Insulin-like growth factors and leucine kinetics during exercise training in children with cystic fibrosis.
BACKGROUND
Little is known about the metabolic effects of exercise training in children with cystic fibrosis. The hypothesis for the current study was that in patients with declining clinical status, exercise increases circulating insulin-like growth factors (IGFs) and improves protein kinetics.


METHODS
This was a prospective intervention study in 10 children with cystic fibrosis who participated in a structured isoenergetic exercise (cycling) training program for 3 months. Measurements of IGFs, protein kinetics (using intravenous [13C]-1-leucine tracer infusions) and nutritional balance studies were conducted at baseline and after 3 months.


RESULTS
Standard deviation scores of plasma IGF-I, IGF-II, and IGF binding protein (BP)-3 were all decreased at baseline (mean +/- SE: -2.0+/-0.2, -2.0+/-0.2. -0.6+/-0.2, respectively). IGF-I and IGF-II concentrations were significantly higher after exercise training (standard deviation scores -1.4+/-0.3 and -1.3 +/-0. 1, respectively; compared with baseline: one-tailed t-test P = 0.03 and 0.002). The standard deviation score of the IGF-I/IGF BP-3 ratio, an indicator of free IGF-I in the circulation, normalized during exercise training (0.0+/-0.6 vs. -1.3+/-0.2 SD units at baseline, one-tailed t-test P = 0.04). There was no significant difference in protein intake and fasting protein breakdown, oxidation, and protein synthesis or in energy balance and fat absorption.


CONCLUSIONS
These results show that isoenergetic exercise training can be safely recommended to patients with cystic fibrosis. It provides a positive anabolic stimulus to IGF status but is not sufficient to adequately augment protein accretion in patients with diminished nutritional status.
Gulmans
V
V
Department of Pediatrics, University Medical Center, Utrecht, The Netherlands.
van der Laag
J
J
Wattimena
D
D
van Doorn
J
J
Oostveen
D
D
Berger
R
R
de Meer
K
K
D000293:Adolescent; D002648:Child; D003550:Cystic Fibrosis / Q000097:blood* / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007553:Isotope Labeling; D007930:Leucine / Q000378:metabolism / Q000493:pharmacokinetics*; D008297:Male; D009752:Nutritional Status; D011446:Prospective Studies; D013002:Somatomedins / Q000032:analysis*
D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins; D007930:Leucine