Altered gut microbiota, SCFAs, and barrier integrity markers in Alzheimer's and Parkinson's disease patients.

Bacteroidetes, Faecalibacterium prausnitzii, Bacteroides spp., Bifidobacterium spp., and Lactobacillus spp. were significantly reduced in both PD and AD patients compared to healthy controls.

• PD group comprised n=25 patients, AD group n=25 patients, compared to HC n=20
• Gut microbiota abundance was measured using real-time PCR on stool samples
• Reductions were observed across multiple beneficial bacterial taxa simultaneously in both neurodegenerative disease groups
• A neurological disorders (ND) control group (n=20) was also included for comparison

Enterobacteriaceae levels were elevated in PD, AD, and ND groups compared to healthy controls.

• Elevation of Enterobacteriaceae was observed across all three patient groups (PD, AD, and ND)
• This was in contrast to Proteobacteria, which were significantly elevated only in ND patients
• Samples were analyzed using real-time PCR methodology
• This finding suggests Enterobacteriaceae expansion may be a broader feature of neurological conditions rather than specific to neurodegenerative diseases

Proteobacteria levels were significantly higher only in neurological disorders (ND) patients compared to healthy controls, not in PD or AD patients.

• ND group comprised n=20 patients with neurological disorders
• The differential elevation of Proteobacteria in ND but not PD or AD suggests distinct microbial signatures across neurological condition subtypes
• Analysis was performed using real-time PCR on stool samples

AD patients showed reduced Actinobacteria and increased Akkermansia muciniphila compared to healthy controls.

• These microbiota alterations were specific to the AD group (n=25)
• Increased Akkermansia muciniphila in AD patients represents a distinct microbiota feature differentiating AD from PD
• Reduced Actinobacteria represents a phylum-level difference in AD patients
• Real-time PCR was used to quantify microbial abundance from stool samples

Inflammatory markers calprotectin and zonulin were markedly elevated in all patient groups (PD, AD, and ND) compared to healthy controls.

• Both calprotectin (a marker of intestinal inflammation) and zonulin (a marker of gut barrier integrity) were elevated
• Elevation was observed across all three disease groups: PD (n=25), AD (n=25), and ND (n=20)
• Markers were measured using enzyme-linked immunosorbent assay (ELISA) from stool and blood samples
• Findings indicate intestinal inflammation and gut barrier dysfunction are common features across these neurological conditions

Short-chain fatty acid (SCFA) levels were analyzed in patient groups and healthy controls using high-performance liquid chromatography.

• SCFAs were measured from stool and/or blood samples using HPLC
• SCFAs were included as a key outcome variable alongside gut microbiota abundance and inflammatory markers
• The study population included Iranian patients from four groups: PD (n=25), AD (n=25), ND (n=20), and HC (n=20)