IGF-I/IGFBP- 3 ratio: a mechanistic insight into the metabolic syndrome
Abstract
Recent reports suggest that insulin-like growth factor 1 (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) have independent and opposing mechanistic effects on insulin. Our aim was to assess the relationship between the IGF-I/IGFBP-3 ratio and the metabolic syndrome. We examined 3,281 subjects (1,463 men; 1,818 women aged 20 to 49 years), otherwise healthy adults, who participated in the Third National Health and Nutrition Examination Survey (NHANES III) and had the recently released measurements of IGF-I and IGFBP-3. Insulin resistance was estimated using the computer homeostatic model assessment (HOMA-2). The updated ATP-III definition of the metabolic syndrome was used. We applied adjusted logistic and linear regression models. After adjusting for age and race, men and women in the lowest quartile of the IGF-I/IGFBP-3 ratio were 3 times more likely to meet the ATP-III definition of the metabolic syndrome and twice as likely to be insulin resistant. Mean values of the IGF-I/IGFBP-3 ratio decreased significantly as the number of metabolic syndrome components increased (ANOVA p<0.0001). Area under the receiver operating characteristics curve for detecting insulin resistance using the IGF-I/IGFBP-3 ratio was 0.760, significantly improving upon either protein alone (p=0.01). In conclusion, the IGF-I/IGFBP-3 ratio is significantly associated with the metabolic syndrome. Calculating the ratio of these two proteins may provide insight into the metabolic syndrome clustering phenomenon.
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