ABSTRACT
Male Sprague-Dawley rats were fed diets varying in fatty acid composition for 24 d. Liver plasma membranes were isolated, and the effect of diet on phospholipid fatty acyl tail composition and glucagon-stimulated adenylate cyclase activity was measured. Dietary linolenic acid influenced membrane phospholipid fatty acid composition and altered the effect of different dietary levels of linoleic acid on membrane composition. At low dietary intakes of linolenic acid, membrane fatty acids derived from linolenic acid increased as dietary intake of C18:2(9,12) increased. At high dietary linolenic acid levels membrane content of fatty acids derived from linolenic acid decreased as dietary intake of linoleic acid increased. Glucagon-stimulated adenylate cyclase activity decreased at high levels of both dietary linoleic acid and linolenic acid. These observations suggest that dietary balance between linoleic and linolenic acids has a role in plasma membrane composition and may control glucagon-stimulated adenylate cyclase activity.
Subject(s)
Adenylyl Cyclases/metabolism , Dietary Fats/pharmacology , Glucagon/pharmacology , Linoleic Acids/pharmacology , Linolenic Acids/pharmacology , Liver/cytology , Membrane Lipids/metabolism , Animals , Dietary Fats/administration & dosage , Linoleic Acid , Linoleic Acids/administration & dosage , Linolenic Acids/administration & dosage , Liver/drug effects , Liver/enzymology , Male , Phospholipids/analysis , Rats , Rats, Inbred Strains , alpha-Linolenic AcidABSTRACT
Current concepts of the biomembrane will be extrapolated to membranes of homeotherms to illustrate the influence of the nature of dietary lipid in nutritionally complete diets on membrane polar head group content and fatty acid composition. Utilizing animal models, the controlling influence of dietary long chain fatty acids on major lipid constituents of the mitochondrial membrane in cardiac tissue, the plasma membrane of liver, and the synaptosomal membrane in brain can be demonstrated. Diet-induced alterations in membrane composition are associated with demonstrable changes in the function of specific membrane proteins. To illustrate this relationship, the effect of diet on mitochondrial ATPase activity and on a hormone receptor-stimulated function in the plasma membrane of the liver will be discussed. These observations suggest that the diet fat modulates enzyme functions in vivo by changing the surrounding lipid environment in the membrane.
Subject(s)
Dietary Fats/pharmacology , Subcellular Fractions/drug effects , Adenosine Triphosphatases/metabolism , Adipose Tissue/metabolism , Animals , Brain Chemistry , Cell Membrane/metabolism , Intestinal Mucosa/metabolism , Liver/metabolism , Membranes/physiology , Mitochondria/enzymology , Mitochondria/metabolism , Models, Biological , Phosphatidylcholines/metabolismABSTRACT
Dietary fiber is one of several variables being considered in the study of the relationship between diet and cancer. Intervention trials in which dietary fiber is increased are the most direct way of assessing the possible role of fiber in this disease. Two dietary snack products have been developed for use in a fiber intervention study: the high-fiber snack (HFS), which supplies 23 g of dietary fiber per day (mostly from wheat bran) and the low-fiber product (LFS), which provides 3.5 g. Over a 12-week period, 28 volunteers consumed the HFS for 6 weeks and the LFS for 6 weeks. Compliance, as assessed by reports, through recovery of a riboflavin marker in the urine and fecal fiber analysis, was good. The only adverse effects reported were mild abdominal discomfort and gas. Serum ferritin and calcium decreased in some subjects, indicating a need to supplement the products with these essential minerals. Consumption of the snacks did not affect total energy intake or the intake of the nutrients monitored.
