In Vivo Inhibition of miR-34a Modestly Limits Cardiac Enlargement and Fibrosis in a Mouse Model with Established Type 1 Diabetes-Induced Cardiomyopathy, but Does Not Improve Diastolic Function

Abstract

MicroRNA 34a (miR-34a) is elevated in the heart in a setting of cardiac stress or pathology, and we previously reported that inhibition of miR-34a in vivo provided protection in a setting of pressure overload-induced pathological cardiac hypertrophy and dilated cardiomyopathy. Prior work had also shown that circulating or cardiac miR-34a was elevated in a setting of diabetes. However, the therapeutic potential of inhibiting miR-34a in vivo in the diabetic heart had not been assessed. In the current study, type 1 diabetes was induced in adult male mice with 5 daily injections of streptozotocin (STZ). At 8 weeks post-STZ, when mice had established type 1 diabetes and diastolic dysfunction, mice were administered locked nucleic acid (LNA)-antimiR-34a or saline-control with an eight-week follow-up. Cardiac function, cardiac morphology, cardiac fibrosis, capillary density and gene expression were assessed. Diabetic mice presented with high blood glucose, elevated liver and kidney weights, diastolic dysfunction, mild cardiac enlargement, cardiac fibrosis and reduced myocardial capillary density. miR-34a was elevated in the heart of diabetic mice in comparison to non-diabetic mice. Inhibition of miR-34a had no significant effect on diastolic function or atrial enlargement, but had a mild effect on preventing an elevation in cardiac enlargement, fibrosis and ventricular gene expression of B-type natriuretic peptide (BNP) and the anti-angiogenic miRNA (miR-92a). A miR-34a target, vinculin, was inversely correlated with miR-34a expression, but other miR-34a targets were unchanged. In summary, inhibition of miR-34a provided limited protection in a mouse model with established type 1 diabetes-induced cardiomyopathy and failed to improve diastolic function. Given diabetes represents a systemic disorder with numerous miRNAs dysregulated in the diabetic heart, as well as other organs, strategies targeting multiple miRNAs and/or earlier intervention is likely to be required.

Cardiac-selective gene delivery of medium-chain acyl-CoA dehydrogenase (MCAD) does not protect against diabetes-induced cardiac dysfunction

“…HbA1c levels were also elevated at study endpoint (16 weeks post-STZ injection) and did not differ between rAAV6:CON and rAAV6:MCAD groups (Figure 1c). Consistent with a diabetic phenotype and prior studies [41], organ weights (wet weight and normalized to body weight or tibia length) of kidney, liver and spleen were increased in diabetic mice. These organ weights were not different between mice administered rAAV6:CON or rAAV6:MCAD (Table 2).…”

“…To induce diabetes, 6-week old FVB/NJ male mice were administered 5 consecutive daily injections of STZ (Supp Figure 1). This protocol induces diastolic dysfunction in mice [41,43], which was evident by pulse wave and tissue Doppler echocardiography 8 weeks post-STZ injection in the current study (Figure 1a, Table 1). Diabetic mice had lower E/A and e'/a' ratios and longer deceleration and isovolumic relaxation times (Figure 1a, Table 1) of impaired relaxation.…”

“…by a single trained individual from the Preclinical Cardiology Microsurgery and Imaging Platform (Baker Heart and Diabetes Institute, Melbourne, Australia), who was blinded to disease and AAV treatment. Images were acquired using a MS550D transducer and a Vevo 2100 High Frequency Ultrasound System (Visual Sonics, Toronto, Canada) as previously described [41]. Echocardiographic evaluation of diastolic function was performed by measurement of transmitral ow parameters including early (E) and late (A) diastolic lling velocities, E/A ratio, deceleration time (DT), and isovolumic relaxation time (IVRT) from an apical four chamber view with pulsed wave Doppler.…”

Deletion of the muscle enriched lncRNA Oip5os1 induces atrial dysfunction in male mice with diabetes

“…To investigate the effects of Oip5os1 deletion on heart parameters in the presence or absence of diabetes, we took several cardiac relevant measurements from animals at the end of the study. Diabetic cardiomyopathy is typically associated with diastolic dysfunction but the impact on heart weight can vary depending on the model and duration of diabetes (Bernardo et al., 2022; Chandramouli et al., 2018). Total heart weight was reduced in both WT and KO animals that had diabetes (Figure 2a).…”

“…To obtain measures of LV and LA function, echocardiography was performed as previously described (Bernardo et al., 2022). Briefly, mice were anesthetized (ketamine/xylazine/atropine, KXA: 80/8/0.96 mg/kg, i.p.…”