Development of hepatic and adipose tissue lipogenic enzymes and insulinemia during suckling and weaning on to a high-fat diet in Zucker rats.

Aug 1, 1982Journal of lipid research

Changes in liver and fat tissue fat-making enzymes and insulin levels during breastfeeding and weaning on a high-fat diet in Zucker rats

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Abstract

Fat pad weight increased by 100% in obese rats by 17 days of age compared to lean rats.

During suckling, liver enzyme activities showed no difference between lean and obese rats.
Adipose tissue enzyme activities increased significantly in obese rats, with a 50% rise in fatty acid synthetase and a 30% increase in citrate cleavage and malic enzymes by 9 days of age.
By 17 days of age, enzyme activities in obese rats were threefold higher for certain enzymes compared to lean rats.
After weaning, the increase in fat pad weight accelerated, especially on a high-fat diet.
Weaning on to a low-fat diet resulted in hepatic lipogenic enzyme increases that were two to three times greater in obese rats than in lean rats.
Overall, lipogenic enzyme activities were three to ten times greater in obese pups compared to lean pups, regardless of diet.

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This study was designed to monitor the developmental changes in insulinemia and lipogenic enzyme activities in both inguinal adipose tissue and liver during suckling (7, 9, 14, and 17 days of age) and weaning (22 and 30 days of age) on to either a low-fat or a high-fat diet in lean (Fa/fa) and obese (fa/fa) rats. Tissues were removed through surgery and genotypes were retrospectively determined. During suckling, there was no difference in liver enzyme activities between the two groups. In contrast, adipose tissue fatty acid synthetase was increased by 50% and citrate cleavage enzyme and malic enzyme by 30% by 9 days of age. By 17 days of age, there was a threefold elevation in these enzyme activities and 6-phosphogluconic dehydrogenase and a twofold increase in glucose-6-phosphate dehydrogenase per inguinal fat pad in fa/fa versus Fa/fa. Consistent with these results, fat pad weight was increased by 20%, 50%, and 100% at 9, 14, and 17 days of age, respectively, in obese as compared to lean pups. However only by 17 days of age could a slight but significant increase in insulin level be detected in obese pups. Enlargement of inguinal fat pad accelerated after weaning on to a low-fat diet and still more after weaning on to a high-fat diet. Weaning on to a low-fat diet elicited an induction of hepatic lipogenic enzymes two or three times greater in fa/fa than in lean pups, while weaning on to a high-fat diet blunted the differences between genotypes. The lipogenic enzyme activities displayed per total inguinal fat were three to ten times greater in obese than in lean pups, regardless of the diet. However, adipose tissue lipogenic enzyme activities were much lower after weaning on to a high-fat than on to a low-fat diet in obese pups. The high-fat diet was as effective as the low-fat diet in triggering hyperinsulinemia in obese pups. The increased adipose tissue capacity for lipogenesis, starting during the suckling period, could play an important etiologic role in the development and maintenance of obesity in the Zucker rat.-Bazin, R., and M. Lavau. Development of hepatic and adipose tissue lipogenic enzymes and insulinemia during suckling and weaning on to a high-fat diet in Zucker rats.

Development of hepatic and adipose tissue lipogenic enzymes and insulinemia during suckling and weaning on to a high-fat diet in Zucker rats.

Abstract

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