Defining the Progression of Diabetic Cardiomyopathy in a Mouse Model of Type 1 Diabetes

Abstract

Integrative Physiology, a section of the journal Frontiers in PhysiologyThe incidence of diabetes and its association with increased cardiovascular disease risk represents a major health issue worldwide. Diabetes-induced hyperglycemia is implicated as a central driver of responses in the diabetic heart such as cardiomyocyte hypertrophy, fibrosis, and oxidative stress, termed diabetic cardiomyopathy. The onset of these responses in the setting of diabetes has not been studied to date. This study aimed to determine the time course of development of diabetic cardiomyopathy in a model of type 1 diabetes (T1D) in vivo. Diabetes was induced in 6-week-old male FVB/N mice via streptozotocin (55 mg/kg i.p. for 5 days; controls received citrate vehicle). At 2, 4, 8, 12, and 16 weeks of untreated diabetes, left ventricular (LV) function was assessed by echocardiography before post-mortem quantification of markers of LV cardiomyocyte hypertrophy, collagen deposition, DNA fragmentation, and changes in components of the hexosamine biosynthesis pathway (HBP) were assessed. Blood glucose and HbA1c levels were elevated by 2 weeks of diabetes. LV and muscle (gastrocnemius) weights were reduced from 8 weeks, whereas liver and kidney weights were increased from 2 and 4 weeks of diabetes, respectively. LV diastolic function declined with diabetes progression, demonstrated by a reduction in E/A ratio from 4 weeks of diabetes, and an increase in peak A-wave amplitude, deceleration time, and isovolumic relaxation time (IVRT) from 4-8 weeks of diabetes. Systemic and local inflammation (TNFα, IL-1β, CD68) were increased with diabetes. The cardiomyocyte hypertrophic marker Nppa was increased from 8 weeks of diabetes while β-myosin heavy chain was increased earlier, from 2 weeks of diabetes. LV fibrosis (picrosirius red; Ctgf and Tgf-β gene expression) and DNA fragmentation (a marker of cardiomyocyte apoptosis) increased with diabetes progression. LV Nox2 and Cd36 expression were elevated after 16 weeks of diabetes. Markers of the LV HBP (Ogt, Oga, Gfat1/2 gene expression), and protein abundance of Frontiers in Physiology | www.frontiersin.org February 2020 | Volume 11 | Article 124De Blasio et al. The Progression of Diabetic CardiomyopathyOGT and total O-GlcNAcylation, were increased by 16 weeks of diabetes. This is the first study to define the progression of cardiac markers contributing to the development of diabetic cardiomyopathy in a mouse model of T1D, confirming multiple pathways contribute to disease progression at various time points.

A novel role of kallikrein-related peptidase 8 in the pathogenesis of diabetic cardiac fibrosis

“…KLK8 -/- mice exhibited significantly smaller left ventricular end-diastolic and end-systolic dimension and higher fractional shortening and ejection fraction than KLK8 +/+ mice (Figure 2 G, Table 2 ). Cardiac fibrosis is closely associated with cardiac diastolic dysfunction 21 , 22 . The present study next observed the effect of KLK8 deficiency on diabetes-induced diastolic dysfunction.…”

Bone Morphogenetic Protein 7 Gene Delivery Improves Cardiac Structure and Function in a Murine Model of Diabetic Cardiomyopathy

“…To obtain measures of LV function, echocardiography was performed in anaesthetised mice (ketamine/xylazine/atropine: 80/8/0.96 mg/kg i.p.) at study endpoint utilising a Philips iE33 ultrasound (North Ryde, NSW, Australia) with 15 MHz linear (M-mode) and 12 MHz sector (Doppler) transducer, as previously described (Prakoso et al, 2017;Tate et al, 2019;De Blasio et al, 2020;Prakoso et al, 2020;Prakoso et al, 2021a). LV chamber dimensions and fractional shortening were assessed from M-mode imaging.…”

“…LV chamber dimensions and fractional shortening were assessed from M-mode imaging. LV filling was assessed using transmitral Doppler; the ratio of early (E) and late (A) peak blood flow velocities (E/A ratio), deceleration time and IVRT were measured (Prakoso et al, 2017;Tate et al, 2019;De Blasio et al, 2020;Prakoso et al, 2020;Prakoso et al, 2021a).…”

“…Ten random fields of view were imaged per LV (20X magnification) for apoptosis with TUNEL positive cells quantified as a percentage of total cardiac cell number per field of view. All images were imaged using a BX43 microscope (Olympus, Japan) and analysed blinded from the experimental group using ImageJ, as previously described (Prakoso et al, 2017;Tate et al, 2019;De Blasio et al, 2020;Prakoso et al, 2020;Prakoso et al, 2021a).…”

“…LV and gastrocnemius tissue were collected, snap-frozen in liquid nitrogen, and stored at −80 °C for gene expression analysis (Prakoso et al, 2017;Tate et al, 2019;De Blasio et al, 2020;Prakoso et al, 2020;Prakoso et al, 2021a). RNA was extracted from frozen LV homogenate using TRIzol ® reagent (Invitrogen Life Technologies, Mount Waverley, VIC, Australia), and cDNA synthesised by reverse transcription (Invitrogen Life Technologies, Mount Waverley, VIC, Australia), both techniques carried out in accordance with manufacturer's instructions.…”