Evaluation of Antidiabetic Potential of AD02 on Key Enzymes of Hepatic Glucose Homeostasis and Bioassay-Guided Fractionation

Abstract

The liver is an essential organ in the regulation of glucose homeostasis and plays an essential role in type 2 diabetes. Our purpose is to evaluate the capacity of AD02, a plant used by the Eastern James Bay Cree (Canada), to modulate key enzymes and kinases implicated in hepatic glucose homeostasis and to identify the active principles. Glucose-6-phosphatase (G6Pase) and glycogen synthase (GS) activities were assessed in cultured hepatocytes treated with AD02; its fractions and pure compounds yielded from the most active fraction. Phosphorylation of AMP-dependent protein kinase (AMPK) and Akt were probed by Western blot. AD02 decreased G6Pase activity by 48% and activated the GS by 10-folds. AD02 increased phosphorylation of key kinases implicated in the insulin-dependent (Akt) and insulin-independent pathway (AMPK) by 2.5- and 3-folds, respectively, compared to DMSO control. The activity of AD02 seems to be concentrated in the hexane fraction, which was able to decrease G6Pase activity by 50% and to increase GS activity by 70-folds. Three pure compounds were yielded from the Hexane fraction and were active in both assays (PK2 was the most active one). We found significant correlations between G6Pase activity and the phosphorylation of Akt and AMPK (R2= 0.92 and R2= 0.82, respectively). The 3 major compounds may be responsible for the antidiabetic effect of AD02. PK2 marked out with the most promising profile powerfully reducing G6Pase activity, increasing GS activity and stimulating the signalling pathways involved in hepatic glucose homeostasis.