Early cardiac changes induced by a hypercaloric Western-type diet in “subclinical” obesity

Puerarin reduces susceptibility to ventricular arrhythmias and inhibits ferroptosis via Sirt1/Nrf2 signaling in high-fat-diet rats

Obesity is a significant risk factor for cardiac arrhythmias, and the ferroptosis is closely related to cardiac arrhythmias. This study aimed to investigate whether puerarin (Pue), a natural isoflavone, could reduce the susceptibility to ventricular arrhythmias (VAs) associated with obesity and inhibit ferroptosis, with a particular focus on the Sirt1/Nrf2 signaling pathway. Male rats were randomly divided into three groups: normal chow diet (NC), high-fat diet (HFD), and HFD with Pue treatment (100mg/kg, HFD + Pue). After 16 weeks, electrophysiological, structural, and molecular analysis were performed. Compared to the NC group, HFD rats exhibited prolonged QT interval and Tpeak-Tend interval, amplified transmural dispersion of ventricular repolarization, and increased susceptibility to VAs. Pue treatment significantly ameliorated these electrophysiological abnormalities and reduced VAs susceptibility. HFD rats showed cardiac hypertrophy, fibrosis, and inflammation, which were alleviated by Pue application. Cardiac lipid peroxidation, iron deposition, mitochondrial abnormality, and ferroptosis marker induction were observed in HFD rats. Further, treatment with Pue improved these alterations. Additionally, molecular docking analysis confirmed the interaction of Pue with Sirt1 and Nrf2. Furthermore, Pue treatment upregulated Sirt1 and Nrf2 expression in HFD rats, thereby reducing reactive oxygen species (ROS) generation and ferroptosis. Moreover, Pue protected cardiomyocytes against palmitic acid (PA)-induced injury by inhibiting ferroptosis via the Sirt1/Nrf2 pathway in H9c2 cells. Overall, our study shows for the first time that Pue reduces susceptibility to VAs and inhibits ferroptosis in HFD rats by modulating the Sirt1/Nrf2 signaling pathway, offering a potential therapeutic strategy for obesity-related cardiac arrhythmias.

A Retrospective Study to Investigate the Relationship Between Body Mass Index and Hemodynamic Characteristics in Hypertensive Patients

The relationship between hemodynamic parameters and body mass index (BMI) in the context of blood pressure regulation in hypertension is unclear. Here, we analyzed data from 1368 uncontrolled hypertensive patients, including key hemodynamic indicators such as heart rate (HR), cardiac index (CI), arterial stiffness (AS), systemic vascular resistance index (SVRI), and thoracic blood ratio (TBR). In this cohort, the average BMI across all hypertension patients was 26.859 ± 3.897 (kg/m2), with obese patients (BMI ≥ 28 kg/m2) averaging 31.01 ± 2.87 kg/m2 and non-obese (BMI<28 kg/m2) averaging 24.70 ± 2.28 kg/m2. Younger obese patients exhibited higher diastolic pressures than non-obese peers (p < 0.01). Hemodynamic analysis showed obese patients had increased HR and SVRI but lower CI and AS (p < 0.01). Hypertensive males aged under 60 with obesity displayed a more prominent peripheral vascular phenotype (p < 0.05) and volemic phenotype (p < 0.01) than non-obese males. Obese females aged under 60 showed a higher incidence of cardiac phenotype (p < 0.01). Across genders, obese hypertensive patients aged over 60 had a greater prevalence of volemic phenotype than non-obese patients (p < 0.05, p < 0.01, respectively). BMI inversely correlated with CI and positively with SVRI across age and gender categories (p < 0.01). Taken together, we find that patients with hypertension exhibit diverse hemodynamic profiles, and BMI significantly correlates with hemodynamic parameters such as SVRI and CI. Our research identifies BMI as a valuable target for personalized hypertension treatment.

Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease

Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction, and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Male mice fed a high fat/sugar diet (HFSD vs. control) exhibited diastolic dysfunction (echo E/e' Doppler ratio). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. E/e' for the HFSD hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from the non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs. control). With stretch, the Ca2+ transient decay time course was prolonged. With increased pacing, cardiomyocyte stiffness was elevated, yet diastolic Ca2+ elevation was attenuated. Our findings show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from cardiomyocyte stiffness. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca2+ interaction contributes to intrinsic cardiomyocyte stiffness in cardiometabolic disease. KEY POINTS: Understanding cardiomyocyte stiffness components is an important priority for identifying new therapeutics for diastolic dysfunction, a key feature of cardiometabolic disease. In this study cardiac function was measured in vivo (echocardiography) for mice fed a high-fat/sugar diet (HFSD, ≥25 weeks). Performance of intact isolated cardiomyocytes derived from the same hearts was measured during pacing under non-loaded, loaded and stretched conditions in vitro. Calibrated cardiomyocyte stretches demonstrated that stiffness (stress/strain) was elevated in HFSD cardiomyocytes in vitro and correlated with diastolic dysfunction (E/e') in vivo. HFSD cardiomyocyte Ca2+ transient decay was prolonged in response to stretch. Stiffness was accentuated with pacing increase while the elevation in diastolic Ca2+ was attenuated. Data show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. These findings suggest that stretch-dependent augmentation of the myofilament-Ca2+ response during diastole partially underlies elevated cardiomyocyte stiffness and diastolic dysfunction of hearts of animals with cardiometabolic disease.

Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease

Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction, and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Male mice fed a high fat/sugar diet (HFSD vs control) exhibited diastolic dysfunction (echo E/e' doppler ratio). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. E/e' for the origin hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs control). With stretch, the Ca2+ transient decay time course was prolonged. With increased pacing, cardiomyocyte stiffness was elevated, yet diastolic Ca2+ elevation was attenuated. Our findings show unequivocally that cardiomyocyte mechanical dysfunction cannot be detected by analysis of non-loaded shortening. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from cardiomyocyte stiffness. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca2+ interaction contributes to intrinsic cardiomyocyte stiffness in cardiometabolic disease.

Cardiac remodeling associated with chronic kidney disease is enhanced in a rat model of metabolic syndrome: Preparation of mesenchymal transition

Cardiac alteration due to chronic kidney disease is described by tissue fibrosis. This remodeling involves myofibroblasts of various origins, including epithelial or endothelial to mesenchymal transitions. In addition, obesity and insulin resistance together or separately seem to exacerbate cardiovascular risk in chronic kidney disease (CKD). The main objective of this study was to assess if pre-existing metabolic disease exacerbates CKD-induced cardiac alterations. In addition, we hypothesised that endothelial to mesenchymal transition participates in this enhancement of cardiac fibrosis. Rats fed cafeteria type diet for 6 months underwent a subtotal nephrectomy at 4 months. Cardiac fibrosis was evaluated by histology and qRT-PCR. Collagens and macrophages were quantified by immunohistochemistry. Endothelial to mesenchymal transitions were assessed by qRT-PCR (CD31, VE-cadherin, α-SMA, nestin) and also by CD31 immunofluorescence staining. Rats fed with cafeteria type regimen were obese, hypertensive and insulin resistant. Cardiac fibrosis was predominant in CKD rats and was highly majored by cafeteria regimen. Collagen-1 and nestin expressions were higher in CKD rats, independently of regimen. Interestingly, in rats with CKD and cafeteria diet we found an increase of CD31 and α-SMA co-staining with suggest an implication of endothelial to mesenchymal transition during heart fibrosis. We showed that rats already obese and insulin resistant had an enhanced cardiac alteration to a subsequent renal injury. Cardiac fibrosis process could be supported by a involvement of the endothelial to mesenchymal transition phenomenon.

The emerging role of leptin in obesity-associated cardiac fibrosis: evidence and mechanism

Cardiac fibrosis is a hallmark of various cardiovascular diseases, which is quite commonly found in obesity, and may contribute to the increased incidence of heart failure arrhythmias, and sudden cardiac death in obese populations. As an endogenous regulator of adiposity metabolism, body mass, and energy balance, obesity, characterized by increased circulating levels of the adipocyte-derived hormone leptin, is a critical contributor to the pathogenesis of cardiac fibrosis. Although there are some gaps in our knowledge linking leptin and cardiac fibrosis, this review will focus on the interplay between leptin and major effectors involved in the pathogenesis underlying cardiac fibrosis at both cellular and molecular levels based on the current reports. The profibrotic effect of leptin is predominantly mediated by activated cardiac fibroblasts but may also involve cardiomyocytes, endothelial cells, and immune cells. Moreover, a series of molecular signals with a known profibrotic property is closely involved in leptin-induced fibrotic events. A more comprehensive understanding of the underlying mechanisms through which leptin contributes to the pathogenesis of cardiac fibrosis may open up a new avenue for the rapid emergence of a novel therapy for preventing or even reversing obesity-associated cardiac fibrosis.

Deficiency of ataxia-telangiectasia mutated kinase attenuates Western-type diet-induced cardiac dysfunction in female mice

Chronic consumption of Western-type diet (WD) induces cardiac structural and functional abnormalities. Previously, we have shown that WD consumption in male ATM (ataxia-telangiectasia mutated kinase) deficient mice associates with accelerated body weight (BW) gain, cardiac systolic dysfunction with increased preload, and exacerbation of hypertrophy, apoptosis, and inflammation. This study investigated the role of ATM deficiency in WD-induced changes in functional and biochemical parameters of the heart in female mice. Six-week-old wild-type (WT) and ATM heterozygous knockout (hKO) female mice were placed on WD or NC (normal chow) for 14 weeks. BW gain, fat accumulation, and cardiac functional and biochemical parameters were measured 14 weeks post-WD. WD-induced subcutaneous and total fat contents normalized to body weight were higher in WT-WD versus hKO-WD. Heart function measured using echocardiography revealed decreased percent fractional shortening and ejection fraction, and increased LV end systolic diameter and volume in WT-WD versus WT-NC. These functional parameters remained unchanged in hKO-WD versus hKO-NC. Myocardial fibrosis, myocyte hypertrophy, and apoptosis were higher in WT-WD versus WT-NC. However, apoptosis was significantly lower and hypertrophy was significantly higher in hKO-WD versus WT-WD. MMP-9 and Bax expression, and Akt activation were higher in WT-WD versus WT-NC. PARP-1 (full-length) expression and mTOR activation were lower in WT-WD versus hKO-WD. Thus, ATM deficiency in female mice attenuates fat weight gain, preserves heart function, and associates with decreased cardiac cell apoptosis in response to WD.

Aging and Heart Failure with Preserved Ejection Fraction

Heart failure is a clinical syndrome characterized by the inability of the cardiovascular system to provide adequate cardiac output at normal filling pressures. This results in a clinical syndrome characterized by dyspnea, edema, and decreased exertional tolerance. Heart failure with preserved ejection fraction (HFpEF) is an increasingly common disease, and the incidence of HFpEF increases with age. There are a variety of factors which contribute to the development of HFpEF, including the presence of hypertension, diabetes, obesity, and other pro-inflammatory states. These comorbid conditions result in changes at the biochemical and cell signaling level which ultimately lead to a disease with a great deal of phenotypic heterogeneity. In general, the physiologic dysfunction of HFpEF is characterized by vascular stiffness, increased cardiac filling pressures, pulmonary hypertension, and impaired volume management. The normal and abnormal processes associated with aging serve as an accelerant in this process, resulting in the hypothesis that HFpEF represents a form of presbycardia. In this article, we aim to review the processes importance of aging in the development of HFpEF by examining the disease and its causes from the biochemical to physiologic level. © 2022 American Physiological Society. Compr Physiol 12: 1-10, 2022.

Emerging roles of Galectin-3 in diabetes and diabetes complications: A snapshot

Galectin-3 is a member of the galectin family, widely expressed in immune cells and plays a role mainly in inflammation, autoimmunity, apoptosis, and chemotaxis. We summarized the roles of Galectin-3 in diabetes and its complications, as well as the underlying mechanisms. Clinical research has determined that the circulating level of Galectin-3 is closely related to diabetes and its complications, thus it is promising to use Galectin-3 as a predictor and biomarker for those diseases. Galectin-3 also may be considered as an ideal therapeutic target, which has broad prospects in the prevention and treatment of diabetes and its complications, especially macrovascular and microvascular complications.

P2X7 Receptor and Heart Function in a Mouse Model of Systemic Inflammation Due to High Fat Diet

Purpose

Low-grade inflammation contributes to heart failure in obesity or type 2 diabetes mellitus. The P2X7 receptor (P2X7R) is a key regulator of several pro-inflammatory responses in multiple tissues and organs; however, its involvement in the onset of heart dysfunction remains unclear. The study evaluated the role of P2X7R as a cardiac function regulator in C57BL/6J wild-type (WT) and P2X7R knockout (KO) mice by inducing systemic inflammation with high fat diet (HFD).

Methods

Specific parameters of systolic and diastolic function and heart morphology were measured in vivo before animal sacrifice by high-frequency ultrasonographic analysis. Gene and protein expression of cardiac biomarkers associated with inflammatory-oxidative pathways were evaluated by real-time PCR and Western Blotting.

Results

P2X7R-mediated up-regulation of the NLRP3-caspase-1 complex, increased expression of key oxidative stress (NOS-2, TNFα), and chemotactic (MCP-1) mediators were revealed in WT-HFD animals. In KO-HFD mice, such inflammatory-oxidative pathway was silent. Nevertheless, HFD induced in vivo a clear alteration of diastolic pattern (E/A: p < 0.03 vs WT-HFD) and a cardiac morphologic remodelling (left ventricular mass: p < 0.05 vs WT-HFD) only in P2X7R KO animals. Surprisingly, the transcriptional and protein expression of IL-1β and IL-6, usually regulated through P2X7R activation, were significantly higher in KO-HFD than in WT-HFD mice (both p < 0.05). Furthermore, an up-regulation of miR-214 and a down-regulation of miR-126 in heart of HFD-KO mice were observed, suggesting a link between such epigenetic dysregulation and cytokine overexpression as a potential pathophysiologic mechanism concurring to the progressive cardiac dysfunction.

Conclusion

These findings seem to suggest a cardioprotective role of P2X7R toward this tissue-specific inflammatory damage, likely through tissue homeostasis and organ functionality preservation.

Sudden cardiac death in diabetes and obesity: mechanisms and therapeutic strategies

Ventricular arrhythmias and sudden cardiac death (SCD) occur most frequently in the setting of coronary artery disease, cardiomyopathy and heart failure, but are also increasingly observed in individuals suffering from diabetes mellitus and obesity. The incidence of these metabolic disorders is rising in Western countries, but adequate prevention and treatment of arrhythmias and SCD in affected patients is limited due to our incomplete knowledge of the underlying disease mechanisms. Here, an overview is presented of the prevalence of electrophysiological disturbances, ventricular arrhythmias and SCD in the clinical setting of diabetes and obesity. Experimental studies are reviewed, which have identified disease pathways and associated modulatory factors, in addition to pro-arrhythmic mechanisms. Key processes are discussed, including mitochondrial dysfunction, oxidative stress, cardiac structural derangements, abnormal cardiac conduction, ion channel dysfunction, prolonged repolarization and dysregulation of intracellular sodium and calcium homeostasis. In addition, the recently identified pro-arrhythmic effects of dysregulated branched chain amino acid metabolism, a common feature in patients with metabolic disorders, are addressed. Finally, current management options are discussed, in addition to the potential development of novel preventive and therapeutic strategies based on recent insight gained from translational studies.

The effects of two types of Western diet on the induction of metabolic syndrome and cardiac remodeling in obese rats

Metabolic syndrome (MetS) include obesity as a critical feature and is strongly associated with risk of cardiovascular disease (CVD). Insights into mechanisms involved in the pathophysiology of these clinical manifestations are essential for the development of therapeutic strategies. Thus, Western diets (WD) have been widely employed in diet-induced obesity (DIO) model. However, there are variations in fat and sugar proportions of such diets, making comparisons challenging. We aimed to assess the impact of two types of the WD on metabolic status and cardiac remodeling, to achieve a DIO model that better mimics the human pathogenesis of MetS-induced CVD. Male Wistar rats were distributed into three groups: control diet, Western diet fat (WDF), and Western diet sugar (WDS) for 41 weeks. Metabolic and inflammatory parameters and cardiac changes were characterized. WDF and WDS feeding promoted higher serum triglycerides, glucose intolerance, and insulin resistance, while just WDF presented inflammation in adipose tissue. WDF-fed rats showed increased catalase activity and malondialdehyde (MDA) and carbonyl protein levels, suggesting cardiac oxidative stress, while WDS-fed rats only raised MDA. Both WD equally elevated protein expressions involved in lipid metabolism, but only WDF downregulated the glycolysis pathway. Furthermore, the mechanical myocardial function was impaired in obese rats, being more relevant in WDF. In conclusion, both WD effectively triggered MetS features, although inflammation was detected just on the WDF-fed animals. Moreover, the WDF promoted a more pronounced functional, metabolic, and oxidative cardiac disorder, suggesting to be an adequate model for studying CVD in the scenario of MetS.

Deficiency of ataxia-telangiectasia mutated kinase modulates functional and biochemical parameters of the heart in response to Western-type diet

Ataxia-telangiectasia mutated (ATM) kinase deficiency exacerbates heart dysfunction late after myocardial infarction. Here, we hypothesized that ATM deficiency modulates Western-type diet (WD)-induced cardiac remodeling with an emphasis on functional and biochemical parameters of the heart. Weight gain was assessed in male wild-type (WT) and ATM heterozygous knockout (hKO) mice on weekly basis, whereas cardiac functional and biochemical parameters were measured 14 wk post-WD. hKO-WD mice exhibited rapid body weight gain at weeks 5, 6, 7, 8, and 10 versus WT-WD. WD decreased percent fractional shortening and ejection fraction, and increased end-systolic volumes and diameters to a similar extent in both genotypes. However, WD decreased stroke volume, cardiac output, peak velocity of early ventricular filling, and aortic ejection time and increased isovolumetric relaxation time (IVRT) and Tei index versus WT-NC (normal chow). Conversely, IVRT, isovolumetric contraction time, and Tei index were lower in hKO-WD versus hKO-NC and WT-WD. Myocyte apoptosis and hypertrophy were higher in hKO-WD versus WT-WD. WD increased fibrosis and expression of collagen-1α1, matrix metalloproteinase (MMP)-2, and MMP-9 in WT. WD enhanced AMPK activation, while decreasing mTOR activation in hKO. Akt and IKK-α/β activation, and Bax, PARP-1, and Glut-4 expression were higher in WT-WD versus WT-NC, whereas NF-κB activation and Glut-4 expression were lower in hKO-WD versus hKO-NC. Circulating concentrations of IL-12(p70), eotaxin, IFN-γ, macrophage inflammatory protein (MIP)-1α, and MIP-1β were higher in hKO-WD versus WT-WD. Thus, ATM deficiency accelerates weight gain, induces systolic dysfunction with increased preload, and associates with increased apoptosis, hypertrophy, and inflammation in response to WD.NEW & NOTEWORTHY Ataxia-telangiectasia mutated (ATM) kinase deficiency in humans associates with enhanced susceptibility to ischemic heart disease. Here, we provide evidence that ATM deficiency accelerates body weight gain and associates with increased cardiac preload, hypertrophy, and apoptosis in mice fed with Western-type diet (WD). Further investigations of the role of ATM deficiency in WD-induced alterations in function and biochemical parameters of the heart may provide clinically applicable information on treatment and/or nutritional counseling for patients with ATM deficiency.

Voluntary activity reverses spermidine-induced myocardial fibrosis and lipid accumulation in the obese male mouse

Obesity due to high calorie intake induces cardiac hypertrophy and dysfunction, thus contributing to cardiovascular morbidity and mortality. Recent studies in aging suggest that oral supplementation with the natural polyamine spermidine has a cardioprotective effect. Here, the hypothesis was tested that spermidine or voluntary activity alone or in combination protect the heart from adverse effects induced by obesity. Therefore, C57Bl/6 mice (n = 8–10 per group) were subjected to control or high fat diet (HFD) and were left untreated, or either received spermidine via drinking water or were voluntarily active or both. After 30 weeks, the mice were killed and the left ventricle of the hearts was processed for light and electron microscopy. Design-based stereology was used to estimate parameters of hypertrophy, fibrosis, and lipid accumulation. HFD induced cardiac hypertrophy as demonstrated by higher volumes of the left ventricle, cardiomyocytes, interstitium, myofibrils and cardiomyocyte mitochondria. These changes were not influenced by spermidine or voluntary activity. HFD also induced myocardial fibrosis and accumulation of lipid droplets within cardiomyocytes. These HFD effects were enhanced in spermidine treated animals but not in voluntarily active mice. This was even the case in voluntarily active mice that received spermidine. In conclusion, the data confirm the induction of left ventricular hypertrophy by high-fat diet and suggest that—under high fat diet—spermidine enhances cardiomyocyte lipid accumulation and interstitial fibrosis which is counteracted by voluntary activity.

AT1Receptor Blockade Improves Myocardial Functional Performance in Obesity

Fundamento

A obesidade tem sido associada com ativação crônica do sistema renina-angiotensina-aldosterona e importantes alterações no desempenho cardíaco.

Objetivo

Avaliar a influência do bloqueio de receptores de angiotensina-II do tipo 1 (AT₁) sobre a morfologia e desempenho cardíaco de ratos obesos por dieta

Métodos

Ratos Wistar (n=48) foram submetidos a dieta controle (2,9 kcal/g) ou hiperlipídica (3,6 kcal/g) durante 20 semanas. Após a 16ª semana, foram distribuídos em quatro grupos: Controle (CO), Obeso (OB), Controle Losartan (CL) e Obeso Losartan (OL). CL e OL receberam losartan (30 mg/kg/dia) na água durante quatro semanas. Posteriormente, foram analisadas composição corporal, pressão arterial sistólica (PAS) e ecocardiograma. A função de músculos papilares foi avaliada em situação basal com concentração de cálcio ([Ca²⁺]_o) de 2,50 mM e após manobras inotrópicas: potencial pós-pausa (PPP), elevação da [Ca²⁺]_o e durante estimulação beta-adrenérgica com isoproterenol. A análise dos resultados foi feita por meio de Two-Way ANOVA e teste de comparações apropriado. O nível de significância considerado foi de 5%.

Resultados

Embora a alteração da PAS não tenha se mantido ao final do experimento, a obesidade se associou com hipertrofia cardíaca e maior velocidade de encurtamento da parede posterior do ventrículo esquerdo.No estudo de músculos papilares em condição basal, CL mostrou menor velocidade máxima de variação negativa da tensão desenvolvida (-dT/dt) do que CO. O PPP de 60s promoveu menor -dT/dt e pico de tensão desenvolvida (TD) em OB e CL, comparados ao CO, e maior variação relativa de TD e velocidade máxima de variação positiva (+dT/dt) no OL em relação a CL e OB. Sob 1,5, 2,0 e 2,5mM de [Ca²⁺]_o, o grupo OL exibiu maior -dT/dt do que CL.

Conclusão

Losartan melhora a função miocárdica de ratos com obesidade induzida por dieta. (Arq Bras Cardiol. 2020; 115(1):17-28)

Mechanical function of cardiac fibre bundles is partly protected by exercise in response to diet-induced obesity in rats

Decrements in contractile function resulting from obesity are thought to be major reasons for the link between obesity and cardiovascular disease, while exercise has been shown to improve cardiac muscle contractile function. The purpose of this study was to evaluate cardiac contractile properties following obesity induction and the potential protective effect of exercise. Twelve-week-old rats (n = 30) were organized into either a chow diet or a high-fat, high-sucrose (HFHS) diet group. Following 12 weeks of obesity induction the HFHS group animals were stratified and grouped into sedentary (HFHS+Sed) and exercise (HFHS+Ex) groups for an additional 12 weeks. Following 24 weeks of diet intervention, with 12 weeks of aerobic exercise (25 m/min, 30 min/day, 5 days/week) for the HFHS+Ex group, skinned cardiac fibre bundle testing was used to evaluate cardiac contractile properties. Body fat and mass were significantly greater in the HFHS-fed animals compared with the chow controls (p < 0.043). Hearts from rats in the HFHS+Sed group had significantly greater mass (p < 0.03), significantly slower maximum shortening velocity (p = 0.001), and tended to have lower calcium sensitivity (p = 0.077) and a lower proportion of α-myosin heavy chain composition (p = 0.074) than the sedentary chow animals. However, 12 weeks of moderate aerobic exercise partially prevented these decrements in contractile properties. Novelty Cardiac muscle from animals exposed to an obesogenic diet for 24 weeks had impaired contractile properties compared with controls. Obesity-induced impairment of contractile properties of the heart were partially prevented by a 12-week aerobic exercise regime.

Temporal Measures in Cardiac Structure and Function During the Development of Obesity Induced by Different Types of Western Diet in a Rat Model

Obesity is recognized worldwide as a complex metabolic disorder that has reached epidemic proportions and is often associated with a high incidence of cardiovascular diseases. To study this pathology and evaluate cardiac function, several models of diet-induced obesity (DIO) have been developed. The Western diet (WD) is one of the most widely used models; however, variations in diet composition and time period of the experimental protocol make comparisons challenging. Thus, this study aimed to evaluate the effects of two different types of Western diet on cardiac remodeling in obese rats with sequential analyses during a long-term follow-up. Male Wistar rats were distributed into three groups fed with control diet (CD), Western diet fat (WDF), and Western diet sugar (WDS) for 41 weeks. The animal nutritional profile and cardiac histology were assessed at the 41st week. Cardiac structure and function were evaluated by echocardiogram at four different moments: 17, 25, 33, and 41 weeks. A noninvasive method was performed to assess systolic blood pressure at the 33rd and 41st week. The animals fed with WD (WDF and WDS) developed pronounced obesity with an average increase of 86.5% in adiposity index at the end of the experiment. WDF and WDS groups also presented hypertension. The echocardiographic data showed no structural differences among the three groups, but WDF animals presented decreased endocardial fractional shortening and ejection fraction at the 33rd and 41st week, suggesting altered systolic function. Moreover, WDF and WFS animals did not present hypertrophy and interstitial collagen accumulation in the left ventricle. In conclusion, both WD were effective in triggering severe obesity in rats; however, only the WDF induced mild cardiac dysfunction after long-term diet exposure. Further studies are needed to search for an appropriate DIO model with relevant cardiac remodeling.

Chronic intermittent electronic cigarette exposure induces cardiac dysfunction and atherosclerosis in apolipoprotein-E knockout mice

Electronic cigarettes (e-cigarettes), also known as electronic nicotine delivery systems, are a popular alternative to conventional nicotine cigarettes, both among smokers and those who have never smoked. In spite of the widespread use of e-cigarettes and the proposed detrimental cardiac and atherosclerotic effects of nicotine, the effects of e-cigarettes on these systems are not known. In this study, we investigated the cardiovascular and cardiac effects of e-cigarettes with and without nicotine in apolipoprotein-E knockout (ApoE^-/-) mice. We developed an e-cigarette exposure model that delivers nicotine in a manner similar to that of human e-cigarettes users. Using commercially available e-cigarettes, bluCig PLUS, ApoE^-/- mice were exposed to saline, e-cigarette without nicotine [e-cigarette (0%)], and e-cigarette with 2.4% nicotine [e-cigarette (2.4%)] aerosol for 12 wk. Echocardiographic data show that mice treated with e-cigarette (2.4%) had decreased left ventricular fractional shortening and ejection fraction compared with e-cigarette (0%) and saline. Ventricular transcriptomic analysis revealed changes in genes associated with metabolism, circadian rhythm, and inflammation in e-cigarette (2.4%)-treated ApoE^-/- mice. Transmission electron microscopy revealed that cardiomyocytes of mice treated with e-cigarette (2.4%) exhibited ultrastructural abnormalities indicative of cardiomyopathy. Additionally, we observed increased oxidative stress and mitochondrial DNA mutations in mice treated with e-cigarette (2.4%). ApoE^-/- mice on e-cigarette (2.4%) had also increased atherosclerotic lesions compared with saline aerosol-treated mice. These results demonstrate adverse effects of e-cigarettes on cardiac function in mice.NEW & NOTEWORTHY The present study is the first to show that mice exposed to nicotine electronic cigarettes (e-cigarettes) have decreased cardiac fractional shortening and ejection fraction in comparison with controls. RNA-seq analysis reveals a proinflammatory phenotype induced by e-cigarettes with nicotine. We also found increased atherosclerosis in the aortic root of mice treated with e-cigarettes with nicotine. Our results show that e-cigarettes with nicotine lead to detrimental effects on the heart that should serve as a warning to e-cigarette users and agencies that regulate them.

Effects of AT1 receptor antagonism on interstitial and ultrastructural remodeling of heart in response to a hypercaloric diet

Palatable hypercaloric feeding has been associated with angiotensin-II type 1 receptor (AT1R) stimulation and cardiac remodeling. This study analyzed whether AT1R antagonism attenuates cardiac remodeling in rats subjected to a palatable hypercaloric diet. Male Wistar-Kyoto rats were subjected to a commercial standard rat chow (CD) or a palatable hypercaloric diet (HD) for 35 weeks and then allocated into four groups: CD, CL, HD, and HL; L groups received losartan in drinking water (30 mg/kg/day) for 5 weeks. Body weight, adiposity, and glycemia were evaluated. The cardiovascular study included echocardiography, and myocardial morphometric and ultrastructural evaluation. Myocardial collagen isoforms Type I and III were analyzed by Western blot. Both HD and HL had higher adiposity than their respective controls. Cardiomyocyte cross-sectional-area (CD 285 ± 49; HD 344 ± 91; CL 327 ± 49; HL 303 ± 49 μm2 ) and interstitial collagen fractional area were significantly higher in HD than CD and unchanged by losartan. HD showed marked ultrastructural alterations such as myofilament loss, and severe mitochondrial swelling. CL presented higher Type I collagen expression when compared to CD and HL groups. The ultrastructural changes and type I collagen expression were attenuated by losartan in HL. Losartan attenuates systolic dysfunction and ultrastructural abnormalities without changing myocardial interstitial remodeling in rats subjected to a palatable hypercaloric diet.

Association between Cardiac Remodeling and Metabolic Alteration in an Experimental Model of Obesity Induced by Western Diet

The high consumption of fat and sugar contributes to the development of obesity and co-morbidities, such as dyslipidemia, hypertension, and cardiovascular disease. The aim of this study was to evaluate the association between dyslipidemia and cardiac dysfunction induced by western diet consumption. Wistar rats were randomly divided into two experimental groups and fed ad libitum for 20 weeks with a control diet (Control, n = 12) or a high-sugar and high-fat diet (HSF, n = 12). The HSF group also received water + sucrose (25%). Evaluations included feed and caloric intake; body weight; plasma glucose; insulin; uric acid; HOMA-IR; lipid profile: [total cholesterol (T-chol), high-density lipoprotein (HDL), non-HDL Chol, triglycerides (TG)]; systolic blood pressure, and Doppler echocardiographic. Compared to the control group, animals that consumed the HSF diet presented higher weight gain, caloric intake, feed efficiency, insulin, HOMA-IR, and glucose levels, and lipid profile impairment (higher TG, T-chol, non-HDL chol and lower HDL). HSF diet was also associated with atrial-ventricular structural impairment and systolic-diastolic dysfunction. Positive correlation was also found among the following parameters: insulin versus estimated LV mass (r = 0.90, p = 0.001); non-HDL versus deceleration time (r = 0.46, p = 0.02); TG versus deceleration time (r = 0.50, p = 0.01). In summary, our results suggest cardiac remodeling lead by western diet is associated with metabolic parameters.

Quercetin Prevents Diastolic Dysfunction Induced by a High-Cholesterol Diet: Role of Oxidative Stress and Bioenergetics in Hyperglycemic Rats

Alterations in cardiac energy metabolism play a key role in the pathogenesis of diabetic cardiomyopathy. Hypercholesterolemia associated with bioenergetic impairment and oxidative stress has not been well characterized in the cardiac function under glycemic control deficiency conditions. This work aimed to determine the cardioprotective effects of quercetin (QUE) against the damage induced by a high-cholesterol (HC) diet in hyperglycemic rats, addressing intracellular antioxidant mechanisms and bioenergetics. Quercetin reduced HC-induced alterations in the lipid profile and glycemia in rats. In addition, QUE attenuated cardiac diastolic dysfunction (increased E:A ratio), prevented cardiac cholesterol accumulation, and reduced the increase in HC-induced myocyte density. Moreover, QUE reduced HC-induced oxidative stress by preventing the decrease in GSH/GSSG ratio, Nrf2 nuclear translocation, HO-1 expression, and antioxidant enzymatic activity. Quercetin also counteracted HC-induced bioenergetic impairment, preventing a reduction in ATP levels and alterations in PGC-1α, UCP2, and PPARγ expression. In conclusion, the mechanisms that support the cardioprotective effect of QUE in rats with HC might be mediated by the upregulation of antioxidant mechanisms and improved bioenergetics on the heart. Targeting bioenergetics with QUE can be used as a pharmacological approach to modulate structural and functional changes of the heart under hypercholesterolemic and hyperglycemic conditions.

Dietary Fat, Sugar Consumption, and Cardiorespiratory Fitness in Patients With Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is associated with obesity and, indirectly, with unhealthy diet. The role of dietary components in HFpEF is, however, largely unknown. In this study, the authors showed that in obese HFpEF patients, consumption of unsaturated fatty acids (UFA), was associated with better cardiorespiratory fitness, and UFA consumption correlated with better diastolic function and with greater fat-free mass. Similarly, mice fed with a high-fat diet rich in UFA and low in sugars had preserved myocardial function and reduced weight gain. Randomized clinical trials increasing dietary UFA consumption and reducing sugar consumption are warranted to confirm and expand our findings.

Saturated high-fat diet-induced obesity increases adenylate cyclase of myocardial β-adrenergic system and does not compromise cardiac function

Obesity is a worldwide pandemic associated with high incidence of cardiovascular disease. The mechanisms by which the obesity leads cardiac dysfunction are not fully elucidated and few studies have evaluated the relationship between obesity and proteins involved in myocardial β‐adrenergic (βA) system. The purpose of this study was to evaluate the cardiac function and βA pathway components in myocardium of obese rats. Male Wistar rats were distributed into two groups: control (n = 17; standard diet) and obese (n = 17; saturated high‐fat diet) fed for 33 weeks. Nutritional profile and comorbidities were assessed. Cardiac structure and function was evaluated by macroscopic postmortem, echocardiographic and isolated papillary muscle analyzes. Myocardial protein expression of β₁‐ and β₂‐adrenergic receptors, Gαs protein, adenylate cyclase (AC) and protein kinase A (PKA) was performed by Western blot. Cardiac cyclic adenosine monophosphate (cAMP) levels and PKA activity were assessed by ELISA. Obese rats showed increased adiposity index (P < 0.001) and several comorbidities as hypertension, glucose intolerance, insulin resistance, and dyslipidemia compared with control rats. Echocardiographic assessment revealed increased left atrium diameter (C: 4.98 ± 0.38 vs. Ob: 5.47 ± 0.53, P = 0.024) and posterior wall shortening velocity (C: 37.1 ± 3.6 vs. Ob: 41.8 ± 3.8, P = 0.007) in obese group. Papillary muscle evaluation indicated that baseline data and myocardial responsiveness to isoproterenol stimulation were similar between the groups. Protein expression of myocardial AC was higher in obese group than in the control (C: 1.00 ± 0.21 vs. Ob: 1.25 ± 0.10, P = 0.025), whereas the other components were unchanged. These results suggest that saturated high‐fat diet‐induced obesity was not effective in triggering cardiac dysfunction and impair the beta‐adrenergic signaling.

Proinflammatory Cytokines Are Soluble Mediators Linked with Ventricular Arrhythmias and Contractile Dysfunction in a Rat Model of Metabolic Syndrome

Metabolic syndrome (MS) increases cardiovascular risk and is associated with cardiac dysfunction and arrhythmias, although the precise mechanisms are still under study. Chronic inflammation in MS has emerged as a possible cause of adverse cardiac events. Male Wistar rats fed with 30% sucrose in drinking water and standard chow for 25–27 weeks were compared to a control group. The MS group showed increased weight, visceral fat, blood pressure, and serum triglycerides. The most important increases in serum cytokines included IL-1β (7-fold), TNF-α (84%), IL-6 (41%), and leptin (2-fold), the latter also showing increased gene expression in heart tissue (35-fold). Heart function ex vivo in MS group showed a decreased mechanical performance response to isoproterenol challenge (ISO). Importantly, MS hearts under ISO showed nearly twofold the incidence of ventricular fibrillation. Healthy rat cardiomyocytes exposed to MS group serum displayed impaired contractile function and Ca²⁺ handling during ISO treatment, showing slightly decreased cell shortening and Ca²⁺ transient amplitude (23%), slower cytosolic calcium removal (17%), and more frequent spontaneous Ca²⁺ release events (7.5-fold). As spontaneous Ca²⁺ releases provide a substrate for ventricular arrhythmias, our study highlights the possible role of serum proinflammatory mediators in the development of arrhythmic events during MS.

Investigating interactions between epicardial adipose tissue and cardiac myocytes: what can we learn from different approaches?

Heart disease is a major cause of morbidity and mortality throughout the world. Some cardiovascular conditions can be modulated by lifestyle factors such as increased exercise or a healthier diet, but many require surgical or pharmacological interventions for their management. More targeted and less invasive therapies would be beneficial. Recently, it has become apparent that epicardial adipose tissue plays an important role in normal and pathological cardiac function, and it is now the focus of considerable research. Epicardial adipose tissue can be studied by imaging of various kinds, and these approaches have yielded much useful information. However, at a molecular level, it is more difficult to study as it is relatively scarce in animal models and, for practical and ethical reasons, not always available in sufficient quantities from patients. What is needed is a robust model system in which the interactions between epicardial adipocytes and cardiac myocytes can be studied, and physiologically relevant manipulations performed. There are drawbacks to conventional culture methods, not least the difficulty of culturing both cardiac myocytes and adipocytes, each of which has special requirements. We discuss the benefits of a three-dimensional co-culture model in which in vivo interactions can be replicated.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Obesity and Heart Failure: Focus on the Obesity Paradox

The escalating prevalence of obesity has been linked to substantial increases in both metabolic and cardiovascular disease. Nevertheless, the direct effects of obesity on cardiovascular health and function require further exploration. In particular, the relationship between obesity and cardiac function has received intense scrutiny. Although obesity increases the risk for development of heart failure (HF), it appears to exert a protective effect in patients in whom HF has already been diagnosed (the "obesity paradox"). The protective effects of obesity in patients with previously diagnosed HF are the focus of particularly intense research. Several explanations have been proposed, but most studies are limited by the use of body mass index to classify obesity. Because body mass index does not distinguish between fat mass, fat-free mass, and lean mass, individuals with similar body mass indices may have vastly different body composition. This article discusses the roles of body composition, diet, cardiorespiratory fitness, and weight loss in the development of cardiac dysfunction and HF and the potential protective role that body composition compartments might play in improving HF prognosis. Based on an intensive literature search (Pubmed, Google Scholar) and critical review of the literature, we also discuss how a multidisciplinary approach including a nutritional intervention targeted to reduce systemic inflammation and lean mass-targeted exercise training could potentially exert beneficial effects for patients with HF.

The Circulatory and Metabolic Responses to Hypoxia in Humans - With Special Reference to Adipose Tissue Physiology and Obesity

Adipose tissue metabolism and circulation play an important role in human health. It is well-known that adipose tissue mass is increased in response to excess caloric intake leading to obesity and further to local hypoxia and inflammatory signaling. Acute exercise increases blood supply to adipose tissue and mobilization of fat stores for energy. However, acute exercise during systemic hypoxia reduces subcutaneous blood flow in healthy young subjects, but the response in overweight or obese subjects remains to be investigated. Emerging evidence also indicates that exercise training during hypoxic exposure may provide additive benefits with respect to many traditional cardiovascular risk factors as compared to exercise performed in normoxia, but unfavorable effects of hypoxia have also been documented. These topics will be covered in this brief review dealing with hypoxia and adipose tissue physiology.