Splanchnic Spillover of Extracellular Lipase–Generated Fatty Acids in Overweight and Obese Humans

OBJECTIVE— Triglyceride-rich lipoproteins, primarily chylomicrons, can contribute to plasma free fatty acid (FFA) concentrations via spillover of fatty acids during intravascular hydrolysis into the venous effluent of some tissues. The present study was undertaken to determine whether spillover occurs in the splanchnic bed of humans. RESEARCH DESIGN AND METHODS— Arterial and hepatic venous blood was sampled in postabsorptive ( n = 6; study A) and postprandial ( n = 5; study B) obese humans during infusion of carbon-labeled ( 14 C or 13 C) oleate and 3 H triolein, the latter incorporated into a lipid emulsion as a surrogate for chylomicrons. Spillover was determined by measuring production of 3 H oleate. RESULTS— Splanchnic spillover was higher than nonsplanchnic systemic spillover in both study A (60 ± 7 vs. 24 ± 6%; P P P CONCLUSIONS— These data confirm previous studies indicating that the transport of FFAs and triglyceride fatty acids are partitioned in tissues and indicate that splanchnic spillover from triglyceride-rich lipoproteins may be a significant source of both portal venous and systemic FFAs.