A bidirectional relationship between anxiety, depression and gastrointestinal symptoms in Parkinson's disease

α-synuclein overexpression and the microbiome shape the gut and brain metabolome in mice

Pathological forms of α-synuclein contribute to synucleinopathies, including Parkinson's disease (PD). Most cases of PD arise from gene-environment interactions. Microbiome composition is altered in PD, and gut bacteria are causal to symptoms in animal models. We quantitatively profiled nearly 630 metabolites in the gut, plasma, and brain of α-synuclein-overexpressing (ASO) mice, compared to wild-type (WT) animals, and comparing germ-free (GF) to specific pathogen-free (SPF) animals (n = 5 WT-SPF; n = 6 ASO-SPF; n = 6 WT-GF; n = 6 ASO-GF). Many differentially expressed metabolites in ASO mice are also dysregulated in human PD patients, including amine oxides, bile acids and indoles. The microbial metabolite trimethylamine N-oxide (TMAO) strongly correlates from the gut to the plasma to the brain in mice, notable since TMAO is elevated in the blood and cerebrospinal fluid of PD patients. These findings uncover broad metabolomic changes that are influenced by the intersection of host genetics and microbiome in a mouse model of PD.

α-Synuclein Overexpression and the Microbiome Shape the Gut and Brain Metabolome in Mice

Pathological forms of the protein α-synuclein contribute to a family of disorders termed synucleinopathies, which includes Parkinson's disease (PD). Most cases of PD are believed to arise from gene-environment interactions. Microbiome composition is altered in PD, and gut bacteria are causal to symptoms and pathology in animal models. To explore how the microbiome may impact PD-associated genetic risks, we quantitatively profiled nearly 630 metabolites from 26 biochemical classes in the gut, plasma, and brain of α-synuclein-overexpressing (ASO) mice with or without microbiota. We observe tissue-specific changes driven by genotype, microbiome, and their interaction. Many differentially expressed metabolites in ASO mice are also dysregulated in human PD patients, including amine oxides, bile acids and indoles. Notably, levels of the microbial metabolite trimethylamine N-oxide (TMAO) strongly correlate from the gut to the plasma to the brain, identifying a product of gene-environment interactions that may influence PD-like outcomes in mice. TMAO is elevated in the blood and cerebral spinal fluid of PD patients. These findings uncover broad metabolomic changes that are influenced by the intersection of host genetics and the microbiome in a mouse model of PD.

The Relationship Between Autonomic Dysfunction and Mood Symptoms in De Novo Parkinson's Disease Patients Over Time

BACKGROUND

Autonomic dysfunction is prevalent in Parkinson's disease (PD) and can worsen quality of life. We examined: (a) whether specific autonomic symptoms were more strongly associated with anxiety or depression in PD and (b) whether overall autonomic dysfunction predicted mood trajectories over a 5-year period.

METHODS

Newly diagnosed individuals with PD (N = 414) from the Parkinson's Progression Markers Initiative completed self-report measures of depression, anxiety, and autonomic symptoms annually. Cross-sectional linear regressions examined relationships between specific autonomic subdomains (gastrointestinal, cardiovascular, thermoregulatory, etc.) and mood. Multilevel modeling examined longitudinal relationships with total autonomic load.

RESULTS

Gastrointestinal symptoms were associated with both higher anxiety (b = 1.04, 95% CI [.55, 1.53], P < .001) and depression (b = .24, 95% CI [.11, .37], P = .012), as were thermoregulatory symptoms (anxiety: b = 1.06, 95% CI [.46, 1.65], P = .004; depression: b = .25, 95% CI [.09, .42], P = .013), while cardiovascular (b = .36, 95% CI [.10, .62], P = .012) and urinary symptoms (b = .10, 95% CI [.01, .20], P = .037) were associated only with depression. Longitudinally, higher total autonomic load was associated with increases in both depression (b = .01, 95% CI [.00, .02], P = .015) and anxiety (b = .04, 95% CI [.01, .06], P < .001) over time, as well as occasion-to-occasion fluctuations (depression: b = .08, 95% CI [.05, .10], P < .001; anxiety: b = .24, 95% CI [.15, .32], P < .001).

CONCLUSION

Findings suggest autonomic dysfunction, particularly gastrointestinal and thermoregulatory symptoms, may be an indicator for elevated anxiety/depression and a potential treatment target early on in PD.

Neuroticism as a moderator of symptom-related distress and depression in 4 noncancer end-of-life populations

OBJECTIVES

Neuroticism is a significant predictor of adverse psychological outcomes in patients with cancer. Less is known about how this relationship manifests in those with noncancer illness at the end-of-life (EOL). The objective of this study was to examine the impact of neuroticism as a moderator of physical symptoms and development of depression in patients with amyotrophic lateral sclerosis (ALS), chronic obstructive pulmonary disease (COPD), end-stage renal disease (ESRD), and frailty in the last 6 months of life.

METHODS

We met this objective using secondary data collected in the Dignity and Distress across End-of-Life Populations study. The data included N = 404 patients with ALS (N = 101), COPD (N = 100), ESRD (N = 101), and frailty (N = 102) in the estimated last 6 months of life, with a range of illness-related symptoms, assessed longitudinally at 2 time points. We examined neuroticism as a moderator of illness-related symptoms at Time 1 (∼6 months before death) and depression at Time 2 (∼3 months before death) using ordinary least squares regression.

RESULTS

Results revealed that neuroticism significantly moderated the relationship between the following symptoms and depression measured 3 months later: drowsiness, fatigue, shortness of breath, wellbeing (ALS); drowsiness, trouble sleeping, will to live, activity (COPD); constipation (ESRD); and weakness and will to live (frailty).

SIGNIFICANCE OF RESULTS

These findings suggest that neuroticism represents a vulnerability factor that either attenuates or amplifies the relationship of specific illness and depressive symptoms in these noncancer illness groups at the EOL. Identifying those high in neuroticism may provide insight into patient populations that require special care at the EOL.

Effects of online mindfulness-based interventions (MBIs) on anxiety symptoms in adults: a systematic review and meta-analysis

BACKGROUND

An increasing number of studies have documented the effectiveness on various types of face-to-face and online mindfulness-based interventions (MBIs) in reducing anxiety among general population, but there is a scarcity of systematic reviews evaluating evidence of online MBIs on anxiety in adults. Therefore, we examined the effects of online mindfulness-based interventions (MBIs) on anxiety symptoms in adults and explored the moderating effects of participant, methods, and intervention characteristics.

METHODS

We systematically searched nine databases through May 2022 without date restrictions. Inclusion criteria were primary studies evaluating online mindfulness-based interventions with adults with anxiety measured as an outcome, a comparison group, and written in English. We used random-effects model to compute effect sizes (ESs) using Hedges' g, a forest plot, and Q and I² statistics as measures of heterogeneity; we also examined moderator analyses.

RESULTS

Twenty-six primary studies included 3,246 participants (39.9 ± 12.9 years old). Overall, online mindfulness-based interventions showed significantly improved anxiety (g = 0.35, 95%CI 0.09, 0.62, I² = 92%) compared to controls. With regards to moderators, researchers reported higher attrition, they reported less beneficial effects on anxiety symptoms (β=-0.001, Q_model=4.59, p = .032). No other quality indicators moderated the effects of online mindfulness-based interventions on anxiety.

CONCLUSION

Online mindfulness-based interventions improved anxiety symptoms in adult population. Thus, it might be used as adjunctive or alternative complementary treatment for adults. However, our findings must be interpreted with caution due to the low and unclear power of the sample in primary studies; hence, high-quality studies are needed to confirm our findings.

Is depression the missing link between inflammatory mediators and cancer?

Patients with cancer are at greater risk of developing depression in comparison to the general population and this is associated with serious adverse effects, such as poorer quality of life, worse prognosis and higher mortality. Although the relationship between depression and cancer is now well established, a common underlying pathophysiological mechanism between the two conditions is yet to be elucidated. Existing theories of depression, based on monoamine neurotransmitter system dysfunction, are insufficient as explanations of the disorder. Recent advances have implicated neuroinflammatory mechanisms in the etiology of depression and it has been demonstrated that inflammation at a peripheral level may be mirrored centrally in astrocytes and microglia serving to promote chronic levels of inflammation in the brain. Three major routes to depression in cancer in which proinflammatory mediators are implicated, seem likely. Activation of the kynurenine pathway involving cytokines, increases tryptophan catabolism, resulting in diminished levels of serotonin which is widely acknowledged as being the hallmark of depression. It also results in neurotoxic effects on brain regions thought to be involved in the evolution of major depression. Proinflammatory mediators also play a crucial role in impairing regulatory glucocorticoid mediated feedback of the hypothalamic-pituitary-adrenal axis, which is activated by stress and considered to be involved in both depression and cancer. The third route is via the glutamatergic pathway, whereby glutamate excitotoxicity may lead to depression associated with cancer. A better understanding of the mechanisms underlying these dysregulated and other newly emerging pathways may provide a rationale for therapeutic targeting, serving to improve the care of cancer patients.

The pathobiological basis of depression in Parkinson disease: challenges and outlooks

Depression, with an estimated prevalence of about 40% is a most common neuropsychiatric disorder in Parkinson disease (PD), with a negative impact on quality of life, cognitive impairment and functional disability, yet the underlying neurobiology is poorly understood. Depression in PD (DPD), one of its most common non-motor symptoms, can precede the onset of motor symptoms but can occur at any stage of the disease. Although its diagnosis is based on standard criteria, due to overlap with other symptoms related to PD or to side effects of treatment, depression is frequently underdiagnosed and undertreated. DPD has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, in particular dysfunction of neurotransmitter systems (dopaminergic, serotonergic and noradrenergic), as well as to disturbances of cortico-limbic, striato-thalamic-prefrontal, mediotemporal-limbic networks, with disruption in the topological organization of functional mood-related, motor and other essential brain network connections due to alterations in the blood-oxygen-level-dependent (BOLD) fluctuations in multiple brain areas. Other hypothetic mechanisms involve neuroinflammation, neuroimmune dysregulation, stress hormones, neurotrophic, toxic or metabolic factors. The pathophysiology and pathogenesis of DPD are multifactorial and complex, and its interactions with genetic factors, age-related changes, cognitive disposition and other co-morbidities awaits further elucidation.

Physical inactivity links depressive symptoms and cognitive functioning among individuals with Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a neurodegenerative disorder caused by disruption of dopamine-producing cells. PD is associated with motor symptoms and nonmotor symptoms including depression and cognitive impairment. Past research suggests an association between depression and cognitive impairment in PD. Physical activity may have a therapeutic effect on both depression and cognitive impairment. The present study investigates if physical activity mediates the association between depressive symptoms and cognition in a longitudinal sample of individuals with PD.

METHOD

Participants include individuals newly diagnosed with PD (N = 487) enrolled in the Parkinson's Progression Marker Initiative (PPMI). Participants completed an array of neuropsychological tests over the course of 5 years, as well as questionnaires of depression and physical activity. Between-person and within-person effects of depression and cognition mediated through physical activity were analyzed using structural equation modeling.

RESULTS

A significant direct effect demonstrated depression was associated with worse global cognitive functioning. Furthermore, there was a significant indirect within-person effect, indicating that physical activity fully mediated the association between depression and cognition. Individuals who became more depressed over time became less physically active and subsequently experienced cognitive decline over the 5-year period.

CONCLUSIONS

Findings have implications for prognostic detection and/or the role of physical activity interventions to buffer effects of depression on cognitive impairment among individuals diagnosed with PD. Physical interventions may potentially be implemented among depressed persons to preserve cognitive functioning. Worsened depression early during PD may be a risk factor for inactivity and cognitive diminishment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).