Background: Mitochondria play a pivotal role in energy production, and their dysfunction not only hampers cells' ability to meet energy requirements but also contributes to the impairment of neural plasticity, a critical feature of depressive disorders. In this study, mitochondrial cross-omics analysis was carried out in the hippocampus of restraint rats to understand the role of mitochondria in depression pathophysiology.
Methods: The expression profiles of hippocampal mitochondrial and nuclear-encoded genes in mitochondrial fractions from restraint and handled control rats were obtained using high-throughput RNA sequencing. Weighted gene co-expression network analysis (WGCNA) was used to identify the gene co-expression and pathways associated with the restraint phenotype. Mutual Information Network algorithm tools Arance, CLR, and MRNET were additionally used to screen the functional modules and hub genes and their similarity with the WGCNA-based network analysis. Finally, cross-species homology followed by gene association analysis was conducted to obtain SNPs and haplotypes related to depression phenotype.
Results: A significant proportion of mitochondrial and nuclear-encoded genes showed differential regulation in the hippocampus of restraint rats. WGCNA and Mutual Information Network analysis yielded distinct functional modules significantly related to restraint phenotype. Further network analysis revealed distinct co-expression patterns associated with differentially expressed genes associated with these modules. Cross-species analysis showed 39 significantly associated SNPs with the depression phenotype, where the most significant SNP, rs10899570, was located within the TENM4 gene. Further, rs1573529 and rs10899570 were distributed into the linkage disequilibrium block where SNPs were highly correlated. Subsequent haplotype analysis showed that rs1573529 and rs10899570 were significantly associated with depressive behavior.
Conclusions: The study demonstrates a significant impact of restraint stress on mitochondrial functions and genetic association, suggesting their critical role in depression pathophysiology.
Background: It is well established that peroxisome proliferator-activated receptor α (PPARα) plays a crucial role in the pathogenesis of depression. Several PPARα agonists, including WY14643, fenofibrate, and gemfibrozil, have been reported to produce antidepressant-like effects in mouse models through PPARα-mediated enhancement of hippocampal brain-derived neurotrophic factor (BDNF) signaling and neurogenesis. Pemafibrate is a novel and highly selective modulator of PPARα; we therefore hypothesized that it might also exhibit antidepressant-like efficacy.
Methods: We employed 2 established mouse models of depression, chronic unpredictable mild stress (CUMS) and chronic restraint stress (CRS), to evaluate the potential antidepressant effects of pemafibrate. Western blotting and immunofluorescence were used to assess whether pemafibrate treatment counteracts chronic stress-induced suppression of hippocampal PPARα, BDNF signaling, and neurogenesis. To investigate the mechanism of action, we utilized pharmacological inhibitors (GW6471 for PPARα and K252a for BDNF signaling) combined with adeno-associated virus-mediated genetic knockdown approaches.
Results: Repeated pemafibrate administration significantly ameliorated chronic stress-induced depressive-like behaviors and restored hippocampal PPARα levels, BDNF signaling, and neurogenesis in both models. These antidepressant effects were markedly attenuated by co-administration of GW6471 or K252a. Similarly, genetic knockdown of either hippocampal PPARα or BDNF abolished pemafibrate's antidepressant-like actions.
Conclusions: Pemafibrate exerts antidepressant-like effects in both CUMS and CRS mouse models by promoting hippocampal PPARα and BDNF signaling.
Studying psychiatric illness has often been limited by difficulties in connecting symptoms and behavior to neurobiology. Computational psychiatry approaches promise to bridge this gap by providing formal accounts of the latent information processing changes that underlie the development and maintenance of psychiatric phenomena. Models based on these theories generate individual-level parameter estimates which can then be tested for relationships to neurobiology. In this review, we explore computational modelling approaches to one key aspect of health and illness: affect. We discuss strengths and limitations of key approaches to modelling affect, with a focus on reinforcement learning, active inference, the hierarchical gaussian filter, and drift-diffusion models. We find that, in this literature, affect is an important source of modulation in decision making, and has a bidirectional influence on how individuals infer both internal and external states. Highlighting the potential role of affect in information processing changes underlying symptom development, we extend an existing model of psychosis, where affective changes are influenced by increasing cortical noise and consequent increases in either perceived environmental instability or expected noise in sensory input, becoming part of a self-reinforcing process generating negatively valenced, over-weighted priors underlying positive symptom development. We then provide testable predictions from this model at computational, neurobiological, and phenomenological levels of description.
Importance: The comorbidity of major depressive disorder (MDD) and alcohol use disorder (AUD) is often treated inadequately. This study evaluated the impact of adding the opioid receptor blocker, naltrexone, to the NMDA glutamate receptor antagonist, ketamine, for the treatment of MDD comorbid with AUD. In so doing, it also attempted to shed light on the contribution of opioid receptor stimulation to the antidepressant effects of ketamine in this population.
Objective: To compare the efficacy of ketamine plus naltrexone to ketamine plus saline and midazolam plus saline for reducing depression and decreasing alcohol consumption in outpatients with comorbid MDD and AUD.
Design, setting, and participants: A 3-arm, randomized, double-blind, parallel-group study was conducted. Participants were 65 adults with current MDD and AUD, with Montgomery-Åsberg Depression Rating Scale (MADRS) total score of 20 or higher and heavy drinking at least 4 times in the month prior to randomization.
Interventions: Randomized (1:1:1) to receive (1) intravenous (IV) ketamine (0.5 mg/kg) once a week for 4 weeks (a total of 4 infusions) plus intramuscular (IM) naltrexone (380 mg), (2) IV ketamine plus IM saline, or (3) IV midazolam (0.045 mg/kg) plus IM saline.
Main outcomes and measures: Co-primary: MADRS; complete alcohol abstinence. Secondary: alcohol craving, anxiety, quality of life, safety.
Results: Of 65 participants, 58 received at least 1 ketamine/midazolam infusion: 20 in ketamine-naltrexone, 19 in ketamine-saline, 19 in midazolam-saline. All groups improved significantly (>80% depression remission). No group differences were observed in MADRS changes during treatment (primary outcome), although antidepressant effects persisted longer in ketamine groups compared to midazolam. There were no significant group differences in alcohol-related outcomes. Ketamine groups showed greater improvement in anxiety and quality of life (secondary outcomes) than midazolam, with the ketamine-naltrexone group showing greater improvement in anxiety than ketamine-saline. No study-related serious adverse events.
Conclusions and relevance: This study found similar antidepressant and anti-alcohol effects across 3 groups. Compared to midazolam, the ketamine groups showed longer-lasting antidepressant effects and greater improvements in anxiety and quality of life. Comparable outcomes between the 2 ketamine groups suggest opioid receptor antagonism did not alter ketamine's therapeutic effects.
Clinical trial registration: The study was registered at ClinicalTrials.gov (Identifier: NCT02461927).
Background: Inadequate sleep is a prevalent health issue in modern society, with unintended consequences in dysregulation of the reward system. For example, acute sleep deprivation (SD) in humans increases craving for and intake of calorie-dense foods, which lead to further health concerns. The circuit and molecular mechanisms underlying sleep regulation of reward, however, remain poorly understood. The hypothalamic orexin (also called hypocretin) system is phylogenetically conserved to dually regulate sleep/arousal and reward. Here, we tested the hypothesis that acute SD engages the orexin (OX) system to modulate food reward seeking.
Methods: We used sucrose self-administration (SA) model in male and female mice to test how acute SD by gentle handling regulates sucrose reward seeking. We then administered specific OX receptor antagonists systemically (Ox1R antagonist SB-334867 10 mg/kg or Ox2R antagonist seltorexant 10 mg/kg) or in selective brain regions (up to 100 μm) to assess their respective roles.
Results: We found that under normal sleep conditions the OX system is minimally involved in sucrose reward seeking. By contrast, SD increased sucrose SA in both male and female mice, and preferentially engaged orexin receptor 2 (Ox2R) signaling in females to mediate this effect. Moreover, in nucleus accumbens or paraventricular nucleus of hypothalamus, key reward regulatory regions enriched in Ox2Rs, blocking Ox2R signaling in each individually did not counteract the SD effects in females. Finally, c-Fos analysis showed highly correlative activity levels between diverse cortical and subcortical regions during sucrose SA in females, revealing differential network engagement following SD, which was partially restored by systemic Ox2R antagonism following SD in females.
Conclusion: These results highlight Ox2R signaling in counteracting the acute SD effects on food reward seeking in females.
Treatment-resistant schizophrenia affects over half of individuals with schizophrenia. Clozapine is the only approved treatment in the United States but often provides limited relief. Augmenting clozapine with cariprazine (CAR) (a D3-preferring dopamine D2-D3 partial agonist) may improve outcomes. This systematic review evaluated the efficacy and safety of this combination in patients with sub-optimal response. A search of PubMed, Embase, and Cochrane Library yielded 52 cases from 21 eligible studies to be included in the analysis. Patient and treatment characteristics and clinical outcomes were synthesized. Cariprazine replaced another antipsychotic or was added to clozapine monotherapy in 44.2% and 34.6% of cases, respectively. Before treatment, 90% of patients had positive and 81% had negative symptoms. Combination therapy improved these symptoms in 66% and 83% of cases, respectively. In 19 patients with Positive and Negative Symptom Scale scores available before and after treatment, total scores decreased by 43.4%, with positive and negative subscale reductions of 23.0% and 59.1%. The combination was generally well tolerated; some patients experienced weight loss and reduced clozapine-related side effects. New adverse events occurred in 19% (most commonly akathisia at 6%). Cariprazine was discontinued in 17% of cases due to side effects or lack of efficacy. Overall, the combination appears safe and promising, especially for persistent negative symptoms, likely due to complementary neuroreceptor effects. Larger controlled trials are needed to confirm these findings.
Background: Treatment for major depressive disorder (MDD) should be optimized as early as possible in the disease course to minimize patient suffering and maximize clinical benefits. This post hoc analysis aimed to investigate the efficacy and safety of adjunctive brexpiprazole in patients who were earlier and later in the disease course.
Methods: Data were pooled from three 6-week, randomized, double-blind, placebo-controlled trials of adjunctive brexpiprazole in adult outpatients with MDD and inadequate response to antidepressant treatment. "Earlier" and "later" disease course subgroups were defined based on the proxies of median age, age at diagnosis, number of episodes, episode duration, and number of prior antidepressants. Efficacy was assessed by changes in Montgomery-Åsberg Depression Rating Scale (MADRS) total score, and safety by treatment-emergent adverse events.
Results: Greater improvement in MADRS total score at week 6 (P < .05) was observed for antidepressant + brexpiprazole 2-3 mg/day (n = 579) versus antidepressant + placebo (n = 583) in all subgroups representing earlier and later disease course, with treatment effects (least-squares mean differences in score change) ranging from -1.79 to -2.92 points. The incidence of treatment-emergent adverse events across subgroups was 53.1%-67.2% for antidepressant + brexpiprazole 2-3 mg/day and 43.0%-51.8% for antidepressant + placebo, with no consistent differences in patients who were earlier or later in the disease course.
Conclusions: Adjunctive brexpiprazole improved depressive symptoms earlier in the disease course, when benefits to patients and healthcare systems can be maximized. Adjunctive brexpiprazole also improved depressive symptoms later in the disease course; there was no advantage of delaying brexpiprazole treatment.
Trial registration: Post hoc analysis of NCT01360645, NCT01360632, NCT02196506 (ClinicalTrials.gov).
Background: Hexahydrocannabinol (HHC) is a new psychoactive substance known for its mind-altering effects and temporary legal status. It is widely used in parts of the Europe and United Kingdom as a legal alternative to ∆9-tetrahydrocannabinol, yet little research has explored its effects and safety. This study examined how HHC is processed in the body, its toxicity, and its impact on behavior in male Wistar rats.
Methods: A 1:1 mixture of (9R)-HHC and (9S)-HHC was administered via intragastric gavage at doses of 1, 5, and 10 mg/kg. Behavioral effects were assessed using the open field test and the prepulse inhibition of acoustic startle response.
Results: Two hours after the highest dose (10 mg/kg), peak concentrations of HHC were detected in blood and brain tissue. The Organization for Economic Co-operation and Development 423 toxicity test classified HHC as a Category 4 substance, estimating a lethal dose of 1000 mg/kg. Compared to controls (administered by sunflower oil), 10 mg/kg HHC reduced movement, increased anxiety, and impaired sensory processing.
Conclusions: Overall, HHC crosses the blood-brain barrier, exhibits mild toxicity, and induces behavioral effects similar to tetrahydrocannabinol. Its dose-dependent anxiogenic properties and impact on information processing highlight the importance of the appropriate dosing in any potential therapeutic use.
Background: Anhedonia is a key symptom and part of the diagnostic criterion of major depressive disorder (MDD). However, the relationship between anhedonia severity and the clinical, humanistic, and economic burden among patients with MDD is poorly understood.
Methods: Adults diagnosed with depression were identified from the 2022 US National Health and Wellness Survey (NHWS). Participants with depression were recontacted to participate in an online cross-sectional survey to collect data on anhedonia, using the Snaith-Hamilton Pleasure Scale (SHAPS). Multivariable analyses assessed the association of SHAPS score with health-related outcomes, while controlling for age, sex, race, comorbidity burden, and insurance status. The SHAPS (score range: 14 to 56) assesses the ability to experience pleasure, with higher scores indicating greater levels of anhedonia.
Results: Of the 8270 NHWS respondents with depression who met inclusion criteria, 665 completed the recontact survey (mean age, 58.4 years; female, 78.3%). Mean SHAPS score was 25.4 (range, 14-47). After adjustments for covariates, higher SHAPS scores were significantly (all P <.05) associated with higher levels of depression (β = 0.211) and anxiety (β = 0.126), poorer mental (β = -0.339) and physical health-related quality of life (β = -0.178), greater impairment while working [rate ratio (RR) = 1.02], and higher direct medical costs (RR = 1.02).
Conclusions: In adults with depression, higher levels of anhedonia were associated with greater clinical, humanistic, and economic burden. These results highlight the need for targeted treatments to help patients with MDD with prominent anhedonia attain improved clinical, humanistic, and work productivity outcomes.
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