Systems biology analysis reveals role of MDM2 in diabetic nephropathy
Rintaro Saito, … , Hans Joachim Anders, Kumar Sharma
Rintaro Saito, … , Hans Joachim Anders, Kumar Sharma
Published October 20, 2016
Citation Information: JCI Insight. 2016;1(17):e87877. https://doi.org/10.1172/jci.insight.87877.
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Categories: Research Article Nephrology

Systems biology analysis reveals role of MDM2 in diabetic nephropathy

Abstract

To derive new insights in diabetic complications, we integrated publicly available human protein-protein interaction (PPI) networks with global metabolic networks using metabolomic data from patients with diabetic nephropathy. We focused on the participating proteins in the network that were computationally predicted to connect the urine metabolites. MDM2 had the highest significant number of PPI connections. As validation, significant downregulation of MDM2 gene expression was found in both glomerular and tubulointerstitial compartments of kidney biopsy tissue from 2 independent cohorts of patients with diabetic nephropathy. In diabetic mice, chemical inhibition of MDM2 with Nutlin-3a led to reduction in the number of podocytes, increased blood urea nitrogen, and increased mortality. Addition of Nutlin-3a decreased WT1+ cells in embryonic kidneys. Both podocyte- and tubule-specific MDM2-knockout mice exhibited severe glomerular and tubular dysfunction, respectively. Interestingly, the only 2 metabolites that were reduced in both podocyte and tubule-specific MDM2-knockout mice were 3-methylcrotonylglycine and uracil, both of which were also reduced in human diabetic kidney disease. Thus, our bioinformatics tool combined with multi-omics studies identified an important functional role for MDM2 in glomeruli and tubules of the diabetic nephropathic kidney and links MDM2 to a reduction in 2 key metabolite biomarkers.

Authors

Rintaro Saito, Anaïs Rocanin-Arjo, Young-Hyun You, Manjula Darshi, Benjamin Van Espen, Satoshi Miyamoto, Jessica Pham, Minya Pu, Simone Romoli, Loki Natarajan, Wenjun Ju, Matthias Kretzler, Robert Nelson, Keiichiro Ono, Dana Thomasova, Shrikant R. Mulay, Trey Ideker, Vivette D’Agati, Ergin Beyret, Juan Carlos Izpisua Belmonte, Hans Joachim Anders, Kumar Sharma

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Figure 7

Pathophysiological analyses of MDM2-knockout mice.

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Pathophysiological analyses of MDM2-knockout mice. Representative photom...
Representative photomicrographs from (A) control, (B) the podocyte-specific MDM2-knockout mouse (PodoMDM2), (C) control, and (D) the tubule-specific MDM2-knockout mouse (TubMDM2KO) subcapsular cortical area. Images B–D are magnified on the right. Representative image (B) shows a focal glomerular sclerosis and a partial glomerular collapse in the periodic acid–Schiff–stained (PAS-stained) kidney sections of the podocyte-specific MDM2-knockout mouse. The representative PAS image (D) depicts the tubular damage in the form of tubular vacuolization, tubular casts, and tubular atrophy in the renal sections of the tubule-specific MDM2-knockout mouse. A and C are representative images of the PAS-stained renal sections of the control mice. Representative from n = 4–5/group. Magnification, ×400 (A and B) and ×200 (C and D), further magnified by ~1.75 (B and D) using Adobe Illustrator. (E and F) Pathophysiological analyses of control and knockout mice. (E) Urine albumin/creatinine ratio of podocyte-specific MDM2-knockout mice compared with controls. (F) Serum creatinine (mg/dl) of tubule-specific MDM2-knockout mice versus control group. Shown P values are based on Mann–Whitney U test. Metabolite levels of (G) 3-methylcrotonyl glycine and (H) uracil in control and MDM2-knockout mice. Distinct control samples for podocyte-specific and tubule-specific mice were used. P values were calculated based on log2(metabolite level) (t test). The pair of P values for podocyte- and tubule-specific knockout mice for each metabolite was combined using Fisher’s method and the combined P values were corrected for multiple testing using Benjamini-Hochberg’s method. For box-and-whisker plots, the horizontal line in each box represents the median (G and H). The whiskers extend to 1.5 × (third quartile – first quartile).