Regulation of cardiac miR-208a, an inducer of obesity, by rapamycin and nebivolol

miRNA and leptin signaling in metabolic diseases and at extreme environments

The burden of growing concern about the dysregulation of metabolic processes arises due to complex interplay between environment and nutrition that has great impact on genetics and epigenetics of an individual. Thereby, any abnormality at the level of food intake regulating hormones may contribute to the development of metabolic diseases in any age group due to malnutrition, overweight, changing lifestyle, and exposure to extreme environments such as heat stress (HS), cold stress, or high altitude (HA). Hormones such as leptin, adiponectin, ghrelin, and cholecystokinin regulate appetite and satiety to maintain energy homeostasis. Leptin, an adipokine and a pleiotropic hormone, play major role in regulating the food intake, energy gain and energy expenditure. Using in silico approach, we have identified the major genes (LEP, LEPR, JAK2, STAT3, NPY, POMC, IRS1, SOCS3) that play crucial role in leptin signaling pathway. Further, eight miRNAs (hsa-miR-204-5p, hsa-miR-211-5p, hsa-miR-30, hsa-miR-3163, hsa-miR-33a-3p, hsa-miR-548, hsa-miR-561-3p, hsa-miR-7856-5p) from TargetScan 8.0 database were screened out that commonly target these genes. The role of these miRNAs should be explored as they might play vital role in regulating the appetite, energy metabolism, metabolic diseases (obesity, type 2 diabetes, cardiovascular diseases, inflammation), and to combat extreme environments. The miRNAs regulating leptin signaling and appetite may be useful for developing novel therapeutics for metabolic diseases.

Comparison of the Protective Effects of Nebivolol and Metoprolol against LPS-Induced Injury in H9c2 Cardiomyoblasts

Here, we, for the first time, compared the cardioprotective effects of third-generation vasodilating beta-blocker nebivolol (Neb) and conventional beta-blocker metoprolol (Met) on LPS-induced injury in H9c2 cardiomyoblasts. Our findings denoted that Neb and Met pretreatment diminish LPS-mediated cytotoxicity and oxidative stress. Concomitantly, LPS-triggered inflammatory cytokines activation was significantly suppressed by Neb but not by Met. Pretreatment with either Neb or Met alleviated LPS-mediated mitochondrial impairment by enhancing the expression of genes related to its biogenesis such as PGC-1α, NRF1, and TFAM. On the contrary, Neb but not Met-upregulated mitochondrial fusion-related genes such as OPA, and MFN2. In summary, our findings suggest that Neb and Met treatment significantly ameliorated the LPS-induced cytotoxicity and oxidative stress. Additionally, these findings suggest that Neb but not Met significantly down-regulates LPS-induced proinflammatory factors, probably by enhancing mitochondrial biogenesis and fusion.

A role for misaligned gene expression of fetal gene program in the loss of female-specific cardiovascular protection in young obese and diabetic females

Healthy, premenopausal women have the advantage of female-specific cardiovascular protection compared to age-matched healthy men. However, pathologies such as obesity and Type 2 diabetes mellitus (T2DM) cause losing of this female-specific cardiovascular protection in young, obese and diabetic females. Molecular mechanisms underlying this loss of female-specific cardiovascular protection in young, obese and diabetic females are not clearly elucidated. This review takes a close look at the latest advances in our understanding of sex differences in adult cardiac gene expression patterns in health and disease. Based on the emerging data, this review proposes that female biased gene expression patterns in healthy adult hearts of human and pre-clinical models support the existence of active fetal gene program in healthy, premenopausal female heart compared to age-matched healthy male heart. However, the misalignment of gene expression pattern in this female-specific active cardiac fetal gene program caused by pathologies such as obesity and T2DM may contribute to the loss of female-specific cardiovascular protection in young, obese and diabetic females.

Inhibition of eNOS Partially Blunts the Beneficial Effects of Nebivolol on Angiotensin II-Induced Signaling in H9c2 Cardiomyoblasts

We have recently illustrated that nebivolol can inhibit angiotensin II (Ang II)-mediated signaling in cardiomyoblasts; however, to date, the detailed mechanism for the beneficial effects of nebivolol has not been studied. Here, we investigated whether the inhibition of NO bioavailability by blocking eNOS (endothelial nitric oxide synthase) using L-NG-nitroarginine methyl ester (L-NAME) would attenuate nebivolol-mediated favorable effects on Ang II-evoked signaling in H9c2 cardiomyoblasts. Our data reveal that the nebivolol-mediated antagonistic effects on Ang II-induced oxidative stress were retreated by concurrent pretreatment with L-NAME and nebivolol. Similarly, the expressions of pro-inflammatory markers TNF-α and iNOS stimulated by Ang II were not decreased with the combination of nebivolol plus L-NAME. In contrast, the nebivolol-induced reduction in the Ang II-triggered mTORC1 pathway and the mRNA levels of hypertrophic markers ANP, BNP, and β-MHC were not reversed with the addition of L-NAME to nebivolol. In compliance with these data, the inhibition of eNOS by L-N⁵-(1-Iminoethyl) ornithine (LNIO) and its upstream regulator AMP-activated kinase (AMPK) with compound C in the presence of nebivolol showed effects similar to those of the L-NAME plus nebivolol combination on Ang II-mediated signaling. Pretreatment with either compound C plus nebivolol or LNIO plus nebivolol showed similar effects to those of the L-NAME plus nebivolol combination on Ang II-mediated signaling. In conclusion, our data indicate that the rise in NO bioavailability caused by nebivolol via the stimulation of AMPK/eNOS signaling is key for its anti-inflammatory and antioxidant properties but not for its antihypertrophic response upon Ang II stimulation.

miR-208a in Cardiac Hypertrophy and Remodeling

Various stresses, including pressure overload and myocardial stretch, can trigger cardiac remodeling and result in heart diseases. The disorders are associated with high risk of morbidity and mortality and are among the major health problems in the world. MicroRNAs, a class of ~22nt-long small non-coding RNAs, have been found to participate in regulating heart development and function. One of them, miR-208a, a cardiac-specific microRNA, plays key role(s) in modulating gene expression in the heart, and is involved in a broad array of processes in cardiac pathogenesis. Genetic deletion or pharmacological inhibition of miR-208a in rodents attenuated stress-induced cardiac hypertrophy and remodeling. Transgenic expression of miR-208a in the heart was sufficient to cause hypertrophic growth of cardiomyocytes. miR-208a is also a key regulator of cardiac conduction system, either deletion or transgenic expression of miR-208a disturbed heart electrophysiology and could induce arrhythmias. In addition, miR-208a appeared to assist in regulating the expression of fast- and slow-twitch myofiber genes in the heart. Notably, this heart-specific miRNA could also modulate the “endocrine” function of cardiac muscle and govern the systemic energy homeostasis in the whole body. Despite of the critical roles, the underlying regulatory networks involving miR-208a are still elusive. Here, we summarize the progress made in understanding the function and mechanisms of this important miRNA in the heart, and propose several topics to be resolved as well as the hypothetical answers. We speculate that miR-208a may play diverse and even opposite roles by being involved in distinct molecular networks depending on the contexts. A deeper understanding of the precise mechanisms of its action under the conditions of cardiac homeostasis and diseases is needed. The clinical implications of miR-208a are also discussed.

Comparative beneficial effects of nebivolol and nebivolol/valsartan combination against mitochondrial dysfunction in angiotensin II-induced pathology in H9c2 cardiomyoblasts

OBJECTIVES

Considering the complementary nature of signalling mechanisms and the therapeutic effects of nebivolol, a β1-adrenoreceptor antagonist, and valsartan, an angiotensin receptor blocker (ARB), here we aimed to investigate whether nebivolol/valsartan combination would complement the cardioprotective effects of nebivolol on angiotensin II (ANG II)-induced pathology in H9c2 cardiomyoblasts.

METHODS

H9c2 cardiomyoblasts were used to investigate the protective effects of nebivolol and nebivolol and valsartan combination against ANG II-induced pathology. Reactive oxygen species (ROS) generation was determined by 2',7'-dichlorofluorescein diacetate (DCFDA) and MitoSOX Red staining. Real-time PCR and immunoblotting were employed to quantify the changes in mRNA and protein expression levels, respectively.

KEY FINDINGS

Our data revealed that pretreatment with nebivolol and nebivolol/valsartan combination significantly reduced ANG II-induced oxidative stress and mTORC1 signalling. Concurrently, ANG II-induced activation of inflammatory cytokines and fetal gene expressions were significantly suppressed by nebivolol and nebivolol/valsartan combination. Pretreatment with nebivolol and nebivolol/valsartan combination alleviated ANG II-induced impairment of mitochondrial biogenesis by restoring the gene expression levels of PGC-1α, TFAM, NRF-1 and SIRT3. Our data further show that nebivolol and nebivolol/valsartan combination mediated up-regulation in mitochondrial biogenesis is accompanied by decrease in ANG II-stimulated mitochondrial ROS generation as well as increase in expression of mitochondrial fusion genes MFN2 and OPA1, indicative of improved mitochondrial dynamics.

SUMMARY

These findings suggest that both nebivolol and nebivolol/valsartan combination exert protective effects on ANG II-induced mitochondrial dysfunction by alleviating its biogenesis and dynamics. Moreover, addition of valsartan to nebivolol do not produce any additive effects compared with nebivolol alone on ANG II-induced cardiac pathology.

Effect of Third-Generation Beta Blockers on Weight Loss in a Population of Overweight-Obese Subjects in a Controlled Dietary Regimen

Background

Overweight and obesity often develop in individuals with genetic susceptibility and concomitant risk factors; however, medications can represent precipitating factors in some cases: evidence suggests that some antihypertensive drugs can adversely affect energy homeostasis and metabolism.

Aim

The primary aim of this study was to investigate whether long-term therapy with a beta blocker impairs weight loss during a period of appropriate personalized hypocaloric diet and standardized physical activity in overweight and obese hypertensive patients in monotherapy and without comorbidities, compared to other antihypertensive drugs and to a control group not taking antihypertensive therapy. Subjects and Methods. We enrolled overweight and obese patients taking antihypertensive drugs; subjects were divided into 3 groups: those taking traditional beta blockers (bB group), those taking third-generation beta blockers (bB-3 group), and those taking other antihypertensive drugs (non-bB group). We also enrolled subjects receiving neither antihypertensive therapy nor other chronic medication in the prior 12 months as controls. All subjects underwent personalized hypocaloric diets for a period of 24 months with monthly follow-up. Anthropometric parameters were measured at enrollment and then monthly after diet prescription. Glucose and lipid values were assessed at baseline and at 12 and 24 months during dietary regimen.

Results

We enrolled a total of 120 overweight and obese patients aged 50.30 ± 1.13 years (mean ± standard deviation) with a mean BMI of 31.79 ± 0.65 kg/m²; 90 were taking antihypertensive drugs (no comorbidity and no polytherapy), while 30 subjects receiving neither antihypertensive therapy nor other chronic medication in the prior 12 months were considered as controls. After 6 months, the percent total weight loss (TWL%) was lower in the bB group (3.62 ± 1.96 versus 5.27 ± 1.76 in the bB-3 group, versus 5.15 ± 1.30 in the non-bB group, and versus 4.70 ± 0.87 in the control group), as well as their BMI. After 24 months, we kept finding the worst result in the bB group (TWL% = 9.22 ± 2.19 versus 12.79 ± 1.72 in the non-bB group and 12.28 ± 1.97 in the control group) with the best trend in the bB-3 group (TWL% = 16.19 ± 2.67).

Emerging roles of microRNA-208a in cardiology and reverse cardio-oncology

Cardiovascular diseases (CVDs) and cancer, which are the leading causes of mortality globally, have been viewed as two distinct diseases. However, the fact that cancer and CVDs may coincide has been noted by cardiologists when taking care of patients with CVDs caused by cancer chemotherapy; this entity is designated cardio-oncology. More recently, patients with CVDs have also been found to have increased risk of cancers, termed reverse cardio-oncology. Although reverse cardio-oncology has been highlighted as an important disease state in recent studies, how the diseased heart affects cancer and the potential mediators of the crosstalk between CVDs and cancer are largely unknown. Here, we focus on the roles of cardiac-specific microRNA-208a (miR-208a) in cardiac and cancer biology and explore its essential roles in reverse cardio-oncology. Accumulating evidence has shown that within the heart, increased miR-208a promotes myocardial injury, arrhythmia, cardiac remodeling, and dysfunction and that secreted miR-208a in the circulation may have novel roles in promoting tumor proliferation and invasion. This review, therefore, provides insights into the novel roles of miR-208a in reverse cardio-oncology and strategies to prevent secondary carcinogenesis in patients with early- or late-stage heart failure.

Renin-angiotensin system at the interface of COVID-19 infection

Angiotensin-converting enzyme 2 (ACE2) has been recognized as a potential entry receptor for SARS-CoV-2 infection. Binding of SARS-CoV-2 to ACE2 allows engagement with pulmonary epithelial cells and pulmonary infection with the virus. ACE2 is an essential component of renin-angiotensin system (RAS), and involved in promoting protective effects to counter-regulate angiotensin (Ang) II-induced pathogenesis. The use of angiotensin receptor blockers (ARBs) and ACE inhibitors (ACEIs) was implicitly negated during the early phase of COVID-19 pandemic, considering the role of these antihypertensive agents in enhancing ACE2 expression thereby promoting the susceptibility to SARS-CoV-2. However, no clinical data has supported this assumption, but indeed evidence demonstrates that ACEIs and ARBs, besides their cardioprotective effects in COVID-19 patients with cardiovascular diseases, might also be beneficial in acute lung injuries by preserving the ACE2 function and switching the balance from deleterious ACE/Ang II/AT1 receptor axis towards a protective ACE2/Ang (1-7)/Mas receptor axis.

Potential roles of mediator Complex Subunit 13 in Cardiac Diseases

Mediator complex subunit 13 (MED13, previously known as THRAP1 and TRAP240) is a subunit of the cyclin-dependent kinase 8 (CDK8) kinase module in the eukaryotic mediator complex. MED13 has been known to play critical roles in cell cycle, development, and growth. The purpose of this review is to comprehensively discuss its newly identified potential roles in myocardial energy metabolism and non-metabolic cardiovascular diseases. Evidence indicates that cardiac MED13 mainly participates in the regulation of nuclear receptor signaling, which drives the transcription of genes involved in modulating cardiac and systemic energy homeostasis. MED13 is also associated with several pathological conditions, such as metabolic syndrome and thyroid disease-associated heart failure. Therefore, MED13 constitutes a potential therapeutic target for the regulation of metabolic disorders and other cardiovascular diseases.

Angiotensin II receptor blocker valsartan ameliorates cardiac fibrosis partly by inhibiting miR-21 expression in diabetic nephropathy mice

Cardiac fibrosis with diabetic nephropathy (DN) is one of major diabetic complications. miR-21 and MMP-9 were closely associated with fibrosis diseases. Angiotensin II receptor blockers (ARB) have cardioprotective effects. However, it remains unclear whether miR-21 was involved in the mechanism of cardiac fibrosis with DN by target MMP-9 and ARB ameliorates cardiac fibrosis partly by inhibiting miR-21 expression. In this study, In Situ Hybridization(ISH), RT-PCR, cell transfection, western blotting and laser confocal telescope were used, respectively. ISH showed that miR-21, concentrated in cytoplasmic foci in the proximity of the nucleus, was mainly localized in cardiac fibroblasts and at relatively low levels in cardiomyocytes within cardiac tissue with DN. RT-PCR showed that miR-21 expression was significantly enhanced in cardiac tissue with DN, accompanied by the increase of col-IV, FN, CVF, PVCA, LVMI, HWI and NT-pro-BNP (p < 0.05). Bioinformatics analysis and Luciferase reporter gene assays showed that MMP-9 was a validated target of miR-21. Furthermore, cell transfection experiments showed that miR-21 overexpression directly decreased MMP-9 expression. Interestingly, miR-21 levels in cardiac tissue was positively correlated with ACR (r = -0.870, P = 0.003), whereas, uncorrelated with SBP, HbA1C and T-Cho (p > 0.05). More importantly, ARB can significantly decrease miR-21 expression in cardiac tissue, cardiac fibroblasts and serum. Overall, our results suggested that miR-21 may contribute to the pathogenesis of cardiac fibrosis with DN by target MMP-9, and that miR-21 may be a new possible therapeutic target for ARB in cardiac fibrosis with DN.

Emerging Role of mTOR Signaling-Related miRNAs in Cardiovascular Diseases

Mechanistic/mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase of the phosphoinositide 3-kinase- (PI3K-) related kinase family, elicits a vital role in diverse cellular processes, including cellular growth, proliferation, survival, protein synthesis, autophagy, and metabolism. In the cardiovascular system, the mTOR signaling pathway integrates both intracellular and extracellular signals and serves as a central regulator of both physiological and pathological processes. MicroRNAs (miRs), a class of short noncoding RNA, are an emerging intricate posttranscriptional modulator of critical gene expression for the development and maintenance of homeostasis across a wide array of tissues, including the cardiovascular system. Over the last decade, numerous studies have revealed an interplay between miRNAs and the mTOR signaling circuit in the different cardiovascular pathophysiology, like myocardial infarction, hypertrophy, fibrosis, heart failure, arrhythmia, inflammation, and atherosclerosis. In this review, we provide a comprehensive state of the current knowledge regarding the mechanisms of interactions between the mTOR signaling pathway and miRs. We have also highlighted the latest advances on mTOR-targeted therapy in clinical trials and the new perspective therapeutic strategies with mTOR-targeting miRs in cardiovascular diseases.

Diabetic Cardiomyopathy: Impact of Biological Sex on Disease Development and Molecular Signatures

Diabetic cardiomyopathy refers to a unique set of heart-specific pathological variables induced by hyperglycemia and insulin resistance. Given that cardiovascular disease (CVD) is the leading cause of death in the world, and type 2 diabetes incidence continues to rise, understanding the complex interplay between these two morbidities and developing novel therapeutic strategies is vital. Two hallmark characteristics specific to diabetic cardiomyopathy are diastolic dysfunction and cardiac structural mal-adaptations, arising from cardiac cellular responses to the complex toxicity induced by hyperglycemia with or without hyperinsulinemia. While type 2 diabetes is more prevalent in men compared to women, cardiovascular risk is higher in diabetic women than in diabetic men, suggesting that diabetic women take a steeper path to cardiomyopathy and heart failure. Accumulating evidence from randomized clinical trials indicate that although pre-menopausal women have lower risk of CVDs, compared to age-matched men, this advantage is lost in diabetic pre-menopausal women, which suggests estrogen availability does not protect from increased cardiovascular risk. Notably, few human studies have assessed molecular and cellular mechanisms regarding similarities and differences in the progression of diabetic cardiomyopathy in men versus women. Additionally, most pre-clinical rodent studies fail to include female animals, leaving a void in available data to truly understand the impact of biological sex differences in diabetes-induced dysfunction of cardiovascular cells. Elegant reviews in the past have discussed in detail the roles of estrogen-mediated signaling in cardiovascular protection, sex differences associated with telomerase activity in the heart, and cardiac responses to exercise. In this review, we focus on the emerging cellular and molecular markers that define sex differences in diabetic cardiomyopathy based on the recent clinical and pre-clinical evidence. We also discuss miR-208a, MED13, and AT2R, which may provide new therapeutic targets with hopes to develop novel treatment paradigms to treat diabetic cardiomyopathy uniquely between men and women.

Cardiovascular disease progression in female Zucker Diabetic Fatty rats occurs via unique mechanisms compared to males

Population studies have shown that compared to diabetic men, diabetic women are at a higher risk of cardiovascular disease. However, the mechanisms underlying this gender disparity are unclear. Our studies in young murine models of type 2 diabetes mellitus (T2DM) and cardiovascular disease show that diabetic male rats develop increased cardiac fibrosis and suppression of intracardiac anti-fibrotic cytokines, while premenopausal diabetic female rats do not. This protection from cardiac fibrosis in female rats can be an estrogen-related effect. However, diabetic female rats develop early subclinical myocardial deformation, cardiac hypertrophy via elevated expression of pro-hypertrophic miR-208a, myocardial damage, and suppression of cardio-reparative Angiotensin II receptor 2 (Agtr2). Diabetic rats of both sexes exhibit a reduction in cardiac capillary density. However, diabetic female rats have reduced expression of neuropilin 1 that attenuates cardiomyopathy compared to diabetic male rats. A combination of cardiac hypertrophy and reduced capillary density likely contributed to increased myocardial structural damage in diabetic female rats. We propose expansion of existing cardiac assessments in diabetic female patients to detect myocardial deformation, cardiac hypertrophy and capillary density via non-invasive imaging, as well as suggest miR-208a, AT2R and neuropilin 1 as potential therapeutic targets and mechanistic biomarkers for cardiac disease in females.

Differential Regulation of Cardiac Function and Intracardiac Cytokines by Rapamycin in Healthy and Diabetic Rats

Diabetes is comorbid with cardiovascular disease and impaired immunity. Rapamycin improves cardiac functions and extends lifespan by inhibiting the mechanistic target of rapamycin complex 1 (mTORC1). However, in diabetic murine models, Rapamycin elevates hyperglycemia and reduces longevity. Since Rapamycin is an immunosuppressant, we examined whether Rapamycin (750 μg/kg/day) modulates intracardiac cytokines, which affect the cardiac immune response, and cardiac function in male lean (ZL) and diabetic obese Zucker (ZO) rats. Rapamycin suppressed levels of fasting triglycerides, insulin, and uric acid in ZO but increased glucose. Although Rapamycin improved multiple diastolic parameters (E/E′, E′/A′, E/Vp) initially, these improvements were reversed or absent in ZO at the end of treatment, despite suppression of cardiac fibrosis and phosphoSer473Akt. Intracardiac cytokine protein profiling and Ingenuity® Pathway Analysis indicated suppression of intracardiac immune defense in ZO, in response to Rapamycin treatment in both ZO and ZL. Rapamycin increased fibrosis in ZL without increasing phosphoSer473Akt and differentially modulated anti-fibrotic IL-10, IFNγ, and GM-CSF in ZL and ZO. Therefore, fundamental difference in intracardiac host defense between diabetic ZO and healthy ZL, combined with differential regulation of intracardiac cytokines by Rapamycin in ZO and ZL hearts, underlies differential cardiac outcomes of Rapamycin treatment in health and diabetes.

MicroRNAs 33, 122, and 208: a potential novel targets in the treatment of obesity, diabetes, and heart-related diseases

Despite decades of research, obesity and diabetes remain major health problems in the USA and worldwide. Among the many complications associated with diabetes is an increased risk of cardiovascular diseases, including myocardial infarction and heart failure. Recently, microRNAs have emerged as important players in heart disease and energy regulation. However, little work has investigated the role of microRNAs in cardiac energy regulation. Both human and animal studies have reported a significant increase in circulating free fatty acids and triacylglycerol, increased cardiac reliance on fatty acid oxidation, and subsequent decrease in glucose oxidation which all contributes to insulin resistance and lipotoxicity seen in obesity and diabetes. Importantly, MED13 was initially identified as a negative regulator of lipid accumulation in Drosophilia. Various metabolic genes were downregulated in MED13 transgenic heart, including sterol regulatory element-binding protein. Moreover, miR-33 and miR-122 have recently revealed as key regulators of lipid metabolism. In this review, we will focus on the role of microRNAs in regulation of cardiac and total body energy metabolism. We will also discuss the pharmacological and non-pharmacological interventions that target microRNAs for the treatment of obesity and diabetes.

Secretory products from epicardial adipose tissue from patients with type 2 diabetes impair mitochondrial β-oxidation in cardiomyocytes via activation of the cardiac renin-angiotensin system and induction of miR-208a

Secretory products from epicardial adipose tissue (EAT) from patients with type 2 diabetes (T2D) impair cardiomyocyte function. These changes associate with alterations in miRNA expression, including the induction of miR-208a. Recent studies suggest that activation of the cardiac-specific renin-angiotensin system (RAS) may affect cardiac energy metabolism via induction of miR-208a. This study investigated whether cardiomyocyte dysfunction induced by conditioned media (CM) from EAT-T2D involves activation of the RAS/miR-208a pathway. Therefore, primary adult rat cardiomyocytes were incubated with CM generated from EAT biopsies from patients with T2D and without T2D (ND). Exposing cardiomyocytes to CM-EAT-T2D reduced sarcomere shortening and increased miR-208a expression versus cells exposed to CM-EAT-ND or control medium. The angiotensin II receptor type 1 (AGTR1) antagonist losartan reversed these effects. Accordingly, incubation with angiotensin II (Ang II) reduced sarcomere shortening, and lowered palmitate-induced mitochondrial respiration and carnitine palmitoyltransferase 1c (CPT1c) expression in cardiomyocytes. Locked-nucleic-acid-mediated inhibition of miR-208a function reversed the detrimental effects induced by Ang II. Interestingly, Ang II levels in CM-EAT-T2D were increased by 2.6-fold after culture with cardiomyocytes. The paracrine activation of the cardiac-specific RAS by CM-EAT-T2D was corroborated by increases in the expression of AGTR1 and renin, as well as a reduction in angiotensin-converting enzyme 2 levels. Collectively, these data show that secretory products from EAT-T2D impair cardiomyocyte contractile function and mitochondrial β-oxidation via activation of the cardiac-specific RAS system and induction of miR-208a, and suggest that alterations in the secretory profile of EAT may contribute to the development of diabetes-related heart disease.

Differential Effects of β-Blockers, Angiotensin II Receptor Blockers, and a Novel AT2R Agonist NP-6A4 on Stress Response of Nutrient-Starved Cardiovascular Cells

In order to determine differences in cardiovascular cell response during nutrient stress to different cardiovascular protective drugs, we investigated cell responses of serum starved mouse cardiomyocyte HL-1 cells and primary cultures of human coronary artery vascular smooth muscles (hCAVSMCs) to treatment with β-blockers (atenolol, metoprolol, carvedilol, nebivolol, 3μM each), AT1R blocker losartan (1μM) and AT2R agonists (CGP42112A and novel agonist NP-6A4, 300nM each). Treatment with nebivolol, carvedilol, metoprolol and atenolol suppressed Cell Index (CI) of serum-starved HL-1 cells (≤17%, ≤8%, ≤15% and ≤15% respectively) as measured by the Xcelligence Real-Time Cell Analyzer (RTCA). Conversely, CI was increased by Ang II (≥9.6%), CGP42112A (≥14%), and NP-6A4 (≥25%) respectively and this effect was blocked by AT2R antagonist PD123319, but not by AT1R antagonist losartan. Thus, the CI signature for each drug could be unique. MTS cell proliferation assay showed that NP-6A4, but not other drugs, increased viability (≥20%) of HL-1 and hCAVSMCs. Wheat Germ Agglutinin (WGA) staining showed that nebivolol was most effective in reducing cell sizes of HL-1 and hCAVSMCs. Myeloid Cell Leukemia 1 (MCL-1) is a protein critical for cardiovascular cell survival and implicated in cell adhesion. β-blockers significantly suppressed and NP-6A4 increased MCL-1 expression in HL-1 and hCAVSMCs as determined by immunofluorescence. Thus, reduction in cell size and/or MCL-1 expression might underlie β-blocker-induced reduction in CI of HL-1. Conversely, increase in cell viability and MCL-1 expression by NP-6A4 through AT2R could have resulted in NP-6A4 mediated increase in CI of HL-1. These data show for the first time that activation of the AT2R-MCL-1 axis by NP-6A4 in nutrient-stressed mouse and human cardiovascular cells (mouse HL-1 cells and primary cultures of hCAVSMCs) might underlie improved survival of cells treated by NP-6A4 compared to other drugs tested in this study.