B-type natriuretic peptide after open-water and hyperbaric chamber exposure to 10 msw

Adaptive response triggered by the repeated SCUBA diving is reflected in cardiovascular, muscular, and immune biomarkers

It has been shown that one recreational SCUBA (rSCUBA) diving session is sufficient to cause changes in plasma level of cardiovascular (CV) and muscular biomarkers. To explore whether repetitive rSCUBA diving triggers an adaptive response of the CV, muscular, and immune system, we measured the cardiac damage (NT-proBNP, hs-TnI, and CK-MB), muscle damage (myoglobin (Mb), galectin-3, CK, and LDH), vascular endothelial activation (ET-1 and VEGF), and inflammatory (leukocyte count (Lkc), CRP, and IL-6) biomarkers. A longitudinal intervention study included divers (N = 14) who conducted one dive per week over 5 weeks at the depth of 20-30 m for 30 min after a non-dive period of 5 months. The blood samples were collected before and after the first, third, and fifth dives and specific biomarkers were measured in plasma or serum by the standard laboratory methods. The concentrations of the majority of measured biomarkers increased after every single dive; the exception was ET-1 concentration that decreased. The cumulative effect of five dives has been reflected in diminishing changes in hs-TnI, Mb, galectin-3, ET-1, VEGF, and IL-6 levels, and more pronounced increases in NT-proBNP and hs-CRP levels. The median values of all measured biomarkers in all time points, except Mb, remained within the corresponding reference range. Repeatedly performed rSCUBA diving activates an adaptive response of the CV, muscular, and immune system that is reflected in changes in the specific biomarker concentration.

Recreational scuba diving: negative or positive effects of oxidative and cardiovascular stress?

Environmental conditions and increased physical activity during scuba diving are followed by increased production of free radicals and disturbed redox balance. Redox balance disorder is associated with damage of cellular components, changes of cellular signaling pathways and alterations of gene expression. Oxidative stress leads to increased expression of sirtuins (SIRTs), molecules which play an important role in the antioxidant defense, due to their sensitivity to the changes in the redox status and their ability to regulate redox homeostasis. These facts make SIRTs interesting to be considered as molecules affected by scuba diving and in that sense, as potential biomarkers of oxidative status or possible drug targets in reduction of reactive oxygen species (ROS) accumulation. In addition, SIRTs effects through currently known targets make them intriguing molecules which can act positively on health in general and whose expression can be induced by scuba diving.A demanding physical activity, as well as other circumstances present in scuba diving, has the greatest load on the cardiovascular function (CV). The mechanisms of CV response during scuba diving are still unclear, but diving-induced oxidative stress and the increase in SIRTs expression could be an important factor in CV adaptation. This review summarizes current knowledge on scuba diving-induced oxidative and CV stress and describes the important roles of SIRTs in the (patho)physiological processes caused by the redox balance disorder.

Effects of hyperbaric oxygen preconditioning on cardiac stress markers after simulated diving

Hyperbaric oxygen preconditioning (HBO-PC) can protect the heart from injury during subsequent ischemia. The presence of high loads of venous gas emboli (VGE) induced by a rapid ambient pressure reduction on ascent from diving may cause ischemia and acute heart failure. The aim of this study was to investigate the effect of diving-induced VGE formation on cardiac stress marker levels and the cardioprotective effect of HBO-PC. To induce high loads of VGE, 63 female Sprague-Dawley rats were subjected to a rapid ambient pressure reduction from a simulated saturation dive (50 min at 709 kPa) in a pressure chamber. VGE loads were measured for 60 min in anesthetized animals by the use of ultrasonography. The animals were divided into five groups. Three groups were exposed to either diving or to HBO-PC (100% oxygen, 38 min at 303 kPa) with a 45 or 180 min interval between HBO-PC and diving. Two additional groups were used as baseline controls for the measurements; one group was exposed to equal handling except for HBO-PC and diving, and the other group was completely unexposed. Diving caused high loads of VGE, as well as elevated levels of the cardiac stress markers, cardiac troponin T (cTnT), natriuretic peptide precursor B (Nppb), and αB-crystallin, in blood and cardiac tissue. There were strong positive correlations between VGE loads and stress marker levels after diving, and HBO-PC appeared to have a cardioprotective effect, as indicated by the lower levels of stress marker expression after diving-induced VGE formation.

B-type natriuretic peptide secretion following scuba diving

AIM

To examine the neurohormonal effects of a scuba dive, focusing on the acute changes in the plasma concentrations of the different peptide fragments from the B-type natriuretic peptide (BNP) precursor.

MATERIALS & METHODS

We studied 12 healthy scuba divers (mean age ± standard deviation: 44 ± 7 years; range: 34-55 years; BMI: 24.8 ± 2.8 kg/m(2)), who performed a 15-m depth dive in salt water, with a bottom time of 30 min. Blood samples for BNPs (pro-B-type natriuretic peptide [pro-BNP], BNP and aminoterminal pro-BNP) and catecholamines were measured in plasma before immersion, and after the dive. A continuous electrocardiographic recording was obtained during the entire protocol.

RESULTS

BNP, aminoterminal pro-BNP and pro-BNP plasma concentrations slightly, but significantly, increased after the scuba dive (18 ± 15 to 21 ± 11 ng/l, p = 0.020; 32 ± 19 to 38 ± 21 ng/l, p = 0.008; and 7.8 ± 1.6 to 10.3 ± 3.6 ng/l, p = 0.028, respectively) in parallel with norepinephrine concentration (743 ± 323 to 1163 ± 656 ng/l, p = 0.014), with no variations in total plasma proteins, hematocrit or osmolality. A persistent sinus tachycardia was observed during all phases of the dive.

CONCLUSIONS

A 15-m depth scuba dive induces an acute slight release of the different peptide fragments from the BNP precursor, likely through the stimulation of a constitutive secretory pathway promoted by adrenergic activation and cardiac chamber dilation.