SGLT2 inhibition improves novel CMR biomarkers of proinflammatory epicardial adipose tissue, the adenosine coronary microvascular response, and diastolic function in a mouse model of early-stage cardiometabolic HFpEF

Background: Sodium-glucose cotransporter-2 (SGLT2) inhibitors have recently been shown to have cardioprotective effects in heart failure with preserved ejection fraction (HFpEF)¹, but the mechanisms underlying their effectiveness are not completely understood. We employed CMR in a mouse model of early-stage cardiometabolic HFpEF to test whether SGLT2 inhibition has beneficial effects on biomarkers of epicardial adipose tissue (EAT) quantity and quality, adenosine myocardial perfusion reserve (MPR), and systolic and diastolic function.

Methods: Mice fed a high-fat high-sucrose (HFHS) diet (40% kcal fat, 40% kcal sucrose) for 18 weeks develop early-stage cardiometabolic HFpEF, with key features including obesity, glucose intolerance, excess EAT, impaired adenosine MPR, and diastolic dysfunction². Mice were fed a HFHS diet initiated at 10 weeks of age. Two groups of mice (n=15/group) were studied with one group on HFHS diet only and one group receiving empagliflozin (EMPA) (30 mg/kg/day) in the HFHS diet. CMR was performed at 18 weeks on diet using a 9.4T system (Bruker). CMR included black-blood cine imaging covering the left ventricle (LV) to assess LV function and EAT volume, an inversion recovery multi-echo gradient echo sequence to measure EAT fatty acid composition (FAC) and T1 relaxation time³, rest and adenosine arterial spin labeling (ASL) to quantify MPR, and DENSE to assess myocardial strain and peak diastolic strain rate (PDSR). Glucose tolerance testing (GTT) was performed one week prior to CMR and coronary arteriolar reactivity was evaluated on excised coronary arterioles at 20 weeks on diet (n=5/group).

Results: EMPA treatment in HFHS diet-fed mice reduced weight gain (41.20 ± 3.43 g vs 44.67 ± 4.15 g, p = 0.019) and improved glucose tolerance (GTT AUC: 724.3 ± 109.1 vs 930.7 ± 116.2 h×mg/dL, p < 0.0001) compared to HFHS controls. CMR analysis demonstrated that EMPA treatment significantly decreased EAT volume (Fig. 1B), saturated fatty acid (SFA) fraction, and proton density fat fraction (PDFF), while increasing the EAT T1 relaxation time (Fig. 1C), indicating decreased EAT quantity and less proinflammatory EAT compared to HFHS controls. Additionally, EMPA-treated mice showed enhanced adenosine-induced myocardial perfusion (9.91 ± 2.25 mL/g/min vs 7.72 ± 2.51 mL/g/min, p = 0.031) and MPR (2.00 ± 0.54 vs 1.37 ± 0.40, p = 0.004) (Fig. 2C-D), improved coronary arteriolar dilation (p< 0.05) (Fig. 2E), and better diastolic and systolic function as measured by increased PDSR  (3.25 ± 0.814 s^-1 vs 2.15 ± 0.979 s^-1, p = 0.009) (Fig. 3B), a trend towards a higher global longitudinal end-systolic strain (Fig. 3C), and increased LV ejection fraction (71.60 ± 7.58 % vs 65.64 ± 7.30 %, p = 0.040). Data written as mean ± standard deviation.

Conclusion: This study is the first to demonstrate that SGLT2 inhibition with empagliflozin improves novel CMR biomarkers reflecting deleterious EAT quality, including SFA, PDFF, and T1. It is also the first to show improved adenosine perfusion without the presence of coronary artery disease, thereby unambiguously showing improved microvascular adenosine responsiveness in a mouse model of early-stage cardiometabolic HFpEF. In line with prior studies^4,5, we have shown that empagliflozin ameliorates diastolic dysfunction. These findings suggest that empagliflozin’s cardiovascular benefits in HFpEF may be mediated through its effects on EAT and microvascular function.
This work is supported by NIH R01HL162872, AHA 23PRE1011280, NIH S10OD025024 and NIH T32GM007267.

Figure 1: (A) Example PDFF, SFA, and T1 maps overlaid on regions of EAT and subcutaneous adipose tissue in short-axis images of a heart from a mouse fed a HFHS diet. (B) EAT volume normalized by body weight (µL/g body weight) in HFHS and HFHS+EMPA mice at 18 weeks post-diet. (C) EAT PDFF, SFA, and T1 in HFHS and HFHS+EMPA mice at 18 weeks post-diet. Data are shown as mean ± standard error of the mean (SEM) and are compared using a Student’s t-test. *p < 0.05 and **p < 0.01 for indicated groups. HFHS = high-fat high-sucrose; EMPA = empagliflozin; SFA = saturated fatty acid; PDFF = proton density fat fraction; EAT = epicardial adipose tissue.

Figure 2: (A) Example rest and adenosine-induced stress myocardial perfusion maps in a HFHS+EMPA mouse. (B) Rest and (C) adenosine-induced stress myocardial perfusion (ml/g/min) in HFHS and HFHS+EMPA mice at 18 weeks post-diet. (D) MPR reported as the ratio of myocardial stress to rest perfusion in HFHS and HFHS+EMPA mice at 18 weeks post-diet. (E) Cumulative dose-response curves to sodium nitroprusside and adenosine of the coronary arterioles in HFHS and HFHS+EMPA mice at 20 weeks post-diet. Data are shown as mean ± SEM and are compared using a Student’s t-test (B-D), or mean ± standard deviation and are compared using a 2-way ANOVA with a Bonferroni’s multiple comparisons test. *p < 0.05, **p < 0.01, †p < 0.001, ‡p < 0.0001 for indicated groups. MPR = myocardial perfusion reserve; other abbreviations as in Figure 1.

Figure 3: (A) Example longitudinal strain maps in a HFHS and HFHS+EMPA mouse. (B) Longitudinal strain measurements in HFHS and HFHS+EMPA mice at 18 weeks post-diet. (C) PDSR measurements in HFHS and HFHS+EMPA mice at 18 weeks post-diet. Data are shown as mean ± SEM and compared using a Student’s t-test. ** p< 0.01 for indicated groups. PDSR = peak diastolic strain rate; other abbreviations as in Figure 1.