Asymmetric Dimethylarginine: A Never-Aging Story

TL;DR

This paper explores how asymmetric dimethylarginine (ADMA) may contribute to aging-related diseases and how removing it could promote healthier aging.

Contribution

The paper highlights ADMA as a novel therapeutic target for delaying aging and reducing age-related diseases.

Findings

ADMA is an independent risk factor for age-associated diseases.

Selective removal of ADMA is a promising strategy to reduce disease burden in aging.

ADMA inhibition of nitric oxide synthase is linked to aging and disease progression.

Abstract

Human aging is intrinsically associated with the onset and the progression of
several disease states causing significant disability and poor quality of life.
Although such association was traditionally considered immutable, recent
advances have led to a better understanding of several critical biochemical
pathways involved in the aging process. This, in turn, has stimulated a
significant body of research to investigate whether reprogramming these pathways
could delay the progression of human ageing and/or prevent relevant disease
states, ultimately favoring healthier aging process. Cellular senescence is
regarded as the principal causative factor implicated in biological and
pathophysiological processes involved in aging. Asymmetric dimethylarginine
(ADMA) is an endogenous inhibitor of nitric oxide synthase and an independent
risk factor for several age-associated diseases. The selective extracorporeal
removal of ADMA is emerging as a promising strategy to reduce the burden of
age-associated disease states. This article discusses the current knowledge
regarding the critical pathways involved in human aging and associated diseases
and the possible role of ADMA as a target for therapies leading to healthier
aging processes.

Figures

Hallmarks of aging. Ten common cellular and molecular traits generally considered to contribute to the process of aging and together determining the aging phenotype.

Selective removal of ADMA as a way to healthy aging. ADMA causes both inhibition and uncoupling of NOS, which lead to decreased production of NO and increased release of superoxide radicals. Selective removal of ADMA by its catabolism to citrulline by DDAH1 immobilized on an apheresis column leads to restoration of NO production and redox balance. These ameliorate diseases that are associated with advanced age and promote healthy aging. ADMA: Asymmetric dimethylarginine; DDAH1: Dimethylarginine dimethylaminohydrolase 1; NOS: Nitric oxide synthase; NO: Nitric oxide.

Full text

Introduction

The rapid change in age distribution represents the most important phenomenon in our society globally. In 2019, about 9% of people worldwide were 65 years and older, and it is estimated that in 2050 one in every six people will be over the age of 65 1 . This demographic transition requires changes in resource allocation and delivery of health care as increased longevity is not necessarily associated with an extended time in good health 2 . Therefore, disease prevention and maintenance of an acceptable level of quality of life and independence in advanced age has become a major public health issue and research focus of gerontology 3 . The process of aging is generally characterized by a gradual functional decline and reduced homeostatic capacity. In mammals, this process is highly heterogeneous, which further adds to the challenges of managing this complex patient group, typically characterized by the coexistence of several disease states.

Multiple epidemiological studies identified the endogenous analogue of L -arginine asymmetric dimethylarginine (ADMA) as an independent predictor of morbidity and mortality in the elderly 4 . Furthermore, elevated levels of ADMA were shown to be associated with adverse outcomes in patients with age-related diseases, such as cardiovascular disease 5 , chronic kidney disease 6 , and peripheral artery disease 7 . What is more, experiments in animal models have convincingly shown the protective effects of ADMA lowering strategies in multiple models of acute and chronic cardiovascular and metabolic injury. The goal of our manuscript is to summarize the role of ADMA as a critical marker and mediator of age-associated pathologies and to discuss promising ADMA lowering strategies favoring healthier aging and increased life expectancy.

Age-related diseases

For several decades it has been suggested that there may be an undervalued, but nevertheless very important link between human aging and many chronic disorders and that aging increases the risk of many common diseases, including cardiovascular disease 8 , dementia 9 , osteoporosis 10 , osteoarthritis 11 , type 2 diabetes 12 , idiopathic pulmonary fibrosis 13 , glaucoma 14 , Alzheimer’s disease 15 , and metabolic-associated fatty liver disease (MAFLD) 16 . Moreover, older patients often suffer from multiple comorbidities requiring combinations of different treatments. However, this increases the risk of drug-drug and drug-disease interactions with consequent reduced treatment efficacy and increased toxicity 17 . In recent years, inflammaging has emerged as a key concept in the field of gerontology. It is now widely recognized that aging is associated with a state of increased pro-inflammatory markers and dysregulated immune responses, which contribute to the development and progression of age-related diseases 18 .

Since human aging is closely interconnected with the pathophysiology of several chronic diseases, understanding the molecular mechanisms underpinning the aging process is likely to facilitate the identification of novel druggable targets for diseases associated with advanced age.

Cellular senescence and other mechanisms of aging

Our understanding of aging remains limited, and its biological causes are largely unknown. However, recent studies have led to the identification of common molecular traits associated with aging, collectively called aging hallmarks, including telomere shortening, mitochondrial dysfunction, cellular senescence, deregulated nutrient sensing, loss of proteostasis, epigenetic alterations and genomic instability, stem cell exhaustion, and alterations in intracellular communication 19 . Over the years, autophagy was also added as the 10th hallmark ( Fig. 1 ) 20 21 . Their recognition has stimulated a considerable body of research to prevent or delay the onset of age-related diseases by reprogramming the aging process itself. The rapidly increasing knowledge regarding the molecular mechanisms of aging has also changed people’s attitudes towards this process. Traditionally, aging was seen as an unavoidable and unchangeable process determined by genetic programs or accidental events ultimately leading to death. However, it was later discovered that the speed of aging can be to some extent modified, for example, by light intensity in Drosophila 22 , or by caloric restriction in mice and rats 23 24 . The results of these studies led to a reconsideration of aging as a modifiable process that can possibly be influenced even at the molecular level 25 . The current state of knowledge on the mechanisms of aging is elegantly described in a review by Guo and colleagues 26 . Here, we focus mainly on cellular senescence, a principal causative factor facilitating aging and aging-associated diseases 26 27 .

Hallmarks of aging. Ten common cellular and molecular traits generally considered to contribute to the process of aging and together determining the aging phenotype.

Cellular senescence, first described by Hayflick and Moorhead in 1961 in cultured human fibroblasts 28 , is defined as a terminal and permanent state of growth arrest, in which cells are unable to proliferate in spite of mitogenic stimuli and optimal growth conditions. Therefore, cellular senescence represents the critical mechanism underpinning tissue ageing, a condition where cells progressively lose their ability to proliferate, consequently replacing damaged cells that otherwise accumulate 29 . Although the contribution of cellular senescence to aging has been long suspected, it was confirmed only recently. Studies investigating the rapidly aging BubR1 (a protein that ensures proper segregation of chromosomes during mitosis) hypomorphic mouse model showed that decreased levels of this protein led to a variety of early aging characteristics, including reduced lifespan, cataracts, lipodystrophy and infertility very early in life 30 and p16 (cyclin-dependent kinase inhibitor) tissue accumulation 31 . In the absence of p16, the age-related phenotype was attenuated, clearly demonstrating the direct relation of cellular senescence and aging. It has later been shown also in other mice models that removing cells expressing p16 is beneficial in age-related diseases, including Parkinson’s disease 32 , Alzheimer’s disease 33 , atherosclerosis 34 , and osteoarthritis 35 . Senescent cells are resistant to apoptosis owing to upregulation of molecular pathways involved in cell survival, including the BCL-2 (regulator of apoptosis) family of proteins 36 . The precise mechanisms determining whether a cell undergoes senescence or apoptosis are not fully understood, but possibly depend on the nature, duration and intensity of the stimulus, as well the cell type 37 . A number of stimuli inducing senescence are discussed in the following sections.

DNA damage response

Damage to nuclear DNA, mainly in the form of DNA double-strand breaks (DSBs) 38 is considered one of the most important factors facilitating cellular senescence. DSBs activate the DNA damage response (DDR) pathway, which is supposed to block the cell cycle to prevent the propagation of damaged genetic information. If the damage cannot be ameliorated by repair mechanisms prolonged DDR signaling results in senescence 39 . This concept is supported by the fact that inhibition of DDR signaling kinases (ATM – Ataxia-telangiectasia mutated, ATR – ataxia telangiectasia and Rad3-related, CHK1 – checkpoint kinase 1 and CHK2 – checkpoint kinase 2) restores the capacity of previously senescent cells to enter the cell cycle 40 41 . The tumor suppressor p53 is at the bottom of the DDR signaling cascade and its activation stimulates the expression of cyclin-dependent kinase inhibitor p21, an important mediator of cell cycle arrest associated with senescence 42 . Another inhibitor, p16 is activated later in the process, presumably to sustain the senescence phenotype 43 .

Telomere shortening

One of the first recognized and best characterized mechanisms leading to cellular senescence is telomere shortening. When the standard DNA duplication machinery is unable to fully duplicate the ends of the chromosomes and the telomere maintenance mechanisms are absent, telomeres are shortened during each round of DNA replication. Below a certain length, the loss of telomere-capping factors, other protective structures, or even one or a few telomeres leads to the activation of DDR through a pathway involving ATM, p53, and p21, which in turn triggers replicative cellular senescence 44 .

Dysregulated autophagy

Autophagy, along with apoptosis and necrosis, is a common type of cell death. It is a process that involves the degradation of organelles and proteins to remove cellular debris and sustain physiological cell functions 45 . Autophagy is tightly regulated and the proteins that need to be degraded through this pathway are ubiquitinated and engulfed by the phagophore, which later forms an autophagosome 46 . Several studies in animal models have demonstrated that the maintenance of proper autophagic activity is associated with extended longevity 47 48 49 . By contrast, disabled autophagy is considered as one of the primary hallmarks of aging 19 and it has been shown to decrease life and health span in lower organisms 50 51 . Recently, similar data were reported in mice models, providing evidence that autophagy modulates longevity also in mammals 52 53 54 . Both a reduction and an increased autophagy are strongly associated with aging and age-related diseases. Previous investigations have shown that autophagy decreases with age, potentially contributing to the accumulation of damaged organelles, metabolic alterations in the cells, and decreased lysosomal proteolytic activity 47 55 . On the other hand, uncontrolled or dysregulated autophagy might also accelerate aging by increasing the number of senescent cells, causing fast muscle fibers atrophy, cardiac hypertrophy, sarcopenia, neurodegeneration, and molecular and metabolic dysregulation 55 56 .

Mitochondrial dysfunction and reactive oxygen species

Dysfunctional mitochondria may play an important role in senescence as this process is induced by the chemical inhibition of mitochondrial function 57 . Alterations of mitochondrial homeostasis have also been shown to drive age-dependent modifications 58 59 60 . Ineffective control of reactive oxygen species (ROS) on mitochondrial supercomplexes causes changes in ROS signaling, leading to cellular stress and age-dependent damage. High levels of mitochondrial ROS significantly contribute to aging, as shown in superoxide dismutase-deficient mice (SOD1-KO and SOD3-KO) 61 62 .

In summary, human lifespan is closely related to the reduction of the regenerative potential of tissues and organs. The aging process is driven by a number of complex molecular pathways, which taken together prevent cell proliferation, alter metabolism and gene expression patterns and induce high levels of reactive oxygen species, ultimately maintaining the cellular senescent phenotype. Even though the amount of early senescent cells is low, they can effectively limit the regenerative potential of tissue stem cells and induce the accumulation of cellular damage, leading to age-related diseases 63 .

Healthy aging

Healthy aging is defined as “the process of developing and maintaining the functional ability that enables well-being in older age” 64 . Maintenance of good health in advanced age has become a major public health challenge. The impact of lifestyle on health status is well established. Dietary habits are one of the key modifiable lifestyle factors for the prevention and/or amelioration of age-associated diseases and the maintenance of healthy aging 65 . Even though the evidence on healthy aging differs by various dietary patterns, it seems that dietary habits focused on plant-based foods promote healthy aging by positively influencing cognition, psychological function, sensory function, and motility. Current recommendations based on a high consumption of fruits, vegetables, whole grains, moderate consumption of dairy, fish and poultry, and low consumption of red meat, saturated fat and sugars are in line with these observations 64 . Although caloric restriction (CR) is not a dietary pattern itself, avoiding excess intake of calories can be applied to any diet and is common in eating habits that are associated with reduced risk of age-linked diseases and improved longevity. In particular, CR refers to the reduction in the total energy intake by 20 to 40%, but without leading to malnutrition or deficiency in essential nutrients. In experimental studies, CR has been shown to increase life expectancy and delay the onset and progression of multiple age-associated diseases in diverse species. In humans, however, long-term CR has been associated with both beneficial and detrimental effects 66 67 68 . Caloric restriction has demonstrated beneficial effects on atherosclerosis, improvement in cardiac function and an obvious reduction in the burden of obesity 66 , but on the other hand, it can be associated with bone loss and fragility fractures 68 . Furthermore, obesity intervention trials have demonstrated that the majority of patients are unable to maintain daily caloric restriction over a long period of time 69 . Intermittent fasting, including alternate-day fasting, full-day fasting patterns and time-restricted eating have been shown to represent viable alternatives to decrease in body weight, also improving lipid and blood pressure control 70 , and reducing markers of oxidative stress and inflammation 71 . Regular physical exercise is the most effective intervention for sarcopenia 72 , defined as the age-related decline in skeletal muscle mass, strength and function, affecting over 50% of individuals at the age of 80 and more. As such, it is a vital component of lifestyle habits associated with healthy aging 73 . Good sleep, regular health monitoring, stress reduction, intellectual and cognitive challenges and non-smoking are other elements necessary to fulfil the goals of healthy aging 74 .

Asymmetric dimethylarginine

Asymmetric dimethylarginine (ADMA) is an endogenous homologue of L -arginine that inhibits nitric oxide (NO) production by all three known isoforms of NO synthases 75 76 . ADMA is a well-established, independent risk factor for cardiovascular and overall mortality in the general population and in patients with diseases of the cardiovascular, pulmonary, renal, endocrine, and gastrointestinal systems 77 78 79 . Lowering ADMA concentrations in animal models resulted in protection against conditions associated with advanced age, including atherosclerosis, adverse myocardial and vascular remodeling, myocardial and renal ischemia/reperfusion damage, and insulin resistance 80 81 82 83 84 . Observational studies have demonstrated that plasma ADMA concentrations increase with age 85 86 , whereas the nitric oxide:superoxide ratio decreases leading to oxidative stress, inflammation, degenerative changes, insulin resistance, and endothelial dysfunction 87 88 . Animal experiments and pre-clinical studies strongly suggest that ADMA is implicated in biological processes relevant to aging, such as telomerase activity, endothelial senescence, and mitochondrial dysfunction 89 90 91 92 93 94 95 .

In addition to inhibition of NO production, ADMA also “uncouples” NO synthases, which results in the production of superoxide radicals (O 2 ^−^ ) instead of NO 96 . The presence of both functional and uncoupled NOS in the cell results in the concomitant production of NO and O 2 ^−^ in close vicinity. O 2 ^−^ reacts with NO, thus scavenging it and forming the harmful peroxynitrite radical (ONOO ^−^ ). This leads to a vicious cycle that potentiates oxidative stress and drives pathological changes 97 . NO is an endogenous metabolic mitochondrial master modulator that mediates antioxidant protection and regeneration 98 . NO has also been shown to determine mitochondrial biogenesis and bioactivity 99 , as well as maintain neurovascular-neuro energetic coupling and synaptic plasticity and, thus, brain development and cognition. The superoxide anion radicals produced during aging are antagonistic mediators that can induce neurodegeneration and cell death by increasing oxidative stress and damage directly and through NO depletion 100 . Many age-associated pathophysiological processes are modulated by NO, especially arterial stiffness, vascular tone, platelet function, myocardial hypertrophy, and contractility 87 101 .

Independently of the NO/NOS pathway, ADMA was recently reported to promote degeneration and senescence of chondrocytes and cartilage, accelerating progression of osteoarthritis 102 . Furthermore, increased ADMA concentrations have been shown to be associated with disuse-related osteoporosis 103 and with frailty in patients without cardiovascular diseases 104 .

Targeting aging: place for ADMA and therapeutic apheresis?

The direct involvement of ADMA at the intersection of molecular pathways involved in the aging process and the association of elevated ADMA concentrations with advanced age-related diseases, together with the strong animal data on beneficial effects of ADMA lowering raise the intriguing possibility of targeting ADMA as an anti-aging therapy. Currently there are no approved clinical approaches to specifically lower ADMA in humans. Driven by this unmet clinical need, we propose the use of an apheresis column with immobilized ADMA-metabolizing enzyme, dimethylarginine dimethylaminohydrolase 1 (DDAH1), to selectively remove ADMA from plasma during apheresis sessions. This strategy should lead to increased production of NO and decreased levels of superoxide radicals, leading to promoting healthy aging through beneficial effects in diseases associated with old age ( Fig. 2 ).

Selective removal of ADMA as a way to healthy aging. ADMA causes both inhibition and uncoupling of NOS, which lead to decreased production of NO and increased release of superoxide radicals. Selective removal of ADMA by its catabolism to citrulline by DDAH1 immobilized on an apheresis column leads to restoration of NO production and redox balance. These ameliorate diseases that are associated with advanced age and promote healthy aging. ADMA: Asymmetric dimethylarginine; DDAH1: Dimethylarginine dimethylaminohydrolase 1; NOS: Nitric oxide synthase; NO: Nitric oxide.

Conclusions

Selective extracorporeal removal of ADMA during apheresis in the elderly population could be a potential strategy to prevent or delay age-associated disease states, consequently favoring healthy aging. Such approach, using an enzyme immobilized on a column, would be the first example of a novel apheresis principle – enzymatic apheresis – and could pave the way for similar strategies to remove other circulating detrimental substances that cannot be therapeutically targeted otherwise.

Notice

This article was changed according to the following Erratum on June 5th 2025.

Erratum

In the above-mentioned article the name of the last author was incomplete. The correct name is Roman N. Rodionov. This was corrected in the online version on 06.06.2025.