[Lipid metabolism in rats fed a diet rich in various carbohydrates. I. Results after I.P. injection of lipogenic precursors].

Male rats, Wistar CF strain, weighing 120 g at the beginning of the experiment, were fed during 7 months with one of the following diets, containing 72 p. 100 (w/w) carbohydrate: starch, fructose, glucose and sucrose. These diets were about 18% (w/w) in protein content and were conveniently balanced with respect to vitamins and mineral nutrients. After an overnight fast, the animals received by the i.p. way, 30 mn before their killing, one of the following lipogenic precursors: glucose (considered as the control treatment), fructose ethanol or acetate, thus forming 16 experimental groups. In their liver, heart and blood were determined the concentrations of 6 lipid compounds: triglycerides, non-esterified fatty acids, free, esterified and total cholesterol, phospholipide. a. The sucrose diet gave the heaviest animals, with a liver and heart which were the richest in triglyceride content. They had also the highest liver and blood cholesterol, but their blood phospholipid was the lowest. The starch diet also increased, compared to the glucose diet, liver and heart triglycerides and liver cholesterol. As regards the fructose diet, it had the same effects than the sucrose one in elevating liver weight, blood triglycerides and cholesterol; conversely, it lowered liver and chiefly heart triglycerides and increased blood phospholipide. The glucose diet was for almost all parameters the one which displayed the lowest values. b. Relative to the glucose injection, other ones increased liver triglycerides, cholesterol and phospholipids and non-esterified fatty acids of the 3 assayed tissues. We observed that some differences between the effects of two given injections varied according to the previous diet, e.g. the sucrose-fed rats had more liver triglycerides and cholesterol, more heart and blood cholesterol after i.p. fructose than after i.p. glucose, which was not the case for the starch-fed animals. The importance of liver esterification reactions, which are increased with a long-term administration of a fructose-containing diet, is emphasized in the discussion. However dietary fructose could not be able to display its lipogenic effets in the absence of dietary glucose and that is why sucrose is more efficient than glucose in promoting a net lipid synthesis.