Mechanistic insights into diabetes and the progression of cardiovascular disease in female rats
Authors: Toedebusch Ryan , Lum‐Naihe Kelly , Mahmood Abuzar , Bajwa Jamal , Kumar Senthil , Ardhanari Sivakumar , Demarco Vincent , Pulakat Lakshmi 
Published: November 2023

Diet and nutrition have important ramifications on the incidence of metabolic disease like type‐2 diabetes mellitus (DM) and resultant cardiovascular disease (CVD). Diabetic women are at an increased risk of CVD compared to diabetic men, however the underlying mechanisms remain unresolved. The purpose of this ongoing research is to elucidate molecular mechanisms underlying sex differences and the occurrence and progression of diabetic‐CVD. In order to understand if the deterioration of cardiac function correlates to the expression of cardioprotective molecules, we investigated early‐stage (3‐month) cardiac parameters using echocardiography and late‐stage (5 month) molecular and pathological differences between female Zucker Lean (ZL, n = 12) and Zucker Diabetic Fatty (ZDF, n = 12) rats. Echocardiography at 3‐months of age showed increased: LV‐mass (p < 0.05), LV PWTd (p < 0.05), relative wall thickness (p < 0.05), heart weight (p < 0.05), and E/E' in ZDF (high‐fat chow fed) compared to ZL (standard chow fed), suggestive of concentric hypertrophy and diastolic dysfunction. In a different cohort of female ZL (n = 6) and ZDF (n = 6) rats, cardiac pathology and gene expression patterns were assessed at 5‐months of age in order to examine diabetic‐CVD progression. Consistent with 3‐month cardiac dysfunction and pathology, immunohistochemistry assessed at 5‐months showed increased cardiomyocyte hypertrophy and reduced capillary density in ZDF vs. ZL. Furthermore, electron transmission micrographs, trichrome and H & E stains indicated disruption and disorganization of the myocardial and mitochondrial structure in ZDF vs. ZL. Suppression of cardiac Med13 (mediator Complex subunit 13) enhances obesity while overexpression confers protection from high‐fat‐diet‐induced obesity. Further, Agtr2 (angiotensin II type 2 receptor), an X‐linked gene, has been shown to be cardioprotective in murine models of cardiovascular disease. Interestingly, qRT‐PCR of these two cardioprotective molecules, Agtr2 and Med13, showed a significant decrease in the myocardium of ZDF vs. ZL with disease progression. Additionally, two classes of microRNAs, miR‐208 and miR‐29, are both emerging as biomarkers for the progression of cardiovascular disease. We have shown previously that increased expression of miR‐29 family of microRNAs in the heart results in cardiomyocyte disorganization. We and others have shown that miR‐208a contributes to contractile dysfunction and fibrosis. In 5‐month old ZDF rat heart tissues, miR‐208a and miR‐29a/b/c showed increased expression, and this was consistent with the increased cardiac structural damage. We conclude that, mechanistically, increased expression of cardiac detrimental microRNAs miR‐208a and miR‐29 family combined with suppression of cardioprotective Agtr2 and Med13 mRNAs underlie increased cardiac structural damage and functional deficiency in ZDF vs. ZL.

Support or Funding Information

Life Science Mission Enhancement Fund from UM‐Columbia (LP), NIH NHLBI 1R01HL118376‐01 (LP), NHLBI Diversity Supplement Award 5 R01 HL118376‐02S (KL), NIH NHLBIR01HL112998 (CAE), Research Services Facilities of HSTM Veterans Hospital.