Diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease in the US, and podocyte injury is an important feature of DKD. However, mechanisms of podocytopenia in DKD are poorly understood. Podocyte apoptosis and activation of RhoA are observed in immortalized human podocytes exposed to the sera of patients with T1D or T2D and DKD in conjunction with cholesterol accumulation and can be prevented by cyclodextrin (CD), an oligosaccharide that removes cholesterol from cells and that protects diabetic mice from the development of proteinuria. Excessive glomerular cholesterol deposition has been described in clinical and experimental DKD, is associated with impaired cholesterol efflux as suggested by the down-regulation of ATP-binding cassette transporter (ABCA1) expression, and can be induced by TNFa. The relative contribution of free and esterifed cholesterol to podocyte injury is unknown. Our long-term goal is to develop therapeutic strategies that target podocyte cholesterol accumulation in DKD. We hypothesize that: 1) TNFa-mediated downregulation of ABCA1 in podocytes results in accumulation of cholesterol; 2) accumulation of esterified cholesterol in early DKD causes podocyte hypertrophy while free cholesterol in late DKD causes podocyte apoptosis; 3) therapeutic strategies that reduce intracellular cholesterol accumulation protect podocytes in DKD. In order to test these hypotheses, we will utilize genetically modified mouse models, NIH approved models of DKD and in vitro experiment in human podocytes with the aim to: 1-Determine if ABCA1 deficiency in podocytes worsens podocyte injury and proteinuria in DKD. 2-Determine the relative contribution of free and esterified cholesterol to podocyte injury. 3-Determine if podocytopenia in DKD can be prevented by podocyte depletion of free cholesterol with CD and/or ABCA1 inducers. This proposal is innovative as the role of intracellular free and esterified cholesterol n the pathogenesis of podocyte injury in DKD has never been explored. In order to match innovation with adequate expertise, we have assembled a unique team of investigators that includes podocyte biologists, lipid biologists, pathologists, nephrologists and endocrinologists.
We aim to advance the knowledge related to DKD by uncovering novel disease mechanisms amenable to therapeutic intervention.

Public Health Relevance

Currently available interventions have demonstrated to slow but not halt the progression of diabetic kidney disease (DKD). As cholesterol accumulates in glomeruli from patients with DKD, we propose to study how free and esterified cholesterol affects podocyte function and survival in DKD. We will also investigate if novel and clinical grade cholesterol depleting agents preserve podocyte function in DKD, thus offering the opportunity for the development of novel therapeutic strategies for DKD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK104753-02
Application #
9032492
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Rys-Sikora, Krystyna E
Project Start
2015-03-20
Project End
2019-02-28
Budget Start
2016-03-01
Budget End
2017-02-28
Support Year
2
Fiscal Year
2016
Total Cost
Indirect Cost
Name
University of Miami School of Medicine
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
052780918
City
Coral Gables
State
FL
Country
United States
Zip Code
33146
Bassi, Roberto; Fornoni, Alessia; Doria, Alessandro et al. (2016) CTLA4-Ig in B7-1-positive diabetic and non-diabetic kidney disease. Diabetologia 59:21-9
Grahammer, Florian; Wigge, Christoph; Schell, Christoph et al. (2016) A flexible, multilayered protein scaffold maintains the slit in between glomerular podocytes. JCI Insight 1:
Pullen, Nick; Fornoni, Alessia (2016) Drug discovery in focal and segmental glomerulosclerosis. Kidney Int 89:1211-20
Wahl, Patricia; Ducasa, Gloria Michelle; Fornoni, Alessia (2016) Systemic and renal lipids in kidney disease development and progression. Am J Physiol Renal Physiol 310:F433-45
Pedigo, Christopher E; Ducasa, Gloria Michelle; Leclercq, Farah et al. (2016) Local TNF causes NFATc1-dependent cholesterol-mediated podocyte injury. J Clin Invest 126:3336-50
Villarreal, Rodrigo; Mitrofanova, Alla; Maiguel, Dony et al. (2016) Nephrin Contributes to Insulin Secretion and Affects Mammalian Target of Rapamycin Signaling Independently of Insulin Receptor. J Am Soc Nephrol 27:1029-41
Coward, Richard; Fornoni, Alessia (2015) Insulin signaling: implications for podocyte biology in diabetic kidney disease. Curr Opin Nephrol Hypertens 24:104-10
Fornoni, Alessia; Vendrame, Francesco (2015) Editorial: current perspectives in diabetes and transplantation. Curr Diabetes Rev 11:134
Chang, William Gee; Fornoni, Alessia; Tietjen, Gregory et al. (2015) Tissue-Engineered Microvasculature to Reperfuse Isolated Renal Glomeruli. Tissue Eng Part A 21:2673-9
Yoo, Tae-Hyun; Fornoni, Alessia (2015) Nonimmunologic targets of immunosuppressive agents in podocytes. Kidney Res Clin Pract 34:69-75

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