Abstract P177: Effects of Gender, Race, and Glucose Tolerance on Lipoprotein Insulin Resistance Index Responses to Exercise Training

Abstract

Introduction: Lipoprotein Insulin Resistance Index (LP-IR) is a novel spectroscopic multimarker linked to future diabetes risk. We recently assessed changes in LP-IR across the three STRRIDE trials, where on average, STRRIDE exercise interventions improved LP-IR. In the present study, we sought to determine if there were effects of gender, race, and glucose tolerance on LP-IR responses across the STRRIDE trials. Methods: A total of 461 adults with dyslipidemia (STRRIDE I and STRRIDE AT/RT) or prediabetes (STRRIDE-PD) were randomized to one of 7 exercise interventions, ranging from doses of 8-22 kcal/kg/week (KKW); intensities of 50-75% VO 2peak ; and durations of 6-9 months. Six groups included aerobic exercise, two groups included resistance training, and one group included dietary intervention (weight loss goal of 7%). Fasting blood samples were obtained at both baseline and 16-24 h after the final exercise bout. In STRRIDE-PD only (n=165), subjects completed oral glucose tolerance tests and were categorized into normal (NGT) and impaired glucose tolerance (IGT) groups at baseline. NMR spectroscopy was performed at LabCorp to determine LP-IR score (comprised of six lipoprotein subclass and size parameters). LP-IR score ranges from 0 (most insulin sensitive) to 100 (most insulin resistant). Irrespective of intervention group, we assessed change in LP-IR in three stratified analyses: by gender, race, and baseline glucose tolerance category. Paired t-tests determined whether the post- minus pre- intervention change scores within each group were significant (p<0.05). Analysis of covariance accounting for baseline values determined difference among groups. Results: At baseline, women had lower LP-IR scores compared to men (47.8 ± 22.3 vs 62.6 ± 21.5; p<0.0001). Both women and men significantly improved LP-IR following exercise training by -4.3 ± 15.0 and -8.0 ± 15.6 points, respectively. There were also significant baseline differences when stratified by race. Black subjects had lower baseline LP-IR scores compared to White subjects (43.2 ± 20.7 vs 56.3 ± 23.0; p<0.0001). After exercise training, Black subjects significantly improved their LP-IR score by -4.0 ± 14.6 points; White subjects significantly improved their LP-IR score by -6.2 ± 15.5 points. As expected, those with NGT had lower baseline LP-IR scores compared to those with IGT in STRRIDE-PD (49.0 ± 20.0 vs 64.4 ± 19.9; p<0.0001). Both NGT and IGT groups significantly improved LP-IR by -4.3 ± 14.6 and -7.6 ± 12.9 points, respectively. In all three stratified analyses, change in LP-IR was not significantly different among groups after controlling for baseline values. Conclusion: There were significant baseline differences in LP-IR among gender, racial, and glucose tolerance groups. However, after adjusting for these baseline differences, there were similar beneficial responses to exercise in this marker of insulin resistance.