Associations Between Antioxidant Capacity And Insulin Sensitivity At Baseline But Not Following Six-weeks Of HIIT Or MIT In Obese Males.

Abstract

Obesity is an independent risk factor for type 2 diabetes and cardiovascular disease. Oxidative stress or low total antioxidant capacity has been shown to be associated with decreased insulin sensitivity (SI) in overweight/obese individuals. Exercise training has been shown to improve systemic antioxidant capacity (TAC) and SI; however whether or not correlations between SI and TAC observed under untrained conditions are associated following exercise training is less clear. PURPOSE: The purpose of this study was twofold: 1) to determine if SI was correlated with serum TAC in a cohort of overweight/obese men at baseline and following six-weeks of exercise training; and 2) to determine if the relationships between SI and TAC responded differently following High Intensity Interval (HIIT) vs Moderate Intensity-Training (MIT). METHODS: 16 sedentary, overweight/obese young men (age = 20 ± 1.5 years, body mass index = 29.5 ± 3.3 kg/m2) were randomly assigned to HIIT or MIT and evaluated at baseline and post-training. Baseline and post training assessments included DXA for body composition assessment, oral glucose tolerance test to measure SI, and the oxygen radical absorbance capacity assay to assess TAC. Additionally, acute serum TAC responses were assessed at pre-exercise (PRE), immediately post exercise (IPE) and 30 minutes post exercise (30min-Post) at baseline and six-weeks post training. RESULTS: A significant correlation was observed between SI and TAC at baseline (R2=0.548, P=0.001). SI significantly improved from baseline to post-training in both groups (P=0.037), with no significant time x group interactions for HIIT or MIT. No significant changes in TAC were found from baseline to post-training. No significant correlations were found between SI and TAC in the trained condition. A significant increase in TAC was observed IPE compared to pre-exercise at baseline and six-weeks post training following HIIT (P<0.05). A significant decrease in TAC was found 30min-Post compared to IPE six-weeks post training in HIIT and MIT. CONCLUSION: The observed baseline correlation between SI and TAC did not persist after training, which suggests that factors other than changes in TAC may be mediating the exercise-induced improvement in SI. Ongoing studies will attempt to identify exercise-induced mediators in SI.