Mechanisms of Malnutrition in Cirrhosis With Portosystemic Shunting

Cirrhosis is characterized by loss of muscle as well as fat mass, which increases morbidity and mortality before, during, and after liver transplantation. A common mechanism for the reduced muscle and fat mass in cirrhosis is an increased expression of the TGF (transforming growth factor)beta superfamily member, myostatin, in the muscle and adipose tissue. The present study will examine the expression of myostatin, its receptor and intracellular signaling pathways in the skeletal muscle and mesenteric adipose tissue in cirrhotic patients undergoing liver transplantation as compared to healthy controls undergoing planned abdominal surgery. 16 cirrhotic patients will be identified from the transplant list, and 16 healthy controls from outpatient surgery lists. Nutritional assessment will be performed, including anthropometry (triceps skinfold thickness, mid arm circumference), dual energy x-ray absorptiometry (DEXA), and bioelectrical impedance analysis (BIA). Rectus abdominis muscle tissue and omental fat tissue will be harvested in the operating room, and the expression of signaling proteins involved in skeletal muscle protein synthesis will be quantified. The investigator will also quantify the expression of genes involved in lipolysis and lipid synthesis. The investigator anticipates that the expression of myostatin will be higher in the skeletal muscle and adipose tissue of cirrhotics as compared to controls. There will be a reduction in the expression of the signaling proteins that regulate skeletal muscle protein synthesis, as well as the expression of genes regulating lipogenesis. The increased expression of myostatin will also correlate with reduced anthropometric and DEXA measurements of lean body mass and fat mass.