Clusterin, also known as Apolipoprotein J, is a heterodimeric glycoprotein that exhibits a wide array of biological functions including lipid transportation, cell death, cell clustering, complement inhibition, tissue remodeling, reproduction, and cancer progresion. Structurally, alpha (Ser228-Glu449) and beta chain (Asp23-Arg227) of mature clusterin are assembled in an anti-parallel fashion, in which the cysteine-rich centers are linked by five disulfide bridges and are flanked by two coiled-coil alpha-helices and three amphipathic alpha-helices. The two chains are coded in a single open reading frame. In blood, circulating clusterin is predominantly associated with HDL. Approximately 22% of clusterin is present in HDL, while only about 9% is present in LDL/VLDL. Insulin resistance, obesity, and dyslipidemia are characteristics of the metabolic syndrome and type 2 diabetes. It has been shown that there is a strong negative correlation between the concentration of clusterin in HDL and both insulin sensitivity and body max index. Thus, clusterin depletion may contribute to the loss of HDL's cardioprotective properties. In fact, clusterin levels in HDL3 increase when patients with cardiovascular diseases are treated with statin and niacin therapy. Importanly, it was shown that people who already have Alzheimer's disease have more clusterin in their blood, and that their clusterin levels correlate with faster cognitive decline in patients sufferring from Alzheimer's disease. These clinical findings suggest that Clusterin may play a role in protein folding. Mature human clusterin shares a 77% amino acid sequence homology with its mouse counterpart.