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Biomedical subjects

R R Brenner

Publications and source records attributed to R R Brenner.

At least 163 records · Page 9Linked to original sources
PubMed1972

Oxidative desaturation of eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid: comparison of different diets on oxidative desaturation at the 5,6 and 6,7 positions.

The oxidative desaturation of [1-(14)C]eicosa-8,11-dienoic acid to eicosa-5,8,11-trienoic acid by rat liver microsomes was studied, and the kinetic conditions appropriate to measure the specific activity of the enzyme were determined. A comparative study of the effects of a balanced diet and essential fatty acid-free diets on the oxidative desaturation of oleic and linoleic acids at the 6,7 position and the oxidative desaturation of eicosadienoic acid at the 5,6 position were made. Eicosadienoic acid showed a higher conversion than oleic acid for all the diets. The conversion of oleic and linoleic acids to Delta6 acids was equally increased by fat-free diets with or without added methyl palmitate, whereas the oxidative 5-desaturation of eicosadienoic acid at the 5,6 position was not changed. The effect was apparently independent of the amount of endogenous free fatty acids. The results suggest that the rate-limiting and principal regulatory step in the biosynthesis of eicosa-5,8,11-trienoic acid is the 6-desaturation of oleic acid. The 5-desaturation of eicosadienoic acid was increased by a protein diet and decreased by alloxan diabetes to a lesser extent than the 6-desaturation of linoleic acid. The 5-desaturation of eicosadienoic acid would constitute a secondary regulatory step.

Animals↗
PubMed1970

Effect of diet on linoleic acid desaturation and on some enzymes of carbohydrate metabolism.

The effect of diet on the desaturation of linoleic acid to gamma-linolenic acid by liver microsomal preparations, on blood glucose and insulin levels, and on activities of glucokinase, hexokinase, pyruvate kinase, and alpha-glycerophosphate dehydrogenase have been studied. The female rats used in these experiments were maintained on one of the following dietary regimes: (a) fasted, (b) fasted for 96 hr and refed glucose, (c) balanced diet, (d) carbohydrate-free diet, (e) lipid-free diet, or (f) protein-free diet. Fasting for 96 hr caused a decrease of both linoleic acid desaturation and glucokinase and pyruvate kinase activity together with a slight decrease of the blood insulin level. Alpha-glycerophosphate dehydrogenase activity was not modified. Refeeding of glucose for 50 hr increased the conversion of linoleic acid to linolenic acid as well as the activities of all the enzymes studied except alpha-glycerophosphate dehydrogenase. The increase in desaturation, however, was transient. The feeding of a lipid-free diet did not modify the tested parameters. Feeding a carbohydrate-free diet for 96 hr resulted in increased linoleic acid desaturation but decreased glucokinase and pyruvate kinase activity, thus apparently eliminating a putative correlation between the fatty acid desaturating activity and glycolytic activity or blood insulin levels under these experimental conditions. The findings suggest that dietary proteins may play an important role in determining the level of fatty acid desaturation.

Animals↗