Regulation by dietary fats of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase in rat liver.
The effects of various dietary fats on the activity of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase in rat liver microsomes, the rate-limiting enzyme in cholesterogenesis, were examined. A series of experiments demonstrated the dependency of the HMG-CoA reductase activity on the nature of dietary fats. When saturated fats with chain length of 12 to 18 were the dietary sources and were fed at the 10% level for 19 days, feeding fats with shorter chain fatty acids caused a lower enzyme activity compared to those with longer chain fatty acids. The activity was also regulated by the degree of unsaturation of dietary fats; when safflower oil, camellia oil or tristearin were fed at the 10% level for 18 days, the higher the unsaturation, the lower the activity. When trimyristin or tripalmitin were fed at the 10% level for 14 days, addition of essential fatty acid, at the level of minimum daily requirement (1% was replaced by safflower oil), did not affect the enzyme activity. Through the rate of incorporation of mevalonate into cholesterol in the 12,500 x g supernatant fraction of the liver was also found to be influenced by the types of dietary fats, the extent of the response appeared much smaller than that of HMG-CoA reductase. No consistent correlation between the HMG-CoA reductase activity and the content of microsomal cholesterol or cholesteryl ester and the fatty acid composition of microsomal lipids was observed.
D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D002940:Circadian Rhythm; D003059:Cocos; D004041:Dietary Fats / Q000008:administration & dosage; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009821:Oils / Q000494:pharmacology; D051381:Rats; D012450:Safflower Oil / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014280:Triglycerides / Q000494:pharmacology; D003313:Zea mays
D004041:Dietary Fats; D009821:Oils; D014280:Triglycerides; D012450:Safflower Oil; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases