Differential rates of protein synthesis in vitro and RNA contents in rat heart ventricular and atrial muscle.
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ABSTRACT:
SUBMITTER: Smith DM
PROVIDER: S-EPMC1152272 | biostudies-other | 1983 Aug
REPOSITORIES: biostudies-other
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Project description:We investigated the effect of an increase in the left-atrial filling pressure on the rate of left-atrial protein synthesis in the left-side-perfused working rat heart preparation of Taegtmeyer, Hems & Krebs [(1980) Biochem. J. 186, 701-711]. An increase in filling pressure (preload) at a constant aortic pressure (afterload) increased both the intra-atrial pressure and the atrial stroke volume. The aortic pressure (afterload) was held constant. An increase in filling pressure from 5 to 20 cmH2O at an aortic pressure of 70 cmH2O, or an increase in filling pressure of 7.5 to 20 cmH2O at an aortic pressure of 100 cmH2O, significantly stimulated the rates of left-atrial protein synthesis by 30-40%. The stimulation was observed when the rates of protein synthesis were expressed relative to either protein or RNA content. Since perfusate entering the right atrium from the coronary circulation left that atrium passively, the rate of protein synthesis in this compartment can be used as an internal control. Rates of right-atrial protein synthesis were similar to those in the left atria exposed to the lower filling pressures and were unaffected by the increases in left-atrial filling pressure. We suggest that the acute effects of increased left-atrial filling pressure on protein synthesis in that compartment may be important in the development of left-atrial hypertrophy. This condition is seen in patients who have raised pulmonary venous pressures in, for example, mitral stenosis.
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Project description:It is known that immobilization of the rat hindlimb by plaster casting leads to muscle atrophy and loss of muscle protein. In the present study, immobilization of the rat hindlimb for 6 h resulted in a significant 27% decrease in the absolute rate of cytochrome c synthesis in the red quadriceps muscle, without any change in the relative amount of cytochrome c mRNA. Cytochrome c mRNA in normal red quadriceps muscle was observed to be of four different lengths (1400, 1050, 650 and 580 bases). After 7 days of immobilization, the absolute rate of cytochrome c synthesis remained depressed and cytochrome c mRNA decreased by 40%; each of the cytochrome c mRNAs decreased, with a preferential disappearance of the 1050- and 1400-base lengths. Immobilization was ended on day 7, and the atrophied muscle was allowed to recover. At day 4 of recovery, the absolute rate of cytochrome c synthesis was 92% higher and the amount of cytochrome c mRNA had returned to control values. The abundances of the 1050- and 1400-base cytochrome c mRNAs had increased more than the shorter cytochrome c mRNAs, so that they were higher than control values. It appears that acute decreases in contractile activity of the red quadriceps muscle alter cytochrome c synthesis rates via translational or post-translational mechanisms, whereas chronic periods of modified contractile activity alter its synthesis rate via pre-translational mechanisms.
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Project description:Heart formation is a complex morphogenetic process, and perturbations in cardiac morphogenesis lead to congenital heart disease. NKX2-5 is a key causative gene associated with cardiac birth defects, presumably because of its essential roles during the early steps of cardiogenesis. Previous studies in model organisms implicate NKX2-5 homologs in numerous processes, including cardiac progenitor specification, progenitor proliferation, and chamber morphogenesis. By inhibiting function of the zebrafish NKX2-5 homologs, nkx2.5 and nkx2.7, we show that nkx genes are essential to establish the original dimensions of the linear heart tube. The nkx-deficient heart tube fails to elongate normally: its ventricular portion is atypically short and wide, and its atrial portion is disorganized and sprawling. This atrial phenotype is associated with a surplus of atrial cardiomyocytes, whereas ventricular cell number is normal at this stage. However, ventricular cell number is decreased in nkx-deficient embryos later in development, when cardiac chambers are emerging. Thus, we conclude that nkx genes regulate heart tube extension and exert differential effects on ventricular and atrial cell number. Our data suggest that morphogenetic errors could originate during early stages of heart tube assembly in patients with NKX2-5 mutations.
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Project description:Heart failure (HF) is a leading cause of mortality and is associated with cardiac remodeling. Vulnerability to atrial fibrillation (AF) has been shown to be greater in the early stages of HF, whereas ventricular tachycardia/fibrillation develop during late stages. Here, we explore changes in gene expression that underlie the differential development of fibrosis and structural alterations that predispose to atrial and ventricular arrhythmias.
2019-01-01 | GSE123823 | GEO
Project description:The mammalian heart is formed from distinct sets of first and second heart field (FHF and SHF, respectively) progenitors. Although multipotent progenitors have previously been shown to give rise to cardiomyocytes, smooth muscle, and endothelial cells, the mechanism governing the generation of large numbers of differentiated progeny remains poorly understood. We have employed a two-colored fluorescent reporter system to isolate FHF and SHF progenitors from developing mouse embryos and embryonic stem cells. Genome-wide profiling of coding and noncoding transcripts revealed distinct molecular signatures of these progenitor populations. We further identify a committed ventricular progenitor cell in the Islet 1 lineage that is capable of limited in vitro expansion, differentiation, and assembly into functional ventricular muscle tissue, representing a combination of tissue engineering and stem cell biology.
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Project description:BackgroundAttempts to characterize cardiac structure in heart failure with preserved ejection fraction (HFpEF) in people with type 2 diabetes (T2D) have yielded inconsistent findings. We aimed to determine whether patients with HFpEF and T2D have a distinct pattern of cardiac remodelling compared with those without diabetes and whether remodelling was related to circulating markers of inflammation and fibrosis and clinical outcomes.MethodsWe recruited 140 patients with HFpEF (75 with T2D and 65 without). Participants underwent comprehensive cardiovascular phenotyping, including echocardiography, cardiac magnetic resonance imaging and plasma biomarker profiling.ResultsPatients with T2D were younger (age 70 ± 9 versus 75 ± 9y, p = 0.002), with evidence of more left ventricular (LV) concentric remodelling (LV mass/volume ratio 0.72 ± 0.15 versus 0.62 ± 0.16, p = 0.024) and smaller indexed left atrial (LA) volumes (maximal LA volume index 48 ± 20 versus 59 ± 29 ml/m2, p = 0.004) than those without diabetes. Plasma biomarkers of inflammation and extracellular matrix remodelling were elevated in those with T2D. Overall, there were 45 hospitalizations for HF and 22 deaths over a median follow-up period of 47 months [interquartile range (IQR) 38-54]. There was no difference in the primary composite endpoint of hospitalization for HF and mortality between groups. On multivariable Cox regression analysis, age, prior HF hospitalization, history of pulmonary disease and LV mass/volume were independent predictors of the primary endpoint.ConclusionsPatients with HFpEF and T2D have increased concentric LV remodelling, smaller LA volumes and evidence of increased systemic inflammation compared with those without diabetes. This suggests the underlying pathophysiology for the development of HFpEF is different in patients with and without T2D.Clinicaltrialsgov identifierNCT03050593.
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Project description:Background: Lamins A/C (encoded by the LMNA gene) can lead to dilated cardiomyopathy (DCM). Objectives: This study sought to undertake proteomic analysis of myocardial tissue to explore the postgenomic phenotype of end-stage lamin heart disease. Methods: Consecutive patients with end-stage lamin heart disease (LMNA-group, n=7) and ischaemic DCM (ICM-group, n=7) undergoing heart transplantation were enrolled. Samples were obtained from left atrium(LA), left ventricle(LV), right atrium(RA), right ventricle(RV) and interventricular septum(IVS). Liquid chromatography combined with mass-spectrometry was used for protein quantification. We compared protein concentrations in cardiac samples between LMNA and ICM groups. Proteins were considered differentially abundant if the quantitative difference was 1.5-fold and corrected p-value <0.05 at a false discovery rate of 0.01. Gene ontology(GO) enrichment analysis explored the related biological processes. Results: 4,247 proteins were identified in LMNA and ICM samples, of which 633 were differentially abundant in LA, 39 in LV, 181 in RA, 52 in RV, and 85 in IVS. Abundance of lamin A/C was reduced but lamin B (LMNB) increased in LMNA LA/RA tissue compared to ICM, but not in LV/RV. Transthyretin was more abundant in the LV/RV of LMNA compared to ICM while sarcomeric proteins such as titin and cardiac myosin heavy chain were generally reduced in RA/LA of LMNA. Protein expression profiling and GO enrichment analysis revealed sarcopenia, extracellular matrix(ECM) remodeling, deficient myocardial energetics, redox imbalances, and abnormal calcium handling in LMNA samples. Conclusion: Lamin heart disease is a biventricular and biatrial disease, characterized by sarcopenia, aberrant metabolism, and ECM remodeling. LMNB and transthyretin were unexpectedly abundant in the atria and ventricles respectively of patients with end-stage lamin heart disease potentially hinting to the possibility of compensatory responses.
2024-01-26 | PXD040488 | Pride
Project description:Starvation of 300 g rats for 3 days decreased ventricular-muscle total protein content and total RNA content by 15 and 22% respectively. Loss of body weight was about 15%. In glucose-perfused working rat hearts in vitro, 3 days of starvation inhibited rates of protein synthesis in ventricles by about 40-50% compared with fed controls. Although the RNA/protein ratio was decreased by about 10%, the major effect of starvation was to decrease the efficiency of protein synthesis (rate of protein synthesis relative to RNA). Insulin stimulated protein synthesis in ventricles of perfused hearts from fed rats by increasing the efficiency of protein synthesis. In vivo, protein-synthesis rates and efficiencies in ventricles from 3-day-starved rats were decreased by about 40% compared with fed controls. Protein-synthesis rates and efficiencies in ventricles from fed rats in vivo were similar to values in vitro when insulin was present in perfusates. In vivo, starvation increased the rate of protein degradation, but decreased it in the glucose-perfused heart in vitro. This contradiction can be rationalized when the effects of insulin are considered. Rates of protein degradation are similar in hearts of fed animals in vivo and in glucose/insulin-perfused hearts. Degradation rates are similar in hearts of starved animals in vivo and in hearts perfused with glucose alone. We conclude that the rates of protein turnover in the anterogradely perfused rat heart in vitro closely approximate to the rates in vivo in absolute terms, and that the effects of starvation in vivo are mirrored in vitro.
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Project description:Here, we have described and validated a strategy for monitoring skeletal muscle protein synthesis rates in rodents and humans over days or weeks from blood samples. We based this approach on label incorporation into proteins that are synthesized specifically in skeletal muscle and escape into the circulation. Heavy water labeling combined with sensitive tandem mass spectrometric analysis allowed integrated synthesis rates of proteins in muscle tissue across the proteome to be measured over several weeks. Fractional synthesis rate (FSR) of plasma creatine kinase M-type (CK-M) and carbonic anhydrase 3 (CA-3) in the blood, more than 90% of which is derived from skeletal muscle, correlated closely with FSR of CK-M, CA-3, and other proteins of various ontologies in skeletal muscle tissue in both rodents and humans. Protein synthesis rates across the muscle proteome generally changed in a coordinate manner in response to a sprint interval exercise training regimen in humans and to denervation or clenbuterol treatment in rodents. FSR of plasma CK-M and CA-3 revealed changes and interindividual differences in muscle tissue proteome dynamics. In human subjects, sprint interval training primarily stimulated synthesis of structural and glycolytic proteins. Together, our results indicate that this approach provides a virtual biopsy, sensitively revealing individualized changes in proteome-wide synthesis rates in skeletal muscle without a muscle biopsy. Accordingly, this approach has potential applications for the diagnosis, management, and treatment of muscle disorders.
| S-EPMC4701543 | biostudies-literature
Project description:In vivo, fractional rates of protein synthesis in atrial muscle of hearts taken from fed rats were 70% greater than in ventricular muscle. After 3 days starvation, atrial protein synthesis is inhibited, but the inhibition is less than in ventricles. A crude subcellular fractionation of the aqueous homogenates by centrifugation at 32000g showed that the supernatant and precipitate proteins were synthesized at the same rate in the ventricles. The fractional rates of protein synthesis and RNA/protein ratios in the right ventricle were 10% greater than in the left ventricle. Protein synthesis in both of these regions was inhibited equally by starvation. In vitro, rates of protein synthesis in atria and ventricles of anterogradely perfused rat hearts were stimulated by saturating insulin concentrations and were inhibited by starvation, but the effects in atria were smaller than in ventricles. Rates of protein synthesis in atria in vitro were 80-95% of rates in vivo. The heart therefore shows considerable regional variation in rates of protein synthesis in vivo and in vitro, and the sensitivity of protein synthesis in the various regions to interventions such as insulin and starvation differs.
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