2.2. Experimental design
SE, MR, T2DM
In an effort to explore the cause-and-effect link between intestinal microflora and T2DM, a bi-sample Mendelian Randomization study was implemented, leveraging data from the MiBioGen consortium and the compiled dataset from GWAS. The instrumental variables (IVs) were initially subjected to a screening process. For an IV to be utilized in MR, it had to meet three primary assumptions: (1) Correlation: the SNPs were robustly linked to exposure; (2) Exclusivity: the SNPs did not correlate with the outcome; (3) Independence: the SNPs showed no association with confounding factors (where in β denotes the effect size of the SNP on exposure and SE represents β's standard error.An F statistic >10 was considered indicative of insignificant weak instrumental bias. Subsequently, data were extracted from both databases and compiled such that the impact values for exposure and outcome corresponded to the same effect allele. The identified SNPs linked with each genus underwent analysis via various statistical methods to deduce causal associations between gut flora and T2DM across the 6 families and 14 genera. Finally, to fulfill MR assumptions (2) and (3), SNPs directly linked to confounding factors and outcomes were excluded using the phenoscanner website (The flow chart outlines the study design and the process of Mendelian randomization (MR) analysis. SNP stands for single nucleotide polymorphism, which serves as the instrumental variables. IVW represents inverse-variance weighted, a method employed in the analysis.