title: Growth-dependent podocyte failure causes glomerulosclerosis.
abstract: Podocyte depletion leads to glomerulosclerosis, but whether an impaired capacity of podocytes to respond to hypertrophic stress also causes glomerulosclerosis is unknown. We generated transgenic Fischer 344 rats that express a dominant negative AA-4E-BP1 transgene driven by the podocin promoter; a member of the mammalian target of rapamycin complex 1 (mTORC1) pathway, 4E-BP1 modulates cap-dependent translation, which is a key determinant of a cell's hypertrophic response to nutrients and growth factors. AA-4E-BP1 rat podocytes expressed the transgene and had normal kidney histology and protein excretion at 100 g of body weight but developed ESRD by 12 months. Proteinuria and glomerulosclerosis were linearly related to both increasing body weight and transgene dose. Uni-nephrectomy reduced the body weight at which proteinuria first developed by 40%-50%. The initial histologic manifestation of disease was the appearance of bare areas of glomerular basement membrane from the pulling apart of podocyte foot processes, followed by adhesions to the Bowman capsule. Morphometric analysis confirmed the mismatch between glomerular tuft volume and total podocyte volume (number × size) per tuft in relation to weight gain and nephrectomy. Proteinuria and glomerulosclerosis did not develop if dietary calorie restriction prevented weight gain and glomerular enlargement. In summary, failure of podocytes to match glomerular tuft growth in response to growth signaling through the mTORC1 pathway can trigger proteinuria, glomerulosclerosis, and progression to ESRD. Reducing body weight and glomerular growth may be useful adjunctive therapies to slow or prevent progression to ESRD.
authors: Nephrology Division, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
authors: Akihiro
authors: A
authors: Fukuda
authors: Mahboob A
authors: MA
authors: Chowdhury
authors: Madhusudan P
authors: MP
authors: Venkatareddy
authors: Su Q
authors: SQ
authors: Wang
authors: Ryuzoh
authors: R
authors: Nishizono
authors: Tsukasa
authors: T
authors: Suzuki
authors: Larysa T
authors: LT
authors: Wickman
authors: Jocelyn E
authors: JE
authors: Wiggins
authors: Timothy
authors: T
authors: Muchayi
authors: Diane
authors: D
authors: Fingar
authors: Kerby A
authors: KA
authors: Shedden
authors: Ken
authors: K
authors: Inoki
authors: Roger C
authors: RC
authors: Wiggins
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D031204:Caloric Restriction; D018797:Cell Cycle Proteins; D005923:Glomerulosclerosis, Focal Segmental / Q000209:etiology* / Q000517:prevention & control; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D006984:Hypertrophy; D007678:Kidney Glomerulus / Q000254:growth & development*; D008297:Male; D009392:Nephrectomy; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D050199:Podocytes / Q000473:pathology / Q000502:physiology*; D011507:Proteinuria / Q000209:etiology / Q000517:prevention & control; D051381:Rats; D011916:Rats, Inbred F344; D055647:Rats, Transgenic; D015430:Weight Gain
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D010750:Phosphoproteins