TABLE 5.
Microbial intervention in Alzheimer’s disease
| Source | Study design | Sample size (n) | Study population | Microbial strains | Study duration | Key finding(s) |
|---|---|---|---|---|---|---|
| Fecal microbiota transplantation | ||||||
| Dodiya et al., 2019 (322) | Preclinical animal study | 8 to 9 per group per analysis | APPPS1-21 transgenic mouse models. Relevant groups (all AB-treated APPPS1-21 male mice): (i) FMT, APPPS1-21-FMT; (ii) no FMT, vehicle | FMT from age-matched APPPS1-21 male donor mice | 24 days | ABX-mediated perturbations of the microbiota have sex-specific, selective influence on microglial homeostasis and brain Aβ amyloidosis. |
| Fujii et al., 2019 (457) | Preclinical animal study | 7 per group | Mice receiving feces from a human AD patient. Relevant groups (FMT (GF [WT mice]): (i) human-HC-FMT and (ii) human-AD-FMT | Subjects with AD and age-matched HC | 71 wks | Alteration of fecal metabolome and behavior in recipient mice via FMT from Alzheimer’s disease patients. |
| Zhan et al., 2018 (458) | Preclinical animal study | 7 to 8 per group per analysis | Mice receiving feces from SAMP8 mice. Relevant groups: FMT, (i) SAMP8-FMT and (ii) SAMR1-FMT; no FMT, (iii) control and (iv) vehicle (pseudo-GF). | Feces from SAMP8 or SAMR1 mice | 21 days from first FMT | Cognitive dysfunction in SAMP8 mice due to abnormal microbial communities of the gut microbiota. |
| Probiotics | ||||||
| Leblhuber et al., 2018 (459) | Explorative intervention study | 20 participants | 11 males, 9 females, aged 76.7 ± 9.6 yrs of patients with AD | Lactobacillus casei W56, L. lactis W19, L. acidophilus W22, L. paracasei W20, L. plantarum W62, L. salivarius W24, Bifidobacterium lactis W51, B. bifidum W23, and B. lactis W52 | 28 days | Influencing the tryptophan metabolism and the composition of gastrointestinal bacteria. |
| Association between neopterin concentrations and Kyn/Trp contributing to the activation of dendritic cells and/or macrophages. | ||||||
| Den et al., 2020 (460) | Meta-analysis of randomized controlled trials | – | Five investigation comprised of 154 and 143 cases in the probiotics and control group, respectively | – | – | Enhancement of cognition in MCI or AD patients or through probiotic administration, potentially reducing the levels of oxidative and inflammatory biomarkers. |
| Tamtaji et al., 2018 (461) | Randomized, double-blind, controlled trial | 79 participants | 27 patients receiving selenium and probiotic supplementation and 26 patients receiving only selenium as Placebo | Selenium (200 μg/day) in addition to probiotic containing Bifidobacterium bifidum, B. longum, and Lactobacillus acidophilus | 12 wks | Ameliorated function of cognition and some improvement in metabolic profiles through cosupplementation of probiotic and selenium to subjects with AD. |
| Hwang et al., 2019 (462) | Multicenter, randomized, double-blind, controlled trial | 100 participants | 100 individuals with Mild cognitive impairment (MCI) were determined to take placebo (800 mg/day, n = 50) or DW2009 randomly (800 mg/day, n = 50) | Lactobacillus plantarum C29 | 12 wks | Safe administration of DW2009 to improve cognitive function in individuals with MCI. |
| Kobayashi et al., 2019 (463) | Randomized, double-blind, controlled trial | 121 participants | Bifidobacterium breve A1 = 61; placebo = 60 | Sole (Bifidobacterium breve A1) | 12 wks | Considerable difference between placebo groups and B. breve A1 and terms of MMSE total score in the MCI patients. |
| Agahi et al., 2018 (464) | Randomized, double-blind, controlled trial | 48 participants | 23 control group receiving placebo capsules (500 mg maltodextrin); 25 probiotic group receiving capsules containing a mixture of probiotic bacteria | Bifidobacterium bifidum, B. longum, B. lactis, Lactobacillus fermentum, L. plantarum, and L. acidophilus | 12 wks | No significant impact of probiotic administration in subjects with severe AD. |