Shih, D. | bioRxiv Science

bioRxiv2026

Primary-Level Meta-Analysis of Diversity Outbred Mice Identifies a Fasting Plasma Trimethylamine N-Oxide (TMAO) Locus Modified by Sex and Diet

Trimethylamine n-oxide (TMAO) is a plasma metabolite linked to adverse cardiometabolic health with complex regulation involving diet, sex, and host genetics. We explored the role of these factors in the genetic regulation of TMAO by performing a primary-level meta-analysis in 1,482 female and male Diversity Outbred (DO) mice from five distinct studies conducted in various regions of the United States. We identified a quantitative trait locus (QTL) associated with TMAO concentration at [~]86 megabase pairs on mouse chromosome 12 with a highly significant LOD score of 67.67. Alleles at the chromosome 12 QTL inherited from the Cast/EiJ (CAST) and PWK/PhJ (PWK) mouse strains primarily drove the association with reduced TMAO concentrations. The chromosome 12 QTL remained significant in sex-stratified analyses and the mode of inheritance appeared additive; furthermore, the QTL was regulated by sex-by-genotype and sex-by-diet interactions. Using a CAST/EiJ X C57BL/6J F2 cross, positional candidates were prioritized by eQTL analysis. Further analysis in a study utilizing the eight DO founding strains identified that Acyp1 was differentially expressed in hepatic tissue from CAST mice, prompting investigation into its genetic regulation. Acyp1 demonstrated relevant cis- and trans-regulation and was significantly correlated with TMAO and hepatic Fmo3. However, no significant relationships between Acyp1 and TMAO were identified in mice inactivated for Acyp1 or with AAV overexpression of Acyp1 in the liver. Genes within the chromosome 12 QTL have synteny with humans and may translate to the genetic regulation of human plasma TMAO concentrations and atherosclerosis. Author SummaryWe explored the roles of diet, sex, and genetics on the regulation of fasting plasma trimethylamine n-oxide (TMAO) concentration by performing a meta-analysis in 1,482 female and male Diversity Outbred (DO) mice from five unique studies. We identified a QTL associated with TMAO concentration on chromosome 12 at [~]86 mega base pair (Mb) with a highly significant LOD score of 67.67. The locus is modified by both sex and diet.

genetics↗

bioRxiv2025

TL1A overexpression in Crohn's Disease and mice alters Paneth cells and microbiota promoting ileal inflammation

Paneth cells regulate host-microbial homeostasis and defects in autophagy and host defense pathways have been associated with inflammatory bowel diseases (IBD). Genetic variants in TL1A (TNFSF15) and its receptor DR3 (TNFRSF25) have been associated with IBD. TL1A expression is increased in IBD patients, particularly in TL1A risk allele carriers. However, effects of TL1A on Paneth cells, resident microbiota, and development of ileitis remain unknown. TL1A overexpression in mice induces Paneth cell hyperplasia and morphological abnormalities preceding the development of ileitis. In Crohns disease (CD) patients, ileal TL1A expression was associated with abnormal Paneth cell phenotypes. We confirmed direct effects of TL1A on Paneth cells in human iPSC-derived human intestinal organoids and mouse Paneth cell-enriched organoids. Resident microbiota was required for TL1A-mediated Paneth cell dysfunction, and ileitis. Tl1a-tg mice were enriched in short chain fatty acid-producing bacteria and the metabolite acetate. Acetate supplementation in WT or Tl1a-tg mice caused ileal inflammation, suggesting that acetate is sufficient to cause ileitis. DR3-deficiency in Paneth cells resulted in Paneth cell abnormalities and microbiome composition changes. Our findings provide a mechanistic link between overexpression of TL1A in CD patients, Paneth cell dysfunction, and enrichment of acetate-producing bacteria and acetate that promotes ileal inflammation. Brief SummaryOverexpression of TL1A drives Paneth cell dysfunction in Crohns Disease and mice leading to microbial and metabolomic changes that promote small bowel inflammation.

immunology↗