LEW.1WR1 Rat Shows an Increased Risk of Developing Malignant Forms of NAFLD

Abstract

Non alcoholic Fatty Liver Disease(NAFLD) is a disease usually found alongside diabetes in patients and is known as a manifestation of the metabolic disorder. The disease describes a progression of increasingly malignant conditions affecting the liver starting from benign steatosis. Steatosis can progress to steatohepatitis, damaging cells and encouraging scar tissue formation. The LEW.1WR1(1WR1) rat overexpresses fat10, a gene which plays a role in age-related inflammation, insulin resistance, adiposity, and hepatocellular carcinoma. This gene has been shown to be essential in maintaining liver cell protein quality control and Mallory Denk body(MDB) formation(Jia, Ji, & French, 2020). 1WR1 rats have been shown to become more glucose intolerant as they age, developing insulin resistance increasing risk of Diabetes and NAFLD. They have also been shown to develop increased body mass while not having significantly different epididymal fat pad deposits and increased fat10 concentration in the liver compared to control animals (Collins, Clopp, Mercado, Gibson, & Love-Rutledge, 2019). Increasing understanding of fat10’s functions is important for future research in reducing disease susceptibility in NAFLD. For this project we hypothesized that because weight was not being added to the fat pads in the previous study it would be added to the organs; therefore these animals would develop increased liver mass or fatty liver as they age increasing risk of NAFLD. This project studied glucose intolerance, triglyceride levels, liver weight, MDBs, and NAFLD Activity score(NAS) of 1WR1 and WF/NHsd(WF) rat livers. These rats were subjected to a 7% sucrose or normal diet type by Research Diets from 5-7 weeks of age. At 21 weeks old a 120 minute human like glucose tolerance test was done after a fasting period of 8 hours. Triglyceride concentrations in the blood, liver, and muscles were measured. Sacrifice occurred at 18 weeks of study and the livers were weighed and formalin fixed. They were then sent to Histowiz for slide processing and digitalization. Scoring for MDBs and NAS were done on the resulting slides. The results of the glucose tolerance test confirmed these rats became more glucose intolerant during the study as their glucose levels were unable to return to baseline after 120 minutes. The Triglyceride assay showed significantly higher concentrations of liver and muscle triglyceride levels to the control. The liver mass measurements showed the 1WR1 rats had significantly heavier livers to the control. The MDB scoring showed their presence primarily in the 1WR1 rats. Finally, the results of our NAS scoring indicated that the 1WR1 rats developed steatosis at a higher rate than the control. The steatosis development at a higher rate correlates to a higher risk of steatohepatitis and further malignant forms of NAFLD. Fat10’s roles in age related glucose intolerance and liver function increases risk of development of later malignant NAFLD forms.