Apolipoprotein C-III, metabolic syndrome, and risk of coronary artery disease.

Apolipoprotein C-III (apoC-III) is a marker of triglyceride (TG)-rich lipoproteins, which are often increased in metabolic syndrome (MS). The T-455C polymorphism in the insulin-responsive element of the APOC3 gene influences TG and apoC-III levels. To evaluate the contribution of apoC-III levels and T-455C polymorphisms in the coronary artery disease (CAD) risk of MS patients, we studied 873 patients, 549 with CAD and 251 with normal coronary arteries. Patients were classified also as having or not having MS (MS, n = 270; MS-free, n = 603). Lipids, insulin, apolipoprotein levels, and APOC3 T-455C genotypes were evaluated. ApoC-III levels were significantly increased in MS patients, and the probability of having MS was correlated with increasing quartiles of apoC-III levels. MS patients with CAD had significantly higher apoC-III levels than did CAD-free MS patients. The carriership for the -455C variant multiplied the probability of CAD in MS in an allele-specific way and was associated with increased apoC-III and TG levels. Obesity was less frequent in MS carriers of the -455C allele than in MS noncarriers (21.6% vs. 34.8%, P < 0.05). In conclusion, apoC-III-rich lipoprotein metabolism and the APOC3 polymorphism have relevant impacts on the CAD risk of MS patents.