TABLE 2.

Association between the gut microbiota and T2D¹

Study (reference)	Description	Results
Karlsson et al. 2013 (37)	Swedish elderly women with T2D (n = 53), impaired glucose tolerance (n = 49), or normal glucose tolerance (n = 43); metagenomics	MGSs most significantly depleted in T2D included Desulfurispirillum indicum, Bacteroides intestinalis, Clostridium thermocellum, C. botulinum, C. beijerinckii, F. prausnitzii, Roseburia, and Eubacterium species. MGSs most significantly enriched in T2D included Lactobacillus gasseri, L. salivarius, L. antri, L. oris, L. crispatus, L. reuteri, Clostridium clostridioforme, and Streptococcus mutans.
Lactobacillus species positively correlated with FBG and HbA1c. Clostridium species negatively correlated with FBG, HbA1c, insulin, C-peptide, and TGs and positively with adiponectin and HDL cholesterol. B. intestinalis negatively correlated with insulin and waist circumference.
Qin et al. 2012 (14)	Chinese adults with T2D (n = 171) and healthy controls (n = 174); metagenomics	Bacterial gene markers enriched in controls largely assigned to butyrate-producing species within Faecalibacterium, Roseburia, and Eubacterium, but also to Haemophilus parainfluenzae.
		Bacterial gene markers enriched in T2D belonged to mucin degrading (Akkermansia muciniphila) and potential pathogenic species such as Bacteroides caccae, Clostridium hathewayi, Clostridium ramosum, Clostridium symbiosum, Eggerthella lenta, and Escherichia coli.
No differences in microbial diversity between patients and controls.
Larsen et al. 2010 (114)	Danish adults with T2D (n = 18) and healthy controls (n = 18); pyrosequencing	Firmicutes including Clostrida reduced in T2D.
		Betaproteobacteria enriched in T2D and positively correlated with FBG. Roseburia species marginally negatively correlated with FBG.
		Lactobacillus species marginally positively correlated with FBG.
No difference in bacterial diversity between groups.

¹All studies have a case-control design, have used gene sequencing to characterize the microbiota, and are based on analyses of stool samples. Description is given as population (n); technique. FBG, fasting blood glucose; HbA1c, glycated hemoglobin; MGS, metagenomic species; T2D, type 2 diabetes.