GDF-15 IN DIABETIC KIDNEY DISEASE: EFFECT ON CYP450 INDUCED ROS PRODUCTION

Abstract

Background: Diabetic Kidney Disease (DKD) is one of the major diabetic complications and the leading cause of end-stage renal disease. The pathogenesis of DKD is complex and includes a myriad of deregulated pathways that are suggested to finally lead to the overproduction of reactive oxygen species (ROS). The CYP450 monooxygenase family has been identified as a significant contributor to oxidative stress in the diabetic state. Specifically, CYP4A upregulation and CYP2C downregulation paralleled by a differential alteration in their respective metabolites 20-hydroxyei- cosatetraenoic acids (20-HETEs) and epoxyeicosatrienoic acids (EETs) have been implicated in the development of DKD. On the other hand, Growth Differentiation Factor 15 (GDF-15)- a distant member of the TGF-B superfamily- has been identified as a high-risk biomarker for diabetes. Increased plasma GDF-15 was linked to the occurrence of DKD and has been shown to be an indicator of the fast deterioration in kidney function. Herein, we investigate the role of GDF-15 in the pathogenesis of DKD and its crosstalk with CYP450 metabolites in type 2 diabetes. Hypothesis: In this thesis work, we explore the hypothesis that hyperglycemia activates NADPH dependent ROS overproduction through a CYP450/GDF-15 dependent mechanism eventually leading to renal injury. Design: T2DM was induced using the high fat diet/STZ model in two sets of experiments. FVB/NJ mice were divided into four groups: control, T2DM, T2DM+HET0016 (CYP4A inhibitor) and T2DM+AUDA ( sEH inhibitor) for 10 weeks. C57BL/6J mice were divided into six groups: control, control receiving GDF-15 monoclonal antibody AV-380 (7.5mg/kg or 20mg/kg), T2DM, and T2DM+AV-380 (7.5mg/kg or 20mg/kg) for 8 weeks. Functional, histopathological, and molecular studies were performed on kidney tissues from all groups. Results : Our results show that T2DM activates ROS through NADPH dependent mechanism increasing 20-HETEs and GDF-15 while reducing EETs. Blocking 20-HETEs formation, EETs metabolism, and GDF-15 activity using HET0016, AUDA, and AV-380 respectively reduced proteinuria, NADPH oxidases and ROS production along with decreased glomerular sclerosis and fibrosis. Of interest, HET0016 and AUDA treatments resulted in downregulation of GDF-15 while AV-380 induced an upregulation of CYP2C dependent EETs and downregulation of CYP4A dependent 20-HETEs . Conclusion : Our findings indicate a crosstalk between GDF-15 and CYP450-derived metabolites leading to NADPH dependent-ROS overproduction. Pharmacological interventions aimed at either inhibiting the activity of GDF-15 and CYP4A dependent 20 HETEs or promoting the synthesis of CYP2C dependent EETs may offer a promising approach for the treatment of DKD.