Project description:Lifestyle and metabolic diseases influence the severity and pathogenesis of cardiovascular disease (CVD) through numerous mechanisms, including regulation via post-translational modifications (PTM). A specific PTM, the addition of O-linked β-N acetylglucosamine (O-GlcNAcylation), has been implicated in both physiological and pathological mechanisms. The current study aimed to test the hypothesis that protein O-GlcNAcylation contributes to cardiac adaptations, and its progression to pathophysiology when sustained in cardiomyocytes. Using an inducible cardiomyocyte-specific dominant-negative O-GlcNAcase (dnOGAh) overexpression transgenic mouse model, we induced dnOGA in 8-10-weeks-old mouse hearts. We examined the effects of 2-weeks (2wk) and 24-weeks (24wk) dnOGA overexpression, which progressed to a 1.8-fold increase in protein O-GlcNAcylation. 2wk increases in protein O-GlcNAc levels did not alter heart weight or function; however, 24wk increases in protein O-GlcNAcylation led to cardiac hypertrophy, reduced mitochondrial function, fibrosis, and diastolic dysfunction. Interestingly, systolic function was maintained in 24wk dnOGA overexpression, despite several changes in gene expression associated with CVD. Specifically, mRNA-seq analysis revealed several gene signatures, including reduction of mitochondrial oxidative phosphorylation, fatty acid and glucose metabolism pathways, and antioxidant response pathways at 24wk. In contrast, cardiac fibrosis pathway genes were induced at 24wk after dnOGA overexpression. Changes in mitochondrial function after 24wk induction were independent of changes in mitochondrial DNA copy number. This study indicates that moderate protein O-GlcNAcylation leads to a differential response with an initial reduction of metabolic pathways (2wk phase), which leads to cardiac remodeling (24wk phase) including cardiac hypertrophy, decreased oxidative phosphorylation pathways, and increased cardiac structural changes. This study shows that sustained exposure of elevated protein O-GlcNAcylation in cardiomyocytes alters gene expression and supports a switch to pathophysiological mechanisms of O-GlcNAcylation in adaptive versus maladaptive changes.

Project description:Full Title: Transition from Compensated Hypertrophy to Systolic Heart Failure in the Spontaneously Hypertensive Rat: Structure, Function, and Transcript Analysis Gene expression changes and left ventricular remodeling associated with the transition to systolic heart failure (HF) were determined in the spontaneously hypertensive rat (SHR). By combining transcriptomics of left ventricles from six SHR with HF with changes in function and structure we aimed to better understand the molecular events underlying the onset of systolic HF compared to six age-matched, SHR with compensated hypertrophy. Left ventricle (LV) ejection fraction was depressed (82Â±4 to 52Â±3 %) in compensated vs. failing animals.Â Systolic blood pressure decreased and LV end-diastolic and systolic volume increased with HF.Â Failing SHR hearts also demonstrated increases in left and right ventricular mass relative to non-failing SHRs.Â Â LV papillary muscle force development and shortening velocity decreased, Î²-adrenergic responsiveness was depressed, myocardial stiffness and myocardial fibrosis increased with HF relative to non-failing animals. Initial micro-array analysis revealed that 1,431 transcripts were differentially expressed with HF compared to non-failing SHR (p<0.05). Of the identified transcripts, lipopolysaccharide binding protein, the most highly expressed transcript with HF, was negatively correlated to myocardial force while elevated expression of the collagen cross-linking enzyme lysyl oxidase correlated positively with muscle stiffness. Besides these individual transcripts, gene set enrichment analysis (GSEA) identified multiple enriched pathways with HF, most prominent of the altered signaling pathways involved TGF-Î² and insulin signaling. GESA analysis additionally identified altered gene sets involving inflammation, oxidative stress, cell degradation and cell death, among others (all p<0.01). In contrast to diastolic HF where few transcripts are reported to be altered, our data indicate multiple genes and pathways involved in a variety of biological processes characterize the onset of systolic HF, consistent with many functional and structural changes present in the failing hypertensive heart. Comprehensive gene expression profiling of heart failure Rat model vs control.

Project description:Background Lifestyle and metabolic diseases influence the severity and pathogenesis of cardiovascular disease through numerous mechanisms, including regulation via posttranslational modifications. A specific posttranslational modification, the addition of O-linked β-N acetylglucosamine (O-GlcNAcylation), has been implicated in molecular mechanisms of both physiological and pathologic adaptations. The current study aimed to test the hypothesis that in cardiomyocytes, sustained protein O-GlcNAcylation contributes to cardiac adaptations, and its progression to pathophysiology. Methods and Results Using a naturally occurring dominant-negative O-GlcNAcase (dnOGA) inducible cardiomyocyte-specific overexpression transgenic mouse model, we induced dnOGA in 8- to 10-week-old mouse hearts. We examined the effects of 2-week and 24-week dnOGA overexpression, which progressed to a 1.8-fold increase in protein O-GlcNAcylation. Two-week increases in protein O-GlcNAc levels did not alter heart weight or function; however, 24-week increases in protein O-GlcNAcylation led to cardiac hypertrophy, mitochondrial dysfunction, fibrosis, and diastolic dysfunction. Interestingly, systolic function was maintained in 24-week dnOGA overexpression, despite several changes in gene expression associated with cardiovascular disease. Specifically, mRNA-sequencing analysis revealed several gene signatures, including reduction of mitochondrial oxidative phosphorylation, fatty acid, and glucose metabolism pathways, and antioxidant response pathways after 24-week dnOGA overexpression. Conclusions This study indicates that moderate increases in cardiomyocyte protein O-GlcNAcylation leads to a differential response with an initial reduction of metabolic pathways (2-week), which leads to cardiac remodeling (24-week). Moreover, the mouse model showed evidence of diastolic dysfunction consistent with a heart failure with preserved ejection fraction. These findings provide insight into the adaptive versus maladaptive responses to increased O-GlcNAcylation in heart.

Project description:Full Title: Transition from Compensated Hypertrophy to Systolic Heart Failure in the Spontaneously Hypertensive Rat: Structure, Function, and Transcript Analysis Gene expression changes and left ventricular remodeling associated with the transition to systolic heart failure (HF) were determined in the spontaneously hypertensive rat (SHR). By combining transcriptomics of left ventricles from six SHR with HF with changes in function and structure we aimed to better understand the molecular events underlying the onset of systolic HF compared to six age-matched, SHR with compensated hypertrophy. Left ventricle (LV) ejection fraction was depressed (82±4 to 52±3 %) in compensated vs. failing animals. Systolic blood pressure decreased and LV end-diastolic and systolic volume increased with HF. Failing SHR hearts also demonstrated increases in left and right ventricular mass relative to non-failing SHRs. LV papillary muscle force development and shortening velocity decreased, β-adrenergic responsiveness was depressed, myocardial stiffness and myocardial fibrosis increased with HF relative to non-failing animals. Initial micro-array analysis revealed that 1,431 transcripts were differentially expressed with HF compared to non-failing SHR (p<0.05). Of the identified transcripts, lipopolysaccharide binding protein, the most highly expressed transcript with HF, was negatively correlated to myocardial force while elevated expression of the collagen cross-linking enzyme lysyl oxidase correlated positively with muscle stiffness. Besides these individual transcripts, gene set enrichment analysis (GSEA) identified multiple enriched pathways with HF, most prominent of the altered signaling pathways involved TGF-β and insulin signaling. GESA analysis additionally identified altered gene sets involving inflammation, oxidative stress, cell degradation and cell death, among others (all p<0.01). In contrast to diastolic HF where few transcripts are reported to be altered, our data indicate multiple genes and pathways involved in a variety of biological processes characterize the onset of systolic HF, consistent with many functional and structural changes present in the failing hypertensive heart.

Project description:Impaired myocardial contractile function is a hallmark of heart failure (HF) which may present under resting conditions and/or during physiological stress. Previous studies reported that high fat feeding in HF is associated with improved myocardial contractile function at baseline. Our goal was to determine whether myocardial function is compromised in response to physiological stress and to evaluate the global gene expression profile of rats fed high dietary fat following infarction. Male Wistar rats underwent ligation or sham surgery and were fed normal (10% kcal fat) (SHAM+NC, HF+NC) or high fat (60% kcal saturated fat) (SHAM+SAT, HF+SAT) for 8 weeks. Myocardial contractile function was assessed using a Millar pressure-volume (PV) conductance catheter at baseline, during inferior vena caval occlusions and dobutamine (DOB) stress. Steady state indices of systolic function, left ventricular (LV)+dP/dtmax, stroke work and maximal power were increased in HF+SAT vs HF+NC; HF+NC were reduced vs SHAM+NC. Preload-recruitable measures of contractility [end systolic PV relationship, maximal elastance, preload recruitable SW and peak+dP/dtmax to end diastolic volume] were decreased in HF+NC but not HF+SAT. β-adrenergic responsiveness (delta-LV+dP/dtmax and delta-cardiac output DOB 0-10 µg•kg-1•min-1) was reduced in HF, but high fat feeding did not further impact contractile reserve in HF. Contractile reserve was reduced by high fat in SHAM+SAT. Microarray gene expression analysis reveals the majority of significantly altered pathways identified to contain multiple gene targets correspond to cell signaling pathways and energy metabolism. These findings suggest that high saturated fat improves myocardial function at rest and during physiological stress in infarcted hearts, but may negatively impact contractile reserve under non-pathological conditions. Furthermore, high fat feeding-induced alterations in gene expression related to energy metabolism and specific signaling pathways reveal promising targets through which high saturated fat potentially mediates cardioprotection in heart failure/LV dysfunction. Comparison of gene expression in heart failure or sham surgery hearts exposed to saturated or normal diets. Male Wistar rats (300-350g) were maintained on a reverse light-dark cycle and all procedures were done 3-6 hours into the dark phase cycle to synchronize with the normal active state of the rodents. Rats were randomly assigned to receive either a sham-operation (SH) or coronary ligation to induce cardiac dysfunction (HF). Heart failure was induced by ligating the left main coronary artery. Following surgery, rats were immediately fed either a normal rodent chow (NC) or a high saturated fat chow (SAT) with 60% caloric content derived from fat (25% palmitic, 33% stearic, 33% oleic acid, Research Diets).

Project description:Impaired myocardial contractile function is a hallmark of heart failure (HF) which may present under resting conditions and/or during physiological stress. Previous studies reported that high fat feeding in HF is associated with improved myocardial contractile function at baseline. Our goal was to determine whether myocardial function is compromised in response to physiological stress and to evaluate the global gene expression profile of rats fed high dietary fat following infarction. Male Wistar rats underwent ligation or sham surgery and were fed normal (10% kcal fat) (SHAM+NC, HF+NC) or high fat (60% kcal saturated fat) (SHAM+SAT, HF+SAT) for 8 weeks. Myocardial contractile function was assessed using a Millar pressure-volume (PV) conductance catheter at baseline, during inferior vena caval occlusions and dobutamine (DOB) stress. Steady state indices of systolic function, left ventricular (LV)+dP/dtmax, stroke work and maximal power were increased in HF+SAT vs HF+NC; HF+NC were reduced vs SHAM+NC. Preload-recruitable measures of contractility [end systolic PV relationship, maximal elastance, preload recruitable SW and peak+dP/dtmax to end diastolic volume] were decreased in HF+NC but not HF+SAT. β-adrenergic responsiveness (delta-LV+dP/dtmax and delta-cardiac output DOB 0-10 µg•kg-1•min-1) was reduced in HF, but high fat feeding did not further impact contractile reserve in HF. Contractile reserve was reduced by high fat in SHAM+SAT. Microarray gene expression analysis reveals the majority of significantly altered pathways identified to contain multiple gene targets correspond to cell signaling pathways and energy metabolism. These findings suggest that high saturated fat improves myocardial function at rest and during physiological stress in infarcted hearts, but may negatively impact contractile reserve under non-pathological conditions. Furthermore, high fat feeding-induced alterations in gene expression related to energy metabolism and specific signaling pathways reveal promising targets through which high saturated fat potentially mediates cardioprotection in heart failure/LV dysfunction.

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Sustained increases in cardiomyocyte protein O-GlcNAc levels leads to cardiac hypertrophy and reduced mitochondrial function without systolic contractile impairment

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