Study on the Effect of a High Fat Diet on Diaphragm and Liver Glycogen and Glycerides in the Rat

Summary

The present work was undertaken to study the effect of nutritional obesity induced by a high fat diet on the consumption of glycogen and glycerides in rat liver and diaphragm. Groups of rats were fed for five weeks from weaning either a fat-rich-carbohydrate (CHO)-poor diet, or a CHO-rich-fat-poor diet. Basal plasma glucose and free fatty acids (FFA) were significantly increased in the animals adapted to the fat-rich diet. Half of the rats were submitted to a 48-h fast. After fast, basal plasma glucose and immunoreactive insulin (IRI) fell significantly, whereas plasma FFA levels were higher than in the group fed the CHO-rich-fat-poor diet.

In the liver, glycogen concentration fell in both groups after fast, with a glycogen breakdown of 1930 ± 244 μmole glycogen glucose/liver in the fat-fed group vs 4636 ± 216 μmole/liver in the CHO-fed group. Glycerides fell by 750 ± 68 μmole glyceride glycerol/liver in the fat-fed rats while remaining unchanged (increased by 82 ± 57 μmole/liver) in the CHO-fed group. In the diaphragm glycogen concentration also fell in both groups, with a glycogen breakdown of 6.0 ± 0.3 μmole glycogen glucose/g wet tissue in the fat-fed rats vs 15.2 ± 1.4 μmole/g wet tissue in the CHO-fed animals. Glycerides fell by 23.1 ± 4.0 μmole/g wet diaphragm in the CHO-fed animals.

The lower breakdown of glycogen in both liver and diaphragm of fat-fed rats demonstrates a decreased utilization of glycogen during fast, with energy consumption originating in larger part from triglycerides. It gives support to the hypothesis that the decreased glucose tolerance observed in fat-adapted rats might result from their preferential use of FFA leading to a decrease in glucose utilization.

Key-Words

Liver Glycogen - Liver Glycerides - Muscle Glycogen - Muscle Glycerides - Nutritional Obesity - Fast