title: Repression of pentose phosphate pathway dehydrogenase synthesis and mRNA by dietary fat in rats.
abstract: We have studied the effects of polyunsaturated fatty acid and its metabolism on the activity, relative synthesis and mRNA levels for rat hepatic glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). Rats were meal-fed high carbohydrate diets containing either no fat, 5% safflower oil or 5% safflower oil + eicosa-5,8,11,14-tetraynoic acid (TYA). Hepatocytes were isolated and used as a source of RNA, de novo radiolabeled protein and postmitochondrial supernatant for enzyme assay. Dietary safflower oil, as a source of linoleic acid, repressed G6PD activity, synthesis and mRNA levels two- to threefold without significantly changing the amount of carbohydrate consumed. Similar but smaller changes were observed for 6PGD. Dietary fat + TYA (an analogue of arachidonate that inhibits normal metabolism of linoleic acid) prevented the fat-dependent lowering of G6PD and 6PGD activity, synthesis and mRNA levels. Our results suggest that a metabolite of linoleic acid regulates the activity of two lipogenic enzymes, G6PD and 6PGD, by lowering gene expression or mRNA processing or stability.
authors.affiliation: Department of Biochemistry, University of California, Riverside 92521.
authors.forename: J E
authors.initials: JE
authors.lastname: Tomlinson
authors.forename: R
authors.initials: R
authors.lastname: Nakayama
authors.forename: D
authors.initials: D
authors.lastname: Holten
mesh_terms: D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005954:Glucosephosphate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D010734:Phosphogluconate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D012333:RNA, Messenger; D015117:5,8,11,14-Eicosatetraynoic Acid; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase