Cardiac Autonomic Neuropathy: A Progressive Consequence of Chronic Low-Grade Inflammation in Type 2 Diabetes and Related Metabolic Disorders.

Cardiac autonomic neuropathy (CAN) is one of the earliest complications of type 2 diabetes (T2D), presenting a silent cause of cardiovascular morbidity and mortality. Recent research relates the pathogenesis of cardiovascular disease in T2D to an ensuing chronic, low-grade proinflammatory and pro-oxidative environment, being the hallmark of the metabolic syndrome. Metabolic inflammation emerges as adipose tissue inflammatory changes extending systemically, on the advent of hyperglycemia, to reach central regions of the brain. In light of changes in glucose and insulin homeostasis, dysbiosis or alteration of the gut microbiome (GM) emerges, further contributing to inflammatory processes through increased gut and blood-brain barrier permeability. Interestingly, studies reveal that the determinants of oxidative stress and inflammation progression exist at the crossroad of CAN manifestations, dictating their evolution along the natural course of T2D development. Indeed, sympathetic and parasympathetic deterioration was shown to correlate with markers of adipose, vascular, and systemic inflammation. Additionally, evidence points out that dysbiosis could promote a sympatho-excitatory state through differentially affecting the secretion of hormones and neuromodulators, such as norepinephrine, serotonin, and γ-aminobutyric acid, and acting along the renin-angiotensin-aldosterone axis. Emerging neuronal inflammation and concomitant autophagic defects in brainstem nuclei were described as possible underlying mechanisms of CAN in experimental models of metabolic syndrome and T2D. Drugs with anti-inflammatory characteristics provide potential avenues for targeting pathways involved in CAN initiation and progression. The aim of this review is to delineate the etiology of CAN in the context of a metabolic disorder characterized by elevated oxidative and inflammatory load.

Impaired Autonomic Nervous System-Microbiome Circuit in Hypertension.

Hypertension affects an estimated 103 million Americans, yet gaps in knowledge continue to limit its successful management. Rapidly emerging evidence is linking gut dysbiosis to many disorders and diseases including hypertension. The evolution of the -omics techniques has allowed determination of the abundance and potential function of gut bacterial species by next-generation bacterial sequencing, whereas metabolomics techniques report shifts in bacterial metabolites in the systemic circulation of hypertensive patients and rodent models of hypertension. The gut microbiome and host have evolved to exist in balance and cooperation, and there is extensive crosstalk between the 2 to maintain this balance, including during regulation of blood pressure. However, an understanding of the mechanisms of dysfunctional host-microbiome interactions in hypertension is still lacking. Here, we synthesize some of our recent data with published reports and present concepts and a rationale for our emerging hypothesis of a dysfunctional gut-brain axis in hypertension. Hopefully, this new information will improve the understanding of hypertension and help to address some of these knowledge gaps.

Gut Microbiota Are Disease-Modifying Factors After Traumatic Spinal Cord Injury.

Spinal cord injury (SCI) disrupts the autonomic nervous system (ANS), impairing its ability to coordinate organ function throughout the body. Emerging data indicate that the systemic pathology that manifests from ANS dysfunction exacerbates intraspinal pathology and neurological impairment. Precisely how this happens is unknown, although new data, in both humans and in rodent models, implicate changes in the composition of bacteria in the gut (i.e., the gut microbiota) as disease-modifying factors that are capable of affecting systemic physiology and pathophysiology. Recent data from rodents indicate that SCI causes gut dysbiosis, which exacerbates intraspinal inflammation and lesion pathology leading to impaired recovery of motor function. Postinjury delivery of probiotics containing various types of "good" bacteria can partially overcome the pathophysiologal effects of gut dysbiosis; immune function, locomotor recovery, and spinal cord integrity are partially restored by a sustained regimen of oral probiotics. More research is needed to determine whether gut dysbiosis varies across a range of clinically relevant variables, including sex, injury level, and injury severity, and whether changes in the gut microbiota can predict the onset or severity of common postinjury comorbidities, including infection, anemia, metabolic syndrome, and, perhaps, secondary neurological deterioration. Those microbial populations that dominate the gut could become "druggable" targets that could be manipulated via dietary interventions. For example, personalized nutraceuticals (e.g., pre- or probiotics) could be developed to treat the above comorbidities and improve health and quality of life after SCI.

Brain injury induces specific changes in the caecal microbiota of mice via altered autonomic activity and mucoprotein production.

Intestinal microbiota are critical for health with changes associated with diverse human diseases. Research suggests that altered intestinal microbiota can profoundly affect brain function. However, whether altering brain function directly affects the microbiota is unknown. Since it is currently unclear how brain injury induces clinical complications such as infections or paralytic ileus, key contributors to prolonged hospitalization and death post-stroke, we tested in mice the hypothesis that brain damage induced changes in the intestinal microbiota. Experimental stroke altered the composition of caecal microbiota, with specific changes in Peptococcaceae and Prevotellaceae correlating with the extent of injury. These effects are mediated by noradrenaline release from the autonomic nervous system with altered caecal mucoprotein production and goblet cell numbers. Traumatic brain injury also caused changes in the gut microbiota, confirming brain injury effects gut microbiota. Changes in intestinal microbiota after brain injury may affect recovery and treatment of patients should appreciate such changes.

The unexplored relationship between urinary tract infections and the autonomic nervous system.

Urinary tract infections (UTIs), the majority of which are caused by uropathogenic E. coli (UPEC), are extremely common infections that preferentially effect women. Additional complicating factors, such as catheterization, diabetes, and spinal cord injuries can increase the frequency and severity of UTIs. The rise of antimicrobial resistant uropathogens and the ability of this disease to chronically recur make the development of alternative preventative and therapeutic modalities a priority. The major symptoms of UTIs, urgency, frequency, and dysuria, are readouts of the autonomic nervous system (ANS) and the majority of the factors that lead to complicated UTIs have been shown to impact ANS function. This review summarizes the decades' long efforts to understand the molecular mechanisms of the interactions between UPEC and the host, with a particular focus on the recent findings revealing the molecular, bacteriological, immunological and epidemiological complexity of pathogenesis. Additionally, we describe the progress that has been made in: i) generating vaccines and anti-virulence compounds that prevent and/or treat UTI by blocking bacterial adherence to urinary tract tissue and; and ii) elucidating the mechanism by which anti-inflammatories are able to alleviate symptoms and improve disease prognosis. Finally, the potential relationships between the ANS and UTI are considered throughout. While these relationships have not been experimentally explored, the known interactions between numerous UTI characteristics (symptoms, complicating factors, and inflammation) and ANS function suggest that UTIs are directly impacting ANS stimulation and that ANS (dys)function may alter UTI prognosis.

Catecholamines and acetylcholine are key regulators of the interaction between microbes and the immune system.

Recent studies suggest that catecholamines (CAs) and acetylcholine (ACh) play essential roles in the crosstalk between microbes and the immune system. Host cholinergic afferent fibers sense pathogen-associated molecular patterns and trigger efferent cholinergic and catecholaminergic pathways that alter immune cell proliferation, differentiation, and cytokine production. On the other hand, microbes have the ability to produce and degrade ACh and also regulate autogenous functions in response to CAs. Understanding the role played by these neurotransmitters in host-microbe interactions may provide valuable information for the development of novel therapies.

Tetanus--a case report with severe autonomic instability and: a review of the literature.

BACKGROUND: Tetanus is an infection that can be associated with a high mortality especially in developing countries. Critical care which may include artificial control of respiration is crucial in survival, but cardiovascular complications from autonomic instability remains an important cause of death. The objective of this report is to highlight this important cause of mortality despite artificial control of ventilation to prevent respiratory arrest. METHOD: The medical record of the patient and relevant literature were reviewed. RESULT: A 29-year old male following a wound on the lower limb presented with clinical features suggestive of tetanus. Incubation period was short and immunization history was uncertain. Basic treatment directed at removing source of infection and neutralisation of unbound toxin was however commenced. Following signs of imminent respiratory failure due to severe uncontrollable spasms, controlled mechanical ventilation was instituted in the critical care unit (CCU). However, the patient succumbed to cardiac arrest as a result of severe autonomic instability, despite aggressive cardiopulmonary resuscitation. CONCLUSION: Cardiovascular arrest from severe autonomic instability remains an important cause of mortality in tetanus despite artificial ventilation. Early management with appropriate therapy is advisable to prevent its occurrence.

Quantitative autonomic testing in the management of botulism.

Even with mild neurological signs, patients with botulism frequently complain of autonomic symptoms. This study aimed at the evaluation of sudomotor and cardiovascular reflex functions by quantitative autonomic testing (QAT), which may identify patients with autonomic involvement but otherwise benign clinical presentation. Five patients with food-borne botulism were subjected to a structured questionnaire on autonomic symptoms, cardiac and neurological examination, and QAT after a median of 2 weeks (baseline) and 12 weeks (follow-up) post intoxication. For calculation of haemodynamic and cardiovascular autonomic parameters, we used the Task Force((R)) Monitor (Version 2.1, CNSystems, Graz, Austria). Cardiovagal function was assessed by Ewing's test battery. Autonomic complaints were more pronounced than neurological symptoms. Baseline tests revealed widely abnormal sudomotor function and marked impairment of heart rate variation and blood pressure response to standing. Prominent features of cardiovascular failure were high resting heart rate, supine hypertension, orthostatic hypotension, and impaired baroreflex function. Three patients reported inability to keep up with their routine amount of physical work. Based on the baseline QAT results, these three patients were instructed to engage in physical activity but avoid physical strain until there was considerable improvement. On follow-up, fatigue was the most frequent residual complaint, sympathetic skin responses were present, and cardiovascular QAT results were significantly improved and did not differ from those of ten control subjects. QAT identified autonomic involvement in botulism patients with otherwise benign neurological presentation. Comprehensive evaluation of autonomic failure may provide useful information for the management of botulism.

Transient dysautonomia and cerebellitis in childhood enteric fever.

A case of childhood enteric fever complicated by transient dysautonomia and cerebellitis is reported. The child was treated with intravenous antibiotics, and the complications were managed conservatively. Dysautonomia and cerebellitis resolved by day 5 and day 8 after admission, respectively. Results of a neurologic examination at the end of 6 months were normal. Dysautonomia complicating the course of childhood enteric fever is previously unreported.

Gamma(2)-melanocyte-stimulating hormone suppression of systemic inflammatory responses to endotoxin is associated with modulation of central autonomic and neuroendocrine activities.

Central autonomic and neuroendocrine activities are important components of the host response to bacterial inflammation. We demonstrate that intravenous infusion of gamma(2)-melanocyte-stimulating hormone (gamma(2)-MSH), a potent autonomic regulating peptide, prevents lipopolysaccharide (LPS)-induced hypotension and tachycardia, and modulates the ACTH response to endotoxin. In the hypothalamic paraventricular nucleus, a major neuroendocrine and autonomic center, gamma(2)-MSH inhibits LPS-induced increases in CRF mRNA levels, but does not suppress LPS-augmented arginine vasopressin heteronuclear RNA expression. In the locus coeruleus, a brainstem noradrenergic center, gamma(2)-MSH inhibits LPS-induced increases in tyrosine hydroxylase mRNA levels. Gamma(2)-MSH inhibits LPS-induced IL-1beta gene expression in the brain, pituitary and thymus, and prevents increases in plasma NO levels. These findings reveal that gamma(2)-MSH attenuates systemic inflammatory responses to endotoxin and suggest that modulation of central autonomic and neuroendocrine activities by gamma(2)-MSH contributes to its anti-inflammatory effects.