Low T3 State Is Correlated with Cardiac Mitochondrial Impairments after Ischemia Reperfusion Injury: Evidence from a Proteomic Approach

Transcriptome, network analysis, and molecular docking approaches to elucidate the modes of action of Astragaloside IV against myocardial infarction with mitochondrial energy metabolism network-targeted regulation

BACKGROUND

Mitochondria play central role in cardiac energy metabolism modulations. Cardiac energy metabolism could be potential therapeutic target for the treatment of ischemic heart disease (IHD). We proposed strategy to analyze the regulation modes of astragaloside IV (AST) by targeting mitochondrial-energy-metabolism (MEM) in IHD based on transcriptome, network analysis, molecular docking (MD) and western blot (WB).

METHOD

IHD-associated genes and AST potential targets were collected from databases and references. MEM-related genes were obtained from MitoProteome. Cytoscape was applied to construct networks, present visualization, and conduct KEGG pathway enrichment. AST regulated energy-metabolism-associated-IHD-network (AEIN) was created, and reverse rates calculated from network analysis of transcriptome from rat myocardial infarction experiments were assigned to AEIN. Binding affinities and modes were evaluated by MD with further WB validation of targets expression.

RESULTS

The study identified 1713 IHD-related genes, 528 MEM-related genes, and 169 potential AST target genes. 21 AST targets were obtained from AEIN, while the top three targets Akt1, ERK1/2 and RPS6KB1 showed good binding affinities with AST (-10, -9.8, -8.6 and -8.8 kcal/mol for Akt1, Erk1, Erk2 and RPS6KB1 respectively). AST reversed the decreased expressions of three targets against OGD injury of H9c2. 13 MEM-associated signaling pathways, including HIF-1, and PI3K-Akt signaling pathways, were retrieved showing certain inter-relationships both in compositions and functions.

CONCLUSIONS

AST may have coordinated roles among multi-pathways in regulating MEM homeostasis in IHD. While further deep investigations should be designed and conducted to decipher and pinpoint the multi-target, multi-pathway modes of action of AST in the future.

Analysis of Risk Factors for Major Adverse Cardiovascular Events in Patients with Coronary Stent Restenosis after Revascularization

Background

To investigate the risk factors for myocardial infarction, recurrent in-stent restenosis (ISR) and target vessel revascularization (TVR) in patients with coronary ISR within 4 years after revascularization.

Methods

A total of 1884 patients who were hospitalized at Fuwai Hospital for ISR and successfully treated with coronary intervention between January 2017 and December 2018 were included to determine whether there were myocardial infarction, recurrent ISR, TVR and other major adverse cardiovascular events (MACEs) within 4 years after intervention. The patients were divided into the MACE group (215 patients) and the non-MACE group (1669 patients). The clinical data of patients in the two groups were compared, and the risk factors for postoperative MACEs in the ISR patients were obtained by multivariate logistic regression analysis. The receiver operating characteristic (ROC) curve was used to determine the optimal prediction threshold for postoperative MACEs in ISR patients. The difference in survival curves between the two groups was compared using Kaplan‒Meier survival analysis.

Results

The albumin (43.42 ± 4.77 vs. 44.17 ± 4.46, p = 0.021), direct bilirubin (2.5 (2, 3.5) vs. 2.8 (2.07, 3.73), p = 0.036) and free triiodothyronine (FT3) (2.85 ± 0.43 vs. 2.92 ± 0.42, p = 0.019) levels in the MACE group were significantly lower than those in the non-MACE group, and there was a significant negative correlation between albumin and FT3 and MACEs. The results of univariate and multivariate logistic regression analyses revealed that FT3 was an independent predictor of postoperative MACEs in ISR patients (Odds Ratio (OR) = 0.626, 95% CI: 0.429-0.913, p = 0.015). The ROC curve analysis determined that an FT3 value of 2.785 pmol/L was the optimal prediction threshold. According to the threshold, ISR patients were divided into the FT3 < 2.785 group and the FT3 ≥ 2.785 group. The Kaplan‒Meier analysis revealed that the postoperative recurrence rate of MACEs of the FT3 < 2.785 group was substantially greater than that of the FT3 ≥ 2.785 group (Hazard Ratio (HR) = 0.76, 95% CI: 0.58-0.994, p = 0.044).

Conclusions

FT3 can be used as an independent predictor of postoperative myocardial infarction, recurrent ISR and TVR in ISR patients. When FT3 is < 2.785 pmol/L, the incidence of postoperative myocardial infarction, recurrent ISR and TVR in ISR patients increases significantly.

Identification of Hub Genes in the Remodeling of Non-Infarcted Myocardium Following Acute Myocardial Infarction

(1) Background: There are few diagnostic and therapeutic targets for myocardial remodeling in the salvageable non-infarcted myocardium. (2) Methods: Hub genes were identified through comprehensive bioinformatics analysis (GSE775, GSE19322, and GSE110209 from the gene expression omnibus (GEO) database) and the biological functions of hub genes were examined by gene ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Furthermore, the differential expression of hub genes in various cell populations between the acute myocardial infarction (AMI) and sham-operation groups was analyzed by processing scRNA data (E-MTAB-7376 from the ArrayExpress database) and RNA-seq data (GSE183168). (3) Results: Ten strongly interlinked hub genes (Timp1, Sparc, Spp1, Tgfb1, Decr1, Vim, Serpine1, Serpina3n, Thbs2, and Vcan) were identified by the construction of a protein-protein interaction network from 135 differentially expressed genes identified through comprehensive bioinformatics analysis and their reliability was verified using GSE119857. In addition, the 10 hub genes were found to influence the ventricular remodeling of non-infarcted tissue by modulating the extracellular matrix (ECM)-mediated myocardial fibrosis, macrophage-driven inflammation, and fatty acid metabolism. (4) Conclusions: Ten hub genes were identified, which may provide novel potential targets for the improvement and treatment of AMI and its complications.

Triiodothyronine (T3), inflammation and mortality risk in patients with acute myocardial infarction

OBJECTIVES

To study the relationship between serum-free T3 (FT3), C-reactive protein (CRP) and all-cause mortality in patients with acute myocardial infarction (AMI).

DESIGN

Prospective multicentre longitudinal cohort study.

METHODS

Between December 2014 and December 2016, thyroid function and CRP were analysed in AMI (both ST-elevation (STEMI) and non-ST-elevation) patients from the Thyroxine in Acute Myocardial Infarction study. The relationship of FT3 and CRP at baseline with all-cause mortality up to June 2020 was assessed. Mediation analysis was performed to evaluate if CRP mediated the relationship between FT3 and mortality.

RESULTS

In 1919 AMI patients (29.2% women, mean (s.d.) age: 64.2 (12.1) years and 48.7% STEMI) followed over a median (interquartile range) period of 51 (46-58) months, there were 277 (14.4%) deaths. Overall, lower serum FT3 and higher CRP levels were associated with higher risk of mortality. When divided the patients into tertiles based on the levels of FT3 and CRP; the group with the lowest FT3 and highest CRP levels had a 2.5-fold increase in mortality risk (adjusted hazard ratio (95% CI) of 2.48 (1.82-3.16)) compared to the group with the highest FT3 and lowest CRP values. CRP mediated 9.8% (95% CI: 6.1-15.0%) of the relationship between FT3 and mortality.

CONCLUSIONS

In AMI patients, lower serum FT3 levels on admission are associated with a higher mortality risk, which is partly mediated by inflammation. Adequately designed trials to explore the potential benefits of T3 in AMI patients are required.

The current debate over treatment of subclinical hypothyroidism to prevent cardiovascular complications

BACKGROUND

Subclinical hypothyroidism (SCH) is an asymptomatic condition associated with increased thyroid-stimulating hormone (TSH) >4 mIU/L with normal thyroxine (T4) and triidothyronine (T3) levels. It is more common in older subjects and especially in women with an overall incidence of 10%.

OBJECTIVE

Because the normal TSH levels increase with age up to 7.5 mIU/L in older people, several studies have reported either no benefits whereas others have reported the benefits of treatment. These studies have caused a great debate over the treatment of SCH, especially in older subjects. Therefore, the objective of this study was to review the current evidence over this debate by reviewing the recent literature on the subject to discern whether treatment of SCH is necessary and under what circumstances.

METHODS

To get a better perspective on the current debate over treatment of SCH, a focused Medline search of the English language literature was conducted from 2012 to 2019 using the terms, hypothyroidism, subclinical, dyslipidaemia, cardiovascular disease, heart failure and 38 papers with pertinent information were selected.

RESULTS

The analysis of results from these papers indicated that the normal levels of TSH are increasing with the advancement of age from 4 mIU/L up to 7.5 mIU/L for patients ≥75 years of age. Also, several of reviewed studies have shown no benefits of treatment whereas, others have shown definite benefits of treatment with levothyroxine supplementation on the clinical and metabolic effects of SBH with reductions in CVD, HF and mortality. The treatment is more effective in younger persons and less so in older persons.

CONCLUSIONS

Based on the overall evidence, treatment of SCH is indicated in younger persons with a TSH level >4.0 mIU/L. In older subjects, treatment should be individualised and based on the presence of symptoms, the level of TSH, and initiated at TSH levels ≥10 mIU/L and at low doses to avoid adverse cardiovascular effects from overtreatment.

Thyroid Stimulating Hormone Triggers Hepatic Mitochondrial Stress through Cyclophilin D Acetylation

BACKGROUND & AIMS

Oxidative stress-related liver diseases were shown to be associated with elevated serum thyroid stimulating hormone (TSH) levels. Mitochondria are the main source of cellular reactive oxygen species. However, the relationship between TSH and hepatic mitochondrial stress/dysfunction and the underlying mechanisms are largely unknown. Here, we focused on exploring the effects and mechanism of TSH on hepatic mitochondrial stress.

METHODS

As the function of TSH is mediated through the TSH receptor (TSHR), Tshr -/- mice and liver-specific Tshr -/- mice and liver-specific Tshr -/- mice and liver-specific.

RESULTS

A relatively lower degree of mitochondrial stress was observed in the livers of Tshr -/- mice and liver-specific in vitro. Microarray and RT-PCR analyses showed that Tshr -/- mice and liver-specific.

CONCLUSIONS

TSH stimulates hepatic CypD acetylation through the lncRNA-AK044604/SIRT1/SIRT3 signaling pathway, indicating an essential role for TSH in mitochondrial stress in the liver.

Protective Effects of Euthyroidism Restoration on Mitochondria Function and Quality Control in Cardiac Pathophysiology

Mitochondrial dysfunctions are major contributors to heart disease onset and progression. Under ischemic injuries or cardiac overload, mitochondrial-derived oxidative stress, Ca²⁺ dis-homeostasis, and inflammation initiate cross-talking vicious cycles leading to defects of mitochondrial DNA, lipids, and proteins, concurrently resulting in fatal energy crisis and cell loss. Blunting such noxious stimuli and preserving mitochondrial homeostasis are essential to cell survival. In this context, mitochondrial quality control (MQC) represents an expanding research topic and therapeutic target in the field of cardiac physiology. MQC is a multi-tier surveillance system operating at the protein, organelle, and cell level to repair or eliminate damaged mitochondrial components and replace them by biogenesis. Novel evidence highlights the critical role of thyroid hormones (TH) in regulating multiple aspects of MQC, resulting in increased organelle turnover, improved mitochondrial bioenergetics, and the retention of cell function. In the present review, these emerging protective effects are discussed in the context of cardiac ischemia-reperfusion (IR) and heart failure, focusing on MQC as a strategy to blunt the propagation of connected dangerous signaling cascades and limit adverse remodeling. A better understanding of such TH-dependent signaling could provide insights into the development of mitochondria-targeted treatments in patients with cardiac disease.

Thyroid hormone protects cardiomyocytes from H2O2-induced oxidative stress via the PI3K-AKT signaling pathway

Oxidative stress plays an important role in the progression of cardiac diseases, including acute myocardial infarction, ischemia/reperfusion (I/R) injury and heart failure. Growing evidence indicates that thyroid hormone has protective properties against cardiovascular diseases. However, little is known about its effect on oxidative stress in cardiomyocytes or the underlying mechanisms. This study showed that T3 pretreatment in vivo significantly reduced cardiac dysfunction by increasing the left ventricular ejection function and ameliorating the pathological changes induced by I/R-induced injury. In an in vitro experiment, T3 inhibited apoptosis in H₂O₂-treated cardiomyocytes, as evidenced by the decreased expression of Bax, cleaved caspase 3 and 9, and increased expression of Bcl-2. In addition, oxidative stress observed in hearts of mice with I/R injury was significantly alleviated by T3 pretreatment, intracellular ROS and mitochondrial ROS overproduction were effectively inhibited, and similar results were also detected in H₂O₂-treated cardiomyocytes in vitro. T3 significantly increased antioxidant protein (Nrf2 and HO-1) expression levels, and inhibited NOX2 and NOX4 protein expression levels in H₂O₂-treated cardiomyocytes. Moreover, T3 preserved mitochondrial functions upon H₂O₂-induced oxidative stress by increasing mitochondrial membrane potential and promoting the expression of mitochondrial biogenesis genes. Notably, the PI3K/AKT signaling was significantly activated by T3 pretreatment in H₂O₂-induced cardiomyocytes. Together, these findings revealed that T3 could be served as potential therapeutic target for protection against cardiac oxidative stress injury through its antioxidant and anti-apoptosis effects, which are mediated by the activation of the PI3K/AKT signaling pathway.

Sirt3 attenuates post-infarction cardiac injury via inhibiting mitochondrial fission and normalization of AMPK-Drp1 pathways

Mitochondrial damage is involved in the pathogenesis of post-infarction cardiac injury. However, the upstream regulators of mitochondrial damage have not yet been identified. The aim of our study is to explore the role of Sirt3 in post-infarction cardiac injury with a particular focus on mitochondrial fission and AMPK-Drp1 pathways. Our results indicated that Sirt3 was downregulated in the progression of post-infarction cardiac injury. Overexpression of Sirt3 attenuated cardiac fibrosis, sustained myocardial function, inhibited the inflammatory response, and reduced cardiomyocyte death. Functional studies illustrated that chronic post-infarction cardiac injury was characterized by increased mitochondrial fission, which triggered mitochondrial oxidative stress, metabolic disorders, mitochondrial potential reduction and caspase-9 apoptosis in cardiomyocytes. However, Sirt3 overexpression attenuated mitochondrial fission and thus preserved mitochondrial homeostasis and cardiomyocyte viability. Furthermore, our results confirmed that Sirt3 repressed mitochondrial fission via normalizing AMPK-Drp1 pathways. Inhibition of AMPK activity re-activated Drp1 and thus abrogated the inhibitory effect of Sirt3 on mitochondrial fission. Altogether, our results indicate that Sirt3 enhancement could be an effective approach to retard the development of post-infarction cardiac injury via disrupting mitochondrial fission and normalizing the AMPK-Drp1 axis.

Cardioprotection and thyroid hormones

The evolution of cardiac disease after an acute ischemic event depends on a complex and dynamic network of mechanisms alternating from ischemic damage due to acute coronary occlusion to reperfusion injury due to the adverse effects of coronary revascularization till post-ischemic remodeling. Cardioprotection is a new purpose of the therapeutic interventions in cardiology with the goal to reduce infarct size and thus prevent the progression toward heart failure after an acute ischemic event. In a complex biological system such as the human one, an effective cardioprotective strategy should diachronically target the network of cross-talking pathways underlying the disease progression. Thyroid system is strictly interconnected with heart homeostasis, and recent studies highlighted its role in cardioprotection, in particular through the preservation of mitochondrial function and morphology, the antifibrotic and proangiogenetic effect and also to the potential induction of cell regeneration and growth. The objective of this review was to highlight the cardioprotective role of triiodothyronine in the complexity of post-ischemic disease evolution.

Applying a systems approach to thyroid physiology: Looking at the whole with a mitochondrial perspective instead of judging single TSH values or why we should know more about mitochondria to understand metabolism

Classical thinking in endocrine physiology squeezes our diagnostic handling into a simple negative feedback mechanism with a controller and a controlled variable. In the case of the thyroid this is reduced to TSH and fT3 and fT4, respectively. The setting of this tight notion has no free space for any additions. In this paper we want to challenge this model of limited application by proposing a construct based on a systems approach departing from two basic considerations. In first place since the majority of cases of thyroid disease develop and appear during life it has to be considered as an acquired condition. In the second place, our experience with the reversibility of morphological changes makes the autoimmune theory inconsistent.

While medical complexity can expand into the era of OMICS as well as into one where manipulations with the use of knock-outs and -ins are common in science, we have preferred to maintain a simple and practical approach. We will describe the interactions of iron, magnesium, zinc, selenium and coenzyme Q10 with the thyroid axis. The discourse will be then brought into the context of ovarian function, i.e. steroid hormone production. Finally the same elemental players will be presented in relation to the basic mitochondrial machinery that supports the endocrine.

We propose that an intact mitochondrial function can guard the normal endocrine function of both the thyroid as well as of the ovarian axis. The basic elements required for this function appear to be magnesium and iron. In the case of the thyroid, magnesium-ATP acts in iodine uptake and the heme protein peroxidase in thyroid hormone synthesis. A similar biochemical process is found in steroid synthesis with cholesterol uptake being the initial energy-dependent step and later the heme protein ferredoxin 1 which is required for steroid synthesis. Magnesium plays a central role in determining the clinical picture associated with thyroid disease and is also involved in maintaining fertility. With the aid of 3D sonography patients needing selenium and/or coenzyme Q10 can be easily identified. By this we firmly believe that physicians should know more about basic biochemistry and the way it fits into mitochondrial function in order to understand metabolism. Contemplating only TSH is highly reductionistic.

Outline

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Author's profiles and motivation for this analysis

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The philosophical alternatives in science and medicine

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Reductionism vs. systems approach in clinical thyroid disease guidelines

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The entry into complexity: the involvement of the musculoskeletal system

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Integrating East and West: teachings from Chinese Medicine and from evidence based medicine (EBM)

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Can a mathematical model represent complexity in the daily thyroid practice?

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How effective is thyroxine treatment?

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Resolving the situation of residual symptoms in treated patients with thyroid disease

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Importance of iron, zinc and magnesium in relation to thyroid function

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Putting together new concepts related to thyroid function for a systems approach

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Expanding our model into general aspects of medicine