Differences in Weight and Fitness Status in Both the GH-IGF1 Axis and Markers of Inflammation in Adolescents Public Deposited

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  • March 20, 2019
  • Hosick, Peter A.
    • Affiliation: School of Medicine, Department of Allied Health Sciences, Curriculum in Human Movement Science
  • PURPOSE: To determine if differences in the GH-IGF1 axis and TNF-α or IL-6 exist in children based on fitness and/or weight status and if expressing fitness in units per fat free mass (FFM) alters the relationship between the GH-IGF1 axis components, TNF-α, and IL-6. Additionally, the influence that inflammatory markers have on the relationship between components of the GH-IGF1 axis was assessed. PARTICIPANTS: Data was collected on 124 youth purposefully selected from a larger study (CHIC III, J.S. Harrell, P.I.) into four groups: normal high fit (NH), normal low fit (NL), obese high fit (OH), and obese low fit (OL). METHODS: Height, weight, skinfolds, body mass index (BMI), body fat percentage and predicted VO2max (mL/min) were measured. Predicted VO2max was scaled to VO2max (mL/kgFFM/min) and used to determine fitness status. Resting growth hormone (GH), total insulin-like growth factor-1 (total IGF1), free insulin-like growth factor-1(free IGF1), insulin, TNF-α, and IL-6 were obtained from fasting blood samples. RESULTS: GH was significantly greater in the NH group compared to the OL group. Total IGF1, free IGF1, and TNF-α were not different in any of the groups. Insulin was greater in the OH and OL groups compared to the NH and NL groups. IL-6 was elevated in the NL and OL groups compared to the NH group and in the OL group compared to the OH group. Significant correlations between GH-IGF1 axis components existed between GH and total IGF1 (r=0.194, p=0.05) and free IGF1 and total IGF1 (r=0.607, p<0.001) only. Neither TNF-α nor IL-6 contributed to the relationship between GH and total IGF1. Only IL-6 had a significant relationship (β=-0.060, p=0.030) between free IGF1 and total IGF1 when fitness was included in the model. CONCLUSIONS: Fitness may reduce the obesity related GH alterations possibly involved with continued weight gain. IL-6 levels appear more affected by fitness then fat mass. When including fitness, IL-6 may influence the GH-IGF1 axis. The relationship between GH-IGF1 axis, TNF-α, or IL-6 does not change when using VO2max scaled to total body mass versus FFM. Findings suggest that elevated aerobic fitness may limit continued weight gain.
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  • "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the School of Medicine (Interdisciplinary Program in Human Movement Science)"
  • McMurray, Robert G.
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  • Chapel Hill, NC
  • Open access

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