RESUMEN
The coordination of food intake, energy storage, and expenditure involves complex interactions between hypothalamic neurons and peripheral tissues including pancreatic islets, adipocytes, muscle, and liver. Previous research shows that deficiency of the transcription factor Alx3 alters pancreatic islet-dependent glucose homeostasis. In this study we carried out a comprehensive assessment of metabolic alterations in Alx3 deficiency. We report that Alx3-deficient mice exhibit decreased food intake without changes in body weight, along with reduced energy expenditure and altered respiratory exchange ratio. Magnetic resonance imaging reveals increased adiposity and decreased muscle mass, which was associated with markers of motor and sympathetic denervation. By contrast, Alx3-deficient mice on a high-fat diet show attenuated weight gain and improved insulin sensitivity, compared to control mice. Gene expression analysis demonstrates altered lipogenic and lipolytic gene profiles. In wild type mice Alx3 is expressed in hypothalamic arcuate nucleus neurons, but not in major peripheral metabolic organs. Functional diffusion-weighted magnetic resonance imaging reveals selective hypothalamic responses to fasting in the arcuate nucleus of Alx3-deficient mice. Additionally, altered expression of proopiomelanocortin and melanocortin-3 receptor mRNA in the hypothalamus suggests impaired regulation of feeding behavior. This study highlights the crucial role for Alx3 in governing food intake, energy homeostasis, and metabolic nutrient partitioning, thereby influencing body mass composition.
Asunto(s)
Composición Corporal , Ingestión de Alimentos , Metabolismo Energético , Proteínas de Homeodominio , Homeostasis , Hipotálamo , Ratones Noqueados , Animales , Metabolismo Energético/genética , Hipotálamo/metabolismo , Ratones , Ingestión de Alimentos/genética , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Dieta Alta en Grasa , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Masculino , Ratones Endogámicos C57BL , Neuronas/metabolismo , Proopiomelanocortina/metabolismo , Proopiomelanocortina/genética , Resistencia a la Insulina/genética , Núcleo Arqueado del Hipotálamo/metabolismoRESUMEN
BACKGROUND: Obesity proceeds with important physiological and microstructural alterations in the brain, but the precise relationships between the diet and feeding status, its physiological responses, and the observed neuroimaging repercussions, remain elusive. Here, we implemented a mouse model of high fat diet (HFD) feeding to explore specific associations between diet, feeding status, phenotypic and endocrine repercussions, and the resulting microstructural and metabolic alterations in the brain, as detected by diffusion tensor imaging (DTI) and neurochemical metabolic profiling. METHODS: Brain DTI images were acquired from adult male C57BL6/J mice after 6 weeks of HFD, or standard diet (SD) administrations, both under the fed, and overnight fasted conditions. Metabolomic profiles of the cortex (Ctx), hippocampus (Hipc), and hypothalamus (Hyp) were determined by 1H high-resolution magic angle spinning (HRMAS) spectroscopy, in cerebral biopsies dissected after microwave fixation. Mean diffusivity (MD), fractional anisotropy (FA) maps, and HRMAS profiles were complemented with determinations of phenotypic alterations and plasma levels of appetite-related hormones, measured by indirect calorimetry and multiplex assays, respectively. We used Z-score and alternating least squares scaling (ALSCAL) analysis to investigate specific associations between diet and feeding status, physiological, and imaging parameters. RESULTS: HFD induced significant increases in body weight and the plasma levels of glucose and fatty acids in the fed and fasted conditions, as well as higher cerebral MD (Ctx, Hipc, Hyp), FA (Hipc), and mobile saturated fatty acids resonances (Ctx, Hipc, Hyp). Z-score and ASLCAL analysis identified the precise associations between physiological and imaging variables. CONCLUSIONS: The present study reveals that diet and feeding conditions elicit prominent effects on specific imaging and spectroscopic parameters of the mouse brain that can be associated to the alterations in phenotypic and endocrine variables. Together, present results disclose a neuro-inflammatory response to HFD, characterized primarily by vasogenic edema and compensatory responses in osmolyte concentrations.
Asunto(s)
Química Encefálica/fisiología , Encéfalo , Dieta Alta en Grasa , Imagen de Difusión Tensora , Animales , Peso Corporal/fisiología , Encéfalo/diagnóstico por imagen , Encéfalo/fisiología , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
Amyotrophic lateral sclerosis (ALS) is a fatal neurological condition where motor neurons (MNs) degenerate. Most of the ALS cases are sporadic (sALS), whereas 10% are hereditarily transmitted (fALS), among which mutations are found in the gene that codes for the enzyme superoxide dismutase 1 (SOD1). A central question in ALS field is whether causative mutations display selective alterations not found in sALS patients, or they converge on shared molecular pathways. To identify specific and common mechanisms for designing appropriate therapeutic interventions, we focused on the SOD1-mutated (SOD1-ALS) versus sALS patients. Since ALS pathology involves different cell types other than MNs, we generated lymphoblastoid cell lines (LCLs) from sALS and SOD1-ALS patients and healthy donors and investigated whether they show changes in oxidative stress, mitochondrial dysfunction, metabolic disturbances, the antioxidant NRF2 pathway, inflammatory profile, and autophagic flux. Both oxidative phosphorylation and glycolysis appear to be upregulated in lymphoblasts from sALS and SOD1-ALS. Our results indicate significant differences in NRF2/ARE pathway between sALS and SOD1-ALS lymphoblasts. Furthermore, levels of inflammatory cytokines and autophagic flux discriminate between sALS and SOD1-ALS lymphoblasts. Overall, different molecular mechanisms are involved in sALS and SOD1-ALS patients and thus, personalized medicine should be developed for each case.
Asunto(s)
Esclerosis Amiotrófica Lateral/enzimología , Esclerosis Amiotrófica Lateral/inmunología , Linfocitos/inmunología , Mutación/genética , Medicina de Precisión , Superóxido Dismutasa-1/genética , Ácidos/metabolismo , Anciano , Anciano de 80 o más Años , Esclerosis Amiotrófica Lateral/genética , Autofagia/genética , Línea Celular Transformada , Metabolismo Energético , Femenino , Heterocigoto , Humanos , Espectroscopía de Resonancia Magnética , Masculino , Metabolómica , Persona de Mediana Edad , Factor 2 Relacionado con NF-E2/metabolismo , Estrés Oxidativo , Consumo de Oxígeno , ARN Mensajero/genética , ARN Mensajero/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal , Superóxido Dismutasa-1/metabolismo , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
Body feminization, as part of gender affirmation process of transgender women, decreases the volume of their cortical and subcortical brain structures. In this work, we implement a rat model of adult male feminization which reproduces the results in the human brain and allows for the longitudinal investigation of the underlying structural and metabolic determinants in the brain of adult male rats undergoing feminization treatments. Structural MRI and Diffusion Tensor Imaging (DTI) were used to non-invasively monitor in vivo cortical brain volume and white matter microstructure over 30â¯days in adult male rats receiving estradiol (E2), estradiol plus cyproterone acetate (CA), an androgen receptor blocker and antigonadotropic agent (E2â¯+â¯CA), or vehicle (control). Ex vivo cerebral metabolic profiles were assessed by 1H High Resolution Magic Angle Spinning NMR (1H HRMAS) at the end of the treatments in samples from brain regions dissected after focused microwave fixation (5â¯kW). We found that; a) Groups receiving E2 and E2â¯+â¯CA showed a generalized bilateral decrease in cortical volume; b) the E2â¯+â¯CA and, to a lesser extent, the E2 groups maintained fractional anisotropy values over the experiment while these values decreased in the control group; c) E2 treatment produced increases in the relative concentration of brain metabolites, including glutamate and glutamine and d) the glutamine relative concentration and fractional anisotropy were negatively correlated with total cortical volume. These results reveal, for the first time to our knowledge, that the volumetric decreases observed in trans women under cross-sex hormone treatment can be reproduced in a rat model. Estrogens are more potent drivers of brain changes in male rats than anti-androgen treatment.
Asunto(s)
Encéfalo/efectos de los fármacos , Acetato de Ciproterona/farmacología , Estradiol/farmacología , Feminización , Metaboloma/efectos de los fármacos , Antagonistas de Andrógenos/farmacología , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Encéfalo/patología , Imagen de Difusión Tensora , Femenino , Feminización/inducido químicamente , Feminización/metabolismo , Feminización/patología , Ácido Glutámico/metabolismo , Hormonas Esteroides Gonadales/metabolismo , Imagen por Resonancia Magnética , Masculino , Ratas , Ratas Wistar , Receptores Androgénicos/metabolismo , Transexualidad/inducido químicamente , Transexualidad/diagnóstico por imagen , Transexualidad/metabolismo , Transexualidad/patologíaRESUMEN
Androgenization in adult natal women, as in transsexual men (TM), affects brain cortical thickness and the volume of subcortical structures. In order to understand the mechanism underlying these changes we have developed an adult female rat model of androgenization. Magnetic resonance imaging and spectroscopy were used to monitor brain volume changes, white matter microstructure and ex vivo metabolic profiles over 32 days in androgenized and control subjects. Supraphysiological doses of testosterone prevents aging decrease of fractional anisotropy values, decreased general cortical volume and the relative concentrations of glutamine (Gln) and myo-Inositol (mI). An increase in the N-acetylaspartate (NAA)/mI ratio was detected d. Since mI and Gln are astrocyte markers and osmolytes, we suspect that the anabolic effects of testosterone change astrocyte osmolarity so as to extrude Mi and Gln from these cells in order to maintain osmotic homeostasis. This mechanism could explain the brain changes observed in TM and other individuals receiving androgenic anabolic steroids.
Asunto(s)
Encéfalo/metabolismo , Encéfalo/patología , Metaboloma/fisiología , Virilismo/patología , Animales , Anisotropía , Encéfalo/diagnóstico por imagen , Encéfalo/efectos de los fármacos , Femenino , Lateralidad Funcional , Ácido Glutámico/metabolismo , Glicina/metabolismo , Inositol/metabolismo , Imagen por Resonancia Magnética , Ratas , Ratas Wistar , Testosterona/sangre , Propionato de Testosterona/farmacología , Tritio/metabolismo , Virilismo/sangre , Virilismo/diagnóstico por imagen , Sustancia Blanca/patologíaRESUMEN
We design, implement and validate a novel image processing strategy to obtain in vivo maps of hunger stimulation in the brain of mice, rats and humans, combining Diffusion Weighted Magnetic Resonance Imaging (DWI) datasets from fed and fasted subjects. Hunger maps were obtained from axial/coronal (rodents/humans) brain sections containing the hypothalamus and coplanar cortico-limbic structures using Fisher's Discriminant Analysis of the combined voxel ensembles from both feeding situations. These maps were validated against those provided by the classical mono-exponential diffusion model as applied over the same subjects and conditions. Mono-exponential fittings revealed significant Apparent Diffusion Coefficient (ADC) decreases through the brain regions stimulated by hunger, but rigorous parameter estimations imposed the rejection of considerable number of pixels. The proposed approach avoided pixel rejections and provided a representation of the combined DWI dataset as a pixel map of the "Hunger Index" (HI), a parameter revealing the hunger score of every pixel. The new methodology proved to be robust both, by yielding consistent results with classical ADC maps and, by reproducing very similar HI maps when applied to newly acquired rodent datasets. ADC and HI maps demonstrated similar patterns of activation by hunger in hypothalamic and cortico-limbic structures of the brain of rodents and humans, albeit with different relative intensities, rodents showing more intense activations by hunger than humans, for similar fasting periods. The proposed methodology may be easily extended to other feeding paradigms or even to alternative imaging methods.
Asunto(s)
Mapeo Encefálico/métodos , Encéfalo/fisiología , Imagen de Difusión por Resonancia Magnética , Hambre/fisiología , Adulto , Animales , Índice de Masa Corporal , Corteza Cerebral/fisiología , Humanos , Hipotálamo/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratas , Ratas Sprague-Dawley , Tálamo/fisiologíaRESUMEN
We used 1H, 13C HRMAS and genomic analysis to investigate regionally the transition from oxidative to glycolytic phenotype and its relationship with altered gene expression in adjacent biopsies through the brain of rats bearing C6 gliomas. Tumor-bearing animals were anesthetized and infused with a solution of [1-13C]-glucose, and small adjacent biopsies were obtained spanning transversally from the contralateral hemisphere (regions I and II), the right and left peritumoral areas (regions III and V, respectively), and the tumor core (region IV). These biopsies were analyzed by 1H, 13C HRMAS and by quantitative gene expression techniques. Glycolytic metabolism, as reflected by the [3-13C]-lactate content, increased clearly from regions I to IV, recovering partially to physiological levels in region V. In contrast, oxidative metabolism, as reflected by the [4-13C]-glutamate labeling, decreased in regions I-IV, recovering partially in region V. This metabolic shift from normal to malignant metabolic phenotype paralleled changes in the expression of HIF1α, HIF2α, HIF3α genes, downstream transporters, and regulatory glycolytic, oxidative, and anaplerotic genes in the same regions. Together, our results indicate that genetic and metabolic alterations occurring in the brain of rats bearing C6 gliomas colocalize in situ and the profile of genetic alterations in every region can be inferred from the metabolomic profiles observed in situ by multinuclear HRMAS.
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Neoplasias Encefálicas/genética , Reprogramación Celular , Glioma/genética , Glucólisis/genética , Fosforilación Oxidativa , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Biopsia , Neoplasias Encefálicas/diagnóstico por imagen , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patología , Isótopos de Carbono , Núcleo Caudado/diagnóstico por imagen , Núcleo Caudado/metabolismo , Núcleo Caudado/patología , Femenino , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Glioma/diagnóstico por imagen , Glioma/metabolismo , Glioma/patología , Glucosa/metabolismo , Ácido Glutámico/metabolismo , Humanos , Subunidad alfa del Factor 1 Inducible por Hipoxia/genética , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Ácido Láctico/metabolismo , Imagen por Resonancia Magnética/métodos , Trasplante de Neoplasias , Ratas , Ratas Wistar , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Trasplante HeterólogoRESUMEN
BACKGROUND: Tumour carbonic anhydrase IX (CAIX), a hypoxia-inducible tumour-associated cell surface enzyme, is thought to acidify the tumour microenvironment by hydrating CO2 to form protons and bicarbonate, but there is no definitive evidence for this in solid tumours in vivo. METHODS: We used 1H magnetic resonance spectroscopic imaging (MRSI) of the extracellular pH probe imidazolyl succinic acid (ISUCA) to measure and spatially map extracellular pH in HCT116 tumours transfected to express CAIX and empty vector controls in SCID mice. We also measured intracellular pH in situ with 31P MRS and measured lactate in freeze-clamped tumours. RESULTS: CAIX-expressing tumours had 0.15 pH-unit lower median extracellular pH than control tumours (pH 6.71 tumour vs pH 6.86 control, P = 0.01). Importantly, CAIX expression imposed an upper limit for tumour extracellular pH at 6.93. Despite the increased lactate concentration in CAIX-expressing tumours, 31P MRS showed no difference in intracellular pH, suggesting that CAIX acidifies only the tumour extracellular space. CONCLUSIONS: CAIX acidifies the tumour microenvironment, and also provides an extracellular pH control mechanism. We propose that CAIX thus acts as an extracellular pH-stat, maintaining an acidic tumour extracellular pH that is tolerated by cancer cells and favours invasion and metastasis.
Asunto(s)
Antígenos de Neoplasias/genética , Antígenos de Neoplasias/metabolismo , Anhidrasa Carbónica IX/genética , Anhidrasa Carbónica IX/metabolismo , Neoplasias Colorrectales/patología , Ácido Láctico/análisis , Animales , Hipoxia de la Célula , Proliferación Celular , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/metabolismo , Células HCT116 , Humanos , Imidazoles/química , Ratones , Trasplante de Neoplasias , Espectroscopía de Protones por Resonancia Magnética , Microambiente TumoralRESUMEN
Cerebral pyruvate recycling is a metabolic pathway deriving carbon skeletons and reducing equivalents from mitochondrial oxaloacetate and malate, to the synthesis of mitochondrial and cytosolic pyruvate, lactate and alanine. The pathway allows both, to provide the tricarboxylic acid cycle with pyruvate molecules produced from alternative substrates to glucose and, to generate reducing equivalents necessary for the operation of NADPH requiring processes. At the cellular level, pyruvate recycling involves the activity of malic enzyme, or the combined activities of phosphoenolpyruvate carboxykinase and pyruvate kinase, as well as of those transporters of the inner mitochondrial membrane exchanging the corresponding intermediates. Its cellular localization between the neuronal or astrocytic compartments of the in vivo brain has been controversial, with evidences favoring either a primarily neuronal or glial localizations, more recently accepted to occur in both environments. This review provides a brief history on the detection and characterization of the pathway, its relations with the early developments of cerebral high resolution 13C NMR, and its potential neuroprotective functions under hypoglycemic conditions or ischemic redox stress.
Asunto(s)
Encéfalo/metabolismo , Ciclo del Ácido Cítrico/fisiología , Ácido Pirúvico/metabolismo , Animales , Glucosa/metabolismo , Ácido Glutámico/metabolismo , Humanos , Espectroscopía de Resonancia Magnética/métodos , Factores de TiempoRESUMEN
The mitochondrial aspartate/glutamate transporter Aralar/AGC1/Slc25a12 is critically involved in brain aspartate synthesis, and AGC1 deficiency results in a drastic fall of brain aspartate levels in humans and mice. It has recently been described that the uncoupling protein UCP2 transports four carbon metabolites including aspartate. Since UCP2 is expressed in several brain cell types and AGC1 is mainly neuronal, we set to test whether UCP2 could be a mitochondrial aspartate carrier in the brain glial compartment. The study of the cerebral metabolism of (1-13C)-glucose in vivo in wild type and UCP2-knockout mice showed no differences in C3 or C2 labeling of aspartate, suggesting that UCP2 does not function as a mitochondrial aspartate carrier in brain. However, surprisingly, a clear decrease (of about 30-35 %) in the fractional enrichment of glutamate, glutamine and GABA was observed in the brains of UCP2-KO mice which was not associated with differences in either glucose or lactate enrichments. The results suggest that the dilution in the labeling of glutamate and its downstream metabolites could originate from the uptake of an unlabeled substrate that could not leave the matrix via UCP2 becoming trapped in the matrix. Understanding the nature of the unlabeled substrate and its precursor(s) as alternative substrates to glucose is of interest in the context of neurological diseases associated with UCP2.
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Corteza Cerebral/metabolismo , Glucosa/metabolismo , Proteína Desacopladora 2/fisiología , Animales , Isótopos de Carbono/metabolismo , Ácido Glutámico/metabolismo , Glutamina/metabolismo , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Noqueados , Proteína Desacopladora 2/deficiencia , Ácido gamma-Aminobutírico/metabolismoRESUMEN
BACKGROUND AND PURPOSE: Translational research is beginning to reveal the importance of trophic factors as a therapy for cellular brain repair. The purpose of this study was to analyze whether brain-derived neurotrophic factor (BDNF) administration could mediate oligodendrogenesis and remyelination after white matter injury in subcortical stroke. METHODS: Ischemia was induced in rats by injection of endothelin-1. At 24 hours, 0.4 µg/kg of BDNF or saline was intravenously administered to the treatment and control groups, respectively. Functional evaluation, MRI, and fiber tract integrity on tractography images were analyzed. Proliferation (KI-67) and white matter repair markers (A2B5, 2',3'-cyclic-nucleotide 3'-phosphodiesterase [CNPase], adenomatous polyposis coli [APC], platelet-derived growth factor receptor alpha [PDGFR-α], oligodendrocyte marker O4 [O4], oligodendrocyte transcription factor [Olig-2], and myelin basic protein [MBP]) were analyzed at 7 and 28 days. RESULTS: The BDNF-treated animals showed less functional deficit at 28 days after treatment than the controls (P<0.05). Although T2-MRI did not show differences in lesion size at 7 and 28 days between groups, diffusion tensor imaging tractography analysis revealed significantly better tract connectivity at 28 days in the BDNF group than in the controls (P<0.05). Increased proliferation of oligodendrocyte progenitors was observed in treated animals at 7 days (P<0.05). Finally, the levels of white matter repair markers (A2B5, CNPase, and O4 at 7 days; Olig-2 and MBP at 28 days) were higher in the BDNF group than in the controls (P<0.05). CONCLUSIONS: BDNF administration exerted better functional outcome, oligodendrogenesis, remyelination, and fiber connectivity than controls in rats subjected to subcortical damage in ischemic stroke.
Asunto(s)
Isquemia Encefálica/patología , Factor Neurotrófico Derivado del Encéfalo/farmacología , Diferenciación Celular/efectos de los fármacos , Vaina de Mielina/efectos de los fármacos , Oligodendroglía/efectos de los fármacos , Accidente Cerebrovascular/patología , Sustancia Blanca/efectos de los fármacos , 2',3'-Nucleótido Cíclico Fosfodiesterasas/efectos de los fármacos , Proteína de la Poliposis Adenomatosa del Colon/efectos de los fármacos , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/efectos de los fármacos , Encéfalo/efectos de los fármacos , Encéfalo/patología , Isquemia Encefálica/complicaciones , Imagen de Difusión Tensora , Imagen por Resonancia Magnética , Proteína Básica de Mielina/efectos de los fármacos , Vaina de Mielina/patología , Vaina de Mielina/fisiología , Ratas , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/efectos de los fármacos , Accidente Cerebrovascular/etiología , Sustancia Blanca/patologíaRESUMEN
There is intense interest in developing non-invasive prognostic biomarkers of tumor response to therapy, particularly with regard to hypoxia. It has been suggested that oxygen sensitive MRI, notably blood oxygen level-dependent (BOLD) and tissue oxygen level-dependent (TOLD) contrast, may provide relevant measurements. This study examined the feasibility of interleaved T2*- and T1-weighted oxygen sensitive MRI, as well as R2* and R1 maps, of rat tumors to assess the relative sensitivity to changes in oxygenation. Investigations used cohorts of Dunning prostate R3327-AT1 and R3327-HI tumors, which are reported to exhibit distinct size-dependent levels of hypoxia and response to hyperoxic gas breathing. Proton MRI R1 and R2* maps were obtained for tumors of anesthetized rats (isoflurane/air) at 4.7 T. Then, interleaved gradient echo T2*- and T1-weighted images were acquired during air breathing and a 10 min challenge with carbogen (95% O2 -5% CO2). Signals were stable during air breathing, and each type of tumor showed a distinct signal response to carbogen. T2* (BOLD) response preceded T1 (TOLD) responses, as expected. Smaller HI tumors (reported to be well oxygenated) showed the largest BOLD and TOLD responses. Larger AT1 tumors (reported to be hypoxic and resist modulation by gas breathing) showed the smallest response. There was a strong correlation between BOLD and TOLD signal responses, but ΔR2* and ΔR1 were only correlated for the HI tumors. The magnitude of BOLD and TOLD signal responses to carbogen breathing reflected expected hypoxic fractions and oxygen dynamics, suggesting potential value of this test as a prognostic biomarker of tumor hypoxia.
Asunto(s)
Biomarcadores de Tumor/metabolismo , Dióxido de Carbono/administración & dosificación , Dióxido de Carbono/farmacocinética , Espectroscopía de Resonancia Magnética/métodos , Oxígeno/metabolismo , Neoplasias de la Próstata/metabolismo , Administración por Inhalación , Animales , Hipoxia de la Célula , Línea Celular Tumoral , Medios de Contraste/administración & dosificación , Medios de Contraste/farmacocinética , Masculino , Oximetría/métodos , Oxígeno/administración & dosificación , Oxígeno/farmacocinética , Neoplasias de la Próstata/diagnóstico , Ratas , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
We evaluate the contribution of leptin-dependent anorexigenic pathways and neuropeptide Y (NPY)-dependent orexigenic pathways to the changes in hypothalamic water diffusion parameters observed in vivo by functional diffusion weighted MRI (fDWI). Mice genetically deficient in leptin (B6.V-Lep (ob) /J) or NPY (129S-Npy (tm1Rpa) /J) and the corresponding wild-type controls, were subjected to sequential isocaloric feeding, fasting and recovery regimes. Non-invasive fDWI measurements were performed under these conditions, and complemented with parallel determinations of food and water consumption, respiratory exchange ratio (RER), locomotor activity and endocrine profiles. Control mice showed significant increases in hypothalamic water diffusion parameters upon fasting, returning to normal values in the recovery period. Leptin deficient mice depicted permanently increased water diffusion parameters under all feeding conditions as compared to wild type controls, without important changes upon fasting or recovery. These results paralleled sustained increases in food and water intake, significantly augmented body weight, and decreased RER values or locomotor activity, thus configuring an obese phenotype. NPY-deficient mice showed significantly reduced increases (or even slight decreases) in the water diffusion parameters upon fasting as compared to wild type controls, paralleled by decreased food and water intake during the recovery period. In conclusion, leptin deficiency results in sustained orexigenic stimulation, leading to increased water diffusion parameters, while NPY deficiency lead to reduced orexigenic stimulation and water diffusion parameters. Diffusion changes are proposed to reflect net astrocytic volume changes induced by the balance between the orexigenic and anorexigenic firings of AgRP/NPY and POMC/CART neurons, respectively. Together, our results suggest that fDWI provides an adequate tool to investigate hypothalamic appetite disorders.
Asunto(s)
Regulación del Apetito/fisiología , Imagen de Difusión por Resonancia Magnética/métodos , Hipotálamo/fisiología , Leptina/fisiología , Vías Nerviosas/fisiología , Neuropéptido Y/fisiología , Animales , Agua Corporal/metabolismo , Ingestión de Líquidos/fisiología , Ingestión de Alimentos/fisiología , Hormonas/metabolismo , Leptina/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Actividad Motora/fisiología , Neuropéptido Y/genética , Intercambio Gaseoso PulmonarRESUMEN
BACKGROUND: After acute ischemia, the tissue that is at risk of infarction can be detected by perfusion-weighted imaging/diffusion-weighted imaging (PWI/DWI) mismatch but the time that is needed to process PWI limits its use. As DWI is highly sensitive to acute ischemic tissue damage, we hypothesized that different ADC patterns represent areas with a different potential for recovery. METHODS: In a model of permanent middle cerebral artery occlusion (pMCAO), Sprague-Dawley rats were randomly distributed to sham surgery and pMCAO. We further separated the pMCAO group according to intralesional ADC pattern (homogeneous or heterogeneous). At 24 h after ischemia induction, we analyzed lesion size, functional outcome, cell death expression, and brain protection markers including ROS enzyme NOX-4. MRI included DWI (ADC maps), DTI (tractography), and PWI (CBF, CBV and MTT). RESULTS: The lesion size was similar in pMCAO rats. Animals with a heterogeneous pattern in ADC maps showed better functional outcome in Rotarod test (p = 0.032), less expression of cell death (p = 0.014) and NOX-4 (p = 0.0063), higher intralesional CBF (p = 0.0026) and larger PWI/DWI mismatch (p = 0.007). CONCLUSIONS: In a rodent model for ischemic stroke, intralesional heterogeneity in ADC maps was related to better functional outcome in lesions of similar size and interval after pMCAO. DWI ADC maps may assist in the early identification of ischemic tissue with an increased potential for recovery as higher expression of acute protection markers, lower expression of cell death, increased PWI/DWI mismatch, and higher intralesional CBF were present in animals with a heterogeneous ADC pattern.
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Isquemia Encefálica/patología , Imagen de Difusión por Resonancia Magnética , Infarto de la Arteria Cerebral Media/patología , Accidente Cerebrovascular/patología , Envejecimiento , Animales , Circulación Cerebrovascular/fisiología , Imagen de Difusión por Resonancia Magnética/métodos , Modelos Animales de Enfermedad , Masculino , Imagen de Perfusión/métodos , Ratas Sprague-Dawley , Accidente Cerebrovascular/fisiopatologíaRESUMEN
Liposomal drug delivery vehicles are promising nanomedicine tools for bringing cytotoxic drugs to cancerous tissues selectively. However, the triggered cargo release from liposomes in response to a target-specific stimulus has remained elusive. We report on functionalizing stealth-liposomes with an engineered ion channel and using these liposomes in vivo for releasing an imaging agent into a cerebral glioma rodent model. If the ambient pH drops below a threshold value, the channel generates temporary pores on the liposomes, thus allowing leakage of the intraluminal medicines. By using magnetic resonance spectroscopy and imaging, we show that engineered liposomes can detect the mildly acidic pH of the tumor microenvironment with 0.2 pH unit precision and they release their content into C6 glioma tumors selectively, in vivo. A drug delivery system with this level of sensitivity and selectivity to environmental stimuli may well serve as an optimal tool for environmentally-triggered and image-guided drug release. FROM THE CLINICAL EDITOR: Cancer remains a leading cause of mortality worldwide. With advances in science, delivery systems of anti-cancer drugs have also become sophisticated. In this article, the authors designed and characterized functionalized liposomal vehicles, which would release the drug payload in a highly sensitive manner in response to a change in pH environment in an animal glioma model. The novel data would enable better future designs of drug delivery systems.
Asunto(s)
Neoplasias Encefálicas/patología , Modelos Animales de Enfermedad , Portadores de Fármacos , Glioblastoma/patología , Concentración de Iones de Hidrógeno , Canales Iónicos/química , Liposomas , Animales , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
BACKGROUND & AIMS: Low-grade cytotoxic oedema is considered a main contributor to the neurological (motor and cognitive) alterations in patients with hepatic encephalopathy (HE). This assumption is mainly based on studies with cultured astrocytes treated with very large ammonia concentrations or with animal models of acute liver failure with strong HE. However, the possible contribution of cerebral oedema (vasogenic or cytotoxic) to cognitive or motor alterations in chronic mild HE has not been demonstrated. The aim of this work was to assess whether cerebral oedema contributes to cognitive and/or motor alterations in rats with chronic mild HE. METHODS: Motor activity and coordination and different types of learning and memory were assessed in rats with porta-caval shunts (PCS). Brain oedema was assessed by gravimetry in cerebellum and cortex and apparent diffusion coefficient (ADC) by magnetic resonance in 16 areas. RESULTS: Four weeks after surgery, PCS rats show reduced motor activity and coordination, impaired ability to learn a conditional discrimination task in the Y maze and reduced spatial memory in the Morris water maze. PCS rats did not show increased brain water content at 4 or 10 weeks or changes in ADC at 4 weeks. At 10 weeks, increased ADC in some areas is compatible with vasogenic but not cytotoxic oedema. CONCLUSION: Cerebral oedema is not involved in motor and cognitive alterations in rats (and likely in humans) with mild HE. Proper understanding of the mechanisms responsible for the neurological alterations in HE is necessary to design efficient treatments.
Asunto(s)
Edema Encefálico/diagnóstico , Cerebelo/diagnóstico por imagen , Encefalopatía Hepática/complicaciones , Animales , Cognición , Modelos Animales de Enfermedad , Imagen por Resonancia Magnética , Masculino , Aprendizaje por Laberinto , Memoria , Actividad Motora , Derivación Portocava Quirúrgica , Cintigrafía , Ratas , Ratas WistarRESUMEN
Hypothalamic appetite regulation is a vital homeostatic process underlying global energy balance in animals and humans, its disturbances resulting in feeding disorders with high morbidity and mortality. The objective evaluation of appetite remains difficult, very often restricted to indirect measurements of food intake and body weight. We report here, the direct, non-invasive visualization of hypothalamic activation by fasting using diffusion weighted magnetic resonance imaging, in the mouse brain as well as in a preliminary study in the human brain. The brain of fed or fasted mice or humans were imaged at 7 or 1.5 Tesla, respectively, by diffusion weighted magnetic resonance imaging using a complete range of b values (10
Asunto(s)
Potenciales de Acción/fisiología
, Algoritmos
, Apetito/fisiología
, Mapeo Encefálico/métodos
, Ayuno/fisiología
, Hipotálamo/fisiología
, Interpretación de Imagen Asistida por Computador/métodos
, Adulto
, Animales
, Imagen de Difusión por Resonancia Magnética
, Humanos
, Aumento de la Imagen/métodos
, Masculino
, Ratones
, Ratones Endogámicos C57BL
, Reproducibilidad de los Resultados
, Sensibilidad y Especificidad
, Especificidad de la Especie
, Adulto Joven
RESUMEN
Development of neovasculature is a necessary requirement for tumour growth and it provides additional opportunities for therapeutic intervention. However, current antiangiogenic therapies have limited efficacy, mostly because of the development of resistance. Hence, characterization of new antiangiogenic molecular targets is of considerable clinical interest. We report that a calmodulin-binding domain (CaM-BD) deletion mutant of the growth factor receptor bound protein 7 (Grb7) (denoted Grb7Δ) impairs tumour growth and associated angiogenesis in vivo. We implanted glioma C6 cells in rat brains transfected with an enhanced yellow fluorescent protein (EYFP) chimera of Grb7∆, its EYFP-Grb7 wild type counterpart, and EYFP alone. We systematically followed intracerebral growth of the tumours, their cellularity and the functional performance of tumour-associated microvasculature using magnetic resonance imaging, including anatomical T1W and T2W images and functional diffusion and perfusion parameters. Tumours grown from implanted C6 cells expressing EYFP-Grb7Δ developed slower, became smaller and presented lower apparent cellularity than those derived from cells expressing EYFP-Grb7 and EYFP. Vascular perfusion measurements within tumours derived from EYFP-Grb7∆-expressing cells showed significantly lower cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) values. These findings were independently validated by histological and immunohistochemical techniques. Taken together, these findings confirm that the CaM-BD of Grb7 plays an important role in tumour growth and associated angiogenesis in vivo, thus identifying this region of the protein as a novel target for antiangiogenic treatment.
Asunto(s)
Inhibidores de la Angiogénesis/metabolismo , Proteína Adaptadora GRB7/metabolismo , Imagen por Resonancia Magnética , Terapia Molecular Dirigida , Neoplasias/irrigación sanguínea , Neoplasias/patología , Neovascularización Patológica/patología , Animales , Proteínas Bacterianas , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Proteínas Luminiscentes , Neoplasias/metabolismo , Ratas , Ratas Wistar , Proteínas Recombinantes de Fusión/metabolismo , Transfección , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
BACKGROUND: Global energy balance is a vital process tightly regulated by the brain that frequently becomes dysregulated during the development of cancer. Glioblastoma (GBM) is one of the most investigated malignancies, but its appetite-related disorders, like anorexia/cachexia symptoms, remain poorly understood. METHODS: We performed manganese enhanced magnetic resonance imaging (MEMRI) and subsequent diffusion tensor imaging (DTI), in adult male GBM-bearing (n = 13) or control Wistar rats (n = 12). A generalized linear model approach was used to assess the effects of fasting in different brain regions involved in the regulation of the global energy metabolism: cortex, hippocampus, hypothalamus and thalamus. The regions were selected on the contralateral side in tumor-bearing animals, and on the left hemisphere in control rats. An additional DTI-only experiment was completed in two additional GBM (n = 5) or healthy cohorts (n = 6) to assess the effects of manganese infusion on diffusion measurements. RESULTS: MEMRI results showed lower T1 values in the cortex (p-value < 0.001) and thalamus (p-value < 0.05) of the fed ad libitum GBM animals, as compared to the control cohort, consistent with increased Mn2+ accumulation. No MEMRI-detectable differences were reported between fed or fasting rats, either in control or in the GBM group. In the MnCl2-infused cohorts, DTI studies showed no mean diffusivity (MD) variations from the fed to the fasted state in any animal cohort. However, the DTI-only set of acquisitions yielded remarkably decreased MD values after fasting only in the healthy control rats (p-value < 0.001), and in all regions, but thalamus, of GBM compared to control animals in the fed state (p-value < 0.01). Fractional anisotropy (FA) decreased in tumor-bearing rats due to the infiltrate nature of the tumor, which was detected in both diffusion sets, with (p-value < 0.01) and without Mn2+ administration (p-value < 0.001). CONCLUSIONS: Our results revealed that an altered physiological brain response to fasting occurred in hunger related regions in GBM animals, detectable with DTI, but not with MEMRI acquisitions. Furthermore, the present results showed that Mn2+ induces neurotoxic inflammation, which interferes with diffusion MRI to detect appetite-induced responses through MD changes.
Asunto(s)
Glioblastoma , Masculino , Ratas , Animales , Glioblastoma/diagnóstico por imagen , Glioblastoma/patología , Imagen de Difusión Tensora/métodos , Manganeso , Anorexia/patología , Ratas Wistar , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Imagen por Resonancia Magnética/métodos , Imagen de Difusión por Resonancia Magnética/métodos , AyunoRESUMEN
BACKGROUND & AIMS: Patients with acute liver failure (ALF) often die of intracranial pressure (IP) and cerebral herniation. Main contributors to increased IP are ammonia, glutamine, edema, and blood flow. The sequence of events and underlying mechanisms, as well as the temporal pattern, regional distribution, and contribution of each parameter to the progression of neurologic deterioration and IP, are unclear. We studied rats with ALF to follow the progression of changes in ammonia, glutamine, grade and type (vasogenic or cytotoxic) of edema, blood-brain barrier permeability, cerebral blood flow, and IP. We assessed whether the changes in these parameters were similar between frontal cortex and cerebellum and evaluated the presence, type, and progression of edema in 12 brain areas. METHODS: ALF was induced by injection of galactosamine. The grade and type of edema was assessed by measuring the apparent diffusion coefficient by magnetic resonance imaging. Cerebral blood flow was measured by magnetic resonance and blood-brain barrier permeability by Evans blue-albumin extravasation. RESULTS: Increased IP arises from an early increase of blood-brain barrier permeability in certain areas (including cerebellum but not frontal cortex) followed by vasogenic edema. Ammonia and glutamine then increase progressively, leading to cytotoxic edema in many areas. Alterations in lactate and cerebral blood flow are later events that further increase IP. CONCLUSIONS: Different mechanisms in specific regions of the brain contribute, with different temporal patterns, to the progression of cerebral alterations and IP in ALF.