[Changes in serum levels of IGF-I and its binding proteins and their relation to microcirculation in obese patients]

The IGF-I system and its binding proteins participate in the pathogenesis of vascular affections under various pathological conditions. The mechanism and mode of its action were however not elucidated in details so far and views on its role are controversial. The objective of the study was to assess the relationship of this system and the blood flow in the microcirculation in obese patients. The authors examined 21 obese patients (BMI 39.7 +/- 7.3 kg/m2) and a group of healthy volunteers. They examined: serum concentrations of total IGF-I, free IGF-I, IGFBP-1,-2,-3, and -6, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides as well as the intimomedial thickness of the common carotid arteries and parameters of blood flow in the microcirculation, evaluated by a laser-Doppler examination. In obese patients there were significantly lower serum concentrations of IGF-I and free-IGF I (p < 0.05) as compared with the control group. Comparison of the function of the microcirculation revealed in obese patients, as compared with the control group, a lower percentage increase of perfusion after occlusion (PORH%, p < 0.05) and after heating (TH%, p < 0.05) and a slower onset of thermal hyperaemia (THmax/t, p < 0.05). In the control group serum concentrations of free-IGF-I correlated inversely with the maximum perfusion after heat induced hyperaemia (THmax (r = -0.54, p < 0.02) and the rate of onset of hyperaemia after heating (THmax/t) (r = 0.51, p < 0.02). In the group of obese patients serum concentrations of free-IGF-I correlated inversely with the maximum perfusion after heat induced hyperaemia (THmax) (r = -0.55, p < 0.02), and IGFBP-3 concentrations correlated inversely with maximum hyperaemia after occlusion (PORGmax) (r = -0.57, p < 0.01). The results suggest that the function of the microcirculation in obese subjects is affected. The activity of the IGF-I system and its binding proteins is related to the affected function of the microcirculation and a negative part is played particularly by serum concentrations of free IGF-I. The negative effect of IGFBP-3 on the function of the microcirculation is surprising.