D2 | Abstract 22

Annual NUTRIM Symposium 18 November 2020


Inhibition of extracellular cathepsin D improves NASH in mice with a human-like lipoprotein profile

Tulasi Yadati1, Tom Houben1, Albert Bitorina1, Marion Gijbels1, Ronny Mohren2, Princy Khurana3, Aditya Kulkarni3, Berta Cillero-Pastor2 and Ronit Shiri-Sverdlov1

1 Department of Molecular Genetics, School of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht University, Maastricht, The Netherlands
2 Maastricht Multimodal Molecular Imaging Institute (M4I), Division of Imaging Mass Spectrometry, Maastricht University, Maastricht, The Netherlands
3 Aten Porus Lifesciences Pvt Ltd, Bengaluru, Karnataka, India.
Non-alcoholic steatohepatitis (NASH) is mainly characterized by abnormal lipid accumulation (steatosis) and inflammation. Lysosomal protease, cathepsin D (CTSD) has been shown to be associated with hepatic inflammation in NASH. While lysosomal fraction of CTSD is involved in cellular protein degradation and turnover, extracellular CTSD is mostly implicated in metabolic inflammatory diseases. Similarly, we have shown that specific inhibition of extracellular CTSD activity led to improved lipid metabolism in Sprague-Dawley rats with steatosis. To gain deeper mechanistic insights into CTSD function, in the current study we compared the individual roles and downstream targets of intracellular and extracellular CTSD in NASH using specific small-molecule inhibitors.

LDL-receptor knock out (Ldlr-/-) mice were fed a high-fat, high cholesterol (HFC) diet for a period of ten weeks to induce NASH. Further, to investigate the effects of CTSD inhibition, mice were injected either with an intracellular (GA-12; 50µg/g body weight) or extracellular (CTD-002; 50µg/g body weight) CTSD inhibitors or vehicle control subcutaneously once in two days for ten weeks.

Specific inhibition of extracellular CTSD reduced hepatic lipid accumulation in mice which coincided with the increased fecal bile acids levels compared to intracellular CTSD inhibition. Furthermore, extracellular CTSD inhibition switched the systemic immune status of the mice to an anti-inflammatory profile. Mass spectroscopy-based proteomics revealed that intra and extracellular CTSD fractions regulate distinct targets. Overall, extracellular CTSD inhibition reduced NASH-related features while intracellular CTSD inhibition led to worsening of hepatic mitochondrial function.

Our work highlights unique and separate roles for the intracellular and extracellular CTSD fractions in NASH pathogenesis. Using a mouse model with ‘human-like’ lipoprotein profile, we have provided a clinically translatable evidence that extracellular CTSD contributes to inflammation and lipid metabolism in NASH. Therefore, specific inhibitors capable of blocking extracellular CTSD activity have a potential as new NASH drugs.

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