SKELETAL-MUSCLE UTILIZATION OF FREE FATTY-ACIDS IN WOMEN WITH VISCERAL OBESITY

Visceral obesity is strongly associated with insulin resistance. One p otential cause is increased availability of FFA. Alternatively, it has been proposed that there is impaired oxidation of lipid in individual s at risk for obesity, The extent to which either concept involves ske letal muscle is uncertain, To examine these opposing hypotheses, 17 he althy lean and obese premenopausal women, among whom cross-sectional a rea of visceral fat ranged from 18 to 180 cm(2), participated in leg b alance studies for measurement of FFA and glucose utilization during b asal and insulin-stimulated conditions, A metabolic profile of skeleta l muscle, based on enzyme activity, was determined in vastus lateralis muscle obtained by percutaneous biopsy. Visceral fat content was nega tively correlated with insulin sensitivity (rates of leg glucose uptak e and storage), but insulin resistance was not caused by glucose-FFA c ompetition, During hyperinsulinemia, neither leg FFA uptake nor oxidat ion was increased in women with visceral obesity, During fasting condi tions, however, rates of FFA uptake across the leg were negatively cor related with visceral adiposity as were activities of muscle carnitine palmitoyl transferase and citrate synthase, In summary, visceral adip osity is clearly associated with skeletal muscle insulin resistance bu t this is not due to glucose-FFA substrate competition, Instead, women with visceral obesity have reduced postabsorptive FFA utilization by muscle.