Diabetes modifies the relationships among carotid plaque calcification, composition and inflammation

Diabetes is traditionally associated with vascular calcification, but the molecular mechanisms are largely unknown. We herein explored the relationships among carotid plaque calcification, composition and gene expression, and how these are modified by diabetes.

We collected carotid endoarterectomy specimen from 59 patients, of whom 23 had diabetes. We analysed histology with pentachromic staining, calcification with Alizarin red and Von Kossa's staining, chemical calcium extraction and quantification, as well as gene expression by quantitative PCR.

We detected no differences in the extent of plaque calcification and in plaque composition between diabetic and non-diabetic patients. In non-diabetic plaques, calcium content was directly correlated with the area occupied by muscle/fibrinoid tissue and inversely correlated with collagen, but such correlations were not seen in plaques from diabetic patients. While consistent correlations were found between calcium content and RUNX2 (direct), as well as Osteopontin (inverse), diabetes modified the association between plaque calcification and inflammatory gene expression. Only in diabetic plaques, calcium content was inversely correlated with MCP1 and IL1b, whereas the direct correlation with TNF-alpha expression seen in non-diabetic plaques was lost in diabetes.

Though plaque composition and calcification were not quantitatively affected, diabetes modified the relationships between plaque calcium, composition and inflammation. These results suggest that the mechanisms and the clinical significance of atherosclerotic calcification in diabetic may be different than in non-diabetic patients.