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.
Excessive exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers
