Carnitine content of liver from genetically diabetic (db/db) and control mice

Carnitine metabolism in chronic liver disease

The liver is a central organ for carnitine metabolism and for the distribution of carnitine to the body. It is therefore not surprising that carnitine metabolism is impaired in patients and experimental animals with certain types of chronic liver disease. In this review, the changes in carnitine metabolism associated with chronic liver disease and the role of carnitine as a therapeutic agent in some of these conditions are discussed.

Effects of oxytetracycline treatment on enzymes of hepatic glycogen metabolism in genetically diabetic (db/db) mice

The effects of daily oxytetracycline treatment on the activities of hepatic glycogen synthase, glycogen phosphorylase, plasma glucose, and insulin, and on liver glycogen, free fatty acid, and triglyceride levels were examined in 8- to 15-week-old genetically diabetic and lean mice. Oxytetracycline administration resulted in substantial reductions in the plasma glucose and immunoreactive-insulin levels in both diabetic and lean mice. The drug had no significant effect on the liver glycogen content in either phenotype, regardless of age, but it increased hepatic lipids and depressed body weights in lean animals. The most prominent effect of the drug was in markedly altering the activities of both glycogen synthase and phosphorylase in the liver of older diabetic mice. Oxytetracycline treatment produced a three-fold increase in the percentage of glycogen synthase I activity and reduced by one-third the percentage of glycogen phosphorylase a activity in 15-week-old diabetic mice. In age-matched lean mice treated with oxytetracycline, the percentage of glycogen synthase I activity increased significantly, but the percentage of phosphorylase a activity was unchanged. These data suggest that the drug may alter an aspect of hepatic glycogen metabolism which might lead to an inhibition of glycogenolysis and subsequent diminution of blood sugar levels in the diabetic. The present results show that, while oxytetracycline may be effective in reducing the severity of some of the diabetic symptoms associated with carbohydrate metabolism in this animal model of maturity-onset diabetes, the drug may have adverse effects on aspects of protein and lipid metabolism in these animals.

Carnitine content of skeletal and cardiac muscle from genetically diabetic (db/db) and control mice

Portions of diaphragm and heart from genetically diabetic and control mice of three age groups were analyzed for free fatty acid, triglyceride, and carnitine content. Triglyceride levels were increased consistently in both cardiac and skeletal muscle from diabetic animals while the amount of free fatty acids was comparable to that measured in tissue from lean littermates. Free carnitine and total carnitine were decreased in diaphragm and heart from db/db mice throughout the course of the study. While the levels of short-chain carnitine were comparable in tissue from control and diabetic animals, the amount of the long-chain derivative was elevated significantly in both diaphragm and heart in the 18-week-old diabetic mice. The results are discussed with respect to (a) alterations in hepatic carnitine metabolism in this animal model reported previously by this laboratory, and (b) changes in carnitine metabolism which we observed in skeletal muscle from streptozotocin-diabetic animals.