such as stroke and vascular dementia [285,286]. However, it is incomprehensible how an increase in spermidine, which is so minuscule that it cannot elicit or enhance a physiological function, can exert any physiological activities. The effects of the stimulation of autophagy by the substances on cognitive function are also not clearly defined in humans. Moreover, even when the disruption of the BBB found in patients with cognitive impairment allows spermidine to enter brain tissue, patients with impaired cognitive function already have higher spermidine levels in the brain and blood than normal volunteers. Inoue et al. showed that patients with neurodegenerative diseases such as Alzheimer’s disease have increased spermidine levels in the frontal and parietal lobes of the brain [287]. Although polyamines cannot cross the BBB, their brain concentrations can be reflected in the blood via cerebrospinal fluid [288]. Sternberg et al. showed that serum levels of spermidine in patients with mild cognitive function are higher than those of healthy controls. Additionally, they reported that high spermidine level is associated with impaired cognitive function [89]. Similarly, the mean value of blood SPD levels in the Parkinson’s disease group was 134% higher than those of the controls [289]. Moreover, Graham et al. reported that spermidine plasma levels in patients with mild cognitive function who subsequently converted to Alzheimer’s disease were higher than those who did not [290]. Elevated spermidine levels in neurodegenerative diseases are consistent with reports of decreased spermine/spermidine ratios in patients with such diseases. Saiki et al. reported that spermine and the spermine/spermidine ratio is decreased in patients with Parkinson’s disease and Alzheimer’s disease [87].

There is evidence indicating a close relationship between chronic inflammation and neurodegenerative diseases [195,291,292,293]. Inflammation activates SSAT, an enzyme that breaks down spermine to spermidine and spermidine to putrescine, decreasing polyamine levels (Figure 1 and Figure 5). Increased polyamine degradation and decreased concentrations of spermine and spermidine activate polyamine recycling pathway, i.e., the activation of enzymes for polyamine synthesis. It is unclear how these metabolic changes affect polyamine concentrations, but it can be inferred by their effects on spermine and spermidine concentrations under different pathological conditions. In cancer tissues, inflammation and autonomous, but not stimulation-induced, increases in polyamine synthesis are observed. In cancer tissues, increases in spermidine concentrations are more prominent than spermine [65,67]. Similarly, in patients with neurodegenerative diseases, there are decreased spermine/spermidine ratios or increased spermidine concentrations [87,89,287,290]. These findings further support that inflammation-induced changes in polyamine metabolism are involved in the background of neurodegenerative diseases and cognitive decline. Our latest research also shows that the spermine/spermidine ratio in the blood of elderly people who can live independently is higher, i.e., increased spermidine concentrations relative to spermine, than that of older people who compelled to live in the elderly care facilities for assistance (manuscript is being prepared).

Figure 5.

Open in a new tab

The effects of chronic inflammation on enzyme activities and substance levels related to polyamine metabolism and gene methylation.

Due to the feedback mechanism, the activation of polyamine degradation by inflammation stimulates the enzymes of polyamine synthesis, and one of these enzymes, AdoMetDC, is also stimulated (Figure 5). Morrison LD et al. reported that autopsied brain of patients suffered Alzheimer’s disease showed an increase in the activity of AdoMetDC [294], also suggesting the involvement of chronic inflammation in the pathogenesis of the disease. AdoMetDC converts SAM to dSAM, and dSAM is used for polyamine synthesis. Thus, increased AdoMetDC activity decreases the SAM available for DNA methylation (Figure 5). Over the long term, this condition results in the progression of aberrant DNA methylation in the entire genome [295].

Age-associated chronic inflammation activates SSAT. SSAT activation enhances spermine degradation and results in decreased spermine concentration. Polyamine synthesis is activated as a compensation for polyamine degradation, resulting in an activation of AdoMetDC. AdoMetDC consumes SAM for polyamine synthesis and results in a decreased supply of methyl groups for DNA methylation. The lack of a methyl group supply results in aberrant methylation of the entire genome and increased demethylation of ITGAL.

Black text indicates the substance name, while spermidine and spermine are shown in green and blue, respectively. Red letters indicate enzyme names. The solid black arrows indicate the metabolic pathway, and the dashed black arrows indicate the transfer of the aminopropyl group from dcSAM. The brown arrows indicate the conditions of enzymatic activities (upward and downward arrows). Upward arrows indicate the activation of the enzyme, and downward arrows indicate the inhibition of enzyme activity. Green arrows indicate the change in enzymatic activity. The thick gray arrows indicate the stimulus given to the target by the upstream substance or enzyme activity, and the thick gray T-bars indicate the inhibitory activities on the target.

The right figures show the condition and changes in DNA methylation status. The length of the line of black circles with bars indicates the progression of demethylation and hyper-methylation. The upward line indicates the progression of demethylation and the downward lines indicate the progression of hyper-methylation.

ODC: ornithine decarboxylase; SSAT: Spermidine/spermine N1-acetyltransferase; APAO: N1-acetylpolyamine oxidase; SAM: S-adenosylmethionine; AdoMetDC: Adenosylmethionine decarboxylase; dcSAM: Decarboxylated S-adenosylmethionine; DNMT: DNA methyltransferase; ITGAL: gene promoter area that is responsible for the LFA-1 expression‎.

Continuously long-term increases in polyamine intake increased only spermine levels in the blood and suppressed aging-associated increases in proinflammatory conditions in humans and mice [53,56], i.e., suppression of LFA-1 protein levels on immune cells, and suppressed aging-associated enhancement of aberrant methylation of the entire genome and extended life span of mice [53]. These changes were associated with increases in blood spermine levels, and the degree of increase in the concentration of spermine was sufficient to make it biologically active in vivo. Increases in blood spermine levels are also sufficient to strongly suppress AdoMetDC activity, resulting in decreased dcSAM concentrations and increased SAM availability (Figure 4). The increase in SAM and the decrease in dcSAM that accompanies increases in spermine concentration activate DNA methyltransferase, which in turn regulates the DNA methylation status of the entire genome of brain tissue, tilting the LFA-1 promoter region toward hypermethylation and leading to a less pro-inflammatory state, i.e., reduced expression‎ of LFA-1.

In both humans and rodents, the global changes in DNA methylation with normal aging are found in various tissues, including the brain [296,297,298,299]. Gene-specific DNA methylation changes are essential for memory formation, neurogenesis, and neuronal plasticity [300,301]. Unlike polyamines, which are difficult to pass through the BBB, SAM and dcSAM can pass through the BBB. It is reasonable to assume that changes in the concentration of substances related to DNA methylation and changes in enzyme activity caused by increased polyamine intake can help improve cognitive dysfunction via the regulation of methylation status and the suppression of proinflammatory condition. Very interestingly, the possible role of SAM supplementation in cognitive function and neuropsychiatric disorders has been discussed [302,303,304]. Our in vitro experiments showed that SAM supplementation reversed polyamine-deficient induced increase in LFA-1 expression‎, indicating a reversal of aberrant methylation status of the entire genome induced by polyamine deficiency [54]. Spermine supplementation not only reversed polyamine-deficient induced increase in LFA-1 but also further decreased LFA-1 expression‎, suggesting its potent effect on the regulation of DNA methylation [54].

10. Conclusions

We started our experiments to investigate the role of polyamines in extending the lifespan and health of mice, when we first discovered that spermine selectively suppresses LFA-1 expression‎ in immune cells in 2005 [49]. After repeated experiments on mice, we confirmed the effect of increased polyamine intake on life span. After a long period of non-responsive and silent review of a submitted paper, we could publish for the first time the effect of increased polyamine intake on the lifespan of mice [52]. I hope this review will be helpful to scientists who are investigating the health and longevity of mammals, especially humans. I summarized the bioactivities and mechanisms of polyamines contributing to the extension of healthy life span (Figure 6).

Figure 6.

Open in a new tab

Bioactivities and mechanism of polyamines contributing to healthy long life.

The mechanism by which increased polyamine intake inhibits onset or progression of aging-associated diseases and senescence. Increased polyamine intake elevates blood spermine levels in humans, in spite the fact that many foods contain spermidine much more than spermine. Polyamine binds to the cell membrane, proteins, and genes by electric charge. Polyamine (spermine and spermidine) protects cells and genes from harmful stimuli indicated in red. Spermine inhibits aberrant DNA methylation and regulates DNA methylation status. These biological activities contribute to a healthy longevity.

폴리아민의 생물학적 활성과 건강한 장수에 기여하는 메커니즘.

폴리아민 섭취 증가가 

노화 관련 질환 및 노화 과정의 발병 또는 진행을 억제하는 메커니즘. 

폴리아민 섭취 증가로 인간 혈중 스퍼민 수치가 상승하며, 

이는 많은 식품에 스퍼민보다 스퍼미딘이 훨씬 더 많이 함유되어 있음에도 불구하고 발생합니다. 

폴리아민은 전기적 전하를 통해 

세포막, 단백질, 유전자에 결합합니다. 

폴리아민(스퍼민과 스퍼미딘)은 빨간색으로 표시된 유해 자극으로부터 세포와 유전자를 보호합니다. 

스퍼민은 비정상적인 DNA 메틸화를 억제하고 DNA 메틸화 상태를 조절합니다. 

이러한 생물학적 활성은 건강한 장수에 기여합니다.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The author declares no conflict of interest.

Footnotes

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

• 1.Nagata C., Wada K., Tamura T., Konishi K., Goto Y., Koda S., Kawachi T., Tsuji M., Nakamura K. Dietary soy and natto intake and cardiovascular disease mortality in Japanese adults: The Takayama study. Am. J. Clin. Nutr. 2017;105:426–431. doi: 10.3945/ajcn.116.137281. [DOI] [PubMed] [Google Scholar]
• 2.Erdman J.W., Jr. AHA Science Advisory: Soy protein and cardiovascular disease: A statement for healthcare professionals from the Nutrition Committee of the AHA. Circulation. 2000;102:2555–2559. doi: 10.1161/01.CIR.102.20.2555. [DOI] [PubMed] [Google Scholar]
• 3.Trock B.J., Hilakivi-Clarke L., Clarke R. Meta-analysis of soy intake and breast cancer risk. J. Natl. Cancer Inst. 2006;98:459–471. doi: 10.1093/jnci/djj102. [DOI] [PubMed] [Google Scholar]
• 4.Kim M.K., Kim J.H., Nam S.J., Ryu S., Kong G. Dietary intake of soy protein and tofu in association with breast cancer risk based on a case-control study. Nutr. Cancer. 2008;60:568–576. doi: 10.1080/01635580801966203. [DOI] [PubMed] [Google Scholar]
• 5.Wu A.H., Yu M.C., Tseng C.C., Pike M.C. Epidemiology of soy exposures and breast cancer risk. Br. J. Cancer. 2008;98:9–14. doi: 10.1038/sj.bjc.6604145. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 6.Yan L., Spitznagel E.L., Bosland M.C. Soy consumption and colorectal cancer risk in humans: A meta-analysis. Cancer Epidemiol. Biomark. Prev. 2010;19:148–158. doi: 10.1158/1055-9965.EPI-09-0856. [DOI] [PubMed] [Google Scholar]
• 7.Yang G., Shu X.O., Li H., Chow W.H., Cai H., Zhang X., Gao Y.T., Zheng W. Prospective cohort study of soy food intake and colorectal cancer risk in women. Am. J. Clin. Nutr. 2009;89:577–583. doi: 10.3945/ajcn.2008.26742. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 8.Oba S., Nagata C., Shimizu N., Shimizu H., Kametani M., Takeyama N., O