Transcriptomic and Phenotypic Changes in Young Bull Liver Caused By Low-Impact and Nutraceutical Diets

The administration of low-impact diets (low in protein and mineral content) and nutraceutical diets (enriched in n-3 fatty acids (FA),and conjugated linoleic acid (CLA)) in young Belgian Blue X Holstein bulls might involve transcriptional modifications in liver. Therefore, the aim of the present study was to identify liver regulatory networks underlying physiological and metabolic responses to specific nutrient ingestion, using RNA-sequencing. A total of 198 differentially expressed (DE) genes were identified when comparing low-impact, nutraceutical and conventional diets, with the nutraceutical diet showing the greatest effects on liver transcriptome. We used ClueGo and Ingenuity Pathway Analysis to gain a better understanding of the biological functions regulated by the DE genes. Notably, DE genes were involved variously in energy reserve metabolic process, glutathione metabolism, and carbohydrate and lipid metabolism. Additionally, nutraceutical diet significantly reduced fat covering in vivo, and liver pH. Dietary treatments did not affect overall liver fat content, but significantly modified the CLA, n-3 and n-6 FA composition, as well as the ratio n-6/n-3. In bulls fed linseed, the percentage of n-3 and CLA FA increased around 2.5-fold compared with the other diets, whereas the ratio of n6/n3 decreased by 2.5-fold. The CLA and n-3 FA were positively correlated with the expression profile of many DE genes, likely regulating their synthesis or metabolism. This study provides interesting insight into the molecular changes occurring after nutrient variation in diets (aiming at reducing the environmental impact and improving human health) and broadens the understanding of relationship between nutrients and phenotypic variations.