High cholesterol diet exacerbates blood-brain barrier disruption in LDLr–/– mice : impact on cognitive function

Background: Evidence has revealed an association between familial hypercholesterolemia and cognitive impairment. In this regard, a connection between cognitive deficits and hippocampal blood-brain barrier (BBB) breakdown was found in low-density lipoprotein receptor knockout mice (LDLr–/–), a mouse model of familial hypercholesterolemia. Objective: Herein we investigated the impact of a hypercholesterolemic diet on cognition and BBB function in C57BL/6 wild-type and LDLr–/– mice. Methods: Animals were fed with normal or high cholesterol diets for 30 days. Thus, wild-type and LDLr–/– mice were submitted to memory paradigms. Additionally, BBB integrity was evaluated in the mice’s prefrontal cortices and hippocampi. Results: A tenfold elevation in plasma cholesterol levels of LDLr–/– mice was observed after a hypercholesterolemic diet, while in wild-type mice, the hypercholesterolemic diet exposure increased plasma cholesterol levels only moderately and did not induce cognitive impairment. LDLr–/– mice presented memory impairment regardless of the diet. We observed BBB disruption as an increased permeability to sodium fluorescein in the prefrontal cortices and hippocampi and a decrease on hippocampal claudin-5 and occludin mRNA levels in both wild-type and LDLr–/– mice treated with a hypercholesterolemic diet. The LDLr–/– mice fed with a regular diet already presented BBB dysfunction. The BBB-increased leakage in the hippocampi of LDLr–/– mice was related to high microvessel content and intense astrogliosis, which did not occur in the control mice. Conclusion: Therefore, LDLr–/– mice seem to be more susceptible to cognitive impairments and BBB damage induced by exposure to a high cholesterol diet. Finally, BBB disruption appears to be a relevant event in hypercholesterolemia-induced brain alterations

Post-intervention Status in Patients With Refractory Myasthenia Gravis Treated With Eculizumab During REGAIN and Its Open-Label Extension

OBJECTIVE: To evaluate whether eculizumab helps patients with anti-acetylcholine receptor-positive (AChR+) refractory generalized myasthenia gravis (gMG) achieve the Myasthenia Gravis Foundation of America (MGFA) post-intervention status of minimal manifestations (MM), we assessed patients' status throughout REGAIN (Safety and Efficacy of Eculizumab in AChR+ Refractory Generalized Myasthenia Gravis) and its open-label extension. METHODS: Patients who completed the REGAIN randomized controlled trial and continued into the open-label extension were included in this tertiary endpoint analysis. Patients were assessed for the MGFA post-intervention status of improved, unchanged, worse, MM, and pharmacologic remission at defined time points during REGAIN and through week 130 of the open-label study. RESULTS: A total of 117 patients completed REGAIN and continued into the open-label study (eculizumab/eculizumab: 56; placebo/eculizumab: 61). At week 26 of REGAIN, more eculizumab-treated patients than placebo-treated patients achieved a status of improved (60.7% vs 41.7%) or MM (25.0% vs 13.3%; common OR: 2.3; 95% CI: 1.1-4.5). After 130 weeks of eculizumab treatment, 88.0% of patients achieved improved status and 57.3% of patients achieved MM status. The safety profile of eculizumab was consistent with its known profile and no new safety signals were detected. CONCLUSION: Eculizumab led to rapid and sustained achievement of MM in patients with AChR+ refractory gMG. These findings support the use of eculizumab in this previously difficult-to-treat patient population. CLINICALTRIALSGOV IDENTIFIER: REGAIN, NCT01997229; REGAIN open-label extension, NCT02301624. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that, after 26 weeks of eculizumab treatment, 25.0% of adults with AChR+ refractory gMG achieved MM, compared with 13.3% who received placebo

Hypothalamic CREB Regulates the Expression of Pomc-Processing Enzyme Pcsk2

Background: The hypothalamic proopiomelanocortin (Pomc) neurons act as first-order sensors of systemic energy stores, providing signals that regulate caloric intake and energy expenditure. In experimental obesity, dietary saturated fatty acids affect Pomc endopeptidases (PCs), resulting in the abnormal production of the neurotransmitters α-melanocyte-stimulating hormone (α-MSH) and β-endorphin, thus impacting energy balance. The cAMP response element-binding protein (CREB) is one of the transcription factors that control the expression of Pomc endopeptidases; however, it was previously unknown if dietary fats could affect CREB and consequently the expression of Pomc endopeptidases. Methods: Here, we used single-cell RNA sequencing analysis, PCR, immunoblot, ELISA and immunofluorescence histological assays to determine the impact of a high-fat diet (HFD) on the expression and function of hypothalamic CREB and its impact on the melanocortinergic system. Results: The results indicate that CREB is expressed in arcuate nucleus Pomc neurons and is activated as early as nine hours after the introduction of a high-fat diet. The inhibition of hypothalamic CREB using a short-hairpin RNA lentiviral vector resulted in increased diet-induced body-mass gain and reduced energy expenditure. This was accompanied by reduced expression of the Pomc endopeptidases, protein convertase 2, which are encoded by Pcsk2, and by the loss of the high-fat-diet-induced effect to inhibit the production of α-MSH. Conclusions: This study provides the first evidence for the involvement of CREB in the abnormal regulation of the hypothalamic Pomc endopeptidase system in experimental obesity

Impaired adult hippocampal neurogenesis in a mouse model of familial hypercholesterolemia: a role for the LDL receptor and cholesterol metabolism in adult neural precursor cells

Objective: In familial hypercholesterolemia (FH), mutations in the low-density lipoprotein (LDL) receptor (LDLr) gene result in increased plasma LDL cholesterol. Clinical and preclinical studies have revealed an association between FH and hippocampus-related memory and mood impairment. We here asked whether hippocampal pathology in FH might be a consequence of compromised adult hippocampal neurogenesis.Methods: We evaluated hippocampus-dependent behavior and neurogenesis in adult C57BU6JRj and LDLr (-/-) mice. We investigated the effects of elevated cholesterol and the function of LDLr in neural precursor cells (NPC) isolated from adult C57BU6JRj mice in vitro.Results: Behavioral tests revealed that adult LDLr -/- mice showed reduced performance in a dentate gyrus (DG)-dependent metric change task. This phenotype was accompanied by a reduction in cell proliferation and adult neurogenesis in the DG of LDLr (-/-) mice, suggesting a potential direct impact of LDLr mutation on NPC. Exposure of NPC to LDL as well as LDLr gene knockdown reduced proliferation and disrupted transcriptional activity of genes involved in endogenous cholesterol synthesis and metabolism. The LDL treatment also induced an increase in intracellular lipid storage. Functional analysis of differentially expressed genes revealed parallel modulation of distinct regulatory networks upon LDL treatment and LDLr knockdown.Conclusions: Together, these results suggest that high LDL levels and a loss of LDLr function, which are characteristic to individuals with FH, might contribute to a disease-related impairment in adult hippocampal neurogenesis and, consequently, cognitive functions. (C) 2019 The Authors. Published by Elsevier GmbH

Hippocampal Function Is Impaired by a Short-Term High-Fat Diet in Mice : Increased Blood-Brain Barrier Permeability and Neuroinflammation as Triggering Events

Worldwide, and especially in Western civilizations, most of the staple diets contain high amounts of fat and refined carbohydrates, leading to an increasing number of obese individuals. In addition to inducing metabolic disorders, energy dense food intake has been suggested to impair brain functions such as cognition and mood control. Here we demonstrate an impaired memory function already 3 days after the start of a high-fat diet (HFD) exposure, and depressive-like behavior, in the tail suspension test, after 5 days. These changes were followed by reduced synaptic density, changes in mitochondrial function and astrocyte activation in the hippocampus. Preceding or coinciding with the behavioral changes, we found an induction of the proinflammatory cytokines TNF-alpha and IL-6 and an increased permeability of the blood-brain barrier (BBB), in the hippocampus. Finally, in mice treated with a TNF-alpha inhibitor, the behavioral and BBB alterations caused by HFD-feeding were mitigated suggesting that inflammatory signaling was critical for the changes. In summary, our findings suggest that HFD rapidly triggers hippocampal dysfunction associated with BBB disruption and neuroinflammation, promoting a progressive breakdown of synaptic and metabolic function. In addition to elucidating the link between diet and cognitive function, our results might be relevant for the comprehension of the neurodegenerative process

Gut microbiota from patients with COVID-19 cause alterations in mice that resemble post-COVID symptoms

ABSTRACTLong-term sequelae of coronavirus disease (COVID)-19 are frequent and of major concern. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection affects the host gut microbiota, which is linked to disease severity in patients with COVID-19. Here, we report that the gut microbiota of post-COVID subjects had a remarkable predominance of Enterobacteriaceae strains with an antibiotic-resistant phenotype compared to healthy controls. Additionally, short-chain fatty acid (SCFA) levels were reduced in feces. Fecal transplantation from post-COVID subjects to germ-free mice led to lung inflammation and worse outcomes during pulmonary infection by multidrug-resistant Klebsiella pneumoniae. transplanted mice also exhibited poor cognitive performance. Overall, we show prolonged impacts of SARS-CoV-2 infection on the gut microbiota that persist after subjects have cleared the virus. Together, these data demonstrate that the gut microbiota can directly contribute to post-COVID sequelae, suggesting that it may be a potential therapeutic target