title: Systemic free fatty acid disposal into very low-density lipoprotein triglycerides.
abstract: We measured the incorporation of systemic free fatty acids (FFA) into circulating very low-density lipoprotein triglycerides (VLDL-TGs) under postabsorptive, postprandial, and walking conditions in humans. Fifty-five men and 85 premenopausal women with BMI 18-24 (lean) and 27-36 kg/m(2) (overweight/obese) received an intravenous bolus injection of [1,1,2,3,3-(2)H5]glycerol (to measure VLDL-TG kinetics) and either [1-(14)C]palmitate or [9,10-(3)H]palmitate to determine the proportion of systemic FFA that is converted to VLDL-TG. Experiments started at 0630 h after a 12-h overnight fast. In the postabsorptive protocol, participants rested and remained fasted until 1330 h. In the postprandial protocol, volunteers ingested frequent portions of a fat-free smoothie. In the walking protocol, participants walked on a treadmill for 5.5 h at ∼3× resting energy expenditure. Approximately 7% of circulating FFA was converted into VLDL-TG. VLDL-TG secretion rates (SRs) were not statistically different among protocols. Visceral fat mass was the only independent predictor of VLDL-TG secretion, explaining 33-57% of the variance. The small proportion of systemic FFA that is converted to VLDL-TG can confound the expected relationship between plasma FFA concentration and VLDL-TG SRs. Regulation of VLDL-TG secretion is complex in that, despite a broad spectrum of physiological FFA concentrations, VLDL-TG SRs did not vary based on different acute substrate availability.
authors: Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota, USA.
authors: Christina
authors: C
authors: Koutsari
authors: Manpreet S
authors: MS
authors: Mundi
authors: Asem H
authors: AH
authors: Ali
authors: Bruce W
authors: BW
authors: Patterson
authors: Michael D
authors: MD
authors: Jensen
mesh_terms: D000328:Adult; D001835:Body Weight / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D008079:Lipoproteins, VLDL / Q000097:blood / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000097:blood / Q000378:metabolism*; D019518:Postprandial Period; D014280:Triglycerides / Q000097:blood / Q000378:metabolism*
chemical_list: D005230:Fatty Acids, Nonesterified; D008079:Lipoproteins, VLDL; D014280:Triglycerides; C030106:very low density lipoprotein triglyceride