Effects of a high protein diet on cognition and brain metabolism in cirrhotic rats

Hepatic encephalopathy (HE) is a neurological complication observed in patients with liver disease. Patients who suffer from HE present neuropsychiatric, neuromuscular and behavioral symptoms. Animal models proposed to study HE resulting from cirrhosis mimic the clinical characteristics of cirrhosis and portal hypertension, and require the administration of hepatotoxins such as thioacetamide (TAA). The aim of this study was to assess the effects of a high protein diet on motor function, anxiety and memory processes in a model of cirrhosis induced by TAA administration. In addition, we used cytochrome c-oxidase (COx) histochemistry to assess the metabolic activity of the limbic system regions. Male rats were distributed into groups: control, animals with cirrhosis, Control rats receiving a high protein diet, and animals with cirrhosis receiving a high protein diet. Results showed preserved motor function and normal anxiety levels in all the groups. The animals with cirrhosis showed an impairment in active avoidance behavior and spatial memory, regardless of the diet they received. However, the animals with cirrhosis and a high protein diet showed longer escape latencies on the spatial memory task. The model of cirrhosis presented an under-activation of the dentate gyrus and CA3 hippocampal subfields and the medial part of the medial mammillary nucleus. The results suggest that a high protein intake worsens spatial memory deficits shown by the TAA-induced model of cirrhosis. However, high protein ingestion has no influence on the COx hypoactivity associated with the model.