Lipid metabolism during fasting

These studies were conducted to understand the relationship between measure s of systemic free fatty acid (FFA) reesterification and regional FFA, glyc erol, and triglyceride metabolism during fasting. Indirect calorimetry was used to measure fatty acid oxidation in six men after a 60-h fast. Systemic and regional (splanchnic, renal, and leg) FFA ([H-3]palmitate) and glycero l ([H-3]glycerol) kinetics, as well as splanchnic triglyceride release, wer e measured. The rate of systemic FFA reesterification was 366 +/- 93 mu mol /min, which was greater (P < 0.05) than splanchnic triglyceride fatty acid output (64 <plus/minus> 6 mu mol/min), a measure of VLDL triglyceride fatty acid export. The majority of glycerol uptake occurred in the splanchnic an d renal beds, although some leg glycerol uptake was detected. Systemic FFA release was approximately double that usually present in overnight postabso rptive men, yet the regional FFA release rates were of the same proportions previously observed in overnight postabsorptive men. In conclusion, FFA re esterification at rest during fasting far exceeds splanchnic triglyceride f atty acid output. This indicates that nonhepatic sites of FFA reesterificat ion are important, and that peripheral reesterification of FFA exceeds the rate of simultaneous intracellular triglyceride fatty acid oxidation.