Effect of sex and obesity on basal VLDL-triacylglycerol kinetics

Background: 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. Objective: 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. Design: VLDL-triacylglycerol kinetics were measured in 20 lean (10 men, 10 women; body mass index, in kg/m²: 23 ± 1) and 20 abdominally obese (10 men, 10 women; body mass index: 35 ± 1) subjects by using a bolus injection of [²H₅]glycerol and compartmental modeling analysis. Results: 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 μmol·L plasma^-1·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 μmol·L plasma^-1·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 (R² = 0.79, P < 0.001) and inversely related to VLDL-triacylglycerol clearance in the women (R² = 0.84, P<0.001). Conclusion: Sex and obesity have independent effects on basal VLDL-triacylglycerol kinetics.