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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

The Elevation of Ingested Lipids within Plasma Chylomicrons Is Prolonged in Men Compared with Women¹

Substrate Metabolism Laboratory, Division of Kinesiology, University of Michigan, Ann Arbor, MI 48109-2214

² To whom correspondence should be addressed. E-mail: jeffhoro{at}umich.edu.

The lipemic response to a high-fat meal is greater in men than in women. However, sex-related differences in the metabolic fate of ingested fat are not well understood. The purpose of this study was to measure the recovery of ingested fat in plasma fractions of chylomicrons (CHYLO), VLDL, and plasma fatty acids, as well as in expired breath (i.e., oxidation) in men and women. Nonobese subjects (n = 10; 5 men, 5 women) consumed 0.7 g fat/kg body weight containing 7 mg/kg of [1,1,1-¹³C]-trioleate the morning after an overnight fast. Plasma total triglyceride (TG) concentration and ¹³C recovery in the CHYLO, VLDL, and plasma fatty acid fractions, as well as expired breath samples, were measured over the 11-h period after the meal. Plasma total TG excursion was greater (P < 0.05) in men than in women during the 11-h period after the meal. Similarly, the recovery of the ingested tracer-labeled fat in the CHYLO fraction was greater in men than in women (main effect for sex; P < 0.05). Recovery of ingested tracer-labeled fat in VLDL, the plasma fatty acid fraction, and expired breath did not differ in men and women. Therefore, the elevated postprandial lipemia found in men compared with women was due to a prolonged availability of the lipid in chylomicrons, but was not related to differences in oxidation rates or incorporation of the ingested lipid into VLDL by the liver.

KEY WORDS: • fat metabolism • VLDL • cardiovascular disease • fatty acids • sexual dimorphism