Abdominal obesity is associated with insulin resistance and reduced glycogen synthetase activity in skeletal muscle

Insulin resistance is commonly associated with obesity. The present study was performed to investigate the relative importance of total fat mass versus localization of adipose tissue in insulin-stimulated glucose disposal (Rd) and skeletal muscle glycogen synthase (GS) activity in obese individuals. Twenty obese women with an average body mass index (BMI) of 37.8 +/- 1.3 kg/m2 and a waist to hip ratio (WHR) ranging from 0.78 to 1.02 were examined during basal conditions and following hyperinsulinemia (hyperinsulinemic euglycemic clamp). To accurately determine body composition, the following three methods were used: anthropometric measurements, dual-energy x-ray absorptiometry scanning (DEXA-scan), and bioelectric impedance measurements. In addition, indirect calorimetry and muscle biopsy were performed. Insulin-stimulated glucose Rd was negatively correlated with WHR (R = -.52, P < .025) whereas there were no correlations with BMI or percent fat (R = .16, NS and R = .16, NS, respectively). Furthermore, a negative correlation between WHR and insulin stimulation of GS activity in skeletal muscle was found (R = -.62, P < .005). In contrast, BMI and percent fat were not correlated with the insulin effect on GS activity in skeletal muscle (R = .34, NS and R = -.35, NS, respectively). The concentration of nonesterified fatty acids (NEFA) during hyperinsulinemia was strongly correlated with WHR and abdominal localization of adipose tissue (determined by DEXA-scan; R = .60, P < .005 and R = .60, P < .007, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)