Resistance to the antilipolytic effect of insulin in adipocytes of African-American compared to Caucasian postmenopausal women.

High fatty acid (FA) flux is associated with systemic insulin resistance, and African-American (AA) women tend to be more insulin resistant. We assessed possible depot and race difference in the antilipolytic effect of insulin in adipocytes isolated from abdominal (Abd) and gluteal (Glt) subcutaneous (sc) adipose tissue of overweight, postmenopausal AA and Caucasian (C) women. Percent body fat, fasting insulin, visceral adiposity, and adipocyte size was higher in AA women. Disinhibited lipolysis (presence of adenosine deaminase) per unit adipocyte surface area was similar in Abd and Glt and in AA and C. However, rates of 'basal' [submaximal phenylisopropyl adenosine (PIA)-suppressed] and insulin-suppressed lipolysis were higher in Abd of AA compared with C women even after adjustment for percent fat and visceral fat area. The race difference in rates of PIA- and insulin-suppressed lipolysis in AA were correlated with their hyperinsulinemia, but AA race, independent of fasting insulin, was associated with lower responsiveness (percent suppression) to submaximal insulin concentrations, although sensitivity (ED50) was not affected. Overall, these data are consistent with the hypothesis that decreased responsiveness of Abd adipocytes to antilipolytic effectors may contribute to higher FA availability and thereby to racial differences in insulin resistance.

Effect of orosensory stimulation on postprandial thermogenesis in humans.

This study assessed the effects of orosensory stimulation by equipalatable stimuli that differed in macronutrient content (lipid and carbohydrate) on postprandial thermogenesis. Sixteen healthy, normal-weight adults (eight males, eight females) participated in six test sessions conducted weekly. The test sessions were administered randomly after overnight fasts and included: ingestion of 50 g of butter in capsules (to avoid oral stimulation with lipids) and 500 ml of water in 15 min followed by no oral stimulation or oral stimulation with a cracker or one of the following foods on a cracker-butter, unsaturated fatty acid (UFA) margarine, jelly, UFA margarine+jelly. Sensory stimulation entailed masticating and expectorating approximately 5.0 g samples of each stimulus every 3 min for 110 min. Blood was drawn immediately after preload ingestion and at minutes 35, 85, 200, 320, and 440 postloading and was analyzed for insulin, glucagon, and glucose. No significant treatment differences were observed for thermogenesis or oxidation of carbohydrate or lipid. Insulin, glucagon, and glucose concentrations were not different between treatments. These data suggest that orosensory stimulation with stimuli differing in lipid and carbohydrate content, but rated similarly in palatability, does not elicit an increased or differential diet-induced thermogenic response.

Racial differences in adipocyte size and relationship to the metabolic syndrome in obese women.

OBJECTIVE: To determine whether racial differences exist in the relationship of the abnormalities defining the metabolic syndrome (MS) to regional adiposity and fat cell size (FCS) in obese postmenopausal women. RESEARCH METHODS AND PROCEDURES: We determined the relationship of metabolic variables associated with the MS to regional body composition and abdominal (ABD) and gluteal (GLT) FCS in 25 white (CAU) and 25 African-American (AF-AMER) older women matched for age (58 +/- 5 years; mean +/- SD) and BMI (35 +/- 4 kg/m2). RESULTS: MS was present in 36% of the AF-AMER and 57% of the CAU women. There were no differences in total body, trunk, gluteofemoral fat mass or regional FCS, but AF-AMER women had 22% lower visceral fat, 24% higher insulin, and 31% lower triglyceride levels than CAU women (p < 0.05). Multiple regression analysis with body fat, visceral ABD fat area, and FCS as independent variables showed that GLT FCS was independently correlated with 2-hour insulin (r = 0.56), triglyceride (r = 0.62), and high-density lipoprotein cholesterol (r = -0.72) levels in AF-AMER women but not in CAU women, where only systolic blood pressure correlated with subcutaneous ABD fat area (r = 0.57) (p < 0.05). DISCUSSION: The associations between GLT FCS and metabolic dysfunction in obese AF-AMER but not CAU women suggest that central obesity is a less valid predictor of the MS in obese postmenopausal AF-AMER women than in CAU women and that GLT FCS may be a more sensitive indicator of risk for the MS in AF-AMER women.