Experimental studies showing cognitive symptoms improvement induced by probiotic interventions in PD.
| Study (year) | Probiotic(s) | Duration | Dose/Presentation | Cognitive outcome |
|---|---|---|---|---|
| Human studies | ||||
| Sun et al. (2022) [82] | Bifidobacterium animalis subsp. lactis Probio-M8 (Probio-M8), Benserazide | 3 months | 3 × 1010 CFU/daily | MMSE scores were greater in the Probio-M8 group than in the placebo group at baseline (p < 0.001), 1 month (p < 0.001), and 3 months (p = 0.042). |
| In vivo studies of animals | ||||
| Valvaikar et al. (2024) [100] | Bifidobacterium breve Bif11 | 21 days | 1 × 1010 CFU daily | It was reported that PD rats had lower cognitive performance in the maze test, and when treated with Bif11, their working memory improved significantly (p = 0.001). |
| Nosrani et al. (2021) [59] | Lactobacillus acidophilus, Bifidobacterium bifidum, Lactobacillus reuteri, Lactobacillus fermentum | 14 days | 2 × 109 CFU of each strain/day, oral administration | In 6-OHDA PD rats, decreased escape latency in the Morris water maze (p < 0.0001) and increased time in the target quadrant during probe trial (p < 0.0001), indicating improved spatial learning and memory. |
| Xie et al. (2020) [95] | Lacticaseibacillus rhamnosus HA-114 | 6 weeks | Rehydrated with distilled water; initial concentration 1 × 109 CFU/mL, reduced to 1 × 108 CFU/mL from day 5; provided in drinking water, changed every 2 days | Novel Object Recognition (hippocampal-independent, 5 min retention): all groups showed good memory retention (sham + probiotics: p = 0.001; PD + placebo: p = 0.031; PD + probiotics: p < 0.001). Novel Place Recognition (hippocampal-dependent, 5 min retention): PD + placebo group impaired: p = 0.62; PD + probiotics group restored memory retention: p = 0.032. |
PD: Parkinson’s disease; MMSE: Mini-Mental State Examination; 6-OHDA: 6-hydroxydopamine.
SPG: Conceptualization, Formal analysis, Investigation, Methodology, Project administration, Resources, Supervision, Visualization, Writing—original draft, Writing—review & editing. DHT: Conceptualization, Formal analysis, Investigation, Resources, Writing—original draft. FES: Conceptualization, Formal analysis, Investigation, Resources, Writing—original draft. GEB: Conceptualization, Project administration, Supervision, Writing—review & editing. MCRO: Conceptualization, Project administration, Supervision, Writing—review & editing. MGB: Conceptualization, Project administration, Supervision, Writing—review & editing, Funding acquisition. All authors read and approved the submitted version.
All authors meet the authorship criteria as defined by the International Committee of Medical Journal Editors (ICMJE), declare that they have no conflicts of interest, and confirm that no related papers from the same study, nor any similar manuscripts, have been published elsewhere.
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Miguel Germán Borda was supported by the Norwegian Health Association. In addition, this paper represents independent research supported by the Norwegian government, through hospital owner Helse Vest (Western Norway Regional Health Authority). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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