Quercetin ameliorates hyperglycemia and dyslipidemia and improves antioxidant status in type 2 diabetic db/db mice

Abstract

This study investigated the hypoglycemic, hypolipidemic, and antioxidant effects of dietary quercetin in an animal model of type 2 diabetes mellitus. Four-week-old C57BL/KsJ-db/db mice (n = 18) were offered an AIN-93G diet or a diet containing quercetin at 0.04% (low quercetin, LQE) or 0.08% of the diet (high quercetin, HQE) for 6 weeks after 1 week of adaptation. Plasma glucose, insulin, adiponectin, and lipid profiles, and lipid peroxidation of the liver were determined. Plasma glucose levels were significantly lower in the LQE group than in the control group, and those in the HQE group were even further reduced compared with the LQE group. The homeostasis model assessment for insulin resistance (HOMA-IR) showed lower values for LQE and HQE than for the control group without significant influence on insulin levels. High quercetin increased plasma adiponectin compared with the control group. Plasma triglycerides in the LQE and HQE groups were lower than those in the control group. Supplementation with high quercetin decreased plasma total cholesterol and increased HDL-cholesterol compared with the control group. Consumption of low and high quercetin reduced thiobarbituric acid reactive substances (TBARS) levels and elevated activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the liver. Thus, quercetin could be effective in improving hyperglycemia, dyslipidemia, and antioxidant status in type 2 diabetes.

Quercetin can reduce insulin resistance without decreasing adipose tissue and skeletal muscle fat accumulation

“…The present results are in good accordance with other published studies carried out in animal models showing insulin resistance or type 2 diabetes (Wein et al 2010;Rivera et al 2008;Kim et al 2011;Jeong et al 2012). Nevertheless, there is no general agreement concerning the effect of quercetin on glycemic control.…”

“…The authors of those studies which found positive effects of quercetin on glycemic control proposed several mechanisms to explain the beneficial effect of this polyphenol: (a) the anti-oxidative protective action on the pancreatic islets (Coskun et al 2005;Babujanarthanam et al 2010;Jeong et al 2012), (b) the increase in adiponectin circulating concentration (Wein et al 2010), (c) the inhibition of small intestine glucosidase activity , (d) the reduction in the intestinal glucose absorption mediated by GLUT2 (Kwon et al 2007), (e) the increase in glucokinase activity (Vessal et al 2003) and (f) the increase in GLUT4 transporters in skeletal muscle (Jung et al 2011;Shen et al 2012;Anhê et al 2012).…”

Quercetin – a flavonoid with a high health-promoting potential

“…A decrease of the glucose level in blood by 56.58% in the individuals with diabetes I and 71.61% in those suffering from diabetes II (Hatware and Annapurna, 2014) was noted. Jeong et al (2012) obtained interesting results, too. During their experiments they administered quercetin at 0.04 or 0.08% of the feed mass for 6 weeks to mice suffering from diabetes II.…”

“…However, no statistically significant differences were spotted between the animal groups to which various quercetin concentrations were administered. Moreover, statistically higher level of adiponectin -a protein released by adipose tissue and responsible for increasing the sensitivity of tissues to insulin (Jeong et al, 2012), was noted in individuals given 0.08% quercetin dose. Another experiment, with rats eating for 7 weeks feed containing 0.08% quercetin, observed a statistically significant decrease of glycated haemoglobin concentration, in respect to the investigated flavonoid addition deprived group.…”

“…The experiment suggested by Jeong (2012) consisted in administering quercetin at 0.04 or 0.08% of the feed mass for 6 weeks to mice suffering from diabetes II. It proved that the flavonoid addition brought about a decrease in the concentration of triglycerides, as well as of total cholesterol in blood.…”