Association Study Of Hypoxic Gene Single Nucleotide Polymorphisms With The Susceptibility Of Acute Mountain Sickness

BACKGROUND AND OBJECTIVE:Acute mountain sickness (AMS) is a potentially serious affliction to health in immigrants to Tibetan Plateau above 2500 m. There are no effective treatment and prevention strategy of AMS now.Interindividual variation in acclimatization and adaptation to high altitude suggest that the probability of developing AMS depends on genetic and environmental factors. So we speculated that genetic factors may be associated with AMS susceptivity. The research aimed to explore the association between single nucleotide polymorphism(SNP) of hypoxic gene and AMS by comparing the difference of hypoxic gene SNP betwween AMS-susceptible and acclimatized individuals.METHODS:The study enrolled Chinese ethnicity soldiers that join the army for the first time flew to high altitude(3658m,Lhasa) from lowland (505m). AMS was diagnosed on the basis of the AMS Questionnaire. Venous blood was collected and then analyzed by ELISA for VEGF and for extraction of genomic DNA and peripheral arterial oxygen saturation (SpO2) was recorded at low altitude and after 24h-48h at high altitude. By case-control study method, we selected 200 cases of AMS as AMS group and 200 individuals which not developed AMS as control group randomly from these soldiers respectively. The selected subjects were genotyped for the fourteen polymorphisms of the hypoxic genes by primer extension of multiplex products with detection by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectroscopy. These hypoxic genes include vascular endothelial growth factor (VEGF), hypoxia inducible factor 1 alpha subunit (HIF1A) Glutathione S-transferase mu 3 (GSTM3), Glutathione S-transferase pi 1 (GSTP1), Nitric oxide synthase 2 (NOS 2) nitric oxide synthase 3 (NOS 3), AngiotensinⅠ converting enzyme (ACE) and heat shock 70kDa protein 4(HSPA4). The association between SNP and AMS was analysed by genetic statistical software.RESULTS:Morbidity of AMS in the soldiers that join the army for the first time flew to high altitude was 35.68%. SpO2 fell from 98.02±1.69% at 505m to 85.16±5.42% at 3,658 m in subjects with AMS (P＜0.01) and from 98.02±1.40% at 505m to 86.30±4.63% at 3,658 m in subjects without AMS (P＜0.01). SpO2 in subjects with AMS fell signifcantly compared with those wothout AMS at a height of 3658 m(P<0.05). Plasma VEGF concentration decreased at an altitude of 3658 m (16.98±11.61 pg/ml vs 41.03±37.37pg/ml,P<0.01,in group without AMS; 55.58±20.19 pg/ml vs 79.27±27.48 pg/ml, P＜0.01, in group with AMS) compared with the baseline level. The plasma VEGF concentration were significantly higher in group with AMS than in group without AMS at baseline level and at altitude of 3658 m (79.27±27.48 pg/ml vs 41.03±37.37 pg/ml,55.58±20.19 pg/ml vs 16.98±11.61 pg/ml,respectively,P<0.01). All 13 gene locuses exist polymorphisms and were in Hardy-Weinberg equilibrium in both AMS group and controls except for HSPA4 which only have a allelee T. The T allele of rs3025039 of VEGF was significantly associated with AMS(P=0.012, OR=0.62,95% CI 0.43 to 0.90). The rs3025039 of VEGF genotypic frequency distribution differed significantly between AMS and control group (P=0.0297).CT genotype of rs3025039 was significantly associated with AMS (P=0.010, OR=0.56,95% CI 0.36 to 0.87) assuming a additive effect of the T allele; CT+TT genotype of rs3025039 was significantly associated with AMS(P=0.008,OR=0.56,95% CI 0.37 to 0.86) assuming a dominant effect of the T allele. The C allele of rs3025030 of VEGF was significantly associated with AMS (P=0.019,OR=0.64,95% CI 0.44 to 0.93). CC+CG genotype of rs3025030 was significantly associated with AMS (P=0.018, OR=1.66,95% CI 1.10 to 2.45) assuming a dominant effect of the T allele. In terms of NOS2, TT genotype of rs1137933 was significantly associated with AMS (P=0.049,OR=3.045,95% CI 0.96 to 9.68) assuming a additive effect of the T allele. TT genotype of rs1137933 was significantly associated with AMS(P=0.04,OR=3.13,95% CI 0.99 to 9.87) assuming a recessive effect of the T allele. For ACE, CC genotype of rs4309 was significantly associated with AMS (P=0.049, OR=1.83,95% CI 1.00 to 3.34) assuming a recessive effect of the C allele. Genotypic and allelic frequencies of the rs2297518 of NOS2; rs8005745, rs2301108, rs10873142 of HIF1A; rs1695 of GSTP1; rs7483 of GSTM3; rs1799983, rs3918188 and rs7830 of NOS3 and rs35853823 of HSPA4 were not significantly different between AMS and control group (P>0.05). At the haplotype level, a haplotype GC/CT frequencies consisting of rs3025030 (G/C) and rs3025039 (C/T) of VEGF was significantly differences between the AMS group and control group (P=0.029).There were no statistically significant differences in the haplotype AGT/TAC/AGC frequencies consisting of rs8005745,rs2301108 and 10873142 of HIF1A between the AMS group and control group at high altitude (P>0.05).CONCLUSIONS:1,Morbidity of AMS in the soldiers that join the army for the first time flew to high altitude was 35.68%; 2,SpO2 and VEGF is down-regulated significantly in AMS group and control at athigh altitude, but VEGF level of AMS group still higher significantly than control not only at high altitude but also at sea level; 3,Polymorphism of rs3025039 and rs3025030 in VEGF gene were significantly associated with AMS. Individuals carrying the allele T of rs3025039 and C of rs3025030 significantly decrease the risk of AMS in a Chinese population. 4,Polymorphic loci of rs1137933 in NOS2 and rs4309 in ACE were significantly associated with AMS. Individuals carrying the genotypic TT of rs1137933and genotypic CC rs4309 significantly increase the risk of AMS.5. This study did not provide evidence that SNPs of the rs2297518 of NOS2, rsl799983, rs3918188, rs7830 of NOS3, rsl695 of GSTP1, rs7483 of GSTM3, rs8005745, rs2301108, rs10873142 of HIF1A and rs35853823 of HSPA4 gene are associated with susceptibility to AMS in a Chinese population.