Reduced capacity of autonomic and baroreflex control associated with sleep pattern in spontaneously hypertensive rats with a nondipping profile

Levilactobacillus brevis SG031 modulates mood-related behaviors and attenuates stress-related sleep disturbance and autonomic dysfunction via gut microbiota modulation in Wistar-Kyoto rats

AIMS

The probiotic bacterium Levilactobacillus brevis (L. brevis) has been proposed as a potential solution to manage mood disorders and alleviate stress-related sleep disturbances. However, the underlying mechanisms of its effects have not been fully elucidated. The aim of this study was to explore the impact and potential mechanisms of L. brevis SG031 supplementation on anxiety/depression-like behaviors and stress-induced changes in sleep patterns and sleep-related autonomic function.

MAIN METHODS

Male Wistar-Kyoto rats were administered low, medium, or high doses of L. brevis SG031 or a vehicle for 4 weeks, followed by behavioral tests to evaluate anxiety and depression. After an additional 2 weeks of SG031 or vehicle administration, a cage-exchange paradigm was performed with 24-hour physiological signal measurements under different stress conditions. Fecal samples were collected to construct a 16S rRNA library and assess fecal short-chain fatty acids (SCFAs).

KEY FINDINGS

High-dose SG031 administration yielded reduced depression-like responses and enhanced social interaction in behavioral tests. It also exhibited a protective effect against stress-induced sleep disturbance characterized by decreased sleep time, increased awake time, and autonomic dysfunction during sleep. Fecal examination indicated that high-dose SG031 administration exerted beneficial effects on gut health by maintaining the gut microbial abundance, preserving stability of the microbial composition, and enriching the gut with SCFAs, which were associated with improvements in sleep and autonomic function.

SIGNIFICANCE

These findings collectively underscore the multifaceted potential of SG031 in addressing mental health and stress-related sleep challenges through the modulation of the gut microbiota.

Reduced slow-wave activity and autonomic dysfunction during sleep precede cognitive deficits in Alzheimer's disease transgenic mice

Occurrence of amyloid-β (Aβ) aggregation in brain begins before the clinical onset of Alzheimer's disease (AD), as preclinical AD. Studies have reported that sleep problems and autonomic dysfunction associate closely with AD. However, whether they, especially the interaction between sleep and autonomic function, play critical roles in preclinical AD are unclear. Therefore, we investigated how sleep patterns and autonomic regulation at different sleep-wake stages changed and whether they were related to cognitive performance in pathogenesis of AD mice. Polysomnographic recordings in freely-moving APP/PS1 and wild-type (WT) littermates were collected to study sleep patterns and autonomic function at 4 (early disease stage) and 8 months of age (advanced disease stage), cognitive tasks including novel object recognition and Morris water maze were performed, and Aβ levels in brain were measured. APP/PS1 mice at early stage of AD pathology with Aβ aggregation but without significant differences in cognitive performance had frequent sleep-wake transitions, lower sleep-related delta power percentage, lower overall autonomic activity, and lower parasympathetic activity mainly during sleep compared with WT mice. The same phenomenon was observed in advanced-stage APP/PS1 mice with significant cognitive deficits. In mice at both disease stages, sleep-related delta power percentage correlated positively with memory performance. At early stage, memory performance correlated positively with sympathetic activity during wakefulness; at advanced stage, memory performance correlated positively with parasympathetic activity during both wakefulness and sleep. In conclusion, sleep quality and distinction between wake- and sleep-related autonomic function may be biomarkers for early AD detection.

Sex differences and sex steroids influence on the presentation and severity of cardiovascular autonomic neuropathy of patients with type 1 diabetes

BACKGROUND

Sex differences characterize cardiovascular outcomes in patients with type 1 diabetes. Cardioautonomic neuropathy is a common complication of type 1 diabetes that associates increased morbi-mortality. Data regarding the interplay between sex and cardiovascular autonomic neuropathy are scarce and controversial in these patients. We aimed to address sex-related differences in the prevalence of seemingly asymptomatic cardioautonomic neuropathy in type 1 diabetes, and their associations with sex steroids.

METHODS

We conducted a cross-sectional study including 322 consecutively recruited patients with type 1 diabetes. Cardioautonomic neuropathy was diagnosed using Ewing's score and power spectral heart rate data. We assessed sex hormones by liquid chromatography/tandem mass spectrometry.

RESULTS

When considering all subjects as a whole, asymptomatic cardioautonomic neuropathy prevalence was not significantly different between women and men. When age was taken into account, the prevalence of cardioautonomic neuropathy was similar among young men and those > 50 years. However, in women > 50 years, the prevalence of cardioautonomic neuropathy doubled that of young women [45.8% (32.6; 59.7) vs. 20.4% (13.7; 29.2), respectively]. The OR of having cardioautonomic neuropathy was 3.3 higher in women > 50 years than in their younger counterparts. Furthermore, women presented more severe cardioautonomic neuropathy than men. These differences were even more marked when women were classified according their menopausal status instead of age. Peri- and menopausal women had an OR 3.5 (1.7; 7.2) of having CAN compared with their reproductive-aged counterparts [CAN prevalence: 51% (37; 65) vs. 23% (16; 32), respectively]. A binary logistic regression model (R²: 0.161; P = 0.001) displayed age > 50 years as a significant determinant of cardioautonomic neuropathy only in women. Androgens were positively associated with heart rate variability in men, and negatively in women. Accordingly, cardioautonomic neuropathy was associated with increased testosterone/estradiol ratio in women but to decreased testosterone concentrations in men.

CONCLUSIONS

Menopause in women with type 1 diabetes is accompanied by an increase in the prevalence of asymptomatic cardioautonomic neuropathy. This age-related excess risk of cardioautonomic neuropathy is not observed in men. Men and women with type 1 diabetes have opposite associations between circulating androgens and indexes of cardioautonomic function. Trial registration ClinicalTrials.gov Identifier: NCT04950634.

Roles of sleep-related cardiovascular autonomic functions in voluntary-exercise-induced alleviation of hypertension in spontaneously hypertensive rats

Autonomic dysfunction and sleep problems are closely associated with hypertension and predict cardiovascular morbidity and mortality. Animal studies and clinical observations have identified exercise as an important factor in preventing and treating hypertension. However, the roles of autonomic function and sleep in the antihypertensive mechanisms of exercise are still not fully understood. This study aimed to clarify the physiological mechanisms associated with autonomic function and sleep through wheel exercise. Male spontaneously hypertensive rats (SHRs) were grouped into a wheel-exercised group and a sedentary group (controls). Electroencephalogram, electromyogram, electrocardiogram, and mean arterial pressure (MAP) were recorded simultaneously for 24 h once a week over 11 weeks. Wheel exercise was initiated in the SHRs at 12 weeks old and continued for another eight weeks. A significant suppression in the age-related elevation of MAP was noted in the SHRs undergoing wheel exercise. The reduction in MAP was correlated with increased parasympathetic activity and baroreflex sensitivity and decreased sympathetic activity, mainly during quiet sleep. Exercise increased the paradoxical sleep time and theta power (associated with cognitive function) but not the delta power (an indicator of sleep depth) or the attenuation of circadian rhythm flattening (characterized by increased wakefulness and less sleep during the light period and the opposite during the dark period). Furthermore, the exercise-induced changes in autonomic function occurred before those in sleep patterns, which were dependent on each other. In conclusion, wheel exercise can modulate sleep-related cardiovascular dysfunction and the flattening of circadian rhythm, preventing the progression of hypertension, which reduces the incidence of cardiovascular diseases.

Biomaterial-induced conversion of quiescent cardiomyocytes into pacemaker cells in rats

Pacemaker cells can be differentiated from stem cells or transdifferentiated from quiescent mature cardiac cells via genetic manipulation. Here we show that the exposure of rat quiescent ventricular cardiomyocytes to a silk-fibroin hydrogel activates the direct conversion of the quiescent cardiomyocytes to pacemaker cardiomyocytes by inducing the ectopic expression of the vascular endothelial cell-adhesion glycoprotein cadherin. The silk-fibroin-induced pacemaker cells exhibited functional and morphological features of genuine sinoatrial-node cardiomyocytes in vitro, and pacemaker cells generated via the injection of silk fibroin in the left ventricles of rats functioned as a surrogate in situ sinoatrial node. Biomaterials with suitable surface structure, mechanics and biochemistry could facilitate the scalable production of biological pacemakers for human use.

Early changes of immunoreactivity to orexin in hypothalamus and to RFamide peptides in brainstem during the development of hypertension

Baroreflex sensitivity (BRS) is an important function of the nervous system and essential for maintaining blood pressure levels in the physiological range. In hypertension, BRS is decreased both in man and animals. Although increased sympathetic activity is thought to be the main cause of decreased BRS, hence the development of hypertension, the BRS is regulated by both sympathetic (SNS) and parasympathetic (PNS) nervous system. Here, we analyzed neuropeptide changes in the lateral hypothalamus (LH), which favours the SNS activity, as well as in PNS nuclei in the brainstem of spontaneously hypertensive rats (SHR) and their normotensive controls (Wistar Kyoto rats- WKY). The analyses revealed that in the WKY rats the hypothalamic orexin system, known for its role in sympathetic activation, showed a substantial decrease when animals age. At the same time, however, such a decrease was not observed when hypertension developed in the SHR. In contrast, Neuropeptide FF (NPFF) and Prolactin Releasing Peptide (PrRP) expression in the PNS associated Nucleus Tractus Solitarius (NTS) and Dorsal Motor Nucleus of the Vagus (DMV) diminished substantially, not only after the establishment of hypertension but also before its onset. Therefore, the current results indicate early changes in areas of the central nervous system involved in SNS and PNS control of blood pressure and associated with the development of hypertension.

A common neuronal mechanism of hypertension and sleep disturbances in spontaneously hypertensive rats: Role of orexinergic neurons

Epidemiologic studies have shown that sleep disorders are associated with the development of hypertension. The present study investigated dynamic changes in sleep patterns during the development of hypertension across the lifespan in spontaneously hypertensive rats (SHRs) and the neural mechanism that underlies these comorbidities, with a focus on the orexinergic system. Blood pressure in rats was measured using a noninvasive blood pressure tail cuff. Sleep was monitored by electroencephalographic and electromyographic recordings. Immunohistochemistry was used to detect the density and activity of orexinergic neurons in the perifornical nucleus. Hcrt2-SAP (400 or 800 ng) was microinjected in the lateral hypothalamus to lesion orexinergic neurons. Compared with Wistar-Kyoto rats, SHRs exhibited various patterns of sleep disturbances. In SHRs, dynamic changes in hypersomnia in the rats' active phase was not synchronized with the development of hypertension, but hyperarousal in the inactive phase and difficulties in falling asleep were observed concurrently with the development of hypertension. Furthermore, the density and activity of orexinergic neurons in the perifornical nucleus were significantly higher in SHRs than in age-matched Wistar-Kyoto rats. The reduction of orexinergic neurons in the lateral hypothalamus partially ameliorated the development of hypertension and prevented difficulties in falling asleep in SHRs. These results indicate that although the correlation between sleep disturbances and hypertension is very complex, common mechanisms may underlie these comorbidities in SHRs. Overactivity of the orexin system may be one such common mechanism.

Exercise Prevents Hypertension and Disrupts the Correlation Between Vascular Sympathetic Activity and Age-Related Increase in Blood Pressure in SHRs

BACKGROUND

Hypertension usually accompanies the elevated sympathetic activity and sleep interruption. Few researches explored the dynamic changes and possible correlations in cardiovascular functions and sleep patterns during the development of hypertension. In contrast, exercise training provides several benefits on cardiovascular and sleep function in hypertensive subjects. However, controlling various factors during a long period of exercise training is difficult in hypertensive subjects, an animal model may be essential. This study aimed to explore dynamic changes in cardiovascular functions and sleep patterns during the development period of hypertension (10-20 weeks old) in spontaneously hypertensive rats (SHRs) and effects of exercise intervention.

METHODS

We used the treadmill exercise model for 8 weeks and started when SHRs were 12 weeks old. Electroencephalogram, electromyogram, electrocardiogram, and blood pressure (BP) were recorded simultaneously for 24 hours once a week over 11 weeks.

RESULTS

Untrained SHRs revealed the age-related increments in BP, and the significant increasing slopes of differences on BP and vascular sympathetic activity were observed during the development period of hypertension. Compared with untrained rats, age-related increases in BP and vascular sympathetic activity were significantly suppressed in trained SHRs. Nevertheless, trained SHRs showed more quiet sleep time at partial weeks. The positive correlation between the differences from 10 weeks of vascular sympathetic activity and BP was disappeared in trained SHRs.

CONCLUSIONS

There existed the significant correlation between the dynamic changes of vascular sympathetic activity and age-related elevation of BP during the development period of hypertension; however, exercise prevented hypertension and disrupted this correlation.

Relationship between arterial stiffness and circadian pattern of blood pressure

Arterial stiffness is a risk factor for cardiovascular morbidity and mortality. The relationship between the arterial stiffness and the circadian pattern of blood pressure (BP) has been controversial. The objective of the present study was to investigate the relationship between arterial stiffness by pulse wave analysis (PWA) and variables of 24-hour ambulatory BP monitoring (ABPM) in patients with high normal BP or hypertension (HTN).Five hundred forty-eight patients (304 males, 48 ± 12-year-old) with high normal BP or HTN were enrolled. BP was measured at the outpatient clinic and 24-hour ABPM was performed. Using radial applanation tonometry, PWA was performed for evaluation of systemic arterial stiffness. Patients were classified into four groups according to the dipping patterns: a nocturnal dipping group, an isolated systolic non-dipping group, an isolated diastolic non-dipping group and a both systolic and diastolic non-dipping group. For adjustment of age, population was divided to 2 groups: old group ≥55 year-old (n = 158, 75 males), young group <55 year-old (n = 390, 229 males).According to the dipping patterns, augmentation pressure (AP), augmentation index (AI) and heart rate (75 bpm) adjusted AI (AI@HR75) showed statistically significant difference (P = .011, .009, and .018, respectively). Multivariate analysis showed that isolated diastolic non-dipping was correlated with arterial stiffness expressed as AI and AI@HR 75, only in young group (β-coefficient = 12.6, P = .04 and β-coefficient = 7.503, P = .028, respectively).Arterial stiffness might be closely related with the pattern of non-dipping in young patients with HTN and high normal BP.

OSA and Cardiovascular Risk in Pediatrics

OSA occurs in approximately 1% to 5% of children in the United States. Long-term cardiovascular risks associated with OSA in the adult population are well documented. Although changes in BP regulation occur in children with OSA, the pathways leading to chronic cardiovascular risks of OSA in children are less clear. Risk factors associated with cardiovascular disease in adult populations could carry the same future risk for children. It is imperative to determine whether known mechanisms of cardiovascular diseases in adults are like those that lead to pediatric disease. Early pathophysiologic changes may lead to a lifetime burden of cardiovascular disease and early mortality. With this perspective in mind, our review discusses pathways leading to cardiovascular pathology in children with OSA and provides a comprehensive overview of recent research findings related to cardiovascular sequelae in the pediatric population.

Circadian clock-mediated regulation of blood pressure

Most bodily functions vary over the course of a 24h day. Circadian rhythms in body temperature, sleep-wake cycles, metabolism, and blood pressure (BP) are just a few examples. These circadian rhythms are controlled by the central clock in the suprachiasmatic nucleus (SCN) of the hypothalamus and peripheral clocks located throughout the body. Light and food cues entrain these clocks to the time of day and this synchronicity contributes to the regulation of a variety of physiological processes with effects on overall health. The kidney, brain, nervous system, vasculature, and heart have been identified through the use of mouse models and clinical trials as peripheral clock regulators of BP. The dysregulation of this circadian pattern of BP, with or without hypertension, is associated with increased risk for cardiovascular disease. The mechanism of this dysregulation is unknown and is a growing area of research. In this review, we highlight research of human and mouse circadian models that has provided insight into the roles of these molecular clocks and their effects on physiological functions. Additional tissue-specific studies of the molecular clock mechanism are needed, as well as clinical studies including more diverse populations (different races, female patients, etc.), which will be critical to fully understand the mechanism of circadian regulation of BP. Understanding how these molecular clocks regulate the circadian rhythm of BP is critical in the treatment of circadian BP dysregulation and hypertension.