, Volume 50, Issue 10, pp 2221-2223
Date: 28 Jul 2007

Regulation of retinol binding protein 4 production in primary human adipocytes by adiponectin, troglitazone and TNF-α

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To the Editor: Adipose tissue has an important endocrine function, producing a variety of bioactive proteins that may regulate energy metabolism and insulin sensitivity. It releases a variety of the so-called adipokines, including retinol binding protein 4 (RBP4), which has recently been described as a link between obesity and insulin resistance [1] in addition to its primary function as a specific carrier of vitamin A in the blood. In diabetic patients, RBP4 levels are correlated with the degree of insulin resistance [2] and with components of the metabolic syndrome, such as BMI, triacylglycerol levels and blood pressure. Conversely, exercise and weight loss have been reported to decrease both RBP4 levels and insulin resistance [2]. However, the link between RBP4 and obesity is controversial, as several other studies have not found RBP4 to be associated with overall obesity or insulin resistance [3, 4]. In addition, one study reported no difference in circulating RBP4 levels between l