Table 1.
Type 1 Diabetes and the Microbiota: Human Studies.
| Study Design | Study Sample | Main Findings | Ref. |
|---|---|---|---|
| Prospective | In total, 33 genetically predisposed infants | Microbial diversity in T1DM progressors in the time window between seroconversion and T1DM onset and inflammation-favoring organisms | [71] |
| Case Control | In total, 18 Ab (+) vs. 18 Ab (-) children matched for HLA | Ab-positive children: microbial diversity, Bacteroidetes (Bacteroides and Prevotella), Bifidobacterium species, short-chain fatty acid (SCFA)-producing bacteria | [72] |
| Case Control (longitudinal data) | In total, four HLA-matched case (Ab+) –control (Ab-) pairs (three time points) | Bacteroidetes (Bacteroidales) and Firmicutes (Clostriales) in cases vs. controls at all time points. Children progressing T1DM: microbial diversity | [73] |
| Case Control | In total, 28 newly diagnosed type 1 diabetes (T1DM) (average duration 4.8 years) vs. 27 age-matched control children | In children < 3 years: Bacteroidetes in cases and Clostridium clusters IV and XIVa in controls | [74] |
| Case Control | In total, 16 T1DM vs. 16 healthy children | Cases: Bacteroidetes, Firmicutes and Actinobacteria | [75] |
| Case Control (longitudinal data) | In total, 29 Ab (+) cases vs. 47 Ab (-) healthy controls | B. dorei and B. vulgatus in cases prior to seroconversion | [76] |
| Prospective | In total, 783 genetically predisposed children | SCFA-producing bacteria genes in children who seroconverted or developed T1DM | [77] |
| Prospective | In total, 19 Ab (+) and 21 Ab (-) children | Bacteroides Akkermansia SCFA-producing bacteria genes. A functional association between diet (early introduction of non-milk diet), gut microbiome (Bacteroides), metagenomic changes (genes for the production of butyrate) and development of islet Ab | [78] |
| Case Control | In total, 33 recent-onset T1DM, 17 Ab (+), 29 Ab (-), and 22 healthy subjects | T1DM: microbial taxa associated with host proteins involved in maintaining the function of the mucous barrier, microvilli adhesion, and exocrine pancreas | [79] |
| Cohort Study | In total, 403 children (age = 1 year) | Genetic risk for developing T1DM autoimmunity is associated with distinct changes in the gut microbiome | [80] |
| RCT | T1DM children (8–17 years) randomized to prebiotic oligofructose-enriched inulin (n = 17) or placebo (n = 21) for 12 weeks | At 3 months, C-peptide was significantly higher in the group that received prebiotics | [81] |
| Prospective Cohort | In total, 7473 children (4–10 years) | Early probiotic supplementation (at the age of 0–27 days) associated with a decreased risk of islet autoimmunity in children with the HLADR3/4 genotype | [82] |
T1DM: type 1 diabetes, RCT: randomized control trial, HLA: human leukocyte antigen, Ab (+): islet auto-antibodies positive, and Ab (-): islet auto-antibodies negative.