Differential effects of dietary fatty acids on genes associated with liver fat metabolism

Background – It has been recognized that specific fatty acids have the ability to directly influence the abundance of gene transcripts in organs such as the liver. However little comparison has been made between the effects of common dietary of fatty acids and there influence on gene expression.
Objectives – To determine the effect of diets rich saturated, monounsaturated and polyunsaturated on gene transcripts associated with liver fat metabolism. Specifically how these three classes of fatty acids influence mRNA levels of key transcriptional regulators (PGC1a, PPARa, PPARd, SREBP1C & ChREBP), fat oxidative (ACO, LCPT1, HMG-CoA lyase & UCP-2) and fat synthetic (ACC, MCD, GPAT & malic enzyme) genes were investigated.
Design - Rats (n=32) were evenly divided into four groups; a saturated fat diet, a monounsaturated fat diet, a polyunsaturated fat diet (each diet contained 23% fat) and standard rat chow (7% fat) diet and fed for 12 weeks. Real-time PCR analysis was performed on liver tissue.
Outcomes – PGC1a and SREBP1C increased 1.9 fold or greater in all groups. Conversely, PPARa, PPARd and ChREBP demonstrated variable changes with diet composition. Monounsaturated and polyunsaturated fat increased HMG-CoA lyase 2.8 fold, a response that was absent in the saturated fat fed animals. UCP-2 was decrease 3.0 fold by all dietary treatments. Malic enzyme was increased 2.8 and 2.4 fold with saturated and polyunsaturated diets respectively, yet was unaltered by the monounsaturated fat diet.
Conclusion – Modifications in common dietary fat composition initiated divergent gene responses in liver. These alterations were complex, with no uniform alteration in transcription factors with closely related functions (PPARfamily) and genes encoding proteins within the same metabolic pathway (fat oxidation or fat synthesis). Further studies are necessary to identify the predominant mechanisms regulating these differences in gene expression.