Autor:innen:
Ahmed Elwakiel | Otto-von-Guericke-Universität Magdeburg Medizinische Fakultät | Germany
Dr. Mohd AL-Dabet | Otto-von-Guericke-Universität Magdeburg Medizinische Fakultät | Germany
Dr. Khurrum Shahzad | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Dr. med. Alba Sulaj | Universitätsklinikum Heidelberg | Germany
PD Dr. med. Stefan Kopf | Universitätsklinikum Heidelberg | Germany
Ihsan Gadi | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Rajiv Rana | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Gupta Dheerendra | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Silke Zimmermann | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Prof. Dr. med. Peter Rene Mertens | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Prof. Dr. med. Peter Nawroth | Universitätsklinikum Heidelberg | Germany
Dr. Christopher Dockendorff | Marquette University | United States
Dr. Shrey Kohli | Universitätsklinikum Leipzig | Germany
Prof. Dr. med. Berend Isermann | Medizinische Fakultät / Universitätsklinikum Otto-von-Guericke-Universität | Germany
Background: Diabetic nephropathy (dNP), which is a major chronic microvascular complication among diabetic patients, is the leading cause of end stage renal disease (ESRD) worldwide. dNP is characterized by albuminuria and / or declining glomerular filtration rate (GFR) and histomorphological changes resulting in ESRD. A major therapeutic obstacle in dNP is the failure of renal recovery upon improved blood glucose levels. The mechanisms underlying this phenomenon, known as the hyperglycemic memory, remain unknown.
Aim: We aimed to identify mechanisms and therapeutically amendable targets contributing to the hyperglycemic memory in dNP.
Methods and materials: Two mouse models with established dNP (16 weeks after STZ-induced persistent hyperglycemia or 16 weeks old db/db mice) were used in the study. Blood glucose was reduced for 6 weeks using an SGLT2-inhibitor, mimicking therapy in diabetic patients. An unbiased approach (mRNA-seq) was used to evaluate pathways involved in hyperglycemic memory. In vitro and in vivo studies were conducted to determine mechanistic and translational relevance.
Results: Despite a marked reduction of blood glucose levels using SGLT2 inhibition, albuminuria, histomorphological changes, and glucose induced altered renal gene expression persisted. Functional annotation of persistently changed gene expression revealed that PI3-kinase-Akt signaling, cellular proliferation and senescence, and complement and coagulation cascades were linked with hyperglycemic memory. Sustained expression of p21, a senescence-associated cyclin-dependent kinase inhibitor, was among the top hits. Sustained tubular expression of p21 despite blood glucose lowering was confirmed in diabetic mice (histology, RNA and protein). Sustained p21 expression was linked with demethylation of its promoter and reduced DNA methyl transferase (DNMT) activity and DNMT1 expression. The nephroprotective zymogen protein C was among genes persistently repressed in dNP. Increased tubular senescence, interstitial fibrosis, and albuminuria were confirmed in diabetic mice with genetically superimposed impaired protein C activation. A role of miR-148a, identified in silico as a potential regulator of DNMT1, was confirmed in tubular cells in vitro. Substituting the protease activated protein C (aPC), mimicking biased aPC-signaling (parmodulin-2), or reducing miR-148a in addition to normalizing blood glucose levels reversed sustained tubular p21 expression, tubular senescence, and renal damage in diabetic mice with already established dNP.
Conclusion: Epigenetically sustained p21expression and associated senescence contribute to the hyperglycemic metabolic memory in dNP. This pathogenic mechanism can be targeted by inhibiting miR-148a or by mimicking cytoprotective aPC-signaling.