OBJECTIVEHighland natives adapt well to the hypoxic environment at high altitude (HA). Several genes have been reported to be linked to HA adaptation. Previous studies showed that the endothelial ni- tric oxide synthase (ENOS) G894T polymorphism contributed to the physiology and pathophysiology of hu- mans at HA by regulating the production of NO. In this meta-analysis, we evaluate the association between the ENOS G894T polymorphism and HA adaptation through analyzing the published data.

METHODSWe searched all relevant literature about the ENOS G894T polymorphism and HA adaptation in PubMed, Med- line, and Embase before Step 2015. A random-effects model was applied (Revman 5.0), and study quality was assessed in duplicate. Six studies with 634 HA native cases and 621 low-altitude controls were included in this meta-analysis.

RESULTSFrom the results, we observed that the wild-type allele G was significantly overrepresented in the HA groups (OR = 1.85; 95% Cl, 1.47-2.33; P < 0.0001). In addition, the GG genotype was significantly associated with HA adaptation (OR = 1.99; 95% Cl, 1.54-2.57; P < 0.0001).

CONCLUSIONOur results showed that in 894 G allele carriers, the GG genotype might be a beneficial factor for HA adaptation through enhancing the level of NO. However, more studies were needed to confirm our findings due to the limited sample size.