Recent developments in oral hypoglycemic agents

In Vitro Anti-diabetic Activity of Sclerocarya Birrea and Ziziphus Mucronata

Type 2 diabetes mellitus is on the increase worldwide. Current treatments possess undesirable side-effects and therefore investigations into alternative remedies, which may be cost-effective and devoid of such side-effects, are on-going. Aqueous and methanol extracts of the bark of Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro (Anacardiaceae) and Ziziphus mucronata Willd. subsp. mucronata (Rhamnaceae) were subjected to testing in order to assess their in vitro anti-diabetic activity. Total polyphenolic content and antioxidant activity, as well as the effect on α-amylase, α-glucosidase and cytotoxicity, were measured. Furthermore, glucose uptake was evaluated in C2C12 myotubes, 3T3-L1 adipocytes and HepG2 hepatocarcinoma cells, and insulin secretion in RIN-m5F rat pancreatic β-cells. The extracts of both plants inhibited the activities of α-amylase and α-glucosidase in a concentration dependent manner, with results being comparable with the positive control, acarbose. All the extracts contained antioxidant activity, with the methanol extracts of S. birrea displaying the strongest free radical scavenging capacity (IC50 = 2.16 μg/mL). Most of the extracts were not cytotoxic to the cell lines with IC50 values > 100 μg/mL. Extracts of both plants significantly increased glucose uptake in C2C12, 3T3-L1 and HepG2 cells. However, insulin secretion from RIN-m5F cells was not altered. This study provides evidence that the plants possess in vitro anti-diabetic properties.

Effect of YM-126414 on glucose uptake and redistribution of glucose transporter isotype 4 in muscle cells

We discovered a novel compound, YM-126414 [1,3, 3-trimethyl-2-(2-phenylaminovinyl)-3H-indolium perchlorate], which stimulates glucose uptake in skeletal muscle cells in vitro. This compound increased the rate of consumption of glucose by C2C12 mouse myoblast cells in a dose-dependent manner (EC(50)=10 nM). To investigate the mechanism of this stimulation, we determined the redistribution of insulin-regulatable glucose transporter isotype 4 (Glut4). When fully differentiated C2C12 cells stably expressing myc-tagged Glut4 protein were treated with YM-126414, redistribution was dramatically increased in a dose-dependent manner (EC(50)=21 nM). These results indicate that YM-126414 is a novel glucose uptake stimulator for muscle cells by causing up-regulation of Glut4 redistribution in differentiated muscle cells. Our findings for the in vitro effects of YM-126414 suggest a direction for the development of new drugs for the treatment of type 2 diabetes.