Renal denervation improves chronic intermittent hypoxia induced hypertension and cardiac fibrosis and balances gut microbiota

Possible Role of Gut Microbiota Alterations in Myocardial Fibrosis and Burden of Heart Failure in Hypertensive Heart Disease

Epidemiological studies have revealed that hypertensive heart disease is a major risk factor for heart failure, and its heart failure burden is growing rapidly. The need to act in the face of this threat requires first an understanding of the multifactorial origin of hypertensive heart disease and second an exploration of new mechanistic pathways involved in myocardial alterations critically involved in cardiac dysfunction and failure (eg, myocardial interstitial fibrosis). Increasing evidence shows that alterations of gut microbiota composition and function (ie, dysbiosis) leading to changes in microbiota-derived metabolites and impairment of the gut barrier and immune functions may be involved in blood pressure elevation and hypertensive organ damage. In this review, we highlight recent advances in the potential contribution of gut microbiota alterations to myocardial interstitial fibrosis in hypertensive heart disease through blood pressure-dependent and blood pressure-independent mechanisms. Achievements in this field should open a new path for more comprehensive treatment of myocardial interstitial fibrosis in hypertensive heart disease and, thus, for the prevention of heart failure.

PPARγ Agonist Rosiglitazone and Antagonist GW9662: Antihypertensive Effects on Chronic Intermittent Hypoxia-Induced Hypertension in Rats

The increased incidence of hypertension associated with obstructive sleep apnea (OSA) presents significant physical, psychological, and economic challenges. Peroxisome proliferator-activated receptor gamma (PPARγ) plays a role in both OSA and hypertension, yet the therapeutic potential of PPARγ agonists and antagonists for OSA-related hypertension remains unexplored. Therefore, we constructed a chronic intermittent hypoxia (CIH)-induced hypertension rat model that mimics the pathogenesis of OSA-related hypertension in humans. The model involved administering PPARγ agonist rosiglitazone (RSG), PPARγ antagonist GW9662, or normal saline, followed by regular monitoring of blood pressure and thoracic aorta analysis using staining and electron microscopy. Intriguingly, our results indicated that both RSG and GW9662 appeared to potently counteract CIH-induced hypertension. In silico study suggested that GW9662's antihypertensive effect might mediated through angiotensin II receptor type 1 (AGTR1). Our findings provide insights into the mechanisms of OSA-related hypertension and propose novel therapeutic targets.

Chronic intermittent hypoxia-induced cardiovascular and renal dysfunction: from adaptation to maladaptation

Chronic intermittent hypoxia (CIH) is the dominant pathological feature of human obstructive sleep apnoea (OSA), which is highly prevalent and associated with cardiovascular and renal diseases. CIH causes hypertension, centred on sympathetic nervous overactivity, which persists following removal of the CIH stimulus. Molecular mechanisms contributing to CIH-induced hypertension have been carefully delineated. However, there is a dearth of knowledge on the efficacy of interventions to ameliorate high blood pressure in established disease. CIH causes endothelial dysfunction, aberrant structural remodelling of vessels and accelerates atherosclerotic processes. Pro-inflammatory and pro-oxidant pathways converge on disrupted nitric oxide signalling driving vascular dysfunction. In addition, CIH has adverse effects on the myocardium, manifesting atrial fibrillation, and cardiac remodelling progressing to contractile dysfunction. Sympatho-vagal imbalance, oxidative stress, inflammation, dysregulated HIF-1α transcriptional responses and resultant pro-apoptotic ER stress, calcium dysregulation, and mitochondrial dysfunction conspire to drive myocardial injury and failure. CIH elaborates direct and indirect effects in the kidney that initially contribute to the development of hypertension and later to chronic kidney disease. CIH-induced morphological damage of the kidney is dependent on TLR4/NF-κB/NLRP3/caspase-1 inflammasome activation and associated pyroptosis. Emerging potential therapies related to the gut-kidney axis and blockade of aryl hydrocarbon receptors (AhR) are promising. Cardiorenal outcomes in response to intermittent hypoxia present along a continuum from adaptation to maladaptation and are dependent on the intensity and duration of exposure to intermittent hypoxia. This heterogeneity of OSA is relevant to therapeutic treatment options and we argue the need for better stratification of OSA phenotypes.

Sacubitril/valsartan mitigated intermittent hypoxia related intestinal microbiota alteration and aortic injury

OBJECTIVE

To investigate the influence of sacubitril valsartan sodium (SVS) on chronic intermittent hypoxia (IH) related gut microbiome composition alteration and aortic injury.

METHODS

Experiments were performed using SD rats, which were divided into three groups: control, IH, and SVS group. O2 concentration was decreased to 7-8% at nadir approximately every 3 min in IH group (8 h per day for 6 weeks) or was left unchanged in control group. Rats in SVS group were orally gavaged with SVS at the dosage of 30 mg/kg/day (2 weeks after chronic IH exposure). At week 6, fecal and aortic samples were harvested for 16 s rDNA analysis and histological analysis, respectively.

RESULTS

Principal coordinate analysis and non-metric multidimensional scaling analysis indicated that the bacterial community was altered by chronic IH exposure, while SVS treatment restored the intestinal microbial communities. Further analysis showed that IH decreased the relative abundance of Lactobacillus and Prevotella, while rats treated with SVS was enriched with Firmicutes, Bacilli, Prevotellaceae, and Lactobacillus, which was similar to control rats. Immunohistochemical staining showed that SVS prevented the upregulation of transforming growth factor-β1 and tumor necrosis factor-alpha in the aorta.

CONCLUSION

SVS prevented aortic adverse response to IH, possibly through modulating intestinal microbiota.

Effect of renal denervation on cardiac remodelling and function in rats with chronic intermittent hypoxia

Chronic intermittent hypoxia (CIH) mimicking obstructive sleep apnea elicits divergent outcomes in the cardiovascular systems. The effect of renal denervation (RDN) on the heart during CIH remains unclear. We aimed to explore the effect of RDN on cardiac remodelling in rats exposed to CIH and to discuss the underlying mechanisms. Adult Sprague Dawley rats were divided into four groups: control, control+RDN, CIH (CIH exposure for 6 weeks, nadir of 5%-7% to peak of 21% O2, 20 cycles/h, 8 h/day) and CIH+ RDN group. Echocardiography, cardiac fibrosis, left ventricle (LV) expressions of nuclear factor-E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway and inflammatory factors were tested at the end of the study. Cardiac structural remodelling and dysfunction were induced by CIH and attenuated by RDN. Myocardial fibrosis was more severe in the CIH group than in the control group and improved in the CIH + RDN group. Sympathetic activity reflected by tyrosine hydroxylase (TH) expression and noradrenaline were significantly elevated after CIH but blunted by RDN. CIH downregulated LV protein expressions of Nrf2 and HO-1, which was activated by RDN. The downstream of Nrf2/HO-1, such as NQO1 and SOD expression, elevated following RDN. RDN also decreased the mRNA expression of IL-1β and IL-6. Notably, control+RDN did not affect cardiac remodelling and Nrf2/HO-1 compared with the control. Taken together, we found that RDN exerted cardio-protective effects in a rat model of CIH involving Nrf2/HO-1 pathway and inflammation.

Impact of Gut Microbiota on the Peripheral Nervous System in Physiological, Regenerative and Pathological Conditions

It has been widely demonstrated that the gut microbiota is responsible for essential functions in human health and that its perturbation is implicated in the development and progression of a growing list of diseases. The number of studies evaluating how the gut microbiota interacts with and influences other organs and systems in the body and vice versa is constantly increasing and several 'gut-organ axes' have already been defined. Recently, the view on the link between the gut microbiota (GM) and the peripheral nervous system (PNS) has become broader by exceeding the fact that the PNS can serve as a systemic carrier of GM-derived metabolites and products to other organs. The PNS as the communication network between the central nervous system and the periphery of the body and internal organs can rather be affected itself by GM perturbation. In this review, we summarize the current knowledge about the impact of gut microbiota on the PNS, with regard to its somatic and autonomic divisions, in physiological, regenerative and pathological conditions.

Is the Gut Microbiome Implicated in the Excess Risk of Hypertension Associated with Obstructive Sleep Apnea? A Contemporary Review

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder and an established risk factor for cardiovascular diseases, including hypertension. The pathogenesis of elevated blood pressure (BP) in OSA is multifactorial, including sympathetic overdrive, vascular aberrations, oxidative stress, inflammation, and metabolic dysregulation. Among the mechanisms potentially involved in OSA-induced hypertension, the role of the gut microbiome is gaining increasing attention. Perturbations in the diversity, composition, and function of the gut microbiota have been causally linked to numerous disorders, and robust evidence has identified gut dysbiosis as a determinant of BP elevation in various populations. In this brief review, we summarize the current body of literature on the implications of altered gut microbiota for hypertension risk in OSA. Data from both preclinical models of OSA and patient populations are presented, and potential mechanistic pathways are highlighted, along with therapeutic considerations. Available evidence suggests that gut dysbiosis may promote the development of hypertension in OSA and may thus be a target for interventions aimed at attenuating the adverse consequences of OSA in relation to cardiovascular risk.

Gut microbiota in hypertensive patients with versus without obstructive sleep apnea

We investigated the alteration of gut microbiota and the associated metabolic risks in hypertensive patients with obstructive sleep apnea (OSA) comorbidity. Fecal and blood samples were collected from 52 hypertensive patients, who were divided into three groups: A (controls, apnea-hypopnea index[AHI] < 5, n = 15), B (mild OSA, 5 < AHI < 20, n = 17), and C (moderate-to-severe OSA, AHI > 20, n = 20). The composition of the gut microbiota was studied through 16s RNA sequencing of variable regions 3-4. Analysis of the results revealed that group C had a significant higher concentration of total cholesterol, low-density lipoprotein, and IL-1β compared with group A. The Shannon index showed that bacterial biodiversity was lower in OSA patients. At the phylum level, the ratio of Firmicutes to Bacteroidetes (F/B) was significantly higher in group C than in groups A and B. At the genus level, the relative abundance of short-chain fatty acids (SCFA)-producing bacteria (e.g., Bacteroides and Prevotella) was lower while the number of inflammation-related bacteria (e.g., Lactobacillus) was increased in patients with OSA. We found that the IL-1β level was negatively correlated with Bacteroidetes. The area under the receiver operating characteristic curve was .672 for F/B ratio in determining hypertensive patients with OSA. In patients with hypertension, OSA was associated with worse gut dysbiosis, as evidenced by decreased levels of short-chain fatty acids-producing bacteria and increased number of inflammation-related bacteria. The differences in gut microbiota discriminate hypertensive patients with OSA from those without and may result in an enhanced inflammatory response and increase the risk of metabolic diseases.

Qige Huxin Formula Attenuates Isoprenaline-Induced Cardiac Fibrosis in Mice via Modulating Gut Microbiota and Protecting Intestinal Integrity

Background

The composition and metabolic activities of gut microbiota are strongly interconnected with cardiac fibrosis (CF) and heart failure (HF). Qige Huxin formula (QHF), a traditional Chinese medicine (TCM) formulation originating from a classical Fangji Huangqi decoction, has been widely used to clinically treat HF for decades. However, it is still unclear whether QHF alleviates CF by modulating gut microbiota and intestinal integrity.

Purpose

This study aimed to investigate the cardioprotective effects of QHF in isoprenaline-induced CF through modulating gut microbiota and intestinal integrity.

Methods

Fifty mice were randomly divided into five groups after one week of acclimatization feeding: control group, model group, 2.56 g/kg/d group (low-dose QHF), 5.12 g/kg/d group (high-dose QHF), and meto group (15 mg/kg/d). The CF model was established by subcutaneously injecting the mice with isoprenaline (10 mg/kg/d for 14 days), followed by QHF treatment. The heart volume, cardiac weight index (CWI), serum myocardial enzymes, serum inflammatory cytokines, serum lipopolysaccharide, histopathology of the heart and colon tissues, ZO-1, and occludin of colon tissues were then measured. Fecal samples from mice were analyzed using 16S rRNA sequencing.

Results

QHF treatment significantly reduced heart volume, CWI, and serum CK and CK-MB levels, attenuated cardiac histopathological alterations, and alleviated CF. QHF treatment also downregulated TNF-α, IL-1β, and IL-6 in serum. Moreover, QHF treatment decreased the serum level of lipopolysaccharide and maintained intestinal integrity by upregulating ZO-1 and occludin. The 16S rRNA microbiota analysis revealed that QHF treatment increased the relative abundance of Marvinbryantia and Phascolarctobacterium.

Conclusions

QHF treatment exerts cardioprotective effects through modulating gut microbiota, protecting intestinal integrity, and alleviating inflammation. This study shows that gut microbiota may enhance heart-gut interaction.

The Effect of Renal Denervation on Cardiac Diastolic Function in Patients with Hypertension and Paroxysmal Atrial Fibrillation

Objective

Renal artery denervation (RDN) can treat hypertension and paroxysmal atrial fibrillation (PAF). Hypertension and PAF can affect cardiac diastolic function. The study aimed to evaluate the effect of RDN on cardiac diastolic function in patients with refractory hypertension and PAF.

Methods

190 consecutive patients with hypertension and PAF were recruited. The levels of NT-proBNP and metrics of echocardiography were measured before and after RDN in patients with refractory hypertension and PAF. The 190 patients were divided into the decreasing HR and nondecreasing HR group, the decreasing MAP and nondecreasing MAP group, the HFPEF group, and the normal diastolic function group, respectively.

Results

Before RDN, the indices about cardiac diastolic function were out of the normal range. After RDN, the diastolic function improved in the indices of NT-proBNP, E/e′, e′. The diastolic function about the indices of NT-proBNP, E/e′, e′ was improved in the decreasing HR group, the decreasing mean arterial pressure (MAP) group, and the HFPEF group, correspondingly compared to the nondecreasing HR group, the non-decreasing MAP group, and the preoperative normal diastolic function group. In the multivariate analysis, the MAP and HR were the only two indicators significantly associated with the improvement of diastolic function.

Conclusion

RDN could improve the diastolic function in patients with refractory hypertension and PAF. Patients with HFPEF could receive benefits through RDN. It was speculated that RDN improved the diastolic function mainly through decreasing HR and MAP.

Hospitalization, mechanical ventilation, and case-fatality outcomes in US veterans with COVID-19 disease between years 2020-2021

PURPOSE

Although veterans represent a significant proportion (7%) of the USA population, the COVID-19 disease impact within this group has been underreported. To bridge this gap, this study was undertaken.

METHOD

A total of 419,559 veterans, who tested positive for COVID-19 disease in the Veterans Affairs hospital system from March 1st, 2020 to December 31st, 2021 with 60-days follow-up, was included in this retrospective review. Primary outcome measures included age-adjusted incidences and relative incidences of COVID-19 hospitalization, mechanical ventilation, and case-fatality outcomes.

RESULTS

Of this veteran cohort with COVID-19 disease, predominately 85.7% were male, 59.1% were White veterans, 27.5% were ages 50-64, and 40.5% were obese. Although Black veterans were at 63% higher relative risk (RR) for hospitalization incidences, they had a similar risk RR for in-hospital deaths compared to the White-veteran referent. Asian, American Indian/Alaska Native races, advanced age ≥65, and the underweight were at high RR for mechanical ventilator and/or in-hospital deaths compared to respective referent groups. Veterans who are ≥85 years old had a nearly 5-fold higher incidence of death compared respective referent group. The monthly outcomes for hospitalization, ventilation, and case-fatality data showed decreasing trends with time.

CONCLUSION

An increased incidence of death was associated with age ≥65 years and underweight veterans compared to the referent group. Age-adjusted data, however, did not show any increased incidence of death in Black veterans compared to White veterans.

RATINGS OF THE QUALITY OF THE EVIDENCE

3 (Case-control studies; retrospective cohort study).

Elevated reactivity of Apelin inhibited renal fibrosis induced by chronic intermittent hypoxia

BACKGROUND

Apelin and its receptor angiotensin receptor - like 1 (APJ) are closely related to renal fibrosis, but their specific roles in renal fibrosis are still controversial. In this article, we discussed the role of Apelin/APJ system in renal fibrosis and its mechanism.

METHODS

Chronic intermittent hypoxia (CIH) rat model was established to induce the environment of renal fibrosis and a competitive antagonist of the APJ receptor ML221 was administered to CIH rats. The rats were divided into Control, CIH and ML221 groups. HE staining was used to detect the inflammatory injury and fibrosis of renal tissue. The expressions of renal fibrosis-related indicators transforming growth factor-β (TGF-β), α-smooth muscle actin (α-SMA) and Human type I collagen (Col-Ⅰ) were detected by immunohistochemistry. The levels of oxidative stress indexes reactive oxygen species (ROS), Malondialdehyde (MDA), Superoxide Dismutase (SOD) and inflammation-related indexes Interleukin (IL) -6, tumor necrosis factor-α (TNF-α) and IL-1β were detected by ELISA. At the same time, the levels of Apelin-13 and AngiotensinII (AngⅡ) were also measured by ELISA. Finally, western blot was used to detect the expression of Apelin pathway and renal fibrosis-related proteins. In addition, at the cellular level, we divided the cells into Control, CIH, Apelin-13 and Apelin-13+ML-221 groups to further verify the specific mechanisms at the cellular level.

RESULTS

The expression of Apeline-13 and its related pathways was significantly increased after the induction of CIH in rats. However, the degree of renal fibrosis in ML221 group was further significantly increased after inhibiting the expression of Apelin. At the cellular level, CIH model cells treated with Apelin-13 significantly reduced cell proliferation, oxidative stress and inflammatory response, and decreased the expression of fibrosis-related proteins, which can be reversed by ML221 administration.

CONCLUSION

The increased reactivity of Apelin may be one of the protective mechanisms against renal fibrosis induced by CIH.

Aryl Hydrocarbon Receptor and Cysteine Redox Dynamics Underlie (Mal)adaptive Mechanisms to Chronic Intermittent Hypoxia in Kidney Cortex

We hypothesized that an interplay between aryl hydrocarbon receptor (AhR) and cysteine-related thiolome at the kidney cortex underlies the mechanisms of (mal)adaptation to chronic intermittent hypoxia (CIH), promoting arterial hypertension (HTN). Using a rat model of CIH-HTN, we investigated the impact of short-term (1 and 7 days), mid-term (14 and 21 days, pre-HTN), and long-term intermittent hypoxia (IH) (up to 60 days, established HTN) on CYP1A1 protein level (a sensitive hallmark of AhR activation) and cysteine-related thiol pools. We found that acute and chronic IH had opposite effects on CYP1A1 and the thiolome. While short-term IH decreased CYP1A1 and increased protein-S-thiolation, long-term IH increased CYP1A1 and free oxidized cysteine. In addition, an in vitro administration of cystine, but not cysteine, to human endothelial cells increased Cyp1a1 expression, supporting cystine as a putative AhR activator. This study supports CYP1A1 as a biomarker of obstructive sleep apnea (OSA) severity and oxidized pools of cysteine as risk indicator of OSA-HTN. This work contributes to a better understanding of the mechanisms underlying the phenotype of OSA-HTN, mimicked by this model, which is in line with precision medicine challenges in OSA.

The Microbiome in Obstructive Sleep Apnea

Recent evidence has highlighted important associations between obstructive sleep apnea and the microbiome. Although the intricacies of the pathophysiologic mechanisms are not well understood, available evidence suggests a bidirectional relationship between OSA and microbiota composition. Sleep fragmentation, intermittent hypoxia, and intermittent hypercapnia all play significant roles in altering the microbiome, and initial evidence has shown that alterations of the microbiota affect sleep patterns. Animal model evidence strongly supports the idea that the microbiome mediates disease states associated with OSA including hypertension, atherosclerosis, and obesity. The majority of evidence focuses on changes in the gut microbiome, which may result from OSA as well as contribute to sleep pattern changes, OSA-related CVD, and obesity. Meanwhile, a developing body of work suggests changes in the upper airway microbiome may be associated with OSA and periodontitis-related oral cavity microbiome changes may have significance in OSA-related CVD. Lastly, while evidence is limited, several studies suggest there may be a role for treatment of OSA and OSA-related comorbidities through alteration of the microbiome with probiotics, prebiotics, and microbiota transplantation. These early animal and human studies begin to characterize the interrelationships of the microbiome and OSA and may lead to new avenues for treatment.