Do T2DM and Hyperglycaemia Affect the Expression Levels of the Regulating Enzymes of Cellular O-GlcNAcylation in Human Saphenous Vein Smooth Muscle Cells?

Protein O-GlcNAcylation, a dynamic and reversible glucose-dependent post-translational modification of serine and threonine residues on target proteins, has been proposed to promote vascular smooth muscle cell proliferation and migration events implicated in vein graft failure (VGF). Therefore, targeting the enzymes (glutamine fructose-6P amidotransferase (GFAT), O-GlcNAc transferase (OGT), and O-GlcNAcase (OGA)) that regulate cellular O-GlcNAcylation could offer therapeutic options to reduce neointimal hyperplasia and venous stenosis responsible for VGF. However, it is unclear how type 2 diabetes mellitus (T2DM) and hyperglycaemia affect the expression of these enzymes in human saphenous vein smooth muscle cells (HSVSMCs), a key cell type involved in the vascular dysfunction responsible for saphenous VGF. Therefore, our aim was to assess whether T2DM and hyperglycaemia affect GFAT, OGT, and OGA expression levels in HSVSMCs in vitro. Expression levels of GFAT, OGT, and OGA were determined in low-passage HSVSMCs from T2DM and non-T2DM patients, and in HSVSMCs treated for 48 h with hyperglycaemic (10 mM and 25 mM) glucose concentrations, by quantitative immunoblotting. Expression levels of OGT, OGA, and GFAT were not significantly different in HSVSMC lysates from T2DM patients versus non-T2DM controls. In addition, treatment with high glucose concentrations (10 mM and 25 mM) had no significant effect on the protein levels of these enzymes in HSVSMC lysates. From our findings, T2DM and hyperglycaemia do not significantly impact the expression levels of the O-GlcNAcylation-regulating enzymes OGT, OGA, and GFAT in HSVSMCs. This study provides a foundation for future studies to assess the role of O-GlcNAcylation on VGF in T2DM.