SEXUAL DIMORPHIC RESPONSE OF METABOLIC VARIABLES IN HIGH FAT DIET-INDUCED OBESITY IN WISTAR RATS ON LOW CALORIE DIET

Abstract

Striking differences exist between men and women in lipid kinetics possibly due to sexual dimorphism in metabolism. However, the effect of prolonged intake of High Animal Fat Diets (HAFD), High Plant Fat Diets (HPFD) and Low Calorie Diets (LCD) in both sexes have not been fully investigated. This study was designed to evaluate the influence of sexual dimorphism on metabolic variables following prolonged intake of HPFD and HAFD in normal, and LCD-treated obese Wistar Rats (WR). Gross energy, fat and fiber content of formulated feeds from proximate composition were HPFD (4.50 Kcal/g, 16.30, 3.60 %), HAFD (5.90 Kcal/g, 31.00, 3.10 %) and LCD (2.66 Kcal/g, 2.27, 20.64%). In experiment one (designed to evaluate sexual dimorphism in high fat diets induced obesity rats), 30 WR were divided into 15 males (mWR) and 15 females (fWR). Each sex group was sub-divided into 3 groups (n=5) and fed with Standard Chow (SC), HPFD and HAFD respectively, for 17 weeks. Serum was obtained from blood, samples of the liver, Small Intestine (SI) and heart were excised. Serum, liver, heart and SI lipid profile [High Density Lipoprotein (HDL), Low Density Lipoprotein (LDL), Total Cholesterol (TC), triglyceride, Free Fatty Acids (FFA)] were measured by spectrophotometry. Serum luteinizing hormone (LH), Apolipoprotein A and B were analysed using ELISA while SI Saturated, Monounsaturated and Polyunsaturated Fatty Acids (SFA, MUFA and PUFA, respectively) were measured by gas chromatography using standard methods. Duodenal section of SI was examined for Cluster of Differentiation 36 (CD36) expression using immunohistochemistry. In experiment two, 30 WR were divided into two sexes (n=15). Each sex subgroup was divided into 3 groups (n=5). Subgroups 1 and 2 were fed on SC and HPFD for 22 weeks while subgroup 3 was fed HPFD for 17 weeks followed by LCD for 5 weeks. The same experimental analyses in study one were thereafter implemented. Data were analysed using descriptive statistics and ANOVA at α0.05. In experiment one, the SC showed no significant difference in LDL, TC and triglyceride between fWR and mWR. In HPFD; serum FFA, heart LDL, SI SFA decreased significantly while heart HDL increased significantly in fWR compared with mWR (815±55.00 vs 1754±75.00µmol/L; 27±1.80 vs 38±2.90mg/dL; 41.03±2.07 vs 50.49±1.31%; 20±1.50 vs 14±1.40mg/dL, respectively). The HAFD significantly increased serum TC, LH, apolipoprotein B:A ratio, SI PUFA in fWR compared with mWR (251±17.00 vs 191±3.90mg/dL; 3.5±0.09 vs 4±0.20µlU/mL; 3.5±0.46 vs 2.8±0.07; 13.47±1.34 vs 8.5±0.75%, respectively). No significant difference was observed for MUFA between the sexes. Duodenal section of SI showed increased CD36 expression in fWR compared with mWR (5.83±0.26 vs 8.65±0.83%). In experiment two, serum TC and triglyceride significantly increased in subgroup 2, while in subgroup 3, liver LDL, TG and FFA significantly reduced in fWR compared with mWR (258±11.00 vs 217±9.80; 272±19.00 vs 202±6.90; 14±0.85 vs 31±1.60; 109±2.1 vs 182±5.8mg/dL; 834±72 vs 1409±74µmol/L respectively). Sexual dimorphic response that was more pronounced in males on low calorie diet may be associated with sexually distinct lipid profile and hormonal modulations between the sexes.