Pancreatic beta cell senescence contributes to the pathogenesis of type 2 diabetes in high-fat diet-induced diabetic mice

Single cell multiome profiling of pancreatic islets reveals physiological changes in cell type-specific regulation associated with diabetes risk

Physiological variability in pancreatic cell type gene regulation and the impact on diabetes risk is poorly understood. In this study we mapped gene regulation in pancreatic cell types using single cell multiomic (joint RNA-seq and ATAC-seq) profiling in 28 non-diabetic donors in combination with single cell data from 35 non-diabetic donors in the Human Pancreas Analysis Program. We identified widespread associations with age, sex, BMI, and HbA1c, where gene regulatory responses were highly cell type- and phenotype-specific. In beta cells, donor age associated with hypoxia, apoptosis, unfolded protein response, and external signal-dependent transcriptional regulators, while HbA1c associated with inflammatory responses and gender with chromatin organization. We identified 10.8K loci where genetic variants were QTLs for cis regulatory element (cRE) accessibility, including 20% with lineage- or cell type-specific effects which disrupted distinct transcription factor motifs. Type 2 diabetes and glycemic trait associated variants were enriched in both phenotype- and QTL-associated beta cell cREs, whereas type 1 diabetes showed limited enrichment. Variants at 226 diabetes and glycemic trait loci were QTLs in beta and other cell types, including 40 that were statistically colocalized, and annotating target genes of colocalized QTLs revealed genes with putatively novel roles in disease. Our findings reveal diverse responses of pancreatic cell types to phenotype and genotype in physiology, and identify pathways, networks, and genes through which physiology impacts diabetes risk.

Sex-dependent intra-islet structural rearrangements affecting alpha-to-beta cell interactions lead to adaptive enhancements of Ca2+ dynamics in prediabetic beta cells

AIMS/HYPOTHESIS

Prediabetic pancreatic beta cells can adapt their function to maintain normoglycaemia for a limited period of time, after which diabetes mellitus will manifest upon beta cell exhaustion. Understanding sex-specific beta cell compensatory mechanisms and their failure in prediabetes (impaired glucose tolerance) is crucial for early disease diagnosis and individualised treatment. Our aims were as follows: (1) to determine the key time points of the progression from beta cells' functional adaptations to their failure in vivo; and (2) to mechanistically explain in vivo sex-specific beta cell compensatory mechanisms and their failure in prediabetes.

METHODS

Islets from male and female transgenic Ins1CreERT2-GCaMP3 mice were transplanted into the anterior chamber of the eye of 10- to 12-week-old sex-matched C57BL/6J mice. Recipient mice were fed either a control diet (CD) or western diet (WD) for a maximum of 4 months. Metabolic variables were evaluated monthly. Beta cell cytoplasmic free calcium concentration ([Ca2+]i) dynamics were monitored in vivo longitudinally by image fluorescence of the GCaMP3 reporter islets. Global islet beta cell [Ca2+]i dynamics in line with single beta cell [Ca2+]i analysis were used for beta cell coordination studies. The glucagon receptor antagonist L-168,049 (4 mmol/l) was applied topically to the transplanted eyes to evaluate in vivo the effect of glucagon on beta cell [Ca2+]idynamics. Human islets from non-diabetic women and men were cultured for 24 h in either a control medium or high-fat/high-glucose medium in the presence or absence of the glucagon receptor antagonist L-168,049. [Ca2+]i dynamics of human islets were evaluated in vitro after 1 h exposure to Fura-10.

RESULTS

Mice fed a WD for 1 month displayed increased beta cell [Ca2+]i dynamics linked to enhanced insulin secretion as a functional compensatory mechanism in prediabetes. Recruitment of inactive beta cells in WD-fed mice explained the improved beta cell function adaptation observed in vivo; this occurred in a sex-specific manner. Mechanistically, this was attributable to an intra-islet structural rearrangement involving alpha cells. These sex-dependent cytoarchitecture reorganisations, observed in both mice and humans, induced enhanced paracrine input from adjacent alpha cells, adjusting the glucose setpoint and amplifying the insulin secretion pathway. When WD feeding was prolonged, female mice maintained the adaptive mechanism due to their intrinsically high proportion of alpha cells. In males, [Ca2+]i dynamics progressively declined subsequent to glucose stimulation while insulin secretion continue to increase, suggesting uncoordinated beta cell function as an early sign of diabetes.

CONCLUSIONS/INTERPRETATION

We identified increased coordination of [Ca2+]i dynamics as a beta cell functional adaptation mechanisms in prediabetes. Importantly, we uncovered the mechanisms by which sex-dependent beta cell [Ca2+]i dynamics coordination is orchestrated by an intra-islet structure reorganisation increasing the paracrine input from alpha cells on beta cell function. Moreover, we identified reduced [Ca2+]i dynamics coordination in response to glucose as an early sign of diabetes preceding beta cell secretory dysfunction, with males being more vulnerable. Alterations in coordination capacity of [Ca2+]i dynamics may thus serve as an early marker for beta cell failure in prediabetes.

Application potential of senolytics in clinical treatment

Of the factors studied in individual ageing, the accumulation of senescent cells has been considered as an essential cause of organ degeneration to eventually initiate age-related diseases. Cellular senescence is attributed to the accumulation of damage for an inducement in the activation of cell cycle inhibitory pathways, resulting the cell permanently withdraw from the cell proliferation cycle. Further, senescent cells will activate the inflammatory factor secretion pathway to promote the development of various age-related diseases. Senolytics, a small molecule compound, can delay disease development and extend mammalian lifespan. The evidence from multiple trials shows that the targeted killing of senescent cells has a significant clinical application for the treatment of age-related diseases. In addition, senolytics are also significant for the development of ageing research in solid organ transplantation, which can fully develop the potential of elderly organs and reduce the age gap between demand and supply. We conclude that the main characteristics of cellular senescence, the anti-ageing drug senolytics in the treatment of chronic diseases and organ transplantation, and the latest clinical progress of related researches in order to provide a theoretical basis for the prevention and treatment of ageing and related diseases.

Senescent Macrophages Release Inflammatory Cytokines and RNA-Loaded Extracellular Vesicles to Circumvent Fibroblast Senescence

Senescent cells, which accumulate with age, exhibit a pro-inflammatory senescence-associated secretory phenotype (SASP) that includes the secretion of cytokines, lipids, and extracellular vesicles (EVs). Here, we established an in vitro model of senescence induced by Raf-1 oncogene in RAW 264.7 murine macrophages (MΦ) and compared them to senescent MΦ found in mouse lung tumors or primary macrophages treated with hydrogen peroxide. The transcriptomic analysis of senescent MΦ revealed an important inflammatory signature regulated by NFkB. We observed an increased secretion of EVs in senescent MΦ, and these EVs presented an enrichment for ribosomal proteins, major vault protein, pro-inflammatory miRNAs, including miR-21a, miR-155, and miR-132, and several mRNAs. The secretion of senescent MΦ allowed senescent murine embryonic fibroblasts to restart cell proliferation. This antisenescence function of the macrophage secretome may explain their pro-tumorigenic activity and suggest that senolytic treatment to eliminate senescent MΦ could potentially prevent these deleterious effects.

Characterization of cell cycle, inflammation, and oxidative stress signaling role in non-communicable diseases: Insights into genetic variants, microRNAs and pathways

Non-Communicable Diseases (NCDs) significantly impact global health, contributing to over 70% of premature deaths, as reported by the World Health Organization (WHO). These diseases have complex and multifactorial origins, involving genetic, epigenetic, environmental and lifestyle factors. While Genome-Wide Association Study (GWAS) is widely recognized as a valuable tool for identifying variants associated with complex phenotypes; the multifactorial nature of NCDs necessitates a more comprehensive exploration, encompassing not only the genetic but also the epigenetic aspect. For this purpose, we employed a bioinformatics-multiomics approach to examine the genetic and epigenetic characteristics of NCDs (i.e. colorectal cancer, coronary atherosclerosis, squamous cell lung cancer, psoriasis, type 2 diabetes, and multiple sclerosis), aiming to identify novel biomarkers for diagnosis and prognosis. Leveraging GWAS summary statistics, we pinpointed Single Nucleotide Polymorphisms (SNPs) independently associated with each NCD. Subsequently, we identified genes linked to cell cycle, inflammation and oxidative stress mechanisms, revealing shared genes across multiple diseases, suggesting common functional pathways. From an epigenetic perspective, we identified microRNAs (miRNAs) with regulatory functions targeting these genes of interest. Our findings underscore critical genetic pathways implicated in these diseases. In colorectal cancer, the dysregulation of the "Cytokine Signaling in Immune System" pathway, involving LAMA5 and SMAD7, regulated by Hsa-miR-21-5p, Hsa-miR-103a-3p, and Hsa-miR-195-5p, emerged as pivotal. In coronary atherosclerosis, the pathway associated with "binding of TCF/LEF:CTNNB1 to target gene promoters" displayed noteworthy implications, with the MYC factor controlled by Hsa-miR-16-5p as a potential regulatory factor. Squamous cell lung carcinoma analysis revealed significant pathways such as "PTK6 promotes HIF1A stabilization," regulated by Hsa-let-7b-5p. In psoriasis, the "Endosomal/Vacuolar pathway," involving HLA-C and Hsa-miR-148a-3p and Hsa-miR-148b-3p, was identified as crucial. Type 2 Diabetes implicated the "Regulation of TP53 Expression" pathway, controlled by Hsa-miR-106a-5p and Hsa-miR-106b-5p. In conclusion, our study elucidates the genetic framework and molecular mechanisms underlying NCDs, offering crucial insights into potential genetic/epigenetic biomarkers for diagnosis and prognosis. The specificity of pathways and related miRNAs in different pathologies highlights promising candidates for further clinical validation, with the potential to advance personalized treatments and alleviate the global burden of NCDs.

Revolutionizing Diabetic Foot Ulcer Care: The Senotherapeutic Approach

Diabetic foot ulcers (DFUs) are a prevalent and profoundly debilitating complication that afflicts individuals with diabetes mellitus (DM). These ulcers are associated with substantial morbidity, recurrence rates, disability, and mortality, imposing substantial economic, psychological, and medical burdens. Timely detection and intervention can mitigate the morbidity and disparities linked to DFU. Nevertheless, current therapeutic approaches for DFU continue to grapple with multifaceted limitations. A growing body of evidence emphasizes the crucial role of cellular senescence in the pathogenesis of chronic wounds. Interventions that try to delay cellular senescence, eliminate senescent cells (SnCs), or suppress the senescence-associated secretory phenotype (SASP) have shown promise for helping chronic wounds to heal. In this context, targeting cellular senescence emerges as a novel therapeutic strategy for DFU. In this comprehensive review, we look at the pathology and treatment of DFU in a systematic way. We also explain the growing importance of investigating SnCs in DFU and highlight the great potential of senotherapeutics that target SnCs in DFU treatment. The development of efficacious and safe senotherapeutics represents a pioneering therapeutic approach aimed at enhancing the quality of life for individuals affected by DFU.

Lifestyle interventions to delay senescence

Senescence is a condition of cell cycle arrest that increases inflammation and contributes to the development of chronic diseases in the aging human body. While several compounds described as senolytics and senomorphics produce health benefits by reducing the burden of senescence, less attention has been devoted to lifestyle interventions that produce similar effects. We describe here the effects of exercise, nutrition, caloric restriction, intermittent fasting, phytochemicals from natural products, prebiotics and probiotics, and adequate sleep on senescence in model organisms and humans. These interventions can be integrated within a healthy lifestyle to reduce senescence and inflammation and delay the consequences of aging.

Accelerated Aging Induced by an Unhealthy High-Fat Diet: Initial Evidence for the Role of Nrf2 Deficiency and Impaired Stress Resilience in Cellular Senescence

High-fat diets (HFDs) have pervaded modern dietary habits, characterized by their excessive saturated fat content and low nutritional value. Epidemiological studies have compellingly linked HFD consumption to obesity and the development of type 2 diabetes mellitus. Moreover, the synergistic interplay of HFD, obesity, and diabetes expedites the aging process and prematurely fosters age-related diseases. However, the underlying mechanisms driving these associations remain enigmatic. One of the most conspicuous hallmarks of aging is the accumulation of highly inflammatory senescent cells, with mounting evidence implicating increased cellular senescence in the pathogenesis of age-related diseases. Our hypothesis posits that HFD consumption amplifies senescence burden across multiple organs. To scrutinize this hypothesis, we subjected mice to a 6-month HFD regimen, assessing senescence biomarker expression in the liver, white adipose tissue, and the brain. Aging is intrinsically linked to impaired cellular stress resilience, driven by dysfunction in Nrf2-mediated cytoprotective pathways that safeguard cells against oxidative stress-induced senescence. To ascertain whether Nrf2-mediated pathways shield against senescence induction in response to HFD consumption, we explored senescence burden in a novel model of aging: Nrf2-deficient (Nrf2+/-) mice, emulating the aging phenotype. Our initial findings unveiled significant Nrf2 dysfunction in Nrf2+/- mice, mirroring aging-related alterations. HFD led to substantial obesity, hyperglycemia, and impaired insulin sensitivity in both Nrf2+/- and Nrf2+/+ mice. In control mice, HFD primarily heightened senescence burden in white adipose tissue, evidenced by increased Cdkn2a senescence biomarker expression. In Nrf2+/- mice, HFD elicited a significant surge in senescence burden across the liver, white adipose tissue, and the brain. We postulate that HFD-induced augmentation of senescence burden may be a pivotal contributor to accelerated organismal aging and the premature onset of age-related diseases.

Cellular senescence of renal tubular epithelial cells in acute kidney injury

Cellular senescence represents an irreversible state of cell-cycle arrest during which cells secrete senescence-associated secretory phenotypes, including inflammatory factors and chemokines. Additionally, these cells exhibit an apoptotic resistance phenotype. Cellular senescence serves a pivotal role not only in embryonic development, tissue regeneration, and tumor suppression but also in the pathogenesis of age-related degenerative diseases, malignancies, metabolic diseases, and kidney diseases. The senescence of renal tubular epithelial cells (RTEC) constitutes a critical cellular event in the progression of acute kidney injury (AKI). RTEC senescence inhibits renal regeneration and repair processes and, concurrently, promotes the transition of AKI to chronic kidney disease via the senescence-associated secretory phenotype. The mechanisms underlying cellular senescence are multifaceted and include telomere shortening or damage, DNA damage, mitochondrial autophagy deficiency, cellular metabolic disorders, endoplasmic reticulum stress, and epigenetic regulation. Strategies aimed at inhibiting RTEC senescence, targeting the clearance of senescent RTEC, or promoting the apoptosis of senescent RTEC hold promise for enhancing the renal prognosis of AKI. This review primarily focuses on the characteristics and mechanisms of RTEC senescence, and the impact of intervening RTEC senescence on the prognosis of AKI, aiming to provide a foundation for understanding the pathogenesis and providing potentially effective approaches for AKI treatment.

Altered Autonomic Function in Metabolic Syndrome: Interactive Effects of Multiple Components

Metabolic syndrome (MetS) describes a set of disorders that collectively influence cardiovascular health, and includes hypertension, obesity, insulin resistance, diabetes, and dyslipidemia. All these components (hypertension, obesity, dyslipidemia, and prediabetes/diabetes) have been shown to modify autonomic function. The major autonomic dysfunction that has been documented with each of these components is in the control of sympathetic outflow to the heart and periphery at rest and during exercise through modulation of the arterial baroreflex and the muscle metaboreflex. Many studies have described MetS components in singularity or in combination with the other major components of metabolic syndrome. However, many studies lack the capability to study all the factors of metabolic syndrome in one model or have not focused on studying the effects of how each component as it arises influences overall autonomic function. The goal of this review is to describe the current understanding of major aspects of metabolic syndrome that most likely contribute to the consequent/associated autonomic alterations during exercise and discuss their effects, as well as bring light to alternative mechanisms of study.

Unraveling the epigenetic fabric of type 2 diabetes mellitus: pathogenic mechanisms and therapeutic implications

Type 2 diabetes mellitus (T2DM) is a rapidly escalating global health concern, with its prevalence projected to increase significantly in the near future. This review delves into the intricate role of epigenetic modifications - including DNA methylation, histone acetylation, and micro-ribonucleic acid (miRNA) expression - in the pathogenesis and progression of T2DM. We critically examine how these epigenetic changes contribute to the onset and exacerbation of T2DM by influencing key pathogenic processes such as obesity, insulin resistance, β-cell dysfunction, cellular senescence, and mitochondrial dysfunction. Furthermore, we explore the involvement of epigenetic dysregulation in T2DM-associated complications, including diabetic retinopathy, atherosclerosis, neuropathy, and cardiomyopathy. This review highlights recent studies that underscore the diagnostic and therapeutic potential of targeting epigenetic modifications in T2DM. We also provide an overview of the impact of lifestyle factors such as exercise and diet on the epigenetic landscape of T2DM, underscoring their relevance in disease management. Our synthesis of the current literature aims to illuminate the complex epigenetic underpinnings of T2DM, offering insights into novel preventative and therapeutic strategies that could revolutionize its management.

Senescent adipocytes and type 2 diabetes - current knowledge and perspective concepts

Among civilization diseases, the number of individuals suffering from type 2 diabetes (T2DM) is expected to increase to more than a billion in less than 20 years, which is associated with, e.g., populational aging, poor diet, sedentary lifestyle, genetic predispositions, and immunological factors. T2DM affects many organs and is characterized by insulin resistance, high glucose levels, and adipocyte dysfunction, which are related to senescence. Although this type of cellular aging has beneficial biological functions, it can also act unfavorable since senescent adipocytes resist apoptosis, enhance cytokine secretion, downregulate cell identity genes, and acquire the senescence-associated secretory phenotype that renders a more oxidative environment. Opposing T2DM is possible via a wide variety of senotherapies, including senolytics and senomorphics; nevertheless, further research is advised to expand therapeutic possibilities and benefits. Consequences that ought to be deeply researched include secretory phenotype, chronic inflammation, increasing insulin resistance, as well as impairment of adipogenesis and functioning of adipocyte cells. Herein, despite reviewing T2DM and fat tissue senescence, we summarized the latest adipocyte-related anti-diabetes solutions and suggested further research directions.

Cellular senescence and ophthalmic diseases: narrative review

PURPOSE

Cellular senescence is a state of permanent growth arrest whereby a cell reaches its replicative limit. However, senescence can also be triggered prematurely in certain stressors including radiation, oxidative stress, and chemotherapy. This stress-induced senescence has been studied in the context of promoting inflammation, tumor development, and several chronic degenerative diseases of aging. Emerging research has elucidated the role of senescence in various ocular diseases.

METHODS

The literature search was performed using PubMed with using the query (senescence OR aging) AND (eye disease OR ocular disease OR ophthalmic disease OR cornea OR glaucoma OR cataract OR retina) on October 20th, 2022. No time restriction was proposed. Articles were excluded if they were not referenced in English.

RESULTS

Overall, 51 articles regarding senescence and ocular diseases were found and summarized in this study. Several signaling pathways have been implicated in the development of senescence. Currently, senescence has been linked to various corneal and retinal pathologies, as well as cataract and glaucoma. Given the number of pathologies, senolytics, which are small molecules with the ability to selective targeting of senescent cells, can be used as therapeutic or prophylactic agents.

CONCLUSIONS

Senescence has been shown to underlie the pathogenesis of numerous ocular diseases. The overall literature on senescence and ocular disease is growing rapidly. There is an ongoing debate whether or not cellular senescence detected in experiments contributes in a significant way to diseases. Research on understanding the mechanism of senescence from ocular cells and tissues is just beginning. Multiple animal models are required to test potential senolytics. Currently, no studies exist to date which have demonstrated the benefits of senolytic therapies in human studies.

Comparative study on main compounds and hypoglycemic effects of dispensing granules of Coptidis Rhizoma and Scutellaria-Coptis herb couple with traditional decoction

BACKGROUND

The clinical applications of dispensing granules (DG) have increased dramatically. However, it is controversial whether the DG has the same quality and efficacy compared with traditional decoction (TD). In this study, the contents of main compounds, hypoglycemic effects, and potential mechanism of Coptidis Rhizoma (CR) and Scutellaria-coptis (SC), constituted of a 1:1 mixture of CR and Scutellariae Radix (SR), in the forms of TD and DG were compared.

METHODS

The quantitative analysis was performed on an UPLC-PDA method. The 6-weeks-old male db/db mice were used as Type 2 Diabetes Mellitus (T2DM) mouse modle to investigate the antidiabetic effects of CR and SC in TD form (CR TD and SC TD), as well as CR and SC in DG form (CR DG and SC DG).

RESULTS

The total content of five alkaloids in CR TD ranged from 71.00 to 78.62 mg, whereas in CR DG it ranged from 38.77 to 53.68 mg in CR DG per 1 g of decoction pieces. Compared to CR TD, CR DG exhibited a 36% reduction on average. For SC samples, the precipitation occurred in the processing of TD but not in the DG, and the relative ratio of alkaloids to flavonoids was determined to be 1:1 in TD and 1:2 in DG. Furthermore, the animal experiments showed that the CR DG (equivalent to 3 g decoction pieces/kg) had almost the same hypoglycemic effect as CR TD when they were administered for 6 weeks. Compared with SC DG (equivalent to 6 g decoction pieces/kg), SC TD showed a better trend in ameliorating T2DM via ameliorating pancreatic structure and function, and activating Akt/AMPK/GLUT4 signaling pathways.

CONCLUSION

This study indicated that the contents of main compounds were generally higher in CR TD than CR DG originated from the same raw materials. Additionally, changes in the contents of the primary components validated that the compound interactions are exclusive to SC TD during co-decoction, rather than SC DG. The disparate prossing of SC DG and SC TD caused differences both in chemical composition and hypoglycemic effect, suggesting that the substitutability of DG and TD requires further research.

CcpA-Knockout Staphylococcus aureus Induces Abnormal Metabolic Phenotype via the Activation of Hepatic STAT5/PDK4 Signaling in Diabetic Mice

Catabolite control protein A (CcpA), an important global regulatory protein, is extensively found in S. aureus. Many studies have reported that CcpA plays a pivotal role in regulating the tricarboxylic acid cycle and pathogenicity. Moreover, the CcpA-knockout Staphylococcus aureus (S. aureus) in diabetic mice, compared with the wild-type, showed a reduced colonization rate in the tissues and organs and decreased inflammatory factor expression. However, the effect of CcpA-knockout S. aureus on the host's energy metabolism in a high-glucose environment and its mechanism of action remain unclear. S. aureus, a common and major human pathogen, is increasingly found in patients with obesity and diabetes, as recent clinical data reveal. To address this issue, we generated CcpA-knockout S. aureus strains with different genetic backgrounds to conduct in-depth investigations. In vitro experiments with high-glucose-treated cells and an in vivo model study with type 1 diabetic mice were used to evaluate the unknown effect of CcpA-knockout strains on both the glucose and lipid metabolism phenotypes of the host. We found that the strains caused an abnormal metabolic phenotype in type 1 diabetic mice, particularly in reducing random and fasting blood glucose and increasing triglyceride and fatty acid contents in the serum. In a high-glucose environment, CcpA-knockout S. aureus may activate the hepatic STAT5/PDK4 pathway and affect pyruvate utilization. An abnormal metabolic phenotype was thus observed in diabetic mice. Our findings provide a better understanding of the molecular mechanism of glucose and lipid metabolism disorders in diabetic patients infected with S. aureus.

Lipids and the hallmarks of ageing: From pathology to interventions

Lipids are critical structural and functional architects of cellular homeostasis. Change in systemic lipid profile is a clinical indicator of underlying metabolic pathologies, and emerging evidence is now defining novel roles of lipids in modulating organismal ageing. Characteristic alterations in lipid metabolism correlate with age, and impaired systemic lipid profile can also accelerate the development of ageing phenotype. The present work provides a comprehensive review of the extent of lipids as regulators of the modern hallmarks of ageing viz., cellular senescence, chronic inflammation, gut dysbiosis, telomere attrition, genome instability, proteostasis and autophagy, epigenetic alterations, and stem cells dysfunctions. Current evidence on the modulation of each of these hallmarks has been discussed with emphasis on inherent age-dependent deficiencies in lipid metabolism as well as exogenous lipid changes. There appears to be sufficient evidence to consider impaired lipid metabolism as key driver of the ageing process although much of knowledge is yet fragmented. Considering dietary lipids, the type and quantity of lipids in the diet is a significant, but often overlooked determinant that governs the effects of lipids on ageing. Further research using integrative approaches amidst the known aging hallmarks is highly desirable for understanding the therapeutics of lipids associated with ageing.

Reversing and modulating cellular senescence in beta cells, a new field of opportunities to treat diabetes

Diabetes constitutes a world-wide pandemic that requires searching for new treatments to halt its progression. Cellular senescence of pancreatic beta cells has been described as a major contributor to development and worsening of diabetes. The concept of reversibility of cellular senescence is critical as is the timing to take actions against this "dormant" senescent state. The reversal of cellular senescence can be considered as rejuvenation of the specific cell if it returns to the original "healthy state" and doesn't behave aberrantly as seen in some cancer cells. In rodents, treatment with senolytics and senomorphics blunted or prevented disease progression, however their use carry drawbacks. Modulators of cellular senescence is a new area of research that seeks to reverse the senescence. More research in each of these modalities should lead to new treatments to stop diabetes development and progression.

Approximate estimation of cell-type resolution transcriptome in bulk tissue through matrix completion

Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful tool for uncovering cellular heterogeneity. However, the high costs associated with this technique have rendered it impractical for studying large patient cohorts. We introduce ENIGMA (Deconvolution based on Regularized Matrix Completion), a method that addresses this limitation through accurately deconvoluting bulk tissue RNA-seq data into a readout with cell-type resolution by leveraging information from scRNA-seq data. By employing a matrix completion strategy, ENIGMA minimizes the distance between the mixture transcriptome obtained with bulk sequencing and a weighted combination of cell-type-specific expression. This allows the quantification of cell-type proportions and reconstruction of cell-type-specific transcriptomes. To validate its performance, ENIGMA was tested on both simulated and real datasets, including disease-related tissues, demonstrating its ability in uncovering novel biological insights.

Interaction between Autophagy and Senescence in Pancreatic Beta Cells

Aging leads to an increase in cellular stress due to the fragility of the organism and the inability to cope with it. In this setting, there is a higher chance of developing different cardiometabolic diseases like diabetes. Cellular senescence and autophagy, both hallmarks of aging and stress-coping mechanisms, have gained increased attention for their role in the pathophysiology of diabetes. Studies show that impairing senescence dampens and even prevents diabetes while the role of autophagy is more contradictory, implying a context- and disease-stage-dependent effect. Reports show conflicting data about the effect of autophagy on senescence while the knowledge about this interaction in beta cells remains scarce. Elucidating this interaction between autophagy and senescence in pancreatic beta cells will lead to an identification of their respective roles and the extent of the effect each mechanism has on beta cells and open new horizons for developing novel therapeutic agents. To help illuminate this relationship we will review the latest findings of cellular senescence and autophagy with a special emphasis on pancreatic beta cells and diabetes.

Melatonin downregulates the increased hepatic alpha-fetoprotein expression and restores pancreatic beta cells in a streptozotocin-induced diabetic rat model: a clinical, biochemical, immunohistochemical, and descriptive histopathological study

Background

Diabetes mellitus (DM) is a chronic metabolic disorder. Hepatopathy is one of the serious effects of DM Melatonin (MT) is a potent endogenous antioxidant that can control insulin output. However, little information is available about the potential association between melatonin and hepatic alpha-fetoprotein expression in diabetes.

Objective

This study was conducted to assess the influence of MT on diabetes-related hepatic injuries and to determine how β-cells of the pancreas in diabetic rats respond to MT administration.

Materials and methods

Forty rats were assigned to four groups at random (ten animals per group). Group I served as a normal control group. Group II was induced with DM, and a single dose of freshly prepared streptozotocin (45 mg/kg body weight) was intraperitoneally injected. In Group III, rats received 10 mg/kg/day of intraperitoneal melatonin (IP MT) intraperitoneally over a period of 4 weeks. In Group IV (DM + MT), following the induction of diabetes, rats received MT (the same as in Group III). Fasting blood sugar, glycosylated hemoglobin (HbA1c), and serum insulin levels were assessed at the end of the experimental period. Serum liver function tests were performed. The pancreas and liver were examined histopathologically and immunohistochemically for insulin and alpha-fetoprotein (AFP) antibodies, respectively.

Results

MT was found to significantly modulate the raised blood glucose, HbA1c, and insulin levels induced by diabetes, as well as the decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Furthermore, MT attenuated diabetic degenerative changes in the pancreas and the hepatic histological structure, increased the β-cell percentage area, and decreased AFP expression in the liver tissue. It attenuated diabetes-induced hepatic injury by restoring pancreatic β-cells; its antioxidant effect also reduced hepatocyte injury.

Conclusion

Collectively, the present study confirmed the potential benefits of MT in downregulating the increased hepatic alpha-fetoprotein expression and in restoring pancreatic β-cells in a streptozotocin-induced diabetic rat model, suggesting its promising role in the treatment of diabetes.

Regulation of Cellular Senescence in Type 2 Diabetes Mellitus: From Mechanisms to Clinical Applications

Cellular senescence is accelerated by hyperglycemia through multiple pathways. Therefore, senescence is an important cellular mechanism to consider in the pathophysiology of type 2 diabetes mellitus (T2DM) and an additional therapeutic target. The use of drugs that remove senescent cells has led to improvements in blood glucose levels and diabetic complications in animal studies. Although the removal of senescent cells is a promising approach for the treatment of T2DM, two main challenges limit its clinical application: the molecular basis of cellular senescence in each organ is yet to be understood, and the specific effect of removing senescent cells in each organ has to be determined. This review aims to discuss future applications of targeting senescence as a therapeutic option in T2DM and elucidate the characteristics of cellular senescence and senescence-associated secretory phenotype in the tissues important for regulating glucose levels: pancreas, liver, adipocytes, and skeletal muscle.

Decreased IGF1R attenuates senescence and improves function in pancreatic β-cells

Introduction

The enhanced β-cell senescence that accompanies insulin resistance and aging contributes to cellular dysfunction and loss of transcriptional identity leading to type 2 diabetes (T2D). While senescence is among the 12 recognized hallmarks of aging, its relation to other hallmarks including altered nutrient sensing (insulin/IGF1 pathway) in β-cells is not fully understood. We previously reported that an increased expression of IGF1R in mouse and human β-cells is a marker of older β-cells; however, its contribution to age-related dysfunction and cellular senescence remains to be determined.

Methods

In this study, we explored the direct role of IGF1R in β-cell function and senescence using two independent mouse models with decreased IGF1/IGF1R signaling: a) Ames Dwarf mice (Dwarf +/+), which lack growth hormone and therefore have reduced circulating levels of IGF1, and b) inducible β-cell-specific IGF1R knockdown (βIgf1rKD) mice.

Results

Compared to Dwarf+/- mice, Dwarf+/+ mice had lower body and pancreas weight, lower circulating IGF1 and insulin levels, and lower IGF1R and p21Cip1 protein expression in β-cells, suggesting the suppression of senescence. Adult βIgf1rKD mice showed improved glucose clearance and glucose-induced insulin secretion, accompanied by decreased p21Cip1 protein expression in β-cells. RNA-Seq of islets isolated from these βIgf1rKD mice revealed the restoration of three signaling pathways known to be downregulated by aging: sulfide oxidation, autophagy, and mTOR signaling. Additionally, deletion of IGF1R in mouse β-cells increased transcription of genes important for maintaining β-cell identity and function, such as Mafa, Nkx6.1, and Kcnj11, while decreasing senescence-related genes, such as Cdkn2a, Il1b, and Serpine 1. Decreased senescence and improved insulin-secretory function of β-cells were also evident when the βIgf1rKD mice were fed a high-fat diet (HFD; 60% kcal from fat, for 5 weeks).

Discussion

These results suggest that IGF1R signaling plays a causal role in aging-induced β-cell dysfunction. Our data also demonstrate a relationship between decreased IGF1R signaling and suppressed cellular senescence in pancreatic β-cells. Future studies can further our understanding of the interaction between senescence and aging, developing interventions that restore β-cell function and identity, therefore preventing the progression to T2D.

Zhx2 maintains islet β-cell mass and function by transcriptionally regulating Pax6

Emerging evidence shows that pancreatic β-cell function and quality are key determinants in the progression of type 2 diabetes (T2D). The transcription factor zinc finger homeobox 2 (Zhx2) is involved in proliferation and development of multiple cells. However, the exact role of Zhx2 in β-cells and T2D remains completely unknown. Here, we report that Zhx2 orchestrates β-cell mass and function by regulating paired box protein pax-6 (Pax6). We found that β-cell-specific knockout Zhx2 (Zhx2BKO) mice showed a decrease in β-cell proliferation and glucose homeostasis. Under prediabetic and diabetic conditions, we discovered glucose intolerance in both Zhx2BKO-HFD mice and Zhx2BKO-db/db mice, with reduced β-cell mass and insulin secretion. Mechanistically, we demonstrated that Zhx2 targeted the Pax6 promoter region (-1740∼-1563; -862∼-559; -251∼+75), enhanced promoter activity. Overall, Zhx2 maintains β-cell function by transcriptionally regulating Pax6, which provides a therapeutic target for diabetes intervention.

The effects of macronutrients metabolism on cellular and organismal aging

Evidence supports the notion that metabolic pathways are major regulators of organismal aging, and that metabolic perturbations can extend health- and lifespan. For this reason, dietary interventions and compounds perturbing metabolism are currently explored as anti-aging strategies. A common target for metabolic interventions delaying aging is cellular senescence, a state of stable growth arrest that is accompanied by various structural and functional changes including the activation of a pro-inflammatory secretome. Here, we summarize the current knowledge on the molecular and cellular events associated with carbohydrate, lipid and protein metabolism, and define how macronutrients can regulate induction or prevention of cellular senescence. We discuss how various dietary interventions can achieve prevention of disease and extension of healthy longevity by partially modulating senescence-associated phenotypes. We also emphasize the importance of developing personalized nutritional interventions that take into account the current health and age status of the individual.

A purified fraction of polysaccharides from the fruits of Lycium barbarum L. improves glucose homeostasis and intestinal barrier function in high-fat diet-fed mice

High-fat diet (HFD) consumption can induce intestinal barrier dysfunction and disrupt glucose metabolism. Our previous studies have demonstrated that polysaccharides obtained from the fruits of Lycium barbarum L. (LBPs) could suppress acute experimental diabetes as well as colitis in mice. In the present study, the modulating effects of a purified fraction of LBPs, named LBPs-4, on glucose homeostasis and intestinal barrier function in mice fed with a HFD were investigated. Our results indicated that the oral administration of LBP-4 (200 mg per kg per day) improved hyperglycemia, glucose intolerance, insulin resistance and islet β-cell hyperplasia in HFD-fed mice. Moreover, LBPs-4 intervention enhanced the intestinal barrier integrity by increasing the expression levels of zonula occludens 1 and claudin-1 and the number of goblet cells in the colon. LBPs-4 also modulated the composition of gut microbiota by increasing the relative abundances of butyrate producer Allobaculum and acetate producer Romboutsia. The results of fecal transplantation experiments, transferring of microbiota from LBPs-4-fed donor mice to HFD-fed recipient mice, validated the cause-effect relationship between LBPs-4-evoked changes in the gut microbiota and improvement of glucose homeostasis and intestinal barrier function. Collectively, these findings suggested that LBPs-4 might be developed as promising prebiotics to improve glucose metabolism and gut health.

Increased Galactosidase Beta 1 Expression as a Senescent Key Factor in β-Cells Function Modulation at the Early Steps of Type 2 Diabetes

BACKGROUND

In type 2 diabetes, insulin resistance is observed, and β-cells are incapable of responding to glycemia demands, leading to hyperglycemia. Although the nature of β-cells dysfunction in this disease is not fully understood, a link between the induction of pancreatic β-cell premature senescence and its metabolic implications has been proposed. This study aimed to understand the relationship between diabetes and pancreatic senescence, particularly at the beginning of the disease.

METHODS

C57Bl/6 J mice were fed two different diets, a normal diet and a high-fat diet, for 16 weeks. Pancreatic histomorphology analysis, insulin quantification, inflammation parameters, and senescence biomarkers for the experimental animals were assessed at weeks 12 and 16.

RESULTS

The results proved that diabetes onset occurred at week 16 in the High Fat Diet group, supported by glycaemia, weight and blood lipid levels. Increased β-cells size and number accompanied by increased insulin expression were observed. Also, an inflammatory status of the diabetic group was noted by increased levels of systemic IL-1β and increased pancreatic fibrosis. Finally, the expression of galactosidase-beta 1 (GLB1) was significantly increased in pancreatic β-cells.

CONCLUSION

The study findings indicate that senescence, as revealed by an increase in GLB1 expression, is a key factor in the initial stage of diabetes.

Therapeutic or lifelong training effects on pancreatic morphological and functional parameters in an animal model of aging and obesity

AIMS

Obesity, aging, and physical training are factors influencing pancreatic functional and morphological parameters. Aiming to clarify the impact of the interaction of these factors, we analyzed the effect of therapeutic or lifelong physical training on body adiposity and pancreatic functional and morphological parameters of aged and obese rats.

METHODS

24 male Wistar rats were (initial age = 4 months and final age = 14 months) randomly divided into three aged and obese experimental groups (n = 8/group): untrained, therapeutic trained, and lifelong trained. Body adiposity, plasmatic concentration and pancreatic immunostaining of insulin, markers of tissue inflammation, lipid peroxidation, activity and immunostaining of antioxidant enzymes, and parameters of pancreatic morphology were evaluated.

RESULTS

Lifelong physical training improved the body adiposity, plasmatic insulin concentration, and macrophage immunostaining in the pancreas. The animals submitted to therapeutic and lifelong training showed an increase in the density of the pancreatic islets; lower insulin, Nuclear Factor Kappa B (NF-κB), and Transforming Growth Factor beta (TGF-β) immunostaining in the pancreatic parenchyma, as well as lower pancreatic tissue lipid peroxidation, lower fibrosis area, increased catalase and glutathione peroxidase (GPx) activity and increased heme oxygenase-1 (HO-1) immunostaining, with the greatest effect in the lifelong training group.

CONCLUSION

Lifelong training promoted greater beneficial effects on the pancreatic functional and morphological parameters of aged and obese animals compared to therapeutic exercise.

The Molecular Mechanism of Polyphenols in the Regulation of Ageing Hallmarks

Ageing is a complex process characterized mainly by a decline in the function of cells, tissues, and organs, resulting in an increased risk of mortality. This process involves several changes, described as hallmarks of ageing, which include genomic instability, telomere attrition, epigenetic changes, loss of proteostasis, dysregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell depletion, and altered intracellular communication. The determining role that environmental factors such as diet and lifestyle play on health, life expectancy, and susceptibility to diseases, including cancer and neurodegenerative diseases, is wellestablished. In view of the growing interest in the beneficial effects of phytochemicals in the prevention of chronic diseases, several studies have been conducted, and they strongly suggest that the intake of dietary polyphenols may bring numerous benefits due to their antioxidant and anti-inflammatory properties, and their intake has been associated with impaired ageing in humans. Polyphenol intake has been shown to be effective in ameliorating several age-related phenotypes, including oxidative stress, inflammatory processes, impaired proteostasis, and cellular senescence, among other features, which contribute to an increased risk of ageing-associated diseases. This review aims to address, in a general way, the main findings described in the literature about the benefits of polyphenols in each of the hallmarks of ageing, as well as the main regulatory mechanisms responsible for the observed antiageing effects.

The Role of Gut Microbiota in High-Fat-Diet-Induced Diabetes: Lessons from Animal Models and Humans

The number of diabetes mellitus patients is increasing rapidly worldwide. Diet and nutrition are strongly believed to play a significant role in the development of diabetes mellitus. However, the specific dietary factors and detailed mechanisms of its development have not been clearly elucidated. Increasing evidence indicates the intestinal microbiota is becoming abundantly apparent in the progression and prevention of insulin resistance in diabetes. Differences in gut microbiota composition, particularly butyrate-producing bacteria, have been observed in preclinical animal models as well as human patients compared to healthy controls. Gut microbiota dysbiosis may disrupt intestinal barrier functions and alter host metabolic pathways, directly or indirectly relating to insulin resistance. In this article, we focus on dietary fat, diabetes, and gut microbiome characterization. The promising probiotic and prebiotic approaches to diabetes, by favorably modifying the composition of the gut microbial community, warrant further investigation through well-designed human clinical studies.

Aging and aging-related diseases: from molecular mechanisms to interventions and treatments

Aging is a gradual and irreversible pathophysiological process. It presents with declines in tissue and cell functions and significant increases in the risks of various aging-related diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic diseases, musculoskeletal diseases, and immune system diseases. Although the development of modern medicine has promoted human health and greatly extended life expectancy, with the aging of society, a variety of chronic diseases have gradually become the most important causes of disability and death in elderly individuals. Current research on aging focuses on elucidating how various endogenous and exogenous stresses (such as genomic instability, telomere dysfunction, epigenetic alterations, loss of proteostasis, compromise of autophagy, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, deregulated nutrient sensing) participate in the regulation of aging. Furthermore, thorough research on the pathogenesis of aging to identify interventions that promote health and longevity (such as caloric restriction, microbiota transplantation, and nutritional intervention) and clinical treatment methods for aging-related diseases (depletion of senescent cells, stem cell therapy, antioxidative and anti-inflammatory treatments, and hormone replacement therapy) could decrease the incidence and development of aging-related diseases and in turn promote healthy aging and longevity.

Does senescence play a role in age-related macular degeneration?

Advanced age is the most established risk factor for developing age-related macular degeneration (AMD), one of the leading causes of visual impairment in the elderly, in Western and developed countries. Similarly, after middle age, there is an exponential increase in pathologic molecular and cellular events that can induce senescence, traditionally defined as an irreversible loss of the cells' ability to divide and most recently reported to also occur in select post-mitotic and terminally differentiated cells, such as neurons. Together these facts raise the question as to whether or not cellular senescence, may play a role in the development of AMD. A number of studies have reported the effect of ocular-relevant inducers of senescence using primarily in vitro models of poorly polarized, actively dividing retinal pigment epithelial (RPE) cell lines. However, in interpretating the data, the fidelity of these culture models to the RPE in vivo, must be considered. Fewer studies have explored the presence and/or impact of senescent cells in in vivo models that present with phenotypic features of AMD, leaving this an open field for further investigation. The goal of this review is to discuss current thoughts on the potential role of senescence in AMD development and progression, with consideration of the model systems used and their relevance to human disease.

Endocrine adverse effects of mono(2-ethylhexyl) phthalate and monobutyl phthalate in male pubertal rats

Considering that research of adverse effects of mono(2-ethylhexyl) phthalate (MEHP) and monobutyl phthalate (MBP), two key metabolites of the most common phthalates used as plasticisers in various daily-life products, has been scattered and limited, the aim of our study was to provide a more comprehensive analysis by focusing on major organ systems, including blood, liver, kidney, and pancreas in 66 male pubertal rats randomised into eleven groups of six. The animals were receiving either metabolite at doses of 25, 50, 100, 200, or 400 mg/kg bw a day by gavage for 28 days. The control group was receiving corn oil. At the end of the experiment, blood samples were collected for biochemical, haematological, and immunological analyses. Samples of kidney, liver, and pancreas were dissected for histopathological analyses. Exposure to either compound resulted in increased liver and decreased pancreas weight, especially at the highest doses. Exposed rats had increased ALT, AST, glucose, and triglyceride levels and decreased total protein and albumin levels. Both compounds increased MCV and decreased haemoglobin levels compared to control. Although they also lowered the insulin level, exposed rats had negative islet cell and insulin antibodies, same as control. Treatment-related histopathological changes included sinusoidal degeneration in the liver, glomerular degeneration in the kidney, and degeneration of pancreatic islets. Our findings document toxic outcomes of MEHP and MBP on endocrine organs in male pubertal rats but also suggest the need for additional studies to better understand the mechanisms behind adverse effects in chronic exposure.

Targeting cellular senescence in metabolic disease

Cellular senescence is a cell fate involving cell cycle arrest, resistance against apoptosis, and the development of a secretome that can be pro-inflammatory. In aging and obesity, senescent cells accumulate in many tissues, including adipose tissue, brain, kidney, pancreas, and liver. These senescent cells and their downstream effects appear to perpetuate inflammation and have been implicated in the pathogenesis of metabolic dysfunction. Senescent cells are cleared in part by the immune system, a process that is diminished in obesity and aging, likely due in part to senescence of immune cells themselves. Targeting senescent cells or their products improves metabolic function in both aging and in animal models of obesity. Novel therapeutics to target senescent cells are on the horizon and are currently being investigated in clinical trials in humans for multiple diseases. Early evidence suggests that senolytic drugs, which transiently disarm the anti-apoptotic defenses of pro-inflammatory senescent cells, are effective in causing depletion of senescent cells in humans. Senescence-targeting therapeutics, including senolytic drugs and strategies to increase immune clearance of senescent cells, hold significant promise for treating metabolic dysfunction in multiple tissues and disease states.

Cellular Senescence in Obesity and Associated Complications: a New Therapeutic Target

PURPOSE OF REVIEW

Obesity has increased worldwide recently and represents a major global health challenge. This review focuses on the obesity-associated cellular senescence in various organs and the role of these senescent cells (SnCs) in driving complications associated with obesity. Also, the ability to target SnCs pharmacologically with drugs termed senotherapeutics as a therapy for these complications is discussed.

RECENT FINDINGS

Several studies have shown a positive correlation between obesity and SnC burden in organs such as adipose tissue, liver, and pancreatic-β-cells. These SnCs produce several secretory factors which affect other cells and tissues in a paracrine manner resulting in organ dysfunction. The accumulation of SnCs in adipocytes affects their lipid storage and impairs adipogenesis. The inflammatory senescence-associated secretory phenotype (SASP) of SnCs downregulates the antioxidant capacity and mitochondrial function in tissues. Senescent hepatocytes cannot oxidize fatty acids, which leads to lipid deposition and senescence in β-cells decrease function. These and other adverse effects of SnCs contribute to insulin resistance and type-2 diabetes. The reduction in the SnC burden genetically or pharmacologically improves the complications associated with obesity. The accumulation of SnCs with age and disease accelerates aging. Obesity is a key driver of SnC accumulation, and the complications associated with obesity can be controlled by reducing the SnC burden. Thus, senotherapeutic drugs have the potential to be an effective therapeutic option.

Sulfated Fucogalactan From Laminaria Japonica Ameliorates β-Cell Failure by Attenuating Mitochondrial Dysfunction via SIRT1-PGC1-α Signaling Pathway Activation

As mitochondrial metabolism is a major determinant of β-cell insulin secretion, mitochondrial dysfunction underlies β-cell failure and type 2 diabetes mellitus progression. An algal polysaccharide of Laminaria japonica, sulfated fucogalactan (SFG) displays various pharmacological effects in a variety of conditions, including metabolic disease. We investigated the protective effects of SFG against hydrogen peroxide (H2O2)-induced β-cell failure in MIN6 cells and islets. SFG significantly promoted the H2O2-inhibited proliferation in the cells and ameliorated their senescence, and potentiated β-cell function by regulating β-cell identity and the insulin exocytosis-related genes and proteins in H2O2-induced β-cells. SFG also attenuated mitochondrial dysfunction, including alterations in ATP content, mitochondrial respiratory chain genes and proteins expression, and reactive oxygen species and superoxide dismutase levels. Furthermore, SFG resulted in SIRT1-PGC1-α pathway activation and upregulated the downstream Nrf2 and Tfam. Taken together, the results show that SFG attenuates H2O2-induced β-cell failure by improving mitochondrial function via SIRT1-PGC1-α signaling pathway activation. Therefore, SFG is implicated as a potential agent for treating pancreatic β-cell failure.

Mitoribosome insufficiency in β cells is associated with type 2 diabetes-like islet failure

Genetic variations in mitoribosomal subunits and mitochondrial transcription factors are related to type 2 diabetes. However, the role of islet mitoribosomes in the development of type 2 diabetes has not been determined. We investigated the effects of the mitoribosomal gene on β-cell function and glucose homeostasis. Mitoribosomal gene expression was analyzed in datasets from the NCBI GEO website (GSE25724, GSE76894, and GSE76895) and the European Nucleotide Archive (ERP017126), which contain the transcriptomes of type 2 diabetic and nondiabetic organ donors. We found deregulation of most mitoribosomal genes in islets from individuals with type 2 diabetes, including partial downregulation of CRIF1. The phenotypes of haploinsufficiency in a single mitoribosomal gene were examined using β-cell-specific Crif1 (Mrpl59) heterozygous-deficient mice. Crif1^beta+/− mice had normal glucose tolerance, but their islets showed a loss of first-phase glucose-stimulated insulin secretion. They also showed increased β-cell mass associated with higher expression of Reg family genes. However, Crif1^beta+/− mice showed earlier islet failure in response to high-fat feeding, which was exacerbated by aging. Haploinsufficiency of a single mitoribosomal gene predisposes rodents to glucose intolerance, which resembles the early stages of type 2 diabetes in humans.

Disruptions in the mitochondrial protein synthesis machinery give rise to metabolic disturbances that lay the foundation for type 2 diabetes. As physiological glucose levels rise, the energy-generating machinery of the mitochondria responds with increased activity, which stimulates insulin secretion. Many proteins responsible for mitochondrial metabolism are produced by ribosomes within this cellular organelle. Researchers led by Hyun Jin Kim and Minho Shong at Chungnam National University, Daejon, South Korea, have determined that mutations affecting a mitochondrial ribosomal protein called CRIF1 can lead to impaired insulin release. Mice with reduced CRIF1 were initially healthy, but as they aged, exhibited signs of impaired pancreatic function similar to those seen in patients with early-stage diabetes. This process was accelerated by consumption of a high-fat diet, and the researchers propose that this mechanism may be directly relevant to human disease.

Revisiting Epithelial Carcinogenesis

The origin of cancer remains one of the most important enigmas in modern biology. This paper presents a hypothesis for the origin of carcinomas in which cellular aging and inflammation enable the recovery of cellular plasticity, which may ultimately result in cancer. The hypothesis describes carcinogenesis as the result of the dedifferentiation undergone by epithelial cells in hyperplasia due to replicative senescence towards a mesenchymal cell state with potentially cancerous behavior. In support of this hypothesis, the molecular, cellular, and histopathological evidence was critically reviewed and reinterpreted when necessary to postulate a plausible generic series of mechanisms for the origin and progression of carcinomas. In addition, the implications of this theoretical framework for the current strategies of cancer treatment are discussed considering recent evidence of the molecular events underlying the epigenetic switches involved in the resistance of breast carcinomas. The hypothesis also proposes an epigenetic landscape for their progression and a potential mechanism for restraining the degree of dedifferentiation and malignant behavior. In addition, the manuscript revisits the gradual degeneration of the nonalcoholic fatty liver disease to propose an integrative generalized mechanistic explanation for the involution and carcinogenesis of tissues associated with aging. The presented hypothesis might serve to understand and structure new findings into a more encompassing view of the genesis of degenerative diseases and may inspire novel approaches for their study and therapy.

The pancreatic β-cell in ageing: Implications in age-related diabetes

The prevalence of type 2 diabetes (T2D) and impaired glucose tolerance (IGT) increases with ageing. T2D generally results from progressive impairment of the pancreatic islets to adapt β-cell mass and function in the setting of insulin resistance and increased insulin demand. Several studies have shown an age-related decline in peripheral insulin sensitivity. However, a precise understanding of the pancreatic β-cell response in ageing is still lacking. In this review, we summarize the age-related alterations, adaptations and/or failures of β-cells at the molecular, morphological and functional levels in mouse and human. Age-associated alterations include processes such as β-cell proliferation, apoptosis and cell identity that can influence β-cell mass. Age-related changes also affect β-cell function at distinct steps including electrical activity, Ca²⁺ signaling and insulin secretion, among others. We will consider the potential impact of these alterations and those mediated by senescence pathways on β-cells and their implications in age-related T2D. Finally, given the great diversity of results in the field of β-cell ageing, we will discuss the sources of this heterogeneity. A better understanding of β-cell biology during ageing, particularly at older ages, will improve our insight into the contribution of β-cells to age-associated T2D and may boost new therapeutic strategies.

Mitochondrially targeted tamoxifen alleviates markers of obesity and type 2 diabetes mellitus in mice

Type 2 diabetes mellitus represents a major health problem with increasing prevalence worldwide. Limited efficacy of current therapies has prompted a search for novel therapeutic options. Here we show that treatment of pre-diabetic mice with mitochondrially targeted tamoxifen, a potential anti-cancer agent with senolytic activity, improves glucose tolerance and reduces body weight with most pronounced reduction of visceral adipose tissue due to reduced food intake, suppressed adipogenesis and elimination of senescent cells. Glucose-lowering effect of mitochondrially targeted tamoxifen is linked to improvement of type 2 diabetes mellitus-related hormones profile and is accompanied by reduced lipid accumulation in liver. Lower senescent cell burden in various tissues, as well as its inhibitory effect on pre-adipocyte differentiation, results in lower level of circulating inflammatory mediators that typically enhance metabolic dysfunction. Targeting senescence with mitochodrially targeted tamoxifen thus represents an approach to the treatment of type 2 diabetes mellitus and its related comorbidities, promising a complex impact on senescence-related pathologies in aging population of patients with type 2 diabetes mellitus with potential translation into the clinic.

Progressive brown adipocyte dysfunction: whitening and impaired nonshivering thermogenesis as long-term obesity complications

Chronic obesity damages the cytoarchitecture of brown adipose tissue (BAT), leading to whitening of brown adipocytes and impaired thermogenesis, characterizing BAT dysfunction. Understanding the pathways of whitening progression can bring new targets to counter obesity. This study aimed to evaluate the chronic effect (12, 16, and 20 weeks) of a high-fat diet (50% energy as fat) upon energy expenditure, thermogenic markers, and pathways involved in BAT whitening in C57BL/6J mice. Sixty adult male mice comprised six nutritional groups, where the letters refer to the diet type (control, C or high-fat, HF), and the numbers refer to the period (in weeks) of diet administration: C12, HF12, C16, HF16, C20, and HF20. After sacrifice, biochemical, molecular, and stereological analyses addressed the outcomes. The HF groups had overweight, oral glucose intolerance, and hyperleptinemia, resulting in progressive whitening of BAT and decreased numerical density of nuclei per area of tissue compared to age-matched control groups. In addition, the whitening maximization was related to altered batokines gene expression, decreased nonshivering thermogenesis, and body temperature, resulting in low energy expenditure. The HF20 group showed enlarged adipocytes with stable and dysfunctional lipid droplets, followed by inflammation and ER stress. In conclusion, chronic HF diet intake caused time-dependent maximization of whitening with defective nonshivering thermogenesis. Long-term BAT dysfunction includes down-regulated vascularization markers, upregulated inflammasome activation, and ER stress markers.

Turnover Kinetics of Pancreatic Macrophages in Lean and Obese Diabetic Mice

Pancreatic resident macrophages, a heterogeneous family of cells with distinct origins and phenotypes, are the main myeloid cells in exocrine and endocrine tissues. Adult exocrine F4/80^hi macrophages consist of three different subsets based on the embryonic marker Tim-4 and MHC II expression. Their frequencies shift during aging and obesity with the Tim-4^-MHCII⁺ fraction becoming the predominant subpopulation in the inter acinar stroma. Endocrine resident F4/80^hi macrophages are more homogenous and represent the prevalent leukocyte fraction residing within the islets in both lean and obese mice. We used an adult fate mapping mouse model to characterize turnover kinetics within the pancreatic resident macrophages under normal homeostasis and obese diabetic conditions. We demonstrate that islet resident macrophages show unique replenishment kinetics, with embryonic macrophages being gradually replaced by bone marrow-derived monocytes with increasing age. Their replenishment was independent of the CCL2/CCR2 axis. Furthermore, we confirmed that both exocrine Tim-4⁺MHCII^low and Tim-4⁺MHCII⁺ fractions are long-lived and primarily independent from bone marrow-derived monocytes. In contrast, exocrine Tim-4^-MHCII⁺ macrophages are gradually replaced through a CCR2-dependent influx of bone marrow-derived monocytes in aging. Moreover, we show that obesity and type 2 diabetes do not affect the turnover kinetics of any macrophage subpopulation residing in the pancreas. Our study uncovers new insights on pancreatic macrophage biology in aging and obesity.

Nutrition and cellular senescence in obesity-related disorders

Adequate nutrition is vital for immune homeostasis. However, the incidence of obesity is increasing worldwide due to the adoption of the Western diet and a sedentary lifestyle. Obesity is associated with chronic inflammation which alters the function of adipose tissue, liver, pancreas, and the nervous system. Inflammation is related to cellular senescence, distinguished by irreversible cell cycle arrest. Senescent cells secrete the senescence-associated secretory phenotype (SASP) which contains pro-inflammatory factors. Targeting processes in senescence might have a salutary approach to obesity. The present review highlights the impact of an unhealthy diet on tissues affected by obesity, and the mechanisms that promote the consequent inflammation and senescence.

Metabolic Stress Impairs Pericyte Response to Optogenetic Stimulation in Pancreatic Islets

Pancreatic islets are highly vascularized micro-organs ensuring whole body glucose homeostasis. Islet vascular cells play an integral part in sustaining adequate insulin release by beta cells. In particular, recent studies have demonstrated that islet pericytes regulate local blood flow velocity and are required for maintenance of beta cell maturity and function. In addition, increased metabolic demand accompanying obesity alters islet pericyte morphology. Here, we sought to explore the effects of metabolic stress on islet pericyte functional response to stimulation in a mouse model of type 2 diabetes, directly in the pancreas in vivo . We found that high fat diet induced islet pericyte hypertrophy without alterations in basal local blood flow. However, optogenetic stimulation of pericyte activity revealed impaired islet vascular responses, despite increased expression of genes encoding proteins directly or indirectly involved in cell contraction. These findings suggest that metabolic stress impinges upon islet pericyte function, which may contribute to beta cell failure during T2D.

Senescence and Type 2 Diabetic Cardiomyopathy: How Young Can You Die of Old Age?

Inflammation is well understood to be a physiological process of ageing however it also underlies many chronic diseases, including conditions without an obvious pathogenic inflammatory element. Recent findings have unequivocally identified type 2 diabetes (T2D) as a chronic inflammatory disease characterized by inflammation and immune senescence. Immunosenescence is a hallmark of the prolonged low-grade systemic inflammation, in particular associated with metabolic syndrome and can be a cause as well as a consequence of T2D. Diabetes is a risk factor for cardiovascular mortality and remodelling and with particular changes to myocardial structure, function, metabolism and energetics collectively resulting in diabetic cardiomyopathy. Both cardiomyocytes and immune cells undergo metabolic remodelling in T2D and as a result become trapped in a vicious cycle of lost metabolic flexibility, thus losing their key adaptive mechanisms to dynamic changes in O₂ and nutrient availability. Immunosenescence driven by metabolic stress may be both the cause and key contributing factor to cardiac dysfunction in diabetic cardiomyopathy by inducing metabolic perturbations that can lead to impaired energetics, a strong predictor of cardiac mortality. Here we review our current understanding of the cross-talk between inflammaging and cardiomyocytes in T2D cardiomyopathy. We discuss potential mechanisms of metabolic convergence between cell types which, we hypothesize, might tip the balance between resolution of the inflammation versus adverse cardiac metabolic remodelling in T2D cardiomyopathy. A better understanding of the multiple biological paradigms leading to T2D cardiomyopathy including the immunosenescence associated with inflammaging will provide a powerful target for successful therapeutic interventions.

Role of Cellular Senescence in Type II Diabetes

Cellular senescence is a cell fate that occurs in response to numerous types of stress and can promote tissue repair or drive inflammation and disruption of tissue homeostasis depending on the context. Aging and obesity lead to an increase in the senescent cell burden in multiple organs. Senescent cells release a myriad of senescence-associated secretory phenotype factors that directly mediate pancreatic β-cell dysfunction, adipose tissue dysfunction, and insulin resistance in peripheral tissues, which promote the onset of type II diabetes mellitus. In addition, hyperglycemia and metabolic changes seen in diabetes promote cellular senescence. Diabetes-induced cellular senescence contributes to various diabetic complications. Thus, type II diabetes is both a cause and consequence of cellular senescence. This review summarizes recent studies on the link between aging, obesity, and diabetes, focusing on the role of cellular senescence in disease processes.

Endoplasmic Reticulum Stress Induced Proliferation Remains Intact in Aging Mouse β-Cells

Aging is associated with loss of proliferation of the insulin-secreting β-cell, a possible contributing factor to the increased prevalence of type 2 diabetes in the elderly. Our group previously discovered that moderate endoplasmic reticulum (ER) stress occurring during glucose exposure increases the adaptive β-cell proliferation response. Specifically, the ATF6α arm of the tripartite Unfolded Protein Response (UPR) promotes β-cell replication in glucose excess conditions. We hypothesized that β-cells from older mice have reduced proliferation due to aberrant UPR signaling or an impaired proliferative response to ER stress or ATF6α activation. To investigate, young and old mouse islet cells were exposed to high glucose with low-dose thapsigargin or activation of overexpressed ATF6α, and β-cell proliferation was quantified by BrdU incorporation. UPR pathway activation was compared by qPCR of target genes and semi-quantitative Xbp1 splicing assay. Intriguingly, although old β-cells had reduced proliferation in high glucose compared to young β-cells, UPR activation and induction of proliferation in response to low-dose thapsigargin or ATF6α activation in high glucose were largely similar between young and old. These results suggest that loss of UPR-led adaptive proliferation does not explain the reduced cell cycle entry in old β-cells, and raise the exciting possibility that future therapies that engage adaptive UPR could increase β-cell number through proliferation even in older individuals.

The role of senescence in the pathogenesis of atrial fibrillation: A target process for health improvement and drug development

Cellular senescence is a state of growth arrest that occurs after cells encounter various stresses. Senescence contributes to tumour suppression, embryonic development, and wound healing. It impacts on the pathology of various diseases by secreting inflammatory chemokines, immune modulators and other bioactive factors. These secretory biosignatures ultimately cause inflammation, tissue fibrosis, immunosenescence and many ageing-related diseases such as atrial fibrillation (AF). Because the molecular mechanisms underpinning AF development remain unclear, current treatments are suboptimal and have serious side effects. In this review, we summarize recent results describing the role of senescence in AF. We propose that senescence factors induce AF and have a causative role. Hence, targeting senescence and its secretory phenotype may attenuate AF.

Keeping zombies alive: The ER-mitochondria Ca2+ transfer in cellular senescence

Cellular senescence generates a permanent cell cycle arrest, characterized by apoptosis resistance and a pro-inflammatory senescence-associated secretory phenotype (SASP). Physiologically, senescent cells promote tissue remodeling during development and after injury. However, when accumulated over a certain threshold as happens during aging or after cellular stress, senescent cells contribute to the functional decline of tissues, participating in the generation of several diseases. Cellular senescence is accompanied by increased mitochondrial metabolism. How mitochondrial function is regulated and what role it plays in senescent cell homeostasis is poorly understood. Mitochondria are functionally and physically coupled to the endoplasmic reticulum (ER), the major calcium (Ca²⁺) storage organelle in mammalian cells, through special domains known as mitochondria-ER contacts (MERCs). In this domain, the release of Ca²⁺ from the ER is mainly regulated by inositol 1,4,5-trisphosphate receptors (IP3Rs), a family of three Ca²⁺ release channels activated by a ligand (IP3). IP3R-mediated Ca²⁺ release is transferred to mitochondria through the mitochondrial Ca²⁺ uniporter (MCU), where it modulates the activity of several enzymes and transporters impacting its bioenergetic and biosynthetic function. Here, we review the possible connection between ER to mitochondria Ca²⁺ transfer and senescence. Understanding the pathways that contribute to senescence is essential to reveal new therapeutic targets that allow either delaying senescent cell accumulation or reduce senescent cell burden to alleviate multiple diseases.