出版社：American Society for Biochemistry and Molecular Biology
摘要：Fatty acids (FA) that are utilized for triglyceride (TG) synthesis in the liver and principally from two sources: FA synthesized de novo in the liver and preformed FA. We have measured the contribution from the two sources to very low density lipoprotein (VLDL) TG synthesis individually for palmitate, oleate, stearate, and linoleate (≈98% of the total FA of VLDL TG (VLDL TGFA)) by isotopomer analysis. Five healthy men were studied in the basal state, and 1 (day 1) and 4 days (day 4) after the start of a hypercaloric carbohydrate-enriched diet (≈2.5 times energy expenditure). The secretion of de novo palmitate was increased 15- and 43-fold after 1 and 4 days of hyperalimentation (2.6 ± 1.2 (basal state), 40.8 ± 20.0 (day 1), and 113.3 ± 42.0 μmol/kg per d (day 4)). Even though 4 days of hyperalimentation increased the secretion of de novo stearate 43-fold and de novo oleate 70-fold (stearate; 0.2 ± 0.2 (basal), 8.6 ± 3.3 μmol/kg per d (day 4), oleate; 0.4 ± 0.4 (basal), 28.2 ± 12.7 μmol/kg per d (day 4)), palmitate accounted for 75–85% of all the de novo VLDL TGFA. One day of carbohydrate hyperalimentation tended to decrease the secretion while 4 days increased the secretion of all preformed FA in VLDL TG. The rate of secretion of preformed palmitate and oleate were almost identical (palmitate; 80.2 ± 22.2 (basal), 45.1 ± 23.8 (day 1), and 256.2 ± 74.1 μmol/kg per d (day 4), oleate; 95.2 ± 22.8 (basal), 46.2 ± 24.2 (day 1), and 356.8 ± 74.1 μmol/kg per d (day 4)) and collectively these two FA accounted for 80–90% of the secretion from the preformed source. Palmitate is the predominant product of acute and prolonged carbohydrate mediated lipogenesis in the human liver. The pathway of further elongation and subsequent desaturation of de novo synthesized palmitate to generate stearate and oleate is inducible but, quantitatively, of minor significance in hepatic lipogenesis.—Aarsland, A., and R. R. Wolfe. Hepatic secretion of VLDL fatty acids during stimulated lipogenesis in men. J. Lipid Res. 1998. 39: 1280–1286.
