Serpin A12, also known as Vaspin, is a secreted adipokine that is found in visceral adipose tissue. It belongs to the serpin superfamily, class A. It's known protease target is KLK7, a member of the kallikrein family. In humans, Serpin A12 expression may increase at the onset of diabetes and decrease when the disease aggravates. The administration of recombinant Serpin A12 in a diet-induced mouse obesity model suggests that it may represent an insulin-sensitizing adipokine. Low serum concentration of Serpin A12 may be a risk factor for the progression of type-2 diabetes mellitus. Although its mechanism of action is not fully understood, KLK7 inhibition seems to be the most likely underlying physiological mechanism for the compensatory effects on obesity-induced insulin resistance. In addition to its relation to diabetes, Serpin A12 exerts protective effects on heart disease. Its low concentrations correlate with coronary artery diseases’ severity and unstable angina pectoris. Serpin A12 may inhibit endothelial cell apoptosis, attenuate high glucose stimulated vascular smooth muscle cell proliferation, and chemokinesis. It also acts as a ligand for the cell surface GRP78/voltage dependent anion channel complex in endothelial cells and promotes proliferation, inhibits apoptosis, and protects against diabetes mellitus associated vascular injuries.