ABSTRACT
OBJECTIVE: We assessed the metabolic characteristics of high-fat-diet-resistant (DR) rats. METHODS: Body weight, energy intake, locomotor activity, oxygen consumption, plasma leptin and lipid levels, size of visceral-fat adipocytes, and mRNA levels of genes related to lipid metabolism were measured in control rats fed standard chow and in obesity-prone (high-fat-diet-induced obesity, DIO) and DR rats fed a high-fat diet. Glucose tolerance and insulin tolerance tests were also performed. RESULTS: DIO rats gained weight more rapidly than did DR and control rats; DR rats gained less weight than did DIO rats despite similar energy intake. Energy expenditure did not differ among the three groups. The diameter of visceral-fat adipocytes was similar in DR and control rats. mRNA levels of genes involved in lipogenesis, such as fatty acid synthase and acetyl-CoA carboxylase, tended to be lower in DR than in control and DIO rats, whereas those of carnitine palmitoyltransferase 1a, which is involved in fatty acid ß-oxidation, were greater in DR rats than in the other groups. DIO rats showed hyperinsulinemia and glucose intolerance, whereas DR rats had high sensitivity to insulin. CONCLUSION: DR rats show suppression of lipogenesis and acceleration of fatty acid ß-oxidation in the visceral fat. These characteristics likely contribute to the anti-obesity phenotype of DR rats.
Subject(s)
Diet, High-Fat , Obesity/metabolism , Acetyl-CoA Carboxylase/genetics , Acetyl-CoA Carboxylase/metabolism , Adipocytes/metabolism , Adipose Tissue/metabolism , Animals , Blood Glucose/metabolism , Body Weight , Cholesterol, HDL/blood , Cholesterol, LDL/blood , Energy Intake , Energy Metabolism , Fatty Acid Synthases/genetics , Fatty Acid Synthases/metabolism , Hyperinsulinism/blood , Insulin/blood , Insulin Resistance , Leptin/blood , Lipogenesis , Male , Obesity/blood , Oxygen Consumption , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Rats, Wistar , Triglycerides/bloodABSTRACT
OBJECTIVE: This study was intended to investigate sex differences in response to a high fat (HF) diet at three stages, pre-puberty, early puberty, and adulthood. METHODS: Body weight, energy intake, glucose, insulin, and leptin concentrations were measured in male and female rats that were fed either a HF or a control chow during each stage of development. The sex hormones of adult rats were also examined. In addition, metabolic factors of male rats pair-fed with females were evaluated. RESULTS: At pre-puberty, the average body weight of pups born to a HF dam exceeded that of the control, whereas there were no significant differences in body weight between males and females. During early puberty and among 15-wk-old rats, males exhibited greater weight gain with higher energy intake than did females. During all three stages, HF rats exhibited significant increases in body weight, insulin and leptin concentrations. Estradiol levels of females were higher than those of males, and those of the HF groups were significantly lower than the control groups. Although the body weight gain in male rats pair-fed with females exceeded that of the females, the insulin and leptin levels of pair-fed HF males decreased to the control levels. CONCLUSION: HF male rats became obese earlier than HF females. This result may be the result of differences in estradiol levels between males and females. The decline of insulin and leptin levels in pair-fed male groups indicates that caloric restriction among male rats could reduce the incidence of metabolic diseases.
