Non-Neuronal Cells in the Hypothalamic Adaptation to Metabolic Signals

Although the brain is composed of numerous cell types, neurons have received the vast majority of attention in the attempt to understand how this organ functions. Neurons are indeed fundamental but, in order for them to function correctly, they rely on the surrounding “non-neuronal” cells. These different cell types, which include glia, epithelial cells, pericytes, and endothelia, supply essential substances to neurons, in addition to protecting them from dangerous substances and situations. Moreover, it is now clear that non-neuronal cells can also actively participate in determining neuronal signaling outcomes. Due to the increasing problem of obesity in industrialized countries, investigation of the central control of energy balance has greatly increased in attempts to identify new therapeutic targets. This has led to interesting advances in our understanding of how appetite and systemic metabolism are modulated by non-neuronal cells. For example, not only are nutrients and hormones transported into the brain by non-neuronal cells, but these cells can also metabolize these metabolic factors, thus modifying the signals reaching the neurons. The hypothalamus is the main integrating center of incoming metabolic and hormonal signals and interprets this information in order to control appetite and systemic metabolism. Hence, the factors transported and released from surrounding non-neuronal cells will undoubtedly influence metabolic homeostasis. This review focuses on what is known to date regarding the involvement of different cell types in the transport and metabolism of nutrients and hormones in the hypothalamus. The possible involvement of non-neuronal cells, in particular glial cells, in physiopathological outcomes of poor dietary habits and excess weight gain are also discussed.The authors are funded by grants from the Spanish Ministry of Science and Innovation (BFU2014-51836-C2-2 to JAC and BFU2014-51836-C2-1 to LG-S), Spanish Ministry of Education, Culture and Sports (university training grant FPU13/00909 to AF-R), Fondo de Investigación Sanitaria (PI-1302195, PI-1600485, and CIBEROBN to JA and CIBERFES to LG-S) and Fondos FEDER.Peer reviewedPeer Reviewe

Impact of long-term hfd intake on the peripheral and central igf system in male and female mice

The insulin-like growth factor (IGF) system is responsible for growth, but also affects metabolism and brain function throughout life. New IGF family members (i.e., pappalysins and stanniocalcins) control the availability/activity of IGFs and are implicated in growth. However, how diet and obesity modify this system has been poorly studied. We explored how intake of a high-fat diet (HFD) or commercial control diet (CCD) affects the IGF system in the circulation, visceral adipose tissue (VAT) and hypothalamus. Male and female C57/BL6J mice received HFD (60% fat, 5.1 kcal/g), CCD (10% fat, 3.7 kcal/g) or chow (3.1 % fat, 3.4 kcal/g) for 8 weeks. After 7 weeks of HFD intake, males had decreased glucose tolerance (p < 0.01) and at sacrifice increased plasma insulin (p < 0.05) and leptin (p < 0.01). Circulating free IGF1 (p < 0.001), total IGF1 (p < 0.001), IGF2 (p < 0.05) and IGFBP3 (p < 0.01) were higher after HFD in both sexes, with CCD increasing IGFBP2 in males (p < 0.001). In VAT, HFD reduced mRNA levels of IGF2 (p < 0.05), PAPP-A (p < 0.001) and stanniocalcin (STC)-1 (p < 0.001) in males. HFD increased hypothalamic IGF1 (p < 0.01), IGF2 (p < 0.05) and IGFBP5 (p < 0.01) mRNA levels, with these changes more apparent in females. Our results show that diet-induced changes in the IGF system are tissue-, sex-and diet-dependent.This research was funded by grants from the Spanish Ministry of Science and Innovation (BFU2017-82565-C21-R2 to J.A.C. and L.M.F.), Spanish Ministry of Education, Culture and Sports (university training grant PU13/00909 to A.F.-R.), Fondo de Investigación Sanitaria (PI1900166 to J.A.) and Fondos FEDER. Centro de Investigación Biomédica en Red Fisiopatología de Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III (J.A.

Estradiol uses different mechanisms in astrocytes from the hippocampus of male and female rats to protect against damage Induced by palmitic acid

An excess of saturated fatty acids can be toxic for tissues, including the brain, and this has been associated with the progression of neurodegenerative diseases. Since palmitic acid (PA) is a free fatty acid that is abundant in the diet and circulation and can be harmful, we have investigated the effects of this fatty acid on lipotoxicity in hippocampal astrocytes and the mechanism involved. Moreover, as males and females have different susceptibilities to some neurodegenerative diseases, we accessed the responses of astrocytes from both sexes, as well as the possible involvement of estrogens in the protection against fatty acid toxicity. PA increased endoplasmic reticulum stress leading to cell death in astrocytes from both males and females. Estradiol (E2) increased the levels of protective factors, such as Hsp70 and the anti-inflammatory cytokine interleukin-10, in astrocytes from both sexes. In male astrocytes, E2 decreased pJNK, TNFα, and caspase-3 activation. In contrast, in female astrocytes E2 did not affect the activation of JNK or TNFα levels, but decreased apoptotic cell death. Hence, although E2 exerted protective effects against the detrimental effects of PA, the mechanisms involved appear to be different between male and female astrocytes. This sexually dimorphic difference in the protective mechanisms induced by E2 could be involved in the different susceptibilities of males and females to some neurodegenerative processesThis work was funded by grants from Ministerio de Ciencia e Innovación (BFU2014-51836-C2-2-R to JC and BFU2014-51836-C2-1-R to LG-S) and Fondos de Investigación Sanitaria (Grant PI16/00485 to JA), co-funded by European FEDER Program, and Centro de Investigación Biomédica en Red Fisiopatología de Obesidad y Nutrición (CIBEROBN) of the Instituto de Salud Carlos III, and Fundación de Endocrinología y Nutrició

Ghrelin regulates glucose and glutamate transporters in hypothalamic astrocytes

Hypothalamic astrocytes can respond to metabolic signals, such as leptin and insulin, to modulate adjacent neuronal circuits and systemic metabolism. Ghrelin regulates appetite, adiposity and glucose metabolism, but little is known regarding the response of astrocytes to this orexigenic hormone. We have used both in vivo and in vitro approaches to demonstrate that acylated ghrelin (acyl-ghrelin) rapidly stimulates glutamate transporter expression and glutamate uptake by astrocytes. Moreover, acyl-ghrelin rapidly reduces glucose transporter (GLUT) 2 levels and glucose uptake by these glial cells. Glutamine synthetase and lactate dehydrogenase decrease, while glycogen phosphorylase and lactate transporters increase in response to acyl-ghrelin, suggesting a change in glutamate and glucose metabolism, as well as glycogen storage by astrocytes. These effects are partially mediated through ghrelin receptor 1A (GHSR-1A) as astrocytes do not respond equally to desacyl-ghrelin, an isoform that does not activate GHSR-1A. Moreover, primary astrocyte cultures from GHSR-1A knock-out mice do not change glutamate transporter or GLUT2 levels in response to acyl-ghrelin. Our results indicate that acyl-ghrelin may mediate part of its metabolic actions through modulation of hypothalamic astrocytes and that this effect could involve astrocyte mediated changes in local glucose and glutamate metabolism that alter the signals/nutrients reaching neighboring neurons.This work was funded by grants from Fondo de Investigación Sanitaria (PI100747; PI1302195), Ministerio de Ciencia e Innovación (BFU2011–27492; BFU2014-51836-C2-2-R) and Fondos FEDER, Centro de Investigación Biomédica en Red Fisiopatología de Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, and Fundación de Endocrinología y Nutrición. SD was funded by the Swedish Research Council (Vetenskapsrådet grant 2012– 1758), Läkarutbildningsavtalet Göteborg grant at Sahlgrenska Hospital (ALFGBG-138741, The European Union Seventh Framework Programme under Grant Agreement 607310, Nudge-it

Sex Differences in Hypothalamic Changes and the Metabolic Response of TgAPP Mice to a High Fat Diet

The propensity to develop neurodegenerative diseases is influenced by diverse factors including genetic background, sex, lifestyle, including dietary habits and being overweight, and age. Indeed, with aging, there is an increased incidence of obesity and neurodegenerative processes, both of which are associated with inflammatory responses, in a sex-specific manner. High fat diet (HFD) commonly leads to obesity and markedly affects metabolism, both peripherally and centrally. Here we analyzed the metabolic and inflammatory responses of middle-aged (11–12 months old) transgenic amyloid precursor protein (TgAPP) mice of both sexes to HFD for 18 weeks (starting at 7–8 months of age). We found clear sex differences with females gaining significantly more weight and fat mass than males, with a larger increase in circulating leptin levels and expression of inflammatory markers in visceral adipose tissue. Glycemia and insulin levels increased in HFD fed mice of both sexes, with TgAPP mice being more affected than wild type (WT) mice. In the hypothalamus, murine amyloid β (Aβ) levels were increased by HFD intake exclusively in males, reaching statistical significance in TgAPP males. On a low fat diet (LFD), TgAPP males had significantly lower mRNA levels of the anorexigenic neuropeptide proopiomelanocortin (POMC) than WT males, with HFD intake decreasing the expression of the orexigenic neuropeptides Agouti-related peptide (AgRP) and neuropeptide Y (NPY), especially in TgAPP mice. In females, HFD increased POMC mRNA levels but had no effect on AgRP or NPY mRNA levels, and with no effect on genotype. There was no effect of diet or genotype on the hypothalamic inflammatory markers analyzed or the astrogliosis marker glial acidic protein (GFAP); however, levels of the microglial marker Iba-1 increased selectively in male TgAPP mice. In summary, the response to HFD intake was significantly affected by sex, with fewer effects due to genotype. Hypothalamic inflammatory cytokine expression and astrogliosis were little affected by HFD in middle-aged mice, although in TgAPP males, which showed increased Aβ, there was microglial activation. Thus, excess intake of diets high in fat should be avoided because of its possible detrimental consequences

The effects of age, sex and genetics on the metabolic response to high fat diet intake in mice

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Medicina, Departamento de Pediatría. Fecha de lectura: 13-12-2019Esta tesis tiene embargado el acceso al texto completo hasta el 13-06-2021La obesidad y sus complicaciones secundarias continúan aumentando en todo el mundo y constituyen uno de los mayores problemas de salud en nuestra sociedad. Ahora sabemos que sus causas son variadas y que cada individuo muestra diferente propensión a desarrollar obesidad y/o patologías asociadas a esta. Sin duda, el desarrollo de estrategias terapéuticas y medicamentos contra esta epidemia abarca un amplio rango de posibles dianas. Sin embargo, todavía queda mucho que aprender sobre el control del metabolismo y sus diferencias individuales. El objetivo de esta tesis es analizar los efectos de la edad, el sexo y el trasfondo genético en la respuesta a una dieta alta en grasas en ratones. La pubertad es un período del desarrollo con múltiples cambios que ocurren tanto en el sistema nervioso central como a nivel periférico. Sin embargo, las respuestas específicas a una mala nutrición durante la pubertad no han sido estudiadas en profundidad. Por tanto, hemos analizado la respuesta metabólica de ratones de ambos sexos en edad peri-puberal, sometiéndoles a una dieta alta en grasa durante un corto período de tiempo. Por otra parte, el envejecimiento aumenta la propensión al sobrepeso y ciertas enfermedades, incluyendo trastornos neurodegenerativos como el de Alzheimer. Por ello, hemos utilizado un modelo genético de enfermedad de Alzheimer en ratones, sometiendo a machos y a hembras a una dieta alta o baja en grasas durante un período largo de tiempo para analizar su respuesta metabólica. Además, dado que los astrocitos están implicados tanto en el control metabólico como en la neuroprotección, hemos analizado la respuesta de astrocitos hipotalámicos de machos y hembras al ácido palmítico, un ácido graso saturado que se encuentra comúnmente en nuestra dieta, y al amiloide-β, un compuesto importante en el desarrollo de la enfermedad de Alzheimer. Los resultados que aquí se exponen indican que los ratones en edad puberal/peripuberal son menos propensos a la ganancia de peso tras un período corto de dieta alta en grasas, en comparación con lo que se ha observado en otros estadios del desarrollo. Los ratones de ambos sexos aumentaron su ingesta calórica sin aumentar de peso. Sin embargo, los perfiles metabólicos se vieron alterados de diferente manera en función del sexo, con un mayor efecto en machos que en hembras. Cuando ratones de mediana edad fueron expuestos a una dieta alta en grasas encontramos que las hembras ganaron más peso y grasa que los machos, lo que contrasta con lo que se suele observar en adultos jóvenes.Obesity and its secondary complications continue to increase worldwide and constitute one of the most important health care problems in many societies. It is now clear that the underlying causes of obesity can vary and that not all individuals have similar propensities to become obese and/or to develop obesity-associated pathologies. Indeed, the development of treatment strategies and drugs to curtail this epidemic span a wide range of targets. However, much is yet to be learned regarding metabolic control and individual differences in this process. The aim of this thesis was to analyze the effects of age, sex and genetic background on the response to a high fat diet in mice. Puberty is a period of development with multiple changes occurring both in the central nervous system and systemically. However, little is known regarding the specific response during puberty to poor nutrition. Hence, we analyzed the metabolic response of both male and female peripubertal mice to a short-term high fat diet protocol. On the other extreme, aging increases the overall propensity to weight gain and some diseases, including neurodegenerative diseases such as Alzheimer’s. Hence, we employed a genetic model of Alzheimer’s disease in mice, submitting male and female mice to a long-term high fat diet or low fat diet and analyzing their metabolic response. Moreover, as astrocytes are involved in both metabolic control and neuroprotection, we analyzed the response of hypothalamic astrocytes from the hypothalamus of males and females to palmitic acid, a saturated fatty acid commonly found in our diet, and to amyloid-β, which is an important component in the development of Alzheimer’s disease. The results reported here indicate that during the peripubertal/pubertal period mice are less prone to excess weight gain to short-term high fat intake compared to that reported at other developmental ages. Mice of both sexes increased their energy intake, but body weight was not affected. However, metabolic profiles were modified in a sex dependant manner with males being more affected than females. When mice were exposed to a high fat diet during later adulthood, we found that females gained more weight and fat mass than males, which is in contrast to what is commonly reported for young adults.Este trabajo ha sido realizado con cargo a proyectos del Ministerio de Ciencia e Innovación (BFU2011-27492 and BFU2014-51836-C2-2-R), del Fondo de Investigación Sanitaria (PI1007047), y del CIBER de Fisiopatología de la Obesidad y Nutrición (CB06-03). Igualmente, ha sido financiado gracias a la Fundación de Endocrinología y Nutrición del Hospital Infantil Universitario Niño Jesús. Alejandra Freire Fernández-Regatillo ha recibido financiación del programa de Ayudas Predoctorales FPU del Ministerio de Educación y Ciencia (FPU13/09009)

Neurogenin 3 mediates sex chromosome effects on the generation of sex differences in hypothalamic neuronal development

The organizational action of testosterone during critical periods of development is the cause of numerous sex differences in the brain. However, sex differences in neuritogenesis have been detected in primary neuronal hypothalamic cultures prepared before the peak of testosterone production by fetal testis. In the present study we assessed the hypothesis of that cell-autonomous action of sex chromosomes can differentially regulate the expression of the neuritogenic gene neurogenin 3 (Ngn3) in male and female hypothalamic neurons, generating sex differences in neuronal development. Neuronal cultures were prepared from male and female E14 mouse hypothalami, before the fetal peak of testosterone. Female neurons showed enhanced neuritogenesis and higher expression of Ngn3 than male neurons. The silencing of Ngn3 abolished sex differences in neuritogenesis, decreasing the differentiation of female neurons. The sex difference in Ngn3 expression was determined by sex chromosomes, as demonstrated using the four core genotypes mouse model, in which a spontaneous deletion of the testis-determining gene Sry from the Y chromosome was combined with the insertion of the Sry gene onto an autosome. In addition, the expression of Ngn3, which is also known to mediate the neuritogenic actions of estradiol, was increased in the cultures treated with the hormone, but only in those from male embryos. Furthermore, the hormone reversed the sex differences in neuritogenesis promoting the differentiation of male neurons. These findings indicate that Ngn3 mediates both cell-autonomous actions of sex chromosomes and hormonal effects on neuritogenesis.Peer reviewedPeer Reviewe

Estradiol Uses Different Mechanisms in Astrocytes from the Hippocampus of Male and Female Rats to Protect against Damage Induced by Palmitic Acid

An excess of saturated fatty acids can be toxic for tissues, including the brain, and this has been associated with the progression of neurodegenerative diseases. Since palmitic acid (PA) is a free fatty acid that is abundant in the diet and circulation and can be harmful, we have investigated the effects of this fatty acid on lipotoxicity in hippocampal astrocytes and the mechanism involved. Moreover, as males and females have different susceptibilities to some neurodegenerative diseases, we accessed the responses of astrocytes from both sexes, as well as the possible involvement of estrogens in the protection against fatty acid toxicity. PA increased endoplasmic reticulum stress leading to cell death in astrocytes from both males and females. Estradiol (E2) increased the levels of protective factors, such as Hsp70 and the anti-inflammatory cytokine interleukin-10, in astrocytes from both sexes. In male astrocytes, E2 decreased pJNK, TNFα, and caspase-3 activation. In contrast, in female astrocytes E2 did not affect the activation of JNK or TNFα levels, but decreased apoptotic cell death. Hence, although E2 exerted protective effects against the detrimental effects of PA, the mechanisms involved appear to be different between male and female astrocytes. This sexually dimorphic difference in the protective mechanisms induced by E2 could be involved in the different susceptibilities of males and females to some neurodegenerative processes

Estradiol uses different mechanisms in astrocytes from the hippocampus of male and female rats to protect against damage induced by palmitic acid

© 2017 Frago, Canelles, Freire-Regatillo, Argente-Arizón, Barrios, Argente, Garcia-Segura and Chowen.An excess of saturated fatty acids can be toxic for tissues, including the brain, and this has been associated with the progression of neurodegenerative diseases. Since palmitic acid (PA) is a free fatty acid that is abundant in the diet and circulation and can be harmful, we have investigated the effects of this fatty acid on lipotoxicity in hippocampal astrocytes and the mechanism involved. Moreover, as males and females have different susceptibilities to some neurodegenerative diseases, we accessed the responses of astrocytes from both sexes, as well as the possible involvement of estrogens in the protection against fatty acid toxicity. PA increased endoplasmic reticulum stress leading to cell death in astrocytes from both males and females. Estradiol (E2) increased the levels of protective factors, such as Hsp70 and the anti-inflammatory cytokine interleukin-10, in astrocytes from both sexes. In male astrocytes, E2 decreased pJNK, TNFα, and caspase-3 activation. In contrast, in female astrocytes E2 did not affect the activation of JNK or TNFα levels, but decreased apoptotic cell death. Hence, although E2 exerted protective effects against the detrimental effects of PA, the mechanisms involved appear to be different between male and female astrocytes. This sexually dimorphic difference in the protective mechanisms induced by E2 could be involved in the different susceptibilities of males and females to some neurodegenerative processes.This work was funded by grants from Ministerio de Ciencia e Innovación (BFU2014-51836-C2-2-R to JC and BFU2014-51836-C2-1-R to LG-S) and Fondos de Investigación Sanitaria (Grant PI16/00485 to JA), co-funded by European FEDER Program, and Centro de Investigación Biomédica en Red Fisiopatología de Obesidad y Nutrición (CIBEROBN) of the Instituto de Salud Carlos III, and Fundación de Endocrinología y Nutrición