Eiko Fukuda

Lipid metabolism in spontaneously hypertensive rats (SHR)

Plasma cholesterol was lower in spontaneously hypertensive rats (SHR), while plasma triglyceride and free fatty acid were increased in comparison with control normotensive Wistar-Kyoto (WK) rats. Correspondingly, [1-14C]-acetate incorporation into liver cholesterol was clearly decreased in SHR as compared with WK. As for lipogenic enzyme activities, glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase in SHR were respectively decreased, increased and not significantly different, in comparison with WK rats. Liver cholesterol was rather low and cardiac triglyceride was slightly increased in SHR. Aortic cholesterol and triglyceride levels were not significantly different between SHR AND WK rats. Thus, SHR have an abnormality in lipid metabolism, especially in cholesterol synthesis, but the pathological implication of this in hypertension and related vascular lesions is not yet clear.

Effect of feeding the shell fish (Corbicula japonica) on lipid metabolism in the rat.

Rats were maintained for 2 weeks on 3 different diets; a basal diet, one containing 0.1% cholate, and one containing 0.1% cholesterol and 0.1% cholate. Each dietary group was further divided into subgroups whose diet contained 0, 5 or 10% (dry weight) of minced corbicula (Corbicula japonica Prime). Feeding corbicula significantly reduced the increase of cholesterol levels in rats fed the cholesterol diet. Though corbicula contains several sterols, sterols other than cholesterol were almost not absorbed. Serum and liver triglyceride levels were significantly reduced by feeding corbicula meat in all the dietary groups. Activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were also markedly reduced by feeding corbicula. The results suggest that corbicula is a hypolipidemic food.

Age-dependent modifications of lipogenic enzymes

When 1-, 2- and 9-month-old rats previously adapted to a commercial stock diet were fed a fat-free diet (induction) and also when the process was reversed (repression), the turnovers of lipogenic enzymes in liver were measured by following time courses for the change of the enzyme activities. The magnitudes of the induction of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were very high in 1-month-old rats and then decreased with aging. In the induction phase, the rates of synthesis of the enzymes were markedly decreased with increasing age as compared with the rate constants of degradation. The age-dependent alterations were not shown so much in the repression phase as in the induction phase. It is suggested that the age-dependent impairment in induction may be due to some alterations in the enzyme-forming system.

Effect of oxidized oil on lipogenic enzymes

Male Wistar rats were fed for 4 wk on diets containing 2% oxidized corn oil. Liver tissue was then studied to determine the effect of feeding peroxidized oil on lipogenic enzymes. Although substances which reacted with thiobarbituric acid increased in liver microsomes and mitochondria with increasing peroxide values of the dietary corn oil fed, the activities of glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase in liver were unchanged. However, when rats were fed for 2 wk on diets containing 10% fat, of which 0.5, 5 or 10% was unoxidized corn oil and the remainder was hydrogenated beef tallow filler, the lipogenic enzyme activities and also the liver triglyceride levels were observed to decrease with increasing amounts of dietary corn oil. Therefore, although a synthetic diet containing corn oil was easy to oxidize spontaneously, the reductions of lipogenic enzymes in rats fed the diet would not have been caused by lipid peroxides but by unsaturated fatty acids themselves.

Method of Feeding Carbohydrate and Lipogenesis in Rat

ラットにショ糖だけ, あるいはショ糖と油を他の栄養素とは別の容器で与えたとき, 血清および肝臓トリグリセリドと肝グリコーゲン量は, 全栄養素を混合して与えた対照群にくらべて増大した。これらの群では脂肪酸合成系の酵素活性が有意に増加していたのでトリグリセリドの合成が増大したことが考えられる。ショ糖をデンプンでおきかえると, これらの現象はみられず, 肝トリグリセリド量に同様な現象がみられたにすぎなかった。ショ糖を別の容器で投与したときのようにもっぱらショ糖を摂取したときには, 脂肪の合成は多量に摂取したときと同じような効果があることが示唆される。