Table 4.
Use of probiotics and FMT to modify the GM in AD and related findings.
| Intervention | Study | Findings | Reference |
|---|---|---|---|
| Lactobacillus plantarum C29-fermented soybean (DW2009) | Human (n = 100) | Administration of DW2009 enhanced the serum BDNF levels that may significantly improve cognitive and memory functions. | [141] |
| VSL#3 | APPNL-G-F mice | Increased in the serum SCFA (lactate, acetate, butyrate, propionate, and isobutyrate). Both serum and brain levels of acetate and lactate in mice correlated with increased expression of the neuronal activity marker. | [142] |
| SLAB51 | 3xTg-AD mice | Oral administration ameliorated glucose uptake by restoring the brain expression levels of GLUT1 and GLUT3, and IGF receptor β, in accordance with reduced phosphorylation of AMPK and Akt. Additionally, decreased phosphorylated tau aggregates and increased glycated hemoglobin and the accumulation of advanced glycation end products in mice and improved memory. | [143] |
| Bifidobacterium longum (NK46) | 5xFAD-transgenic mice | Oral administration ameliorated GM composition, decreased blood and fecal LPS levels, increased tight junction protein expression in the colon and suppressed TNF-α expression and NF-κB activation. Additionally, decreased the cognitive decline, β/γ-secretases, Aβ accumulation, and caspase-3 expression in the hippocampus of mice. | [144] |
| Clostridium butyricum | APP/PS1 transgenic mice | Treatment restored the GM impairment and butyrate. It prevented Aβ accumulation, cognitive impairment, production of TNF-α, IL-1β, and microglia activation. | [145] |
| Lactobacillus lactis strain carrying one plasmid (pExu) | 3xTg-AD mice | Oral administration ameliorated memory, decreased levels of Aβ peptides, modulated ubiquitin-proteasome system and autophagy, and reduced neuronal inflammatory and oxidative processes. | [135] |
| Bifidobacterium breve A1 (MCC1274) | Human (n = 79) | Probiotic treatment improved the visuospatial/constructional, immediate memory, and delayed memory. | [146] |
| 5 Lactobacillus and 5 Enterococcus strains | C57BL/6J male mice | Reduction in leaky gut by increasing tight junctions, and decreasing inflammation. This study concluded that probiotics could prevent or treat aging-related leaky gut and inflammation that leads to AD. | [147] |
| Lactobacillus plantarum ATCC 8014 | APP/PS1 mice | Decreased Αβ levels in the hippocampus, ameliorated cognitive deterioration and protected neuronal integrity and plasticity | [148] |
| Bacteroides thetaiotaomicron | APP/PS1TG mice | Decreased Αβ levels in the hippocampus and significantly improved memory function. | [149] |
| Multispecies probiotics | Human (n = 23) | Decreased the inflammation-causing bacteria and fecal zonulin concentrations, and enhanced serum kynurenine concentrations. | [150] |
| FMT | ADLPAPT transgenic mice | Mice showed reductions in chronic intestinal and systemic inflammation and loss of epithelial barrier integrity. FMT ameliorated the formation of glial reactivity, neurofibrillary tangles, Aβ plaques, and cognitive impairment. Additionally, abnormalities in intestinal macrophage activity were also reversed. | [84] |
| FMT | APPswe/PSEN1dE9 transgenic mice | Increase in synaptic plasticity, synapsin I expression, decrease in Aβ40–42, tau protein phosphorylation, COX-2 and CD11b levels were observed after FMT. It also restored GM impairment and short-chain fatty acids levels. | [139] |
SCFA: short-chain fatty acids, BDNF: brain-derived neurotrophic factor, AMPK: adenosine monophosphate-activated protein kinase, GLUT: glucose transporter, IGF: insulin-like growth factor, Akt: protein-kinase B, GM: gut microbiota, TNF-α: tumor necrosis factor alpha, LPS: lipopolysaccharides, NF-κB: nuclear factor kappa B, IL: interleukin-1β, FMT: fecal microbiota transplantation, COX-2: cyclooxygenase-2, CD11b: cluster of differentiation molecule 11B, n:number of total subjects in the study but the column of findings is only showing the data of diseased ones. VSL#3: a probiotic formulation (commercially available) having 8 bacterial strains: 4 strains of Lactobacillus (L. delbrueckii subspecies bulgaricus, L. casei, Lactobacillus plantarum, and L. acidophilus), 3 strains of Bifidobacterium (B. infantis, B. breve, and B. longum), and strain of Streptococcus (S. salivarius subspecies thermophilus) [151]. SLAB51: a probiotic mixture having 8 bacterial strains L. brevis DSM 27961, L. acidophilus DSM 32241, L. helveticus DSM 32242, L. paracasei DSM 32243, L. plantarum DSM 32244, B. lactis DSM 32246, B. lactis DSM 32247, S. thermophilus DSM 32,245 [143]. Multispecies probiotics: two types of capsules each containing 3 bacteria either L. fermentum, L. plantarum, and B. lactis, or L. acidophilus, B. bifidum, and B. longum.