A network analysis of depressive symptoms and metabolomics.

BACKGROUND: Depression is associated with metabolic alterations including lipid dysregulation, whereby associations may vary across individual symptoms. Evaluating these associations using a network perspective yields a more complete insight than single outcome-single predictor models. METHODS: We used data from the Netherlands Study of Depression and Anxiety (N = 2498) and leveraged networks capturing associations between 30 depressive symptoms (Inventory of Depressive Symptomatology) and 46 metabolites. Analyses involved 4 steps: creating a network with Mixed Graphical Models; calculating centrality measures; bootstrapping for stability testing; validating central, stable associations by extra covariate-adjustment; and validation using another data wave collected 6 years later. RESULTS: The network yielded 28 symptom-metabolite associations. There were 15 highly-central variables (8 symptoms, 7 metabolites), and 3 stable links involving the symptoms Low energy (fatigue), and Hypersomnia. Specifically, fatigue showed consistent associations with higher mean diameter for VLDL particles and lower estimated degree of (fatty acid) unsaturation. These remained present after adjustment for lifestyle and health-related factors and using another data wave. CONCLUSIONS: The somatic symptoms Fatigue and Hypersomnia and cholesterol and fatty acid measures showed central, stable, and consistent relationships in our network. The present analyses showed how metabolic alterations are more consistently linked to specific symptom profiles.

A cross-sectional study on fatigue, anxiety, and symptoms of depression and their relation with medical status in adult patients with Marfan syndrome. Psychological consequences in Marfan syndrome.

Marfan syndrome (MFS) is a connective tissue disorder affecting the cardiovascular, ocular, and skeletal system, which may be accompanied by psychological features. This study aimed to determine the prevalence of fatigue, anxiety, and symptoms of depression in MFS patients, and to assess the degree to which sociodemographic and clinical variables are associated with fatigue and psychological aspects. The prevalence of fatigue, anxiety, and symptoms of depression were assessed in two cohorts of MFS patients and compared with healthy controls. The checklist individual strength (CIS), and hospital anxiety and depression scale (HADS) questionnaires were utilized. Medical status was assessed (family history of MFS, aortic root dilatation >40 mm, previous aortic surgery, aortic dissection, chronic pain, skeletal involvement, and scoliosis). Severe fatigue was experienced by 37% of the total MFS cohort (n = 155). MFS patients scored significantly higher on the CIS questionnaire, concerning severe fatigue, as compared with the general Dutch population (p < 0.0001). There were no differences in HADS anxiety or depression scores. In older MFS patients, with a more severe cardiovascular phenotype, chronic pain, and a higher unemployment rate, significantly more symptoms of depression were observed, when compared with the general population (p = 0.027) or compared with younger MFS patients (p = 0.026). Multivariate analysis, showed that anxiety was associated with chronic pain (p = 0.022) and symptoms of depression with unemployment (p = 0.024). MFS patients report significantly more severe fatigue as compared with the general population. Since the cause of fatigue is unclear, more research may be needed. Psychological intervention, for example, cognitive behavioral therapy, may contribute to a reduction in psychological symptoms.

Stress at work is associated with intima media thickness in older male employees, independent of other sources of stress perception.

Chronic stress at work shows a moderate but robust longitudinal association with cardiovascular disease (CVD). Atherosclerosis is a pathophysiological process of most CVD, for which intima media thickness (IMT) of the carotid artery is used as an early marker. Its relationship with stress at work has remained largely unexplored, and the present study therefore aimed to elucidate the association between stress at work, assessed as effort-reward imbalance (ERI), and IMT. This cross-sectional study comprised of 501 male German employees aged 42 (19-64) years at enrollment into the Mannheim Industrial Cohort Study. Clinical assessments used fasting blood samples and IMT measurement. Self-report questionnaires assessed sources of perceived stress. Analyses adjusted for medical history, life style, and socio-economic status (SES) indicators as well as general perceived stress and worries to determine the specificity of ERI. Linear regression models estimated the association of ERI with IMT, stratifying for age groups and adjusting for potential confounders. ERI ratio increased until the age of 50 years and abated thereafter. In participants younger than 50 years IMT measurements were not associated with ERI ratios. However, despite lower mean ERI ratios in participants older than 50 years, this age group showed a significant relationship with IMT (standardized Beta = .36, p < .01), adjusting for multiple confounders including general perceived stress and worries. These analyses suggest that atherosclerosis in older employees is specifically related to stress at work. Longitudinal studies will help to elucidate the temporal relationship between stress exposure and downstream biological mechanisms.Lay summaryOur study explored the association of job stress and the calcification of the carotid artery in German employees. We found out that this association is stronger in employees older than 50 years. In addition, it is independent of medical risk factors and stress caused by private issues.

Motivational factors mediate the association of general self-efficacy and performance outcomes in acutely hospitalised older patients.

OBJECTIVES: To study (i) the association of general self-efficacy (GSE) on the course of subjective (i.e. basic and instrumental activities of daily living (ADLs and IADLs) and objective physical performance outcomes (short physical performance battery (SPPB)) among older persons from discharge up to 3 months post-discharge and (ii) the extent to whether motivational factors such as depressive symptoms, apathy and fatigue mediate this association. METHODS: Prospective multi-centre cohort of acutely hospitalised patients aged ≥70 (Hospital-ADL study). Structural equation modelling was used to analyse the structural relationships. RESULTS: The analytic sample included 236 acutely hospitalised patients. GSE had a significant total effect on the course of subjective and objective performance outcomes (ADLs: ß = -0.21, P < 0.001, IADLs: ß = -0.24, P < 0.001 and SPPB: ß = 0.17, P < 0.001). However, when motivational factors as mediator were included into the same model, motivational factors (IADLs: ß = 0.51, P < 0.001; SPPB: ß = 0.49, P < 0.001) but not GSE remained significantly associated with IADLs (ß = -0.06, P = 0.16) and SPPB (ß = 0.002, P = 0.97). Motivational factors partially mediated the relationship between GSE and ADLs (ß = -0.09, P = 0.04). The percentage of mediation was 55, 74 and 99% for ADLs, IADLs and SPPB, respectively. CONCLUSIONS: Motivational factors and GSE are both associated with subjective and objective performance outcomes. However, the relationship between GSE and subjective and objective performance outcomes was highly mediated by motivational factors. Taken together, this suggests that GSE is important to being physically active but not sufficient to becoming more physical active in acutely hospitalised older patients; motivation is important to improving both subjective and objective performance.

Selective effects of acute low-grade inflammation on human visual attention.

Illness is often accompanied by perceived cognitive sluggishness, a symptom that may stem from immune system activation. The current study used electroencephalography (EEG) to assess how inflammation affected three different distinct attentional processes: alerting, orienting and executive control. In a double-blinded placebo-controlled within-subjects design (20 healthy males, mean age = 24.5, SD = 3.4), Salmonella typhoid vaccination (0.025 mg; Typhim Vi, Sanofi Pasteur) was used to induce transient mild inflammation, while a saline injection served as a placebo-control. Participants completed the Attention Network Test with concurrent EEG recorded 6 h post-injection. Analyses focused on behavioral task performance and on modulation of oscillatory EEG activity in the alpha band (9-12 Hz) for alerting as well as orienting attention and frontal theta band (4-8 Hz) for executive control. Vaccination induced mild systemic inflammation, as assessed by interleukin-6 (IL-6) levels. While no behavioral task performance differences between the inflammation and placebo condition were evident, inflammation caused significant alterations to task-related brain activity. Specifically, inflammation produced greater cue-induced suppression of alpha power in the alerting aspect of attention and individual variation in the inflammatory response was significantly correlated with the degree of alpha power suppression. Notably, inflammation did not affect orienting (i.e., alpha lateralization) or executive control (i.e., frontal theta activity). These results reveal a unique neurophysiological sensitivity to acute mild inflammation of the neural network that underpins attentional alerting functions. Observed in the absence of performance decrements, these novel findings suggest that acute inflammation requires individuals to exert greater cognitive effort when preparing for a task in order to maintain adequate behavioral performance.

Self-Rated Health and Inflammation: A Test of Depression and Sleep Quality as Mediators.

OBJECTIVE: Despite its simplicity, single-item measures of self-rated health have been associated with mortality independent of objective health conditions. However, little is known about the mechanisms potentially responsible for such associations. This study tested the association between self-rated heath and inflammatory markers as biological pathways, and whether sleep quality and/or depression statistically mediated such links. METHOD: Eighty-six heterosexual married couples completed a standard measure of self-rated health, the Center of Epidemiological Studies-Depression Scale, and the Pittsburgh Sleep Quality Index. Participants also had blood drawn for determination of plasma levels of interleukin 6 and high-sensitivity C-reactive protein. The Monte Carlo method was used to construct confidence intervals for mediation analyses. RESULTS: Results indicated that poor self-rated health was associated with higher CRP levels (B = .31, SE = .14, p = .028). Importantly, the Monte Carlo mediational analyses showed that these results were statistically mediated by sleep quality (aXb = 0.10, 95% confidence interval = 0.003 to 0.217) but not depressive symptoms (aXb = 0.03, 95% confidence interval = -0.03 to 0.10). CONCLUSIONS: These results highlight the biological and behavioral mechanisms potentially linking self-rated health to longer-term health outcomes. Such work can inform basic theory in the area as well as intervention approaches that target such pathways.

Hopelessness and Other Depressive Symptoms in Adults 70 Years and Older as Predictors of All-Cause Mortality Within 3 Months After Acute Hospitalization: The Hospital-ADL Study.

OBJECTIVE: Depression among older adults predicts mortality after acute hospitalization. Depression is highly heterogeneous in its presentation of symptoms, whereas individual symptoms may differ in predictive value. This study aimed to investigate the prevalence of individual cognitive-affective depressive symptoms during acute hospitalization and investigate the predictive value of both overall and individual cognitive-affective depressive symptoms for mortality between admission up to 3-month postdischarge among older patients. METHODS: A prospective multicenter cohort study enrolled 401 acutely hospitalized patients 70 years and older (Hospitalization-Associated Disability and impact on daily Life Study). The predictive value of depressive symptoms, assessed using the Geriatric Depression Scale 15, during acute hospitalization on mortality was analyzed with multiple logistic regression. RESULTS: The analytic sample included 398 patients (M (SD) = 79.6 (6.6) years; 51% men). Results showed that 9.3% of participants died within 3 months, with symptoms of apathy being most frequently reported. The depression total score during hospitalization was associated with increased mortality risk (admission: odds ratio [OR] = 1.2, 95% confidence interval [CI] = 1.2-1.3; discharge: OR = 1.2, 95% CI = 1.2-1.4). Stepwise multiple logistic regression analyses yielded the finding that feelings of hopelessness during acute hospitalization were a strong unique predictor of mortality (admission: OR = 3.6, 95% CI = 1.8-7.4; discharge: OR = 5.7, 95% CI = 2.5-13.1). These associations were robust to adjustment for demographic factors, somatic symptoms, and medical comorbidities. CONCLUSIONS: Symptoms of apathy were most frequently reported in response to acute hospitalization. However, feelings of hopelessness about their situation were the strongest cognitive-affective predictor of mortality. These results imply that this item is important in identifying patients who are in the last phase of their lives and for whom palliative care may be important.

Loneliness in healthy young adults predicts inflammatory responsiveness to a mild immune challenge in vivo.

The established link between loneliness and poor health outcomes may stem from aberrant inflammatory regulation. The present study tested whether loneliness predicted the inflammatory response to a standardised in vivo immune challenge. Using a within-subjects double blind placebo-controlled design, 40 healthy men (mean age = 25, SD = 5) received a Salmonella Typhi vaccination (0.025 mg; Typhim Vi, Sanofi Pasteur, UK) and placebo (saline) on two separate occasions. Loneliness was assessed using the R-UCLA loneliness scale. Regression analyses showed that those that reported feeling more lonely exhibited an elevated interleukin-6 response (ß = 0.564, 95% confidence interval [0.003, 0.042], p < .05). This association withstood adjustment for potentially confounding variables, including age, sleep quality, socio-emotional factors, and health factors. The present findings are in line with evidence that loneliness may shift immune system responsivity, suggesting a potential biobehavioural pathway linking loneliness to impaired health.

Effectiveness of Stress-Reducing Interventions on the Response to Challenges to the Immune System: A Meta-Analytic Review.

BACKGROUND: There is consistent evidence showing an interplay between psychological processes and immune function in health and disease processes. OBJECTIVES: The present systematic review and meta-analysis aims to provide a concise overview of the effectiveness of stress-reducing psychological interventions on the activation of immune responses in both healthy subjects and patients. METHODS: Included are 3 types of challenges: in vivo, in vitro, and psychophysiological. Such challenges are designed to mimic naturally occurring immune-related threats. RESULTS: A systematic literature search was conducted using PubMed, EMBASE, and PsychInfo, resulting in 75 eligible studies. The risk of bias was assessed with the Cochrane risk-of-bias tool. Across all studies, a small-to-medium effect size was found for the effects of psychological interventions on optimization of the immune function (g = 0.33; 95% CI 0.22-0.43). While the largest effects were found for in vivo immune-related challenges (g = 0.61; 95% CI 0.34-0.88; especially on studies that incorporated skin tests and wound healing), studies incorporating psychophysiological challenges and in vitro immune-related stimulations similarly suggest more optimal immune responses among those receiving stress-reducing interventions (g = 0.28; 95% CI 0.15-0.42). CONCLUSION: These findings showed substantial heterogeneity depending on the type of challenge, the study populations, and the intervention types. These data demonstrate support for the effectiveness of stress-reducing psychological interventions in improving immunity in studies that tested immune function by means of incorporating an in vivo,in vitro, or psychophysiological challenge. Future research should more consistently incorporate challenges into the study design to gather more insights in the mechanisms underlying the optimized immune function following a psychological intervention. This is also relevant for clinical practice, as psychological interventions can possibly supplement, or at least partially replace, current drug treatments in various somatic conditions to reduce side effects.

Associations of ambivalent leadership with distress and cortisol secretion.

Ambivalent social ties, i.e., whereby a relationship is evaluated simultaneously in positive and negative terms, are a potential source of distress and can perturb health-relevant biological functions. Social interactions at the workplace, in particular with supervisors, are often described in ambivalent terms, but the psychological and psychobiological impact of such interactions has received little scientific attention. The current study examined associations between ambivalent attitudes towards one's supervisor, perceived distress (general and work-related), and diurnal dynamics of the stress hormone cortisol. 613 employees evaluated their supervisor in terms of positive and negative behaviors, which was combined into an ambivalent index. Higher ambivalence was associated with higher perceived distress and work-related stress (p < .001), and with a larger cortisol awakening response and higher day-time secretion post-awakening (p < .01). The present study is the first to identify ambivalence towards supervisors as a predictor of employee distress and stress-related endocrine dysregulation. In consequence, focusing solely on positive or negative leader behavior may insufficiently capture the true complexity of workplace interactions and attempts to compensate negative behaviors with positive are unlikely to reduce distress-but quite the opposite-by increasing ambivalence.

Sleep Quality and Inflammation in Married Heterosexual Couples: an Actor-Partner Analysis.

BACKGROUND: Subjective sleep quality is a predictor of important health outcomes, but little work has examined the social context of sleep that might inform theoretical models and intervention approaches. The present study tested actor-partner models of sleep quality and its links to inflammatory markers. METHOD: Participants were 84 middle-age to older adult heterosexual married couples who completed the Pittsburgh Sleep Quality Index and had blood drawn for determination of CRP and IL-6 levels. RESULTS: Main results indicated that only actor levels of poor global sleep quality predicted higher CRP levels. No actor × partner or gender × actor/partner interactions were significant. These results were also not moderated by relationship quality. Secondary analyses, focused on the different components of sleep quality, revealed marginally significant evidence for partner's poor sleep (i.e., sleep disturbances, sleep latency) on one's own inflammatory outcomes. CONCLUSION: These results suggest the promise of modeling sleep quality as a dyadic process that can impact inflammation and potentially related health outcomes.

The Associations of Muscle Strength, Muscle Mass, and Adiposity With Clinical Outcomes and Quality of Life in Prevalent Kidney Transplant Recipients.

OBJECTIVE: Sarcopenia, defined as loss of both muscle strength and mass, is associated with inferior clinical outcomes and quality of life (QoL) in chronic kidney disease, but its effects are unknown in kidney transplantation. Obesity confers increased mortality risk and compromises QoL in kidney transplant recipients (KTRs), but the impacts of sarcopenic obesity remain unexplored. This study aimed to evaluate the associations of muscle strength and mass, sarcopenia, and sarcopenic obesity with clinical outcomes and QoL in KTRs. METHODS: This prospective longitudinal study enrolled 128 KTRs ≥1-year posttransplantation. Low muscle strength (by handgrip strength) and mass (by bioimpedance analysis), and a combination of both (sarcopenia) were defined as < reference cutoffs for corresponding indices. Sarcopenic obesity was defined as sarcopenia combined with fulfillment of ≥2 out of 3 criteria from (1) body mass index ≥30 kg/m2, (2) bioimpedance analysis-derived fat mass > reference cutoffs, and (3) waist circumference > World Health Organization cutoffs. Prospective follow-up data on mortality and hospitalization were collected. QoL was evaluated using Medical Outcomes Study Short Form-36 questionnaire. RESULTS: Median follow-up duration was 64 (60-72) months. Low muscle strength was independently associated with the composite endpoint of mortality and hospitalization (hazard ratio = 2.45; P = .006), and QoL (physical-related: ß = -12.2; P = .04; mental-related: ß = -9.9; P = .04). Low muscle mass (ß = -8.8; P = .04) and sarcopenia (ß = -14.7; P = .03) were associated with physical-related QoL only. No independent associations were found between muscle mass, sarcopenia, and sarcopenic obesity with the composite outcome of mortality and hospitalization. CONCLUSION: Low muscle strength is common among KTRs, conferring poor prognosis in the medium term. Future research on strength training may prove valuable in improving kidney transplantation outcomes.

Low-grade inflammation decreases emotion recognition - Evidence from the vaccination model of inflammation.

The ability to adequately interpret the mental state of another person is key to complex human social interaction. Recent evidence suggests that this ability, considered a hallmark of 'theory of mind' (ToM), becomes impaired by inflammation. However, extant supportive empirical evidence is based on experiments that induce not only inflammation but also induce discomfort and sickness, factors that could also account for temporary social impairment. Hence, an experimental inflammation manipulation was applied that avoided this confound, isolating effects of inflammation and social interaction. Forty healthy male participants (mean age = 25, SD = 5 years) participated in this double-blind placebo-controlled crossover trial. Inflammation was induced using Salmonella Typhi vaccination (0.025 mg; Typhim Vi, Sanofi Pasteur, UK); saline-injection was used as a control. About 6 h 30 m after injection in each condition, participants completed the Reading the Mind in the Eyes Test (RMET), a validated test for assessing how well the mental states of others can be inferred through observation of the eyes region of the face. Vaccination induced systemic inflammation, elevating IL-6 by +419% (p < .001), without fever, sickness symptoms (e.g., nausea, light-headedness), or mood changes (all p's > .21). Importantly, compared to placebo, vaccination significantly reduced RMET accuracy (p < .05). RMET stimuli selected on valence (positive, negative, neutral) provided no evidence of a selective impact of treatment. By utilizing an inflammation-induction procedure that avoided concurrent sicknesses or symptoms in a double-blinded design, the present study provides further support for the hypothesis that immune activation impairs ToM. Such impairment may provide a mechanistic link explaining social-cognitive deficits in psychopathologies that exhibit low-grade inflammation, such as major depression.

The Associations of Endotoxemia With Systemic Inflammation, Endothelial Activation, and Cardiovascular Outcome in Kidney Transplantation.

OBJECTIVE: Cardiovascular disease is the leading cause of death in kidney transplant recipients (KTRs), yet incompletely accountable by traditional risk factors. Inflammation is an unconventional cardiovascular risk factor, with gut-derived endotoxemia potentially driving inflammation and endothelial disease. Comparable data are lacking in kidney transplantation. This study investigated the associations of endotoxemia with inflammation, endothelial activation, and 5-year cardiovascular events in KTRs. Determinants of endotoxemia were also explored. DESIGN AND METHODS: This is a single-center cross-sectional study with prospective follow-up from a prevalent cohort of 128 KTRs. MAIN OUTCOME MEASURES: Demographic, nutritional and clinical predictors of inflammation (high-sensitivity C-reactive protein [hsCRP]), endothelial activation (sE-selectin), and endotoxemia (endotoxin) were assessed. Follow-up data on 5-year cardiovascular event rates were collected. RESULTS: Endotoxemia (P = .03), reduced 25-hydroxyvitamin D (P = .04), high fructose intake (P < .001), decreased fiber intake (P < .001), and abdominal obesity (P = .002) were independently associated with elevated hsCRP. In turn, endotoxemia (P = .007) and increasing hsCRP (P = .02) were both independently associated with raised sE-selectin. Furthermore, endotoxemia predicted increased cardiovascular event rate (P = .02), independent of hsCRP and a global measure of cardiovascular risk estimated by a validated algorithm of 7-year risk for major adverse cardiac events in kidney transplantation. Determinants of endotoxemia included reduced 25-hydroxyvitamin D (P < .001), hypertriglyceridemia (P < .001), increased fructose intake (P = .01), and abdominal obesity (P = .01). CONCLUSIONS: Endotoxemia in KTRs contributes to inflammation, endothelial activation, and increased cardiovascular events. This study highlights the clinical relevance of endotoxemia in KTRs, suggesting future interventional targets.

Bidirectional associations between psychological distress and hearing problems: an 18-year longitudinal analysis of the British Household Panel Survey.

OBJECTIVE: Hearing problems are a significant public health concern. It has been suggested that psychological distress may represent both a cause and a consequence of hearing problems. Prospective data that allow testing such potential bi-directionality have thus far been lacking. The present study aimed to address this knowledge gap. Random (RE) and fixed effects (FE) panel regression models estimated the association of psychological distress (GHQ-12) and participant-reported hearing problems. Data from 18 annual waves of the British Household Panel Survey were used (n = 10,008). Psychological distress was prospectively associated with self-reported hearing problems in women (multivariable odds ratios (ORs) ≥1.44; one-year time lag ≥ 1.16) and men (ORs ≥ 1.15; time lag ≥ 1.17). Conversely, self-reported hearing problems were associated with increases in psychological distress in both sexes (OR ≥ 1.26; time lag ≥ 1.08). These associations were independent of the analytical strategy and of adjustment for sociodemographic variables, lifestyle factors, and measurement period. We present first evidence of a bidirectional association between psychological distress and self-reported hearing problems. These findings suggest that stress management interventions may contribute to the prevention of self-reported hearing problems, and, in turn, alleviating self-reported hearing problems may reduce psychological distress.

Persistent Herpesvirus Infections and Telomere Attrition Over 3 Years in the Whitehall II Cohort.

The determinants of telomere attrition, a potential marker of cellular aging, are not well understood. Persistent herpesvirus infections including cytomegalovirus (CMV) infection may be particularly important for telomere dynamics via mechanisms such as inflammation, oxidative stress, and their impact on peripheral blood lymphocyte composition. This study examined the association of 4 human herpesviruses (CMV, herpes simplex virus type 1, human herpesvirus type 6, and Epstein-Barr virus) with change in leukocyte telomere length (LTL) over 3 years in 400 healthy individuals (aged 53-76 years) from the Whitehall II cohort. CMV, herpes simplex virus type 1, and human herpesvirus 6 infection were independently associated with greater 3-year LTL attrition, with no association found for Epstein-Barr virus. The magnitudes of these associations were large, for example, the equivalent of almost 12 years of chronological age for those CMV seropositive. Seropositivity to more herpesviruses was additively associated with greater LTL attrition (3 herpesviruses vs none, ß = -0.07 and P = .02; 4 infections vs none, ß = -0.14 and P < .001). Higher immunoglobulin G antibody levels among those seropositive to CMV were also associated with shorter LTL at follow-up. These associations were robust to adjustment for age, sex, employment grade, body mass index, and smoking status. These results suggest that exposure to infectious agents should be an important consideration in future studies of telomere dynamics.

Catecholamine-Mediated Increases in Gain Enhance the Precision of Cortical Representations.

UNLABELLED: Neurophysiological evidence suggests that neuromodulators, such as norepinephrine and dopamine, increase neural gain in target brain areas. Computational models and prominent theoretical frameworks indicate that this should enhance the precision of neural representations, but direct empirical evidence for this hypothesis is lacking. In two functional MRI studies, we examine the effect of baseline catecholamine levels (as indexed by pupil diameter and manipulated pharmacologically) on the precision of object representations in the human ventral temporal cortex using angular dispersion, a powerful, multivariate metric of representational similarity (precision). We first report the results of computational model simulations indicating that increasing catecholaminergic gain should reduce the angular dispersion, and thus increase the precision, of object representations from the same category, as well as reduce the angular dispersion of object representations from distinct categories when distinct-category representations overlap. In Study 1 (N = 24), we show that angular dispersion covaries with pupil diameter, an index of baseline catecholamine levels. In Study 2 (N = 24), we manipulate catecholamine levels and neural gain using the norepinephrine transporter blocker atomoxetine and demonstrate consistent, causal effects on angular dispersion and brain-wide functional connectivity. Despite the use of very different methods of examining the effect of baseline catecholamine levels, our results show a striking convergence and demonstrate that catecholamines increase the precision of neural representations. SIGNIFICANCE STATEMENT: Norepinephrine and dopamine are among the most widely distributed and ubiquitous neuromodulators in the mammalian brain and have a profound and pervasive impact on cognition. Baseline catecholamine levels tend to increase with increasing task engagement in tasks involving perceptual decisions, yet there is currently no direct evidence of the specific impact of these increases in catecholamine levels on perceptual encoding. Our results fill this void by showing that catecholamines enhance the precision of encoding cortical object representations, and by suggesting that this effect is mediated by increases in neural gain, thus offering a mechanistic account of our key finding.

Salivary Gluten Degradation and Oral Microbial Profiles in Healthy Individuals and Celiac Disease Patients.

Celiac disease (CD) is a chronic immune-mediated enteropathy induced by dietary gluten in genetically predisposed individuals. Saliva harbors the second highest bacterial load of the gastrointestinal (GI) tract after the colon. We hypothesized that enzymes produced by oral bacteria may be involved in gluten processing in the intestine and susceptibility to celiac disease. The aim of this study was to investigate salivary enzymatic activities and oral microbial profiles in healthy subjects versus patients with classical and refractory CD. Stimulated whole saliva was collected from patients with CD in remission (n = 21) and refractory CD (RCD; n = 8) and was compared to healthy controls (HC; n = 20) and subjects with functional GI complaints (n = 12). Salivary gluten-degrading activities were monitored with the tripeptide substrate Z-Tyr-Pro-Gln-pNA and the α-gliadin-derived immunogenic 33-mer peptide. The oral microbiome was profiled by 16S rRNA-based MiSeq analysis. Salivary glutenase activities were higher in CD patients compared to controls, both before and after normalization for protein concentration or bacterial load. The oral microbiomes of CD and RCD patients showed significant differences from that of healthy subjects, e.g., higher salivary levels of lactobacilli (P < 0.05), which may partly explain the observed higher gluten-degrading activities. While the pathophysiological link between the oral and gut microbiomes in CD needs further exploration, the presented data suggest that oral microbe-derived enzyme activities are elevated in subjects with CD, which may impact gluten processing and the presentation of immunogenic gluten epitopes to the immune system in the small intestine.IMPORTANCE Ingested gluten proteins are the triggers of intestinal inflammation in celiac disease (CD). Certain immunogenic gluten domains are resistant to intestinal proteases but can be hydrolyzed by oral microbial enzymes. Very little is known about the endogenous proteolytic processing of gluten proteins in the oral cavity. Given that this occurs prior to gluten reaching the small intestine, such enzymes are likely to contribute to the composition of the gluten digest that ultimately reaches the small intestine and causes CD. We demonstrated that endogenous salivary protease activities are incomplete, likely liberating peptides from larger gluten proteins. The potentially responsible microbes were identified. The study included refractory CD patients, who have been studied less with regard to CD pathogenesis.

Are psychophysiological arousal and self-reported emotional stress during an oncological consultation related to memory of medical information? An experimental study.

Patients forget 20-80% of information provided during medical consultations. The emotional stress often experienced by patients during consultations could be one of the mechanisms that lead to limited recall. The current experimental study therefore investigated the associations between (analog) patients' psychophysiological arousal, self-reported emotional stress and their (long term) memory of information provided by the physician. One hundred and eighty one cancer-naïve individuals acted as so-called analog patients (APs), i.e. they were instructed to watch a scripted video-recoding of an oncological bad news consultation while imagining themselves being in the patient's situation. Electrodermal and cardiovascular activity (e.g. skin conductance level and heart rate) were recorded during watching. Self-reported emotional stress was assessed before and after watching, using the STAI-State and seven Visual Analog Scales. Memory, both free recall and recognition, was assessed after 24-28 h. Watching the consultation evoked significant psychophysiological and self-reported stress responses. However, investigating the associations between 24 psychophysiological arousal measures, eight self-reported stress measures and free recall and recognition of information resulted in one significant, small (partial) correlation (r = 0.19). Considering multiple testing, this significant result was probably due to chance. Alternative analytical methods yielded identical results, strengthening our conclusion that no evidence was found for relationships between variables of interest. These null-findings are highly relevant, as they may be considered to refute the long-standing, but yet untested assumption that a relationship between stress and memory exists within this context. Moreover, these findings suggest that lowering patients' stress levels during the consultation would probably not be sufficient to raise memory of information to an optimal level. Alternative explanations for these findings are discussed.

Cardiovascular, muscular and perceptual contributions to physical fatigue in prevalent kidney transplant recipients.

Physical fatigue is debilitating and common among kidney transplant recipients (KTRs). This study investigated the mechanistic aetiology of physical fatigue in this setting through examinations of muscle mass, muscular and cardiovascular function, and perceived exertion. The incidence of physical fatigue, its association with quality of life (QoL), and the predictors of perceived exertion, were evaluated. This single-centre observational cross-sectional study enrolled 55 KTRs. Muscle mass was quantified using dual-energy x-ray absorptiometry. Muscular function was assessed by jumping mechanography. Cardiovascular function (maximal oxygen consumption and oxygen pulse) was estimated during submaximal exercise testing, with perceived exertion determined using age-adjusted Borg scale-ratings. Physical fatigue was measured using Multi-Dimensional Fatigue Inventory-20. QoL was assessed using Medical Outcomes Study Short Form-36. Demographic, clinical, nutritional, psychosocial and behavioural predictors of perceived exertion were assessed. Of clinical importance, increased perceived exertion was the only independent predictor of physical fatigue (P = 0.001), with no association found between physical fatigue and muscular or cardiovascular parameters. Physical fatigue occurred in 22% of KTRs, and negatively impacted on QoL (P < 0.001). Predictors of heightened perception included anxiety (P < 0.05) and mental fatigue (P < 0.05). Perception is a key determinant of physical fatigue in KTRs, paving the way for future interventions.