SGLT2 Mediates Glucose-Induced Angiotensinogen Synthesis in Proximal Tubule Cells

Tulane University Of Louisiana, New Orleans LA

Investigators

Abstract

? DESCRIPTION (provided by applicant): The intra-renal renin-angiotensin system (RAS) has been implicated in the development of hypertension and the progression of kidney injury that results from diabetes mellitus. RAS blockade is an effective strategy in preventing diabetic nephropathy and hypertension during diabetes. The production of angiotensinogen (AGT) is upregulated in the renal proximal tubular cells under high glucose conditions. This process is partially mediated by the formation of reactive oxygen species (ROS) as a result of glucose metabolism and mitochondrial respiration. AGT forms angiotensin II (Ang II) which causes oxidative stress by activating the Ang II Type 1 Receptor (AT1R). AT1R activation is also a major source of ROS generation in proximal tubular cells. The overall aim of this proposal is to elucidate the mechanisms underlying the up-regulation of AGT in the proximal tubule during diabetes and chronic hyperglycemia. The sodium-glucose cotransporter 2 (SGLT2) is the primary mechanism responsible for reabsorbing filtered glucose in the kidney. It is not known if SGLT2- mediated glucose reabsorption is responsible for the increased intratubular AGT expression reported during diabetes. Therefore, our overall hypothesis is that the increase in AGT expression in proximal tubular cells under high glucose conditions is mediated by increased glucose entry via SGLT2 which synergizes with the effects of AT1R activation. This will provide insight into the molecular mechanisms that occur in the kidney in the early stages of diabetes. To test this hypothesis, we will establish an increase in ROS accumulation and AGT expression in proximal tubular cells cultured in high glucose conditions and that this upregulation is dependent on glucose entry via SGLT2. We will demonstrate that glucose entry and mitochondrial respiration are increased by Ang II through AT1R activation. In addition, we will show that AT1R activation synergizes with the effects of high glucose to augment AGT expression. The experimental design will utilize immortalized proximal tubular cell lines derived from the wild type and AT1R knockout mice. Canagliflozin, a highly selective pharmaceutical blocker of SGLT2, will be used to demonstrate the role of SGLT2 on the production of AGT during high glucose conditions and address the overall hypothesis.