The premise that the central nervous system is immune-privileged arose from the fact that direct contact between immune and nervous cells is hindered by the blood-brain barrier. However, the blood-brain barrier also comprises the interface between the immune and nervous systems by secreting chemo-attractant molecules and by modulating immune cell entry into the brain. The majority of published studies on the blood-brain barrier focus on endothelial cells, which are a critical component, but not the only one; other cellular components include astroglia, microglia, and pericytes. Pericytes are poorly studied in comparison with astrocytes or endothelial cells; they are mesenchymal cells that can modify their ultrastructure and gene expression in response to changes in the central nervous system microenvironment. Pericytes have a unique synergistic relationship with brain endothelial cells in the regulation of capillary permeability through secretion of cytokines, chemokines, nitric oxide, matrix metallo-proteinases, and by means of capillary contraction. Those pericyte manifestations are related to changes in blood-brain barrier permeability by an increase in endocytosis-mediated transport and by tight junction disruption. In addition, recent reports demonstrate that pericytes control the migration of leukocytes in response to inflammatory mediators by up-regulating the expression of adhesion molecules and releasing chemo-attractants; however, under physiological conditions they appear to be immune-suppressors. Better understanding of the immune properties of pericytes and their participation in the effects of brain infections, neurodegenerative diseases, and sleep loss will be achieved by analyzing pericyte ultrastructure, capillary coverage, and protein expression. That knowledge may provide a mechanism by which pericytes participate in the maintenance of the proper function of the brain-immune interface.

Sleep has a major role in learning, memory consolidation, and metabolic function. Although it is known that sleep restriction increases the accumulation of amyloid β peptide (Aβ) and the risk to develop Alzheimer’s disease (AD), the mechanism behind these effects remains unknown. In this review, we discuss how chronic sleep restriction induces metabolic and cognitive impairments that could result in the development of AD in late life. Here, we integrate evidence regarding mechanisms whereby metabolic signaling becomes disturbed after short or chronic sleep restriction in the context of cognitive impairment, particularly in the accumulation of Aβ in the brain. We also discuss the role of the blood-brain barrier in sleep restriction with an emphasis on the transport of metabolic signals into the brain and Aβ clearance. This review presents the unexplored possibility that the alteration of peripheral metabolic signals induced by sleep restriction, especially insulin resistance, is responsible for cognitive deficit and, subsequently, implicated in AD development.

Background and Objectives: The pathogenesis of liver steatosis is associated with obesity and systemic inflammation, particularly in subjects with body mass index (BMI) above 40 kg/m² and altered serum levels of tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10). Recent evidence suggests that disruption of the blood–brain barrier (BBB) may be associated with the development of steatosis, although limited data are available in humans. Thus, we assessed serum levels of neuron-specific enolase (NSE), transglutaminase 2 (TGM2), and glial fibrillary acidic protein (GFAP) as indirect markers of BBB dysfunction and examined their associations with steatosis severity, TNF-α and IL-10 in patients with morbid obesity. Materials and Methods: We biopsied the liver during bariatric surgery to assess steatosis by histology and serum markers by ELISA. Results: Most study subjects were women aged 38.7 ± 9.9 years with an average BMI of 42.3 ± 7.9 kg/m² and a steatosis prevalence of 78.9%. After grading steatosis as none (n = 8), mild (n = 17), moderate (n = 8), or severe (n = 5), we found no differences in sex, age, BMI, comorbidities, or laboratory variables, including liver enzymes. One-way ANOVA showed that serum IL-10 was 4-fold less in severe steatosis than in mild steatosis (p = 0.038), whereas TNF-α levels increased twice in severe steatosis compared to no steatosis (p = 0.029). NSE and GFAP serum levels, but not TGM2, increased proportionally to steatosis stage, showing differences between severe steatosis and no steatosis (p = 0.012 and p = 0.0002, respectively). Pearson correlation coefficients showed that NSE and GFAP were significantly associated with TNF-α (r = 0.600 and r = 0.402, respectively), but not with IL-10. Conclusions: Steatosis severity is significantly associated with markers of BBB disruption and systemic inflammation in patients with morbid obesity, suggesting a link between the BBB and liver steatosis.

Epidemiological and clinical research on neurodegenerative diseases has shown that metabolic dysregulations increase the risk of developing Alzheimer’s Disease (AD). Many metabolic changes can be grouped into metabolic syndrome (MetS), which is defined as the presence of three or more risk factors, including insulin resistance, hyperglycemia, hypertension, central obesity, and dyslipidemia. These changes cause systemic effects that are crucial in triggering neuroinflammation and neurodegeneration, key factors in AD development. All these factors impair energy metabolism in peripheral tissues and the brain by decreasing glucose utilization, leading to alterations in O-GlcNAcylation, glycosylation, mitochondrial function, oxidative stress, chronic inflammation, synaptic dysfunction, autophagy impairment, and blood–brain barrier (BBB) dysfunction. However, these factors are modified and largely influenced by lifestyle choices. A newer perspective emphasizes that regular exercise is vital for maintaining brain metabolism as we age. Current evidence suggests that engaging in physical activity for individuals with metabolic syndrome reduces their risk of Alzheimer’s disease, enhances prognosis, and improves cognitive abilities. This review explores how metabolic syndrome relates to Alzheimer’s and highlights possible strategies for prevention and treatment.

Epidemiological and clinical research on neurodegenerative diseases have indicated that metabolic dysregulations increase the risk of developing Alzheimer's Disease (AD). Many metabolic alterations can be grouped within the metabolic syndrome (MetS), defined as the coexistence of three or more risk factors, such as insulin resistance, hyperglycemia, hypertension, central obesity, and dyslipidemia. These changes induce a systemic change that plays a critical role in inducing neuroinflammation and neurodegeneration as essential causes of AD pathogenesis. All these factors compromise peripheral tissues and brain energy metabolism through reduced glucose utilization, which contributes to alterations in O-GlcNAcylation, glycosylation, mitochondrial dysfunction, oxidative stress, chronic inflammation, synaptic dysfunction, impaired autophagy, and blood-brain barrier (BBB) dysfunction. However, these factors are modifiable elements that depend on lifestyle. A relatively new perspective proposes that exercise regularly plays an essential role in maintaining brain metabolism in ageing. Physical activity in MetS decreases the risk of developing Alzheimer's disease, is associated with better prognosis, and positively affects cognitive function in those patients. In this review, we discuss the mechanisms involved in MetS and their implication in AD and identify potential areas for preventive and therapeutic interventions.