Rat Pancreatic Islets

Dietary Supplementation with Yerba Mate Infusion Increases IRS-1 and PI3K mRNA Levels and Enhances Insulin Sensitivity and Secretion in Rat Pancreatic Islets

Yerba mate (YM), possesses antioxidant, diuretic, cardio-protective and hypoglycaemic effects. However, the mechanisms involved in YM pancreatic islets have not been determined. Maiztegui et al. analyzed YM effects on insulin sensitivity and glucose stimulated insulin secretion (GSIS), hoping to identify key pathways involved in YM regulation of glucose homeostasis.

Isolated fresh islets of Langerhans from rats of each group displayed an increased glucose stimulated insulin secretion as a percentage of glucose concentration in the media (Fig. 1A). There were no differences between experimental groups when the rats were incubated with 3.3 mM glucose. Islets harvested from YM rats released significantly higher amounts of insulin when stimulated with 16.7 mM glucose compared to control animals (Fig. 1A). They observed significant increases in IRS-1 and PI3K (p110 catalytic subunit) mRNA when islets were isolated from YM rats (Fig. 1C, E). There were no significant differences between any group in insulin receptor and IRS-2 mRNA levels (Fig. 1B, D). Figure 2 shows that insulin secretion by pancreatic islets was dose-dependent upon addition of glucose in all experimental conditions. When incubated with basal glucose concentration (3.3 mM), islets treated with Yerba mate freeze-dried extract or the phenolic compounds released similar amounts of insulin as compared to control. However, at high glucose concentration (16.7 mM), insulin secretion was significantly higher when incubated with 100 µg/mL YM freeze-dried extract, 1 µM chlorogenic acid, 0.1 and 1 µM rutin, 1 µM caffeic acid or 1 µM quercetin as compared to control conditions (Fig. 2).