Exercise and obesity in fibromyalgia: beneficial roles of IGF-1 and resistin?
INTRODUCTION
Severe fatigue is a major health problem in fibromyalgia (FM). Obesity is common in FM, but the influence of adipokines and growth factors is not clear. The aim was to examine effects of exercise on fatigue, in lean, overweight and obese FM patients.


METHODS
In a longitudinal study, 48 FM patients (median 52 years) exercised for 15 weeks. Nine patients were lean (body mass index, BMI 18.5 to 24.9), 26 overweight (BMI 25 to 29.9) and 13 obese. Fatigue was rated on a 0 to 100 mm scale (fibromyalgia impact questionnaire [FIQ] fatigue) and multidimensional fatigue inventory (MFI-20) general fatigue (MFIGF). Higher levels in FIQ fatigue and MFIGF indicate greater degree of fatigue. Free and total IGF-1, neuropeptides, adipokines were determined in serum and cerebrospinal fluid (CSF).


RESULTS
Baseline FIQ fatigue correlated negatively with serum leptin (r=-0.345; P=0.016) and nerve growth factor (NGF; r=-0.412; P=0.037). In lean patients, baseline MFIGF associated negatively with serum resistin (r=-0.694; P=0.038). FIQ Fatigue associated negatively with CSF resistin (r=-0.365; P=0.073). Similarly, FIQ fatigue (r=-0.444; P=0.026) and MFIGF correlated negatively with CSF adiponectin (r=-0.508; P=0.01). In lean patients, FIQ fatigue (P=0.046) decreased after 15 weeks. After 30 weeks, MFIGF decreased significantly in lean (MFIGF: P=0.017), overweight (MFIGF: P=0.001), and obese patients (MFIGF: P=0.016). After 15 weeks, total IGF-1 increased in lean (P=0.043) patients. ∆Total IGF-1 differed significantly between lean and obese patients (P=0.010). ∆Total IGF-1 related negatively with ∆MFIGF after 15 weeks (r=-0.329; P=0.050). After 30 weeks, ∆FIQ fatigue negatively correlated with ∆NGF (r=-0.463; P=0.034) and positively with ∆neuropeptide Y (NPY) (r=0.469; P=0.032). Resistin increased after 30 weeks (P=0.034). ∆MFIGF correlated negatively with ∆resistin (r=-0.346; P=0.031), being strongest in obese patients (r=-0.815; P=0.007). In obese patients, ∆FIQ fatigue after 30 weeks correlated negatively with ∆free IGF-1 (r=-0.711; P=0.032).


CONCLUSIONS
Exercise reduced fatigue in all FM patients, this effect was achieved earlier in lean patients. Baseline levels of resistin in both serum and CSF associated negatively with fatigue. Resistin was increased after the exercise period which correlated with decreased fatigue. Changes in IGF-1 indicate similar long-term effects in obese patients. This study shows reduced fatigue after moderate exercise in FM and indicates the involvement of IGF-1 and resistin in these beneficial effects.


TRIAL REGISTRATION
ClinicalTrials.gov: NCT00643006.