Experimental studies showing gastrointestinal symptoms improvement induced by probiotic interventions in PD.
| Study (year) | Probiotic(s) | Duration | Dose/Presentation | Outcome |
|---|---|---|---|---|
| Human studies | ||||
| Barichella et al. (2016) [77] | Fermented milk with strains of (Streptococcus, Enterococcus, Lactobacillus, Bifidobacterium) and prebiotic fiber | 4 weeks | 125 g of fermented milk containing 250 × 109 CFU, once daily | Superior to placebo in improving the number of complete bowel movements (p = 0.002). |
| Ibrahim et al. (2020) [79] | Multi-strain probiotic (Hexbio) (Lactobacillus spp., Bifidobacterium spp.) with fructo-oligosaccharides (FOS) | 8 weeks | Hexbio sachet with 30 × 109 CFU, 2% FOS, and lactose, twice daily | Improved bowel movement frequency (p < 0.001) and total gut transit time (p = 0.028). |
| Tan et al. (2021) [78] | Multistrain (Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus gasseri, Lactobacillus rhamnosus, Bifidobacterium bifidum, Bifidobacterium longum, Enterococcus faecalis, Enterococcus faecium) | 4 weeks | 10 × 109 CFU capsule, once daily | Increased spontaneous bowel movements by 1.3/week (p < 0.001); improved stool consistency (p = 0.009) and quality of life (p = 0.001). |
| Sun et al. (2022) [82] | Probio-M8 (Bifidobacterium animalis subsp. lactis) | 3 months | 2 g of Probio-M8 powder (3 × 1010 CFU/day; maltodextrin as excipient) daily | Significant improvement in gastrointestinal symptoms, including Bristol scores (p < 0.001) and Patient Assessment of Constipation Quality of Life Questionnaire (p < 0.001). |
| Du et al. (2022) [81] | Bacillus licheniformis, Lactobacillus acidophilus, Bifidobacterium longum; Enterococcus faecalis | 12 weeks | 2.5 × 109 CFU two capsules, three times daily | Increased complete bowel movements by 1.09/week (p < 0.001); improved Bristol Stool Scale, Patient Assessment of Constipation Symptoms Questionnaire, and Patient Assessment of Constipation Quality of Life Questionnaire scores (p < 0.05 for all). |
| Ghalandari et al. (2023) [80] | Comflor® (Lactobacillus plantarum, Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus bulgaricus, Bifidobacterium infantis, Bifidobacterium longum, Bifidobacterium breve, and Streptococcus thermophilus) | 8 weeks | 4.5 × 1011 CFU capsule, once daily | Doubled bowel movement frequency (p = 0.02) and improved stool consistency (p = 0.04). |
| In vivo studies of animals | ||||
| Chu et al. (2023) [83] | Lactobacillus plantarum CCFM405 | 8 weeks | 1 × 109 CFU/0–2 mL in saline by oral gavage, once daily | Alleviated motor deficits (p < 0.05) and constipation symptoms (p < 0.05). Reduced dopaminergic neuron loss (p < 0.05), intestinal inflammation, and neuroinflammation (p < 0.05). Increased number of fecal pellets in PD mice (p < 0.05) and fecal/serum branched-chain amino acids. |
| Dong et al. (2024) [84] | Bifidobacterium animalis subsp. lactis NJ241 | 28 days | 1 × 109 CFU/0.2 mL in saline by oral gavage, once daily | Mitigated gastrointestinal dysfunction (p = 0.024) and motor deficits (p < 0.05). Protected dopaminergic neurons (p < 0.05). Reduced neuroinflammation (p < 0.05). Increased SCFAs and colonic GLP-1 (p < 0.05). |
PD: Parkinson’s disease; SCFAs: short-chain fatty acids; GLP-1: glucagon-like peptide-1.
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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