A high-fructose diet worsens eccentric left ventricular hypertrophy in experimental volume overload

Aging Increases Susceptibility to Develop Cardiac Hypertrophy following High Sugar Consumption

Aging and poor diet are independent risk factors for heart disease, but the impact of high-sucrose (HS) consumption in the aging heart is understudied. Aging leads to impairments in mitochondrial function that result in muscle dysfunction (e.g., cardiac remodeling and sarcopenia). We tested whether HS diet (60%kcal sucrose) would accelerate muscle dysfunction in 24-month-old male CB6F1 mice. By week 1 on HS diet, mice developed significant cardiac hypertrophy compared to age-matched chow-fed controls. The increased weight of the heart persisted throughout the 4-week treatment, while body weight and strength declined more rapidly than controls. We then tested whether HS diet could worsen cardiac dysfunction in old mice and if the mitochondrial-targeted drug, elamipretide (ELAM), could prevent the diet-induced effect. Old and young mice were treated with either ELAM or saline as a control for 2 weeks, and provided with HS diet or chow on the last week. As demonstrated in the previous experiment, old mice had age-related cardiac hypertrophy that worsened after one week on HS and was prevented by ELAM treatment, while the HS diet had no detectable effect on hypertrophy in the young mice. As expected, mitochondrial respiration and reactive oxygen species (ROS) production were altered by age, but were not significantly affected by HS diet or ELAM. Our findings highlight the vulnerability of the aged heart to HS diet that can be prevented by systemic targeting of the mitochondria with ELAM.

Dietary sucrose induces metabolic inflammation and atherosclerotic cardiovascular diseases more than dietary fat in LDLr-/-ApoB100/100 mice

BACKGROUND AND AIMS

Poor dietary habits contribute to the obesity pandemic and related cardiovascular diseases but the respective impact of high saturated fat versus added sugar consumption remains debated. Herein, we aimed to disentangle the individual role of dietary fat versus sugar in cardiometabolic disease progression.

METHODS

We fed pro-atherogenic LDLr^-/-ApoB^100/100 mice either a low-fat/high-sucrose (LFHS) or a high-fat/low-sucrose (HFLS) diet for 24 weeks. Weekly body weight gain was registered. 16S rRNA gene-based gut microbial analysis was performed to investigate gut microbial modulations. Intraperitoneal insulin (ipITT) and oral glucose tolerance test (oGTT) were conducted to assess glucose homeostasis and insulin sensitivity. Cytokines were assessed in fasted plasma, epididymal white adipose tissue and liver lysates. Heart function was evaluated by echocardiography. Aortic atheroma lesions were quantified according to the en face technique.

RESULTS

HFLS feeding increased obesity, insulin resistance and dyslipidemia compared to LFHS feeding. Conversely, high sucrose consumption decreased gut microbial diversity while augmenting inflammation and the adaptative immune defense against metabolic endotoxemia and reduced macrophage cholesterol efflux capacity. This led to more severe cardiovascular complications as revealed by remarkably high level of atherosclerotic lesions and the early development of cardiac dysfunction in LFHS vs HFLS fed mice.

CONCLUSIONS

We uncoupled obesity-associated insulin resistance from cardiovascular diseases and provided novel evidence that dietary sucrose, not fat, is the main driver of metabolic inflammation accelerating severe atherosclerosis in hyperlipidemic mice.

Level of Physical Activity, Left Ventricular Mass, Hypertension, and Prognosis

Left ventricular hypertrophy is a strong predictor of prognosis in hypertension. Physical activity is associated with higher left ventricular mass but also reduced risk of cardiovascular outcomes. The aims were to explore whether (1) presence of hypertension modifies the association between physical activity and left ventricular mass; (2) the beneficial association between physical activity and prognostic outcome is modified by left ventricular hypertrophy. Randomly selected number of 3078 persons from the general population underwent echocardiogram. Left ventricular mass was indexed to body surface area. Level of physical activity was self-reported: inactivity, light activity, and moderate/high activity. Blood pressure was measured in rest: normal BP (<140/90 mm Hg) and hypertension (≥140/90 mm Hg or in pharmacological treatment for hypertension). Presence of hypertension modified the association between physical activity and left ventricular mass index significantly (test for interaction: P =0.01): in normal BP, higher levels of physical activity were associated with significantly higher left ventricular mass index ( P <0.001), but this was not present in hypertension ( P =0.90). Level of physical activity was associated with reduction in mortality and cardiovascular outcome independent of the presence of LVH (Persons with LVH: light activity HR, 0.77 [0.52–1.15], moderate/high activity HR, 0.61 [0.38–0.97]; test for interaction between LVH and level of physical activity P =0.71). In conclusion, persons with normal BP had higher left ventricular mass index at increased levels of physical activity, whereas this association was not present among persons with hypertension. Level of physical activity was associated with better prognosis independent of whether left ventricular hypertrophy was present or not.

Heart Plasticity in Response to Pressure- and Volume-Overload: A Review of Findings in Compensated and Decompensated Phenotypes

The adult human heart has an exceptional ability to alter its phenotype to adapt to changes in environmental demand. This response involves metabolic, mechanical, electrical, and structural alterations, and is known as cardiac plasticity. Understanding the drivers of cardiac plasticity is essential for development of therapeutic agents. This is particularly important in contemporary cardiology, which uses treatments with peripheral effects (e.g., on kidneys, adrenal glands). This review focuses on the effects of different hemodynamic loads on myocardial phenotype. We examine mechanical scenarios of pressure- and volume overload, from the initial insult, to compensated, and ultimately decompensated stage. We discuss how different hemodynamic conditions occur and are underlined by distinct phenotypic and molecular changes. We complete the review by exploring how current basic cardiac research should leverage available cardiac models to study mechanical load in its different presentations.

Aerobic exercise modulates cardiac NAD(P)H oxidase and the NRF2/KEAP1 pathway in a mouse model of chronic fructose consumption

The present study investigated the effects of exercise on the cardiac nuclear factor (erythroid-derived 2) factor 2 (NRF2)/Kelch-like ECH-associated protein 1 (KEAP1) pathway in an experimental model of chronic fructose consumption. Male C57BL/6 mice were assigned to Control, Fructose (20% fructose in drinking water), Exercise (treadmill exercise at moderate intensity), and Fructose + Exercise groups ( n = 10). After 12 wk, the energy intake and body weight in the groups were similar. Maximum exercise testing, resting energy expenditure, resting oxygen consumption, and carbon dioxide production increased in the exercise groups (Exercise and Fructose + Exercise vs. Control and Fructose groups, P < 0.05). Chronic fructose intake induced circulating hypercholesterolemia, hypertriglyceridemia, and hyperleptinemia and increased white adipose tissue depots, with no changes in blood pressure. This metabolic environment increased circulating IL-6, IL-1β, IL-10, cardiac hypertrophy, and cardiac NF-κB-p65 and TNF-α expression, which were reduced by exercise ( P < 0.05). Cardiac ANG II type 1 receptor and NAD(P)H oxidase 2 (NOX2) were increased by fructose intake and exercise decreased this response ( P < 0.05). Exercise increased the cardiac expression of the NRF2-to-KEAP1 ratio and phase II antioxidants in fructose-fed mice ( P < 0.05). NOX4, glutathione reductase, and catalase protein expression were similar between the groups. These findings suggest that exercise confers modulatory cardiac effects, improving antioxidant defenses through the NRF2/KEAP1 pathway and decreasing oxidative stress, representing a potential nonpharmacological approach to protect against fructose-induced cardiometabolic diseases.

NEW & NOTEWORTHY This is the first study to evaluate the cardiac modulation of NAD(P)H oxidase (NOX), the NRF2/Kelch-like ECH-associated protein 1 pathway (KEAP), and the thioredoxin (TRX1) system through exercise in the presence of moderate fructose intake. We demonstrated a novel mechanism by which exercise improves cardiac antioxidant defenses in an experimental model of chronic fructose intake, which involves NRF2-to-KEAP1 ratio modulation, enhancing the local phase II antioxidants hemoxygenase-1, thioredoxin reductase (TXNRD1), and peroxiredoxin1B (PDRX1), and inhibiting cardiac NOX2 overexpression.

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.

Sex differences in the response to angiotensin II receptor blockade in a rat model of eccentric cardiac hypertrophy

Background. Men and women differ in their susceptibility to cardiovascular disease, though the underlying mechanism has remained elusive. Heart disease symptoms, evolution and response to treatment are often sex-specific. This has been studied in animal models of hypertension or myocardial infarction in the past but has received less attention in the context of heart valve regurgitation. The aim of the study was to evaluate the development of cardiac hypertrophy (CH) in response to left ventricle (LV) volume overload (VO) caused by chronic aortic valve regurgitation (AR) in male and female rats treated or not with angiotensin II receptor blocker (ARB), valsartan. We studied eight groups of Wistar rats: male or female, AR or sham-operated (sham) and treated or not with valsartan (30 mg/kg/day) for 9 weeks starting one week before AR surgical induction.

Results. As expected, VO from AR resulted for both male and female rats in significant LV dilation (39% vs. 40% end-diastolic LV diameter increase, respectively; p < 0.0001) and CH (53% vs. 64% heart weight increase, respectively; p < 0.0001) compared to sham. Sex differences were observed in LV wall thickening in response to VO. In untreated AR males, relative LV wall thickness (a ratio of wall thickness to end-diastolic diameter) was reduced compared to sham, whereas this ratio in females remained unchanged. ARB treatment did not prevent LV dilation in both male and female animals but reversed LV wall thickening in females. Systolic and diastolic functions in AR animals were altered similarly for both sexes. ARB treatment did not improve systolic function but helped normalizing diastolic parameters such as left atrial mass and E wave slope in female AR rats. Increased LV gene expression of Anp and Bnp was normalized by ARB treatment in AR females but not in males. Other hypertrophy gene markers (Fos, Trpc6, Klf15, Myh6 and Myh7) were not modulated by ARB treatment. The same was true for genes related to LV extracellular matrix remodeling (Col1a1, Col3a1, Fn1, Mmp2, Timp1 and Lox). In summary, ARB treatment of rats with severe AR blocked the female-specific hypertrophic response characterized by LV chamber wall thickening. LV dilation, on the other hand, was not significantly decreased by ARB treatment. This also indicates that activation of the angiotensin II receptor is probably more involved in the early steps of LV remodeling caused by AR in females than in males.

Preventive effects of l-glutamine on gestational fructose-induced cardiac hypertrophy: involvement of pyruvate dehydrogenase kinase-4

Gestational fructose exposure has detrimental health consequences on both the maternal and fetus or offspring in the early or later life, contributing to epidemic rise in cardiometabolic syndrome including cardiac events. l-Glutamine has been shown to mitigate cardiac metabolic stress. However, the effect of l-glutamine on cardiac hypertrophy induced by gestational fructose exposure is not known. We therefore hypothesized that l-glutamine would prevent gestational fructose-induced cardiac hypertrophy, possibly by suppression of pyruvate dehydrogenase kinase-4 (PDK-4). Pregnant Wistar rats were allotted into the control, l-glutamine, gestational fructose exposure, and gestational fructose exposure plus l-glutamine groups (6 rats in each group). The groups received distilled water (vehicle, per os), 1 g/kg body weight l-glutamine (per os), 10% fructose (w/v) and 10% fructose (w/v) plus 1 g/kg l-glutamine (per os), respectively, daily for 19 days. Data from this study showed that gestational fructose-enriched drink caused cardiac hypertrophy with correspondent body weight gain, glucose dysregulation, increased cardiac PDK-4, triglyceride, glycogen, lactate, and uric acid production. On the other hand, defective glutathione-dependent antioxidant barrier was also observed in pregnant rats taking fructose-enriched drink. However, the gestational fructose-induced cardiac hypertrophy and its correlates were attenuated by l-glutamine. The present results demonstrate that gestational fructose-enriched drink induces cardiac hypertrophy that is accompanied by increased PDK-4. The findings also suggest that the inhibitory effect of l-glutamine on PDK-4 prevents the development of cardiac hypertrophy, thereby implying that PDK-4 may be a potential novel therapeutic intervention for cardiac hypertrophy especially in pregnancy.

Testosterone deficiency reduces cardiac hypertrophy in a rat model of severe volume overload

The aim of the study was to characterize if the development of cardiac hypertrophy (CH) caused by severe left ventricle (LV) volume overload (VO) from chronic aortic valve regurgitation (AR) in male rats was influenced by androgens. We studied Wistar rats with/without orchiectomy (Ocx) either sham-operated (S) or with severe AR for 26 weeks. Loss of testosterone induced by Ocx decreased general body growth. Cardiac hypertrophy resulting from AR was relatively more important in intact (non-Ocx) animals than in Ocx ones compared to their respective S group (60% vs. 40%; P = 0.019). The intact AR group had more LV dilation, end-diastolic LV diameter being increased by 37% over S group and by 17% in AROcx rats (P < 0.0001). Fractional shortening (an index of systolic function) decreased only by 15% in AROcx compared to 26% for intact AR animals (P = 0.029). Changes in LV gene expression resulting from CH were more marked in intact rats than in AROcx animals, especially for genes linked to extracellular matrix remodeling and energy metabolism. The ratio of hydroxyacyl-Coenzyme A dehydrogenase activity over hexokinase activity, an index of the shift of myocardial substrate use toward glucose from the preferred fatty acids, was significantly decreased in the AR group but not in AROcx. Finally, pJnk2 LV protein content was more abundant in AR than in AROcx rats, indicating decreased activation of this stress pathway in the absence of androgens. In summary, testosterone deficiency in rats with severe LV VO resulted in less CH and a normalization of the LV gene expression profile.

Oral ethinylestradiol-levonorgestrel attenuates cardiac glycogen and triglyceride accumulation in high fructose female rats by suppressing pyruvate dehydrogenase kinase-4

Fructose (FRU) intake has increased dramatically in recent decades with a corresponding increased incidence of insulin resistance (IR), particularly in young adults. The use of oral ethinylestradiol-levonorgestrel (EEL) formulation is also common among young women worldwide. The present study aimed at determining the effect of EEL on high fructose-induced cardiac triglyceride (TG) and glycogen accumulation. The study also investigated the possible involvement of pyruvate dehydrogenase kinase-4 (PDK-4) in EEL and/or high fructose metabolic effects on the heart. Ten-week-old female Wistar rats were allotted into four groups. The control, EEL, FRU, and EEL + FRU rats received distilled water (vehicle, p.o.), 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel (p.o.), 10% fructose (w/v), and 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel and 10% fructose, respectively, daily for 8 weeks. Data showed that EEL or high fructose caused IR' impaired glucose tolerance' hyperlipidemia' increased plasma lactate, lactate dehydrogenase, PDK-4, uric acid, xanthine oxidase (XO), adenosine deaminase (ADA), malondialdehyde (MDA), cardiac uric acid, TG, TG/HDL- cholesterol, glycogen synthesis, MDA, and visceral fat content and reduced glutathione. High fructose also resulted in impaired pancreatic β-cell function, hyperglycemia, and increased cardiac PDK-4, lactate synthesis, and mass. Nonetheless, these alterations were ameliorated in EEL plus high fructose rats. This study demonstrates that high fructose-induced myocardial TG and glycogen accumulation is attributable to increased PDK-4. Besides, EEL could be a useful pharmacological utility for protection against cardiac dysmetabolism by inhibiting PDK-4.

Amelioration of High Fructose-Induced Cardiac Hypertrophy by Naringin

Heart failure is a frequent unfavorable outcome of pathological cardiac hypertrophy. Recent increase in dietary fructose consumption mirrors the rise in prevalence of cardiovascular diseases such as cardiac hypertrophy leading to concerns raised by public health experts. Mitochondria, comprising 30% of cardiomyocyte volume, play a central role in modulating redox-dependent cellular processes such as metabolism and apoptosis. Furthermore, mitochondrial dysfunction is a key cause of pathogenesis of fructose-induced cardiac hypertrophy. Naringin, a major flavanone glycoside in citrus species, has displayed strong antioxidant potential in models of oxidative stress. In this study, we evaluated protective effects of naringin against fructose-induced cardiac hypertrophy and associated mechanisms of action, using in vitro and in vivo models. We found that naringin suppressed mitochondrial ROS production and mitochondrial dysfunction in cardiomyocytes exposed to fructose and consequently reduced cardiomyocyte hypertrophy by regulating AMPK-mTOR signaling axis. Furthermore, naringin counteracted fructose-induced cardiomyocyte apoptosis, and this function of naringin was linked to its ability to inhibit ROS-dependent ATM-mediated p53 signaling. This result was supported by observations in in vivo mouse model of cardiac hypertrophy. These findings indicate a novel role for naringin in protecting against fructose-induced cardiac hypertrophy and suggest unique therapeutic strategies for prevention of cardiovascular diseases.

Cardioprotective effect of Phyllanthus amarus against high fructose diet induced myocardial and aortic stress in rat model

Increased number of population with heart stroke/attack is attributed to sedentary lifestyle and consumption of high-sugar diets, especially fructose. The objective of this study is to investigate the cardio-protective activity of aqueous extract of Phyllanthus amarus (PAAE) against high-fructose (HF) diet induced cardiac damage in Wistar rats. Male Wistar rats were randomly assigned into five groups of six animals each: Control (C), Control treated with PAAE (C+PAAE), High fructose diet fed (F), High fructose diet fed treated with PAAE (F+PAAE) and High fructose diet fed treated with Pioglitazone (F+Pio). PAAE was orally administered at a dosage of 200mg/kg body weight/day to C+PAAE and F+PAAE group rats for 60days. Pioglitazone (10mg/kg body weight/day) was used to compare the efficacy of PAAE. After 60days, heart and aorta samples were collected for biochemical and histological analysis. Co-administration of PAAE along with HF-diet for 60days prevented the increase in levels of cardiac and aortic lipids i.e., total lipids, triglycerides, total cholesterol and free fatty acids and decreased phospholipids. Further, enhanced activities of cardiac aldose reductase (15.3%) and sorbital dehydrogenase (6.9%) and decreased activity of creatine kinase (35.6%) in group-F were also prevented by PAAE treatment with the recovery of 126% for AR, 122% for SDH and 118% for CK. PAAE treatment showed protection from HF-diet induced increase in stress markers (LPO and PO), decreased non-enzymatic (GSH and Vit-C) and enzymatic (GR, GPx, GST, SOD, and CAT) antioxidants in the heart and aorta. Histopathological examination of the heart and aorta indicated that PAAE/Pio treatment reduced fat deposition and necrosis. The present study clearly indicates the cardio protection efficacy of PAAE against HF-diet induced oxidative stress in rats.

Female rats with severe left ventricle volume overload exhibit more cardiac hypertrophy but fewer myocardial transcriptional changes than males

Aortic valve regurgitation (AR) imposes a volume overload (VO) to the left ventricle (LV). Male rats with a pathological heart overload usually progress more quickly towards heart failure than females. We examined whether a sexual dimorphism exists in the myocardial transcriptional adaptations to AR. Adult Wistar male and female rats either underwent a sham operation or were induced with AR and then followed for 26 weeks. Female AR rats gained relatively more LV mass than males (75 vs. 42%). They had a similar increase in LV chamber dimensions compared to males but more wall thickening. On the other hand, fatty acid oxidation (FAO)-related LV enzyme activity was only decreased in AR males. The expression of genes encoding FAO-related enzymes was only reduced in AR males and not in females. A similar situation was observed for the expression of genes involved in mitochondrial biogenesis or function as well as for genes encoding for transcription factors implicated in the control of bioenergetics and mitochondrial function (Errα, Errγ or Pgc1α). Although females develop more LV hypertrophy from severe VO, their myocardial gene expression remains closer to normal. This could provide survival benefits for females with severe VO.

High-fructose and high-fat feeding correspondingly lead to the development of lysoPC-associated apoptotic cardiomyopathy and adrenergic signaling-related cardiac hypertrophy

BACKGROUND

The heart is a highly adaptive organ that demonstrates remarkable structural, functional, and metabolic remodeling in response to physiological and pathological stimuli. We hypothesize that the heart undergoes differential adaptations in high-fat and high-fructose diet, resulting in a distinct phenotype.

METHODS

High-fat and high-fructose diet-induced obese and non-obese insulin resistance (IR) rat models were used to understand how the heart adapts to long-term (12-week) overnutrition.

RESULTS

Rats fed the high-fat diet developed obese IR, whereas high-fructose diet developed non-obese IR. Obese IR rats developed fibrotic hypertrophy with impairment of preload-independent contractility. The sympathetic and renin-angiotensin-aldosterone (RAA) systems and myocardial adrenergic signaling were activated in obese IR rats. Non-obese IR rats developed apoptotic cardiomyopathy with severe systolic dysfunction. Myocardial calcium cycling regulatory proteins (CCRPs) were dysregulated in non-obese IR rats; specifically, troponin I protein expression was downregulated. Moreover, compared with the controls, lipidomics analysis revealed substantial differences in lipid metabolites in non-obese IR and obese IR rats. The overproduction of lysophosphatidylcholine (lysoPC) and fatty acids was observed in non-obese IR rat hearts. A strong correlation was observed between the myocardial lysoPC and plasma troponin I levels. Treatment of cardiomyocytes with lysoPC resulted in cell death in a dose- and time-dependent manner. The overproduction of myocardial lysoPCs was associated with circulating sPLA2 levels.

CONCLUSION

Obese IR rats developed severe fibrotic hypertrophy with the activation of adrenergic signaling and sympathetic and RAA systems. The sPLA2-lysoPC may play a crucial role in the induction of apoptotic cardiomyopathy in high fructose-induced non-obese IR rats.

Ryanodine receptor phosphorylation by CaMKII promotes spontaneous Ca(2+) release events in a rodent model of early stage diabetes: The arrhythmogenic substrate

BACKGROUND

Heart failure and arrhythmias occur more frequently in patients with type 2 diabetes (T2DM) than in the general population. T2DM is preceded by a prediabetic condition marked by elevated reactive oxygen species (ROS) and subclinical cardiovascular defects. Although multifunctional Ca2+ calmodulin-dependent protein kinase II (CaMKII) is ROS-activated and CaMKII hyperactivity promotes cardiac diseases, a link between prediabetes and CaMKII in the heart is unprecedented.

OBJECTIVES

To prove the hypothesis that increased ROS and CaMKII activity contribute to heart failure and arrhythmogenic mechanisms in early stage diabetes.

METHODS-RESULTS

Echocardiography, electrocardiography, biochemical and intracellular Ca2+ (Ca2+i) determinations were performed in fructose-rich diet-induced impaired glucose tolerance, a prediabetes model, in rodents. Fructose-rich diet rats showed decreased contractility and hypertrophy associated with increased CaMKII activity, ROS production, oxidized CaMKII and enhanced CaMKII-dependent ryanodine receptor (RyR2) phosphorylation compared to rats fed with control diet. Isolated cardiomyocytes from fructose-rich diet showed increased spontaneous Ca2+i release events associated with spontaneous contractions, which were prevented by KN-93, a CaMKII inhibitor, or addition of Tempol, a ROS scavenger, to the diet. Moreover, fructose-rich diet myocytes showed increased diastolic Ca2+ during the burst of spontaneous Ca2+i release events. Mice treated with Tempol or with sarcoplasmic reticulum-targeted CaMKII-inhibition by transgenic expression of the CaMKII inhibitory peptide AIP, were protected from fructose-rich diet-induced spontaneous Ca2+i release events, spontaneous contractions and arrhythmogenesis in vivo, despite ROS increases.

CONCLUSIONS

RyR2 phosphorylation by ROS-activated CaMKII, contributes to impaired glucose tolerance-induced arrhythmogenic mechanisms, suggesting that CaMKII inhibition could prevent prediabetic cardiovascular complications and/or evolution.

Transcriptional Changes Associated with Long-Term Left Ventricle Volume Overload in Rats: Impact on Enzymes Related to Myocardial Energy Metabolism

Patients with left ventricle (LV) volume overload (VO) remain in a compensated state for many years although severe dilation is present. The myocardial capacity to fulfill its energetic demand may delay decompensation. We performed a gene expression profile, a model of chronic VO in rat LV with severe aortic valve regurgitation (AR) for 9 months, and focused on the study of genes associated with myocardial energetics. Methods. LV gene expression profile was performed in rats after 9 months of AR and compared to sham-operated controls. LV glucose and fatty acid (FA) uptake was also evaluated in vivo by positron emission tomography in 8-week AR rats treated or not with fenofibrate, an activator of FA oxidation (FAO). Results. Many LV genes associated with mitochondrial function and metabolism were downregulated in AR rats. FA β-oxidation capacity was significantly impaired as early as two weeks after AR. Treatment with fenofibrate, a PPARα agonist, normalized both FA and glucose uptake while reducing LV dilation caused by AR. Conclusion. Myocardial energy substrate preference is affected early in the evolution of LV-VO cardiomyopathy. Maintaining a relatively normal FA utilization in the myocardium could translate into less glucose uptake and possibly lesser LV remodeling.

Blockade of the acute activation of mTOR complex 1 decreases hypertrophy development in rats with severe aortic valve regurgitation

Background

Hypertrophy (H) is an adaptive response of the heart to a hemodynamic overload. Severe left ventricular (LV) volume overload (VO) from valve regurgitations (aortic (AR) or mitral regurgitation) leads to eccentric LVH. Increased protein turnover is a major event during development of LVH and the mechanistic target of rapamycin (mTOR) is a key molecule for its control. The role of mTOR inhibition in the development of LVH using rapamycin for relatively short periods of time (days to a few weeks) has been studied in the past in pressure overload models but not in VO models. We investigated if mTOR pathway was activated during LVH development in a model of severe VO (AR) in rats and if a rapamycin treatment can slow heart remodeling in this situation.

Methods and Results

Male rats with severe AR were studied acutely at 2 days, at 8 weeks (compensated phase) and 6 months (late phase) after VO induction. mTOR complex (mTORC) 1 (ribosomal S6 protein phosphorylation) was activated early after AR induction but not later in the disease whereas mTORC2 activity levels (Akt phosphorylation at Ser473) remained stable. We observed that a moderate dose of rapamycin (2 mg/kg/day; orally) for 8 weeks prevented severe LVH caused by AR (−46 %: p < 0.001). Rapamycin treatment specifically inhibited LV mTORC1 without altering mTORC2 activity at 8 weeks. Rapamycin also prevented cardiac myocyte hypertrophy caused by AR.

Conclusion

Rapamycin slows hypertrophy in LV VO by inhibiting early activation of mTORC1 without modulating mTORC2.

Endurance training or beta-blockade can partially block the energy metabolism remodeling taking place in experimental chronic left ventricle volume overload

Background

Patients with chronic aortic valve regurgitation (AR) causing left ventricular (LV) volume overload can remain asymptomatic for many years despite having a severely dilated heart. The sudden development of heart failure is not well understood but alterations of myocardial energy metabolism may be contributive. We studied the evolution of LV energy metabolism in experimental AR.

Methods

LV glucose utilization was evaluated in vivo by positron emission tomography (microPET) scanning of 6-month AR rats. Sham-operated or AR rats (n = 10-30 animals/group) were evaluated 3, 6 or 9 months post-surgery. We also tested treatment intervention in order to evaluate their impact on metabolism. AR rats (20 animals) were trained on a treadmill 5 times a week for 9 months and another group of rats received a beta-blockade treatment (carvedilol) for 6 months.

Results

MicroPET revealed an abnormal increase in glucose consumption in the LV free wall of AR rats at 6 months. On the other hand, fatty acid beta-oxidation was significantly reduced compared to sham control rats 6 months post AR induction. A significant decrease in citrate synthase and complex 1 activity suggested that mitochondrial oxidative phosphorylation was also affected maybe as soon as 3 months post-AR.

Moderate intensity endurance training starting 2 weeks post-AR was able to partially normalize the activity of various myocardial enzymes implicated in energy metabolism. The same was true for the AR rats treated with carvedilol (30 mg/kg/d). Responses to these interventions were different at the level of gene expression. We measured mRNA levels of a number of genes implicated in the transport of energy substrates and we observed that training did not reverse the general down-regulation of these genes in AR rats whereas carvedilol normalized the expression of most of them.

Conclusion

This study shows that myocardial energy metabolism remodeling taking place in the dilated left ventricle submitted to severe volume overload from AR can be partially avoided by exercise or beta-blockade in rats.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2261-14-190) contains supplementary material, which is available to authorized users.

Chronic high-fat diet-induced obesity decreased survival and increased hypertrophy of rats with experimental eccentric hypertrophy from chronic aortic regurgitation

Background

The composition of a diet can influence myocardial metabolism and development of left ventricular hypertrophy (LVH). The impact of a high-fat diet in chronic left ventricular volume overload (VO) causing eccentric LVH is unknown. This study examined the effects of chronic ingestion of a high-fat diet in rats with chronic VO caused by severe aortic valve regurgitation (AR) on LVH, function and on myocardial energetics and survival.

Methods

Male Wistar rats were divided in four groups: Shams on control or high-fat (HF) diet (15 rats/group) and AR rats fed with the same diets (ARC (n = 56) and ARHF (n = 32)). HF diet was started one week before AR induction and the protocol was stopped 30 weeks later.

Results

As expected, AR caused significant LV dilation and hypertrophy and this was exacerbated in the ARHF group. Moreover, survival in the ARHF group was significantly decreased compared the ARC group. Although the sham animals on HF also developed significant obesity compared to those on control diet, this was not associated with heart hypertrophy. The HF diet in AR rats partially countered the expected shift in myocardial energy substrate preference usually observed in heart hypertrophy (from fatty acids towards glucose). Systolic function was decreased in AR rats but HF diet had no impact on this parameter. The response to HF diet of different fatty acid oxidation markers as well as the increase in glucose transporter-4 translocation to the plasma membrane compared to ARC was blunted in AR animals compared to those on control diet.

Conclusions

HF diet for 30 weeks decreased survival of AR rats and worsened eccentric hypertrophy without affecting systolic function. The expected adaptation of myocardial energetics to volume-overload left ventricle hypertrophy in AR animals seemed to be impaired by the high-fat diet suggesting less metabolic flexibility.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2261-14-123) contains supplementary material, which is available to authorized users.

Hypertrophy signaling pathways in experimental chronic aortic regurgitation

The development of left ventricular hypertrophy and dysfunction in aortic regurgitation (AR) has only been sparsely studied experimentally. In a new model of chronic AR in rats, we examined activation of molecular pathways involved in myocardial hypertrophy. Chronic AR was produced by damaging one or two valve cusps, resulting in eccentric remodeling and left ventricular dysfunction, with no increase in overall fibrosis. Western blotting showed increased activation of Akt and p38 at 12 weeks and of c-Jun amino-terminal kinase at 2 weeks, decreased activation of extracellular regulated kinase 5 at both 2 and 12 weeks, while activation of calcium/calmodulin-dependent protein kinase II and extracellular regulated kinase 1/2 was unchanged. Expression of calcineurin and ANF was also unchanged. Eccentric hypertrophy and early cardiac dysfunction in experimental AR are associated with a pattern of activation of intracellular pathways different from that seen with pathological hypertrophy in pressure overload, and more similar to that associated with benign physiological hypertrophy.

Angiotensin II-converting enzyme inhibition improves survival, ventricular remodeling, and myocardial energetics in experimental aortic regurgitation

BACKGROUND

Aortic valve regurgitation (AR) is a volume-overload disease causing severe eccentric left ventricular (LV) hypertrophy and eventually heart failure. There is currently no approved drug to treat patients with AR. Many vasodilators including angiotensin-converting enzyme inhibitors have been evaluated in clinical trials, but although some results were promising, others were inconclusive. Overall, no drug has yet been able to improve clinical outcome in AR and the controversy remains. We have previously shown in an animal model that captopril (Cpt) reduced LV hypertrophy and protected LV systolic function, but we had not evaluated the clinical outcome. This protocol was designed to evaluate the effects of a long-term Cpt treatment on survival in the same animal model of severe aortic valve regurgitation.

METHODS AND RESULTS

Forty Wistar rats with AR were treated or untreated with Cpt (1 g/L in drinking water) for a period of 7 months to evaluate survival, myocardial remodeling, and function by echocardiography as well as myocardial metabolism by µ positron emission tomography scan. Survival was significantly improved in Cpt-treated animals with a survival benefit visible as soon as after 4 months of treatment. Cpt reduced LV dilatation and LV hypertrophy. It also significantly improved the myocardial metabolic profile by restoring the level of fatty acids metabolic enzymes and use.

CONCLUSIONS

In a controlled animal model of pure severe aortic valve regurgitation, Cpt treatment reduced LV remodeling and LV hypertrophy and improved myocardial metabolic profile and survival. These results support the need to reevaluate the role of angiotensin-converting enzyme inhibitors in humans with AR in a large, carefully designed prospective clinical trial.

Way back for fructose and liver metabolism: Bench side to molecular insights

The World Health Organization recommends that the daily intake of added sugars should make up no more than 10% of total energy. The consumption of sugar-sweetened beverages is the main source of added sugars. Fructose, together with glucose, as a component of high fructose corn syrups or as a component of the sucrose molecule, is one of the main sweeteners present in this kind of beverages. Data from prospective and intervention studies clearly point to high fructose consumption, mainly in the form of sweetened beverages, as a risk factor for several metabolic diseases in humans. The incidence of hypertension, nonalcoholic fatty liver disease (NAFLD), dyslipidemia (mainly hypertriglyceridemia), insulin resistance, type 2 diabetes mellitus, obesity, and the cluster of many of these pathologies in the form of metabolic syndrome is higher in human population segments that show high intake of fructose. Adolescent and young adults from low-income families are especially at risk. We recently reviewed evidence from experimental animals and human data that confirms the deleterious effect of fructose on lipid and glucose metabolism. In this present review we update the information generated in the past 2 years about high consumption of fructose-enriched beverages and the occurrence of metabolic disturbances, especially NAFLD, type 2 diabetes mellitus, and metabolic syndrome. We have explored recent data from observational and experimental human studies, as well as experimental data from animal and cell models. Finally, using information generated in our laboratory and others, we provide a view of the molecular mechanisms that may be specifically involved in the development of liver lipid and glucose metabolic alterations after fructose consumption in liquid form.

Glucose 6-phosphate dehydrogenase deficiency increases redox stress and moderately accelerates the development of heart failure

BACKGROUND

Glucose 6-phosphate dehydrogenase (G6PD) is the most common deficient enzyme in the world. In failing hearts, G6PD is upregulated and generates reduced nicotinamide adenine dinucleotide phosphate (NADPH) that is used by the glutathione pathway to remove reactive oxygen species but also as a substrate by reactive oxygen species-generating enzymes. Therefore, G6PD deficiency might prevent heart failure by decreasing NADPH and reactive oxygen species production.

METHODS AND RESULTS

This hypothesis was evaluated in a mouse model of human G6PD deficiency (G6PDX mice, ≈40% normal activity). Myocardial infarction with 3 months follow-up resulted in left ventricular dilation and dysfunction in both wild-type and G6PDX mice but significantly greater end diastolic volume and wall thinning in G6PDX mice. Similarly, pressure overload induced by transverse aortic constriction (TAC) for 6 weeks caused greater left ventricular dilation in G6PDX mice than wild-type mice. We further stressed transverse aortic constriction mice by feeding a high fructose diet to increase flux through G6PD and reactive oxygen species production and again observed worse left ventricular remodeling and a lower ejection fraction in G6PDX than wild-type mice. Tissue content of lipid peroxidation products was increased in G6PDX mice in response to infarction and aconitase activity was decreased with transverse aortic constriction, suggesting that G6PD deficiency increases myocardial oxidative stress and subsequent damage.

CONCLUSIONS

Contrary to our hypothesis, G6PD deficiency increased redox stress in response to infarction or pressure overload. However, we found only a modest acceleration of left ventricular remodeling, suggesting that, in individuals with G6PD deficiency and concurrent hypertension or myocardial infarction, the risk for developing heart failure is higher but limited by compensatory mechanisms.

Renal sympathetic denervation suppresses de novo podocyte injury and albuminuria in rats with aortic regurgitation

BACKGROUND

The presence of chronic kidney disease is a significant independent risk factor for poor prognosis in patients with chronic heart failure. However, the mechanisms and mediators underlying this interaction are poorly understood. In this study, we tested our hypothesis that chronic cardiac volume overload leads to de novo renal dysfunction by coactivating the sympathetic nervous system and renin-angiotensin system in the kidney. We also examined the therapeutic potential of renal denervation and renin-angiotensin system inhibition to suppress renal injury in chronic heart failure.

METHODS AND RESULTS

Sprague-Dawley rats underwent aortic regurgitation and were treated for 6 months with vehicle, olmesartan (an angiotensin II receptor blocker), or hydralazine. At 6 months, albuminuria and glomerular podocyte injury were significantly increased in aortic regurgitation rats. These changes were associated with increased urinary angiotensinogen excretion, kidney angiotensin II and norepinephrine (NE) levels, and enhanced angiotensinogen and angiotensin type 1a receptor gene expression and oxidative stress in renal cortical tissues. Aortic regurgitation rats with renal denervation had decreased albuminuria and glomerular podocyte injury, which were associated with reduced kidney NE, angiotensinogen, angiotensin II, and oxidative stress. Renal denervation combined with olmesartan prevented podocyte injury and albuminuria induced by aortic regurgitation.

CONCLUSIONS

In this chronic cardiac volume-overload animal model, activation of the sympathetic nervous system augments kidney renin-angiotensin system and oxidative stress, which act as crucial cardiorenal mediators. Renal denervation and olmesartan prevent the onset and progression of renal injury, providing new insight into the treatment of cardiorenal syndrome.

High-sugar intake does not exacerbate metabolic abnormalities or cardiac dysfunction in genetic cardiomyopathy

OBJECTIVE

A high-sugar intake increases heart disease risk in humans. In animals, sugar intake accelerates heart failure development by increased reactive oxygen species (ROS). Glucose-6-phosphate dehydrogenase (G6PD) can fuel ROS production by providing reduced nicotinamide adenine dinucleotide phosphate (NADPH) for superoxide generation by NADPH oxidase. Conversely, G6PD also facilitates ROS scavenging using the glutathione pathway. We hypothesized that a high-sugar intake would increase flux through G6PD to increase myocardial NADPH and ROS and accelerate cardiac dysfunction and death.

METHODS

Six-week-old TO-2 hamsters, a non-hypertensive model of genetic cardiomyopathy caused by a δ-sarcoglycan mutation, were fed a long-term diet of high starch or high sugar (57% of energy from sucrose plus fructose).

RESULTS

After 24 wk, the δ-sarcoglycan-deficient animals displayed expected decreases in survival and cardiac function associated with cardiomyopathy (ejection fraction: control 68.7 ± 4.5%, TO-2 starch 46.1 ± 3.7%, P < 0.05 for TO-2 starch versus control; TO-2 sugar 58.0 ± 4.2%, NS, versus TO-2 starch or control; median survival: TO-2 starch 278 d, TO-2 sugar 318 d, P = 0.133). Although the high-sugar intake was expected to exacerbate cardiomyopathy, surprisingly, there was no further decrease in ejection fraction or survival with high sugar compared with starch in cardiomyopathic animals. Cardiomyopathic animals had systemic and cardiac metabolic abnormalities (increased serum lipids and glucose and decreased myocardial oxidative enzymes) that were unaffected by diet. The high-sugar intake increased myocardial superoxide, but NADPH and lipid peroxidation were unaffected.

CONCLUSION

A sugar-enriched diet did not exacerbate ventricular function, metabolic abnormalities, or survival in heart failure despite an increase in superoxide production.

Metabolic characterization of volume overload heart failure due to aorto-caval fistula in rats

Metabolic interactions between adipose tissue and the heart may play an active role in progression of heart failure (HF). The aim of the study was to examine changes in myocardial and adipose tissue metabolism and gene expression in a rat HF model induced by chronic volume overload. HF was induced by volume overload from aorto-caval fistula (ACF) in 3-month-old male Wistar rats and animals were studied in the phase of decompensated HF (22nd week). HF rats showed marked eccentric cardiac hypertrophy, pulmonary congestion, increased LV end-diastolic pressure, and intraabdominal fat depletion. HF rats had preserved glucose tolerance, but increased circulating free fatty acids (FFA) and attenuated insulin response during oral glucose challenge. Isolated organ studies showed preserved responsiveness of adipose tissue lipolysis and lipogenesis to epinephrine and insulin in ACF. The heart of HF animals had markedly reduced triglyceride content (almost to half of controls), attenuated anti-oxidative reserve (GSH/GSSG), upregulated HF markers (ANP, periostin, thrombospondin-4), specific signaling pathways (Wnt, TGF-β), and downregulated enzymes of mitochondrial fatty acid oxidation, citric acid cycle, and respiratory chain. Adipose tissue transcription profiling showed upregulated receptor for gastric inhibitory polypeptide. In conclusion, ACF-induced HF model displays several deregulations of systemic metabolism. Despite elevation of systemic FFAs, myocardial triglycerides are low and insulin levels are attenuated, arguing against a role of lipotoxicity or insulin resistance in this model. Attenuated postprandial insulin response and relative lack of its antilipolytic effects may facilitate intraabdominal fat depletion observed in ACF-HF animals.