doi: 10.1111/j.1472-8206.2009.00771.x ORIGINAL ARTICLE Quercitrin, a bioflavonoid improves glucose homeostasis in streptozotocin-induced diabetic tissues by altering glycolytic and gluconeogenic enzymes Ranganathan Babujanarthanam a , Purushothaman Kavitha a , Moses Rajasekara Pandian b * a Department of Biochemistry, K.M.G College of Arts and Science, Gudiyatham, Vellore District, Tamil Nadu 632 602, India b Department of Zoology, Arignar Anna Government Arts College, Namakkal, Namakkal District, Tamil Nadu 637 001, India INTRODUCTION Diabetes mellitus is the world’s largest endocrine disorder resulting in multiple etiologies, involving metabolic disorders of carbohydrate, fat and protein. All forms of diabetes are due to a decrease in the circulating concentration of insulin (insulin deficiency) and a decrease in the response of peripheral tissues to insulin, that is, insulin resistance. According to the World Health Organization projections, the prevalence of diabetes is likely to increase by 35% by the year 2025 [1]. Alterations in glucose metabolism in diabetes are frequently accompanied by changes in the activities of the enzymes that control glycolysis and gluconeogenesis in liver and muscle, such that the latter process becomes favored [2]. Increased rates of hepatic glucose production result in the development of overt hyperglycemia, especially fasting hyperglycemia, in patients with type 2 diabetes [3]. There are several important enzymatic checkpoints that act to control hepatic glycolysis and glycogen synthesis (glucokinase, glycogen synthase kinase-3), glycogenolysis (phosphorylase), gluconeogen- esis (phosphoenolpyruvate carboxykinase, fructose 1,6 Keywords antioxidants, diabetes mellitus, gluconeogenesis, pancreas, quercitrin, streptozotocin Received 27 November 2008; revised 9 June 2009; accepted 8 July 2009 *Correspondence and reprints: drrspandianm@gmail.com ABSTRACT The present study is an investigation into the role of quercitrin on carbohydrate metabolism in normal and streptozotocin (STZ)-induced diabetic rats. Administration of STZ leads to a significant increase (P < 0.05) in fasting plasma glucose and a decrease in insulin levels. The content of glycogen is significantly decreased (P < 0.05) in liver and muscle, but increased in the kidney. The activity of hexokinase decreased whereas the activities of glucose 6-phosphatase and fructose 1,6-bisphosphatase significantly increased (P < 0.05) in the tissues. Oral adminis- tration of quercitrin (30 mg/kg) to diabetic rats for a period of 30 days resulted in significant (P < 0.05) alterations in the parameters studied but not in normal rats. A decrease of plasma glucose and increase in insulin levels were observed along with the restoration of glycogen content and the activities of carbohydrate metabolic enzymes in quercitrin-treated diabetic rats. The histopathological study of the pancreas revealed the protective role of quercitrin. There was an expansion of the islets and decreased fatty infiltrate of the islets in quercitrin treated diabetic rats. In normal rats treated with quercitrin, we could not observe any significant change in all the parameters studied. Combined, these results show that quercitrin plays a positive role in carbohydrate metabolism and antioxidant status in diabetic rats. ª 2009 The Authors Journal compilation ª 2009 Socie ´ te ´ Franc ¸aise de Pharmacologie et de The ´ rapeutique Fundamental & Clinical Pharmacology 24 (2010) 357–364 357 Fundamental & Clinical Pharmacology