Expression of IGF-I and IGF-binding protein genes in cirrhotic liver

The liver plays a central role in the IGF-I axis producing the majority of circulating hormone and some of its binding proteins (IGFBPs). Cirrhosis of the liver is characterised by changes in IGF-I and IGFBPs associated with liver fibrosis and regeneration. We have studied steady state levels of mRNA for the genes in the IGF-I axis in normal and cirrhotic human liver, localised the most highly expressed gene, IGFBP-1, and measured circulating IGFBP-3 by radioimmunoassay (RIA), IGFBP-2 and IGFBP-3 by Western ligand blot (WLB), and protease activity for IGFBP-3 in cirrhotic patients. Messenger RNA for IGF-I, IGFBP-I, IGFBP-2, and IGFBP-3 was detectable by Northern blotting in normal and cirrhotic liver although there was considerable variation in expression. IGFBP-2 and IGFBP-3 tended to be more highly expressed in cirrhotic liver and IGFBP-1 was more highly expressed in normal liver, although there were no significant differences. In normal liver, in situ hybridisation localised IGFBP-1 to hepatocytes. In cirrhotic liver the regenerating nodules showed expression of IGFBP-1 while there was none in fibrotic tissue. Circulating IGFBP-3 levels were low as measured by RIA and WLB but protease activity was only found in one patient. IGFBP-2 levels, assessed by WLB, were similar to the normal serum pool. Our data show that key mRNAs involved in the IGF-I axis continue to be expressed in cirrhotic liver despite end stage liver disease. The low levels of IGFBP-3 do not appear to be due to reduced gene transcription or increased protease activity.