Effects of Empagliflozin on Myocardial Flow Reserve in Patients With Type 2 Diabetes Mellitus: The SIMPLE Trial

Large lessons learned from small vessels: coronary microvascular dysfunction in HIV

PURPOSE OF REVIEW

Large cohort studies have consistently shown the presence of heart failure is approximately doubled among persons with HIV (PWH). Early studies of cardiovascular disease (CVD) in HIV were primarily focused on atherosclerotic burden, and we now have a greater understanding of large vessel disease in HIV. More recent studies have begun to inform us about small vessel disease, or coronary microvascular dysfunction (CMD), in HIV. CMD is recognized to be an important risk factor for adverse events related to heart failure, associated with cardiovascular mortality, and often presents without overt atherosclerotic disease.

RECENT FINDINGS

In this review, we highlight implications for CMD and relevant clinical studies in HIV. Inflammation and endothelial dysfunction, well known risk factors in HIV, may mediate the pathogenesis of CMD. Initial studies suggest that CMD worsens with ART initiation. Newer studies reveal CMD is present among well treated PWH without known CVD. In addition, myocardial flow reserve (MFR), a marker of CMD, is reduced in HIV similar to diabetes. There also appears to be sex differences, such that CMD is worse among women vs. men with HIV.

SUMMARY

Alterations in the coronary microvasculature may be an important mediator of subclinical myocardial dysfunction that deserves further clinical attention among PWH without known CVD.

The effect of SGLT2 inhibitors on the endothelium and the microcirculation: from bench to bedside and beyond

AIMS

The beneficial cardiovascular effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors irrespective of the presence of diabetes mellitus are nowadays well established and they already constitute a significant pillar for the management of heart failure, irrespective of the ejection fraction. The exact underlying mechanisms accountable for these effects, however, remain largely unknown. The direct effect on endothelial function and microcirculation is one of the most well studied. The broad range of studies presented in this review aims to link all available data from the bench to bedside and highlight the existing gaps as well as the future directions in the investigations concerning the effects of SGLT2 inhibitors on the endothelium and the microcirculation.

METHODS AND RESULTS

An extensive search has been conducted using the MEDLINE/PubMed database in order to identify the relevant studies. Preclinical data suggest that SGLT2 inhibitors directly affect endothelial function independently of glucose and specifically via several interplaying molecular pathways, resulting in improved vasodilation, increased NO production, enhanced mitochondrial homeostasis, endothelial cell viability, and angiogenesis as well as attenuation of oxidative stress and inflammation. Clinical data systematically confirm this beneficial effect on the endothelium, whereas the evidence concerning the effect on the microcirculation is conflicting.

CONCLUSION

Preclinical and clinical studies indicate that SGLT2 inhibitors attenuate endothelial and microvascular dysfunction via a combination of mechanisms, which play a role in their beneficial cardiovascular effect.

The effects of empagliflozin on measured glomerular filtration rate and estimated extracellular and plasma volumes in patients with type 2 diabetes

AIMS

To investigate the effects of empagliflozin on measured glomerular filtration rate (mGFR), estimated plasma volume (PV) and estimated extracellular volume (ECV) in a cohort of patients with type 2 diabetes (T2D) and high risk of cardiovascular events.

MATERIALS AND METHODS

In this prespecified substudy of the randomized, placebo-controlled SIMPLE trial, patients with T2D at high risk of cardiovascular events were allocated to either empagliflozin 25 mg or placebo once daily for 13 weeks. The prespecified outcome was between-group change in mGFR, measured by the 51 Cr-EDTA method after 13 weeks; changes in estimated PV and estimated ECV were included.

RESULTS

From April 4, 2017 to May 11, 2020, 91 participants were randomized. Of these, 45 patients from the empagliflozin group and 45 patients from the placebo group were included in the intention-to-treat analysis. Treatment with empagliflozin reduced mGFR by -7.9 mL/min (95% confidence interval [CI] -11.1 to -4.7; P < 0.001), estimated ECV by -192.5 mL (95% CI -318.0 to -66.9; P = 0.003) and estimated PV by -128.9 mL (95% CI -218.0 to 39.8; P = 0.005) at Week 13.

CONCLUSIONS

Treatment with empagliflozin for 13 weeks reduced mGFR, estimated ECV and estimated PV in patients with T2D and high risk of cardiovascular events.

Coronary microvascular dysfunction in heart failure patients

Coronary microcirculation has multiple layers of autoregulatory function to maintain resting flow and augment hyperemic flow in response to myocardial demands. Functional or structural alterations in the coronary microvascular function are frequently observed in patients with heart failure with preserved or reduced ejection fraction, which may lead to myocardial ischemic injury and resultant worsening of clinical outcomes. In this review, we describe our current understanding of coronary microvascular dysfunction in the pathogenesis of heart failure with preserved and reduced ejection fraction.

Reduction of cardiac adipose tissue volume with short-term empagliflozin treatment in patients with type 2 diabetes: A substudy from the SIMPLE randomized clinical trial

OBJECTIVE

Ectopic accumulation of cardiac adipose tissue volume (CAT) has been associated with cardiac remodelling and cardiac dysfunction in type 2 diabetes and may be a future therapeutic target. In this substudy from the SIMPLE-trial, we investigated short-term empagliflozin therapy's effects on CAT in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Between 4 April 2017 and 11 May 2020, we randomized 90 patients with type 2 diabetes and established or high risk of cardiovascular disease to 25 mg empagliflozin or placebo for 13 weeks. The substudy focused on change in CAT evaluated by images acquired during ⁸² Rubidium-positron emissions tomography/computed tomography. The analysis included 78 patients who had at least one scan. Furthermore, we report on the relation to the concurrent effects on left ventricular mass, end-diastolic volume and end-systolic volume, body composition and glucometabolic status.

RESULTS

Mean ± SD baseline CAT was 258.5 ± 117.9 ml. Empagliflozin reduced CAT after 13 weeks by 12.41 ml [95% CI (-23.83 to -0.99), p = .034] as compared with placebo. Similarly, left ventricular mass [-5.16 g, 95% CI (-8.80 to -1.52), p = .006], end-diastolic volume and end-systolic volume decreased with empagliflozin. In addition, significant improvements were observed in body composition, with reduced total fat mass, and in measures of glucose and lipid metabolism. However, no correlation was observed between changes in CAT and changes in cardiac parameters and change in CAT appeared mediated primarily by concurrent change in weight.

CONCLUSIONS

Empagliflozin provides an early reduction of CAT; however, no association was observed with concurrent changes in cardiac volumetrics.

The Therapeutic Role of SGLT-2 Inhibitors in Acute Heart Failure: From Pathophysiologic Mechanisms to Clinical Evidence with Pooled Analysis of Relevant Studies across Safety and Efficacy Endpoints of Interest

(1) Background: Sodium-glucose co-transporter-2 (SGLT-2) inhibitors constitute a novel drug class with remarkable cardiovascular benefits for patients with chronic heart failure (HF). Recently, this class has been utilized in acute HF as an additional treatment option to classic diuretics, which remain the cornerstone of treatment. (2) Methods: We attempted to identify those pathophysiologic mechanisms targeted by SGLT-2 inhibitors, which could be of benefit to patients with acute HF. We then conducted a comprehensive review of the literature within the PubMed database in order to identify relevant studies, both randomized controlled trials (RCTs) and observational studies, assessing the safety and efficacy of SGLT-2 inhibitors in acute HF. (3) Results: SGLT-2 inhibitors induce significant osmotic diuresis and natriuresis, decrease interstitial fluid volume and blood pressure, improve left ventricular (LV) function, ameliorate LV remodeling and prevent atrial arrhythmia occurrence, mechanisms that seem to be beneficial in acute HF. However, currently available studies, including six RCTs and two real-world studies, provide conflicting results concerning the true efficacy of SGLT-2 inhibitors, including "hard" surrogate endpoints. (4) Conclusions: Current evidence appears insufficient to substantiate the use of SGLT-2 inhibitors in acute HF. Further trials are required to shed more light on this issue.

Coronary Microvascular Dysfunction in Diabetes Mellitus: Pathogenetic Mechanisms and Potential Therapeutic Options

Diabetic patients are frequently affected by coronary microvascular dysfunction (CMD), a condition consisting of a combination of altered vasomotion and long-term structural change to coronary arterioles leading to impaired regulation of blood flow in response to changing cardiomyocyte oxygen requirements. The pathogenesis of this microvascular complication is complex and not completely known, involving several alterations among which hyperglycemia and insulin resistance play particularly central roles leading to oxidative stress, inflammatory activation and altered barrier function of endothelium. CMD significantly contributes to cardiac events such as angina or infarction without obstructive coronary artery disease, as well as heart failure, especially the phenotype associated with preserved ejection fraction, which greatly impact cardiovascular (CV) prognosis. To date, no treatments specifically target this vascular damage, but recent experimental studies and some clinical investigations have produced data in favor of potential beneficial effects on coronary micro vessels caused by two classes of glucose-lowering drugs: glucagon-like peptide 1 (GLP-1)-based therapy and inhibitors of sodium-glucose cotransporter-2 (SGLT2). The purpose of this review is to describe pathophysiological mechanisms, clinical manifestations of CMD with particular reference to diabetes, and to summarize the protective effects of antidiabetic drugs on the myocardial microvascular compartment.

Dapagliflozin improves myocardial flow reserve in patients with type 2 diabetes: the DAPAHEART Trial: a preliminary report

Objective

Cardiovascular (CV) outcome trials have shown that in patients with type 2 diabetes (T2D), treatment with sodium-glucose cotransporter-2 inhibitors (SGLT-2i) reduces CV mortality and hospital admission rates for heart failure (HF). However, the mechanisms behind these benefits are not fully understood. This study was performed to investigate the effects of the SGLT-2i dapagliflozin on myocardial perfusion and glucose metabolism in patients with T2D and stable coronary artery disease (coronary stenosis ≥ 30% and < 80%), with or without previous percutaneous coronary intervention (> 6 months) but no HF.

Methods

This was a single-center, prospective, randomized, double-blind, controlled clinical trial including 16 patients with T2D randomized to SGLT-2i dapagliflozin (10 mg daily) or placebo. The primary outcome was to detect changes in myocardial glucose uptake (MGU) from baseline to 4 weeks after treatment initiation by [(18)F]2-deoxy-2-fluoro-D-glucose (FDG) PET/CT during hyperinsulinemic euglycemic clamp. The main secondary outcome was to assess whether the hypothetical changes in MGU were associated with changes in myocardial blood flow (MBF) and myocardial flow reserve (MFR) measured by ¹³N-ammonia PET/CT. The study was registered at eudract.ema.europa.eu (EudraCT No. 2016-003614-27) and ClinicalTrials.gov (NCT 03313752).

Results

16 patients were randomized to dapagliflozin (n = 8) or placebo (n = 8). The groups were well-matched for baseline characteristics (age, diabetes duration, HbA1c, renal and heart function). There was no significant change in MGU during euglycemic hyperinsulinemic clamp in the dapagliflozin group (2.22 ± 0.59 vs 1.92 ± 0.42 μmol/100 g/min, p = 0.41) compared with the placebo group (2.00 ± 0.55 vs 1.60 ± 0.45 μmol/100 g/min, p = 0.5). Dapagliflozin significantly improved MFR (2.56 ± 0.26 vs 3.59 ± 0.35 p = 0.006 compared with the placebo group 2.34 ± 0.21 vs 2.38 ± 0.24 p = 0.81; p_int = 0.001) associated with a reduction in resting MBF corrected for cardiac workload (p = 0.005; p_int = 0.045). A trend toward an increase in stress MBF was also detected (p = 0.054).

Conclusions

SGLT-2 inhibition increases MFR in T2D patients. We provide new insight into SGLT-2i CV benefits, as our data show that patients on SGLT-2i are more resistant to the detrimental effects of obstructive coronary atherosclerosis due to increased MFR, probably caused by an improvement in coronary microvascular dysfunction.

Trial registration EudraCT No. 2016-003614-27; ClinicalTrials.gov Identifier: NCT03313752

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01607-4.

Sodium Glucose Cotransporter-2 Inhibitors: Spotlight on Favorable Effects on Clinical Outcomes beyond Diabetes

Sodium glucose transporter type 2 (SGLT2) molecules are found in proximal tubules of the kidney, and perhaps in the brain or intestine, but rarely in any other tissue. However, their inhibitors, intended to improve diabetes compensation, have many more beneficial effects. They improve kidney and cardiovascular outcomes and decrease mortality. These benefits are not limited to diabetics but were also found in non-diabetic individuals. The pathophysiological pathways underlying the treatment success have been investigated in both clinical and experimental studies. There have been numerous excellent reviews, but these were mostly restricted to limited aspects of the knowledge. The aim of this review is to summarize the known experimental and clinical evidence of SGLT2 inhibitors' effects on individual organs (kidney, heart, liver, etc.), as well as the systemic changes that lead to an improvement in clinical outcomes.

Effect of empagliflozin on coronary microvascular function in patients with type 2 diabetes mellitus–A randomized, placebo-controlled cross-over study

Purpose

Results from large scale cardiovascular outcome trials in patients with type 2 diabetes mellitus (DM2) have found that sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce cardiovascular death and hospitalization for heart failure, but the mechanisms behind the beneficial cardiovascular effects are not fully understood. We tested the hypothesis that the SGLT2i, empagliflozin, improves non-endothelial dependent coronary microvascular function, thereby leading to better cardiac function.

Methods

Patients with DM2 followed at the endocrinology outpatient clinic at Bispebjerg University Hospital were included in a double blinded, placebo-controlled cross-over study. Participants were allocated equally to each treatment sequence using simple randomization and treated with empagliflozin 25 mg and placebo for 12 weeks, interrupted by 2 weeks wash-out period. The primary outcome was coronary microvascular function, assessed as coronary flow velocity reserve (CFVR) and measured with transthoracic doppler echocardiography. Echocardiographic parameters of cardiac function were measured, and blood samples were analyzed for a broad panel of cardiovascular biomarkers.

Results

Thirteen patients were randomized to each sequence and 10 and 9 completed the study according to protocol, respectively, and were included in the analysis of outcome parameters. We found no improvement in CFVR (change in the empagliflozin period was -0.16 (SD 0.58)). There were no effects on cardiac systolic function or indicators of cardiac filling pressure. Well-known effects of empagliflozin were obtained, such as weight loss and reduction in Hba1c level. Creatinine level increased but remained within normal range. We observed a clear trend of reduction in cardiovascular biomarkers after empagliflozin treatment and increased levels after the placebo period. No serious adverse reactions were reported.

Conclusions

Despite effect on weight-loss, Hba1c and biomarkers, treatment with empagliflozin for 12 weeks did not improve CFVR in patients with DM2.

Effect of empagliflozin on myocardial structure and function in patients with type 2 diabetes at high cardiovascular risk: the SIMPLE randomized clinical trial

To investigate the effects of 13 weeks treatment with empagliflozin in patients with high-risk type-2 diabetes mellitus on echocardiographic measures of left ventricular (LV) structure and function compared to placebo. A total of 91 patients were randomized to treatment with empagliflozin (25 mg/day, n = 45) or matching placebo (n = 45) for 13 weeks. Left ventricular (LV) mass, volumes and geometry as well as measures of LV systolic and diastolic function were measured using echocardiography at baseline and follow up. Mean LV mass index (LVMi) was reduced by - 11.5 g/m² (95% CI - 56.4; 33.4, p = 0.03) with empagliflozin compared to - 1.4 g/m² (95% CI - 36.5; 33.8, p = 0.63) for placebo. The proportion of patients with LV hypertrophy was reduced by 16.3% (p = 0.04) in the empagliflozin group compared to 1.1% in the placebo group (p = 1.00). The proportion of patients with left atrial volume index > 34 mL/m² was reduced by 20.0% (p = 0.02) with empagliflozin compared to 9.5% for placebo (p = 0.45) and the E/e' ratio decreased (∆-0.8 (1.9) vs. ∆0.5 (2.0), p < 0.01). 13 weeks empagliflozin treatment in patients with type-2 diabetes at high CV risk significantly reduced LV mass, improved LV geometry and improved diastolic function compared to placebo.