Aspalathin Improves Hyperglycemia and Glucose Intolerance in Obese Diabetic ob/ob Mice

Eur J Nutr. 2013 Sep;52(6):1607-19. doi: 10.1007/s00394-012-0466-6. Epub 2012 Dec 13.

Abstract

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. We also measured the antioxidative ability of aspalathin against reactive oxygen species (ROS) generated by artificial advanced glycation end product (AGE) in RIN-5F cells. In vivo, ob/ob mice were fed 0.1 % aspalathin-containing diet for 5 weeks, and the effect of aspalathin on fasting blood glucose level, glucose intolerance, and hepatic gene expression was studied.

Results: Aspalathin dose dependently increased glucose uptake by L6 myotubes and promoted AMP-activated protein kinase (AMPK) phosphorylation. Aspalathin enhanced GLUT4 translocation to plasma membrane in L6 myoblasts and myotubes. In RIN-5F cells, aspalathin suppressed AGE-induced rises in ROS. In vivo, aspalathin significantly suppressed the increase in fasting blood glucose levels and improved glucose intolerance. Furthermore, aspalathin decreased expression of hepatic genes related to gluconeogenesis and lipogenesis.

Conclusions: Hypoglycemic effect of aspalathin is related to increased GLUT4 translocation to plasma membrane via AMPK activation. In addition, aspalathin reduces the gene expression of hepatic enzymes related to glucose production and lipogenesis. These results strongly suggest that aspalathin has anti-diabetic potential.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism
  • Adiponectin / blood
  • Animals
  • Blood Glucose / drug effects
  • Blood Glucose / metabolism
  • Body Weight
  • Cell Line
  • Chalcones / pharmacology*
  • Cholesterol / blood
  • Diabetes Mellitus, Experimental / drug therapy*
  • Diabetes Mellitus, Experimental / metabolism
  • Gluconeogenesis / drug effects
  • Glucose Intolerance / drug therapy*
  • Glucose Transporter Type 4 / genetics
  • Glucose Transporter Type 4 / metabolism
  • Glycogenolysis / drug effects
  • Hyperglycemia / drug therapy*
  • Hypoglycemic Agents
  • Insulin / blood
  • Insulin-Secreting Cells / drug effects
  • Insulin-Secreting Cells / metabolism
  • Leptin / blood
  • Lipogenesis / drug effects
  • Mice
  • Mice, Obese
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / metabolism
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / drug effects
  • Phosphorylation
  • Rats
  • Reactive Oxygen Species / metabolism

Substances

  • Adiponectin
  • Blood Glucose
  • Chalcones
  • Glucose Transporter Type 4
  • Hypoglycemic Agents
  • Insulin
  • Leptin
  • Reactive Oxygen Species
  • aspalathin
  • Cholesterol
  • AMP-Activated Protein Kinases