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Impaired cellular contractile function in thiamine‐deficient rat cardiomyocytes
2009; Elsevier BV; Volume: 11; Issue: 12 Linguagem: Inglês
10.1093/eurjhf/hfp146
ISSN1879-0844
AutoresCarolina Rosa Gioda, Danilo Roman‐Campos, Miguel Araújo Carneiro‐Júnior, Karina Ana da Silva, Matheus Ornelas de Souza, Liliane Jorge Mendes, Antônio José Natali, Jáder Santos Cruz,
Tópico(s)Neurological and metabolic disorders
ResumoEuropean Journal of Heart FailureVolume 11, Issue 12 p. 1126-1128 ExperimentalFree Access Impaired cellular contractile function in thiamine-deficient rat cardiomyocytes Carolina Rosa Gioda, Carolina Rosa Gioda Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorDanilo Roman-Campos, Danilo Roman-Campos Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorMiguel Araújo Carneiro-Júnior, Miguel Araújo Carneiro-Júnior Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorKarina Ana da Silva, Karina Ana da Silva Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorMatheus Ornelas de Souza, Matheus Ornelas de Souza Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorLiliane Jorge Mendes, Liliane Jorge Mendes Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorAntônio José Natali, Antônio José Natali Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorJader Santos Cruz, Corresponding Author Jader Santos Cruz Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilCorresponding author. Tel: +55 31 3409 2668, Email: jcruz@icb.ufmg.brSearch for more papers by this author Carolina Rosa Gioda, Carolina Rosa Gioda Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorDanilo Roman-Campos, Danilo Roman-Campos Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorMiguel Araújo Carneiro-Júnior, Miguel Araújo Carneiro-Júnior Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorKarina Ana da Silva, Karina Ana da Silva Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorMatheus Ornelas de Souza, Matheus Ornelas de Souza Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorLiliane Jorge Mendes, Liliane Jorge Mendes Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilSearch for more papers by this authorAntônio José Natali, Antônio José Natali Department of Physical Education, Federal University of Viçosa, Viçosa, MG, BrazilSearch for more papers by this authorJader Santos Cruz, Corresponding Author Jader Santos Cruz Laboratory of Excitable Membranes and Cardiovascular Biology, Department of Biochemistry and Immunology, Federal University of Minas Gerais, Belo Horizonte, MG, BrazilCorresponding author. Tel: +55 31 3409 2668, Email: jcruz@icb.ufmg.brSearch for more papers by this author First published: 19 November 2009 https://doi.org/10.1093/eurjhf/hfp146Citations: 9AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Background Thiamine (vitamin B1) is an essential cofactor of important metabolic enzymes.1,2 Studies have demonstrated that thiamine deficiency (TD) leads to changes in cardiac morphological, electrophysiological and mechanical properties, as well as in cardiac metabolism.3–9 Clinical studies have indicated that the use of loop diuretics can induce TD and eventually cause heart dysfunction. The most important reported clinical manifestation of TD involves high-output heart failure. In humans, TD damages the cardiovascular system causing heart failure.10–12 The altered excitation-contraction coupling that characterizes cardiac failure occurs due to changes in Ca2+ dynamics, action potential duration, global Ca2+ transient, and contraction and relaxation rates.13 Oliveira et al.8 found that thiamine deprivation decreased the global Ca2+ release from the sarcoplasmic reticulum (SR) due to the lower SR Ca2+ load without changes in Ca2+ current density. Aim According to data in the literature, TD may elicit deregulation of SR Ca2+ handling in the heart, with implications on cellular cardiac contractility. However, it is unknown whether TD would cause contractile dysfunction at the cellular level. In this study, we sought to determine if TD affects cellular contractility. Methods Male Wistar rats (200–250 g) were randomly allocated to receive a diet containing thiamine (control, n = 6) or a TD diet (TD, n = 6) for 35 days as described previously by our group.8,9 All experimental procedures were conducted in accordance with international guidelines (Declaration of Helsinki). Cell isolation Ventricular cardiomyocytes from age-matched control and TD rats were enzymatically isolated as described previously.8,9 Briefly, the heart was mounted on a custom-designed Langendorff system, perfused for ~3–5 min with calcium-free solution following perfusion with 1 mg/mL collagenase type II (Worthington, USA). After 10–15 min, single cells were isolated by mechanical dispersion and stored in Dulbecco's modified Eagle's medium. The average cell yield under these conditions is 60–70%. Measurement of cellular contractility Cellular contractility was measured as described previously.14 Briefly, isolated cells were placed in an experimental chamber with a glass cover-slip base mounted on the stage of an inverted microscope. Cells were perfused with Tyrodés solution containing 1.8 mM CaCl2 and field stimulated at frequencies of 1 and 3 Hz (20 V, 5 ms duration square pulses). Cells were imaged using a NTSC camera in a partial scanning mode. Cell shortening in response to electrical stimulation was measured with a video-edge detection system at 240 Hz frame rate (Ionoptix). All parameters were evaluated using customized software developed in MatLab® platform.14 Experiments were performed at room temperature (~25°C). Only calcium-tolerant, quiescent, rod-shaped myocytes showing clear cross striations were studied. Statistical analysis All results are expressed as mean ± standard error of the mean. For statistical analysis, we used Student's t-test and ANOVA for repeated measurements with Bonferroni post hoc testing. Values of P < 0.05 were considered significant. Results After 35 days of thiamine deprivation, cellular ATP availability decreases, leading to impairment of heart contraction as we reported in a previous study.8 Thus, we hypothesized that a reduction in circulating thiamine levels would affect cardiomyocyte contractility. In accordance with this hypothesis, fractional shortening in TD cardiomyocytes was significantly decreased by ~25% (Figure 1, control: 14.7 ± 1.1%, n = 30; TD: 11.1 ± 0.9%, n = 39; P < 0.05) when field stimulated at 1 Hz. Interestingly, when TD cardiomyocytes were stimulated at 3 Hz fractional shortening increased by ~23% (TD: 13.7 ± 0.9% at 3 Hz vs. 11.1 ± 0.9% at 1 Hz). Figure 1. Frequency dependence of fractional cell shortening in rat cardiac myocytes. (A) Example of cell shortening measurements in an unloaded cell, field stimulated at 1 Hz and 3 Hz. Top panel represents control and bottom panel TD cardiac myocytes. (B) Average data for control and TD cells. Bars indicate mean ± SE, *P < 0.05 vs. 1 HzOpen in figure viewerPowerPoint The dynamics of cell shortening in control and TD cardiomyocytes at 1 and 3 Hz were also evaluated. Figure 2 shows composite data of time to half contraction and relaxation, and maximal contraction and relaxation rates (as shown by ± dL/dt values). The time to half contraction was shorter when cardiomyocytes were stimulated at 3 Hz in the TD rat model (Figure 2A). However, time to half relaxation did not show any significant difference when the stimulation frequency was increased to 3 Hz (Figure 2B). Figure 2. Half time for contraction (A) and relaxation (B) with increasing stimulation rate for control and TD cells. Maximal rates of contraction (C) and relaxation (D) with increasing stimulation frequency for control and TD cardiac cells. Bars indicate mean ± SE; *P < 0.05 vs. 1 Hz, #P < 0.05 when comparing TD and control cells at 1 HzOpen in figure viewerPowerPoint There were significant differences in the maximal contraction rate between the two groups (Figure 2C). With increasing stimulation frequency, the maximal contraction rate for TD cardiomyocytes clearly increased (1 Hz: 158.1 ± 11.8 µm/s, n = 39; and 3 Hz: 227.9 ± 15.1 µm/s, n = 41; P < 0.05). Figure 2D summarizes the mean data for maximal relaxation rate. With increasing stimulation frequency, the rate of relaxation accelerated in TD cardiomyocytes (1 Hz: 149.9 ± 11.8 µm/s, n = 39; 3 Hz: 219.6 ± 14.9 µm/s, n = 41; P < 0.05). Conclusions In this study, we showed that (i) fractional shortening increased over the range of stimulation frequencies (from 1 to 3 Hz) only in TD cardiac cells; and (ii) TD cells have increased rates of contraction and relaxation. Using a whole-heart preparation, Oliveira et al.8 observed that systolic tension was significantly lower (~27%) for TD hearts compared with controls. In addition, contraction and relaxation rates were found to be diminished in TD cells relative to control cardiac cells. Taking into account these previously reported results one would expect a compromised left ventricular pump function in TD hearts. Thiamine deficiency decreases the ability of cells to generate ATP by oxidative metabolism which lowers the cellular content of ATP. Such a cellular environment leads to cardiac structural and biochemical abnormalities resulting in heart failure. Sarcoplasmic reticulum Ca2+ content is an important determinant of systolic Ca2+ transient amplitude.15 Dibb et al.16 provided evidence that over the physiological range of stimulation frequencies for rats, an increase in SR Ca2+ load occurred and therefore one would predict a similar increase in Ca2+ transient amplitude producing a larger fractional shortening. In a previous study, we examined and demonstrated that TD cardiomyocytes have a smaller SR Ca2+ content that could lead to the observed diminution of the intracellular Ca2+ transient.8 It is generally accepted that the lack of a positive-frequency relationship in rats is mostly related to an inability to increase SR Ca2+ content further.17 As TD cells have a lower SR Ca2+ content, by increasing the stimulation frequency, it is reasonable to think that more Ca2+ will probably enter the cells leading to the SR re-filling allowing the increase in fractional shortening. At this point any correlation of our results to the management of heart failure is not an easy task. Patients with a thiamine-deficient form of heart failure exhibit water retention, vasodilation, and a significant reduction in ejection fraction. Whether a change to higher stimulation rates will produce a full recovery in TD patients has to be further examined in more detail. On the other hand, thiamine repletion has been reported to improve cardiac performance. Evidence provided by this study in a rat TD model indicates that cardiac contractility is depressed at lower stimulation rates, and this dysfunction was reversed to almost normal by increasing stimulation frequency. These results suggest that during the development of TD, a functional reserve is built to support contractile recovery of the cardiac cells. Conflict of interest: none declared. Funding This study was supported by FAPEMIG (J.S.C. and A.J.N.), CNPq (J.S.C.), and CAPES. D.R.-C. and C.R.G. held a scholarship from FAPEMIG. 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