Sex Differences in the Expression of Cardiac miR‐29 Family microRNAs in Diabetic Male and Female Rats and its Correlation with Increased Risk for Coronary Artery Disease in Diabetic Females

Diabetic females are at increased risk of heart failure (HF) and coronary artery disease (CAD) than age‐matched diabetic males and non‐diabetic females. Factors contributing to this sex difference in diabetic heart disease are not understood. We have previously shown that progression of diabetes mellitus (DM) in male rats correlates with increased expression of cardiac miR‐29 family of microRNAs. The miR‐29 family is composed of three members who share an identical seed sequence, however, they exhibit different roles in vivo : miR‐29a is a biomarker of hypertrophy and fibrosis, miR‐29b is involved in aneurysm formation in Marfan's syndrome, and miR‐29c is a marker of hyperglycemia. Here we investigated whether sex differences exist in the expression of cardiac miR‐29 family in 5‐month old Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats, and examined whether overexpression of the miR‐29 family miRNAs is detrimental to human male and female coronary artery vascular smooth muscle cells (hCAVSMCs). Cardiac miR‐29 expression was assessed by qRT‐PCR and cardiac structure was examined by histological analysis. Expression of miR‐29a, b and c were elevated in both diabetic female (ZDF‐F) and male (ZDF‐M) rats when compared to lean female (ZL‐F) and male (ZL‐M) rats ( p ‐values for ZDF‐F vs. ZL‐F: miR‐29a, 0.054, miR‐29b, 0.03, miR‐29c, 0.02; for ZDF‐M vs. ZL‐M: miR‐29a, 0.0001, miR‐29b, 0.0015, miR‐29c, 0.0001), however, relative to lean controls, miR‐29a and miR‐29c were increased to a greater extent in ZDF‐M (~10.3‐ and 26.3‐fold greater, respectively) than in ZDF‐F (~4.8‐ and 8.8‐fold, respectively). In contrast, in ZDF‐F, miR‐29b was ~18.1‐fold greater than ZL‐F, while in ZDF‐M, miR‐29b was ~4.7‐fold higher than ZL‐M. Examination of cardiac sections stained with H&E or Masson's trichrome revealed structural damage in ZDF‐F, which was not observed in any other group. Transfection of primary cultures of male and female hCAVSMCS with miR‐29 mimics individually showed that 48‐hour post‐transfection, loss of cell membrane integrity, as assessed by propidium iodide (PI) exclusion assay, was highest in cells transfected with miR‐29b compared to those transfected with miR‐29a or miR‐29c. TUNEL assay further confirmed this detrimental effect of miR‐29b in hCAVSMCs. Since miR‐29b expression was higher in heart tissues of ZDF‐F compared to all other groups, and miR‐29b was most effective in inducing cell death compared to other miR‐29 family miRNAs in human CAVSMCs, we conclude that the sex difference in miR‐29b expression may underlie higher risk for CAD in diabetic females. Support or Funding Information LSME, UM‐Columbia(LP), NIH 1R01HL118376‐01(LP)