RBP4: From Retinol Transporter to Biomarker?

Overweight and obesity are major risk factors for type 2 diabetes mellitus and cardiovascular diseases. The coexistence of these 2 conditions may be characterized by the term cardiometabolic disease, the cause of which appears to be multifactorial, involving intricate interactions of environment, behavior, and biology. It is now well recognized that adipose tissue is not only just a site of energy storage, but it also has a crucial endocrine function as a major source of many functionally important signaling proteins (adipokines). Many of these adipokines have been shown to directly or indirectly affect insulin sensitivity through modulation of insulin signaling and the molecules involved in glucose, muscle, and lipid metabolism. Of these adipokines, retinol binding protein (RBP4) has recently attracted much attention because of its newly demonstrated function as a potential determinant of insulin resistance, diabetes, and cardiovascular risks. Although research and our understanding of cardiometabolic disease have advanced, major gaps exist with regard to the obesity-driven mechanisms that increase the progression of cardiometabolic disease, especially in children. One opportunity for elucidating these mechanisms involves validating potential contributing factors resulting from obesity, which independently enhance future susceptibility for cardiometabolic disease. In this context, insulin resistance appears to be a key factor in the development of cardiometabolic disease. Retinol binding protein 4 (RBP4) in its role as a potential signal in mediating obesity-driven insulin resistance seems to be an adipokine of considerable interest.