Methyltetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism, and its single nucleotide polymorphism (SNP) site C677T may be associated with gastrointestinal cancer. However, the relationship between MTHFR C677T polymorphism and gastrointestinal tumor markers carcinoma embryonic antigen (CEA), carbohydrate antigen 199 (CA199) and carbohydrate antigen 724 (CA724) in Helicobacter pylori (H. pylori) infection is not specified. This study aims to identify the association between MTHFR C677T polymorphism and gastrointestinal tumor markers (CEA, CA199 and CA724) in H. pylori infection. The relationship between MTHFR C677T polymorphism and gastrointestinal tumor markers in 58 patients with H. pylori infection and 94 non-infected patients was studied. We found that TT genotype was a susceptibility factor of H. pylori infection, which was also associated with increased CEA and CA724 levels. Moreover, there was a negative additive interaction between MTHFR gene C677T polymorphism and CEA levels in H.pylori infection. Meanwhile, there were significant differences in CEA levels between MTHFR C677T polymorphism and H.pylori infection. The presence of T allele led to a decrease in CEA levels when ¹³C urea breath test (¹³C-UBT) was positive, while the presence of T allele led to an increase in CEA levels when ¹³C-UBT was negative. Therefore, we suggest that healthy people should take MTHFR C677T polymorphism screening, combined with ¹³C-UBT and gastrointestinal tumor markers detection, which can screen out the susceptible population of H. pylori, and help to detect gastrointestinal cancer in the early stage.

甲基四氢叶酸还原酶（MTHFR）是叶酸代谢的关键酶，其单核苷酸多态性（SNP）位点C677T可能与胃肠道癌症有关。然而，MTHFR C677T多态性与幽门螺杆菌（H. pylori）胃肠道肿瘤标志物癌胚抗原（CEA）、碳水化合物抗原199（CA199）和碳水化合物抗原724（CA724）的关系) 感染未指定。本研究旨在确定幽门螺杆菌感染中 MTHFR C677T 多态性与胃肠道肿瘤标志物（CEA、CA199 和 CA724）之间的关联。研究了 58 例 H. pylori 感染患者和 94 例未感染患者的 MTHFR C677T 多态性与胃肠道肿瘤标志物的关系。我们发现 TT 基因型是幽门螺杆菌感染的易感因素，这也与 CEA 和 CA724 水平升高有关。此外，在H.pylori感染中，MTHFR基因 C677T 多态性与 CEA 水平之间存在负相加相互作用。同时，MTHFR C677T多态性与H.pylori的CEA水平存在显着差异感染。当¹³ C 尿素呼气试验（¹³ C-UBT）为阳性时，T 等位基因的存在导致 CEA 水平降低，而当¹³ C-UBT 为阴性时，T 等位基因的存在导致 CEA 水平升高。因此，我们建议健康人群进行MTHFR C677T多态性筛查，结合¹³ C-UBT和胃肠道肿瘤标志物检测，可以筛查出幽门螺杆菌的易感人群，有助于早期发现胃肠道肿瘤。