Hepatology : official journal of the American Association for the Study of Liver Diseases
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Previous studies suggest reduced hepatic endothelial nitric oxide synthase activity contributes to increased intrahepatic resistance. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, undergoes hepatic metabolism via dimethylarginine-dimethylamino-hydrolase, and is derived by the action of protein-arginine-methyltransferases. Our study assessed whether ADMA, and its stereo-isomer symmetric dimethylarginine (SDMA), are increased in alcoholic hepatitis patients, and determined any relationship with severity of portal hypertension (hepatic venous pressure gradient measurement) and outcome. Fifty-two patients with decompensated alcoholic cirrhosis were studied, 27 with acute alcoholic hepatitis and cirrhosis, in whom hepatic venous pressure gradient was higher (P = 0.001) than cirrhosis alone, and correlated with ADMA measurement. Plasma ADMA and SDMA were significantly higher in alcoholic hepatitis patients and in nonsurvivors. Dimethylarginine-dimethylamino-hydrolase protein expression was reduced and protein-arginine-methyltransferase-1 increased in alcoholic hepatitis livers. ADMA, SDMA and their combined sum, which we termed a dimethylarginine score, were better predictors of outcome compared with Pugh score, MELD and Maddrey's discriminant-function. ⋯ Alcoholic hepatitis patients have higher portal pressures associated with increased ADMA, which may result from both decreased breakdown (decreased hepatic dimethylarginine-dimethylamino-hydrolase) and/or increased production. Elevated dimethylarginines may serve as important biological markers of deleterious outcome in alcoholic hepatitis.
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The Wnt signaling pathway is essential for a wide array of developmental and physiological processes. Wnts are extracellular ligands that bind to frizzled (Fz) receptors at the membrane, canonically inducing beta-catenin nuclear translocation and activation. Although beta-catenin has been shown to be critical in liver biology, the expression of the 19 Wnt and 10 Fz genes in liver remains undetermined. We report comprehensive analysis of Wnt and Fz expression in whole liver as well as individual cell types: freshly isolated and plated hepatocytes, biliary epithelial cells, normal and activated stellate and Kupffer cells, and sinusoidal endothelial cells (SECs). Oligonucleotides for the 19 Wnt, 10 frizzled receptors genes, and secreted Frizzled-related protein-1 (sFRP or Fzb) were synthesized based on the available sequences. A total of 11 Wnts and 8 Fz genes and Fzb were expressed in normal liver. Although only 6 Wnt and 5 Fz genes were expressed in freshly isolated hepatocytes, 8 Wnt genes, 7 Fz genes, and Fzb were expressed in plated hepatocytes. Although 12 Wnt and 7 Fz genes were expressed in biliary tree, additional Fz9 and Fzb were only expressed in cultured biliary epithelial cells. The same 14 Wnt and 7 Fz genes were expressed in both activated and normal stellate and Kupffer cells; only Fzb was expressed in their activated state. Also, 11 Wnt, seven Fz, and Fzb genes were expressed in SECs. ⋯ These data indicate that most Wnt and frizzled genes are expressed in the liver and might be playing important roles in liver pathobiology via canonical and noncanonical pathways.