SREBP1c-PARP1 axis tunes anti-senescence activity of adipocytes and ameliorates metabolic imbalance in obesity

Myriocin Restores Metabolic Homeostasis in dAGE-Exposed Mice via AMPK-PGC1α-Mediated Mitochondrial Activation and Systemic Lipid/Glucose Regulation

Background: Diet-derived advanced glycation end products (dAGEs) are closely associated with obesity and metabolic disorders. This study investigates the therapeutic potential of myriocin (Myr), a sphingolipid synthesis inhibitor, in counteracting dAGE-induced obesity and its underlying mechanisms. Methods: Male C57BL/6J wild-type mice were randomly assigned to receive either a low-AGE diet or a high-AGE diet with or without the administration of myriocin for a duration of 24 weeks. At the end of the experimental period, blood samples, whole livers, and adipose tissues were harvested for subsequent biochemical, histological, and molecular analyses. Results: Using a 24-week high-AGE diet mouse model, we demonstrate that Myr significantly reduces body weight gain (by 76%) and adipose tissue accumulation, while alleviating hepatic steatosis. Myr improves glucose homeostasis by lowering fasting blood glucose (a 44.5% reduction), enhancing oral glucose tolerance, and restoring hepatic glycolysis/gluconeogenesis balance via upregulating glucokinase and suppressing G6pc. Notably, Myr reduces serum LDL-C, TG, and TC levels by 52.3%, 51.8%, and 48.8%, respectively, and ameliorates liver dysfunction as evidenced by normalized ALT/AST activities. Metabolomics reveal Myr reshapes amino acid, carbohydrate, and lipid metabolism pathways. Mechanistically, Myr suppresses lipogenesis by downregulating Srebp1, Fasn, and Acc, while activating AMPK-PGC1α signaling to enhance mitochondrial biogenesis (a 2.1-fold increase in mtDNA) and thermogenesis via Ucp1 upregulation in brown and white adipose tissues. Conclusions: Our findings unveil Myr as a novel dual regulator of lipid and glucose metabolism through AMPK-PGC1α-mediated mitochondrial activation, providing the first evidence of sphingolipid inhibition as a therapeutic strategy against dAGE-induced metabolic syndrome. This study establishes a multifaceted mechanism involving hepatic lipid regulation, adipose browning, and systemic metabolic reprogramming, advancing potential clinical applications for obesity-related disorders.

Obesity accelerates cardiovascular ageing

A global obesity pandemic, coupled with an increasingly ageing population, is exacerbating the burden of cardiovascular disease. Indeed, clinical and experimental evidence underscores a potential connection between obesity and ageing in the pathogenesis of various cardiovascular disorders. This is further supported by the notion that weight reduction not only effectively reduces major cardiovascular events in elderly individuals but is also considered the gold standard for lifespan extension, in obese and non-obese model organisms. This review evaluates the intricate interplay between obesity and ageing from molecular mechanisms to whole organ function within the cardiovascular system. By comparatively analysing their characteristic features, shared molecular and cell biological signatures between obesity and ageing are unveiled, with the intent to shed light on how obesity accelerates cardiovascular ageing. This review also elaborates on how emerging metabolic interventions targeting obesity might protect from cardiovascular diseases largely through antagonizing key molecular mechanisms of the ageing process itself. In sum, this review aims to provide valuable insight into how understanding these interconnected processes could guide the development of novel and effective cardiovascular therapeutics for a growing aged population with a concerning obesity problem.

Systemic aging and aging-related diseases

Aging is a biological process along with systemic and multiple organ dysfunction. It is more and more recognized that aging is a systemic disease instead of a single-organ functional disorder. Systemic aging plays a profound role in multiple diseases including neurodegenerative diseases, cardiovascular diseases, and malignant diseases. Aged organs communicate with other organs and accelerate aging. Skeletal muscle, heart, bone marrow, skin, and liver communicate with each other through organ-organ crosstalk. The crosstalk can be mediated by metabolites including lipids, glucose, short-chain fatty acids (SCFA), inflammatory cytokines, and exosomes. Metabolic disorders including hyperglycemia, hyperinsulinemia, and hypercholesterolemia caused by chronic diseases accelerate hallmarks of aging. Systemic aging leads to the destruction of systemic hemostasis, causes the release of inflammatory cytokines, senescence-associated secretory phenotype (SASP), and the imbalance of microbiota composition. Released inflammatory factors further aggregate senescence, which promotes the aging of multiple solid organs. Targeting senescence or delaying aging is emerging as a critical health strategy for solving age-related diseases, especially in the old population. In the current review, we will delineate the mechanisms of organ crosstalk in systemic aging and age-related diseases to provide therapeutic targets for delaying aging.

Hepatotoxicity in Carp (Carassius auratus) Exposed to Perfluorooctane Sulfonate (PFOS): Integrative Histopathology and Transcriptomics Analysis

Perfluorooctane sulfonate (PFOS) contamination poses a significant environmental threat due to its widespread distribution and persistence. However, the hepatotoxic effects of PFOS on key aquatic species, such as crucian carp, remain understudied. This study systematically investigated the hepatotoxicity and underlying molecular mechanisms associated with PFOS exposure in crucian carp over a 21 day period. We determined a 96 h 50% lethal concentration (LC50) of 23.17 mg/L. Histopathological and transcriptomic analyses confirmed PFOS-induced liver damage in the carp, characterized by venous congestion, nucleolar dissolution and cellular vacuolation. Transcriptomic profiling further identified 1036 differentially expressed genes (DEGs), involving critical pathways related to lipid and energy metabolism, immunity, and endocrine regulation. These pathways are integral to the development of nonalcoholic fatty liver disease (NAFLD). Specifically, DEGs related to lipid metabolism showed significant changes, while those involved in energy metabolism indicated disrupted ATP production and mitochondrial function. Genes associated with immune response revealed an upregulation of pro-inflammatory markers, and hormone regulation genes highlighted alterations in endocrine signaling. Our findings emphasized that PFOS exhibits acute toxicity to crucian carp, potentially inducing hepatotoxicity by disrupting multiple physiological systems. This research provides a theoretical foundation for mitigating aquatic pollution and protecting eco-health, contributing to broader ecological and conservation biology discussions.

SREBP1c-Mediated Transcriptional Repression of YME1L1 Contributes to Acute Kidney Injury by Inducing Mitochondrial Dysfunction in Tubular Epithelial Cells

Acute kidney injury (AKI) is a prevalent clinical syndrome with high morbidity and mortality. Accumulating studies suggest mitochondrial dysfunction as the typical characteristics and key process of AKI, but the underlying mechanism remains elusive. The YME1-like 1 (YME1L1) ATPase, an inner mitochondrial membrane protein, is screened and identified to be downregulated in renal tubular epithelial cells of various mouse models and patients of AKI. Dramatically, restoration of YME1L1 expression significantly alleviates cisplatin-induced AKI and subsequent chronic kidney disease (CKD) through attenuating mitochondrial dysfunction via maintaining optic atrophy 1 (OPA1)-mediated mitochondrial energy metabolism homeostasis. Mechanistically, the upregulated expression of sterol regulatory element binding transcription factor 1c (SREBP1c) is demonstrated to be responsible for cisplatin-mediated transcriptional inhibition of YME1L1 via directly binding to its promoter region. Moreover, cisplatin-induced methyltransferase-like 3 (METTL3)-mediated m6A modification enhances SREBP1c mRNA stability, thereby upregulating its expression. Notably, both depletion of SREBP1c and renal tubule-specific overexpression of YME1L1 markedly ameliorate cisplatin-induced AKI and its transition to CKD. Taken together, these findings suggest that METTL3-mediated SREBP1c upregulation contributes to AKI and its progression to CKD through disrupting mitochondrial energy metabolism via transcriptionally suppressing YME1L1. Targeting the SREBP1c/YME1L1 signaling may serve as a novel therapeutic strategy against AKI.

OTUB1 mediates PARP1 deubiquitination to alleviate NAFLD by regulating HMGB1

Nonalcoholic fatty liver disease (NAFLD) is a common chronic disease characterized by hepatocyte steatosis, which excludes alcohol, drugs and other definite liver damage-related factors. It has been reported that OTUB1 serves a significant role in the regulation of glucose and lipid metabolism. The present study aimed to investigate the molecular mechanism underlying the effect of OTUB1 on regulating NAFLD. The NAFLD mouse model was induced via high-fat-diet, and glucose and insulin tolerance tests were then performed. In addition, the serum levels of total cholesterol (TC) and triglycerides (TG) were detected. The serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were assessed using the corresponding biochemical assays. Hematoxylin and eosin, and periodic acid-Schiff staining was carried out to evaluate the liver pathology in mice. The expression levels of the NAFLD-related genes and inflammatory genes were determined by reverse transcription-quantitative PCR, Western blot analysis and immunofluorescence staining. Furthermore, the regulatory association between OTUB1 and poly (adenosine diphosphate-ribose) polymerase (PARP)-1 was assessed by co-immunoprecipitation assay. The results showed that OTUB1 was significantly upregulated in both in vitro and in vivo NAFLD models. Knockout of OTUB1 significantly improved affected glucose tolerance and insulin sensitivity, decreased TG and TC content, and decreased ALT, AST and ALP levels. In addition, the results show that OTUB1 can regulate the expression of PARP1 by inhibiting the ubiquitination of PARP1, while PARP1 knockout can inhibit liver inflammation by regulating HMGB1, thereby improving NAFLD. Targeting OTUB1 could be a potential therapeutic strategy for the NAFLD.

How obesity affects adipocyte turnover

Cellular turnover is fundamental for tissue homeostasis and integrity. Adipocyte turnover, accounting for 4% of the total cellular mass turnover in humans, is essential for adipose tissue homeostasis during metabolic stress. In obesity, an altered adipose tissue microenvironment promotes adipocyte death. To clear dead adipocytes, macrophages are recruited and form a distinctive structure known as crown-like structure; subsequently, new adipocytes are generated from adipose stem and progenitor cells in the adipogenic niche to replace dead adipocytes. Accumulating evidence indicates that adipocyte death, clearance, and adipogenesis are sophisticatedly orchestrated during adipocyte turnover. In this Review, we summarize our current understandings of each step in adipocyte turnover, discussing its key players and regulatory mechanisms.

Myristoylated Eepd1 Enhances Lipolysis and Thermogenesis through PKA Activation to Combat Obesity

Middle-aged obesity, characterized by excessive fat accumulation and systemic energy imbalance, often precedes various health complications. Recent research has unveiled a surprising link between DNA damage response and energy metabolism. Here, we explore the role of Eepd1, a DNA repair enzyme, in regulating adipose tissue function and obesity onset. Eepd1 is primarily expressed in adipose tissue, where its downregulation or deletion accelerates obesity development. We show that Eepd1 ablation hinders PKA activation, thereby inhibiting lipolysis and thermogenesis in adipose tissue. Notably, cold exposure enhances Eepd1's myristoylation, facilitating its anchorage to adipocyte membranes and subsequent activation of PKA, while a mutation at the myristoylation site of Eepd1 disrupts this process. Moreover, individuals with obesity exhibit reduced Eepd1 expression. Pharmacological restoration of Eepd1 with Retigabine dihydrochloride effectively mitigates obesity. This study reveals Eepd1's unexpected role in promoting adipose lipolysis and thermogenesis, underscoring its potential as a promising therapeutic target to combat obesity.

Pachymic acid promotes brown/beige adipocyte differentiation and lipid metabolism in preadipocytes 3T3-L1 MBX

OBJECTIVES

To investigate the effect of pachymic acid on brown/beige adipocyte differentiation and lipid metabolism in preadipocytes 3T3-L1 MBX.

METHODS

The brown cocktail method was employed to induce 3T3-L1 MBX cells to differentiate into beige adipocytes. The impact of pachymic acid on the viability of 3T3-L1 MBX preadipocytes was evaluated using the CCK-8 assay. The formation of lipid droplets following treatment with pachymic acid was observed through oil red O staining, and the content of lipids in differentiated cells was determined. The expression levels of key browning genes, including uncoupling protein (Ucp) 1, the peroxisome proliferation-activating receptor gamma coactivator (Pgc)-1α, and the transcription factor containing PR domain 16 (Prdm16) were detected by quantitative reverse transcription polymerase chain reaction. The expression of sterol regulatory element binding protein (Srebp) 1c, acetyl-CoA carboxylase (Acc), fatty acid synthetase (Fas), and steroid-sensitive lipase (Hsl), fatty triglyceride hydrolase (Atgl), and carnitine palmitoyl transferase (Cpt) 1 of lipolysis-related genes were also examined.

RESULTS

The 3T3-L1 MBX was induced in vitro to form beige adipocytes with high expression of key browning genes, including Ucp1, Pgc-1α, Prdm16, and beige adipose-marker genes, including Cd137, Tbx1, and Tmem26. The concentration range of 0-80 μM pachymic acid was non-cytotoxic to 3T3-L1 MBX. Pachymic acid treatment significantly inhibited the differentiation of 3T3-L1 MBX, resulting in a notable decrease in lipid accumulation content (P<0.01). Additionally, there was a marked increase in the expression of key browning genes and their proteins, such as Ucp1, Pgc-1α, and Prdm16, while the expressions of fat synthesis-related genes Srebp1c, Acc and Fas were significantly decreased (all P<0.05). The expressions of lipolysis-related genes, including Hsl, Atgl, and Cpt1, were significantly increased (all P<0.05). Besides, treating with 20 μmol/L pachymic acid showed the most pronounced effect.

CONCLUSIONS

Pachymic acid can inhibit fat synthesis and promote lipid decomposition by regulating the brown formation and lipid differentiation of 3T3-L1 MBX preadipocytes.

Bisphenol S Induces Lipid Metabolism Disorders in HepG2 and SK-Hep-1 Cells via Oxidative Stress

Bisphenol S (BPS) is a typical endocrine disruptor associated with obesity. To observe BPS effects on lipid metabolism in HepG2 and SK-Hep-1 human HCC cells, a CCK-8 assay was used to assess cell proliferation in response to BPS, and the optimal concentration of BPS was selected. Biochemical indices such as triglyceride (TG) and total cholesterol (T-CHO), and oxidative stress indices such as malondialdehyde (MDA) and catalase (CAT) were measured. ROS and MDA levels were significantly increased after BPS treatment for 24 h and 48 h (p < 0.05), indicating an oxidative stress response. Alanine aminotransferase (ALT), T-CHO, and low-density lipoprotein cholesterol (LDL-C) levels also increased significantly after 24 or 48 h BPS treatments (p < 0.05). RT-PCR and Western blot analyses detected mRNA or protein expression levels of peroxisome proliferator-activated receptor α (PPARα) and sterol regulatory element-binding protein 1c (SREBP1C). The results indicated that BPS could inhibit the mRNA expression of PPARα and carnitine palmitoyl transferase 1B (CPT1B), reduce lipid metabolism, promote mRNA or protein expression of SREBP1C and fatty acid synthase (FASN), and increase lipid synthesis. Increased lipid droplets were observed using morphological Oil Red O staining. Our study demonstrates that BPS may cause lipid accumulation by increasing oxidative stress and perturbing cellular lipid metabolism.

Multi-omics reveals the mechanism of Trimethylamine N-oxide derived from gut microbiota inducing liver fatty of dairy cows

BACKGROUND

Trimethylamine N-oxide (TMAO) is a metabolite produced by gut microbiota, and its potential impact on lipid metabolism in mammals has garnered widespread attention in the scientific community. Bovine fatty liver disease, a metabolic disorder that severely affects the health and productivity of dairy cows, poses a significant economic burden on the global dairy industry. However, the specific role and pathogenesis of TMAO in bovine fatty liver disease remain unclear, limiting our understanding and treatment of the condition. This study aims to construct a bovine fatty liver cell model using an integrated approach that combines transcriptomic, proteomic, and metabolomic data. The objective is to investigate the impact of TMAO on lipid metabolism at the molecular level and explore its potential regulatory mechanisms.

RESULTS

We established an in vitro bovine fatty liver cell model and conducted a comprehensive analysis of cells treated with TMAO using high-throughput omics sequencing technologies. Bioinformatics methods were employed to delve into the regulatory effects on lipid metabolism, and several key genes were validated through RT-qPCR. Treatment with TMAO significantly affected 4790 genes, 397 proteins, and 137 metabolites. KEGG enrichment analysis revealed that the significantly altered molecules were primarily involved in pathways related to the pathology of fatty liver disease, such as metabolic pathways, insulin resistance, hepatitis B, and the AMPK signaling pathway. Moreover, through joint analysis, we further uncovered that the interaction between TMAO-mediated AMPK signaling and oxidative phosphorylation pathways might be a key mechanism promoting lipid accumulation in the liver.

CONCLUSIONS

Our study provides new insights into the role of TMAO in the pathogenesis of bovine fatty liver disease and offers a scientific basis for developing more effective treatment strategies.

Senescent cell depletion alleviates obesity-related metabolic and cardiac disorders

Obesity is a major contributor to metabolic and cardiovascular disease. Although senescent cells have been shown to accumulate in adipose tissue, the role of senescence in obesity-induced metabolic disorders and in cardiac dysfunction is not yet clear; therefore, the therapeutic potential of managing senescence in obesity-related metabolic and cardiac disorders remains to be fully defined.

OBJECTIVE

We investigated the beneficial effects of a senolytic cocktail (dasatinib and quercetin) on senescence and its influence on obesity-related parameters.

METHODS AND RESULTS

We found that the increase in body weight and adiposity, glucose intolerance, insulin resistance, dyslipidemia, hyperleptinemia, and hepatic disorders which were induced by an obesogenic diet were alleviated by senolytic cocktail treatment in mice. Treatment with senolytic compounds eliminated senescent cells, counteracting the activation of the senescence program and DNA damage in white adipose tissue (WAT) observed with an obesogenic diet. Moreover, the senolytic cocktail prevented the brown adipose tissue (BAT) whitening and increased the expression of the thermogenic gene profile in BAT and pWAT. In the hearts of obese mice, senolytic combination abolished myocardial maladaptation, reducing the senescence-associated secretory phenotype (SASP) and DNA damage, repressing cardiac hypertrophy, and improving diastolic dysfunction. Additionally, we showed that treatment with the senolytic cocktail corrected gene expression programs associated with fatty acid metabolism, oxidative phosphorylation, the P53 pathway, and DNA repair, which were all downregulated in obese mice.

CONCLUSIONS

Collectively, these data suggest that a senolytic cocktail can prevent the activation of the senescence program in the heart and WAT and activate the thermogenic program in BAT. Our results suggest that targeting senescent cells may be a novel therapeutic strategy for alleviating obesity-related metabolic and cardiac disorders.

Ameliorating Oxidative Stress-Aggravated Adipose Tissue Senescence by Sesamol in Aged Obese Mice via Nrf2/p38MAPK Signaling

Adipocyte senescence is one of the major common features correlated with aging, which can also lead to obesity, and aggravated oxidative stress contributes to cell senescence. Sesamol, a lignan from plants found in sesame, has been proven to alleviate obesity. However, the effects and mechanisms of sesamol on adipose tissue senescence remain unclear. In the current research, we used an aged model of obesity by feeding old mice high-fat diet (HFD), and a senescent cell model by treating 3T3-L1 mature adipocytes with repeated exposure to hydrogen peroxide (H2O2). Both HFD induced aged obesity mice and H2O2 treated cells presented features associated with senescence. Additionally, obesity in aged mice accelerated the expression of adipose tissue senescence-associated markers. Notably, the presence of sesamol showed marked activation of Nrf2 and inhibition of p-p38MAPK, along with the suppression of oxidative stress (ROS, MDA, SOD), inflammatory factors (IL-6, TNFα) and cell cycle inhibitors (p53, p21, p16). A pretreatment of ML385, an inhibitor of Nrf2, reversed the effects induced by sesamol treatment. In conclusion, our results demonstrated that obesity contributed to deteriorated adipose tissue senescence during aging. Furthermore, sesamol, acted as an activator of Nrf2 and exerted negative impacts on the activation of p38MAPK, which were associated with amelioration of adipose senescence, thereby indicating it could be a potential nutritional intervention for preventing and treating aging-related disorders.

Inhibition of the RXRA-PPARα-FABP4 signaling pathway alleviates vascular cellular aging by an SGLT2 inhibitor in an atherosclerotic mice model

Atherosclerosis is the pathological cause of atherosclerotic cardiovascular disease (ASCVD), which rapidly progresses during the cellular senescence. Sodium-glucose cotransporter 2 inhibitors (SGLT2is) reduce major cardiovascular events in patients with ASCVD and have potential antisenescence effects. Here, we investigate the effects of the SGLT2 inhibitor dapagliflozin on cellular senescence in atherosclerotic mice. Compared with ApoE-/- control mice treated with normal saline, those in the ApoE-/- dapagliflozin group, receiving intragastric dapagliflozin (0.1 mg kg-1 d-1) for 14 weeks, exhibited the reduction in the total aortic plaque area (48.8%±6.6% vs. 74.6%±8.0%, P<0.05), the decrease in the lipid core area ((0.019±0.0037) mm2vs. (0.032±0.0062) mm2, P<0.05) and in the percentage of senescent cells within the plaques (16.4%±3.7% vs. 30.7%±2.0%, P<0.01), while the increase in the thickness of the fibrous cap ((21.6±2.1) µm vs. (14.6±1.5) µm, P<0.01). Transcriptome sequencing of the aortic arch in the mice revealed the involvement of the PPARα and the fatty acid metabolic signaling pathways in dapagliflozin's mechanism of ameliorating cellular aging and plaque progression. In vitro, dapagliflozin inhibited the expression of PPARα and its downstream signal FABP4, by which the accumulation of senescent cells in human aortic smooth muscle cells (HASMCs) was reduced under high-fat conditions. This effect was accompanied by a reduction in the intracellular lipid content and alleviation of oxidative stress. However, these beneficial effects of dapagliflozin could be reversed by the PPARα overexpression. Bioinformatics analysis and molecular docking simulations revealed that dapagliflozin might exert its effects by directly interacting with the RXRA protein, thereby influencing the expression of the PPARα signaling pathway. In conclusion, the cellular senescence of aortic smooth muscle cells is potentially altered by dapagliflozin through the suppression of the RXRA-PPARα-FABP4 signaling pathway, resulting in a deceleration of atherosclerotic progression.

SenNet recommendations for detecting senescent cells in different tissues

Once considered a tissue culture-specific phenomenon, cellular senescence has now been linked to various biological processes with both beneficial and detrimental roles in humans, rodents and other species. Much of our understanding of senescent cell biology still originates from tissue culture studies, where each cell in the culture is driven to an irreversible cell cycle arrest. By contrast, in tissues, these cells are relatively rare and difficult to characterize, and it is now established that fully differentiated, postmitotic cells can also acquire a senescence phenotype. The SenNet Biomarkers Working Group was formed to provide recommendations for the use of cellular senescence markers to identify and characterize senescent cells in tissues. Here, we provide recommendations for detecting senescent cells in different tissues based on a comprehensive analysis of existing literature reporting senescence markers in 14 tissues in mice and humans. We discuss some of the recent advances in detecting and characterizing cellular senescence, including molecular senescence signatures and morphological features, and the use of circulating markers. We aim for this work to be a valuable resource for both seasoned investigators in senescence-related studies and newcomers to the field.

PONYTA: prioritization of phenotype-related genes from mouse KO events using PU learning on a biological network

MOTIVATION

Transcriptome data from gene knock-out (KO) experiments in mice provide crucial insights into the intricate interactions between genotype and phenotype. Differentially expressed gene (DEG) analysis and network propagation (NP) are well-established methods for analysing transcriptome data. To determine genes related to phenotype changes from a KO experiment, we need to choose a cutoff value for the corresponding criterion based on the specific method. Using a rigorous cutoff value for DEG analysis and NP is likely to select mostly positive genes related to the phenotype, but many will be rejected as false negatives. On the other hand, using a loose cutoff value for either method is prone to include a number of genes that are not phenotype-related, which are false positives. Thus, the research problem at hand is how to deal with the trade-off between false negatives and false positives.

RESULTS

We propose a novel framework called PONYTA for gene prioritization via positive-unlabeled (PU) learning on biological networks. Beginning with the selection of true phenotype-related genes using a rigorous cutoff value for DEG analysis and NP, we address the issue of handling false negatives by rescuing them through PU learning. Evaluations on transcriptome data from multiple studies show that our approach has superior gene prioritization ability compared to benchmark models. Therefore, PONYTA effectively prioritizes genes related to phenotypes derived from gene KO events and guides in vitro and in vivo gene KO experiments for increased efficiency.

AVAILABILITY AND IMPLEMENTATION

The source code of PONYTA is available at https://github.com/Jun-Hyeong-Kim/PONYTA.

Adipose tissue senescence: Biological changes, hallmarks and therapeutic approaches

Adipose tissue (AT), the largest energy storage reservoir and endocrine organ, plays a crucial role in regulating systemic energy metabolism. As one of the most vulnerable tissues during aging, the plasticity of AT is impaired. With age, AT undergoes redistribution, characterized by expansion of visceral adipose tissue (VAT) and reduction of peripheral subcutaneous adipose tissue (SAT). Additionally, age-related changes in AT include reduced adipogenesis of white adipocytes, decreased proliferation and differentiation capacity of mesenchymal stromal/stem cells (MSCs), diminished thermogenic capacity in brown/beige adipocytes, and dysregulation of immune cells. Specific and sensitive hallmarks enable the monitoring and evaluation of the biological changes associated with aging. In this study, we have innovatively proposed seven characteristic hallmarks of AT senescence, including telomere attrition, epigenetic alterations, genomic instability, mitochondrial dysfunction, disabled macroautophagy, cellular senescence, and chronic inflammation, which are intricately interconnected and mutually regulated. Finally, we discussed anti-aging strategies targeting AT, offering insights into mitigating or delaying metabolic disturbances caused by AT senescence.

A nutrigeroscience approach: Dietary macronutrients and cellular senescence

Cellular senescence, a process in which a cell exits the cell cycle in response to stressors, is one of the hallmarks of aging. Senescence and the senescence-associated secretory phenotype (SASP)-a heterogeneous set of secreted factors that disrupt tissue homeostasis and promote the accumulation of senescent cells-reprogram metabolism and can lead to metabolic dysfunction. Dietary interventions have long been studied as methods to combat age-associated metabolic dysfunction, promote health, and increase lifespan. A growing body of literature suggests that senescence is responsive to diet, both to calories and specific dietary macronutrients, and that the metabolic benefits of dietary interventions may arise in part through reducing senescence. Here, we review what is currently known about dietary macronutrients' effect on senescence and the SASP, the nutrient-responsive molecular mechanisms that may mediate these effects, and the potential for these findings to inform the development of a nutrigeroscience approach to healthy aging.

Enhancing adipose tissue functionality in obesity: senotherapeutics, autophagy and cellular senescence as a target

Obesity, a global health crisis, disrupts multiple systemic processes, contributing to a cascade of metabolic dysfunctions by promoting the pathological expansion of visceral adipose tissue (VAT). This expansion is characterized by impaired differentiation of pre-adipocytes and an increase in senescent cells, leading to a pro-inflammatory state and exacerbated oxidative stress. Particularly, the senescence-associated secretory phenotype (SASP) and adipose tissue hypoxia further impair cellular function, promoting chronic disease development. This review delves into the potential of autophagy modulation and the therapeutic application of senolytics and senomorphics as novel strategies to mitigate adipose tissue senescence. By exploring the intricate mechanisms underlying adipocyte dysfunction and the emerging role of natural compounds in senescence modulation, we underscore the promising horizon of senotherapeutics in restoring adipose health. This approach not only offers a pathway to combat the metabolic complications of obesity, but also opens new avenues for enhancing life quality and managing the global burden of obesity-related conditions. Our analysis aims to bridge the gap between current scientific progress and clinical application, offering new perspectives on preventing and treating obesity-induced adipose dysfunction.

The Roles of White Adipose Tissue and Liver NADPH in Dietary Restriction-Induced Longevity

Dietary restriction (DR) protocols frequently employ intermittent fasting. Following a period of fasting, meal consumption increases lipogenic gene expression, including that of NADPH-generating enzymes that fuel lipogenesis in white adipose tissue (WAT) through the induction of transcriptional regulators SREBP-1c and CHREBP. SREBP-1c knockout mice, unlike controls, did not show an extended lifespan on the DR diet. WAT cytoplasmic NADPH is generated by both malic enzyme 1 (ME1) and the pentose phosphate pathway (PPP), while liver cytoplasmic NADPH is primarily synthesized by folate cycle enzymes provided one-carbon units through serine catabolism. During the daily fasting period of the DR diet, fatty acids are released from WAT and are transported to peripheral tissues, where they are used for beta-oxidation and for phospholipid and lipid droplet synthesis, where monounsaturated fatty acids (MUFAs) may activate Nrf1 and inhibit ferroptosis to promote longevity. Decreased WAT NADPH from PPP gene knockout stimulated the browning of WAT and protected from a high-fat diet, while high levels of NADPH-generating enzymes in WAT and macrophages are linked to obesity. But oscillations in WAT [NADPH]/[NADP+] from feeding and fasting cycles may play an important role in maintaining metabolic plasticity to drive longevity. Studies measuring the WAT malate/pyruvate as a proxy for the cytoplasmic [NADPH]/[NADP+], as well as studies using fluorescent biosensors expressed in the WAT of animal models to monitor the changes in cytoplasmic [NADPH]/[NADP+], are needed during ad libitum and DR diets to determine the changes that are associated with longevity.

Tubular insulin-induced gene 1 deficiency promotes NAD+ consumption and exacerbates kidney fibrosis

Profibrotic proximal tubules (PT) were identified as a unique phenotype of proximal tubule cells (PTCs) in renal fibrosis by single-cell RNA sequencing (scRNA-seq). Controlling the process of renal fibrosis requires understanding how to manage the S1 subset's branch to the S3 subset rather than to the profibrotic PT subset. Insulin-induced gene 1 (Insig1) is one of the branch-dependent genes involved in controlling this process, although its role in renal fibrosis is unknown. Here, we discovered that tubular Insig1 deficiency, rather than fibroblast Insig1 deficiency, plays a detrimental role in the pathogenesis of renal fibrosis in vivo and in vitro. Overexpression of Insig1 profoundly inhibited renal fibrosis. Mechanistically, Insig1 deletion in PTCs boosted SREBP1 nuclear localization, increasing Aldh1a1 transcriptional activity, causing excessive NAD+ consumption and ER enlargement, as well as accelerating renal fibrosis. We also identified nicardipine as a selective inhibitor of Aldh1a1, which could restore NAD+ and maintain ER homeostasis, as well as improve renal fibrosis. Together, our findings support tubular Insig1 as a new therapeutic target for chronic kidney disease (CKD).

DNA damage, obesity and obesity-related health complications: what are new data telling us?

PURPOSE OF REVIEW

Obesity is associated with increased DNA damage, which may in turn contribute to the development of obesity-related complications. DNA damage can also affect adipocyte biology, resulting in increased adiposity. Carefully managed weight loss programs can reverse this process. This article surveys new data that support these contentions.

RECENT FINDINGS

Whole exome sequencing analyses have identified rare variants linked to high BMI and adiposity. Two of the identified genes are linked to DNA damage and DNA repair, suggesting that DNA damage itself may play a role in the cause of obesity. It has also been recognized that obesity increases DNA damage in breast tissue of carriers of BRCA mutations and rates of tumour formation in BRCA1+ mice, indicating effect of obesity on cancer development in high-risk populations. In addition, obesity promotes cancer cell chemoresistance by decreasing fatty acid oxidation involved in cellular DNA damage response, leading to apoptotic cellular death. Obesity is also associated with a reduced capacity of oocytes to repair sperm DNA damage, leading to lower in-vitro fertilization rates in women with obesity.

SUMMARY

DNA damage and cellular responses to DNA damage can be both the result and the cause of obesity and can strongly influence the development and treatment of obesity-associated diseases.

Lactobacillus acidophilus CICC 6075 attenuates high-fat diet-induced obesity by improving gut microbiota composition and histidine biosynthesis

This study aimed to investigate the potential anti-obesity efficacy of Lactobacillus acidophilus CICC 6075. The study analyzed fecal metagenomic data from 120 obese and 100 non-obese individuals. C57BL/6 mice on normal diet or high-fat diet (HFD) were treated with L. acidophilus CICC 6075 by daily oral gavage for 12 weeks, followed by evaluations of the obesity phenotype. Metagenomic analysis revealed depletion of L. acidophilus in obese individuals. Administration of L. acidophilus CICC 6075 attenuated excessive weight gain and fat accumulation and maintained the intestinal barrier in HFD-induced obese mice. Sequencing results showed that HFD hindered α- and β-diversity while reducing the relative abundance of Lactobacillus and norank_f_Muribaculaceae and significantly increasing the relative abundance of Ileibacterium. L. acidophilus CICC 6075 reversed these results and reduced the Firmicutes/Bacteroidetes ratio. Supplementation of L. acidophilus CICC 6075 enhanced histidine biosynthesis, inhibited the NF-κB pathway, and significantly reduced the expression levels of inflammatory factors in adipose tissue. These results indicate that L. acidophilus CICC 6075 alleviates HFD-induced obesity in mice by inhibiting the activation of the NF-κB pathway and enhancing gut microbiota functionality. This suggests that L. acidophilus CICC 6075 may be a good candidate probiotic for preventing obesity.

Lipids and lipid metabolism in cellular senescence: Emerging targets for age-related diseases

Cellular senescence is a kind of cellular state triggered by endogenous or exogenous stimuli, which is mainly characterized by stable cell cycle arrest and complex senescence-associated secretory phenotype (SASP). Once senescent cells accumulate in tissues, they may eventually accelerate the progression of age-related diseases, such as atherosclerosis, osteoarthritis, chronic lung diseases, cancers, etc. Recent studies have shown that the disorders of lipid metabolism are not only related to age-related diseases, but also regulate the cellular senescence process. Based on existing research evidences, the changes in lipid metabolism in senescent cells are mainly concentrated in the metabolic processes of phospholipids, fatty acids and cholesterol. Obviously, the changes in lipid-metabolizing enzymes and proteins involved in these pathways play a critical role in senescence. However, the link between cellular senescence, changes in lipid metabolism and age-related disease remains to be elucidated. Herein, we summarize the lipid metabolism changes in senescent cells, especially the senescent cells that promote age-related diseases, as well as focusing on the role of lipid-related enzymes or proteins in senescence. Finally, we explore the prospect of lipids in cellular senescence and their potential as drug targets for preventing and delaying age-related diseases.

Gut microbiota-bile acid crosstalk and metabolic fatty liver in spotted seabass (Lateolabrax maculatus): The role of a cholesterol, taurine and glycine supplement

The prevalent practice of substituting fishmeal with plant protein frequently leads to disturbances in bile acid metabolism, subsequently increasing the incidence of metabolic liver diseases. Bile acid nutrients such as cholesterol, taurine and glycine have been shown to enhance bile acid synthesis and confer beneficial effects on growth. Therefore, this study aimed to investigate the effects of cholesterol-taurine-glycine (Ch-Tau-Gly) supplement on bile acid metabolism and liver health in spotted seabass (Lateolabrax maculatus) fed a plant-based diet. Two isonitrogenous and isolipidic diets were formulated: (1) plant protein-based diet (PP); (2) PP supplemented 0.5% cholesterol, 0.5% taurine and 1.3% glycine (CTG). Each experimental diet was randomly fed to quadruplicate groups of 30 feed-trained spotted seabass in each tank. The results revealed that supplementing plant-based diet with Ch-Tau-Gly supplement led to an increase in carcass ratio (meat yield) in spotted seabass (P < 0.05), indirectly contributing positively to their growth. The dietary supplement effectively suppressed endogenous cholesterol synthesis in the liver, promoted the expression of bile acid synthesis enzyme synthesis, and simultaneously the expression of intestinal fxr and its downstream genes, including hnf4α and shp (P < 0.05). The reduction in Lactobacillus_salivarius and bile salt hydrolase (BSH) were observed in CTG group with concurrently increased conjugated chenodeoxycholic acid (CDCA) bile acids (P < 0.05), suggesting the enhancement of the hydrophilicity of the bile acid pool. In CTG group, fatty liver was alleviated with a corresponding increase in lipid metabolism, characterized by a downregulation of genes associated with lipogenesis and lipid droplet deposition, along with an upregulation of genes related to lipolysis. Our study underscored the ability of Ch-Tau-Gly supplement to influence the gut microbiota, leading to an increase in the levels of conjugated CDCA (P < 0.05) in the bile acid pool of spotted seabass. The interplay between the gut microbiota and bile acids might constitute a crucial pathway in the promotion of liver health. These findings offer a promising solution, suggesting that Ch-Tau-Gly supplement have the potential to promote the growth of aquatic species and livestock fed on plant-based diets while addressing issues related to metabolic fatty liver.

M2 macrophage-derived TGF-β induces age-associated loss of adipogenesis through progenitor cell senescence

OBJECTIVES

Adipose tissue is an endocrine and energy storage organ composed of several different cell types, including mature adipocytes, stromal cells, endothelial cells, and a variety of immune cells. Adipose tissue aging contributes to the pathogenesis of metabolic dysfunction and is likely induced by crosstalk between adipose progenitor cells (APCs) and immune cells, but the underlying molecular mechanisms remain largely unknown. In this study, we revealed the biological role of p16high senescent APCs, and investigated the crosstalk between each cell type in the aged white adipose tissue.

METHODS

We performed the single-cell RNA sequencing (scRNA-seq) analysis on the p16high adipose cells sorted from aged p16-CreERT2/Rosa26-LSL-tdTomato mice. We also performed the time serial analysis on the age-dependent bulk RNA-seq datasets of human and mouse white adipose tissues to infer the transcriptome alteration of adipogenic potential within aging.

RESULTS

We show that M2 macrophage-derived TGF-β induces APCs senescence which impairs adipogenesis in vivo. p16high senescent APCs increase with age and show loss of adipogenic potential. The ligand-receptor interaction analysis reveals that M2 macrophages are the donors for TGF-β and the senescent APCs are the recipients. Indeed, treatment of APCs with TGF-β1 induces senescent phenotypes through mitochondrial ROS-mediated DNA damage in vitro. TGF-β1 injection into gonadal white adipose tissue (gWAT) suppresses adipogenic potential and induces fibrotic genes as well as p16 in APCs. A gWAT atrophy is observed in cancer cachexia by APCs senescence, whose induction appeared to be independent of TGF-β induction.

CONCLUSIONS

Our results suggest that M2 macrophage-derived TGF-β induces age-related lipodystrophy by APCs senescence. The TGF-β treatment induced DNA damage, mitochondrial ROS, and finally cellular senescence in APCs.

Ex vivo Anti-Senescence Activity of N-Acetylcysteine in Visceral Adipose Tissue of Obese Volunteers

INTRODUCTION

Excessive visceral adiposity is known to drive the onset of metabolic derangements, mostly involving oxidative stress, prolonged inflammation, and cellular senescence. N-acetylcysteine (NAC) is a synthetic form of l-cysteine with potential antioxidant, anti-inflammatory, and anti-senescence properties. This ex-vivo study aimed to determine the effect of NAC on some markers of senescence including β-galactosidase activity and p16, p53, p21, IL-6, and TNF-α gene expressions in visceral adipose tissue in obese adults.

METHODS

This ex-vivo experimental study involved 10 obese participants who were candidates for bariatric surgery. Duplicate biopsies from the abdominal visceral adipose tissue were obtained from the omentum. The biopsies were treated with or without NAC (5 and 10 mm). To evaluate adipose tissue senescence, beta-galactosidase (β-gal) activity and the expression of P16, P21, P53, IL-6, and TNF-α were determined. ANOVA test was employed to analyze the varying markers of cellular senescence and inflammation between treatment groups.

RESULTS

The NAC at concentrations of 5 mm and 10 mm resulted in a noteworthy reduction β-gal activity compared to the control group (p < 0.001). Additionally, the expression of P16, P21, and IL-6 was significantly reduced following treatment with NAC (5 mm) and NAC (10 mm) compared to the control group (All p < 0.001).

DISCUSSION/CONCLUSION

Taken together, these data suggest the senotherapeutic effect of NAC, as it effectively reduces the activity of SA-β-gal and the expression of IL-6, P16, and P21 genes in the visceral adipose tissue of obese individuals.

Androgens exacerbate hepatic triglyceride accumulation in rats with polycystic ovary syndrome by downregulating MTTP expression

PURPOSE

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder, which is closely associated with insulin resistance, glucose and lipid metabolism disorders. Patients with PCOS have a significantly higher risk of non-alcoholic fatty liver disease and are associated with hyperandrogenemia (HA). However, the exact mechanism by which HA exacerbates hepatic steatosis in PCOS has not yet been fully elucidated. This work aims to investigate the effects and underlying mechanisms of androgens on hepatic triglyceride (TG) metabolism in rats with PCOS.

METHODS

Twenty-four female Sprague-Dawley rats were randomly divided into four groups (6 rats/group): control, high-fat diet (HFD), PCOS, and PCOS + flutamide (Flu). Changes in the estrous cycle, liver and ovarian tissue sections, serum total testosterone, serum and liver biochemical indicators, and key enzymes involved in TG metabolism were studied.

RESULTS

Hepatocyte steatosis and TG accumulation were more evident in the PCOS group than in the control and HFD groups. The PCOS group showed apparent increases in the levels of serum alanine aminotransferase, aspartate aminotransferase, TG, free fatty acid, fasting insulin, and homeostasis model assessment of insulin resistance. Hepatic VLDL and apoB-100 levels decreased in the PCOS group. After Flu was administered to block the actions of androgens, the above abnormalities had been improved. The expression of MTTP was greatly decreased in the PCOS group and significantly increased after Flu administration.

CONCLUSION

Hepatic steatosis in PCOS rats was correlated with HA. Androgens may exacerbate hepatic TG accumulation by downregulating MTTP expression in PCOS.

Body composition and inflammation variables as the potential prognostic factors in epithelial ovarian cancer treated with Olaparib

Background

Epithelial ovarian cancer (EOC) is a significant cause of mortality among gynecological cancers. While Olaparib, a PARP inhibitor, has demonstrated efficacy in EOC maintenance therapy, individual responses vary. This study aims to assess the prognostic significance of body composition and systemic inflammation markers in EOC patients undergoing initial Olaparib treatment.

Methods

A retrospective analysis was conducted on 133 EOC patients initiating Olaparib therapy. Progression-free survival (PFS) was assessed through Kaplan-Meier analysis and Cox proportional hazards regression. Pre-treatment computed tomography images were utilized to evaluate body composition parameters including subcutaneous adipose tissue index (SATI), visceral adipose tissue index (VATI), skeletal muscle area index (SMI), and body mineral density (BMD). Inflammatory markers, such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), serum albumin, and hemoglobin levels, were also measured.

Results

The median follow-up duration was 16 months (range: 5-49 months). Survival analysis indicated that high SATI, high VATI, high SMI, high BMD, low NLR, and low PLR were associated with decreased risk of disease progression (all p < 0.05). Multivariate analysis identified several factors independently associated with poor PFS, including second or further lines of therapy (HR = 2.16; 95% CI = 1.09-4.27, p = 0.027), low VATI (HR = 3.79; 95% CI = 1.48-9.70, p = 0.005), low SMI (HR = 2.52; 95% CI = 1.11-5.72, p = 0.027), low BMD (HR = 2.36; 95% CI = 1.22-4.54, p = 0.010), and high NLR (HR = 0.31; 95% CI = 0.14-0.69, p = 0.004). Subgroup analysis in serous adenocarcinoma patients revealed distinct prognostic capabilities of SATI, VATI, SMI, PLR, and NLR.

Conclusion

Body composition and inflammation variables hold promise as predictors of therapeutic response to Olaparib in EOC patients. Understanding their prognostic significance could facilitate tailored treatment strategies, potentially improving patient outcomes.

The Past and Future of Inflammation as a Target to Cancer Prevention

Inflammation is an essential defense mechanism in which innate immune cells are coordinately activated on encounter of harmful stimuli, including pathogens, tissue injury, and toxic compounds and metabolites to neutralize and eliminate the instigator and initiate healing and regeneration. Properly terminated inflammation is vital to health, but uncontrolled runaway inflammation that becomes chronic begets a variety of inflammatory and metabolic diseases and increases cancer risk. Making damaged tissues behave as "wounds that do not heal" and sustaining the production of growth factors whose physiologic function is tissue healing, chronic inflammation accelerates cancer emergence from premalignant lesions. In 1863, Rudolf Virchow, a leading German pathologist, suggested a possible association between inflammation and tumor formation, but it took another 140 years to fully elucidate and appreciate the tumorigenic role of inflammation. Key findings outlined molecular events in the inflammatory cascade that promote cancer onset and progression and enabled a better appreciation of when and where inflammation should be inhibited. These efforts triggered ongoing research work to discover and develop inflammation-reducing chemopreventive strategies for decreasing cancer risk and incidence.

The transcription factor GATA6 accelerates vascular smooth muscle cell senescence-related arterial calcification by counteracting the role of anti-aging factor SIRT6 and impeding DNA damage repair

Arterial calcification is a hallmark of vascular pathology in the elderly and in individuals with chronic kidney disease (CKD). Vascular smooth muscle cells (VSMCs), after attaining a senescent phenotype, are implicated in the calcifying process. However, the underlying mechanism remains to be elucidated. Here, we reveal an aberrant upregulation of transcriptional factor GATA6 in the calcified aortas of humans, mice with CKD and mice subjected to vitamin D3 injection. Knockdown of GATA6, via recombinant adeno-associated virus carrying GATA6 shRNA, inhibited the development of arterial calcification in mice with CKD. Further gain- and loss-of function experiments in vitro verified the contribution of GATA6 in osteogenic differentiation of VSMCs. Samples of human aorta exhibited a positive relationship between age and GATA6 expression and GATA6 was also elevated in the aortas of old as compared to young mice. Calcified aortas displayed senescent features with VSMCs undergoing premature senescence, blunted by GATA6 downregulation. Notably, abnormal induction of GATA6 in senescent and calcified aortas was rescued in Sirtuin 6 (SIRT6)-transgenic mice, a well-established longevity mouse model. Suppression of GATA6 accounted for the favorable effect of SIRT6 on VSMCs senescence prevention. Mechanistically, SIRT6 inhibited the transcription of GATA6 by deacetylation and increased degradation of transcription factor Nkx2.5. Moreover, GATA6 was induced by DNA damage stress during arterial calcification and subsequently impeded the Ataxia-telangiectasia mutated (ATM)-mediated DNA damage repair process, leading to accelerated VSMCs senescence and osteogenic differentiation. Thus, GATA6 is a novel regulator in VSMCs senescence. Our findings provide novel insight in arterial calcification and a potential new target for intervention.

Longevity-Associated Transcription Factor ATF7 Promotes Healthspan by Suppressing Cellular Senescence and Systematic Inflammation

Aging is characterized by persistent low-grade systematic inflammation, which is largely responsible for the occurrence of various age-associated diseases. We and others have previously reported that long-lived people (such as centenarians) can delay the onset of or even escape certain major age-related diseases. Here, by screening blood transcriptome and inflammatory profiles, we found that long-lived individuals had a relatively lower inflammation level (IL6, TNFα), accompanied by up-regulation of activating transcription factor 7 (ATF7). Interestingly, ATF7 expression was gradually reduced during cellular senescence. Loss of ATF7 induced cellular senescence, while overexpression delayed senescence progress and senescence-associated secretory phenotype (SASP) secretion. We showed that the anti-senescence effects of ATF7 were achieved by inhibiting nuclear factor kappa B (NF-κB) signaling and increasing histone H3K9 dimethylation (H3K9me2). In Caenorhabditis elegans, ATF7 overexpression significantly suppressed aging biomarkers and extended lifespan. Our findings suggest that ATF7 is a longevity-promoting factor that lowers cellular senescence and inflammation in long-lived individuals.

From the Sun to the Cell: Examining Obesity through the Lens of Vitamin D and Inflammation

Obesity affects more than one billion people worldwide and often leads to cardiometabolic chronic comorbidities. It induces senescence-related alterations in adipose tissue, and senescence is closely linked to obesity. Fully elucidating the pathways through which vitamin D exerts anti-inflammatory effects may improve our understanding of local adipose tissue inflammation and the pathogenesis of metabolic disorders. In this narrative review, we compiled and analyzed the literature from diverse academic sources, focusing on recent developments to provide a comprehensive overview of the effect of vitamin D on inflammation associated with obesity and senescence. The article reveals that the activation of the NF-κB (nuclear factor kappa B subunit 1) and NLRP3 inflammasome (nucleotide-binding domain, leucine-rich-containing, pyrin domain-containing-3) pathways through the toll-like receptors, which increases oxidative stress and cytokine release, is a common mechanism underlying inflammation associated with obesity and senescence, and it discusses the potential beneficial effect of vitamin D in alleviating the development of subclinical inflammation. Investigating the main target cells and pathways of vitamin D action in adipose tissue could help uncover complex mechanisms of obesity and cellular senescence. This review summarizes significant findings related to opportunities for improving metabolic health.

Fatty acid oxidation regulates cellular senescence by modulating the autophagy-SIRT1 axis

Senescence, a cellular process through which damaged or dysfunctional cells suppress the cell cycle, contributes to aging or age-related functional decline. Cell metabolism has been closely correlated with aging processes, and it has been widely recognized that metabolic changes underlie the cellular alterations that occur with aging. Here, we report that fatty acid oxidation (FAO) serves as a critical regulator of cellular senescence and uncover the underlying mechanism by which FAO inhibition induces senescence. Pharmacological or genetic ablation of FAO results in a p53-dependent induction of cellular senescence in human fibroblasts, whereas enhancing FAO suppresses replicative senescence. We found that FAO inhibition promotes cellular senescence through acetyl-CoA, independent of energy depletion. Mechanistically, increased formation of autophagosomes following FAO inhibition leads to a reduction in SIRT1 protein levels, thereby contributing to senescence induction. Finally, we found that inhibition of autophagy or enforced expression of SIRT1 can rescue the induction of senescence as a result of FAO inhibition. Collectively, our study reveals a distinctive role for the FAO-autophagy-SIRT1 axis in the regulation of cellular senescence. [BMB Reports 2023; 56(12): 651-656].

Fatty acid oxidation regulates cellular senescence by modulating the autophagy-SIRT1 axis

Senescence, a cellular process through which damaged or dysfunctional cells suppress the cell cycle, contributes to aging or age-related functional decline. Cell metabolism has been closely correlated with aging processes, and it has been widely recognized that metabolic changes underlie the cellular alterations that occur with aging. Here, we report that fatty acid oxidation (FAO) serves as a critical regulator of cellular senescence and uncover the underlying mechanism by which FAO inhibition induces senescence. Pharmacological or genetic ablation of FAO results in a p53-dependent induction of cellular senescence in human fibroblasts, whereas enhancing FAO suppresses replicative senescence. We found that FAO inhibition promotes cellular senescence through acetyl-CoA, independent of energy depletion. Mechanistically, increased formation of autophagosomes following FAO inhibition leads to a reduction in SIRT1 protein levels, thereby contributing to senescence induction. Finally, we found that inhibition of autophagy or enforced expression of SIRT1 can rescue the induction of senescence as a result of FAO inhibition. Collectively, our study reveals a distinctive role for the FAO-autophagy-SIRT1 axis in the regulation of cellular senescence. [BMB Reports 2023; 56(12): 651-656].

Single-base editing in IGF2 improves meat production and intramuscular fat deposition in Liang Guang Small Spotted pigs

BACKGROUND

Chinese indigenous pigs are popular with consumers for their juiciness, flavour and meat quality, but they have lower meat production. Insulin-like growth factor 2 (IGF2) is a maternally imprinted growth factor that promotes skeletal muscle growth by regulating cell proliferation and differentiation. A single nucleotide polymorphism (SNP) within intron 3 of porcine IGF2 disrupts a binding site for the repressor, zinc finger BED-type containing 6 (ZBED6), leading to up-regulation of IGF2 and causing major effects on muscle growth, heart size, and backfat thickness. This favorable mutation is common in Western commercial pig populations, but absent in most Chinese indigenous pig breeds. To improve meat production of Chinese indigenous pigs, we used cytosine base editor 3 (CBE3) to introduce IGF2-intron3-C3071T mutation into porcine embryonic fibroblasts (PEFs) isolated from a male Liang Guang Small Spotted pig (LGSS), and single-cell clones harboring the desired mutation were selected for somatic cell nuclear transfer (SCNT) to generate the founder line of IGF2T/T pigs.

RESULTS

We found the heterozygous progeny IGF2C/T pigs exhibited enhanced expression of IGF2, increased lean meat by 18%-36%, enlarged loin muscle area by 3%-17%, improved intramuscular fat (IMF) content by 18%-39%, marbling score by 0.75-1, meat color score by 0.53-1.25, and reduced backfat thickness by 5%-16%. The enhanced accumulation of intramuscular fat in IGF2C/T pigs was identified to be regulated by the PI3K-AKT/AMPK pathway, which activated SREBP1 to promote adipogenesis.

CONCLUSIONS

We demonstrated the introduction of IGF2-intron3-C3071T in Chinese LGSS can improve both meat production and quality, and first identified the regulation of IMF deposition by IGF2 through SREBP1 via the PI3K-AKT/AMPK signaling pathways. Our study provides a further understanding of the biological functions of IGF2 and an example for improving porcine economic traits through precise base editing.

GOAT: Gene-level biomarker discovery from multi-Omics data using graph ATtention neural network for eosinophilic asthma subtype

MOTIVATION

Asthma is a heterogeneous disease where various subtypes are established and molecular biomarkers of the subtypes are yet to be discovered. Recent availability of multi-omics data paved a way to discover molecular biomarkers for the subtypes. However, multi-omics biomarker discovery is challenging because of the complex interplay between different omics layers.

RESULTS

We propose a deep attention model named Gene-level biomarker discovery from multi-Omics data using graph ATtention neural network (GOAT) for identifying molecular biomarkers for eosinophilic asthma subtypes with multi-omics data. GOAT identifies genes that discriminate subtypes using a graph neural network by modeling complex interactions among genes as the attention mechanism in the deep learning model. In experiments with multi-omics profiles of the COREA (Cohort for Reality and Evolution of Adult Asthma in Korea) asthma cohort of 300 patients, GOAT outperforms existing models and suggests interpretable biological mechanisms underlying asthma subtypes. Importantly, GOAT identified genes that are distinct only in terms of relationship with other genes through attention. To better understand the role of biomarkers, we further investigated two transcription factors, CTNNB1 and JUN, captured by GOAT. We were successful in showing the role of the transcription factors in eosinophilic asthma pathophysiology in a network propagation and transcriptional network analysis, which were not distinct in terms of gene expression level differences.

AVAILABILITY AND IMPLEMENTATION

Source code is available https://github.com/DabinJeong/Multi-omics_biomarker. The preprocessed data underlying this article is accessible in data folder of the github repository. Raw data are available in Multi-Omics Platform at http://203.252.206.90:5566/, and it can be accessible when requested.

Large-scale exome sequence analysis identifies sex- and age-specific determinants of obesity

Obesity contributes substantially to the global burden of disease and has a significant heritable component. Recent large-scale exome sequencing studies identified several genes in which rare, protein-coding variants have large effects on adult body mass index (BMI). Here we extended such work by performing sex-stratified associations in the UK Biobank study (N∼420,000). We identified genes in which rare heterozygous loss-of-function increases adult BMI in women (DIDO1, PTPRG, and SLC12A5) and in men (SLTM), with effect sizes up to ∼8 kg/m2. This is complemented by analyses implicating rare variants in OBSCN and MADD for recalled childhood adiposity. The known functions of these genes, as well as findings of common variant genome-wide pathway enrichment analyses, suggest a role for neuron death, apoptosis, and DNA damage response mechanisms in the susceptibility to obesity across the life-course. These findings highlight the importance of considering sex-specific and life-course effects in the genetic regulation of obesity.

Fatty acid oxidation facilitates DNA double-strand break repair by promoting PARP1 acetylation

DNA repair is a tightly coordinated stress response to DNA damage, which is critical for preserving genome integrity. Accruing evidence suggests that metabolic pathways have been correlated with cellular response to DNA damage. Here, we show that fatty acid oxidation (FAO) is a crucial regulator of DNA double-strand break repair, particularly homologous recombination repair. Mechanistically, FAO contributes to DNA repair by activating poly(ADP-ribose) polymerase 1 (PARP1), an enzyme that detects DNA breaks and promotes DNA repair pathway. Upon DNA damage, FAO facilitates PARP1 acetylation by providing acetyl-CoA, which is required for proper PARP1 activity. Indeed, cells reconstituted with PARP1 acetylation mutants display impaired DNA repair and enhanced sensitivity to DNA damage. Consequently, FAO inhibition reduces PARP1 activity, leading to increased genomic instability and decreased cell viability upon DNA damage. Finally, our data indicate that FAO serves as an important participant of cellular response to DNA damage, supporting DNA repair and genome stability.

Increased cell senescence in human metabolic disorders

Cell senescence (CS) is at the nexus between aging and associated chronic disorders, and aging increases the burden of CS in all major metabolic tissues. However, CS is also increased in adult obesity, type 2 diabetes (T2D), and nonalcoholic fatty liver disease independent of aging. Senescent tissues are characterized by dysfunctional cells and increased inflammation, and both progenitor cells and mature, fully differentiated and nonproliferating cells are afflicted. Recent studies have shown that hyperinsulinemia and associated insulin resistance (IR) promote CS in both human adipose and liver cells. Similarly, increased CS promotes cellular IR, showing their interdependence. Furthermore, the increased adipose CS in T2D is independent of age, BMI, and degree of hyperinsulinemia, suggesting premature aging. These results suggest that senomorphic/senolytic therapy may become important for treating these common metabolic disorders.

PTPN2 targets TAK1 for dephosphorylation to improve cellular senescence and promote adipose tissue browning in T2DM

Introduction: The energy imbalance when energy intake exceeds expenditure acts as an essential factor in the development of insulin resistance (IR). The activity of brown adipose tissue, which is involved in the dissipation of energy via heat expenditure decreases under type 2 diabetic mellitus (T2DM) state when the number of pathological aging adipocytes increases. Protein tyrosine phosphatase non-receptor type 2 (PTPN2) regulates several biological processes by dephosphorylating several cellular substrates; however, whether PTPN2 regulates cellular senescence in adipocytes and the underlying mechanism has not been reported. Methods: We constructed a model of type 2 diabetic mice with PTPN2 overexpression to explore the role of PTPN2 in T2DM. Results: We revealed that PTPN2 facilitated adipose tissue browning by alleviating pathological senescence, thus improving glucose tolerance and IR in T2DM. Mechanistically, we are the first to report that PTPN2 could bind with transforming growth factor-activated kinase 1 (TAK1) directly for dephosphorylation to inhibit the downstream MAPK/NF-κB pathway in adipocytes and regulate cellular senescence and the browning process subsequently. Discussion: Our study revealed a critical mechanism of adipocytes browning progression and provided a potential target for the treatment of related diseases.

Physiological and pathological roles of lipogenesis

Lipids are essential metabolites, which function as energy sources, structural components and signalling mediators. Most cells are able to convert carbohydrates into fatty acids, which are often converted into neutral lipids for storage in the form of lipid droplets. Accumulating evidence suggests that lipogenesis plays a crucial role not only in metabolic tissues for systemic energy homoeostasis but also in immune and nervous systems for their proliferation, differentiation and even pathophysiological roles. Thus, excessive or insufficient lipogenesis is closely associated with aberrations in lipid homoeostasis, potentially leading to pathological consequences, such as dyslipidaemia, diabetes, fatty liver, autoimmune diseases, neurodegenerative diseases and cancers. For systemic energy homoeostasis, multiple enzymes involved in lipogenesis are tightly controlled by transcriptional and post-translational modifications. In this Review, we discuss recent findings regarding the regulatory mechanisms, physiological roles and pathological importance of lipogenesis in multiple tissues such as adipose tissue and the liver, as well as the immune and nervous systems. Furthermore, we briefly introduce the therapeutic implications of lipogenesis modulation.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Liraglutide promotes angiogenesis in adipose tissue via suppression of adipocyte-derived IL-6

Accumulating evidence suggests that Liraglutide is a favorable treatment for obese people. Obesity induces cellular senescence and accumulated senescent adipocytes in adipose tissue. However, the role of Liraglutide in adipose tissue (AT) senescence and the underlying mechanisms remain obscure. In this study, we found that HFD induces adipocyte senescence and impaired angiogenesis in AT. The deleterious effects provoked unhealthy adipose tissue remodeling and metabolic disturbance. In contrast, treatment of Liraglutide promoted weight reduction, alleviated adipose tissue senescence, and improved angiogenesis in AT. Notably, we demonstrated that Liraglutide promotes angiogenesis in AT dependent on adipocyte-derived IL-6. These findings revealed distinctive roles of Liraglutide in the regulation of adipocyte senescence and provide a therapeutic potential to obesity-associated metabolic disorders.

Inflammation and DNA damage: cause, effect or both

Inflammation is a biological response involving immune cells, blood vessels and mediators induced by endogenous and exogenous stimuli, such as pathogens, damaged cells or chemicals. Unresolved (chronic) inflammation is characterized by the secretion of cytokines that maintain inflammation and redox stress. Mitochondrial or nuclear redox imbalance induces DNA damage, which triggers the DNA damage response (DDR) that is orchestrated by ATM and ATR kinases, which modify gene expression and metabolism and, eventually, establish the senescent phenotype. DDR-mediated senescence is induced by the signalling proteins p53, p16 and p21, which arrest the cell cycle in G1 or G2 and promote cytokine secretion, producing the senescence-associated secretory phenotype. Senescence and inflammation phenotypes are intimately associated, but highly heterogeneous because they vary according to the cell type that is involved. The vicious cycle of inflammation, DNA damage and DDR-mediated senescence, along with the constitutive activation of the immune system, is the core of an evolutionarily conserved circuitry, which arrests the cell cycle to reduce the accumulation of mutations generated by DNA replication during redox stress caused by infection or inflammation. Evidence suggests that specific organ dysfunctions in apparently unrelated diseases of autoimmune, rheumatic, degenerative and vascular origins are caused by inflammation resulting from DNA damage-induced senescence.

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

Heterogeneity of white adipocytes in metabolic disease

PURPOSE OF REVIEW

This review aims to discuss the most recent evidence identifying the presence of distinct white adipocyte subpopulations in white adipose tissue (WAT) and how these may be altered with increasing adiposity and/or metabolic disease. We conceptualize how changes in adipocyte subpopulations may contribute to alterations in WAT function and the development of metabolic diseases such as type 2 diabetes mellitus (T2DM), nonalcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD).

RECENT FINDINGS

Studies utilizing novel analytical approaches support the existence of distinct white adipocyte subpopulations in both human and murine WAT. Adipocyte subtypes are potentially functionally distinct and may have different roles in WAT function and obesity-associated metabolic diseases.

SUMMARY

The exploration of white adipocyte heterogeneity using novel analytical technologies, has unveiled a new layer of complexity in the study of WAT biology. Interrogation of potential functional differences between adipocyte subpopulations and their role in the function of different WAT depots is now needed. Through understanding the mechanisms regulating white adipocyte subtype development and potential pathophysiological consequences of changes in the presence of adipocyte subpopulations, studies could provide novel therapeutic targets for the treatment of T2DM, NAFLD, and CVD.

Ablation of miRNA-22 protects against obesity-induced adipocyte senescence and ameliorates metabolic disorders in middle-aged mice

High-fat diet (HFD) promotes obesity-related metabolic complications by activating cellular senescence in white adipose tissue (WAT). Growing evidence supports the importance of microRNA-22 (miR-22) in metabolic disorders and cellular senescence. Recently, we showed that miR-22 deletion attenuates obesity-related metabolic abnormalities. However, whether miR-22 mediates HFD-induced cellular senescence of WAT remains unknown. Here, we uncovered that obese mice displayed increased pri-miR-22 levels and cellular senescence in WAT. However, miR-22 ablation protected mice against HFD-induced WAT senescence. In addition, in vitro studies showed that miR-22 deletion prevented preadipocyte senescence in response to Doxorubicin (Doxo). Loss-of-function studies in vitro and in vivo revealed that miR-22 increases H2ax mRNA and γH2ax levels in preadipocytes and WAT without inducing DNA damage. Intriguingly, miR-22 ablation prevented HFD-induced increase in γH2ax levels and DNA damage in WAT. Similarly, miR-22 deletion prevented Doxo-induced increase in γH2ax levels in preadipocytes. Adipose miR-22 levels were enhanced in middle-aged mice fed a HFD than those found in young mice. Furthermore, miR-22 deletion attenuated fat mass gain and glucose imbalance induced by HFD in middle-aged mice. Overall, our findings indicate that miR-22 is a key regulator of obesity-induced WAT senescence and metabolic disorders in middle-aged mice.

Mechanic Insight into the Distinct and Common Roles of Ovariectomy Versus Adrenalectomy on Adipose Tissue Remodeling in Female Mice

Dysfunctions of the ovaries and adrenal glands are both evidenced to cause aberrant adipose tissue (AT) remodeling and resultant metabolic disorders, but their distinct and common roles are poorly understood. In this study, through biochemical, histological and RNA-seq analyses, we comprehensively explored the mechanisms underpinning subcutaneous (SAT) and visceral adipose tissue (VAT) remodeling, in response to ovariectomy (OVX) versus adrenalectomy (ADX) in female mice. OVX promoted adipocyte differentiation and fat accumulation in both SAT and VAT, by potentiating the Pparg signaling, while ADX universally prevented the cell proliferation and extracellular matrix organization in both SAT and VAT, likely by inactivating the Nr3c1 signaling, thus causing lipoatrophy in females. ADX, but not OVX, exerted great effects on the intrinsic difference between SAT and VAT. Specifically, ADX reversed a large cluster of genes differentially expressed between SAT and VAT, by activating 12 key transcription factors, and thereby caused senescent cell accumulation, massive B cell infiltration and the development of selective inflammatory response in SAT. Commonly, both OVX and ADX enhance circadian rhythmicity in VAT, and impair cell proliferation, neurogenesis, tissue morphogenesis, as well as extracellular matrix organization in SAT, thus causing dysfunction of adipose tissues and concomitant metabolic disorders.

Obesity-related kidney disease: Beyond hypertension and insulin-resistance

Chronic kidney disease (CKD) causes considerable morbidity, mortality, and health expenditures worldwide. Obesity is a significant risk factor for CKD development, partially explained by the high prevalence of diabetes mellitus and hypertension in obese patients. However, adipocytes also possess potent endocrine functions, secreting a myriad of cytokines and adipokines that contribute to insulin resistance and induce a chronic low-grade inflammatory state thereby damaging the kidney. CKD development itself is associated with various metabolic alterations that exacerbate adipose tissue dysfunction and insulin resistance. This adipose-renal axis is a major focus of current research, given the rising incidence of CKD and obesity. Cellular senescence is a biologic hallmark of aging, and age is another significant risk factor for obesity and CKD. An elevated senescent cell burden in adipose tissue predicts renal dysfunction in animal models, and senotherapies may alleviate these phenotypes. In this review, we discuss the direct mechanisms by which adipose tissue contributes to CKD development, emphasizing the potential clinical importance of such pathways in augmenting the care of CKD.