Dietary High and Low Copper‐Fructose Interactions Induce Hepatic Steatosis Associated with Distinct Alterations of Gut Microbial Activity in Male Rats

Abstract

ObjectiveDietary copper‐fructose interactions play critical roles in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The aim of this study was to determine the effect of different dietary doses of copper and their interactions with high fructose on gut microbial activity and the development of steatosis.MethodsMale weanling Sprague‐Dawley rats were fed diets with adequate copper (6 ppm, CuA), marginal copper (1.5 ppm, CuM) (low‐copper) or copper supplementation (20 ppm, CuS) (high‐copper) for 4 weeks. Deionized water or deionized water containing 30% fructose (w/v) was given ad lib. Copper status, liver enzymes, histology, gut barrier function and gut microbial activity were evaluated.ResultsCopper levels were significantly lower in rats fed with a marginal copper diet than in those fed with an adequate copper diet. However, high‐copper diet did not lead to excessive copper accumulation in the liver, likely due to the downregulation of copper transporter‐1(Ctr‐1) mRNA. Both low‐ and high‐copper diets led to liver injury and fat accumulation in high fructose fed rats, and this accumulation was associated with gut barrier dysfunction. The increased abundance of the gut Gram‐negative bacteria, Enterobacteriaceae, did not parallel plasma endotoxin levels, with low copper‐fructose induced steatosis being characterized with endotoxemia, whereas high copper‐fructose induced steatosis was not, despite the fact that both of these regimens resulted in increased gut permeability. Fecal metabolomics study and 16S rRNA gene expression analysis revealed distinct gut microbial metabolic characteristics in response to dietary low‐ and high‐copper high‐fructose feeding.ConclusionOur data demonstrated that dietary copper‐fructose interaction regulates gut microbial metabolic activity, which might contribute to the development of hepatic steatosis. The distinct alterations of gut microbial activity which were associated with the different dietary doses of copper and fructose imply that separate mechanism(s) may be involved.Support or Funding InformationThis study was supported in part by NIH Grants U01AA021901, U01AA022489, R01AA023681, an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM113226 and by the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health under Award Number P50AA024337. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health (C.J.M.); K23AA018399, R01ES021375 (M.C.); the Veterans Administration (C.J.M.); and the U of L Clinical and Translational Pilot Program (C.J.M.).