The relationship between glucose variability and insulin sensitivity and oxidative stress in subjects with prediabetes

Aim: The present study assessed the relationship between glucose variability (GV) and insulin levels, insulin resistance and oxidative stress at early stages of glucose intolerance. Material and methods: A total of 50 subjects - 12 males and 38 females, mean age 55.6 +/- 9.7 years, mean BMI 28.4 +/- 6.4 kg/m(2), divided into 2 groups according to glucose tolerance: 32 with prediabetes and 18 with normal glucose tolerance were included. Glucose tolerance was assessed by OGTT according to WHO 2006 criteria. Plasma glucose and serum insulin were measured at fasting, 120-minute and 180-minute during the test; and oxLDL and 3-Nitrotyrosine - at fasting and 120-minute. HOMA-IR and OGIS indexes were calculated. HbA1c and lipid levels was assessed. Continuous glucose monitoring was performed with a blind sensor (FreeStyle Libre Pro) for a mean period of 13.6 +/- 2.3 days. Results: Our results demonstrate significantly increased insulin resistance in subjects with prediabetes, whereas there is no difference in oxidative stress markers between the two groups. OxLDL and 3-NT correlate positively with insulin levels and HOMA-IR and negatively with OGIS in both groups. There is a positive association between oxidative stress markers and 120-minute glucose in the prediabetes group. Insulin levels and HOMA-IR are positively related to plasma glucose and reciprocally to CV and M-Value in prediabetes, since the latter association is with borderline significance after adjustment for hypertension and smoking. Conclusions: Our results demonstrate a significant correlation between oxidative stress and insulin resistance at early stages of glucose intolerance. Both chronic hyperglycemia and GV seem to be related to insulin levels and insulin resistance, and just postload glycaemia to oxidative stress in prediabetes. (C) 2019 Elsevier B.V. All rights reserved.