Shared Dysregulation of Homeostatic Brain-Body Pathways in Depression and Type 2 Diabetes

Social determinants of inflammatory markers linking depression and type 2 diabetes among women: A scoping review

OBJECTIVE

Inflammation is implicated in the pathophysiology of depression and type 2 diabetes (T2D) and is linked to social determinants of health (SDoH) associated with socioeconomic disadvantage. The objective of this review is to identify and map the range of SDoHs associated with inflammation in depression, T2D, or their co-occurrence among women.

METHODS

PubMed, CINAHL, PsychINFO, and Web of Science were searched March-July 2023 to identify studies where 1) an SDoH was a predictor or independent variable, 2) depression or T2D was a clinical focus, 3) inflammatory markers were collected, and 4) analysis was specific to women. We used the National Institute on Minority Health and Health Disparities research framework to guide searching SDoHs, organize findings, and identify gaps.

RESULTS

Of the 1135 studies retrieved, 46 met criteria. Within the reviewed studies, the most used inflammatory measures were C-reactive protein, interleukin-6, and tumor necrosis factor-α, and the most studied SDoHs were early life stress and socioeconomic status. Individual and interpersonal-level variables comprised the bulk of SDoHs in the included studies, while few to no studies examined built environment (n = 6) or health system level (n = 0) factors. Disadvantageous SDoHs were associated with higher levels of inflammation across the included studies.

CONCLUSION

The scope and intersection of depression and T2D represent a syndemic that contributes to and results from socioeconomic inequities and disproportionately affects women. Simultaneous inclusion of social and inflammatory measures, particularly understudied SDoHs, is needed to clarify potent targets aimed at advancing health and equity.

Gut microbiota and type 2 diabetes mellitus: a focus on the gut-brain axis

Type 2 diabetes mellitus (T2DM) has become one of the most serious public healthcare challenges, contributing to increased mortality and disability. In the past decades, significant progress has been made in understanding the pathogenesis of T2DM. Mounting evidence suggested that gut microbiota (GM) plays a significant role in the development of T2DM. Communication between the GM and the brain is a complex bidirectional connection, known as the "gut-brain axis," via the nervous, neuroendocrine, and immune systems. Gut-brain axis has an essential impact on various physiological processes, including glucose metabolism, food intake, gut motility, etc. In this review, we provide an outline of the gut-brain axis. We also highlight how the dysbiosis of the gut-brain axis affects glucose homeostasis and even results in T2DM.

Insomnia and common mental disorder among patients with pre-existing chronic non-communicable diseases in southern Ethiopia: a survey during COVID-19 pandemic

Background

COVID-19 has been causing significant mental health problems and other health-related issues. Despite the fact that COVID-19 has a significant impact on chronic disease patients, there is scant research on insomnia, common mental health disorders (CMD), and their associated factors among chronic disease patients.

Objective

The purpose of this study was to assess the prevalence of insomnia and common mental disorders (CMD) and their associated factors among patients with pre-existing chronic NCDs in Sidama, southern Ethiopia.

Methods

A multicenter cross-sectional study was undertaken between June 1 and September 1, 2021. The study included 633 participants. CMD and insomnia were assessed using a 20-item Self-Reported Questionnaire (SRQ-20) and a 7-item Insomnia Severity Index (ISI) scale, respectively. To describe the various variables, descriptive statistics were used. We performed multivariable logistic regression analysis to identify independent factors associated with CMD and insomnia. A value of p < 0.05 was considered statistically significant at a 95% confidence interval.

Results

The prevalence of insomnia and CMD was found to be 39.3% and 46.8%, respectively. Being merchant (AOR = 0.33; 95% CI = 0.13, 0.82), having a diagnosis of diabetes mellitus (AOR = 1.89; 95% CI = 1.04, 3.46), comorbid diagnosis (AOR = 3.96; 95% CI = 2.27, 6.89), low social support (poor (AOR = 3.37; 95% CI = 1.51, 7.57) and moderate (AOR = 3.13; 95% CI = 1.46, 6.69)), symptoms of insomnia (AOR = 12.08; 95% CI = 7.41, 19.72) and poor quality of life (QOL) (AOR = 1.67; 95% CI = 1.04, 2.72) were independent predictors of CMD. We also found out that, having cardiovascular disorders (CVDs) (AOR = 2.48; 95% CI = 1.18, 5.19), CMD (AOR = 12.09; 95% CI = 7.46, 19.61), and poor QOL (AOR = 2.04; 95% CI = 1.27, 3.26) were significantly associated with insomnia symptoms.

Conclusion

Our study suggests that substantially high prevalence of CMD and insomnia. Significant association between CMD and occupation, diagnosis, comorbidity, social support, insomnia, and QOL were found. We also revealed that having CVDs, CMD, and poor QOL were significantly associated with insomnia symptoms. Therefore, dealing with the mental health problems of patients with chronic NCDs is an essential component of public health intervention during the COVID-19 pandemic.

Antidepressants and type 2 diabetes: highways to knowns and unknowns

Type 2 diabetes (T2D) is a metabolic disease caused by the development of insulin resistance (IR), relative insulin deficiency, and hyperglycemia. Hyperglycemia-induced neurochemical dysregulation activates the progression of depression in T2D patients. Therefore, management of depression by antidepressant agents improves glucose homeostasis and insulin sensitivity. However, prolong use of antidepressant drugs may increase the risk for the development of T2D. However, there is strong controversy concerning the use of antidepressant drugs in T2D. Therefore, this review try to elucidate the potential effects of antidepressant drugs in T2D regarding their detrimental and beneficial effects.

Effects of long-chain omega-3 polyunsaturated fatty acids on reducing anxiety and/or depression in adults; A systematic review and meta-analysis of randomised controlled trials

The omega-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic- (EPA), docosahexaenoic- (DHA) and docosapentaenoic acid (DPAn-3) are promising therapeutic options in reducing the severity of anxious and depressive symptoms. However, meta-analyses of randomised controlled trials (RCTs) yield mixed findings. This systematic review and meta-analysis reviewed the evidence and assessed the efficacy of EPA, DHA and DPAn-3 in reducing the severity of anxiety and depression with specific consideration to methodological complications unique to the field e.g., dose and ratio of omega-3 PUFAs and placebo composition. Random-effects meta-analysis of ten RCTs comprising 1426 participants revealed statistically significant reduction in depression severity with EPA-enriched interventions at proportions ≥ 60% of total EPA + DHA (SMD: -0.36; 95% CI: -0.68, -0.05; p = 0.02) (I² = 86%) and EPA doses between ≥ 1 g/day and < 2 g/day (SMD: -0.43; 95% CI: -0.79, -0.07; p = 0.02) (I² = 88%); however, EPA doses ≥ 2 g/day were not associated with significant therapeutic effects (SMD: -0.20; 95% CI: -0.48, 0.07; p = 0.14). Only one study reported significant reduction in anxiety severity with 2.1 g/day EPA (85.6% of total EPA + DHA), therefore meta-analysis was not possible. No trials administering DPAn-3 were identified. Visual examination of the funnel plot revealed asymmetry, suggesting publication bias and heterogeneity amongst the trials. These results support the therapeutic potential of EPA in depression at proportions ≥ 60% of total EPA + DHA and doses ≥ 1 g/day and < 2 g/day. The observed publication bias and heterogeneity amongst the trials reflect the need for more high-quality trials in this area with consideration to the unique nature of omega-3 PUFAs research, to more fully elucidate the therapeutic potential of EPA, DHA and DPAn-3.

Manifold epigenetics: A conceptual model that guides engineering strategies to improve whole-body regenerative health

Despite the promising advances in regenerative medicine, there is a critical need for improved therapies. For example, delaying aging and improving healthspan is an imminent societal challenge. Our ability to identify biological cues as well as communications between cells and organs are keys to enhance regenerative health and improve patient care. Epigenetics represents one of the major biological mechanisms involving in tissue regeneration, and therefore can be viewed as a systemic (body-wide) control. However, how epigenetic regulations concertedly lead to the development of biological memories at the whole-body level remains unclear. Here, we review the evolving definitions of epigenetics and identify missing links. We then propose our Manifold Epigenetic Model (MEMo) as a conceptual framework to explain how epigenetic memory arises and discuss what strategies can be applied to manipulate the body-wide memory. In summary we provide a conceptual roadmap for the development of new engineering approaches to improve regenerative health.

Targeting the Arginine Vasopressin V1b Receptor System and Stress Response in Depression and Other Neuropsychiatric Disorders

A healthy stress response is critical for good mental and overall health and promotes neuronal growth and adaptation, but the intricately balanced biological mechanisms that facilitate a stress response can also result in predisposition to disease when that equilibrium is disrupted. The hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine system plays a critical role in the body's response and adaptation to stress, and vasopressinergic regulation of the HPA axis is critical to maintaining system responsiveness during chronic stress. However, exposure to repeated or excessive physical or emotional stress or trauma can shift the body's stress response equilibrium to a "new normal" underpinned by enduring changes in HPA axis function. Exposure to early life stress due to adverse childhood experiences can also lead to lasting neurobiological changes, including in HPA axis function. HPA axis impairment in patients with depression is considered among the most reliable findings in biological psychiatry, and chronic stress has been shown to play a major role in the pathogenesis and onset of depression and other neuropsychiatric disorders. Modulating HPA axis activity, for example via targeted antagonism of the vasopressin V_1b receptor, is a promising approach for patients with depression and other neuropsychiatric disorders associated with HPA axis impairment. Despite favorable preclinical indications in animal models, demonstration of clinical efficacy for the treatment of depressive disorders by targeting HPA axis dysfunction has been challenging, possibly due to the heterogeneity and syndromal nature of depressive disorders. Measures of HPA axis function, such as elevated cortisol levels, may be useful biomarkers for identifying patients who may benefit from treatments that modulate HPA axis activity. Utilizing clinical biomarkers to identify subsets of patients with impaired HPA axis function who may benefit is a promising next step in fine-tuning HPA axis activity via targeted antagonism of the V_1b receptor.

The TELE-DD Randomised Controlled Trial on Treatment Adherence in Patients with Type 2 Diabetes and Comorbid Depression: Clinical Outcomes after 18-Month Follow-Up

Clinical depression is associated with poorer adherence to hypoglycaemic medication in patients with diabetes mellitus, leading to poorer glycaemic control, diabetes management, and increased complications. The main aim of the TELE-DD trial was to demonstrate the efficacy of a proactive and psychoeducational telephonic intervention based on motivational interviewing and collaborative care to reduce nonadherence and improve prognosis in individuals with diabetes mellitus and concurrent depression.

DESIGN

The TELE-DD project is a three-phased prospective study including a nested randomised controlled trial.

METHODS

The baseline cohort included the entire population of adult patients diagnosed with type 2 diabetes and concurrent depression. A randomised controlled trial was conducted in a selection of patients from the baseline cohort, distributed into a control group (n = 192) and an intervention group (n = 192). Monthly telephonic interventions delivered by specifically trained research nurses were centred on a psychoeducational individualised monitoring protocol including motivational interviewing and collaborative care strategies. Clinical and patient-centred data were systematically collected during an 18-month follow-up including HbA1c, Patient Health Questionnaire, and the Diabetes Distress Scale.

RESULTS

During the trial, 18-month follow-up HbA1C levels significantly (p < 0.001) decreased in the intervention group at every follow-up from an average of 8.72 (SD:1.49) to 7.03 (SD:1.09), but slightly increased in the control group from 8.65 (SD:1.40) to 8.84 (SD:1.38). Similar positive results were obtained in depression severity and diabetes distress, LDL-cholesterol, and systolic and diastolic blood pressure, but only at the 18-month follow-up in body mass index reduction.

CONCLUSIONS

This is the first trial to concurrently decrease biological and psychological outcomes with a monthly brief telephonic intervention, pointing out that a combined biopsychosocial intervention and collaborative care strategy is essential for current world health challenges.

CLINICALTRIALS

gov Identifier: NCT04097483. Patient or Public Contribution: Diabetic patients not belonging to the TELE-DD population or trial sample were consulted during the study design to review and guarantee the clarity and understanding of the trial psychoeducational materials.

Identifying pathways to early-onset metabolic dysfunction, insulin resistance and inflammation in young adult inpatients with emerging affective and major mood disorders

AIM

Young people with common mood disorders face the prospect of shortened life expectancy largely due to premature cardiovascular disease. Metabolic dysfunction is a risk factor for premature cardiovascular disease. There is an ongoing debate whether metabolic dysfunction can be simply explained by weight gain secondary to psychotropic medications or whether shared genetic vulnerability, intrinsic immune-metabolic disturbances or other system perturbations (e.g. dysregulated sympathetic nervous system, circadian dysfunction) are more relevant determinants of premature cardiovascular disease. Thus, we aimed to investigate underlying drivers of metabolic dysfunction and premature cardiovascular disease in young people in the early phases of common mood disorders.

METHODS

We evaluated the relationships between insulin resistance (assessed by HOMA2-IR) and body mass index (BMI), sex, diagnosis, medication, inflammatory markers and hormonal factors in 327 inpatients with emerging affective and major mood disorders admitted to the Young Adult Mental Health Unit, St Vincent's Private Hospital, Sydney.

RESULTS

While HOMA2-IR scores were positively associated with BMI (r_s  = 0.465, p < .001), they were also higher in those prescribed mood stabilizers (p = .044) but were not associated with specific diagnoses, other medication types or the number of prescribed medications. Further, high-sensitivity C-reactive protein levels (but not thyroid-stimulating hormone and ferritin levels) were positively associated with HOMA2-IR (r_s  = 0. 272, p < .001) and BMI (r_s  = . 409, p < .001).

CONCLUSIONS

In addition to BMI, other non-specific markers of inflammation are associated with early metabolic dysfunction in young people with emerging affective and major mood disorders.

The interface of COVID-19, diabetes, and depression

Comorbid diabetes with depression is a challenging and often under-recognized clinical problem. During the current COVID-19 pandemic, a communicable disease is thriving on the increasing incidences of these non-communicable diseases. These three different health problems are bidirectionally connected forming a vicious cycle. Firstly, depressed individuals show a higher risk of developing diabetes and patients with diabetes have a higher risk of developing symptoms of depression. Secondly, patients with diabetes have a higher risk of developing severe COVID-19 as well as of experiencing breakthrough infections. Thirdly, in both patients with type 2 diabetes and in COVID-19 survivors the prevalence of depression seems to be increased. Fourthly, lockdown and quarantine measurements during the COVID-19 pandemic has led to an increase in depression. Therefore, it is of importance to increase the awareness of this interface between depression, diabetes and COVID-19. Finally, as symptoms of post-COVID, diabetes and depression may be overlapping, there is a need for educating skilled personnel in the management of these comorbidities.

The TELE-DD project on treatment nonadherence in the population with type 2 diabetes and comorbid depression

Diabetic patients have increased depression rates, diminished quality of life, and higher death rates due to depression comorbidity or diabetes complications. Treatment adherence (TA) and the maintenance of an adequate and competent self-care are crucial factors to reach optimal glycaemic control and stable quality of life in these patients. In this report, we present the baseline population analyses in phase I of the TELE-DD project, a three-phased population-based study in 23 Health Centres from the Aragonian Health Service Sector II in Zaragoza, Spain. The objectives of the present report are: (1) to determine the point prevalence of T2D and clinical depression comorbidity and treatment nonadherence; (2) to test if HbA1c and LDL-C, as primary DM outcomes, are related to TA in this population; and (3) to test if these DM primary outcomes are associated with TA independently of shared risk factors for DM and depression, and patients' health behaviours. A population of 7,271 patients with type-2 diabetes and comorbid clinical depression was investigated for inclusion. Individuals with confirmed diagnoses and drug treatment for both illnesses (n = 3340) were included in the current phase I. A point prevalence of 1.9% was found for the T2D-depression comorbidity. The prevalence of patients nonadherent to treatment for these diseases was 35.4%. Multivariate analyses confirmed that lower diabetes duration, increased yearly PCS visits, HbA1c and LDL-C levels were independently related to treatment nonadherence. These findings informed the development of a telephonic monitoring platform for treatment of nonadherence for people with diabetes and comorbid depression and further trial, cost-effectiveness, and prognostic studies (phases II and III).

Distress and Type 2 Diabetes Self-Care: Putting the Pieces Together

BACKGROUND

Conflicting research emphasizes depression, diabetes distress, or well-being in relation to diabetes self-care and risk for poor health outcomes.

PURPOSE

The purpose of this study was to test whether a latent variable for general psychological distress derived from shared variance of depression symptoms, diabetes distress, and well-being predicts a latent variable of diabetes self-care and to examine evidence for unique effects once shared effects are adjusted for.

METHODS

Adults with suboptimally controlled diabetes were recruited from the South Bronx, NY, for a telephonic diabetes self-management support trial. Baseline diabetes self-care, medication adherence, depression symptoms, diabetes distress, and well-being were measured by validated self-report. Structural equation modeling specified a latent variable for general psychological distress derived from shared variance of depression symptoms, diabetes distress, and well-being. Diabetes self-care was a latent variable indicated by diet, glucose self-monitoring, and medication adherence.

RESULTS

Participants (N = 627, 65% female) were predominantly ethnic minority (70% Hispanic; 45% Black) and 77% reported household income <$20K/year. Mean (standard deviation) age = 56 (12) years; A1c = 9.1% (1.9%); body mass index = 32 (8) kg/m2. The latent variable for psychological distress was a robust predictor of poorer diabetes self-care (coefficient = -0.59 [confidence interval = -0.71, -0.46], p < .001) with good model fit. Unique paths from depression symptoms, diabetes distress, and well-being (all ps > .99) to self-care were not observed.

CONCLUSIONS

In this population of disadvantaged adults with suboptimally controlled diabetes, general psychological distress was strongly associated with poorer diabetes self-care and fully accounted for the effects of depression, diabetes distress, and positive well-being. This suggests that general distress may underlie previously reported associations between these constructs and diabetes self-care.

Depression in Youth-Onset Type 2 Diabetes

PURPOSE OF REVIEW

The current review summarizes extant knowledge regarding the prevalence of depression in youth-onset type 2 diabetes (T2D) and how depression might impact glycemic control through stress-related behavioral and physiological mechanisms. The current review also discusses depression intervention studies in adult-onset T2D, as there are no such studies in youth-onset T2D, and provides recommendations for clinical research.

RECENT FINDINGS

The prevalence of elevated depression symptoms in youth-onset T2D is approximately 20%. Some studies suggest depression may negatively impact glycemic control through inadequate medication adherence and disordered eating, but there is a dearth of studies investigating associations with depression and physical activity/sedentary time, sleep, and stress-related physiological mechanisms. In adult-onset T2D, evidence-based behavioral interventions tailored to address diabetes-related issues have shown positive effects for depression and glycemic control. Future research is needed to characterize the epidemiology of depression in youth-onset T2D and test interventions to improve depression, glycemic control, and health outcomes in this specific pediatric population.

Depressive symptoms mediate the relationship between sleep disturbances and type 2 diabetes mellitus

BACKGROUND

The current study aimed at examining whether individuals diagnosed with type 2 diabetes mellitus (T2DM) have more severe sleep disturbances compared to individuals who are healthy or have prediabetes and whether depressive symptoms mediate the relationship between sleep disturbances and having T2DM.

METHODS

T2DM patients (n = 107) were compared to individuals with prediabetes (n = 48) and healthy individuals (n = 154) regarding the severity of depressive symptoms, measured via the Beck Depression Inventory-II (BDI-II), and sleep disturbances, measured via the Mini Sleep Questionnaire (MSQ). Mediation analysis examined whether depressive symptoms mediated the relationship between sleep disturbances and T2DM.

RESULTS

Compared to healthy individuals and individuals with prediabetes, T2DM patients had more depressive symptoms and higher levels of insomnia, hypersomnia, and overall more sleep disturbances. The prediabetes group did not differ from the healthy control group on these measures, and these groups were thus combined for further analysis. Sleep disturbances were correlated with severity of depressive symptoms (r =0.43). After controlling for age, gender, and ethnic background, both severity of sleep disturbances (odds ratio [OR]: 1.04; 95% CI: 1.01-1.07, P <.001) and severity of depressive symptoms (OR: 8.54, 95% CI: 3.37-21.69, P <.001) predicted T2DM. Depression symptoms mediated the relationship between sleep disturbances and T2DM, whereas the direct relationship between sleep disturbances and T2DM was nonsignificant.

CONCLUSIONS

The findings imply that sleep disturbances may contribute to the development and progression of T2DM by promoting depressive symptoms. Thus, treatments for the emotional distress associated with sleep disturbances may help reduce the risk for T2DM and the progression of the disease.

How 25 years of psychosocial research has contributed to a better understanding of the links between depression and diabetes

This narrative review of the literature provides a summary and discussion of 25 years of research into the complex links between depression and diabetes. Systematic reviews have shown that depression occurs more frequently in people with type 1 or type 2 diabetes compared with people without diabetes. Currently, it remains unclear whether depression is also more common in people with impaired glucose metabolism or undiagnosed type 2 diabetes compared with people without diabetes. More prospective epidemiological research into the course of depression and an exploration of mechanisms in individuals with diabetes are needed. Depression in diabetes is associated with less optimal self-care behaviours, suboptimal glycaemic control, impaired quality of life, incident micro- and macrovascular diseases, and elevated mortality rates. Randomized controlled trails concluded that depression in diabetes can be treated with antidepressant medication, cognitive-behavioural therapy (individual, group-based or web-based), mindfulness-based cognitive therapy and stepped care. Although big strides forward have been made in the past 25 years, scientific evidence about depression in diabetes remains incomplete. Future studies should investigate mechanisms that link both conditions and test new diabetes-specific web- or app-based interventions for depression in diabetes. It is important to determine whether treatment or prevention of depression prevents future diabetes complications and lowers mortality rates.

Plant- and Nutraceutical-based Approach for the Management of Diabetes and its Neurological Complications: A Narrative Review

Diabetes is an important metabolic disease affecting many organs and systems in the body. The nervous system is one of the body systems affected by diabetes and neuropathic complications are troublesome in diabetic patients with many consequences. As diabetes has deleterious influences almost on bodily systems, an integrative approach seems to be necessary accepting the body as a whole and integrating body systems with lifestyle and living environment. Like some traditional health systems such as Ayurveda, integrative approach includes additional modalities to overcome both diabetes and diabetic complications. In general, these modalities consist of nutraceuticals and plant products. Prebiotics and probiotics are two types of nutraceuticals having active ingredients, such as antioxidants, nutrient factors, microorganisms, etc. Many plants are indicated for the cure of diabetes. All of these may be employed in the prevention and in the non-pharmacological management of mildto- moderate diabetes. Severe diabetes should require appropriate drug selection. Being complementary, prebiotics, probiotics, plants and exercise may be additive for the drug therapy of diabetes. Similarly, there are complementary approaches to prevent and cure neurological and/or behavioral manifestations of diabetes, which may be included in therapy and prevention plans. A scheme is given for the prevention and therapy of comorbid depression, which is one of the most common behavioral complications of diabetes. Within this scheme, the main criterion for the selection of modalities is the severity of diseases, so that personalized management may be developed for diabetic patients using prebiotics and probiotics in their diets, plants and drugs avoiding possible interactions.

What is the prevalence, and what are the clinical correlates, of insulin resistance in young people presenting for mental health care? A cross-sectional study

OBJECTIVES

To report the distribution and predictors of insulin resistance (IR) in young people presenting to primary care-based mental health services.

DESIGN

Cross-sectional.

SETTING

Headspace-linked clinics operated by the Brain and Mind Centre of the University of Sydney.

PARTICIPANTS

768 young people (66% female, mean age 19.7±3.5, range 12-30 years).

MAIN OUTCOME MEASURES

IR was estimated using the updated homeostatic model assessment (HOMA2-IR). Height and weight were collected from direct measurement or self-report for body mass index (BMI).

RESULTS

For BMI, 20.6% of the cohort were overweight and 10.2% were obese. However, <1% had an abnormally high fasting blood glucose (>6.9 mmol/L). By contrast, 9.9% had a HOMA2-IR score >2.0 (suggesting development of IR) and 11.7% (n=90) had a score between 1.5 and 2. Further, there was a positive correlation between BMI and HOMA2-IR (r=0.44, p<0.001). Participants in the upper third of HOMA2-IR scores are characterised by younger age, higher BMIs and depression as a primary diagnosis. HOMA2-IR was predicted by younger age (β=0.19, p<0.001) and higher BMI (β=0.49, p<0.001), together explaining 22% of the variance (F_(2,361)=52.1, p<0.001).

CONCLUSIONS

Emerging IR is evident in a significant subgroup of young people presenting to primary care-based mental health services. While the major modifiable risk factor is BMI, a large proportion of the variance is not accounted for by other demographic, clinical or treatment factors. Given the early emergence of IR, secondary prevention interventions may need to commence prior to the development of full-threshold or major mood or psychotic disorders.

Harnessing the Power of Microbiome Assessment Tools as Part of Neuroprotective Nutrition and Lifestyle Medicine Interventions

An extensive body of evidence documents the importance of the gut microbiome both in health and in a variety of human diseases. Cell and animal studies describing this relationship abound, whilst clinical studies exploring the associations between changes in gut microbiota and the corresponding metabolites with neurodegeneration in the human brain have only begun to emerge more recently. Further, the findings of such studies are often difficult to translate into simple clinical applications that result in measurable health outcomes. The purpose of this paper is to appraise the literature on a select set of faecal biomarkers from a clinician’s perspective. This practical review aims to examine key physiological processes that influence both gastrointestinal, as well as brain health, and to discuss how tools such as the characterisation of commensal bacteria, the identification of potential opportunistic, pathogenic and parasitic organisms and the quantification of gut microbiome biomarkers and metabolites can help inform clinical decisions of nutrition and lifestyle medicine practitioners.

Loss of eIF4E Phosphorylation Engenders Depression-like Behaviors via Selective mRNA Translation

The MAPK/ERK (mitogen-activated protein kinases/extracellular signal-regulated kinase) pathway is a cardinal regulator of synaptic plasticity, learning, and memory in the hippocampus. One of major endpoints of this signaling cascade is the 5′ mRNA cap binding protein eIF4E (eukaryotic Initiation Factor 4E), which is phosphorylated on Ser 209 by MNK (MAPK-interacting protein kinases) and controls mRNA translation. The precise role of phospho-eIF4E in the brain is yet to be determined. Herein, we demonstrate that ablation of eIF4E phosphorylation in male mice (4Eki mice) does not impair long-term spatial or contextual fear memory, or the late phase of LTP. Using unbiased translational profiling in mouse brain, we show that phospho-eIF4E differentially regulates the translation of a subset of mRNAs linked to inflammation, the extracellular matrix, pituitary hormones, and the serotonin pathway. Consequently, 4Eki male mice display exaggerated inflammatory responses and reduced levels of serotonin, concomitant with depression and anxiety-like behaviors. Remarkably, eIF4E phosphorylation is required for the chronic antidepressant action of the selective serotonin reuptake inhibitor fluoxetine. Finally, we propose a novel phospho-eIF4E-dependent translational control mechanism in the brain, via the GAIT complex (gamma IFN activated inhibitor of translation). In summary, our work proposes a novel translational control mechanism involved in the regulation of inflammation and depression, which could be exploited to design novel therapeutics.

SIGNIFICANCE STATEMENT We demonstrate that downstream of the MAPK (mitogen-activated protein kinase) pathway, eukaryotic Initiation Factor 4E (eIF4E) Ser209 phosphorylation is not required for classical forms of hippocampal LTP and memory. We reveal a novel role for eIF4E phosphorylation in inflammatory responses and depression-like behaviors. eIF4E phosphorylation is required for the chronic action of antidepressants, such as fluoxetine in mice. These phenotypes are accompanied by selective translation of extracellular matrix, pituitary hormones, and serotonin pathway genes, in eIF4E phospho-mutant mice. We also describe a previously unidentified translational control mechanism in the brain, whereby eIF4E phosphorylation is required for inhibiting the translation of gamma IFN activated inhibitor of translation element-containing mRNAs. These findings can be used to design novel therapeutics for depression.