Molecular Mechanisms Responsible for Diastolic Dysfunction in Diabetes Mellitus Patients

Impact of Sex and Diabetes in Patients with Heart Failure

PURPOSE OF REVIEW

Heart failure (HF) is a complex clinical syndrome with a growing global health burden. This review explores the intersection of HF, diabetes mellitus, and sex, highlighting epidemiological patterns, pathophysiological mechanisms, and treatment implications.

RECENT FINDINGS

Despite similar HF prevalence in men and women, diabetes mellitus (DM) appears to exert a more pronounced impact on HF outcomes in women. Pathophysiological differences involve cardiovascular risk factors, severe left ventricular dysfunction, and coronary artery disease, as well as hormonal influences and inflammatory markers. Diabetic cardiomyopathy introduces a sex-specific challenge, with women experiencing common adverse outcomes related to increased fibrosis and myocardial remodeling. Treatment strategies, particularly sodium-glucose cotransporter 2 inhibitors, exhibit cardiovascular benefits, but their response may differ in women. The link between HF and DM is bidirectional, with diabetes significantly increasing the risk of HF, and vice versa. Additionally, the impact of diabetes on mortality appears more pronounced in women than in men, leading to a modification of the traditional gender gap observed in HF outcomes. A personalized approach is crucial, and further research to improve outcomes in the complex interplay of HF, diabetes, and sex is needed.

Indole-3-Propionic Acid Protects Against Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a common but poorly understood form of heart failure, characterized by impaired diastolic function. It is highly heterogeneous with multiple comorbidities, including obesity and diabetes, making human studies difficult.

METHODS

Metabolomic analyses in a mouse model of HFpEF showed that levels of indole-3-propionic acid (IPA), a metabolite produced by gut bacteria from tryptophan, were reduced in the plasma and heart tissue of HFpEF mice as compared with controls. We then examined the role of IPA in mouse models of HFpEF as well as 2 human HFpEF cohorts.

RESULTS

The protective role and therapeutic effects of IPA were confirmed in mouse models of HFpEF using IPA dietary supplementation. IPA attenuated diastolic dysfunction, metabolic remodeling, oxidative stress, inflammation, gut microbiota dysbiosis, and intestinal epithelial barrier damage. In the heart, IPA suppressed the expression of NNMT (nicotinamide N-methyl transferase), restored nicotinamide, NAD+/NADH, and SIRT3 (sirtuin 3) levels. IPA mediates the protective effects on diastolic dysfunction, at least in part, by promoting the expression of SIRT3. SIRT3 regulation was mediated by IPA binding to the aryl hydrocarbon receptor, as Sirt3 knockdown diminished the effects of IPA on diastolic dysfunction in vivo. The role of the nicotinamide adenine dinucleotide circuit in HFpEF was further confirmed by nicotinamide supplementation, Nnmt knockdown, and Nnmt overexpression in vivo. IPA levels were significantly reduced in patients with HFpEF in 2 independent human cohorts, consistent with a protective function in humans, as well as mice.

CONCLUSIONS

Our findings reveal that IPA protects against diastolic dysfunction in HFpEF by enhancing the nicotinamide adenine dinucleotide salvage pathway, suggesting the possibility of therapeutic management by either altering the gut microbiome composition or supplementing the diet with IPA.

Unlocking the Full Potential of SGLT2 Inhibitors: Expanding Applications beyond Glycemic Control

The number of diabetic patients has risen dramatically in recent decades, owing mostly to the rising incidence of type 2 diabetes mellitus (T2DM). Several oral antidiabetic medications are used for the treatment of T2DM including, α-glucosidases inhibitors, biguanides, sulfonylureas, meglitinides, GLP-1 receptor agonists, PPAR-γ agonists, DDP4 inhibitors, and SGLT2 inhibitors. In this review we focus on the possible effects of SGLT2 inhibitors on different body systems. Beyond the diabetic state, SGLT2 inhibitors have revealed a demonstrable ability to ameliorate cardiac remodeling, enhance myocardial function, and lower heart failure mortality. Additionally, SGLT2 inhibitors can modify adipocytes and their production of cytokines, such as adipokines and adiponectin, which enhances insulin sensitivity and delays diabetes onset. On the other hand, SGLT2 inhibitors have been linked to decreased total hip bone mineral deposition and increased hip bone resorption in T2DM patients. More data are needed to evaluate the role of SGLT2 inhibitors on cancer. Finally, the effects of SGLT2 inhibitors on neuroprotection appear to be both direct and indirect, according to scientific investigations utilizing various experimental models. SGLT2 inhibitors improve vascular tone, elasticity, and contractility by reducing oxidative stress, inflammation, insulin signaling pathways, and endothelial cell proliferation. They also improve brain function, synaptic plasticity, acetylcholinesterase activity, and reduce amyloid plaque formation, as well as regulation of the mTOR pathway in the brain, which reduces brain damage and cognitive decline.

Effect of stress on the chronotropic and inotropic responses to β-adrenergic agonists in isolated atria of KOβ2 mice

Altered sensitivity to the chronotropic and inotropic effects of catecholamines and reduction in β₁/β₂-adrenoceptor (β₁/β₂-AR) ratio were reported in failing and in senescent human heart, as well as in isolated atria and ventricle of rats submitted to stress. This was due to downregulation of β₁-AR with or without up-regulation of β₂-AR.

AIMS

To investigate the stress-induced behavior of β₁-AR in the heart of mice expressing a non-functional β₂-AR subtype. The guiding hypothesis is that the absence of β₂-AR signaling will not affect the behavior of β₁-AR during stress and that those are independent processes.

MATERIALS AND METHODS

The chronotropic and inotropic responses to β-AR agonists in isolated atria of stressed mice expressing a non-functional β₂-AR were analyzed. The mRNA and protein expressions of β₁- and β₂-AR were also determined.

KEY FINDINGS

No deaths were observed in mice under stress protocol. Atria of stressed mice displayed reduced sensitivity to isoprenaline compared to the controls, an effect that was abolished by the β₂- and β₁-AR antagonists 50 nM ICI118,551 and 300 nM CGP20712A, respectively. Sensitivity and maximum response to the β-agonists dobutamine and salbutamol were not altered by stress or ICI118,551. The responses to dobutamine and salbutamol were prevented by CGP20712A. The expression of β₁-AR was reduced at protein levels.

SIGNIFICANCE

Collectively, our data provide evidence that the cardiac β₂-AR is not essential for survival in a stressful situation and that the stress-induced reduction of β₁-AR expression was independent of the β₂-AR presence.

Endothelial cell-specific mineralocorticoid receptor activation promotes diastolic dysfunction in diet-induced obese male mice

Widespread consumption of diets high in fat and fructose (Western diet, WD) has led to increased prevalence of obesity and diastolic dysfunction (DD). DD is a prominent feature of heart failure with preserved ejection fraction (HFpEF). However, the underlying mechanisms of DD are poorly understood, and treatment options are still limited. We have previously shown that deletion of the cell-specific mineralocorticoid receptor in endothelial cells (ECMR) abrogates DD induced by WD feeding in female mice. However, the specific role of ECMR activation in the pathogenesis of DD in male mice has not been clarified. Therefore, we fed 4-wk-old ECMR knockout (ECMRKO) male mice and littermates (LM) with either a WD or chow diet (CD) for 16 wk. WD feeding resulted in DD characterized by increased left ventricle (LV) filling pressure (E/e') and diastolic stiffness [E/e'/LV inner diameter at end diastole (LVIDd)]. Compared with CD, WD in LM resulted in increased myocardial macrophage infiltration, oxidative stress, and increased myocardial phosphorylation of Akt, in concert with decreased phospholamban phosphorylation. WD also resulted in focal cardiomyocyte remodeling, characterized by areas of sarcomeric disorganization, loss of mitochondrial electron density, and mitochondrial fragmentation. Conversely, WD-induced DD and associated biochemical and structural abnormalities were prevented by ECMR deletion. In contrast with our previously reported observations in females, WD-fed male mice exhibited enhanced Akt signaling and a lower magnitude of cardiac injury. Collectively, our data support a critical role for ECMR in obesity-induced DD and suggest critical mechanistic differences in the genesis of DD between males and females.

Effects of altered cellular ultrastructure on energy metabolism in diabetic cardiomyopathy: an in silico study

Diabetic cardiomyopathy is a leading cause of heart failure in diabetes. At the cellular level, diabetic cardiomyopathy leads to altered mitochondrial energy metabolism and cardiomyocyte ultrastructure. We combined electron microscopy (EM) and computational modelling to understand the impact of diabetes-induced ultrastructural changes on cardiac bioenergetics. We collected transverse micrographs of multiple control and type I diabetic rat cardiomyocytes using EM. Micrographs were converted to finite-element meshes, and bioenergetics was simulated over them using a biophysical model. The simulations also incorporated depressed mitochondrial capacity for oxidative phosphorylation (OXPHOS) and creatine kinase (CK) reactions to simulate diabetes-induced mitochondrial dysfunction. Analysis of micrographs revealed a 14% decline in mitochondrial area fraction in diabetic cardiomyocytes, and an irregular arrangement of mitochondria and myofibrils. Simulations predicted that this irregular arrangement, coupled with the depressed activity of mitochondrial CK enzymes, leads to large spatial variation in adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio profile of diabetic cardiomyocytes. However, when spatially averaged, myofibrillar ADP/ATP ratios of a cardiomyocyte do not change with diabetes. Instead, average concentration of inorganic phosphate rises by 40% owing to lower mitochondrial area fraction and dysfunction in OXPHOS. These simulations indicate that a disorganized cellular ultrastructure negatively impacts metabolite transport in diabetic cardiomyopathy.

This article is part of the theme issue ‘The cardiomyocyte: new revelations on the interplay between architecture and function in growth, health, and disease’.

Impact of Long Non-Coding RNA Metastasis-Associated Lung Adenocarcinoma Transcript 1 on the Susceptibility of High Glucose-Treated Cardiomyocytes to Hypoxia/Reoxygenation

To estimate the effect of lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) on susceptibility of high glucose (HG)-treated cardiomyocytes (CMs) to hypoxia/reoxygenation (H/R). Forty healthy rats were assigned to the control, diabetes mellitus (DM), DM + ischemia/reperfusion injury (IRI) control, and DM IRI groups (n = 10 for each group). Rat CMs (H9C2) were subjected to HG and H/R treatments. LncRNA MALAT1 and cyclic-AMP responsive element modulator (CREM) mRNA levels were measured using quantitative polymerase chain reaction, and protein levels of CREM, myeloid differentiation primary response protein 88 (MyD88), interleukin-1 receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor associated factor 6 (TRAF6), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were quantified using western blotting. Flow cytometry was applied for detection of apoptosis, and a cell viability analyzer determined the number of living cells. IRI induced myocardial apoptosis and elevated lncRNA MALAT1, CREM, and MyD88/IRAK1/TRAF6 levels in DM group mice. In H9C2 cells, HG treatment downregulated CREM expression, which resulted in the downregulation of lncRNA MALAT1 expression, reducing the susceptibility to H/R, increasing cell viability and apoptosis, decreasing the activity of the MyD88/IRAK1/TRAF6 signaling pathway, and suppressing TNF-α and IL-6 expression. LncRNA MALAT1 regulates the susceptibility of HG-treated CMs to H/R through the MyD88 signaling pathway.

RBM20, a Therapeutic Target to Alleviate Myocardial Stiffness via Titin Isoforms Switching in HFpEF

Increased myocardial stiffness is critically involved in heart diseases with impaired cardiac compliance, especially heart failure with preserved ejection fraction (HFpEF). Myocardial stiffness mainly derives from cardiomyocyte- and extracellular matrix (ECM)-derived passive stiffness. Titin, a major component of sarcomeres, participates in myocardial passive stiffness and stress-sensitive signaling. The ratio of two titin isoforms, N2BA to N2B, was validated to influence diastolic dysfunction via several pathways. RNA binding motif protein 20 (RBM20) is a well-studied splicing factor of titin, functional deficiency of RBM20 in mice profile improved cardiac compliance and function, which indicated that RBM20 functions as a potential therapeutic target for mitigating myocardial stiffness by modulating titin isoforms. This minor review summarized how RBM20 and other splicing factors modify the titin isoforms ratio, therefore providing a promising target for improving the myocardial compliance of HFpEF.

Lipids and diastolic dysfunction: Recent evidence and findings

AIM

Diastolic dysfunction is the decreased flexibility of the left ventricle due to the impaired ability of the myocardium to relax and plays an important role in the pathogenesis of heart failure. Lipid metabolism is a well-known contributor to cardiac conditions, including ventricular function. In this article, we aimed to review the literature addressing the connections between lipids, their storage, and metabolism with left ventricular diastolic dysfunction.

DATA SYNTHESIS

We searched Google scholar, Pubmed, Embase and Researchgate for our keywords: "Diastolic function", "Fat" and "Lipid profile". Initially, 250 articles were selected by title and 84 of them were chosen as most relevant and directly reviewed.

CONCLUSIONS

Alterations of lipid metabolism in cardiac muscle and cardiac lipid content can occur in many conditions, including consumption of a high-fat diet, obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). These conditions induce alterations in myocardial lipid metabolism, increase myocardial fat content and epicardial fat thickness and increase inflammation and oxidative stress which ultimately lead to cardiac lipotoxicity and diastolic dysfunction. The effects of lipids on diastolic function can differ based on gender. Lipid profile and metabolism are as important in the pathogenesis of diastolic dysfunction as they are in other cardiovascular disorders. A more careful look at cardiac lipid metabolism in molecular, histological and gross levels results in more precise understanding of its role in myocardial function and leads to development of potential treatments for diastolic dysfunction.

Knockdown of ILK Alleviates High Glucose-Induced Damage of H9C2 Cells through TLR4/MyD88/NF-κB Pathway

The aim of this study was to explore the role of ILK in an in vitro model of diabetic cardiomyopathy. We used 30 mmol/L high glucose to treat H9C2 cells to construct an in vitro model, knocked down the ILK expression level of H9C2 cells by small interference technology, and detected the activity of antioxidant enzymes and inflammatory factors in the supernatant. The expression levels of SOD1 and IL-1β were detected by immunofluorescence staining. The expression levels of the TLR4/MyD88/NF-κB signaling pathway and its downstream factors were detected by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Compared with the control group, after high-glucose culture of H9C2 cells, the cell activity decreased, while the apoptosis rate increased, with the TLR4/MyD88/NF-κB signaling pathway activated, thereby inducing oxidative stress and inflammation. Compared with the high-glucose group, the HG+si-ILK group increased cell activity, decreased the apoptosis rate, and inhibited the excessive activation of the TLR4/MyD88/NF-κB signaling pathway, thereby improving oxidative stress and inflammation. Knockdown of ILK expression can protect H9C2 cells from reducing high glucose-induced inflammation, oxidative stress, and apoptosis by inhibiting the TLR4/MyD88/NF-κB signaling pathway.

Novel oral edaravone attenuates diastolic dysfunction of diabetic cardiomyopathy by activating the Nrf2 signaling pathway

Oxidative stress plays a crucial role in the pathophysiology of diastolic dysfunction associated with diabetic cardiomyopathy. Novel oral edaravone (OED) alleviates oxidative stress by scavenging free radicals and may be suitable for the treatment of chronic diseases such as diabetic cardiomyopathy. Oral administration of OED to type 2 diabetic rats (induced by high-sugar/high-fat diet and intraperitoneal injection of streptozotocin) for 4 w decreased malondialdehyde and increased superoxide dismutase. Moreover, it significantly improved ratios of early to late diastolic peak velocity, myocardium hypertrophy accompanied by decreased cross-sectional areas of cardiomyocytes, the proportion of apoptotic cells, collagen volume fractions, and deposition of collagen I/III. In H9c2 cells, OED reduced reactive oxygen species, cell surface area, and numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling-positive cells induced by glucolipotoxicity. OED remarkably upregulated expression of the nuclear factor E2-related factor (Nrf2) signaling pathway both in vivo and in vitro. In addition, OED promoted Nrf2 nuclear translocation and upregulated nicotinamide adenine dinucleotide phosphate quinone oxidoreductase and heme oxygenase. Silencing of Nrf2 abolished the protective effect of OED in H9c2 cells. Our findings demonstrate that OED has the therapeutic potential to ameliorate diastolic dysfunction associated with diabetic cardiomyopathy. Its effect was mainly achieved by attenuating hyperglycemia and hyperlipidemia-induced cardiomyocyte hypertrophy, apoptosis, and fibrosis by activating the Nrf2 signaling pathway.

Impact of preexisting diabetes mellitus on cardiovascular and all-cause mortality in patients with atrial fibrillation: A meta-analysis

OBJECTIVE

To determine the impact of preexisting diabetes mellitus on cardiovascular and all-cause mortality in patients with atrial fibrillation (AF) by conducting a meta-analysis.

METHODS

PubMed and Embase databases were comprehensively searched for relevant studies publishing until May 19, 2022. Cohort studies or post-hoc analyses of clinical trials that investigated the association of diabetes mellitus with cardiovascular or all-cause mortality in AF patients were included.

RESULTS

A total of 21 studies with 526,136 AF patients were identified. The pooled prevalence of diabetes mellitus in patients with AF was 26%. The summary multivariable-adjusted risk ratio (RR) of all-cause mortality was 1.37 (95% confidence intervals [CIs] 1.23-1.53) for patients with diabetes versus those without diabetes. Moreover, diabetes mellitus was also associated with an increased risk of cardiovascular mortality (RR 1.46; 95% CI 1.34-1.58). Stratified analyses suggested that the impact of diabetes on all-cause and cardiovascular mortality was consistently observed in each named subgroup.

CONCLUSION

The presence of diabetes mellitus in patients with AF is associated with an increased risk of cardiovascular and all-cause mortality, even after adjustment for important confounding factors.

Heart failure in diabetes

Heart failure and cardiovascular disorders represent the leading cause of death in diabetic patients. Here we present a systematic review of the main mechanisms underlying the development of diabetic cardiomyopathy. We also provide an excursus on the relative contribution of cardiomyocytes, fibroblasts, endothelial and smooth muscle cells to the pathophysiology of heart failure in diabetes. After having described the preclinical tools currently available to dissect the mechanisms of this complex disease, we conclude with a section on the most recent updates of the literature on clinical management.

Beneficial effects of sodium glucose cotransporter 2 inhibitors on left ventricular mass in patients with diabetes mellitus

BACKGROUND

Sodium glucose cotransporter 2 inhibitor (SGLT2i) has recently been suggested to reduce the risk of cardiovascular events. Left ventricular hypertrophy (LVH) is associated with cardiovascular events. Diabetic macroangiopathy is a crucial complication in patients with diabetes mellitus (DM). This study examined the effect of SGLT2i on LVH in patients with type 2 DM (T2DM).

METHODS

The retrospective cohort study was conducted in consecutive outpatients with T2DM from 2010 to 2020. Left ventricular mass index (LVMI) was used as an indicator of LVH based on echocardiography. The minimum follow-up period was 1 year. After propensity score-matching for clinical profiles, patients who underwent annual echocardiography twice for a routine checkup and took SGLT2i were defined to the SGLT2i group, whereas patients without SGLT2 inhibitors were defined to the non-SGLT2 group. SGLT2i was administered after baseline echocardiography followed by a second examination.

RESULTS

LVMI levels in the SGLT2i group (n = 169) significantly decreased from baseline compared with those in the non-SGLT2i group (n = 169), % changes in LVMI2.7(g/m^2.7 ) in median (interquartile ranges [IQR]) were - 7.7 (-18.7, 2.5) vs -3.6 (-14.3, 5.8), respectively, P = 0.017). In a subgroup analysis, LVMI levels in the patients who had LVH in the SGLT2i group more significantly decreased than those without LVH, % changes in LVMI2.7(g/m^2.7 ) in median (IQR) were -13.5 (-22.1, -2.4) vs -2.8 (-12.6, 9.8), respectively, P < 0.001).

CONCLUSIONS

SGLT2i treatment was shown to improve LVH in patients with T2DM and may play a pivotal role in the future treatment of diabetic cardiovascular complications.

Fructose plus High-Salt Diet in Early Life Results in Salt-Sensitive Cardiovascular Changes in Mature Male Sprague Dawley Rats

Fructose and salt intake remain high, particularly in adolescents and young adults. The present studies were designed to evaluate the impact of high fructose and/or salt during pre- and early adolescence on salt sensitivity, blood pressure, arterial compliance, and left ventricular (LV) function in maturity. Male 5-week-old Sprague Dawley rats were studied over three 3-week phases (Phases I, II, and III). Two reference groups received either 20% glucose + 0.4% NaCl (GCS-GCS) or 20% fructose + 4% NaCl (FHS-FHS) throughout this study. The two test groups ingested fructose + 0.4% NaCl (FCS) or FHS during Phase I, then GCS in Phase II, and were then challenged with 20% glucose + 4% NaCl (GHS) in Phase III: FCS-GHS and FHS-GHS, respectively. Compared with GCS-GCS, systolic and mean pressures were significantly higher at the end of Phase III in all groups fed fructose during Phase I. Aortic pulse wave velocity (PWV) was elevated at the end of Phase I in FHS-GHS and FHS-FHS (vs. GCS-GCS). At the end of Phase III, PWV and renal resistive index were higher in FHS-GHS and FHS-FHS vs. GCS-GCS. Diastolic, but not systolic, LV function was impaired in the FHS-GHS and FHS-FHS but not FCS-FHS rats. Consumption of 20% fructose by male rats during adolescence results in salt-sensitive hypertension in maturity. When ingested with a high-salt diet during this early plastic phase, dietary fructose also predisposes to vascular stiffening and LV diastolic dysfunction in later life.

Myocardial Tissue Characterization in Heart Failure with Preserved Ejection Fraction: From Histopathology and Cardiac Magnetic Resonance Findings to Therapeutic Targets

Heart failure with preserved ejection fraction (HFpEF) is a complex clinical syndrome responsible for high mortality and morbidity rates. It has an ever growing social and economic impact and a deeper knowledge of molecular and pathophysiological basis is essential for the ideal management of HFpEF patients. The association between HFpEF and traditional cardiovascular risk factors is known. However, myocardial alterations, as well as pathophysiological mechanisms involved are not completely defined. Under the definition of HFpEF there is a wide spectrum of different myocardial structural alterations. Myocardial hypertrophy and fibrosis, coronary microvascular dysfunction, oxidative stress and inflammation are only some of the main pathological detectable processes. Furthermore, there is a lack of effective pharmacological targets to improve HFpEF patients' outcomes and risk factors control is the primary and unique approach to treat those patients. Myocardial tissue characterization, through invasive and non-invasive techniques, such as endomyocardial biopsy and cardiac magnetic resonance respectively, may represent the starting point to understand the genetic, molecular and pathophysiological mechanisms underlying this complex syndrome. The correlation between histopathological findings and imaging aspects may be the future challenge for the earlier and large-scale HFpEF diagnosis, in order to plan a specific and effective treatment able to modify the disease's natural course.

Impact of admission hyperglycaemia on clinical outcomes in non-diabetic heart failure with preserved ejection fraction

Aims

At present, the clinical significance of admission hyperglycaemia in heart failure with preserved ejection fraction (HFpEF) patients remains unknown. This study was designed to evaluate the relationship between admission hyperglycaemia and clinical outcome in HFpEF patients, especially in non‐diabetic patients.

Methods and results

We enrolled 486 non‐diabetic HFpEF (left ventricular ejection fraction ≥50%) patients hospitalized due to acute decompensated heart failure from the PURSUIT‐HFpEF registry, a prospective, multicentre observational study. We divided non‐diabetic patients into two groups, an admission hyperglycaemia group whose blood glucose on admission was ≥7.0 mmol/L (148 patients) and a normoglycaemic group whose blood glucose on admission was <7.0 mmol/L (338 patients). The primary endpoint was all‐cause mortality, and the secondary endpoints were heart failure death and other causes of cardiac death. During a mean follow‐up period of 400 ± 335 days, all‐cause mortality was 69 patients. Twenty‐five patients suffered cardiac death. All‐cause mortality (P = 0.002), cardiac death (P = 0.009), and heart failure death (P = 0.001) were significantly more frequent in the admission hyperglycaemia group than in the normoglycaemic group. Admission hyperglycaemia was independently and significantly associated with all‐cause mortality and cardiac death (HR 2.01, 95% CI 1.20–3.34, P = 0.008 and HR 3.03, 95% CI 1.35–6.96, P = 0.007, respectively).

Conclusions

Non‐diabetic HFpEF patients with admission hyperglycaemia when hospitalized for heart failure had poorer clinical outcomes than normoglycaemic patients.

Sacubitril/valsartan inhibits obesity-associated diastolic dysfunction through suppression of ventricular-vascular stiffness

OBJECTIVE

Cardiac diastolic dysfunction (DD) and arterial stiffness are early manifestations of obesity-associated prediabetes, and both serve as risk factors for the development of heart failure with preserved ejection fraction (HFpEF). Since the incidence of DD and arterial stiffness are increasing worldwide due to exponential growth in obesity, an effective treatment is urgently needed to blunt their development and progression. Here we investigated whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses DD and arterial stiffness in an animal model of prediabetes more effectively than valsartan monotherapy.

METHODS

Sixteen-week-old male Zucker Obese rats (ZO; n = 64) were assigned randomly to 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val; 68 mg•kg-1•day-1; ZOSV); Group 3: valsartan (31 mg•kg-1•day-1; ZOV) and Group 4: hydralazine, an anti-hypertensive drug (30 mg•kg-1•day-1; ZOH). Six Zucker Lean (ZL) rats that received saline only (Group 5) served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage.

RESULTS

Sac/val improved echocardiographic parameters of impaired left ventricular (LV) stiffness in untreated ZO rats, without altering the amount of food consumed or body weight gained. In addition to improving DD, sac/val decreased aortic stiffness and reversed impairment in nitric oxide-induced vascular relaxation in ZO rats. However, sac/val had no impact on LV hypertrophy. Notably, sac/val was more effective than val in ameliorating DD. Although, hydralazine was as effective as sac/val in improving these parameters, it adversely affected LV mass index. Further, cytokine array revealed distinct effects of sac/val, including marked suppression of Notch-1 by both valsartan and sac/val, suggesting that cardiovascular protection afforded by both share some common mechanisms; however, sac/val, but not val, increased IL-4, which is increasingly recognized for its cardiovascular protection, possibly contributing, in part, to more favorable effects of sac/val over val alone in improving obesity-associated DD.

CONCLUSIONS

These studies suggest that sac/val is superior to val in reversing obesity-associated DD. It is an effective drug combination to blunt progression of asymptomatic DD and vascular stiffness to HFpEF development in a preclinical model of obesity-associated prediabetes.

Microvascular Dysfunction in Diabetes Mellitus and Cardiometabolic Disease

This review takes an inclusive approach to microvascular dysfunction in diabetes mellitus and cardiometabolic disease. In virtually every organ, dynamic interactions between the microvasculature and resident tissue elements normally modulate vascular and tissue function in a homeostatic fashion. This regulation is disordered by diabetes mellitus, by hypertension, by obesity, and by dyslipidemia individually (or combined in cardiometabolic disease), with dysfunction serving as an early marker of change. In particular, we suggest that the familiar retinal, renal, and neural complications of diabetes mellitus are late-stage manifestations of microvascular injury that begins years earlier and is often abetted by other cardiometabolic disease elements (eg, hypertension, obesity, dyslipidemia). We focus on evidence that microvascular dysfunction precedes anatomic microvascular disease in these organs as well as in heart, muscle, and brain. We suggest that early on, diabetes mellitus and/or cardiometabolic disease can each cause reversible microvascular injury with accompanying dysfunction, which in time may or may not become irreversible and anatomically identifiable disease (eg, vascular basement membrane thickening, capillary rarefaction, pericyte loss, etc.). Consequences can include the familiar vision loss, renal insufficiency, and neuropathy, but also heart failure, sarcopenia, cognitive impairment, and escalating metabolic dysfunction. Our understanding of normal microvascular function and early dysfunction is rapidly evolving, aided by innovative genetic and imaging tools. This is leading, in tissues like the retina, to testing novel preventive interventions at early, reversible stages of microvascular injury. Great hope lies in the possibility that some of these interventions may develop into effective therapies.

Pathophysiology, Clinical Characteristics of Diabetic Cardiomyopathy: Therapeutic Potential of Natural Polyphenols

Diabetic cardiomyopathy (DCM) is an outcome of disturbances in metabolic activities through oxidative stress, local inflammation, and fibrosis, as well as a prime cause of fatality worldwide. Cardiovascular disorders in diabetic individuals have become a challenge in diagnosis and formulation of treatment prototype. It is necessary to have a better understanding of cellular pathophysiology that reveal the therapeutic targets and prevent the progression of cardiovascular diseases due to hyperglycemia. Critical changes in levels of collagen and integrin have been observed in the extracellular matrix of heart, which was responsible for cardiac remodeling in diabetic patients. This review explored the understanding of the mechanisms of how the phytochemicals provide cardioprotection under diabetes along with the caveats and provide future perspectives on these agents as prototypes for the development of drugs for managing DCM. Thus, here we summarized the effect of various plant extracts and natural polyphenols tested in preclinical and cell culture models of diabetic cardiomyopathy. Further, the potential use of selected polyphenols that improved the therapeutic efficacy against diabetic cardiomyopathy is also illustrated.

Diabetic Cardiomiopathy Progression is Triggered by miR122-5p and Involves Extracellular Matrix: A 5-Year Prospective Study

OBJECTIVES

The purpose of this study was to follow the long-term progression of diabetic cardiomyopathy by combining cardiac magnetic resonance (CMR) and molecular analysis.

BACKGROUND

The evolution of diabetic cardiomyopathy to heart failure affects patients'morbidity and mortality. CMR is the gold standard to assess cardiac remodeling, but there is a lack of markers linked to the mechanism of diabetic cardiomyopathy progression.

METHODS

Five-year longitudinal study on patients with type 2 diabetes mellitus (T2DM) enrolled in the CECSID (Cardiovascular Effects of Chronic Sildenafil in Men With Type 2 Diabetes) trial compared with nondiabetic age-matched controls. CMR with tagging together with metabolic and molecular assessments were performed at baseline and 5-year follow-up.

RESULTS

A total of 79 men (age 64 ± 8 years) enrolled, comprising 59 men with T2DM compared with 20 nondiabetic age-matched controls. Longitudinal CMR with tagging showed an increase in ventricular mass (ΔLVMi = 13.47 ± 29.66 g/m²; p = 0.014) and a borderline increase in end-diastolic volume (ΔEDVi = 5.16 ± 14.71 ml/m²; p = 0.056) in men with T2DM. Cardiac strain worsened (Δσ = 1.52 ± 3.85%; p = 0.033) whereas torsion was unchanged (Δθ = 0.24 ± 4.04°; p = 0.737), revealing a loss of the adaptive equilibrium between strain and torsion. Contraction dynamics showed a decrease in the systolic time-to-peak (ΔTtP = -35.18 ± 28.81 ms; p < 0.001) and diastolic early recoil-rate (ΔRR = -20.01 ± 19.07 s^-1; p < 0.001). The ejection fraction and metabolic parameters were unchanged. Circulating miR microarray revealed an up-regulation of miR122-5p. Network analysis predicted the matrix metalloproteinases (MMPs) MMP-16 and MMP-2 and their regulator (tissue inhibitors of metalloproteinases) as targets. In db/db mice we demonstrated that miR122-5p expression is associated with diabetic cardiomyopathy, that in the diabetic heart is overexpressed, and that, in vitro, it regulates MMP-2. Finally, we demonstrated that miR122-5p overexpression affects the extracellular matrix through MMP-2 modulation.

CONCLUSIONS

Within 5 years of diabetic cardiomyopathy onset, increasing cardiac hypertrophy is associated with progressive impairment in strain, depletion of the compensatory role of torsion, and changes in viscoelastic contraction dynamics. These changes are independent of glycemic control and paralleled by the up-regulation of specific microRNAs targeting the extracellular matrix. (Cardiovascular Effects of Chronic Sildenafil in Men With Type 2 Diabetes [CECSID]; NCT00692237).

Role of the vascular endothelial sodium channel activation in the genesis of pathologically increased cardiovascular stiffness

Cardiovascular (CV) stiffening represents a complex series of events evolving from pathological changes in individual cells of the vasculature and heart which leads to overt tissue fibrosis. While vascular stiffening occurs naturally with ageing it is accelerated in states of insulin (INS) resistance, such as obesity and type 2 diabetes. CV stiffening is clinically manifested as increased arterial pulse wave velocity and myocardial fibrosis-induced diastolic dysfunction. A key question that remains is how are these events mechanistically linked. In this regard, heightened activation of vascular mineralocorticoid receptors (MR) and hyperinsulinaemia occur in obesity and INS resistance states. Further, a downstream mediator of MR and INS receptor activation, the endothelial cell Na+ channel (EnNaC), has recently been identified as a key molecular determinant of endothelial dysfunction and CV fibrosis and stiffening. Increased activity of the EnNaC results in a number of negative consequences including stiffening of the cortical actin cytoskeleton in endothelial cells, impaired endothelial NO release, increased oxidative stress-meditated NO destruction, increased vascular permeability, and stimulation of an inflammatory environment. Such endothelial alterations impact vascular function and stiffening through regulation of vascular tone and stimulation of tissue remodelling including fibrosis. In the case of the heart, obesity and INS resistance are associated with coronary vascular endothelial stiffening and associated reductions in bioavailable NO leading to heart failure with preserved systolic function (HFpEF). After a brief discussion on mechanisms leading to vascular stiffness per se, this review then focuses on recent findings regarding the role of INS and aldosterone to enhance EnNaC activity and associated CV stiffness in obesity/INS resistance states. Finally, we discuss how coronary artery-mediated EnNaC activation may lead to cardiac fibrosis and HFpEF, a condition that is especially pronounced in obese and diabetic females.

Syringaresinol Protects against Type 1 Diabetic Cardiomyopathy by Alleviating Inflammation Responses, Cardiac Fibrosis, and Oxidative Stress

SCOPE

Syringaresinol (SYR) is a phenolic compound, which could be found in various cereals and medicinal plants. It exerts both anti-inflammatory and antioxidant pharmacological properties. However, little is known about the effect of SYR on modulating diabetic cardiomyopathy. The present study aimed to investigate the pharmacodynamic effect of SYR on diabetic cardiomyopathy and the underlying molecular mechanism.

METHODS AND RESULTS

In STZ-induced type 1 diabetic mice, orally administration with SYR in every other day for 8 weeks significantly improves cardiac dysfunction and preventes cardiac hypertrophy and fibrosis. The macrophage infiltration and oxidative stress biomarkers are also suppressed by SYR without affecting hyperglycemia and body weight. In neonatal cardiomyocytes, high glucose-induced cell apoptosis and fibrosis are potently decreased by SYR, and the inflammatory response and oxidant stress are also alleviated by SYR incubation. Mechanistically, SYR may exert protective effects by restoring suppression of antioxidant kelch-like ECH-associated protein 1 (Keap1)/nuclear factor-E2-related factor 2 (Nrf2) system and abnormal activation of transforming growth factor-β (TGF-β)/mothers against decapentaplegic homolog (Smad) signaling pathway in vitro and in vivo.

CONCLUSION

The results indicated that SYR could be a potential therapeutic agent for the treatment of diabetic cardiomyopathy by inhibiting inflammation, fibrosis, and oxidative stress. The signaling pathway of Keap1/Nrf2 and TGF-β/Smad could be used as therapeutic targets for diabetic complications.

Neutrophil: lymphocyte ratio is positively associated with subclinical diabetic cardiomyopathy

BACKGROUND

Subclinical diabetic cardiomyopathy (DCM) occurs frequently in asymptomatic subjects with Type 2 diabetes mellitus (T2DM). The direct association between the immune system and DCM with effective biomarkers has been demonstrated in previous studies.

METHODS

Five hundred seven subjects with T2DM were recruited from April 2018 to October 2019 and divided into T2DM with cardiac dysfunction (DCM) group and T2DM without cardiac dysfunction (non-DCM) group. The relationship between the quartiles of Neutrophil: lymphocyte ratio (NLR) and subclinical DCM was evaluated by using adjusted logistic regression models.(covariates: age, sex, BMI, duration of diabetes, and hyperlipidemia).

RESULTS

Blood NLR was significantly upregulated in DCM group compared to non-DCM group (P = 0.05). Then the adjusted odds ratio (95% CI) of the highest NLR quartile was 14.32 (2.92-70.31) compared with the lowest quartile of NLR after multiple adjusted (P < 0.001). However, there was no significant relation between neutrophil and lymphocyte counts and the occurrence of DCM in T2DM patients.

CONCLUSIONS

This study demonstrated that NLR was associated with the occurrence of subclinical DCM, suggesting that NLR may be a biomarker for predicting DCM with effectiveness and accuracy.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR1900027080) . Registered 30 October 2019. Retrospectively registered: www.medresman.org.

Alpha-Mangostin Improves Cardiac Hypertrophy and Fibrosis and Associated Biochemical Parameters in High-Fat/High-Glucose Diet and Low-Dose Streptozotocin Injection-Induced Type 2 Diabetic Rats

PURPOSE

The aim of present study was to analyze the effect of alpha-mangostin on cardiac hypertrophy and fibrosis and biochemical parameters in high-fat/high-glucose diet and low-dose streptozotocin injection (HF/HG/STZ)-induced type 2 diabetic rats.

METHODS

Diabetes was induced in male Wistar rats by giving a combination of high-fat/high-glucose (HF/HG) diet for 3 weeks and followed by low-dose streptozotocin intraperitoneal injection (STZ; 35 mg/kg) at Week-3 and the HF/HG diet was continued until 8 weeks. The diabetic rats were then divided into four groups (each, n=6): untreated diabetic group (HF/HG/STZ); diabetic group treated with metformin 200 mg/kg/day (HF/HG/STZ+Metformin); diabetic group treated with alpha-mangostin 100 mg/kg/day (HF/HG/STZ+AM100); and diabetic group treated with alpha-mangostin 200 mg/kg/day (HF/HG/STZ+AM200) and all were given by oral gavage for 8 weeks. We also included a control group (C) treated with AM200 (C+AM200). The role of alpha-mangostin was assessed through its effect on blood glucose levels, HOMA-IR, blood pressure, body weight, pro-inflammatory cytokines in cardiac tissue, serum aminotransferases (ALT and AST), lipid profiles (cholesterol and triglyceride), blood urea nitrogen (BUN), uric acid, cardiac hypertrophy and fibrosis.

RESULTS

Diabetic rats treated with alpha-mangostin in both doses for 8 weeks showed decrease in blood glucose levels, HOMA-IR, and blood pressure. Alpha-mangostin treatment also prevented HF/HG/STZ-induced changes in the activities of ALT, AST, BUN, uric acid, lipid profiles, and pro-inflammatory cytokines, which were comparable with the standard drug metformin, while alpha-mangostin did not show any significant effects on control rats (p>0.05). The cardiac hypertrophy and fibrosis were also attenuated in diabetic rats treated with alpha-mangostin in both doses.

CONCLUSION

These data suggest that administration of alpha-mangostin can effectively attenuate diabetes-induced alteration in cardiac hypertrophy and fibrosis as well as biochemical parameters in HF/HG/STZ rats.

Subclinical left ventricular dysfunction assessed by two-dimensional speckle tracking echocardiography in asymptomatic patients with carotid stenosis

The relationship between subclinical left ventricular (LV) dysfunction and atherosclerosis may have been underestimated in the past, which might be responsible for the high incidence of premature death in individuals with carotid stenosis. We sought to evaluate the underlying myocardial dysfunction in asymptomatic carotid stenosis patients using speckle tracking echocardiography (STE). Fifty patients with carotid stenosis ≥ 50% and a preserved LV ejection fraction (LVEF), and 45 controls without carotid stenosis who were matched in terms of vascular comorbidities were enrolled. All participants underwent carotid ultrasound and echocardiographic examination. The global LV longitudinal strain (GLS) was measured using STE. Compared with the control group, the e' of the mitral annular velocity and GLS were decreased in asymptomatic carotid stenosis patients (p < 0.05), however, the LVEF was well preserved. Based on a predefined cutoff for subclinical LV systolic dysfunction that was defined at a GLS <  - 18%, this dysfunction was detected in 22 patients with carotid stenosis (44%) and in 10 patients in the control group (22%) (p < 0.05). The GLS was negatively correlated with the levels of low-density lipoprotein cholesterol (r =  - 0.356, p < 0.05) and triglyceride (r =  - 0.396, p < 0.05). In conclusion, LV diastolic and systolic functioning were significantly decreased in patients with asymptomatic carotid stenosis, and dyslipidemia likely contributed to the subclinical LV dysfunction in these patients. Our findings indicated the importance of detecting LV subclinical dysfunction and early intervention in this patient population.

Inhibition of Sodium Glucose Cotransporters Improves Cardiac Performance

The sodium-glucose cotransporter (SGLT) inhibitors represent a new alternative for treating patients with diabetes mellitus. They act primarily by inhibiting glucose reabsorption in the renal tubule and therefore, decreasing blood glucose levels. While little is yet known about SGLT subtype 1, SGLT2 inhibitors have demonstrated to significantly reduce cardiovascular mortality and heart failure hospitalizations. This cardioprotective benefit seems to be independent of their glucose-lowering properties; however, the underlying mechanism(s) remains still unclear and numerous hypotheses have been postulated to date. Moreover, preclinical research has suggested an important role of SGLT1 receptors on myocardial ischemia. Following acute phase of cardiac injury there is an increased activity of SGLT1 cotransport that ensures adequate energy supply to the cardiac cells. Nonetheless, a long-term upregulation of this receptor may not be that beneficial and whether its inhibition is positive or not should be further addressed. This review aims to present the most cutting-edge insights into SGLT receptors.