Mental stress, hypertension and the baroreflex: what's new?

Role of alginate in the mechanism by which brown seaweed Saccharina japonica intake alleviates an increase in blood pressure in 2-kidney, 1-clip renovascular hypertensive rats

BACKGROUND

The intake of Saccharina japonica (SJ), a widely consumed brown seaweed, has been reported to decrease blood pressure (BP) in hypertensive rats. It has been suggested that this effect is related to an increase in fecal sodium excretion (SE) by alginate (Alg) to the gastrointestinal tract; however, the mechanism is still unclear. This study investigated how different seaweeds with different amounts of Alg suppressed BP increase and enhanced fecal SE in 2-kidney, 1-clip renovascular hypertensive (2K1C) rats given SJ diet.

METHODS

Rats with 2K1C or sham operation were fed a normal-/high-salt diet with some kinds of seaweeds (5.0%, w/w) or SJ extract with different Alg contents for 6 weeks. We measured systolic BP every week and mean arterial pressure at the end, and measured the total and molecular weights of Alg in each seaweed. Then, we evaluated the relationship of the Alg amount in each seaweed with the suppression of BP increase in 2K1C rats. Finally, urinary and fecal SE for 24 h was measured.

RESULTS

The intake of SJ, SJ extract, Saccharina ochotensis (SO) blades and SO roots suppressed BP increase in 2K1C rats, but the strength was not proportional to the amounts of Alg contained in the seaweeds. Although SJ intake increased fecal SE in 2K1C rats fed a high-salt diet, the fecal SE was much less than urinary SE.

CONCLUSION

The sodium excretion in feces by Alg in SJ may not be one of the major mechanisms by which SJ intake attenuates hypertension in 2K1C rats.

Obstructive Sleep Apnea and Hypertension in Adolescents: Effect on Neurobehavioral and Cognitive Functioning

Background. There are limited published data in regard to the relationship between obstructive sleep apnea (OSA) and hypertension and neurobehavioral and mental status in adolescence. The aim of our study was to evaluate neurobehavioral patterns and cognitive functions in adolescents with hypertension according to absence or presence of OSA. Methods. This was a retrospective cohort study completed at the Scientific Center for Family Health and Human Reproduction Problems. Participants included adolescents aged 14–17 years and referred for 24-hour ambulance blood pressure monitoring (ABPM) and polysomnographic (PSG) studies between 2007 and 2009, inclusive. Results. 18 hypertensive OSA (the 1st group) and 20 hypertensive non-OSA adolescents (the 2nd group) were included in the study. Significant changes of neurobehavioral functioning in OSA patients were shown. Cognitive abilities also were impaired. Verbal and visual memory indexes and attention index were 2.1 and 2.2 times lower, accordingly, in the 1st group than in the 2nd group (P < 0.05). Speech index was significantly 2.8 times lower in OSA patients than in non-OSA patients (P < 0.05). In hypertensive OSA adolescents more significant Spearman correlations between classic sleep parameters and cognitive measures were found compared to patients without OSA. Conclusions. These results suggest that OSA is closely associated with neurobehavioral and cognitive functioning in hypertensive adolescents.

Stressing 'mental stress' in hypertension: a rural background study

BACKGROUND

Modern life is full of hassles, deadlines, frustrations and demands. Mental stress or psychosocial stress is one of the major risk factor for hypertension which itself is the risk factor for various other cardiovascular diseases.

OBJECTIVES

To find out the prevalence of hypertension among rural study population above 40 years of age and analyze the relationship between mental stress and Hypertension amongst them.

METHODOLOGY

A cross-sectional descriptive study was undertaken in rural Maharashtra from January 2007 till December 2008. Systematic random sampling was done to cover 3600 sample size above 40 years of age. A protocol was devised containing requisite items of socio-demographic data and data was collected from individual households with the help of ancillary staff. Mental stress score based on Presumptive stressful life event score (PSLES) was used. For statistical analysis, Chi-square test, F-test and Z-test were used.

RESULTS

Prevalence of hypertension was found to be 5.92%. Males had maximum cases of hypertension [169 (7.27%)] compared to females [44 (3.44%)] which was statistically significant (χ2 = 21.63, p < 0.001). The rise in number of cases with increasing age was observed. Significant number of cases [127 (7.68%, p= 0.00006)] were found in study population belonging to 'More stress' group. Mean mental stress score of hypertensive study subjects was significantly higher (219) than normotensive study subjects (157). Males had significant higher stress score in both hypertensive and Normotensive group.

CONCLUSION

Total 213 cases of hypertension were detected (5.92%). As the stress increases, risk of hypertension increases. Statistically significant association was found between mental stress and hypertension for males. But in females, no such association was found. Mental stress definitely acts as risk factor for hypertension. Invention, propagation and practical application of various stress relieving measures & exercises should be done.

Autonomic mechanisms underpinning the stress response in borderline hypertensive rats

This study investigates blood pressure (BP) and heart rate (HR) short-term variability and spontaneous baroreflex functioning in adult borderline hypertensive rats and normotensive control animals kept on normal-salt diet. Arterial pulse pressure was recorded by radio telemetry. Systolic BP, diastolic BP and HR variabilities and baroreflex were assessed by spectral analysis and the sequence method, respectively. In all experimental conditions (baseline and stress), borderline hypertensive rats exhibited higher BP, increased baroreflex sensitivity and resetting, relative to control animals. Acute shaker stress (single exposure to 200 cycles min-1 shaking platform) increased BP in both strains, while chronic shaker stress (3-day exposure to shaking platform) increased systolic BP in borderline hypertensive rats alone. Low- and high-frequency HR variability increased only in control animals in response to acute and chronic shaker (single exposure to restrainer) stress. Acute restraint stress increased BP, HR, low- and high-frequency variability of BP and HR in both strains to a greater extent than acute shaker stress. Only normotensive rats exhibited a reduced ratio of low- to high-frequency HR variability, pointing to domination of vagal cardiac control. In borderline hypertensive rats, but not in control animals, chronic restraint stress (9-day exposure to restrainer) increased low- and high-frequency BP and HR variability and their ratio, indicating a shift towards sympathetic cardiovascular control. It is concluded that maintenance of BP in borderline hypertensive rats in basal conditions and during stress is associated with enhanced baroreflex sensitivity and resetting. Imbalance in sympathovagal control was evident only during exposure of borderline hypertensive rats to stressors.