In vitro Enhancement of Pancreatic β Cells MIN6 Proliferation by Insulinotropic Gymnema sylvestre Aqueous Extracts: Evidence-based Regenerative Therapeutic Capacity of a Medicinal Herb

Abstract

Aim: To show that Gymnema sylvestre (Roxb.) Asclepiadaceae not only has antidiabetic propensities, but it most likely works by regeneration of pancreatic β cells which is imperative in anti-obesity-diabetes therapeutic applications of medicinal plants. Study Design: The present study design investigated the effects of G. sylvestre leaves crude aqueous extracts (AEs), traditionally utilized in diabetes treatment, on the pancreatic β-cell MIN6 proliferation and insulin secretion and extrapancreatic dietary carbohydrate and lipid digestion Place and Duration of Study: Faculty of Pharmacy, The University of Jordan, 2008-2012. Results: Comparable to GLP-1 (500 nM) pancreatic proliferative capacity; G. sylvestre AE concentrations (0.01 and 0.1 mg/mL) induced MIN6 monolayers expansion by respective 130.3% and 127.4% (P<0.001 vs. spontaneous control). Like L-alanine (10 mM) insulinotropic efficacy and without exerting cytotoxicity, glucose-stimulated insulin secretion was potentiated by G. sylvestre AEs (5, 10 and 25 mg/mL) (711.0%, 843.0% and 906.5%, respectively, P<0.001 vs. basal control). The potent plants’ insulin secretory bioactivities were abolished in the depleted Ca2+ conditions (P<0.001). Similar to orlistat antilipolytic efficacy, pancreatic lipase IC50 value for G. sylvestre AEs was 106.3±7.2 μg/mL. Unlike acarbose (100 μg/mL) dual inhibition of α-amylase/α-glucosidase, G. sylvestre AE was inactive at used doses. Dissimilar to guar gum (50 mg/mL) diffusional hindrance in a simple dialysis model, G. sylvestre AEs (10, 25 and 50 mg/mL) proved inactive. This in vitro ineffectiveness was mirrored in respective in vivo oral carbohydrate tolerance tests in overnight fasting normoglycemic rats. Conclusion: This evaluation has revealed that G. sylvestre leaves AEs augmented β-cell expansion and potentiated glucose-evoked Ca2+-regulated insulin secretion; combined with impressive antilipolytic activity. These actions depend on the bioactive water soluble phyto-principles intact absorption in vivo. Future directives may assess the potential of G. sylvestre as a new alternative for anti-obesity-diabetes pharmacotherapy and prevention.