Dietary copper-fructose interactions alter gut microbial activity in male rats Original paper

What was studied?

This study tested how dietary copper-fructose interactions alter gut microbial activity in male rats and linked these shifts to gut barrier injury and liver stress that model early NAFLD. Investigators fed defined copper diets with or without high fructose and profiled fecal and intestinal microbiota by 16S rDNA sequencing, measured tight junction proteins and goblet cells, and tracked plasma endotoxin, LBP, and liver enzymes. The work asked whether marginal or supplemental copper, when combined with fructose, reshapes the gut community in ways that favor pathobionts, reduces protective taxa, and weakens the epithelial barrier. It also examined copper handling genes and systemic copper status to connect luminal changes with host metal routing.

Who was studied?

Researchers studied healthy weanling male Sprague–Dawley rats on AIN-76–based diets providing marginal copper, adequate copper, or supplemental copper for four weeks, with ad libitum water or 30% fructose water. They collected feces and intestinal tissue for microbiome analysis and barrier assays, and drew blood for copper indices, LBP, endotoxin, and liver enzymes. The design allowed clear contrasts between copper levels with and without fructose, so the team could pinpoint whether copper status alone, fructose alone, or their interaction best explained microbe shifts, barrier damage, endotoxemia, and liver injury markers.

Most important findings

Both low and high copper, when paired with fructose, changed the microbiome without improving growth and with clear signs of tissue stress. At the phylum level, Firmicutes rose in both copper-fructose states, while Bacteroidetes fell most with low copper plus fructose, producing a higher Firmicutes/Bacteroidetes ratio. Proteobacteria trended upward with fructose and copper, and Enterobacteriaceae expanded in the high copper plus fructose group. Verrucomicrobia dropped across copper-altered groups, driven by a marked loss of Akkermansia, a mucin-utilizing commensal linked to barrier integrity. Within Firmicutes, family-level patterns diverged by copper dose: low copper favored Peptostreptococcaceae and higher Lachnospiraceae, whereas high copper favored Lactobacillaceae and Erysipelotrichaceae alongside reduced Ruminococcaceae, a butyrate-producing family tied to epithelial health.

Barrier assays showed reduced claudin-1 and occludin protein and fewer goblet cells with both copper extremes, while Reg3B rose, consistent with an antimicrobial stress response; IL-22 trended higher in the same direction. Systemically, LBP rose with fructose independent of copper, and plasma endotoxin increased most with low copper, even though high copper plus fructose also raised Proteobacteria and Enterobacteriaceae, suggesting distinct injury routes. Liver enzymes (ALT/AST) increased in copper-fructose groups, indicating hepatic injury consistent with early NAFLD. Copper transport features shifted as well: intestine and liver Ctr1 expression fell under fructose, and ceruloplasmin activity rose when fructose accompanied high copper, pointing to active host copper routing during inflammation. Together, these data define a microbiome signature of copper-fructose exposure that includes Akkermansia loss, reduced Ruminococcaceae, expansion of Enterobacteriaceae under high copper, and dose-specific Firmicutes family changes that align with impaired barrier function and liver stress.

Key implications

Clinicians should recognize copper status and fructose load as joint drivers of dysbiosis and barrier failure that can precede and fuel NAFLD. In a microbiome signatures database, you can tag dietary copper-fructose interactions with Akkermansia depletion, reduced Ruminococcaceae, increased Lactobacillaceae or Peptostreptococcaceae depending on copper dose, and Enterobacteriaceae rise with high copper plus fructose. These shifts track with tight junction loss, goblet cell loss, higher LBP, and liver enzyme elevation. Assessing diet, copper intake, and fructose exposure may help stratify risk in patients with metabolic liver disease or barrier complaints, while interventions that restore Akkermansia, support butyrate producers, and correct copper imbalance may protect the barrier and reduce hepatic injury signals.