Sex-specific effects of high-fat and ketogenic diet on inflammatory responses in the hippocampus

Poor diet and metabolic diseases (obesity, Type 2 diabetes) are associated with increased risk of neurodegenerative and neuropsychiatric disorders, including Alzheimer’s disease, anxiety, and depression. Studies indicate that inflammation in the hippocampus could be one mechanism linking these conditions. Previous findings on inflammation, specifically glial activity in response to a high-fat diet, indicate sex differences in microglial responses in the hippocampus. The ketogenic diet is characterized by a high-fat, low-carbohydrate, and moderate-protein diet. While the ketogenic diet is very high in fat content, it may also possess neuroprotective properties against brain aging and neurodegenerative disorders, as well as boost mood and cognitive function. The aim of the experiment is to examine further the sex-specific effects of a high-fat diet (HFD) and a translationally relevant ketogenic diet (KD) on inflammation in the hippocampus, with a specific focus on astrocytes. Male and female C57BL/6J mice were fed high-fat, ketogenic, or low-fat control diets starting at 9 weeks of age and remained on the diet for ~5 months. Mice were assessed for weight gain, adiposity, ketone body levels, and diabetic status using glucose tolerance testing. Immunofluorescence was performed using a GFAP antibody for the analysis of astrocytes in the hippocampus. In males, there was no effect of diet on GFAP labeling in any subregion of the hippocampus. However, in female KD mice, there was a decrease in GFAP percent area covered in the CA1 and CA2 regions of the hippocampus, with similar but non-significant trends in other hippocampus regions (CA3 and dentate gyrus). These findings suggest that KD affects hippocampal astrocytes in a sex-specific manner, though further research is necessary to evaluate the downstream and functional effects of these changes

Effects of dietary fat manipulation on cognition in mice and rats:protocol for a systematic review and meta-analysis

INTRODUCTION AND OBJECTIVE: The Western diet that comprises high levels of long-chain saturated fats and sugar is associated not only with metabolic disorders such as obesity and type 2 diabetes but also has been recently linked to brain changes and cognitive dysfunction. However, in animal studies, reported effects are variable, and the mechanisms underlying these effects are unclear. In the proposed review, we aim to summarise the diverse evidence of the effects of so-called ‘high-fat’ and ketogenic diets on behavioural measures of cognition in postweaning mice and rats, relative to animals on standard diets and to determine potential underlying mechanisms of high-fat diet-induced effects. SEARCH STRATEGY: A comprehensive search strategy was designed to retrieve studies reporting use of a high-fat or ketogenic diet in postweaning mice and rats that included cognitive assessments. Three databases (Medline, SCOPUS and Web of Science) were searched and 4487 unique references were retrieved. SCREENING AND ANNOTATION: Studies were screened for inclusion by two independent reviewers, with 330 studies retained for analysis. Characteristics of disease model choice, experimental design, intervention use and outcome assessment are to be extracted using the Systematic Review Facility (http://syrf.org.uk/) tool. Studies will be assessed for study quality and risk of bias and confidence of mechanistic involvement. DATA MANAGEMENT AND REPORTING: For cognitive outcomes, effect sizes will be calculated using normalised mean difference and summarised using a random effects model. The contribution of potential sources of heterogeneity to the observed effects of diet on cognition will be assessed using multivariable meta-regression, with partitioning of heterogeneity as a sensitivity analysis. A preliminary version of this protocol was published on 9 April 2019 on the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies website (http://www.dcn.ed.ac.uk/camarades/research.html%23protocols). ETHICS AND DISSEMINATION: No ethical approval is required as there are no subjects in the proposed study

The effects of Abelmoschus esculentus (L.) moench seed on high fat diet induced metabolic and cognitive impairments in C57BL/6J mice

Okra is known for its neuroprotective and antioxidant properties. We aimed to investigate the potential effects of okra seed powder in alleviating high far diet HFD-induced cognitive deficit and hypercholesterolemia. We randomly allocated thirty-six C57BL/6J male mice into: (i) control, mice fed with a normal fat level diet; (ii) HFD, mice fed with HFD; (iii) HFD-OS1; (iv) HFD-OS2; (v) HFD-OS3, mice fed with HFD and okra seed powder (200, 400, or 800 mg/kg/day, respectively); (vi) HFD-SIM, mice fed with HFD and simvastatin (20 mg/kg/day). After 10 weeks of treatment period, the mice were tested with an episodic-like memory test (EMT) and Morris water maze (MWM). We found significantly higher total and LDL cholesterol levels in mice fed with HFD. Compared to the HFD group, the control group performed better in the EMT test, and also learned and retrieved spatial reference memory better in the MWM test. The okra seed powder significantly improved spatial learning in four days of acquisition trials and the highest dose of okra profoundly improved spatial reference memory retention during the probe trial. Contrary to the MWM results, the okra-treated animals did not perform significantly better than the HFD-treated animals in EMT. At present, we recommend future studies testing the potential neuroprotective or cognitive enhancing effects of okra to assess different cognitive domains using various disease models to have a better understanding on the potential neuroprotective properties of okra

Short high fat diet triggers reversible and region specific effects in DCX+ hippocampal immature neurons of adolescent male mice

Adolescence represents a crucial period for maturation of brain structures involved in cognition. Early in life unhealthy dietary patterns are associated with inferior cognitive outcomes at later ages; conversely, healthy diet is associated with better cognitive results. In this study we analyzed the effects of a short period of hypercaloric diet on newborn hippocampal doublecortin+ (DCX) immature neurons in adolescent mice. Male mice received high fat diet (HFD) or control low fat diet (LFD) from the 5th week of age for 1 or 2 weeks, or 1 week HFD followed by 1 week LFD. After diet supply, mice were either perfused for immunohistochemical (IHC) analysis or their hippocampi were dissected for biochemical assays. Detailed morphometric analysis was performed in DCX+ cells that displayed features of immature neurons. We report that 1 week-HFD was sufficient to dramatically reduce dendritic tree complexity of DCX+ cells. This effect occurred specifically in dorsal and not ventral hippocampus and correlated with reduced BDNF expression levels in dorsal hippocampus. Both structural and biochemical changes were reversed by a return to LFD. Altogether these studies increase our current knowledge on potential consequences of hypercaloric diet on brain and in particular on dorsal hippocampal neuroplasticity

The role of IGF-1 in exercise to improve obesity-related cognitive dysfunction

Obesity is an important factor that threatens human health. The occurrence of many chronic diseases is related to obesity, and cognitive function decline often occurs with the onset of obesity. With the further prevalence of obesity, it is bound to lead to a wider range of cognitive dysfunction (ORCD). Therefore, it is crucial to suppress ORCD through intervention. In this regard, exercise has been shown to be effective in preventing obesity and improving cognitive function as a non-drug treatment. There is sufficient evidence that exercise has a regulatory effect on a growth factor closely related to cognitive function—insulin-like growth factor 1 (IGF-1). IGF-1 may be an important mediator in improving ORCD through exercise. This article reviews the effects of obesity and IGF-1 on cognitive function and the regulation of exercise on IGF-1. It analyzes the mechanism by which exercise can improve ORCD by regulating IGF-1. Overall, this review provides evidence from relevant animal studies and human studies, showing that exercise plays a role in improving ORCD. It emphasizes the importance of IGF-1, which helps to understand the health effects of exercise and promotes research on the treatment of ORCD

Effects of diabetes on microglial physiology: a systematic review of in vitro, preclinical and clinical studies

Diabetes mellitus is a heterogeneous chronic metabolic disorder characterized by the presence of hyperglycemia, commonly preceded by a prediabetic state. The excess of blood glucose can damage multiple organs, including the brain. In fact, cognitive decline and dementia are increasingly being recognized as important comorbidities of diabetes. Despite the largely consistent link between diabetes and dementia, the underlying causes of neurodegeneration in diabetic patients remain to be elucidated. A common factor for almost all neurological disorders is neuroinflammation, a complex inflammatory process in the central nervous system for the most part orchestrated by microglial cells, the main representatives of the immune system in the brain. In this context, our research question aimed to understand how diabetes affects brain and/or retinal microglia physiology. We conducted a systematic search in PubMed and Web of Science to identify research items addressing the effects of diabetes on microglial phenotypic modulation, including critical neuroinflammatory mediators and their pathways. The literature search yielded 1327 records, including 18 patents. Based on the title and abstracts, 830 papers were screened from which 250 primary research papers met the eligibility criteria (original research articles with patients or with a strict diabetes model without comorbidities, that included direct data about microglia in the brain or retina), and 17 additional research papers were included through forward and backward citations, resulting in a total of 267 primary research articles included in the scoping systematic review. We reviewed all primary publications investigating the effects of diabetes and/or its main pathophysiological traits on microglia, including in vitro studies, preclinical models of diabetes and clinical studies on diabetic patients. Although a strict classification of microglia remains elusive given their capacity to adapt to the environment and their morphological, ultrastructural and molecular dynamism, diabetes modulates microglial phenotypic states, triggering specific responses that include upregulation of activity markers (such as Iba1, CD11b, CD68, MHC-II and F4/80), morphological shift to amoeboid shape, secretion of a wide variety of cytokines and chemokines, metabolic reprogramming and generalized increase of oxidative stress. Pathways commonly activated by diabetes-related conditions include NF-κB, NLRP3 inflammasome, fractalkine/CX3CR1, MAPKs, AGEs/RAGE and Akt/mTOR. Altogether, the detailed portrait of complex interactions between diabetes and microglia physiology presented here can be regarded as an important starting point for future research focused on the microglia–metabolism interface.30 página

The impact of adult neurogenesis in mood disorders

Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2021, Universidade de Lisboa, Faculdade de Farmácia.A neurogénese adulta consiste na síntese de novos neurónios em zonas específicas do cérebro adulto. As células estaminais neuronais, presentes quer no sistema nervoso central em desenvolvimento, quer no adulto, são classificadas como células multipotentes e atuam como ponto de partida para a neurogénese. Os neurónios recém-sintetizados no cérebro adulto parecem atuar em funções importantes, como o olfato, a reparação tecidular, a memória, a aprendizagem e a regulação do humor. Curiosamente, fatores como a idade, o stress, a dieta rica em gorduras, o exercício físico, a restrição calórica, o enriquecimento ambiental e a interação/suporte social influenciam fortemente o processo de neurogénese adulta. As doenças de humor são um grupo de doenças psiquiátricas, das quais se destaca a depressão major. De facto, a depressão major afeta mundialmente um número significativo de indivíduos, sendo que parte deles não responde aos tratamentos atuais. Além disso, esta doença encontra-se associada a uma morbilidade elevada. São várias as hipóteses que pretendem explicar a fisiopatologia da depressão major, nomeadamente a hipótese monoaminérgica, inflamatória e neurotrófica. Nos últimos anos a hipótese neurogénica tem emergido, na qual a depressão pode resultar da redução do processo de neurogénese adulta. Efetivamente, estudos post-mortem revelaram a existência de menor proliferação celular, que constitui uma das etapas da neurogénese adulta, no hipocampo de doentes deprimidos. Adicionalmente, tem-se verificado que os fatores que afetam a neurogénese adulta, como o stress, os hábitos alimentares, o exercício físico, a restrição calórica, o enriquecimento ambiental e a interação social, impactam de forma semelhante a depressão. A descoberta de que terapêutica antidepressiva crónica estimula a neurogénese hipocampal adulta e que esta é requerida para parte das melhorias comportamentais dos antidepressivos fortalece a hipótese neurogénica da depressão, permitindo estabelecer uma ligação entre a neurogénese adulta e a depressão major. No entanto, os mecanismos subjacentes à relação neurogénese adulta-depressão não estão ainda esclarecidos. Nesta monografia irei abordar o papel de vias de sinalização, nomeadamente a via de sinalização Wnt, JNK e CREB na regulação da neurogénese adulta durante a depressão major. O esclarecimento futuro destes mecanismos moleculares será um passo importante nesta área da ciência, permitindo a identificação de alvos terapêuticos inovadores e mais eficazes para o tratamento da depressão major.Adult neurogenesis consists in the synthesis of new neurons in specific areas of the adult brain. Neural stem cells, present in both the developing and adult central nervous system, are classified as multipotent cells and act as a starting point for neurogenesis. Newly synthesized neurons in the adult brain appear to have such important functions as olfaction, tissue repair, memory, learning, and mood regulation. Interestingly, factors as age, stress, high-fat diet, exercise, calorie restriction, environmental enrichment and social interaction/support were shown to deeply influence adult neurogenesis process. Mood disorders are a group of psychiatric illnesses, of which major depressive disorder stands out. In fact, major depressive disorder affects a significant number of individuals worldwide, some of whom do not respond to current antidepressant treatments. Furthermore, it is associated with high morbidity. There are several hypotheses that try to explain the pathophysiology of major depressive disorder, namely the monoaminergic, inflammatory and neurotrophic hypothesis. In recent years, the neurogenic hypothesis has emerged, in which depression may result from a reduction in adult neurogenesis. Indeed, post-mortem studies revealed the existence of reduced cell proliferation, one of the stages of adult neurogenesis, in the hippocampus of depressed patients. Additionally, it has been found that factors that affect adult neurogenesis, i.e., stress, high-fat diet, physical exercise, calorie restriction, environmental enrichment and social interaction, similarly impact major depressive disorder. The discovery that chronic antidepressant treatment stimulates adult hippocampal neurogenesis and that this is required for part of the behavioral improvements of antidepressants strengthens the neurogenic hypothesis of depression, allowing a link to be established between adult neurogenesis and major depressive disorder. However, the mechanisms underlying the adult neurogenesis-depression relationship are not clear. In this monograph, it will be addressed and discussed the role of signaling pathways, namely the Wnt, JNK and CREB signaling pathways in mediating adult neurogenesis in major depressive disorder. The future understanding of these molecular mechanisms will be an important step in this area of science, contributing to the identification of innovative and effective therapeutic targets for the treatment of major depressive disorder

Veränderungen des Insulinmetabolismus und der synaptischen Plastizität des Hippocampus durch Diäten verschiedener Fett- und Zuckergehalte

Vor dem Hintergrund der steigenden Prävalenz von Übergewicht und Adipositas soll im Rahmen dieses Promotionsprojektes eine quantitative und qualitative Analyse die unterschiedlichen Effekte zwei verschiedener adipogener Diäten im Mausmodell auf die hippocampale Insulinsensitivität und synaptische Plastizität beleuchten und insbesondere auf die unterschiedliche Beeinflussung zwischen den beiden adipogenen Diäten eingegangen werden. Nach Aufzucht und Fütterung von drei Kohorten von Versuchstieren mit je einer Standarddiät (SD), einer fetthaltigen Diät (HFD) und einer zuckerreichen Diät (DIO) erfolgte an den Lebenstagen 96-103 die Blut- und Organentnahme. Untersucht wurden neben phänotypischen Daten der Tiere die Blutseren mittels ELISA auf Insulin und Leptingehalt. In den Hippocampi der Tiere wurden mittels Western Blot und mittels Immunhistochemie mit dem Insulinstoffwechsel in Zusammenhang stehende Proteine quantifiziert und Marker der synaptischen Proliferation und Plastizität untersucht. Die Induktion eines adipogenen Phänotyps ist sowohl mit Fütterung der HFD als auch mit der DIO gelungen. HFD und DIO- Tiere präsentierten beide Hyperinsulinämie, Hyperleptinämie sowie einen gestörten Glukosemetabolismus in vivo, wobei der Effekt bei den DIO-Tieren stärker ausgeprägt war. Sowohl in der HFD als auch in der DIO-Gruppe ergaben sich Hinweise, die auf eine hippocampale Insulinresistenz hindeuteten. Hier war allerdings die Abgrenzung zum Effekt einer möglicherweise vorliegenden Leptinresistenz schwierig. Es ergaben sich insbesondere keine abgrenzbaren unterschiedlichen Effekte unter den beiden adipogenen Diäten, obwohl die Hyperinsulinämie und Hyperleptinämie durch die DIO stärker ausgeprägt war. Leider blieb die Untersuchung hinsichtlich weitere im Zusammenhang mit dem Leptinmetabolismus stehender Proteine ohne Erfolg, dieser hätte noch eine weitere Differenzierung zwischen Effekten der Hyperinsulinämie und Hyperleptinämie erlaubt. Eine Beeinflussung der hippocampalen Neurogenese wurde durch die Fütterung mit beiden adipogenen Diäten nicht nachgewiesen. Bei der Evaluation des Effektes der HFD und DIO auf synaptische Plastizität ergaben sich Anhaltspunkte für eine unterschiedliche Beeinflussung. Die zucker- und fettreiche DIO induzierte eine Verringerung von Synaptophysin präsynaptisch sowie eine Verminderung von Neuroligin 1 und 3 postsynaptisch an exzitatorischen Synapsen, welche ihrerseits wahrscheinlich die verminderte Konzentration des NMDA1-Rezeptors verursachte. Die HFD induzierte dagegen eine Reduktion von SNAP25 präsynaptisch sowie eine Verringerung von Neuroligin 2 postsynaptisch, welche mit einer verminderten Menge des GABA A-Rezeptors einherging. Beide adipogenen Diäten führten durch unterschiedliche Beeinflussung prä- und postsynaptischer Marker zu einer Imbalance des sensibel aufeinander abgestimmten Verbundes exzitatorischer und inhibitorischer Synapsen. Die Literatur zeigt, dass dies mit der E/I Imbalance assoziierten Erkrankungen wie Schizophrenie oder Autismusspektrumstörungen einhergehen könnte. Die HFD wirkt über die Veränderung der gabaergen Achse, während die DIO über die Beeinflussung der glutamatergen Achse wirkt

Paracrine Regulation of the Neurogenic Niche by Neural Stem Cells

Studies on neural stem cells (NSCs) largely focus on their differentiation into neurons in the adult brain, a process known as adult neurogenesis. However, new evidence suggests NSCs also regulate their surroundings through paracrine signaling. Their location in the brain, close to the vasculature and the cerebrospinal fluid, places them in an ideal position to receive extrinsic cues from the environment and relay them to the members of the neurogenic niches. Here, we aimed to explore how metabolic regula- tors and insults influence the NSC conditioned media (CM) and its effects on three components of the niches: differentiating NSCs, microglia, and endothelial cells. NSCs were pre-conditioned with metabolic regulators—tauroursodeoxycholic acid, propionate, and an exercise-mimicking cocktail of growth factors—and the resulting secretomes (mitCMs) seemed to increase neuronal differentiation. NSCs pre-conditioned with CM from injured cells released a secre- tome (boosted CM) which seemed to promote neuronal differentiation and microglial phagocytosis. Contrastingly, the secretome of NSCs pre-conditioned with serum of depressed mice (uCMS CM) de- creased neuronal differentiation and microglial phagocytosis. No alterations in blood vessel formation by endothelial cells exposed to these CMs were detected. To understand how CMs trigger these changes, we analyzed their composition. MitCMs and boosted CM seemed to be enriched in metabolites involved in neuroprotection and metabolic remodeling, such as lactate and 3-methyl-2-oxovalerate. Boosted CM also appeared to be enriched in miRNAs involved in neurogenesis and microglial modulation, such as miRNA-21, miRNA-125b, and miRNA-424. Summarily, our findings highlight a new role for the paracrine regulation of the neurogenic niche by NSCs. In the context of increased metabolic activity, but also of injury, NSCs appear to release a neuroprotective secretome, modulating differentiating NSCs and microglia towards a neurogenesis-fa- voring phenotype. However, depression-associated factors induce the release of a neurogenesis-sup- pressing secretome, as it appears to decrease neuronal differentiation and microglial phagocytosis.A neurogénese adulta, em que células estaminais neurais (NSCs) se diferenciam em neurónios, é um processo fundamental para o funcionamento adequado do cérebro. Novos estudos sugerem que, para além da sua capacidade de diferenciação neuronal, as NSCs conseguem regular a sua vizinhança através de sinalização parácrina. A sua localização no cérebro, perto da vasculatura e do líquido cefalorraquidi- ano, é ideal para a receção de sinais sistémicos. Neste trabalho, procurámos explorar o impacto de re- guladores metabólicos e insultos no meio condicionado (CM) de NSCs e o seu efeito em três compo- nentes dos nichos neurogénicos: NSCs em diferenciação, microglia, e células endoteliais. As NSCs foram pré-condicionadas com reguladores metabólicos—ácido tauroursodesoxicólico, propionato, e um cocktail de fatores de crescimento elevados durante o exercício—e os resultantes se- cretomas (mitCMs) pareceram aumentar a diferenciação neuronal. NSCs pré-condicionadas com o CM de células danificadas libertaram um secretoma (boosted CM) que aparentou promover diferenciação neuronal e a capacidade fagocítica da microglia, enquanto que o secretoma de NSCs pré-condicionadas com soro de murganhos deprimidos (uCMS CM) teve o efeito oposto. Não foram detetadas alterações na formação de vasos sanguíneos por células endoteliais expostas a estes CMs. Para clarificar potenciais mecanismos de ação, a composição dos CMs foi analisada. Foram detetados níveis aparentemente ele- vados de metabolitos neuroprotetores e envolvidos em remodelação metabólica (lactato e 3-metil-2- oxovalerato) nos mitCMs e boosted CM. Adicionalmente, foram detetados níveis elevados de miRNAs envolvidos na neurogénese e modulação de microglia (miRNA-21, miRNA-125b, miRNA-424) no bo- osted CM. Em resumo, estes resultados realçam um novo papel para as NSCs na regulação parácrina dos nichos neurogénicos. Em situações de maior atividade metabólica, mas também de dano, as NSCs apa- rentam libertar um secretoma neuroregenerativo, promovendo diferenciação neuronal e fagocitose por microglia. Por outro lado, sinais no soro de murganhos deprimidos parecem suprimir as propriedades neuroregenerativas do secretoma