Progressive cardiovascular autonomic dysfunction in rats with evolving metabolic syndrome

Noninvasive Biomarkers for Cardiovascular Dysfunction Programmed in Male Offspring of Adverse Pregnancy

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Very low frequency component of heart rate variability as a marker for therapeutic efficacy in patients with obstructive sleep apnea: Preliminary study

BACKGROUND

Although positive airway pressure (PAP) therapy is effective for treating obstructive sleep apnea (OSA), some patients with severe OSA are intolerable to this treatment, which may lead to an increase in the mortality and morbidity of cardiovascular diseases. We investigated the relationship between heart rate variability (HRV) and sleep parameters during natural sleep and treatment of patients with OSA.

MATERIALS AND METHODS

This was the cross-sectional observation study. Patients were 17 males with severe OSA who were unable to accept continuous PAP. Standard polysomnography was performed for two consecutive nights, i.e., during natural sleep and following night with bilevel PAP (BiPAP) treatment. Time-dependent responses of the amplitudes of low frequency (LF), very low frequency (VLF), and high frequency components of HRV were assessed with the technique of complex demodulation.

RESULTS

Apnea-hypopnea index, oxygen desaturation time, and percentage of stage 1 sleep were significantly reduced, whereas the percentages of rapid eye movement and stages 3 + 4 sleep were increased, by BiPAP treatment. Therapy also reduced the amplitudes of VLF and LF components of HRV. Difference in amplitudes of VLF during natural sleep and treatment with BiPAP was significantly correlated with difference in percentages of stage 1 and stages 3 + 4 sleep.

CONCLUSION

Therapy-induced amelioration of OSA and sleep quality was accompanied by decrease in the amplitudes of VLF components of HRV. The VLF component may thus reflect physiological changes in both autonomic activity and sleep structure and serve as an objective marker for therapeutic efficacy in patients with severe OSA.

Translating carotid body function into clinical medicine

The carotid body (CB) is considered the main O₂ chemoreceptor, which contributes to cardiorespiratory homeostasis and ventilatory acclimatization. In clinical medicine, the most common pathologies associated with the CB are tumours. However, a growing body of evidence supports the novel idea that an enhanced CB chemosensory discharge contributes to the autonomic dysfunction and pathological consequences in obstructive sleep apnoea (OSA), hypertension, systolic heart failure (HF) and cardiometabolic diseases. Heightened CB chemosensory reactivity elicited by oxidative stress has been involved in sympathetic hyperactivity, cardiorespiratory instability, hypertension and insulin resistance. CB ablation, which reduces sympathetic hyperactivity, decreases hypertension in animal models of OSA and hypertension, eliminates breathing instability and improves animal survival in HF, and restores insulin tolerance in cardiometabolic models. Thus, data obtained from preclinical studies highlight the importance of the CB in the progression of sympathetic-related diseases, supporting the idea that appeasing the enhanced CB chemosensory drive may be useful in improving cardiovascular, respiratory and endocrine alterations. Accordingly, CB ablation has been proposed and used as a treatment for moderating resistant hypertension and HF-induced sympathetic hyperactivity in humans. First-in-human studies have shown that CB ablation reduces sympathetic overactivity, transiently reduces severe hypertension and improves quality of life in HF patients. Thus, CB ablation would be a useful therapy to reverse sympathetic overactivation in HF and severe hypertension, but caution is required before it is widely used due to the crucial physiological function played by the CB. Further studies in preclinical models are required to assess side-effects of CB ablation.

Kefir reduces insulin resistance and inflammatory cytokine expression in an animal model of metabolic syndrome

There is growing evidence that kefir can be a promising tool in decreasing the risk of many diseases, including metabolic syndrome (MetS). The aim of the present study was to evaluate the effect of kefir supplementation in the diet of Spontaneously Hypertensive Rats (SHR) in which MetS was induced with monosodium glutamate (MSG), and to determine its effect on metabolic parameters, inflammatory and oxidation marker expression and glycemic index control. Thirty animals were used in this experiment. For the induction of MetS, twenty two-day-old male SHR received five consecutive intradermal injections of MSG. For the Negative Control, ten newborn male SHR received intradermal injections of saline solution (0.9% saline solution). After weaning, animals received standard diet and water ad libitum until reaching 3 months old, for the development of MetS. They were then divided into three groups (n = 10): negative control (NC, 1 mL saline solution per day), positive control (PC, 1 mL saline solution per day) and the Kefir group (1 mL kefir per day). Feeding was carried out by gavage for 10 weeks and the animals received standard food and water ad libitum. Obesity, insulin resistance, pro- and anti-inflammatory markers, and the histology of pancreatic and adipose tissues were among the main variables evaluated. Compared to the PC group, kefir supplementation reduced plasma triglycerides, liver lipids, liver triglycerides, insulin resistance, fasting glucose, fasting insulin, thoracic circumference, abdominal circumference, products of lipid oxidation, pro-inflammatory cytokine expression (IL-1β) and increased anti-inflammatory cytokine expression (IL-10). The present findings indicate that kefir has the potential to benefit the management of MetS.

Beneficial Effect of Moderate Exercise in Kidney of Rat after Chronic Consumption of Cola Drinks

Aim

The purpose of this study was to investigate the effect of moderate intensity exercise on kidney in an animal model of high consumption of cola soft drinks.

Methods

Forty-eight Wistar Kyoto rats (age: 16 weeks; weight: 350–400 g) were assigned to the following groups: WR (water runners) drank water and submitted to aerobic exercise; CR (cola runners) drank cola and submitted to aerobic exercise; WS (water sedentary) and CS (cola sedentary), not exercised groups. The aerobic exercise was performed for 5 days per week throughout the study (24 weeks) and the exercise intensity was gradually increased during the first 8 weeks until it reached 20 meters / minute for 30 minutes. Body weight, lipid profile, glycemia, plasma creatinine levels, atherogenic index of plasma (AIP) and systolic blood pressure (SBP) were determined. After 6 months all rats were sacrificed. A kidney histopathological score was obtained using a semiquantitative scale. Glomerular size and glomerulosclerosis were estimated by point-counting. The oxidative stress and pro-inflammatory status were explored by immunohistochemistry. A one way analysis of variance (ANOVA) with Tukey-Kramer post-hoc test or the Kruskal-Wallis test with Dunn’s post-hoc test was used for statistics. A value of p < 0.05 was considered significant.

Results

At 6 months, an increased consumption of cola soft drink was shown in CS and CR compared with water consumers (p<0.0001). Chronic cola consumption was associated with increased plasma triglycerides, AIP, heart rate, histopathological score, glomerulosclerosis, oxidative stress and pro-inflammatory status. On the other hand, moderate exercise prevented these findings. No difference was observed in the body weight, SBP, glycemia, cholesterol and plasma creatinine levels across experimental groups.

Conclusions

This study warns about the consequences of chronic consumption of cola drinks on lipid metabolism, especially regarding renal health. Additionally, these findings emphasize the protective role of exercise training on renal damage.

Carotid body chemoreceptors, sympathetic neural activation, and cardiometabolic disease

The carotid body (CB) is the main peripheral chemoreceptor that senses the arterial PO₂, PCO₂ and pH. In response to hypoxemia, hypercapnia and acidosis, carotid chemosensory discharge elicits reflex respiratory, autonomic and cardiovascular adjustments. The classical construct considers the CB as the main peripheral oxygen sensor, triggering reflex physiological responses to acute hypoxemia and facilitating the ventilatory acclimation to chronic hypoxemia at high altitude. However, a growing body of experimental evidence supports the novel concept that an abnormally enhanced CB chemosensory input to the brainstem contributes to overactivation of the sympathetic nervous system, and consequent pathology. Indeed, the CB has been implicated in several diseases associated with increases in central sympathetic outflow. These include hypertension, heart failure, sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome. Indeed, ablation of the CB has been proposed for the treatment of severe and resistant hypertension in humans. In this review, we will analyze and discuss new evidence supporting an important role for the CB chemoreceptor in the progression of autonomic and cardiorespiratory alterations induced by heart failure, obstructive sleep apnea, chronic obstructive pulmonary disease and metabolic syndrome.

Sympathovagal imbalance contributes to prehypertension status and cardiovascular risks attributed by insulin resistance, inflammation, dyslipidemia and oxidative stress in first degree relatives of type 2 diabetics

BACKGROUND

Though cardiovascular (CV) risks are reported in first-degree relatives (FDR) of type 2 diabetics, the pathophysiological mechanisms contributing to these risks are not known. We investigated the association of sympathovagal imbalance (SVI) with CV risks in these subjects.

SUBJECTS AND METHODS

Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate-pressure product (RPP), spectral indices of heart rate variability (HRV), autonomic function tests, insulin resistance (HOMA-IR), lipid profile, inflammatory markers, oxidative stress (OS) marker, rennin, thyroid profile and serum electrolytes were measured and analyzed in subjects of study group (FDR of type 2 diabetics, n = 72) and control group (subjects with no family history of diabetes, n = 104).

RESULTS

BMI, BP, BHR, HOMA-IR, lipid profile, inflammatory and OS markers, renin, LF-HF (ratio of low-frequency to high-frequency power of HRV, a sensitive marker of SVI) were significantly increased (p<0.0001) in study group compared to the control group. SVI in study group was due to concomitant sympathetic activation and vagal inhibition. There was significant correlation and independent contribution of markers of insulin resistance, dyslipidemia, inflammation and OS to LF-HF ratio. Multiple-regression analysis demonstrated an independent contribution of LF-HF ratio to prehypertension status (standardized beta 0.415, p<0.001) and bivariate logistic-regression showed significant prediction (OR 2.40, CI 1.128-5.326, p = 0.002) of LF-HF ratio of HRV to increased RPP, the marker of CV risk, in study group.

CONCLUSION

SVI in FDR of type 2 diabetics occurs due to sympathetic activation and vagal withdrawal. The SVI contributes to prehypertension status and CV risks caused by insulin resistance, dyslipidemia, inflammation and oxidative stress in FDR of type 2 diabetics.

Capsaicin-induced metabolic and cardiovascular autonomic improvement in an animal model of the metabolic syndrome

The metabolic syndrome (MetS) is associated with an increased risk of cardiac mortality, as it is characterised by the clustering of multiple cardiovascular risk factors. Studies have shown that capsaicin (red pepper) may be useful as a nutraceutical, ameliorating metabolic profile and cardiovascular function. The aim of the present study was to investigate the cardiovascular and metabolic effects of orally administered capsaicin in rats with the MetS. Neonate spontaneously hypertensive rats were injected with monosodium glutamate and subjected to one of the following three treatments by oral administration for 14 d, between 27 and 30 weeks: low-dose capsaicin (CAP05,n18, synthetic capsaicin powder diluted in a vehicle (10 % ethyl alcohol) plus 0·5 mg/kg body weight (BW) of capsaicin); high-dose capsaicin (CAP1,n19, synthetic capsaicin powder diluted in a vehicle (10 % ethyl alcohol) plus 1 mg/kg BW of capsaicin); control (C,n18, vehicle). Lee's index, lipid/metabolic profile, and cardiovascular parameters with the rats being conscious, including arterial pressure (AP) and heart rate (HR) variability, as well as aortic wall thickness (haematoxylin and eosin staining) and CD68 (cluster of differentiation 68) antibody levels (monocyte/macrophage immunostaining) were evaluated. Weight, Lee's index, and lipid and metabolic parameters, as well as AP and HR and aortic wall thickness, were similar between the groups. Capsaicin determined HR variability improvement (16·0 (sem9·0), 31·0 (sem28·2) and 31·3 (sem19·0) ms2for the C, CAP05 and CAP1 groups, respectively,P= 0·003), increased vascular sympathetic drive (low-frequency component of systolic AP variability: 3·3 (sem2·8), 8·2 (sem7·7) and 12·1 (sem8·8) mmHg2for the C, CAP05 and CAP1 groups, respectively,P< 0·001) and increased α-index (spontaneous baroreflex sensitivity). The present data show that capsaicin did not improve lipid and glucose abnormalities in rats with the MetS. However, beneficial cardiovascular effects were observed with this nutraceutical.