Relation between insulin resistance and plasma concentrations of lipid hydroperoxides, carotenoids, and tocopherols

Background: It is not known whether total circulating lipid hydroperoxides are increased in insulin-resistant individuals and whether this correlates with depletion of liposoluble antioxidant vitamins that are consumed during lipid peroxidation. Objective: The goal of this study was to define the relation between resist ance to insulin-mediated glucose disposal and plasma concentrations of lipi d hydroperoxides and liposoluble antioxidant vitamins in healthy volunteers . Design: Insulin-mediated glucose disposal was determined in 36 healthy, non diabetic volunteers by measuring their steady-stats plasma insulin (SSPI) a nd glucose (SSPG) concentrations in response to a 180-min constant infusion of octreotide, insulin, and glucose. In addition, fasting plasma concentra tions of lipid hydroperoxides and liposoluble antioxidant vitamins were det ermined by using the FOX 2 assay and liquid chromatography. Results: Statistically significant direct relations were observed between S SPG and mean arterial blood pressure (r = 0.44, P = 0.008) and plasma lipid hydroperoxide concentrations (r = 0.42, P = 0.01), whereas significant inv erse correlations were found between SSPG and a-carotene (r = -0.58, P = 0. 0002), beta-carotene (r = -0.49, P = 0.004), lutein (r = -0.35, P = 0.04), alpha-tocopherol (r = -0.36, P = 0.04), and delta-tocopherol (r = -0.45, P = 0.007). Conclusions: Variations in insulin-mediated glucose disposal in healthy ind ividuals are significantly related to plasma concentrations of lipid hydrop eroxides and liposoluble antioxidant vitamins. These findings suggest that total plasma lipid peroxidation is increased in insulin-resistant individua ls at an early, preclinical stage, ie, well before the development of gluco se intolerance and type 2 diabetes.