Dietary restriction prevents diabetogenic effect of streptozotocin in mice

The beneficial role of dietary restriction (DR) was studied in streptozotocin (STZ)-induced diabetes in mice. The DR mice exhibited the lower blood glucose (mg/dl) level as compared to ad libitum (AL) fed ones. After 3 months' DR, STZ treatment to both AL and DR mice showed significant (p < 0.001) elevation of the blood glucose level in AL-fed mice, while a lower level of glucose was maintained in DR-fed mice. The ability of maintaining a low blood glucose level in STZ-treated DR mice indicated that STZ might have been ineffective from its action on beta cells of pancreas by long-term DR. Thus, these findings suggested that DR may be an important tool for preventing the diabetic conditions. However, further studies are required to know the mechanism(s) of DR protection against diabetogenic action of STZ in experimental animals.     

Dietary restriction and triiodothyronine (T3) regulation of malate-aspartate shuttle enzymes in the liver and kidney of mice

The activities of malate-aspartate shuttle enzymes viz., cytosolic and mitochondrial aspartate aminotransferase (c- and m-AsAT) and malate dehydrogenase (c- and m-MDH) were measured in liver and kidney of ad libitum (AL) and dietary-restricted (DR) mice and also on triiodothyronine (T3) treatment. The results show that the activity (U/mg protein) of c-AsAT is increased significantly in liver and the activities of c-MDH and m-AsAT are increased significantly in kidney during DR. On T3 treatment, the activities of both the isoenzymes (c- and m-) of MDH and AsAT are increased significantly in the liver of AL- and DR-fed mice. In the kidney, m-MDH showed no effect by T3 treatment, however, c-MDH increased significantly in both AL- and DR-fed mice. In contrast, m-AsAT is increased significantly in the kidney in AL-fed mice, but was not affected in DR-fed animals. In vitro reconstitution of malate-aspartate shuttle showed a higher activity in the liver and kidney of DR-fed mice, as compared to AL-fed ones and also in the T3-treated mice, compared to untreated ones. These findings suggest that malate-aspartate shuttle enzymes are differentially regulated during DR in mice, in order to adapt to the metabolic need of liver and kidney. T3 potentially regulates the shuttle enzymes, albeit to a varying degree in the liver and kidney of AL- and DR-fed mice.