The effects of wild blueberry consumption on plasma markers and gene expression related to glucose metabolism in the obese Zucker rat.

ABSTRACT

Impaired fasting blood glucose is one of the landmark signs of metabolic syndrome, together with hyperinsulinemia, dyslipidemia, hypertension, and a chronic proinflammatory, pro-oxidative, and prothrombotic environment. This study investigates the effect of wild blueberry (WB) consumption on blood glucose levels and other parameters involved in glucose metabolism in the obese Zucker rat (OZR), an experimental model of metabolic syndrome. Sixteen OZRs and 16 lean littermate controls (lean Zucker rat [LZR]) were fed an 8% enriched WB diet or a control (C) diet for 8 weeks. Plasma concentrations of glucose, insulin, glycated hemoglobin GHbA1c, resistin, and retinol-binding protein 4 (RBP4) were measured. Expression of the resistin, RBP4, and glucose transporter GLUT4 genes was also determined both in the liver and the abdominal adipose tissue (AAT). Plasma glycated hemoglobin HbA1c, RBP4, and resistin concentrations were significantly lower in OZRs following the WB diet (-20%, -22%, and -27%, respectively, compared to C diet, P<.05). Following WB consumption, resistin expression was significantly downregulated in the liver of both OZRs and LZRs (-28% and -61%, respectively, P<.05), while RBP4 expression was significantly downregulated in the AAT of both OZRs and LZRs (-87% and -43%, respectively, P<.05). All other markers were not significantly affected following WB consumption. In conclusion, WB consumption normalizes some markers related to glucose metabolism in the OZR model of metabolic syndrome, but has no effect on fasting blood glucose or insulin concentrations.