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The bidirectional communication between brain structures and the gastrointestinal tract involving the microbiota defines the scientific concept of the brain–gut–microbiome axis. The intestinal microbiome plays an important role in many physiological and biochemical processes in the body, in the immune response, in the maintenance of homeostasis, and in the regulation of circadian rhythms. There is a relationship between higher prevalences of a number of neurological disorders, sleep disorders, and changes in the intestinal microbiota, so it is important to study the complex mechanisms of such correlations for the development of new treatment and prevention strategies. Environmental factors associated with excessive exposure to light can aggravate dysbiosis of the intestinal microflora, producing sleep disorders as a result. This review discusses the integrative mechanisms of regulation of sleep involving the intestinal microbiota (the roles of neurotransmitters, short-chain fatty acids, unconjugated bile acids, bacterial cell wall components, and cytokines). Taking account of the influences of intestinal dysbiosis as a risk factor in the development of various diseases, this review systematizes the key aspects and modern scientific data on the importance of the balance of the microflora to ensure optimal interactions along the brain–gut–microbiome axis in the context of the regulatory role of the sleep-waking cycle and its disorders. [ABSTRACT FROM AUTHOR]

Selective and progressive neuronal death is a characteristic feature of the neurodegenerative process and leads to corresponding neuronal dysfunctions. Neurodegenerative diseases constitute a heterogeneous group of nosologies with different clinical presentations but similar molecular mechanisms of pathogenesis. They are based on the processes of abnormal protein aggregation, the formation of fibrillar insoluble structures, and their deposition as histopathological inclusions in nervous system tissues. Disruption of homeostatic functions regulating neuronal ion and energy metabolism, protein and nucleotide biosynthesis and degradation, chronic hypoxia, and penetration of toxic and inflammatory substances into the brain from the bloodstream not only cause age-related metabolic changes and disturbances in the sleep–waking cycle, but also contribute to the development of neurodegenerative processes. Animal studies have identified pathways for the perivascular clearance of solutes and specific tracers into the meningeal lymphatics. The glymphatic network facilitates the clearance of metabolites, including amyloid β and tau protein, from the parenchymal extracellular space of the brain. This review discusses the observations that the glymphatic system is more efficient during natural sleep and that the fluid dynamics through this pathway exhibit daily fluctuations and are under circadian control. The discussion addresses key aspects and scientific data from recent studies on the role of the glymphatic pathway and astroglial aquaporin type 4 as its main determinant in maintaining homeostatic fluid circulation in the brain in normal and pathological conditions, particularly in connection with the regulatory role of the sleep–waking cycle and during the development of neurodegenerative processes. [ABSTRACT FROM AUTHOR]

Selective and progressive neuron death is a characteristic feature of the neurodegenerative process and leads to corresponding neuron dysfunctions. Neurodegenerative diseases constitute a heterogeneous group of nosologies with different clinical presentations but similar molecular mechanisms of pathogenesis. They are based on processes of abnormal protein aggregation and the formation of fibrillar insoluble structures and their deposition as histopathological inclusions in nervous system tissues. Disruption of homeostatic functions regulating neuron ion and energy metabolism, protein and nucleotide biosynthesis and degradation, chronic hypoxia, and penetration of toxic and inflammatory substances into the brain from the bloodstream not only cause age-related metabolic changes and disturbances in the sleep–waking cycle, but also contribute to the development of neurodegenerative processes. Animal studies have identified pathways of clearance in which solutes and specific tracers are cleared by a perivascular pathway into meningeal lymphatic vessels. The glymphatic network facilitates the clearance of metabolites, including beta-amyloid and tau protein, from the extracellular space of the brain. The glymphatic system is more efficient during natural sleep; fluid dynamics through this pathway display daily fluctuations and are under circadian control. The review systematizes the key aspects and scientific data from recent studies on the role of the glymphatic pathway and astroglial aquaporin type 4 as its main determinant in maintaining homeostatic fluid circulation in the brain in normal and pathological conditions, particularly in relation to the regulatory role of the sleep–waking cycle and during the development of neurodegenerative processes. [ABSTRACT FROM AUTHOR]