The origin of intermuscular adipose tissue and its pathophysiological implications.

The intermuscular adipose tissue (IMAT) is a depot of adipocytes located between muscle bundles. Several investigations have recently been carried out to define the phenotype, the functional characteristics, and the origin of the adipocytes present in this depot. Among the different mechanisms that could be responsible for the accumulation of fat in this site, the dysdifferentiation of muscle-derived stem cells or other mesenchymal progenitors has been postulated, turning them into cells with an adipocyte phenotype. In particular, muscle satellite cells (SCs), a heterogeneous stem cell population characterized by plasticity and self-renewal that allow muscular growth and regeneration, can acquire features of adipocytes, including the abilities to express adipocyte-specific genes and accumulate lipids. Failure to express the transcription factors that direct mesenchymal precursors into fully differentiated functionally specialized cells may be responsible for their phenotypic switch into the adipogenic lineage. We proved that human SCs also possess a clear adipogenic potential that could explain the presence of mature adipocytes within skeletal muscle. This occurs under some pathological conditions (i.e., primary myodystrophies, obesity, hyperglycemia, high plasma free fatty acids, hypoxia, etc.) or as a consequence of thiazolidinedione treatment or simply because of a sedentary lifestyle or during aging. Several pathways and factors (PPARs, WNT growth factors, myokines, GEF-GAP-Rho, p66(shc), mitochondrial ROS production, PKCß) could be implicated in the adipogenic conversion of SCs. The understanding of the molecular pathways that regulate muscle-to-fat conversion and SC behavior could explain the increase in IMAT depots that characterize many metabolic diseases and age-related sarcopenia.

Loss-of-function mutation of the GPR40 gene associates with abnormal stimulated insulin secretion by acting on intracellular calcium mobilization.

BACKGROUND: Free fatty acids (FFAs) acutely stimulate but chronically impair glucose-stimulated insulin secretion from beta-cells. The G protein-coupled transmembrane receptor 40 (GPR40) mediates both acute and chronic effects of FFAs on insulin secretion and plays a role in glucose homeostasis. Limited information is available on the effect of GPR40 genetic abnormalities on insulin secretion and metabolic regulation in human subjects. STUDY DESIGN AND RESULTS: For in vivo studies, we screened 734 subjects for the coding region of GPR40 and identified a new single-nucleotide mutation (Gly180Ser). The mean allele frequency was 0.75%, which progressively increased (P < 0.05) from nonobese subjects (0.42%) to moderately obese (body mass index = 30-39.9 kg/m2, 1.07%) and severely obese patients (body mass index > or = 40 kg/m2, 2.60%). The relationship between the GPR40 mutation, insulin secretion, and metabolic alterations was studied in 11 Gly/Ser mutation carriers. In these subjects, insulin secretion (insulinogenic index derived from oral glucose tolerance test) was significantly lower than in 692 Gly/Gly carriers (86.0 +/- 48.2 vs. 183.7 +/- 134.4, P < 0.005). Moreover, a case-control study indicated that plasma insulin and C-peptide responses to a lipid load were significantly (P < 0.05) lower in six Gly/Ser than in 12 Gly/Gly carriers. In vitro experiments in HeLa cells cotransfected with aequorin and the mutated Gly/Ser GPR40 indicated that intracellular Ca2+ concentration increase after oleic acid was significantly lower than in Gly/Gly GPR40-transfected cells. This fact was confirmed using fura-2 acetoxymethyl ester. CONCLUSIONS: This newly identified GPR40 variant results in a loss of function that prevents the beta-cell ability to adequately sense lipids as an insulin secretory stimulus because of impaired intracellular Ca2+ concentration increase.

Nonalcoholic fatty liver disease, adiponectin and insulin resistance in dipper and nondipper essential hypertensive patients.

OBJECTIVE: The pathogenesis of nonalcoholic fatty liver disease (NAFLD) is multifactorial, and the presence of insulin resistance is recognized as the pathophysiological hallmark of this condition. Arterial hypertension is referred as an insulin-resistant state, and insulin resistance may substantially contribute to the cardiovascular risk in this disorder. We examined the inter-relationship between insulin sensitivity, adiponectin levels, and NAFLD in hypertensive patients with different circadian blood pressure profiles. METHODS: Eighty never-treated patients with essential hypertension were selected for having a nocturnal decrement of blood pressure that was at least 10% (dippers, n=47) or less than 10% (nondippers, n=33) of daytime values. No patient had diabetes mellitus, obesity, hyperlipidemia, or other risk factors for hepatic disease. The two groups were similar as to sex, age, and BMI. Abdominal fat distribution and NAFLD were assessed by ultrasonography. RESULTS: Hepatic steatosis was detected in 57.5% of all patients. Nondippers showed a higher prevalence of NAFLD than dippers (81.8 vs. 40.4%, P<0.005). Insulin and the homeostasis model of assessment index were higher (P<0.001) and adiponectin was lower (P<0.001) in nondippers than in dippers, whereas no difference was found in regional fat, liver enzymes, and other metabolic parameters. At multivariate analysis, factors independently associated with nondipping were insulin (P<0.05) and adiponectin (P<0.01) with the homeostasis model of assessment index being of borderline significance. CONCLUSION: In the absence of major risk factors for the development of NAFLD, a high prevalence of liver steatosis was associated with insulin resistance and low adiponectin levels in essential hypertensive patients with a nondipping profile.

The metabolic syndrome in primary aldosteronism.

Patients with hypertension have a high prevalence of concurrent metabolic abnormalities (eg, obesity, dyslipidemia, and hyperglycemia). Clustering of these risk factors, defined as the metabolic syndrome, is associated with a high cardiovascular risk profile. This review summarizes current knowledge about the prevalence and characteristics of the metabolic syndrome in primary aldosteronism, and discusses the possible pathophysiological link between aldosterone and individual components of the metabolic syndrome, other than hypertension. Impaired glucose metabolism due to insulin resistance appears to be the major contributor to metabolic dysfunction in primary aldosteronism. Experimental observations support the possibility that aldosterone could act directly on insulin receptor function. The potential proadipogenic role of aldosterone and its negative effect on insulin sensitivity through production of cytokines remains to be investigated. Higher rates of cardiovascular events reported in primary aldosteronism could be due in part to the increased prevalence of the metabolic syndrome in this disorder.

Heart lipid accumulation in obese non-diabetic rats: effect of weight loss.

BACKGROUND AND AIM: The aim of this study was to investigate lipid content and expression of genes involved in lipid metabolism, in lean and obese non-diabetic rats and in obese rats undergoing food restriction and weight loss. METHODS AND RESULTS: We studied lean and genetically obese Zucker rats (fa/fa). Another group of obese rats were food restricted to lose 20% of initial body weight. We measured expression of genes involved in lipid oxidation and synthesis. Tissue triglyceride content, cell apoptosis and tissue fibrosis were also evaluated. The hearts of obese rats have higher triglyceride content compared to lean controls despite an increased expression of genes involved in fatty acid oxidation (PPAR alpha, PGC-1 alpha, CPT-I, ACO, UCP3). No differences were found in apoptosis and tissue fibrosis between the two phenotypes. Weight loss resulted in a significant reduction in heart lipid content, while the expression of genes involved in fatty acid oxidation remained elevated. CONCLUSION: In contrast to data reported in diabetic rats, pathways of lipid oxidation are increased rather than decreased in insulin-resistant obese rats. Food restriction reduced heart triglyceride content while lipid-oxidizing genes remained elevated, probably as a consequence of lipid oversupply coming from the endogenous source.

The endogenous cannabinoid system stimulates glucose uptake in human fat cells via phosphatidylinositol 3-kinase and calcium-dependent mechanisms.

BACKGROUND: The endogenous cannabinoid system participates in the regulation of energy balance, and its dysregulation may be implicated in the pathogenesis of obesity. Adipose tissue endocannabinoids may produce metabolic and endocrine effects, but very few data are available in human adipose tissue and in primary human fat cells. EXPERIMENTAL DESIGN: We measured expression of type 1 and type 2 cannabinoid receptors (CNR), enzymes of cannabinoids synthesis and degradation in human omental, sc abdominal, and gluteal adipose tissue from lean and obese subjects. Furthermore, we assessed the effect of CNR1 stimulation on glucose uptake and intracellular transduction mechanisms in primary human adipocytes. Then we assessed the reciprocal regulation between CNR1 and peroxisome proliferator-activated receptor-gamma (PPARgamma). Finally, we tested whether leptin and adiponectin are regulated by CNR1 in human adipocytes. RESULTS: We found that most genes of the endocannabinoid system are down-regulated in gluteal fat and up-regulated in visceral and sc abdominal adipose tissue of obese patients. Treatment of adipocytes with rosiglitazone markedly down-regulated CNR1 expression, whereas Win 55,212 up-regulated PPARgamma. Win 55,212 increased (+50%) glucose uptake, the translocation of glucose transporter 4, and intracellular calcium in fat cells. All these effects were inhibited by SR141716 and wortmannin and by removing extracellular calcium. Win 55,212 and SR141716 had no effect on expression of adiponectin and leptin. CONCLUSIONS: These results indicate a role for the local endocannabinoids in the regulation of glucose metabolism in human adipocytes and suggest a role in channeling excess energy fuels to adipose tissue in obese humans.

Prevalence and characteristics of the metabolic syndrome in primary aldosteronism.

CONTEXT: Patients with hypertension have a high prevalence of concurrent metabolic abnormalities, including obesity, dyslipidemia, and hyperglycemia. Clustering of these cardiovascular risk factors, defined as metabolic syndrome, causes a more pronounced target organ damage. Aldosterone excess has been found to be associated with glucose disorders and may contribute to cardiovascular damage. OBJECTIVE: The aim of our study was to assess the prevalence and the characteristics of the metabolic syndrome in a group of patients with hypertension due to primary aldosteronism compared with patients with essential hypertension. METHODS: The National Cholesterol Education Program Adult Treatment Panel III definition of the metabolic syndrome was used. Eighty-five patients with primary aldosteronism and 381 patients with essential hypertension were studied. Most patients were not receiving antihypertensive therapy during the investigation. RESULTS: Blood glucose and systolic blood pressure were higher (P < 0.05 and P < 0.01, respectively) and duration of hypertension was longer (P < 0.05) in primary aldosteronism than in essential hypertension. The prevalence of metabolic syndrome was higher in primary aldosteronism than in essential hypertension (41.1% vs. 29.6%; P < 0.05). Distribution of single components of the metabolic syndrome other than hypertension showed a higher prevalence of hyperglycemia in primary aldosteronism than in essential hypertension (27.0% vs. 15.2%; P < 0.05). CONCLUSIONS: Our findings confirm a negative effect of aldosterone excess on glucose metabolism and suggest that the recently reported higher rates of cardiovascular events in primary aldosteronism than in essential hypertension might be due to increased prevalence of the metabolic syndrome in the former condition.

Reduced plasma visfatin/pre-B cell colony-enhancing factor in obesity is not related to insulin resistance in humans.

CONTEXT: Visfatin was recently identified as a protein highly expressed and secreted in adipose tissue with insulin-mimetic effect and is a candidate hormone to help explain the association among adipose tissue expansion, insulin resistance, and type 2 diabetes. OBJECTIVE: The objective of the study was to assess expression of visfatin in lean and obese subjects and in sc and visceral adipose tissue and moreover to explore the role of visfatin on insulin resistance in humans. DESIGN: We measured circulating visfatin and its mRNA expression in sc adipose tissue (SAT) in lean and obese subjects. Furthermore, we measured visfatin mRNA in visceral adipose (VAT) and SAT by quantitative RT-PCR. Finally, plasma visfatin and its mRNA in SAT were measured under free fatty acid-induced insulin resistance in healthy subjects. RESULTS: Plasma visfatin and its mRNA in SAT were significantly lower in obese subjects, compared with normal-weight controls. Both circulating visfatin and SAT visfatin mRNA were negatively correlated with body mass index, whereas no correlation was found with homeostasis model assessment. Significantly higher visfatin mRNA was found in VAT of obese subjects, compared with lean controls. Interestingly, visfatin mRNA in VAT was positively correlated with BMI. Elevation of free fatty acid induced a condition of insulin resistance but did not affect either circulating visfatin or its mRNA. CONCLUSIONS: Our findings show that, in human obesity, plasma visfatin is reduced, whereas visfatin mRNA is differentially regulated in SAT and VAT. Visfatin is not related to insulin resistance either as assessed by homeostasis model assessment or during lipid infusion.

Increased serum resistin in nonalcoholic fatty liver disease is related to liver disease severity and not to insulin resistance.

CONTEXT: The recently discovered hormone resistin is linked to the development of insulin resistance, but direct evidence of resistin levels in humans with nonalcoholic fatty liver disease (NAFLD) is lacking. METHODS: We conducted this study to assess the relationship between serum resistin and NAFLD. We measured serum resistin and biochemical, hormonal, and histological correlates in 28 NAFLD patients, 33 controls, and 30 obese patients [body mass index (BMI), >30 kg/m2] without NAFLD. RESULTS: Resistin and adiponectin expression were measured in sc adipose tissue by quantitative RT-PCR. Resistin was higher in NAFLD patients compared with controls (5.87 +/- 0.49 vs. 4.30 +/- 0.20 ng/ml; P = 0.002) and obese patients (4.37 +/- 0.27 ng/ml; P = 0.002). Increased resistin mRNA was also found in the adipose tissue of NAFLD patients compared with controls and obese subjects. CONCLUSIONS: Both NAFLD and obese patients had lower adiponectin levels, whereas leptin was increased only in the obese group. No correlation was found between resistin and high-sensitivity C-reactive protein, BMI, homeostasis model assessment, insulin, glucose, transaminases, and lipid values. A positive correlation was found between resistin and histological inflammatory score. These data report increased resistin in NAFLD patients that is related to the histological severity of the disease, but do not support a link between resistin and insulin resistance or BMI in these patients.

Effect of sibutramine on weight management and metabolic control in type 2 diabetes: a meta-analysis of clinical studies.

OBJECTIVE: The aim of this study was to provide a comprehensive meta-analysis of randomized controlled clinical studies on the effects of sibutramine on weight loss and glycemic control in obese subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: Controlled clinical trials assessing the effect sizes of sibutramine on weight loss effects on glycemia in obese subjects with type 2 diabetes were identified and reviewed using the Cochrane Library, Medline, EMBASE, and a manual search. RESULTS: Eight placebo-controlled, double-blind, randomized trials of sibutramine were included. After sibutramine treatment, the decrease in body weight and waist circumference was significantly greater than in the placebo group. Fasting blood glucose and HbA(1c) significantly decreased after sibutramine treatment. Treatment benefits were seen in plasma triglycerides and HDL, without significant variations in serum total and LDL cholesterol. No differences in systolic blood pressure between the sibutramine and the placebo groups were seen, while recording of diastolic blood pressure and heart rate showed that sibutramine produced a small increase relative to placebo. CONCLUSIONS: A pharmacological approach in a weight management program for patients with type 2 diabetes may be helpful in glycemic control and in the management of other risk factors. Sibutramine may help improve glucose control because it is conducive to weight loss. The reviewed data on the effect of sibutramine further enforce the recommendations that weight management may be the most important therapeutic task for most obese subjects with type 2 diabetes.

Do oestrogen receptors play a role in the pathogenesis of HIV-associated lipodystrophy?

Epidemiological data show an increased risk of HIV-associated lipodystrophy in women, and sex hormone abnormalities have been reported with highly active antiretroviral therapy (HAART). This study, which demonstrates that oestrogen receptor beta expression is significantly reduced in the subcutaneous adipose tissue of HIV-infected lipodystrophic patients, downregulated by HAART regimens including protease inhibitors (PI), and restored after switching from PI, opens perspectives for the investigation of selective oestrogen receptor modifiers for the management of this syndrome.

Increased serum resistin in adults with prader-willi syndrome is related to obesity and not to insulin resistance.

CONTEXT: Determinants of insulin resistance in Prader-Willi syndrome (PWS) are not completely understood. The discovery of several adipokines with relevant effects on insulin resistance and cardiovascular complications of metabolic syndrome offered new tools of investigation of insulin resistance in PWS. OBJECTIVE: The purpose of this study was to measure serum resistin and mRNA in adipose tissue of patients with PWS, those with simple obesity, and healthy controls and correlate resistin levels with anthropometric and biochemical features. DESIGN: Twenty-eight adult PWS patients, 29 obese patients, and 25 healthy controls were studied. Anthropometric variables were measured and fasting serum and plasma were collected for measurement of resistin, adiponectin, leptin, lipid profile, glucose, and insulin. RESULTS: Serum resistin and resistin mRNA expression in adipose tissue was significantly higher in PWS patients, compared with both healthy lean controls and obese patients. Moreover, on regression analysis resistin was significantly correlated with body mass index, whereas no significant association was found between resistin and homeostasis model assessment index. A weak association between resistin and adiponectin was found in the PWS group only. However, on multivariate analysis only the correlation between resistin and body mass index remained significant. CONCLUSIONS: These results support a link between circulating resistin and obesity in humans but do not support a role for resistin in human insulin resistance.

Acute adrenal failure as the heralding symptom of primary antiphospholipid syndrome: report of a case and review of the literature.

Acute adrenal failure is a potentially fatal condition if overlooked. Occasionally, acute adrenal insufficiency may ensue from bilateral adrenal haemorrhage in patients with known antiphospholipid syndrome (APS). APS is characterized by recurrent arterial and venous thrombosis, pregnancy complications and detection of autoantibodies to phospholipids. This syndrome may be associated with non-organ specific diseases (e.g. connective tissue disorders) or with malignancies, but it may also appear in isolated form (primary APS). In a very few cases the heralding manifestation is given by adrenal failure. We report here a 63-year-old man presenting with acute adrenal insufficiency as the opening clinical manifestation of an APS. We also carried out a computer-aided search of the literature to identify all cases of primary adrenal failure as the first-recognized expression of a primary APS, a condition that not so infrequently may be tackled by endocrinologists. 20 patients fulfilled the inclusion criteria. The great majority of them were males (75%) with a mean age of 42 years. Abdominal pain was present in 14 patients, followed by fever (13 patients) and hypotension (12 patients). The main morphological findings by computed tomography or magnetic resonance were consistent with bilateral adrenal haemorrhage in 11 patients. Lupus anticoagulant was present in all of the 19 tested patients. Our observations emphasize the importance in the assessment of clotting times, and possibly of antiphospholipid antibodies, in all patients with diagnosis of rapidly progressive adrenal failure and concurrent abdominal pain.

Plasma adiponectin is decreased in nonalcoholic fatty liver disease.

OBJECTIVES: Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver-related morbidity and is frequently associated with obesity and metabolic syndrome. The recently discovered hormone adiponectin is produced by adipose tissue, and low plasma adiponectin is considered a key factor in the development of the insulin resistance underlying metabolic syndrome. Animal studies suggest that adiponectin may protect against non-alcoholic steatohepatitis, but direct evidence in humans is lacking. We therefore conducted this study to assess the relationship between plasma adiponectin and nonalcoholic fatty liver disease to explore its role in the pathogenesis of this disease. DESIGN AND METHODS: We measured plasma adiponectin and anthropometric, biochemical, hormonal and metabolic correlates in a group of 17 NAFLD patients with diagnosis confirmed by biopsy, and 20 controls with comparable age, body-mass index and sex. Furthermore we compared plasma adiponectin in patients with simple steatosis and steatohepatitis. RESULTS: Plasma adiponectin was significantly lower in NAFLD patients than controls (5.93+/-0.45 vs 15.67+/-1.60ng/ml). Moreover, NAFLD patients were significantly more insulin resistant while having similar serum leptin. Adiponectin was similar in simple steatosis and in steatohepatitis (6.16+/-0.78 vs 5.69+/-0.49ng/ml). An inverse correlation was observed between adiponectin and homeostatic model assessment (HOMA) of insulin resistance (P = 0.008), while adiponectin did not correlate with serum transaminases and lipid values. CONCLUSIONS: These data support a role for low circulating adiponectin in the pathogenesis of NAFLD and confirm the strict association between reduced adiponectin production by adipose tissue, NAFLD and insulin resistance.

Late potentials and ventricular arrhythmias in acromegaly.

BACKGROUND: Sudden death and increased prevalence of ventricular arrhythmias have already been described in acromegaly. Although late potentials (LPs) have been proved to be a new technique in detecting patients at risk for ventricular tachyarrhythmias its use in acromegaly is still unknown. METHODS: We studied 70 acromegalic patients [32 males, 38 females; age 49+/-12 years (mean+/-S.D.)] and 70 control subjects age- and sex-matched [(35 males and 35 females; 46+/-12 years (mean+/-S.D.)]. Besides hormonal tests, we performed the following cardiovascular investigations: ECG, 24-h ECG Holter monitoring, echocardiography, and signal-averaged ECG (SAECG) time-domain analysis. RESULTS: LPs occurrence was significantly higher in acromegalic patients as compared to the control group (22.9% vs. 2.9%; p=0.001). A greater duration of disease in patients with positive LPs compared to negative ones was pointed out (18 vs. 12 years; p=0.024). In the group of acromegalic patients with positive LPs we observed a significant association with premature ventricular complexes (PVCs) detected by means of 24-h Holter ECG recording (13 out of 15 patients: 86.7%; p=0.024). The positivity or negativity of LPs proved to be significantly associated with Lown scale PVC trends recorded by 24-h Holter ECG (p=0.014). In the group of patients with left ventricular hypertrophy a significant and pathological worsening of SAECG signals (QRS, LAS, RMS) was documented. CONCLUSIONS: We observed a higher prevalence of LPs in acromegaly which significantly correlated with Lown scale of PVCs.

Anorexia nervosa is characterized by increased adiponectin plasma levels and reduced nonoxidative glucose metabolism.

The aim of the present study was to examine the effects of anorexia nervosa (AN) on adipocytokines (leptin and adiponectin) plasma concentrations and insulin-stimulated glucose disposal in adolescent and young adult women. Adiponectin and leptin plasma levels, along with insulin-stimulated glucose disposal (as measured by the euglycemic-hyperinsulinemic glucose clamp) and oxidative and nonoxidative glucose metabolism (as measured by indirect calorimetry during the last 60 min of the insulin clamp), were measured in 11 anorectic patients and 26 normal-weight healthy female controls. Leptin levels were significantly lower in AN patients, according to the reduced body mass index and their respective fat mass. On the contrary, adiponectin plasma levels were significantly higher in AN patients than in control women. Likewise, insulin-stimulated glucose disposal and nonoxidative glucose metabolism were significantly lower in AN patients. In conclusion, our study shows that young women affected by AN have higher adiponectin plasma levels than healthy female controls of similar age, despite the presence of an impairment of insulin-stimulated glucose disposal, with a prevalent failure of nonoxidative glucose metabolism. Taken together, these data suggest that the reduction of fat mass may play the major role in the control of adiponectin release, with respect to changes in insulin sensitivity.

Effect of glucocorticoids on adiponectin: a study in healthy subjects and in Cushing's syndrome.

OBJECTIVE: Glucocorticoids were found to inhibit adiponectin gene expression and secretion both in vitro and in animal models. We evaluated first the acute effect of i.v. glucocorticoids on adiponectin in normal subjects and secondly plasma adiponectin levels in a series of patients with Cushing's syndrome compared with controls. DESIGN AND METHODS: Hydrocortisone (25 mg) was administered i.v. to five healthy volunteers, with blood samples taken at -15, 0, 30, 60, 120 and 180 min. Twenty-one patients with Cushing's syndrome were divided in two groups: one with 11 obese and the other with 10 non-obese Cushing's patients. Each group was compared with controls that were matched for sex, age, body mass index, waist circumference, glucose, insulin, lipid levels and blood pressure. RESULTS: In normal subjects, hydrocortisone produced a decrease in adiponectin at 30 and 60 min, compared with placebo (P<0.05). Adiponectin was lower in non-obese Cushing's patients than in non-obese controls (P<0.004). In contrast, there was no difference in adiponectin levels in obese Cushing's patients and in obese controls. Adiponectin was inversely correlated (P<0.05) with homeostasis model assessment index in both obese and non-obese Cushing's patients; in non-obese Cushing's patients only, adiponectin was inversely correlated with urinary cortisol (P<0.05). CONCLUSIONS: Glucocorticoids inhibit adiponectin in man, as shown by both exogenous administration to healthy subjects and endogenous cortisol hyperproduction. Similar levels of adiponectin in obese Cushing's patients and their obese controls indicate that obesity per se may act as a predominant factor in masking the relationship between adiponectin and cortisol.

Reduced expression of uncoupling proteins-2 and -3 in adipose tissue in post-obese patients submitted to biliopancreatic diversion.

OBJECTIVE: Little is known about the physiological role and the regulation of uncoupling proteins-2 and -3 (UCP-2 and -3) in adipose tissue. We investigated whether the expression of UCP-2 and -3 in adipose tissue was affected by weight loss due to a biliopancreatic diversion (BPD) and related to the daily energy expenditure (24-h EE). DESIGN: Ten morbidly obese subjects (mean body mass index +/- s.e.m.=49.80 +/- 2.51 kg/m(2)) were studied before and 18+/-2 Months after BPD. METHODS: We determined body composition using tritiated water and 24-h EE in a respiratory chamber. Adipose tissue UCP-2 and -3 mRNA, plasma insulin, glucose, free fatty acids (NEFA), free triiodothyronine (FT3), free thyroxine (FT4) and leptin were assayed before and after BPD. RESULTS: BPD treatment resulted in a marked weight loss (P<0.001) mainly due to a fat mass reduction. A significant decrease in 24-h EE/fat-free mass (FFM) (P<0.05) and in UCP-2 (P<0.05) and UCP-3 (P<0.05) mRNA was observed. A significant reduction in plasma insulin, glucose, NEFA, FT3, FT4 and leptin was seen after BPD. The decline in plasma leptin and FFA was tightly correlated with the decrease in both UCP-2 and -3. A significant correlation was found between changes in FT3 and variations in 24-h EE (r=0.64, P<0.05). In a multiple-regression analysis changes in 24-h EE/FFM after BPD were significantly correlated with changes in UCP-3 expression (P<0.05). CONCLUSION: These findings suggest that UCPs in adipose tissue may play a role in the reduction in 24-h EE observed in post-obese individuals.

Molecular and morphometric description of adipose tissue during weight changes: a quantitative tool for assessment of tissue texture.

The aim of this study was to evaluate the morphometric changes of adipose tissue of lean and obese rats as assessed by computerized image analysis (IA) system in experimental conditions, with different degrees of adiposity. Moreover, to validate measures obtained by image analysis by correlation with direct measures of adiposity (body weight, epididimal fat, mean fat cell size and serum leptin). Finally to correlate these changes to expression of genes involved in lipid deposition and mobilization in adipose tissue. Lean (Fa/?) and genetically obese (fa/fa) Zucker rats were studied. Obese rats were food-restricted or treated with retinoic acid (ATRA) in order to reduce body weight and fat content. Moreover, gene expression of two key enzymes involved in fat metabolism (HSL and DGAT) were assessed in adipose tissue by RT-PCR. Our results show that HSL expression in adipose tissue was lower in obese compared to lean rats (1.47+/-0.02 vs 0.35+/-0.03, p<0.005) and was upregulated during food restriction in obese rats. DGAT expression was similar in lean and obese rats and was reduced by treatment with ATRA in obese rats. Tissue texture assessed by IA was significantly higher in lean compared to obese rats (23.2+/-0.6 vs 11.6+/-2.4%; p=0.01). Tissue structure highly correlated with adiposity in obese rats with different amount of body fat (area fraction vs epididimal fat depot: p=0.001). Distribution of measures for each sample, an index of spread of adipose tissue texture, as expressed by the standard deviation, correlated with adiposity (standard deviation vs epididimal fat depot: p=0.002) thus suggesting that adipose tissue texture increases its heterogeneity when adiposity is lower. This observation is in agreement with the hypothesis that the process of lipid mobilization from adipose tissue is not uniform, but a subpopulation of slimming adipocytes undergoes a complete release of their fat content while the rest of the tissue is much less affected. Moreover, image analysis system seems a reliable quantitative tool for assessment of adipose tissue texture.

Lowering of circulating free-fatty acids levels and reduced expression of leptin in white adipose tissue in postobesity status.

BACKGROUND: Our aim was to investigate the regulation of the gene expression of leptin in subcutaneous adipose tissue biopsies in morbid obesity before and after biliopancreatic diversion (BPD). METHODS: Longitudinal study in morbidly obese subjects investigated twice: before and 6 months after BPD. Fourteen morbidly obese women, 37+/-13 years old and with a body mass index of 51.6+/-8.2 kg/m2, were studied before and 6 months after BPD (40.6+/-8.0 kg/m2). Using reverse transcriptase polymerase chain reaction analysis, the mRNA expression of leptin was investigated in adipose tissue. Plasma leptin was measured by radioimmunoassay; plasma insulin was measured by microparticle enzyme immunoassay. Free fatty acids (FFA) were measured using a colorimetric kit. RESULTS: A significant decrease in leptin mRNA level was observed in comparison with pretreatment in BPD patients (59+/-34 vs 143+/-85 arbitrary units, P<0.01). A strict relationship between adipose tissue leptin mRNA and plasma leptin either before (R2=0.80, P<0.0001) or after BPD (R2=0.86, P<0.0001) and between plasma FFA concentration and insulin either before (R2=0.65, P<0.001) or after BPD (R2=0.92, P<0.0001) was observed. Finally, a significant correlation was found between changes in FFA and insulin (R2=0.64, P<0.001), insulin and leptin (R2=0.88, P<0.0001), and insulin and leptin mRNA (R2=0.83, P<0.0001). CONCLUSION: These data demonstrate a high correlation between leptin mRNA expression in adipose tissue and plasma leptin in postobese subjects after BPD. The significant relationship between both leptin mRNA and plasma leptin with insulin suggests that circulating insulin might regulate leptin expression. It might be hypothesized that plasma FFA concentration can act on the insulin secretion and subsequently on the leptin secretory pathway.