Role of gut microbiome in regulating the effectiveness of metformin in reducing colorectal cancer in type 2 diabetes

Table 3 Summary of alteration of gut microbiota by metformin in patients with type 2 diabetes mellitus that may affect colorectal cancer from 2014 to 2020

Status	Classification	Metformin-related		CRC-related
				Multiple polypoid	Stage 0/pTis	Stage SI/II	Stage SIII/IV
Increased1	Phyla	Bacteroidetes, Actinobacteria, Proteobacteria	Proteobacteria		Firmicutes, Fusobacteria Bacteroidetes	Firmicutes, Fusobacteria Bacteroidetes	Firmicutes, Fusobacteria Bacteroidetes
	Genus	Bacteroides, Streptococcus, Collinsella, Escherichia, Clostridium, Subdoligranulum			F. nucleatum	F. nucleatum	F. nucleatum
	Species	Escherichia spp., Anaerostipes, Blautia, Akkermansia muciniphila	Atopobium parvulum		Solobacterium moorei, Lactobacillus sanfranciscensis, Gemella morbillorum, Actinomyces odontolyticus, Desulfovibrio longreachensis, Phascolarctobacterium succinatutens	Solobacterium moorei, Peptostreptococcus stomatis, Peptostreptococcus anaerobius, Parvimonas micra, Gemella morbillorum	Solobacterium moorei, Peptostreptococcus stomatis, Peptostreptococcus anaerobius, Lactobacillus sanfranciscensis, Parvimonas micra, Gemella morbillorum
Decreased1	Phyla	Firmicutes, Verrucomicrobia
	Genus	Faecalibacterium, Ruminococcus			Bifidobacterium
	Species	Intestinibacter spp., Intestinibacter bartlettii., Alistipes, Oscillibacter, un-Ruminococcaceae
Other axes	Increased1	Lactobacillus (Glucose-SGLT1-Sensing Glucoregulatory Pathway)
		E. coli, Proteobacteria (Host-GUDCA-intestinal FXR axis)
	Decreased1	Bacteroides fragilis (B. fragilis–GUDCA–intestinal FXR axis)

¹Compared with metformin untreated. CRC: Colorectal cancer; T2DM: Type 2 diabetes mellitus.