No abstract

In obese subjects, the dynamic strength training resulted in an improvement of whole-body insulin sensitivity. The increase in insulin sensitivity was not associated with training-induced modifications of plasma levels or adipose tissue gene expression of adipokines supposedly involved in the development of insulin resistance.

With the use of the microdialysis method, exercise-induced lipolysis was investigated in subcutaneous adipose tissue (SCAT) in obese subjects and compared with lean ones, and the effect of blockade of alpha(2)-adrenergic receptors (ARs) on lipolysis during exercise was explored. Changes in extracellular glycerol concentrations and blood flow were measured in SCAT in a control microdialysis probe at rest and during 60-min exercise bouts (50% of heart rate reserve) and in a probe supplemented with the alpha(2)-AR antagonist phentolamine. At rest and during exercise, plasma norepinephrine and epinephrine concentrations were not different in obese compared with lean men. In the basal state, plasma and extracellular glycerol concentrations were higher, whereas blood flow was lower in SCAT of obese subjects. During exercise, the increase of plasma glycerol was higher in obese subjects (115 +/- 35 vs. 65 +/- 21 micromol/l). Oppositely, the exercise-induced increase in extracellular glycerol concentrations in SCAT was five- to sixfold lower in obese than in lean subjects (50 +/- 14 vs. 318 +/- 53 micromol/l). The exercise-induced increase in extracellular glycerol concentration was not significantly modified by phentolamine infusion in lean subjects but was strongly enhanced in the obese subjects and reached the concentrations found in lean sujects (297 +/- 46 micromol/l). These findings demonstrate that the physiological stimulation of SCAT adipocyte alpha(2)-ARs during exercice-induced sympathetic nervous system activation contributes to the blunted lipolysis noted in obese men.

Objective: Apelin is a novel adipokine acting on APJ receptor, regulated by insulin and tumor necrosis factor-a (TNF-a) 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-a 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 32.2G6.4 kg/m 2 ). Twelve healthy women with a BMI of 20.7G 0.6 kg/m 2 served as reference. Results: Plasma levels of apelin and TNF-a were higher in obese compared with lean controls. The hypocaloric diet resulted in a significant decrease of BMI to 29.8G6.3 kg/m 2 , plasma insulin (8.16G 0.73 to 6.58G0.66 mU/l), apelin (369G25 pg/ml to 257G12 pg/ml), TNF-a levels (0.66G 0.04 pg/ml to 0.56G0.04 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.European Journal of Endocrinology 158 905-910

Context: Retinol-binding protein 4 (RBP4) may play a role in the development of insulin resistance. Objective:We investigated whether RBP4 adipose tissue mRNA expression and plasma level are related to insulin sensitivity during a diet-induced weight loss.Design, Setting, Patients, and Intervention: Obese women followed a dietary intervention composed of a 4-wk very low-calorie diet (VLCD), a 2-month low-calorie diet, and 3-4 months of a weight maintenance (WM) phase. Main Outcome Measures:Clinical investigation was performed before and at the end of each phase. Insulin sensitivity was assessed with the euglycemic hyperinsulinemic clamp. Adipose tissue mRNA and plasma levels of RBP4 were determined using reverse transcription-quantitative PCR and ELISA, respectively.Results: Weight and fat mass decreased during VLCD and were stabilized during WM. Glucose disposal rate increased during VLCD and remained elevated thereafter. Plasma levels of RBP4 decreased after VLCD and, although increasing at subsequent phases, remained lower than prediet values. Adipose tissue mRNA levels were diminished after VLCD, and increased during low-calorie diet and WM to reach basal values. Basal RBP4 levels or diet-induced variations of RBP4 were not different in lean women and two groups of obese women with high-and low-insulin sensitivity. Conclusions:Severe calorie restriction promotes a reduction in adipose tissue and plasma levels of RBP4. The study does not bring evidence for a role for RBP4 in the regulation of diet-induced changes in insulin sensitivity.