Apelin and insulin resistance: another arrow for the quiver?

Apelin is a newly discovered peptide hormone that has recently been linked to insulin resistance and obesity. Data collected from both the clinical and basic research settings show that apelin: (i) is correlated with the states of insulin resistance and obesity; (ii) stimulates glucose utilization; (iii) decreases insulin secretion; and (iv) negatively regulates catecholamine-mediated lipolysis. These and other lines of evidence demonstrate that apelin may be a potentially viable candidate in the search for treatments for Type 2 diabetes and the insulin resistance (metabolic syndrome). The present review summarizes the literature on the regulation by apelin of glucose and lipid metabolism and the signaling pathways involved.