Abstract

Introduction Diabetes Mellitus (DM) is globally the most prevalent metabolic disorder, characterised by an increased risk of heart failure (HF). Diabetic cardiomyopathy (dbCM) can initially present with normal systolic but impaired diastolic dysfunction [heart failure with preserved ejection fraction (HFpEF)]. Creating a pre-clinical model reflecting human DM including dbCM presenting as HFpEF is challenging. Whilst high fat diet (HFD) has been used for induction of experimental DM models, its sole administration can lead to obesogenic and insulin-resistant phenotype but not achieve induction of DM. Emerging data shows that combination of HFD and anomer-equilibrated streptozotocin (STZ) produces a robust DM model. Methods The aim of this study was to develop a novel protocol of stable murine experimental DM reflecting human pathology, including presence of dbCM. Our study compared four groups (C57/BL6J mice) (8-week protocol): 1. HFD (n=8), 2. HFD+1 dose of anomer-equilibrated STZ (75 mg/Kg) (n=8), 3. HFD+3 doses of anomer-equilibrated STZ (25 mg/Kg) (n=8), 4. Controls (chow) (n=8). Animals were characterised by phenotyping in vivo (echocardiography, glucose homeostasis) and ex vivo (plasma profiling). Results All three groups (HFD, HFD+1STZ and HFD+3STZ) developed an obese phenotype compared to controls. In contrast, whilst the first intraperitoneal glucose tolerance test (IPGTT) at 5 weeks of study showed glucose intolerance in all three groups, the second IPGTT at 8 weeks showed significant difference in glucose homeostasis indicative of development of DM, in the HFD+1STZ and HFD+3STZ groups only [total area under the curve (AUC) of IPGTT (0–120 minutes): HFD+1STZ (p=0.0006) and HFD+3STZ (p=0.0003); HFD (p=0.1016) versus control]. HFD and HFD+3STZ groups developed diastolic dysfunction with preservation of ejection fraction (EF) [HFD E'/A' (p=0.0032); HFD+3STZ E'/A' (p=0.0009); HFD EF (p=0.9279), HFD+3STZ EF (p=0.3366) versus control], whilst the HFD+1STZ group developed diastolic and systolic dysfunction [E'/A' (p=0.0092), EF (p=0.0010) versus control]. Plasma analysis showed hyperinsulinemia in the HFD+1STZ (p=0.0322) and HFD+3STZ (p=0.0027) groups and raised free fatty acid (FFA) concentration in the HFD (p=0.0070)and HFD+3STZ (p<0.0001) groups. Conclusions This study has demonstrated that the sole use of HFD causes obesity but does not lead to the development of stable DM. HFD+1STZ leads to development of DM with presence of systolic and diastolic cardiac dysfunction. In contrast, the HFD+3STZ protocol is characterised by systemic impairment of glucose homeostasis, hyperinsulinemia and hyperlipidaemia reflective of peripheral metabolic changes, as well as cardiac diastolic dysfunction. In conclusion, the combination of HFD and multiple low doses of anomer-equilibrated STZ can be safely used for the induction of pre-clinical early onset DM analogous to human featuring dbCM. Conflict of Interest No conflict of interest