Autonomic Nervous System Function in Anorexia Nervosa: A Systematic Review

Gut-derived appetite regulating hormones across the anorexia nervosa spectrum

BACKGROUND

Appetite-regulating hormones are implicated in anorexia nervosa (AN) pathophysiology, however, data are limited for appetite-regulating hormones across the AN weight spectrum. We aimed to investigate fasting and post-prandial concentrations of appetite-regulating hormones - peptide YY (PYY), cholecystokinin (CCK), and ghrelin - among adolescent and young adult females across the AN weight spectrum, specifically those with AN and Atypical AN, and healthy controls (HC).

METHODS

Participants (N = 95; ages 11-22 years) included 33 with AN, 25 with Atypical AN, and 37 HC. AN was differentiated from Atypical AN by BMI < 10th percentile for age and sex (if <18 years) or < 18.5 kg/m2(if ≥18 years). Blood samples were collected fasting and 30, 60 and 120 minutes following a standardized meal to assess total PYY, CCK, and total ghrelin concentrations.

RESULTS

Median fasting and post-prandial PYY concentrations were significantly higher in AN vs. HC with medium differences (p = .001-.006, r = .34-.43). Atypical AN had significantly higher PYY concentrations compared to HC at T-0 (p = .027, r = .29) only, and did not significantly differ from concentrations in AN (p = .105-.413, r = .11-.22). Area under the curve (AUC; p = .001; r = .41) and peak PYY concentrations (p = .003; r = .41) were also significantly higher in AN vs. HC with medium differences. There were no significant differences in fasting (p = .885) or post-prandial (p = .846-.993) CCK concentrations across groups. AN and Atypical AN each had significantly higher ghrelin concentrations than HC with small to medium effect (AN vs HC p = .004-.025, r = .27-.36; Atypical AN vs HC p = .004-.033; r = .28-.28).

CONCLUSIONS

Higher peak postprandial concentrations of anorexigenic PYY in AN (compared to HC) may facilitate dietary restriction and contribute to maintenance of lower weight. Lack of CCK suppression in AN is maladaptive in the context of undernutrition. Despite continued restriction, ghrelin is adaptively higher in AN overall and may not be differentiated by weight status.

Momentary physiological indices related to eating disorders: A systematic and methodological review

Eating disorders (ED) are serious psychiatric illnesses, with no everyday support to intervene on the high rates of relapse. Understanding physiological indices that can be measured by wearable sensor technologies may provide new momentary interventions for individuals with ED. This systematic review, searching large databases, synthesises studies investigating peripheral physiological (PP) indices commonly included in wearable wristbands (heart rate [HR], heart rate variability [HRV], electrodermal activity [EDA], peripheral skin temperature [PST], and acceleration) in ED. Inclusion criteria included: (a) full peer-reviewed empirical articles in English; (b) human participants with active ED; and (c) containing one of five wearable physiological measures. Kmet risk of bias was assessed. Ninety-four studies were included (Anorexia nervosa [AN; N = 4418], bulimia nervosa [BN; N = 916], binge eating disorder [BED; N = 1604], other specified feeding and eating disorders [OSFED; N = 424], and transdiagnostic [N = 47]). Participants with AN displayed lower HR and EDA and higher HRV compared to healthy individuals. Those with BN showed higher HRV, and lower EDA and PST compared to healthy individuals. Other ED and Transdiagnostic samples showed mixed results. PP differences are indicated through various assessments in ED, which may suggest diagnostic associations, although more studies are needed to validate observed patterns. Results suggest important therapeutic potential for PP in ED, and larger studies including diverse participants and diagnostic groups are needed to fully uncover their role in ED.

Does hypoleptinemia trigger entrapment in anorexia nervosa? Etiological and clinical considerations

Based on the recent observation that human recombinant leptin (r-Met-hu-leptin; metreleptin) may induce a profound alleviation of the complex symptomatology of patients with anorexia nervosa (AN), we examine the implications for our conceptualisation of this eating disorder. Hypoleptinemia as a core endocrine feature of AN serves as a central and peripheral trigger of tissue-specific adaptations to starvation. In this narrative review, we argue that leptin deficiency may explain many of the puzzling features of this eating disorder. Weight loss can be viewed as a two-step process, with only the second step entailing hypoleptinemia and thereby the entrapment characteristic of AN. We discuss the central and peripheral distribution of leptin receptors and consider possible functional implications of hypoleptinemia. We contrast the slow psychological recovery of patients with AN and of people who experienced starvation upon weight recovery with the rapid onset of improvements upon off-label metreleptin treatment. Characteristics of the sex and age dependent secretion of leptin may contribute to the elevated vulnerability of young females to develop AN.

Do the therapeutic effects of psilocybin involve actions in the gut?

The psychedelic compound psilocybin has recently emerged as a therapeutic intervention for various mental health conditions. Psilocybin is a potent agonist of serotonin (5-HT) receptors (5-HTRs), which are expressed in the brain and throughout peripheral tissues, with particularly high expression in the gastrointestinal (GI) tract. However, no studies have investigated the possibility that peripheral actions of psilocybin may contribute to improvements in mental health outcomes. This is despite strong evidence for disturbed gut-brain signalling in conditions in which psilocybin is being tested clinically. In this Opinion, we highlight the likely actions of psychedelics in the gut and provide initial support for the premise that peripheral actions may be involved in rapid and long-term therapeutic effects. A greater understanding of all sites and modes of action will guide more targeted approaches to drug development.

The involvement of the adrenergic system in feeding and eating disorders. A systematic review

BACKGROUND

Adrenergic dysregulation has been proposed as a possible underlying mechanism in feeding and eating disorders (FED). This review aims to synthesise the current evidence on the role of adrenergic dysregulation in the pathogenesis and management of FED.

METHODS

A systematic review was conducted in MEDLINE, Cochrane Library, and Clinicaltrials.gov. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was adopted. Preclinical, clinical, and pharmacological studies assessing the adrenergic system in FED were included.

RESULTS

Thirty-one out of 1415 recognised studies were included. Preclinically, studies on adrenaline's anorectic impact, receptor subtypes, and effects on hepatic function in rats show that catecholamine anorexia is primarily alpha-adrenergic, whereas beta-adrenergic anorexia can be obtained only after puberty, implying an impact of sexual hormones. Clinically, catecholamine levels may be higher in FED patients than in healthy controls (HC). Individuals with anorexia nervosa (AN) may show higher epinephrine-induced platelet aggregability response than HC. Pharmacological trials suggest that the alpha-2-adrenergic medication clonidine may not lower AN symptoms, but agents regulating the adrenaline-noradrenaline neurotransmission (bupropion, reboxetine, duloxetine, sibutramine) have been found to improve binge eating symptoms.

CONCLUSION

Adrenergic dysregulation may be involved in the pathophysiology of FED. More research is needed to comprehend underlying mechanisms and treatment implications.

Pulse wave velocity during re-feeding and with weight gain in underweight female adolescents with anorexia nervosa

Anorexia Nervosa (AN) causes harmful underweight and important cardiovascular acute complications however less is known about longer-term cardiovascular risk. We measured carotid femoral pulse wave velocity (PWV) in a group of underweight young women with AN at baseline and weekly as they were refed and gained weight. PWV decreased over time and was negatively associated with increasing BMI and calorific meal content suggesting potential positive cardiovascular benefits for refeeding and weight gain in AN and supports current consensus for the importance of weight gain in underweight young women with AN.

Sensor Technology and Intelligent Systems in Anorexia Nervosa: Providing Smarter Healthcare Delivery Systems

Ubiquitous technology, big data, more efficient electronic health records, and predictive analytics are now at the core of smart healthcare systems supported by artificial intelligence. In the present narrative review, we focus on sensing technologies for the healthcare of Anorexia Nervosa (AN). We employed a framework inspired by the Interpersonal Neurobiology Theory (IPNB), which posits that human experience is characterized by a flow of energy and information both within us (within our whole body), and between us (in the connections we have with others and with nature). In line with this framework, we focused on sensors designed to evaluate bodily processes (body sensors such as implantable sensors, epidermal sensors, and wearable and portable sensors), human social interaction (sociometric sensors), and the physical environment (indoor and outdoor ambient sensors). There is a myriad of man-made sensors as well as nature-based sensors such as plants that can be used to design and deploy intelligent systems for human monitoring and healthcare. In conclusion, sensing technologies and intelligent systems can be employed for smarter healthcare of AN and help to relieve the burden of health professionals. However, there are technical, ethical, and environmental sustainability issues that must be considered prior to implementing these systems. A joint collaboration of professionals and other members of the society involved in the healthcare of individuals with AN can help in the development of these systems. The evolution of cyberphysical systems should also be considered in these collaborations.

Real-Life Self-Control Conflicts in Anorexia Nervosa: An Ecological Momentary Assessment Investigation

Background

Individuals with anorexia nervosa (AN) are often thought to show heightened self-control and increased ability to inhibit desires. In addition to inhibitory self-control, antecedent-focused strategies (e.g., cognitive reconstrual—the re-evaluation of tempting situations) might contribute to disorder maintenance and enable disorder-typical, maladaptive behaviors.

Methods

Over a period of 14 days, 40 acutely underweight young female patients with anorexia nervosa (AN) and 40 healthy control (HC) participants reported their affect and behavior in self-control situations via ecological momentary assessment during inpatient treatment (AN) and everyday life (HC). Data were analyzed via hierarchical analyses (linear and logistic modeling).

Results

Conflict strength had a significantly lower impact on self-control success in AN compared to HC. While AN and HC did not generally differ in the number or strength of self-control conflicts or in the percentage of self-control success, AN reported self-controlled behavior to be less dependent on conflict strength.

Conclusions

While patients with AN were not generally more successful at self-control, they appeared to resolve self-control conflicts more effectively. These findings suggest that the magnitude of self-control conflicts has comparatively little impact on individuals with AN, possibly due to the use of antecedent-focused strategies. If confirmed, cognitive-behavioral therapy might focus on and help patients to exploit these alternative self-control strategies in the battle against their illness.

Anorexia nervosa and gut microbiome: implications for weight change and novel treatments

INTRODUCTION

Host-microbiota interactions may be involved in many physical and psychological functions ranging from the digestion of food, maintenance of immune homeostasis, to the regulation of mood and cognition. Microbiome dysbiosis has been consistently described in many diseases. The pathogenesis and weight regulation mechanism in anorexia nervosa (AN) also seem to be implicated in the dynamic bidirectional adjustment of the microbiota-gut-brain axis. This review aims at elucidating this relationship.

AREA COVERED

This review starts with a description of pathogenic gut-brain pathways. Next, we focus on the latest research on the associations between gut microbiota and weight change in the condition of AN. The strategies to alter the intestinal microbiome for the treatment of this disorder are discussed, including dietary, probiotics, prebiotics, synbiotics, and fecal microbiota transplantation.

EXPERT OPINION

Gut microbiome is inextricably linked to AN. It may regulate weight gain in the process of refeeding via the microbiota-gut-brain axis, while the specific mechanism has yet to be clearly established. In the future, a better understanding of gut microbiome could have implications for developing microbiome-based prevention, diagnostics and therapies.

Autonomic nervous system function in women with anorexia nervosa

PURPOSE

Abnormalities in autonomic function have been observed in people with anorexia nervosa. However, the majority of investigations have utilised heart rate variability as the sole assessment of autonomic activity. The current study utilised a variety of methodologies to assess autonomic nervous system function in women with a current diagnosis of anorexia, a past diagnosis of anorexia who were weight-restored, and healthy controls.

METHODS

The sample included 37 participants: 10 participants with anorexia, 17 weight-restored participants (minimum body mass index > 18.5 for minimum of 12 months) and 10 controls. Assessments of autonomic function included muscle sympathetic nerve activity (MSNA) using microneurography, heart rate variability, baroreflex sensitivity, blood pressure variability, head-up tilt table test, sudomotor function and assessment of plasma catecholamines.

RESULTS

MSNA (bursts/min) was significantly decreased in both anorexia (10.22 ± 6.24) and weight-restored (17.58 ± 1.68) groups, as compared to controls (23.62 ± 1.01, p < 0.001 and p = 0.033, respectively). Participants with anorexia had a significantly lower standard deviation in heart rate, lower blood pressure variability and decreased sudomotor function as compared to controls. Weight-restored participants demonstrated decreased baroreflex sensitivity in response to head-up tilt as compared to controls.

CONCLUSION

Women with a current or previous diagnosis of anorexia have significantly decreased sympathetic activity, which may reflect a physiological response to decreased energy intake. During the state of starvation, women with anorexia also displayed decreased sudomotor function. The consequences of a sustained decrease in MSNA are unknown, and future studies should investigate autonomic function in long-term weight-restored participants to determine whether activity returns to normal.

Arterial stiffness in underweight and weight-restored anorexia nervosa

Cardiovascular complications have been demonstrated in patients with anorexia nervosa (AN) in both the state of starvation and during weight restoration, however, the underlying mechanisms remain unclear. The current study aimed to assess arterial stiffness via carotid-femoral pulse wave velocity (cfPWV) in the acute and weight-restored states of AN. The study also aimed to determine the association between psychological distress and cfPWV. The sample included 37 participants; 10 participants with AN, 17 who were weight-restored (AN-WR; minimum body mass index >18.5 for at least 12 months) and 10 healthy controls (HCs). cfPWV via applanation tonometry was conducted to assess arterial stiffness. Psychological distress was assessed using the depression anxiety stress scale (DASS-21) and the state-trait anxiety inventory (STAI). Between-group comparisons were performed to determine differences between groups, a two-stage hierarchical regression model was performed to determine the contribution of physiological and psychological variables on cfPWV and correlation analyses were also performed. Vascular stiffness was significantly increased in the AN and AN-WR groups, relative to HCs. The total DASS score was the only significant predictor of cfPWV across the sample. There were positive associations between cfPWV and depression, anxiety and stress, as assessed by the DASS. Furthermore, cfPWV was positively associated with STAI trait anxiety. Arterial stiffness was increased in individuals in the acute and weight-restored states of AN, demonstrating early signs of the development of arteriosclerotic cardiovascular disease. Increased arterial stiffness was associated with increased psychological distress, which may be a contributing mechanism to the increased cardiovascular risk in AN.