Aspalathin improves hyperglycemia and glucose intolerance in obese diabetic ob/ob mice.

Purpose: Although several researches have demonstrated that rooibos extract has hypoglycemic effect, the role of aspalathin, a main polyphenol in the extract, remains unclear. Our aims were to find specific mechanisms for anti-diabetic action of aspalathin employing a rat skeletal muscle-derived cell line (L6 myocytes) and a rat-derived pancreatic β-cell line (RIN-5F cells) and to investigate its effect in type 2 diabetic model ob/ob mice.

Methods: We investigated in vitro the effect of aspalathin on the glucose metabolism through the studies on molecular mechanisms of glucose uptake using cultured L6 myotubes.

Piceatannol, a resveratrol derivative, promotes glucose uptake through glucose transporter 4 translocation to plasma membrane in L6 myocytes and suppresses blood glucose levels in type 2 diabetic model db/db mice.

The skeletal muscle cells are one of the main sites of glucose uptake through glucose transporter 4 (GLUT4) in response to insulin. In muscle cells, 5' adenosine monophosphate-activated protein kinase (AMPK) is known as another GLUT4 translocation promoter. Natural compounds that activate AMPK have a possibility to overcome insulin resistance in the diabetic state.

Hypoglycemic effect of resveratrol in type 2 diabetic model db/db mice and its actions in cultured L6 myotubes and RIN-5F pancreatic β-cells.

Resveratrol, a phytoalexin present in the skin of grapes and red wine, has been demonstrated to possess a wide range of health promoting activities including anti-diabetic properties. In the present study, we investigated the effect of resveratrol in both type 2 diabetic mice and cell culture systems. In cultured L6 myotubes, we studied the effect of resveratrol on glucose uptake and translocation of glucose transporter 4 to plasma membrane from the aspects of insulin signaling and AMP-activated protein kinase signaling.

Hypoglycemic effect of aspalathin, a rooibos tea component from Aspalathus linearis, in type 2 diabetic model db/db mice.

Effects of aspalathin, a green rooibos tea component, on glucose metabolism were studied in vitro and in vivo. We first examined the effect of aspalathin on glucose uptake by cultured L6 myotubes and on insulin secretion from cultured RIN-5F pancreatic beta-cells in vitro, and then investigated the effect of dietary aspalathin on fasting blood glucose level and conducted an intraperitoneal glucose tolerance test (IPGTT) using type 2 diabetes model mice in vivo. Aspalathin dose-dependently and significantly increased glucose uptake by L6 myotubes at concentrations 1-100 microM.

Regulation of the nuclear factor (NF)-kappaB pathway by ISGylation.

Post-translational modification with ISG15 (interferon-stimulated gene 15 kDa) (ISGylation) is mediated by a sequential reaction similar to ubiquitination, and various target proteins for ISGylation have been identified. We previously reported that ISGylation of the E2 ubiquitin-conjugating enzyme Ubc13 suppresses its E2 activity. Ubc13 forms a heterodimer with Uev1A, a ubiquitin-conjugating enzyme variant, and the Ubc13-Uev1A complex catalyzes the assembly of a Lys63-linked polyubiquitin chain, which plays a non-proteolytic role in the nuclear factor (NF)-kappaB pathway.

Evidence for the hydrophobic cavity of heme oxygenase-1 to be a CO-trapping site.

Carbon monoxide (CO) is produced during the heme catabolism by heme oxygenase. In brain or blood vessels, CO functions as a neurotransmitter or an endothelial-derived relaxing factor. To verify whether crystallographically proposed CO-trapping sites of rat and cyanobacterial heme oxygenase-1 really work, heme catabolism by heme oxygenase-1 from rat and cyanobacterial Synechocystis sp.