Berberis integerrima ameliorates insulin resistance in high- fructose-fed insulin-resistant rats

OBJECTIVE(S): This study was aimed to investigate the effect of Berberis integerrima (B. integerrima) extract on insulin sensitivity in high-fructose-fed insulin-resistant rats. MATERIALS AND METHODS: Experimental rats were randomly divided into two groups: the control group was fed a regular chow diet while other group fed with a high-fructose diet for 8 weeks. After the first six weeks, the animals were treated with B. integerrima extract or pioglitazone for two weeks. Insulin and adiponectin levels were measured by ELISA. Additionally, Insulin resistance was calculated using a Homeostasis Model Assessment of Insulin resistance (HOMA-IR). The plasma free fatty acid (FFA) profile was obtained by gas chromatography. PPARγ and GLUT4 gene expression were assessed by real-time polymerase chain reaction (PCR) and western-blotting. RESULTS: Comparing the B. integerrima treated group with the control group, weight gain (P=0.009) and levels of insulin (P=0.001), blood glucose (P<0.0001), and HOMA-IR (P<0.0001) were significantly reduced. Additionally, the adiponectin concentration was significantly increased (P<0.0001). Among the FFA fractions, the mean concentration of palmitoleic acid and stearic acid in the B. integerrima group were significantly higher than the control group (P<0.0001 and P=0.005, respectively). However, there was no significant difference at the mRNA and protein level of GLUT4 and PPAR-γ between B. integerrima treated group and control group. CONCLUSION: The study findings revealed that B. integerrima might be a protective candidate against Type 2 diabetes/insulin resistance through direct insulin-like effect and an increase in adiponectin levels. However, the mechanism of B. integerrima was independent of GLUT4 and PPARγ.