New hypothesis: a gut-lipid-kidney axis in constipated CKD patients-insights from multi-omics triangulation.

Patients with chronic kidney disease (CKD) frequently experience constipation, often linked to gut microbiota disruptions. We hypothesized that constipation is not merely a comorbidity but a driver of adverse outcomes through a specific host-microbial metabolic axis. Employing a multi-cohort design for evidence triangulation, we first employed a large U.S. database and mortality data up to 31 December 2019 to investigate the association between constipation and overall mortality in patients with CKD using weighted Cox proportional hazards models. To explore potential microbial and metabolic mechanisms that could underlie such clinical observations, we then used genetic data from the independent FINRISK cohort to investigate causal relationships between specific gut microbiota, their metabolites, and CKD. In the observational cohort, we identified functional constipation as a potent, independent predictor of both all-cause (HR: 1.33; 95% CI: 1.11-1.58) and cardiovascular mortality. This association remained robust across sensitivity analyses and showed a distinct U-shaped dose-response relationship with stool frequency. In the causal inference phase, while the direct causal effect of constipation on CKD was not significant, MR identified a significant causal depletion of the genus