Repetitive hypoglycaemia increases serum adrenaline and induces monocyte adhesion to the endothelium in rat thoracic...

Severe hypoglycaemia associated with diabetes management is a potential risk for cardiovascular diseases. However, the effect and mechanism of hypoglycaemia on the progression of atherosclerosis remains largely unknown. As a first step towards elucidating the above, we investigated the effect of hypoglycaemia on monocyte-endothelial interaction.

Insulin was injected intraperitoneally once every 3 days for 5 weeks in Goto-Kakizaki rats, a non-obese rat model of type 2 diabetes. We counted the number of monocytes adherent to the endothelium of thoracic aorta as an index of early atherosclerogenesis. Cultured HUVEC were used to investigate the mechanism of action.

Insulin treatment increased the number of monocytes adherent to the vascular endothelium. This increase was abrogated by injection of glucose with insulin. Amosulalol, an α-1 and β-adrenoreceptor antagonist, suppressed monocyte adhesion to endothelium and levels of adhesion molecules (intercellular adhesion molecule-1 and vascular cell adhesion molecule-1) in the endothelial surface, which had been enhanced by insulin-induced hypoglycaemia. In HUVEC, adrenaline (epinephrine) significantly increased nuclear translocation of nuclear factor-κB (NF-κB) p65 and levels of adhesion molecules, effects that were abrogated following addition of SQ22536, a specific adenyl cyclase inhibitor.

Our data indicate that repetitive hypoglycaemia induced by insulin enhanced monocyte adhesion to endothelial cells in Goto-Kakizaki rat aorta through enhanced adrenaline activity and that the latter stimulated intracellular cAMP, leading to nuclear translocation of NF-κB with subsequent production of adhesion molecules in endothelial cells.