Triacylglycerol contents and in vivo lipogenesis of ob/ob, db/db and Avy/a mice.

The triacylglycerol content and the in vivo lipogenesis rates of the liver and the carcass of 12 groups of mice were studied. They were mice of three strains and affected by mutations at three loci: C57BL/6J-ob/ob and normal mice; C57BL/KsJ-db/db and normal mice; and VY/WfL-Avy/a and normal mice. Each type of mice was studied at two body weight levels, before and after the mutants became grossly obese. It was found that the C57BL/6J-ob/ob and the C57BL/KsJ-db/db mice had the characteristics of juvenile type obesity. They had higher lipogenesis rates and accumulated more triacylglycerol when they were young. They gained weight rapidly mainly due to the accumulation of more triacylglycerol as they matured. Their total triacylglycerol content could reach 50% of their body weight. At maturity, their lipogenesis rates had decreased to normal. In contrast, the VY/WfL-Avy/a mice had the characteristics of maturity-onset type obesity. When they were young, they did not have higher lipogenesis rates and had only a moderate amount of triacylglycerol stored. They did not gain weight rapidly as they matured. However, when they reached maturity, their lipogenesis rate did not decrease. Their body triacylglycerol content was about 25% of their weight.