Furthermore, Tianyi Li et al. (Li et al., 2019) and Yongcheng Ni et al. (Ni et al., 2018) discovered that Firmicutes abundance was positively correlated with blood glucose level and sensitivity to insulin treatment in elderly T2DM patients, while the abundance of anaerobic bacteria (such as Bacteroidetes) was negatively correlated. The gene discussed is INS; the disease is type 2 diabetes mellitus.