The kynurenine pathway in treatment-resistant schizophrenia at the crossroads between pathophysiology and pharmacotherapy.

Two cardinal elements in the complex and multifaceted pathophysiology of schizophrenia (SCZ) are neuroinflammation and dysregulation of glutamatergic neurotransmission, with the latter being especially involved in treatment-resistant schizophrenia (TRS). Interestingly, the Kynurenine (KYN) pathway (KP) is at the crossroad between them, constituting a potential causal link and a therapeutic target. Although there is preclinical and clinical evidence indicating a dysregulation of KP associated with the clinical phenotype of SCZ, clinical studies investigating the possible relationship between changes in biomarkers of the KP and response to pharmacotherapy are still limited. Therefore, we have studied possible differences in the circulating levels of biomarkers of the metabolism of tryptophan along the KP in 43 responders to first-line treatments (FLR) and 32 TRS patients treated with clozapine, and their possible associations with psychopathology in the two subgroups. Plasma levels of KYN were significantly higher in TRS patients than in FLR patients, indicating a greater activation of KP. Furthermore, the levels of quinolinic (NMDA receptor agonist) and kynurenic acid (NMDA negative allosteric modulator) showed a negative and a positive correlation with several dimensions and the overall symptomatology in the whole sample and in FLR, but not in TRS, suggesting a putative modulating effect of clozapine elicited through the NMDA receptors. Despite the cross-sectional design of the study that prevents us from demonstrating causation, these findings show a significant relationship among circulating KP biomarkers, psychopathology, and response to pharmacotherapy in SCZ. Therefore, plasma KP biomarkers should be further investigated for developing personalized medicine approaches in SCZ.

Depression in Heart Failure with Reduced Ejection Fraction, an Undervalued Comorbidity: An Up-To-Date Review.

Introduction: Depression is a common and severe comorbidity among individuals with heart failure (HF). Up to a third of all HF patients are depressed, and an even higher proportion have symptoms of depression. Aim: In this review, we evaluate the relationship between HF and depression, explain the pathophysiology and epidemiology of both diseases and their relationship, and highlight novel diagnostic and therapeutic options for HF patients with depression. Materials and Methods: This narrative review involved keyword searches of PubMed and Web of Science. Review search terms included ["Depression" OR "Depres*" OR "major depr*"] AND ["Heart Failure" OR "HF" OR "HFrEF" OR "HFmrEF" OR "HFpEF" OR "HFimpEF"] in all fields. Studies included in the review met the following criteria: (A) published in a peer-reviewed journal; (B) described the impact of depression on HF and vice versa; and (C) were opinion papers, guidelines, case studies, descriptive studies, randomized control trials, prospective studies, retrospective studies, narrative reviews, and systematic reviews. Results: Depression is an emergent HF risk factor and strongly relates with worse clinical outcomes. HF and depression share multiple pathways, including platelet dis-reactivity, neuroendocrine malfunction, inappropriate inflammation, tachi-arrhythmias, and frailty in the social and community setting. Existing HF guidelines urge evaluation of depression in all HF patients, and numerous screening tools are available. Depression is ultimately diagnosed based on DSM-5 criteria. There are both non-pharmaceutical and pharmaceutical treatments for depression. Regarding depressed symptoms, non-pharmaceutical treatments, such as cognitive-behavioral therapy and physical exercise, have shown therapeutic results, under medical supervision and with an effort level adapted to the patient's physical resources, together with optimal HF treatment. In randomized clinical studies, selective serotonin reuptake inhibitors, the backbone of antidepressant treatment, did not demonstrate advantage over the placebo in patients with HF. New antidepressant medications are currently being studied and could provide a chance to enhance management, treatment, and control of depression in patients with HF. Conclusions: Despite the substantial link between depression and HF, their combination is underdiagnosed and undertreated. Considering the hopeful yet unclear findings of antidepressant trials, further research is required to identify people who may benefit from antidepressant medication. The goal of future research should be a complete approach to the care of these patients, who are anticipated to become a significant medical burden in the future.