Advanced glycation end products (AGEs) are involved in the progression of diabetic nephropathy. AGEs filtered by glomeruli or delivered from the circulation are endocytosed and degraded in the lysosomes of kidney proximal tubular epithelial cells (PTECs). Autophagy is a highly conserved degradation system which regulates intracellular homeostasis by engulfing cytoplasmic components. We have recently demonstrated that autophagic degradation of damaged lysosomes is indispensable for cellular homeostasis in some settings. Here we tested the hypothesis that autophagy could contribute to the degradation of AGEs in the diabetic kidney by modulating lysosomal biogenesis. Both a high-glucose and exogenous AGE overload gradually blunted autophagic flux in the cultured PTECs. AGE overload upregulated lysosomal biogenesis and function in vitro, which was inhibited in autophagy-deficient PTECs due to the impaired nuclear translocation of transcription factor EB (TFEB). Consistently, streptozotocin-treated PTEC-specific autophagy-deficient mice failed to upregulate lysosomal biogenesis and exhibited the accumulation of AGEs in the glomeruli and renal vasculature as well as in the PTECs, along with worsened inflammation and fibrosis. These results indicate that autophagy contributes to the degradation of AGEs by the upregulation of lysosomal biogenesis and function in diabetic nephropathy. Strategies aimed at promoting lysosomal function hold promise for treating diabetic nephropathy.
This article contains Supplementary Data online at http://diabetes.diabetesjournals.org/lookup/suppl/doi:10.2337/db16-0397/-/DC1.
- Received March 25, 2016.
- Accepted February 20, 2017.
- © 2017 by the American Diabetes Association.