Metformin improves healthspan and lifespan in mice

Quantification of healthspan in aging mice: introducing FAMY and GRAIL

The population around the world is graying, and as many of these individuals will spend years suffering from the burdens of age associated diseases, understanding how to increase healthspan, defined as the period of life free from disease and disability, is an urgent priority of geroscience research. The lack of agreed-upon quantitative metrics for measuring healthspan in aging mice has slowed progress in identifying interventions that do not simply increase lifespan, but also healthspan. Here, we define FAMY (Frailty-Adjusted Mouse Years) and GRAIL (Gauging Robust Aging when Increasing Lifespan) as new summary statistics for quantifying healthspan in mice. FAMY integrates lifespan data with longitudinal measurements of a widely utilized clinical frailty index, while GRAIL incorporates these measures and also adds information from widely utilized healthspan assays and the hallmarks of aging. Both metrics are conceptually similar to quality-adjusted life years (QALY), a widely utilized measure of disease burden in humans, and can be readily calculated from data acquired during longitudinal and cross-sectional studies of mouse aging. We find that interventions generally thought to promote health, including calorie restriction, robustly improve healthspan as measured by FAMY and GRAIL. Finally, we show that the use of GRAIL provides new insights, and identify dietary restriction of protein or isoleucine as interventions that robustly promote healthspan but not longevity in female HET3 mice. We suggest that the routine integration of these measures into studies of aging in mice will allow the identification and development of interventions that promote healthy aging even in the absence of increased lifespan.

The Gehan test identifies life-extending compounds overlooked by the log-rank test in the NIA Interventions Testing Program: Metformin, Enalapril, caffeic acid phenethyl ester, green tea extract, and 17-dimethylaminoethylamino-17-demethoxygeldanamycin hydrochloride

The National Institute on Aging Interventions Testing Program (ITP) has so far identified 12 compounds that extend the lifespan of genetically heterogeneous mice using the log-rank test. However, the log-rank test is relatively insensitive to any compound that does not uniformly reduce mortality across the lifespan. This test may thus miss compounds that only reduce mortality before midlife, for example, a plausible outcome if a compound only mitigates risk factors before midlife or if its efficacy is reduced at later ages. We therefore reanalyzed all data collected by the ITP from 2004-2022 using the Gehan test, which is more sensitive to mortality differences earlier in the life course and does not assume a uniformly reduced mortality hazard across the lifespan. The Gehan test identified 5 additional compounds, metformin, enalapril, 17-dimethylaminoethylamino-17-demethoxygeldanamycin hydrochloride (17-DMAG), caffeic acid phenethyl ester (CAPE), and green tea extract (GTE), which significantly increased survival but were previously missed by the log-rank test. Three (metformin, enalapril, and 17-DMAG) were only effective in males and two (CAPE and GTE) were only effective in females. In addition, 1,3-butanediol, which by log-rank analysis increased survival in females but not males, increased survival in males by the Gehan test. These results suggest that statistical tests sensitive to non-uniformity of drug efficacy across the lifespan should be included in the standard statistical testing protocol to minimize overlooking geroprotective interventions.

Hypothalamic circuits and aging: keeping the circadian clock updated

Over the past century, age-related diseases, such as cancer, type-2 diabetes, obesity, and mental illness, have shown a significant increase, negatively impacting overall quality of life. Studies on aged animal models have unveiled a progressive discoordination at multiple regulatory levels, including transcriptional, translational, and post-translational processes, resulting from cellular stress and circadian derangements. The circadian clock emerges as a key regulator, sustaining physiological homeostasis and promoting healthy aging through timely molecular coordination of pivotal cellular processes, such as stem-cell function, cellular stress responses, and inter-tissue communication, which become disrupted during aging. Given the crucial role of hypothalamic circuits in regulating organismal physiology, metabolic control, sleep homeostasis, and circadian rhythms, and their dependence on these processes, strategies aimed at enhancing hypothalamic and circadian function, including pharmacological and non-pharmacological approaches, offer systemic benefits for healthy aging. Intranasal brain-directed drug administration represents a promising avenue for effectively targeting specific brain regions, like the hypothalamus, while reducing side effects associated with systemic drug delivery, thereby presenting new therapeutic possibilities for diverse age-related conditions.

Targeting multiple hallmarks of mammalian aging with combinations of interventions

Aging is currently viewed as a result of multiple biological processes that manifest themselves independently, reinforce each other and in their totality lead to the aged phenotype. Genetic and pharmaceutical approaches targeting specific underlying causes of aging have been used to extend the lifespan and healthspan of model organisms ranging from yeast to mammals. However, most interventions display only a modest benefit. This outcome is to be expected if we consider that even if one aging process is successfully treated, other aging pathways may remain intact. Hence solving the problem of aging may require targeting not one but many of its underlying causes at once. Here we review the challenges and successes of combination therapies aimed at increasing the lifespan of mammals and propose novel directions for their development. We conclude that both additive and synergistic effects on mammalian lifespan can be achieved by combining interventions that target the same or different hallmarks of aging. However, the number of studies in which multiple hallmarks were targeted simultaneously is surprisingly limited. We argue that this approach is as promising as it is understudied.

A comprehensive model for the biochemistry of ageing, senescence and longevity

Various models for ageing, each focussing on different biochemical and/or cellular pathways have been proposed. This has resulted in a complex and non-coherent portrayal of ageing. Here, we describe a concise and comprehensive model for the biochemistry of ageing consisting of three interacting signalling hubs. These are the nuclear factor kappa B complex (NFκB), controlling the innate immune system, the mammalian target for rapamycin complex, controlling cell growth, and the integrated stress responses, controlling homeostasis. This model provides a framework for most other, more detailed, biochemical pathways involved in ageing, and explains why ageing involves chronic inflammation, cellular senescence, and vulnerability to environmental stress, while starting with the spontaneous formation of advanced glycation end products. The totality of data underlying this model suggest that the gradual inhibition of the AMPK-ISR probably determines the maximal lifespan. Based on this model, anti-ageing drugs in general, are expected to show hormetic dose response curves. This complicates the process of dose-optimization. Due to its specific mechanism of action, the anti-aging drug alkaline phosphatase is an exception to this rule, because it probably exhibits saturation kinetics.

Long COVID as a disease of accelerated biological aging: An opportunity to translate geroscience interventions

It has been four years since long COVID-the protracted consequences that survivors of COVID-19 face-was first described. Yet, this entity continues to devastate the quality of life of an increasing number of COVID-19 survivors without any approved therapy and a paucity of clinical trials addressing its biological root causes. Notably, many of the symptoms of long COVID are typically seen with advancing age. Leveraging this similarity, we posit that Geroscience-which aims to target the biological drivers of aging to prevent age-associated conditions as a group-could offer promising therapeutic avenues for long COVID. Bearing this in mind, this review presents a translational framework for studying long COVID as a state of effectively accelerated biological aging, identifying research gaps and offering recommendations for future preclinical and clinical studies.

Preclinical Studies on the Effects of Frailty in the Aging Heart

Age is a major risk factor for the development of cardiovascular diseases in men and in women. However, not all people age at the same rate and those who are aging rapidly are considered frail, compared with their fit counterparts. Frailty is an important clinical challenge because those who are frail are more likely to develop and die from illnesses, including cardiovascular diseases, than fit people of the same age. This increase in susceptibility to cardiovascular diseases in older individuals might occur as the cellular and molecular mechanisms involved in the aging process facilitate structural and functional damage in the heart. Consistent with this, recent studies in murine frailty models have provided strong evidence that maladaptive cardiac remodelling in older mice is the most pronounced in mice with a high level of frailty. For example, there is evidence that ventricular hypertrophy and contractile dysfunction increase as frailty increases in aging mice. Additionally, fibrosis and slowing of conduction in the sinoatrial node and atria are proportional to the level of frailty. These modifications could predispose frail older adults to diseases like heart failure and atrial fibrillation. This preclinical work also raises the possibility that emerging interventions designed to "treat frailty" might also treat or prevent cardiovascular diseases. These findings might help to explain why frail older people are most likely to develop these disorders as they age.

Metformin beyond type 2 diabetes: Emerging and potential new indications

Metformin is best known as a foundational therapy for type 2 diabetes but is also used in other contexts in clinical medicine with a number of emerging and potential indications. Many of its beneficial effects may be mediated by modest effects on weight loss and insulin sensitivity, but it has multiple other known mechanisms of action. Current clinical uses beyond type 2 diabetes include: polycystic ovarian syndrome; diabetes in pregnancy/gestational diabetes; prevention of type 2 diabetes in prediabetes; and adjunct therapy in type 1 diabetes. As metformin has been in clinical use for almost 70 years, much of the underpinning evidence for its use in these conditions is, by definition, based on trials conducted before the advent of contemporary evidence-based medicine. As a result, some of the above-established uses are 'off-label' in many regulatory territories and their use varies accordingly in different countries. Going forward, several current 'repurposing' investigational uses of metformin are also being investigated: prevention of cancer (including in Li Fraumeni syndrome), renal protection, Alzheimer's disease, metabolic dysfunction-associated steatotic liver disease and promotion of healthy ageing. Despite the longevity of metformin and its important current roles beyond type 2 diabetes in clinical medicine, it has further potential and much research is ongoing.

Rejuvenation of the Aging Heart: Molecular Determinants and Applications

In Canada and worldwide, the elderly population (ie, individuals > 65 years of age) is increasing disproportionately relative to the total population. This is expected to have a substantial impact on the health care system, as increased aged is associated with a greater incidence of chronic noncommunicable diseases. Within the elderly population, cardiovascular disease is a leading cause of death, therefore developing therapies that can prevent or slow disease progression in this group is highly desirable. Historically, aging research has focused on the development of anti-aging therapies that are implemented early in life and slow the age-dependent decline in cell and organ function. However, accumulating evidence supports that late-in-life therapies can also benefit the aged cardiovascular system by limiting age-dependent functional decline. Moreover, recent studies have demonstrated that rejuvenation (ie, reverting cellular function to that of a younger phenotype) of the already aged cardiovascular system is possible, opening new avenues to develop therapies for older individuals. In this review, we first provide an overview of the functional changes that occur in the cardiomyocyte with aging and how this contributes to the age-dependent decline in heart function. We then discuss the various anti-aging and rejuvenation strategies that have been pursued to improve the function of the aged cardiomyocyte, with a focus on therapies implemented late in life. These strategies include 1) established systemic approaches (caloric restriction, exercise), 2) pharmacologic approaches (mTOR, AMPK, SIRT1, and autophagy-targeting molecules), and 3) emerging rejuvenation approaches (partial reprogramming, parabiosis/modulation of circulating factors, targeting endogenous stem cell populations, and senotherapeutics). Collectively, these studies demonstrate the exciting potential and limitations of current rejuvenation strategies and highlight future areas of investigation that will contribute to the development of rejuvenation therapies for the aged heart.

Revealing the role of metformin in gastric intestinal metaplasia treatment

Objective

Gastric intestinal metaplasia (IM) is a precancerous stage associated with gastric cancer. Despite the observed beneficial effects of metformin on IM, its molecular mechanism remains not fully elucidated. This study aims to reveal the effects and potential mechanisms of metformin in treating IM based on both bioinformatics and in vivo investigations.

Methods

The seven public databases (GeneCards, DisGeNET, OMIM, SuperPred, Pharm Mapper, Swiss Target Prediction, TargetNet) were used in this work to identify targeted genes related to intestinal metaplasia (IM) and metformin. The shared targeted genes between metformin and IM were further analyzed by network pharmacology, while the interactions in-between were investigated by molecular docking. In parallel, the therapeutic effect of metformin was evaluated in IM mice model, while the core targets and pathways effected by metformin were verified in vivo.

Results

We screened out 1,751 IM-related genes and 318 metformin-targeted genes, 99 common genes identified in between were visualized by constructing the protein-protein interaction (PPI) network. The top ten core targeted genes were EGFR, MMP9, HIF1A, HSP90AA1, SIRT1, IL2, MAPK8, STAT1, PIK3CA, and ICAM1. The functional enrichment analysis confirmed that carcinogenesis and HIF-1 signaling pathways were primarily involved in the metformin treatment of IM. Based on molecular docking and dynamics, we found metformin affected the function of its targets by inhibiting receptor binding. Furthermore, metformin administration reduced the progression of IM lesions in Atp4a-/- mice model significantly. Notably, metformin enhanced the expression level of MUC5AC, while inhibited the expression level of CDX2. Our results also showed that metformin modulated the expression of core targets in vivo by reducing the activity of NF-κB and the PI3K/AKT/mTOR/HIF-1α signaling pathway.

Conclusion

This study confirms that metformin improves the efficacy of IM treatment by regulating a complex molecular network. Metformin plays a functional role in inhibiting inflammation/apoptosis-related pathways of further IM progression. Our work provides a molecular foundation for understanding metformin and other guanidine medicines in IM treatment.

Skeletal muscle dysfunction with advancing age

As a result of advances in medical treatments and associated policy over the last century, life expectancy has risen substantially and continues to increase globally. However, the disconnect between lifespan and 'health span' (the length of time spent in a healthy, disease-free state) has also increased, with skeletal muscle being a substantial contributor to this. Biological ageing is accompanied by declines in both skeletal muscle mass and function, termed sarcopenia. The mechanisms underpinning sarcopenia are multifactorial and are known to include marked alterations in muscle protein turnover and adaptations to the neural input to muscle. However, to date, the relative contribution of each factor remains largely unexplored. Specifically, muscle protein synthetic responses to key anabolic stimuli are blunted with advancing age, whilst alterations to neural components, spanning from the motor cortex and motoneuron excitability to the neuromuscular junction, may explain the greater magnitude of function losses when compared with mass. The consequences of these losses can be devastating for individuals, their support networks, and healthcare services; with clear detrimental impacts on both clinical (e.g., mortality, frailty, and post-treatment complications) and societal (e.g., independence maintenance) outcomes. Whether declines in muscle quantity and quality are an inevitable component of ageing remains to be completely understood. Nevertheless, strategies to mitigate these declines are of vital importance to improve the health span of older adults. This review aims to provide an overview of the declines in skeletal muscle mass and function with advancing age, describes the wide-ranging implications of these declines, and finally suggests strategies to mitigate them, including the merits of emerging pharmaceutical agents.

Metformin augments major cytoplasmic organization except for spindle organization in oocytes cultured under hyperglycemic and hyperlipidemic conditions: An in vitro study

The present study aimed to investigate the role of antidiabetic drug metformin on the cytoplasmic organization of oocytes. Germinal vesicle (GV) stage oocytes were collected from adult female Swiss albino mice and subjected to in vitro maturation (IVM) in various experimental groups- control, vehicle control (0.3% ethanol), metformin (50 μg/mL), high glucose and high lipid (HGHL, 10 mM glucose; 150 μM palmitic acid; 75 μM stearic acid and 200 μM oleic acid in ethanol), and HGHL supplemented with metformin. The metaphase II (MII) oocytes were analyzed for lipid accumulation, mitochondrial and endoplasmic reticulum (ER) distribution pattern, oxidative and ER stress, actin filament organization, cortical granule distribution pattern, spindle organization and chromosome alignment. An early polar body extrusion was observed in the HGHL group. However, the maturation rate at 24 h did not differ significantly among the experimental groups compared to the control. The HGHL conditions exhibited significantly higher levels of oxidative stress, ER stress, poor actin filament organization, increased lipid accumulation, altered mitochondrial distribution, spindle abnormalities, and chromosome misalignment compared to the control. Except for spindle organization, supplementation of metformin to the HGHL conditions improved all the parameters (non-significant for ER and actin distribution pattern). These results show that metformin exposure in the culture media helped to improve the hyperglycemia and hyperlipidemia-induced cytoplasmic anomalies except for spindle organization. Given the crucial role of spindle organization in proper chromosome segregation during oocyte maturation and meiotic resumption, the implications of metformin's limitations in this aspect warrant careful evaluation and further investigation.

Metformin ameliorates neuroinflammatory environment for neurons and astrocytes during in vitro and in vivo stroke and tobacco smoke chemical exposure: Role of Nrf2 activation

Despite the protective nature of the blood-brain barrier (BBB) and brain-protecting tissues, some types of CNS injury or stress can cause cerebral cytokine production and profound alterations in brain function. Neuroinflammation, which can also be accompanied by increased cerebral cytokine production, has a remarkable impact on the pathogenesis of many neurological illnesses, including loss of BBB integrity and ischemic stroke, yet effective treatment choices for these diseases are currently lacking. Although little is known about the brain effects of Metformin (MF), a commonly prescribed first-line antidiabetic drug, prior research suggested that it may be useful in preventing BBB deterioration and the increased risk of stroke caused by tobacco smoking (TS). Therefore, reducing neuroinflammation by escalating anti-inflammatory cytokine production and declining pro-inflammatory cytokine production could prove an effective therapeutic strategy for ischemic stroke. Hence, the current investigation was planned to explore the potential role of MF against stroke and TS-induced neuroinflammation and reactive oxygen species (ROS) production. Our studies revealed that MF suppressed releasing pro-inflammatory mediators like tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) by aiming at the nuclear factor kappa B (NF-κB) signaling pathway in primary neurons and astrocytes. MF also upregulated anti-inflammatory mediators, like interleukin-10 (IL-10), and interleukin-4 (IL-4), by upregulating the Nrf2-ARE signaling pathway. Adolescent mice receiving MF along with TS exposure also showed a notable decrease in NF-κB expression compared to the mice not treated with MF and significantly decreased the level of TNF-α, IL-1β, MCP-1, and MIP-2 and increased the levels of IL-10 and IL-4 through the activation of Nrf2-ARE signaling pathway. These results suggest that MF has anti-neuroinflammatory effects via inhibiting NF-κB signaling by activating Nrf2-ARE. These studies support that MF could be a strong candidate drug for treating and or preventing TS-induced neuroinflammation and ischemic stroke.

A mechanistic analysis of metformin's biphasic effects on lifespan and healthspan in C. elegans: Elixir in youth, poison in elder

Aging, a complex biological process influenced by genetic, environmental, and pharmacological factors, presents a significant challenge in understanding its underlying mechanisms. In this study, we explored the divergent impacts of metformin treatment on the lifespan and healthspan of young and old C. elegans, demonstrating a intriguing "elixir in youth, poison in elder" phenomenon. By scrutinizing the gene expression changes in response to metformin in young (day 1 of adulthood) and old (days 8) groups, we identified nhr-57 and C46G7.1 as potential modulators of age-specific responses. Notably, nhr-57 and C46G7.1 exhibit contrasting regulation patterns, being up-regulated in young worms but down-regulated in old counterparts following metformin treatment. Functional studies employing knockdown approaches targeting nhr-57, a gene under the control of hif-1 with a documented protective function against pore-forming toxins in C. elegans, and C46G7.1, unveiled their critical roles in modulating lifespan and healthspan, as well as in mediating the biphasic effects of metformin. Furthermore, deletion of hif-1 retarded the influence of metformin, implicating the involvement of hif-1/nhr-57 in age-specific drug responses. These findings underscored the necessity of deciphering the mechanisms governing age-related susceptibility to pharmacological agents to tailor interventions for promoting successful aging.

Unveiling the impact of aging on BBB and Alzheimer's disease: Factors and therapeutic implications

Alzheimer's disease (AD) is a highly prevalent neurodegenerative condition that has devastating effects on individuals, often resulting in dementia. AD is primarily defined by the presence of extracellular plaques containing insoluble β-amyloid peptide (Aβ) and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein (P-tau). In addition, individuals afflicted by these age-related illnesses experience a diminished state of health, which places significant financial strain on their loved ones. Several risk factors play a significant role in the development of AD. These factors include genetics, diet, smoking, certain diseases (such as cerebrovascular diseases, obesity, hypertension, and dyslipidemia), age, and alcohol consumption. Age-related factors are key contributors to the development of vascular-based neurodegenerative diseases such as AD. In general, the process of aging can lead to changes in the immune system's responses and can also initiate inflammation in the brain. The chronic inflammation and the inflammatory mediators found in the brain play a crucial role in the dysfunction of the blood-brain barrier (BBB). Furthermore, maintaining BBB integrity is of utmost importance in preventing a wide range of neurological disorders. Therefore, in this review, we discussed the role of age and its related factors in the breakdown of the blood-brain barrier and the development of AD. We also discussed the importance of different compounds, such as those with anti-aging properties, and other compounds that can help maintain the integrity of the blood-brain barrier in the prevention of AD. This review builds a strong correlation between age-related factors, degradation of the BBB, and its impact on AD.

Attojoule Hexagonal Boron Nitride-Based Memristor for High-Performance Neuromorphic Computing

In next-generation neuromorphic computing applications, the primary challenge lies in achieving energy-efficient and reliable memristors while minimizing their energy consumption to a level comparable to that of biological synapses. In this work, hexagonal boron nitride (h-BN)-based metal-insulator-semiconductor (MIS) memristors operating is presented at the attojoule-level tailored for high-performance artificial neural networks. The memristors benefit from a wafer-scale uniform h-BN resistive switching medium grown directly on a highly doped Si wafer using metal-organic chemical vapor deposition (MOCVD), resulting in outstanding reliability and low variability. Notably, the h-BN-based memristors exhibit exceptionally low energy consumption of attojoule levels, coupled with fast switching speed. The switching mechanisms are systematically substantiated by electrical and nano-structural analysis, confirming that the h-BN layer facilitates the resistive switching with extremely low high resistance states (HRS) and the native SiOx on Si contributes to suppressing excessive current, enabling attojoule-level energy consumption. Furthermore, the formation of atomic-scale conductive filaments leads to remarkably fast response times within the nanosecond range, and allows for the attainment of multi-resistance states, making these memristors well-suited for next-generation neuromorphic applications. The h-BN-based MIS memristors hold the potential to revolutionize energy consumption limitations in neuromorphic devices, bridging the gap between artificial and biological synapses.

Enhancing healthy aging with small molecules: A mitochondrial perspective

The pursuit of enhanced health during aging has prompted the exploration of various strategies focused on reducing the decline associated with the aging process. A key area of this exploration is the management of mitochondrial dysfunction, a notable characteristic of aging. This review sheds light on the crucial role that small molecules play in augmenting healthy aging, particularly through influencing mitochondrial functions. Mitochondrial oxidative damage, a significant aspect of aging, can potentially be lessened through interventions such as coenzyme Q10, alpha-lipoic acid, and a variety of antioxidants. Additionally, this review discusses approaches for enhancing mitochondrial proteostasis, emphasizing the importance of mitochondrial unfolded protein response inducers like doxycycline, and agents that affect mitophagy, such as urolithin A, spermidine, trehalose, and taurine, which are vital for sustaining protein quality control. Of equal importance are methods for modulating mitochondrial energy production, which involve nicotinamide adenine dinucleotide boosters, adenosine 5'-monophosphate-activated protein kinase activators, and compounds like metformin and mitochondria-targeted tamoxifen that enhance metabolic function. Furthermore, the review delves into emerging strategies that encourage mitochondrial biogenesis. Together, these interventions present a promising avenue for addressing age-related mitochondrial degradation, thereby setting the stage for the development of innovative treatment approaches to meet this extensive challenge.

Translatability of life-extending pharmacological treatments between different species

Anti-aging research has made significant strides in identifying treatments capable of extending lifespan across a range of organisms, from simple invertebrates to mammals. This review showcases the current state of anti-aging interventions, highlighting the lifespan extensions observed in animal models through various treatments and the challenges encountered in translating these findings to humans. Despite promising results in lower organisms, the translation of anti-aging treatments to human applications presents a considerable challenge. This discrepancy can be attributed to the increasing complexity of biological systems, species-specific metabolic and genetic differences, and the redundancy of metabolic pathways linked to longevity. Our review focuses on analyzing these challenges, offering insights into the efficacy of anti-aging mechanisms across species and identifying key barriers to their translation into human treatments. By synthesizing current knowledge and identifying gaps in translatability, this review aims to underscore the importance of advancing these therapies for human benefit. Bridging this gap is essential to assess the potential of such treatments in extending the human healthspan.

Sch9S6K controls DNA repair and DNA damage response efficiency in aging cells

Survival from UV-induced DNA lesions relies on nucleotide excision repair (NER) and the Mec1ATR DNA damage response (DDR). We study DDR and NER in aging cells and find that old cells struggle to repair DNA and activate Mec1ATR. We employ pharmacological and genetic approaches to rescue DDR and NER during aging. Conditions activating Snf1AMPK rescue DDR functionality, but not NER, while inhibition of the TORC1-Sch9S6K axis restores NER and enhances DDR by tuning PP2A activity, specifically in aging cells. Age-related repair deficiency depends on Snf1AMPK-mediated phosphorylation of Sch9S6K on Ser160 and Ser163. PP2A activity in old cells is detrimental for DDR and influences NER by modulating Snf1AMPK and Sch9S6K. Hence, the DDR and repair pathways in aging cells are influenced by the metabolic tuning of opposing AMPK and TORC1 networks and by PP2A activity. Specific Sch9S6K phospho-isoforms control DDR and NER efficiency, specifically during aging.

Delaying Renal Aging: Metformin Holds Promise as a Potential Treatment

Given the rapid aging of the population, age-related diseases have become an excessive burden on global health care. The kidney, a crucial metabolic organ, ages relatively quickly. While the aging process itself does not directly cause kidney damage, the physiological changes that accompany it can impair the kidney's capacity for self-repair. This makes aging kidneys more susceptible to diseases, including increased risks of chronic kidney disease and end-stage renal disease. Therefore, delaying the progression of renal aging and preserving the youthful vitality of the kidney are crucial for preventing kidney diseases. However, effective strategies against renal aging are still lacking due to the underlying mechanisms of renal aging, which have not been fully elucidated. Accumulating evidence suggests that metformin has beneficial effects in mitigating renal aging. Metformin has shown promising anti-aging results in animal models but has not been tested for this purpose yet in clinical trials. These findings indicate the potential of metformin as an anti-renal aging drug. In this review, we primarily discuss the characteristics and mechanisms of kidney aging and the potential effects of metformin against renal aging.

Towards Healthy Longevity: Comprehensive Insights from Molecular Targets and Biomarkers to Biological Clocks

Aging is a complex and time-dependent decline in physiological function that affects most organisms, leading to increased risk of age-related diseases. Investigating the molecular underpinnings of aging is crucial to identify geroprotectors, precisely quantify biological age, and propose healthy longevity approaches. This review explores pathways that are currently being investigated as intervention targets and aging biomarkers spanning molecular, cellular, and systemic dimensions. Interventions that target these hallmarks may ameliorate the aging process, with some progressing to clinical trials. Biomarkers of these hallmarks are used to estimate biological aging and risk of aging-associated disease. Utilizing aging biomarkers, biological aging clocks can be constructed that predict a state of abnormal aging, age-related diseases, and increased mortality. Biological age estimation can therefore provide the basis for a fine-grained risk stratification by predicting all-cause mortality well ahead of the onset of specific diseases, thus offering a window for intervention. Yet, despite technological advancements, challenges persist due to individual variability and the dynamic nature of these biomarkers. Addressing this requires longitudinal studies for robust biomarker identification. Overall, utilizing the hallmarks of aging to discover new drug targets and develop new biomarkers opens new frontiers in medicine. Prospects involve multi-omics integration, machine learning, and personalized approaches for targeted interventions, promising a healthier aging population.

Repurposing effect of cardiovascular-metabolic drug to increase lifespan: a systematic review of animal studies and current clinical trial progress

With the increase in life expectancy, aging has emerged as a significant health concern. Due to its various mechanisms of action, cardiometabolic drugs are often repurposed for other indications, including aging. This systematic review analyzed and highlighted the repositioning potential of cardiometabolic drugs to increase lifespan as an aging parameter in animal studies and supplemented by information from current clinical trial registries. Systematic searching in animal studies was performed based on PICO: "animal," "cardiometabolic drug," and "lifespan." All clinical trial registries were also searched from the WHO International Clinical Trial Registry Platform (ICTRP). Analysis of 49 animal trials and 10 clinical trial registries show that various cardiovascular and metabolic drugs have the potential to target lifespan. Metformin, acarbose, and aspirin are the three most studied drugs in animal trials. Aspirin and acarbose are the promising ones, whereas metformin exhibits various results. In clinical trial registries, metformin, omega-3 fatty acid, acarbose, and atorvastatin are currently cardiometabolic drugs that are repurposed to target aging. Published clinical trial results show great potential for omega-3 and metformin in healthspan. Systematic Review Registration: crd.york.ac.uk/prospero/display_record.php?RecordID=457358, identifier: CRD42023457358.

Longitudinal urinary neopterin is associated with hearing threshold change over time in independent older adults

Low-grade chronic inflammation is associated with many age-related conditions. Non-invasive methods to monitor low-grade chronic inflammation may improve the management of older people at risk of poorer outcomes. This longitudinal cohort study has determined baseline inflammation using neopterin volatility in monthly urine samples of 45 independent older adults (aged 65-75 years). Measurement of neopterin, an inflammatory metabolite, enabled stratification of individuals into risk categories based on how often in a 12-month period their neopterin level was raised. Hearing was measured (pure-tone audiometry) at baseline, 1 year and 3 years of the study. Results show that those in the highest risk category (neopterin raised greater than 50% of the time) saw greater deterioration, particularly in high-frequency, hearing. A one-way Welch's ANOVA showed a significant difference between the risk categories for change in high-frequency hearing (W (3, 19.6) = 9.164, p = 0.0005). Despite the study size and duration individuals in the highest risk category were more than twice as likely to have an additional age-related morbidity than those in the lowest risk category. We conclude that volatility of neopterin in urine may enable stratification of those at greatest risk of progression of hearing loss.

Exploring the Complexity and Promise of Tumor Immunotherapy in Drug Development

Cancer represents a significant threat to human health, and traditional chemotherapy or cytotoxic therapy is no longer the sole or preferred approach for managing malignant tumors. With advanced research into the immunogenicity of tumor cells and the growing elderly population, tumor immunotherapy has emerged as a prominent therapeutic option. Its significance in treating elderly cancer patients is increasingly recognized. In this study, we review the conceptual classifications and benefits of immunotherapy, and discuss recent developments in new drugs and clinical progress in cancer treatment through various immunotherapeutic modalities with different mechanisms. Additionally, we explore the impact of immunosenescence on the effectiveness of cancer immunotherapy and propose innovative and effective strategies to rejuvenate senescent T cells.

Model biological systems demonstrate the inducibility of pathways that strongly reduce cryoprotectant toxicity

Cryoprotectant toxicity is a limiting factor for the cryopreservation of many living systems. We were moved to address this problem by the potential of organ vitrification to relieve the severe shortage of viable donor organs available for human transplantation. The M22 vitrification solution is presently the only solution that has enabled the vitrification and subsequent transplantation with survival of large mammalian organs, but its toxicity remains an obstacle to organ stockpiling for transplantation. We therefore undertook a series of exploratory studies to identify potential pretreatment interventions that might reduce the toxic effects of M22. Hormesis, in which a living system becomes more resistant to toxic stress after prior subtoxic exposure to a related stress, was investigated as a potential remedy for M22 toxicity in yeast, in the nematode worm C. elegans, and in mouse kidney slices. In yeast, heat shock pretreatment increased survival by 18-fold after exposure to formamide and by over 9-fold after exposure to M22 at 30 °C; at 0 °C and with two-step addition, treatment with 90% M22 resulted in 100% yeast survival. In nematodes, surveying a panel of pretreatment interventions revealed 3 that conferred nearly total protection from acute whole-worm M22-induced damage. One of these protective pretreatments (exposure to hydrogen peroxide) was applied to mouse kidney slices in vitro and was found to strongly protect nuclear and plasma membrane integrity in both cortical and medullary renal cells exposed to 75-100% M22 at room temperature for 40 min. These studies demonstrate for the first time that endogenous cellular defenses, conserved from yeast to mammals, can be marshalled to substantially ameliorate the toxic effects of one of the most toxic single cryoprotectants and the toxicity of the most concentrated vitrification solution so far described for whole organs.

The role of the immunosuppressive PD-1/PD-L1 checkpoint pathway in the aging process and age-related diseases

The accumulation of senescent cells within tissues is a hallmark of the aging process. Senescent cells are also commonly present in many age-related diseases and in the cancer microenvironment. The escape of abnormal cells from immune surveillance indicates that there is some defect in the function of cytotoxic immune cells, e.g., CD8+ T cells and natural killer (NK) cells. Recent studies have revealed that the expression of programmed death-ligand 1 (PD-L1) protein is abundantly increased in senescent cells. An increase in the amount of PD-L1 protein protects senescent cells from clearance by the PD-1 checkpoint receptor in cytotoxic immune cells. In fact, the activation of the PD-1 receptor suppresses the cytotoxic properties of CD8+ T and NK cells, promoting a state of immunosenescence. The inhibitory PD-1/PD-L1 checkpoint pathway acts in cooperation with immunosuppressive cells; for example, activation of PD-1 receptor can enhance the differentiation of regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and M2 macrophages, whereas the cytokines secreted by immunosuppressive cells stimulate the expression of the immunosuppressive PD-L1 protein. Interestingly, many signaling pathways known to promote cellular senescence and the aging process are crucial stimulators of the expression of PD-L1 protein, e.g., epigenetic regulation, inflammatory mediators, mTOR-related signaling, cGAS-STING pathway, and AhR signaling. It seems that the inhibitory PD-1/PD-L1 immune checkpoint axis has a crucial role in the accumulation of senescent cells and thus it promotes the aging process in tissues. Thus, the blockade of the PD-1/PD-L1 checkpoint signaling might be a potential anti-aging senolytic therapy. KEY MESSAGES: Senescent cells accumulate within tissues during aging and age-related diseases. Senescent cells are able to escape immune surveillance by cytotoxic immune cells. Expression of programmed death-ligand 1 (PD-L1) markedly increases in senescent cells. Age-related signaling stimulates the expression of PD-L1 protein in senescent cells. Inhibitory PD-1/PD-L1 checkpoint pathway suppresses clearance of senescent cells.

In the land of not-unhappiness: On the state-of-the-art of targeting aging and age-related diseases by biomedical research

The concept of the Land of Not-Unhappiness refers to the potential achievement of eliminating the pathologies of the aging process. To inform of how close we are to settling in the land, we summarize and review the achievements of research on anti-aging interventions over the last hundred years with a specific focus on strategies that slow down metabolism, compensate for aging-related losses, and target a broad range of age-related diseases. We critically evaluate the existing interventions labeled as "anti-aging," such as calorie restriction, exercise, stem cell administration, and senolytics, to provide a down-to-earth evaluation of their current applicability in counteracting aging. Throughout the text, we have maintained a light tone to make it accessible to non-experts in biogerontology, and provide a broad overview for those considering conducting studies, research, or seeking to understand the scientific basis of anti-aging medicine.

Depression, Inflammation, and the Moderating Role of Metformin: Results From the Midlife in the United States Study and Sacramento Area Latino Study on Aging

OBJECTIVE

Depression can promote inflammation and accelerate aging. Metformin, a widely prescribed antidiabetic, has shown promising preclinical evidence of aging-related health benefits, including decreased inflammation. The current study examined whether metformin usage buffers the association between depressive symptoms and inflammatory markers in two large samples of middle-aged and older, primarily White adults, and older Latino adults.

METHODS

Data from the Midlife in the United States Study ( N = 1255) and the Sacramento Area Latino Study on Aging ( N = 1786) included information on medication use, depressive symptoms, and inflammatory markers, namely, interleukin 6 (IL-6), tumor necrosis factor α, and C-reactive protein (CRP). These data were merged into a harmonized sample, and the sample group variable was included in a three-way interaction for analysis.

RESULTS

Specifically, in the Midlife in the United States Study sample, metformin buffered the association between depressive symptoms and CRP ( b = -0.029, standard error [SE] = 0.013, p = .007) and IL-6 ( b = 0.21, SE = 0.010, p = .046), whereas no significant association was found with tumor necrosis factor α. Metformin nonusers displayed higher depressive symptoms associated with elevated CRP ( b = 0.01, SE = 0.003, p < .001) and IL-6 ( b = 0.011, SE = 0.003, p < .001), whereas this association was not present among metformin users ( p values > .068). Conversely, in the Sacramento Area Latino Study on Aging sample, metformin use did not show a significant protective link.

CONCLUSIONS

Results from mostly White, highly educated adults supported a mitigating role of metformin in ties between depression, a well-known behavioral risk factor, and inflammation, a key source of biological aging. However, the benefits did not extend to a large sample of older Mexican Americans. The findings reveal a hidden potential benefit of this therapeutic agent and raise important questions around its health equity.

TRIAL REGISTRATION

The study was preregistered on OSF ( https://osf.io/c92vw/ ).

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

Tissue fibroblasts are versatile immune regulators: An evaluation of their impact on the aging process

Fibroblasts are abundant stromal cells which not only control the integrity of extracellular matrix (ECM) but also act as immune regulators. It is known that the structural cells within tissues can establish an organ-specific immunity expressing many immune-related genes and closely interact with immune cells. In fact, fibroblasts can modify their immune properties to display both pro-inflammatory and immunosuppressive activities in a context-dependent manner. After acute insults, fibroblasts promote tissue inflammation although they concurrently recruit immunosuppressive cells to enhance the resolution of inflammation. In chronic pathological states, tissue fibroblasts, especially senescent fibroblasts, can display many pro-inflammatory and immunosuppressive properties and stimulate the activities of different immunosuppressive cells. In return, immunosuppressive cells, such as M2 macrophages and myeloid-derived suppressor cells (MDSC), evoke an excessive conversion of fibroblasts into myofibroblasts, thus aggravating the severity of tissue fibrosis. Single-cell transcriptome studies on fibroblasts isolated from aged tissues have confirmed that tissue fibroblasts express many genes coding for cytokines, chemokines, and complement factors, whereas they lose some fibrogenic properties. The versatile immune properties of fibroblasts and their close cooperation with immune cells indicate that tissue fibroblasts have a crucial role in the aging process and age-related diseases.

Metformin treatment of juvenile mice alters aging-related developmental and metabolic phenotypes in sex-dependent and sex-independent manners

Metformin has attracted increasing interest for its potential benefits in extending healthspan and longevity. This study examined the effects of early-life metformin treatment on the development and metabolism of C57BL/6 J (B6) mice, with metformin administered to juvenile mice from 15 to 56 days of age. Metformin treatment led to decreased body weight in both sexes (P < 0.05, t-test). At 9 weeks of age, mice were euthanized and organ weights were recorded. The relative weight of retroperitoneal fat was decreased in females, while relative weights of perigonadal and retroperitoneal fat were decreased, and relative liver weight was increased in males (P < 0.05, t-test). Glucose and insulin tolerance tests (GTT and ITT) were conducted at the age of 7 weeks. ANOVA revealed a significant impairment in insulin sensitivity by the treatment, and a significantly interactive effect on glucose tolerance between sex and treatment, underscoring a disparity in GTT between sexes in response to the treatment. Metformin treatment reduced circulating insulin levels in fasting and non-fasting conditions for male mice, with no significant alterations observed in female mice. qRT-PCR analysis of glucose metabolism-related genes (Akt2, Glut2, Glut4, Irs1, Nrip1, Pi3k, Pi3kca, Pkca) in the liver and skeletal muscle reveals metformin-induced sex- and organ-specific effects on gene expression. Comparison with previous studies in heterogeneous UM-HET3 mice receiving the same treatment suggests that genetic differences may contribute to variability in the effects of metformin treatment on development and metabolism. These findings indicate that early-life metformin treatment affects development and metabolism in both sex- and genetics-dependent manners.

Pharmaceutical therapies targeting autophagy for the treatment of age-related macular degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible vision loss in the elderly. Although new therapies have recently emerged, there are currently no ways of preventing the development of the disease. Changes in intracellular recycling processes. Changes in intracellular recycling processes, called autophagy, lead to debris accumulation and cellular dysfunction in AMD models and AMD patients. Drugs that enhance autophagy hold promise as therapies for slowing AMD progression in preclinical models; however, more studies in humans are required. While a definitive cure for AMD will likely hinge on a personalized medicine approach, treatments that enhance autophagy hold promise for slowing vision loss.

Early life interventions metformin and trodusquemine metabolically reprogram the developing mouse liver through transcriptomic alterations

Recent studies have demonstrated the remarkable potential of early life intervention strategies at influencing the course of postnatal development, thereby offering exciting possibilities for enhancing longevity and improving overall health. Metformin (MF), an FDA-approved medication for type II diabetes mellitus, has recently gained attention for its promising anti-aging properties, acting as a calorie restriction mimetic, and delaying precocious puberty. Additionally, trodusquemine (MSI-1436), an investigational drug, has been shown to combat obesity and metabolic disorders by inhibiting the enzyme protein tyrosine phosphatase 1b (Ptp1b), consequently reducing hepatic lipogenesis and counteracting insulin and leptin resistance. In this study, we aimed to further explore the effects of these compounds on young, developing mice to uncover biomolecular signatures that are central to liver metabolic processes. We found that MSI-1436 more potently alters mRNA and miRNA expression in the liver compared with MF, with bioinformatic analysis suggesting that cohorts of differentially expressed miRNAs inhibit the action of phosphoinositide 3-kinase (Pi3k), protein kinase B (Akt), and mammalian target of rapamycin (Mtor) to regulate the downstream processes of de novo lipogenesis, fatty acid oxidation, very-low-density lipoprotein transport, and cholesterol biosynthesis and efflux. In summary, our study demonstrates that administering these compounds during the postnatal window metabolically reprograms the liver through induction of potent epigenetic changes in the transcriptome, potentially forestalling the onset of age-related diseases and enhancing longevity. Future studies are necessary to determine the impacts on lifespan and overall quality of life.

Anti-Inflammatory Potential of the Anti-Diabetic Drug Metformin in the Prevention of Inflammatory Complications and Infectious Diseases Including COVID-19: A Narrative Review

Metformin, a widely used first-line anti-diabetic therapy for the treatment of type-2 diabetes, has been shown to lower hyperglycemia levels in the blood by enhancing insulin actions. For several decades this drug has been used globally to successfully control hyperglycemia. Lactic acidosis has been shown to be a major adverse effect of metformin in some type-2 diabetic patients, but several studies suggest that it is a typically well-tolerated and safe drug in most patients. Further, recent studies also indicate its potential to reduce the symptoms associated with various inflammatory complications and infectious diseases including coronavirus disease 2019 (COVID-19). These studies suggest that besides diabetes, metformin could be used as an adjuvant drug to control inflammatory and infectious diseases. In this article, we discuss the current understanding of the role of the anti-diabetic drug metformin in the prevention of various inflammatory complications and infectious diseases in both diabetics and non-diabetics.

The intersection of frailty and metabolism

On average, aging is associated with unfavorable changes in cellular metabolism, which are the processes involved in the storage and expenditure of energy. However, metabolic dysregulation may not occur to the same extent in all older individuals as people age at different rates. Those who are aging rapidly are at increased risk of adverse health outcomes and are said to be "frail." Here, we explore the links between frailty and metabolism, including metabolic contributors and consequences of frailty. We examine how metabolic diseases may modify the degree of frailty in old age and suggest that frailty may predispose toward metabolic disease. Metabolic interventions that can mitigate the degree of frailty in people are reviewed. New treatment strategies developed in animal models that are poised for translation to humans are also considered. We suggest that maintaining a youthful metabolism into older age may be protective against frailty.

Promising use of metformin in treating neurological disorders: biomarker-guided therapies

Neurological disorders are a diverse group of conditions that affect the nervous system and include neurodegenerative diseases (Alzheimer's disease, multiple sclerosis, Parkinson's disease, Huntington's disease), cerebrovascular conditions (stroke), and neurodevelopmental disorders (autism spectrum disorder). Although they affect millions of individuals around the world, only a limited number of effective treatment options are available today. Since most neurological disorders express mitochondria-related metabolic perturbations, metformin, a biguanide type II antidiabetic drug, has attracted a lot of attention to be repurposed to treat neurological disorders by correcting their perturbed energy metabolism. However, controversial research emerges regarding the beneficial/detrimental effects of metformin on these neurological disorders. Given that most neurological disorders have complex etiology in their pathophysiology and are influenced by various risk factors such as aging, lifestyle, genetics, and environment, it is important to identify perturbed molecular functions that can be targeted by metformin in these neurological disorders. These molecules can then be used as biomarkers to stratify subpopulations of patients who show distinct molecular/pathological properties and can respond to metformin treatment, ultimately developing targeted therapy. In this review, we will discuss mitochondria-related metabolic perturbations and impaired molecular pathways in these neurological disorders and how these can be used as biomarkers to guide metformin-responsive treatment for the targeted therapy to treat neurological disorders.

Hallmark Molecular and Pathological Features of POLG Disease are Recapitulated in Cerebral Organoids

In this research, a 3D brain organoid model is developed to study POLG-related encephalopathy, a mitochondrial disease stemming from POLG mutations. Induced pluripotent stem cells (iPSCs) derived from patients with these mutations is utilized to generate cortical organoids, which exhibited typical features of the diseases with POLG mutations, such as altered morphology, neuronal loss, and mitochondiral DNA (mtDNA) depletion. Significant dysregulation is also identified in pathways crucial for neuronal development and function, alongside upregulated NOTCH and JAK-STAT signaling pathways. Metformin treatment ameliorated many of these abnormalities, except for the persistent affliction of inhibitory dopamine-glutamate (DA GLU) neurons. This novel model effectively mirrors both the molecular and pathological attributes of diseases with POLG mutations, providing a valuable tool for mechanistic understanding and therapeutic screening for POLG-related disorders and other conditions characterized by compromised neuronal mtDNA maintenance and complex I deficiency.

AMP-activated protein kinase activators have compound and concentration-specific effects on brain metabolism

AMP-activated protein kinase (AMPK) is a key sensor of energy balance playing important roles in the balancing of anabolic and catabolic activities. The high energy demands of the brain and its limited capacity to store energy indicate that AMPK may play a significant role in brain metabolism. Here, we activated AMPK in guinea pig cortical tissue slices, both directly with A769662 and PF 06409577 and indirectly with AICAR and metformin. We studied the resultant metabolism of [1-13C]glucose and [1,2-13C]acetate using NMR spectroscopy. We found distinct activator concentration-dependent effects on metabolism, which ranged from decreased metabolic pool sizes at EC50 activator concentrations with no expected stimulation in glycolytic flux to increased aerobic glycolysis and decreased pyruvate metabolism with certain activators. Further, activation with direct versus indirect activators produced distinct metabolic outcomes at both low (EC50) and higher (EC50 × 10) concentrations. Specific direct activation of β1-containing AMPK isoforms with PF 06409577 resulted in increased Krebs cycle activity, restoring pyruvate metabolism while A769662 increased lactate and alanine production, as well as labelling of citrate and glutamine. These results reveal a complex metabolic response to AMPK activators in brain beyond increased aerobic glycolysis and indicate that further research is warranted into their concentration- and mechanism-dependent impact.

Nutrient-epigenome interactions: Implications for personalized nutrition against aging-associated diseases

Aging is a multifaceted process involving genetic and environmental interactions often resulting in epigenetic changes, potentially leading to aging-related diseases. Various strategies, like dietary interventions and calorie restrictions, have been employed to modify these epigenetic landscapes. A burgeoning field of interest focuses on the role of microbiota in human health, emphasizing system biology and computational approaches. These methods help decipher the intricate interplay between diet and gut microbiota, facilitating the creation of personalized nutrition strategies. In this review, we analysed the mechanisms related to nutritional interventions while highlighting the influence of dietary strategies, like calorie restriction and intermittent fasting, on microbial composition and function. We explore how gut microbiota affects the efficacy of interventions using tools like multi-omics data integration, network analysis, and machine learning. These tools enable us to pinpoint critical regulatory elements and generate individualized models for dietary responses. Lastly, we emphasize the need for a deeper comprehension of nutrient-epigenome interactions and the potential of personalized nutrition informed by individual genetic and epigenetic profiles. As knowledge and technology advance, dietary epigenetics stands on the cusp of reshaping our strategy against aging and related diseases.

Impaired Remodeling of White Adipose Tissue in Obesity and Aging: From Defective Adipogenesis to Adipose Organ Dysfunction

The adipose organ adapts and responds to internal and environmental stimuli by remodeling both its cellular and extracellular components. Under conditions of energy surplus, the subcutaneous white adipose tissue (WAT) is capable of expanding through the enlargement of existing adipocytes (hypertrophy), followed by de novo adipogenesis (hyperplasia), which is impaired in hypertrophic obesity. However, an impaired hyperplastic response may result from various defects in adipogenesis, leading to different WAT features and metabolic consequences, as discussed here by reviewing the results of the studies in animal models with either overexpression or knockdown of the main molecular regulators of the two steps of the adipogenesis process. Moreover, impaired WAT remodeling with aging has been associated with various age-related conditions and reduced lifespan expectancy. Here, we delve into the latest advancements in comprehending the molecular and cellular processes underlying age-related changes in WAT function, their involvement in common aging pathologies, and their potential as therapeutic targets to influence both the health of elderly people and longevity. Overall, this review aims to encourage research on the mechanisms of WAT maladaptation common to conditions of both excessive and insufficient fat tissue. The goal is to devise adipocyte-targeted therapies that are effective against both obesity- and age-related disorders.

Interplay between lipid dysregulation and ferroptosis in chondrocytes and the targeted therapy effect of metformin on osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a devastating whole-joint disease affecting a large population worldwide; the role of lipid dysregulation in OA and mechanisms underlying targeted therapy effect of lipid-lowering metformin on OA remains poorly defined.

OBJECTIVES

To investigate the effects of lipid dysregulation on OA progression and to explore lipid dysregulation-targeting OA treatment of metformin.

METHODS

RNA-Seq data, biochemical, and histochemical assays in human and murine OA cartilage as well as primary chondrocytes were utilized to determine lipid dysregulation. Effects of metformin, a potent lipid-lowering medication, on ACSL4 expression and chondrocyte metabolism were determined. Further molecular experiments, including RT-qPCR, western blotting, flow cytometry, and immunofluorescence staining, were performed to investigate underlying mechanisms. Mice with intra-articular injection of metformin were utilized to determine the effects on ACLT-induced OA progression.

RESULTS

ACSL4 and 4-HNE expressions were elevated in human and ACLT-induced mouse OA cartilage and IL-1β-treated chondrocytes (P < 0.05). Ferrostatin-1 largely rescued IL-1β-induced MDA, lipid peroxidation, and ferroptotic mitochondrial morphology (P < 0.05). Metformin decreased the levels of OA-related genes (P < 0.05) and increased the levels of p-AMPK and p-ACC in IL-1β-treated chondrocytes. Intra-articular injection of metformin alleviated ACLT-induced OA lesions in mice, and reverted the percentage of chondrocytes positive for MMP13, Col2a1, ACSL4 and 4-HNE in ACLT mice (P < 0.05). Ferroptotic chondrocytes promoted the recruitment and chemotaxis of RAW264.7 cells via CCL2, which was blocked by metformin in vitro (P < 0.05).

CONCLUSION

We establish a critical role of polyunsaturated fatty acids metabolic process in OA cartilage degradation and define metformin as a potential OA treatment. Metformin reshapes lipid availability and ameliorates chondrocyte ferroptosis sensitivity via the AMPK/ACC pathway. In the future, gene-edited animals and extensive omics technologies will be utilized to reveal detailed lipids' involvement in cartilage lesions.

Polyphenolic Compounds: Orchestrating Intestinal Microbiota Harmony during Aging

In the aging process, physiological decline occurs, posing a substantial threat to the physical and mental well-being of the elderly and contributing to the onset of age-related diseases. While traditional perspectives considered the maintenance of life as influenced by a myriad of factors, including environmental, genetic, epigenetic, and lifestyle elements such as exercise and diet, the pivotal role of symbiotic microorganisms had been understated. Presently, it is acknowledged that the intestinal microbiota plays a profound role in overall health by signaling to both the central and peripheral nervous systems, as well as other distant organs. Disruption in this bidirectional communication between bacteria and the host results in dysbiosis, fostering the development of various diseases, including neurological disorders, cardiovascular diseases, and cancer. This review aims to delve into the intricate biological mechanisms underpinning dysbiosis associated with aging and the clinical ramifications of such dysregulation. Furthermore, we aspire to explore bioactive compounds endowed with functional properties capable of modulating and restoring balance in this aging-related dysbiotic process through epigenetics alterations.

Metformin in elderly type 2 diabetes mellitus: dose-dependent dementia risk reduction

This study aimed to investigate the controversial association between metformin use and diabetes-associated dementia in elderly patients with type 2 diabetes mellitus (T2DM) and evaluate the potential protective effects of metformin, as well as its intensity of use and dose-dependency, against dementia in this population. The study used a time-dependent Cox hazards model to evaluate the effect of metformin use on the incidence of dementia. The case group included elderly patients with T2DM (≥60 years old) who received metformin, while the control group consisted of elderly patients with T2DM who did not receive metformin during the follow-up period. Our analysis revealed a significant reduction in the risk of dementia among elderly individuals using metformin, with an adjusted hazard ratio of 0.34 (95% confidence interval: 0.33 to 0.36). Notably, metformin users with a daily intensity of 1 defined daily dose (DDD) or higher had a lower risk of dementia, with an adjusted hazard ratio (95% confidence interval) of 0.46 (0.22 to 0.6), compared to those with a daily intensity of <1 DDD. Additionally, the analysis of cumulative DDDs of metformin showed a dose-response relationship, with progressively lower adjusted hazard ratio across quartiles (0.15, 0.21, 0.28, and 0.53 for quartiles 4, 3, 2 and 1, respectively), compared to never metformin users (P for trend < 0.0001). Metformin use in elderly patients with T2DM is significantly associated with a substantial reduction in the risk of dementia. Notably, the protective effect of metformin demonstrates a dose-dependent relationship, with higher daily and cumulative dosages of metformin showing a greater risk reduction.

Does diet influence aging? Evidence from animal studies

Nutrition profoundly influences the risk for many age-related diseases. Whether nutrition influences human aging biology directly is less clear. Studies in different animal species indicate that reducing food intake ("caloric restriction" [CR]) can increase lifespan and delay the onset of diseases and the biological hallmarks of aging. Obesity has been described as "accelerated aging" and therefore the lifespan and health benefits generated by CR in both aging and obesity may occur via similar mechanisms. Beyond calorie intake, studies based on nutritional geometry have shown that protein intake and the interaction between dietary protein and carbohydrates influence age-related health and lifespan. Studies where animals are calorically restricted by providing free access to diluted diets have had less impact on lifespan than those studies where animals are given a reduced aliquot of food each day and are fasting between meals. This has drawn attention to the role of fasting in health and aging, and exploration of the health effects of various fasting regimes. Although definitive human clinical trials of nutrition and aging would need to be unfeasibly long and unrealistically controlled, there is good evidence from animal experiments that some nutritional interventions based on CR, manipulating dietary macronutrients, and fasting can influence aging biology and lifespan.

Phytochemicals targeting Alzheimer's disease via the AMP-activated protein kinase pathway, effects, and mechanisms of action

Alzheimer's disease (AD), characterized by cognitive dysfunction and other behavioral abnormalities, is a progressive neurodegenerative disease that occurs due to aging. Currently, effective drugs to mitigate or treat AD remain unavailable. AD is associated with several abnormalities in neuronal energy metabolism, such as decreased glucose uptake, mitochondrial dysfunction, and defects in cholesterol metabolism. Amp-activated protein kinase (AMPK) is an important serine/threonine protein kinase that regulates the energy status of cells. AMPK is widely present in eukaryotic cells and can sense and regulate energy metabolism to maintain energy supply and demand balance, making it a promising target for energy metabolism-based AD therapy. Therefore, this review aimed to discuss the molecular mechanism of AMPK in the pathogenesis of AD to provide a theoretical basis for the development of new anti-AD drugs. To review the mechanisms of phytochemicals in the treatment of AD via AMPK pathway regulation, we searched PubMed, Google Scholar, Web of Science, and Embase databases using specific keywords related to AD and phytochemicals in September 2023. Phytochemicals can activate AMPK or regulate the AMPK pathway to exert therapeutic effects in AD. The anti-AD mechanisms of these phytochemicals include inhibiting Aβ aggregation, preventing Tau hyperphosphorylation, inhibiting inflammatory response and glial activation, promoting autophagy, and suppressing anti-oxidative stress. Additionally, several AMPK-related pathways are involved in the anti-AD mechanism, including the AMPK/CaMKKβ/mTOR, AMPK/SIRT1/PGC-1α, AMPK/NF-κB/NLRP3, AMPK/mTOR, and PERK/eIF2α pathways. Notably, urolithin A, artemisinin, justicidin A, berberine, stigmasterol, arctigenin, and rutaecarpine are promising AMPK agonists with anti-AD effects. Several phytochemicals are effective AMPK agonists and may have potential applications in AD treatment. Overall, phytochemical-based drugs may overcome the barriers to the effective treatment of neurodegenerative diseases.

Metformin and the Liver: Unlocking the Full Therapeutic Potential

Metformin is a highly effective medication for managing type 2 diabetes mellitus. Recent studies have shown that it has significant therapeutic benefits in various organ systems, particularly the liver. Although the effects of metformin on metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis are still being debated, it has positive effects on cirrhosis and anti-tumoral properties, which can help prevent the development of hepatocellular carcinoma. Furthermore, it has been proven to improve insulin resistance and dyslipidaemia, commonly associated with liver diseases. While more studies are needed to fully determine the safety and effectiveness of metformin use in liver diseases, the results are highly promising. Indeed, metformin has a terrific potential for extending its full therapeutic properties beyond its traditional use in managing diabetes.

Quantification of healthspan in aging mice: Introducing FAMY and GRAIL

The population around the world is graying, and as many of these individuals will spend years suffering from the burdens of age associated diseases, understanding how to increase healthspan, defined as the period of life free from disease and disability, is an urgent priority of geroscience research. The lack of agreed-upon quantitative metrics for measuring healthspan in aging mice has slowed progress in identifying interventions that do not simply increase lifespan, but also healthspan. Here, we define FAMY (Frailty-Adjusted Mouse Years) and GRAIL (Gauging Robust Aging when Increasing Lifespan) as new summary statistics for quantifying healthspan in mice. FAMY integrates lifespan data with longitudinal measurements of a widely utilized clinical frailty index, while GRAIL incorporates these measures and also adds information from widely utilized healthspan assays and the hallmarks of aging. Both metrics are conceptually similar to quality-adjusted life years (QALY), a widely-utilized measure of disease burden in humans, and can be readily calculated from data acquired during longitudinal and cross-sectional studies of mouse aging. We find that interventions generally thought to promote health, including calorie restriction, robustly improve healthspan as measured by FAMY and GRAIL. Finally, we show that the use of GRAIL provides new insights, and identify dietary restriction of protein or isoleucine as interventions that robustly promote healthspan but not longevity in female HET3 mice. We suggest that the routine integration of these measures into studies of aging in mice will allow the identification and development of interventions that promote healthy aging even in the absence of increased lifespan.

Disrupting the SKN-1 homeostat: mechanistic insights and phenotypic outcomes

The mechanisms that govern maintenance of cellular homeostasis are crucial to the lifespan and healthspan of all living systems. As an organism ages, there is a gradual decline in cellular homeostasis that leads to senescence and death. As an organism lives into advanced age, the cells within will attempt to abate age-related decline by enhancing the activity of cellular stress pathways. The regulation of cellular stress responses by transcription factors SKN-1/Nrf2 is a well characterized pathway in which cellular stress, particularly xenobiotic stress, is abated by SKN-1/Nrf2-mediated transcriptional activation of the Phase II detoxification pathway. However, SKN-1/Nrf2 also regulates a multitude of other processes including development, pathogenic stress responses, proteostasis, and lipid metabolism. While this process is typically tightly regulated, constitutive activation of SKN-1/Nrf2 is detrimental to organismal health, this raises interesting questions surrounding the tradeoff between SKN-1/Nrf2 cryoprotection and cellular health and the ability of cells to deactivate stress response pathways post stress. Recent work has determined that transcriptional programs of SKN-1 can be redirected or suppressed to abate negative health outcomes of constitutive activation. Here we will detail the mechanisms by which SKN-1 is controlled, which are important for our understanding of SKN-1/Nrf2 cytoprotection across the lifespan.

Insulin signalling regulates Pink1 mRNA localization via modulation of AMPK activity to support PINK1 function in neurons

Mitochondrial quality control failure is frequently observed in neurodegenerative diseases. The detection of damaged mitochondria by stabilization of PTEN-induced kinase 1 (PINK1) requires transport of Pink1 messenger RNA (mRNA) by tethering it to the mitochondrial surface. Here, we report that inhibition of AMP-activated protein kinase (AMPK) by activation of the insulin signalling cascade prevents Pink1 mRNA binding to mitochondria. Mechanistically, AMPK phosphorylates the RNA anchor complex subunit SYNJ2BP within its PDZ domain, a phosphorylation site that is necessary for its interaction with the RNA-binding protein SYNJ2. Notably, loss of mitochondrial Pink1 mRNA association upon insulin addition is required for PINK1 protein activation and its function as a ubiquitin kinase in the mitophagy pathway, thus placing PINK1 function under metabolic control. Induction of insulin resistance in vitro by the key genetic Alzheimer risk factor apolipoprotein E4 retains Pink1 mRNA at the mitochondria and prevents proper PINK1 activity, especially in neurites. Our results thus identify a metabolic switch controlling Pink1 mRNA localization and PINK1 activity via insulin and AMPK signalling in neurons and propose a mechanistic connection between insulin resistance and mitochondrial dysfunction.