Association Between Environmental Cd Exposure And Mitochondrial MtDNA Gene Polymorphisms And Their Interactions With The Risk Of Early Embryonic Arrest

Research background Early embryonic arrest（EEA）seriously affects the IVF outcome of infertile women.Therefore,it is of great clinical significance to explore the risk factors for EEA Objective Based on a case-control study,this study analyzed the correlation of blood cadmium（Cd）levels,mitochondrial gene polymorphisms in D-loop region and their interactions with the risk of EEA in infertile women undergoing IVF cycles,and further explored the adverse effects of the above two risk factors on relevant indicators of oogenesis and embryonic development,so as to explain the potential reasons behind the above association.Method A case-control study design was conducted in the present study.74 infertile women with EEA（case group,a total of 123 IVF fresh cycles）and 157 age and BMI matched infertile women（control group,a total of 180 IVF fresh cycles,having at least70% high-quality blastocysts in each fresh cycle）who adopted clinical treatment at the reproductive center of the First Affiliated Hospital of Anhui Medical University from June2017 to March 2020 were included.The demographic and clinical data of 231 infertile women were collected via the hospital network treatment system.ICPMS was used to detect the concentrations of Cd in bloods collected on the day of egg retrieval in order to evaluate their environmental Cd exposure levels;PCR amplification and sequencing were conducted to screen the polymorphic sites of mt DNA gene in D-loop region at the same time.The generalized estimating equation（GEE）model was used to assess the association between environmental Cd exposure level,mitochondrial DNA D-loop gene polymorphism and their interactions and EEA risk;the excel calculator compiled by Andersson et al was used to calculate the estimated values of RERI,AP and S and their 95% confidence intervals.The impacts of Cd exposure level and mitochondrial DNA D-loop gene polymorphism on relevant indicators of oogenesis and embryonic development were alsoevaluated by GEE model.Result:The blood concentration of Cd（geometric mean: 2.06 μg/L）at the case group was significantly higher than that at the control group（geometric mean: 1.69 μg/L）（P < 0.001）.Compared with women at the low Cd concentration group（≤1.62 μg/L）,women in the high concentration group（> 1.62 μ g/L）had a significantly increased risk of EEA,and the adjusted OR（95% CI）was 2.84（1.42,5.70）The relationship between mt DNA polymorphisms in D-loop region depended on the polymorphic sites.Among 286 gene sites with polymorphisms detected,there were 27 sites with the frequency of minor alleles >10%,and only two gene polymorphisms were statistically associated with EEA（T16519T vs.T16519 C,and A16182 A vs.A16182C）.Compared with infertile women with wild-type16519 gene（T16519T）,the adjusted OR（95% CI）of EEA risk of women with variant type（T16519C）was 3.11（1.70,5.72）,while for 16182 gene,the adjusted OR（95% CI）of EEA risk of infertile women with variant type（A16182C）was 0.14（0.04,0.50）when compared with infertile women with wild-type（A16182A）.In terms of interaction,the adjusted OR（95% CI）for EEA risk of women at T16519 C ＆ high Cd exposure group was 48.04（5.30,435.24）,when compared with women at T16519 T ＆ low Cd exposure group,and the estimated values of RERI,AP and S and their 95% CI were-5.20（-44.96,34.56）,-0.11（-0.94,0.72）,0.90（0.42,1.93）,respectively,which suggested that there was no additive interaction;compared with women at the low Cd exposure level ＆ wild-type of 16182 gene（A16182A）group,the adjusted OR（95% CI）for EEA risk of women at high Cd exposure＆ 16182 variant gene（A16182C）type was 0.09（0.004,1.84）,and the corresponding estimates and 95% CIs of RERI,AP and S were-6.16（-12.73,0.41）,-71.12（-297.98,155.73）and-0.17,respectively,suggesting that there was no additive interaction.Cd exposure and mt DNA 16519 gene and 16182 gene had significant effects on oogenesis and embryonic development.Conclusions In the present study,high level Cd exposure was related with the increased risk of EEA;polymorphisms of only two mt DNA gene sites（16519 gene and 16182 gene）were significantly associated with EEA: variant type of 16519 gene was related with increased risk of EEA,while variant type of 16182 gene was related with decreased risk of EEA,when compared to their respective wild type;women with variant type of 16519 gene＆ high Cd exposure had more higher risk of EEA,while women with variant type of 16182 gene ＆ high Cd exposure did not associate with the risk for EEA significantly any more.In addition,these relationships might originate from the impact of Cd exposure or polymorphisms of 16519 and 16182 gene on the oogenesis and embryonic development.Further studies are warranted to elucidate the potential mechanisms of these associations.