Gender Differences in the Recovery of Ingested Fat in Chylomicron, VLDL, and Plasma Fatty Acids

Abstract

1014 The lipemic response to a high fat meal differs in men and women. However, gender differences in the metabolic fate of ingested lipids are not well understood. PURPOSE: To determine the recovery of ingested lipids in chylomicron, very-low density lipoprotein (VLDL), and plasma fatty acid fractions in men and women. METHODS: Ten non-obese subjects (5 men, 5 women) consumed 0.7g fat/kg body weight containing 13C-triolein the morning after a 12 h fast. Plasma glucose, insulin, and total triglycerides (TG) were measured hourly for 11 h after the meal. TG concentration in plasma chylomicron (CHYLO-TG) and VLDL (VLDL-TG) fractions were measured after separation by density gradient centrifugation. TG and fatty acids were further isolated by thin layer chromatography and 13C recovery in these fractions was assessed using gas chromatography/mass spectrometry. TG concentration data was expressed as the integrated area under the curve (AUC) after correcting for plasma volume during the 11 h period after the meal. Tracer recovery in each lipid fraction was calculated as the percent of the total tracer recovered at each time-point. RESULTS: Total plasma TG (1903 ± 183 and 1239 ± 94 mmol*min, P < 0.05) and CHYLO-TG (547.8 ± 67.3 and 356.3 ± 27.3 mmol*min, P = 0.05) were greater in men than women during the 11 h period after the meal, but no difference existed in VLDLTG (362.7 ± 50.1 and 285.0 ± 61.6 mmol*min). Despite differences in CHYLO-TG concentration, the percent of 13C-oleate recovered in the chylomicron fraction was the same in men and women. However, tracer recovery in the VLDL fraction tended to be greater in men, while tracer recovery in the plasma fatty acid pool tended to be greater in women. CONCLUSIONS: Gender differences in the lipemic response to a fat meal are associated with differential fates of the ingested lipids. In men, more of the ingested lipids may be incorporated into VLDL by the liver in the hours after the meal, while in women, more of the ingested fat is released into the plasma fatty acid pool. Funding sources: NIH – #M01-RR00042 and the Michigan Memorial Phoenix Project