Neural amino acid transporter B(0) (ATB or ASCT2 encoded by SLC1A5) is a glutamine transporter that also plays an important role in metabolism and amino acid homeostasis of cells in most tissues and it may be relevant in glutamine-derived ammonia production 7. ![]() ![]() In a damaged liver, especially a cirrhotic one which can have up to four times more ammonia producing activity, hepatocytes cannot handle the overload and urea cycle is saturated 6. The majority of the gut ammonia is a by-product derived from glutamine metabolism into glutamate and ammonia by the enzyme glutaminase (EC 3.5.1.2) 4. The pathophysiological mechanisms include alteration of blood-brain-barrier permeability, cytokine production, changes in neurotransmitter synthesis and release, neuronal oxidative stress, impaired mitochondrial function and osmotic disturbances resulting from astrocytic metabolism 4.Īmmonia is mainly produced in the small intestine during protein digestion and nitrogen metabolism carried out by epithelial cells and bacterial flora 5. Clinical studies strongly suggest a major role of ammonia in the development of brain disturbances in liver disease and systemic hyperammonemia is commonly found in patients with cirrhosis and HE 3. This syndrome involves neuropsychiatric dysfunction ranging from subtle psychological abnormalities to profound coma due to a metabolic disturbance 2. Hepatic encephalopathy (HE) is a common entity caused by liver failure that results from acute and chronic disorders such as hepatitis and cirrhosis and is one of the main complications of cirrhosis 1.
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