Human embryonic stem cell-derived cardiomyocytes as an in vitro model to study cardiac insulin resistance

Modelling Diabetic Cardiomyopathy: Using Human Stem Cell-Derived Cardiomyocytes to Complement Animal Models

Diabetes is a global epidemic, with cardiovascular disease being the leading cause of death in diabetic patients. There is a pressing need for an in vitro model to aid understanding of the mechanisms driving diabetic heart disease, and to provide an accurate, reliable tool for drug testing. Human induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have potential as a disease modelling tool. There are several factors that drive molecular changes inside cardiomyocytes contributing to diabetic cardiomyopathy, including hyperglycaemia, lipotoxicity and hyperinsulinemia. Here we discuss these factors and how they can be seen in animal models and utilised in cell culture to mimic the diabetic heart. The use of human iPSC-CMs will allow for a greater understanding of disease pathogenesis and open up new avenues for drug testing.

Insulin Resistance Promotes the Formation of Aortic Dissection by Inducing the Phenotypic Switch of Vascular Smooth Muscle Cells

Background

Insulin resistance (IR) plays a key role in the development of type 2 diabetes mellitus (T2DM) and is one of its most important characteristics. Previous studies have shown that IR and T2DM were independent risk factors for a variety of cardiovascular and cerebrovascular diseases. However, there are few studies on the relationship between IR and aortic dissection (AD). The goal of this research was to find evidence that IR promotes the occurrence of AD.

Methods

Through the statistical analysis, we determined the proportion of glycosylated hemoglobin (HbA1c) abnormalities (HbA1c > 5.7) in people with acute thoracic aortic dissection (ATAD) and compared the difference of messenger RNA (mRNA) and protein expression of GluT1 in the thoracic aorta of normal people and those with ATAD to find evidence that IR is a causative factor in AD. The mouse model of IR and AD and the IR model of human aortic vascular smooth muscle cells (HA-VSMC) were established. Real time-PCR (RT-PCR) and Western blotting were used to study the mRNA and protein expression. Hematoxylin and eosin (H&E), Masson, and elastic fiber staining, and immunofluorescence were used to study the morphological structure.

Results

The proportion of HbA1c abnormalities in patients with ATAD was 59.37%, and the mRNA and protein expression of GluT1 were significantly lower than that in normal people. Fasting glucose concentration (FGC), serum insulin concentration (SIC), and the homeostasis model assessment of insulin resistance (HOMA-IR) of mice was obviously increased in the high-fat diet group and the protein expressions of Glut1 and GluT4 were reduced, indicating that the mouse IR model was successfully established. The incidence of AD was different between the two groups (IR: 13/14, Ctrl: 6/14), and the protein expression of MMP2, MMP9, and OPN were upregulated and SM22 and α-SMA were downregulated in mice. The expressions of mRNA and protein of GluT1 and SM22 in HA-VSMCs with IR were reduced and OPN was increased.

Conclusion

Combined results of clinical findings, mouse models, and cell experiments show that IR induced the phenotypic switching of vascular smooth muscle cells (VSMCs) from contractile to synthetic, which contributes to the occurrence of AD. It provides a basis for further research on the specific mechanism of how IR results in AD and a new approach for the prevention and treatment of AD.

Computational and in vitro validation of cardiogenic induction of quercetin on adipose-derived mesenchymal stromal cells through the inhibition of Wnt and non-Smad-dependent TGF-β pathways

Exploiting human mesenchymal stem cells (hMSCs) was proposed as a promising therapeutic approach for cardiovascular disease due to their capacity to differentiate into cardiac cells. Though modulation of the intracellular signaling pathways dominantly WNT/β catenin and transforming growth factor-β (TGF-β) have been reported to promote differentiation of hMSCs into cardiomyocytes in the prevailing literature, a safe and reproducible system for their clinical application has not yet turned into reality. In the present study, the molecular docking-based strategy was first applied for evaluating the potency of some natural phenolic compounds in the modulation of Wnt and TGF-β signaling pathways using a vital class of crystallographic protein structures of WNT signaling regulators such as Frizzled, Disheveled, GSK3-β, β-catenin, LRP 5/6 extracellular domain, Tankyrase and their variety of active pockets. Then, the impacts of plant-derived chemical compounds on the regulation of the relevant signals for the differentiation of hMSCs into the definitive mesoderm lineage and cardiac progenitors were assessed in vitro. Data obtained revealed the synergistic activity of Wnt and TGF-β superfamily to direct cardiac differentiation in human cardiogenesis by comparing cardiac gene expression in the presence and absence of the TGF-β inhibitors. We found that the inhibitory effect of canonical Wnt/β-catenin is sufficient to cause proper cardiomyocyte differentiation, but the TGF-β pathway plays a vital role in enhancing the expression of the cardiomyocyte-specific marker (cTnT). It was found that quercetin, a p38MAPK inhibitor with the high energy dock to the active pocket of Wnt receptors, promotes cardiac differentiation via the inhibition of both Wnt and non-Smad TGF-β pathways. Altogether, data presented here can contribute to the development of a feasible and efficient cardiac differentiation protocol as an "off-the-shelf" therapeutic source using novel natural agents for cardiac repair or regeneration.

Medium & long-chain acylcarnitine's relation to lipid metabolism as potential predictors for diabetic cardiomyopathy: a metabolomic study

Background

Acylcarnitine is an intermediate product of fatty acid oxidation. It is reported to be closely associated with the occurrence of diabetic cardiomyopathy (DCM). However, the mechanism of acylcarnitine affecting myocardial disorders is yet to be explored. This current research explores the different chain lengths of acylcarnitines as biomarkers for the early diagnosis of DCM and the mechanism of acylcarnitines for the development of DCM in-vitro.

Methods

In a retrospective non-interventional study, 50 simple type 2 diabetes mellitus patients and 50 DCM patients were recruited. Plasma samples from both groups were analyzed by high throughput metabolomics and cluster heat map using mass spectrometry. Principal component analysis was used to compare the changes occurring in the studied 25 acylcarnitines. Multivariable binary logistic regression was used to analyze the odds ratio of each group for factors and the 95% confidence interval in DCM. Myristoylcarnitine (C14) exogenous intervention was given to H9c2 cells to verify the expression of lipid metabolism-related protein, inflammation-related protein expression, apoptosis-related protein expression, and cardiomyocyte hypertrophy and fibrosis-related protein expression.

Results

Factor 1 (C14, lauroylcarnitine, tetradecanoyldiacylcarnitine, 3-hydroxyl-tetradecanoylcarnitine, arachidic carnitine, octadecanoylcarnitine, 3-hydroxypalmitoleylcarnitine) and factor 4 (octanoylcarnitine, hexanoylcarnitine, decanoylcarnitine) were positively correlated with the risk of DCM. Exogenous C14 supplementation to cardiomyocytes led to increased lipid deposition in cardiomyocytes along with the obstacles in adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathways and affecting fatty acid oxidation. This further caused myocardial lipotoxicity, ultimately leading to cardiomyocyte hypertrophy, fibrotic remodeling, and increased apoptosis. However, this effect was mitigated by the AMPK agonist acadesine.

Conclusions

The increased plasma levels in medium and long-chain acylcarnitine extracted from factors 1 and 4 are closely related to the risk of DCM, indicating that these factors can be an important tool for DCM risk assessment. C14 supplementation associated lipid accumulation by inhibiting the AMPK/ACC/CPT1 signaling pathway, aggravated myocardial lipotoxicity, increased apoptosis apart from cardiomyocyte hypertrophy and fibrosis were alleviated by the acadesine.

Comparison of human and rodent cell models to study myocardial lipid-induced insulin resistance

Isolated or cultured cells have proven to be valuable model systems to investigate cellular (patho)biology and for screening of the efficacy of drugs or their possible side-effects. Pluripotent stem cells (PSC) can be readily obtained from healthy individuals as well as from diseased patients, and protocols have been developed to differentiate these cells into cardiomyocytes. Hence, these cellular models are moving center stage for a broader application. In this review, we focus on comparing mouse HL-1 cardiomyocytes, isolated adult rat cardiomyocytes, human embryonic stem cell-derived cardiomyocytes (hESC-CMs) and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) for the study of metabolic aspects of cardiac functioning in health and disease. Various studies have reported that these cellular models are suitable for assessing substrate uptake and utilization, in that each display an adequate and similar response to physiological triggers, in particular the presence of insulin. Likewise, disease conditions, such as excess lipid supply, similarly affect each of these rodent and human cardiomyocyte models. It is concluded that PSC-CMs obtained from patients with cardiogenetic abnormalities are promising models to evaluate the functional consequence of gene variants with unknown significance.

Considerations for using isolated cell systems to understand cardiac metabolism and biology

Changes in myocardial metabolic activity are fundamentally linked to cardiac health and remodeling. Primary cardiomyocytes, induced pluripotent stem cell-derived cardiomyocytes, and transformed cardiomyocyte cell lines are common models used to understand how (patho)physiological conditions or stimuli contribute to changes in cardiac metabolism. These cell models are helpful also for defining metabolic mechanisms of cardiac dysfunction and remodeling. Although technical advances have improved our capacity to measure cardiomyocyte metabolism, there is often heterogeneity in metabolic assay protocols and cell models, which could hinder data interpretation and discernment of the mechanisms of cardiac (patho)physiology. In this review, we discuss considerations for integrating cardiomyocyte cell models with techniques that have become relatively common in the field, such as respirometry and extracellular flux analysis. Furthermore, we provide overviews of metabolic assays that complement XF analyses and that provide information on not only catabolic pathway activity, but biosynthetic pathway activity and redox status as well. Cultivating a more widespread understanding of the advantages and limitations of metabolic measurements in cardiomyocyte cell models will continue to be essential for the development of coherent metabolic mechanisms of cardiac health and pathophysiology.

Cardiac hypertrophy in a dish: a human stem cell based model

Cardiac hypertrophy is an important and independent risk factor for the development of heart failure. To better understand the mechanisms and regulatory pathways involved in cardiac hypertrophy, there is a need for improved in vitro models. In this study, we investigated how hypertrophic stimulation affected human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). The cells were stimulated with endothelin-1 (ET-1) for 8, 24, 48, 72, or 96 h. Parameters including cell size, ANP-, proBNP-, and lactate concentration were analyzed. Moreover, transcriptional profiling using RNA-sequencing was performed to identify differentially expressed genes following ET-1 stimulation. The results show that the CMs increase in size by approximately 13% when exposed to ET-1 in parallel to increases in ANP and proBNP protein and mRNA levels. Furthermore, the lactate concentration in the media was increased indicating that the CMs consume more glucose, a hallmark of cardiac hypertrophy. Using RNA-seq, a hypertrophic gene expression pattern was also observed in the stimulated CMs. Taken together, these results show that hiPSC-derived CMs stimulated with ET-1 display a hypertrophic response. The results from this study also provide new molecular insights about the underlying mechanisms of cardiac hypertrophy and may help accelerate the development of new drugs against this condition.

Diabetic Cardiomyopathy Modelling Using Induced Pluripotent Stem Cell Derived Cardiomyocytes: Recent Advances and Emerging Models

The global burden of diabetes has drastically increased over the past decades and in 2017 approximately 4 million deaths were caused by diabetes and cardiovascular complications. Diabetic cardiomyopathy is a common complication of diabetes with early manifestations of diastolic dysfunction and left ventricular hypertrophy with subsequent progression to systolic dysfunction and ultimately heart failure. An in vitro model accurately recapitulating key processes of diabetic cardiomyopathy would provide a useful tool for investigations of underlying disease mechanisms to further our understanding of the disease and thereby potentially advance treatment strategies for patients. With their proliferative capacity and differentiation potential, human induced pluripotent stem cells (iPSCs) represent an appealing cell source for such a model system and cardiomyocytes derived from induced pluripotent stem cells have been used to establish other cardiovascular related disease models. Here we review recently made advances and discuss challenges still to be overcome with regard to diabetic cardiomyopathy models, with a special focus on iPSC-based systems. Recent publications as well as preliminary data presented here demonstrate the feasibility of generating cardiomyocytes with a diabetic phenotype, displaying insulin resistance, impaired calcium handling and hypertrophy. However, capturing the full metabolic- and functional phenotype of the diabetic cardiomyocyte remains to be accomplished.

Beyond the myocardium? SGLT2 inhibitors target peripheral components of reduced oxygen flux in the diabetic patient with heart failure with preserved ejection fraction

Recent cardiovascular outcome trials have highlighted the propensity of the antidiabetic agents, SGLT2 inhibitors (SGLT2is or -flozin drugs), to exert positive clinical outcomes in patients with cardiovascular disease at risk for major adverse cardiovascular events (MACEs). Of interest in cardiac diabetology is the physiological status of the patient with T2DM and heart failure with preserved ejection fraction (HFpEF), a well-examined association. Underlying this pathologic tandem are the effects that long-standing hyperglycemia has on the ability of the HFpEF heart to adequately deliver oxygen. It is believed that shortcomings in oxygen diffusion or utilization and the resulting hypoxia thereafter may play a role in underlying the clinical sequelae of patients with T2DM and HFpEF, with implications in the long-term decline of extra-cardiac tissue. Oxygen consumption is one of the most critical factors in indexing heart failure disease burden, warranting a probe into the role of SGLT2i on oxygen utility in HFpEF and T2DM. We investigated the role of oxygen flux in the patient with T2DM and HFpEF extending beyond the heart with focuses on cellular metabolism, perivascular fibrosis with endothelial dysfunction, hematologic changes, and renal effects with neurohormonal considerations in the patient with HFpEF and T2DM. Moreover, we give a commentary on potential therapeutic targets of these components with SGLT2i to gain insight into disease burden amelioration in patients with HFpEF and T2DM.

Contribution of Impaired Insulin Signaling to the Pathogenesis of Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) has emerged as a relevant cause of heart failure among the diabetic population. Defined as a cardiac dysfunction that develops in diabetic patients independently of other major cardiovascular risks factors, such as high blood pressure and coronary artery disease, the underlying cause of DCMremains to be unveiled. Several pathogenic factors, including glucose and lipid toxicity, mitochondrial dysfunction, increased oxidative stress, sustained activation of the renin-angiotensin system (RAS) or altered calcium homeostasis, have been shown to contribute to the structural and functional alterations that characterize diabetic hearts. However, all these pathogenic mechanisms appear to stem from the metabolic inflexibility imposed by insulin resistance or lack of insulin signaling. This results in absolute reliance on fatty acids for the synthesis of ATP and impairment of glucose oxidation. Glucose is then rerouted to other metabolic pathways, with harmful effects on cardiomyocyte function. Here, we discuss the role that impaired cardiac insulin signaling in diabetic or insulin-resistant individuals plays in the onset and progression of DCM.

Stem cells as therapy for heart disease: iPSCs, ESCs, CSCs, and skeletal myoblasts

Heart Diseases are serious and global public health concern. In spite of remarkable therapeutic developments, the prediction of patients with Heart Failure (HF) is weak, and present therapeutic attitudes do not report the fundamental problem of the cardiac tissue loss. Innovative therapies are required to reduce mortality and limit or abolish the necessity for cardiac transplantation. Stem cell-based therapies applied to the treatment of heart disease is according to the understanding that natural self-renewing procedures are inherent to the myocardium, nonetheless may not be adequate to recover the infarcted heart muscle. Following the first account of cell therapy in heart diseases, examination has kept up to rapidity; besides, several animals and human clinical trials have been conducted to preserve the capacity of numerous stem cell population in advance cardiac function and decrease infarct size. The purpose of this study was to censoriously evaluate the works performed regarding the usage of four major subgroups of stem cells, including induced Pluripotent Stem Cells (iPSC), Embryonic Stem Cells (ESCs), Cardiac Stem Cells (CDC), and Skeletal Myoblasts, in heart diseases, at the preclinical and clinical studies. Moreover, it is aimed to argue the existing disagreements, unsolved problems, and prospect directions.