Role Of Adipose Tissue Dysfunction Research Articles

The role of adipose tissue dysfunction in hepatic insulin resistance and T2D.

The root cause of type 2 diabetes (T2D) is insulin resistance (IR), defined by the failure of cells to respond to circulating insulin to maintain lipid and glucose homeostasis. While the causes of whole-body insulin resistance are multifactorial, a major contributing factor is dysregulation of liver and adipose tissue function. Adipose dysfunction, particularly adipose tissue-IR (adipo-IR), plays a crucial role in the development of hepatic insulin resistance and the progression of metabolic dysfunction-associated steatotic liver disease (MASLD) in the context of T2D. In this review, we will focus on molecular mechanisms of hepatic insulin resistance and its association with adipose tissue function. A deeper understanding of the pathophysiological mechanisms of the transition from a healthy state to insulin resistance, impaired glucose tolerance, and T2D may enable us to prevent and intervene in the progression to T2D.

The effects of myosteatosis on skeletal muscle function in older adults.

Myosteatosis, or the infiltration of fatty deposits into skeletal muscle, occurs with advancing age and contributes to the health and functional decline of older adults. Myosteatosis and its inflammatory milieu play a larger role in adipose tissue dysfunction, muscle tissue dysfunction, and increased passive muscle stiffness. Combined with the age-related decline of sex hormones and development of anabolic resistance, myosteatosis also contributes to insulin resistance, impaired muscle mechanics, loss of force production from the muscle, and increased risk of chronic disease. Due to its highly inflammatory secretome and the downstream negative effects on muscle metabolism and mechanics, myosteatosis has become an area of interest for aging researchers and clinicians. Thus far, myosteatosis treatments have had limited success, as many lack the potency to completely rescue the metabolic and physical consequences of myosteatosis. Future research is encouraged for the development of reliable assessment methods for myosteatosis, as well as the continued exploration of pharmacological, nutritional, and exercise-related interventions that may lead to the success in attenuating myosteatosis and its clinical consequences within the aging population.

Obesity as a main component of metabolic syndrome and a risk factor for comorbidity

Obesity is an important medical and social problem, it occupies one of the leading places among cardiovascular risk factors. Obesity is a major component of the metabolic syndrome. It has a close pathogenetic relationship with its other manifestations, as a result of which a portrait of a comorbid patient is formed. The article presents data on the prevalence, criteria for diagnosing obesity, the relationship of obesity with other components of the metabolic syndrome is shown. The role of adipose tissue dysfunction in obesity on the development and progression of insulin resistance, atherosclerosis, as well as its relationship with non-alcoholic fatty liver disease and arterial hypertension is discussed. It is shown that obesity is a comorbidity factor and the basis of the metabolic syndrome, the leading pathogenetic mechanism in the formation and progression of its components, preceding their occurrence. This allows us to conclude that weight loss can reduce cardiovascular risks, reduce the manifestations of the metabolic syndrome, and in some cases even eliminate them completely.

Clinical and molecular profiling of human visceral adipose tissue reveals impairment of vascular architecture and remodeling as an early hallmark of dysfunction

Adipose tissue dysfunction is more related to insulin resistance than body mass index itself and an alteration in adipose tissue function is thought to underlie the shift from metabolically healthy to unhealthy obesity. Herein, we performed a clustering analysis that revealed distinct visceral adipose tissue gene expression patterns in patients with obesity at distinct stages of metabolic dysregulation. We have built a cross-sectional cohort that aims at reflecting the evolution of the metabolic sequelae of obesity with the main objective to map the sequential events that play a role in adipose tissue dysfunction from the metabolically healthy (insulin-sensitive) state to several incremental degrees of metabolic dysregulation, encompassing insulin resistance establishment, pre-diabetes, and type 2 diabetes. We found that insulin resistance is mainly marked by the downregulation of adipose tissue vasculature remodeling-associated gene expression, suggesting that processes like angiogenesis and adaptative expansion/retraction ability suffer early dysregulation. Prediabetes was characterized by compensatory growth factor-dependent signaling and increased response to hypoxia, while type 2 diabetes was associated with loss of cellular response to insulin and hypoxia and concomitant upregulation of inflammatory markers. Our findings suggest a putative sequence of dysregulation of biological processes that is not linear and has multiple distinct phases across the metabolic dysregulation process, ultimately culminating in the climax of adipose tissue dysfunction in type 2 diabetes. Several studies have addressed the transcriptomic changes in adipose tissue of patients with obesity. However, to the best of our knowledge, this is the first study unraveling the potential molecular mechanisms associated with the multi-step evolution of adipose tissue dysfunction along the metabolic sequelae of obesity.

EGFR-mediated activation of adipose tissue macrophages promotes obesity and insulin resistance

Obesity and obesity-related health complications are increasing in prevalence. Adipose tissue from obese subjects has low-grade, chronic inflammation, leading to insulin resistance. Adipose tissue macrophages (ATMs) are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. In response to a high fat diet (HFD), ATM numbers initially increase by proliferation of resident macrophages, but subsequent increases also result from infiltration in response to chemotactic signals from inflamed adipose tissue. To elucidate the underlying mechanisms regulating the increases in ATMs and their proinflammatory phenotype, we investigated the role of activation of ATM epidermal growth factor receptor (EGFR). A high fat diet increased expression of EGFR and its ligand amphiregulin in ATMs. Selective deletion of EGFR in ATMs inhibited both resident ATM proliferation and monocyte infiltration into adipose tissue and decreased obesity and development of insulin resistance. Therefore, ATM EGFR activation plays an important role in adipose tissue dysfunction.

Obesity-Related Insulin Resistance: The Central Role of Adipose Tissue Dysfunction.

Obesity is a key player in the onset and progression of insulin resistance (IR), a state by which insulin-sensitive cells fail to adequately respond to insulin action. IR is a reversible condition, but if untreated leads to type 2 diabetes alongside increasing cardiovascular risk. The link between obesity and IR has been widely investigated; however, some aspects are still not fully characterized.In this chapter, we introduce key aspects of the pathophysiology of IR and its intimate connection with obesity. Specifically, we focus on the role of adipose tissue dysfunction (quantity, quality, and distribution) as a driver of whole-body IR. Furthermore, we discuss the obesity-related lipidomic remodeling occurring in adipose tissue, liver, and skeletal muscle. Key mechanisms linking lipotoxicity to IR in different tissues and metabolic alterations (i.e., fatty liver and diabetes) and the effect of weight loss on IR are also reported while highlighting knowledge gaps.

P001 Succinate, a gut microbiota-derived metabolite, modulates the inflammatory status of the creeping fat in Crohn’s disease

Abstract Background Crohn’s disease [CD] is characterized by severe transmural inflammation with subsequent destruction of the intestinal barrier. Recent works suggest that bacterial infiltration across this leaky gut facilitates access to the mesenteric fat and the development of a subsequent inflammatory reaction in the surrounding adipose tissue named creeping fat [CF]. Dysbiosis in CD patients has been associated with an increase in succinate-producing bacteria and a decrease in succinate-consuming bacteria. In fact, elevated succinate levels have been found in the intestinal and faeces of CD patients. Succinate has been classically considered as a marker of hypoxia and tissue damage, assisting as a pro-inflammatory signal that triggers immune activation. However, recent observations support potential additional functions of succinate. We and others have shown that succinate plays a key role in fine-tuning of the inflammatory response, acting both as an alarmin and resolving molecule. Our hypothesis is that succinate, a microbiota-derived metabolite, is a new determinant of adipose tissue dysfunction in CD. Methods A well-characterized cohort was used to obtained mesenteric adipose tissue biopsies including a) 10 subjects with active CD that require surgery for their underlying pathology b) 10 subjects with inactive CD and c) 10 healthy controls undergoing surgery for non-acute process (herniorrhaphy, cholecystectomy for lithiasis, etc.). The groups were comparable in age, sex, and body mass index. We studied the effect of exogenous succinate in adipose tissue explants, adipose-stem cells (ASC), and adipose tissue macrophages (ATM) isolated from adipose tissue biopsies of CD patients with different clinical activity. Circulating succinate levels and inflammatory variables including hs-CRP and faecal calprotectin were also measured. Results We observed an increased expression of SUCNR1 in CF, including ASCs and ATMs, mainly in patients suffering from an active disease (figure 1A). Furthermore, succinate appears to elicit a different response in adipose tissue from CD patients, when activity status is considered. Thus, our results indicate that in an inflammatory local and systemic environment, such as occurs in CD active patients, succinate triggers a pro-inflammatory response in VAT depot, while when subjects are in a remission period, the response of VAT explants to succinate is similar to than the observed in healthy subjects, promoting an anti-inflammatory expression profile (Figure 1B). Interestingly, we found elevated circulating succinate levels in active CD patients but those decrease drastically in patients in remission of the disease (Figure 1C). Conclusion Succinate has a relevant role in adipose tissue dysfunction in CD.

Plasticizers and Cardiovascular Health: Role of Adipose Tissue Dysfunction.

Since the 1950s, the production of plastics has increased 200-fold, reaching 360 million tonnes in 2019. Plasticizers, additives that modify the flexibility and rigidity of the product, are ingested as they migrate into food and beverages. Human exposure is continuous and widespread; between 75 and 97% of urine samples contain detectable levels of bisphenols and phthalates, the most common plasticizers. Concern over the toxicity of plasticizers arose in the late 1990s, largely focused around adverse developmental and reproductive effects. More recently, many studies have demonstrated that exposure to plasticizers increases the risk for obesity, type 2 diabetes, and cardiovascular disease (CVD). In the 2000s, many governments including Canada, the United States and European countries restricted the use of certain plasticizers in products targeted towards infants and children. Resultant consumer pressure motivated manufacturers to substitute plasticizers with analogues, which have been marketed as safe. However, data on the effects of these new substitutes are limited and data available to-date suggest that many exhibit similar properties to the chemicals they replaced. The adverse effects of plasticizers have largely been attributed to their endocrine disrupting properties, which modulate hormone signaling. Adipose tissue has been well-documented to be a target of the disrupting effects of both bisphenols and phthalates. Since adipose tissue function is a key determinant of cardiovascular health, adverse effects of plasticizers on adipocyte signaling and function may underlie their link to cardiovascular disease. Herein, we discuss the current evidence linking bisphenols and phthalates to obesity and CVD and consider how documented impacts of these plasticizers on adipocyte function may contribute to the development of CVD.

White adipose tissue-infiltrated CD11b+ myeloid cells are a source of S100A4, a new potential marker of hepatic damage

The endocrine and immunological properties of subcutaneous vs visceral adipose tissue (sWAT and vWAT, respectively) have turned a milestone in the study of metabolic diseases. The cytokine S100A4 is increased in obesity and has a role in adipose tissue dysfunction. However, the cellular source and its potential role in hepatic damage in obesity has not been elucidated. We aim to study the regulation of S100A4 in immune cells present in sWAT and vWAT, as well as its potential role as a circulating marker of hepatic inflammation and steatosis. A cohort of 60 patients with obesity and distinct metabolic status was analyzed. CD11b+ myeloid cells and T cells were isolated from sWAT and vWAT by magnetic-activating cell sorting, and RNA was obtained. S100A4 gene expression was measured, and correlation analysis with clinical data was performed. Liver biopsies were obtained from 20 patients, and S100A4 circulating levels were measured to check the link with hepatic inflammation and steatosis. S100A4 gene expression was strongly upregulated in sWAT- vs vWAT-infiltrated CD11b+ cells, but this modulation was not observed in T cells. S100A4 mRNA levels from sWAT (and not from vWAT) CD11b+ cells positively correlated with glycemia, triglycerides, TNF-α gene expression and proliferation markers. Finally, circulating S100A4 directly correlated with liver steatosis and hepatic inflammatory markers. Our data suggest that sWAT-infiltrated CD11b+ cells could be a major source of S100A4 in obesity. Moreover, our correlations identify circulating S100A4 as a potential novel biomarker of hepatic damage and steatosis.

Hyperandrogenism, Insulin Resistance, and Acanthosis Nigricans (HAIR-AN) Syndrome Reflects Adipose Tissue Dysfunction (“Adiposopathy” or “Sick Fat”) in Asian Indian Girls

Background: Whether HAIR-AN syndrome and polycystic ovarian syndrome (PCOS) are distinct entities or represent a phenotypic spectrum of the same syndrome is still unclear. HAIR-AN syndrome is characterized by high insulin resistance, obesity, and hyperinsulinemia as compared to PCOS and could represent adipose tissue dysfunction as the primary pathophysiologic trigger. This study was undertaken to study the role of adipose tissue dysfunction in HAIR-AN syndrome and PCOS using adipocytokines as surrogate markers of “adiposopathy.” Materials and Methods: A cross-sectional observational study was conducted at a tertiary care hospital over a period of 1 year. Serum adiponectin, leptin, IL-6, and TNF-α levels were measured in 30 women with HAIR-AN syndrome and in 30 women with PCOS. Correlations between adipocytokines, inflammatory markers, serum testosterone, and serum insulin were determined. Data analysis was performed using the SPSS version 23.0 (IBM SPSS Statistics Inc., Chicago, IL, USA) software program. Results: Women with HAIR-AN syndrome had significantly higher hyperandrogenemia, hyperinsulinemia, and insulin resistance as compared to PCOS women. They also had high leptin levels and lower adiponectin levels (p < 0.001). However, the levels of inflammatory markers (TNF-α and IL-6) were similar in both the groups (p > 0.05). Serum adiponectin showed a negative correlation with HOMA-IR and testosterone levels, while leptin showed a positive correlation with both in HAIR-AN patients while no such correlation was found in the PCOS group. Conclusion: The significantly raised adipocytokines in HAIR-AN syndrome patients as compared to PCOS patients indicates the primary role of adipose tissue dysfunction (“adiposopathy”) in the pathogenesis of HAIR-AN syndrome while only a minor role, if any, in PCOS. Both these syndromes stand as distinct entities pathogenically with an overlapping phenotype.

Pain in women with knee and/or hip osteoarthritis is related to systemic inflammation and to adipose tissue dysfunction: Cross-sectional results of the KHOALA cohort

BackgroundConsidering the role of metabolic diseases in osteoarthritis (OA), we investigated whether biomarkers of adipose tissue dysfunction could be associated with OA-related pain. DesignWe cross-sectionally analyzed patients with knee and/or hip OA at inclusion in the KHOALA cohort. We used visual analogic scale (VAS) for pain, the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) pain subscores. At inclusion, we measured ultra-sensitive CRP (usCRP), leptin and adiponectin for calculation of leptin:adiponectin ratio (LAR), a marker of adipose tissue dysfunction associated with central adiposity, high-molecular-weight adiponectin, visfatin and apolipoproteins. Univariate and multivariable analyses using stepwise linear regression models were performed to search for correlation between pain assessments and these biomarkers, with systematic adjustment on age. ResultsIn 596 women with hip and/or knee OA, multivariable analyses indicated that higher pain intensity was associated with higher LAR (VAS pain: β=0.49; p = 0.0001, OAKHQOL pain: β=-0.46; p = 0.0002, WOMAC pain: β=0.30; p = 0.001) in the whole group as well as in hip or knee OA patients considered separately. Pain intensity correlated also with usCRP level (VAS pain: β= 0.27; p = 0.02, OAKHQOL pain: β =-0.30; p = 0.01) and Kellgren-Lawrence score. In 267 men, no correlation between biomarkers and pain was found. ConclusionSerum LAR and usCRP level are associated with pain level, independently of radiographic structural severity in women with hip and/or knee OA, emphasizing the role of adipose tissue dysfunction and of meta-inflammation in pain experience in the female population.

The impact of endotrophin on the progression of chronic liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and can lead to multiple complications, including non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. The fibrotic liver is characterized by the pathological accumulation of extracellular matrix (ECM) proteins. Type VI collagen alpha3 (Col6a3) is a biomarker of hepatic fibrosis, and its cleaved form, endotrophin (ETP), plays a critical role in adipose tissue dysfunction, insulin resistance, and breast cancer development. Here, we studied the effects of the Col6a3-derived peptide ETP on the progression of chronic liver diseases, such as NASH and liver cancer. We used a doxycycline (Dox)-inducible liver-specific ETP-overexpressing mouse model on a NAFLD-prone (liver-specific SREBP1a transgenic) background. For this, we evaluated the consequences of local ETP expression in the liver and its effect on hepatic inflammation, fibrosis, and insulin resistance. Accumulation of ETP in the liver induced hepatic inflammation and the development of fibrosis with associated insulin resistance. Surprisingly, ETP overexpression also led to the emergence of liver cancer within 10 months in the SREBP1a transgenic background. Our data revealed that ETP can act as a “second hit” during the progression of NAFLD and can play an important role in the development of NASH and hepatocellular carcinoma (HCC). These observations firmly link elevated levels of ETP to chronic liver disease.

Programming of a Pro‐Adipogenic Phenotype in Offspring Born to Metabolically Compromised Pregnancies

ObjectivesDetermine the role of adipose tissue dysfunction in programming of cardiovascular disease risk in offspring born to dams with metabolic dysfunction.MethodsThe female mouse heterozygous for leptin receptor deficiency (Hetdb) was used as a model of maternal metabolic dysfunction. These females exhibit higher adiposity, dyslipidemia and hyperinsulinemia during pregnancy. Our data show that this model reproduces programming of early‐onset cardiovascular disease risk reported in human offspring born to obese or diabetic mothers. We sought to test the hypothesis that programming of cardiovascular disease risk is attributable to perturbed adipose tissue development leading to later‐life adipose tissue dysfunction. Wild type (Wt) offspring from both Wt and Hetdb pregnancies were studied as neonates and adults. At 7 weeks of age, offspring were placed on either a control or high fat/sugar (HF/HS) diet. Adipogenic potential was examined in preadipocytes isolated from the stromal vascular fraction (SVF) of inguinal subcutaneous adipose tissue (iSAT) in both neonatal and adult Wt offspring. After induction of differentiation, Oil Red O staining was used to measure lipid droplet accumulation and qPCR was used to measure adipogenic markers. Flow cytometry was utilized to quantify adipogenic progenitors in SVF. Adipokine secretion was measured with ELISA. Several indices of adipose tissue function were measured in adult offspring, including adipose tissue insulin resistance (Adipo‐IR).ResultsNMR whole‐body fat mass was 1.3 fold higher (p &lt; 0.01) and plasma resistin levels were 1.7 fold higher (p &lt; 0.01) in Wt neonates born to Hetdb pregnancies. The iSAT of Wt neonates and adults born to Hetdb vs. Wt dams exhibited a shift in the cell size distribution from smaller adipocytes to larger adipocytes (p &lt; 0.05), indicating that adipogenesis was accelerated in the iSAT of Hetdb neonates. The percentage of CD31‐CD45‐CD29+CD34+ viable SVF cells was higher in neonates from the Hetdb vs. Wt pregnancy. Preadipocytes isolated from Hetdb offspring exhibited a pro‐adipogenic phenotype in early life that persisted into adulthood. After HF/HS feeding, preadipocytes isolated from Wt female (p &lt; 0.05) and male (p &lt; 0.05) adult offspring born to Hetdb pregnancies accumulated more lipid during differentiation. Heightened adipogenesis in adult offspring was also accompanied by impaired insulin‐stimulated inhibition of lipolysis.ConclusionsAdipose tissue dysfunction in offspring born to metabolically adverse pregnancies stems from in utero programming of a pro‐adipogenic phenotype in preadipocytes.Support or Funding InformationCanadian Institutes of Health Research, Alberta Children’s Hospital Research Institute, Heart &amp; Stroke Foundation of Canada and Libin Cardiovascular Institute of Alberta

Towards precision medicine: defining and characterizing adipose tissue dysfunction to identify early immunometabolic risk in symptom-free adults from the GEMM family study

ABSTRACT Interactions between macrophages and adipocytes are early molecular factors influencing adipose tissue (AT) dysfunction, resulting in high leptin, low adiponectin circulating levels and low-grade metaflammation, leading to insulin resistance (IR) with increased cardiovascular risk. We report the characterization of AT dysfunction through measurements of the adiponectin/leptin ratio (ALR), the adipo-insulin resistance index (Adipo-IRi), fasting/postprandial (F/P) immunometabolic phenotyping and direct F/P differential gene expression in AT biopsies obtained from symptom-free adults from the GEMM family study. AT dysfunction was evaluated through associations of the ALR with F/P insulin-glucose axis, lipid-lipoprotein metabolism, and inflammatory markers. A relevant pattern of negative associations between decreased ALR and markers of systemic low-grade metaflammation, HOMA, and postprandial cardiovascular risk hyperinsulinemic, triglyceride and GLP-1 curves was found. We also analysed their plasma non-coding microRNAs and shotgun lipidomics profiles finding trends that may reflect a pattern of adipose tissue dysfunction in the fed and fasted state. Direct gene differential expression data showed initial patterns of AT molecular signatures of key immunometabolic genes involved in AT expansion, angiogenic remodelling and immune cell migration. These data reinforce the central, early role of AT dysfunction at the molecular and systemic level in the pathogenesis of IR and immunometabolic disorders.

Adipose Tissue Mediates Associations of Birth Weight with Glucose Metabolism Disorders in Children.

This study aimed to examine the associations between low birth weight (LBW) versus high birth weight (HBW) and dysglycemia, including insulin resistance (IR) and impaired fasting glucose (IFG) in children, and aimed to explore the role of adipose tissue in these relationships. A total of 2,935 subjects aged 6 to 18years were recruited to examine the relationship between birth weight and IR (defined as homeostasis model assessment of IR>2.3) and IFG. Mediation analyses were conducted to examine the roles of various adipokines and anthropometrics in these relationships. Children with LBW had a nearly twofold increased risk of IR and IFG compared with children with normal birth weight, even after adjusting for BMI. Decreased circulating adiponectin levels contributed to 21.2% of the LBW-IR relationship, whereas none of the selected adipose markers mediated the LBW-IFG relationship. In contrast, after controlling for current BMI or waist circumference, HBW reduced the risk of IR by 34%, but it was not associated with IFG. The HBW-IR relationship was significantly mediated by reduced leptin levels (21.4%) and fat mass percentage (8.8%), after controlling for BMI. These findings suggest the potential role of adipose tissue dysfunction as an underlying mechanism for the birth weight-type 2 diabetes relationship.

Metabolic syndrome: what changed during last 30 years?

Metabolic syndrome (MS) is a cluster of cardiometabolic factors that are strongly associated with the risk of serious chronic diseases. The prevalence of MS continues to grow, including among children, adolescents and people of active reproductive age. For the sphere of reproductive medicine, the problem of MS is of particular importance not only because of its negative impact on fertility, the frequency of complications of pregnancy and childbirth, but also because of its transgenerative effect on the health of offspring: it is proved that each of the components of the metabolic syndrome is a powerful epigenetic factor. Recent studies have revealed many new facets of the pathogenesis of MS and expanded the range of its etiologic factors beyond the alimentary factors, which determines the possibility of finding new approaches to prevention and treatment of this pathology. The review presents: evolution of diagnostic criteria for MS and reflection of this process in epidemiology and clinical approaches to the disease; epidemiological data on the prevalence of MS in young adults. A brief overview of a large array of scientific research of the last decade on etiology and pathogenesis of MS, in particular the role of adipose tissue dysfunction of visceral, ileofemoral and ectopic depots, causes of the tendency to prevail in one or another adipose tissue depot, new obesity classification, as well as the role of perinatal and epigenetic, ecological (environmental obesogenes, artificial light contamination), composition of intestinal microbiota, state of the sympathetic nervous system, nutritional deficiencies in the development of obesity and MS is provided. The gender differences of pathogenesis and clinical features of MS, as well as the association of MS with dyshormonal and other pathologies (PCOS, hyperprolactinemia, uterine myoma, endometriosis) of female reproductive health are considered.

Abstract 604: Anti-apoptotic Role of Leptin in Adipose Tissue

Background: Leptin contributes to obesity-related cardiometabolic pathology. While the role of adipose tissue dysfunction in altering metabolic profile in obesity is recognized, the direct effects of leptin signaling in adipose tissue are not completely understood. Among factors impacting adipose tissue function in obesity, adipocyte death is associated with increased inflammation with consequent adipose tissue insulin-resistance. Furthermore, apoptosis of adipocyte progenitor cells (preadipocytes) is important as it lowers adipose tissue capacity to maintain and expand fat storage. Objective: To determine the effects of leptin on regulation of proteins important to apoptotic pathways in cultured human white preadipocytes (HWP) and differentiated HWP (dHWP). Methods: Cells were exposed to increasing concentrations of leptin to evaluate the role of leptin on regulation of anti-apoptotic Bcl2, and pro-apoptotic Bax and CD95 expression. Next, we examined if pre-exposure to leptin attenuated TNF-α and FasL induced apoptosis. Results: Leptin upregulated transcription of Bcl2 (p=0.02) and down-regulated transcription of Bax (p=0.02) and CD95 (p=0.04) in a leptin-concentration dependent manner in dHWP. Leptin dependent increases in Bcl2 (p=0.004) and decreases in Bax (p=0.003) and CD95 (P=0.03) protein expression were also observed. Furthermore, 24 hour pre-exposure to leptin protected cells from TNF-α (p=0.01; p=0.006) and FasL (p=0.03; p=0.007) induced apoptosis in dHWP and HWP respectively. Additionally, leptin attenuated TNF-mediated activation of the p53 pathway, suggesting another mechanism by which leptin mediates its inhibitory effects on TNF-induced apoptosis. Conclusion: Leptin regulates the expression of proteins involved in the apoptotic pathway such that it decreases the apoptotic potential of adipose tissue by increasing anti-apoptotic Bcl2 and decreasing pro-apoptotic Bax and CD95 protein expression. In contrast to our in-vitro findings, prior studies in adipose tissue from obese humans report decreased Bcl2 and increased Bax protein expression, along with high leptin expression. This suggests that increased adipose tissue apoptosis in obesity may at least in part be secondary to altered leptin signaling.

The Role of Adipose Tissue Dysfunction in Cardio-Metabolic Disorders

The Role of Adipose Tissue Dysfunction in Cardio-Metabolic Disorders

Pathological Role of Adipose Tissue Dysfunction in Cardio-Metabolic Disorders

Obesity has dramatically increased throughout the world, and has become one of the chief healthcare problems in many societies. Evidence has emerged that adipose tissue dysfunction associated with obesity is critically involved in the development of cardiovascular and metabolic disorders. In this review, we delineate the link between adipose tissue abnormalities and systemic metabolic dysfunction in patients with cardio-metabolic diseases and discuss the underlying mechanisms.

Coxsackie and adenovirus receptor is increased in adipose tissue of obese subjects: a role for adenovirus infection?

The coxsackie and adenovirus receptor (CAR) was originally identified as a common receptor for coxsackie B viruses and type C adenoviruses. The objective was to investigate CAR gene expression in human adipose tissue to explore its associations with adipocyte physiology. This was an ex vivo study in 91 visceral adipose tissue (VAT) and 109 sc adipose tissue (SAT) human samples (61 paired) obtained during elective surgical procedures. Patients were recruited at the Endocrinology Service of the Hospital Universitari Dr Josep Trueta. CAR mRNA was measured in human adipose tissue samples and confirmed at the protein level and in adipose tissue fractions. The effects of inflammatory stimuli on CAR gene expression were also evaluated. In paired samples, CAR was 46-fold higher in VAT vs SAT (P < .0001), being higher also at the protein level (P = .04). CAR was predominantly found in stromal vascular cell fractions (SVFs) in both fat depots. CAR mRNA (P = .006) and protein levels (P = .01) in VAT were significantly increased in obese vs nonobese subjects. In fact, CAR mRNA levels in SAT were positively associated with body mass index (r = 0.26; P = .008) and percentage fat mass (r = 0.28; P = .004). In VAT, MGLL, FSP27, AKAP, omentin, TKT, S14, and FABP contributed independently to CAR mRNA variation after adjusting for age and body mass index. Macrophage-conditioned medium led to increased CAR gene expression in mature adipocytes in vitro. The increased expression of CAR in adipose tissue from obese subjects, mainly in SVFs, suggests that CAR might play a role in adipose tissue dysfunction, given its dual associations with adipogenic and inflammatory genes.