N-3 polyunsaturated fatty acid regulation of hepatic gene transcription.
OBJECTIVE
The liver plays a central role in whole body lipid metabolism and adapts rapidly to changes in dietary fat composition. This adaption involves changes in the expression of genes involved in glycolysis, de-novo lipogenesis, fatty acid elongation, desaturation and oxidation. This review brings together metabolic and molecular studies that help explain n-3 (omega-3) polyunsaturated fatty acid regulation of hepatic gene transcription.


RESULTS
Dietary n-3 polyunsaturated fatty acid regulates hepatic gene expression by targeting three major transcriptional regulatory networks: peroxisome proliferator-activated receptor alpha, sterol regulatory element binding protein-1 and the carbohydrate regulatory element binding protein/Max-like factor X heterodimer. 22:6,n-3, the most prominent n-3 polyunsaturated fatty acid in tissues, is a weak activator of peroxisome proliferator-activated receptor alpha. Hepatic metabolism of 22:6,n-3, however, generates 20:5,n-3, a strong peroxisome proliferator-activated receptor alpha activator. In contrast to peroxisome proliferator-activated receptor alpha, 22:6,n-3 is the most potent fatty acid regulator of hepatic sterol regulatory element binding protein-1. 22:6,n-3 suppresses sterol regulatory element binding protein-1 gene expression while enhancing degradation of nuclear sterol regulatory element binding protein-1 through 26S proteasome and Erk1/2-dependent mechanisms. Both n-3 and n-6 polyunsaturated fatty acid suppress carbohydrate regulatory element binding protein and Max-like factor X nuclear abundance and interfere with glucose-regulated hepatic metabolism.


CONCLUSIONS
These studies have revealed unique mechanisms by which specific polyunsaturated fatty acids control peroxisome proliferator activated receptor alpha, sterol regulatory element binding protein-1 and carbohydrate regulatory element binding protein/Max-like factor X function. As such, specific metabolic and signal transduction pathways contribute significantly to the fatty acid regulation of these transcription factors and their corresponding regulatory networks.
Jump
Donald B
DB
Department of Nutrition and Exercise Sciences, Linus Pauling Institute, Oregon State University, Corvallis, Oregon 97331-5109, USA. Donald.Jump@oregonstate.edu
D000818:Animals; D004042:Dietary Fats, Unsaturated / Q000494:pharmacology*; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D006019:Glycolysis; D006801:Humans; D050155:Lipogenesis; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D047493:PPAR alpha / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*
D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D047493:PPAR alpha