PCB and OCP accumulation and evidence of hepatic alteration in the Atlantic bluefin tuna, T. thynnus, from the Mediterranean Sea

• PCBs and OCPs were measured in tuna liver and morphological changes were observed.
• The expression of perilipin correlated with PPARγ and RXRα gene expression.
• Metabolomics showed alterations in fatty acid biosynthesis and ketogenesis.
• The alterations observed in tuna liver suggest a potential onset of hepatic steatosis.

Persistent organic pollutants (POPs) are known to act as “obesogens”, being fat-soluble and affecting lipid metabolism. The Atlantic bluefin tuna, Thunnus thynnus, are top pelagic predators prone to bioaccumulate and biomagnify environmental contaminants. This study aimed at evaluating POPs-induced ectopic lipid accumulation in liver of adult tuna from the Mediterranean Sea. PCBs and organochlorine pesticides were measured in tuna liver, and marked morphological changes observed, namely poorly compacted tissues, intense vacuolization, erythrocyte infiltration and presence of melanomacrophages. The expression of perilipin, a lipid-droplet marker, positively correlated with the gene expression of PPARγ, a master regulator of adipogenesis, and its heterodimeric partner, RXRα. Changes in metabolites involved in fatty acid biosynthesis and ketogenesis were also observed. Although male bluefin tuna appeared to be more sensitive than females to the adverse effects of environmental obesogens, the alterations observed in tuna liver of both sexes suggest a potential onset of hepatic steatosis.