Norepinephrine release is reduced in cardiac tissue of Type 2 diabetic patients

Insulin and takotsubo syndrome: plausible pathophysiologic, diagnostic, prognostic, and therapeutic roles

The pathophysiology of takotsubo syndrome (TTS) is elusive. Heightened adrenergic surge via the sympathetic nervous system (mainly by norepinephrine secretion) and/or elevated blood-borne catecholamines (mainly epinephrine, secreted by the adrenals) probably mediate TTS. Patients with TTS have a low prevalence of diabetes mellitus (DM), and it has been postulated that DM, via its associated neuropathy, prevents the emergence of TTS. Insulin, in animal experiments, has been shown to greatly attenuate the effects of NE on the cardiomyocytes; also, insulin in a limited clinical experience, has been found to improve heart function in patients with neurogenic stress-cardiomyopathy and TTS. Accordingly, it is postulated that high levels of insulin encountered in patients with type 2 DM are at the roots of the protective effect of DM for the emergence of TTS. Thus, a role of insulin in the pathophysiology, diagnosis, prognosis, and therapy of TTS appears to be plausible, and needs exploration.

Enhanced Catecholamine Flux and Impaired Carbonyl Metabolism Disrupt Cardiac Mitochondrial Oxidative Phosphorylation in Diabetes Patients

Aims: Catecholamine metabolism via monoamine oxidase (MAO) contributes to cardiac injury in models of ischemia and diabetes, but the pathogenic mechanisms involved are unclear. MAO deaminates norepinephrine (NE) and dopamine to produce H₂O₂ and highly reactive "catecholaldehydes," which may be toxic to mitochondria due to the localization of MAO to the outer mitochondrial membrane. We performed a comprehensive analysis of catecholamine metabolism and its impact on mitochondrial energetics in atrial myocardium obtained from patients with and without type 2 diabetes. Results: Content and maximal activity of MAO-A and MAO-B were higher in the myocardium of patients with diabetes and they were associated with body mass index. Metabolomic analysis of atrial tissue from these patients showed decreased catecholamine levels in the myocardium, supporting an increased flux through MAOs. Catecholaldehyde-modified protein adducts were more abundant in myocardial tissue extracts from patients with diabetes and were confirmed to be MAO dependent. NE treatment suppressed mitochondrial ATP production in permeabilized myofibers from patients with diabetes in an MAO-dependent manner. Aldehyde dehydrogenase (ALDH) activity was substantially decreased in atrial myocardium from these patients, and metabolomics confirmed lower levels of ALDH-catalyzed catecholamine metabolites. Proteomic analysis of catechol-modified proteins in isolated cardiac mitochondria from these patients identified >300 mitochondrial proteins to be potential targets of these unique carbonyls. Innovation and Conclusion: These findings illustrate a unique form of carbonyl toxicity driven by MAO-mediated metabolism of catecholamines, and they reveal pathogenic factors underlying cardiometabolic disease. Importantly, they suggest that pharmacotherapies targeting aldehyde stress and catecholamine metabolism in heart may be beneficial in patients with diabetes and cardiac disease. Antioxid. Redox Signal. 35, 235-251.

Autonomic nervous system in Takotsubo syndrome

Takotsubo syndrome (TTS) is an acute and usually reversible heart failure syndrome with symptoms resembling acute myocardial infarction, however, without obstruction of coronary arteries. In the majority of cases, TTS is preceded by emotional or physical stress and the disease concerns mainly postmenopausal women. Although several hypotheses have been introduced, the pathogenesis of TTS is controversial and still remains to be determined. As reported in recent studies, the role of the autonomic nervous system (ANS) seems to be pivotal in the pathogenesis of TTS. Therefore, the aim of this article is to summarize and discuss the current knowledge of the pathogenesis of TTS with a special focus on the ANS.

Chronic type 2 but not type 1 diabetes impairs myocardial ischaemic tolerance and preconditioning in C57Bl/6 mice

NEW FINDINGS

• What is the central question of this study? What is the impact of chronic adult-onset diabetes on cardiac ischaemic outcomes and preconditioning? • What is the main finding and its importance? Chronic adult-onset type 2 but not type 1 diabetes significantly impairs myocardial ischaemic tolerance and ischaemic preconditioning. Preconditioning may be detrimental in type 2 diabetes, exaggerating nitrosative stress and apoptotic protein expression.

ABSTRACT

Effects of diabetes on myocardial responses to ischaemia-reperfusion (I-R) and cardioprotective stimuli remain contentious, potentially reflecting influences of disease duration and time of onset. Chronic adult-onset type 1 diabetes (T1D) and type 2 diabetes (T2D) were modelled non-genetically in male C57Bl/6 mice via 5 × 50 mg kg^-1 daily streptozotocin (STZ) injections + 12 weeks' standard chow or 1 × 75 mg kg^-1 STZ injection + 12 weeks' obesogenic diet (32% calories as fat, 57% carbohydrate, 11% protein), respectively. Systemic outcomes were assessed and myocardial responses to I-R ± ischaemic preconditioning (IPC; 3 × 5 min I-R) determined in Langendorff perfused hearts. Uncontrolled T1D was characterised by pronounced hyperglycaemia (25 mm fasting glucose), glucose intolerance and ∼10% body weight loss, whereas T2D mice exhibited moderate hyperglycaemia (15 mm), hyperinsulinaemia, glucose intolerance and 17% weight gain. Circulating ghrelin, resistin and noradrenaline were unchanged with T1D, while leptin increased and noradrenaline declined in T2D mice. Ischaemic tolerance and IPC were preserved in T1D hearts. In contrast, T2D worsened post-ischaemic function (∼40% greater diastolic and contractile dysfunction) and cell death (100% higher troponin efflux), and abolished IPC protection. Whereas IPC reduced post-ischaemic nitrotyrosine and pro-apoptotic Bak and Bax levels in non-diabetic hearts, these effects were reduced in T1D and IPC augmented Bax and nitrosylation in T2D hearts. The data demonstrate chronic T1D does not inhibit myocardial I-R tolerance or IPC, whereas metabolic and endocrine disruption in T2D is associated with ischaemic intolerance and inhibition of IPC. Indeed, normally protective IPC may exaggerate damage mechanisms in T2D hearts.

Prevalence and Prognostic Impact of Diabetes in Takotsubo Syndrome: Insights From the International, Multicenter GEIST Registry

OBJECTIVE

In view of low prevalence rates, diabetes is discussed as a protective factor for the occurrence of Takotsubo syndrome (TTS). Furthermore, it was associated with improved outcome in a small single-center analysis. Therefore, this study assessed the prevalence and prognostic relevance of concomitant diabetes in TTS.

RESEARCH DESIGN AND METHODS

A total of 826 patients with TTS were enrolled in an international, multicenter, registry-based study (eight centers in Italy and Germany). All-cause mortality was compared between patients with diabetes and patients without diabetes, and the independent predictive value of diabetes was evaluated in multivariate regression analysis.

RESULTS

The prevalence of diabetes was 21.1% (n = 174). TTS patients with diabetes were older (P < 0.001), were more frequently male (P = 0.003), had a higher prevalence of hypertension (P < 0.001), physical triggers (P = 0.041), and typical apical ballooning (P = 0.010), had a lower left ventricular ejection fraction (P = 0.008), had a higher rate of pulmonary edema (P = 0.032), and had a longer hospital stay (P = 0.009). However, 28-day all-cause mortality did not differ between patients with diabetes and patients without diabetes (6.4% vs. 5.7%; hazard ratio [HR] 1.11 [95% CI 0.55-2.25]; P = 0.772). Longer-term follow-up after a median of 2.5 years revealed a significantly higher mortality among TTS patients with diabetes (31.4% vs. 16.5%; P < 0.001), and multivariate regression analysis identified diabetes as an independent predictor of adverse outcome (HR 1.66 [95% CI 1.16-2.39]; P = 0.006).

CONCLUSIONS

Diabetes is not uncommon in patients with TTS, is associated with increased longer-term mortality rates, and is an independent predictor of adverse outcome irrespective of additional risk factors.

Diabetes mellitus prevalence in patients with takotsubo syndrome: the case of the brain-heart disconnect

BACKGROUND

Hyperactive autonomic nervous system (ANS) is among the postulated pathophysiologic mechanisms of takotsubo syndrome (TTS). Diabetes mellitus (DM) with its associated ANS peripheral neuropathy could exert a "protective" influence for the emergence of TTS.

METHODS

A patient-based meta-analysis of the data obtained from all patients presented individually was carried out, focusing on age, gender, and history of hypertension (HTN) and DM.

RESULTS

The prevalences of HTN and DM for all 2,342 patients, aged 61.1 ± 17.3, 85.1% female, were 37.4% and 9.5%, for patients ≥ 60 years old were 45.8% and 11.7%, and for patients ≥65 years old were 48.2% and 12.3%, correspondingly. The prevalence of DM in patients with TTS is less than half of the world's and USA's elderly populations.

CONCLUSIONS

Prevalence of DM in patients with TTS is lower than in the general population, suggesting that DM, may have a "protective" effect for the emergence of TTS.

Low prevalence of diabetes mellitus in patients with Takotsubo syndrome: A plausible 'protective' effect with pathophysiologic connotations

AIMS

The pathophysiology of Takotsubo syndrome is still elusive; coronary vasospasm, microvascular dysfunction, or catecholamine-mediated injury to the cardiomyocytes, effected by local release from the autonomic nerves and/or blood-borne catecholamines, are considered as tentative cause(s). Diabetes mellitus-induced autonomic neuropathy leads to a brain-heart disconnection, and it can conceivably ameliorate/block the effect of an unbridled adrenergic storm to the heart, and the emergence of Takotsubo syndrome. This study sought to evaluate the prevalence of diabetes mellitus in patients with Takotsubo syndrome.

METHODS AND RESULTS

All the papers accessed in PubMed were reviewed, to evaluate the prevalence of diabetes mellitus and hypertension in Takotsubo syndrome patients, employing the rate of the latter as an index of how representative of the general population were the study patients, and the rate of the former as the focus of this investigation. Out of the 1932 papers, 959 were suitable for analysis, reporting on 33,894 patients (88.9% women) with Takotsubo syndrome. In five subanalyses, of all patients, patients reported individually, patients reported collectively in case series, patients ⩾ 60 years old reported individually, and patients ⩾ 65 years old reported individually, the prevalence of hypertension was 57.4%, 42.8%, 57.9%, 50.4%, and 52.2%, correspondingly, and comparable to the 65.4% shown by the National Health and Nutrition Examination Survey (NHANES). The prevalence of diabetes mellitus in the five subgroups was 16.8%, 10.2%, 17.0%, 11.9%, and 12.5%, correspondingly, and lower than the 26.9% found by the NHANES.

CONCLUSION

The prevalence of diabetes mellitus in patients with Takotsubo syndrome is low. This insight may be useful for the diagnosis, pathophysiology unraveling, and employment of autonomic adrenergic blocking agents in the management of patients with Takotsubo syndrome.

Impairment of Presynaptic ??2-Adrenoceptor-Regulated Norepinephrine Overflow in Failing Hearts from Zucker Diabetic Fatty Rats

The aim of this study was to assess whether cardiac norepinephrine overflow is affected in Type 2 diabetes mellitus. Homozygous (fa/fa) Zucker diabetic fatty (ZDF) rats were used as a model of Type 2 diabetes; heterozygous (fa/+) ZDF rats served as non-diabetic controls. Cardiac performance was determined in isolated working hearts; release of endogenous norepinephrine was induced by electrical field stimulation in Langendorff-perfused hearts. At a mean age of 30 weeks, left ventricular contraction, relaxation, and developed pressure were reduced by 20% to 35% in ZDF-fa/fa rats compared with ZDF-fa/+ rats. Stepwise increase of stimulation frequency gradually increased norepinephrine overflow in isolated hearts from both rat strains. Compared to ZDF-fa/+ rats, cardiac norepinephrine overflow was suppressed by 25% to 45% in ZDF-fa/fa rats. During presynaptic alpha2-adrenoceptor blockade with rauwolscine, increase of norepinephrine overflow was significantly higher in ZDF-fa/fa rats than in ZDF-fa/+ rats whereas alpha2-adrenoceptor activation with UK 14,304 suppressed norepinephrine overflow solely in ZDF-fa/+ rats. Myocardial tissue content of norepinephrine did not differ markedly between the two groups. In conclusion, cardiac norepinephrine overflow is inhibited in failing hearts from ZDF-fa/fa rats. This inhibition may result from a hyperactive status of presynaptic alpha2-adrenoceptors.