 Effects of Solanum-Based Diets on the Metabolic State and Expression of the Fat Mass and Obesity Gene in Diet-Induced Obese Female Rats 

Abstract

This study investigated the anti-obesity potentials of Solanum melongena fruit (SMF) and Solanum aethiopicum fruit (SAF) in experimentally high-fat diet induced female obesity rats and also the expression of the fat mass and obesity (FTO) gene in the diet induced obesity rats. Qualitative analysis of both Solanum fruit samples revealed the presence of the following: cardiac glycosides, flavonoids, alkaloids, saponins, tannins, anthocyanins, anthraquinones and phenols. They were also shown to contain calcium, sodium, potassium, iron magnesium, manganese, zinc, copper and phosphorus. Proximate analysis of both fruit samples revealed their very high moisture content and very low amounts fat. While potassium had the highest concentration in both fruits while copper and zinc were the lowest in concentration. Amino acid analysis revealed that arginine was the highest in concentration for both fruits while methionine had the lowest concentration. Acute toxicity testing of both fruit samples, singly or in combination showed no toxicity and lethality up to 5000 mg/kg body weight. Ten groups of 6 Wistar albino rats were used for obesity study which lasted for 12 weeks (84 days). But for Group 1 animals, the rest were fed high-fat diet (HFD) for six consecutive weeks to induce obesity. There after their diet was supplemented with the fruit samples (SMF and SAF) at different percentages (10%, 20% and 30% respectively). Results from the HFD induced groups showed significant (p < 0.05) increases in the body weight, adiposity index, feed intake, fasting blood sugar, serum total cholesterol, triglycerides LDL-cholesterol MDA and leptin amounts and serum liver function enzyme (AST, ALT and ALP) activities. They cause significant (p < 0.05) decreases in serum HDL-cholesterol and ghrelin amounts as well as antioxidant enzyme (SOD, GPX and CAT) activities of the induced group as compared with control group (Group 1). Feeding of diets supplemented with different percentages of SMF and SAF (singly and in combination) for six weeks produced significant (p < 0.05) decreases in body weight, adiposity index, feed intake, fasting blood sugar, serum total cholesterol, triglycerides LDL-cholesterol, serum liver function enzyme activities (AST, ALT and ALP), kidney function parameters (urea and creatinine), MDA and leptin amounts but significant (p < 0.05) increases in HDL-cholesterol and ghrelin in the serum level as compared with the untreated control. Histopathological studies of the liver, hypothalamus and white adipose tissues showed changes consistent with obesity; change in neurons, enlarged adipocytes and consistent macrovessicular steatosis in the induced group when compared with normal control (Group 1). Treatments with fruit supplemented diets caused positive morphological changes in the organs of induced rats. There was no morphological change in brown adipose tissues after induction and after both treatment phases. Semi-quantitative RT-PCR revealed that the mRNA levels of FTO gene in the hypothalamus and white adipose tissues was upregulated in the induced group when compared to normal control. Administration of both supplemented diets for 42 days downregulated the mRNA levels in both tissues when compared with untreated control (Group 2). The mRNA levels in the brown adipose tissue was downregulated after induction of obesity and was further downregulated after the administration of both supplemented diets when compared with normal control, which might be due to the thermogenic potency of this tissue. These results demonstrate that the fruits of Solanum melongena and Solanum aethiopicum possess anti-obesity potentials evidenced by the reduction of weight gain and positive outlook of other biochemical parameters. However, this indicates that SMF and SAF might ameliorate obesity and its induced problems possibly attributable to the FTO gene as its molecular basis.