B-23. 飼料中脂質及び飼料摂取量の正常及び糖尿RAT肝HMG-CoA Reductase活性に及ぼす影響

抄録

The effects of dietary lipid and daily food-uptake on hepatic HMG-CoA reductase activity and serum cholesterol level of the normal and diabetic rats were studied. The animals were maintained on either carbohydrate diet (dextrose 75%, casein 20%, and vitamin and salts 5%) or on fat diet (dextrose 30%, casein 20%, vitamins and salts 5%, corn oil 20% and indigestible fibers 25%) for five days from 8 o'clock in the morning till 6 o'clock in the evening. Daily food consumption per animal under these conditions were nearly 60 calories per day and no significant differences were observed. The other groups of normal and diabetic animals, forcedly fed one of the two kinds of diets 76 calories daily for four days, were also studied. The measurements of the enzyme activity were done at noon and midnight. The serum samples were obtained at noon and used for cholesterol analysis.
The diurnal variations of the enzyme activity were shown on the all groups observed. The lipid feeding markedly stimulated the HMG-CoA reductase activity of both normal (6.7 folds) and diabetic (20 folds) rats. Increased consumption of the diets also stimulated the enzyme activity in most of normal and diabetic rats (1.4 folds). However, these stimulatory effects on the reductase activity by these variouse different dietary states were not accompanied by increase nor decrease of serum cholesterol level.
These discrepancies between the hepatic cholesterogenesis and serum cholesterol level suggest that the liver has rather limited contribution to the whole cholesterogenesis or that the catabolism of cholesterol is also stimulated coordinately with its production by these dietary manipulations.
The possible mechanism of the induction of hepatic HMG-CoA reductase by dietary lipid and increased food consumption were discussed.