Growth factors in anorexia nervosa: a systematic review and meta-analysis of cross-sectional and longitudinal data

Longitudinal changes in brain-derived neurotrophic factor (BDNF) but not cytokines contribute to hippocampal recovery in anorexia nervosa above increases in body mass index

BACKGROUND

Physical sequelae of anorexia nervosa (AN) include a marked reduction in whole brain volume and subcortical structures such as the hippocampus. Previous research has indicated aberrant levels of inflammatory markers and growth factors in AN, which in other populations have been shown to influence hippocampal integrity.

METHODS

Here we investigated the influence of concentrations of two pro-inflammatory cytokines (tumor necrosis factor-alpha [TNF-α] and interleukin-6 [IL-6]) and brain-derived neurotrophic factor (BDNF) on the whole hippocampal volume, as well as the volumes of three regions (the hippocampal body, head, and tail) and 18 subfields bilaterally. Investigations occurred both cross-sectionally between acutely underweight adolescent/young adult females with AN (acAN; n = 82) and people recovered from AN (recAN; n = 20), each independently pairwise age-matched with healthy controls (HC), and longitudinally in acAN after partial renourishment (n = 58). Hippocampal subfield volumes were quantified using FreeSurfer. Concentrations of molecular factors were analyzed in linear models with hippocampal (subfield) volumes as the dependent variable.

RESULTS

Cross-sectionally, there was no evidence for an association between IL-6, TNF-α, or BDNF and between-group differences in hippocampal subfield volumes. Longitudinally, increasing concentrations of BDNF were positively associated with longitudinal increases in bilateral global hippocampal volumes after controlling for age, age2, estimated total intracranial volume, and increases in body mass index (BMI).

CONCLUSIONS

These findings suggest that increases in BDNF may contribute to global hippocampal recovery over and above increases in BMI during renourishment. Investigations into treatments targeted toward increasing BDNF in AN may be warranted.

Reversibility of disturbed pituitary function in pediatric conditions with psychological stressors: implications for clinical practice

The complex communication network between the central nervous system and the hypothalamic-pituitary axis forms the basis of endocrine functional plasticity, which facilitates adaptation to changing internal and external conditions, but also makes it vulnerable to the negative effects of stressful psychological factors. Herein, clinical conditions such as functional hypothalamic amenorrhea, eating disorders, growth faltering, post-traumatic stress disorder, and pubertal disorders that may emerge during childhood or adolescence, their origin possibly including psychological stressors, are analyzed regarding their genetic susceptibility and reversibility of endocrine function. A discussion on the optimization of therapeutic management defined by managing stress and maximizing the degree and rate of reversibility follows.

New understandings meet old treatments: putting a contemporary face on established protocols

In the twenty years since the publication of the most widely used treatment manuals describing evidence-based therapies for eating disorders, there have been some substantial advances in the field. New methods of delivering treatments have been trialled and our perception of mental health has advanced; significant cultural changes have led to shifts in our societal landscape; and new technologies have allowed for more in-depth research to be conducted. As a result, our understanding of eating disorders and their treatment has broadened considerably. However, these new insights have not necessarily been translated into improved clinical practice. This paper highlights the changes we consider to have had the greatest impact on our work as experienced clinical psychologists in the field and suggests a list of new learnings that might be incorporated into clinical practice and research design.

Novel treatments for anorexia nervosa: Insights from neuroplasticity research

OBJECTIVE

Treatment for anorexia nervosa (AN) remains challenging; there are no approved psychopharmacological interventions and psychotherapeutic strategies have variable efficacy. The investigation of evidence-based treatments has so far been compounded by an underdeveloped understanding into the neurobiological changes associated with the acute stages of AN. There is converging evidence of deficiencies in neuroplasticity in AN.

METHOD

This paper provides an overview of neuroimaging, neuropsychological, molecular and qualitative findings relating to neuroplasticity in AN, translating these findings to the identification of novel biological and psychotherapeutic strategies.

RESULTS

Novel psychopharmacological approaches that may ameliorate deficiencies in neuroplasticity include medications such as ketamine, psilocybin and human recombinant leptin. Anti-inflammatory medications and brain-derived neurotrophic factor mimetics may emerge as potential treatments following further research. Psychotherapeutic strategies that may target neuroplastic deficiencies, as well as having wider effects on identity, include imagery rescripting, memory specificity training, cognitive remediation therapy, exposure therapies, narrative therapies, cultural interventions (e.g. music and arts therapies) and yoga/mindfulness-based interventions.

CONCLUSIONS

Treatments specifically targeted towards mitigating the neurobiological sequalae of AN are warranted, and emerging neurobiological and neuropsychological research utilising longitudinal designs and large sample sizes, as well as initial feasibility studies, are necessitated to bolster translational efforts.

Endocrinology of Underweight and Anorexia Nervosa

More than any other mental illness, the course, prognosis, and therapy of anorexia nervosa are shaped by the physical changes associated with being underweight. This article provides an overview of the endocrine changes associated with malnutrition and underweight. This overview serves as a basis for understanding the other articles in this special issue, which deal with the health risks associated with being underweight. In this context, the differences between underweight in anorexia nervosa and in constitutional thinness are of particular importance in assessing the impact of intentional weight loss. In this context, the regulation of hunger and satiety deserves special interest, as this is the area in which the intentional influence on body weight comes into play. Clinical consequences on, for example, fertility, bone metabolism, the homeostasis of, for example, serum glucose levels, or body temperature have been observed for a long time; nonetheless, the medical responses, apart from vitamin supplementations and advice to gain weight, are still limited. Therefore, emphasis was placed on the potential improvement of outcomes through the administration of central or peripheral hormones. Studies were identified on PubMed via a selection of relevant keywords; original texts that were cited in reviews were studied where it was advantageous. This review found some promising data on bone health and the administration of transdermal oestrogen, which is not yet widely used, as well as distinct hormonal markers to differentiate between CT and AN. We concluded that the continuous efforts to investigate the role of endocrinology in underweight and/or anorexia nervosa lead to outcome benefits and that more and higher-powered studies are needed.

The role of the brain-derived neurotrophic factor (BDNF) in anorexia nervosa

The brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the neurotrophin family which plays a pivotal role in the differentiation, survival, and plasticity of neurons in the central nervous system. Evidence suggests that BDNF is an important signal molecule in the regulation of energy balance and thus implicated in body weight control. The discovery of BDNF-expressing neurons in the paraventricular hypothalamus which is important in the regulation of energy intake, physical activity, and thermogenesis gives more evidence to the suggested participation of BDNF in eating behavior. Until now it remains questionable whether BDNF can be used as a reliable biomarker for eating disorders such as anorexia nervosa (AN) as available findings on BDNF levels in patients with AN are ambiguous. AN is an eating disorder characterized by a pathological low body weight in combination with a body image disturbance typically developing during adolescence. A severe drive for thinness leads to restrictive eating behavior often accompanied by physical hyperactivity. During therapeutic weight restoration an increase of BDNF expression levels seems desirable as it might improve neuronal plasticity and survival which is essential for learning processes and thereby essential for the success of the psychotherapeutic treatment of patients. On the contrary, the well-known anorexigenic effect of BDNF might favor relapse in patients as soon as the BDNF levels significantly increase during weight rehabilitation. The present review summarizes the association between BDNF and general eating behavior and especially focuses on the eating disorder AN. In this regard findings from preclinical AN studies (activity-based anorexia model) are outlined as well.

The Role of Brain-Derived Neurotrophic Factor (BDNF) in Diagnosis and Treatment of Epilepsy, Depression, Schizophrenia, Anorexia Nervosa and Alzheimer's Disease as Highly Drug-Resistant Diseases: A Narrative Review

Brain-derived neurotrophic factor (BDNF) belongs to the family of neurotrophins, which are growth factors with trophic effects on neurons. BDNF is the most widely distributed neurotrophin in the central nervous system (CNS) and is highly expressed in the prefrontal cortex (PFC) and hippocampus. Its distribution outside the CNS has also been demonstrated, but most studies have focused on its effects in neuropsychiatric disorders. Despite the advances in medicine in recent decades, neurological and psychiatric diseases are still characterized by high drug resistance. This review focuses on the use of BDNF in the developmental assessment, treatment monitoring, and pharmacotherapy of selected diseases, with a particular emphasis on epilepsy, depression, anorexia, obesity, schizophrenia, and Alzheimer's disease. The limitations of using a molecule with such a wide distribution range and inconsistent method of determination are also highlighted.

Ketamine and Zinc: Treatment of Anorexia Nervosa Via Dual NMDA Receptor Modulation

Anorexia nervosa is a disorder associated with serious adverse health outcomes, for which there is currently considerable treatment ineffectiveness. Characterised by restrictive eating behaviours, distorted body image perceptions and excessive physical activity, there is growing recognition anorexia nervosa is associated with underlying dysfunction in excitatory and inhibitory neurometabolite metabolism and signalling. This narrative review critically explores the role of N-methyl-D-aspartate receptor-mediated excitatory and inhibitory neurometabolite dysfunction in anorexia nervosa and its associated biomarkers. The existing magnetic resonance spectroscopy literature in anorexia nervosa is reviewed and we outline the brain region-specific neurometabolite changes that have been reported and their connection to anorexia nervosa psychopathology. Considering the proposed role of dysfunctional neurotransmission in anorexia nervosa, the potential utility of zinc supplementation and sub-anaesthetic doses of ketamine in normalising this is discussed with reference to previous research in anorexia nervosa and other neuropsychiatric conditions. The rationale for future research to investigate the combined use of low-dose ketamine and zinc supplementation to potentially extend the therapeutic benefits in anorexia nervosa is subsequently explored and promising biological markers for assessing and potentially predicting treatment response are outlined.

"Your mind doesn't have room for anything else": a qualitative study of perceptions of cognitive functioning during and after recovery from anorexia nervosa

BACKGROUND

Past research has indicated the presence of cognitive difficulties in individuals with anorexia nervosa (AN), although it is unclear how these are experienced in real life. Moreover, it is unclear how and whether the experience of cognitive difficulties changes in nature and intensity over the course of the illness and following recovery.

METHODS

Twenty-one female participants (AN = 11; recovered AN = 10) participated in online semi-structured interviews, utilising open-ended questions and exploring topics relating to their experiences of their cognitive function, changes over time and their perspectives on the future. Reflexive thematic analysis was conducted on the resulting transcripts.

RESULTS

Six themes were identified, centred around the effects of the illness on mental and physical function, cognition, adaptation to living with the illness, similarities between AN and other psychopathology, tentative optimism for the future and recovery as a representation of liberation. Whilst respondents with AN appeared to perform remarkably well in their professional and educational lives, the cognitive difficulties were described as significantly impacting their ability to engage in life, particularly in the context of leisure and socialising. Respondents recovered from AN noted the importance of developing a non-AN identity as well as better emotion-regulation skills as central to recovery.

CONCLUSIONS

Whilst people with AN may be able to adapt their lives to the demands of the illness, they report significant cognitive difficulties that interfere with their engagement in many aspects of daily life. This should be considered by professionals working in the clinical management of AN. Treatments focused on ameliorating cognitive difficulties, and promoting emotional regulation and identity in AN are warranted.

Apelin-13 and Asprosin in Adolescents with Anorexia Nervosa and Their Association with Psychometric and Metabolic Variables

Anorexia nervosa (AN) is a widespread, metabo-psychiatric disorder with high relapse rates, comorbidity, and mortality. Many regulatory proteins and neurohormones studied to date play essential roles in the etiopathogenesis of eating disorders and the maintenance of psychopathological symptoms. Nevertheless, the regulatory and pathophysiological mechanisms of AN are still poorly understood. In the presented study, the plasma levels of apelin-13 (APE-13) and asprosin (ASP), as well as carbohydrate metabolism parameters and psychometric parameters, were evaluated in low-weight adolescent female patients with AN (AN1), after partial weight normalization (AN2) and in an age-matched healthy control group (CG) were evaluated. APE-13 levels were higher in the AN1 group than in the post-realimentation and the CG group. APE-13 levels were independent of insulin and glucose levels. Plasma ASP levels increased with increasing body weight in patients with AN, correlating with the severity of eating disorder symptoms in emaciation. The presented data suggest that APE-13 and ASP may be AN’s biomarkers-regulation of eating behavior by APE-13 and ASP, the close relationship between them and emotional behavior, and changes in neurohormone levels in patients with eating and affective disorders seem to support these hypotheses. Moreover, their plasma levels seem to be related to the severity of psychopathological symptoms of eating disorders.

Barking up the wrong biomarker? Correspondence to Shobeiri et al. (2022) "Serum and plasma levels of brain-derived neurotrophic factor in individuals with eating disorders (EDs): a systematic review and meta-analysis"

Despite intensified research efforts into the underlying (neuro-)biology of eating disorders (EDs), only few reliable biomarkers of diagnostic or prognostic value have been identified to date. One promising line of research has focused on the role of peripheral blood-based biomarkers as potential contributors to the complex pathophysiology of EDs. One such candidate marker is brain-derived neurotrophic factor (BDNF), a neurotrophin broadly implicated in neuronal plasticity and food-intake regulation. A growing number of studies have targeted BDNF in EDs; culminating in several recent well-powered and controlled case-control studies, comprehensive meta-analyses, and review articles. In the current correspondence, we aim to put the recent meta-analysis of Shobeiri et al. (J Eat Disord 10(1):105, 2022) into perspective and argue that the finding suggestive of lower BDNF concentrations across individuals with EDs in comparison to healthy controls needs to be interpreted with caution. While this finding is compatible with those from earlier meta-analyses, it may be biased due to several reasons; most notably by the applied study selection procedures, insufficient consideration of influential determinants of BDNF concentrations, and generalization of results across the ED spectrum without sufficient statistical power. Further controlled and comprehensive studies are necessary to establish BDNF as a clinically informative biomarker of EDs.

Serum and plasma levels of brain-derived neurotrophic factor in individuals with eating disorders (EDs): a systematic review and meta-analysis

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is essential for neuronal survival, differentiation, development, and plasticity. Evidence suggests that fluctuations in peripheral levels (i.e., plasma or serum) of BDNF are associated with eating behaviors. Nevertheless, the findings are inconsistent. The purpose of this study is to determine if serum or plasma levels of BDNF are altered in individuals with eating disorders (EDs) compared to controls.

METHODS

We conducted a systematic search of the core electronic medical databases from inception to March 2022 and identified observational studies that compared individuals with EDs to controls without EDs on serum or plasma levels of BDNF. R version 4.0.4 was used for all visualizations and calculations.

RESULTS

The current meta-analysis comprised 15 studies that fulfilled the inclusion criteria. Subjects with EDs (n = 795) showed lower BDNF levels compared to non-EDs controls (n = 552) (SMD: - 0.49, 95% CI [- 0.89; - 0.08], p-value = 0.01). Moreover, subgroup analysis was conducted based on the specimen (plasma and serum), which revealed no statistically significant difference in the levels of BDNF between the two subgroups (p-value = 0.92). Additionally, meta-regression results revealed that publication year, mean age of the individuals with EDs, NOS scores, and the number of individuals with EDs collectively accounted for 25.99% percent of the existing heterogeneity.

CONCLUSION

Lower BDNF levels are associated with EDs.

Short communication: Serum levels of brain-derived neurotrophic factor and association with pro-inflammatory cytokines in acute and recovered anorexia nervosa

Brain-derived neurotrophic factor (BDNF) is a neuroprotective molecule known to be involved in neuroplasticity, learning and memory. Additionally, it may mitigate the effects of inflammation on the brain. There is inconclusive evidence as to whether reductions in BDNF found in AN are related to features associated with the illness such as changes in inflammatory markers and comorbidities, and whether they persist after recovery. This cross-sectional study measured BDNF and 36 inflammatory markers in the serum of individuals recovered from AN (rec-AN; n = 24), with acute AN (n = 56), and healthy controls (n = 51). We (a) compared BDNF concentrations between AN, rec-AN and controls including four pre-determined covariates; (b) assessed the relationship between BDNF and body mass index, eating disorder (ED) psychopathology and depression; and (c) correlated BDNF with inflammatory markers, stratified by group. The AN group showed reductions in BDNF compared to controls and rec-AN. BDNF was negatively associated with depression and ED psychopathology in the whole sample, but not the AN sample. BDNF was positively correlated with three inflammatory markers in the control group (interleukin (IL)-8, Eotaxin-3, tumor necrosis factor (TNF)-α) and negatively correlated with one (IL-16). The only pro-inflammatory marker associated with BDNF in the AN group was TNF-α, and no pro-inflammatory markers were associated with BDNF in the rec-AN group. These results indicate that BDNF serum concentrations may be a state marker of AN. In people with acute AN, BDNF levels seem to be linked to TNF-α signalling. However, BDNF concentrations do not appear to reflect AN symptom severity.