Transcription factor c-Maf deletion improves streptozotocin-induced diabetic nephropathy by directly regulating Sglt2 and Glut2
Mitsunori Fujino, Naoki Morito, Takuto Hayashi, Masami Ojima, Shun Ishibashi, Akihiro Kuno, Seizo Koshiba, Kunihiro Yamagata, Satoru Takahashi
Mitsunori Fujino, Naoki Morito, Takuto Hayashi, Masami Ojima, Shun Ishibashi, Akihiro Kuno, Seizo Koshiba, Kunihiro Yamagata, Satoru Takahashi
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Research Article Nephrology

Transcription factor c-Maf deletion improves streptozotocin-induced diabetic nephropathy by directly regulating Sglt2 and Glut2

Abstract

The transcription factor c-Maf has been widely studied and has been reported to play a critical role in embryonic kidney development; however, the postnatal functions of c-Maf in adult kidneys remain unknown as c-Maf–null C57BL/6J mice exhibit embryonic lethality. In this study, we investigated the role of c-Maf in adult mouse kidneys by comparing the phenotypes of tamoxifen-inducible (TAM-inducible) c-Maf–knockout mice (c-Maffl/fl; CAG-Cre-ERTM mice named “c-MafΔTAM”) with those of c-Maffl/fl control mice, 10 days after TAM injection [TAM(10d)]. In addition, we examined the effects of c-Maf deletion on diabetic conditions by injecting the mice with streptozotocin, 4 weeks before TAM injection. c-MafΔTAM mice displayed primary glycosuria caused by sodium-glucose cotransporter 2 (Sglt2) and glucose transporter 2 (Glut2) downregulation in the kidneys without diabetes, as well as morphological changes and life-threatening injuries in the kidneys on TAM(10d). Under diabetic conditions, c-Maf deletion promoted recovery from hyperglycemia and suppressed albuminuria and diabetic nephropathy by causing similar effects as did Sglt2 knockout and SGLT2 inhibitors. In addition to demonstrating the potentially unique gene regulation of c-Maf, these findings highlight the renoprotective effects of c-Maf deficiency under diabetic conditions and suggest that c-Maf could be a novel therapeutic target gene for treating diabetic nephropathy.

Authors

Mitsunori Fujino, Naoki Morito, Takuto Hayashi, Masami Ojima, Shun Ishibashi, Akihiro Kuno, Seizo Koshiba, Kunihiro Yamagata, Satoru Takahashi

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Figure 4

c-Maf as a potentially novel Sglt2- and Glut2-regulating transcription factor.

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c-Maf as a potentially novel Sglt2- and Glut2-regulating transcription f...
ChIP assay and luciferase reporter assay revealed the direct regulation of Sglt2 and Glut2 by c-Maf. Quantitative ChIP confirmed direct binding of c-Maf to MARE sites in (A and B) Sglt2 and (E and F) Glut2 loci; ChIP assay was performed upstream of the transcription start sites (primer pairs 1 for Sglt2 and 3 for Glut2), and intron sites as an additional negative control (primer pairs 2 for Sglt2 and 4 for Glut2). The luciferase reporter system examined the activation of (C and D) Sglt2 and (G and H) Glut2. Dual-luciferase reporter plasmids with or without a mutation in Sglt2 and Glut2 were cotransfected with the vectors carrying c-Maf (0–90 ng). Experiments were repeated 3 times. B and F were presented as the mean and the standard error of the mean (SEM). To assess whether differences between c-MafΔTAM and c-Maffl/fl mice were statistically significant, a minimum of 3 biological replicates were analyzed using Welch’s t test, and a P value < 0.05 was considered significant. Holm-Šídák corrections were applied for multiple statistical tests in D and H. *P < 0.05, **P < 0.01, and ***P < 0.001. White circles: c-Maffl/fl groups, and black circles: c-MafΔTAM groups.