Dietary fatty acids affect mitochondrial phospholipid compositions and mitochondrial gene expression of rainbow trout liver at different ages

Mitochondria are among the first responders to various stressors that challenge the homeostasis of cells and organisms. Mitochondrial decay is generally associated with impairment in the organelle bioenergetics function and increased oxidative stress, and it appears that deterioration of mitochondrial inner membrane phospholipids (PL), particularly cardiolipin (CL), and accumulation of mitochondrial DNA (mtDNA) mutations are among the main mechanisms involved in this process. In the present study, liver mitochondrial membrane PL compositions, lipid peroxidation, and mtDNA gene expression were analyzed in rainbow trout fed three diets with the same base formulation but with lipid supplied either by fish oil (FO), rapeseed oil (RO), or high DHA oil (DHA) during 6 weeks. Specifically, two feeding trials were performed using fish from the same population of two ages (1 and 3 years), and PL class compositions of liver mitochondria, fatty acid composition of individual PL classes, TBARS content, and mtDNA expression were determined. Dietary fatty acid composition strongly affected mitochondrial membrane composition from trout liver but observed changes did not fully reflect the diet, particularly when it contained high DHA. The changes were PL specific, CL being particularly resistant to changes in DHA. Some significant differences observed in expression of mtDNA with diet may suggest long-term dietary effects in mitochondrial gene expression which could affect electron transport chain function. All the changes were influenced by fish age, which could be related to the different growth rates observed between 1- and 3-year-old trout but that could also indicate age-related changes in the ability to maintain structural homeostasis of mitochondrial membranes.