Efectos de la actividad locomotriz voluntaria gestacional sobre la morfología cardiaca en crías murinas / Effects of gestational voluntary locomotor activity on cardiac morphology in murine offspring

RESUMEN: El objetivo del presente estudio es analizar los efectos de la actividad locomotriz voluntaria gestacional, como un tipo de entrenamiento físico, sobre la morfología de la bomba cardíaca de la cría, en modelo murino de la cepa CF-1. 12 hembras gestantes fueron divididas aleatoriamente en un grupo control y un grupo que realizó actividad locomotriz voluntaria, accediendo a una rueda de actividad durante los primero 12 días de gestación. Se evaluó la morfología cardiaca mediante cortes transversales, midiendo espesor y área de las paredes del ventrículo derecho, ventrículo izquierdo y septum, tanto en valores absolutos como en valores relativos a la masa corporal del individuo. Se observó que la masa corporal de las crías control (GC) fue significativamente mayor que las del grupo cuyas hembras accedieron a la rueda de actividad (GE) (p<0.01). Solo hubo diferencias en los valores absolutos de espesores y áreas miocárdicas de ventrículo derecho, entre el grupo GE y GC (p<0.05), pero al evaluar los espesores y áreas relativos a la masa corporal se observó que las crías del grupo GE presentaron espesores y áreas significativamente mayores que las que grupo GC (p<0.01). En conclusión, la actividad física gestacional altera el desarrollo morfológico de la bomba cardíaca en ratones CF-1, aumentando significativamente el espesor y área de las paredes miocárdicas en relación a la masa corporal total de la cría.

SUMMARY: The objective of the present study is to analyze the effects of gestational voluntary locomotor activity, as a type of physical training, on the morphology of the offspring´s heart pump, in a murine model of the CF-1 strain. Twelve (12) pregnant females were randomly divided in a control group and a group performing voluntary locomotor activity, by accessing an activity wheel during the first 12 days of gestation. Cardiac morphology was evaluated using cross sections, measuring thickness and area of the walls of the right ventricle, left ventricle, and septum, both in absolute values and values relative to the individual's body mass. It was observed that the body mass of the control pups (CG) was significantly higher than those of the group whose females accessed the activity wheel (GE) (p <0.01). Differences were observed only in absolute values of thickness and myocardial areas of the right ventricle, between the GE and GC group (p <0.05). However, when evaluating the thickness and areas relative to body mass, it was observed that the offspring of the GE group presented thicknesses and areas significantly larger than those in the GC group (p <0.01). In conclusion, gestational physical activity alters the morphological development of the heart pump in CF-1 mice, significantly increasing the thickness and area of the myocardial walls in relation to offspring total body mass.

Long-term effects of early overfeeding and food restriction during puberty on cardiac remodeling in adult rats.

Nutritional disorders during the perinatal period cause cardiometabolic dysfunction, which is observable in the early overfeeding (EO) experimental model. Therefore, severe caloric restriction has the potential of affecting homeostasis through the same epigenetic mechanisms, and its effects need elucidation. This work aims to determine the impact of food restriction (FR) during puberty in early overfed obese and non-obese animals in adult life. Three days after delivery (PN3), Wistar rats were separated into two groups: normal litter (NL; 9 pups) and small litter (SL; 3 pups). At PN30, some offspring were subjected to FR (50%) until PN60, or maintained with free access to standard chow. NL and SL animals submitted to food restriction (NLFR and SLFR groups) were kept in recovery with free access to standard chow from PN60 until PN120. Body weight and food intake were monitored throughout the experimental period. At PN120 cardiovascular parameters were analyzed and the animals were euthanized for sample collection. SLNF and SLFR offspring were overweight and had increased adiposity. Differences in blood pressure were observed only between obese and non-obese animals. Obese and FR animals have cardiac remodeling showing cardiomyocyte hypertrophy and the presence of interstitial and perivascular fibrosis. FR animals also show increased expression of AT1 and AT2 receptors and of total ERK and p-ERK. The present study showed that EO leads to the obese phenotype and cardiovascular disruptions. Interestingly, we demonstrated that severe FR during puberty leads to cardiac remodeling.

Maternal nutritional restriction during gestation impacts differently on offspring muscular and elastic arteries and is associated with increased carotid resistance and ventricular afterload in maturity.

BACKGROUND: Intrauterine undernutrition could impact offspring left ventricle (LV) afterload and arterial function. The changes observed in adulthood could differ depending on the arterial type, pathway and properties studied. Aim: To analyze whether undernutrition during early and mid-gestation is associated with changes in cardiovascular properties in adulthood. METHODS: Pregnant ewes were assigned to one of the two treatment groups: (1) standard nutritional offer (high pasture-allowance, HPA; n = 16) or (2) nutritional restriction (50-75% of control intake) from before conception until day 122 of gestation (≈85% term) (low pasture allowance, LPA; n = 17). When offspring reached adult life, cardiovascular parameters were assessed in conscious animals (applanation tonometry, vascular echography). MEASUREMENTS: Peripheral and aortic pressure, carotid and femoral arteries diameters, intima-media thickness and stiffness, blood flow, local and regional resistances and LV afterload were measured. Blood samples were collected. Parameters were compared before and after adjustment for nutritional characteristics at birth and at the time of the cardiovascular evaluation. RESULTS: Doppler-derived cerebral vascular resistances, mean pressure/flow ratio (carotid resistance) and afterload indexes were higher in descendants from LPA than in descendants from HPA ewes (p < 0.05). Descendants from LPA had lower femoral diameters (p < 0.05). Cardiovascular changes associated with nutritional restriction during pregnancy did not depend on the offsprings' nutritional conditions at birth and/or in adult life. CONCLUSION: Pregnant ewes that experienced undernutrition gave birth to female offspring that exhibited increased carotid pathway resistances (cerebral microcirculatory resistances) and LV afterload when they reached the age of 2.5 years. There were differences in the impact of nutritional deficiency on elastic and muscular arteries.

miRNAs, target genes expression and morphological analysis on the heart in gestational protein-restricted offspring.

Gestational protein restriction was associated with low birth weight, hypertension and higher prevalence of cardiac disorders in adults. Several mechanisms, including epigenetics, could be related with the cardiovascular phenotype on protein-restricted offspring. Thus, we investigated the morphological cardiac effects of gestational protein restriction and left ventricle miRNAs and target genes expression pattern in both 12-day and 16-week old gestational protein-restricted male offspring. Pregnant Wistar rats were allocated into two groups, according to protein supply during pregnancy: NP (normal protein diet- 17%) or LP (low protein diet-6%). Dams on the gestational protein-restricted diet had lower body weight gain and higher food intake. Gestational protein-restricted offspring had low birth weight, followed by rapidly body weight recovery, hypertension, and increased myocytes cross-sectional area and collagen fraction at 16-week old age. At 12-days old, miR-184, miR-192, miR-376c, miR-380-3p, miR-380-5p, miR-451, and miR-582-3p had increased expression, and miR-547 and miR-743a had decreased expression in the gestational protein-restricted left ventricle. At 16-week old, let-7b, miR-125a-3p, miR-142-3p, miR-182 and miR-188-5p had increased expression and let-7g, miR-107, miR-127, miR-181a, miR-181c, miR-184, miR-324-5p, miR-383, miR-423-5p and miR-484 had decreased expression in gestational protein-restricted left ventricle. Target predicted gene expression analysis showed higher expression of Dnmt3a, Oxct1, Rictor and Trps1 and lower expression of Bbs1 and Calml3 in 12-day old protein-restricted offspring. 16-week old protein-restricted offspring had higher expression of Adrbk1, Bbs1, Dnmt3a, Gpr22, Inppl1, and Oxct1 genes. In conclusion, gestational protein restriction was related to offspring low birth weight, increased systolic blood pressure and morphological heart alterations that could be related to early heart miRNA expression changes that perpetuate into adulthood and which are associated with the regulation of essential genes involved in cardiovascular development, heart morphology, function, and metabolism.

Reference Intervals and Percentile Curves of Echocardiographic Left Ventricular Mass, Relative Wall Thickness and Ejection Fraction in Healthy Children and Adolescents.

Despite the clinical utility of echocardiography to measure cardiac target organ injury (TOI) there are scarcities of data about the reference intervals (RIs) and percentiles of left ventricular (LV) mass (LVM) and derived indexes (LVMI and LVMI2.7), relative wall thickness (LVRWT) and ejection fraction (LVEF) from population-based studies in children and adolescents. The aim of this study was to generate reference intervals RIs of LVM and derived indexes (LVMI and LVMI2.7), LVRWT, and LVEF obtained in healthy children, adolescents, and young adults from a South-American population. Echocardiographic studies were obtained in 1096 healthy subjects (5-24 years). Age and sex-specific RIs of LVM, LVMI, LVMI2.7, LVRWT, and LVEF were generated using parametric regression based on fractional polynomials. After covariate analysis (i.e., adjusting by age, body surface area) specific sex-specific RIs were evidenced as necessaries. Age and sex-specific 1st, 2.5th, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97.5th, and 99th percentile and curves were reported and compared with previously reported RIs. RIs showed high concordance and complementarity with what was previously reported for the population of North-American children (0-18 years old). In conclusion, in children and adolescents the interpretation of the LVM, LVMIs, LVRWT, and LVEF RIs requires sex-related RIs. This study provides the largest Argentinean database concerning RIs and percentile curves of LVM, LVMIs, LVRWT, and LVEF as markers of cardiac TOI obtained in healthy children and adolescents. These data are valuable in that they provide RIs values with which data of populations of children, adolescents can be compared.

Cavß2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes.

In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVß2. To date, five distinct CaVß2 transcriptional start site (TSS) variants (CaVß2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVß2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVß2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVß2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVß2a and smaller in CaVß2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVß2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVß2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.

AMPK signaling pathway is rapidly activated by T3 and regulates the cardiomyocyte growth.

Previous studies have indicated that AMP-activated protein kinase (AMPK) plays a critical role in the control of cardiac hypertrophy mediated by different stimuli such as thyroid hormone (TH). Although the classical effects of TH mediating cardiac hypertrophy occur by transcriptional mechanisms, recent studies have identified other responses to TH, which are more rapid and take place in seconds or minutes evidencing that TH rapidly modulates distinct signaling pathway, which might contribute to the regulation of cardiomyocyte growth. Here, we evaluated the rapid effects of TH on AMPK signaling pathway in cultured cardiomyocytes and determined the involvement of AMPK in T3-induced cardiomyocyte growth. We found for the first time that T3 rapidly activated AMPK signaling pathway. The use of small interfering RNA against AMPK resulted in increased cardiomyocyte hypertrophy while the pharmacological stimulation of AMPK attenuated this process, demonstrating that AMPK contributes to regulation of T3-induced cardiomyocyte growth.

Impact of corticosteroids on late growth of radiofrequency lesions in infant pigs: histopathological and electroanatomical findings.

AIMS: Corticosteroids attenuate late growth of radiofrequency (RF) lesions in the thigh muscle of infant rats. We sought to assess the impact of these drugs on the late growth of RF lesions in immature swine myocardium and to determine the electroanatomical mapping (EAM) characteristics of these lesions. METHODS AND RESULTS: Radiofrequency (60°C; 60 s) lesions were created in the right atrium (n = 2) and ventricle (n = 2) of 14 piglets (age 65 days; weight 5 kg) and 3 adults. Piglets were divided into: controls (n = 7) and treated (n = 7), receiving hydrocortisone (10 mg/kg iv after RF) and prednisone (1 mg/kg/day) for 29 days. After 8 months, animals were sacrificed for histological analysis. In four piglets, endocardial and epicardial voltage EAM were performed. In infant groups, the dimensions of atrial (11 ± 5 vs. 13 ± 7 mm) and ventricular (12 ± 3 vs. 11 ± 3 mm) lesions were similar. In adults, atrial (6 ± 1 mm) and ventricular (6 ± 1 mm) lesions were smaller. In controls, ventricular lesions depicted dense fibrosis and multiple strands of fibrous tissue extending from the lesion into normal muscle. Treated piglets revealed scars exhibiting less dense fibrosis with predominance of fibroadipose tissue and less collagen proliferation. Large atrial and ventricular low-voltage areas corresponding to the macroscopic lesions were identified in all animals. CONCLUSION: Radiofrequency lesions in infant pigs reveal late growth and invasion of normal muscle by intense collagen proliferation. Corticosteroids do not prevent late enlargement of the lesions but modulate the fibrotic proliferation. The expressive growth of the lesion may generate low-voltage areas detectable by EAM.

The heart and pulmonary circulation at high altitudes: healthy highlanders and chronic mountain sickness.

More than 140 million people worldwide live >2500 m above sea level. Of them, 80 million live in Asia, and 35 million live in the Andean mountains. This latter region has its major population density living above 3500 m. The primary objective of the present study is to review the physiology, pathology, pathogenesis, and clinical features of the heart and pulmonary circulation in healthy highlanders and patients with chronic mountain sickness. A systematic review of worldwide literature was undertaken, beginning with the pioneering work done in the Andes several decades ago. Original articles were analyzed in most cases and English abstracts or translations of articles written in Chinese were reviewed. Pulmonary hypertension in healthy highlanders is related to a delayed postnatal remodeling of the distal pulmonary arterial branches. The magnitude of pulmonary hypertension increases with the altitude level and the degree of exercise. There is reversal of pulmonary hypertension after prolonged residence at sea level. Chronic mountain sickness develops when the capacity for altitude adaptation is lost. These patients have moderate to severe pulmonary hypertension with accentuated hypoxemia and exaggerated polycythemia. The clinical picture of chronic mountain sickness differs from subacute mountain sickness and resembles other chronic altitude diseases described in China and Kyrgyzstan. The heart and pulmonary circulation in healthy highlanders have distinct features in comparison with residents at sea level. Chronic mountain sickness is a public health problem in the Andean mountains and other mountainous regions around the world. Therefore, dissemination of preventive and therapeutic measures is essential.

Myocardium of the left ventricular apex of chagasic hearts: morphologic and morphometric aspects

Utilizando a morfometria, o autor estudou o comportamento do miocárdio apical em 10 corações controle e 10 com aneurisma de ponta. Além das alterações em relação aos cadiomíócitos, estudou o tecido conjuntivo fibroso e alterações vasculares. Os resultados foram submetidos a tratamentos estatísticos da análise do Qui-quadrado confrontados com a literatura pertinente. Foi constatada diminuição significativa de cardiomiócitos e capilares, assim como acenturado aumento na quantidade de tecido fibroso. Além disso, os cardiomiócitos remanescentes sofrem considerável hipertrofia

Decrease in the ratio of high- to low-affinity isozymes of (Na+ +K+)-ATPase during the development of rat cardiac ventricles.

The ratio of (Na+ +K+)-ATPase (EC 3.6.1.3.)isoforms with high and low affinity for cardiac glycosides was studied in heart preparations from neonatal, 3-month and 6-month old Wistar rats. Biphasic ouabain inhibition curves of (Na+ +K+)-ATPase activity indicated that the relative contribution of the high-affinity process decreased from 34% at 9 days to 23% at 3 months and to 10% at 6 months. Scatchard plots for [3H]ouabain binding were curvilinear and indicated that the relative contribution of the high-affinity sites (Kd = 0.1-0.25 microM) decreased by about one-half between 3 months (19-24%, N = 2) and 6 months (9-11%, N = 2).

Echocardiography shows persistent thickness of the wall of the right ventricle in infants at high altitude.

We have applied M-mode and two-dimensional echocardiography to infants living at high altitude in La Paz, Bolivia (3800m) and infants living at low altitude in Santa Cruz, Bolivia (400m). At low altitude, the thickness of the anterior wall of the right ventricle decreases during the first month of extrauterine life to a dimension which remains constant for the rest of infancy. At high altitude, the thickness of the anterior wall of the right ventricle at birth is similar to that found at low altitude but does not decrease in the succeeding twelve months. The ratio of the diameter of the aorta to that of the pulmonary artery was higher at low altitude in all age-groups. The observations are consistent with the persistence of a high pulmonary arterial pressure during infancy at high altitude.

Evaluation of right and left ventricular size in SHR-Wistar hybrids.

The relative right and left ventricular sizes were evaluated in hybrid rats obtained by crossing spontaneously hypertensive (SHR) and pure Wistar strains to detect cardiac hypertrophy dissociated from the hypertension genetically transmitted by the SHR strain. In female hybrids of the the F1, F2, and F3 generations, both ventricles were found to have bigger size in relation to body weight than in the pure Wistar, whereas only the F3 group was hypertensive. All generations of male hybrids had arterial pressure values in the hypertensive range, which were not consistently accompanied by increases in the ventricle mass. The correlation between arterial pressure and indexes of ventricular size was assessed in sex-age matched groups. In a range of systolic pressure values of 100-200 mmHg, the variables showed no correlation or poor positive correlation (correlation coefficient values from -0.3641 to 0.6153). The correlation was not improved in the F3 generation as would be expected, because these hybrids underwent higher left pressure load than the preceding generations. The results indicate that increased ventricular size in SHR-Wistar hybrids may be independent from the hypertension genetically transmitted by the SHR strain and suggest that some of the previously proposed factors, i.e., cardioadrenergic activity or the growth factor isolated from SHR hearts, may be playing a role in the ventricular hypertrophy process in this strain. If this characteristic of hybrids is a constant in pure SHR strain, its validity as a model of cardiac hypertrophy due to left pressure overload would be questioned.