Effects of dietary carbohydrate on the development of obesity in heterozygous Zucker rats.
Rats carrying one copy of the fa allele are predisposed to diet-induced metabolic disturbances which contribute to hyperinsulinemia, obesity and dyslipidemia. To investigate the role of dietary carbohydrate and fat in the development of these conditions, we fed 6-week old male heterozygous (fa/+) lean rats carbohydrate-free diets containing primarily saturated fat either ad libitum or pair-fed. These diets were compared to standard chow and to a high saturated fat mixed diet containing 10% energy from sucrose for 4 weeks. The carbohydrate-free diet resulted in significantly lower circulating glucose levels compared to all other groups (p = 0.006). Weight gain was negligible in the carbohydrate free groups compared to standard diet and 10% sucrose diet (p = 0.03). This was reflected in energy efficiency which was markedly reduced (90%) in the carbohydrate-free groups compared to the other groups (p = 0.04). Corresponding changes were noted in fat pad mass. The subscapular and epididymal fat pads were increased 42% and 44%, respectively, in animals consuming the 10% sucrose diet compared to all other groups (p < 0.01). Comparable changes in fatty acid synthase (FAS) mRNA were observed in response to the carbohydrate-free diet, which resulted in a 53% decrease in adipocyte FAS mRNA (p < 0.001). Addition of 10% sucrose to the diet completely reversed this effect resulting in a 69% increase in adipocyte FAS mRNA compared to the carbohydrate-free groups (p = 0.01). Similarly, hepatic FAS mRNA was elevated by 51% and 66% in the 10% sucrose and standard diet groups respectively, compared to the carbohydrate-free groups. Therefore, diets that contain minimal carbohydrate may minimize net lipid storage and adiposity.
Morris
Kristin L
KL
Department of Nutrition, The University of Tennessee, Knoxville, TN 37996, USA.
Namey
Thomas C
TC
Zemel
Michael B
MB
D017667:Adipocytes / Q000737:chemistry; D000273:Adipose Tissue / Q000187:drug effects; D000818:Animals; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004041:Dietary Fats / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects; D064429:Fatty Acid Synthases / Q000096:biosynthesis; D008055:Lipids / Q000032:analysis; D008297:Male; D009765:Obesity / Q000209:etiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011924:Rats, Zucker; D015430:Weight Gain / Q000187:drug effects
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D008055:Lipids; D012333:RNA, Messenger; D064429:Fatty Acid Synthases