Circulating visfatin is associated with parameters of iron metabolism in subjects with altered glucose tolerance

OBJECTIVE - Visfatin is a novel adipokine that is predominantly secreted by visceral adipose tissue. Accumulation of visceral adipose tissue is also associated with iron metabolism. Despite the coincidence of visfatin expression in iron-rich tissues, no study has investigated the possible interaction of visfatin with parameters of iron metabolism. RESEARCH DESIGN AND METHODS - We evaluated insulin sensitivity and parameters of iron metabolism in 95 men with normal glucose tolerance (NGT) and 43 men with altered glucose tolerance. RESULTS - Men with newly diagnosed type 2 diabetes had significantly increased serum visfatin in parallel with increased serum prohepcidin and serum ferritin compared with the other groups. In all subjects as a whole, circulating visfatin was not found to be significantly linked to insulin sensitivity (r = 0.07, P = 0.4) but was significantly associated with serum prohepcidin concentration (r = 0.40, P < 0.0001). Obesity status and glucose tolerance status influenced the relationships among visfatin, insulin sensitivity, and parameters of iron metabolism. Among men with altered glucose tolerance, serum visfatin was strongly associated with serum prohepcidin (r = 0.61, P < 0.0001) and serum soluble transferrin receptor (sTfR) (r = -0.51, P < 0.0001). In nonobese subjects, sTfR (P = 0.02) and prohepcidin (P = 0.04) contributed independently to visfatin variance after controlling for age and BMI. When insulin sensitivity was added to the model, only the latter (P = 0.006) contributed to 17% of visfatin variance. In obese men, however, only sTfR (P = 0.04) contributed independently to visfatin variance in this latter model. CONCLUSIONS - Serum visfatin concentration is significantly associated with parameters of iron metabolism, especially in subjects with altered glucose tolerance.