Investigations of NASH and hepatic fibrosis in the guinea pig model:

PhD Student: Josephine Skat-Rørdam

Email: jsr@sund.ku.dk

A copy of the thesis: Investigations of NASH and hepatic fibrosis in the guinea pig model (invivofarm.dk)

THE PROJECT
Non-alcoholic fatty liver disease (NAFLD) affects a quarter of the worlds’ population, and disease prevalence increases concomitant with the global obesity and diabetes pandemics. Defined by >5% liver fat, NAFLD ranges from mild disease states to non-alcoholic steatohepatitis (NASH) and cirrhosis characterized by inflammation, cellular damage and vast tissue scarring, ultimately requiring a liver transplant.

Diagnosis of NASH relies on an invasive liver biopsy, and treatment options are limited as there are currently no approved drugs. Consequently, development of non-invasive markers and treatment options are of critical priority. Development of successful drugs is heavily reliant on animal models mimicking the human disease. An ideal animal model should develop diet induced NASH with advanced liver fibrosis and metabolic components such as obesity and insulin resistance. In this regard, previous studies have demonstrated that the guinea pig model develops NASH with advanced fibrosis resembling human disease, although animals did not display obesity or insulin resistance.

As a central disease mechanism, several large clinical trials have investigated drug candidates targeting inflammation, and of these vitamin E and pentoxifylline have demonstrated positive effects. Despite this, another antioxidant, vitamin C, has not been investigated to the same extent. Unlike most other animal models the guinea pig, like humans, is reliant on dietary vitamin C intake, thus making it an ideal model for studying the effect of vitamin C on NASH.

PURPOSE
The purpose of this project was to investigate the translational potential of the guinea pig model by elucidating molecular mechanisms driving disease progression and comparing these to humans. This model was then used to assess two different intervention strategies targeting inflammation, and to identify novel biomarkers of fibrotic NASH.

RESULTS
In support of previous findings, the data presented in this thesis show a high transcriptional similarity between guinea pig and human NASH. This underscores the development of a hepatic phenotype closely resembling humans. Furthermore, the introduction of a low starch low fat diet, demonstrated increased weights and glucose intolerance in high fat/NASH animals compared to low fat diet fed animals, indicative of a metabolic phenotype more closely resembling that of patients.

In combination with a low fat diet, vitamin C improved recovery of the hepatic transcriptome, and nominally more animals showed improved inflammation, ballooning and fibrosis scores compared to vitamin C deficient animals. Collectively this may indicate a potential beneficial effect of vitamin C on the regression of NASH. In contrast, vitamin C did not appear to have an effect on disease progression in guinea pigs. Deficient animals displayed similar disease severity to non-deficient animals, rather the high fat diet seems to be the primary driver of disease progression.

CT-scanning was investigated as a non-invasive tool for NASH in an intervention study assessing the effect of acetylsalicylic acid and pentoxifylline treatment. While the chosen intervention did not indicate any effect on NASH, CT-scanning was able to detect steatosis, but not fibrosis in NASH guinea pigs. Thus to enable detection of fibrosis, RNA-sequencing data was used to identify potential markers identifiable by a simple blood test. This yielded two markers of interest, of which SERPINB9 has not previously been investigated as a biomarker for fibrotic NASH.

THE FUTURE 
A study is currently ongoing investigating the potential of SERPINB9 as a non-invasive marker for fibrotic NASH in a patient cohort.