Abstract.Microemulsions with limited stability in mimetic gastrointestinal environments have previously demonstrated potential for the effective removal of ammonia from artificial colonic fluid. Specialized pH-sensitive microemulsion-based gels for the removal of colonic ammonia (MBG-RCA), however, possess relative stability in the gastrointestinal (GI) tract of normal rats, indicating potential use in in vivo applications. An investigation of the effects of oral MBG-RCA was conducted in order to evaluate the reduction of intestinal ammonia and the prevention of hepatic encephalopathy (HE) in rat models. Eighty rats were allocated into eight 4-day treatment groups: The HE model (intraperitoneal injection of thioacetamide) group; the high-, medium-and low-dose MBG-RCA therapeutic groups (15, 10 and 5 ml/kg MBG-RCA, respectively); and the normal, blank, lactulose and acetic acid control groups, each of which received daily treatment administration. Oral MBG-RCA effects were identified using behavioral monitoring observed by an infrared night vision supervisory control system, electroencephalograms, blood ammonia levels, intestinal ammonia levels, liver functionality and pathological observation. High-and medium-dose oral administrations of MBG-RCA significantly decreased the blood and intestinal ammonia levels (P<0.05), improved liver functionality and reduced the clinical manifestations of HE in rats. MBG-RCA demonstrated high clearance of rat colonic ammonia while maintaining sufficient stability in the GI tract, indicating the potential for the development of new clinically relevant oral preparations for the prevention of HE. Additionally, such preparations are advantageous in that ammonia is eliminated without the production of potentially harmful metabolic byproducts.
IntroductionElimination of excess ammonia is the primary method of prevention and treatment of hepatic encephalopathy (HE), a progressive condition in which neurological function is impaired as the liver fails to remove toxic metabolites, particularly ammonia, from the bloodstream. The majority of intestinal ammonia is produced in the colon; however, no clinically viable oral treatment exists for the elimination of this excess ammonia, resulting in continuous low clearance levels due to poor ammonia elimination in the body.HE is a syndrome caused by serious hepatic diseases as a result of metabolic disturbance and dysfunction of the central nervous system. Its clinical manifestation includes deposition changes, ethological abnormalities and mental retardation. In severe cases, it may develop into a coma or even be life-threatening. A number of researchers have divided HE into three categories: Type A is associated with acute liver failure; type B is caused by severe portosystemic shunting without liver disease; and type C is associated with chronic liver disease and hepatic cirrhosis (1). Acute liver failure models are well recognized as a representative model of type A HE. These models may be used to examine the pathological response of HE to v...