title: Fatty acids are novel nutrient factors to regulate mTORC1 lysosomal localization and apoptosis in podocytes.
abstract: Podocyte apoptosis is a potent mechanism of proteinuria in diabetic nephropathy. More detailed mechanistic insight into podocyte apoptosis is needed to better understand the pathogenesis of diabetic nephropathy. An elevated level of serum free fatty acid (FFA), as well as hyperglycemia, is a clinical characteristic in diabetes, although its causal role in podocyte apoptosis remains unclear. This study examined the effect of three types of FFAs, saturated, monounsaturated and polyunsaturated FFAs, on podocyte apoptosis. Palmitate, a saturated FFA, induced endoplasmic reticulum (ER) stress-dependent apoptosis in podocytes. Oleate, a monounsaturated FFA, and eicosapentaenoic acid (EPA), an ω-3 polyunsaturated FFA did not induce apoptosis; rather, they antagonized palmitate-induced apoptosis. Palmitate activated mammalian target of rapamycin (mTOR) complex 1 (mTORC1), a nutrient-sensing kinase regulating a wide range of cell biology. Furthermore, inhibition of mTORC1 activity by rapamycin or siRNA for Raptor, a component of mTORC1, ameliorated palmitate-induced ER stress and apoptosis in podocytes. Activity of mTORC1 is regulated by upstream kinases and Rag/Ragulator-dependent recruitment of mTOR onto lysosomal membranes. Palmitate activated mTORC1 by enhancing recruitment of mTOR onto lysosomal membranes, which was inhibited by co-incubation with oleate or EPA. Inhibition of mTOR translocation onto lysosomes by transfection with dominant-negative forms of Rag ameliorated palmitate-induced apoptosis. This study suggests that saturated and unsaturated FFAs have opposite effects on podocyte apoptosis by regulating mTORC1 activity via its translocation onto lysosomal membranes, and the results provide a better understanding of the pathogenesis in diabetic nephropathy and a novel role of mTORC1 in cell apoptosis.
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Mako
authors.initials: M
authors.lastname: Yasuda
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan. Electronic address: skume@belle.shiga-med.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kume
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Yoshikata
authors.initials: Y
authors.lastname: Morita
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Chin-Kanasaki
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Hisazumi
authors.initials: H
authors.lastname: Araki
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Isshiki
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Araki
authors.affiliation: Division of Diabetology and Endocrinology, Kanazawa Medical University, Kahoku-Gun, Ishikawa, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koya
authors.affiliation: Department of Medicine, Asahikawa Medical University, Asahikawa, Hokkaido, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Haneda
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kashiwagi
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maegawa
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Uzu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D003928:Diabetic Nephropathies / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000502:physiology; D005227:Fatty Acids / Q000378:metabolism*; D005502:Food; D057809:HEK293 Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism*; D019301:Oleic Acid / Q000378:metabolism; D010168:Palmitates / Q000378:metabolism; D050199:Podocytes / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D046912:Multiprotein Complexes; D010168:Palmitates; D019301:Oleic Acid; D015118:Eicosapentaenoic Acid; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases
keywords: Diabetic nephropathy; Free fatty acid; Lysosome; Podocyte apoptosis; mTORC1