OBJECTIVES: The gut microbiota plays a crucial role in the pathophysiology of various types of diabetes. However, the causal relationship between them has yet to be systematically elucidated. This study aims to explore the potential causal associations between gut microbiota and diabetes using a two-sample Mendelian randomization (MR) analysis, based on multiple taxonomic levels. METHODS: Eligible instrumental variables were extracted from the selected genome-wide association study (GWAS) data on gut microbiota. These were combined with GWAS datasets on type 1 diabetes (T1D), type 2 diabetes (T2D), and gestational diabetes mellitus (GDM) to conduct forward MR analysis, sensitivity analysis, reverse MR analysis, and validation of significant estimates. Microbial taxa with causal effects on T1D, T2D, and GDM were identified based on a comprehensive assessment of all analytical stages. RESULTS: A total of 2 179, 2 176, and 2 166 single nucleotide polymorphisms (SNP) were included in the MR analyses for gut microbiota with T1D, T2D, and GDM, respectively. MR results indicated causal associations between: Six microbial taxa (Eggerthella, Lachnospira, Bacillales, Desulfovibrionales, Parasutterella, and Turicibacter) and T1D; 9 microbial taxa (Verrucomicrobia, Deltaproteobacteria, Actinomycetales, Desulfovibrionale, Actinomycetaceae, Desulfovibrionaceae, Actinomyces, Alcaligenaceae, and Lachnospiraceae NC2004 group) and T2D; 10 microbial taxa (Betaproteobacteria, Coprobacter, Ruminococcus2, Tenericutes, Clostridia, Methanobacteria, Mollicutes, Methanobacteriales, Methanobacteriaceae, and Methanobrevibacter) and GDM. CONCLUSIONS This study identified specific gut microbial taxa that may significantly increase or decrease the risk of developing diabetes. Some findings were fully replicated in independent validation datasets. However, the underlying biological mechanisms of these causal relationships warrant further investigation through mechanistic studies and population-based research.
Gastrointestinal Microbiome/genetics* ; Humans ; Mendelian Randomization Analysis ; Genome-Wide Association Study ; Diabetes Mellitus, Type 2/genetics* ; Diabetes Mellitus, Type 1/genetics* ; Female ; Polymorphism, Single Nucleotide ; Diabetes, Gestational/genetics* ; Pregnancy

Objective:To explore the association of human betaine-homocysteine methyltransferase ( BHMT) and BHMT2 gene polymorphisms with non-syndromic congenital heart disease (CHD). Methods:A hospital-based case-control study was conducted, in which children with CHD who attended Hunan Children′s Hospital from January 2018 to May 2019 were enrolled as the case group, and children without any congenital deformity who attended the hospital during the same period were enrolled as the control group on a 1∶1 basis. A self-administered questionnaire survey was performed to collect information about the study subjects and their mothers, and then venous blood samples were collected from the subjects to detect BHMT and BHMT2 gene polymorphisms. Logistic regression analyses were used to evaluate the association of BHMT and BHMT2 gene polymorphisms and their haplotypes with CHD. Crossover analyses and logistic regression were used to explore the gene-gene and gene-environment interactions. Results:The case and control group both enrolled 620 children. The multivariate logistic regression showed that BHMT gene polymorphisms at rs3733890 (AA vs. GG: OR=3.476, Q FDR<0.001; GA vs. GG: OR=1.525, Q FDR=0.036), at rs1915706 (CC vs. TT: OR=3.464, Q FDR<0.001) and at rs1316753 (GG vs. CC: OR=1.875, Q FDR=0.020) increased the risk of CHD. Children with haplotype of A-G-A had an increased risk of CHD ( OR=1.468, 95% CI: 1.222-1.762). Interaction analysis showed that a statistically significant positive interaction between rs3733890 and rs1915706 on both additive ( RERI=0.628, 95% CI: 0.298-0.958) and multiplicative ( OR=3.754, 95% CI: 1.875-7.519) scales. Gene-environment interactions were found between the BHMT gene with secondhand smoke exposure before pregnancy and in early pregnancy, tea consumption before pregnancy and in early pregnancy, alcohol consumption before pregnancy, and folic acid supplementation before or during pregnancy. Conclusion:BHMT gene rs3733890, rs1915706 and rs1316753 polymorphisms may be associated with the risk of CHD. In addition, there is an association of cooperative interaction between rs3733890 and rs1915706 on both additive and multiplicative scales with the risk of CHD, and the BHMT gene interacts with multiple environmental factors.

Objective:To explore the association of human betaine-homocysteine methyltransferase ( BHMT) and BHMT2 gene polymorphisms with non-syndromic congenital heart disease (CHD). Methods:A hospital-based case-control study was conducted, in which children with CHD who attended Hunan Children′s Hospital from January 2018 to May 2019 were enrolled as the case group, and children without any congenital deformity who attended the hospital during the same period were enrolled as the control group on a 1∶1 basis. A self-administered questionnaire survey was performed to collect information about the study subjects and their mothers, and then venous blood samples were collected from the subjects to detect BHMT and BHMT2 gene polymorphisms. Logistic regression analyses were used to evaluate the association of BHMT and BHMT2 gene polymorphisms and their haplotypes with CHD. Crossover analyses and logistic regression were used to explore the gene-gene and gene-environment interactions. Results:The case and control group both enrolled 620 children. The multivariate logistic regression showed that BHMT gene polymorphisms at rs3733890 (AA vs. GG: OR=3.476, Q FDR<0.001; GA vs. GG: OR=1.525, Q FDR=0.036), at rs1915706 (CC vs. TT: OR=3.464, Q FDR<0.001) and at rs1316753 (GG vs. CC: OR=1.875, Q FDR=0.020) increased the risk of CHD. Children with haplotype of A-G-A had an increased risk of CHD ( OR=1.468, 95% CI: 1.222-1.762). Interaction analysis showed that a statistically significant positive interaction between rs3733890 and rs1915706 on both additive ( RERI=0.628, 95% CI: 0.298-0.958) and multiplicative ( OR=3.754, 95% CI: 1.875-7.519) scales. Gene-environment interactions were found between the BHMT gene with secondhand smoke exposure before pregnancy and in early pregnancy, tea consumption before pregnancy and in early pregnancy, alcohol consumption before pregnancy, and folic acid supplementation before or during pregnancy. Conclusion:BHMT gene rs3733890, rs1915706 and rs1316753 polymorphisms may be associated with the risk of CHD. In addition, there is an association of cooperative interaction between rs3733890 and rs1915706 on both additive and multiplicative scales with the risk of CHD, and the BHMT gene interacts with multiple environmental factors.