Is metformin beneficial for heart failure in patients with type 2 diabetes?

Heart Failure and Diabetes Mellitus: Dangerous Liaisons

Patients with diabetes mellitus (DM) have a higher prevalence of heart failure (HF) than those without it. Approximately 40% of HF patients have DM, having poorer outcomes than those without DM. Myocardial ischemia caused by endothelial dysfunction, renal dysfunction, obesity, and impaired myocardial energetics is pathophysiology of DM-induced HF (DM-HF). Also, patients with HF show an increased risk for the onset of DM due to several mechanisms including insulin resistance. This review is focused on the epidemiology, pathogenic mechanism and treatment strategy of DM-HF.

Pharmacotherapy of diabetes mellitus in patients with heart failure - a nation-wide analysis of contemporary treatment

AIM

Retrospective national sub-analysis of antidiabetic pharmacotherapy in patients with diabetes mellitus (DM) and heart failure (HF) based on data reported to the National Register of Paid Health Services in the Czech Republic between 2012-2018.

METHODOLOGY AND RESULTS

In 2012, there were 75,022 patients with HF and DM (i.e. 42.5% of patients with HF), 6 years later 117,265 (i.e. 41.0% of HF patients in 2018). The most represented antidiabetic drug was metformin (45.6%). Of the insulins and analogues, glargine showed the largest positive trend (5.8% 2012; 14.8% 2018). Empagliflozin was the most prescribed SGLT-2 inhibitor (1.8% in 2018). A decrease in prescribing was observed for saxagliptin (0.5% 2012; 0.1% 2018) and for sulfonylurea derivates - gliclazide (13.0% 2012; 10.3% in 2018) and glimepiride (12.9% 2012; 9.0% 2018). Linagliptin was the most prescribed dipeptidyl peptidase inhibitor (0.7% 2012; 6.8% 2018).

CONCLUSION

In the Czech Republic, between 2012 and 2008, there was an increase in prevalence of patients with heart failure and concomitant diabetes mellitus, their proportion being similar. In correspondence with other registries, metformin was used mostly. A positive trend was observed in prescription of DDP-4 and SGLT-2 inhibitors, while there was a significant decrease in patients taking sulfonylureas.

Differential Pathophysiological Mechanisms in Heart Failure With a Reduced or Preserved Ejection Fraction in Diabetes

Diabetes promotes the development of both heart failure with a reduced ejection fraction and heart failure with a preserved ejection fraction through diverse mechanisms, which are likely mediated through hyperinsulinemia rather than hyperglycemia. Diabetes promotes nutrient surplus signaling (through Akt and mammalian target of rapamycin complex 1) and inhibits nutrient deprivation signaling (through sirtuin-1 and its downstream effectors); this suppresses autophagy and promotes endoplasmic reticulum and oxidative stress and mitochondrial dysfunction, thereby undermining the health of diabetic cardiomyocytes. The hyperinsulinemia of diabetes may also activate sodium-hydrogen exchangers in cardiomyocytes (leading to injury and loss) and in the proximal renal tubules (leading to sodium retention). Diabetes may cause epicardial adipose tissue expansion, and the resulting secretion of proinflammatory adipocytokines onto the adjoining myocardium can lead to coronary microcirculatory dysfunction and myocardial inflammation and fibrosis. Interestingly, sodium-glucose cotransporter 2 (SGLT2) inhibitors-the only class of antidiabetic medication that reduces serious heart failure events-may act to mitigate each of these mechanisms. SGLT2 inhibitors up-regulate sirtuin-1 and its downstream effectors and autophagic flux, thus explaining the actions of these drugs to reduce oxidative stress, normalize mitochondrial structure and function, and mute proinflammatory pathways in the stressed myocardium. Inhibition of SGLT2 may also lead to a reduction in the activity of sodium-hydrogen exchangers in the kidney (leading to diuresis) and in the heart (attenuating the development of cardiac hypertrophy and systolic dysfunction). Finally, SGLT2 inhibitors reduce the mass and mute the adverse biology of epicardial adipose tissue (and reduce the secretion of leptin), thus explaining the capacity of these drugs to mitigate myocardial inflammation, microcirculatory dysfunction, and fibrosis, and improve ventricular filling dynamics. The pathophysiological mechanisms by which SGLT2 inhibitors may benefit heart failure likely differ depending on ejection fraction, but each represents interference with distinct pathways by which hyperinsulinemia may adversely affect cardiac structure and function.

Longevity genes, cardiac ageing, and the pathogenesis of cardiomyopathy: implications for understanding the effects of current and future treatments for heart failure

The two primary molecular regulators of lifespan are sirtuin-1 (SIRT1) and mammalian target of rapamycin complex 1 (mTORC1). Each plays a central role in two highly interconnected pathways that modulate the balance between cellular growth and survival. The activation of SIRT1 [along with peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) and adenosine monophosphate-activated protein kinase (AMPK)] and the suppression of mTORC1 (along with its upstream regulator, Akt) act to prolong organismal longevity and retard cardiac ageing. Both activation of SIRT1/PGC-1α and inhibition of mTORC1 shifts the balance of cellular priorities so as to promote cardiomyocyte survival over growth, leading to cardioprotective effects in experimental models. These benefits may be related to direct actions to modulate oxidative stress, organellar function, proinflammatory pathways, and maladaptive hypertrophy. In addition, a primary shared benefit of both SIRT1/PGC-1α/AMPK activation and Akt/mTORC1 inhibition is the enhancement of autophagy, a lysosome-dependent degradative pathway, which clears the cytosol of dysfunctional organelles and misfolded proteins that drive the ageing process by increasing oxidative and endoplasmic reticulum stress. Autophagy underlies the ability of SIRT1/PGC-1α/AMPK activation and Akt/mTORC1 suppression to extend lifespan, mitigate cardiac ageing, alleviate cellular stress, and ameliorate the development and progression of cardiomyopathy; silencing of autophagy genes abolishes these benefits. Loss of SIRT1/PGC-1α/AMPK function or hyperactivation of Akt/mTORC1 is a consistent feature of experimental cardiomyopathy, and reversal of these abnormalities mitigates the development of heart failure. Interestingly, most treatments that have been shown to be clinically effective in the treatment of chronic heart failure with a reduced ejection fraction have been reported experimentally to exert favourable effects to activate SIRT1/PGC-1α/AMPK and/or suppress Akt/mTORC1, and thereby, to promote autophagic flux. Therefore, the impairment of autophagy resulting from derangements in longevity gene signalling is likely to represent a seminal event in the evolution and progression of cardiomyopathy.

Immunomodulation in Heart Failure with Preserved Ejection Fraction: Current State and Future Perspectives

The heart failure (HF) epidemic is growing and approximately half of the HF patients have heart failure with preserved ejection fraction (HFpEF). HFpEF is a heterogeneous syndrome, characterized by a preserved left ventricular ejection fraction (LVEF ≥ 50%) with diastolic dysfunction, and is associated with high morbidity and mortality. Underlying comorbidities of HFpEF, i.e., hypertension, type 2 diabetes mellitus, obesity, and renal failure, lead to a systemic pro-inflammatory state, thereby affecting normal cardiac function. Increased inflammatory biomarkers predict incident HFpEF and are higher in patients with HFpEF as compared with heart failure with reduced ejection fraction (HFrEF). Randomized trials in HFpEF patients using traditional HF medication failed to demonstrate a clear benefit on hard endpoints (mortality and/or HF hospitalization). Therefore, therapies targeting underlying comorbidities and systemic inflammation in early HFpEF may provide better opportunities. Here, we provide an overview of the current state and future perspectives of immunomodulatory therapies for HFpEF.

Cardioprotective Effects of Sirtuin-1 and Its Downstream Effectors: Potential Role in Mediating the Heart Failure Benefits of SGLT2 (Sodium-Glucose Cotransporter 2) Inhibitors

The cardioprotective effects of SGLT2 (sodium-glucose cotransporter 2) inhibitors may be related to their ability to induce a fasting-like paradigm, which triggers the activation of nutrient deprivation pathways to promote cellular homeostasis. The most distinctive metabolic manifestations of this fasting mimicry are enhanced gluconeogenesis and ketogenesis, which are not seen with other antihyperglycemic drugs. The principal molecular stimulus to gluconeogenesis and ketogenesis is activation of SIRT1 (sirtuin-1) and its downstream mediators: PGC-1α (proliferator-activated receptor gamma coactivator 1-alpha) and FGF21 (fibroblast growth factor 21). These three nutrient deprivation sensors exert striking cardioprotective effects in a broad range of experimental models. This benefit appears to be related to their actions to alleviate oxidative stress and promote autophagy-a lysosome-dependent degradative pathway that disposes of dysfunctional organelles that are major sources of cellular injury. Nutrient deprivation sensors are suppressed in states of perceived energy surplus (ie, type 2 diabetes mellitus and chronic heart failure), but SGLT2 inhibitors activate SIRT1/PGC-1α/FGF21 signaling and promote autophagy. This effect may be related to their action to trigger the perception of a system-wide decrease in environmental nutrients, but SGLT2 inhibitors may also upregulate SIRT1, PGC-1α, and FGF21 by a direct effect on the heart. Interestingly, metformin-induced stimulation of AMP-activated protein kinase (a nutrient deprivation sensor that does not promote ketogenesis) has not been shown to reduce heart failure events in clinical trials. Therefore, promotion of ketogenic nutrient deprivation signaling by SGLT2 inhibitors may explain their cardioprotective effects, even though SGLT2 is not expressed in the heart.

Pharmacological treatment initiation for type 2 diabetes in Australia: are the guidelines being followed?

AIM

To determine the patterns and predictors of pharmacological treatment initiation for type 2 diabetes and whether treatment initiation is consistent with Australian clinical practice guidelines that recommend metformin monotherapy.

METHODS

Individuals aged 40-99 years initiating a non-insulin type 2 diabetes medication between July 2013 and February 2018 were identified from a 10% random national sample of pharmacy dispensing data. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the predictors of initiating sulfonylurea monotherapy, non-guideline monotherapy and combination therapy compared with metformin monotherapy. Predictors included age, sex, initiation year and comorbidities determined using the Rx-Risk comorbidity index.

RESULTS

Of the 47 860 initiators, [47% women, mean age 60.7 (sd 12.1) years], 85.8%, 4.6%, 1.9% and 7.7% received metformin monotherapy, sulfonylurea monotherapy, non-guideline monotherapy and combination therapy, respectively. Increasing age was associated with increasing odds of initiating sulfonylurea monotherapy and non-guideline monotherapy. Combination therapy initiation was less likely in women (OR 0.74, 95% CI 0.69-0.79) and people with more comorbidities (e.g. OR 0.36, 95% CI 0.29-0.44 for seven or more comorbidities vs. no comorbidities) but more likely in congestive heart failure (OR 1.42, 95% CI 1.22-1.65), cerebrovascular disease (OR 1.50, 95% CI 1.32-1.69) and dyslipidaemia (OR 1.29, 95% CI 1.19-1.40).

CONCLUSION

Treatment initiation in Australia is largely consistent with clinical practice guidelines, with 86% of individuals initiating metformin monotherapy. Initiation on combination therapy was more common in men and in those with fewer comorbidities.

Autophagy-dependent and -independent modulation of oxidative and organellar stress in the diabetic heart by glucose-lowering drugs

Autophagy is a lysosome-dependent intracellular degradative pathway, which mediates the cellular adaptation to nutrient and oxygen depletion as well as to oxidative and endoplasmic reticulum stress. The molecular mechanisms that stimulate autophagy include the activation of energy deprivation sensors, sirtuin-1 (SIRT1) and adenosine monophosphate-activated protein kinase (AMPK). These enzymes not only promote organellar integrity directly, but they also enhance autophagic flux, which leads to the removal of dysfunctional mitochondria and peroxisomes. Type 2 diabetes is characterized by suppression of SIRT1 and AMPK signaling as well as an impairment of autophagy; these derangements contribute to an increase in oxidative stress and the development of cardiomyopathy. Antihyperglycemic drugs that signal through insulin may further suppress autophagy and worsen heart failure. In contrast, metformin and SGLT2 inhibitors activate SIRT1 and/or AMPK and promote autophagic flux to varying degrees in cardiomyocytes, which may explain their benefits in experimental cardiomyopathy. However, metformin and SGLT2 inhibitors differ meaningfully in the molecular mechanisms that underlie their effects on the heart. Whereas metformin primarily acts as an agonist of AMPK, SGLT2 inhibitors induce a fasting-like state that is accompanied by ketogenesis, a biomarker of enhanced SIRT1 signaling. Preferential SIRT1 activation may also explain the ability of SGLT2 inhibitors to stimulate erythropoiesis and reduce uric acid (a biomarker of oxidative stress)—effects that are not seen with metformin. Changes in both hematocrit and serum urate are the most important predictors of the ability of SGLT2 inhibitors to reduce the risk of cardiovascular death and hospitalization for heart failure in large-scale trials. Metformin and SGLT2 inhibitors may also differ in their ability to mitigate diabetes-related increases in intracellular sodium concentration and its adverse effects on mitochondrial functional integrity. Differences in the actions of SGLT2 inhibitors and metformin may reflect the distinctive molecular pathways that explain differences in the cardioprotective effects of these drugs.

Critical examination of mechanisms underlying the reduction in heart failure events with SGLT2 inhibitors: identification of a molecular link between their actions to stimulate erythrocytosis and to alleviate cellular stress

Sodium-glucose co-transporter 2 (SGLT2) inhibitors reduce the risk of serious heart failure events, even though SGLT2 is not expressed in the myocardium. This cardioprotective benefit is not related to an effect of these drugs to lower blood glucose, promote ketone body utilization or enhance natriuresis, but it is linked statistically with their action to increase haematocrit. SGLT2 inhibitors increase both erythropoietin and erythropoiesis, but the increase in red blood cell mass does not directly prevent heart failure events. Instead, erythrocytosis is a biomarker of a state of hypoxia mimicry, which is induced by SGLT2 inhibitors in manner akin to cobalt chloride. The primary mediators of the cellular response to states of energy depletion are sirtuin-1 and hypoxia-inducible factors (HIF-1α/HIF-2α). These master regulators promote the cellular adaptation to states of nutrient and oxygen deprivation, promoting mitochondrial capacity and minimizing the generation of oxidative stress. Activation of sirtuin-1 and HIF-1α/HIF-2α also stimulates autophagy, a lysosome-mediated degradative pathway that maintains cellular homoeostasis by removing dangerous constituents (particularly unhealthy mitochondria and peroxisomes), which are a major source of oxidative stress and cardiomyocyte dysfunction and demise. SGLT2 inhibitors can activate SIRT-1 and stimulate autophagy in the heart, and thereby, favourably influence the course of cardiomyopathy. Therefore, the linkage between erythrocytosis and the reduction in heart failure events with SGLT2 inhibitors may be related to a shared underlying molecular mechanism that is triggered by the action of these drugs to induce a perceived state of oxygen and nutrient deprivation.

Metformin treatment for patients with diabetes and chronic kidney disease: A Korean Diabetes Association and Korean Society of Nephrology consensus statement

The safety of metformin use for patients with type 2 diabetes mellitus (T2DM) and advanced kidney disease is controversial, and more recent guidelines have suggested that metformin be used cautiously in this group until more definitive evidence concerning its safety is available. The Korean Diabetes Association and the Korean Society of Nephrology have agreed on consensus statements concerning metformin use for patients with T2DM and renal dysfunction, particularly when these patients undergo imaging studies using iodinated contrast media (ICM). Metformin can be used safely when the estimated glomerular filtration rate (eGFR) is ≥ 45 mL/min/1.73 m². If the eGFR is between 30 and 44 mL/min/1.73 m², metformin treatment should not be started. If metformin is already in use, a daily dose of ≤ 1,000 mg is recommended. Metformin is contraindicated when the eGFR is < 30 mL/min/1.73 m². Renal function should be evaluated prior to any ICM-related procedures. During procedures involving intravenous administration of ICM, metformin should be discontinued starting the day of the procedures and up to 48 hours post-procedures if the eGFR is < 60 mL/min/1.73 m².

Cardiometabolic-Based Chronic Disease, Addressing Knowledge and Clinical Practice Gaps: JACC State-of-the-Art Review

In the second part of this JACC State-of-the-Art Review, an early and sustainable preventive care plan is described for cardiometabolic-based chronic disease. This plan can improve cardiometabolic health by targeting early mechanistic events to decrease the risk for certain cardiovascular diseases (e.g., coronary heart disease, heart failure, and atrial fibrillation). Included are various prevention modalities, intensive lifestyle interventions, pharmacotherapy and cardiovascular outcome trial evidence, and bariatric/metabolic procedures. A tactical approach of implementing published clinical practice guidelines/algorithms for early behavioral, adiposity, and dysglycemia targeting is emphasized, as well as relevant educational and research implications.

Metformin Treatment for Patients with Diabetes and Chronic Kidney Disease: A Korean Diabetes Association and Korean Society of Nephrology Consensus Statement

The safety of metformin use for patients with type 2 diabetes mellitus (T2DM) and advanced kidney disease is controversial, and more recent guidelines have suggested that metformin be used cautiously in this group until more definitive evidence concerning its safety is available. The Korean Diabetes Association and the Korean Society of Nephrology have agreed on consensus statements concerning metformin use for patients with T2DM and renal dysfunction, particularly when these patients undergo imaging studies using iodinated contrast media (ICM). Metformin can be used safely when the estimated glomerular filtration rate (eGFR) is ≥45 mL/min/1.73 m². If the eGFR is between 30 and 44 mL/min/1.73 m², metformin treatment should not be started. If metformin is already in use, a daily dose of ≤1,000 mg is recommended. Metformin is contraindicated when the eGFR is <30 mL/min/1.73 m². Renal function should be evaluated prior to any ICM-related procedures. During procedures involving intravenous administration of ICM, metformin should be discontinued starting the day of the procedures and up to 48 hours post-procedures if the eGFR is <60 mL/min/1.73 m².

Metformin Use Is Associated With a Lower Risk of Hospitalization for Heart Failure in Patients With Type 2 Diabetes Mellitus: a Retrospective Cohort Analysis

Background A beneficial effect of metformin on heart failure requires confirmation. Methods and Results Patients with new-onset type 2 diabetes mellitus during 1999 to 2005 were enrolled from Taiwan's National Health Insurance database and followed up from January 1, 2006, until December 31, 2011. Main analyses were conducted in an unmatched cohort (172 542 metformin ever users and 43 744 never users) and a propensity score matched-pair cohort (matched cohort I, 41 714 ever users and 41 714 never users). Hazard ratios were estimated by Cox hazard regression incorporated with the inverse probability of treatment weighting using the propensity score in the unmatched cohort and by naïve method in the matched cohort I. Results showed that the respective incidence rates of heart failure hospitalization in ever users and never users were 304.25 and 864.31 per 100 000 person-years in the unmatched cohort (hazard ratio, 0.350; 95% CI, 0.329-0.373) and were 469.66 and 817.01 per 100 000 person-years in the matched cohort I (hazard ratio, 0.571; 95% CI, 0.526-0.620). A dose-response pattern was consistently observed while estimating hazard ratios for the tertiles of cumulative duration of metformin therapy. Findings were supported by another propensity score-matched cohort created after excluding 10 potential instrumental variables in the estimation of propensity score (matched cohort II). An approximately 40% lower risk was consistently observed among ever users in different models derived from the matched cohorts I and II, but models from the matched cohort II were less subject to model misspecification. Conclusions Metformin use is associated with a lower risk of heart failure hospitalization.

Heart failure and diabetes: management and open issues

Diabetes mellitus is an important comorbidity in patients with heart failure. The presence of heart failure in diabetes worsens the prognosis of patients. Recent studies suggest that appropriate diagnostic approaches followed by differential medical treatment are of crucial importance to improve patient outcomes. This article summarizes important aspects of the association between diabetes mellitus and heart failure.

The safety of empagliflozin plus metformin for the treatment of type 2 diabetes

INTRODUCTION

Metformin is the first-line glucose-lowering medication in type 2 diabetes mellitus (T2DM), but it generally requires soon or later the addition of a second-line therapy, among which a sodium-glucose cotransporter type 2 (SGLT-2) inhibitor, to reach and maintain adequate glucose control. Areas covered: This narrative review provides an analysis of both efficacy and safety of a dual therapy combining metformin and empagliflozin, a SGLT-2 inhibitor that has proven its' potential to reduce major cardiovascular (CV) events, mortality, and renal outcomes in patients with T2DM and established CV disease. Pharmacokinetic studies showed the absence of drug-drug interactions and demonstrate bioequivalence between fixed-dose combination (FDC) and individual tablets of empagliflozin and metformin. Focus will be put on the use of this dual therapy in special populations. Expert opinion: The addition of empagliflozin to metformin therapy improves glucose control, with a minimal risk of hypoglycemia, while reducing body weight and arterial blood pressure. EMPA-REG OUTCOME showed that this combined therapy may be used in patients with established CV disease or heart failure. However, caution may be required in fragile elderly patients and in patients with severe impaired renal function. Further post-marketing surveillance is recommended to demonstrate long-term safety. FDC may improve adherence.