Michaela Kovacikova

Macrophages and adipocytes in human obesity: adipose tissue gene expression and insulin sensitivity during calorie restriction and weight stabilization.

OBJECTIVE We investigated the regulation of adipose tissue gene expression during different phases of a dietary weight loss program and its relation with insulin sensitivity. RESEARCH DESIGN AND METHODS Twenty-two obese women followed a dietary intervention program composed of an energy restriction phase with a 4-week very-low-calorie diet and a weight stabilization period composed of a 2-month low-calorie diet followed by 3–4 months of a weight maintenance diet. At each time point, a euglycemic-hyperinsulinemic clamp and subcutaneous adipose tissue biopsies were performed. Adipose tissue gene expression profiling was performed using a DNA microarray in a subgroup of eight women. RT–quantitative PCR was used for determination of mRNA levels of 31 adipose tissue macrophage markers (n = 22). RESULTS Body weight, fat mass, and C-reactive protein level decreased and glucose disposal rate increased during the dietary intervention program. Transcriptome profiling revealed two main patterns of variations. The first involved 464 mostly adipocyte genes involved in metabolism that were downregulated during energy restriction, upregulated during weight stabilization, and unchanged during the dietary intervention. The second comprised 511 mainly macrophage genes involved in inflammatory pathways that were not changed or upregulated during energy restriction and downregulated during weight stabilization and dietary intervention. Accordingly, macrophage markers were upregulated during energy restriction and downregulated during weight stabilization and dietary intervention. The increase in glucose disposal rates in each dietary phase was associated with variation in expression of sets of 80–110 genes that differed among energy restriction, weight stabilization, and dietary intervention. CONCLUSIONS Adipose tissue macrophages and adipocytes show distinct patterns of gene regulation and association with insulin sensitivity during the various phases of a dietary weight loss program.

Effect of hypocaloric diet-induced weight loss in obese women on plasma apelin and adipose tissue expression of apelin and APJ

OBJECTIVE Apelin is a novel adipokine acting on APJ receptor, regulated by insulin and tumor necrosis factor-alpha (TNF-alpha) in adipose tissue (AT). Plasma apelin levels are increased in obese hyperinsulinemic subjects. The aim was to investigate whether the hypocaloric diet associated with weight loss modifies the elevated plasma apelin levels and the expression of apelin and APJ receptor in AT in obese women. DESIGN AND METHODS Fasting plasma levels of apelin and TNF-alpha as well as mRNA levels of apelin and APJ in AT were measured before and after a 12-week hypocaloric weight-reducing diet in 20 obese women (body mass index (BMI) before diet 32.2+/-6.4 kg/m(2)). Twelve healthy women with a BMI of 20.7+/-0.6 kg/m(2) served as reference. RESULTS Plasma levels of apelin and TNF-alpha were higher in obese compared with lean controls. The hypocaloric diet resulted in a significant decrease of BMI to 29.8+/-6.3 kg/m(2), plasma insulin (8.16+/-0.73 to 6.58+/-0.66 mU/l), apelin (369+/-25 pg/ml to 257+/-12 pg/ml), TNF-alpha levels (0.66+/-0.04 pg/ml to 0.56+/-0.04 pg/ml), and AT mRNAs of apelin and APJ. In addition, changes in AT mRNA apelin were related to changes in AT mRNA APJ levels. CONCLUSION The hypocaloric diet associated with weight loss reduces the increased plasma and AT expression of apelin in obese women. This reduced apelin expression in AT could contribute to decreased circulating apelin levels.

Worsening of Obesity and Metabolic Status Yields Similar Molecular Adaptations in Human Subcutaneous and Visceral Adipose Tissue: Decreased Metabolism and Increased Immune Response

CONTEXT It is not known whether biological differences reported between sc adipose tissue (SAT) and visceral adipose tissue (VAT) depots underlie the pathogenicity of visceral fat. OBJECTIVE We compared SAT and VAT gene expression according to obesity, visceral fat accumulation, insulin resistance, and presence of the metabolic syndrome. DESIGN Subjects were assigned into four groups (lean, overweight, obese, and obese with metabolic syndrome). SETTING Subjects were recruited at a university hospital. PATIENTS Thirty-two women were included. MAIN OUTCOME MEASURES Anthropometric measurements, euglycemic-hyperinsulinemic clamps, blood analyses, and computed tomography scans were performed, and paired samples of SAT and VAT were obtained for DNA microarray-based gene expression profiling. RESULTS Considering the two fat depots together, 1125 genes were more and 1025 genes were less expressed in lean compared with metabolic syndrome subjects. Functional annotation clustering showed, from lean to metabolic syndrome subjects, progressive down-regulation of metabolic pathways including branched-chain amino acid, fatty acid, carbohydrate, and mitochondrial energy metabolism and up-regulation of immune response genes involved in toll-like receptor, TNF, nuclear factor-κB, and apoptosis pathways. Metabolism and immune response genes showed an opposite correlation with fat mass, fat distribution, or insulin resistance indices. These associations were similar in SAT and VAT, although about 1000 genes showed differential expression between SAT and VAT. CONCLUSIONS The increase in adiposity and the worsening of metabolic status are associated with a coordinated down-regulation of metabolism-related and up-regulation of immune response-related gene expression. Molecular adaptations in SAT prove as discriminating as those in VAT.

Adipokines and dietary interventions in human obesity.

Obesity is a multisystem disorder associated with cardiovascular and metabolic complications. According to recent studies, it is characterized as a condition of low‐grade inflammation with altered adipose tissue function and secretion of various adipokines. One of the strategies in obesity treatment is dietary intervention (DI) that could modulate cytokine levels in a favourable way. The aim of this review was to summarize the results of studies performed in the last 13 years investigating DI programmes accompanied with weight loss in relation to profile of adipokines at different level (adipose tissue mRNA, adipose tissue secretion and circulating level) and identify whether modulations of adipokines are implicated in the positive effects of DIs. The overall finding is that DIs leading to 5–10% weight loss modulate production of certain adipokines and generally induce improvement of clinical parameters, e.g. insulin sensitivity, but the amelioration of obesity complications is not coherent with the pattern of adipokine regulation, except maybe for leptin. Global analysis of the adipose tissue secretome and measurement of panels of adipokines may prove more informative than studies on individual molecules.

Macrophage gene expression is related to obesity and the metabolic syndrome in human subcutaneous fat as well as in visceral fat

Aims/hypothesisOur goal was to identify a set of human adipose tissue macrophage (ATM)-specific markers and investigate whether their gene expression in subcutaneous adipose tissue (SAT) as well as in visceral adipose tissue (VAT) is related to obesity and to the occurrence of the metabolic syndrome.MethodsATM-specific markers were identified by DNA microarray analysis of adipose tissue cell types isolated from SAT of lean and obese individuals. We then analysed gene expression of these markers by reverse transcription quantitative PCR in paired samples of SAT and VAT from 53 women stratified into four groups (lean, overweight, obese and obese with the metabolic syndrome). Anthropometric measurements, euglycaemic–hyperinsulinaemic clamp, blood analysis and computed tomography scans were performed.ResultsA panel of 24 genes was selected as ATM-specific markers based on overexpression in ATM compared with other adipose tissue cell types. In SAT and VAT, gene expression of ATM markers was lowest in lean and highest in the metabolic syndrome group. mRNA levels in the two fat depots were negatively correlated with glucose disposal rate and positively associated with indices of adiposity and the metabolic syndrome.Conclusions/interpretationIn humans, expression of ATM-specific genes increases with the degree of adiposity and correlates with markers of insulin resistance and the metabolic syndrome to a similar degree in SAT and in VAT.

Visfatin expression in subcutaneous adipose tissue of pre-menopausal women: relation to hormones and weight reduction

Background   A novel adipokine, visfatin, was found to be related to adiposity in humans and regulated by a number of hormonal signals. The aim of this study was to investigate the relationships of visfatin expression in adipose tissue with potential regulatory factors such as insulin, testosterone and tumor necrosis factor‐α (TNF‐α) and to elucidate the effect of a diet induced weight reduction on adipose tissue mRNA expression and plasma levels of visfatin.

Effect of hyperinsulinemia and very-low-calorie diet on interstitial cytokine levels in subcutaneous adipose tissue of obese women

Type 2 diabetes and obesity are associated with an enhanced release of a number of adipocytokines. Hyperinsulinemia, frequently present in type 2 diabetes and obesity, might be one of the drivers of the enhanced production of adipocytokines. The aim of this study was to investigate the interstitial levels of cytokines in subcutaneous adipose tissue (SCAT) in response to hyperinsulinemia and the effect of weight-reducing hypocaloric diet on this regulation in obese subjects. Thirteen obese premenopausal women participated in the study. Concentrations of seven cytokines were measured in plasma and in AT interstitial fluid collected by microdialysis during a euglycemic-hyperinsulinemic clamp and during control infusion of physiological saline. A subgroup of six women underwent a 4-wk very-low-calorie diet (VLCD). Microdialysis during the clamp was performed before and at the end of VLCD. Hyperinsulinemia induced an increase of monocyte chemoatractant protein (MCP-1) and IL-6 SCAT interstitial and plasma levels and elevated IL-8 levels in SCAT. The relative changes of IL-6 levels in the dialysate correlated with changes of IL-8 and MCP-1. The interstitial and plasma levels of IL-1β, IL-10, TNFα, and plasminogen activator inhibitor (PAI-1) remained unchanged in response to hyperinsulinemia. VLCD resulted in enhancement of the hyperinsulinemia-induced augmentation of MCP-1, IL-6, and IL-8 interstitial levels. In conclusion, hyperinsulinemia upregulates the interstitial levels of MCP-1, IL-6, and IL-8 in SCAT in obese women, whereas it does not affect IL-1β, IL-10, TNFα, and PAI-1 levels. Hypocaloric diet associated with weight reduction enhances the hyperinsulinemia-induced upregulation of MCP-1, IL-6, and IL-8 in SCAT.

Secretion of adiponectin multimeric complexes from adipose tissue explants is not modified by very low calorie diet

OBJECTIVE Adiponectin is a protein abundantly secreted by the adipose tissue (AT). Plasma adiponectin levels are decreased in obese, insulin-resistant, and type 2 diabetic patients. Various multimeric complexes, i.e. high-, middle-, and low-molecular weight isoforms (HMW, MMW and LMW), are present in plasma. Here, we investigated the effect of weight reducing diet on the distribution of adiponectin isoforms in plasma and on their secretion in AT explants from obese subjects. DESIGN A total of 20 obese subjects (age 37.8+/-7.3 years, body mass index 33.9+/-5.0 kg/m(2)) underwent eight weeks of very low-calorie diet (VLCD). A needle biopsy of subcutaneous abdominal AT and blood samples were taken before and after dietary intervention. AT explants were incubated in culture medium for 4 h. ELISA assay and western blot analyses were used to identify adiponectin complexes in culture media and in plasma. RESULTS The distribution of adiponectin polymers in plasma was different from that secreted in human AT explants. Before VLCD, the relative amount of HMW isoform was 75.5+/-9.1% of total adiponectin in culture media and 52.2+/-11.2% in plasma. Despite the diet-induced weight loss and improvement of insulin sensitivity, VLCD neither induced change in total adiponectin level nor in the ratio of HMW to total adiponectin in plasma and in culture media of AT explants. CONCLUSIONS The profile of adiponectin polymeric isoforms secreted by AT explants into culture media differs from the plasma profile. A dietary intervention leading to weight loss and improvement of insulin sensitivity was not associated with modifications of AT secretion of total or HMW adiponectin.