Inflammatory dietary potential and gut microbiota in older adults with overweight or obesity and metabolic syndrome

Introduction: Understanding how inflammatory dietary potential modulates the gut microbiota diversity, composition, and function remains a topic of ongoing debate. The present study aims to assess the longitudinal relationship between inflammatory dietary potential and gut microbiota characteristics in older adults with overweight/obesity and metabolic syndrome. Methods: This longitudinal sub-study and secondary analyses nested under the context of the PREvención con Dieta Mediterránea-Plus (PREDIMED-Plus) randomized clinical trial included 648 participants (mean age 65 ± 5 years, 47 % women) . Inflammatory dietary potential was based on energy-adjusted dietary inflammatory index ( E -DII) score, assessed using a validated 143-item food frequency questionnaire. Gut microbiota was characterized using 16S rRNA sequencing and 518 identified faecal metabolites were analysed through liquid chromatography-tandem mass spectrometry. The relationship between E -DII score (exposure) and gut microbiota alpha and beta diversity and composition, in terms of microbial genera, and faecal metabolites (outcome) with available data at two timepoints (baseline and 1-year thereafter), and longitudinally, was subsequently analysed. Results: Anti-inflammatory dietary potential as measured by lower E -DII score, either as continuous or categorical, demonstrated significant associations with increased alpha diversity indices (i.e., Chao1, Inverse Simpson and Shannon; all P < 0.05), and distinct beta diversity profiles at baseline (R 2 = 0.004; PERMANOVA P = 0.047) and after 1-year (R 2 = 0.006; PERMANOVA P = 0.003). Furthermore, anti-inflammatory E -DII score was associated with 24 microbial genera, 4 faecal metabolites, and 1 metabolomic network (all FDR < 0.05). Pro-inflammatory E -DII score was also associated with 1 microbial genera and 2 faecal metabolites (all FDR < 0.05). Results remained significant when evaluating changes in E -DII over time with changes in alpha diversity indices and metabolomic network. Conclusion: Anti-inflammatory dietary potential of diet may enhance gut microbiota diversity and potentially modulate its composition in older adults with metabolic syndrome. • Anti-inflammatory dietary potential is associated with greater gut microbiota diversity. • Anti-inflammatory dietary potential correlates with 24 microbial genera and 4 faecal metabolites. • Pro-inflammatory dietary potential correlates with 1 microbial genera and 2 faecal metabolites. • Anti-inflammatory dietary potential correlates with 1 metabolomic network. • Personalized dietary interventions based on inflammatory dietary potential may optimize gut microbiota.