Association of apoE gene expression and its gene polymorphism with nephrotic syndrome susceptibility: a meta-analysis of experimental and human studies

Apolipoprotein E (apoE) is a major protein in the lipoprotein transport system that plays a well established role in lipids metabolism. apoE gene contains three potential alleles: epsilon 2, epsilon 3 and epsilon 4, forming six genotypes: epsilon 2 epsilon 2, epsilon 2 epsilon 3, epsilon 2 epsilon 4, epsilon 3 epsilon 3, epsilon 3 epsilon 3 and epsilon 4 epsilon 4. The disorder of lipids metabolism is an important feature for nephrotic syndrome (NS). There were some investigations reporting that apoE and its gene polymorphism was associated with NS susceptibility. However, the mechanism was unclear and the association was still controversial. This meta-analysis was performed to evaluate the association between apoE and NS risk in experimental and human studies. A predefined literature search and selection of eligible relevant studies were performed to collect the data from electronic databases, and eligible investigations were synthesized using meta-analysis method. In experimental models, twelve comparisons were included and a definitely positive association was observed between apoE protein expression and NS susceptibility (WMD = 1.88, P < 0.00001). However, in human, there was only two studies included for meta-analysis and a positive association between apoE protein expression and NS susceptibility wasn't found (OR = 108.10, P = 0.32). Interestingly, epsilon 3 epsilon 3, epsilon 3 epsilon 4, epsilon 3 and epsilon 4 were associated with NS susceptibility (epsilon 3 epsilon 3: OR = 0.56, P = 0.002; epsilon 3 epsilon 4: OR = 1.91, P = 0.02; epsilon 3: OR = 0.61, P = 0.001; epsilon 4: OR = 1.85, P = 0.009). In conclusion, the apoE gene expression was associated with the NS susceptibility in experimental studies, and the apoE epsilon 3 epsilon 3, epsilon 3 epsilon 4, epsilon 3 and epsilon 4 were associated with the onset of NS in human studies. This study supported that the disorder of apoE was one of the possible causes for NS risk. However, more studies should be performed to investigate this relationship in the future.