Estrogen-Dependent Disruption of Adiponectin-Connexin43 Signaling Underlies Exacerbated Myocardial Dysfunction in Diabetic Female Rats

Estrogen replacement restores period 2-mediated inhibition of ferroptosis and mitigates cardiac dysfunction in estrogen-deficient rats

The ovarian hormone 17β-estradiol (E2) confers cardioprotection via upregulating cardiac circadian rhythm period 2 (Per2) and is associated cardioprotective microRNA (miRNAs). However, whether Per2-mediated downregulation of ferroptosis-induced oxidative stress and injury in noncardiac tissues extends to the heart remains unknown. Therefore, studying the interplay between E2 and cardiac ferroptosis will have important ramifications for female cardiovascular health. We hypothesized that Per2-mediated suppression of cardiac ferroptosis contributes to E2-dependent cardioprotection while E2 deficiency promotes ferroptosis and cardiac dysfunction in female rats. The study used Sprague-Dawley rats with sham operation (sham), bilateral ovariectomy (E2-deficient) followed by E2 or vehicle treatment for 8 weeks. Cardiovascular function was assessed via radiotelemetry and echocardiography, with ex vivo analyses of ferroptosis markers, Per2, and associated miRNAs in heart tissues. E2-replete (sham and ovariectomy + E2) rats showed lower body weight gain, heart weight/body weight ratio, fat mass, and blood pressure compared with E2-deficient rats. Echocardiography data revealed reduced contractility indices in E2-deficient rats, which were restored to sham levels with E2 treatment. Molecular analyses revealed that E2-treated E2-deficient rats had upregulated Per2, cardioprotective miRNAs (499, 192, 194, and 144), and improved redox balance, along with decreased cardiodetrimental miRNAs (652 and 208b) and reactive oxygen species. In E2-deficient rats, glutathione depletion led to reduced glutathione peroxidase-4, iron overload from heme oxygenase-1 upregulation, and increased lipid peroxidation. This study highlights possible contribution of Per2-mediated inhibition of ferroptosis to E2-mediated cardioprotection in females, offering new insights for women's heart health. SIGNIFICANCE STATEMENT: This study describes the contribution of estrogen-mediated upregulation of cardiac circadian clock protein Per2 to the inhibition of ferroptosis and the improvement of cardiac function. The findings offer new perspective for understanding the intersection between hormonal regulation, circadian clock protein, microRNA, and ferroptosis in cardiovascular health. The research adds new knowledge on female molecular cardiology, particularly those related to ferroptosis. This perspective broadens current understanding of the complex molecular underpinnings of female heart health in presence or absence of estrogen.

Diabesity alters the protective effects of estrogens on endothelial function through adipose tissue secretome

Estrogens have a well-known protective role in the development of the metabolic syndrome. Nevertheless, recent epidemiological data question the cardioprotective effect of estrogens in obese and diabetic women. In this context, white adipose tissue (WAT) becomes dysfunctional, which has an impact on the cardiovascular system. The aim of the study was to elucidate the role of 17β-estradiol (E2) in the interplay between adipose tissue and endothelial function in an animal model of diabesity. We used ZDF (fa/fa) female rats subjected to ovariectomy (OVA), OVA + E2 or sham operated, as well as non-obese non-diabetic ZDF (fa/+) rats. Endothelial function and vascular remodeling markers were assessed in the aorta, while mitochondrial function, oxidative stress, and adiponectin production were analyzed in gonadal WAT. Conditioned media from gonadal WAT explants were used to assess the effects of WAT secretome on HUVEC. Additionally, the adiponectin receptor agonist AdipoRON and E2 were utilized to examine potential interactions. Ovariectomy ameliorated the WAT dysfunction associated to the obese and diabetic state and promoted adiponectin secretion, effects that were linked to a reduction of endothelial dysfunction and inflammatory markers in the aorta of OVA rats and in HUVEC treated with OVA-conditioned media. Our findings provide evidence supporting the idea that in the context of obesity and diabetes, ovariectomy improves WAT secretome and positively impacts endothelial function, suggesting a detrimental role for E2. Additionally, our results point to adiponectin as the primary driver of the effects exerted by ovariectomy on the adipovascular axis.

Potential clinical biomarkers and perspectives in diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a serious cardiovascular complication and the leading cause of death in diabetic patients. Patients typically do not experience any symptoms and have normal systolic and diastolic cardiac functions in the early stages of DCM. Because the majority of cardiac tissue has already been destroyed by the time DCM is detected, research must be conducted on biomarkers for early DCM, early diagnosis of DCM patients, and early symptomatic management to minimize mortality rates among DCM patients. Most of the existing implemented clinical markers are not very specific for DCM, especially in the early stages of DCM. Recent studies have shown that a number of new novel markers, such as galactin-3 (Gal-3), adiponectin (APN), and irisin, have significant changes in the clinical course of the various stages of DCM, suggesting that we may have a positive effect on the identification of DCM. As a summary of the current state of knowledge regarding DCM biomarkers, this review aims to inspire new ideas for identifying clinical markers and related pathophysiologic mechanisms that could be used in the early diagnosis and treatment of DCM.

Cellular mechanisms and molecular pathways linking bitter taste receptor signalling to cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction in heart diseases

Heart diseases and related complications constitute a leading cause of death and socioeconomic threat worldwide. Despite intense efforts and research on the pathogenetic mechanisms of these diseases, the underlying cellular and molecular mechanisms are yet to be completely understood. Several lines of evidence indicate a critical role of inflammatory and oxidative stress responses in the development and progression of heart diseases. Nevertheless, the molecular machinery that drives cardiac inflammation and oxidative stress is not completely known. Recent data suggest an important role of cardiac bitter taste receptors (TAS2Rs) in the pathogenetic mechanism of heart diseases. Independent groups of researchers have demonstrated a central role of TAS2Rs in mediating inflammatory, oxidative stress responses, autophagy, impulse generation/propagation and contractile activities in the heart, suggesting that dysfunctional TAS2R signalling may predispose to cardiac inflammatory and oxidative stress disorders, characterised by contractile dysfunction and arrhythmia. Moreover, cardiac TAS2Rs act as gateway surveillance units that monitor and detect toxigenic or pathogenic molecules, including microbial components, and initiate responses that ultimately culminate in protection of the host against the aggression. Unfortunately, however, the molecular mechanisms that link TAS2R sensing of the cardiac milieu to inflammatory and oxidative stress responses are not clearly known. Therefore, we sought to review the possible role of TAS2R signalling in the pathophysiology of cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction in heart diseases. Potential therapeutic significance of targeting TAS2R or its downstream signalling molecules in cardiac inflammation, oxidative stress, arrhythmia and contractile dysfunction is also discussed.

Heart Failure in Menopause: Treatment and New Approaches

Aging is an important risk factor for the development of heart failure (HF) and half of patients with HF have preserved ejection fraction (HFpEF) which is more common in elderly women. In general, sex differences that lead to discrepancies in risk factors and to the development of cardiovascular disease (CVD) have been attributed to the reduced level of circulating estrogen during menopause. Estrogen receptors adaptively modulate fibrotic, apoptotic, inflammatory processes and calcium homeostasis, factors that are directly involved in the HFpEF. Therefore, during menopause, estrogen depletion reduces the cardioprotection. Preclinical menopause models demonstrated that several signaling pathways and organ systems are closely involved in the development of HFpEF, including dysregulation of the renin-angiotensin system (RAS), chronic inflammatory process and alteration in the sympathetic nervous system. Thus, this review explores thealterations observed in the condition of HFpEF induced by menopause and the therapeutic targets with potential to interfere with the disease progress.

Does Myocardial Atrophy Represent Anti-Arrhythmic Phenotype?

This review focuses on cardiac atrophy resulting from mechanical or metabolic unloading due to various conditions, describing some mechanisms and discussing possible strategies or interventions to prevent, attenuate or reverse myocardial atrophy. An improved awareness of these conditions and an increased focus on the identification of mechanisms and therapeutic targets may facilitate the development of the effective treatment or reversion for cardiac atrophy. It appears that a decrement in the left ventricular mass itself may be the central component in cardiac deconditioning, which avoids the occurrence of life-threatening arrhythmias. The depressed myocardial contractility of atrophied myocardium along with the upregulation of electrical coupling protein, connexin43, the maintenance of its topology, and enhanced PKCƐ signalling may be involved in the anti-arrhythmic phenotype. Meanwhile, persistent myocardial atrophy accompanied by oxidative stress and inflammation, as well as extracellular matrix fibrosis, may lead to severe cardiac dysfunction, and heart failure. Data in the literature suggest that the prevention of heart failure via the attenuation or reversion of myocardial atrophy is possible, although this requires further research.

Estrogen Dampens Central Cannabinoid Receptor 1-mediated Neuroexcitation and Pressor Response in Conscious Female Rats

Activation of the rostral ventrolateral medulla (RVLM) cannabinoid receptor-1 (CB₁R) causes nNOS-dependent increases in sympathetic activity, blood pressure (BP) and heart rate (HR) in male rats. However, it remains unknown if the CB₁R-mediated neurochemical and cardiovascular responses are influenced by the ovarian sex hormones, particularly estrogen (E₂). Therefore, we studied the effects of intra-RVLM CB₁R activation (WIN 55,212-2) on BP and HR in conscious female rats under the following hormonal states: (1) highest E₂ level (proestrus sham-operated, SO); (2) E₂-deprivation (ovariectomized, OVX); (3) OVX with E₂ replacement (OVXE2). Intra-RVLM WIN55,212-2 elicited dose (100-400 pmol) dependent pressor and tachycardic responses, in OVX rats, which replicated the reported responses in male rats. However, in SO and OVXE2 rats, the CB₁R-mediated pressor response was attenuated and the tachycardic response reverted to bradycardic response. The neurochemical findings suggested a key role for the upregulated RVLM sympathoexcitatory molecules phosphorated protein kinase B, phosphorated neuronal nitric oxide synthase and reactive oxygen species in the exaggerated CB₁R-mediated BP and HR responses in OVX rats, and an E₂-dependent dampening of these responses. The intra-RVLM WIN55212-2-evoked cardiovascular and neurochemical responses were CB₁R-mediated because they were attenuated by prior CB₁R blockade (AM251). Our findings suggest that attenuation of RVLM neuroexcitation and oxidative stress underlies the protection conferred by E₂, in female rats, against the CB₁R-mediated adverse cardiovascular effects.

Estrogen Impairs Adipose Tissue Expansion and Cardiometabolic Profile in Obese-Diabetic Female Rats

It has been reported that 17β-estradiol (E2) can exert beneficial effects against the development of obesity, providing women with a healthier metabolic profile and conferring cardiovascular protection. However, a growing body of evidence questions this role in the context of obesity and diabetes. We focus on the adipose tissue–heart axis to address the question of whether E2 can have metabolically detrimental effects in an obese-diabetic rat model. Female Zucker Diabetic Fatty rats were used: LEAN, fa/+; SHAM, sham-operated fa/fa; OVA, ovariectomized fa/fa, and OVA+E2, ovariectomized and E2 treated fa/fa. The secretory expression profile, tissue expansion parameters and composition of visceral adipose tissue, as well as systemic and cardiac parameters related to insulin resistance, fibrosis, and inflammation were analyzed. Ovariectomy induced an attenuation of both diabetic condition and metabolic dysfunction of adipose tissue and cardiac muscle in fa/fa rats, suggesting that E2, in the context of diabetes and obesity, loses its cardioprotective role and could even contribute to greater metabolic alterations. Adipose tissue from OVA rats showed a healthier hyperplastic expansion pattern, which could help maintain tissue function, increase adiponectin expression, and decrease pro-inflammatory adipokines. These findings should be taken into account when considering hormone replacement therapy for obese-diabetic women.

Hyperglycemia aggravates monocyte-endothelial adhesion in human umbilical vein endothelial cells from women with gestational diabetes mellitus by inducing Cx43 overexpression

Background

Gestational diabetes mellitus (GDM) is among the most common metabolic diseases during pregnancy and inevitably leads to maternal and fetal complications. Hyperglycemia results in injury to vascular endothelial cells, including monocyte-endothelial adhesion, which is considered to be the initiating factor of vascular endothelial cell injury. Connexin 43 (Cx43) plays a key role in this adhesion process. Therefore, this study aimed to explore the effects of Cx43 on monocyte-endothelial adhesion in GDM-induced injury of vascular endothelial cells.

Methods

Human umbilical vein endothelial cells (HUVECs) were isolated from umbilical cords from pregnant women with and without GDM. THP-1 cells (a human leukemia monocytic cell line) adhering to HUVECs, related molecules [intracellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1)], and the activity of the phosphoinositide 3-kinase/protein kinase B/Nuclear factor- kappa B (PI3K/AKT/NF-κB) signaling pathway were compared between the normal and GDM-HUVECs. Oleamide and specific small interfering ribonucleic acids (siRNAs) were used to inhibit Cx43 expression in GDM-HUVECs to observe the effects of Cx43 on the adhesion of THP-1 cells and HUVECs.

Results

A much higher number of THP-1 cells adhered to GDM-HUVECs than to normal HUVECs. This was accompanied by an increased expression of Cx43, ICAM-1, and VCAM-1, as well as activation of the PI3K/AKT/NF-κB signaling pathway. After the inhibition of Cx43 expression in GDM-HUVECs with oleamide and specific siRNA, THP-1-HUVEC adhesion, ICAM-1 and VCAM-1 expression, and activation of PI3K/AKT/NF-κB signaling pathway were all attenuated. Hyperglycemia was able to increase expression of Cx43 in HUVECs.

Conclusions

For the first time, Cx43 expression was found to be substantially higher in GDM-HUVECs than in normal HUVECs. Hyperglycemia caused the overexpression of Cx43 in HUVECs, which resulted in the activation of the PI3K/AKT/NF-κB signaling pathway and the increase of its downstream adhesion molecules, including ICAM-1 and VCAM-1, ultimately leading to increased monocyte-endothelial adhesion.

Alcohol suppresses cardiovascular diurnal variations in male normotensive rats: Role of reduced PER2 expression and CYP2E1 hyperactivity in the heart

BACKGROUND AND AIMS

The molecular mechanism of the adverse effects of ethanol on diurnal cardiovascular regulation remains unknown. In separate studies, the cardiac circadian rhythm protein period-2 (PER2) confers cardioprotection and, in other organs, PER2 interaction with the ethanol-metabolizing enzyme CYP2E1 underlies, via heme oxygenase-1 (HO-1) upregulation, tissue injury/dysfunction. Here, we hypothesized that suppressed PER2 expression and elevated CYP2E1/HO-1 levels in the heart underlie the disrupted diurnal cardiovascular rhythm/function in alcohol-fed normotensive rats.

METHODS

In ethanol-fed (5%, w/v; 8 weeks) or isocaloric liquid diet-fed male rats, diurnal changes in blood pressure (BP), heart rate (HR), HR vagal variability index, root mean square of successive beat-to-beat differences in beat-interval duration (rMSSD), and cardiac function were measured by radiotelemetry and echocardiography followed by ex vivo molecular studies.

RESULTS

Radiotelemetry findings showed ethanol-evoked reductions in BP (during the dark cycle), rMSSD (during both cycles), and in diurnal differences in BP and rMSSD. Echocardiography findings revealed significant (p < 0.05) reductions in ejection fraction and fractional shortening (weeks 4-6) in the absence of cardiac remodeling (collagen content). Hearts of ethanol-fed rats exhibited higher (p < 0.05) CYP2E1 activity (50%) and HO-1 expression (63%), along with reduction (p < 0.05) in PER2 levels (29%), compared with the hearts of isocaloric diet-fed control rats.

CONCLUSIONS

Our novel findings implicate upregulations of CYP2E1/HO-1 and downregulation of the circadian rhythm cardioprotective protein PER2, in the heart, in the chronic deleterious diurnal cardiovascular effects of alcohol in male rats.

Estrogen-dependent hypersensitivity to diabetes-evoked cardiac autonomic dysregulation: Role of hypothalamic neuroinflammation

AIMS

To investigate if autonomic dysregulation is exacerbated in female rats, subjected to diabetes mellitus (DM), via a paradoxical estrogen (E2)-evoked provocation of neuroinflammation/injury of the hypothalamic paraventricular nucleus (PVN).

MAIN METHODS

We measured cardiac autonomic function and conducted subsequent PVN neurochemical studies, in DM rats, and their respective controls, divided as follows: male, sham operated (SO), ovariectomized (OVX), and OVX with E2 supplementation (OVX/E2).

KEY FINDINGS

Autonomic dysregulation, expressed as sympathetic dominance (higher low frequency, LF, band), only occurred in DM E2-replete (SO and OVX/E2) rats, and was associated with higher neuronal activity (c-Fos) and higher levels of TNFα and phosphorylated death associated protein kinase-3 (p-DAPK3) in the PVN. These proinflammatory molecules likely contributed to the heightened PVN oxidative stress, injury and apoptosis. The PVN of these E2-replete DM rats also exhibited upregulations of estrogen receptors, ERα and ERβ, and proinflammatory adenosine A1 and A2a receptors.

SIGNIFICANCE

The E2-dependent autonomic dysregulation likely predisposes DM female rats and women to hypersensitivity to cardiac dysfunction. Further, upregulations of proinflammatory mediators including adenosine A1 and A2 receptors, TNFα and DAPK3, conceivably explain the paradoxical hypersensitivity of DM females to PVN inflammation/injury and the subsequent autonomic dysregulation in the presence of E2.

Restoration of Adiponectin-Connexin43 Signaling Mitigates Myocardial Inflammation and Dysfunction in Diabetic Female Rats

ur preclinical findings replicated women's hypersensitivity to type-2 diabetes mellitus (T2DM)-evoked cardiac dysfunction along with demonstrating estrogen (E2)-dependent disruption of the cardiac adiponectin (APN)-connexin43 (Cx43) signaling. Whether the latter molecular anomaly underlies this women's cardiovascular health problem remains unknown. We hypothesized that restoration of the disrupted APN-Cx43 signaling alleviates this sex/E2-dependent cardiac dysfunction in diabetic female rats. To test this hypothesis, we administered the adiponectin receptor 1 (AdipoR1) agonist AdipoRon (30 mg/kg/d for 10 days) to female sham operated (SO) and ovariectomized (OVX) rats, which exhibited and lacked the T2DM left ventricular (LV) dysfunction, respectively, when fed high-fat diet and received low dose streptozotocin regimen; nondiabetic control SO and OVX rats received control diet and vehicle for streptozotocin. In T2DM SO rats, LV dysfunction, AdipoRon mitigated: (1) LV hypertrophy, (2) reductions in fractional shortening, LV developed pressure, dP/dtmax, dP/dtmin, and Tau. In LV tissues of the same rats, AdipoRon reversed reduction in Cx43 and elevations in TNFα, heme-oxygenase 1 (HO-1), and circulating cardiovascular risk factor asymmetric dimethylarginine. The findings also revealed ovarian hormones independent effects of AdipoRon, which included dampening of the pro-oxidant enzyme HO-1. These novel findings yield new insight into a causal role for compromised APN-Cx43 signaling in the E2-dependent hypersensitivity to T2DM-evoked cardiac inflammation and dysfunction. Equally important, the findings identify restoration of Cx43 signaling as a viable therapeutic modality for alleviating this women's cardiovascular health-related problem.