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. 2019 May 1:10:528.
doi: 10.3389/fphys.2019.00528. eCollection 2019.

Impaired Muscular Fat Metabolism in Juvenile Idiopathic Arthritis in Inactive Disease

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Impaired Muscular Fat Metabolism in Juvenile Idiopathic Arthritis in Inactive Disease

Emmanuelle Rochette et al. Front Physiol. .

Abstract

Objectives: The objective of this study was to evaluate muscular metabolic function in children with inactive juvenile idiopathic arthritis (JIA). Methods: Fifteen children with inactive JIA and fifteen healthy controls were matched by sex, biological age, and Tanner stage. Participants completed a submaximal incremental exercise test to determine their fat and carbohydrate oxidation rates. Results: Between the two groups, heart rate values and carbohydrate oxidation rates were the same, regardless of the relative intensity of exercise. Lipid oxidation rates were lower in JIA patients, regardless of the percentage of VO2 peak (p < 0.05). Respiratory exchange ratios beyond 50% of VO2 peak were higher in patients with JIA (p < 0.05). Respective maximal fat oxidation rates (MFO) for controls and children with JIA were 218.7 ± 92.2 vs. 157.5 ± 65.9 mg ⋅ min-1 (p = 0.03) and 4.9 ± 1.9 vs. 3.4 ± 1.2 mg ⋅ min-1 ⋅ kg-1 (p = 0.04). There was no difference between the two groups in heart rate, percentage of VO2 peak, or power of exercise to achieve MFO. Controls reached their MFO at an exercise power significantly higher than did JIA subjects (42.8 ± 16.8 and 31.9 ± 9.8 W, p = 0.004). Conclusion: Children with JIA show metabolic disturbance during exercise, even when the disease is considered inactive. This disturbance is seen in a lower lipid oxidation rate during submaximal exercise.

Keywords: fat oxidation; inflammation; metabolism; pediatric; physical activity.

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Figures

FIGURE 1
FIGURE 1
Carbohydrates (CHO) (A) and fat (B) oxidation rate, respiratory exchange ratio (RER) (C), and heart rate (D) according to percentage of VO2 peak. Data are means ± 95% CI. Bt, beats; JIA, juvenile idiopathic arthritis.
FIGURE 2
FIGURE 2
Comparison of maximal fat oxidation (MFO) (A) and maximal fat oxidation per kg of total body mass (B). Boxes represent interquartile ranges and whiskers give minimum and maximum values. Data are means (×) and medians (–). JIA, juvenile idiopathic arthritis.
FIGURE 3
FIGURE 3
Comparison of power (A), % VO2 peak (B), and heart rate (HR) (C) at the maximal fat oxidation rate (MFO). Boxes represent interquartile ranges and whiskers give minimum and maximum values. Data are means (×) and medians (–). Bt, beats; JIA, juvenile idiopathic arthritis.

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