RESUMO
Objective: To evaluate the insulin sensitivity action of ferulic acid (FA) in skeletal muscle and hypothalamus of high-fat diet (HFD)-induced obese mice. Methods: Obese mouse model was induced by HFD (45 kcal% lard fat) for 16 weeks. After 8 weeks of HFD feeding, these obese mice were orally treated with FA at doses of 25 and 50 mg/kg/day for 8 weeks. At the end of all treatments, the epididymal fat, pancreas, skeletal muscle and hypothalamus were removed for biochemical parameter and protein expression examinations. Results: FA treatment significantly decreased leptin level in fat tissue and insulin level in pancreas (P < 0.05). Interestingly, obese mice treated with FA increased the protein expressions of insulin receptor substrate-1, phosphatidylinositol 3-kinase, and phosphorylated-protein kinase B in both muscle and brain (P < 0.05). The phosphorylations of adenosine monophosphate-activated protein kinase and acetyl-CoA carboxylase in muscle, and leptin receptor protein in hypothalamus were also increased (P < 0.05). The pancreatic islets histology showed smaller size in obese mice treated with FA compared to untreated obese mice. Conclusions: These findings indicate the beneficial effect of FA in improving insulin resistance in HFD-induced obese mice. These effects are probably mediated via modulating the insulin receptor substrate/phosphatidylinositol 3-kinase/protein kinase B or adenosine monophosphate-activated protein kinase pathways.
RESUMO
Objective: To investigate the effect of Rhinacanthus nasutus (R. nasutus) leaf extract on impaired glucose and lipid metabolism in obese ICR mice. Methods: Obesity was induced in the male ICR mice by feeding them a high-fat diet (60 kcal% fat) for 12 weeks. After the first six weeks of the diet, the obese mice were administered with the water extract of R. nasutus leaves at 250 and 500 mg/kg per day for the next six weeks. Subsequently, the blood glucose, lipid profiles, insulin, leptin, and adiponectin levels were measured. The liver and adipose tissues were excised for histopathological examination and protein expression study. Results: After six weeks of the treatment, R. nasutus extract (at 250 and 500 mg/kg per day) was found to reduce the elevated blood glucose level, improve the insulin sensitivity, decrease the serum leptin, and increase the serum adiponectin levels. The obese mice treated with R. nasutus were found to have a reduction in the increased lipid concentrations in their serum and liver tissues. Moreover, treatment with R. nasutus reduced the fat accumulation in the liver and the large adipocyte size in the fat tissues. Interestingly, the administration with R. nasutus extract was marked by an increase in the hepatic peroxisome proliferators-activated receptor alpha, fat cell adiponectin, and glucose transporter 4 proteins. Conclusions: To the best of our knowledge, the present study is the first report on the impact of R. nasutus extract in improving the impaired glucose and lipid metabolism in high-fat diet-induced obesity in mice via stimulating the insulin sensitivity in the liver and adipose tissues.