Endocrine Abstracts

Introduction: In the UK alone, diabetes affects nearly 4 million people and an additional 13.6 million people are estimated to be at high risk of developing type 2 diabetes (T2DM). Diabetes is associated with vascular complications which path the development of cardiovascular diseases such as strokes and heart attacks. Previous studies have shown various pathways in which hyperglycaemia leads to endothelial dysfunction and insulin resistance. However, current reports of in vitro studies employed supraphysiological concentration of glucose which induces apoptosis in cell cultures, limiting the translational value of the research and failing to provide insights into the effect of pathophysiological hyperglycaemia in prediabetes and T2DM on endothelial function.

Hypothesis: Pathophysiological hyperglycaemia in prediabetes and T2DM impairs vascular endothelial insulin sensitivity.

Methods: To mimic the effect of chronic hyperglycaemia on the endothelium in patients with prediabetes or T2DM, primary human umbilical vein endothelial cells (HUVECs) were incubated in growth media supplemented with glucose at pathophysiological concentrations (control: 5.55mM; prediabetes: 6.9mM; T2DM: 7.8mM) for 72 hours. HUVECs were then lysed (unstimulated) or stimulated with 100nM insulin for 15 min. Protein expression was determined using Western blot.

Results: Hyperglycaemia (7.8mM)-treated HUVECs expressed a higher unstimulated level of Akt (S473) and RAPTOR (S792) phosphorylation compared to the control, despite Akt (T308) phosphorylation level was unchanged. Upon insulin stimulation, hyperglycaemia (6.8mM and 7.8mM)-treated HUVECs possessed a higher expression of insulin receptor β, but a smaller extent of insulin-stimulated Akt (S473) phosphorylation. No changes in phosphorylation of endothelial nitric oxide synthase (eNOS) or extracellular signal regulated protein kinase (ERK)1/2 were detected across all treatment groups.

Conclusion: Prolonged hyperglycaemia in prediabetes and T2DM conditions increased basal Akt phosphorylation and impaired insulin-induced Akt phosphorylation in endothelial cells in vitro. Future work shall focus on examining the functional readout and determining the changes in downstream Akt signalling of hyperglycaemia-treated cells.