Diabetic Nephropathy from RAAS to Autophagy: The Era for New Players

Abstract

Diabetic nephropathy is a leading cause of end-stage renal disease (ESRD) and increased cardiovascular morbidity and mortality worldwide in patients with type 2 diabetes mellitus. The mechanisms behind the pathophysiology of DN are complex and continue to be not fully understood. Both metabolic (hyperglycaemia) and haemodynamic alterations interact synergistically, and have been reported to activate local RAAS resulting in increased angiotensin-2. In spite the early and chronic treatment with converting enzyme inhibitors and angiotensin receptor blocking drugs, the number of patients reaching end stage renal disease and replacement therapy are increasing. Recently different pathways were proposed to be involved in the pathogenesis of diabetic nephropathy, including the autophagy process, Klotho and the selective agonist vitamin D and his receptor. Under hyperglycemic stress especially in podocytes and proximal convolute tubule cells, there is decrease in the protective autophagic process and increase in cellular damage. α-Klotho is a multifunctional protein highly expressed in the kidney. The klotho protein has endogenous anti fibrotic function via antagonism of Wnt/β-catenin signaling, which promotes fibrogenesis, suggesting that loss of Klotho in early stage of diabetic nephropathy may contribute to the progression of DN by accelerated fibrogenesis. The selective vitamin D agonist and his receptor, play a protective pathway in diabetic nephropathy. A key reno-protective function of vitamin D is to reduce albuminuria or proteinuria, major risk factors for CKD progression, renal failure, cardiovascular events, and death. This anti-proteinuric effect and the deceleration of DN progression is mediated primarily via the blocking of the renin angiotensin aldosterone system. In this review we will discuss the different new mechanisms involved in diabetic nephropathy and future therapeutic agents like the mTorc1 blocker, Rapamycin, that can upregulate the autophagy process, the new sodium-glucose transport inhibitors and Paricalcitol, the selective active vitamin D.