Changes in metabolism of rat kidney and liver caused by experimental diabetes and by dietary sucrose.

Two groups of rats were fed diets in which the carbohydrate components was either starch or sucrose. A third group was fed on a stock diet. Half of the animals in each group were made diabetic by injection of either streptozotocin, in two of the groups, or alloxan, in the third group. Both diabetes and sucrose-feeding increased renal gluconeogenesis as indicated by increased activities of fructose-1,6-diphosphatase and glucose-6-phosphatase. Sucrose-feeding increased fatty acid synthesis both in the liver and kidney. However, the effect of diabetes on fatty acid synthesis was different at the two tissue sites. Diabetes, whether induced by streptozotocin or alloxan, decreased fatty acid synthesis in the liver but increased the rate in the kidney. The latter response was obtained for each diet but was additive with the effect of sucrose. We conclude that the effect of diabetes on renal lipid metabolism may reflect, in part, the accelerated glucose flux. The response to both diabetes and sucrose-feeding is also possibly associated with the increased lipid required for the membrane synthesis reported previously.

Comparative effects of some carbohydrates on serum sugars, triglycerides and digestive hydrolases.

For 3 weeks, rats were fed diets containing 60 p. 100 carbohydrate in the form of starch (wheat flour), purified sucrose, commercial sugar or a commercial sweetener containing a mixture of glucose and fructose. Glycemia was lower during the day than at night, and it was lowest in the starch-fed group. Fructosemia, high in all groups during the day, suggested endogenous production; it was low at night, showing efficient clearance of exogenous fructose. Triglyceridemia was highest in the rats fed purified sucrose and exhibited no light/dark variation in that group. It was higher in all the other groups during the day. Regarding pancreatic hydrolases, starch, rather than sugars, raised pancreatic amylase, while lipase did not correlate with endogenous hyperglyceridemia and was similar in all groups. Commercial preparations significantly lowered chymotrypsinogen contents. These results confirm that sucrose and equimolar mixtures of glucose and fructose are not equivalent (disaccharide effect). The data evidence an endogenous fructose production during the day and suggest that commercial sugar, often used in the preparation of diets, may have different effects than purified sucrose.