Effect of fish oil supplementation on lipogenic gene expression in mammary gland and liver in mice

The long chain n‐3 polyunsaturated fatty acids (PUFA), EPA and DHA, represent a unique class of biologically active fatty acids. We reported previously that dietary fish oil had no effect on mouse mammary lipogenesis as measured by C14‐glucose incorporation by mammary explants but liver lipid content was reduced. To investigate the molecular mechanism of the tissue specific effects of long chain n‐3 PUFA, we measured mRNA abundance of genes involved in lipid synthesis in mammary and hepatic tissues using RT‐qPCR. Female C57BL/6J mice were fed a semi‐purified low fat control diet beginning 1 wk prepartum. On d 6 of lactation, mice were maintained on the low fat control diet ( 5 % dietary oil) or shifted to high fat diets (10 % dietary oil) enriched in either n‐3 PUFA (fish oil) or oleic acid (high fat control ) for 7 d (n = 8 mice/group). There was no treatment effect on mammary mRNA abundance for key lipogenic enzymes Fasn and Acaca or transcription signaling genes associated with the regulation of lipid synthesis; Srebf1‐c, S14, Insig1, Insig2, Scap or Sp1. In contrast, hepatic mRNA abundance for Fasn, Acaca, Gpam, Scd‐1, S14 and Insig1 was reduced by 50 – 80 % for the fish oil treatment as compared to the control groups. Overall, results indicate that long chain n‐3 PUFA downregulate expression of genes related to fatty acid synthesis in liver but the regulation of lipogenesis in mammary tissue was unresponsive to n‐3 PUFA