The gut-liver-kidney-brain axis in Wilson disease: copper speciation-flux and barrier-mediated organ crosstalk.

Wilson disease (WD) has long been framed as a hepatocentric disorder of copper accumulation. That view is now giving way to a broader model centered on the gut-liver-kidney-brain axis. In WD, copper is not simply stored in tissues as an inert burden. It circulates in dynamic, bioactive pools-particularly relative exchangeable copper (REC)-that disrupt barrier structures, including the intestinal epithelium and blood-brain barrier, and spread toxicity through measurable biochemical mediators. Major pathogenic processes include copper-induced suppression of autophagy, disruption of FXR-regulated bile acid signaling, and direct injury to the intestinal barrier. Gut dysbiosis, supported by fecal microbiota transplantation (FMT) studies in ATP7B-deficient mice, further amplifies hepatic inflammation and favors copper retention. Renal tubular dysfunction and neurotoxicity appear to reflect copper species-dependent passage across biological barriers together with secondary metabolic disturbances, including the recently described pathway of cuproptosis. In the clinic, this shift has been accompanied by greater use of copper-species biomarkers such as ceruloplasmin oxidase activity and REC, along with advanced imaging approaches such as