Blood viscosity in subjects with normoglycemia and prediabetes Running title: Blood viscosity and blood glucose

Objective: Blood Viscosity (BV) is higher in diabetic patients, and might represent a risk factor for the development of insulin resistance and type 2 diabetes. However, data in subjects with normal glucose or prediabetes are missing. In the present study we evaluated the relationship between BV and blood glucose in subjects with normal glucose or prediabetes. Research Design and Methods: Enrolled subjects were divided in three groups according to blood glucose: Group A (n=74): blood glucose < 90 mg/dl; Group B (n=96): blood glucose ranging 90-99 mg/dl; Group C (n=94): blood glucose ranging 100-125 mg/dl. BV was measured at 37° C with a cone-plate viscometer at shear rates ranging 225–22.5 s -1 . Results: Blood pressure, blood lipids, fibrinogen and plasma viscosity were similar in the three groups. BMI and waist were significantly increased in Group C. Hematocrit (p<0.05) and BV (p between 0.01 and 0.001) were significantly higher in Group B and C, compared to Group A. Blood glucose was significantly and inversely correlated with HDL cholesterol and directly with BMI, waist, hematocrit (r=0.134), and BV (from 225 sec -1 to 22.5 sec -1 , r ranging from 0.162 to 0.131). BV at shear rate 225 sec -1 resulted independently associated with blood glucose. Conclusions: The present study shows a direct relationship between BV and blood glucose in nondiabetic subjects. It also suggests that, even within glucose values considered completely normal, individuals with higher blood sugar levels have increased BV comparable to that observed in subjects with prediabetes. Page 2 of 15 Diabetes Care