Characteristics and mechanisms of subcutaneous and visceral adipose tissue aging

Aging is one of the most significant health challenges worldwide and is a primary cause of chronic diseases and physiological decline.Among the myriad changes that occur with aging,alterations in adipose tissue distribution and function have gained considerable attention because of their profound impact on metabolic health and overall well-being.Subcutaneous adipose tissue(SAT)and visceral adipose tissue(VAT)are the two major depots of white adipose tissue,each with distinct roles in metabolism and health.Understanding the characteristics and underlying mechanisms of SAT and VAT is crucial for elucidating the aging process and developing strategies to promote healthy aging.This review focuses on delineating and analyzing the characteristics and intrinsic mechanisms underlying the aging of subcutaneous and visceral adipose tissue during the aging process,which can contribute to a better understanding of the aging process and enhance healthy aging.

Hysteresis of White Adipose Tissue

Objective: This study was performed to analyze the modifications within adipose tissue during calorie restriction and more specifically to state whether hysteresis occurs during fat mass reduction. Method: Rats male Wistar increased their body weight by 130 g under control conditions and were then submitted to a calorie restriction (CR) at 30% or 60% of control. Experiment has been stopped when the body weight of the group CR60% returned back to its initial value. Samples of retroperitoneal adipose tissue were collected by biopsies along the study. Adipose cell size was analyzed using multisizer IV (Beckman Coulter) to determine the size distribution curves during natural growth and after calorie restriction. Results: After CR60%, body weights and adipose tissue masses were similar to the ones at the beginning of the experiment. Adipose cell size distribution curve was shifted to the left compared to the one of initial control. Adipose cell sizes were significantly lower after CR60% than those of control at the beginning of the experiment. Conclusions: These results state for the first time that hysteresis occurs in white adipose tissue after calorie restriction. The composition of adipose tissue after calorie restriction was significantly different than the one of initial control. After significant weight loss, organisms must be considered as different from the initial controls, they are most likely governed by different regulations which will have to be identified.

Ginsenoside F1 administration promotes UCP1-dependent fat browning and ameliorates obesity-associated insulin resistance

Obesity-induced type 2 diabetes is mainly due to excessive free fatty acids leading to insulin resistance.Increasing thermogenesis is regarded as an effective strategy for hypolipidemia and hypoglycemia.Ginsenoside is a natural active component in Panax ginseng C.A.Meyer,and some of them enhance thermogenesis.However,there are few studies on the mechanism and target of ginsenosides enhancing thermogenesis.Using thermogenic protein uncoupling protein 1(UCP1)-luciferase reporter assay,we identifi ed ginsenoside F1 as a novel UCP1 activator in the ginsenosides library.Using pull down assay and inhibitor interference,we found F1 binds toβ3-adrenergic receptors(β3-AR)to enhance UCP1 expression via cAMP/PKA/CREB pathway.We also investigated the ability of F1 on energy metabolism in obesity-induced diabetic mice,including body weight,body composition and energy expenditure.The results of proteomics showed that F1 signifi cantly up-regulated thermogenesis proteins and lipolytic proteins,but down-regulated fatty acid synthesis proteins.Ginsenoside F1 increased thermogenesis and ameliorated insulin resistance specifi cally by promoting the browning of white adipose tissue in obese mice.Additionally,ginsenoside F1 improves norepinephrine-induced insulin resistance in adipocytes and hepatocytes,and shows a stronger mitochondria respiration ability than norepinephrine.These fi ndings suggest that ginsenoside F1 is a promising lead compound in the improvement of insulin resistance.

Single-nucleus RNA sequencing reveals heterogeneity among multiple white adipose tissue depots

Regardless of its anatomical site,adipose tissue shares a common energy-storage role but exhibits distinctive properties.Exploring the cellular and molecular heterogeneity of white adipose tissue(WAT)is crucial for comprehending its function and properties.However,existing single-nucleus RNA sequencing(snRNA-seq)studies of adipose tissue heterogeneity have examined only one or two depots.In this study,we employed snRNA-seq to test five representative depots including inguinal,epididymal,mesenteric,perirenal,and pericardial adipose tissues in mice under physiological conditions.By analyzing the contents of main cell catego-ries and gene profiles of various depots,we identified their distinctive physiological properties.Immune cells and fibro-adipogenic progenitor cells(FAPs)showed dramatic differences among WAT depots,while adipocytes seemed to be conserved.The heightened presence of regulatory macrophages and B cells in pericardial adipose tissues implied their potential contribution to the preservation of coronary vascular function.Moreover,the selective aggregation of pericytes within mesenteric adipose tissue was likely associated with the maintenance of intestinal barrier homeostasis.Using a combination of RNA sequencing and snRNA-seq analysis,the major subpopulations of FAPs derived from these depots determined the site characteristics of FAPs to a certain extent.Our work estab-lishes a systematic and reliable foundation for investigating the heterogeneity of WAT depots and elucidating the unique roles these depots play in coordinating the function of adjacent organs.

Cidea controls lipid droplet fusion and lipid storage in brown and white adipose tissue

Excess lipid storage in adipose tissue results in the development of obesity and other metabolic disorders including diabetes,fatty liver and cardiovascular diseases.The lipid droplet(LD)is an important subcellular organelle responsible for lipid storage.We previously observed that Fsp27,a member of the CIDE family proteins,is localized to LD-contact sites and promotes atypical LD fusion and growth.Cidea,a close homolog of Fsp27,is expressed at high levels in brown adipose tissue.However,the exact role of Cidea in promoting LD fusion and lipid storage in adipose tissue remains unknown.Here,we expressed Cidea in Fsp27-knockdown adipocytes and observed that Cidea has similar activity to Fsp27 in promoting lipid storage and LD fusion and growth.Next,we generated Cidea and Fsp27 double-deficient mice and observed that these animals had drastically reduced adipose tissue mass and a strong lean phenotype.In addition,Cidea/Fsp27 double-deficient mice had improved insulin sensitivity and were intolerant to cold.Furthermore,we observed that the brown and white adipose tissues of Cidea/Fsp27double-deficient mice had significantly reduced lipid storage and contained smaller LDs compared to those of Cidea or Fsp27single deficient mice.Overall,these data reveal an important role of Cidea in controlling lipid droplet fusion,lipid storage in brown and white adipose tissue,and the development of obesity.

Recent developments in natural products for white adipose tissue browning

Excess accumulation of white adipose tissue(WAT) causes obesity which is an imbalance between energy intake and energy expenditure. Obesity is a serious concern because it has been the leading causes of death worldwide, including diabetes, stroke,heart disease and cancer. Therefore, uncovering the mechanism of obesity and discovering anti-obesity drugs are crucial to prevent obesity and its complications. Browning, inducing white adipose tissue to brown or beige(brite) fat which is brown-like fat emerging in WAT, becomes an appealing therapeutic strategy for obesity and metabolic disorders. Due to lack of efficacy or intolerable side-effects, the clinical trials that promote brown adipose tissue(BAT) thermogenesis and browning of WAT have not been successful in humans. Obviously, more specific means still need to be developed to activate browning of white adipose tissue. In this review, we summarized seven kinds of natural products(alkaloids, flavonoids, terpenoids, long chain fatty acids, phenolic acids, else and extract) promoting white adipose tissue browning which can ameliorate the metabolic disorders, including obesity, dislipidemia, insulin resistance and diabetes. Since natural products are important drug sources and the browning property plays a significant role in not only obesity treatment but also in type 2 diabetes(T2 DM) improvement, natural products of inducing browning may be an irreplaceable drug discovery orientation for obesity, diabetes and even other metabolic disorders.

Fat deposition deficiency is critical for the high mortality of pre-weanling newborn piglets

Background: The high mortality of pre-weanling piglets is a dominant challenge which severely restricts the development of pig industry. A number of factors including nutrients imbalance and temperature variation during postnatal period of piglets have been reported to closely associated with the high mortality of postnatal piglets.This study aims to find out the relationship between fat deposition and survival of newborn piglets.Results: There were no differences in organ coefficient and bone density between the surviving and dead piglets(P > 0.05). The body weight and the fat deposition in the dead piglets were lower than the live individuals(P < 0.05).Consistently, the average sizes of white adipocytes in back and abdominal adipose tissues of dead piglets were smaller than the survivals(P < 0.05). The protein expression levels of adipocyte differentiation markers PPARγ and C/EBPα in the back and abdominal adipose tissues were lower in dead piglets compared to live piglets. The mRNA expressions of thermogenic markers PGC1α and PRDM16 in adipose tissues were decreased in the dead piglets(P < 0.05). The microarray of back fat samples from the surviving and dead piglets were conducted; two down-regulated genes namely AAMDC and CASTOR1 were identified from the dead piglets. According to quantitative real-time PCR(RT-PCR) analysis, the mRNA expression of AAMDC decreased, whereas CASTOR1 expression elevated in the dead piglets compared to the surviving piglets(P < 0.05).Conclusions: The fat deposition and adipocyte differentiation in the dead piglets are insufficient compared to the surviving piglets, which may attenuate the thermogenic ability of white adipose tissue(WAT). Our data indicate that fat deposition in newborn piglets is vital to their survival.

Construction of a niche-specific spinal white matter-like tissue to promote directional axon regeneration and myelination for rat spinal cord injury repair

Directional axon regeneration and remyelination are crucial for repair of spinal cord injury(SCI),but existing treatments do not effectively promote those processes.Here,we propose a strategy for construction of niche-specific spinal white matter-like tissue(WMLT)using decellularized optic nerve(DON)loaded with neurotrophin-3(NT-3)-overexpressing oligodendrocyte precursor cells.A rat model with a white matter defect in the dorsal spinal cord of the T10 segment was used.The WMLT transplantation group showed significant improvement in coordinated motor functions compared with the control groups.WMLT transplants integrated well with host spinal cord white matter,effectively addressing several barriers to directional axonal regeneration and myelination during SCI repair.In WMLT,laminin was found to promote development of oligodendroglial lineage(OL)cells by binding to laminin receptors.Interestingly,laminin could also guide linear axon regeneration via interactions with specific integrins on the axon surface.The WMLT developed here utilizes the unique microstructure and bioactive matrix of DON to create a niche rich in laminin,NT-3 and OL cells to achieve significant structural repair of SCI.Our protocol can help to promote research on repair of nerve injury and construction of neural tissues and organoids that form specific cell niches.

Adipose-derived stromal/stem cells from different adipose depots in obesity development

The increasing prevalence of obesity is alarming because it is a risk factor for cardiovascular and metabolic diseases(such as type 2 diabetes). The occurrence of these comorbidities in obese patients can arise from white adipose tissue(WAT) dysfunctions, which affect metabolism, insulin sensitivity and promote local and systemic inflammation. In mammals, WAT depots at different anatomical locations(subcutaneous, preperitoneal and visceral) are highly heterogeneous in their morpho-phenotypic profiles and contribute differently to homeostasis and obesity development, depending on their ability to trigger and modulate WAT inflammation. This heterogeneity is likely due to the differential behavior of cells from each depot. Numerous studies suggest that adiposederived stem/stromal cells(ASC; referred to as adipose progenitor cells, in vivo)with depot-specific gene expression profiles and adipogenic and immunomodulatory potentials are keys for the establishment of the morphofunctional heterogeneity between WAT depots, as well as for the development of depot-specific responses to metabolic challenges. In this review, we discuss depot-specific ASC properties and how they can contribute to the pathophysiology of obesity and metabolic disorders, to provide guidance for researchers and clinicians in the development of ASC-based therapeutic approaches.

Apolipoprotein E in diet-induced obesity:a paradigm shift from conventional perception

Apolipoprotein E（APOE） is a major protein component of peripheral and brain lipoprotein transport systems.APOE in peripheral circulation does not cross the blood brain barrier or blood cerebrospinal fluid barrier. As a result,peripheral APOE expression does not affect brain APOE levels and vice versa. Numerous epidemiological studies suggest a key role of peripherally expressed APOE in the development and progression of coronary heart disease while brain APOE has been associated with dementia and Alzheimer＇s disease. More recent studies, mainly in experimental mice, suggested a link between Apoe and morbid obesity. According to the latest findings, expression of human apolipoprotein E3（APOE3） isoform in the brain of mice is associated with a potent inhibition of visceral white adipose tissue（WAT） mitochondrial oxidative phosphorylation leading to significantly reduced substrate oxidation,increased fat accumulation and obesity. In contrast, hepatically expressed APOE3 is associated with a notable shift of substrate oxidation towards non-shivering thermogenesis in visceral WAT mitochondria, leading to resistance to obesity. These novel findings constitute a major paradigm shift from the widely accepted perception that APOE promotes obesity via receptor-mediated postprandial lipid delivery to WAT. Here, we provide a critical review of the latest facts on the role of APOE in morbid obesity.

Transcriptomic analysis reveals the effects of maternal exposure to bisphenol AF on hypothalamic development in male neonatal mice

Fragmented data suggest that bisphenol AF(BPAF),a chemical widely used in a variety of products,might have potential impacts on the hypothalamus.Here,we employed male neonatal mice following maternal exposure to explore the effects of low-dose BPAF on hypothalamic development by RNA-sequencing.We found that maternal exposure to approximately 50μg/(kg·day)BPAF from postanal day(PND)0 to PND 15 altered the hypothalamic transcriptome,primarily involving the pathways and genes associated with extracellular matrix(ECM)and intercellular adhesion,neuroendocrine regulation,and neurological processes.Further RNA analysis confirmed the changes in the expression levels of concerned genes.Importantly,we further revealed that low-dose BPAF posed a stimulatory impact on pro-opiomelanocortin(POMC)neurons in the arcuate nucleus of the hypothalamus and induced the browning of inguinal white adipose tissue.All findings indicate that developmental exposure to low-dose BPAF could interfere with hypothalamic development and thereby lead to alterations in the metabolism.Interestingly,5000μg/(kg·day)BPAF caused slighter,non-significant or even inverse alterations than the low dose of 50μg/(kg·day),displaying a dose-independent effect.Further observations suggest that the the dose-independent effects of BPAF might be associated with oxidative stress and inflammatory responses caused by the high dose.Overall,our study highlights a risk of low-dose BPAF to human neuroendocrine regulation and metabolism.

Supplementation of branched-chain amino acids in protein-restricted diets modulates the expression levels of amino acid transporters and energy metabolism associated regulators in the adipose tissue of growing pigs

This experiment was conducted to investigate the effects of branched-chain amino acids(BCAA)supplemented in protein-restricted diets on the growth performance and the expression profile of amino acid transporters and energy metabolism related regulators in the white adipose tissue(WAT)of different regional depots including dorsal subcutaneous adipose(DSA) and abdominal subcutaneous adipose(ASA), A total of 24 crossbred barrows(7.40 ± 0.70 kg) were randomly divided into 4 groups and were fed the following isocaloric diets for 33 days: 1) a recommended adequate protein diet(AP, 20% CP, as a positive control); 2) a low protein diet(LP, 17% CP); 3) the LP diet supplemented with BCAA(LP + B, 17% CP) to reach the same level of the AP diet group; 4) the LP diet supplemented with 2 times the amount of BCAA(LP + 2B, 17% CP). The daily gain and daily feed intake of the LP diet group were the lowest among all the treatments(P < 0.01). The feed conversion was improved markedly in the group of LP + B compared with the LP diet group(P < 0.05). No significant difference was noted for the serum biochemical parameter concentrations of glucose, triglyceride, nonesterified fatty acid and insulin among the groups(P > 0.05). Moreover, BCAA supplementation down-regulated the expression levels of amino acid transporters including L-type amino acid transporter 1 and sodium-coupled neutral amino acid transporter 2 in DSA, but up-regulated the expression level of Ltype amino acid transporter 4 in ASA(P < 0.05), Meanwhile, the energy sensor AMP-activated protein kinase α was activated in the DSA of pigs fed LP diet and in the ASA of the pigs fed AP or LP + 2B diets(P < 0.05). The mRNA expression profile of the selected mitochondrial component and mitochondrial biogenesis associated regulators in DSA and ASA also responded differently to dietary BCAA supplementation. These results suggested that the growth performance of growing pigs fed protein restricted diets supplemented with BCAA could catch up to that of the pigs fed AP diets. The results also partly demonstrated that the regulation mechanisms of BCAA are different in the adipose tissues of different depots.

Mulberry leaf flavonoids activate BAT and induce browning of WAT to improve type 2 diabetes via regulating the AMPK/SIRT1/PGC-1α signaling pathway

Mulberry (Morus alba L.) leaf is a well-established traditional Chinese botanical and culinary resource. It has found widespread application in the management of diabetes. The bioactive constituents of mulberry leaf, specifically mulberry leaf flavonoids (MLFs), exhibit pronounced potential in the amelioration of type 2 diabetes (T2D). This potential is attributed to their ability to safeguard pancreatic β cells, enhance insulin resistance, and inhibit α-glucosidase activity. Our antecedent research findings underscore the substantial therapeutic efficacy of MLFs in treating T2D. However, the precise mechanistic underpinnings of MLF’s anti-T2D effects remain the subject of inquiry. Activation of brown/beige adipocytes is a novel and promising strategy for T2D treatment. In the present study, our primary objective was to elucidate the impact of MLFs on adipose tissue browning in db/db mice and 3T3-L1 cells and elucidate its underlying mechanism. The results manifested that MLFs reduced body weight and food intake, alleviated hepatic steatosis, improved insulin sensitivity, and increased lipolysis and thermogenesis in db/db mice. Moreover, MLFs activated brown adipose tissue (BAT) and induced the browning of inguinal white adipose tissue (IWAT) and 3T3-L1 adipocytes by increasing the expressions of brown adipocyte marker genes and proteins such as uncoupling protein 1 (UCP1) and beige adipocyte marker genes such as transmembrane protein 26 (Tmem26), thereby promoting mitochondrial biogenesis. Mechanistically, MLFs facilitated the activation of BAT and the induction of WAT browning to ameliorate T2D primarily through the activation of AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling pathway. These findings highlight the unique capacity of MLF to counteract T2D by enhancing BAT activation and inducing browning of IWAT, thereby ameliorating glucose and lipid metabolism disorders. As such, MLFs emerge as a prospective and innovative browning agent for the treatment of T2D.

Commentary:Indirect action pattern:A remote and cross-organ pharmacological mechanism for drug innovation

The development of molecular medicine has greatly promoted the research and development (R&D) of innovative drugs. However,drug design and development for those novel targets remains a big challenge with low success rates and high attrition of drug candidates1. The current methodology of new drug R&D is deeply influenced by the idea of allopathic medicine, which directly inhibits biological targets.

Ablation of steroid receptor coactivator-3 in mice impairsadipogenesis and enhances energy expenditure

Obesity is a medical condition in which excess body fat has accumulated to an extent and may have an adverse effect on health,leading to reduced life expec-tancy,impaired energy homeostasis and increased health problems.The p160 steroid receptor coactivator(SRC)gene family members have been suggested to be involved in energy homeostasis,but the impact of SRC-3 ablation on white and brown adipose tissue needs to be elucidated.In the current study,we collected in vivo data and carried out morphological studies on the effect of SRC-3 deficiency on white adipose tissue(WAT)and brown adipose tissue(BAT).Primary cells were cultured to investigate the differentiation ability of both adipocytes.Western blot was applied to detect the expression of master genes governing adipogenesis and thermogenesis.We observed that SRC-3^(–/–)mice were lean,with reduced WAT and decreased serum leptin levels,mainly due to the smaller white adipocyte size caused by impaired adipo-genesis,presented by decreased peroxisome proliferator activated receptor g(PPARg)expression.In the BAT,the lipid droplets decreased significantly in SRC-3^(–/–)mice as demonstrated by histological analysis and electron micro-scopic observation,which could be explained by enhanced thermogenesis.The expression of thermogenic marker gene PPARg coactivator 1αand uncoupling protein-1 increased in BAT of SRC-3^(–/–)mice,which proved our observations.Collectively,these results demonstrate that SRC-3 plays a key role in adipogenesis and energy expenditure.