title: Meta-analysis of association between the Pro12Ala polymorphism of the peroxisome proliferator-activated receptor-γ2 gene and diabetic retinopathy in Caucasians and Asians.
abstract: OBJECTIVE
  The Pro12Ala polymorphism of the peroxisome proliferator-activated receptor-γ2 (PPARγ2) gene is reported to be associated with diabetes. However, the gene's association with diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM) has been investigated in numerous epidemiologic studies with controversial results. This meta-analysis aimed to collectively assess the association of the Pro12Ala polymorphism with DR in T2DM.
  
  
  METHODS
  An electronic literature search was conducted on PubMed, ISI Web of Knowledge, EMBASE, and the China National Knowledge Internet. A dominant model [(Pro/Ala +Ala/Ala) versus Pro/Pro] was used to ensure adequate statistical power. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using the fixed effect model. Potential sources of heterogeneity and bias were explored.
  
  
  RESULTS
  This meta-analysis included genotype data from 2,720 cases with DR and 2,450 controls free of DR from eight eligible publications. The results showed the Ala allele had a protective effect on DR in T2DM (OR=0.81; 95% CI: 0.68-0.98, p=0.03). There was no significant evidence against homogeneity (I(2)=46%, P(heterogeneity)=0.07). The sensitivity analysis showed a robust association of the Pro12Ala polymorphism with DR in T2DM after a study involving Caucasians that presented a big effect on heterogeneity (OR=0.75; 95% CI: 0.62-0.91, p=0.003) was excluded. Possible ethnic differences in the association of the Pro12Ala single nucleotide polymorphism and DR were demonstrated; a significant association was illustrated in the Caucasian subgroup (OR=0.74; 95% CI: 0.59-0.94, p=0.01) but was not found in the Asian subgroup (OR=0.77; 95% CI: 0.55-1.07, p=0.12). No publication bias was observed.
  
  
  CONCLUSIONS
  This meta-analysis suggested a significant association exists between the Pro12Ala polymorphism and DR in T2DM with ethnic differences. The Ala allele had a significant protective effect against DR in T2DM.
authors.affiliation: Department of Ophthalmology, Qilu Hospital of Shandong University, Jinan, China.
authors.forename: Jinlan
authors.initials: J
authors.lastname: Ma
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Fang
authors.initials: F
authors.lastname: Zhou
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Xu
authors.forename: Gang
authors.initials: G
authors.lastname: Guo
authors.forename: Yi
authors.initials: Y
authors.lastname: Qu
mesh_terms: D000368:Aged; D000483:Alleles; D001208:Asia / Q000453:epidemiology; D044466:Asian People; D016206:Databases, Bibliographic; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000208:ethnology* / Q000235:genetics*; D003930:Diabetic Retinopathy / Q000150:complications / Q000208:ethnology* / Q000235:genetics*; D005060:Europe / Q000453:epidemiology; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D047495:PPAR gamma / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors; D014481:United States / Q000453:epidemiology; D044465:White People
chemical_list: D047495:PPAR gamma