Previous experimental findings regarding lysosomal acid lipase deficiency (LAL-D) induced by lalistat-1 (L1) and/or lalistat-2 (L2) in mice might not be as accurate as initially thought, according to a new study published in Molecular Metabolism.

The experimental study led by Bradić analyzed the off-target effects of lysosomal acid lipase (LAL) inhibitors L1 and L2 and discovered some key differences between pharmacological LAL-D vs the biological disease. These drugs are regularly used in in vitro and in vivo experiments in mice to mimic LAL-D and later extrapolate the results to the human population.

“Our findings are critically important since they demonstrate that commonly used concentrations of these inhibitors are not suitable to investigate the role of LAL-specific lipolysis in lysosomal function, signaling pathways, and autophagy,” the authors wrote. “The interpretation of their effects on lipid metabolism should be taken with caution and the applied inhibitor concentrations in cell culture studies should not exceed 1 μM.”


Continue Reading

Read more about LAL-D etiology

In contrast with the genetic disease, a pharmacological downregulation or knockdown of LAL also interferes with other enzymatic activities, including major cytosolic lipid hydrolases such as neutral triglyceride and cholesteryl ester hydrolase, hormone-sensitive lipase, monoacylglycerol lipase, and adipose triglyceride lipase, among others. This results in an overall impairment of lipid degradation in primary cells at neutral pH.

These results may suggest that previous research on LAL-D using L1 and L2 for their experimental models may be misleading when interpreting such data in humans. Furthermore, the authors determined that to achieve a degree of LAL inhibition comparable to the disease, experiments must use 1 μM or higher concentrations. Most studies have indeed employed concentrations of 10 μM to 100 μM, and although complying with this goal, these quantities also interfere with neutral lipases.

“Our findings raise questions regarding the data interpretation of studies in which higher concentrations of L2 or L1 were used to distinguish between the roles of LAL and neutral lipid hydrolases,” the authors concluded.

“Results addressing specific signaling pathways dependent on lysosomal-derived free fatty acid and cholesterol should be re-evaluated. Hence, this study critically questions the use of these inhibitors to investigate lysosomal lipid hydrolysis because they act on both the neutral and the acid lipid degradation pathways.”

Reference

Bradić I, Kuentzel K, Honeder S, et al. Off-target effects of the lysosomal acid lipase inhibitors Lalistat-1 and Lalistat-2 on neutral lipid hydrolases. Mol Metab. Published online April 30, 2022. doi:10.1016/j.molmet.2022.101510