Role of Lipophilic Bile Acids in the Development of Cirrhotic Cardiomyopathy

Marked hemodynamic changes occur in humans and experimental animals with cirrhotic liver disease. In the heart, basal contractility, responsiveness to β-adrenoceptor activation, and excitation-contraction coupling (ECC) are negatively affected in models of cirrhosis and portal hypertension with portosystemic shunting (PVS), and comprise what has been called cirrhotic cardiomyopathy. These effects are accompanied by elevated circulating levels of bile acids. We investigated whether elevated bile acids act as a myocardial toxicant by exposing cardiac muscle in vitro to bile acids and compared these results with two models of cirrhotic cardiomyopathy with elevated bile acids: CCl₄-induced cirrhosis and PVS. Cholic acid, a lipophilic bile acid, produced a decrease in basal cardiac contractility and responsiveness to β-adrenoceptor activation, both of which appeared to result from altered ECC. β-Adrenoceptor density and signaling were unaffected. Acutely, ursodeoxycholic acid, a more hydrophilic bile acid, had no effect. Cirrhosis produced a decrease in basal force, depressed β-adrenoceptor responsiveness, and altered ECC similar to cholic acid. However, cirrhosis also altered β-adrenoceptor signaling including decreases in cyclic AMP formation, expression of the stimulatory G protein, GS, and β-adrenoceptor density. Displacement of lipophilic bile acids by chronic administration of ursodeoxycholic acid to rats during the development of cirrhotic cardiomyopathy produced by PVS produced attenuation of the effect on ECC. These results suggest a possible role for lipophilic bile acids in some, but not all of the myocardial consequences of chronic portal vein stenosis and CCl₄-induced cirrhosis.