Effects of sympathetic modulation in metabolic disease

Pyridostigmine attenuated high-fat-diet induced liver injury by the reduction of mitochondrial damage and oxidative stress via α7nAChR and M3AChR

Obesity is a major cause of nonalcohol fatty liver disease (NAFLD), which is characterized by hepatic fibrosis, lipotoxicity, inflammation, and apoptosis. Previous studies have shown that an imbalance in the autonomic nervous system is closely related to the pathogenesis of NAFLD. In this study, we investigated the effects of pyridostigmine (PYR), a cholinesterase (AChE) inhibitor, on HFD-induced liver injury and explored the potential mechanisms involving mitochondrial damage and oxidative stress. A murine model of HFD-induced obesity was established using the C57BL/6 mice, and PYR (3 mg/kg/d) or placebo was administered for 20 weeks. PYR reduced the body weight and liver weight of the HFD-fed mice. Additionally, the serum levels of IL-6, TNF-α, cholesterol, and triglyceride were significantly lower in the PYR-treated versus the untreated mice, corresponding to a decrease in hepatic fibrosis, lipid accumulation, and apoptosis in the former. Furthermore, the mitochondrial morphology improved significantly in the PYR-treated group. Consistently, PYR upregulated ATP production and the mRNA level of the mitochondrial dynamic factors OPA1, Drp1 and Fis1, and the mitochondrial unfolded protein response (UPRmt) factors LONP1 and HSP60. Moreover, PYR treatment activated the Keap1/Nrf2 pathway and upregulated HO-1 and NQO-1, which mitigated oxidative injury as indicated by decreased 8-OHDG, MDA and H2 O2 levels, and increased SOD activity. Finally, PYR elevated acetylcholine (ACh) levels by inhibiting AChE, and upregulated the α7nAChR and M3AChR proteins in the HFD-fed mice. PYR alleviated obesity-induced hepatic injury in mice by mitigating mitochondrial damage and oxidative stress via α7nAChR and M3AChR.

Sympathetic circuits regulating hepatic glucose metabolism: where we stand

The prevalence of metabolic disorders, including type 2 diabetes mellitus, continues to increase worldwide. Although newer and more advanced therapies are available, current treatments are still inadequate and the search for solutions remains. The regulation of energy homeostasis, including glucose metabolism, involves an exchange of information between the nervous systems and peripheral organs and tissues; therefore, developing treatments to alter central and/or peripheral neural pathways could be an alternative solution to modulate whole body metabolism. Liver glucose production and storage are major mechanisms controlling glycemia, and the autonomic nervous system plays an important role in the regulation of hepatic functions. Autonomic nervous system imbalance contributes to excessive hepatic glucose production and thus to the development and progression of type 2 diabetes mellitus. At cellular levels, change in neuronal activity is one of the underlying mechanisms of autonomic imbalance; therefore, modulation of the excitability of neurons involved in autonomic outflow governance has the potential to improve glycemic status. Tissue-specific subsets of preautonomic neurons differentially control autonomic outflow; therefore, detailed information about neural circuits and properties of liver-related neurons is necessary for the development of strategies to regulate liver functions via the autonomic nerves. This review provides an overview of our current understanding of the hypothalamus-ventral brainstem-liver pathway involved in the sympathetic regulation of the liver, outlines strategies to identify organ-related neurons, and summarizes neuronal plasticity during diabetic conditions with a particular focus on liver-related neurons in the paraventricular nucleus.

A critical review on brain and heart axis response in COVID-19 patients: Molecular mechanisms, mediators, biomarkers, and therapeutics

Since the outbreak of highly virulent coronaviruses, significant interest was assessed to the brain and heart axis (BHA) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-affected patients. The majority of clinical reports accounted for unusual symptoms associated with SARS-CoV-2 infections which are of the neurological type, such as headache, nausea, dysgeusia, anosmia, and cerebral infarction. The SARS-CoV-2 enters the cells through the angiotensin-converting enzyme (ACE-2) receptor. Patients with prior cardiovascular disease (CVD) have a higher risk of COVID-19 infection and it has related to various cardiovascular (CV) complications. Infected patients with pre-existing CVDs are also particularly exposed to critical health outcomes. Overall, COVID-19 affected patients admitted to intensive care units (ICU) and exposed to stressful environmental constraints, featured with a cluster of neurological and CV complications. In this review, we summarized the main contributions in the literature on how SARS-CoV-2 could interfere with the BHA and its role in affecting multiorgan disorders. Specifically, the central nervous system involvement, mainly in relation to CV alterations in COVID-19-affected patients, is considered. This review also emphasizes the biomarkers and therapy options for COVID-19 patients presenting with CV problems.

Multi-organ denervation: a novel approach to combat cardiometabolic disease

Cardiometabolic disorders are associated with a substantial loss in quality of life and pose a large burden on healthcare systems worldwide. Overactivation of the sympathetic nervous system has been shown to be a key player in several aspects relating to cardiometabolic disturbances. While diet- and exercise-induced approaches to help reduce weight remains the main strategy to combat metabolic disorders, this is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication side effects and non-adherence in the long term. There is a clear clinical need for complementary therapies to curb the burden of cardiometabolic disease. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. Data from sham-controlled clinical trials demonstrate the feasibility, safety and efficacy of catheter-based renal denervation. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multi-organ neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum including blood pressure, glucose and lipid control.

12,13-diHOME and noradrenaline are associated with the occurrence of acute myocardial infarction in patients with type 2 diabetes mellitus

BACKGROUND

Acute myocardial infarction (AMI) is the most prevalent cause of mortality and morbidity in patients with type 2 diabetes mellitus (T2DM). However, strict blood glucose control does not always prevent the development and progression of AMI. Therefore, the present study aimed to explore potential new biomarkers associated with the occurrence of AMI in T2DM patients.

METHODS

A total of 82 participants were recruited, including the control group (n = 28), T2DM without AMI group (T2DM, n = 30) and T2DM with initial AMI group (T2DM + AMI, n = 24). The untargeted metabolomics using liquid chromatography-mass spectrometry (LC-MS) analysis was performed to evaluate the changes in serum metabolites. Then, candidate metabolites were determined using ELISA method in the validation study (n = 126/T2DM group, n = 122/T2DM + AMI group).

RESULTS

The results showed that 146 differential serum metabolites were identified among the control, T2DM and T2DM + AMI, Moreover, 16 differentially-expressed metabolites were significantly altered in T2DM + AMI compared to T2DM. Amino acid and lipid pathways were the major involved pathways. Furthermore, three candidate differential metabolites, 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), noradrenaline (NE) and estrone sulfate (ES), were selected for validation study. Serum levels of 12,13-diHOME and NE in T2DM + AMI were significantly higher than those in T2DM. Multivariate logistic analyses showed that 12,13-diHOME (OR, 1.491; 95% CI 1.230-1.807, P < 0.001) and NE (OR, 8.636; 95% CI 2.303-32.392, P = 0.001) were independent risk factors for AMI occurrence in T2T2DM patients. The area under receiver operating characteristic (ROC) curve (AUC) were 0.757 (95% CI 0.697-0.817, P < 0.001) and 0.711(95% CI 0.648-0.775, P < 0.001), respectively. The combination of both significantly improved the AUC to 0.816 (95% CI 0.763-0.869, P < 0.001).

CONCLUSIONS

12,13-diHOME and NE may lead to understanding the possible metabolic alterations associated with AMI onset in T2DM population and serve as promising risk factors and therapeutic targets.

Autonomic heart rate modulation in patients with coronavirus disease 2019 in mechanical ventilation

BACKGROUND

Patients with coronavirus disease 2019 on automatic mechanical ventilation have greater heart rate modulation with greater parasympathetic modulation.

OBJECTIVE

To analyze the autonomic modulation of heart rate in critically ill patients with coronavirus disease 2019 on invasive mechanical ventilation.

METHODS

A cross-section study was carried out with 36 individuals divided into two groups. The control group included patients of both genders, in orotracheal intubation with invasive mechanical ventilation under controlled assisted mode, hospitalized in the intensive care unit for another 24 h. In the non-COVID group, patients diagnosed with coronavirus disease 2019 in the same condition mentioned in the control group.

RESULTS

There was a significant increase in heart rate variability (standard deviation of all normal RR intervals recorded at an interval of time; p=0.001; triangular interpolation histogram of RR intervals; p=0.048; and SD2; p=0.014) in the coronavirus disease group compared to the non-COVID group. Successively, the parameters that demonstrate parasympathetic modulation are shown to be higher in the group of patients with coronavirus disease 2019 (root mean square of the square of differences between adjacent normal RR intervals in an interval of time; p<0.001; pNN50; p<0.001; SD1; p=0.002; and high frequency; p=0.022).

CONCLUSIONS

There was a greater autonomic modulation of heart rate with a greater parasympathetic modulation in patients with coronavirus disease 2019 on mechanical ventilation.

Non-alcoholic fatty liver disease (NAFLD) and mental illness: Mechanisms linking mood, metabolism and medicines

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the world and one of the leading indications for liver transplantation. It is one of the many manifestations of insulin resistance and metabolic syndrome as well as an independent risk factor for cardiovascular disease. There is growing evidence linking the incidence of NAFLD with psychiatric illnesses such as schizophrenia, bipolar disorder and depression mechanistically via genetic, metabolic, inflammatory and environmental factors including smoking and psychiatric medications. Indeed, patients prescribed antipsychotic medications, regardless of diagnosis, have higher incidence of NAFLD than population norms. The mechanistic pharmacology of antipsychotic-associated NAFLD is beginning to emerge. In this review, we aim to discuss the pathophysiology of NAFLD including its risk factors, insulin resistance and systemic inflammation as well as its intersection with psychiatric illnesses.

Renal Denervation: A Review

Uncontrolled hypertension persists as an important health issue despite the availability of many medications and nondrug therapies that lower blood pressure. Increasingly, nonadherence to medication is found in approximately 2 of every 5 patients with uncontrolled hypertension. In the search for interventions that lower blood pressure that do not rely on adherence to a regimen requiring daily ingestion of medication or repeated physical activity, device-based methods that denervate the renal arteries have emerged as a potential complement to standard antihypertensive treatments. At least 3 different approaches to renal artery denervation are under active investigation, including the use of radiofrequency energy, ultrasound, or the injection of neurolytic agents into the renal perivascular tissue. In this review, we cover what is currently known about the mechanisms of antihypertensive effects of renal denervation, summarize the efficacy and safety of renal denervation using recent controlled trial publications in a number of hypertensive populations, and conclude with some thoughts about challenges in the field, including the optimization of patient selection for the procedure and what the reader can expect in the near future in this rapidly developing field.

Renal denervation in the antihypertensive arsenal - knowns and known unknowns

Even though it has been more than a decade since renal denervation (RDN) was first used to treat hypertension and an intense effort on researching this therapy has been made, it is still not clear how RDN fits into the antihypertensive arsenal. There is no question that RDN lowers blood pressure (BP), it does so to an extent at best corresponding to one antihypertensive drug. The procedure has an excellent safety record. However, it remains clinically impossible to predict whose BP responds to RDN and whose does not. Long-term efficacy data on BP reduction are still unconvincing despite the recent results in the SPYRAL HTN-ON MED trial; experimental studies indicate that reinnervation is occurring after RDN. Although BP is an acceptable surrogate endpoint, there is complete lack of outcome data with RDN. Clear indications for RDN are lacking although patients with resistant hypertension, those with documented increase in activity of the sympathetic system and perhaps those who desire to take fewest medication may be considered.

Targeting Features of the Metabolic Syndrome Through Sympatholytic Effects of SGLT2 Inhibition

PURPOSE OF REVIEW

The moderate glucose-lowering effect of sodium glucose co-transporter 2 (SGLT2) inhibitors is unlikely to explain SGLT2 inhibitor-mediated beneficial outcomes, and unravelling the underlying mechanisms is a high priority in the research community. Given the dominant pathophysiologic role of the sympathetic nervous system activation in conditions such as hypertension and perturbed glucose homeostasis, it is pertinent to postulate that SGLT2 inhibitors may exert their beneficial effects at least in part via sympathetic inhibition.

RECENT FINDINGS

SGLT2 inhibitors have shown enormous potential to improve cardiovascular outcomes in patients with type 2 diabetes, and their therapeutic potential is currently being investigated in a range of associated comorbidities such as heart failure and chronic kidney disease. Indeed, recent experimental data in relevant animal models highlight a bidirectional interaction between sympathetic nervous system activation and SGLT2 expression, and this facilitates several of the features associated with SGLT2 inhibition observed in clinical trials including improved glucose metabolism, weight loss, increased diuresis, and lowering of blood pressure. Currently available data highlight the various levels of interaction between the sympathetic nervous system and SGLT2 expression and explores the potential for SGLT2 inhibition as a therapeutic strategy in conditions commonly characterised by sympathetic activation.

Interaction between sodium-glucose co-transporter 2 and the sympathetic nervous system

PURPOSE OF REVIEW

Sodium-glucose co-transporter 2 (SGLT2) inhibitors have taken centre stage in research and therapeutic efforts to modulate hard clinical outcomes in patients with heightened cardiovascular and renal risk profiles. Sympathetic nervous system (SNS) activation is a prominent feature across several cardiovascular and renal disease states. This review reflects on the remarkable clinical impact of SGLT2 inhibitors on cardiorenal outcomes, and navigates the evidence for a proposed clinically relevant interaction between SGLT2 and the SNS.

RECENT FINDINGS

SGLT2 inhibitors exert several pleiotropic effects beyond glucose-lowering. These include, but are not limited to, diuresis and natriuresis, blood pressure lowering, reduction in inflammation and oxidative stress, stimulation of erythropoiesis, and improvement in cardiac energetics. Treatment with SGLT2 inhibitors is associated with significant improvement in cardiorenal outcomes irrespective of diabetes status. In addition, evidence from preclinical studies points to a strong signal of a bidirectional temporal association between SGLT2 inhibition and reduction in SNS activation.

SUMMARY

Ongoing preclinical and clinical trials aimed at unravelling the proposed interaction between SGLT and SNS will enhance our understanding of their individual and/or collective contributions to cardiovascular disease progression and guide future targeted therapeutic interventions.

K-means panning - Developing a new standard in automated MSNA signal recognition with a weakly supervised learning approach

BACKGROUND

Accessibility of labelled datasets is often a key limitation for the application of Machine Learning in clinical research. A novel semi-automated weak-labelling approach based on unsupervised clustering was developed to classify a large dataset of microneurography signals and subsequently used to train a Neural Network to reproduce the labelling process.

METHODS

Clusters of microneurography signals were created with k-means and then labelled in terms of the validity of the signals contained in each cluster. Only purely positive or negative clusters were labelled, whereas clusters with mixed content were passed on to the next iteration of the algorithm to undergo another cycle of unsupervised clustering and labelling of the clusters. After several iterations of this process, only pure labelled clusters remained which were used to train a Deep Neural Network.

RESULTS

Overall, 334,548 individual signal peaks form the integrated data were extracted and more than 99.99% of the data was labelled in six iterations of this novel application of weak labelling with the help of a domain expert. A Deep Neural Network trained based on this dataset achieved consistent accuracies above 95%.

DISCUSSION

Data extraction and the novel iterative approach of labelling unsupervised clusters enabled creation of a large, labelled dataset combining unsupervised learning and expert ratings of signal-peaks on cluster basis in a time effective manner. Further research is needed to validate the methodology and employ it on other types of physiologic data for which it may enable efficient generation of large labelled datasets.

Covid-19-Induced Dysautonomia: A Menace of Sympathetic Storm

Among the plethora of debilitating neurological disorders of COVID-19 syndrome in survivors, the scope of SARS-CoV-2-induced dysautonomia (DNS) is yet to be understood, though the implications are enormous. Herein, we present an inclusive mini-review of SARS-CoV-2-induced DNS and its associated complications. Although, the direct link between Covid-19 and DSN is still speculative, the hypothetical links are thought to be either a direct neuronal injury of the autonomic pathway or a para/post-infectious immune-induced mechanism. SARS-CoV-2 infection-induced stress may activate the sympathetic nervous system (SNS) leading to neuro-hormonal stimulation and activation of pro-inflammatory cytokines with further development of sympathetic storm. Sympathetic over-activation in Covid-19 is correlated with increase in capillary pulmonary leakage, alveolar damage, and development of acute respiratory distress syndrome. Furthermore, SARS-CoV-2 can spread through pulmonary mechanoreceptors and chemoreceptors to medullary respiratory center in a retrograde manner resulting in sudden respiratory failure. Taken together, DSN in Covid-19 is developed due to sympathetic storm and inhibition of Parasympathetic nervous system-mediated anti-inflammatory effect with development of cytokine storm. Therefore, sympathetic and cytokine storms together with activation of Renin-Angiotensin-System are the chief final pathway involved in the development of DSN in Covid-19.

How COVID-19 can cause autonomic dysfunctions and postural orthostatic syndrome? A Review of mechanisms and evidence

Coronavirus disease 2019 (COVID-19) is a viral disease spread by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Because the recent pandemic has resulted in significant morbidity and mortality, understanding various aspects of this disease has become critical. SARS-CoV-2 can affect a variety of organs and systems in the body. The autonomic nervous system plays an important role in regulating body functions, and its dysfunction can cause a great deal of discomfort for patients. In this study, we focused on the effect of COVID-19 on the autonomic system and syndromes associated with it, such as postural orthostatic syndrome (POTS).

Heart rate and cardiac autonomic responses to concomitant deep breathing, hand grip exercise, and circulatory occlusion in healthy young adult men and women

BACKGROUND

Deep breathing (DB) and handgrip (HG) exercise -with and without circulatory occlusion (OC) in muscle-, have been shown to have beneficial effects on cardiovascular function; however, the combination of these maneuvers on heart rate (HR) and cardiac sympathovagal balance have not been previously investigated. Therefore, the aim of the present study was to evaluate the effect of simultaneous DB, HG, and OC maneuvers on the sympathovagal balance in healthy women and men subjects.

METHODS AND RESULTS

Electrocardiogram and ventilation were measured in 20 healthy subjects (Women: n = 10; age = 27 ± 4 years; weight = 67.1 ± 8.4 kg; and height = 1.6 ± 0.1 m. Men: n = 10; age = 27 ± 3 years; weight = 77.5 ± 10.1 kg; and height = 1.7 ± 0.1 m) at baseline and during DB, DB + HG, or DB + HG + OC protocols. Heart rate (HR) and respiratory rate were continuously recorded, and spectral analysis of heart rate variability (HRV) were calculated to indirectly estimate cardiac autonomic function. Men and women showed similar HR responses to DB, DB + HG and DB + HG + OC. Men exhibited a significant HR decrease following DB + HG + OC protocol which was accompanied by an improvement in cardiac autonomic control evidenced by spectral changes in HRV towards parasympathetic predominance (HRV High frequency: 83.95 ± 1.45 vs. 81.87 ± 1.50 n.u., DB + HG + OC vs. baseline; p < 0.05). In women, there was a marked decrease in HR after completion of both DB + HG and DB + HG + OC tests which was accompanied by a significant increase in cardiac vagal tone (HRV High frequency: 85.29 ± 1.19 vs. 77.93 ± 0.92 n.u., DB + HG vs. baseline; p < 0.05). No adverse effects or discomfort were reported by men or women during experimental procedures. Independent of sex, combination of DB, HG, and OC was tolerable and resulted in decreases in resting HR and elevations in cardiac parasympathetic tone.

CONCLUSIONS

These data indicate that combined DB, HG and OC are effective in altering cardiac sympathovagal balance and reducing resting HR in healthy men and women.

Autonomic nervous system activity changes in patients with hypertension and overweight: role and therapeutic implications

The incidence and prevalence of hypertension is increasing worldwide, with approximately 1.13 billion of people currently affected by the disease, often in association with other diseases such as diabetes mellitus, chronic kidney disease, dyslipidemia/hypercholesterolemia, and obesity. The autonomic nervous system has been implicated in the pathophysiology of hypertension, and treatments targeting the sympathetic nervous system (SNS), a key component of the autonomic nervous system, have been developed; however, current recommendations provide little guidance on their use. This review discusses the etiology of hypertension, and more specifically the role of the SNS in the pathophysiology of hypertension and its associated disorders. In addition, the effects of current antihypertensive management strategies, including pharmacotherapies, on the SNS are examined, with a focus on imidazoline receptor agonists.

Effects of carotid baroreceptor stimulation on aortic remodeling in obese rats

BACKGROUND AND AIM

Our previous study found carotid baroreceptor stimulation (CBS) reduces body weight and white adipose tissue (WAT) weight, restores abnormal secretion of adipocytokines and inflammation factors, decreases systolic blood pressure (SBP) by inhibiting activation of sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in obese rats. In this study, we explore effects of CBS on aortic remodeling in obese rats.

METHODS AND RESULTS

Rats were fed high-fat diet (HFD) for 16 weeks to induce obesity and underwent either CBS device implantation and stimulation or sham operation at 8 weeks. BP and body weight were measured weekly. RAS activity of WAT, histological, biochemical and functional profiles of aortas were detected after 16 weeks. CBS effectively decreased BP in obese rats, downregulated mRNA expression of angiotensinogen (AGT) and renin in WAT, concentrations of AGT, renin, angiotensin II (Ang II), protein levels of Ang II receptor 1 (AT1R) and Ang II receptor 2 (AT2R) in WAT were declined. CBS inhibited reactive oxygen species (ROS) generation, inflammatory response and endoplasmic reticulum (ER) stress in aortas of obese rats, restrained vascular wall thickening and vascular smooth muscle cells (VSMCs) phenotypic switching, increased nitric oxide (NO) synthesis, promoted endothelium-dependent vasodilatation by decreasing protein expression of AT1R and leptin receptor (LepR), increasing protein expression of adiponectin receptor 1 (AdipoR1) in aortic VSMCs.

CONCLUSION

CBS reduced BP and reversed aortic remodeling in obese rats, the underlying mechanism might be related to the suppressed SNS activity, restored adipocytokine secretion and restrained RAS activity of WAT.

Capillary vascular density in the retina of hypertensive patients is associated with a non-dipping pattern independent of mean ambulatory blood pressure

BACKGROUND

A nocturnal non-dipping pattern has been associated with hypertension-mediated organ damage (HMOD), morbidity and mortality. Retinal imaging through application of modern technologies including optical coherence tomography angiography (OCT-A) can provide detailed insights into early vascular damage. In this observational study, we investigated the relationship of microscopic vascular density in the retina measured with OCT-A and nocturnal blood pressure (BP) dipping.

METHODS

Retinal OCT-A and ambulatory BP monitoring (ABPM) data prospectively obtained from 142 patients referred to a tertiary hypertension clinic were analysed with regression models for associations between BP night-time dipping and retinal capillary vascular density in three different zones around the fovea.

RESULTS

More pronounced nocturnal SBP and DBP dipping was significantly associated with increased vascular density in the central foveal area of the retina. These associations were robust to adjustment for other available risk factors including mean daytime BP. Parafoveal and whole image vascular density did not show equivalent significant associations with nocturnal BP dipping. The results were reproducible when assessed in a subgroup of patients who had concomitant type 2 diabetes.

CONCLUSION

Foveal vascular density was associated with the nocturnal BP dipping pattern in hypertensive patients. These associations were robust to adjustment of relevant factors such as daytime BP. Our findings highlight the importance of nocturnal BP features reflected in ambulatory BP monitoring in the assessment of HMOD. Whether routine assessment of retinal damage markers may improve risk management of hypertensive patients remains to be determined.

FGF19 in the Hindbrain Lowers Blood Glucose and Alters Excitability of Vagal Motor Neurons in Hyperglycemic Mice

Fibroblast growth factor 19 (FGF19) is a protein hormone that produces antidiabetic effects when administered intracerebroventricularly in the forebrain. However, no studies have examined how FGF19 affects hindbrain neurons that participate directly in autonomic control of systemic glucose regulation. Within the dorsal hindbrain, parasympathetic motor neurons of the dorsal motor nucleus of the vagus (DMV) express fibroblast growth factor receptors and their activity regulates visceral homeostatic processes, including energy balance. This study tested the hypothesis that FGF19 acts in the hindbrain to alter DMV neuron excitability and lower blood glucose concentration. Fourth ventricle administration of FGF19 produced no effect on blood glucose concentration in control mice, but induced a significant, peripheral muscarinic receptor-dependent decrease in systemic hyperglycemia for up to 12 h in streptozotocin-treated mice, a model of type 1 diabetes. Patch-clamp recordings from DMV neurons in vitro revealed that FGF19 application altered synaptic and intrinsic membrane properties of DMV neurons, with the balance of FGF19 effects being significantly modified by a recent history of systemic hyperglycemia. These findings identify central parasympathetic circuitry as a novel target for FGF19 and suggest that FGF19 acting in the dorsal hindbrain can alter vagal output to produce its beneficial metabolic effects.

Role of the sympathetic nervous system in cardiometabolic control: implications for targeted multiorgan neuromodulation approaches

Sympathetic overdrive plays a key role in the perturbation of cardiometabolic homeostasis. Diet-induced and exercise-induced weight loss remains a key strategy to combat metabolic disorders, but is often difficult to achieve. Current pharmacological approaches result in variable responses in different patient cohorts and long-term efficacy may be limited by medication intolerance and nonadherence. A clinical need exists for complementary therapies to curb the burden of cardiometabolic diseases. One such approach may include interventional sympathetic neuromodulation of organs relevant to cardiometabolic control. The experience from catheter-based renal denervation studies clearly demonstrates the feasibility, safety and efficacy of such an approach. In analogy, denervation of the common hepatic artery is now feasible in humans and may prove to be similarly useful in modulating sympathetic overdrive directed towards the liver, pancreas and duodenum. Such a targeted multiorgan neuromodulation strategy may beneficially influence multiple aspects of the cardiometabolic disease continuum offering a holistic approach.

Combined renal and common hepatic artery denervation as a novel approach to reduce cardiometabolic risk: technical approach, feasibility and safety in a pre-clinical model

Background

Cardiovascular and metabolic regulation is governed by neurohumoral signalling in relevant organs such as kidney, liver, pancreas, duodenum, adipose tissue, and skeletal muscle. Combined targeting of relevant neural outflows may provide a unique therapeutic opportunity for cardiometabolic disease.

Objectives

We aimed to investigate the feasibility, safety, and performance of a novel device-based approach for multi-organ denervation in a swine model over 30 and 90 days of follow-up.

Methods

Five Yorkshire cross pigs underwent combined percutaneous denervation in the renal arteries and the common hepatic artery (CHA) with the iRF Denervation System. Control animals (n = 3) were also studied. Specific energy doses were administered in the renal arteries and CHA. Blood was collected at 30 and 90 days. All animals had a pre-terminal procedure angiography. Tissue samples were collected for norepinephrine (NEPI) bioanalysis. Histopathological evaluation of collateral structures and tissues near the treatment sites was performed to assess treatment safety.

Results

All animals entered and exited the study in good health. No stenosis or vessel abnormalities were present. No significant changes in serum chemistry occurred. NEPI concentrations were significantly reduced in the liver (− 88%, p = 0.005), kidneys (− 78%, p < 0.001), pancreas (− 78%, p = 0.018) and duodenum (− 95%, p = 0.028) following multi-organ denervation treatment compared to control animals. Histologic findings were consistent with favourable tissue responses at 90 days follow-up.

Conclusions

Significant and sustained denervation of the treated organs was achieved at 90 days without major safety events. Our findings demonstrate the feasibility of multi-organ denervation using a novel iRF Denervation System in a single procedure.

Mercury in the human adrenal medulla could contribute to increased plasma noradrenaline in aging

Plasma noradrenaline levels increase with aging, and this could contribute to the sympathetic overactivity that is associated with essential hypertension and the metabolic syndrome. The underlying cause of this rise in noradrenaline is unknown, but a clue may be that mercury increases noradrenaline output from the adrenal medulla of experimental animals. We therefore determined the proportion of people from 2 to 104 years of age who had mercury in their adrenal medulla. Mercury was detected in paraffin sections of autopsied adrenal glands using two methods of elemental bioimaging, autometallography and laser ablation-inductively coupled plasma-mass spectrometry. Mercury first appeared in cells of the adrenal medulla in the 21–40 years group, where it was present in 52% of samples, and increased progressively in frequency in older age groups, until it was detected in 90% of samples from people aged over 80 years. In conclusion, the proportion of people having mercury in their adrenal medulla increases with aging. Mercury could alter the metabolism of catecholamines in the adrenal medulla that leads to the raised levels of plasma noradrenaline in aging. This retrospective autopsy study was not able to provide a definitive link between adrenal mercury, noradrenaline levels and hypertension, but future functional human and experimental studies could provide further evidence for these associations.