Diet Induced Zebrafish Model of Steatosis (NAFLD) and Steatohepatitis (NASH)

Non-Alcoholic Fatty Liver Disease (NAFLD) and Steatohepatitis (NASH) has been established now in zebrafish. NASH is characterized by lobular inflammation; hepatocyte ballooning and degeneration progressing to liver fibrosis is fully reproducible in our zebrafish model. 

A classical method to model NASH is the use of methionine and choline diet induced obesity. In such a method of induction, NASH pathogenisis in zebrafish is characterized by  accumulation of fat, visceral adiposity, obesity, insulin resistance, glucose Intolerance, type 2 diabetes with systemic high cholesterol and high triglycerides.

Established Scientific Hypothesis of NASH :  The progress of the disease is in the order of obesity followed by insulin resistance, steatosis, inflammation, apoptosis and fibrosis.

 

Pentagrit Model Description: Wildtype juvenile fish are fed with high cholesterol diet from the period of 6 weeks.6 weeks after induction, NASH phenotype is observed. The fish is graded and experimental groups can be set. Key phenotype observations includes increased liver size as % of body weight, deviation in ALT, hepatomegaly with proceeds to  steatosis and ballooning.

 Oral Dosing Outcomes: 25mg (Translated Dose) of OCA  given for 3 weeks in Zebrafish is equivalent to a 72 week study period in humans.  The outcomes were statistical significant improvements in  histological endpoints leading to decrease in the NAFLD Activity Score, with no worsening of fibrosis.  Also administration of OCA at 25 mg (Translated Dose)  daily for 1 week reduced markers of liver inflammation and also increased insulin sensitivity similar to that of the study in humans.

Managing Adverse Effects:  Maximum tolerable dose for high cholesterol groups and QT interval studies can be performed to evaluate  long-term safety issues  for the concomitant use of statins in OCA treatment.

NASH Liver Biopsy:  Red O stained liver sections of  DIO NASH Zebrafish showing lipid accumulation correlations with an increase in gross liver size.  The progress is with an increased Liver/Body weight ratio reaching to a  window of ratio 0.022 between WT and NASH Zebrafish. NASH progress is also with an increasingly yellow colored liver indicating fat accumulation. Quantitative determinations using chemometric method identified a severe steatosis  with >67% fat in NASH zebrafish.

Genetic Zebrafish Model of NASH

Genetic Zebrafish Model of NASH is induced through a precise knockout of genes that predispose the animal to NASH. Following a knock out of the selected gene, the animal may be fed with enriched diet to drive the require NASH pathophysiology. In such as case the genetic model can therefore carry the metabolic environment and the genetic predisposition with increased relevance of the disease progress in humans - replicating the heterogeneity of patient metabolic profile for NASH. The genetic NASH model in zebrafish therefore covers a wide range of pathophysiology as observed in the human population providing more meaningful  dose outcomes meausures.

 NASH Model Trials in Zebrafish

 Zebrafish NASH Model as an alternative model of NASH could be further refined as per genetic predisposition. An animal trial study would consist of multiple arms with subjects carrying atleast one gene that predispose a NASH mileu. Therefore a single study group of animals is able to represent the the heterogeneity of human  population. The table below represents, selected genes that  predispose zebrafish to a varying degree of NASH.

References: 

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