Mitochondrial respiration in peripheral blood mononuclear cells correlates with depressive subsymptoms and severity of major depression

The brain, rapid eye movement sleep, and major depressive disorder: A multimodal neuroimaging study

BACKGROUND

Evidence has established the prominent involvement of rapid eye movement (REM) sleep disturbance in major depressive disorder (MDD). However, the neural correlates of REM sleep in MDD and their clinical significance are less clear.

METHODS

Cross-sectional and longitudinal polysomnography and resting-state functional MRI data were collected from 131 MDD patients and 71 healthy controls to measure REM sleep and voxel-mirrored homotopic connectivity (VMHC). Correlation and mediation analyses were performed to examine the associations between REM sleep, VMHC, and clinical variables. Moreover, we conducted spatial correlations between the neural correlates of REM sleep and a multimodal collection of reference brain maps to facilitate genetic, structural and functional annotations.

RESULTS

MDD patients exhibited REM sleep abnormalities manifesting as higher REM sleep latency and lower REM sleep duration, which were correlated with decreased VMHC of the precentral gyrus and inferior parietal lobe and mediated their associations with more severe anxiety symptoms. Longitudinal data showed that VMHC increase of the inferior parietal lobe was related to improvement of depression symptoms in MDD patients. Spatial correlation analyses revealed that the neural correlates of REM sleep in MDD were linked to gene categories primarily involving cellular metabolic process, signal pathway, and ion channel activity as well as linked to cortical microstructure, metabolism, electrophysiology, and cannabinoid receptor.

CONCLUSION

These findings may add important context to the growing literature on the complex interplay between sleep and MDD, and more broadly may inform future treatment for depression via regulating sleep.

Role of mitochondria-associated membranes in the hippocampus in the pathogenesis of depression

BACKGROUND

Pathological changes, such as microglia activation in the hippocampus frequently occur in individuals with animal models of depression; however, they may share a common cellular mechanism, such as endoplasmic reticulum (ER) stress and mitochondrial dysfunction. Mitochondria associated membranes (MAMs) are communication platforms between ER and mitochondria. This study aimed to investigate the role of intracellular stress responses, especially structural and functional changes of MAMs in depression.

METHODS

We used chronic social defeat stress (CSDS) to mimic depression in C57 mice to investigate the pathophysiological changes in the hippocampus associated with depression and assess the antidepressant effect of electroacupuncture (EA). Molecular, histological, and electron microscopic techniques were utilized to study intracellular stress responses, including the ER stress pathway reaction, mitochondrial damage, and structural and functional changes in MAMs in the hippocampus after CSDS. Proteomics technology was employed to explore protein-level changes in MAMs caused by CSDS.

RESULTS

CSDS caused mitochondrial dysfunction, ER stress, closer contact between ER and mitochondria, and enrichment of functional protein clusters at MAMs in hippocampus along with depressive-like behaviors. Also, EA showed beneficial effects on intracellular stress responses and depressive-like behaviors in CSDS mice.

LIMITATION

The cellular specificity of MAMs related protein changes in CSDS mice was not explored.

CONCLUSIONS

In the hippocampus, ER stress and mitochondrial damage occur, along with enriched mitochondria-ER interactions and MAM-related protein enrichment, which may contribute to depression's pathophysiology. EA may improve depression by regulating intracellular stress responses.

Serotonin effects on human iPSC-derived neural cell functions: from mitochondria to depression

Depression's link to serotonin dysregulation is well-known. The monoamine theory posits that depression results from impaired serotonin activity, leading to the development of antidepressants targeting serotonin levels. However, their limited efficacy suggests a more complex cause. Recent studies highlight mitochondria as key players in depression's pathophysiology. Mounting evidence indicates that mitochondrial dysfunction significantly correlates with major depressive disorder (MDD), underscoring its pivotal role in depression. Exploring the serotonin-mitochondrial connection, our study investigated the effects of chronic serotonin treatment on induced-pluripotent stem cell-derived astrocytes and neurons from healthy controls and two case study patients. One was a patient with antidepressant non-responding MDD ("Non-R") and another had a non-genetic mitochondrial disorder ("Mito"). The results revealed that serotonin altered the expression of genes related to mitochondrial function and dynamics in neurons and had an equalizing effect on calcium homeostasis in astrocytes, while ATP levels seemed increased. Serotonin significantly decreased cytosolic and mitochondrial calcium in neurons. Electrophysiological measurements evidenced that serotonin depolarized the resting membrane potential, increased both sodium and potassium current density and ultimately improved the overall excitability of neurons. Specifically, neurons from the Non-R patient appeared responsive to serotonin in vitro, which seemed to improve neurotransmission. While it is unclear how this translates to the systemic level and AD resistance mechanisms are not fully elucidated, our observations show that despite his treatment resistance, this patient's cortical neurons are responsive to serotonergic signals. In the Mito patient, evidence suggested that serotonin, by increasing excitability, exacerbated an existing hyperexcitability highlighting the importance of considering mitochondrial disorders in patients with MDD, and avoiding serotonin-increasing medication. Taken together, our findings suggested that serotonin positively affects calcium homeostasis in astrocytes and increases neuronal excitability. The latter effect must be considered carefully, as it could have beneficial or detrimental implications based on individual pathologies.

Increased expression of ER stress, inflammasome activation, and mitochondrial biogenesis-related genes in peripheral blood mononuclear cells in major depressive disorder

A subset of major depressive disorder (MDD) is characterized by immune system dysfunction, but the intracellular origin of these immune changes remains unclear. Here we tested the hypothesis that abnormalities in endoplasmic reticulum (ER) stress, inflammasome activity and mitochondrial biogenesis contribute to the development of systemic inflammation in MDD. RT-qPCR was used to measure mRNA expression of key organellar genes from peripheral blood mononuclear cells (PBMCs) isolated from 186 MDD and 67 healthy control (HC) subjects. The comparative CT (2-ΔΔCT) method was applied to quantify mRNA expression using GAPDH as the reference gene. After controlling for age, sex, BMI, and medication status using linear regression models, expression of the inflammasome (NLRC4 and NLRP3) and the ER stress (XBP1u, XBP1s, and ATF4) genes was found to be significantly increased in the MDD versus the HC group. Sensitivity analyses excluding covariates yielded similar results. After excluding outliers, expression of the inflammasome genes was no longer statistically significant but expression of the ER stress genes (XBP1u, XBP1s, and ATF4) remained significant and the mitochondrial biogenesis gene, MFN2, was significantly increased in the MDD group. NLRC4 and MFN2 were positively correlated with serum C-reactive protein concentrations, while ASC trended significant. The altered expression of inflammasome activation, ER stress, and mitochondrial biogenesis pathway components suggest that dysfunction of these organelles may play a role in the pathogenesis of MDD.

Psychosocial experiences are associated with human brain mitochondrial biology

Psychosocial experiences affect brain health and aging trajectories, but the molecular pathways underlying these associations remain unclear. Normal brain function relies on energy transformation by mitochondria oxidative phosphorylation (OxPhos). Two main lines of evidence position mitochondria both as targets and drivers of psychosocial experiences. On the one hand, chronic stress exposure and mood states may alter multiple aspects of mitochondrial biology; on the other hand, functional variations in mitochondrial OxPhos capacity may alter social behavior, stress reactivity, and mood. But are psychosocial exposures and subjective experiences linked to mitochondrial biology in the human brain? By combining longitudinal antemortem assessments of psychosocial factors with postmortem brain (dorsolateral prefrontal cortex) proteomics in older adults, we find that higher well-being is linked to greater abundance of the mitochondrial OxPhos machinery, whereas higher negative mood is linked to lower OxPhos protein content. Combined, positive and negative psychosocial factors explained 18 to 25% of the variance in the abundance of OxPhos complex I, the primary biochemical entry point that energizes brain mitochondria. Moreover, interrogating mitochondrial psychobiological associations in specific neuronal and nonneuronal brain cells with single-nucleus RNA sequencing (RNA-seq) revealed strong cell-type-specific associations for positive psychosocial experiences and mitochondria in glia but opposite associations in neurons. As a result, these "mind-mitochondria" associations were masked in bulk RNA-seq, highlighting the likely underestimation of true psychobiological effect sizes in bulk brain tissues. Thus, self-reported psychosocial experiences are linked to human brain mitochondrial phenotypes.

Vitamin-mediated interaction between the gut microbiome and mitochondria in depression: A systematic review-based integrated perspective

Depression is one of the world's most prevalent mental disorders and its treatment remains suboptimal. Depression is a systemic disease with highly complex biological mechanisms. Emerging evidence points towards the involvement of mitochondria, microbiome and vitamins in its pathophysiology. Mitochondrial energy production was shown to be lowered in patients with depression. Mitochondrial energy production depends on vitamins, which are available from food, but are also synthesized by the gut microbiota. Several studies reported altered vitamin levels as well as changes in the gut microbiome composition and its vitamin metabolism in patients with depression. Therefore, the question of a connection between mitochondria and gut microbiome and vitamins influencing the mental health arises. This review aims to systematically investigate a combination of the topics - depression, mitochondria, microbiome, and vitamins - to generate an overview of a novel yet extremely complex and interconnected research field. A systematic literature search yielded 34 articles, and the results were summarized and bundled to develop this new integrative perspective on mitochondrial function mediated by the microbiome and microbiome-derived vitamins in depression. Furthermore, by discussing the research gaps this review aims to encourage innovative research approaches to better understand the biology of depression, which could result in optimized therapeutic approaches.

Choice of medium affects PBMC quantification, cell size, and downstream respiratory analysis

High-resolution respirometry (HRR) can assess peripheral blood mononuclear cell (PBMC) bioenergetics, but no standardized medium for PBMC preparation and HRR analysis exist. Here, we study the effect of four different media (MiR05, PBS, RPMI, Plasmax) on the count, size, and HRR (Oxygraph-O2k) of intact PBMCs. Remarkably, the cell count was 21 % higher when PBMCs were resuspended in MiR05 than in PBS or Plasmax, causing O2 flux underestimation during HRR due to inherent adjustments. Moreover, smaller cell size and cell aggregation was observed in MiR05. Based on our findings, we propose that Plasmax, PBS or RPMI is more suitable than MiR05 for HRR of intact PBMCs. We provide oxygen solubility factors for Plasmax and PBS and encourage further optimization of a standardized HRR protocol for intact PBMCs.

Development and validation of a risk prediction model for physical frailty in older adults who are disabled

Physical frailty is highly prevalent among the older adults who are disabled. The aim of this study was to explore the risk factors for physical frailty in older adults who are disabled and construct a nomogram prediction model. The data source was the China Health and Retirement Longitudinal Study (CHARLS). The prediction model was validated with a cohort of 1183 older adults who are disabled. The results showed that sleep quality, depression, fatigue, and chronic disease were the best predictive factors. These factors were used to construct the nomogram model, which showed good concordance and accuracy. The prediction model yielded an Area under the curve (AUC) value of 0.760. Calibration curves showed significant agreement between the nomogram model and actual observations. Receiver operating characteristic (ROC) and Decision curve analysis (DCA) showed that the nomogram had good predictive performance. The nomogram is contributed to the screening of specific populations by clinicians.

Muscle Mitochondrial Bioenergetic Capacities Are Associated With Multimorbidity Burden in Older Adults: The Study of Muscle, Mobility and Aging

BACKGROUND

The geroscience hypothesis posits that aging biological processes contribute to many age-related deficits, including the accumulation of multiple chronic diseases. Though only one facet of mitochondrial function, declines in muscle mitochondrial bioenergetic capacities may contribute to this increased susceptibility to multimorbidity.

METHODS

The Study of Muscle, Mobility and Aging (SOMMA) assessed ex vivo muscle mitochondrial energetics in 764 older adults (mean age = 76.4, 56.5% women, and 85.9% non-Hispanic White) by high-resolution respirometry of permeabilized muscle fibers. We estimated the proportional odds ratio (POR [95% CI]) for the likelihood of greater multimorbidity (4 levels: 0 conditions, N = 332; 1 condition, N = 299; 2 conditions, N = 98; or 3+ conditions, N = 35) from an index of 11 conditions, per SD decrement in muscle mitochondrial energetic parameters. Distribution of conditions allowed for testing the associations of maximal muscle energetics with some individual conditions.

RESULTS

Lower oxidative phosphorylation supported by fatty acids and/or complex I- and II-linked carbohydrates (eg, Max OXPHOSCI+CII) was associated with a greater multimorbidity index score (POR = 1.32 [1.13, 1.54]) and separately with diabetes mellitus (OR = 1.62 [1.26, 2.09]), depressive symptoms (OR = 1.45 [1.04, 2.00]) and possibly chronic kidney disease (OR = 1.57 [0.98, 2.52]) but not significantly with other conditions (eg, cardiac arrhythmia, chronic obstructive pulmonary disease).

CONCLUSIONS

Lower muscle mitochondrial bioenergetic capacities were associated with a worse composite multimorbidity index score. Our results suggest that decrements in muscle mitochondrial energetics may contribute to a greater global burden of disease and are more strongly related to some conditions than others.

Induced neural progenitor cells and iPS-neurons from major depressive disorder patients show altered bioenergetics and electrophysiological properties

The molecular pathomechanisms of major depressive disorder (MDD) are still not completely understood. Here, we follow the hypothesis, that mitochondria dysfunction which is inevitably associated with bioenergetic disbalance is a risk factor that contributes to the susceptibility of an individual to develop MDD. Thus, we investigated molecular mechanisms related to mitochondrial function in induced neuronal progenitor cells (NPCs) which were reprogrammed from fibroblasts of eight MDD patients and eight non-depressed controls. We found significantly lower maximal respiration rates, altered cytosolic basal calcium levels, and smaller soma size in NPCs derived from MDD patients. These findings are partially consistent with our earlier observations in MDD patient-derived fibroblasts. Furthermore, we differentiated MDD and control NPCs into iPS-neurons and analyzed their passive biophysical and active electrophysiological properties to investigate whether neuronal function can be related to altered mitochondrial activity and bioenergetics. Interestingly, MDD patient-derived iPS-neurons showed significantly lower membrane capacitance, a less hyperpolarized membrane potential, increased Na+ current density and increased spontaneous electrical activity. Our findings indicate that functional differences evident in fibroblasts derived from MDD patients are partially present after reprogramming to induced-NPCs, could relate to altered function of iPS-neurons and thus might be associated with the aetiology of major depressive disorder.

Identification of 7 mitochondria-related genes as diagnostic biomarkers of MDD and their correlation with immune infiltration: New insights from bioinformatics analysis

BACKGROUND

Major depressive disorder (MDD) is one of the most prevalent and debilitating psychiatric disorders. It becomes more recognized that mitochondrial dysfunction contributes to the pathophysiology of depression. However, little research has systematically investigated the mitochondria-related biomarkers for MDD diagnosis. This study aimed to develop a novel diagnostic gene signature in MDD based on mitochondria-related genes.

METHOD

We identified the differentially expressed mitochondrial-related genes (DeMRGs) by combing the gene expression data of the GEO database with mitochondria-related gene lists obtained from the MitoCarta3.0 database. Next, three kinds of machine-learning algorithms were used to screen characteristic DeMRGs. Then, we constructed a multivariable diagnostic model based on these characteristic genes and evaluated the diagnostic ability of this model. Subsequently, the immune landscape of infiltrated immune cells between MDD patients and controls was evaluated by CIBERSORT. Using consensus clustering analysis, we divided MDD patients into different clusters based on the characteristic DeMRGs expression patterns. Finally, the variations in immune cell infiltration between different clusters, and the correlation between characteristic DeMRGs and immune cell infiltration were analyzed.

RESULTS

Seven characteristic genes, including PMPCB, MRPS28, LYRM2, MGST1, COX20, PTPMT1, and STX17, were identified from the 31 DeMRGs. Based on the seven characteristic genes, we successfully constructed a diagnostic model which had relatively good diagnostic performance and potential application in the clinical diagnosis of MDD. In addition, our results also imply an intimate and comprehensive association between the characteristic DeMRGs and immune infiltrating cells.

CONCLUSION

A novel mitochondria-related gene signature with a good diagnostic performance and a relationship with immune microenvironment were identified in major depressive disorder.

Effects of 30 days bed rest and exercise countermeasures on PBMC bioenergetics

AIM

Altered mitochondrial function across various tissues is a key determinant of spaceflight-induced physical deconditioning. In comparison to tissue biopsies, blood cell bioenergetics holds promise as a systemic and more readily accessible biomarker, which was evaluated during head-down tilt bed rest (HDTBR), an established ground-based analog for spaceflight-induced physiological changes in humans. More specifically, this study explored the effects of HDTBR and an exercise countermeasure on mitochondrial respiration in peripheral blood mononuclear cells (PBMCs).

METHODS

We subjected 24 healthy participants to a strict 30-day HDTBR protocol. The control group (n = 12) underwent HDTBR only, while the countermeasure group (n = 12) engaged in regular supine cycling exercise followed by veno-occlusive thigh cuffs post-exercise for 6 h. We assessed routine blood parameters 14 days before bed rest, the respiratory capacity of PBMCs via high-resolution respirometry, and citrate synthase activity 2 days before and at day 30 of bed rest. We confirmed PBMC composition by flow cytometry.

RESULTS

The change of the PBMC maximal oxidative phosphorylation capacity (OXPHOS) amounted to an 11% increase in the countermeasure group, while it decreased by 10% in the control group (p = 0.04). The limitation of OXPHOS increased in control only while other respiratory states were not affected by either intervention. Correlation analysis revealed positive associations between white blood cells, lymphocytes, and basophils with PBMC bioenergetics in both groups.

CONCLUSION

This study reveals that a regular exercise countermeasure has a positive impact on PBMC mitochondrial function, confirming the potential application of blood cell bioenergetics for human spaceflight.

Integrating mitoepigenetics into research in mood disorders: a state-of-the-art review

Mood disorders, including major depressive disorder and bipolar disorder, are highly prevalent and stand among the leading causes of disability. Despite the largely elusive nature of the molecular mechanisms underpinning these disorders, two pivotal contributors-mitochondrial dysfunctions and epigenetic alterations-have emerged as significant players in their pathogenesis. This state-of-the-art review aims to present existing data on epigenetic alterations in the mitochondrial genome in mood disorders, laying the groundwork for future research into their pathogenesis. Associations between abnormalities in mitochondrial function and mood disorders have been observed, with evidence pointing to notable changes in mitochondrial DNA (mtDNA). These changes encompass variations in copy number and oxidative damage. However, information on additional epigenetic alterations in the mitochondrial genome remains limited. Recent studies have delved into alterations in mtDNA and regulations in the mitochondrial genome, giving rise to the burgeoning field of mitochondrial epigenetics. Mitochondrial epigenetics encompasses three main categories of modifications: mtDNA methylation/hydroxymethylation, modifications of mitochondrial nucleoids, and mitochondrial RNA alterations. The epigenetic modulation of mitochondrial nucleoids, lacking histones, may impact mtDNA function. Additionally, mitochondrial RNAs, including non-coding RNAs, present a complex landscape influencing interactions between the mitochondria and the nucleus. The exploration of mitochondrial epigenetics offers valuable perspectives on how these alterations impact neurodegenerative diseases, presenting an intriguing avenue for research on mood disorders. Investigations into post-translational modifications and the role of mitochondrial non-coding RNAs hold promise to unravel the dynamics of mitoepigenetics in mood disorders, providing crucial insights for future therapeutic interventions.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Mitochondrial and Cellular Function in Fibroblasts, Induced Neurons, and Astrocytes Derived from Case Study Patients: Insights into Major Depression as a Mitochondria-Associated Disease

The link between mitochondria and major depressive disorder (MDD) is increasingly evident, underscored both by mitochondria's involvement in many mechanisms identified in depression and the high prevalence of MDD in individuals with mitochondrial disorders. Mitochondrial functions and energy metabolism are increasingly considered to be involved in MDD's pathogenesis. This study focused on cellular and mitochondrial (dys)function in two atypical cases: an antidepressant non-responding MDD patient ("Non-R") and another with an unexplained mitochondrial disorder ("Mito"). Skin biopsies from these patients and controls were used to generate various cell types, including astrocytes and neurons, and cellular and mitochondrial functions were analyzed. Similarities were observed between the Mito patient and a broader MDD cohort, including decreased respiration and mitochondrial function. Conversely, the Non-R patient exhibited increased respiratory rates, mitochondrial calcium, and resting membrane potential. In conclusion, the Non-R patient's data offered a new perspective on MDD, suggesting a detrimental imbalance in mitochondrial and cellular processes, rather than simply reduced functions. Meanwhile, the Mito patient's data revealed the extensive effects of mitochondrial dysfunctions on cellular functions, potentially highlighting new MDD-associated impairments. Together, these case studies enhance our comprehension of MDD.

Increased expression of ER stress, inflammasome activation, and mitochondrial biogenesis-related genes in peripheral blood mononuclear cells in major depressive disorder

A subset of major depressive disorder (MDD) is characterized by immune system dysfunction, but the intracellular origin of these immune changes remains unclear. Here we tested the hypothesis that abnormalities in the endoplasmic reticulum (ER) stress, inflammasome activity and mitochondrial biogenesis contribute to the development of systemic inflammation in MDD. RT-qPCR was used to measure mRNA expression of key organellar genes from peripheral blood mononuclear cells (PBMCs) isolated from 186 MDD and 67 healthy control (HC) subjects. The comparative CT (2-ΔΔCT) method was applied to quantify mRNA expression using GAPDH as the reference gene. After controlling for age, sex, BMI, and medication status using linear regression models, expression of the inflammasome (NLRC4 and NLRP3) and the ER stress (XBP1u, XBP1s, and ATF4) genes was found to be significantly increased in the MDD versus the HC group. After excluding outliers, expression of the inflammasome genes was no longer statistically significant but expression of the ER stress genes (XBP1u, XBP1s, and ATF4) and the mitochondrial biogenesis gene, MFN2, was significantly increased in the MDD group. ASC and MFN2 were positively correlated with serum C-reactive protein concentrations. The altered expression of inflammasome activation, ER stress, and mitochondrial biogenesis pathway components suggest that dysfunction of these organelles may play a role in the pathogenesis of MDD.

Effects of Xiaoyao San on exercise capacity and liver mitochondrial metabolomics in rat depression model

Objective

This study aimed to investigate the therapeutic effects of Xiaoyao San (XYS), a herbal medicine formula, on exercise capacity and liver mitochondrial metabolomics in a rat model of depression induced by chronic unpredictable mild stress (CUMS).

Methods

A total of 24 male SD rats were randomly divided into four groups: control group (C), CUMS control group (M), Venlafaxine positive treatment group (V), and XYS treatment group (X). Depressive behaviour and exercise capacity of rats were assessed by body weight, sugar-water preference test, open field test, pole test, and rotarod test. The liver mitochondria metabolomics were analyzed by using liquid chromatography-mass spectrometry (LC-MS) method. TCMSP database and GeneCards database were used to screen XYS for potential targets for depression, and GO and KEGG enrichment analyses were performed.

Results

Compared with C group, rats in M group showed significantly lower body weight, sugar water preference rate, number of crossing and rearing in the open field test, climbing down time in the pole test, and retention time on the rotarod test (P < 0.01). The above behaviors and exercise capacity indices were significantly modulated in rats in V and X groups compared with M group (P < 0.05, 0.01). Compared with C group, a total of 18 different metabolites were changed in the liver mitochondria of rats in M group. Nine different metabolites and six metabolic pathways were regulated in the liver mitochondria of rats in X group compared with M group. The results of network pharmacology showed that 88 intersecting targets for depression and XYS were obtained, among which 15 key targets such as IL-1β, IL-6, and TNF were predicted to be the main differential targets for the treatment of depression. Additionally, a total of 1 553 GO signaling pathways and 181 KEGG signaling pathways were identified, and the main biological pathways were AGE-RAGE signaling pathway, HIF-1 signaling pathway, and calcium signaling pathway.

Conclusion

XYS treatment could improve depressive symptoms, enhance exercise capacity, positively regulate the changes of mitochondrial metabolites and improve energy metabolism in the liver of depressed rats. These findings suggest that XYS exerts antidepressant effects through multi-target and multi-pathway.

Association of transient mitochondrial functional impairment with acute heat exposure in children from Muzaffarpur region of Bihar, India

Over the past several years, the Muzaffarpur district of Bihar (India) has witnessed recurrent outbreaks of acute encephalitis illness of unknown etiology, called acute encephalitis syndrome (AES) among young children, especially during the peak-summer season. Pesticide exposure, viral encephalitis, and litchi toxin intake have all been postulated as potential sources of the ailment. However, no conclusive etiology for AES has been identified in the affected children. During recent rounds of the outbreak, metabolic abnormalities have been documented in these children, and a direct correlation was observed between higher environmental temperature during the peak-summer month and AES caseload. The clinical and metabolic profiles of these children suggested the possible involvement of mitochondrial dysfunction during heat stress as one of the several contributory factors leading to multisystem metabolic derangement. The present study observed that mitochondrial function parameters such as cell death, mitochondrial membrane potential, oxidative stress, and mitochondrial pathway-related gene expression in peripheral blood mononuclear cells (PBMCs) isolated from children were affected in peak-summer when compared to post-summer months. Similar observations of mitochondrial function parameters along with impaired bioenergetic parameters were demonstrated in the heat-exposed model of PBMCs isolated from healthy adult individuals. In conclusion, the results suggested that there is an association of transient mitochondrial dysfunction when exposed to sustained heat during the summer months. One may consider mitochondrial dysfunction as one of the important factors leading to an outbreak of AES among the children from affected regions though this needs to be substantiated with further studies.

A Brief Review of Low-Level Light Therapy in Depression Disorder

Introduction: Low-level laser therapy (LLLT), also called Photobiomodulation, has gained widespread acceptance as a mainstream modality, particularly in the form of photobiostimulation (PBM). Here in our review, we aim to present the application of LLLT to help with depression, explore potential action mechanisms and pathways, discuss existing limitations, and address the challenges associated with its clinical implementation. Methods: In biological systems, the visible light with a wavelength range of 400-700 nm activates photoreceptors involved in vision and circadian rhythm regulation. The near-infrared (NIR) light with a wavelength range of 800-1100 nm exhibits superior tissue penetration capabilities compared to the visible light, which enables the non-invasive application of LLLT to various tissues. Results: By enhancing adenosine triphosphate (ATP) production using the respiratory chain, LLLT is able to enhance blood flow, reduce inflammation, support repair and healing, and enhance stem cell growth and proliferation. Preclinical studies using animal models have shown promising neuroprotective effects of the LLLT method on central nervous system (CNS) diseases, suggesting potential improvements in brain function for patients suffering from Alzheimer's disease. In addition, it helps Parkinson's patients with their movement problems and ameliorates mental disorders in individuals with depression. Conclusion: patients' quality of life can be significantly enhanced. A comprehensive understanding of the protective effects and underlying mechanisms of LLLT will facilitate its therapeutic application in the future.

Targeting mitophagy for depression amelioration: a novel therapeutic strategy

Major depressive disorder is a global psychiatric condition characterized by persistent low mood and anhedonia, which seriously jeopardizes the physical and mental well-being of affected individuals. While various hypotheses have been proposed to explicate the etiology of depression, the precise pathogenesis and effective treatment of this disorder remain elusive. Mitochondria, as the primary organelles responsible for cellular energy production, possess the ability to meet the essential energy demands of the brain. Research indicated that the accumulation of damaged mitochondria is associated with the onset of depression. Mitophagy, a type of cellular autophagy, specifically targets and removes excess or damaged mitochondria. Emerging evidence demonstrated that mitophagy dysfunction was involved in the progression of depression, and several pharmacological interventions that stimulating mitophagy exerted excellent antidepressant actions. We provided an overview of updated advancements on the regulatory mechanism of mitophagy and the mitophagy abnormality in depressed patients and animals, as well as in cell models of depression. Meanwhile, various therapeutic strategies to restore mitophagy for depression alleviation were also discussed in this review.

Randomized controlled trial investigating potential effects of relaxation on mitochondrial function in immune cells: A pilot experiment

This study aimed to investigate the effect of a relaxation response induced by hypnosis on the mitochondrial energy production of immune cells compared to an everyday relaxing situation. Chronically stressed individuals (88% women) with at least moderate suggestibility were randomized to a hypnosis (20 min relaxation hypnosis; n = 20) or a control condition (20 min documentary; n = 22). Before and after intervention, peripheral blood was collected. The primary outcomes were mitochondrial respiration and density in immune cells measured by high-resolution respirometry and citrate synthase activity assays. As secondary outcome, perceived stress, anxiety, and depressive mood were assessed. The intervention led to no significant Group × Time effects on mitochondrial bioenergetic parameters but a significant Time effect (ηp2 = .09 -.10). Thus, there were no differences in the experimental conditions concerning the measured parameters of mitochondrial bioenergetics. Exploratory subanalyses indicated that stress, anxiety, and depressive mood were linked to lower mitochondrial respiration. Individuals with higher anxiety had less decrease in routine respiration over time than those with lower anxiety (ηp2 = .09). This study explores the effects of relaxation in the form of hypnosis compared to watching a video on the energy metabolism of immune cells. Relaxation, whether in targeted (hypnosis) or untargeted (documentary) form, affected mitochondrial respiration. Further research should focus on the long-term effects of relaxation on bioenergetics. The trial was retrospectively registered on 07/12/2021, DRKS00027356, https://drks.de/search/de/trial/DRKS00027356.

Comorbidity between major depressive disorder and physical diseases: a comprehensive review of epidemiology, mechanisms and management

Populations with common physical diseases - such as cardiovascular diseases, cancer and neurodegenerative disorders - experience substantially higher rates of major depressive disorder (MDD) than the general population. On the other hand, people living with MDD have a greater risk for many physical diseases. This high level of comorbidity is associated with worse outcomes, reduced adherence to treatment, increased mortality, and greater health care utilization and costs. Comorbidity can also result in a range of clinical challenges, such as a more complicated therapeutic alliance, issues pertaining to adaptive health behaviors, drug-drug interactions and adverse events induced by medications used for physical and mental disorders. Potential explanations for the high prevalence of the above comorbidity involve shared genetic and biological pathways. These latter include inflammation, the gut microbiome, mitochondrial function and energy metabolism, hypothalamic-pituitary-adrenal axis dysregulation, and brain structure and function. Furthermore, MDD and physical diseases have in common several antecedents related to social factors (e.g., socioeconomic status), lifestyle variables (e.g., physical activity, diet, sleep), and stressful live events (e.g., childhood trauma). Pharmacotherapies and psychotherapies are effective treatments for comorbid MDD, and the introduction of lifestyle interventions as well as collaborative care models and digital technologies provide promising strategies for improving management. This paper aims to provide a detailed overview of the epidemiology of the comorbidity of MDD and specific physical diseases, including prevalence and bidirectional risk; of shared biological pathways potentially implicated in the pathogenesis of MDD and common physical diseases; of socio-environmental factors that serve as both shared risk and protective factors; and of management of MDD and physical diseases, including prevention and treatment. We conclude with future directions and emerging research related to optimal care of people with comorbid MDD and physical diseases.

Peripheral blood mononuclear cells exhibit increased mitochondrial respiration after adjuvant chemo- and radiotherapy for early breast cancer

BACKGROUND

Adjuvant chemo- and radiotherapy cause cellular damage to tumorous and healthy dividing cells. Chemotherapy has been shown to cause mitochondrial respiratory dysfunction in non-tumorous tissues, but the effects on human peripheral blood mononuclear cells (PBMCs) remain unknown.

AIM

We aimed to investigate mitochondrial respiration of PBMCs before and after adjuvant chemo- and radiotherapy in postmenopausal patients with early breast cancer (EBC) and relate these to metabolic parameters of the patients.

METHODS

Twenty-three postmenopausal women diagnosed with EBC were examined before and shortly after chemotherapy with (n = 18) or without (n = 5) radiotherapy. Respiration (O2 flux per million PBMCs) was assessed by high-resolution respirometry of intact and permeabilized PBMCs. Clinical metabolic characteristics and mitochondrial DNA (mtDNA) content of PBMCs (mtDN relative to nuclear DNA) were furthermore assessed.

RESULTS

Respiration of intact and permeabilized PBMCs from EBC patients significantly increased with adjuvant chemo- and radiotherapy (p = 6 × 10-5 and p = 1 × 10-7 , respectively). The oxygen flux attributed to specific mitochondrial complexes and respiratory states increased by 17-43% compared to before therapy initiation. Similarly, PBMC mtDNA content increased by 40% (p = 0.002). Leukocytes (p = 0.0001), hemoglobin (p = 0.0003), and HDL cholesterol (p = 0.003) concentrations decreased whereas triglyceride (p = 0.01) and LDL (p = 0.02) concentrations increased after treatment suggesting a worsened metabolic state. None of the metabolic parameters or the mtDNA content of PBMCs correlated significantly with PBMC respiration.

CONCLUSION

This study shows that mitochondrial respiration and mtDNA content in circulating PBMCs increase after adjuvant chemo- and radiotherapy in postmenopausal patients with EBC. Besides the increased mtDNA content, a shift in PBMC subpopulation proportions towards cells relying on oxidative phosphorylation, who may be less sensitive to chemotherapy, might influence the increased mitochondrial respiration observed iafter chemotherapy.

Investigating mitochondrial bioenergetics in peripheral blood mononuclear cells of women with childhood maltreatment from post-parturition period to one-year follow-up

BACKGROUND

Childhood maltreatment (CM) exerts various long-lasting psychological and biological changes in affected individuals, with inflammation being an interconnecting element. Besides chronic low-grade inflammation, CM might also affect the energy production of cells by altering the function and density of mitochondria, i.e. the body's main energy suppliers. Here, we compared mitochondrial respiration and density in intact peripheral blood mononuclear cells (PBMC), from women with and without CM between two time points, i.e. at the highly inflammatory phase within 1 week after parturition (t0) and again after 1 year (t2).

METHODS

CM exposure was assessed with the Childhood Trauma Questionnaire. Whole blood was collected from n = 52 healthy women within the study 'My Childhood - Your Childhood' at both time points to isolate and cryopreserve PBMC. Thawed PBMC were used to measure mitochondrial respiration and density by high-resolution respirometry followed by spectrophotometric analyses of citrate-synthase activity.

RESULTS

Over time, quantitative respiratory parameters increased, while qualitative flux control ratios decreased, independently of CM. Women with CM showed higher mitochondrial respiration and density at t0, but not at t2. We found significant CM group × time interaction effects for ATP-turnover-related respiration and mitochondrial density.

CONCLUSIONS

This is the first study to longitudinally investigate mitochondrial bioenergetics in postpartum women with and without CM. Our results indicate that CM-related mitochondrial alterations reflect allostatic load, probably due to higher inflammatory states during parturition, which normalize later. However, later inflammatory states might moderate the vulnerability for a second-hit on the level of mitochondrial bioenergetics, at least in immune cells.

Depressive and Biopsychosocial Frailty Phenotypes: Impact on Late-life Cognitive Disorders

 In older age, frailty is a detrimental transitional status of the aging process featuring an increased susceptibility to stressors defined by a clinical reduction of homoeostatic reserves. Multidimensional frailty phenotypes have been associated with all-cause dementia, mild cognitive impairment (MCI), Alzheimer's disease (AD), AD neuropathology, vascular dementia, and non-AD dementias. In the present article, we reviewed current evidence on the existing links among depressive and biopsychosocial frailty phenotypes and late-life cognitive disorders, also examining common pathways and mechanisms underlying these links. The depressive frailty phenotype suggested by the construct of late-life depression (LLD) plus physical frailty is poorly operationalized. The biopsychosocial frailty phenotype, with its coexistent biological/physical and psychosocial dimensions, defines a biological aging status and includes motivational, emotional, and socioeconomic domains. Shared biological pathways/substrates among depressive and biopsychosocial frailty phenotypes and late-life cognitive disorders are hypothesized to be inflammatory and cardiometabolic processes, together with multimorbidity, loneliness, mitochondrial dysfunction, dopaminergic neurotransmission, specific personality traits, lack of subjective/objective social support, and neuroendocrine dysregulation. The cognitive frailty phenotype, combining frailty and cognitive impairment, may be a risk factor for LLD and vice versa, and a construct of depressive frailty linking physical frailty and LLD may be a good dementia predictor. Frailty assessment may enable clinicians to better target the pharmacological and psychological treatment of LLD. Given the epidemiological links of biopsychosocial frailty with dementia and MCI, multidomain interventions might contribute to delay the onset of late-life cognitive disorders and other adverse health-related outcomes, such as institutionalization, more frequent hospitalization, disability, and mortality.

Mitochondria-wide association study observed significant interactions of mitochondrial respiratory and the inflammatory in the development of anxiety and depression

The aim of this study was to investigate the possible interaction of mitochondrial dysfunction and inflammatory cytokines in the risk of anxiety and depression. We utilized the UK Biobank for the sample of this study. A mitochondria-wide association(MiWAS) and interaction analysis was performed to investigate the interaction effects of mitochondrial DNA (mtDNA)×C-reactive protein (CRP) on the risks of self-reported anxiety (N = 72,476), general anxiety disorder (GAD-7) scores (N = 80,853), self-reported depression (N = 80,778), Patient Health Questionnaire (PHQ-9) scores (N = 80,520) in total samples, females and males, respectively, adjusting for sex, age, Townsend deprivation index (TDI), education score, alcohol intake, smoking and 10 principal components. In all, 25 mtSNPs and 10 mtSNPs showed significant level of association with self-reported anxiety and GAD-7 score respectively. A total of seven significant mtDNA × CRP interactions were found for anxiety, such as m.3915G>A(MT-ND1) for self-reported anxiety in total subjects (P = 6.59 × 10^-3), m.4561T>C(MT-ND2) (P = 3.04 × 10^-3) for GAD-7 score in total subjects. For depression, MiWAS identified 17 significant mtSNPs for self-reported depression and 14 significant mtSNPs for PHQ-9 scores. 17 significant mtDNA associations (2 for self-reported depression and 15 for PHQ-9 score) was identified, such as m.14869G>A(MT-CYB; P = 2.22 × 10^-3) associated with self-reported depression and m.4561T>C (MT-ND2; P value = 3.02 × 10^-8) associated with PHQ-9 score in all subjects. In addition, 5 common mtDNA shared with anxiety and depression were found in MiWAS, and 4 common mtDNA variants were detected to interact with CRP for anxiety and depression, such as m.9899T>C(MT-CO3). Our study suggests the important interaction effects of mitochondrial function and CRP on the risks of anxiety and depression.

Different Effects of SSRIs, Bupropion, and Trazodone on Mitochondrial Functions and Monoamine Oxidase Isoform Activity

Mitochondrial dysfunction is involved in the pathophysiology of psychiatric and neurodegenerative disorders and can be used as a modulator and/or predictor of treatment responsiveness. Understanding the mitochondrial effects of antidepressants is important to connect mitochondria with their therapeutic and/or adverse effects. Pig brain-isolated mitochondria were used to evaluate antidepressant-induced changes in the activity of electron transport chain (ETC) complexes, monoamine oxidase (MAO), mitochondrial respiratory rate, and ATP. Bupropion, escitalopram, fluvoxamine, sertraline, paroxetine, and trazodone were tested. All tested antidepressants showed significant inhibition of complex I and IV activities at high concentrations (50 and 100 µmol/L); complex II + III activity was reduced by all antidepressants except bupropion. Complex I-linked respiration was reduced by escitalopram >> trazodone >> sertraline. Complex II-linked respiration was reduced only by bupropion. Significant positive correlations were confirmed between complex I-linked respiration and the activities of individual ETC complexes. MAO activity was inhibited by all tested antidepressants, with SSRIs causing a greater effect than trazodone and bupropion. The results indicate a probable association between the adverse effects of high doses of antidepressants and drug-induced changes in the activity of ETC complexes and the respiratory rate of mitochondria. In contrast, MAO inhibition could be linked to the antidepressant, procognitive, and neuroprotective effects of the tested antidepressants.

Effects of serotonergic psychedelics on mitochondria: Transdiagnostic implications for mitochondria-related pathologies

The use of serotonergic psychedelics has gained increasing attention in research, clinical practice and society. Growing evidence suggests fast-acting, transdiagnostic health benefits of these 5-hydroxytryptamine 2A receptor agonists. Here, we provide a brief overview of their benefits for psychological, cardiovascular, metabolic, neurodegenerative, and immunological pathologies. We then review their effect on mitochondria including mitochondrial biogenesis, functioning and transport. Mitochondrial dysregulation is a transdiagnostic mechanism that contributes to the aforementioned pathologies. Hence, we postulate that psychedelic-induced effects on mitochondria partially underlie their transdiagnostic benefits. Based on this assumption, we propose new treatment indications for psychedelics and that the health benefits induced by psychedelics depend on patient-specific mitochondrial dysregulation.

The shared molecular mechanisms underlying aging of the brain, major depressive disorder, and Alzheimer's disease: The role of circadian rhythm disturbances

An association with circadian clock function and pathophysiology of aging, major depressive disorder (MDD), and Alzheimer's disease (AD) is well established and has been proposed as a factor in the development of these diseases. Depression and changes in circadian rhythm have been increasingly suggested as the two primary overlapping and interpenetrating changes that occur with aging. The relationship between AD and depression in late life is not completely understood and probably is complex. Patients with major depression or AD suffer from disturbed sleep/wake cycles and altered rhythms in daily activities. Although classical monoaminergic hypotheses are traditionally proposed to explain the pathophysiology of MDD, several clinical and preclinical studies have reported a strong association between circadian rhythm and mood regulation. In addition, a large body of evidence supports an association between disruption of circadian rhythm and AD. Some clock genes are dysregulated in rodent models of depression. If aging, AD, and MDD share a common biological basis in pathophysiology, common therapeutic tools could be investigated for their prevention and treatment. Nitro-oxidative stress (NOS), for example, plays a fundamental role in aging, as well as in the pathogenesis of AD and MDD and is associated with circadian clock disturbances. Thus, development of therapeutic possibilities with these NOS-related conditions is advisable. This review describes recent findings that link disrupted circadian clocks to aging, MDD, and AD and summarizes the experimental evidence that supports connections between the circadian clock and molecular pathologic factors as shared common pathophysiological mechanisms underlying aging, AD, and MDD.

Enhanced mitochondrial oxidative metabolism in peripheral blood mononuclear cells is associated with fatty liver in obese young adults

Systemic inflammation underlies the association between obesity and nonalcoholic fatty liver disease (NAFLD). Here, we investigated functional changes in leukocytes' mitochondria in obese individuals and their associations with NAFLD. We analyzed 14 obese male Japanese university students whose body mass index was > 30 kg/m2 and 15 healthy age- and sex-matched lean university students as controls. We observed that the mitochondrial oxidative phosphorylation (OXPHOS) capacity with complex I + II-linked substrates in peripheral blood mononuclear cells (PBMCs), which was measured using a high-resolution respirometry, was significantly higher in the obese group versus the controls. The PBMCs' mitochondrial complex IV capacity was also higher in the obese subjects. All of the obese subjects had hepatic steatosis defined by a fatty liver index (FLI) score ≥ 60, and there was a positive correlation between their FLI scores and their PBMCs' mitochondrial OXPHOS capacity. The increased PBMCs' mitochondrial OXPHOS capacity was associated with insulin resistance, systemic inflammation, and higher serum levels of interleukin-6 in the entire series of subjects. Our results suggest that the mitochondrial respiratory capacity is increased in the PBMCs at the early stage of obesity, and the enhanced PBMCs' mitochondrial oxidative metabolism is associated with hepatic steatosis in obese young adults.

Mitochondrial oxygen respiration is associated with loneliness in a sample of community-dwelling adults

Loneliness, a distressing perception of insufficient social support, is associated with physical illness and premature mortality that may be explained by reduced mitochondrial efficiency. In this human study (n = 50), loneliness was associated with less efficient mitochondrial functioning, indicated by the bioenergetic health index (BHI; r = -.39, p = .009), coupling efficiency (r = -.34, p = .021), and phosphorylating respiration (r = .39, p = .009). These findings remained significant when controlling for age, sex, and body mass index. The association between loneliness and mitochondrial functioning is important, given that both have been associated with age-related diseases.

Downregulation of cyclic adenosine monophosphate levels in leukocytes of hibernating captive black bears is similar to reported cyclic adenosine monophosphate findings in major depressive disorder

Introduction

Cyclic adenosine monophosphate (cAMP) levels in the lymphoblasts and leukocytes of patients with major depressive disorder (MDD) have been reported to be downregulated compared to in controls. cAMP is a derivative of adenosine triphosphate (ATP), and low ATP turnover has been reported in the state of hypometabolism associated with human MDD and with mammalian hibernation due to suppression of mitochondrial metabolism. Similarities have been noted between many state-dependent neurobiological changes associated with MDD in humans and with mammalian hibernation.

Methods

To compare cAMP levels between human MDD and mammalian hibernation and to investigate whether cAMP downregulation is another state-dependent neurobiological finding, we measured cAMP concentrations in lysed leukocytes, plasma, and serum in serial blood specimens from nine female captive black bears (Ursus americanus; CBBs), and cortisol levels in serum from 10 CBBs.

Results

Cortisol levels were significantly higher during hibernation in CBBs, confirming previous findings in hibernating black bears and similar to findings in humans with MDD. cAMP levels were significantly lower during hibernation versus active states (pre-hibernation and exit from hibernation) and were similar to the cAMP downregulation reported in MDD patients versus euthymic patients or controls. cAMP level changes during the different states (hibernation, pre-hibernation, active) confirm their state-dependent status.

Discussion

These findings are similar to the neurobiological findings associated with the hypometabolism (metabolic depression) observed during mammalian hibernation and reported during MDD. A sudden increase in cAMP levels was observed before entrance into pre-hibernation and during exit from hibernation. Further investigation is suggested into the possible role of elevated cAMP levels in initiation of the chain reaction of changes in gene expression, proteins, and enzymes leading to the suppression of mitochondrial metabolism and to low ATP turnover. This process leads to hypometabolism, the old adaptive mechanism that is used by organisms for energy preservation and is associated with both mammalian hibernation and human MDD.

Decreased β-hydroxybutyrate and ketogenic amino acid levels in depressed human adults

β-hydroxybutyrate (BHB) is a major ketone body synthesized mainly in the liver mitochondria and is associated with stress and severity of depression in humans. It is known to alleviate depressive-like behaviors in mouse models of depression. In this study, plasma BHB, ketogenic and glucogenic amino acids selected from the Tohoku Medical Megabank Project Community-Based Cohort Study were analysed and measured using nuclear magnetic resonance spectroscopy. The Center for Epidemiologic Studies Depression Scale (CES-D) was utilized to select adult participants with depressive symptoms (CES-D ≥ 16; n = 5722) and control participants (CES-D < 16; n = 18,150). We observed significantly reduced plasma BHB, leucine, and tryptophan levels in participants with depressive symptoms. Using social defeat stress (SDS) mice models, we found that BHB levels in mice sera increased after acute SDS, but showed no change after chronic SDS, which differed from human plasma results. Furthermore, acute SDS increased mitochondrial BHB levels in the prefrontal cortex at 6 h. In contrast, chronic SDS significantly increased the amount of food intake but reduced hepatic mitochondrial BHB levels in mice. Moreover, gene transcriptions of voltage-dependent anion-selective channel 1 (Vdac1) and monocarboxylic acid transporter 1 (Mct1), major molecules relevant to mitochondrial biogenesis and BHB transporter, significantly decreased in the liver and PFC after chronic SDS exposure. These results provide evidence that hepatic and prefrontal mitochondrial biogenesis plays an important role in BHB synthesis under chronic stress and in humans with depressive symptoms.

The mitochondrial Ahi1/GR participates the regulation on mtDNA copy numbers and brain ATP levels and modulates depressive behaviors in mice

BACKGROUND

Previous studies have shown that depression is often accompanied by an increase in mtDNA copy number and a decrease in ATP levels; however, the exact regulatory mechanisms remain unclear.

METHODS

In the present study, Western blot, cell knockdown, immunofluorescence, immunoprecipitation and ChIP-qPCR assays were used to detect changes in the Ahi1/GR-TFAM-mtDNA pathway in the brains of neuronal Abelson helper integration site-1 (Ahi1) KO mice and dexamethasone (Dex)-induced mice to elucidate the pathogenesis of depression. In addition, a rescue experiment was performed to determine the effects of regular exercise on the Ahi1/GR-TFAM-mtDNA-ATP pathway and depression-like behavior in Dex-induced mice and Ahi1 KO mice under stress.

RESULTS

In this study, we found that ATP levels decreased and mitochondrial DNA (mtDNA) copy numbers increased in depression-related brain regions in Dex-induced depressive mice and Ahi1 knockout (KO) mice. In addition, Ahi1 and glucocorticoid receptor (GR), two important proteins related to stress and depressive behaviors, were significantly decreased in the mitochondria under stress. Intriguingly, GR can bind to the D-loop control region of mitochondria and regulate mitochondrial replication and transcription. Importantly, regular exercise significantly increased mitochondrial Ahi1/GR levels and ATP levels and thus improved depression-like behaviors in Dex-induced depressive mice but not in Ahi1 KO mice under stress.

CONCLUSIONS

In summary, our findings demonstrated that the mitochondrial Ahi1/GR complex and TFAM coordinately regulate mtDNA copy numbers and brain ATP levels by binding to the D-loop region of mtDNA Regular exercise increases the levels of the mitochondrial Ahi1/GR complex and improves depressive behaviors. Video Abstract.

Type 2 Diabetes Related Mitochondrial Defects in Peripheral Mononucleated Blood Cells from Overweight Postmenopausal Women

Type 2 diabetes (T2D) is a multisystem disease that is the subject of many studies, but the earliest cause of the disease has yet to be elucidated. Mitochondrial impairment has been associated with diabetes in several tissues. To extend the association between T2D and mitochondrial impairment to blood cells, we investigated T2D-related changes in peripheral mononucleated blood cells’ (PBMCs) mitochondrial function in two groups of women (CTRL vs. T2D; mean age: 54.1 ± 3.8 vs. 60.9 ± 4.8; mean BMI 25.6 ± 5.2 vs. 30.0 ± 5), together with a panel of blood biomarkers, anthropometric measurements and physiological parameters (VO2max and strength tests). Dual-energy X-ray absorptiometry (DXA) scan analysis, cardio-pulmonary exercise test and blood biomarkers confirmed hallmarks of diabetes in the T2D group. Mitochondrial function assays performed with high resolution respirometry highlighted a significant reduction of mitochondrial respiration in the ADP-stimulated state (OXPHOS; −30%, p = 0.006) and maximal non-coupled respiration (ET; −30%, p = 0.004) in PBMCs samples from the T2D group. The total glutathione antioxidant pool (GSHt) was significantly reduced (−38%: p = 0.04) in plasma samples from the T2D group. The fraction of glycated hemoglobin (Hb1Ac) was positively associated with markers of inflammation (C-reactive protein-CRP r = 0.618; p = 0.006) and of dyslipidemia (triglycerides-TG r = 0.815; p < 0.0001). The same marker (Hb1Ac) was negatively associated with mitochondrial activity levels (OXPHOS r = −0.502; p = 0.034; ET r = −0.529; p = 0.024). The results obtained in overweight postmenopausal women from analysis of PBMCs mitochondrial respiration and their association with anthropometric and physiological parameters indicate that PBMC could represent a reliable model for studying T2D-related metabolic impairment and could be useful for testing the effectiveness of interventions targeting mitochondria.

Modifiable risk factors of dementia linked to excitation-inhibition imbalance

Recent evidence identifies 12 potentially modifiable risk factors for dementia to which 40% of dementia cases are attributed. While the recognition of these risk factors has paved the way for the development of new prevention measures, the link between these risk factors and the underlying pathophysiology of dementia is yet not well understood. A growing number of recent clinical and preclinical studies support a role of Excitation-Inhibition (E-I) imbalance in the pathophysiology of dementia. In this review, we aim to propose a conceptual model on the links between the modifiable risk factors and the E-I imbalance in dementia. This model, which aims to address the current gap in the literature, is based on 12 mediating common mechanisms: the hypothalamic-pituitary-adrenal (HPA) axis dysfunction, neuroinflammation, oxidative stress, mitochondrial dysfunction, cerebral hypo-perfusion, blood-brain barrier (BBB) dysfunction, beta-amyloid deposition, elevated homocysteine level, impaired neurogenesis, tau tangles, GABAergic dysfunction, and glutamatergic dysfunction. We believe this model serves as a framework for future studies in this field and facilitates future research on dementia prevention, discovery of new biomarkers, and developing new interventions.

Baicalin ameliorates CUMS-induced depression-like behaviors through activating AMPK/PGC-1α pathway and enhancing NIX-mediated mitophagy in mice

Mitochondrial dysfunction has been reported to be involved in the pathogenesis of depression, and mitophagy is a key pathway for mitochondrial quality control. This study aimed to investigate the effect of baicalin on mitophagy in the hippocampus of mice exposed to chronic unpredictable mild stress (CUMS) and explore its potential mechanism. After exposure to CUMS for 6 weeks, mice were given baicalin (20 mg/kg) or fluoxetine (20 mg/kg) by oral gavage for 4 weeks, and HT22 cells were injured by corticosterone (CORT) in vitro. Depression-like behaviors were assessed by sucrose preference test and tail suspension test. The mitochondrial structure was observed by transmission electron microscopy. Detection of mitophagy and mitophagy-related protein by mitophagy kit and Western blot. The results showed that baicalin improved depressive-like behaviors in CUMS mice, and ameliorated mitochondrial structural impairment in the hippocampus neuron. Baicalin significantly down-regulated light chain 3(LC3)II/I, protein sequestosome 1 (P62), and translocase of the outer membrane 20 (TOM20), and up-regulated Nip-like protein (NIX), Adenylate activated protein kinase (AMPK), and Peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α. Furthermore, molecular docking showed that baicalin interacts with AMPK through hydrogen bonding. Baicalin increased NIX and AMPK, and improved mitophagy level and mitochondrial function in HT22 cells. Treatment with Phorbol 12-Myristate 13-acetate demonstrated that up-regulation of NIX ameliorated CORT-induced mitochondrial dysfunction in HT22 cells. In conclusion, the present study suggested that the antidepressant effect of baicalin may be related to the enhancement of NIX-mediated mitophagy through activating the AMPK/PGC-1α pathway by directly binding to AMPK.

A molecular framework for autistic experiences: Mitochondrial allostatic load as a mediator between autism and psychopathology

Molecular autism research is evolving toward a biopsychosocial framework that is more informed by autistic experiences. In this context, research aims are moving away from correcting external autistic behaviors and toward alleviating internal distress. Autism Spectrum Conditions (ASCs) are associated with high rates of depression, suicidality and other comorbid psychopathologies, but this relationship is poorly understood. Here, we integrate emerging characterizations of internal autistic experiences within a molecular framework to yield insight into the prevalence of psychopathology in ASC. We demonstrate that descriptions of social camouflaging and autistic burnout resonate closely with the accepted definitions for early life stress (ELS) and chronic adolescent stress (CAS). We propose that social camouflaging could be considered a distinct form of CAS that contributes to allostatic overload, culminating in a pathophysiological state that is experienced as autistic burnout. Autistic burnout is thought to contribute to psychopathology via psychological and physiological mechanisms, but these remain largely unexplored by molecular researchers. Building on converging fields in molecular neuroscience, we discuss the substantial evidence implicating mitochondrial dysfunction in ASC to propose a novel role for mitochondrial allostatic load in the relationship between autism and psychopathology. An interplay between mitochondrial, neuroimmune and neuroendocrine signaling is increasingly implicated in stress-related psychopathologies, and these molecular players are also associated with neurodevelopmental, neurophysiological and neurochemical aspects of ASC. Together, this suggests an increased exposure and underlying molecular susceptibility to ELS that increases the risk of psychopathology in ASC. This article describes an integrative framework shaped by autistic experiences that highlights novel avenues for molecular research into mechanisms that directly affect the quality of life and wellbeing of autistic individuals. Moreover, this framework emphasizes the need for increased access to diagnoses, accommodations, and resources to improve mental health outcomes in autism.

Agomelatine, Ketamine and Vortioxetine Attenuate Energy Cell Metabolism-In Vitro Study

This determination of the mitochondrial effect of pharmacologically different antidepressants (agomelatine, ketamine and vortioxetine) was evaluated and quantified in vitro in pig brain-isolated mitochondria. We measured the activity of mitochondrial complexes, citrate synthase, malate dehydrogenase and monoamine oxidase, and the mitochondrial respiratory rate. Total hydrogen peroxide production and ATP production were assayed. The most potent inhibitor of all mitochondrial complexes and complex I-linked respiration was vortioxetine. Agomelatine and ketamine inhibited only complex IV activity. None of the drugs affected complex II-linked respiration, citrate synthase or malate dehydrogenase activity. Hydrogen peroxide production was mildly increased by agomelatine, which might contribute to increased oxidative damage and adverse effects at high drug concentrations. Vortioxetine significantly reduced hydrogen peroxide concentrations, which might suggest antioxidant mechanism activation. All tested antidepressants were partial MAO-A inhibitors, which might contribute to their antidepressant effect. We observed vortioxetine-induced MAO-B inhibition, which might be linked to decreased hydrogen peroxide formation and contribute to its procognitive and neuroprotective effects. Mitochondrial dysfunction could be linked to the adverse effects of vortioxetine, as vortioxetine is the most potent inhibitor of mitochondrial complexes and complex I-linked respiration. Clarifying the molecular interaction between drugs and mitochondria is important to fully understand their mechanism of action and the connection between their mechanisms and their therapeutic and/or adverse effects.

Expression of DNA repair genes and its relevance for DNA repair in peripheral immune cells of patients with posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) involves elevated levels of cellular oxidative stress which jeopardizes the integrity of essential cell compartments. Previously, we demonstrated higher levels of DNA lesions in peripheral blood mononuclear cells (PBMCs) in PTSD. Retaining vital levels of DNA integrity requires cells to mobilize compensatory efforts in elevating their DNA-repair capacity. Accordingly, we hypothesized to find increased expression rates of the DNA-repair genes X-ray repair cross complementing 1 (XRCC1), poly (ADP-ribose) polymerase 1 (PARP1), and polymerase β (Polβ) in PBMCs of PTSD patients as compared to controls, leading to functionally relevant changes in DNA-repair kinetics. In a cohort of 14 refugees with PTSD and 15 without PTSD, we found significantly higher XRCC1 expression in PTSD patients than controls (U = 161.0, p = 0.009, Cohen's r = 0.49), and positive correlations between the severity of PTSD symptoms and the expression of XRCC1 (r_S = 0.57, p = 0.002) and PARP1 (r_S = 0.43, p = 0.022). Higher XRCC1 (F = 2.39, p = 0.010, η²_p = 0.10) and PARP1 (F = 2.15, p = 0.022, η²_p = 0.09) expression accounted for slower repair of experimentally X-ray irradiation-induced DNA damage, highlighting the possible physiological relevance of altered DNA-repair gene expression in PTSD. Our study provides first evidence for a compensatory regulation of DNA-repair mechanisms in PTSD. We discuss the implications of increased DNA damage and altered DNA-repair mechanisms in immune senescence, premature aging, and increased physical morbidity in PTSD.

Associations between cardiorespiratory fitness, monocyte polarization, and exercise-related changes in mnemonic discrimination performance in older adults

Biological aging is accompanied by a chronic pro-inflammatory state that may facilitate losses in hippocampal-dependent mnemonic discrimination. Aerobic exercise training promotes adaptations that include improved immune competency, higher cardiorespiratory fitness, and maintenance of hippocampal function. However, it is poorly understood whether, in active older adults, baseline immune cell profiles and cardiorespiratory fitness are possible mechanisms that facilitate the long-term benefits to hippocampal dependent mnemonic discrimination performance. This within-subjects study with counterbalanced conditions aimed to investigate whether baseline monocyte polarization and cardiorespiratory fitness influenced performance in the mnemonic similarity task (MST) and related Lure Discrimination Index (LDI) score after an acute bout of exercise. Twenty-one active older adults (M = 68 ± 5 yrs) underwent baseline testing in which blood samples were collected and cardiorespiratory fitness measured. Participants then returned and completed a seated rest or moderate intensity aerobic exercise condition in which the MST was proctored prior to and 5 min after each condition. A linear mixed effects model was used in which Participant ID was a random effect and Condition (rest v. exercise), Time (pre- v post-), and order were fixed main effects. Simple linear regression models were used to determine the variance accounted for by monocyte phenotypes and cardiorespiratory fitness for LDI scores post-condition. Post-rest LDI scores were significantly lower than post-exercise LDI scores (t(20) = -2.65, p < 0.02, d = -0.57). Intermediate monocytes were significant predictors of the change in pre- to post-exercise LDI scores (F(1, 19) = 6.03, p = 0.024, R² = 0.24) and cardiorespiratory fitness was a significant predictor of the difference between post-condition LDI scores (F(1, 19) = 6.71, p = 0.018, R² = 0.26). Our results suggest baseline cardiorespiratory fitness and intermediate monocytes may relate to the integrity of hippocampal-dependent mnemonic discrimination performance, and possibly the degree of responsiveness to aerobic exercise interventions.

Störungsspezifische und transdiagnostische Veränderung der Inflammationsaktivität bei psychischen Störungen

Zusammenfassung. Theoretischer Hintergrund: Empirische Befunde deuten vermehrt auf eine erhöhte Entzündungsaktivität im Zusammenhang mit psychischen Störungen hin. Inwieweit sich inflammatorische Veränderungen über Störungen hinweg unterscheiden bzw. ob Inflammation ein transdiagnostisches Korrelat psychischer Störungen darstellt, ist bisher jedoch noch nicht eindeutig beantwortet. Fragestellung: Liegen spezifische inflammatorische Marker (z. B. Zytokine) über psychische Störungen hinweg verändert vor und/oder gibt es störungsspezifische Zytokinveränderungen bei Major Depression (MDD), Bipolarer Störung, Schizophrenie und Angststörungen inkl. Posttraumatischer Belastungsstörung (PTBS). Methode: Basierend auf einer Literaturrecherche werden aktuelle metaanalytische Befunde, die Studien bei Patient_innen mit MDD, Bipolarer Störung, Schizophrenie oder Angststörungen inkl. PTBS im Vergleich zu gesunden Kontrollen betrachten, zusammengetragen und vergleichend dargestellt. Ergebnisse: Aktuelle Evidenz verweist relativ konsistent auf Veränderungen des Immunsystems, wobei v. a. das Zytokin Interleukin (IL–) 6 und das C-reaktive Protein (CRP) störungsübergreifend leicht erhöht sind. Schlussfolgerungen: Perspektivisch könnten Patient_innen mit chronisch inflammatorischen Erkrankungen und psychischen Störungen von psychotherapiebegleitenden antiinflammatorischen Maßnahmen wie bspw. körperlicher Aktivität, antiinflammatorischer Ernährung und Entspannungsverfahren profitieren.

Mitochondrial Genome Alterations, Cytochrome C Oxidase Activity, and Oxidative Stress: Implications in Primary Open-angle Glaucoma

Aim

To evaluate mitochondrial genome alterations, cytochrome c oxidase (COX) activity, and oxidative stress in primary open-angle glaucoma (POAG).

Methodology

Whole mitochondrial genome was screened in 75 POAG cases and 105 controls by polymerase chain reaction (PCR) sequencing. COX activity was measured from peripheral blood mononuclear cells (PBMCs). A protein modeling study was done to evaluate the impact of G222E variant on protein function. Levels of 8-hydroxy-2-deoxyguanosine (8-OHdG), 8-isoprostane (8-IP), and total antioxidant capacity (TAC) were also measured.

Results

A total of 156 and 79 mitochondrial nucleotide variations were found in the cohort of 75 POAG patients and 105 controls, respectively. Ninety-four (60.26%) variations spanned the coding region, and 62 (39.74%) variations spanned noncoding regions (D-loop, 12SrRNA, and 16SrRNA) of mitochondrial genome in POAG patients. Out of 94 nucleotide changes in coding region, 68 (72.34%) were synonymous changes, 23 (24.46%) non-synonymous, and three (3.19%) were found in the region coding for transfer ribonucleic acid (tRNA). Three changes (p.E192K in ND1, p.L128Q in ND2, and p.G222E in COX2) were found to be pathogenic. Twenty-four (32.0%) patients were positive for either of these pathogenic mitochondrial deoxyribonucleic acid (mtDNA) nucleotide changes. Majority of cases (18.7%) had pathogenic mutation in COX2 gene. Patients who harbored pathogenic mtDNA change in COX2 gene had significantly lower levels of COX activity (p < 0.0001) and TAC (p = 0.004), and higher levels of 8-IP (p = 0.01) as compared to patients who did not harbor this mtDNA. G222E changed the electrostatic potential and adversely impacted protein function of COX2 by affecting nonpolar interactions with neighboring subunits.

Conclusion

Pathogenic mtDNA mutations were present in POAG patients, which were associated with reduced COX activity and increased levels of oxidative stress.

Clinical significance

POAG patients should be evaluated for mitochondrial mutations and oxidative stress and may be managed accordingly with antioxidant therapies.

How to cite this article

Mohanty K, Mishra S, Dada R, et al. Mitochondrial Genome Alterations, Cytochrome C Oxidase Activity, and Oxidative Stress: Implications in Primary Open-angle Glaucoma. J Curr Glaucoma Pract 2022;16(3):158-165.

Hair cortisol level might be indicative for a 3PM approach towards suicide risk assessment in depression: comparative analysis of mentally stable and depressed individuals versus individuals after completing suicide

Depression and suicidal behavior are interrelated, stress-associated mental health conditions, each lacking biological verifiability. Concepts of predictive, preventive, and personalized medicine (3PM) are almost completely missing for both conditions but are of utmost importance. Prior research reported altered levels of the stress hormone cortisol in the scalp hair of depressed individuals, however, data on hair cortisol levels (HCL) for suicide completers (SC) are missing. Here, we aimed to identify differences in HCL between subject with depression (n = 20), SC (n = 45) and mentally stable control subjects (n = 12) to establish the usage of HCL as a new target for 3PM. HCL was measured in extracts of pulverized hair (1-cm and 3-cm hair segments) using ELISA. In 3-cm hair segments, an average increase in HCL for depressed patients (1.66 times higher; p = .011) and SC (5.46 times higher; p = 1.65 × 10⁻⁵) compared to that for controls was observed. Furthermore, the average HCL in SC was significantly increased compared to that in the depressed group (3.28 times higher; p = 1.4 × 10⁻⁵). A significant correlation between HCL in the 1-cm and the 3-cm hair segments, as well as a significant association between the severity of depressive symptoms and HCL (3-cm segment) was found. To conclude, findings of increased HCL in subjects with depression compared to that in controls were replicated and an additional increase in HCL was seen in SC in comparison to patients with depression. The usage of HCL for creating effective patient stratification and predictive approach followed by the targeted prevention and personalization of medical services needs to be validated in follow-up studies.

The aging of ER-mitochondria communication: A journey from undifferentiated to aged cells

The complex physiology of eukaryotic cells requires that a variety of subcellular organelles perform unique tasks, even though they form highly dynamic communication networks. In the case of the endoplasmic reticulum (ER) and mitochondria, their functional coupling relies on the physical interaction between their membranes, mediated by domains known as mitochondria-ER contacts (MERCs). MERCs act as shuttles for calcium and lipid transfer between organelles, and for the nucleation of other subcellular processes. Of note, mounting evidence shows that they are heterogeneous structures, which display divergent behaviors depending on the cell type. Furthermore, MERCs are plastic structures that remodel according to intra- and extracellular cues, thereby adjusting the function of both organelles to the cellular needs. In consonance with this notion, the malfunction of MERCs reportedly contributes to the development of several age-related disorders. Here, we integrate current literature to describe how MERCs change, starting from undifferentiated cells, and their transit through specialization, malignant transformation (i.e., dedifferentiation), and aging/senescence. Along this journey, we will review the function of MERCs and their relevance for pivotal cell types, such as stem and cancer cells, cardiac, skeletal, and smooth myocytes, neurons, leukocytes, and hepatocytes, which intervene in the progression of chronic diseases related to age.

Peripheral blood mononuclear cell mitochondrial enzyme activity is associated with parity and lactation performance in early lactation Holstein dairy cows

Mitochondria are central to metabolism and are the primary energy producers for all biosynthesis, including lactation. The objectives of this study were to determine if high- and low-producing dairy cows exhibit differences in peripheral blood mononuclear cell mitochondrial enzyme activities of citrate synthase, complex I, complex IV, and complex V during early lactation and, thus, to determine whether those differences were related to differences in lactation performance in the dairy cow. Fifty-six Holstein cows were assigned to 1 of 4 groups: (1) primiparous high, (2) primiparous low, (3) multiparous high, or (4) multiparous low. Primiparous and multiparous cows were analyzed separately. Then, cows were divided into high or low production groups for each production parameter [peak milk, average milk, energy-corrected milk (ECM), fat-corrected milk (FCM), milk lactose, milk fat, milk protein, total solids (TS), solids-not-fat, feed efficiency, and somatic cell count (SCC)]. For all data analysis, production parameters are expressed as yields (kg/d) and SCC (10³ cells/mL). High and low production groups were defined by their respective mean production parameters for the 56 cows, with below average cows defined as low and above average cows defined as high. Whole blood samples were collected at one time point, approximately 70 d in milk at 0800 h, and processed for crude mitochondrial extracts from peripheral blood mononuclear cells to determine the activity rates of mitochondrial enzymes. Milk samples were collected 9 times (3 d, 3 times per d) during the week of blood collection and analyzed for major components (fat, protein, lactose, TS, and SCC). Multiparous cows had lower citrate synthase activity than primiparous cows across all production parameters. High-producing cows had greater complex I activity for peak milk, milk yield, ECM, FCM, milk fat, TS, and feed efficiency, and greater complex V activity for ECM, FCM, milk lactose, milk fat, and TS across parities. These findings imply that the most influential respiratory chain enzymes on the level of milk production are those responsible for electron transport chain initialization and ATP production.

The Link Between Energy-Related Sensations and Metabolism: Implications for Treating Fatigue

Energy-related sensations include sensation of energy and fatigue as well as subjective energizability and fatigability. First, we introduce interdisciplinary useful definitions of all constructs and review findings regarding the question of whether sensations of fatigue and energy are two separate constructs or two ends of a single dimension. Second, we describe different components of the bodily energy metabolism system (e.g., mitochondria; autonomic nervous system). Third, we review the link between sensation of fatigue and different components of energy metabolism. Finally, we present an overview of different treatments shown to affect both energy-related sensations and metabolism before outlining future research perspectives.

Genomics-based identification of a potential causal role for acylcarnitine metabolism in depression

BACKGROUND

Altered metabolism of acylcarnitines - transporting fatty acids to mitochondria - may link cellular energy dysfunction to depression. We examined the potential causal role of acylcarnitine metabolism in depression by leveraging genomics and Mendelian randomization.

METHODS

Summary statistics were obtained from large GWAS: the Fenland Study (N = 9363), and the Psychiatric Genomics Consortium (246,363 depression cases and 561,190 controls). Two-sample Mendelian randomization analyses tested the potential causal link of 15 endogenous acylcarnitines with depression.

RESULTS

In univariable analyses, genetically-predicted lower levels of short-chain acylcarnitines C2 (odds ratio [OR] 0.97, 95% confidence intervals [CIs] 0.95-1.00) and C3 (OR 0.97, 95%CIs 0.96-0.99) and higher levels of medium-chain acylcarnitines C8 (OR 1.04, 95%CIs 1.01-1.06) and C10 (OR 1.04, 95%CIs 1.02-1.06) were associated with increased depression risk. No reverse potential causal role of depression genetic liability on acylcarnitines levels was found. Multivariable analyses showed that the association with depression was driven by the medium-chain acylcarnitines C8 (OR 1.04, 95%CIs 1.02-1.06) and C10 (OR 1.04, 95%CIs 1.02-1.06), suggesting a potential causal role in the risk of depression. Causal estimates for C8 (OR = 1.05, 95%CIs = 1.02-1.07) and C10 (OR = 1.05, 95%CIs = 1.02-1.08) were confirmed in follow-up analyses using genetic instruments derived from a GWAS meta-analysis including up to 16,841 samples.

DISCUSSION

Accumulation of medium-chain acylcarnitines is a signature of inborn errors of fatty acid metabolism and age-related metabolic conditions. Our findings point to a link between altered mitochondrial energy production and depression pathogenesis. Acylcarnitine metabolism represents a promising access point for the development of novel therapeutic approaches for depression.

Frailty and Depression in Late Life: A High-Risk Comorbidity With Distinctive Clinical Presentation and Poor Antidepressant Response

BACKGROUND

To investigate the longitudinal relationship between physical frailty, the clinical representation of accelerated biological aging, and antidepressant medication response in older adults with depressive illness.

METHODS

An 8-week randomized placebo-controlled trial (escitalopram or duloxetine) followed by 10 months of open antidepressant medication treatment (augmentation, switch strategies) was conducted in an outpatient research clinic. 121 adults aged 60 years or older with major depressive disorder (MDD) or persistent depressive disorder and a 24-item Hamilton Rating Scale for Depression (HRSD) ≥16 were enrolled. Primary measures assessed serially over 12 months include response (50% reduction from baseline HRSD score), remission (HRSD score <10), and frailty (non/intermediate frail [0-2 deficits] vs frail [≥3 deficits]); latent class analysis was used to classify longitudinal frailty trajectories.

RESULTS

A 2-class model best fit the data, identifying a consistently low frailty risk (63% of the sample) and consistently high frailty risk (37% of the sample) trajectory. Response and remission rates (ps ≤ .002) for adults in the high-risk frailty class were at least 21 percentage points worse than those in the low-risk class over 12 months. Furthermore, subsequent frailty was associated with previous frailty (ps ≤ .01) but not previous response or remission (ps ≥ .10).

CONCLUSIONS

Antidepressant medication is poorly effective for MDD occurring in the context of frailty in older adults. Furthermore, even when an antidepressant response is achieved, this response does little to improve their frailty. These data suggest that standard psychiatric assessment of depressed older adults should include frailty measures and that novel therapeutic strategies to address comorbid frailty and depression are needed.

Augmented T-cell mitochondrial reactive oxygen species in adults with major depressive disorder

The prevalence of major depressive disorder (MDD) is highest in young adulthood, an effect that has been magnified by the COVID-19 pandemic. Importantly, individuals with MDD are at a greater risk of developing cardiovascular disease (CVD). Accumulating evidence supports immune system dysregulation as a major contributor to the elevated CVD risk in older adults with MDD; however, whether this is present in young adults with MDD without comorbid disease remains unclear. Interestingly, recent data suggest augmented T-cell mitochondrial reactive oxygen species (T-cell mitoROS) as a potent driver of immune dysregulation in animal models of psychiatric disease. With this background in mind, we tested the hypothesis that young adults with MDD would have augmented T-cell mitoROS and circulating proinflammatory cytokines compared with healthy young adults without MDD (HA). Whole blood was drawn from 14 young adults with MDD (age: 23 ± 2 yr) and 11 HA (age: 22 ± 1 yr). T-cell mitoROS (MitoSOX red; total: CD3+, T-helper: CD4+, T cytotoxic: CD8+) and serum cytokines were assessed by flow cytometry. Total T-cell mitoROS was significantly greater in adults with MDD compared with HA [median: 14,089 arbitrary units (AU); median: 1,362 AU, P = 0.01]. Likewise, both T-helper and T-cytotoxic cell mitoROS were significantly greater in adults with MDD compared with HA (both: P < 0.05). There were no differences in circulating cytokines between groups (all cytokines: P > 0.05). Collectively, these findings suggest that elevated T-cell mitoROS may represent an early marker of immune system dysregulation in young, otherwise healthy, adults with MDD.NEW & NOTEWORTHY To our knowledge, we provide the first evidence of augmented T-cell mitochondrial reactive oxygen species (T-cell mitoROS) in young, otherwise healthy adults with MDD. Although the elevated T-cell mitoROS did not correspond to a proinflammatory profile, these findings suggest that elevated T-cell mitoROS may be an early marker of immune system dysregulation in young adults with MDD.