SUN-664 Effects of Acute Hyperglycemia on Monocytes in Type 2 Diabetes

Background: Type 2 diabetes is linked to accelerated atherosclerosis, however the mechanisms behind this association are unclear. Inadequate glycemic control is an important contributor for cardiovascular disease (CVD). Episodic hyperglycemia as a surrogate for glycemic variability (GV) promotes monocyte adhesion and increases proinflammatory monocytes within plaques of patients with diabetes. Monocytes are precursors to macrophages which play a vital role in atherosclerosis and are capable of delivering cholesterol content to plaques. Therefore, elucidating the mechanism by which acute hyperglycemia promotes proatherogenic monocytes in diabetes can lead to novel therapies slowing atherosclerosis progression in these patients. Methods: To assess the effects of acute hyperglycemia on monocyte cholesterol metabolism, we isolated monocytes from 28 patients with Type 2 diabetes cultured for 2 and 6 hours in normoglycemic (90mg/dL) or hyperglycemic media (300mg/dL). Cholesterol content was measured by lipid extraction and fluorometric cholesterol oxidase assay. Cholesterol uptake was assessed by incubating monocytes with Dil-oxidized LDL (Dil-OxLDL). Cholesterol synthesis was performed by incubating monocytes with 2-14C-Acetate in both glycemic conditions for 6 hours followed by lipid saponification, and separated via TLC on silica gel plates. Cholesterol efflux was assessed by labeling cells with 3H-Cholesterol-OxLDL in both glycemic conditions for 6 hours followed by APO-A1 or HDL stimulation for 4 hours. Results: Acute hyperglycemia for 2 and 6 hours induced foamy monocytes with increased total cholesterol content (22 and 32%, respectively), cholesterol ester (40% and 43%, respectively), and free cholesterol content (14% and 25%, respectively) due to enhanced DiI-OxLDL uptake. There was no significant increase in monocyte cholesterol synthesis or cholesterol efflux after stimulation with HDL or APO A-1. Conclusions: Increased monocyte cholesterol content during acute hyperglycemia is a potential mechanism promoting atherosclerosis in patients with Type 2 diabetes.