Myocardial Infarction Does Not Accelerate Atherosclerosis in a Mouse Model of Type 1 Diabetes

In addition to increasing the risk of an initial myocardial infarction (MI), diabetes increases the risk of a recurrent MI. Previous work suggests that an experimental MI can accelerate atherosclerosis via monocytosis. To test whether diabetes and experimental MI synergize to accelerate atherosclerosis, we performed ligation of the left anterior descending coronary artery to induce experimental MI or sham surgery in nondiabetic and diabetic mice with preexisting atherosclerosis. All mice subjected to experimental MI had significantly reduced left ventricular function. In our model, in comparisons with nondiabetic sham mice, neither diabetes nor MI resulted in monocytosis. Neither diabetes nor MI led to increased atherosclerotic lesion size, but diabetes accelerated lesion progression, exemplified by necrotic core expansion. The necrotic core expansion was dependent on monocyte recruitment, as mice with myeloid cells deficient in the adhesion molecule integrin α4 were protected from necrotic core expansion. In summary, diabetes, but not MI, accelerates lesion progression, suggesting that the increased risk of recurrent MI in diabetes is due to a higher lesional burden and/or elevated risk factors rather than the acceleration of the underlying pathology from a previous MI.