Summary:
Gastrointestinal (GI) motility is important for digestion, nutrient absorption and waste removal, and is regulated by interactions between the gut, brain, immune system and gut microbiome. Disruptions to these processes are associated with irritable bowel syndrome (IBS) and other disorders of gut-brain interaction. A better understanding of the genetic factors that influence gut motility may help identify new treatment targets. This study was a genome-based meta-analysis investigating genetic factors associated with stool frequency, an indirect measure of gut motility. The analysis included 268,606 people and also examined genetic relationships between stool frequency and other health conditions. Higher stool frequency was genetically associated with several gastrointestinal and psychiatric conditions, including IBS, and was also linked to cardiovascular traits. The analysis identified 21 independent genetic regions, including 10 that had not previously been associated with stool frequency. Further analysis identified a potential role for vitamin B1 (thiamine) metabolism in regulating gut motility. In a separate analysis of 98,449 UK Biobank participants, higher dietary thiamine intake was associated with greater stool frequency. In conclusion, this study identified several genetic pathways that may regulate gut motility and highlighted vitamin B1 metabolism as a previously unrecognised potential contributor. Further research is needed to determine whether these findings could inform new approaches to treating IBS and other conditions involving abnormal gut motility.
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Abstract:
Background Genetic studies of stool frequency (SF), an indirect proxy for gastrointestinal transit, may reveal therapeutically tractable pathways relevant to IBS and other dysmotility disorders. Objective To identify genes and mechanisms involved in gut motility, providing a foundation for clinical translation. Design We performed a multiancestry genome-wide association study (GWAS) meta-analysis of SF in 268 606 European and East Asian individuals. Heritability and genetic correlations with other traits were estimated, and Mendelian randomisation was used to test causal relationships. GWAS signals were fine-mapped and functionally annotated to prioritise candidate genes and pathways. Findings implicating thiamine metabolism were followed-up with dietary interaction analyses in UK Biobank (UKB). Results SF heritability was comparable in Europeans (7.0%) and East Asians (5.6%). We observed strong genetic correlations with gastrointestinal and psychiatric disorders (rg=0.18–0.47), and causal effects on IBS. Novel correlations with cardiovascular traits (rg=0.12–0.14) were supported by drug signature enrichment analyses. We identified 21 independent loci, including 10 novel signals implicating bile acid synthesis (KLB) and cholinergic signalling (COLQ). Fine-mapping converged on vitamin B1 metabolism, highlighting single-variant causal effects at SLC35F3 (a thiamine transporter) and XPR1 (phosphate exporter essential for thiamine activation). In 98 449 UKB participants, thiamine intake was positively associated with SF (p<0.0001), and a combined SLC35F3/XPR1 genotype score significantly modulated this effect (p<0.0001). Conclusions We identify therapeutically tractable mechanisms involved in the control of gut motility, including a previously unrecognised role for vitamin B1. These findings warrant mechanistic and clinical studies to evaluate their translational potential in IBS and other dysmotility syndromes.
Article Publication Date: 20/01/2026
DOI: 10.1136/gutjnl-2025-337059
