When rats were fed for 2 weeks on 3% fat diets containing 0.5 or 1%corbicula (Corbicula japonica PRIME), clam (Tapes japonica) or oyster (Callocorchina) triglycerides, serum and liver triglyceride levels were significantly lowered. The activities of hepatic glucose-6-phosphate dehydrogenase, malic enzyme and acetyl-CoA carboxylase were markedly reduced in the rats. Cholesterol synthesis by liver slices was also reduced. The results of immunochemical titrations and Ouchterlony double-diffusion analysis indicated that the decreases in the activities of acetyl-CoA carboxylase and glucose-6-phosphate dehydrogenase were due to decreases in the enzyme quantities. The shellfish triglycerides include a high percentage of long chain and polyunsaturated fatty acids, which are common to and characteristic of the three kinds of shellfish. They would be effective components in these observations.
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.
Three groups of male rats were maintained on 10% fat diets containing 0.5, 5 or 10% corn oil or olive oil with 80--400 mg DL-alpha-tocopherol per kilogram. After 4 weeks on such regimens, TBA (thiobarbituric acid) values in serum, liver mitochondria and microsomes, and adipose tissue increased with rising amounts of dietary corn oil. TBA values in rats fed the 10% corn oil diet were reduced with the increase of dietary tocopherol but were still higher than the corresponding values of the 10% olive oil and 0.5% corn oil groups. When the liver microsomes were incubated with Fe3+-ADP and NADPH, the relative chemiluminescence emission in the visible region with the peroxidative cleavage of endogenous lipid was higher in the 5 and 10% corn oil groups than in the 0.5% group. On the other hand, when oxidized corn oil was given orally to rats with thoracic lymph fistula, TBA-reacting substances were recovered in thoracic lymph, but iodometric peroxide was undetectable. Therefore, TBA-reacting substances in rats fed the corn oil diets could have originated from the oxidative product of linoleic acid metabolism and also from the diet.
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