(P39-12-26) Higher Saturated Fat Intake Associated With Increased Binding of sIgA to Pro-inflammatory Gut Bacteria in Healthy Adults

Objectives: We previously showed that elevated fecal sIgA was associated with lower total Healthy Eating Index (HEI) scores, higher gut (calprotectin, myeloperoxidase) and systemic (white blood cell ct.) inflammation, and bacteria with inflammatory potential (i.e. Escherichia coli). The objectives of this study were (1) to determine whether specific dietary components drive the association between sIgA and HEI, (2) whether microbes positively correlated with total sIgA are bound to sIgA and (3) whether sIgA-microbe binding patterns vary between participants with high and low fecal sIgA.

Methods: Healthy adults (n = 350) completed an observational, cross-sectional study balanced for age, sex, and BMI. HEI-2015 components were calculated from three 24hr recalls. Individuals in the upper quartile of fecal sIgA concentration (high) were compared to the lower 3 quartiles (low). A subset of samples from the high (n=20) and low (n=25) sIgA groups were selected for sIgA sequencing: sIgA-bound bacteria were enriched using magnetic cell sorting and sequenced with shotgun metagenomics.

Mann-Whitney U tests were used for two group comparisons, with FDR multiple hypothesis correction as appropriate (p-adj). To compare sIgA-bound (sIgA+) vs. native microbiotas, beta diversity was assessed using Weighted UniFrac. IgA probability scores (IgA-prob) determined whether a microbe is likely bound to sIgA (rel. abundance of taxa(i) in sIgA+ / rel. abundance of taxa(i) in native) x (% of microbes bound to sIgA in sIgA+).

Results: Saturated fat intake was significantly higher in the high vs. low sIgA group (p-adj = 0.037). IgA+ samples had lower alpha diversity compared to native (Shannon diversity p< 0.001). Novel to this study, we found that sIgA+ microbiota was more similar to the native microbiota in high vs. low sIgA groups (p=0.0078). IgA-prob of Gammaproteobacteria (median 2.73 vs 0.37, p< 0.001) and Streptococcaceae (median 3.07 vs. 1.91, p=0.006) were significantly higher in the high vs. low sIgA groups.

Conclusions: Greater saturated fat intake was associated with higher sIgA. While sIgA binds a specific subset of the microbiota, higher sIgA production may lead to non-specific binding of the native microbiota. The increased binding of pro-inflammatory bacteria in high sIgA could be a host response to a pro-inflammatory diet.

Funding Sources: USDA ARS, Eugene Cota-Robles Fellowship