Relationship between reduced serum IGF-I levels and accumulation of visceral fat in Japanese men

OBJECTIVE: To investigate whether the changes in IGF-I concentrations after weight reduction in Japanese overweight men are associated with changes in visceral and subcutaneous fat. DESIGN: Cross-sectional and longitudinal clinical intervention study with exercise education. SUBJECTS: One-hundred and twelve Japanese overweight men aged 30-59 y (body mass index (BMI) 28.4+/-2.5 kg/m(2)) and 33 normal-weight men aged 30-39 y (BMI 22.1+/-1.5 kg/m(2)) at baseline. From the participants, 56 randomly selected overweight men (BMI 28.8+/-2.8) were further enrolled into a 1 y exercise program. MEASUREMENTS: Fat distribution was evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography scanning at umbilical levels, metabolic parameters and hormones including insulin, leptin and IGF-I at baseline and after 1 y. RESULTS: In 112 overweight subjects at baseline, insulin (10.5+/-5.0 microU/ml) and leptin (6.4+/-3.7 ng/ml) significantly correlated with both V (r=0.260, P=0.0073; r=0.410, P<0.0001) and S areas (r=0.377, P<0.0001; r=0.613, P<0.0001), respectively. IGF-I (156.8+/-48.7 microU/ml) significantly and negatively correlated with V area (r=-0.242, P=0.0125) and age (r=-0.192, P=0.0480). In normal-weight men aged 30-39 y (n=33) and age-matched subjects (n=30) selected from the 112 overweight men, the serum IGF-I further tightly correlated with V area (r=-0.467, P<0.0001). Visceral fat area and age were independently related to serum IGF-I levels by multiple regression analysis. By intervention with exercise education, 56 overweight subjects showed an increase in daily steps (6224+/-2781 to 7898+/-4141 steps/day) and reduction of BMI (28.8+/-2.8 to 27.7+/-2.9). deltaIGF-I significantly correlated with deltaV area (r=-0.432, P=0.0009) but not with DeltaS area or deltaBMI. CONCLUSION: The present study indicated a negative correlation between IGF-I levels and visceral fat at baseline as well as an association between the reduction in visceral fat and increase in IGF-I levels after an exercise intervention.