Application of high-performance liquid chromatography of plasma fatty acids as their phenacyl esters to evaluate splanchnic and renal fatty acid balance in vivo.

Plasma fatty acids from renal and hepatic veins, and arterialized hand vein obtained in 20 subjects before and after insulin infusion were separated by reversed-phase high-performance liquid chromatography following phenacyl esterification. Separation and quantification over the range 1.0-100 nmol per injection of nine fatty acids was achieved within 60 min using [2H31]palmitic acid as internal standard. Analytical recoveries were greater than 90% and the intra- and inter-assay coefficients of variation were less than 2.5 and 4.0%, respectively. Following insulin infusion, net splanchnic uptake of total fatty acids decreased from 3.0+/-0.3 to 1.0+/-0.1 micromol/kg min (p<0.01), whereas net renal balance remained neutral (-0.04+/-0.04 vs. -0.06+/-0.03 micromol/kg min, p=N.S.). Individual fatty acid balance varied from a low of 0.012+/-0.005 (myristic acid) to a high of 0.95+/-0.08 (oleic acid) micromol/kg min across the splanchnic tissues and from 0.005+/-0.002 (stearic acid) to 0.21+/-0.1 (oleic acid) micromol/kg min across the kidney. There is a substantial diversity in changes in plasma concentration and regional balance of individual fatty acid during short-term fasting and hyperinsulinemia. This method is simple, accurate, and can be applied to assess individual fatty acid metabolism in vivo.