Alpha-Ketoglutarate, an Endogenous Metabolite, Extends Lifespan and Compresses Morbidity in Aging Mice

Reprogramming of ovarian aging epigenome by resveratrol

Resveratrol is an antiaging, antioxidant, and anti-inflammatory natural polyphenolic compound. Growing evidence indicates that resveratrol has potential therapeutic effects for improving aging ovarian function. However, the mechanisms underlying prolonged reproductive longevity remain elusive. We found that resveratrol ameliorates ovarian aging transcriptome, some of which are associated with specific changes in methylome. In addition to known aging transcriptome of oocytes and granulosa cells such as decline in oxidoreductase activity, metabolism and mitochondria function, and elevated DNA damage and apoptosis, actin cytoskeleton are notably downregulated with age, and these defects are mostly rescued by resveratrol. Moreover, the aging-associated hypermethylation of actin cytoskeleton is decreased by resveratrol. In contrast, deletion of Tet2, involved in DNA demethylation, abrogates resveratrol-reprogrammed ovarian aging transcriptome. Consistently, Tet2 deficiency results in additional altered pathways as shown by increased mTOR and Wnt signaling, as well as reduced DNA repair and actin cytoskeleton with mouse age. Moreover, genes associated with oxidoreductase activity and oxidation-reduction process were hypermethylated in Tet2-deficient oocytes from middle-age mice treated with resveratrol, indicating that loss of Tet2 abolishes the antioxidant effect of resveratrol. Taking together, our finding provides a comprehensive landscape of transcriptome and epigenetic changes associated with ovarian aging that can be reprogrammed by resveratrol administration, and suggests that aberrantly increased DNA methylation by Tet2 deficiency promotes additional aging epigenome that cannot be effectively restored to younger state by resveratrol.

Enhancement of α-Ketoglutaric Acid Production by Yarrowia lipolytica Grown on Mixed Renewable Carbon Sources through Adjustment of Culture Conditions

α-Ketoglutaric acid (KGA) is a valuable compound with a wide range of applications, e.g., in the cosmetics, pharmaceutical, chemical and food industries. The present study aimed to enhance the efficiency of KGA production by Yarrowia lipolytica CBS146773 from renewable carbon sources. In the investigation, various factors that may potentially affect KGA biosynthesis were examined in bioreactor cultures performed on a simple medium containing glycerol (20 g/L) and fed with four portions of a substrate mixture (15 + 15 g/L of glycerol and rapeseed oil). It was found that the process may be stimulated by regulation of the medium pH and aeration, application of selected neutralizing agents, supplementation with thiamine and addition of sorbitan monolaurate, whereas presence of biotin and iron ions had no positive effect on KGA biosynthesis. Adjustment of the parameters improved the process efficiency and allowed 82.4 g/L of KGA to be obtained, corresponding to productivity of 0.57 g/L h and yield of 0.59 g/g. In addition, the production of KGA was characterized by a low level (≤6.3 g/L) of by-products, i.e., citric and pyruvic acids. The results confirmed the high potential of renewable carbon sources (glycerol + rapeseed oil) for effective KGA biosynthesis by Yarrowia lipolytica.

Alpha Ketoglutarate Downregulates the Neutral Endopeptidase and Enhances the Growth Inhibitory Activity of Thiorphan in Highly Aggressive Osteosarcoma Cells

Since natural substances are widely explored as epigenetic modulators of gene expression and epigenetic abnormalities are important causes of cancerogenesis, factors with pro-tumor activities subjected to epigenetic control, e.g., neutral endopeptidase (NEP, neprilysin), are promising anticancer targets for potential therapies acting via epigenetic regulation of gene expression. Alpha-ketoglutarate (AKG) is a naturally occurring co-substrate for enzymes involved in histone and DNA demethylation with suggested anti-cancer activity. Hence, we investigated a potential effect of AKG on the NEP expression in cells derived from various cancers (cervical, colon, osteosarcoma) and normal epithelial cells and osteoblasts. Moreover, the overall methylation status of histone H3 was explored to establish the molecular target of AKG activity. Additionally, it was investigated whether AKG in combination with thiorphan (NEP specific inhibitor) exhibited enhanced anticancer activity. The results revealed that AKG downregulated the expression of NEP at the protein level only in highly aggressive osteosarcoma HOS cells (flow cytometry and fluorometric assays), and this protease was found to be involved in AKG-induced growth inhibition in osteosarcoma cells (siRNA NEP silencing, BrdU assay, flow cytometry). Unexpectedly, AKG-induced hypermethylation of H3K27 in HOS cells, which was partially dependent on EZH2 activity. However, this effect was not implicated in the AKG-induced NEP downregulation (flow cytometry). Finally, the combined treatment with AKG and thiorphan was shown to significantly enhance the growth inhibitory potential of each one towards HOS cells (BrdU assay). These preliminary studies have shown for the first time that the downregulation of NEP expression is a promising target in therapies of NEP-implicating HOS cells. Moreover, this therapeutic goal can be achieved via AKG-induced downregulation of NEP and synergistic activity of AKG with thiorphan, i.e., a NEP specific inhibitor. Furthermore, this study has reported for the first time that exogenous AKG can influence the activity of histone methyltransferase, EZH2. However, this issue needs further investigation to elucidate the mechanisms of this phenomenon.

High plasma concentrations of acyl-coenzyme A binding protein (ACBP) predispose to cardiovascular disease: Evidence for a phylogenetically conserved proaging function of ACBP

Autophagy defects accelerate aging, while stimulation of autophagy decelerates aging. Acyl-coenzyme A binding protein (ACBP), which is encoded by a diazepam-binding inhibitor (DBI), acts as an extracellular feedback regulator of autophagy. As shown here, knockout of the gene coding for the yeast orthologue of ACBP/DBI (ACB1) improves chronological aging, and this effect is reversed by knockout of essential autophagy genes (ATG5, ATG7) but less so by knockout of an essential mitophagy gene (ATG32). In humans, ACBP/DBI levels independently correlate with body mass index (BMI) as well as with chronological age. In still-healthy individuals, we find that high ACBP/DBI levels correlate with future cardiovascular events (such as heart surgery, myocardial infarction, and stroke), an association that is independent of BMI and chronological age, suggesting that ACBP/DBI is indeed a biomarker of "biological" aging. Concurringly, ACBP/DBI plasma concentrations correlate with established cardiovascular risk factors (fasting glucose levels, systolic blood pressure, total free cholesterol, triglycerides), but are inversely correlated with atheroprotective high-density lipoprotein (HDL). In mice, neutralization of ACBP/DBI through a monoclonal antibody attenuates anthracycline-induced cardiotoxicity, which is a model of accelerated heart aging. In conclusion, plasma elevation of ACBP/DBI constitutes a novel biomarker of chronological aging and facets of biological aging with a prognostic value in cardiovascular disease.

Three Tiers to biological escape velocity: The quest to outwit aging

As longevity companies emerge with new products and the fields of anti-aging research develop new cutting-edge therapies, three distinct classes of longevity methodologies emerge. This discussion finds that there are three clear classes (Tiers) of longevity systems that are currently under development, and all three will be paramount to achieve biological escape velocity (where tissues can be repaired faster than aging can damage them). These classes are referred to as Tier 1, Tier 2, and Tier 3 treatments and are described in detail below. These three Tiers are required for easy identification for pharmaceutical companies and research companies to determine the type of therapy they may choose to deliver being noninvasive, invasive, time consuming, or simple end user products. Specific targets and goals need to be defined clearly from an early perspective in the development of these technologies for future precision medicines. This allows consumers of future anti-aging technologies to consider which Tier a particular therapy may be, delivering a more informed choice.

Early Systemic Glycolytic Shift After Aneurysmal Subarachnoid Hemorrhage is Associated with Functional Outcomes

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) leads to a robust systemic inflammatory response. We hypothesized that an early systemic glycolytic shift occurs after aSAH, resulting in a unique metabolic signature and affecting systemic inflammation.

METHODS

Control patients and patients with aSAH were analyzed. Samples from patients with aSAH were collected within 24 h of aneurysmal rupture. Mass spectrometry-based metabolomics was performed to assess relative abundance of 16 metabolites involved in the tricarboxylic acid cycle, glycolysis, and pentose phosphate pathway. Principal component analysis was used to segregate control patients from patients with aSAH. Dendrograms were developed to depict correlations between metabolites and cytokines. Analytic models predicting functional outcomes were developed, and receiver operating curves were compared.

RESULTS

A total of 122 patients with aSAH and 38 control patients were included. Patients with aSAH had higher levels of glycolytic metabolites (3-phosphoglycerate/2-phosphoglycerate, lactate) but lower levels of oxidative metabolites (succinate, malate, fumarate, and oxalate). Patients with higher clinical severity (Hunt-Hess Scale score ≥ 4) had higher levels of glyceraldehyde 3-phosphate and citrate but lower levels of α-ketoglutarate and glutamine. Principal component analysis readily segregated control patients from patients with aSAH. Correlation analysis revealed distinct clusters in control patients that were not observed in patients with aSAH. Higher levels of fumarate were associated with good functional outcomes at discharge (odds ratio [OR] 1.76, 95% confidence interval [CI] 1.15-2.82) in multivariable models, whereas higher levels of citrate were associated with poor functional outcomes at discharge (OR 0.36, 95% CI 0.16-0.73) and at 3 months (OR 0.35, 95% CI 0.14-0.81). No associations were found with delayed cerebral ischemia. Levels of α-ketoglutarate and glutamine correlated with lower levels of interleukin-8, whereas fumarate was associated with lower levels of tumor necrosis factor alpha.

CONCLUSIONS

Aneurysmal subarachnoid hemorrhage results in a unique pattern of plasma metabolites, indicating a shift toward glycolysis. Higher levels of fumarate and lower levels of citrate were associated with better functional outcomes. These metabolites may represent targets to improve metabolism after aSAH.

Nuclear Receptor NR1D1 Regulates Abdominal Aortic Aneurysm Development by Targeting the Mitochondrial Tricarboxylic Acid Cycle Enzyme Aconitase-2

BACKGROUND

Metabolic disorder increases the risk of abdominal aortic aneurysm (AAA). NRs (nuclear receptors) have been increasingly recognized as important regulators of cell metabolism. However, the role of NRs in AAA development remains largely unknown.

METHODS

We analyzed the expression profile of the NR superfamily in AAA tissues and identified NR1D1 (NR subfamily 1 group D member 1) as the most highly upregulated NR in AAA tissues. To examine the role of NR1D1 in AAA formation, we used vascular smooth muscle cell (VSMC)-specific, endothelial cell-specific, and myeloid cell-specific conditional Nr1d1 knockout mice in both AngII (angiotensin II)- and CaPO₄-induced AAA models.

RESULTS

Nr1d1 gene expression exhibited the highest fold change among all 49 NRs in AAA tissues, and NR1D1 protein was upregulated in both human and murine VSMCs from AAA tissues. The knockout of Nr1d1 in VSMCs but not endothelial cells and myeloid cells inhibited AAA formation in both AngII- and CaPO₄-induced AAA models. Mechanistic studies identified ACO2 (aconitase-2), a key enzyme of the mitochondrial tricarboxylic acid cycle, as a direct target trans-repressed by NR1D1 that mediated the regulatory effects of NR1D1 on mitochondrial metabolism. NR1D1 deficiency restored the ACO2 dysregulation and mitochondrial dysfunction at the early stage of AngII infusion before AAA formation. Supplementation with αKG (α-ketoglutarate, a downstream metabolite of ACO2) was beneficial in preventing and treating AAA in mice in a manner that required NR1D1 in VSMCs.

CONCLUSIONS

Our data define a previously unrecognized role of nuclear receptor NR1D1 in AAA pathogenesis and an undescribed NR1D1-ACO2 axis involved in regulating mitochondrial metabolism in VSMCs. It is important that our findings suggest αKG supplementation as an effective therapeutic approach for AAA treatment.

Mechanism of Mitochondrial Homeostasis Controlling Ovarian Physiology

Ovarian cells, including oocytes, granulosa/cumulus cells, theca cells, and stromal cells, contain abundant mitochondria, which play indispensable roles in the processes of ovarian follicle development. Ovarian function is closely controlled by mitochondrial proteostasis and mitostasis. While mitochondrial proteostasis and mitostasis are disturbed by several factors, leading to dysfunction of ovarian function and initiating the mitochondrial unfolded protein response (UPRmt) and mitophagy to maintain or recover ovarian function and mitochondrial function, clear interactions between the 2 pathways in the ovary have not been fully elucidated. Here, we comprehensively summarize the molecular networks or regulatory mechanisms behind further mitochondrial research in the ovary. This review provides novel insights into the interactions between the UPRmt and mitophagy in ovarian functions.

α-Ketoglutarate Restores Intestinal Barrier Function through Promoting Intestinal Stem Cells-Mediated Epithelial Regeneration in Colitis

This study investigated the preventive effects of α-ketoglutarate (α-KG, in the form of sodium salt) on a Citrobacter rodentium (CR)-induced colitis and explored potential mechanisms. The results demonstrated that CR caused body weight loss and colon length shortening, which were abrogated by the α-KG administration. The colon length of mice in the α-KG plus CR group was significantly higher than that of mice in the CR group (6.9 ± 0.59 (mean ± SD) vs 6.1 ± 0.55; P < 0.05). This beneficial effect was associated with regulating endoplasmic reticulum (ER) stress signaling. In addition, small intestinal organoids generated from intestinal crypts of mice were exposed to α-KG in the presence of TNF-α or IWR-1 to assess stem cell activity in vitro. The results demonstrated that TNF-α exposure decreased the viability of organoids and impaired barrier function by suppressing Wnt signaling, which was abolished by α-KG. Interestingly, the protective effect of α-KG on intestinal barrier function was abrogated by the inhibitor of Wnt signaling in the intestinal organoids. Taken together, α-KG restored barrier function by regulating ER stress and activating Wnt/β-catenin-medicated intestinal stem cell proliferation and differentiation.

mTOR/α-ketoglutarate-mediated signaling pathways in the context of brain neurodegeneration and neuroprotection

Cerebral disorders are largely associated with impaired cellular metabolism, despite the regulatory mechanisms designed to ensure cell viability and adequate brain function. Mechanistic target of rapamycin (mTOR) signaling is one of the most crucial factors in the regulation of energy homeostasis and its imbalance is linked with a variety of neurodegenerative diseases. Recent advances in the metabolic pathways' modulation indicate the role of α-ketoglutarate (AKG) as a major signaling hub, additionally highlighting its anti-aging and neuroprotective properties, but the mechanisms of its action are not entirely clear. In this review, we analyzed the physiological and pathophysiological aspects of mTOR in the brain. We also discussed AKG's multifunctional properties, as well as mTOR/AKG-mediated functional communications in cellular metabolism. Thus, this article provides a broad overview of the mTOR/AKG-mediated signaling pathways, in the context of neurodegeneration and endogenous neuroprotection, with the aim to find novel therapeutic strategies.

Response of circulating metabolites to an oral glucose challenge and risk of cardiovascular disease and mortality in the community

Background

New biomarkers to identify cardiovascular disease (CVD) risk earlier in its course are needed to enable targeted approaches for primordial prevention. We evaluated whether intraindividual changes in blood metabolites in response to an oral glucose tolerance test (OGTT) may provide incremental information regarding the risk of future CVD and mortality in the community.

Methods

An OGTT (75 g glucose) was administered to a subsample of Framingham Heart Study participants free from diabetes (n = 361). Profiling of 211 plasma metabolites was performed from blood samples drawn before and 2 h after OGTT. The log2(post/pre) metabolite levels (Δmetabolites) were related to incident CVD and mortality in Cox regression models adjusted for age, sex, baseline metabolite level, systolic blood pressure, hypertension treatment, body mass index, smoking, and total/high-density lipoprotein cholesterol. Select metabolites were related to subclinical cardiometabolic phenotypes using Spearman correlations adjusted for age, sex, and fasting metabolite level.

Results

Our sample included 42% women, with a mean age of 56 ± 9 years and a body mass index of 30.2 ± 5.3 kg/m². The pre- to post-OGTT changes (Δmetabolite) were non-zero for 168 metabolites (at FDR ≤ 5%). A total of 132 CVD events and 144 deaths occurred during median follow-up of 24.9 years. In Cox models adjusted for clinical risk factors, four Δmetabolites were associated with incident CVD (higher glutamate and deoxycholate, lower inosine and lysophosphatidylcholine 18:2) and six Δmetabolites (higher hydroxyphenylacetate, triacylglycerol 56:5, alpha-ketogluturate, and lower phosphatidylcholine 32:0, glucuronate, N-monomethyl-arginine) were associated with death (P < 0.05). Notably, baseline metabolite levels were not associated with either outcome in models excluding Δmetabolites. The Δmetabolites exhibited varying cross-sectional correlation with subclinical risk factors such as visceral adiposity, insulin resistance, and vascular stiffness, but overall relations were modest. Significant Δmetabolites included those with established roles in cardiometabolic disease (e.g., glutamate, alpha-ketoglutarate) and metabolites with less defined roles (e.g., glucuronate, lipid species).

Conclusions

Dynamic changes in metabolite levels with an OGTT are associated with incident CVD and mortality and have potential relevance for identifying CVD risk earlier in its development and for discovering new potential therapeutic targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01647-w.

A machine learning-based data mining in medical examination data: a biological features-based biological age prediction model

Background

Biological age (BA) has been recognized as a more accurate indicator of aging than chronological age (CA). However, the current limitations include: insufficient attention to the incompleteness of medical data for constructing BA; Lack of machine learning-based BA (ML-BA) on the Chinese population; Neglect of the influence of model overfitting degree on the stability of the association results.

Methods and results

Based on the medical examination data of the Chinese population (45–90 years), we first evaluated the most suitable missing interpolation method, then constructed 14 ML-BAs based on biomarkers, and finally explored the associations between ML-BAs and health statuses (healthy risk indicators and disease). We found that round-robin linear regression interpolation performed best, while AutoEncoder showed the highest interpolation stability. We further illustrated the potential overfitting problem in ML-BAs, which affected the stability of ML-Bas’ associations with health statuses. We then proposed a composite ML-BA based on the Stacking method with a simple meta-model (STK-BA), which overcame the overfitting problem, and associated more strongly with CA (r = 0.66, P < 0.001), healthy risk indicators, disease counts, and six types of disease.

Conclusion

We provided an improved aging measurement method for middle-aged and elderly groups in China, which can more stably capture aging characteristics other than CA, supporting the emerging application potential of machine learning in aging research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-022-04966-7.

The landscape of aging

Aging is characterized by a progressive deterioration of physiological integrity, leading to impaired functional ability and ultimately increased susceptibility to death. It is a major risk factor for chronic human diseases, including cardiovascular disease, diabetes, neurological degeneration, and cancer. Therefore, the growing emphasis on “healthy aging” raises a series of important questions in life and social sciences. In recent years, there has been unprecedented progress in aging research, particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes. In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases, we review the descriptive, conceptual, and interventive aspects of the landscape of aging composed of a number of layers at the cellular, tissue, organ, organ system, and organismal levels.

Serum metabolomics reveal pathways associated with protective effect of ginsenoside Rg3 on immune stress

Our previous study has demonstrated that administration of ginsenoside Rg3 ameliorates immune stress by inhibiting inflammatory responses, reducing oxidative damage and upregulating mRNA expression of mTOR, SOD-1, and HO-1. However, the specific mechanism in relation to the protective effect of ginsenoside Rg3 on stressed broilers especially the metabolites alteration remains obscure. The present study aimed to investigate the underlined mechanism in relation to the pathogenesis and protective effect of ginsenoside Rg3 on stressed broilers using liquid chromatograph-mass spectrometry profiling. Eighteen broiler chicks were randomly allocated to 3 treatments: Control, Model and Rg3. Chickens in Rg3 group received intraperitoneally administered 1 mg/kg Rg3 2 h before LPS challenge. Then the broilers were intraperitoneally injection of 250 µg/kg LPS at the age of 12, 14, 33, and 35 d to induce immune stress. Control group was injected with an equivalent amount of sterile saline. At the end of the experiment, the serum was obtained for metabolomics analysis. The changes in serum metabolic profiles were investigated with the application of metabolomics approach. Distinct changes in metabolite patterns in serum were observed by orthogonal partial least square-discriminate analysis. In total, 35 metabolites were identified, among which 17 differential metabolites were found between Control and Model group, and 18 differential metabolites were identified between Model and Rg3 group. Metabolic pathway analysis revealed potential serum metabolites involved in oxidative stress and inflammation, degradation of lipid and protein in broiler chicks with immune stress. In addition, the protective effect of Rg3 on the stressed chicks may be largely mediated by BCAA metabolism, apoptosis and mTOR signaling pathway. These results suggested the potential biomarkers involved in pathogenesis and prevention of stress induced by Escherichia coli lipopolysaccharide.

MOG analogues to explore the MCT2 pharmacophore, α-ketoglutarate biology and cellular effects of N-oxalylglycine

α-ketoglutarate (αKG) is a central metabolic node with a broad influence on cellular physiology. The αKG analogue N-oxalylglycine (NOG) and its membrane-permeable pro-drug derivative dimethyl-oxalylglycine (DMOG) have been extensively used as tools to study prolyl hydroxylases (PHDs) and other αKG-dependent processes. In cell culture media, DMOG is rapidly converted to MOG, which enters cells through monocarboxylate transporter MCT2, leading to intracellular NOG concentrations that are sufficiently high to inhibit glutaminolysis enzymes and cause cytotoxicity. Therefore, the degree of (D)MOG instability together with MCT2 expression levels determine the intracellular targets NOG engages with and, ultimately, its effects on cell viability. Here we designed and characterised a series of MOG analogues with the aims of improving compound stability and exploring the functional requirements for interaction with MCT2, a relatively understudied member of the SLC16 family. We report MOG analogues that maintain ability to enter cells via MCT2, and identify compounds that do not inhibit glutaminolysis or cause cytotoxicity but can still inhibit PHDs. We use these analogues to show that, under our experimental conditions, glutaminolysis-induced activation of mTORC1 can be uncoupled from PHD activity. Therefore, these new compounds can help deconvolute cellular effects that result from the polypharmacological action of NOG.

An aqueous extract of the brown alga Eisenia bicyclis extends lifespan in a sex-specific manner by interfering with the Tor-FoxO axis

Food has a decisive influence on our health, to the extent where even lifespan can be directly affected by it. In the present work, we have examined the effects of an aqueous extract of the marine brown alga Eisenia bicyclis in terms of its potential to extend lifespan. For this purpose, we used the fruit fly Drosophila melanogaster as a model. The experiments showed that small amounts of Eisenia extract can extend lifespan by up to 40%. This effect is not only related to the median but also to the maximum lifespan. Interestingly, this life-extending effect is sex-specific, i.e. it occurs exclusively in females. Even under stressful nutritional conditions such as a high sugar diet, this effect is detectable. Mechanistic studies showed that this life-prolonging effect depends on a functional Tor and a functional FoxO signaling pathway. It can be concluded that components of the Eisenia extract prolong lifespan by interacting with the Tor-FoxO axis. This study may serve to stimulate further investigations, which on the one hand show such a life-prolonging effect also in other organisms and on the other hand identify the substances responsible for this effect. Finally, it may also encourage the increased use of arame as a health-promoting food supplement.

An Epigenetic Role of Mitochondria in Cancer

Mitochondria are not only the main energy supplier but are also the cell metabolic center regulating multiple key metaborates that play pivotal roles in epigenetics regulation. These metabolites include acetyl-CoA, α-ketoglutarate (α-KG), S-adenosyl methionine (SAM), NAD⁺, and O-linked beta-N-acetylglucosamine (O-GlcNAc), which are the main substrates for DNA methylation and histone post-translation modifications, essential for gene transcriptional regulation and cell fate determination. Tumorigenesis is attributed to many factors, including gene mutations and tumor microenvironment. Mitochondria and epigenetics play essential roles in tumor initiation, evolution, metastasis, and recurrence. Targeting mitochondrial metabolism and epigenetics are promising therapeutic strategies for tumor treatment. In this review, we summarize the roles of mitochondria in key metabolites required for epigenetics modification and in cell fate regulation and discuss the current strategy in cancer therapies via targeting epigenetic modifiers and related enzymes in metabolic regulation. This review is an important contribution to the understanding of the current metabolic-epigenetic-tumorigenesis concept.

Metabolomics in rheumatoid arthritis: Advances and review

Rheumatoid arthritis (RA) is an autoimmune disease accompanied by metabolic alterations. The metabolic profiles of patients with RA can be determined using targeted and non-targeted metabolomics technology. Metabolic changes in glucose, lipid, and amino acid levels are involved in glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway, the arachidonic acid metabolic pathway, and amino acid metabolism. These alterations in metabolic pathways and metabolites can fulfill bio-energetic requirements, promote cell proliferation, drive inflammatory mediator secretion, mediate leukocyte infiltration, induce joint destruction and muscle atrophy, and regulate cell proliferation, which may reflect the etiologies of RA. Differential metabolites can be used as biomarkers for the diagnosis, prognosis, and risk prediction, improving the specificity and accuracy of diagnostics and prognosis prediction. Additionally, metabolic changes associated with therapeutic responses can improve the understanding of drug mechanism. Metabolic homeostasis and regulation are new therapeutic strategies for RA. In this review, we provide a comprehensive overview of advances in metabolomics for RA.

The road ahead of dietary restriction on anti-aging: focusing on personalized nutrition

Dietary restriction (DR), including caloric restriction (CR), intermittent fasting (IF), and restriction of specific food compositions, can delay aging, and the main mechanisms include regulation of nutrient-sensing pathways and gut microbiota. However, the effects of DR regimens on longevity remain controversial, as some studies have demonstrated that IF, rather than CR or diet composition, influences longevity, while other studies have shown that the restricted-carbohydrate or -protein diets, rather than CR, determine health and longevity. Many factors, including DR-related factors (carbohydrate or protein composition, degree and duration of DR), and individual differences (health status, sex, genotype, and age of starting DR), would be used to explain the controversial anti-aging effects of DR, thus highlighting the necessity of precise DR intervention for anti-aging. Personalized DR intervention in humans is challenging because of the lack of accurate aging molecular biomarkers and vast individual variability. Using machine learning to build a predictive model based on the data set of clinical features, gut microbiome and metabolome, may be a good method to achieve precise DR intervention. Therefore, this review analyzed the anti-aging effects of various DR regimens, summarized their mechanisms and influencing factors, and proposed a future research direction for achieving personalized DR regimens for slowing aging.

NADPH and Mitochondrial Quality Control as Targets for a Circadian-Based Fasting and Exercise Therapy for the Treatment of Parkinson's Disease

Dysfunctional mitochondrial quality control (MQC) is implicated in the pathogenesis of Parkinson's disease (PD). The improper selection of mitochondria for mitophagy increases reactive oxygen species (ROS) levels and lowers ATP levels. The downstream effects include oxidative damage, failure to maintain proteostasis and ion gradients, and decreased NAD⁺ and NADPH levels, resulting in insufficient energy metabolism and neurotransmitter synthesis. A ketosis-based metabolic therapy that increases the levels of (R)-3-hydroxybutyrate (BHB) may reverse the dysfunctional MQC by partially replacing glucose as an energy source, by stimulating mitophagy, and by decreasing inflammation. Fasting can potentially raise cytoplasmic NADPH levels by increasing the mitochondrial export and cytoplasmic metabolism of ketone body-derived citrate that increases flux through isocitrate dehydrogenase 1 (IDH1). NADPH is an essential cofactor for nitric oxide synthase, and the nitric oxide synthesized can diffuse into the mitochondrial matrix and react with electron transport chain-synthesized superoxide to form peroxynitrite. Excessive superoxide and peroxynitrite production can cause the opening of the mitochondrial permeability transition pore (mPTP) to depolarize the mitochondria and activate PINK1-dependent mitophagy. Both fasting and exercise increase ketogenesis and increase the cellular NAD⁺/NADH ratio, both of which are beneficial for neuronal metabolism. In addition, both fasting and exercise engage the adaptive cellular stress response signaling pathways that protect neurons against the oxidative and proteotoxic stress implicated in PD. Here, we discuss how intermittent fasting from the evening meal through to the next-day lunch together with morning exercise, when circadian NAD⁺/NADH is most oxidized, circadian NADP⁺/NADPH is most reduced, and circadian mitophagy gene expression is high, may slow the progression of PD.

GDH promotes isoprenaline-induced cardiac hypertrophy by activating mTOR signaling via elevation of α-ketoglutarate level

Numerous studies reveal that metabolism dysfunction contributes to the development of pathological cardiac hypertrophy. While the abnormal lipid and glucose utilization in cardiomyocytes responding to hypertrophic stimuli have been extensively studied, the alteration and implication of glutaminolysis are rarely discussed. In the present work, we provide the first evidence that glutamate dehydrogenase (GDH), an enzyme that catalyzes conversion of glutamate into ɑ-ketoglutarate (AKG), participates in isoprenaline (ISO)-induced cardiac hypertrophy through activating mammalian target of rapamycin (mTOR) signaling. The expression and activity of GDH were enhanced in cultured cardiomyocytes and rat hearts following ISO treatment. Overexpression of GDH, but not its enzymatically inactive mutant, provoked cardiac hypertrophy. In contrast, GDH knockdown could relieve ISO-triggered hypertrophic responses. The intracellular AKG level was elevated by ISO or GDH overexpression, which led to increased phosphorylation of mTOR and downstream effector ribosomal protein S6 kinase (S6K). Exogenous supplement of AKG also resulted in mTOR activation and cardiomyocyte hypertrophy. However, incubation with rapamycin, an mTOR inhibitor, attenuated hypertrophic responses in cardiomyocytes. Furthermore, GDH silencing protected rats from ISO-induced cardiac hypertrophy. These findings give a further insight into the role of GDH in cardiac hypertrophy and suggest it as a potential target for hypertrophy-related cardiomyopathy.

Non-alcoholic fatty liver disease-related fibrosis and sarcopenia: An altered liver-muscle crosstalk leading to increased mortality risk

In the last few decades, the loss of skeletal muscle mass and function, known as sarcopenia, has significantly increased in prevalence, becoming a major global public health concern. On the other hand, the prevalence of non-alcoholic fatty liver disease (NAFLD) has also reached pandemic proportions, constituting the leading cause of hepatic fibrosis worldwide. Remarkably, while sarcopenia and NAFLD-related fibrosis are independently associated with all-cause mortality, the combination of both conditions entails a greater risk for all-cause and cardiac-specific mortality. Interestingly, both sarcopenia and NAFLD-related fibrosis share common pathophysiological pathways, including insulin resistance, chronic inflammation, hyperammonemia, alterations in the regulation of myokines, sex hormones and growth hormone/insulin-like growth factor-1 signaling, which may explain reciprocal connections between these two disorders. Additional contributing factors, such as the gut microbiome, may also play a role in this relationship. In skeletal muscle, phosphatidylinositol 3-kinase/Akt and myostatin signaling are the central anabolic and catabolic pathways, respectively, and the imbalance between them can lead to muscle wasting in patients with NAFLD-related fibrosis. In this review, we summarize the bidirectional influence between NAFLD-related fibrosis and sarcopenia, highlighting the main potential mechanisms involved in this complex crosstalk, and we discuss the synergistic effects of both conditions in overall and cardiovascular mortality.

Frailty and cytokines in preclinical models: Comparisons with humans

Chronic low-grade elevations of blood-borne cytokines/chemokines in older age tend to associate with frailty in humans. This persistent inflammation is often called "inflammageing" and likely contributes to frailty progression. Preclinical models such as ageing and/or genetically modified mice offer a unique opportunity to mechanistically study how these inflammatory mediators affect frailty. In this review, we summarize and contrast evidence relating cytokines/chemokines to frailty in humans and in mouse models of frailty. In humans and mice, higher levels of the pro-inflammatory cytokine interleukin-6 regularly increased in proportion to the degree of frailty. Evidence linking other cytokines/chemokines to frailty in humans and mice is less certain. The chemokines CXCL-10 and monocyte chemoattractant protein-1 related to frailty across both species, but evidence is limited and inconsistent. Several other cytokines/chemokines, including tumour necrosis factor-α relate to frailty in humans or in mice, but evidence to date is species- and tissue-dependent. It is important for future studies to validate common mechanistic inflammatory biomarkers of frailty between humans and mice. Achieving this goal will accelerate the search for drugs to treat frailty.

The Use of Dietary Supplements and Amino Acid Restriction Interventions to Reduce Frailty in Pre-Clinical Models

Frailty is a state of accelerated aging that increases susceptibility to adverse health outcomes. Due to its high societal and personal costs, there is growing interest in discovering beneficial interventions to attenuate frailty. Many of these interventions involve the use of lifestyle modifications such as dietary supplements. Testing these interventions in pre-clinical models can facilitate our understanding of their impact on underlying mechanisms of frailty. We conducted a narrative review of studies that investigated the impact of dietary modifications on measures of frailty or overall health in rodent models. These interventions include vitamin supplements, dietary supplements, or amino acid restriction diets. We found that vitamins, amino acid restriction diets, and dietary supplements can have beneficial effects on frailty and other measures of overall health in rodent models. Mechanistic studies show that these effects are mediated by modifying one or more mechanisms underlying frailty, in particular effects on chronic inflammation. However, many interventions do not measure frailty directly and most do not investigate effects in both sexes, which limits their applicability. Examining dietary interventions in animal models allows for detailed investigation of underlying mechanisms involved in their beneficial effects. This may lead to more successful, translatable interventions to attenuate frailty.

Human age reversal: Fact or fiction?

Although chronological age correlates with various age‐related diseases and conditions, it does not adequately reflect an individual's functional capacity, well‐being, or mortality risk. In contrast, biological age provides information about overall health and indicates how rapidly or slowly a person is aging. Estimates of biological age are thought to be provided by aging clocks, which are computational models (e.g., elastic net) that use a set of inputs (e.g., DNA methylation sites) to make a prediction. In the past decade, aging clock studies have shown that several age‐related diseases, social variables, and mental health conditions associate with an increase in predicted biological age relative to chronological age. This phenomenon of age acceleration is linked to a higher risk of premature mortality. More recent research has demonstrated that predicted biological age is sensitive to specific interventions. Human trials have reported that caloric restriction, a plant‐based diet, lifestyle changes involving exercise, a drug regime including metformin, and vitamin D3 supplementation are all capable of slowing down or reversing an aging clock. Non‐interventional studies have connected high‐quality sleep, physical activity, a healthy diet, and other factors to age deceleration. Specific molecules have been associated with the reduction or reversal of predicted biological age, such as the antihypertensive drug doxazosin or the metabolite alpha‐ketoglutarate. Although rigorous clinical trials are needed to validate these initial findings, existing data suggest that aging clocks are malleable in humans. Additional research is warranted to better understand these computational models and the clinical significance of lowering or reversing their outputs.

Locally Delivered Metabolite Derivative Promotes Bone Regeneration in Aged Mice

Repair of large bone defects is still a major challenge, especially for the aged population. One alternative to address this issue is using the biomaterial-mediated bone morphogenetic protein 2 (BMP2) delivery technique, although high-dose BMP2 can cause serious concerns. α-Ketoglutarate (AKG) is a key intermediate in the tricarboxylic acid cycle and emerging as an intriguing antiaging molecule to extend the life/health span in different organisms. While one recent study indicates that the dietary AKG could significantly reduce bone loss and improve bone anabolism in aged mice, the therapeutic potential of AKG for bone regeneration has not been studied so far. Moreover, the poor cell permeability, large dose requirement, and long-term systemic administration of AKG hinder its applications in clinics and cellular mechanism studies. Dimethyl α-ketoglutarate (DMAKG) is a cell-permeable derivative of AKG with promising potential, although its role in osteogenesis is still elusive. Therefore, we aim to study the potential roles of DMAKG for bone regeneration using both in vitro cell culture and in vivo aged mouse models. Compared to AKG, our data indicated that DMAKG could more effectively improve osteoblastic differentiation. In addition, DMAKG significantly reduced adipogenic differentiation and improved osteogenic differentiation of a mouse multipotential mesenchymal stem cell line. Importantly, our result indicated that DMAKG significantly promoted BMP2-induced osteoblastic differentiation and mineralization in vitro. Moreover, DMAKG could not only significantly mitigate lipopolysaccharide (LPS)-stimulated inflammation in macrophages but also largely rescue LPS-inhibited osteoblastic differentiation. Consistently, our in vivo study demonstrated that gelatin scaffold-mediated local release of DMAKG significantly promoted BMP2-induced bone regeneration in aged mice, which is compromised by chronic inflammation and high adipogenesis. Overall, we, for the first time, report that locally delivered metabolite derivative, DMAKG, could improve BMP2-induced bone regeneration in aged mice. Our study suggests DMAKG has a promising therapeutic potential for bone regeneration through modulating local inflammation and stem cell differentiation.

Global stable-isotope tracing metabolomics reveals system-wide metabolic alternations in aging Drosophila

System-wide metabolic homeostasis is crucial for maintaining physiological functions of living organisms. Stable-isotope tracing metabolomics allows to unravel metabolic activity quantitatively by measuring the isotopically labeled metabolites, but has been largely restricted by coverage. Delineating system-wide metabolic homeostasis at the whole-organism level remains challenging. Here, we develop a global isotope tracing metabolomics technology to measure labeled metabolites with a metabolome-wide coverage. Using Drosophila as an aging model organism, we probe the in vivo tracing kinetics with quantitative information on labeling patterns, extents and rates on a metabolome-wide scale. We curate a system-wide metabolic network to characterize metabolic homeostasis and disclose a system-wide loss of metabolic coordinations that impacts both intra- and inter-tissue metabolic homeostasis significantly during Drosophila aging. Importantly, we reveal an unappreciated metabolic diversion from glycolysis to serine metabolism and purine metabolism as Drosophila aging. The developed technology facilitates a system-level understanding of metabolic regulation in living organisms.

Stable-isotope tracing allows quantifying metabolic activity by measuring isotopically labeled metabolites, but its metabolome coverage has been limited. Here, the authors develop a global isotope tracing approach with metabolome-wide coverage and use it to characterize metabolic activities in aging Drosophila.

The metabolome of Mexican cavefish shows a convergent signature highlighting sugar, antioxidant, and Ageing-Related metabolites

Insights from organisms, which have evolved natural strategies for promoting survivability under extreme environmental pressures, may help guide future research into novel approaches for enhancing human longevity. The cave-adapted Mexican tetra, Astyanax mexicanus, has attracted interest as a model system for metabolic resilience, a term we use to denote the property of maintaining health and longevity under conditions that would be highly deleterious in other organisms (Figure 1). Cave-dwelling populations of Mexican tetra exhibit elevated blood glucose, insulin resistance and hypertrophic visceral adipocytes compared to surface-dwelling counterparts. However, cavefish appear to avoid pathologies typically associated with these conditions, such as accumulation of advanced-glycation-end-products (AGEs) and chronic tissue inflammation. The metabolic strategies underlying the resilience properties of A. mexicanus cavefish, and how they relate to environmental challenges of the cave environment, are poorly understood. Here, we provide an untargeted metabolomics study of long- and short-term fasting in two A. mexicanus cave populations and one surface population. We find that, although the metabolome of cavefish bears many similarities with pathological conditions such as metabolic syndrome, cavefish also exhibit features not commonly associated with a pathological condition, and in some cases considered indicative of an overall robust metabolic condition. These include a reduction in cholesteryl esters and intermediates of protein glycation, and an increase in antioxidants and metabolites associated with hypoxia and longevity. This work suggests that certain metabolic features associated with human pathologies are either not intrinsically harmful, or can be counteracted by reciprocal adaptations. We provide a transparent pipeline for reproducing our analysis and a Shiny app for other researchers to explore and visualize our dataset.

Frailty in rodents: Models, underlying mechanisms, and management

Frailty is a clinical geriatric syndrome characterized by decreased multisystem function and increased vulnerability to adverse outcomes. Although numerous studies have been conducted on frailty, the underlying mechanisms and management strategies remain unclear. As rodents share homology with humans, they are used extensively as animal models to study human diseases. Rodent frailty models can be classified broadly into the genetic modification and non-genetic modification models, the latter of which include frailty assessment models (based on the Fried frailty phenotype and frailty index methods) and induced frailty models. Such models were developed for use in investigating frailty-related physiological changes at the gene, cellular, molecular, and system levels, including the organ system level. Furthermore, exercise, diet, and medication interventions, in addition to their combinations, could improve frailty status in rodents. Rodent frailty models provide novel and effective tools for frailty research. In the present paper, we review research progress in rodent frailty models, mechanisms, and management, which could facilitate and guide further clinical research on frailty in older adults.

Pharmaceutical and nutraceutical activation of FOXO3 for healthy longevity

Life expectancy has increased substantially over the last 150 years. Yet this means that now most people also spend a greater length of time suffering from various age-associated diseases. As such, delaying age-related functional decline and extending healthspan, the period of active older years free from disease and disability, is an overarching objective of current aging research. Geroprotectors, compounds that target pathways that causally influence aging, are increasingly recognized as a means to extend healthspan in the aging population. Meanwhile, FOXO3 has emerged as a geroprotective gene intricately involved in aging and healthspan. FOXO3 genetic variants are linked to human longevity, reduced disease risks, and even self-reported health. Therefore, identification of FOXO3-activating compounds represents one of the most direct candidate approaches to extending healthspan in aging humans. In this work, we review compounds that activate FOXO3, or influence healthspan or lifespan in a FOXO3-dependent manner. These compounds can be classified as pharmaceuticals, including PI3K/AKT inhibitors and AMPK activators, antidepressants and antipsychotics, muscle relaxants, and HDAC inhibitors, or as nutraceuticals, including primary metabolites involved in cell growth and sustenance, and secondary metabolites including extracts, polyphenols, terpenoids, and other purified natural compounds. The compounds documented here provide a basis and resource for further research and development, with the ultimate goal of promoting healthy longevity in humans.

Metabolomic Analysis Reveals Changes of Bioactive Compounds in Mung Beans (Vigna radiata) during γ-Aminobutyric Acid Enrichment Treatment

Soaking together with Heat and Relative Humidity (HRH) treatment has been applied successfully to enrich γ-aminobutyric acid (GABA) in mung beans. However, whether and how the above GABA enrichment processing influences the other bioactive molecules is elusive. In the present study, mung beans were soaked and then treated by HRH for 5 or 7 h. By using metabolomics techniques, the changes of 496 metabolites were determined. The relative content of flavonoids and phenolic acids increased during soaking but slightly decreased during HRH. Intriguingly, soaking and HRH had the opposite effects on the glycosylation of polyphenols. The relative content of glycosylated or un-glycosylated polyphenols increased during soaking or HRH, respectively. The relative content of α-ketoglutaric acid increased more than 20 times after 5 h HRH treatment. Bioactive molecules could be enriched during GABA enrichment processing. Depending on the desired bioactive compounds, soaking and different duration of HRH treatment could be selected.

AKG Attenuates Cerebral Ischemia-Reperfusion Injury through c-Fos/IL-10/Stat3 Signaling Pathway

Inflammation is dominant in the pathogenesis of ischemic stroke (IS). Alpha-ketoglutarate (AKG), according to previous studies, has demonstrated a variety of pharmacological effects such as antioxidation and inhibitive inflammation activities. However, whether AKG ameliorates cerebral ischemic injury, as well as the underlying molecular events, is still unclear. Therefore, the effect and underlying mechanisms of AKG on ischemic brain injury should be identified. The study established a cerebral ischemia-reperfusion (I/R) model in mice as well as an oxygen-glucose deprivation/reperfusion (OGD/R) model in SH-SY5Y cells, respectively. It was observed that AKG markedly suppressed infarction volume and neuronal injuries and improved the neurological score in vivo. Moreover, AKG reduced the inflammatory response and lowered the expression of proinflammatory cytokines. In vitro, AKG treatment strongly inhibited OGD/R-induced neuronal injury and the proinflammatory factors. It was also found that the increased SOD and GSH levels, as well as the lower ROS levels, showed that AKG reduced oxidative stress in OGD/R-treated SY-SY5Y cells. Mechanistically, AKG largely promoted IL-10 expression in ischemic brain injury and OGD/R-induced neuronal injury. Furthermore, IL-10 silencing neutralized the protective effect of AKG on inflammation. Notably, it was discovered that AKG could upregulate IL-10 expression by promoting the translocation of c-Fos from the cytoplasm to the nucleus. The results indicated that AKG demonstrated neuroprotection on cerebral ischemia while inhibiting inflammation through c-Fos/IL-10/stat3 pathway.

Antiaging agents: safe interventions to slow aging and healthy life span extension

Human longevity has increased dramatically during the past century. More than 20% of the 9 billion population of the world will exceed the age of 60 in 2050. Since the last three decades, some interventions and many preclinical studies have been found to show slowing aging and increasing the healthy lifespan of organisms from yeast, flies, rodents to nonhuman primates. The interventions are classified into two groups: lifestyle modifications and pharmacological/genetic manipulations. Some genetic pathways have been characterized to have a specific role in controlling aging and lifespan. Thus, all genes in the pathways are potential antiaging targets. Currently, many antiaging compounds target the calorie-restriction mimetic, autophagy induction, and putative enhancement of cell regeneration, epigenetic modulation of gene activity such as inhibition of histone deacetylases and DNA methyltransferases, are under development. It appears evident that the exploration of new targets for these antiaging agents based on biogerontological research provides an incredible opportunity for the healthcare and pharmaceutical industries. The present review focus on the properties of slow aging and healthy life span extension of natural products from various biological resources, endogenous substances, drugs, and synthetic compounds, as well as the mechanisms of targets for antiaging evaluation. These bioactive compounds that could benefit healthy aging and the potential role of life span extension are discussed.

Making sense of the ageing methylome

Over time, the human DNA methylation landscape accrues substantial damage, which has been associated with a broad range of age-related diseases, including cardiovascular disease and cancer. Various age-related DNA methylation changes have been described, including at the level of individual CpGs, such as differential and variable methylation, and at the level of the whole methylome, including entropy and correlation networks. Here, we review these changes in the ageing methylome as well as the statistical tools that can be used to quantify them. We detail the evidence linking DNA methylation to ageing phenotypes and the longevity strategies aimed at altering both DNA methylation patterns and machinery to extend healthspan and lifespan. Lastly, we discuss theories on the mechanistic causes of epigenetic ageing.

Non-oxidative pentose phosphate pathway controls regulatory T cell function by integrating metabolism and epigenetics

Regulatory T (T_reg) cells are critical for maintaining immune homeostasis and preventing autoimmunity. Here, we show that the non-oxidative pentose phosphate pathway (PPP) regulates T_reg function to prevent autoimmunity. Deletion of transketolase (TKT), an indispensable enzyme of non-oxidative PPP, in T_reg cells causes a fatal autoimmune disease in mice, with impaired T_reg suppressive capability despite regular T_reg numbers and normal Foxp3 expression levels. Mechanistically, reduced glycolysis and enhanced oxidative stress induced by TKT deficiency triggers excessive fatty acid and amino acid catabolism, resulting in uncontrolled oxidative phosphorylation and impaired mitochondrial fitness. Reduced α-KG levels as a result of reductive TCA cycle activity leads to DNA hypermethylation, thereby limiting functional gene expression and suppressive activity of TKT-deficient T_reg cells. We also find that TKT levels are frequently downregulated in T_reg cells of people with autoimmune disorders. Our study identifies the non-oxidative PPP as an integrator of metabolic and epigenetic processes that control T_reg function.

Alpha-Ketoglutarate Attenuates Colitis in Mice by Increasing Lactobacillus Abundance and Regulating Stem Cell Proliferation via Wnt-Hippo Signaling

SCOPE

Inflammatory bowel disease is an inflammatory gastrointestinal disorder associated with intestinal barrier damage, cell proliferation disorder, and dysbiosis of the intestinal microbiota. It remains unknown whether alpha-ketoglutarate (α-KG) can alleviate colitis in mice.

METHODS AND RESULTS

Six-week-old male C57BL/6 mice supplemented with or without 0.5% α-KG (delivered in the form of sodium salt) are subjected to drinking water or 2.5% DSS to induce colitis. The results show that α-KG administration is attenuated the severity of colitis, as is indicated by reduced body-weight loss, colon shortening and colonic hyperplasia, and repressed proinflammatory cytokine secretion in DSS-challenged mice. Additionally, DSS-induced increases in malondialdehyde (MDA) and hydrogen peroxide (H₂ O₂ ), and decreases in glutathione (GSH) levels are attenuated by α-KG administration. Further study shows that the protective effect of α-KG is associated with restoring gut barrier integrity by enhancing the expression of tight junction proteins, increasing Lactobacillus levels, and regulating gut hyperplasia by the Wnt-Hippo signaling pathway in DSS-induced colitis.

CONCLUSION

Collectively, the data provided herein demonstrate that α-KG administration is attenuated mucosal inflammation, barrier dysfunction, and gut microflora dysbiosis. This beneficial effect is associated with increased Lactobacillus levels and regulated colon hyperplasia by the Wnt-Hippo signaling pathway.

Nutrition, longevity and disease: From molecular mechanisms to interventions

Diet as a whole, encompassing food composition, calorie intake, and the length and frequency of fasting periods, affects the time span in which health and functional capacity are maintained. Here, we analyze aging and nutrition studies in simple organisms, rodents, monkeys, and humans to link longevity to conserved growth and metabolic pathways and outline their role in aging and age-related disease. We focus on feasible nutritional strategies shown to delay aging and/or prevent diseases through epidemiological, model organism, clinical, and centenarian studies and underline the need to avoid malnourishment and frailty. These findings are integrated to define a longevity diet based on a multi-pillar approach adjusted for age and health status to optimize lifespan and healthspan in humans.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD⁺ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

The metabolomic profiling identifies N, N-dimethylglycine as a facilitator of dorsal root ganglia neuron axon regeneration after injury

Identifying novel molecules involved in axon regeneration of neurons in the peripheral nervous system (PNS) will be of benefit in obtaining a therapeutic strategy for repairing axon damage both in the PNS and the central nervous system (CNS). Metabolism and axon regeneration are tightly connected. However, the overall metabolic processes and the landscape of the metabolites in axon regeneration of PNS neurons are uncovered. Here, we used an ultra high performance liquid tandem chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOFMS)-based untargeted metabolomics to analyze dorsal root ganglia (DRG) metabolic characteristics at different time points post sciatic nerve injury and acquired hundreds of differentially changed metabolites. In addition, the results reveal that several metabolic pathways were significantly altered, such as 'Histidine metabolism', 'Glycine serine and threonine metabolism', 'Arginine and proline metabolism', 'taurine and hypotaurine metabolism' and so on. Given metabolite could alter a cell's or an organism's phenotype, further investigation demonstrated that N, N-dimethylglycine (DMG) has a promoting effect on the regenerative ability post injury. Overall, our data may serve as a resource useful for further understanding how metabolites contribute to axon regeneration in DRG during sciatic nerve regeneration and suggest DMG may be a candidate drug to repair nerve injury.

MYC, mitochondrial metabolism and O-GlcNAcylation converge to modulate the activity and subcellular localization of DNA and RNA demethylases

Mitochondria can function as signaling organelles, and part of this output leads to epigenetic remodeling. The full extent of this far-reaching interplay remains undefined. Here, we show that MYC transcriptionally activates IDH2 and increases alpha-ketoglutarate (αKG) levels. This regulatory step induces the activity of αKG-dependent DNA hydroxylases and RNA demethylases, thus reducing global DNA and RNA methylation. MYC, in a IDH2-dependent manner, also promotes the nuclear accumulation of TET1-TET2-TET3, FTO and ALKBH5. Notably, this subcellular movement correlated with the ability of MYC, in an IDH2-dependent manner, and, unexpectedly, of αKG to directly induce O-GlcNAcylation. Concordantly, modulation of the activity of OGT and OGA, enzymes that control the cycling of this non-canonical mono-glycosylation, largely recapitulated the effects of the MYC-IDH2-αKG axis on the subcellular movement of DNA and RNA demethylases. Together, we uncovered a hitherto unsuspected crosstalk between MYC, αKG and O-GlcNAcylation which could influence the epigenome and epitranscriptome homeostasis.

Maintenance of glutamine synthetase expression alleviates endotoxin-induced sepsis via alpha-ketoglutarate-mediated demethylation

Glutamine synthetase (Glul) is the enzyme that synthesizes endogenous glutamine, which is responsible for critical metabolic pathways and the immune system. However, the role of Glul in regulating endotoxin (lipopolysaccharide, LPS)-induced sepsis remains unclear. Here, we found that Glul expression in macrophages was significantly inhibited in endotoxemia, and that Glul deletion induced macrophages to differentiate into the pro-inflammatory type and aggravated sepsis in mice. Mechanistically, TLR4/NF-κB-induced alpha-ketoglutarate (α-KG) depletion inhibits Glul expression through H3K27me3-mediated methylation in septic mice. Both Glul overexpression with adeno-associated virus (AAV) and restoration by replenishing α-KG can alleviate the severity of sepsis. In conclusion, the study demonstrated that Glul can regulate LPS-induced sepsis and provides a novel strategy for the treatment of this disease.

Potential clinical applications of alpha‑ketoglutaric acid in diseases (Review)

As an intermediate of the tricarboxylic acid cycle, also known as 2‑oxoglutarate, α‑ketoglutaric acid (AKG) plays an important role in maintaining physiological functions and cell metabolism. AKG is involved in both energy metabolism, and carbon and nitrogen metabolism; thus, exhibiting a variety of functions. Moreover, AKG plays an important role in various systems of the body. Results of previous research indicated that AKG may act as a regulator in the progression of a variety of diseases; thus, it exhibits potential as a novel drug for the clinical treatment of age‑related diseases. The present review aimed to summarize the latest research progress and potential clinical applications of AKG and provided novel directions and scope for future research.

Iron Supplementation Delays Aging and Extends Cellular Lifespan through Potentiation of Mitochondrial Function

Aging is the greatest challenge to humankind worldwide. Aging is associated with a progressive loss of physiological integrity due to a decline in cellular metabolism and functions. Such metabolic changes lead to age-related diseases, thereby compromising human health for the remaining life. Thus, there is an urgent need to identify geroprotectors that regulate metabolic functions to target the aging biological processes. Nutrients are the major regulator of metabolic activities to coordinate cell growth and development. Iron is an important nutrient involved in several biological functions, including metabolism. In this study using yeast as an aging model organism, we show that iron supplementation delays aging and increases the cellular lifespan. To determine how iron supplementation increases lifespan, we performed a gene expression analysis of mitochondria, the main cellular hub of iron utilization. Quantitative analysis of gene expression data reveals that iron supplementation upregulates the expression of the mitochondrial tricarboxylic acid (TCA) cycle and electron transport chain (ETC) genes. Furthermore, in agreement with the expression profiles of mitochondrial genes, ATP level is elevated by iron supplementation, which is required for increasing the cellular lifespan. To confirm, we tested the role of iron supplementation in the AMPK knockout mutant. AMPK is a highly conserved controller of mitochondrial metabolism and energy homeostasis. Remarkably, iron supplementation rescued the short lifespan of the AMPK knockout mutant and confirmed its anti-aging role through the enhancement of mitochondrial functions. Thus, our results suggest a potential therapeutic use of iron supplementation to delay aging and prolong healthspan.

Pleiotropic effects of mitochondria in aging

Aging is typified by a progressive decline in mitochondrial activity and stress resilience. Here, we review how mitochondrial stress pathways have pleiotropic effects on cellular and systemic homeostasis, which can comprise protective or detrimental responses during aging. We describe recent evidence arguing that defects in these conserved adaptive pathways contribute to aging and age-related diseases. Signaling pathways regulating the mitochondrial unfolded protein response, mitochondrial membrane dynamics, and mitophagy are discussed, emphasizing how their failure contributes to heteroplasmy and de-regulation of key metabolites. Our current understanding of how these processes are controlled and interconnected explains how mitochondria can widely impact fundamental aspects of aging.

The Endogenous Metabolite Glycerophosphocholine Promotes Longevity and Fitness in Caenorhabditis elegans

Metabolism and aging are closely connected. The choline derivative glycerophosphocholine (GPC), an important precursor of the neurotransmitter acetylcholine, plays important roles in brain and nervous system function. Although it has been reported to alleviate cognitive decline in aged mice, whether GPC could promote longevity and other fitness factors remains unclear. Here, we find endogenous GPC level declines in the plasma of ageing humans. In Caenorhabditis elegans (C. elegans), GPC extends lifespan and improves exercise capacity during aging. Likewise, GPC inhibits lipofuscin accumulation. We further show that GPC treatment has no adverse effect on nematodes’ reproductive abilities and body length. In addition to its benefits under normal conditions, GPC enhances the stress resistance of C. elegans. Mechanically, we find GPC significantly inhibits the reactive oxygen species (ROS) accumulation in worms. Our findings indicate the health benefits of GPC and its potential application in strategies to improve lifespan and healthspan.

Targeting whole body metabolism and mitochondrial bioenergetics in the drug development for Alzheimer's disease

Aging is by far the most prominent risk factor for Alzheimer's disease (AD), and both aging and AD are associated with apparent metabolic alterations. As developing effective therapeutic interventions to treat AD is clearly in urgent need, the impact of modulating whole-body and intracellular metabolism in preclinical models and in human patients, on disease pathogenesis, have been explored. There is also an increasing awareness of differential risk and potential targeting strategies related to biological sex, microbiome, and circadian regulation. As a major part of intracellular metabolism, mitochondrial bioenergetics, mitochondrial quality-control mechanisms, and mitochondria-linked inflammatory responses have been considered for AD therapeutic interventions. This review summarizes and highlights these efforts.

Alpha-Ketoglutarate dietary supplementation to improve health in humans

Alpha-ketoglutarate (AKG) is an intermediate in the Krebs cycle involved in various metabolic and cellular pathways. As an antioxidant, AKG interferes in nitrogen and ammonia balance, and affects epigenetic and immune regulation. These pleiotropic functions of AKG suggest it may also extend human healthspan. Recent studies in worms and mice support this concept. A few studies published in the 1980s and 1990s in humans suggested the potential benefits of AKG in muscle growth, wound healing, and in promoting faster recovery after surgery. So far there are no recently published studies demonstrating the role of AKG in treating aging and age-related diseases; hence, further clinical studies are required to better understand the role of AKG in humans. This review will discuss the regulatory role of AKG in aging, as well as its potential therapeutic use in humans to treat age-related diseases.