1.
Immediate and long-term consequences of COVID-19 infections for the development of neurological disease.
Heneka, MT, Golenbock, D, Latz, E, Morgan, D, Brown, R
Alzheimer's research & therapy. 2020;12(1):69
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Covid-19 may cause brain dysfunction evidenced by symptoms individuals experience once they have contracted the disease. Loss of smell, taste and confusion have all been reported by patients and a number of severe cases have reported incidences of stroke. These are all of concern, as Covid-19 can severely affect the elderly who ordinarily are the most likely to suffer from brain disorders. This small review paper of 27 studies stated that there are four possible ways in which Covid-19 may affect the brain, which put Covid-19 sufferers at an increased risk of long-term brain disorders. This was supported by findings, which showed one third of Covid-19 patients leave hospital with evidence of brain dysfunction. Inflammation was heavily reviewed by the authors as a possible causal factor. It was concluded that patients who survive Covid-19 infection are at an increased risk for developing brain disorders such as Alzheimer's disease, however it was acknowledged that further studies are required. Clinicians could use this study to understand the possible need for both short-term and long-term monitoring of brain function in individuals who have survived Covid-19, especially if they are elderly.
Abstract
Increasing evidence suggests that infection with Sars-CoV-2 causes neurological deficits in a substantial proportion of affected patients. While these symptoms arise acutely during the course of infection, less is known about the possible long-term consequences for the brain. Severely affected COVID-19 cases experience high levels of proinflammatory cytokines and acute respiratory dysfunction and often require assisted ventilation. All these factors have been suggested to cause cognitive decline. Pathogenetically, this may result from direct negative effects of the immune reaction, acceleration or aggravation of pre-existing cognitive deficits, or de novo induction of a neurodegenerative disease. This article summarizes the current understanding of neurological symptoms of COVID-19 and hypothesizes that affected patients may be at higher risk of developing cognitive decline after overcoming the primary COVID-19 infection. A structured prospective evaluation should analyze the likelihood, time course, and severity of cognitive impairment following the COVID-19 pandemic.
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Tryptophan Metabolism in Inflammaging: From Biomarker to Therapeutic Target.
Sorgdrager, FJH, Naudé, PJW, Kema, IP, Nollen, EA, Deyn, PP
Frontiers in immunology. 2019;10:2565
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Inflammation is a normal physiological process activated by the immune system in response to injury or infection. As we age, the immune system changes and the balance between pro- and anti-inflammatory agents can shift. This causes a chronic inflammatory state referred to as inflammaging. The rate of inflammaging is strongly associated with age-related disability, disease and mortality. The way in which the essential amino acid tryptophan (Trp) is broken down affects inflammation. If it is converted to kynurenine (Kyn) and its metabolites, inflammation is modulated. Studies have shown that the Kyn/Trp ratio, measured in blood, is strongly associated with ageing in humans. It could therefore be a useful marker to predict the onset of age-related diseases. This review discusses the metabolism of Trp and the links to inflammation. The authors hypothesize how intervening in these pathways could impact health- and lifespan. Future studies are needed to confirm the value of Trp metabolism as a biomarker for (un)healthy ageing and as drug target for inflammaging-related disease.
Abstract
Inflammation aims to restore tissue homeostasis after injury or infection. Age-related decline of tissue homeostasis causes a physiological low-grade chronic inflammatory phenotype known as inflammaging that is involved in many age-related diseases. Activation of tryptophan (Trp) metabolism along the kynurenine (Kyn) pathway prevents hyperinflammation and induces long-term immune tolerance. Systemic Trp and Kyn levels change upon aging and in age-related diseases. Moreover, modulation of Trp metabolism can either aggravate or prevent inflammaging-related diseases. In this review, we discuss how age-related Kyn/Trp activation is necessary to control inflammaging and alters the functioning of other metabolic faiths of Trp including Kyn metabolites, microbiota-derived indoles and nicotinamide adenine dinucleotide (NAD+). We explore the potential of the Kyn/Trp ratio as a biomarker of inflammaging and discuss how intervening in Trp metabolism might extend health- and lifespan.
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Effects of Probiotics on Cognitive Reactivity, Mood, and Sleep Quality.
Marotta, A, Sarno, E, Del Casale, A, Pane, M, Mogna, L, Amoruso, A, Felis, GE, Fiorio, M
Frontiers in psychiatry. 2019;10:164
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Gut and brain communicate with each other via the so-called gut-brain axis, which involves the neural, endocrine, and immune systems. The intestinal microbiota are thought to play a crucial role in this bidirectional communication. The aim of this double-blind, placebo-controlled pilot study was to investigate whether a multi-strain probiotic supplement can improve psychological wellbeing in healthy volunteers. 33 participants completed the trial and received either the probiotic powder or placebo for 6 weeks. Psychological assessments through a number of questionnaires relating to mood, sleep and personality aspects were carried out at baseline, weeks 3 and 6 and after a 3 week washout period. Significant improvements were seen in sleep and several aspects of mood in the probiotic but not the control group, although there were no statistically significant differences between the two groups. The authors conclude that probiotics might help to promote psychological well-being and speculate that probiotics, by interacting with intestinal microbiota, can facilitate the production of precursors of neuroactive substances involved in modulating emotional processing, sleep, and other brain functions.
Abstract
Recent demonstration that probiotics administration has positive effects on mood state in healthy populations suggests its possible role as an adjunctive therapy for depression in clinical populations and as a non-invasive strategy to prevent depressive mood state in healthy individuals. The present study extends current knowledge on the beneficial effects of probiotics on psychological well-being, as measured by changes in mood (e.g., cognitive reactivity to sad mood, depression, and anxiety), personality dimensions, and quality of sleep, which have been considered as related to mood. For this double-blind, placebo-controlled study 38 healthy volunteers assigned to an experimental or control group assumed a daily dose of a probiotic mixture (containing Lactobacillus fermentum LF16, L. rhamnosus LR06, L. plantarum LP01, and Bifidobacterium longum BL04) or placebo, respectively, for 6 weeks. Mood, personality dimensions, and sleep quality were assessed four times (before the beginning of the study, at 3 and 6 weeks, and at 3 weeks of washout). A significant improvement in mood was observed in the experimental group, with a reduction in depressive mood state, anger, and fatigue, and an improvement in sleep quality. No between-groups differences were found. These findings corroborate the positive effect of probiotics on mood state and suggest that probiotics administration may improve psychological well-being by ameliorating aspects of mood and sleep quality.