Empagliflozin Improves Left Ventricular Diastolic Dysfunction in a Genetic Model of Type 2 Diabetes

PURPOSE

Cardiovascular (CV) diseases in type 2 diabetes (T2DM) represent an enormous burden with high mortality and morbidity. Sodium-glucose cotransporter 2 (SGLT2) inhibitors have recently emerged as a new antidiabetic class that improves glucose control, as well as body weight and blood pressure with no increased risk of hypoglycemia. The first CV outcome study terminated with empagliflozin, a specific SGLT2 inhibitor, has shown a reduction in CV mortality and in heart failure hospitalization, suggesting a beneficial impact on cardiac function which remains to be demonstrated. This study was designed to examine the chronic effect of empagliflozin on left ventricular (LV) systolic and diastolic functions in a genetic model of T2DM, ob/ob mice.

METHODS AND RESULTS

Cardiac phenotype was characterized by echocardiography, in vivo hemodynamics, histology, and molecular profiling. Our results demonstrate that empagliflozin significantly lowered HbA1c and slightly reduced body weight compared to vehicle treatment with no obvious changes in insulin levels. Empagliflozin also improved LV maximum pressure and in vivo indices of diastolic function. While systolic function was grossly not affected in both groups at steady state, response to dobutamine stimulation was significantly improved in the empagliflozin-treated group, suggesting amelioration of contractile reserve. This was paralleled by an increase in phospholamban (PLN) phosphorylation and increased SERCA2a/PLN ratio, indicative of enhanced SERCA2a function, further supporting improved cardiac relaxation and diastolic function. In addition, empagliflozin reconciled diabetes-associated increase in MAPKs and dysregulated phosphorylation of IRS1 and Akt, leading to improvement in myocardial insulin sensitivity and glucose utilization.

CONCLUSION

The data show that chronic treatment with empagliflozin improves diastolic function, preserves calcium handling and growth signaling pathways and attenuates myocardial insulin resistance in ob/ob mice, findings suggestive of a potential clinical utility for empagliflozin in the treatment of diastolic dysfunction.

Speckle-Tracking Echocardiographic Strain Analysis Reliably Estimates Degree of Acute LV Unloading During Mechanical LV Support by Impella

Non-invasive means of evaluating appropriate cardiac unloading remain to be established. We hypothesized that myocardial deformation assessed by echocardiographic speckle-tracking strain analysis can reliably estimate the degree of left ventricular (LV) unloading under mechanical circulatory support. A total of 24 Yorkshire pigs underwent Impella-mediated acute LV unloading 1-2 weeks after myocardial infarction (MI). Echocardiographic and invasive pressure-volume measurements were used to evaluate the degree of LV unloading. Pressure-volume analysis before and after LV unloading exhibited a significant decrease in stroke work (3399 ± 1440 to 1244 ± 659 mmHg ml, p < 0.001), suggesting reduced external cardiac work. Both longitudinal strain (- 14.6 ± 4.1% to - 10.6 ± 2.3%, p < 0.001) and circumferential strain (- 18.7 ± 6.1% to - 9.3 ± 3.5%, p < 0.001) decreased after LV unloading, and there were linear relationships between stroke work and echocardiographic longitudinal (r = - 0.61, p < 0.001) as well as circumferential strains (r = - 0.75, p < 0.001). Echocardiographic LV strain analysis offers a non-invasive assessment of LV unloading in subacute MI.

Chronic Pulmonary Artery Embolization Models in Large Animals

A wide range of approaches have been described to develop animal models of pulmonary vascular disease (PVD). Clinical heterogeneity in patients with pulmonary hypertension (PH) has prompted development of different techniques to create PH models in several animal species with the objective to recapitulate specific PH/PVD phenotypes. Chronic thromboembolic PH (CTEPH) is a clinically important phenotype of PH with a documented prevalence of 0.4-9.1% in patients with history of pulmonary embolism. A well-established large animal model of CTEPH is thus necessary for studying this disease in preclinical research. Different experimental protocols with inconsistent outcomes have been reported in the literature.We have focused on characterizing PH large animal models in a common framework; pulmonary hemodynamics, right ventricular (RV) function, and histological characterization of PVD. This research framework allows optimal evaluation of novel diagnostic tools, as well as new therapeutic strategies. The purpose of this protocol is to describe approaches to create experimental CTEPH models using recurrent pulmonary embolizations of dextran microspheres in swine. The key features of this experimental modeling approach are (1) nonsurgical, fully percutaneous techniques, (2) a minimum of four embolization procedures, with 1-2 month time period, (3) mild to moderate PH hemodynamics (mean PA pressure increase ~20-60%), (4) severe pulmonary vascular remodeling, (5) mild RV remodeling, and (6) a high reproducibility and low mortality (<10%).

Complex Association of Sex Hormones on Left Ventricular Systolic Function: Insight into Sexual Dimorphism

BACKGROUND

Normal values of left ventricular ejection fraction (LVEF) and absolute values of global longitudinal strain (GLS) are lower in men than in women. Data concerning the association of sex hormone levels on these left ventricular systolic function surrogates are scarce. The aim of this study was to determine the association of sex hormones with systolic left ventricular function in healthy subjects and patients with congenital adrenal hyperplasia (CAH) as a model of testosterone dysregulation.

METHODS

Eighty-four adult patients with CAH (58 women; median age, 27 years; interquartile range, 23-36 years) and 84 healthy subjects matched for sex and age were prospectively included. Circulating concentrations of sex hormones were measured within 48 hours of echocardiography with assessment of LVEF and left ventricular longitudinal, radial, and circumferential strain.

RESULTS

LVEF and GLS were higher in healthy women than in healthy men (63.9 ± 4.2% vs 60.9 ± 5.1% [P < .05] and 20.0 ± 1.9% vs 17.9 ± 2.4% [P < .001], respectively), while there was no difference in LVEF or GLS between women and men with CAH (63.9 ± 4.5% vs 63.0 ± 4.6% [P = NS] and 19.4 ± 2.2% vs 18.3 ± 1.8% [P = NS], respectively). Bioavailable testosterone levels were higher in women with CAH than in female control subjects (0.08 ng/mL [interquartile range, 0.04-0.14 ng/mL] vs 0.16 ng/mL [interquartile range, 0.04-0.3 ng/mL], P < .001) and lower in men with CAH than in male control subjects (2.3 ng/mL [interquartile range, 1.3-3 ng/mL] vs 2.9 ng/mL [interquartile range, 2.5-3.4 ng/mL], P < .05). In men, LVEF and GLS were negatively correlated with bioavailable testosterone levels (r = -0.3, P ≤ .05, and r = -0.45, P < .01, respectively), while midventricular radial strain was positively correlated with bioavailable testosterone level (r = 0.38, P < .05). The absolute value of circumferential strain was positively correlated with follicle-stimulating hormone (r = 0.65, P < .0001).

CONCLUSIONS

These data support that the existence of sex dimorphism concerning left ventricular systolic cardiac function is significantly associated with testosterone levels.

Reduced longitudinal contraction is associated with ischemic mitral regurgitation after posterior MI

The role of left ventricular (LV) longitudinal contraction in ischemic mitral regurgitation (MR) remains unclear. We hypothesized that reduced longitudinal contraction disrupts normal mitral valve plane displacement during systole and leads to mitral valve tethering, thereby inducing ischemic MR. Twenty-three Yorkshire pigs underwent induction of different-sized posterior myocardial infarction (MI) using a percutaneous approach. The incidence of MR and its association with LV longitudinal strain were examined using speckle-tracking echocardiography at 1 mo post-MI to determine their relationship. A total of 17 pigs survived MI and completed the study. Pigs developed no more than mild MR after proximal left circumflex artery (LCx) occlusion (LCx group; n = 7). Addition of a first diagonal branch (D1) occlusion to LCx-MI (LCx + D1 group; n = 7) resulted in moderate to severe MR development 1 mo post-MI. LCx + D1 animals had lower longitudinal strain compared with the LCx group, whereas circumferential strain and LV rotation did not differ significantly. Posterolateral annular displacement toward the apex was significantly reduced in LCx + D1 animals, whereas the septal annular displacement was similar, suggesting an asymmetric mitral annular plane excursion in the LCx + D1 group. To exclude the contribution of papillary muscle infarction in MR development in our model, three pigs underwent obtuse marginal branch + D1 occlusion. None of these pigs developed significant MR after 1 mo. In conclusion, reduced longitudinal contraction contributes to the development of ischemic MR in a large posterior MI. NEW & NOTEWORTHY In this study, using our unique swine models of different-sized myocardial infarction, we showed, for the first time, that reduced longitudinal contraction contributes to the development of ischemic mitral regurgitation in a large posterior myocardial infarction. Our study adds new insights into the mechanisms of ischemic mitral regurgitation pathophysiology.

[Epidemiology of early repolarization pattern in Maghreb]

An early repolarization variant (ERV) in inferolateral leads has recently been associated with vulnerability to ventricular fibrillation. These studies have been conducted in the occidental countries. The prevalence of ERV in the population of the Maghreb is unknown. The aim of this study was to evaluate the prevalence and risk factors of ERV in a young population from Algeria.

METHODS

We assessed the prevalence of ERV within a population of 441 healthy subjects (mean age 25 years) using 12-lead electrocardiography. ERV was stratified by three independent cardiologists according to the J-point elevation (≥0.1mV) in the inferior, apicolateral or both leads with QRS slurring or notching.

RESULTS

The inferolateral ERV pattern was present in 55 subjects (12.4%). A malign ERV (>2mm) was present in 5 subjects (9% of ER) and ER in inferior and lateral leads in 40% of ER. An ERV pattern was more frequently associated with young age, male, bradycardia and T wave in V1 lead.

CONCLUSION

An ERV is a common finding in a healthy Algerian young population. This prevalence seems to be more important than other studies due to young age and not to a racial difference. Our population were more at risk that other studies, and we found more T waves in V1 lead in this people, due to an ethnic particularities or a phenotypic association with the Brugada syndrome.

Coronary capillary blood flow in a rat model of congestive heart failure

The aim of this study was to explore the role of abnormal coronary microvasculature morphology and hemodynamics in the development of congestive heart failure (CHF). CHF was induced in rats by aortic banding, followed by ischemia-reperfusion and later aortic debanding. Polymerized casts of coronary vasculature were imaged under a scanning electron microscope (SEM). Matrix Laboratory (MATLAB) software was used to calculate capillary structure index (CSI), a measure of structural alignment also called mean vector length (MVL), for 93 SEM images of coronary capillaries (CSI→1 perfect linearity; CSI→0 circular disarray). CSI was incorporated as a constant to represent tortuosity and nonlaminar flow in Poiseuille's equation to estimate the differences in capillary blood flow rate, velocity, and resistance for CHF vs.

CONTROL

The morphology of CHF capillaries is significantly disordered and tortuous compared with control (CSI: 0.35 ± 0.02 for 61 images from 7 CHF rats; 0.58 ± 0.02 for 32 images from 7 control rats; P < 0.01). Estimated capillary resistance in CHF is elevated by 173% relative to control, while blood flow rate and blood velocity are 56 and 43% slower than control. Capillary resistance increased 67% due to the significantly narrower capillary diameter in CHF, while it increased an additional 105% due to tortuosity. The significant structural abnormalities of CHF coronary capillaries may drastically stagnate hemodynamics in myocardium and increase resistance to blood flow. This could play a role in the development of CHF. NEW & NOTEWORTHY In the present study, coronary capillary tortuosity was measured by applying Matrix Laboratory software to scanning electron microscope images of capillaries in a rat model of congestive heart failure. Stagnant blood flow in coronary capillaries may play a role in the development of congestive heart failure. The application of computer modeling to histological and physiological data to characterize the hemodynamics of coronary microcirculation is a new area of study.

Impact of negative inotropic drugs on accuracy of diastolic stress echocardiography for evaluation of left ventricular filling pressure

The ratio of early diastolic trans-mitral flow velocity to tissue-Doppler mitral annular early diastolic velocity (E/e′), and left ventricular end-diastolic pressure(LVEDP) have been shown to be correlated at rest, provided that patients are not on positive inotropic drugs. Data concerning the latter correlation during exercise stress are conflicting. Therefore, we investigated if use of negative inotropic drugs (NID), impacts the accuracy of E/e′ as a surrogate for LVEDP during low-level exercise. An exercise(50 watts) during cardiac invasive hemodynamic monitoring and an exercise echocardiography were performed prospectively within 24 hours in 54 patients (81%male, 62 ± 9years) with preserved LV Ejection-Fraction. Before exercise, the patients had scattered LVEDP (13.8 ± 5.8 mmHg) and septal E/e′ (8.7 ± 2.7). Half of them were on NID, mainly betablockers(n = 26). The correlation between septal-E/e′ and LVEDP was low for examinations performed at rest (r = 0.35,p = 0.01) with no significant impact of NID. For measurements performed at 50 Watts, NID had a significant impact on the association between septal-E/e′50 watts and LVEDP50 watts (β = −0.28,p = 0.03). Correlation between septal-E/e′50 watts and LVEDP50 watts persisted in patients on NID (r = 0.61,p = 0.001) while it disappeared in the group of patients with no NID (r = 0.15,p = 0.47). NID use is an important confounding factor to take into consideration when assessing exercise LVFP using stress E/e′ in patients with preserved LVEF.

Intratracheal Gene Delivery of SERCA2a Ameliorates Chronic Post-Capillary Pulmonary Hypertension: A Large Animal Model

BACKGROUND

Pulmonary hypertension (PH) is characterized by pulmonary arterial remodeling that results in increased pulmonary vascular resistance, right ventricular (RV) failure, and premature death. Down-regulation of sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA2a) in the pulmonary vasculature leads to perturbations in calcium ion (Ca(2+)) homeostasis and transition of pulmonary artery smooth muscle cells to a proliferative phenotype.

OBJECTIVES

We assessed the feasibility of sustained pulmonary vascular SERCA2a gene expression using aerosolized delivery of adeno-associated virus type 1 (AAV1) in a large animal model of chronic PH and evaluated the efficacy of gene transfer regarding progression of pulmonary vascular and RV remodeling.

METHODS

A model of chronic post-capillary PH was created in Yorkshire swine by partial pulmonary vein banding. Development of chronic PH was confirmed hemodynamically, and animals were randomized to intratracheal administration of aerosolized AAV1 carrying the human SERCA2a gene (n = 10, AAV1.SERCA2a group) or saline (n = 10). Therapeutic efficacy was evaluated 2 months after gene delivery.

RESULTS

Transduction efficacy after intratracheal delivery of AAV1 was confirmed by β-galactosidase detection in the distal pulmonary vasculature. Treatment with aerosolized AAV1.SERCA2a prevented disease progression as evaluated by mean pulmonary artery pressure, vascular resistance, and limited vascular remodeling quantified by histology. Therapeutic efficacy was supported further by the preservation of RV ejection fraction (p = 0.014) and improvement of the RV end-diastolic pressure-volume relationship in PH pigs treated with aerosolized AAV1.SERCA2a.

CONCLUSIONS

Airway-based delivery of AAV vectors to the pulmonary arteries was feasible, efficient, and safe in a clinically relevant chronic PH model. Vascular SERCA2a overexpression resulted in beneficial effects on pulmonary arterial remodeling, with attendant improvements in pulmonary hemodynamics and RV performance, and might offer therapeutic benefit by modifying fundamental pathophysiology in pulmonary vascular diseases.