title: Smad3 deficiency protects mice from obesity-induced podocyte injury that precedes insulin resistance.
abstract: Signaling by TGF-β/Smad3 plays a key role in renal fibrosis. As obesity is one of the major risk factors of chronic and end-stage renal disease, we studied the role of Smad3 signaling in the pathogenesis of obesity-related renal disease. After switching to a high fat diet, the onset of Smad3 C-terminal phosphorylation, increase in albuminuria, and the early stages of peripheral and renal insulin resistance occurred at 1 day, and 4 and 8 weeks, respectively, in C57BL/6 mice. The loss of synaptopodin, a functional marker of podocytes, and phosphorylation of the Smad3 linker region (T179 and S213) appeared after 4 weeks of the high fat diet. This suggests a temporal pattern of Smad3 signaling activation leading to kidney injury and subsequent insulin resistance in the development of obesity-related renal disease. In vivo, Smad3 knockout attenuated the high fat diet-induced proteinuria, renal fibrosis, overall podocyte injury, and mitochondrial dysfunction in podocytes. In vitro palmitate caused a rapid activation of Smad3 in 30 min, loss of synaptopodin in 2 days, and impaired insulin signaling in 3 days in isolated mouse podocytes. Blockade of either Smad3 phosphorylation by SIS3 (a Smad3 inhibitor) or T179 phosphorylation by flavopiridol (a CDK9 inhibitor) prevented the palmitate-induced loss of synaptopodin and mitochondrial function in podocytes. Thus, Smad3 signaling plays essential roles in obesity-related renal disease and may be a novel therapeutic target.
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: Yu B Y
authors.initials: YB
authors.lastname: Sun
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: Xinli
authors.initials: X
authors.lastname: Qu
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia [2] Department of Physiology, Monash University, Clayton, VIC, Australia.
authors.forename: Victor
authors.initials: V
authors.lastname: Howard
authors.affiliation: Department of Rheumatology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, People's Republic of China.
authors.forename: Lie
authors.initials: L
authors.lastname: Dai
authors.affiliation: Department of Pediatrics, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, People's Republic of China.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Florida State University College of Medicine, Tallahassee, Florida, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.affiliation: Division of Nephrology, Department of Internal Medicine, West China Hospital of Sichuan University, Chengdu, People's Republic of China.
authors.forename: Ping
authors.initials: P
authors.lastname: Fu
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: Victor G
authors.initials: VG
authors.lastname: Puelles
authors.affiliation: Department of Nephrology, Monash Health and Monash University Department of Medicine, Clayton, VIC, Australia.
authors.forename: David J
authors.initials: DJ
authors.lastname: Nikolic-Paterson
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: Georgina
authors.initials: G
authors.lastname: Caruana
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: John F
authors.initials: JF
authors.lastname: Bertram
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia [2] Department of Physiology, Monash University, Clayton, VIC, Australia.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Sleeman
authors.affiliation: Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004041:Dietary Fats / Q000008:administration & dosage; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005355:Fibrosis; D005419:Flavonoids / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009765:Obesity / Q000150:complications* / Q000378:metabolism*; D019308:Palmitic Acid / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism*; D065840:Protective Factors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000172:deficiency* / Q000235:genetics
chemical_list: C508504:6,7-dimethyl-2-(2E)-3-(1-methyl-2-phenyl-1H-pyrrolo(2,3-b)pyridin-3-yl-prop-2-enoyl)-1,2,3,4-tetrahydroisoquinoline hydrochloride; D004041:Dietary Fats; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007328:Insulin; D007546:Isoquinolines; D008840:Microfilament Proteins; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D011758:Pyrroles; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C503968:Synpo protein, mouse; D019308:Palmitic Acid; C077990:alvocidib