Metformin Enhances Autophagy and Normalizes Mitochondrial Function to Alleviate Aging-Associated Inflammation

Dysregulation of Systemic Immunity in Aging and Dementia

Neuroinflammation and the tissue-resident innate immune cells, the microglia, respond and contribute to neurodegenerative pathology. Although microglia have been the focus of work linking neuroinflammation and associated dementias like Alzheimer's Disease, the inflammatory milieu of brain is a conglomerate of cross-talk amongst microglia, systemic immune cells and soluble mediators like cytokines. Age-related changes in the inflammatory profile at the levels of both the brain and periphery are largely orchestrated by immune system cells. Strong evidence indicates that both innate and adaptive immune cells, the latter including T cells and B cells, contribute to chronic neuroinflammation and thus dementia. Neurodegenerative hallmarks coupled with more traditional immune system stimuli like infection or injury likely combine to trigger and maintain persistent microglial and thus brain inflammation. This review summarizes age-related changes in immune cell function, with special emphasis on lymphocytes as a source of inflammation, and discusses how such changes may potentiate both systemic and central nervous system inflammation to culminate in dementia. We recap the understudied area of AD-associated changes in systemic lymphocytes in greater detail to provide a unifying perspective of inflammation-fueled dementia, with an eye toward evidence of two-way communication between the brain parenchyma and blood immune cells. We focused our review on human subjects studies, adding key data from animal models as relevant.

Vascular Endothelial Senescence: Pathobiological Insights, Emerging Long Noncoding RNA Targets, Challenges and Therapeutic Opportunities

Cellular senescence is a stable form of cell cycle arrest in response to various stressors. While it serves as an endogenous pro-resolving mechanism, detrimental effects ensue when it is dysregulated. In this review, we introduce recent advances for cellular senescence and inflammaging, the underlying mechanisms for the reduction of nicotinamide adenine dinucleotide in tissues during aging, new knowledge learned from p16 reporter mice, and the development of machine learning algorithms in cellular senescence. We focus on pathobiological insights underlying cellular senescence of the vascular endothelium, a critical interface between blood and all tissues. Common causes and hallmarks of endothelial senescence are highlighted as well as recent advances in endothelial senescence. The regulation of cellular senescence involves multiple mechanistic layers involving chromatin, DNA, RNA, and protein levels. New targets are discussed including the roles of long noncoding RNAs in regulating endothelial cellular senescence. Emerging small molecules are highlighted that have anti-aging or anti-senescence effects in age-related diseases and impact homeostatic control of the vascular endothelium. Lastly, challenges and future directions are discussed including heterogeneity of endothelial cells and endothelial senescence, senescent markers and detection of senescent endothelial cells, evolutionary differences for immune surveillance in mice and humans, and long noncoding RNAs as therapeutic targets in attenuating cellular senescence. Accumulating studies indicate that cellular senescence is reversible. A better understanding of endothelial cellular senescence through lifestyle and pharmacological interventions holds promise to foster a new frontier in the management of cardiovascular disease risk.

The Link between Oxidative Stress, Redox Status, Bioenergetics and Mitochondria in the Pathophysiology of ALS

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease of the motor system. It is characterized by the degeneration of both upper and lower motor neurons, which leads to muscle weakness and paralysis. ALS is incurable and has a bleak prognosis, with median survival of 3-5 years after the initial symptomatology. In ALS, motor neurons gradually degenerate and die. Many features of mitochondrial dysfunction are manifested in neurodegenerative diseases, including ALS. Mitochondria have shown to be an early target in ALS pathophysiology and contribute to disease progression. Disruption of their axonal transport, excessive generation of reactive oxygen species, disruption of the mitochondrial structure, dynamics, mitophagy, energy production, calcium buffering and apoptotic triggering have all been directly involved in disease pathogenesis and extensively reported in ALS patients and animal model systems. Alterations in energy production by motor neurons, which severely limit their survival capacity, are tightly linked to the redox status and mitochondria. The present review focuses on this link. Placing oxidative stress as a main pathophysiological mechanism, the molecular interactions and metabolic flows involved are analyzed. This leads to discussing potential therapeutic approaches targeting mitochondrial biology to slow disease progression.

Immune cells in lens injury repair and fibrosis

Immune cells, both tissue resident immune cells and those immune cells recruited in response to wounding or degenerative conditions, are essential to both the maintenance and restoration of homeostasis in most tissues. These cells are typically provided to tissues by their closely associated vasculatures. However, the lens, like many of the tissues in the eye, are considered immune privileged sites because they have no associated vasculature. Such absence of immune cells was thought to protect the lens from inflammatory responses that would bring with them the danger of causing vision impairing opacities. However, it has now been shown, as occurs in other immune privileged sites in the eye, that novel pathways exist by which immune cells come to associate with the lens to protect it, maintain its homeostasis, and function in its regenerative repair. Here we review the discoveries that have revealed there are both innate and adaptive immune system responses to lens, and that, like most other tissues, the lens harbors a population of resident immune cells, which are the sentinels of danger or injury to a tissue. While resident and recruited immune cells are essential elements of lens homeostasis and repair, they also become the agents of disease, particularly as progenitors of pro-fibrogenic myofibroblasts. There still remains much to learn about the function of lens-associated immune cells in protection, repair and disease, the knowledge of which will provide new tools for maintaining the core functions of the lens in the visual system.

Metabolomic Profiling Demonstrates Postprandial Changes in Fatty Acids and Glycerophospholipids Are Associated with Fasting Inflammation in Guatemalan Adults

BACKGROUND

Metabolic flexibility is the responsiveness to heterogeneous physiological conditions, such as food ingestion. A key unresolved question is how inflammation affects metabolic flexibility.

OBJECTIVES

Our study objective was to compare metabolic flexibility, specifically the metabolomic response to a standardized meal, by fasting inflammation status.

METHODS

Participants in Guatemala (n = 302, median age 44 y, 43.7% men) received a standardized, mixed-macronutrient liquid meal. Plasma samples (fasting, 2 h postmeal) were assayed by dual-column LC [reverse phase (C18) and hydrophilic interaction LC (HILIC)] with ultra-high-resolution MS, for concentrations of 6 inflammation biomarkers: high-sensitivity C-reactive protein (hsCRP), leptin, resistin, IL-10, adiponectin, and soluble TNF receptor II (TNFsR). We summed the individual inflammation biomarker z-scores, after reverse-coding of anti-inflammation biomarkers. We identified features with peak areas that differed between fasting and postmeal (false discovery rate-adjusted q <0.05) and compared median log2 postprandial/fasting peak area ratios by inflammation indicators.

RESULTS

We found 1397 C18 and 974 HILIC features with significant postprandial/fasting feature ratios (q <0.05). Overall inflammation z-score was directly associated with the postprandial/fasting feature ratios of arachidic acid, and inversely associated with the feature ratio of lysophosphatidic acid (LPA), adjusting for age and sex (all P < 0.05). The postprandial/fasting ratio of arachidic acid was negatively correlated with resistin, IL-10, adiponectin, and TNFsR concentrations (all P < 0.05). Feature ratios of several fatty acids-myristic acid [m/z 227.2018, retention time (RT) 229], heptadecanoic acid (m/z 269.2491, RT 276), linoleic acid (m/z 280.2358, RT 236)-were negatively correlated with fasting plasma concentrations of leptin (nanograms per milliliter) and adiponectin (micrograms per milliliter), respectively (all P < 0.05). The postprandial/fasting ratio of LPA was positively correlated with IL-10 and adiponectin (both P < 0.05); and the ratio of phosphatidylinositol was positively correlated with hsCRP (P < 0.05).

CONCLUSIONS

Postprandial responses of fatty acids and glycerophospholipids are associated with fasting inflammation status in adults in Guatemala.

The role of T cells in age-related diseases

Age-related T cell dysfunction can lead to failure of immune tolerance mechanisms, resulting in aberrant T cell-driven cytokine and cytotoxic responses that ultimately cause tissue damage. In this Review, we discuss the role of T cells in the onset and progression of age-associated conditions, focusing on cardiovascular disorders, metabolic dysfunction, neuroinflammation and defective tissue repair and regeneration. We present different mechanisms by which T cells contribute to inflammageing and might act as modulators of age-associated diseases, including through enhanced pro-inflammatory and cytotoxic activity, defective clearance of senescent cells or regulation of the gut microbiota. Finally, we propose that 'resetting' immune system tolerance or targeting pathogenic T cells could open up new therapeutic opportunities to boost resilience to age-related diseases.

Diabetes induces macrophage dysfunction through cytoplasmic dsDNA/AIM2 associated pyroptosis

Diabetes is emerging as a severe global health problem that threatens health and increases socioeconomic burden. Periodontal impairment is one of its well-recognized complications. The destruction of the periodontal defense barrier makes it easier for periodontal pathogens to invade in, triggering a greater inflammatory response, and causing secondary impairment. Macrophages are the major immune cells in periodontium, forming the frontier line of local innate immune barrier. Here, we explored the periodontal impairments and functional changes of macrophages under the diabetic and aging conditions. Besides, we further explored the molecular mechanism of how hyperglycemia and aging contribute to this pathogenesis. To test this, we used young and aged mice to build diabetic mice, and metformin treatment was applied to a group of them. We demonstrated that under hyperglycemia conditions, macrophage functions, such as inflammatory cytokines secretion, phagocytosis, chemotaxis, and immune response, were disturbed. Simultaneously, this condition elevated the local senescent cell burden and induced secretion of senescence-associated secretory phenotype. Meanwhile, we found that expressions of Gasdermin D (GSDMD) and caspase-1 were up-regulated in diabetic conditions, suggesting that the local senescent burden and systemic proinflammatory state during diabetes were accompanied by the initiation of pyroptosis. Furthermore, we found that the changes in aged condition were similar to those in diabetes, suggesting a hyperglycemia-induced pre-aging state. In addition, we show that metformin treatment alleviated and remarkably reversed these functional abnormalities. Our data demonstrated that diabetes initiated macrophage pyroptosis, which further triggered macrophage function impairments and gingival destructions. This pathogenesis could be reversed by metformin.

Carbon monoxide alleviates senescence in diabetic nephropathy by improving autophagy

OBJECTIVES

Senescence, characterized by permanent cycle arrest, plays an important role in diabetic nephropathy (DN). However, the mechanism of renal senescence is still unclear, and the treatment targeting it remains to be further explored.

MATERIALS AND METHODS

The DN mice were induced by HFD and STZ, and 3 types of renal cells were treated with high glucose (HG) to establish in vitro model. Senescence-related and autophagy-related markers were detected by qRT-PCR and Western blot. Further, autophagy inhibitors and co-immunoprecipitation were used to clarify the mechanism of CO. Additionally, the specific relationship between autophagy and senescence was explored by immunofluorescence triple co-localization and ELISA.

RESULTS

We unravelled that senescence occurred in vivo and in vitro, which could be reversed by CO. Mechanistically, we demonstrated that CO inhibited the dysfunction of autophagy in DN mice partly through dissociating Beclin-1-Bcl-2 complex. Further results showed that autophagy inhibitors blocked the improvement of CO on senescence. In addition, the data revealed that autophagy regulated the degradation of senescence-related secretory phenotype (SASP) including Il-1β, Il-6, Tgf-β and Vegf.

CONCLUSIONS

These results suggested that CO protects DN mice from renal senescence and function loss via improving autophagy partly mediated by dissociating Beclin-1-Bcl-2 complex, which is possibly ascribed to the degradation of SASP. These findings bring new ideas for the prevention and treatment of DN and the regulation of senescence.

Augmentation of RBP4/STRA6 signaling leads to insulin resistance and inflammation and the plausible therapeutic role of vildagliptin and metformin

A role of Retinol Binding Protein-4 (RBP4) in insulin resistance is widely studied. However, there is paucity of information on its receptor viz., Stimulated by Retinoic Acid-6 (STRA6) with insulin resistance. To address this, we investigated the regulation of RBP4/STRA6 expression in 3T3-L1 adipocytes exposed to glucolipotoxicity (GLT) and in visceral adipose tissue (VAT) from high fat diet (HFD) fed insulin-resistant rats. 3T3-L1 adipocytes were subjected to GLT and other experimental maneuvers with and without vildagliptin or metformin. Real-time PCR and western-blot experiments were performed to analyze RBP4, STRA6, PPARγ gene and protein expression. Adipored staining and glucose uptake assay were performed to evaluate lipid and glucose metabolism. Oral glucose tolerance test (OGTT) and Insulin Tolerance Test (ITT) were performed to determine the extent of insulin resistance in HFD fed male Wistar rats. Total serum RBP4 was measured by quantitative sandwich enzyme-linked immunosorbent assay kit. Adipocytes under GLT exhibited significantly increased RBP4/STRA6 expressions and decreased insulin sensitivity/glucose uptake. Vildagliptin and metformin not only restored the above but also decreased the expression of IL-6, NFκB, SOCS-3 along with lipid accumulation. Furthermore, HFD fed rats exhibited significantly increased serum levels of RBP4 along with VAT expression of RBP4, STRA6, PPARγ, IL-6. These molecules were significantly altered by the vildagliptin/ metformin treatment. We conclude that RBP4/STRA6 pathway is primarily involved in mediating inflammation and insulin resistance in adipocytes and visceral adipose tissues under glucolipotoxicity and in insulin resistant rats.

Senescent T cells: a potential biomarker and target for cancer therapy

The failure of T cells to eradicate tumour cells in the tumour microenvironment is mainly due to the dysfunction of T cells. Senescent T cells, with defects in proliferation and effector functions, accumulate in ageing, chronic viral infections, and autoimmune disorders where antigen stimulation persists. Increasing evidence suggests that inducing T cell senescence is a key strategy used by malignant tumours to evade immune surveillance. In this review, we summarize the general features, functional regulation, and signalling network of senescent T cells in tumour development and highlight their potential as prognostic biomarkers in multiple cancer treatments, including chemotherapy, radiotherapy, and immunotherapy. Moreover, we discuss possible therapeutic strategies for preventing or rejuvenating senescence in tumour-specific T cells. Understanding these critical issues may provide novel strategies to enhance cancer immunotherapy.

Beneficial Effects of Metformin on the Central Nervous System, with a Focus on Epilepsy and Lafora Disease

Metformin is a drug in the family of biguanide compounds that is widely used in the treatment of type 2 diabetes (T2D). Interestingly, the therapeutic potential of metformin expands its prescribed use as an anti-diabetic drug. In this sense, it has been described that metformin administration has beneficial effects on different neurological conditions. In this work, we review the beneficial effects of this drug as a neuroprotective agent in different neurological diseases, with a special focus on epileptic disorders and Lafora disease, a particular type of progressive myoclonus epilepsy. In addition, we review the different proposed mechanisms of action of metformin to understand its function at the neurological level.

Hallmarks of T cell aging

The aged adaptive immune system is characterized by progressive dysfunction as well as increased autoimmunity. This decline is responsible for elevated susceptibility to infection and cancer, as well as decreased vaccination efficacy. Recent evidence indicates that CD4⁺ T cell-intrinsic alteratins contribute to chronic inflammation and are sufficient to accelerate an organism-wide aging phenotype, supporting the idea that T cell aging plays a major role in body-wide deterioration. In this Review, we propose ten molecular hallmarks to represent common denominators of T cell aging. These hallmarks are grouped into four primary hallmarks (thymic involution, mitochondrial dysfunction, genetic and epigenetic alterations, and loss of proteostasis) and four secondary hallmarks (reduction of the TCR repertoire, naive-memory imbalance, T cell senescence, and lack of effector plasticity), and together they explain the manifestation of the two integrative hallmarks (immunodeficiency and inflammaging). A major challenge now is weighing the relative impact of these hallmarks on T cell aging and understanding their interconnections, with the final goal of defining molecular targets for interventions in the aging process.

Cross talk between autophagy and oncogenic signaling pathways and implications for cancer therapy

Autophagy is a highly conserved metabolic process involved in the degradation of intracellular components including proteins and organelles. Consequently, it plays a critical role in recycling metabolic energy for the maintenance of cellular homeostasis in response to various stressors. In cancer, autophagy either suppresses or promotes cancer progression depending on the stage and cancer type. Epithelial-mesenchymal transition (EMT) and cancer metastasis are directly mediated by oncogenic signal proteins including SNAI1, SLUG, ZEB1/2, and NOTCH1, which are functionally correlated with autophagy. In this report, we discuss the crosstalk between oncogenic signaling pathways and autophagy followed by possible strategies for cancer treatment via regulation of autophagy. Although autophagy affects EMT and cancer metastasis, the overall signaling pathways connecting cancer progression and autophagy are still illusive. In general, autophagy plays a critical role in cancer cell survival by providing a minimum level of energy via self-digestion. Thus, cancer cells face nutrient limitations and challenges under stress during EMT and metastasis. Conversely, autophagy acts as a potential cancer suppressor by degrading oncogenic proteins, which are essential for cancer progression, and by removing damaged components such as mitochondria to enhance genomic stability. Therefore, autophagy activators or inhibitors represent possible cancer therapeutics. We further discuss the regulation of autophagy-dependent degradation of oncogenic proteins and its functional correlation with oncogenic signaling pathways, with potential applications in cancer therapy.

Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease associated with human aging. Ten percent of individuals over 65 years have AD and its prevalence continues to rise with increasing age. There are currently no effective disease modifying treatments for AD, resulting in increasingly large socioeconomic and personal costs. Increasing age is associated with an increase in low-grade chronic inflammation (inflammaging) that may contribute to the neurodegenerative process in AD. Although the exact mechanisms remain unclear, aberrant elevation of reactive oxygen and nitrogen species (RONS) levels from several endogenous and exogenous processes in the brain may not only affect cell signaling, but also trigger cellular senescence, inflammation, and pyroptosis. Moreover, a compromised immune privilege of the brain that allows the infiltration of peripheral immune cells and infectious agents may play a role. Additionally, meta-inflammation as well as gut microbiota dysbiosis may drive the neuroinflammatory process. Considering that inflammatory/immune pathways are dysregulated in parallel with cognitive dysfunction in AD, elucidating the relationship between the central nervous system and the immune system may facilitate the development of a safe and effective therapy for AD. We discuss some current ideas on processes in inflammaging that appear to drive the neurodegenerative process in AD and summarize details on a few immunomodulatory strategies being developed to selectively target the detrimental aspects of neuroinflammation without affecting defense mechanisms against pathogens and tissue damage.

Molecular mechanisms and cardiovascular implications of cancer therapy-induced senescence

Cancer treatment has been associated with accelerated aging that can lead to early-onset health complications typically experienced by older populations. In particular, cancer survivors have an increased risk of developing premature cardiovascular complications. In the last two decades, cellular senescence has been proposed as an important mechanism of premature cardiovascular diseases. Cancer treatments, specifically anthracyclines and radiation, have been shown to induce senescence in different types of cardiovascular cells. Additionally, clinical studies identified increased systemic markers of senescence in cancer survivors. Preclinical research has demonstrated the potential of several approaches to mitigate cancer therapy-induced senescence. However, strategies to prevent and/or treat therapy-induced cardiovascular senescence have not yet been translated to the clinic. In this review, we will discuss how therapy-induced senescence can contribute to cardiovascular complications. Thereafter, we will summarize the current in vitro, in vivo, and clinical evidence regarding cancer therapy-induced cardiovascular senescence. Then, we will discuss interventional strategies that have the potential to protect against therapy-induced cardiovascular senescence. To conclude, we will highlight challenges and future research directions to mitigate therapy-induced cardiovascular senescence in cancer survivors.

Is early life adversity a trigger towards inflammageing?

There are many 'faces' of early life adversity (ELA), such as childhood trauma, institutionalisation, abuse or exposure to environmental toxins. These have been implicated in the onset and severity of a wide range of chronic non-communicable diseases later in life. The later-life disease risk has a well-established immunological component. This raises the question as to whether accelerated immune-ageing mechanistically links early-life adversity to the lifelong health trajectory resulting in either 'poor' or 'healthy' ageing. Here we examine observational and mechanistic studies of ELA and inflammageing, highlighting common and distinct features in these two life stages. Many biological processes appear in common including reduction in telomere length, increased immunosenescence, metabolic distortions and chronic (viral) infections. We propose that ELA shapes the developing immune, endocrine and nervous system in a non-reversible way, creating a distinct phenotype with accelerated immunosenescence and systemic inflammation. We conclude that ELA might act as an accelerator for inflammageing and age-related diseases. Furthermore, we now have the tools and cohorts to be able to dissect the interaction between ELA and later life phenotype. This should, in the near future, allow us to identify the ecological and mechanistic processes that are involved in 'healthy' or accelerated immune-ageing.

A review of possible therapies for multiple sclerosis

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system with a wide range of symptoms, like executive function defect, cognitive dysfunction, blurred vision, decreased sensation, spasticity, fatigue, and other symptoms. This neurological disease is characterized by the destruction of the blood-brain barrier, loss of myelin, and damage to neurons. It is the result of immune cells crossing the blood-brain barrier into the central nervous system and attacking self-antigens. Heretofore, many treatments proved that they can retard the progression of the disease even though there is no cure. Therefore, treatments aimed at improving patients' quality of life and reducing adverse drug reactions and costs are essential. In this review, the treatment approaches to alleviate the progress of MS include the following: pharmacotherapy, antibody therapy, cell therapy, gene therapy, and surgery. The current treatment methods of MS are described in terms of the prevention of myelin shedding, the promotion of myelin regeneration, and the protection of neurons.

Metformin Modulates T Cell Function and Alleviates Liver Injury Through Bioenergetic Regulation in Viral Hepatitis

Metformin is not only the first-line medication for the treatment of type 2 diabetes, but it is also effective as an anti-inflammatory, anti-oxidative and anti-tumor agent. However, the effect of metformin during viral hepatitis remains elusive. Using an adenovirus (Ad)-induced viral hepatitis mouse model, we found that metformin treatment significantly attenuated liver injury, with reduced serum aspartate transaminase (AST) and alanine transaminase (ALT) levels and liver histological changes, presumably via decreased effector T cell responses. We then demonstrated that metformin reduced mTORC1 activity in T cells from infected mice, as evidenced by decreased phosphorylation of ribosome protein S6 (p-S6). The inhibitory effects on the mTORC1 signaling by metformin was dependent on the tuberous sclerosis complex 1 (TSC1). Mechanistically, metformin treatment modulated the phosphorylation of dynamin-related protein 1 (Drp-1) and mitochondrial fission 1 protein (FIS1), resulting in increased mass in effector T cells. Moreover, metformin treatment promoted mitochondrial superoxide production, which can inhibit excessive T cell activation in viral hepatitis. Together, our results revealed a protective role and therapeutic potential of metformin against liver injury in acute viral hepatitis via modulating effector T cell activation via regulating the mTORC1 pathway and mitochondrial functions.

G6PD deficiency, redox homeostasis, and viral infections: implications for SARS-CoV-2 (COVID-19)

The COVID-19 pandemic has so far affected more than 45 million people and has caused over 1 million deaths worldwide. Infection with SARS-CoV-2, the pathogenic agent, which is associated with an imbalanced redox status, causes hyperinflammation and a cytokine storm, leading to cell death. Glucose-6-phosphate dehydrogenase (G6PD) deficient individuals may experience a hemolytic crisis after being exposed to oxidants or infection. Individuals with G6PD deficiency are more susceptible to coronavirus infection than individuals with normally functioning G6PD. An altered immune response to viral infections is found in individuals with G6PD deficiency. Evidence indicates that G6PD deficiency is a predisposing factor of COVID-19.

Association Between Preadmission Metformin Use and Outcomes in Intensive Care Unit Patients With Sepsis and Type 2 Diabetes: A Cohort Study

Background: Sepsis is a deadly disease worldwide. Effective treatment strategy of sepsis remains limited. There still was a controversial about association between preadmission metformin use and mortality in sepsis patients with diabetes. We aimed to assess sepsis-related mortality in patients with type 2 diabetes (T2DM) who were preadmission metformin and non-metformin users.

Methods: The patients with sepsis and T2DM were included from Medical Information Mart for Intensive Care -III database. Outcome was 30-day mortality. We used multivariable Cox regression analyses to calculate adjusted hazard ratio (HR) with 95% CI.

Results: We included 2,383 sepsis patients with T2DM (476 and 1,907 patients were preadmission metformin and non-metformin uses) between 2001 and 2012. The overall 30-day mortality was 20.1% (480/2,383); it was 21.9% (418/1,907), and 13.0% (62/476) for non-metformin and metformin users, respectively. After adjusted for potential confounders, we found that preadmission metformin use was associated with 39% lower of 30-day mortality (HR = 0.61, 95% CI: 0.46–0.81, p = 0.007). In sensitivity analyses, subgroups analyses, and propensity score matching, the results remain stable.

Conclusions: Preadmission metformin use may be associated with reduced risk-adjusted mortality in patients with sepsis and T2DM. It is worthy to further investigate this association.

Targeting the Mitochondria-Proteostasis Axis to Delay Aging

Human life expectancy continues to grow globally, and so does the prevalence of age-related chronic diseases, causing a huge medical and economic burden on society. Effective therapeutic options for these disorders are scarce, and even if available, are typically limited to a single comorbidity in a multifaceted dysfunction that inevitably affects all organ systems. Thus, novel therapies that target fundamental processes of aging itself are desperately needed. In this article, we summarize current strategies that successfully delay aging and related diseases by targeting mitochondria and protein homeostasis. In particular, we focus on autophagy, as a fundamental proteostatic process that is intimately linked to mitochondrial quality control. We present genetic and pharmacological interventions that effectively extend health- and life-span by acting on specific mitochondrial and pro-autophagic molecular targets. In the end, we delve into the crosstalk between autophagy and mitochondria, in what we refer to as the mitochondria-proteostasis axis, and explore the prospect of targeting this crosstalk to harness maximal therapeutic potential of anti-aging interventions.

The intersection of metformin and inflammation

The biguanide metformin is the most commonly used antidiabetic drug. Recent studies show that metformin not only improves chronic inflammation by improving metabolic parameters but also has a direct anti-inflammatory effect. In light of these findings, it is essential to identify the inflammatory pathways targeted by metformin to develop a comprehensive understanding of the mechanisms of action of this drug. Commonly accepted mechanisms of metformin action include AMPK activation and inhibition of mTOR pathways, which are evaluated in multiple diseases. Additionally, metformin's action on mitochondrial function and cellular homeostasis processes such as autophagy is of particular interest because of the importance of these mechanisms in maintaining cellular health. Both dysregulated mitochondria and failure of the autophagy pathways, the latter of which impair clearance of dysfunctional, damaged, or excess organelles, affect cellular health drastically and can trigger the onset of metabolic and age-related diseases. Immune cells are the fundamental cell types that govern the health of an organism. Thus, dysregulation of autophagy or mitochondrial function in immune cells has a remarkable effect on susceptibility to infections, response to vaccination, tumor onset, and the development of inflammatory and autoimmune conditions. In this study, we summarize the latest research on metformin's regulation of immune cell mitochondrial function and autophagy as evidence that new clinical trials on metformin with primary outcomes related to the immune system should be considered to treat immune-mediated diseases over the near term.

Intersection of immunometabolism and immunosenescence during aging

Aging is associated with the highest risk for morbidity and mortality to chronic or metabolic diseases, which are present in 50% of the elderly. Improving metabolic and immune function of the elderly would improve quality of life and reduce the risk for all other diseases. Tissue-resident macrophages and the NLRP3 inflammasome are established drivers of inflammaging and metabolic dysfunction. Energy-sensing signaling pathways connect sterile and metabolic inflammation with cellular senescence and tissue dysfunction. We discuss recent advances in the immunometabolism field. Common themes revealed by recent publications include the alterations in metabolic signaling (SIRTUIN, AMPK, or mTOR pathways) in aged immune cells, the impact of senescence on inflammaging and tissue dysfunction, and the age-related changes in metabolic tissues, especially adipose tissue, as an immunological organ. Promising gerotherapeutics are candidates to broadly target nutrient and energy sensing, inflammatory and senescence pathways, and have potential to improve healthspan and treat age-related diseases.

Hyper-metabolic B cells in the spleens of old mice make antibodies with autoimmune specificities

BACKGROUND

Aging is associated with increased intrinsic B cell inflammation, decreased protective antibody responses and increased autoimmune antibody responses. The effects of aging on the metabolic phenotype of B cells and on the metabolic programs that lead to the secretion of protective versus autoimmune antibodies are not known.

METHODS

Splenic B cells and the major splenic B cell subsets, Follicular (FO) and Age-associated B cells (ABCs), were isolated from the spleens of young and old mice and left unstimulated. The RNA was collected to measure the expression of markers associated with intrinsic inflammation and autoimmune antibody production by qPCR. B cells and B cell subsets were also stimulated with CpG and supernatants collected after 7 days to measure autoimmune IgG secretion by ELISA. Metabolic measures (oxygen consumption rate, extracellular acidification rate and glucose uptake) were performed using a Seahorse XFp extracellular flux analyzer.

RESULTS

Results have identified the subset of ABCs, whose frequencies and numbers increase with age and represent the most pro-inflammatory B cell subset, as the cell type mainly if not exclusively responsible for the expression of inflammatory markers and for the secretion of autoimmune antibodies in the spleen of old mice. Hyper-inflammatory ABCs from old mice are also hyper-metabolic, as compared to those from young mice and to the subset of FO B cells, a feature needed not only to support their higher expression of RNA for inflammatory markers but also their higher autoimmune antibody secretion.

CONCLUSIONS

These results identify a relationship between intrinsic inflammation, metabolism and autoimmune B cells and suggest possible ways to understand cellular mechanisms that lead to the generation of pathogenic B cells, that are hyper-inflammatory and hyper-metabolic, and secrete IgG antibodies with autoimmune specificities.

Hallmarks and detection techniques of cellular senescence and cellular ageing in immune cells

The ageing of the global population brings about unprecedented challenges. Chronic age‐related diseases in an increasing number of people represent an enormous burden for health and social care. The immune system deteriorates during ageing and contributes to many of these age‐associated diseases due to its pivotal role in pathogen clearance, tissue homeostasis and maintenance. Moreover, in order to develop treatments for COVID‐19, we urgently need to acquire more knowledge about the aged immune system, as older adults are disproportionally and more severely affected. Changes with age lead to impaired responses to infections, malignancies and vaccination, and are accompanied by chronic, low‐degree inflammation, which together is termed immunosenescence. However, the molecular and cellular mechanisms that underlie immunosenescence, termed immune cell senescence, are mostly unknown. Cellular senescence, characterised by an irreversible cell cycle arrest, is thought to be the cause of tissue and organismal ageing. Thus, better understanding of cellular senescence in immune populations at single‐cell level may provide us with insight into how immune cell senescence develops over the life time of an individual. In this review, we will briefly introduce the phenotypic characterisation of aged innate and adaptive immune cells, which also contributes to overall immunosenescence, including subsets and function. Next, we will focus on the different hallmarks of cellular senescence and cellular ageing, and the detection techniques most suitable for immune cells. Applying these techniques will deepen our understanding of immune cell senescence and to discover potential druggable pathways, which can be modulated to reverse immune ageing.

Metformin treatment in late middle age improves cognitive function with alleviation of microglial activation and enhancement of autophagy in the hippocampus

Metformin, a drug widely used for treating diabetes, can prolong the lifespan in several species. Metformin also has the promise to slow down age‐related cognitive impairment. However, metformin's therapeutic use as an anti‐aging drug is yet to be accepted because of conflicting animal and human studies results. We examined the effects of metformin treatment in late middle age on cognitive function in old age. Eighteen‐month‐old male C57BL6/J mice received metformin or no treatment for 10 weeks. A series of behavioral tests revealed improved cognitive function in animals that received metformin. Such findings were evident from a better ability for pattern separation, object location, and recognition memory function. Quantification of microglia revealed that metformin treatment reduced the incidence of pathological microglial clusters with alternative activation of microglia into an M2 phenotype, displaying highly ramified processes in the hippocampus. Metformin treatment also seemed to reduce astrocyte hypertrophy. Additional analysis demonstrated that metformin treatment in late middle age increased adenosine monophosphate‐activated protein kinase activation, reduced proinflammatory cytokine levels, and the mammalian target of rapamycin signaling, and enhanced autophagy in the hippocampus. However, metformin treatment did not alter neurogenesis or synapses in the hippocampus, implying that improved cognitive function with metformin did not involve enhanced neurogenesis or neosynaptogenesis. The results provide new evidence that metformin treatment commencing in late middle age has promise for improving cognitive function in old age. Modulation of microglia, proinflammatory cytokines, and autophagy appear to be the mechanisms by which metformin facilitated functional benefits in the aged brain.

Metformin: A Novel Weapon Against Inflammation

It has become widely accepted that inflammation is a driving force behind a variety of chronic diseases, such as cardiovascular disease, diabetes, kidney disease, cancer, neurodegenerative disorders, etc. However, the existing nonsteroidal anti-inflammatory drugs show a limited utility in clinical patients. Therefore, the novel agents with different inflammation-inhibitory mechanisms are worth pursuing. Metformin, a synthetic derivative of guanidine, has a history of more than 50 years of clinical experience in treating patients with type 2 diabetes. Intense research efforts have been dedicated to proving metformin’s inflammation-inhibitory effects in cells, animal models, patient records, and randomized clinical trials. The emerging evidence also indicates its therapeutic potential in clinical domains other than type 2 diabetes. Herein, this article appraises current pre-clinical and clinical findings, emphasizing metformin’s anti-inflammatory properties under individual pathophysiological scenarios. In summary, the anti-inflammatory effects of metformin are evident in pre-clinical models. By comparison, there are still clinical perplexities to be addressed in repurposing metformin to inflammation-driven chronic diseases. Future randomized controlled trials, incorporating better stratification/targeting, would establish metformin’s utility in this clinical setting.

Cellular and Molecular Mechanisms of Metformin Action

Metformin is a first-line therapy for the treatment of type 2 diabetes, due to its robust glucose-lowering effects, well-established safety profile, and relatively low cost. While metformin has been shown to have pleotropic effects on glucose metabolism, there is a general consensus that the major glucose-lowering effect in patients with type 2 diabetes is mostly mediated through inhibition of hepatic gluconeogenesis. However, despite decades of research, the mechanism by which metformin inhibits this process is still highly debated. A key reason for these discrepant effects is likely due to the inconsistency in dosage of metformin across studies. Widely studied mechanisms of action, such as complex I inhibition leading to AMPK activation, have only been observed in the context of supra-pharmacological (>1 mM) metformin concentrations, which do not occur in the clinical setting. Thus, these mechanisms have been challenged in recent years and new mechanisms have been proposed. Based on the observation that metformin alters cellular redox balance, a redox-dependent mechanism of action has been described by several groups. Recent studies have shown that clinically relevant (50-100 μM) concentrations of metformin inhibit hepatic gluconeogenesis in a substrate-selective manner both in vitro and in vivo, supporting a redox-dependent mechanism of metformin action. Here, we review the current literature regarding metformin's cellular and molecular mechanisms of action.

Short-term metformin ingestion by healthy older adults improves myoblast function

Muscle progenitor cells (MPCs) in aged muscle exhibit impaired activation into proliferating myoblasts, thereby impairing fusion and changes in secreted factors. The antihyperglycemic drug metformin, currently studied as a candidate antiaging therapy, may have potential to promote function of aged MPCs. We evaluated the impact of 2 wk of metformin ingestion on primary myoblast function measured in vitro after being extracted from muscle biopsies of older adult participants. MPCs were isolated from muscle biopsies of community-dwelling older (4 male/4 female, ∼69 yr) adult participants before (pre) and after (post) the metformin ingestion period and studied in vitro. Cells were extracted from Young participants (4 male/4 female, ∼27 yr) to serve as a "youthful" comparator. MPCs from Old subjects had lower fusion index and myoblast-endothelial cell homing compared with Young, while Old MPCs, extracted after short-term metformin ingestion, performed better at both tasks. Transcriptomic analyses of Old MPCs (vs. Young) revealed decreased histone expression and increased myogenic pathway activity, yet this phenotype was partially restored by metformin. However, metformin ingestion exacerbated pathways related to inflammation signaling. Together, this study demonstrated that 2 wk of metformin ingestion induced persistent effects on Old MPCs that improved function in vitro and altered their transcriptional signature including histone and chromatin remodeling.

Association of Preadmission Metformin Use and Prognosis in Patients With Sepsis and Diabetes Mellitus: A Systematic Review and Meta-Analysis

BACKGROUND AND AIM

A growing body of evidence suggests that preadmission metformin use could decrease the mortality of septic patients with diabetes mellitus (DM); however, the findings remain controversial. Therefore, this meta-analysis was conducted on available studies to confirm the relationship between preadmission metformin use and mortality in patients with sepsis and DM.

METHODS

A comprehensive search of the PubMed, Embase, and Cochrane Library databases was performed for studies published before August 8, 2021. Observational studies assessing the correlation between metformin use and mortality in patients with sepsis and DM were considered eligible studies. We used the Newcastle-Ottawa Scale (NOS) to assess the outcome quality of each included article. Furthermore, the odds ratios (ORs) and 95% confidence intervals (CIs) were analyzed using the inverse variance method with random effects modeling.

RESULTS

Eleven articles including 8195 patients were analyzed in this meta-analysis. All the included articles were scored as low risk of bias. Our results showed that preadmission metformin use had a lower mortality rate (OR, 0.74; 95% CIs, 0.62-0.88, P < 0.01) in patients with sepsis and DM. Surprisingly, there was no statistically significant difference in the levels of serum creatinine (weighted mean difference (WMD), 0.36; 95% CIs, -0.03-0.75; P = 0.84) and lactic acid (WMD, -0.16; 95% CIs, -0.49-0.18; P = 0.07) between preadmission metformin use and non-metformin use.

CONCLUSIONS

This study is the most comprehensive meta-analysis at present, which shows that preadmission metformin use may reduce mortality and not increase the levels of serum creatinine and lactic acid in adult patients with sepsis and DM. Therefore, these data suggest that the potential efficacy of metformin could be assessed in future clinical studies.

SYSTEMATIC REVIEW REGISTRATION

https://inplasy.com/?s=INPLASY2021100113, identifier INPLASY2021100113.

Metformin and Malignant Tumors: Not Over the Hill

Malignant tumors are a major cause of death, and their incidence is increasing worldwide. Although the survival rate for some cancers has improved, treatments for other malignant tumors are limited, and their mortality rate continues to increase. People with type 2 diabetes have a higher risk of malignant tumors and a higher mortality rate than those without diabetes. Metformin is a commonly used hypoglycemic drug. In recent years, a growing number of studies have indicated that metformin has antitumor effects and increases the sensitivity of malignant tumors to chemotherapy. However, the effect of metformin on different tumors is currently controversial, and the mechanism of metformin's antitumor action is not fully understood. Insights into the effect of metformin on malignant tumors and the possible mechanism may contribute to the development of antitumor drugs.

Thymus involution sets the clock of the aging T-cell landscape: Implications for declined immunity and tissue repair

Aging is generally characterized as a gradual increase in tissue damage, which is associated with senescence and chronic systemic inflammation and is evident in a variety of age-related diseases. The extent to which such tissue damage is a result of a gradual decline in immune regulation, which consequently compromises the capacity of the body to repair damages, has not been fully explored. Whereas CD4 T lymphocytes play a critical role in the orchestration of immunity, thymus involution initiates gradual changes in the CD4 T-cell landscape, which may significantly compromise tissue repair. In this review, we describe the lifespan accumulation of specific dysregulated CD4 T-cell subsets and their coevolution with systemic inflammation in the process of declined immunity and tissue repair capacity with age. Then, we discuss the process of thymus involution-which appears to be most pronounced around puberty-as a possible driver of the aging T-cell landscape. Finally, we identify individualized T cell-based early diagnostic biomarkers and therapeutic strategies for age-related diseases.

Effect of metformin on stem cells: Molecular mechanism and clinical prospect

Metformin is a first-line medication for type II diabetes. Numerous studies have shown that metformin not only has hypoglycemic effects, but also modulates many physiological and pathological processes ranging from aging and cancer to fracture healing. During these different physiological activities and pathological changes, stem cells usually play a core role. Thus, many studies have investigated the effects of metformin on stem cells. Metformin affects cell differentiation and has promising applications in stem cell medicine. It exerts anti-aging effects and can be applied to gerontology and regenerative medicine. The potential anti-cancer stem cell effect of metformin indicates that it can be an adjuvant therapy for cancers. Furthermore, metformin has beneficial effects against many other diseases including cardiovascular and autoimmune diseases. In this review, we summarize the effects of metformin on stem cells and provide an overview of its molecular mechanisms and clinical prospects.

Association between metformin use on admission and outcomes in intensive care unit patients with acute kidney injury and type 2 diabetes: A retrospective cohort study

PURPOSE

Acute kidney injury (AKI) occurs in more than half of intensive care unit patients. Effective prevention and treatment strategies for AKI remain limited. We aimed to assess AKI-related mortality in patients with diabetes who were metformin and non-metformin users.

MATERIALS AND METHODS

We included patients with AKI and type 2 diabetes (T2DM) from the Medical Information Mart for Intensive Care database. The 30-day mortality, neutrophil-to-lymphocyte ratio, and length of hospital stay were compared between patients with and without metformin prescriptions. We used multivariable Cox proportional hazards regression, propensity score analysis, and an inverse probability-weighting model to ensure the robustness of our findings.

RESULTS

We included 4328 patients with AKI and T2DM (998 and 3330 patients were metformin and non-metformin users, respectively). The overall 30-day mortality was 14.2% (613/4328); it was 15.7% (523/3330) and 9.0% (90/998) for non-metformin and metformin users, respectively. In the inverse probability-weighting model, metformin use was associated with 37% lower 30-day mortality (HR = 0.63, 95% CI: 0.50-0.80, p < 0.0001).

CONCLUSIONS

Metformin use may be associated with reduced risk-adjusted mortality in patients with AKI and T2DM. Further randomized controlled trials are needed to clarify this association.

Can Blood-Circulating Factors Unveil and Delay Your Biological Aging?

According to the World Health Organization, the population of over 60 will double in the next 30 years in the developed countries, which will enforce a further raise of the retirement age and increase the burden on the healthcare system. Therefore, there is an acute issue of maintaining health and prolonging active working longevity, as well as implementation of early monitoring and prevention of premature aging and age-related disorders to avoid early disability. Traditional indicators of biological age are not always informative and often require extensive and expensive analysis. The study of blood factors is a simple and easily accessible way to assess individual health and supplement the traditional indicators of a person's biological age with new objective criteria. With age, the processes of growth and development, tissue regeneration and repair decline; they are gradually replaced by enhanced catabolism, inflammatory cell activity, and insulin resistance. The number of senescent cells supporting the inflammatory loop rises; cellular clearance by autophagy and mitophagy slows down, resulting in mitochondrial and cellular damage and dysfunction. Monitoring of circulated blood factors not only reflects these processes, but also allows suggesting medical intervention to prevent or decelerate the development of age-related diseases. We review the age-related blood factors discussed in recent publications, as well as approaches to slowing aging for healthy and active longevity.

COVID-19: A Challenge to Physiology of Aging

The death toll of the current COVID-19 pandemic is strongly biased toward the elderly. COVID-19 case fatality rate (CFR) increases with age exponentially, its doubling time being about 7 years, irrespective of countries and epidemic stages. The same age-dependent mortality pattern known as the Gompertz law is featured by the total mortality and its main constituents attributed to cardiovascular, metabolic, neurological, and oncological diseases. Among patients dying of COVID-19, most have at least one of these conditions, whereas none is found in most of those who pass it successfully. Thus, gerontology is indispensable in dealing with the pandemic, which becomes a benchmark for validating the gerontological concepts and advances. The two basic alternative gerontological concepts imply that either aging results from the accumulation of stochastic damage, or is programmed. Based on these different grounds, several putative anti-aging drugs have been proposed as adjuvant means for COVID-19 prevention and/or treatment. These proposals are reviewed in the context of attributing the molecular targets of these drugs to the signaling pathways between the sensors of resource availability and the molecular mechanisms that allocate resources to storage, growth and reproduction or to self-maintenance and repair. Each of the drugs appears to reproduce only a part of the physiological responses to reduced resource availability caused by either dietary calories restriction or physical activity promotion, which are the most robust means of mitigating the adverse manifestations of aging. In the pathophysiological terms, the conditions of the endothelium, which worsen as age increases and may be significantly improved by the physical activity, is a common limiting factor for the abilities to withstand both physical stresses and challenges imposed by COVID-19. However, the current anti-epidemic measures promote sedentary indoor lifestyles, at odds with the most efficient behavioral interventions known to decrease the vulnerability to both the severe forms of COVID-19 and the prevalent aging-associated diseases. To achieve a proper balance in public health approaches to COVID-19, gerontologists should be involved in crosstalk between virologists, therapists, epidemiologists, and policy makers. The present publication suggests a conceptual background for that.

Fate of Hematopoiesis During Aging. What Do We Really Know, and What are its Implications?

There is an ongoing shift in demographics such that older persons will outnumber young persons in the coming years, and with it age-associated tissue attrition and increased diseases and disorders. There has been increased information on the association of the aging process with dysregulation of hematopoietic stem (HSC) and progenitor (HPC) cells, and hematopoiesis. This review provides an extensive up-to date summary on the literature of aged hematopoiesis and HSCs placed in context of potential artifacts of the collection and processing procedure, that may not be totally representative of the status of HSCs in their in vivo bone marrow microenvironment, and what the implications of this are for understanding aged hematopoiesis. This review covers a number of interactive areas, many of which have not been adequately explored. There are still many unknowns and mechanistic insights to be elucidated to better understand effects of aging on the hematopoietic system, efforts that will take multidisciplinary approaches, and that could lead to means to ameliorate at least some of the dysregulation of HSCs and HPCs associated with the aging process. Graphical Abstract.

Innate and Adaptive Immunity in Aging and Longevity: The Foundation of Resilience

The interrelation of the processes of immunity and senescence now receives an unprecedented emphasis during the COVID-19 pandemic, which brings to the fore the critical need to combat immunosenescence and improve the immune function and resilience of older persons. Here we review the historical origins and the current state of the science of innate and adaptive immunity in aging and longevity. From the modern point of view, innate and adaptive immunity are not only affected by aging but also are important parts of its underlying mechanisms. Excessive levels or activity of antimicrobial peptides, C-reactive protein, complement system, TLR/NF-κB, cGAS/STING/IFN 1,3 and AGEs/RAGE pathways, myeloid cells and NLRP3 inflammasome, declined levels of NK cells in innate immunity, thymus involution and decreased amount of naive T-cells in adaptive immunity, are biomarkers of aging and predisposition factors for cellular senescence and aging-related pathologies. Long-living species, human centenarians, and women are characterized by less inflamm-aging and decelerated immunosenescence. Despite recent progress in understanding, the harmonious theory of immunosenescence is still developing. Geroprotectors targeting these mechanisms are just emerging and are comprehensively discussed in this article.

Age-related mitochondrial dysfunction as a key factor in COVID-19 disease

SARS-CoV-2 causes a severe pneumonia (COVID-19) that affects essentially elderly people. In COVID-19, macrophage infiltration into the lung causes a rapid and intense cytokine storm leading finally to a multi-organ failure and death. Comorbidities such as metabolic syndrome, obesity, type 2 diabetes, lung and cardiovascular diseases, all of them age-associated diseases, increase the severity and lethality of COVID-19. Mitochondrial dysfunction is one of the hallmarks of aging and COVID-19 risk factors. Dysfunctional mitochondria is associated with defective immunological response to viral infections and chronic inflammation. This review discuss how mitochondrial dysfunction is associated with defective immune response in aging and different age-related diseases, and with many of the comorbidities associated with poor prognosis in the progression of COVID-19. We suggest here that chronic inflammation caused by mitochondrial dysfunction is responsible of the explosive release of inflammatory cytokines causing severe pneumonia, multi-organ failure and finally death in COVID-19 patients. Preventive treatments based on therapies improving mitochondrial turnover, dynamics and activity would be essential to protect against COVID-19 severity.

Targeting Senescent Cells for a Healthier Aging: Challenges and Opportunities

Aging is a physiological decline in both structural homeostasis and functional integrity, progressively affecting organismal health. A major hallmark of aging is the accumulation of senescent cells, which have entered a state of irreversible cell cycle arrest after experiencing inherent or environmental stresses. Although cellular senescence is essential in several physiological events, it plays a detrimental role in a large array of age-related pathologies. Recent biomedical advances in specifically targeting senescent cells to improve healthy aging, or alternatively, postpone natural aging and age-related diseases, a strategy termed senotherapy, have attracted substantial interest in both scientific and medical communities. Challenges for aging research are highlighted and potential avenues that can be leveraged for therapeutic interventions to control aging and age-related disorders in the current era of precision medicine.

Integrating the Hallmarks of Aging Throughout the Tree of Life: A Focus on Mitochondrial Dysfunction

Since the identification and definition of the hallmarks of aging, these aspects of molecular and cellular decline have been most often described as isolated or distinct mechanisms. However, there is significant evidence demonstrating interplay between most of these hallmarks and that they have the capacity to influence and regulate one another. These interactions are demonstrable across the tree of life, yet not all aspects are conserved. Here, we describe an integrative view on the hallmarks of aging by using the hallmark "mitochondrial dysfunction" as a focus point, and illustrate its capacity to both influence and be influenced by the other hallmarks of aging. We discuss the effects of mitochondrial pathways involved in aging, such as oxidative phosphorylation, mitochondrial dynamics, mitochondrial protein synthesis, mitophagy, reactive oxygen species and mitochondrial DNA damage in relation to each of the primary, antagonistic and integrative hallmarks. We discuss the similarities and differences in these interactions throughout the tree of life, and speculate how speciation may play a role in the variation in these mechanisms. We propose that the hallmarks are critically intertwined, and that mapping the full extent of these interactions would be of significant benefit to the aging research community.

PGC-1α-Targeted Therapeutic Approaches to Enhance Muscle Recovery in Aging

Impaired muscle recovery (size and strength) following a disuse period commonly occurs in older adults. Many of these individuals are not able to adequately exercise due to pain and logistic barriers. Thus, nutritional and pharmacological therapeutics, that are translatable, are needed to promote muscle recovery following disuse in older individuals. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) may be a suitable therapeutic target due to pleiotropic regulation of skeletal muscle. This review focuses on nutritional and pharmacological interventions that target PGC-1α and related Sirtuin 1 (SIRT1) and 5' AMP-activated protein kinase (AMPKα) signaling in muscle and thus may be rapidly translated to prevent muscle disuse atrophy and promote recovery. In this review, we present several therapeutics that target PGC-1α in skeletal muscle such as leucine, β-hydroxy-β-methylbuyrate (HMB), arginine, resveratrol, metformin and combination therapies that may have future application to conditions of disuse and recovery in humans.

The effects of age and systemic metabolism on anti-tumor T cell responses

Average age and obesity prevalence are increasing globally. Both aging and obesity are characterized by profound systemic metabolic and immunologic changes and are cancer risk factors. The mechanisms linking age and body weight to cancer are incompletely understood, but recent studies have provided evidence that the anti-tumor immune response is reduced in both conditions, while responsiveness to immune checkpoint blockade, a form of cancer immunotherapy, is paradoxically intact. Dietary restriction, which promotes health and lifespan, may enhance cancer immunity. These findings illustrate that the systemic context can impact anti-tumor immunity and immunotherapy responsiveness. Here, we review the current knowledge of how age and systemic metabolic state affect the anti-tumor immune response, with an emphasis on CD8+ T cells, which are key players in anti-tumor immunity. A better understanding of the underlying mechanisms may lead to novel therapies enhancing anti-tumor immunity in the context of aging or metabolic dysfunction.

Loss of metabolic plasticity underlies metformin toxicity in aged Caenorhabditis elegans

Current clinical trials are testing the life-extending benefits of the diabetes drug metformin in healthy individuals without diabetes. However, the metabolic response of a non-diabetic cohort to metformin treatment has not been studied. Here, we show in C. elegans and human primary cells that metformin shortens lifespan when provided in late life, contrary to its positive effects in young organisms. We find that metformin exacerbates ageing-associated mitochondrial dysfunction, causing respiratory failure. Age-related failure to induce glycolysis and activate the dietary-restriction-like mobilization of lipid reserves in response to metformin result in lethal ATP exhaustion in metformin-treated aged worms and late-passage human cells, which can be rescued by ectopic stabilization of cellular ATP content. Metformin toxicity is alleviated in worms harbouring disruptions in insulin-receptor signalling, which show enhanced resilience to mitochondrial distortions at old age. Together, our data show that metformin induces deleterious changes of conserved metabolic pathways in late life, which could bring into question its benefits for older individuals without diabetes.

The Impact of Aging in Acute Respiratory Distress Syndrome: A Clinical and Mechanistic Overview

Acute respiratory distress syndrome (ARDS) is associated with increased morbidity and mortality in the elderly population (≥65 years of age). Additionally, age is widely reported as a risk factor for the development of ARDS. However, the underlying pathophysiological mechanisms behind the increased risk of developing, and increased severity of, ARDS in the elderly population are not fully understood. This is compounded by the significant heterogeneity observed in patients with ARDS. With an aging population worldwide, a better understanding of these mechanisms could facilitate the development of therapies to improve outcomes in this population. In this review, the current clinical evidence of age as a risk factor and prognostic indicator in ARDS and the potential underlying mechanisms that may contribute to these factors are outlined. In addition, research on age-dependent treatment options and biomarkers, as well as future prospects for targeting these underlying mechanisms, are discussed.

Mitochondria: In the Cross Fire of SARS-CoV-2 and Immunity

The pathophysiology, immune reaction, and differential vulnerability of different population groups and viral host immune system evasion strategies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are not yet well understood. Here, we reviewed the multitude of known strategies of coronaviruses and other viruses to usurp mitochondria-associated mechanisms involved in the host innate immune response and put them in context with the current knowledge on SARS-CoV-2. We argue that maintenance of mitochondrial integrity is essential for adequate innate immune system responses and to blunt mitochondrial modulation by SARS-CoV-2. Mitochondrial health thus may determine differential vulnerabilities to SARS-CoV-2 infection rendering markers of mitochondrial functions promising potential biomarkers for SARS-CoV-2 infection risk and severity of outcome. Current knowledge gaps on our understanding of mitochondrial involvement in SARS-CoV-2 infection, lifestyle, and pharmacological strategies to improve mitochondrial integrity and potential reciprocal interactions with chronic and age-related diseases, e.g., Parkinson disease, are pointed out.

Metformin enhances anti-mycobacterial responses by educating CD8+ T-cell immunometabolic circuits

Patients with type 2 diabetes (T2D) have a lower risk of Mycobacterium tuberculosis infection, progression from infection to tuberculosis (TB) disease, TB morality and TB recurrence, when being treated with metformin. However, a detailed mechanistic understanding of these protective effects is lacking. Here, we use mass cytometry to show that metformin treatment expands a population of memory-like antigen-inexperienced CD8+CXCR3+ T cells in naive mice, and in healthy individuals and patients with T2D. Metformin-educated CD8+ T cells have increased (i) mitochondrial mass, oxidative phosphorylation, and fatty acid oxidation; (ii) survival capacity; and (iii) anti-mycobacterial properties. CD8+ T cells from Cxcr3-/- mice do not exhibit this metformin-mediated metabolic programming. In BCG-vaccinated mice and guinea pigs, metformin enhances immunogenicity and protective efficacy against M. tuberculosis challenge. Collectively, these results demonstrate an important function of CD8+ T cells in metformin-derived host metabolic-fitness towards M. tuberculosis infection.

HIV-1 Infection and Glucose Metabolism Reprogramming of T Cells: Another Approach Toward Functional Cure and Reservoir Eradication

With the emerging of highly active antiretroviral therapy, HIV-1 infection has transferred from a fatal threat to a chronic disease that could be managed. Nevertheless, inextricable systemic immune activation and chronic inflammation despite viral suppression render patients still at higher risk of HIV-1-associated non-AIDS complications. Immunometabolism has nowadays raised more and more attention for that targeting metabolism may become a promising approach to modulate immune system and play a role in treating cancer, HIV-1 infection and autoimmune diseases. HIV-1 mainly infects CD4+ T cells and accumulating evidence has brought to light the association between T cell metabolism reprogramming and HIV-1 pathogenesis. Here, we will focus on the interplay of glycometabolism reprogramming of T cells and HIV-1 infection, making an effort to delineate the possibility of utilizing immunometabolism as a new target towards HIV-1 management and even sterilizing cure through eliminating viral reservoir.