Viability of primary cultured podocytes is associated with extracellular high glucose-dependent autophagy downregulation

Structural and functional impairment of podocytes plays an important role in the development of diabetic nephropathy, a chronic complication of diabetes mellitus and leading cause of renal failure requiring renal replacement therapy. Autophagy plays a crucial role in podocyte viability and function, and its activity is modulated by a variety of pathophysiological factors found in diabetic milieu. Here we show that downregulation of autophagy is critical for podocyte survival in hyperglycemic environment. Moreover, long-term exposure to high glucose leads to inhibition of autophagy as well as to the development of insulin resistance in podocytes. Furthermore, impairment of autophagy is involved in alteration of insulin-dependent glucose uptake in podocytes, suggesting a relationship between these two processes. Taken together, our findings suggest that downregulation of podocyte autophagy, observed after long-term exposure to high glucose, results from their suppressed sensitivity to insulin, and may therefore lead to diminished podocyte cell viability as well as their reduced number in glomerulus.