Free radical scavenging polyphenols isolated from Phyllanthus niruri L. ameliorates hyperglycemia via SIRT1 induction and GLUT4 translocation in in vitro and in vivo models.

Type 2 diabetes milletus (T2DM) is a complex multifaceted disorder characterized by insulin resistance in skeletal muscle. Phyllanthus niruri L. is well reported sub-tropical therapeutically beneficial ayurvedic medicinal plant from Euphorbiaceae family used in various body ailments such as metabolic disorder including diabetes. The present study emphasizes on the therapeutic potential of Phyllanthus niruri L. and its phytochemical(s) against insulin resistance conditions and impaired antioxidant activity thereby aiding as an anti-hyperglycemic agent in targeting T2DM. Three compounds were isolated from the most active ethyl acetate fraction namely compound 1 as 1-O-galloyl-6-O-luteoyl-ß-D-glucoside, compound 2 as brevifolincarboxylic acid and compound 3 as ricinoleic acid. Compounds 1 and 2, the two polyphenols enhanced the uptake of glucose and inhibited ROS levels in palmitate induced C2C12 myotubes. PNEAF showed the potent enhancement of glucose uptake in palmitate-induced insulin resistance condition in C2C12 myotubes and significant ROS inhibition was observed in skeletal muscle cell line. PNEAF treated IR C2C12 myotubes and STZ induced Wistar rats elevated SIRT1, PGC1-α signaling cascade through phosphorylation of AMPK and GLUT4 translocation resulting in insulin sensitization. Our study revealed an insight into the efficacy of marker compounds isolated from P. niruri and its enriched ethyl acetate fraction as ROS scavenging agent and helps in attenuating insulin resistance condition in C2C12 myotubes as well as in STZ induced Wistar rat by restoring glucose metabolism. Overall, this study can provide prospects for the marker-assisted development of P. niruri as a phytopharmaceutical drug for the insulin resistance related diabetic complications.

Taxifolin-3-O-glucoside from Osbeckia nepalensis Hook. mediates antihyperglycemic activity in CC1 hepatocytes and in diabetic Wistar rats via regulating AMPK/G6Pase/PEPCK signaling axis.

ETHNOPHARMACOLOGICAL RELEVANCE: Osbeckia nepalensis Hook. f. is an ICMR documented plant well known for its antidiabetic uses among the folk people of Northeast Region of India. In-depth study with scientific substantiation of the plant may uphold the therapeutic potential against the treatment of type 2 diabetes mellitus (T2DM). AIM OF THE STUDY: The present study evaluates the traditionally claimed prophylactic potential of O. nepalensis and its extracts along with the isolated compound taxifolin-3-O-glucoside (TG) against the downregulation of T2DM related hepatic gluconeogenesis through in vitro, in vivo and in silico conditions as a means of ameliorating hyperglycemia. MATERIALS AND METHODS: Antidiabetic potential of O. nepalensis was carried out in both CC1 hepatocytes (in vitro) and STZ-induced diabetic male Wistar rats (in vivo). Enriched bioactive fraction and bioactive molecules were isolated through bioactivity-guided fractionation, yielding two major molecules, taxifolin-3-O-glucoside and quercitin-3-O-rhamnoside. The bioactivity of taxifolin-3-O-glucoside was validated through immunoblotting techniques aided by in silico molecular docking and simulations. RESULTS: Methanolic extract of O. nepalensis and taxifolin-3-O-glucoside (TG) isolated thereof enhanced the uptake of glucose in CC1 hepatocytes and downregulates the gluconeogenic enzymes (G6Pase and PEPCK) and its related transcription factors (FOXO1, HNF4α and PGC1α) through the stimulation of AMPK phosphorylation in in vitro condition. Moreover, in in vivo experiments, the in vitro most active fraction BuSFr1 (consisting of the two active major compounds taxifolin-3-O-glucoside and quercitin-3-O-rhamnoside) exhibited a substantial decrease in elevated blood glucose level and increase the glucose tolerance as well as plasma insulin level. In silico molecular docking and simulations for TG with the protein G6Pase inferred the docking sites and stability and showed taxifolin-3-O-glucoside as more potent and non-toxic as compared to quercitin-3-O-rhamnoside. CONCLUSION: The traditionally claimed antidiabetic effect of O. nepalensis has been proved to be effective in lowering the blood glucose level through in vitro, in vivo and in silico analysis which will pave a way for the development of antidiabetic phytopharmaceutical drugs which can be validated through further clinical studies.

Xanthosine, a purine glycoside mediates hepatic glucose homeostasis through inhibition of gluconeogenesis and activation of glycogenesis via regulating the AMPK/ FoxO1/AKT/GSK3ß signaling cascade.

Type 2 Diabetes Mellitus (T2DM) is characterized by hepatic insulin resistance, which results in increased glucose production and reduced glycogen storage in the liver. There is no previous study in the literature that has explored the role of Xanthosine in hepatic insulin resistance. Moreover, mechanistic explanation for the beneficial effects of Xanthosine in lowering glucose production in diabetes is yet to be determined. This study for the first time investigated the beneficial effects of Tribulus terrestris (TT) and its active constituent, Xanthosine on gluconeogenesis and glycogenesis in Free Fatty Acid (FFA)-induced CC1 hepatocytes and streptozotocin (STZ)-induced Wistar rats. Xanthosine enhanced glucose uptake and decreased glucose production through phosphorylation of AMP-activated protein kinase (AMPK) and forkhead box transcription factor O1 (FoxO1), and downregulation of two rate limiting enzymes of gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) expression in FFA-induced CC1 cells. Xanthosine also prevented FFA-induced decreases in the phosphorylation of AKT/Protein kinase B, glycogen synthase kinase-3ß (GSK3ß), and increased glycogen synthase (GS) phosphorylation to increase the glycogen content in the hepatocytes. Moreover, in STZ-induced diabetic rats, oral administration of TT n-butanol fraction (TTBF) enriched with compound Xanthosine (10, 50 & 100 mg/kg body weight) improved insulin sensitivity, reduced fasting blood glucose levels, improved glucose homeostasis by reducing gluconeogenesis via AMPK/FoxO1-mediated PEPCK and G6Pase down-regulation and increasing glycogenesis via AKT/GSK3ß-mediated GS activation. Overall, Xanthosine may be developed further for treating insulin resistance and hyperglycemia in T2DM.