Standardized extract of Ficus deltoidea stimulates insulin secretion and blocks hepatic glucose production by regulating the expression of glucose-metabolic genes in streptozitocin-induced diabetic rats

Abstract

Background: Recently, there has been increasing interest in Ficus deltoidea Jack. (Moraceae) due to its chemical composition and the potential health benefits. The present study was undertaken to investigate the effect of extracts of F. deltoidea leaves on diabetes.

Methods: The petroleum ether, chloroform and methanol extracts of F. deltoidea were prepared and subjected to standardization using preliminary phytochemical and HPLC analysis. Dose selection was made on the basis of acute oral toxicity study (50-5000 mg/kg b. w.) as per OECD guidelines. Diabetes mellitus was induced with streptozotocin and rats found diabetic were orally administered with the extract (250, 500 and 1000 mg/kg) for 14 days. Levels of blood glucose and insulin were measured in control as well as diabetic rats on 0, 7 and 14th day. In addition, glucose metabolism regulating gene expression was assessed using RT-PCR.

Results: HPLC analysis revealed that the methanol extract is enriched with C-glycosylflavones particularly, vitexin and isovitexin. In oral glucose tolerance test, oral administration of the methanol extract increased the glucose tolerance. The methanol extract showed significant (P < 0.01) antidiabetic activity. The extract treatment caused significant reduction (p < 0.01) in elevated fasting blood glucose level in streptozotocin-induced diabetic rats. The streptozotocin-related weight loss in rats was noticeably reversed by the extract treatment. Finally, RT-PCR analysis revealed a novel mechanisms for the anti-diabetic action of methanol extract of F. deltoidea. The extract exerted its effect via an increase of insulin secretion which impeded the hepatic glucose production, via down-regulation of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase genes expression on one hand, and up-regulation of hepatic GK and PPARγ genes expression on the other hand. The extract caused an increased expression of GLUT-4 gene expression in skeletal muscles which leads to normalize the hyperglycemia. The extract also nullified the toxic effects of streptozitocin by blocking its entry into the islet β-cells through reducing the expression of GLUT-2 gene.

Conclusion: It can be concluded that, F. deltoidea could potentially inhibits the streptozitocin-induced hyperglycemia in rats. Further the herb can be utilized as useful remedy for alleviation of diabetes complications.

Figure 1

HPLC chromatogram of vitexin and isovitexin in different leaves extracts of F. deltoidea. A: vitexin and isovitexin, B: vitexin and isovitexin in petroleum ether extract, C: vitexin and isovitexin in chloroform extract, D: vitexin and isovitexin in methanol extract and E: vitexin and isovitexin in aqueous extract.

Figure 2

The effect of oral administration of F. deltoidea leaf extracts (1000 mg/kg) on the blood glucose levels of rats dosed with 1000 mg/kg of glucose. FPE = Petroleum ether extract; FCE = Chloroform extract; FME = Methanol extract and FEW = Water extract. The values are expressed as mean ± SEM (n = 6 in each group). **p < 0.01 compared to the control group (10 ml/kg vehicle).

Figure 3

The effect of daily oral administration of F. deltoidea leaf extracts (1000 mg/kg) on the blood glucose levels of streptozitocin-induced diabetic rats. FPE = Petroleum ether extract; FCE = Chloroform extract; FME = Methanol extract and FEW = Water extract. The values are expressed as mean ± SEM (n = 6 in each group). **p < 0.01 compared to the diabetic control group (10 ml/kg vehicle).

Figure 4

The effect of daily oral administration of F. deltoidea leaf methanol extract (FME) on the blood glucose levels of streptozitocin-induced diabetic rats. The methanol extract (FME) was administered to the animals at different doses (500 mg/kg or 250 mg/kg). The values are expressed as mean ± SEM (n = 6 in each group). *p < 0.05 and **p < 0.01 compared to the diabetic control group (10 ml/kg vehicle).

Figure 5

The effect of daily oral administration of F. deltoidea leaf extracts on the plasma insulin level of streptozitocin-induced diabetic rats. The data was collected on the first and the last days of extract administration. FPE = Petroleum ether extract; FCE = Chloroform extract; FME = Methanol extract and FEW = Water extract. The values are expressed as mean ± SEM (n = 6 in each group). **p < 0.01 compared to the diabetic control group (10 ml/kg vehicle).

Figure 6

The effect of daily oral administration of F. deltoidea leaf extracts (1000 mg/kg) on the body weight gain of streptozitocin-induced diabetic rats. FPE = Petroleum ether extract; FCE = Chloroform extract; FME = Methanol extract and FEW = Water extract. The values are expressed as mean ± SEM (n = 6 in each group). *p < 0.05 and **p < 0.01 compared to the diabetic control group (10 ml/kg vehicle).

Figure 7

The effect of daily oral treatment with different doses (500 mg/kg or 250 mg/kg) of F. deltoidea leaf methanol extract (FME) on the body weight of streptozitocin-diabetic rats. The values are expressed as the mean SEM (n = 6 in each group). *p < 0.05 and **p < 0.01 compared to diabetic control group (10 ml/kg vehicle).

Figure 8

Semi-quantitative PCR analysis of (A) GK, (B) Glc-6-Pase, (C) PEPCK, (D) GLUT2 and (E) PPARγ transcripts in the liver of untreated (Un) and methanol extract-treated (T) streptozitocin-induced diabetic rats. PCR product bands were measured using scanning densitometry. The densities are shown as mean ± SEM from three independent experiments. *p < 0.05 was regarded as statistically significant.

Figure 9

Semi-quantitative PCR analysis of (A) GLUT4 and (B) PPARγ transcripts in the muscle of untreated (Un) and methanol extract-treated (T) streptozitocin-induced diabetic rats. PCR product bands were measured using scanning densitometry. The densities are shown as mean ± SEM from three independent experiments. *p < 0.05 was regarded as statistically significant.