Effect of Individual Fatty Acids on Synthesis and Secretion of Apolipoprotein and Lipoprotein in hep-G2 Cells

The effects of individual fatty acids, differing in their degree of unsaturation(18:0, 18:1, 18:2 and 18:3) on the biosynthesis and secretion and lipids were investigated in Hep-G2 cells. Synthesis of apolipoprotein was measured by the incorporation of 3H-leucine into apolipoprotein(d<1.21g/ml) and synthesis of lipids was measured by the incorporation of 3H-glycerol and 14C-acetate into various lipid classes. Inclusion of 1.0mM of each fatty acids into the culture medium significantly increased the synthesis of total apolipoprotein and Apo B(p<0.05). However, addition of fatty acid did not affect the synthesis of cellular and medium protein. Among different fatty acids tested, oleic acid had the greatest effect on Apo B synthesis. While stearic, linoleic and linolenic acid, all had similar effects. The secretion of triglyceride into the medium markedly increased in all fatty acid groups being 5-6 times over the albumin control. The triglyceride secretion was the highest int he oleic acid group. The secretion of phospholipid and cholesterol also increased with triglyceride output. A positive relationship existed between the output of lipoprotein-triglyceride and Apo B. Since the synthesis of Apo B was significantly increased when various fatty acids were included into the culture medium, part of the apparently stimulated synthesis of the apolipoprotein may be in response to the increased formation and secretion of lipoprotein lipids.