A high-calorie diet may cause earlier onset of more severe Wilson disease, according to a rodent study.
If translatable to humans, the results could explain “striking phenotype-genotype discrepancies” between patients with Wilson disease, and may give reason to monitor nutrition more closely, particularly dietary levels of fat and sugar, reported lead author, a PhD candidate at the German Research Center for Environmental Health in Neuherberg, Germany, and her colleagues. Their findings clarify an association between impaired copper metabolism, which defines Wilson disease, and liver steatosis, a common finding in affected patients.
“Indeed, Wilson disease often may be misdiagnosed as nonalcoholic fatty liver disease (NAFLD),” the investigators wrote in. They noted that previous reports showed similar mitochondrial alterations in the livers of patients with NAFLD and those with Wilson disease. Furthermore, in a case report of two twins with Wilson disease, the twin with bulimia nervosa developed severe liver disease, whereas the other twin, who was undernourished, had mild liver disease. Considering these observations and other supportive evidence, the investigators tested this apparent relationship between a high-fat diet and liver damage in Wilson disease.
“The rationale of this study was that both enriched copper and fatty acids cause bioenergetic defects and therefore synergistically and detrimentally may coincide on hepatic mitochondria, which was found to be dramatically the case,” the investigators wrote.
The study involved homozygous Atp7b–/– rats, which mirror Wilson disease, and heterozygous Atp7b+/– rats, which served as control subjects because they lack copper accumulation. The high-calorie diet contained high fat and sugar levels to mirror “the eating habits in Western society, causing the ‘American-lifestyle-induced-obesity syndrome.’ ”
Within several weeks of starting the high-calorie diet, both control and Wilson disease rats showed higher liver triglyceride levels and visceral fat mass compared with rats on the normal diet, with liver histology also showing macrosteatosis and increased NAFLD Activity Score (NAS). Control rats maintained similar body and liver weights regardless of diet; in contrast, Wilson disease rats on the high-calorie diet showed increased liver weight, compared with Wilson disease rats on the normal diet. In addition, Wilson disease rats fed the high-calorie diet had clinical liver injury, supported by elevated aspartate aminotransferase (AST) levels and gross hepatic damage. Under the microscope, histology revealed widespread necrosis, apoptosis, inflammation, and fibrosis; findings were sufficient to constitute nonalcoholic steatohepatitis in all Wilson disease rats fed the high-calorie diet, compared with just one-third of the control rats receiving high calories. Additional testing showed that Wilson disease rats fed the high-calorie diet had disease onset 20 days sooner than did Wilson disease rats fed the normal diet.
“This is a remarkable disease acceleration,” the investigators noted, highlighting the median survival of 106 days in Wilson disease rats fed a normal diet.