Effects of Supplementation with Probiotics in Experimental Models of Alzheimer's Disease: A Systematic Review of Animal Experiments.

BACKGROUND: Conditions along the brain-gut-microbiota (BGM) axis can significantly contribute to the pathogenesis of Alzheimer's disease (AD). Evidence from animal studies indicates a role of probiotics in regulating mood, cognition, and stress response via the BGM axis. However, the effect of probiotics on AD needs to be better clarified in preclinical and clinical studies. METHODS: We prepared this systematic review according to PRISMA. PubMed, Web of Science, Embase, and Virtual Health Library (VHL) were searched for original articles concerning the effects of probiotics in experimental AD. RESULTS: Results were presented as a narrative synthesis according to the Synthesis Without Metaanalysis (SWiM) Guideline. Seventeen studies met the inclusion criteria. The results showed significant effects in the experimental models of AD treated with probiotics alone or in mixture due to expressive improvements in cognitive tests. CONCLUSION: Furthermore, in most of the included studies, it was possible to observe a reduction in inflammatory processes, an increase in the concentration of peptide hormones, insulin homeostasis in the brain, increased antioxidant enzymes, and a decrease in beta-amyloid deposition and tau hyperphosphorylation. Supplementation of probiotics seems to improve performance in cognitive tests and increase the concentration of substances capable of delaying the neurodegenerative process of AD in experimental models.

Pathophysiology and possible treatments for olfactory-gustatory disorders in patients affected by COVID-19.

SARS-CoV-2 infects host cells mainly through the interaction between the virus's Spike protein and the viral receptors namely Angiotensin-Converting Enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2). Both are highly expressed in the gastrointestinal tract, in the nasal and bronchial epithelium, as well as in the type II alveolar epithelial cells. The aim of this review is to report the evidences from the scientific literature on the pathophysiology and the available treatments for olfactory-gustatory disorders in patients with COVID-19. The mechanisms involved in these disorders are still unclear and studies on specific therapies are scarce. However, it has been hypothesized that a decrease in the sensitivity of the sensory neurons as well as the co-expression of ACE2 and TMPRSS2 in the alveolar epithelial cells are the main causes of olfactory-gustatory disorders. The possible mechanisms described in the literature for changes in taste perception in patients with COVID-19 include olfactory disorders and a competitive activity of COVID-19 on ACE2 receptors in the taste buds. In addition, SARS-CoV-2 can bind to sialic acid receptors in the taste buds. In general, evidences show that there is no specific treatment for olfactory-taste disorders induced by SARS-CoV-2, even though some treatments have been used and have shown some promising results, such as olfactory training, intranasal application of sodium citrate and vitamin A, as well as systemic use of omega-3 and zinc. Corticosteroids have also been used as a pharmacological approach to treat patients with olfactory dysfunction with some contradictory results. The knowledge of the mechanisms by which SARS-CoV-2 influences the sensory systems and how effective therapies can treat the loss of smell and taste will have important implications on the understanding and clinical management of olfactory-taste disorders.

Essential Oils in Experimental Models of Neuropsychiatric Disorders: A Systematic Review.

BACKGROUND: Neural cells undergo functional or sensory loss due to neurological disorders. In addition to environmental or genetic factors, oxidative stress is a major contributor to neurodegeneration. In this context, there has been a growing interest in investigating the effects of EOs (EOs) in recent years, especially in the treatment of neuropathologies. The chemical and biological effects of EOs have led to important treatment tools for the management of various neurological disorders. OBJECTIVE: In the present study we performed a systematic review that sought to comprehend the neuroprotective effects of different EOs. METHOD: This work is a systematic review where an electronic search was performed on PubMed, ScienceDirect, Cochrane Library and SciELO (Scientific Electronic Library Online) databases, covering the last 10 years, using "Essential oil" and "Neuroprotective effect" as reference terms. RESULTS: A total of 9 articles were identified, in which the efficacy of EOs was described in experimental models of anxiety, dementia, oxidative stress, cerebral ischemia, Alzheimer's disease, and oxidative toxicity. CONCLUSION: EOs from different species of medicinal plants have shown positive responses in neurological disorders such as anxiety, dementia, oxidative stress, cerebral ischemia, and oxidative toxicity. Thus, EOs emerges with the potential to be used as alternative agents in the treatment of neurological disorders.