Endothelial adhesion molecule expression is enhanced in the aorta and internal mammary artery of diabetic patients

BACKGROUND

Diabetes mellitus is a major risk factor for the development of atherosclerosis but the mechanisms involved remain unclear. The expression of leukocyte adhesion molecules at the endothelial surface is a primary step in the recruitment of leukocytes into the intima and the subsequent development of lipid-containing foam cell lesions. Increased levels of circulating adhesion molecules have been identified in diabetic patients, but the distribution in the arterial wall has not been described.

MATERIALS AND METHODS

Frozen sections were prepared from aorta and internal mammary artery obtained during bypass surgery from 12 diabetic and 16 nondiabetic patients. Adhesion molecules (intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-Selectin), macrophages, and lymphocytes were identified and quantified using immunohistochemistry; intimal hyperplasia was quantified.

RESULTS

Endothelial expression of VCAM-1 and intimal smooth muscle cell expression of both VCAM-1 and ICAM-1 was increased in the aortas from diabetic patients. Intimal hyperplasia in aorta and internal mammary artery sections was significantly greater in diabetic tissue. Macrophages, T-lymphocytes, oil-red-O-stained lipid, glycated albumin, and glycated LDL were observed in the aorta of both diabetic and nondiabetic samples.

CONCLUSIONS

The increased incidence of VCAM-1 and ICAM-1 in the aorta may partly explain the enhanced atherosclerosis associated with diabetes mellitus, and their presence in established lesions may emphasize their long-term importance. The intimal hyperplasia observed in the bypass vessel may be a contributing factor to the increased incidence of restenosis in diabetic patients.

Proteoglycan alterations in the aortic intima-media of alloxan-diabetic rabbits: an ultrastructural and biochemical study

Proteoglycans and glycosaminoglycans in the aortic intima of diabetic rabbits and age-matched controls were examined at 2 weeks and 3, 6, and 12 months after alloxan (or saline) treatment. Measurements were made by morphometric analysis of ruthenium red-stained large proteoglycan granules (LPG) in electron micrographs and by analysis of 35S-labeled glycosaminoglycans, extracted and purified from the intima-media of aortas of rabbits which had been injected with 35S-sulfate 18 hr before exsanguination. There was a progressive increase in the area of the aortic intima with time which was greater in diabetic than in control rabbits. The concentration of proteoglycan (LPG/microns 2) and the concentration of the 35S-glycosaminoglycans in diabetic intima-media were similar to respective values of control intima-media throughout the 12 months. However, the specific radioactivity of the [35S]glycosaminoglycan pool from intima-media of diabetic rabbits was significantly less than that from controls (P < 0.001) at 6 and 12 months. In addition, the staining intensity of LPG of the diabetic compared to control extracellular matrix was decreased at these times. The profile and electrophoretic mobility of the glycosaminoglycan types were similar in diabetic and control intima-media. We conclude that the onset of diabetes in the rabbit has altered the metabolic turnover but not the concentration, sulfate content or profile of aortic intima-media proteoglycan and glycosaminoglycans.

Increased expression in vivo of VCAM-1 and E-selectin by the aortic endothelium of normolipemic and hyperlipemic diabetic rabbits

Atherosclerosis is enhanced in humans with diabetes mellitus, but the mechanism(s) involved remains unclear. Increased leukocyte-endothelium interaction may be involved, since mononuclear leukocyte adherence to the endothelium is an early event in both experimental atherosclerosis and alloxan-induced diabetes in rabbits. In situ immunohistochemistry was used in en face Häutchen endothelial preparations to identify endothelial cells that stained with antibodies to endothelial leukocyte adhesion molecules (vascular cell adhesion molecule-1 [VCAM-1] and E-selectin), and the number of stained cells per 10,000 cells was determined. Preparations from aortas of diabetic normolipemic and egg yolk diet-induced hyperlipemic diabetic rabbits were compared with those from normoglycemic animals on similar diets. Cross sections of the vessel wall were stained with oil red O and antibodies to VCAM-1, E-selectin, and RAM-11-positive macrophages. After 4 weeks of hyperlipemia the frequency of cells expressing VCAM-1 or E-selectin was significantly increased compared with normolipemic controls; this frequency was further increased in the aortas of hyperlipemic diabetic rabbits. VCAM-1 and E-selectin expression was more frequent in normolipemic diabetic rabbit aortas than in hyperlipemic, normoglycemic vessels. The potentiation of expression of these adhesion molecules in diabetic animals may provide part of the explanation for the enhanced atherosclerosis associated with diabetes mellitus.

Altered levels of antithrombin III and fibrinogen in the aortic wall of the alloxan-induced diabetic rabbit: evidence of a prothrombotic state

The distribution and behavior of the rabbit plasma proteins albumin, fibrinogen, and antithrombin III (ATIII) (isoforms alpha and beta), have been examined in groups of alloxan-induced diabetic rabbits and control rabbits. By injecting radiolabeled preparations intravenously, measurements of plasma clearance, rates of catabolism, and compartmental distribution were made for each protein. In addition, after allowing the radiolabeled proteins to circulate for 12 hours, we excised aortas after exsanguination and determined the content of these proteins in the endothelium and subendothelium. The respective fractional catabolic rates of ATIII-alpha and ATIII-beta were similar in the diabetic and control rabbits, but fibrinogen and albumin were catabolized more slowly in the diabetic rabbit than in the control rabbit. The distributions of albumin and the ATIII isoforms between the intravascular, noncirculating vascular, and extravascular compartments in the diabetic rabbit were similar to the respective proteins in the control rabbit, but a smaller proportion of fibrinogen was associated with the vascular compartment of the diabetic rabbit when compared with that in the control rabbit. At 12 hours after injection, the quantities of fibrinogen and albumin associated with the diabetic aorta endothelium and particularly the subendothelium were increased, whereas ATIII-alpha and ATIII-beta were decreased relative to the control aorta. The fibrinogen-to-ATIII ratio in the diabetic aorta was increased twofold to threefold when compared with that in the control aorta. We conclude that the increased ratio of fibrinogen to ATIII in the aorta wall of the diabetic rabbit may be characteristic of the prothrombotic state that is conspicuous in insulin-dependent diabetes.