Insulin-like eect of pinitol

1 D-pinitol (3-O-methyl-chiroinositol), an active principle of the traditional antidiabetic plant Bougainvillea spectabilis, is claimed to exert insulin-like e€ects. This study investigates the e€ect of D-pinitol on glucose homeostasis in animal models of diabetes, and on glucose transport by cultured muscle cells. 2 Plasma glucose concentrations were measured in normal, obese-diabetic (ob/ob) and streptozotocin (STZ)-diabetic mice after oral (p.o.) and intraperitoneal (i.p.) administration of Dpinitol. Glucose transport was measured in L6 rat muscle cells by 2-deoxyglucose (2DG) uptake. 3 In STZ-diabetic mice, 100 mg kg p.o. D-pinitol acutely decreased the hyperglycaemia (by 22% at 6 h). A similar decrease in plasma glucose (by 21%) was observed after 100 mg kg i.p. Dpinitol. Insulin concentrations and the rate of insulin-induced (1 unit kg actrapid i.p.) glucose disappearance were not altered by 100 mg kg p.o. D-pinitol. Chronic administration of D-pinitol (100 mg kg i.p. twice daily for 11 days) to STZ-diabetic mice maintained a reduction in plasma glucose concentrations from about 14 to 10 mmol l. 4 In normal non-diabetic and severely insulin resistant ob/ob mice, 100 mg kg p.o. D-pinitol did not signi®cantly a€ect plasma glucose or insulin during acute studies. 5 Incubation of L6 muscle cells with D-pinitol (10 M) increased basal 2DG uptake by 41% after 10 min and by 34% after 4 h. The e€ect of D-pinitol was inhibited by the phosphatidylinositol 3kinase inhibitor LY294002. D-pinitol did not increase insulin-stimulated 2DG uptake by L6 cells. 6 The data support the view that D-pinitol can exert an insulin-like e€ect to improve glycaemic control in hypoinsulinaemic STZ-diabetic mice. D-pinitol may act via a post-receptor pathway of insulin action a€ecting glucose uptake. British Journal of Pharmacology (2000) 130, 1944 ± 1948