The carbon pathway for lipogenesis in isolated adipocytes from rat, guinea pig, and human adipose tissue

The synthesis of fatty acids from a variety of labeled substrates by isolated adipocytes of the rat, guinea pig, and human was investigated. The incorporation of radioactive glucose and pyruvate into triglyceride fatty acids was considerably lower in human than either rat or guinea pig adipose tissue. By contrast, the incorporation of palmitate into adipose tissue triglycerides was approximately the same in all three species. End carbon analysis of fatty acids isolated from adipocytes incubated with pyruvate-U-14C indicated that although the synthesis of fatty acids in human adipose tissue was extremely low compared to that of the rat and guinea pig, it represented de novo biosynthesis rather than chain elongation of existing fatty acids. It is suggested that in the human, fatty acids are synthetised de novo primarily in the liver. In adipose tissue, lipogenesis consists essentially of the esterification of fatty acids, obtained from plasma, into triglycerides.