The relationship between insulin resistance assessed by HOMA-IR and serum osteoprotegerin levels in obesity

Abstract

Aim: We investigated the relationship between insulin resistance and serum osteoprotegerin (OPG) levels in healthy obese subjects and healthy lean controls. Methods: Fifty obese subjects (age: 31 ± 8 years) and 24 lean controls (age: 30 ± 7 years) were included in the study. We used the homeostasis model assessment for insulin resistance (HOMA-IR) index as the index of insulin resistance. OPG levels were measured with the commercial ELISA kit. Obese subjects were studied in three groups: Group I ( n = 25) HOMA-IR index < 2.24, Group II ( n = 13) index 2.24–3.59, Group III ( n = 12) index > 3.59. Group IV ( n = 24) was the lean controls with HOMA-IR index < 2.24. Results: Obese subjects with increased insulin resistance (Group III) had lower OPG values than other groups (11.88 ± 7.43 pg/ml, 16.39 ± 6.39 pg/ml, 17.37 ± 9.61 pg/ml, and 18.1 ± 6.65 pg/ml, respectively; Group I versus Group III p = 0.036; Group III versus Group IV p = 0.012). We also found significant inverse correlations between OPGc (corrected for BMI) and fasting glucose ( r = −0.325, p = 0.005), fasting insulin ( r = −0.404, p = 0.0001) as well as HOMA-IR ( r = −0.428, p = 0.0001). Increased fibrinogen level was found in Group III than Group IV (9.32 ± 1.97 μmol/l versus 7.47 ± 1.65 μmol/l, respectively; p = 0.005). In conclusion, insulin resistance in obesity is associated with decreased serum OPG levels and increased fibrinogen levels. The relationship between serum OPG levels and HOMA-IR may provide an insight into vascular endothelial dysfunction in obesity.