Lack of circulating bioactive and immunoreactive IGF-I changes despite improved fitness in chronic kidney disease patients following 48 weeks of physical training.
OBJECTIVE
As known abnormalities exist in the insulin-like growth factor (IGF) system in chronic kidney disease (CKD) patients, the measurement of bioactive IGF-I may provide further insight into the therapeutic potential of long-term exercise training.


METHODS
Patients (N=21) with stages 3 and 4 CKD were recruited from a local nephrology practice in Springfield, MA and randomized into matched treatment and control groups. The treatment group participated in 48 weeks of supervised, progressive exercise training and dietary counseling, while the control group received only usual care. Treadmill testing, anthropometric measurements, and blood samples for analysis of immunoreactive IGF-I, IGF-II, IGFBP-1 and -2, and bioactive IGF-I were taken at baseline, 24 weeks, and 48 weeks.


RESULTS
There were no significant differences in any of the components of the IGF system (all p-values>0.05). Immunoreactive IGF-I levels correlated significantly with bioactive IGF-I at baseline (r=0.50, p=0.02) and at 48 weeks (r=0.64, p=0.01). There was a significant interaction between group and time for both VO(2peak) (p=0.03) and total treadmill time (TT) (p<0.01).


CONCLUSIONS
Despite improvements in physical performance, a 48-week training program did not affect any of the circulating IGF system measurements. Disparities between these findings and those of other researchers reporting a biphasic response to long-term training may be explained by differences in study groups and exercise programs.
Exercise Science Program, Department of Exercise Science and Sports Studies, Springfield College, Springfield, MA 01109, USA. sgregory@spfldcol.edu
Sara M
SM
Gregory
Samuel A
SA
Headley
Michael
M
Germain
Allan
A
Flyvbjerg
Jan
J
Frystyk
Mary Ann
MA
Coughlin
Charles M
CM
Milch
Sheila
S
Sullivan
Bradley C
BC
Nindl
D000328:Adult; D000368:Aged; D054874:Athletic Performance; D001823:Body Composition / Q000502:physiology; D002478:Cells, Cultured; D005081:Exercise Therapy; D005260:Female; D015200:Fluoroimmunoassay / Q000379:methods; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D010809:Physical Fitness / Q000502:physiology*; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000378:metabolism / Q000628:therapy*
D007334:Insulin-Like Growth Factor I