Endothelial glycocalyx hyaluronan: regulation and role in prevention of diabetic complications.

The endothelial glycocalyx is critically involved in vascular integrity and homeostasis, by regulating vascular permeability, mechanotransduction, and reducing inflammation and coagulation. The turnover of the glycocalyx is very dynamic to fine-tune these processes. This is in particular true for its main structural component hyaluronan (HA). Degradation and shedding of the glycocalyx by enzymes, such as hyaluronidase 1 and hyaluronidase 2, are responsible for regulation of the glycocalyx thickness and hence access of circulating cells and factors to the endothelial cell membrane and its receptors. This degradation process will at the same time also allow for re-synthesis and adaptive chemical modification of the glycocalyx. The (re)synthesis of HA is dependent on the availability of its sugar substrates, thus linking glycocalyx biology directly to cellular glucose metabolism. It is therefore of particular interest to consider the consequences of dysregulated cellular glucose in diabetes for glycocalyx biology and its implications for endothelial function. This review summarizes the metabolic regulation of endothelial glycocalyx HA and its potential as a therapeutic target in diabetic vascular complications.