In this article the researchers wanted to measure the physiological responses to psychological stress. They already knew that stress activiates the hypothalamic-pituitary-adrenocortical (HPA) system and therefore, releases cortisol from the adrenal cortex. Brain natriuretic peptide (BNP) controls vascular and body fluid homeostasis and the increase of circulating BNP, and N-terminal pro-BNP, are connected with heart failure and disease. BNP and NT-P-BNP greatly affect the "hemodynamic, body fluid, and eletrolyte homeostasis" and may act to suppress the immune system and increase cortisol horomones. The present study tries to "clarify their role in responding to acute mental stress." They hypothesize BNP will suppress or inhibit ACTH (adrenocorticotropic horomone) release, which will affect cortisol levels. They wanted to find a relationship between BNP and mental stressors.
The researchers recruited 174 male and female college students; the overall average age was 25. Prior to the study, all students were tested to ensure they were healthy subjects (i.e. no history of heart disease, etc.) They were studied twice, once 15-30 minutes prior to a major final examination and once again when they were rested and had not been studying (this served as their baseline). Before taking the examination, students rated how stressed they were on a scale from 1 (not stressed) to 10 (extremely stressed). Afterwards, on the exam day and rest day, their heart rate and blood pressure (diastolic and systolic) were recorded and blood samples were taken to check cortisol levels. A Mann-Whitney U was performed to find differences between genders for NT-proBNP and a Multivariate ANOVA was performed to analyze BNP, cortisol, heart rate, and blood pressure responses to the stress event. They found, for both genders, blood pressure and cortisol levels were higher and NT-proBNP was lower on the examination day. However, blood pressure and cortisol was higher for women than men. Their main discovery was the response of lower concentration of NT-proBNP to the life stressor. This finding provides evidence for past research that found BNP inhibits ACTH, which will increase cortisol levels. Brain BNP is different from circulating BNP, in that "ANP is released from the hypothalmo-hypophyseal pathway in response to stressful stimuli and suppresses ACTH secretion and thus constitutes a hypothalamic corticotrophin-release inhibiting pathway." In this study, both central and peripheral natriuretic systems were measured at the same time. In summary, stress causes the reduction of NT-proBNP, which increases cortisol levels. At the time of the stressful event, such as the examination, the brain will release BNP into the circulatory system, which , in turn, increases cortisol.
I think this is why if we let our stress get out of hand, we will end up producing more cortisol or fat cells. If we could train ourselves and physiological responses to react calmly to potentially stressing events, like big tests, then our body would ultimately thank us years down the road.
Amir, O., Sagiv, M., Eynon, N., Yamin, C., Rogowski, O., Gerzy, Y., & Amir, R.E. (2010). The response of circulating brain natriuretic peptide to academic stress in college students. The International Journal on the Biology of Stress, 13(1), 83-90. Retrieved from EbscoHost. doi: 10.3109/10253890902818357
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