title: Free fatty acids promote hepatic lipotoxicity by stimulating TNF-alpha expression via a lysosomal pathway.
abstract: Nonalcoholic fatty liver disease (NAFLD) is a serious health problem. Although NAFLD represents a form of lipotoxicity, its pathogenesis remains poorly understood. The aim of this study was to examine the cellular mechanisms involved in free fatty acid (FFA)-mediated hepatic lipotoxicity. FFA treatment of liver cells resulted in Bax translocation to lysosomes and lysosomal destabilization with release of cathepsin B (ctsb), a lysosomal cysteine protease, into the cytosol. This process was also partially dependent on ctsb. Lysosomal destabilization resulted in nuclear factor kappa B-dependent tumor necrosis factor alpha expression. Release of ctsb into the cytoplasm was also observed in humans with NAFLD and correlated with disease severity. In a dietary murine model of NAFLD, either genetic or pharmacological inactivation of ctsb protected against development of hepatic steatosis, liver injury, and insulin resistance with its associated "dysmetabolic syndrome." In conclusion, these data support a lipotoxic model of FFA-mediated lysosomal destabilization.
authors.affiliation: Department of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors.forename: Ariel E
authors.initials: AE
authors.lastname: Feldstein
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Werneburg
authors.forename: Ali
authors.initials: A
authors.lastname: Canbay
authors.forename: Maria Eugenia
authors.initials: ME
authors.lastname: Guicciardi
authors.forename: Steven F
authors.initials: SF
authors.lastname: Bronk
authors.forename: Robert
authors.initials: R
authors.lastname: Rydzewski
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Burgart
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004032:Diet / Q000009:adverse effects; D004338:Drug Combinations; D005230:Fatty Acids, Nonesterified / Q000502:physiology*; D005234:Fatty Liver / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D008099:Liver / Q000187:drug effects*; D008247:Lysosomes / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D019301:Oleic Acid / Q000506:poisoning*; D010168:Palmitates / Q000506:poisoning*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D012720:Severity of Illness Index; D014018:Tissue Distribution; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
chemical_list: D015703:Antigens, CD; C494826:BAX protein, human; C494827:Bax protein, mouse; D004338:Drug Combinations; D005230:Fatty Acids, Nonesterified; D016328:NF-kappa B; D010168:Palmitates; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D019301:Oleic Acid; D002401:Cathepsin B