The gene and protein expressions of MAFA, which is a marker of β-cell maturation, and MAFB, which is a marker of β-cell dedifferentiation, were significantly downregulated in the islets of rats with pre-DM following both A. muciniphila treatment and dietary intervention, particularly in those of the CD + AKK and HFD + AKK groups (p < 0.01) (Fig. 2H-J). Here, MAFB is linked to diabetes mellitus.