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背景与目的:蛋氨酸合成酶(Methionine synthase,MS)以同型半胱氨酸(Homocysteine,HC)为底物合成蛋氨酸(Methionine,Met);继而合成S_腺苷蛋氨酸(S_adenosylmethionine,SAM),为DNA甲基化提供甲基;维生素B12(B12)作为MS的辅酶亦可影响Met的合成。我们研究旨在探讨Met和B12缺乏对人类BRCA1基因突变淋巴细胞株基因组稳定性的影响。材料与方法:以Met和B12生理浓度为依据(分别约25μmol/L和150pmol/L),实验设置了15μmol/L和50μmol/L的Met分别与100、300、600、800、1200pmol/LB12组合的测试组,常规RPMI1640培养基作为对照(其Met、B12浓度分别为101μmol/L和3690pm/L),培养携带BRCA1突变的乳腺癌患者淋巴细胞株9d,利用细胞质阻断微核分析(Cytokinesis_blockmicronucleusassay,CBMN),评价B12与Met缺乏对该细胞株遗传稳定性的影响。结果:①在15μmol/LMet与B12的所有组合测试组中,双核细胞微核率(Micronucleatedbinucleatedcell,MNBN)均高于Met为50μmol/L、B12在600pmol/L以上的所有组合,除B12在600pmol/L以上的测试组外,其他各组之间MNBN差异均有统计学意义(P<0.05～0.001);②当50μmol/LMet与B12组合时,MNBN降幅尤为显著,当B12浓度在600pmol/L以下时各组间MNBN差异有统计学意义,B12浓度为600pmol/L时MNBN降至最低,与800、1200pmol/L以及RPMI培养基中的MNBN差异无统计学意义。结论:结果提示B12、Met在600pmol/L～50μmol/L组合时可维持受试细胞株遗传稳定性的最佳状态。这二种微量营养素的适量补充有可能通过叶酸代谢对带有BRCA1突变的个体遗传物质形成一定的保护作用。鉴于研究提出的B12(600pmol/L),Met(50μmol/L)浓度高于人体血浆正常生理浓度,有必要以提高基因组稳定性为目标,进一步评价提高这两种微量营养素的摄取量并调整其比例的意义。
BACKGROUND & AIM: Methionine synthase (MS) synthesizes methionine (Met) with homocysteine (HC) as substrate and then synthesizes S_adenosylmethionine (SAM) Methylation provides methyl; Vitamin B12 (B12) as a coenzyme for MS can also affect Met synthesis. Our study aimed to investigate the effects of Met and B12 deficiency on the genomic stability of human BRCA1-mutant lymphocyte strains. MATERIALS AND METHODS: Based on Met and B12 physiological concentrations (about 25 μmol / L and 150 pmol / L respectively), 15 μmol / L and 50 μmol / L Met were set up in combination with 100, 300, 600, 800 and 1200 pmol / The lymphocytes of breast cancer patients with BRCA1 mutation were cultured for 9d in the conventional RPMI1640 medium (Met, B12 concentrations of 101μmol / L and 3690pm / L respectively). Cytokinesis_blockmicronucleusassay CBMN) to evaluate the effect of B12 and Met deficiency on the genetic stability of this cell line. RESULTS: In all the combination groups of 15μmol / LMet and B12, the micronucleated nucleated cells (MNBN) were all higher than those with 50μmol / L Met and 600μmol / L B12. (P <0.05 ~ 0.001). ② When the combination of 50μmol / LMet and B12, the decrease of MNBN was especially significant. When the concentration of B12 was below 600pmol / L, the difference of MNBN between the other groups was statistically significant There was a significant difference in MNBN between groups. MNBN was lowest when B12 concentration was 600 pmol / L, but not with MNBN at 800, 1200 pmol / L and RPMI medium. Conclusion: The results suggest that B12 and Met can maintain the best genetic stability of the tested cell line when the combination of 600 pmol / L ~ 50 μmol / L. The proper amount of supplementation of these two micronutrients may have some protective effect on the genetic material of individuals with the BRCA1 mutation through folic acid metabolism. In view of the proposed B12 (600pmol / L) and Met (50μmol / L) concentration higher than the normal physiological concentration of human plasma, it is necessary to improve the stability of the genome as the goal, further evaluation of raising the intake of these two micronutrients and adjust The significance of the ratio.