Impact of artificial sunlight therapy on the progress of non-alcoholic fatty liver disease in rats

Abstract

Non-alcoholic steatohepatitis (NASH) is recognized as the most severe form of non-alcoholic fatty liver disease, with likely progression to liver cirrhosis and hepatocellular carcinoma. However, there is no unified standard for diagnosis and therapeutics. This study aimed to characterize lipid transfer/metabolic proteins as non-invasive diagnostic markers, and to evaluate the therapeutic effects of phototherapy on the progression of NASH in rats. Lewis rats given a choline-deficient and iron-supplemented l-amino acid-defined (CDAA) diet and Zucker fa/fa rats were used as a diet-induced and an obesity-related NASH models, respectively, with or without phototherapy. Serum apolipoprotein E and low molecular weight-adiponectin levels were gradually reduced and reached the lowest level at fatty liver/NASH stage both in CDAA diet-induced NASH model and in genetically obese model. Total-adiponectin levels were dramatically elevated after NASH was established in CDAA diet-induced NASH model. Phototherapy ameliorated hepatocyte apoptosis, inflammation, fibrosis, and insulin/leptin resistance caused by CDAA diet with alteration of the levels of lipid transfer/metabolic proteins and elevation of the circulating active form of vitamin D(3). Vitamin D(3) supplementation ameliorated NASH progression in CDAA diet-induced NASH model. However, phototherapy failed to ameliorate the obesity and steatosis, suggesting that phototherapy may possess anti-inflammatory/fibrotic activity rather than anti-obesity/steatotic activity. These results suggest that serum lipid transfer/metabolic proteins and vitamin D(3) status may be effective biomarkers for non-invasive diagnosis of NASH progression, and that phototherapy may be a good complementary therapy for NASH because of its regulation of lipid transfer/metabolic proteins and vitamin D(3).