Low-light-level therapy as a treatment for minimal hepatic encephalopathy: behavioural and brain assessment

Abstract

Minimal hepatic encephalopathy (MHE) has been shown to affect daily functioning, quality of life, driving and overall mortality. However, little is known about treating or diagnosing early impairments involved in MHE. We studied one of its precipitating factors, portal hypertension. The purpose was to evaluate an enhancement in neuronal metabolism through low-light-level therapy (LLLT) and whether this therapy has effects on behavioural task acquisition. Rats were trained to perform a stimulus-response task using the Morris water maze. Three groups of animals were used: a SHAM (sham-operated) group (n = 7), a portal hypertension (PH) group (n = 7) and a PH + LLLT group (n = 7). The triple portal vein ligation method was used to create an animal model of the early developmental phase of HE, and then the animals were exposed to 670 + 10 nm LED light at a dose of 9 J/cm² once a day for 7 days. The metabolic activity of the brains was studied with cytochrome c oxidase histochemistry. There were differences in behavioural performance, with an improvement in the PH + LLLT group. Energetic brain metabolism revealed significant differences between the groups in all the brain structures analysed, except the anterodorsal thalamus. At the same time, in different brain networks, the PH group showed a more complicated relationship among the structures, while the SHAM and PH + LLLT groups had similar patterns. In this study, we provide the first preliminary insights into the validity of LLLT as a possible intervention to improve memory under minimal hepatic encephalopathy conditions.

Keywords: Brain; Cytochrome c oxidase; Low-light-level therapy; Minimal hepatic encephalopathy; Rat; Stimulus-response task.