Effect of sex and obesity on basal VLDL-triacylglycerol kinetics.

Plasma fatty acid availability is a major regulator of VLDL-triacylglycerol production. Basal whole-body lipolysis is higher in women than in men and is higher in persons with abdominal obesity than in lean individuals. Our goal was to determine whether sex and abdominal obesity affect VLDL-triacylglycerol kinetics. We hypothesized that basal VLDL-triacylglycerol production would be greater in women than in men and greater in obese than in lean subjects. VLDL-triacylglycerol kinetics were measured in 20 lean (10 men, 10 women; body mass index, in kg/m(2): 23 +/- 1) and 20 abdominally obese (10 men, 10 women; body mass index: 35 +/- 1) subjects by using a bolus injection of [(2)H(5)]glycerol and compartmental modeling analysis. The rate of VLDL-triacylglycerol secretion was greater in the lean women than in the lean men (5.1 +/- 0.7 and 2.6 +/- 0.3 micro mol x L plasma(-1) x min(-1), respectively; P < 0.002). Obesity was associated with increased VLDL-triacylglycerol secretion in the men (P < 0.001) but not in the women, which resulted in greater rates of VLDL-triacylglycerol secretion in the obese men than in the obese women (6.8 +/- 0.5 and 5.0 +/- 0.5 micro mol x L plasma(-1) x min(-1), respectively; P < 0.05). The clearance of VLDL-triacylglycerol from plasma was greater (P < 0.05) in the lean women than in the lean men (42 +/- 7 and 27 +/- 4 mL plasma/min, respectively) or in the obese men and obese women (28 +/- 3 and 20 +/- 4 mL plasma/min, respectively). The plasma VLDL-triacylglycerol concentration was directly related to the rate of VLDL-triacylglycerol secretion in the men (R(2) = 0.79, P < 0.001) and inversely related to VLDL-triacylglycerol clearance in the women (R(2) = 0.84, P<0.001). Sex and obesity have independent effects on basal VLDL-triacylglycerol kinetics.