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.
