Re-evaluation of lipogenesis from dietary glucose carbon in liver and carcass of mice.

We have estimated rates of fatty acid synthesis from glucose carbon and from all 2-carbon units in liver and carcass of mice using [U-14C] glucose and 3H2O under four different nutritional states. The liver synthesized only a small fraction (2--9%) of the fatty acids that were formed from glucose carbon in mice that were fasted 24 hr, fasted--refed, or fed ad libitum. However, in fed-refed mice, the liver's role increased and now accounted for 40% of the fatty acids that were formed from glucose carbon. Under the latter conditions (fed-refed), the liver synthesized 50% of the fatty acids that were formed from all 2-carbon units. At least five-sixths of all the fatty acids synthesized de novo in the fed-refed mouse were derived from carbon fed in the glucose test meal. These studies, in contrast to most earlier studies, provide direct evidence in mice of the major contribution that dietary carbohydrate makes, especially in the liver, to the synthesis of fatty acids. In addition, we have shown that lipogenic inhibition (fasting) and activation (feeding) are most marked in liver and greater for glucose than for non-glucose-carbon. Possible implications for dietary control of carbohydrate-induced hyperlipemia and obesity are discussed.