title: MicroRNA148b-3p inhibits mTORC1-dependent apoptosis in diabetes by repressing TNFR2 in proximal tubular cells.
abstract: Hypoxia causes proximal tubular cell damage in diabetes, even though proximal tubular cells have an adaptive system to combat hypoxia involving induction of hypoxia factor-1 (HIF-1) and inhibition of mechanistic target of rapamycin complex 1 (mTORC1). Here, we examined the interference effect of altered glucose and lipid metabolism on the hypoxia responses in proximal tubular cells. In culture, hypoxia alone induced HIF-1 and inhibited mTORC1, preventing death in proximal tubular cells. However, hypoxia with high glucose and palmitate increased mTORC1 activity and promoted apoptosis in proximal tubular cells, which was inhibited by pharmacological and genetic inactivation of mTORC1. Since inhibition of all mTORC1's physiological functions regulated by growth factors including insulin causes various adverse effects, we screened for a microRNA that can inhibit only pro-apoptotic effects of mTORC1 to discover a safe therapeutic target. This screen found microRNA-148b-3p was able to specifically inhibit mTORC1-dependent apoptosis in hypoxic proximal tubular cells exposed to high glucose and palmitate, without affecting insulin-dependent mTORC1 activation. Furthermore, tumor necrosis factor receptor (TNFR) 2 was the target of microRNA-148b-3p and its suppression inhibited apoptosis. Finally, enhanced apoptosis with TNFR2 overexpression was found in hypoxic and mTORC1-activated proximal tubular cells in diabetic rats. Thus, diabetes activated mTORC1 even in hypoxic proximal tubular cells, leading to apoptosis by reducing microRNA-148b-3p expression. Modulating this pathogenic pathway may be a novel therapy for proximal tubular cell damage in diabetes.
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Shogo
authors: S
authors: Kuwagata
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan. Electronic address: skume@belle.shiga-med.ac.jp.
authors: Shinji
authors: S
authors: Kume
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Masami
authors: M
authors: Chin-Kanasaki
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Hisazumi
authors: H
authors: Araki
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Shinichi
authors: S
authors: Araki
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Jun
authors: J
authors: Nakazawa
authors: Department of Internal Medicine, St. Marianna University School of Medicine, Kanagawa, Japan.
authors: Takeshi
authors: T
authors: Sugaya
authors: Division of Diabetology and Endocrinology, Kanazawa Medical University, Kahoku-Gun, Ishikawa, Japan.
authors: Daisuke
authors: D
authors: Koya
authors: Department of Medicine, Asahikawa Medical University, Asahikawa, Hokkaido, Japan.
authors: Masakazu
authors: M
authors: Haneda
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Hiroshi
authors: H
authors: Maegawa
authors: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors: Takashi
authors: T
authors: Uzu
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005947:Glucose; D000860:Hypoxia / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D050356:Lipid Metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D019308:Palmitic Acid; D051381:Rats; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: C000623169:MIRN148a microRNA, rat; D035683:MicroRNAs; D046912:Multiprotein Complexes; D047889:Receptors, Tumor Necrosis Factor, Type II; D019308:Palmitic Acid; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D005947:Glucose
keywords: TNF-α; TNF-α receptor; apoptosis; diabetic nephropathy; free fatty acids; high glucose; hypoxia; mammalian target of rapamycin complex 1; microRNA; proximal tubular cell