Circulating Alpha-Tocopherol and Insulin Sensitivity Among Older Men With Chronic Kidney Disease

Objective: Insulin resistance is common in individuals with chronic kidney disease (CKD) and may be partly explained by modifiable risk factors. In the general population, vitamin E supplementation has been suggested to improve both insulin sensitivity and secretion. We here explore the potential role of vitamin E as a modifiable risk factor for insulin resistance among individuals with CKD. Design: Observational study. Setting: A total of 273 nondiabetic men aged 70 to 71 years with CKD defined as either cystatin C estimated glomerular filtration rate, < 60 mL/minute/1.73 m(2) or urinary albumin excretion rate >= 20 mg/minute from the third examination cycle of Uppsala Longitudinal Study of Adult Men. Subjects: A total of 273 nondiabetic men aged 70 to 71 years with CKD defined as either cystatin C estimated glomerular filtration rate, 60 mL/minute/1.73 m(2) or urinary albumin excretion rate >= 20 mu g/minute. Methods: Serum alpha-, beta-, and gamma-tocopherol concentrations were measured by high-performance liquid chromatography and expressed as mmol/total serum cholesterol and triglycerides (in mmol). Dietary vitamin E intake was estimated from 7-day food records. Main Outcome Measure: Insulin sensitivity index (M/I ratio) was measured by hyperinsulinemic-euglycemic glucose clamps. Univariate and multivariate regression models were fitted to assess the association between M/I and circulating concentrations of tocopherols. Results: The mean serum concentration of alpha-, beta-, and gamma- was 37.4 +/- 6.58, 0.89 +/- 0.23, and 4.32 +/- 1.69 mu mol/mmol, respectively. Median dietary vitamin E intake was 6.14 (interquartile range, 5.48-6.82) mg/day. In crude and fully-adjusted multivariate regression analyses, serum alpha-tocopherol levels were directly and strongly associated with M/I (standard beta = 0.17, P = .003). No such association was observed for dietary vitamin E, serum beta-, and gamma-tocopherol concentrations. Conclusions: Serum a-tocopherol concentration associates with insulin sensitivity in nondiabetic older men with CKD. (C) 2016 by the National Kidney Foundation, Inc. All rights reserved.