Recent studies demonstrated reduced blood lysosomal acid lipase (LAL) activity in patients with nonalcoholic fatty liver disease (NAFLD). We aimed to verify hepatic LAL protein content and activity in in vitro and in vivo models of fat overload and in NAFLD patients. LAL protein content and activity were firstly evaluated in Huh7 cells exposed to high-glucose/high-lipid (HGHL) medium and in the liver of C57BL/6 mice fed with high-fat diet (HFD) for 4 and 8 months. LAL protein was also evaluated by immunohistochemistry in liver biopsies from 87 NAFLD patients and 10 controls, and correlated with hepatic histology. Huh7 cells treated with HGHL medium showed a significant reduction of LAL activity, which was consistent with reduced LAL protein levels by western blotting using an antibody towards the N-term of the enzyme. Conversely, antibodies towards the C-term of the enzyme evidenced LAL accumulation, suggesting a post-translational modification that masks the LAL N-term epitope and affects enzymatic activity. Indeed, we found a high rate of ubiquitination and extra-lysosomal localization of LAL protein in cells treated with HGHL medium. Consistent with these findings, inhibition of proteasome triggered dysfunctional LAL accumulation and affected LAL activity. Accumulation of ubiquitinated/dysfunctional LAL was also found in the liver of HFD fed mice. In NAFLD patients, hepatic levels of non-ubiquitinated/functional LAL were lower than in controls and inversely correlated with disease activity and some of the hallmarks of reduced LAL. Fat overload leads to LAL ubiquitination and impairs its function, possibly reducing hepatic fat disposal and promoting NAFLD activity.

Carotti, S., Lettieri-Barbato, D., Piemonte, F., Ruggiero, S., Rosina, M., Zalfa, F., et al. (2021). Molecular and histological traits of reduced lysosomal acid lipase activity in the fatty liver. CELL DEATH & DISEASE, 12(12), 1092 [10.1038/s41419-021-04382-4].

Molecular and histological traits of reduced lysosomal acid lipase activity in the fatty liver

Lettieri-Barbato, Daniele;Rosina, Marco;Aquilano, Katia;
2021-11-18

Abstract

Recent studies demonstrated reduced blood lysosomal acid lipase (LAL) activity in patients with nonalcoholic fatty liver disease (NAFLD). We aimed to verify hepatic LAL protein content and activity in in vitro and in vivo models of fat overload and in NAFLD patients. LAL protein content and activity were firstly evaluated in Huh7 cells exposed to high-glucose/high-lipid (HGHL) medium and in the liver of C57BL/6 mice fed with high-fat diet (HFD) for 4 and 8 months. LAL protein was also evaluated by immunohistochemistry in liver biopsies from 87 NAFLD patients and 10 controls, and correlated with hepatic histology. Huh7 cells treated with HGHL medium showed a significant reduction of LAL activity, which was consistent with reduced LAL protein levels by western blotting using an antibody towards the N-term of the enzyme. Conversely, antibodies towards the C-term of the enzyme evidenced LAL accumulation, suggesting a post-translational modification that masks the LAL N-term epitope and affects enzymatic activity. Indeed, we found a high rate of ubiquitination and extra-lysosomal localization of LAL protein in cells treated with HGHL medium. Consistent with these findings, inhibition of proteasome triggered dysfunctional LAL accumulation and affected LAL activity. Accumulation of ubiquitinated/dysfunctional LAL was also found in the liver of HFD fed mice. In NAFLD patients, hepatic levels of non-ubiquitinated/functional LAL were lower than in controls and inversely correlated with disease activity and some of the hallmarks of reduced LAL. Fat overload leads to LAL ubiquitination and impairs its function, possibly reducing hepatic fat disposal and promoting NAFLD activity.
18-nov-2021
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore BIO/10 - BIOCHIMICA
Settore BIO/09 - FISIOLOGIA
English
Carotti, S., Lettieri-Barbato, D., Piemonte, F., Ruggiero, S., Rosina, M., Zalfa, F., et al. (2021). Molecular and histological traits of reduced lysosomal acid lipase activity in the fatty liver. CELL DEATH & DISEASE, 12(12), 1092 [10.1038/s41419-021-04382-4].
Carotti, S; Lettieri-Barbato, D; Piemonte, F; Ruggiero, S; Rosina, M; Zalfa, F; Zingariello, M; Arciprete, F; Valentini, F; Francesconi, M; D'Amico, J...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/284825
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