(P27-22-26) Dietary Carbohydrate Complexity Distinctly Shapes Gut Microbiome Profile in an Age-Dependent Manner

Objectives: To characterize age-specific gut microbiome dynamics following fermentation of different simple sugars and diverse dietary carbohydrates in a simulated human fecal fermentation system.

Methods: Fecal samples from 12 healthy young adults (mean 26.4 years) and 5 older adults (64.2 years) were subjected to simulated in-vitro fecal fermentation in an anaerobic workstation. Thirteen carbohydrate substrates were tested, including mono- (glucose and fructose), disaccharides (sucrose and lactose), oligosaccharides (fructo-, galacto-, and human milk oligosaccharides), inulin, potato starch, and resistant starches isolated from pulses (black-eyed peas, pinto beans, lentils, and chickpeas). Stool samples were inoculated with each substrate at 5% (w/v) final concentration and incubated anaerobically at 37°C for 24 h. Metagenomic DNA was extracted from the fermented samples and subjected to the 16S rRNA gene sequencing.

Results: Microbial diversity decreased during fermentation across all treatments, likely due to simulated conditions; however, the reduction was less pronounced with resistant starch and potato starch. Bifidobacterium and Dorea were significantly lower in older individuals (q < 0.001) and were differentially modulated by carbohydrate substrate treatments. Bifidobacterium exhibited a strong negative correlation with pH changes (ρ = -0.516, q < 0.001) and was significantly enriched by all carbohydrate types. In contrast, Dorea showed a positive correlation with pH (ρ = 0.428, q < 0.001) and was significantly reduced by all carbohydrates except potato starch. Most carbohydrate treatments, except monosaccharides, also promoted an increase in Faecalibacterium abundance. Functional predictions revealed that bacterial chemotaxis was significantly downregulated following sugar treatments but remained relatively preserved with resistant starches. Additionally, the Parkinson’s disease-associated pathway was overall more prevalent in older cohorts; however, sugar treatments, particularly mono-, di-, and oligosaccharides, significantly reduced its predicted prevalence.

Conclusions: These findings demonstrate that substrate complexity and host age shape gut microbiome profile and functional potential, with key taxa and metabolic pathways responding differentially.

Funding Sources: USDA