Update on diabetic cardiomyopathy: inches forward, miles to go

Alpha-lipoic acid treatment improves adverse cardiac remodelling in the diabetic heart - The role of cardiac hydrogen sulfide-synthesizing enzymes

INTRODUCTION

Alpha-lipoic acid (ALA) is a licensed drug for the treatment of diabetic neuropathy. We recently reported that it also improves diabetic cardiomyopathy (DCM) in type 2 diabetes mellitus (T2DM). In this study, we present evidence supporting our hypothesis that the cardioprotective effect of ALA is via upregulation of cardiac hydrogen sulfide (H₂S)-synthesizing enzymes.

METHODS

Following 12 h of overnight fasting, T2DM was induced in 23 out of 30 male Sprague-Dawley rats by intraperitoneal administration of nicotinamide (110 mg/kg) followed by streptozotocin (55 mg/kg) while the rest served as healthy control (HC). T2DM rats then received either oral administration of ALA (60 mg/kg/day; n = 7) or 40 mg/kg/day DL-propargylglycine (PAG, an endogenous H₂S inhibitor; n = 7) intraperitoneally for 6 weeks after which all rats were sacrificed and samples collected for analysis. Untreated T2DM rats served as diabetic control (DCM; n = 9).

RESULTS

T2DM resulted in weight loss, islet destruction, reduced pancreatic β-cell function and hyperglycemia. Histologically, DCM rats showed significant myocardial damage evidenced by myocardial degeneration, cardiomyocyte vacuolation and apoptosis, cardiac fibrosis and inflammation, which positively correlated with elevated levels of cardiac damage markers compared to HC rats (p < 0.001). These pathological alterations worsened significantly in PAG-treated rats (p < 0.05). However, ALA treatment restored normoinsulemia, normoglycemia, prevented DCM, and improved lipid and antioxidant status. Mechanistically, ALA significantly upregulated the expression of cardiac H₂S-synthesizing enzymes and increased plasma H₂S concentration compared to DCM rats (p < 0.001).

CONCLUSION

ALA preserves myocardial integrity in T2DM likely by maintaining the expression of cardiac H₂S-synthezing enzymes and increasing plasma H₂S level.

Combination Therapy of Alpha-Lipoic Acid, Gliclazide and Ramipril Protects Against Development of Diabetic Cardiomyopathy via Inhibition of TGF-β/Smad Pathway

Background: Diabetic cardiomyopathy (DCM) is a major long-term complication of diabetes mellitus, accounting for over 20% of annual mortality rate of diabetic patients globally. Although several existing anti-diabetic drugs have improved glycemic status in diabetic patients, prevalence of DCM is still high. This study investigates cardiac effect of alpha-lipoic acid (ALA) supplementation of anti-diabetic therapy in experimental DCM. Methods: Following 12 h of overnight fasting, 44 male Sprague Dawley rats were randomly assigned to two groups of healthy control (n = 7) and diabetic (n = 37) groups, and fasting blood glucose was measured. Type 2 diabetes mellitus (T2DM) was induced in diabetic group by intraperitoneal (i.p.) administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). After confirmation of T2DM on day 3, diabetic rats received monotherapies with ALA (60 mg/kg; n = 7), gliclazide (15 mg/kg; n = 7), ramipril (10 mg/kg; n = 7) or combination of the three drugs (n = 7) for 6 weeks while untreated diabetic rats received distilled water and were used as diabetic control (n = 9). Rats were then sacrificed, and blood, pancreas and heart tissues were harvested for analyses using standard methods. Results: T2DM induction caused pancreatic islet destruction, hyperglycemia, weight loss, high relative heart weight, and development of DCM, which was characterized by myocardial degeneration and vacuolation, cardiac fibrosis, elevated cardiac damage markers (plasma and cardiac creatine kinase-myocardial band, brain natriuretic peptide and cardiac troponin I). Triple combination therapy of ALA, gliclazide and ramipril preserved islet structure, maintained body weight and blood glucose level, and prevented DCM development compared to diabetic control (p < 0.001). In addition, the combination therapy markedly reduced plasma levels of inflammatory markers (IL-1β, IL-6 and TNF-α), plasma and cardiac tissue malondialdehyde, triglycerides and total cholesterol while significantly increasing cardiac glutathione and superoxide dismutase activity and high-density lipoprotein-cholesterol compared to diabetic control (p < 0.001). Mechanistically, induction of T2DM upregulated cardiac expression of TGF-β1, phosphorylated Smad2 and Smad3 proteins, which were downregulated following triple combination therapy (p < 0.001). Conclusion: Triple combination therapy of ALA, gliclazide and ramipril prevented DCM development by inhibiting TGF-β1/Smad pathway. Our findings can be extrapolated to the human heart, which would provide effective additional pharmacological therapy against DCM in T2DM patients.

Diabetic cardiomyopathy: Clinical phenotype and practice

Diabetic cardiomyopathy (DCM) is a pathophysiological condition of cardiac structure and function changes in diabetic patients without coronary artery disease, hypertension, and other types of heart diseases. DCM is not uncommon in people with diabetes, which increases the risk of heart failure. However, the treatment is scarce, and the prognosis is poor. Since 1972, one clinical study after another on DCM has been conducted. However, the complex phenotype of DCM still has not been fully revealed. This dilemma hinders the pace of understanding the essence of DCM and makes it difficult to carry out penetrating clinical or basic research. This review summarizes the literature on DCM over the last 40 years and discusses the overall perspective of DCM, phase of progression, potential clinical indicators, diagnostic and screening criteria, and related randomized controlled trials to understand DCM better.

Role of inflammation in diabetic cardiomyopathy

The prevalence of type 2 diabetes (T2D) has reached a pandemic scale. Systemic chronic inflammation dominates the diabetes pathophysiology and has been implicated as a causal factor for the development of vascular complications. Heart failure (HF) is regarded as the most common cardiovascular complication of T2D and the diabetic diagnosis is an independent risk factor for HF development. Key molecular mechanisms pivotal to the development of diabetic cardiomyopathy include the NF-κB pathway and renin-angiotensin-aldosterone system, in addition to advanced glycation end product accumulation and inflammatory interleukin overexpression. Chronic myocardial inflammation in T2D mediates structural and metabolic changes, including cardiomyocyte apoptosis, impaired calcium handling, myocardial hypertrophy and fibrosis, all of which contribute to the diabetic HF phenotype. Advanced cardiovascular magnetic resonance imaging (CMR) has emerged as a gold standard non-invasive tool to delineate myocardial structural and functional changes. This review explores the role of chronic inflammation in diabetic cardiomyopathy and the ability of CMR to identify inflammation-mediated myocardial sequelae, such as oedema and diffuse fibrosis.

Characteristics of Myocardial Perfusion in Type 2 Diabetes Mellitus and Its Association with Left Ventricular Diastolic Dysfunction: A Study of Myocardial Contrast Echocardiography

Background

Diabetic cardiomyopathy (DCM) will gradually progress to heart failure without intervention. The timely identification of left ventricular diastolic dysfunction (LVDD) in the early stage and active intervention helps delay the onset of heart failure. Although myocardial contrast echocardiography (MCE) allows an accurate evaluation of myocardial perfusion (MP), the characteristics of MP in early-stage or even sub-clinical LVDD are still unclear.

Objective

This study aims to reveal the characteristics of MP in asymptomatic and normotensive patients with type 2 diabetes mellitus (T2DM) using MCE and investigate its association with LVDD development.

Methods

A total of 327 T2DM patients were retrospectively analyzed. Patients diagnosed with LVDD were included in the LVDD+ group (n = 76), and those with normal left ventricular diastolic function were included in the LVDD- group (n = 251). The clinical characteristics, general echocardiographic findings, and MCE parameters were compared between the two groups. The accuracy of MCE parameters in the diagnosis of LVDD and their correlations with characteristics of T2DM were evaluated.

Results

In the LVDD+ group, the A×β (derived from the replenishment curve of MCE, presenting myocardial blood flow) was significantly lower, and the HbA1c and diabetes duration were significantly higher compared to the LVDD- group (all P < 0.05). The decrease of A×β helped warn the occurrence of LVDD although it was not suitable for the independent diagnosis of LVDD (AUC = 0.745). A×β was negatively correlated with diabetes duration and HbA1c (r = -0.350 and -0.226, both P < 0.001).

Conclusion

MCE was feasible for detecting MP abnormalities in asymptomatic T2DM patients. Although the A×β values of T2DM patients with subclinical LVDD were better than those with diagnosed LVDD, it impaired with the increase of HbA1c and diabetes duration. It suggested that MCE might be useful for monitoring glycemic control in T2DM patients with DCM.

Echocardiographic predictors of long-term adverse cardiovascular outcomes in participants with and without diabetes mellitus: A follow-up analysis of the Copenhagen City Heart Study

BACKGROUND

Previous studies have identified several echocardiographic markers of cardiac dysfunction in participants with diabetes mellitus, including E/e'. However, previous studies have been limited by short follow-up duration or low statistical power, and none have assessed whether echocardiographic predictors of adverse cardiovascular outcome differ between individuals with DM and individuals without DM.

METHODS

A total of 1997 individuals from the general population without heart disease had an echocardiogram performed in 2001 to 2003. Diabetes was defined as HbA_1c ≥6.5% (≥48 mmol/mol), non-fasted blood glucose ≥11.1 mmol/L or the use of glucose lowering medication. The end-point was a composite of heart failure (HF), ischemic heart disease (IHD) and cardiovascular death (CVD).

RESULTS

At baseline, a total of 292 participants (15%) had diabetes. Median follow-up time was 12.4 years (interquartile-range: 9.8-12.8 years) and follow-up was 100%. During follow-up, 101 participants (35%) with diabetes and 281 participants without diabetes (16%) reached the composite end-point. The prognostic value of E/e' was significantly modified by diabetes (p for interaction: 0.003). In participants with diabetes, only E/e' remained an independent predictor of outcome in a final multivariable model adjusted for clinical and echocardiographic parameters (HR 1.08, 95% CI 1.00-1.17, p = 0.0041, per 1 increase). In participants without diabetes, left ventricular mass index (LVMI), left ventricular ejection fraction (LVEF) and a' remained independent predictors of outcome when adjusted for clinical and echocardiographic parameters. In individuals with diabetes, only E/e' added incremental prognostic value to risk factors from the SCORE risk chart and the ACC/AHA Pooled Cohort Equation.

CONCLUSION

In individuals with diabetes from the general population, E/e' is a stronger predictor of cardiovascular mortality and morbidity than in individuals without diabetes and contributes with incremental prognostic value in addition to established cardiovascular risk factors.

Role of novel biomarkers in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is commonly defined as cardiomyopathy in patients with diabetes mellitus in the absence of coronary artery disease and hypertension. As DCM is now recognized as a cause of substantial morbidity and mortality among patients with diabetes mellitus and clinical diagnosis is still inappropriate, various expert groups struggled to identify a suitable biomarker that will help in the recognition and management of DCM, with little success so far. Hence, we thought it important to address the role of biomarkers that have shown potential in either human or animal studies and which could eventually result in mitigating the poor outcomes of DCM. Among the array of biomarkers we thoroughly analyzed, long noncoding ribonucleic acids, soluble form of suppression of tumorigenicity 2 and galectin-3 seem to be most beneficial for DCM detection, as their plasma/serum levels accurately correlate with the early stages of DCM. The combination of relatively inexpensive and accurate speckle tracking echocardiography with some of the highlighted biomarkers may be a promising screening method for newly diagnosed diabetes mellitus type 2 patients. The purpose of the screening test would be to direct affected patients to more specific confirmation tests. This perspective is in concordance with current guidelines that accentuate the importance of an interdisciplinary team-based approach.

Hydrogen Sulfide Plays an Important Role in Diabetic Cardiomyopathy

Diabetic cardiomyopathy is an important complication of diabetes mellitus and the main cause of diabetes death. Diabetic cardiomyopathy is related with many factors, such as hyperglycemia, lipid accumulation, oxidative stress, myocarditis, and apoptosis. Hydrogen sulfide (H₂S) is a newly discovered signal molecule, which plays an important role in many physiological and pathological processes. Recent studies have shown that H₂S is involved in improving diabetic cardiomyopathy, but its mechanism has not been fully elucidated. This review summarizes the research on the roles and mechanisms of H₂S in diabetic cardiomyopathy in recent years to provide the basis for in-depth research in the future.

The influence of diabetes and prediabetes on left heart remodeling: A population-based study

BACKGROUND

Diabetes was regarded as an independent risk factor for abnormal left heart remodeling. However, there was lacking population-based data on the relationship of glucose status with left ventricular hypertrophy (LVH) or left atrial enlargement (LAE). This study intended to clarify the influence of diabetes and prediabetes on the prevalence and incidence of LVH and LAE based on a northeast rural population of China.

METHODS

We analyzed clinical, laboratory and echocardiographic data of a total of 2824 participants aged over 35 years from a population-based prospective cohort NCRCHS study with 2 years of follow-up, which was carried out in rural areas of northeast China. All measurements were performed according to standardized protocols.

RESULTS

There were 2179 controls, 342 subjects with prediabetes and 303 ones with diabetes. The baseline distribution of LAD, IVSd, LVIDd, LVIDs, LVMI, E wave, A wave, E/A, E/e', diastolic dysfunction, LVEDV, LVESV and SV was significantly different among three groups (all P_trend<0.05). After the adjustment for age, gender, BMI, waist circumference, heart rate, hypertension and dyslipidemia, glucose status remained associated with LVIDd and E/e' (all P < 0.05). At baseline, diabetes was independently related to the prevalence of LVH (OR = 1.53; 95%CI = 1.12-2.10; P < 0.01) and LAE (OR = 1.71; 95%CI = 1.19-2.43; P < 0.01) in the overall population, and the same significant results were also found in gender specific subgroups. During the 2-year follow-up, Cox regression models revealed that baseline diabetes had an independent association with the incidence of LAE in the total subjects (HR = 1.83; 95%CI = 1.10-3.06; P = 0.02) and females (HR = 1.90; 95%CI = 1.05-3.46; P = 0.04) after adjusting the potential confounders.

CONCLUSION

Diabetes, but not prediabetes, is an independent predictor for the prevalence of LVH and LAE, and for the new-onset LAE, it should be considered in the assessment of diabetes and cardiac structural remodeling.

Brahma-Related Gene 1 Deficiency in Endothelial Cells Ameliorates Vascular Inflammatory Responses in Mice

Endothelial dysfunction plays an important role in promoting the progression of disease genesis such as atherosclerosis and abdominal aortic aneurysm (AAA). The physiological unbalance of endothelial cells is a major pathological basis. In this present study, we investigated Brahma-related gene 1 (BRG1), a chromatin remodeling protein, was in mouse models of diabetic atherosclerosis and AAA, focusing on its role in endothelial dysfunction. We report that compared with their wild-type (WT, ApoE^–/–; BRG1^fl/fl) littermates, endothelium conditional BRG1 knockout mice (CKO, ApoE^–/–; BRG1^fl/fl; CDH5-cre) exhibited an alleviated phenotype of diabetic atherosclerosis. Immunohistochemically staining and real-time PCR analysis demonstrated fewer macrophages recruitment with a reduction of vascular inflammatory in CKO mice compared with WT mice. Further research in the Ang-II induced AAA model revealed that BRG1 deficiency had the protective effects on endothelium conditional BRG1 deletion, evidenced by the downregulation of pro-inflammatory mediators [interleukin (IL)-1β and IL-6, not tumor necrosis factor-α (TNF-α)] in the vessels of CKO mice compared with WT mice. In Ea.hy926 cell lines, anti-BRG1 small interfering RNA and PFI-3 treatment obviously alleviated tumor necrosis factor-α-induced IL-6 and CCL2 expression, and further research demonstrated that the BRG1 inhibition in endothelial cells not only decreased c-Fos expression but also blocked the c-Fos translocation into nuclei. In conclusion, our results suggest that endothelial BRG1 deficiency may protect the mice from diabetic atherosclerosis and AAA via inhibiting inflammatory response in vessels.

Incidence of Hospitalization for Heart Failure and Case-Fatality Among 3.25 Million People With and Without Diabetes Mellitus

Supplemental Digital Content is available in the text.

Background:

Recent clinical trials of new glucose-lowering treatments have drawn attention to the importance of hospitalization for heart failure as a complication of diabetes mellitus. However, the epidemiology is not well described, particularly for type 1 diabetes mellitus. We examined the incidence and case-fatality of heart failure hospitalizations in the entire population aged ≥30 years resident in Scotland during 2004 to 2013.

Methods:

Date and type of diabetes mellitus diagnosis were linked to heart failure hospitalizations and deaths using the national Scottish registers. Incidence rates and case-fatality were estimated in regression models (quasi-Poisson and logistic regression respectively). All estimates are adjusted for age, sex, socioeconomic status, and calendar-year.

Results:

Over the 10-year period of the study, among 3.25 million people there were 91, 429, 22 959, and 1313 incident heart failure events among those without diabetes mellitus, with type 2, and type 1 diabetes mellitus, respectively. The crude incidence rates of heart failure hospitalization were therefore 2.4, 12.4, and 5.6 per 1000 person-years for these 3 groups. Heart failure hospitalization incidence was higher in people with diabetes mellitus, regardless of type, than in people without. Relative differences were smallest for older men, in whom the difference was nonetheless large (men aged 80, rate ratio 1.78; 95% CI, 1.45–2.19). Rates declined similarly, by 0.2% per calendar-year, in people with type 2 diabetes mellitus and without diabetes mellitus. Rates fell faster, however, in those with type 1 diabetes mellitus (2.2% per calendar-year, rate ratio for type 1/calendar-year interaction 0.978; 95% CI, 0.959–0.998).

Thirty-day case-fatality was similar among people with type 2 diabetes mellitus and without diabetes mellitus, but was higher in type 1 diabetes mellitus for men (odds ratio, 0.96; 95% CI, 0.95–0.96) and women (odds ratio, 0.98; 95% CI, 0.97–0.98). Case-fatality declined over time for all groups (3.3% per calendar-year, odds ratio per calendar-year 0.967; 95% CI, 0.961–0.973).

Conclusions:

Despite falling incidence, particularly in type 1 diabetes mellitus, heart failure remains ≈2-fold higher than in people without diabetes mellitus, with higher case-fatality in those with type 1 diabetes mellitus. These findings support the view that heart failure is an under-recognized and important complication in diabetes mellitus, particularly for type 1 disease.

Evaluation of myocardial fibrosis in diabetes with cardiac magnetic resonance T1-mapping: Correlation with the high-level hemoglobin A1c

AIM

The aim of the study was to assess the extracellular volume fraction (ECV) in type 2 diabetes mellitus (T2DM) patients with different level of hemoglobin A1c (HbA1c) by cardiac magnetic resonance (CMR), and the ability of HbA1c to predict myocardial fibrosis.

METHODS

In total, 80 T2DM patients and 20 age- and sex-matched controls were prospective enrolled and underwent CMR to obtain ECV value and LV function parameters. We divided all patients into a group of HbA1c < 7.0% and a group of HbA1c ≥ 7.0%.

RESULTS

In the higher HbA1c group the ECV value (all p < 0.001) was higher than both lower HbA1c group (36.23% vs. 32.19%, p < 0.001) and controls (36.23% vs. 29.73%, p < 0.001). HbA1c was positively associated (β = 0.36, p = 0.004) with ECV, and it was also an independent predictor of myocardial fibrosis (OR = 2.00, P = 0.014). The ROC analysis showed that 7.1% was the optimal cutoff value of HbA1c that predicted the risk of myocardial fibrosis with high diagnostic accuracy (area under the curve = 0.78).

CONCLUSION

T1 mapping provided myocardial fibrosis information in T2DM patients. HbA1c is positively correlated with myocardial fibrosis and can be an independently predictor of myocardial fibrosis, which may be helpful for the clinical decision-making of blood glucose control.

Diabetic cardiomyopathy: prevalence, determinants and potential treatments

The prevalence of type 2 diabetes (T2D) has reached a pandemic scale. These patients are at a substantially elevated risk of developing cardiovascular disease, with heart failure (HF) being a leading cause of morbidity and mortality. Even in the absence of traditional risk factors, diabetes still confers up to a twofold increased risk of developing HF. This has led to identifying diabetes as an independent risk factor for HF and recognition of the distinct clinical entity, diabetic cardiomyopathy. Despite a wealth of research interest, the prevalence and determinants of diabetic cardiomyopathy remain uncertain. This limited understanding of the pathophysiology of diabetic heart disease has also hindered development of effective treatments. Tight blood-glucose and blood-pressure control have not convincingly been shown to reduce macrovascular outcomes in T2D. There is, however, emerging evidence that T2D is reversible and that the metabolic abnormalities can be reversed with weight loss. Increased aerobic exercise capacity is associated with significantly lower cardiovascular and overall mortality in diabetes. Whether such lifestyle modifications as weight loss and exercise may ameliorate the structural and functional derangements of the diabetic heart has yet to be established. In this review, the link between T2D and myocardial dysfunction is explored. Insights into the structural and functional perturbations that typify the diabetic heart are first described. This is followed by an examination of the pathophysiological mechanisms that contribute to the development of cardiovascular disease in T2D. Lastly, the current and emerging therapeutic strategies to prevent or ameliorate cardiac dysfunction in T2D are evaluated.

Left ventricular concentric geometry predicts incident diabetes mellitus independent of established risk factors in the general population: the Copenhagen City Heart Study

Background

Subtle impairments in left ventricular (LV) function and geometry are common findings in individuals with diabetes. However, whether these impairments precede the development of diabetes mellitus (DM) is not entirely clear.

Methods

Echocardiograms from 1710 individuals from the general population free of prevalent diabetes mellitus were analyzed. Left ventricular (LV) concentric geometry was defined as either LV concentric remodeling or LV concentric hypertrophy as directed in contemporary guidelines. The severity of LV concentricity was assessed by relative wall thickness (RWT) calculated as posterior wall thickness (PWT) indexed to left ventricular internal diameter at end diastole (LVIDd) (RWT = 2 * PWT/LVIDd). End-point was incident DM.

Results

Median follow-up time was 12.6 years (IQR: 12.0–12.8 years). Follow-up was a 100%. A total of 55 participants (3.3%) developed DM during follow-up. At baseline, the prevalence of a concentric LV geometric pattern was significantly higher (41.8% vs 20.3%, p < 0.001) in individuals who developed DM during follow-up. In a final multivariable model adjusting for established DM risk factors including HbA1c, BMI and plasma glucose, LV concentric geometry and RWT remained significantly associated with incident DM (LV concentric geometry: HR 1.99, 95% CI 1.11–3.57, p = 0.021) (RWT: HR 1.41, 95% CI 1.06–1.86, p = 0.017, per 0.1 increase). This association remained despite adjustment for established risk factors for DM.

Conclusion

Altered LV geometry may precede the development of DM. LV concentric geometry determined by echocardiography and the severity of LV concentricity evaluated as RWT are associated with incident DM in the general population.

Electronic supplementary material

The online version of this article (10.1186/s12933-019-0842-0) contains supplementary material, which is available to authorized users.

Exogenous hydrogen sulfide attenuates the development of diabetic cardiomyopathy via the FoxO1 pathway

BACKGROUND

Previous studies have suggested that exogenous hydrogen sulfide can alleviate the development of diabetic cardiomyopathy (DCM) by inhibiting oxidative stress, inflammation, and apoptosis. However, the underlying mechanism is not fully understood. Nuclear expression and function of the transcription factor Forkhead box protein O (FoxO1) have been associated with cardiovascular diseases, and thus, the importance of FoxO1 in DCM has gained increasing attention. This study was designed to investigate the interactions between hydrogen sulfide (H₂ S) and nuclear FoxO1 in DCM.

METHODS

Diabetes was induced in adult male C57BL/6J mice by intraperitoneal injection of streptozotocin and was treated with H₂ S donor sodium hydrosulfide for 12 weeks. The H9C2 cardiomyoblast cell line and neonatal rat cardiomyocytes (NRCMs) were treated with the slow-releasing H₂ S donor GYY4137 before high-glucose (HG) exposure with or without pretreatment with the Akt inhibitor MK-2206 2HCl. Changes in FoxO1 protein phosphorylation and subcellular localization were determined in H9C2 cells, NRCMs, and cardiac tissues from normal and diabetic mice. Cardiac structure and function in the diabetic mice were evaluated by echocardiography and histological analysis and compared with those in control animals.

RESULTS

The echocardiographic and histopathological data indicated that exogenous H₂ S improved cardiac function and attenuated cardiac hypertrophy and myocardial fibrosis in diabetic mice. H₂ S also improved HG-induced oxidative stress and apoptosis in cardiac tissue and NRCMs. In addition, H₂ S induced FoxO1 phosphorylation and nuclear exclusion in vitro and in vivo, and this function was not inhibited by MK-2206 2HCl. Alanine substitution mutation of three sites in FoxO1-enhanced FoxO1 transcriptional activity, and subsequent treatment with exogenous H₂ S could not prevent HG-induced nuclear retention.

CONCLUSIONS

Our data indicate that H₂ S is a novel regulator of FoxO1 in cardiac cells and provide evidence supporting the potential of H₂ S in inhibiting the progression of DCM.

Diagnostic approaches for diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a cardiac dysfunction which affects approximately 12% of diabetic patients, leading to overt heart failure and death. However, there is not an efficient and specific methodology for DCM diagnosis, possibly because molecular mechanisms are not fully elucidated, and it remains asymptomatic for many years. Also, DCM frequently coexists with other comorbidities such as hypertension, obesity, dyslipidemia, and vasculopathies. Thus, human DCM is not specifically identified after heart failure is established. In this sense, echocardiography has been traditionally considered the gold standard imaging test to evaluate the presence of cardiac dysfunction, although other techniques may cover earlier DCM detection by quantification of altered myocardial metabolism and strain. In this sense, Phase-Magnetic Resonance Imaging and 2D/3D-Speckle Tracking Echocardiography may potentially diagnose and stratify diabetic patients. Additionally, this information could be completed with a quantification of specific plasma biomarkers related to related to initial stages of the disease. Cardiotrophin-1, activin A, insulin-like growth factor binding protein-7 (IGFBP-7) and Heart fatty-acid binding protein have demonstrated a stable positive correlation with cardiac hypertrophy, contractibility and steatosis responses. Thus, we suggest a combination of minimally-invasive diagnosis tools for human DCM recognition based on imaging techniques and measurements of related plasma biomarkers.

High-fat diet induces protein kinase A and G-protein receptor kinase phosphorylation of β2 -adrenergic receptor and impairs cardiac adrenergic reserve in animal hearts

Key points

Patients with diabetes show a blunted cardiac inotropic response to β‐adrenergic stimulation despite normal cardiac contractile reserve.

Acute insulin stimulation impairs β‐adrenergically induced contractile function in isolated cardiomyocytes and Langendorff‐perfused hearts.

In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high‐fat diet (HFD) feeding on the cardiac β₂‐adrenergic receptor signalling and the impacts on cardiac contractile function.

We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β‐adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β₂‐adrenergic receptor phosphorylation at protein kinase A and G‐protein receptor kinase sites in the myocardium.

The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications.

Abstract

Patients with diabetes display reduced exercise capability and impaired cardiac contractile reserve in response to adrenergic stimulation. We have recently uncovered an insulin receptor and adrenergic receptor signal network in the heart. The aim of this study was to understand the impacts of high‐fat diet (HFD) on the insulin–adrenergic receptor signal network in hearts. After 8 weeks of HFD feeding, mice exhibited diabetes, with elevated insulin and glucose concentrations associated with body weight gain. Mice fed an HFD had normal cardiac structure and function. However, the HFD‐fed mice displayed a significant elevation of phosphorylation of the β₂‐adrenergic receptor (β₂AR) at both the protein kinase A site serine 261/262 and the G‐protein‐coupled receptor kinase site serine 355/356 and impaired adrenergic reserve when compared with mice fed on normal chow. Isolated myocytes from HFD‐fed mice also displayed a reduced contractile response to adrenergic stimulation when compared with those of control mice fed normal chow. Genetic deletion of the β₂AR led to a normalized adrenergic response and preserved cardiac contractile reserve in HFD‐fed mice. Together, these data indicate that HFD promotes phosphorylation of the β₂AR, contributing to impairment of cardiac contractile reserve before cardiac structural and functional remodelling, suggesting that early intervention in the insulin–adrenergic signalling network might be effective in prevention of cardiac complications in diabetes.

Patients with diabetes show a blunted cardiac inotropic response to β‐adrenergic stimulation despite normal cardiac contractile reserve.

Acute insulin stimulation impairs β‐adrenergically induced contractile function in isolated cardiomyocytes and Langendorff‐perfused hearts.

In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high‐fat diet (HFD) feeding on the cardiac β₂‐adrenergic receptor signalling and the impacts on cardiac contractile function.

We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β‐adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β₂‐adrenergic receptor phosphorylation at protein kinase A and G‐protein receptor kinase sites in the myocardium.

The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications.

Assessment of Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance T1 Mapping: Correlation with Left-Ventricular Diastolic Dysfunction and Diabetic Duration

PURPOSE

To quantify extracellular matrix expansion with the cardiovascular magnetic resonance (CMR) T1 mapping technique and the derived extracellular volume fraction (ECV) in diabetic cardiomyopathy (DbCM) patients and to detect the relationship among ECV, duration of diabetes, and diastolic function.

MATERIALS

Thirty-eight patients with diabetic cardiomyopathy (20 males, age 54.6 ± 8.6 years) and thirty-two matched normal controls (15 males, age 51.4 ± 13.6 years) were prospectively enrolled. All of them were scanned by T1 mapping to obtain the native and postcontrast T1 values of myocardium and blood, and ECV was calculated accordingly. All patients also underwent transthoracic echocardiographic tissue Doppler imaging to assess left-ventricular diastolic function.

RESULTS

There was a significant difference in ECV between the two groups (DbCMs 30.4 ± 2.9% versus controls 27.1 ± 2.4%, P < 0.001). The duration of diabetes was positively and strongly associated with ECV (R = 0.539, P = 0.0005). There was also a significant difference in ECV (P ≤ 0.001) among four groups (A, controls; B, DbCM patients with duration of diabetes <5 years; C, 5-10 years; and D, >10 years). ECV was negatively associated with LV E'/A' (R = -0.403, P = 0.012).

CONCLUSION

CMR T1 mapping can reflect myocardial extracellular matrix expansion in DbCM and can be a powerful technique for the early diagnosis of DbCM.

Rationale and design of the randomised controlled trial to assess the impact of liraglutide on cardiac function and structure in young adults with type 2 diabetes (the LYDIA study)

BACKGROUND

The prevalence of type 2 diabetes (T2DM) in younger adults is growing. Compared to the late onset T2DM, it is well recognized that the disease tends to behave more aggressively in the younger age group with evidence of premature micro and macrovasular diseases and shorter life span. This increased mortality is largely attributed to cardiovascular complications. In a recent pilot study, young adults with T2DM were found to have significantly lower peak diastolic strain rate (PEDSR) on cardiac MRI (CMR), a forerunner of diabetic cardiomyopathy. Liraglutide, a glucagon like peptide-1 (GLP-1) analogue, is one of the new classes of glucose lowering therapies licensed to be used in management of T2DM. In randomised controlled trials, liraglutide improves glycaemic control by 1-1.5 % with an added benefit of weight loss of 2-3 kg. In addition, there is emerging evidence elucidating the cardioprotective effects of GLP-1 analogues independent of glycaemic control. In a small study, liraglutide has also been shown to improve cardiac function in patients with coronary ischaemia or congestive heart failure.

METHODS AND AIMS

This is a prospective, randomised, open-label, blind end-point (PROBE) active-comparator trial. A total of 90 obese eligible participants with T2DM (18-50 years) will be randomised to either liraglutide 1.8 mg once daily or sitagliptin 100 mg once daily for 26 weeks. The primary aim is to assess whether liraglutide improves diastolic function compared to sitagliptin as measured by PEDSR using CMR.

DISCUSSION

Although newer classes of GLP-1 analogues are made available in recent years, there are very few published studies demonstrating the beneficial effect of GLP-1 analogues on cardiovascular endpoints. In a recently published LEADER study, liraglutide has shown superiority to placebo in a population of type 2 diabetes with high risk of cardiovascular disease. To the best of our knowledge, there are no published studies establishing the effect of liraglutide on cardiac function in younger patients with T2DM on a larger scale. The LYDIA study will comprehensively describe changes in various parameters of cardiac structure and function in patients treated with liraglutide aiming to provide new evidence on effect of liraglutide on diastolic function in young obese people with T2DM. Trial Registration ClinicalTrials.gov identifier: NCT02043054.

Improvement of cardiac dysfunction by bilateral surgical renal denervation in animals with diabetes induced by high fructose and high fat diet

AIMS

Insulin resistance (IR) and sympathetic over-activation play a critical role in diabetic cardiomyopathy (DCM). Percutaneous renal sympathetic denervation (RDN) was tested to treat refractory hypertension. However, the benefits of RDN for DCM and IR still remain unknown. The present study aimed to investigate the effect and associated mechanisms of bilateral surgical RDN (bsRDN) on cardiac function and glucose metabolism in animals with diabetes.

METHODS

Thirty-two male New Zealand white rabbits were randomly assigned to Chow (n=8, normal diet) and TEST (n=24, high-fructose fat diet [HFD]) groups. At 48 weeks after HFD feeding, animals in the TEST group were randomized to the Sham, HFD, and RDN subgroups and were fed a HFD for an additional 8 weeks. Repeated measurements of cardiac function, IR, apoptosis/autophagy, and histopathological assessment were performed at 48 and 56 weeks.

RESULTS

HFD feeding for 56 weeks induced IR and diastolic cardiac dysfunction with hypertrophy in septum but well preserved eject fraction in the animals. Impaired IR further deteriorated over the time in the RDN group, featured by a more profound reduction in GLUT4 mRNA and its translocation to the plasma membrane. Successful denervation was associated with improvement of cardiac function via preventing myocardial fibrosis and over-expression of procollagen III, mammalian target of rapamycin, and cardiac apoptosis. Cardiac autophagy, assessed by either electron microscopy or Western blot, was enhanced by bsRDN.

CONCLUSIONS

Renal sympathetic denervation led to a significant improvement of HFD-induced cardiac dysfunction by shifting the cardiac apoptosis to autophagy, but worsening IR. Further study is required to identify the clinical benefits of RDN.

Assessment of Left Ventricular Structural Remodelling in Patients with Diabetic Cardiomyopathy by Cardiovascular Magnetic Resonance

Background. Diabetic cardiomyopathy (DCM) is always accompanied with alteration of left ventricular structure and function. The aims of this study were to assess the structural remodelling in patients with DCM by cardiovascular magnetic resonance (CMR) and correlation of structural remodelling with severity of DCM. Methods. Twenty-five patients (53.8 ± 8.8 years, 52.0% males) with DCM and thirty-one normal healthy controls (51.9 ± 13.6 years, 45.2% males) were scanned by CMR cine to assess function and structure of left ventricular. Length of diabetic history and results of cardiac echocardiography (E', A', and E'/A') were also measured. Results. Compared with normal controls group, DCM group was associated with significantly increased ratio of left ventricular mass at end diastole to end-diastolic volume (MVR) (P < 0.05) and no significant difference was in mass at end diastole (P > 0.05). The ratio correlated with both length of diabetic history and echocardiographic Doppler tissue imaging E' (all P < 0.05). Conclusions. CMR can be a powerful technique to assess LV remodelling, and MVR may be considered as an imaging marker to evaluate the severity of LV remodelling in patients with DCM.

Long-term excess risk of heart failure in people with type 1 diabetes: a prospective case-control study

BACKGROUND

Diabetes is an established risk factor for heart failure, but because nearly all heart failure occurs in older individuals, the excess risk and risk factors for heart failure in individuals with type 1 diabetes are not known. We aimed to determine the excess risk of heart failure in individuals with type 1 diabetes overall and by different levels of glycaemic control and albuminuria.

METHODS

In this prospective case-control study, we identified all individuals with type 1 diabetes registered in the Swedish National Diabetes Registry between Jan 1, 1998, and Dec 31, 2011, and five controls randomly selected from the general population for each patient, matched according to age, sex, and county, and compared them with respect to subsequent hospital admissions for heart failure, with hazard ratios calculated with Cox regression.

FINDINGS

In a cohort of 33 402 patients (mean age at baseline 35 years [SD 14], 15 058 [45%] women, and mean duration of diabetes 20·1 years [SD 14·5]), over a mean follow-up of 7·9 years, 1062 (3%) patients were admitted to hospital with a diagnosis of heart failure, compared with 1325 (1%) of 166 228 matched controls over 8·3 years, giving a HR 4·69 (95% CI 3·64-6·04), after adjustment for time-updated age, sex, time-updated diabetes duration, birth in Sweden, educational level, and baseline comorbidities. Worse glycaemic control was associated with increased risk of heart failure in a graded fashion, and so was the presence of albuminuria. Risk of heart failure was also increased among those with well controlled diabetes (adjusted HR 2·16 [95% CI 1·55-3·01]) and in those with no albuminuria (3·38 [2·51-4·57]), but not in the subgroup both well-controlled and with normoalbuminuria (1·59 [0·70-3·58]).

INTERPRETATION

Individuals with type 1 diabetes had a four-times increase in the risk of being admitted to hospital with heart failure compared with population-based controls. Poor glycaemic control and impaired renal function substantially increased the risk of heart failure.

FUNDING

The Swedish state, Swedish Society for Physicians, the Health & Medical Care Committee of the Regional Executive Board (Region Vastra Gotaland, Sweden), the Swedish Heart-Lung Foundation, Diabetes Wellness, Novo Nordisk Foundation (PI M Lind), the Swedish Research Council, and the Swedish Council for working life and social research (Epilife).

cAMP-dependent Protein Kinase (PKA) Signaling Is Impaired in the Diabetic Heart

Diabetes mellitus causes cardiac dysfunction and heart failure that is associated with metabolic abnormalities and autonomic impairment. Autonomic control of ventricular function occurs through regulation of cAMP-dependent protein kinase (PKA). The diabetic heart has suppressed β-adrenergic responsiveness, partly attributable to receptor changes, yet little is known about how PKA signaling is directly affected. Control and streptozotocin-induced diabetic mice were therefore administered 8-bromo-cAMP (8Br-cAMP) acutely to activate PKA in a receptor-independent manner, and cardiac hemodynamic function and PKA signaling were evaluated. In response to 8Br-cAMP treatment, diabetic mice had impaired inotropic and lusitropic responses, thus demonstrating postreceptor defects. This impaired signaling was mediated by reduced PKA activity and PKA catalytic subunit content in the cytoplasm and myofilaments. Compartment-specific loss of PKA was reflected by reduced phosphorylation of discrete substrates. In response to 8Br-cAMP treatment, the glycolytic activator PFK-2 was robustly phosphorylated in control animals but not diabetics. Control adult cardiomyocytes cultured in lipid-supplemented media developed similar changes in PKA signaling, suggesting that lipotoxicity is a contributor to diabetes-induced β-adrenergic signaling dysfunction. This work demonstrates that PKA signaling is impaired in diabetes and suggests that treating hyperlipidemia is vital for proper cardiac signaling and function.

Subclinical diastolic dysfunction in young adults with Type 2 diabetes mellitus: a multiparametric contrast-enhanced cardiovascular magnetic resonance pilot study assessing potential mechanisms

AIMS

To assess the cardiac, vascular, anthropometric, and biochemical determinants of subclinical diastolic dysfunction in younger adults with Type 2 diabetes mellitus (T2DM) using multiparametric contrast-enhanced cardiovascular magnetic resonance (CMR) imaging.

METHODS AND RESULTS

Twenty adults <40 years with T2DM [mean age 31.8(6.6) years, T2DM duration 4.7(4.0) years] and 20 age and sex-matched controls [10 obese non-diabetic controls and 10 lean controls (LC)] were studied. Cardiac volumes and function, circumferential strain and peak early diastolic strain rate (PEDSR), myocardial perfusion reserve, aortic stiffness (distensibility, pulse-wave velocity), focal fibrosis on late gadolinium enhancement, and pre- and post-contrast T1 mapping for contrast agent partition coefficient (subset, n = 26) were determined by CMR. In the T2DM cohort, mean aortic distensibility correlated with PEDSR (r = 0.564, P = 0.023) and diabetes duration correlated inversely with PEDSR (r = -0.534, P = 0.015) on univariate analysis. There was a close association between PEDSR and peak systolic strain (r = -0.580, P = 0.007).

CONCLUSION

In young adults with T2DM, diabetes duration and aortic distensibility were associated with diastolic dysfunction. Interventional studies are required to assess whether cardiac dysfunction can be reversed in this phenotype of patients.

Molecular Mechanisms of Retinoid Receptors in Diabetes-Induced Cardiac Remodeling

Diabetic cardiomyopathy (DCM), a significant contributor to morbidity and mortality in diabetic patients, is characterized by ventricular dysfunction, in the absence of coronary atherosclerosis and hypertension. There is no specific therapeutic strategy to effectively treat patients with DCM, due to a lack of a mechanistic understanding of the disease process. Retinoic acid, the active metabolite of vitamin A, is involved in a wide range of biological processes, through binding and activation of nuclear receptors: retinoic acid receptors (RAR) and retinoid X receptors (RXR). RAR/RXR-mediated signaling has been implicated in the regulation of glucose and lipid metabolism. Recently, it has been reported that activation of RAR/RXR has an important role in preventing the development of diabetic cardiomyopathy, through improving cardiac insulin resistance, inhibition of intracellular oxidative stress, NF-κB-mediated inflammatory responses and the renin-angiotensin system. Moreover, downregulated RAR/RXR signaling has been demonstrated in diabetic myocardium, suggesting that impaired RAR/RXR signaling may be a trigger to accelerate diabetes-induced development of DCM. Understanding the molecular mechanisms of retinoid receptors in the regulation of cardiac metabolism and remodeling under diabetic conditions is important in providing the impetus for generating novel therapeutic approaches for the prevention and treatment of diabetes-induced cardiac complications and heart failure.

The relationships between cardiovascular disease and diabetes: focus on pathogenesis

There is a looming global epidemic of obesity and diabetes. Of all the end-organ effects caused by diabetes, the cardiovascular system is particularly susceptible to the biologic perturbations caused by this disease, and many patients may die from diabetes-related cardiovascular complications. Substantial progress has been made in understanding the pathobiology of the diabetic vasculature and heart. Clinical studies have illuminated the optimal way to treat patients with cardiovascular manifestations of this disease. This article reviews these aspects of diabetes and the cardiovascular system, broadly classified into diabetic vascular disease, diabetic cardiomyopathy, and the clinical management of the diabetic cardiovascular disease patient.

Vascular imaging in diabetes

Diabetes is a global epidemic affecting individuals of all socioeconomic backgrounds. Despite intensive efforts, morbidity and mortality secondary to the micro- and macrovascular complications remain unacceptably high. As a result, the use of imaging modalities to determine the underlying pathophysiology, early onset of complications, and disease progression has become an integral component of the management of such individuals. Echocardiography, stress echocardiography, and nuclear imaging have been the mainstay of noninvasive cardiovascular imaging tools to detect myocardial ischemia, but newer modalities such as cardiac MRI, cardiac CT, and PET imaging provide incremental information not available with standard imaging. While vascular imaging to detect cerebrovascular and peripheral arterial disease non-invasively has traditionally used ultrasound, CT- and MRI-based techniques are increasingly being employed. In this review, we will provide an outline of recent studies utilizing non-invasive imaging techniques to assist in disease diagnosis as well as monitoring disease progression. In addition, we will review the evidence for newer modalities such as MR spectroscopy, 3D intravascular ultrasound, and optical coherence tomography that provide exquisite detail of metabolic function and coronary anatomy not available with standard imaging, but that have not yet become mainstream.

Sex, sex steroids, and diabetic cardiomyopathy: making the case for experimental focus

More than three decades ago, the Framingham study revealed that cardiovascular risk is elevated for all diabetics and that this jeopardy is substantially accentuated for women in particular. Numerous studies have subsequently documented worsened cardiac outcomes for women. Given that estrogen and insulin exert major regulatory effects through common intracellular signaling pathways prominent in maintenance of cardiomyocyte function, a sex-hormone:diabetic-disease interaction is plausible. Underlying aspects of female cardiovascular pathophysiology that exaggerate cardiovascular diabetic risk may be identified, including increased vulnerability to coronary microvascular disease, age-dependent impairment of insulin-sensitivity, and differential susceptibility to hyperglycemia. Since Framingham, considerable progress has been made in the development of experimental models of diabetic disease states, including a diversity of genetic rodent models. Ample evidence indicates that animal models of both type 1 and 2 diabetes variably recapitulate aspects of diabetic cardiomyopathy including diastolic and systolic dysfunction, and cardiac structural pathology including fibrosis, loss of compliance, and in some instances ventricular hypertrophy. Perplexingly, little of this work has explored the relevance and mechanisms of sexual dimorphism in diabetic cardiomyopathy. Only a small number of experimental studies have addressed this question, yet the prospects for gaining important mechanistic insights from further experimental enquiry are considerable. The case for experimental interrogation of sex differences, and of sex steroid influences in the aetiology of diabetic cardiomyopathy, is particularly compelling-providing incentive for future investigation with ultimate therapeutic potential.

Depressed calcium-handling proteins due to endoplasmic reticulum stress and apoptosis in the diabetic heart are attenuated by argirein

Diabetic cardiomyopathy (DC) is a unique disease frequently complicated to diabetes mellitus, manifesting endoplasmic reticulum (ER) stress and depressed calcium-handling proteins. We hypothesized that the abnormal FKBP12.6, SERCA2a, and CASQ2 are consequent to ER stress and apoptosis that are likely due to an entity of inflammation. These abnormalities may be attributed to reactive oxygen species genesis from activated NADPH oxidase which could respond to argirein (AR) through its anti-inflammatory activity. Sprague Dawley rats were randomly divided into six groups. Except the normal group, rats were injected with streptozotocin (STZ; 60 mg/kg, i.p.) once. During weeks 5 to 8 following STZ injection, rats were treated (in milligrams per kilogram per day, i.g.) with aminoguanidine (AMG, 100; an inducible nitric oxide synthase and AGEs inhibitor) or three doses of AR (50, 100, and 200). FKBP12.6, SERCA2a, and CASQ2 and ER stress chaperones Bip and PERK and apoptotic molecules were monitored in vivo and in vitro. Impaired cardiac performance and downregulated FKBP12.6, SERCA2a, and CASQ2 were significant in DC in vivo, and abnormal calcium-handling proteins were also found in high-glucose-incubated myocytes in vitro. ER stress manifested by upregulated Bip and PERK was predominant in association with DNA ladder and upregulated Bax and downregulated BCL-2 in vivo and in vitro. AR is effective to attenuate these abnormalities compared to AMG. Diabetic myocardium has inflammatory entity expressed as ER stress contributing to downregulated calcium-handling proteins. AR has potential in managing DC through attenuating depressed calcium-handling proteins, activated ER stress, and apoptosis in the myocardium.