188 NAT19 is novel biomarker for sensing glucose in healthy and type I diabetic skin

Abstract

Calcium signaling is an important pathway in the maintenance of skin homeostasis. In addition, there is a well-known dynamic crosslink between endoplasmic reticulum and mitochondria via calcium signaling. Herein, we investigated keratinocytes responses to increased blood glucose concentration in the healthy and type I diabetic mouse model. Lifetime imaging of calcium using Fluo-4 on keratinocytes indicated that high glucose level in culture medium leads to a significant increase in the intracellular calcium concentration and a marked modification in mitochondrial network morphology. The increased calcium level and the modification in mitochondrial network morphology were abolished in the presence of BAPTA, a known calcium chelator. Looking at the skin of healthy and type I diabetic mice received intraperitoneal injection of glucose (2gr/Kg), we found that the morphology of mitochondrial network is modified in both models. Proteomic analysis on the skin biopsies revealed a significant increase of NAT19 expression in both glucose-treated healthy and type I diabetic mice compared with their control counterparts, indicating that increased blood glucose level results in increased expression of NAT19 in keratinocytes. Luciferase reporter assay, in which the region upstream from the ATG translation initiation codon of NAT19 had been cloned upstream of luciferase, further confirmed that increased glucose level enhances NAT19 expression. However, the skin and its freshly isolated keratinocytes from NAT19 knockout mouse did not show the transient modification in mitochondrial network morphology following receiving glucose injection. Taking together, our results indicate that the increased blood glucose level is sensed by keratinocytes via NAT19, which in its turn, triggers modification in mitochondrial network via calcium signaling.