Background: GlycA is a novel serum marker of systemic inflammation. There is no information on GlycA in pediatric populations, how it differs by gender or its association with body mass index (BMI) or fitness. Lipoprotein insulin resistance index (LP-IR) is a serum measure of insulin resistance, which is related to changes in BMI group in adolescents, but its relationship with fitness is unknown. The current study examined the independent associations between fitness and BMI with GlycA and LP-IR among US adolescents.
Methods: Participants were 1664 US adolescents from the HEALTHY study with complete 6th and 8th grade BMI, fitness and blood data. GlycA and LP-IR were measured by nuclear magnetic resonance spectroscopy. Three BMI groups and three fitness groups were created. Linear mixed models examined associations between GlycA, LP-IR, fitness and BMI.
Results: LP-IR decreased between 6th and 8th grade. GlycA increased among girls but decreased among boys. At 8th grade, median GlycA values were 27 (7.6%) μmol l(-1) higher (381 versus 354) for girls than boys. Median GlycA 6th grade values were 9% higher in obese girls than healthy weight girls. Overall, there was strong evidence (P<0.001) that GlycA was higher in higher BMI groups. Fitness was negatively associated with GlycA (r=-0.37 and -0.35) and LP-IR (r=-0.34 and -0.18) at the 6th and 8th grade assessments. As BMI category increased and fitness category decreased, GlycA and LP-IR levels increased. Lowest GlycA was found in the low BMI/high fitness group.
Conclusions: GlycA was associated with BMI and fitness among in US adolescents. These findings suggest that there are independent effects for BMI and fitness group with both GlycA and LP-IR. Future studies should validate the role of GlycA and LP-IR to evaluate the effects of interventions to modify obesity and fitness to improve systemic inflammation and insulin resistance.