An analysis of the relationships among obesity, plasma insulin and hepatic lipogenic enzymes in "viable yellow obese" mice (Avy/a).

The development of obesity, hyperinsulinemia and six hepatic lipogenic enzymes in Avy/a mice were compared to that in a/a mice. Correlation between body weight, liver weight, plasma insulin concentration and activities of hepatic enzymes was analyzed. In the Avy/a mice, body weight, liver weight and plasma insulin level increased steadily as the mice aged. In the a/a mice, the change of these three parameters was much slower. Plasma insulin concentration in a/a mice did not increase until eight months of age. Compared with a/a mice, Avy/a mice had higher 6-phosphogluconate dehydrogenase and fatty acid synthetase activities at two months of age; lower citrate cleavage enzyme, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities at three months of age; lower citrate cleavage enzyme and glucose-6-phosphate dehydrogenase and higher acetyl CoA carboxylase activities at five months of age; and higher malic enzyme, citrate cleavage enzyme and 6-phosphogluconate dehydrogenase activities at eight months of age. There were significant correlations between plasma insulin level and body weight and between plasma insulin level and the activities of malic enzyme and citrate cleavage enzyme in Avy/a mice. The correlation between body weight and malic enzyme and citrate cleavage enzyme activities disappeared after the analysis was adjusted for plasma insulin level.