Assessing Firmicutes and Bacteroidetes Distributions in relation to Age, Gender, and APOE-ε4 allele Status in an Aging Australian Cohort — The Association Specialists
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Assessing Firmicutes and Bacteroidetes Distributions in relation to Age, Gender, and APOE-ε4 allele Status in an Aging Australian Cohort (22210)

Samantha Ramachandra 1 , Hamid Sohrabi 2 3 , Vincent Ho 4 , BGDNK De Silva 5 , Ralph Martins 1 3 6 , Binosha WMAD fernando 1 3
  1. School of Medical and Health Sciences , Edith Cowan University, Perth, WA, Australia
  2. Centre for Healthy Aging, Murdoch University, Perth, WA, Australia
  3. Alzheimer's Research Australia, Perth, WA, Australia
  4. Western Sydney University, Sydney, NSW
  5. University of Sri Jayewardenepura, Colombo, Sri Lanka
  6. Macquarie University, Sydney, NSW, Australia

Alzheimer’s disease (AD) is a neurodegenerative condition marked by cognitive decline and impairment in daily functioning. Emerging research suggests that gut microbiota may contribute to disease progression via the gut-brain axis. This cross-sectional study investigated the gut microbiota composition among older adults in the Australian Imaging, Biomarkers, and Lifestyle (AIBL) and Western Australian Memory Study (WAMS) cohorts to understand microbial patterns associated with AD risk (age, sex, and APOE).

Participants included 123 individuals (55% female), 17% with apolipoprotein E (APOE-ε4 allele), the major genetic risk factor for AD. Faecal samples were analysed using shotgun metagenomic sequencing to characterise gut microbiota composition. Analysis (ANOVA and T-test) revealed that Bacteroidetes was the dominant phylum, followed by Firmicutes, consistent with age-related microbial composition trends in older populations.

The Firmicute/Bacteroidetes (F/B) ratio, a marker of gut health, appeared to decrease with age (0.956 for <65yrs, 0.935 for 65-75yrs, and 0.846 for >75yrs), though this trend was not statistically significant. Though it is insignificant, a higher (F/B) ratio was seen in male and non-carriers. The most abundant 10 phyla, classes, and order distribution showed no statistically significant difference against demographic variables except phylum Verrucomicrobia against gender (p = 0.008) and age categories (p=0.05). Alpha diversity, representing species richness within samples, showed no significant associations with age, sex, or APOE-ε4 status but showed a decreasing trend in advancing age and the presence of APOE-ε4.

These findings provide a basic understanding of gut microbiota in an aging Australian cohort, with Bacteroidetes and Firmicutes as the prevalent phyla.