A case-control study of apoA5 −1131T→C polymorphism that examines the role of triglyceride levels in diabetic nephropathy

Patients with diabetic nephropathy (DN) have increased plasma fasting triglyceride (TG) levels, and most prospective studies report that elevated TG precedes DN. TG-rich lipoprotein particles might promote progression of DN. To test the hypothesis that elevated TG levels contribute to the development of DN, one may examine whether a polymorphism strongly associated with TG levels affects DN risk. The apolipoprotein A5 (apoA5) −1131T→C polymorphism has a large effect on the TG level, and all three genotypes are relatively common in East Asians. Therefore, we sought to examine the association of this polymorphism with DN. We genotyped the apoA5 −1131T→C polymorphism in a case-control study involving 367 Chinese Type 2 diabetes patients with DN and 382 without DN, as well as 198 subjects without diabetes. Mean fasting TG levels were higher in CC than in TT carriers by 41%, 54%, and 62% in each of the three subject groups, respectively. However, the genotype distributions did not differ between patients with and without nephropathy (P=.69). Therefore, these results weigh against the hypothesis that high fasting TG per se causes DN. The strong association between TG level and DN may be due to a factor that is usually closely linked to TG level but that is not affected by the apoA5 polymorphism.