Atrial natriuretic peptide response to endurance physical training in the rat

Characterization of zebrafish (Danio rerio) muscle ankyrin repeat proteins reveals their conserved response to endurance exercise

Muscle proteins with ankyrin repeats (MARPs) ANKRD1 and ANKRD2 are titin-associated proteins with a putative role as transcriptional co-regulators in striated muscle, involved in the cellular response to mechanical, oxidative and metabolic stress. Since many aspects of the biology of MARPs, particularly exact mechanisms of their action, in striated muscle are still elusive, research in this field will benefit from novel animal model system. Here we investigated the MARPs found in zebrafish for protein structure, evolutionary conservation, spatiotemporal expression profiles and response to increased muscle activity. Ankrd1 and Ankrd2 show overall moderate conservation at the protein level, more pronounced in the region of ankyrin repeats, motifs indispensable for their function. The two zebrafish genes, ankrd1a and ankrd1b, counterparts of mammalian ANKRD1/Ankrd1, have different expression profiles during first seven days of development. Mild increase of ankrd1a transcript levels was detected at 72 hpf (1.74±0.24 fold increase relative to 24 hpf time point), while ankrd1b expression was markedly upregulated from 24 hpf onward and peaked at 72 hpf (92.18±36.95 fold increase relative to 24 hpf time point). Spatially, they exhibited non-overlapping expression patterns during skeletal muscle development in trunk (ankrd1a) and tail (ankrd1b) somites. Expression of ankrd2 was barely detectable. Zebrafish MARPs, expressed at a relatively low level in adult striated muscle, were found to be responsive to endurance exercise training consisting of two bouts of 3 hours of forced swimming daily, for five consecutive days. Three hours after the last exercise bout, ankrd1a expression increased in cardiac muscle (6.19±5.05 fold change), while ankrd1b and ankrd2 were upregulated in skeletal muscle (1.97±1.05 and 1.84±0.58 fold change, respectively). This study provides the foundation to establish zebrafish as a novel in vivo model for further investigation of MARPs function in striated muscle.

The Epigenetic Regulation of GATA4-Dependent Brain Natriuretic Peptide Expression during Alcohol Withdrawal

OBJECTIVE

Natriuretic peptides participate in the collection of metabolic effects during alcohol withdrawal. Having witnessed modulation of other natriuretic peptides in alcohol-dependent patients during alcohol withdrawal, we were interested in the relation of brain natriuretic peptide (BNP) methylation with protein expression and craving in this longitudinal study.

METHODS

Ninety-nine male patients were compared to 101 healthy controls concerning epigenetic regulation and protein expression during detoxification treatment.

RESULTS

With BNP expression being GATA4 dependent, we observed a correlation of GATA4 binding site methylation and protein expression. BNP serum levels and Obsessive Compulsive Drinking Scale scores are significantly decreased during withdrawal. Focusing on the two CpGs that are between GATA transcription factor binding sites, statistical analysis revealed a reversely proportional methylation pattern, significantly increasing with ongoing detoxification and thereby supporting the observed serum level changes.

CONCLUSION

Without the functional knowledge about regulation of BNP expression via the GATA transcription factor, it would have been easy to take the mean results of the global CpG data and propose a direct relationship between methylation and expression. Thus, these findings are a voice for functionally and mechanistically approved results. There was no causal relationship between protein expression levels and epigenetic changes. Further research is needed which includes protein expression and other approaches.

Involvement of the atrial natriuretic peptide in the reduction of arterial pressure induced by swimming but not by running training in hypertensive rats

The aim of this study was to compare, under resting conditions, the influence of chronic training in swimming or running on mean arterial pressure (MAP) and the involvement of the natriuretic peptide system in this response. Two-month-old male spontaneously hypertensive rats (SHR) were divided into three groups-sedentary (SD), swimming (SW) and running (RN)-and were trained for eight weeks under regimens of similar intensities. Atria tissue and plasma atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay. ANP mRNA levels in the right and left atria as well as the natriuretic peptide receptors (NPR), NPR-A and NPR-C, mRNA levels in the kidney were determined by real-time PCR. Autoradiography was used to quantify NPR-A and NPR-C in mesenteric adipose tissue. Both training modalities, swimming and running, reduced the mean arterial pressure (MAP) of SHR. Swimming, but not running, training increased plasma levels of ANP compared to the sedentary group (P<0.05). Expression of ANP mRNA in the left atrium was reduced in the RN compared to the SD group (P<0.05). Expression of NPR-A and NPR-C in the kidneys of the SW group decreased significantly (P<0.05) compared to the SD group. Although swimming increased (125)I-ANP binding to mesenteric adipose tissue, displacement by c-ANF was reduced, indicating a reduction of NPR-C. These results suggest that the MAP reduction induced by exercise in SHR differs in its mechanisms between the training modalities, as evidenced by the finding that increased levels of ANP were only observed after the swimming regimen.

Plasma ANP and BNP during exercise in patients with major depressive disorder and in healthy controls

BACKGROUND

Increased levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) have been shown to reduce the hormones in the HPA axis. In this study we addressed the question whether patients with unmedicated major depressive disorder (MDD) might have altered baseline levels of these natriuretic peptides and an altered response to acute exercise.

METHODS

An incremental exercise test was performed in 18 patients with MDD and in 18 healthy controls. Plasma concentrations of ANP and BNP were determined at rest, during the exercise test and 30 min post exercise using immunoradiometric assays.

RESULTS

During the exercise test the concentrations of ANP and BNP increased significantly in both groups. The MDD group showed significantly lower levels of ANP than the controls at rest, at maximal work rate and post exercise and of BNP at rest and at maximal work rate. The dynamic changes of both ANP and BNP, respectively, from baseline to maximal work rate were significantly lower in the MDD group. A slightly lower (non-significant) maximal work rate was observed in the MDD group compared with the controls.

LIMITATIONS

Group sizes are relatively limited.

CONCLUSION

Lower concentrations of ANP and BNP during rest and exercise were observed in the MDD patients together with a decreased dynamic response to maximal exercise. Hypothetically, the reduced ANP and BNP concentration contributes to the high hormone levels in the HPA system seen in depressive disorders. Of interest for future research is whether physical training might increase the levels of ANP and BNP and thereby diminish depressive symptoms.

Effect of exercise on gene expression of atrial natriuretic peptide receptor of kidney

To study the effect of exercise on gene expression of natriuretic peptide receptors (NPRs) in the kidney, with in situ hybridization and the computerized image analysis, we investigated the alterations of gene expression of NPRs on the animal model of exercise training of different intensity. We found that after exercise training of different intensity, renal NPR-A mRNA and NPR-C mRNA expression showed different changes, the expression of NPR-A mRNA upregulated and NPR-C mRNA downregulated in the kidney. With the increase exercise intensity, change in NPR-A mRNA expression was insignificant, but downregulation in NPR-C mRNA expression was more significant. The result suggested that the effect of exercise on renal NPRs mRNA expression was mainly on the modulation level of NPR-C mRNA, it could reduce the clearance rate of ANP, increase the level of ANP, and enhance the biological effect of ANP on the kidney and regulative action of kidney in exercise.

Cellular adaptations of the myocardium to chronic exercise

The heart responds positively to programs of chronic dynamic exercise. Hallmark adaptations of the heart include a training bradycardia, increases in end-diastolic dimension and maximal stroke volume, and a general improvement in ventricular performance and contractile function. Of considerable clinical significance are the general observations that chronic exercise renders the myocardium less susceptible to the deleterious effects of acute ischemic episodes and can effectively prevent and/or reverse many of the cardiac functional deficits that are known to occur in settings of chronic hypertension, advanced age, and myocardial infarction. In the text that follows, information gathered over the last 25 to 30 years has been reviewed in an attempt to identify cellular myocardial adaptations, both known and hypothetical, that are responsible for the observed effects of chronic dynamic exercise on the function and morphology of the heart in both normal and selected pathophysiologic settings. Finally, a variety of unresolved issues regarding the ability of chronic exercise to elicit adaptive cardiocyte responses has been identified. In so doing, it is hoped that creative thought and future work in the area will be stimulated.

Heart and plasma atrial natriuretic peptide (ANP) in response to long-term endurance training in rats

Long-term endurance training effects on heart and plasma ANP were investigated in male Wistar rats. Maximal O2 uptake (VO2max) was significantly higher in trained groups, when they are used as their own control. After 3, 4, and 5 weeks of endurance training, VO2max was respectively increased by 7.7% (p less than 0.05), 13.7% (p less than 0.01), and 18.4% (p less than 0.001). Plasma ANP and glomerular ANP receptor density showed no clear variations in trained rats. However, cardiac ANP content decreased significantly in left and right atrial tissues by 35-36% (p less than 0.05) after 5 weeks of training. ANP immunoreactivity was investigated to show the distribution of ANP within the atria. ANP was found in diffuse and granular forms. The diffuse pattern (immature ANP) disappeared in cardiocytes of trained rats, while the granular form persisted, especially in the left atrial tissue. These data suggest that chronic endurance training might cause a decrease in ANP synthesis with no change in ANP storage. Such results are in agreement with the hypothesis that the left atrium could be especially involved in long-term fluid volume control.