Elevated serum retinol-binding protein 4 is associated with insulin resistance in older women

Retinol-binding protein 4 (RBP4), a molecule secreted from adipocytes and hepatocytes, may contribute to insulin resistance and is a potential predictor for type 2 diabetes mellitus. We investigated the association between serum RBP4 concentrations and insulin resistance in perimenopausal women. In addition, we examined associations of serum RBP4 concentrations with age, risk factors of cardiovascular disease, and metabolic syndrome. A total of 73 healthy women were included in this study. Subjects' anthropometric measurements were taken, and body mass index and waist-hip ratio were calculated. Fasting glucose, fasting insulin, serum RBP4, and lipid parameters were examined. These various parameters were compared in subjects younger than and older than 50 years. Serum RBP4 concentrations in women at least 50 years of age were significantly higher than those in women younger than 50 years. In all subjects, serum RBP4 concentrations positively correlated with age, diastolic blood pressure, fasting glucose, and homeostatic assessment model of insulin resistance. After subgroup analysis, serum RBP4 concentrations positively correlated with age, fasting glucose, and homeostatic assessment model of insulin resistance in women at least 50 years of age. In women younger than 50 years, serum RBP4 concentrations positively correlated only with fasting glucose. Serum RBP4 appears to identify age-induced insulin resistance by physiologic changes due to aging or menopause and by increasing hepatic glucose production. However, the clinical implication of RBP4 for detecting cardiovascular disease and metabolic syndrome is not clear.