Increased FNDC5/Irisin expression in human hepatocellular carcinoma

The fibronectin type III domain containing 5 (FNDC5)/Irisin, a novel energy-regulating hormone, is associated with lipid and carbohydrate metabolism. It is produced in low amounts by normal hepatic tissue, while in human hepatocellular carcinoma (HCC), in which aberrant de novo lipogenesis (DNL) occurs, the hepatic expression of FNDC5/Irisin is still unknown. The gene expression of FNDC5/Irisin, associated to key regulators of DNL, inflammation and cancer progression was evaluated in liver tissue of 18 patients with HCC undergoing liver transplantation and of 18 deceased donors. Hepatic mRNA expression of FNDC5/Irisin and stearoyl-CoA desaturase (SCD-1), main enzymatic regulator of DNL, were significantly higher in HCC patients than in donors (p<0.0001 and p=0.015, respectively). The hepatic mRNA expression of the neurogenic locus notch homolog protein 1 (NOTCH1) tended to be higher in HCC patients than in donors (p=0.06). Only in HCC patients, hepatic FNDC5/Irisin strongly correlated with the transcription factor sterol regulatory element-binding factor 1, SCD-1, NOTCH1, tumor necrosis factor-α and Interleukin-6 mRNA expression. Further, in HCC patients, FNDC5/Irisin mRNA tended to correlate to plasma lipid profile namely triglycerides, palmitic/linoleic acid and polyunsaturated fatty acid/saturated fatty acid ratios. In conclusion, HCC-liver tissue over-expressed FNDC5/Irisin in association with gene expression of mediators involved in lipogenesis, inflammation and cancer, suggesting a possible protective role of the hormone from the liver damage.