Heart rate and arterial pressure variability and baroreflex sensitivity in ovariectomized spontaneously hypertensive rats

Cardiovascular and neuroimmune adaptations to enalapril and exercise training: A comparative study in male and ovariectomized female spontaneously hypertensive rats

Antihypertensive drug and exercise training are commonly prescribed to treat arterial hypertension. However, there is a considerable gap in understanding how physiological mechanisms of male and female adapt to the combination of these approaches. Therefore, we focused to investigate sexual differences in cardiovascular, autonomic, inflammation and systemic oxidative stress adaptations in male and OVX female ovariectomized spontaneously hypertensive rats (SHR) treated with enalapril associated with moderate-intensity concurrent exercise training. Enalapril (3 mg/kg, diluted in drinking water) and exercise training (3 days/week, moderate intensity) was carried out for 8 weeks. Blood pressure (BP), heart rate (HR) and its variabilities were assessed. Serum and plasma were used for inflammatory and oxidative stress analyses. Enalapril, associated or not with exercise training, induced a reduction in diastolic and mean BP in both sexes; however, only the OVX female groups showed a reduction in systolic BP, as well as resting bradycardia. Both sexes showed improvements in BP and HR variability following the treatments; however, improvement in SD2/SD1 ratio, which indicates how much the heartbeats occur at irregular intervals, and in variance of systolic BP were observed only in trained groups. A higher spontaneous baroreflex sensitivity, as well as reduced IL-6/IL-10 were found only in the trained groups. Increased IL-10 was observed in male trained group (vs. other groups). Finally, combination enalapril and exercise training reduced systemic pro-oxidants such as NADPH oxidase and hydrogen peroxide. The findings of our study showed that OVX female SHR, after ovarian hormone deprivation, presented more pronounced effects on hemodynamics, BP variability, and anti-inflammatory profile than hypertensive males with the combination of treatments.

BACKGROUND

Researchers are investigating how the body responds differently in males and females. These differences are also evident when examining how pharmacological and non-pharmacological approaches help the body control arterial hypertension. This study aimed to investigate how drug medication combined with exercise affects the heart's ability to self-regulate and how it relates to immune and oxidant defense, with a focus on differences in male and ovariectomized (OVX) female adaptations.

METHODS

The study was conducted using hypertensive male and OVX female rats, allocated into: a) sedentary, b) enalapril, or c) enalapril plus exercise groups, totaling six groups (3 males and 3 OVX females, respectively). Enalapril (3 mg/kg/day) and exercise (aerobic and resistance exercises) were prescribed for eight weeks. The effects on blood pressure control, serum, and plasma were assessed.

RESULTS

Although both males and OVX females showed improvements in blood pressure after medication, combined or not with exercise, OVX females had better control of blood pressure and heart rhythm regulation. Furthermore, including an exercise program during medication treatment improved immune defense in OVX females only, as well as the levels of key enzymes involved in the process of organ damage development in both sexes.

CONCLUSION

OVX female rats benefited more from the combination of medication and exercise compared to male rats. This suggests that OVX females may experience additional health benefits from the combination of antihypertensive approaches, highlighting the importance of understanding how exercise impacts the body differently in males and OVX females, which could contribute to better long-term disease management.

Blunted cardiac autonomic dynamics to active standing test in postmenopausal women

Introduction

Although both aging and menopause influence cardiovascular autonomic control, the effect of menopause per se remains unclear. The current study was undertaken to test the hypothesis that post-menopausal women (PMW) have a blunted cardiovascular autonomic adjustment to active standing compared to pre-menopausal women. Thus, we compared the heart rate variability (HRV) indexes from supine (SUP) to orthostatic (ORT) positions among young women (YW), young men (YM), older men (OM), and PMW.

Methods

The participants rested for 10 min in SUP and then stood up and remained for 5 min in ORT. ECG was continuously recorded, and R-R time series of about 300 beats were analyzed using linear (spectral analysis) and non-linear (symbolic analysis) methods. The variation from SUP to ORT was calculated (Δ = ORT-SUP) for each HRV index.

Results

In SUP, no difference was found for any HRV index among groups. However, Δ0V% and ΔLFn (cardiac sympathetic modulation) were reduced in PWM compared to all groups (OM, YW, and YM), while Δ2UV% and ΔHFn (cardiac vagal modulation) were reduced in PMW than the younger group (YW and YM). No differences were found among the male groups (OM and YM).

Discussion

In light of our results, the cardiac autonomic dynamic response to orthostatic stress is blunted in post-menopausal women compared to younger women and older men, a finding that might be influenced not only by aging.

Hypertension after the Menopause: What Can We Learn from Experimental Studies?

Hypertension is the most prevalent cardiovascular disease of the adult population and is closely associated with serious cardiovascular events. The burden of hypertension with respect to vascular and other organ damage is greater in women. These sex differences are not fully understood. The unique feature in women is their transition to menopause accompanied by profound hormonal changes that affect the vasculature that are also associated with changes of blood pressure. Results from studies of hormone replacement therapy and its effects on the cardiovascular system are controversial, and the timing of treatment after menopause seems to be important. Therefore, revealing potential sex- and sex hormone-dependent pathophysiological mechanisms of hypertension in experimental studies could provide valuable information for better treatment of hypertension and vascular impairment, especially in postmenopausal women. The experimental rat models subjected to ovariectomy mimicking menopause could be useful tools for studying the mechanisms of blood pressure regulation after menopause and during subsequent therapy.

Role of aerobic physical training on cardiac autonomic and morphophysiological dysfunction in hypertensive rats subjected to ovarian hormone deprivation

Here we investigated the effects of physical training on cardiovascular autonomic control and cardiac morphofunctional parameters in spontaneously hypertensive rats (SHRs) subjected to ovarian hormone deprivation. Forty-eight 10-week-old SHRs were divided into two groups: ovariectomized (OVX, n=24) and sham (SHAM, n=24). Half of each group (n=12) was trained by swimming for 12 weeks (OVX-T and SHAM-T). Cardiac morphology and functionality were assessed using echocardiography, and autonomic parameters were assessed using double pharmacological autonomic block, baroreflex sensitivity (BRS), and analyses of heart rate variability (HRV) and blood pressure variability (BPV). Ovariectomy did not influence the cardiac autonomic tonus balance unlike physical training, which favored greater participation of the vagal autonomic tonus. Ovariectomy and aerobic physical training did not modify HRV and BRS, unlike BPV, for which both methods reduced low-frequency oscillations, suggesting a reduction in sympathetic vascular modulation. Untrained ovariectomized animals showed a reduced relative wall thickness (RWT) and increased diastolic and systolic volumes and left ventricular diameters, resulting in increased stroke volume. Trained ovariectomized animals presented reduced posterior wall thickness and RWT as well as increased final diastolic diameter, left ventricular mass, and stroke volume. Ovarian hormone deprivation in SHRs promoted morphofunctional adaptations but did not alter the evaluation of cardiac autonomic parameters. In turn, aerobic physical training contributed to a more favorable cardiac autonomic balance to the vagal autonomic component and promoted morphological adaptations but had little effect on cardiac functionality.

Purification and characterization of a novel angiotensin I-converting enzyme inhibitory peptide derived from an enzymatic hydrolysate of duck skin byproducts

An angiotensin I-converting enzyme (ACE) inhibitory peptide was isolated and identified from hydrolysates of duck skin byproducts. Duck skin byproducts were hydrolyzed using nine proteases (Alcalase, Collagenase, Flavourzyme, Neutrase, papain, pepsin, Protamex, trypsin, and α-chymotrypsin) to produce an antihypertensive peptide. Of the various hydrolysates produced, the α-chymotrypsin hydrolysate exhibited the highest ACE inhibitory activity. The hydrolysate was purified using fast protein liquid chromatography (FPLC) and high-performance liquid chromatography (HPLC). The amino acid sequence of the ACE inhibitory peptide was identified as a hexapeptide Trp-Tyr-Pro-Ala-Ala-Pro, with a molecular weight of 693.90 Da. The peptide had an IC50 value of 137 μM, and the inhibitory pattern of the purified ACE inhibitor from duck skin byproducts was determined to be competitive by Lineweaver-Burk plots. In addition, the peptide was synthesized and the ACE inhibitory activity was verified in vivo. Spontaneously hypertensive rats (SHR) exhibited significantly decreased blood pressure and heart rate after peptide injection. Taken together, the results suggest that Trp-Tyr-Pro-Ala-Ala-Pro may be useful as a new antihypertensive agent.

Comparison of the effects of aerobic and resistance training on cardiac autonomic adaptations in ovariectomized rats

We have compared the effects of two types of physical training on the cardiac autonomic control in ovariectomized and sham-operated rats according to different approaches: double autonomic blockade (DAB) with methylatropine and propranolol; baroreflex sensibility (BRS) and spectral analysis of heart rate variability (HRV). Wistar female rats (±250g) were divided into two groups: sham-operated and ovariectomized. Each group was subdivided into three subgroups: sedentary rats, rats submitted to aerobic trained and rats submitted to resistance training. Ovariectomy did not change arterial pressure, basal heart rate (HR), DAB and BRS responses, but interfered with HRV by reducing the low-frequency oscillations (LF=0.20-0.75Hz) in relation to sedentary sham-operated rats. The DAB showed that both types of training promoted an increase in the predominance of vagal tonus in sham-operated rats, but HR variations due to methylatropine were decreased in the resistance trained rats compared to sedentary rats. Evaluation of BRS showed that resistance training for sham-operated and ovariectomized rats reduced the tachycardic responses in relation to aerobic training. Evaluation of HRV in trained rats showed that aerobic training reduced LF oscillations in sham-operated rats, whereas resistance training had a contrary effect. In the ovariectomized rats, aerobic training increased high frequency oscillations (HF=0.75-2.5Hz), whereas resistance training produced no effect. In sham-operated rats, both types of training increased the vagal autonomic tonus, but resistance training reduced HF oscillations and BRS as well. In turn, both types of training had similar results in ovariectomized rats, except for HRV, as aerobic training promoted an increase in HF oscillations.