Calcification of the Medial Layer of the Internal Thoracic Artery in Diabetic Patients: Relevance of Glycoxidation

Abstract

Objective: The aim of this study was to evaluate the role of glycoxidation in the calcification of the internal thoracic artery (ITA) in diabetes mellitus (DM). Methods: ITA samples were obtained from 17 patients with type 2 DM (age 62.9 ± 10.5 years) and 12 age-matched, nondiabetic patients (age 62.5 ± 10.2 years) who underwent coronary artery bypass grafting. These samples were analyzed histopathologically and assessed for calcification by von Kossa staining and for glycoxidation by immunohistochemistry using anti-N^Ε-(carboxymethyl)lysine (CML) antibody. Morphometric evaluation of calcification of the medial layer, intimal thickness and intima-to-media ratio was performed using NIH image software. To evaluate the mechanism of the interaction between calcification and glycoxidation, we developed an in vitro model of calcification of collagen that was chemically modified by glucose, glutaraldehyde or epoxy compound. The calcium-binding activity of these collagens was determined in hydrolysates using atomic absorption spectrophotometry. Results: ITAs of both diabetic and nondiabetic patients were free of atherosclerosis, and no differences were found between the two groups with regard to intimal thickness and intima-to-media ratio. Areas of calcification were noticed in both groups in the tunica media, but not in the tunica intima. Calcium deposits were localized within the extracellular matrix, which was immunohistochemically positive for CML. The extent of medial layer calcification was significantly greater in diabetic patients than nondiabetic subjects, but was independent of known risk factors such as hypertension, hyperlipidemia, obesity and history of old myocardial infarction. The binding activity of collagen was time-dependently increased with in vitro incubation of glucose. A significant increase in the calcium-binding ability was observed in glucose- and glutaraldehyde-modified collagens, but not in epoxy compound-modified collagen. Conclusion: Our results suggest that glycoxidative modification of the extracellular matrix, in particular collagen, of the vascular wall may enhance the development of ITA calcification in diabetic patients.

Modification of collagen in vitro with respect to formation of Nɛ-carboxymethyllysine

“…It is established that the formation of crystals in pathological mineralization follows the same routes as normal calcifications [36]. In in vivo studies on calcification of the medial layer of the internal thoracic artery in diabetic patients it was shown that calcium deposits were localized within the extracellular matrix, which was immunohistochemically positive for CML [37]. Moreover, the accumulation of CML in the cartilage-bone border of osteoarthritic cartilage samples suggests that this AGE is involved in abnormal calcification in vivo [37,38].…”

Association of Coronary Artery Calcification with MDA-LDL-C/LDL-C and Urinary 8-Isoprostane in Japanese Patients with Type 2 Diabetes

“…The reason for this discrepancy is unclear. A role for advanced glycation endproducts (AGEs), the formation of which is associated with oxidative stress, was also indicated to have a role in the calcification of the arteries in diabetes mellitus (23).…”

Identification of Differentially Expressed Genes in Human Varicose Veins: Involvement of Matrix Gla Protein in Extracellular Matrix Remodeling

“…Nevertheless, the MGP signaling pathway has a crucial role in the inhibition of venous calcification as confirmed by the specific inhibition of MGP transcripts. High MGP mRNA expression and protein accumulation have been demonstrated in calcified arterial lesions and atherosclerotic plaques [26,47,48,49,50,51]. Recently, Schürgers et al [52] have shown that increased expression of MGP in atherosclerotic lesions was associated with a specific staining of GluMGP.…”