RESUMEN
Albeit aging is an inevitable process, the rate of aging is susceptible to modifications. Dietary restriction (DR) is a vigorous nongenetic and nonpharmacological intervention that is known to delay aging and increase healthspan in diverse species. This study aimed to compare the impact of different restricting feeding regimes such as limited daily feeding (LDF, 60% AL) and intermittent feeding (IF) on brain energy homeostasis during aging. The analysis was focused on the key molecules in glucose and cholesterol metabolism in the cortex and hippocampus of middle-aged (12-month-old) and aged (24-month-old) male Wistar rats. We measured the impact of different DRs on the expression levels of AMPK, glucose transporters (GLUT1, GLUT3, GLUT4), and the rate-limiting enzyme in the cholesterol synthesis pathway (HMGCR). Additionally, we assessed the changes in the amounts of cholesterol, its metabolite, and precursors following LDF and IF. IF decreased the levels of AMPK and pAMPK in the cortex while the increased levels were detected in the hippocampus. Glucose metabolism was more affected in the cortex, while cholesterol metabolism was more influenced in the hippocampus. Overall, the hippocampus was more resilient to the DRs, with fewer changes compared to the cortex. We showed that LDF and IF differently affected the brain energy homeostasis during aging and that specific brain regions exhibited distinct vulnerabilities towards DRs. Consequently, special attention should be paid to the DR application among elderly as different phases of aging do not respond equally to altered nutritional regimes.
Asunto(s)
Envejecimiento/metabolismo , Encéfalo/metabolismo , Restricción Calórica/métodos , Adenilato Quinasa/metabolismo , Animales , Glucemia/metabolismo , Corteza Cerebral/metabolismo , Colesterol/metabolismo , Metabolismo Energético , Glucosa/metabolismo , Proteínas Facilitadoras del Transporte de la Glucosa/metabolismo , Hipocampo/metabolismo , Homeostasis , Metabolismo de los Lípidos , Masculino , Modelos Animales , Ratas , Ratas WistarRESUMEN
Dietary restriction (DR) exerts significant beneficial effects in terms of aging and age-related diseases in many organisms including humans. The present study aimed to examine the influence of long-term DR on the BDNF system at the transcriptional and translational levels in the cortex and hippocampus of middle-aged (12-month-old) and aged (24-month-old) male Wistar rats. The obtained results revealed that the DR upregulated the expression of exon-specific BDNF transcripts in both regions, followed by elevated levels of mBDNF only in the cortex in middle-aged animals. In aged animals, DR modulated BDNF protein levels by increasing proBDNF and by declining mBDNF levels. Additionally, elevated levels of the full-length TrkB accompanied by a decreased level of the less-glycosylated TrkB protein were observed in middle-aged rats following DR, while in aged rats, DR amplified only the expression of the less-glycosylated form of TrkB. The levels of phosphorylated TrkB(Y816) were stable during aging regardless of feeding. Reduced levels of p75(NTR) were detected in both regions of middle-aged DR-fed animals, while a significant increase was measured in the cortex of aged DR-fed rats. These findings shed additional light on DR as a modulator of BDNF system revealing its disparate effects in middle-aged and aged animals. Given the importance of the proBDNF/BDNF circuit-level expression in different brain functions and various aspects of behavior, it is necessary to further elucidate the optimal duration of the applied dietary regimen with regard to the animal age in order to achieve its most favorable effects.
Asunto(s)
Envejecimiento/metabolismo , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Restricción Calórica , Corteza Cerebral/metabolismo , Hipocampo/metabolismo , Receptor trkB/metabolismo , Animales , Glucemia/metabolismo , Peso Corporal/fisiología , Factor Neurotrófico Derivado del Encéfalo/genética , Masculino , Modelos Animales , Proteínas Tirosina Quinasas/metabolismo , ARN Mensajero/metabolismo , Ratas Wistar , Receptor de Factor de Crecimiento Nervioso/metabolismo , Receptor trkB/genética , Factores de TiempoRESUMEN
Significance: It is well established that lifestyle and dietary habits have a tremendous impact on life span, the rate of aging, and the onset/progression of age-related diseases. Specifically, dietary restriction (DR) and other healthy dietary patterns are usually accompanied by physical activity and differ from Western diet that is rich in fat and sugars. Moreover, as the generation of reactive oxidative species is the major causative factor of aging, while DR could modify the level of oxidative stress, it has been proposed that DR increases both survival and longevity. Recent Advances: Despite the documented links between DR, aging, and oxidative stress, many issues remain to be addressed. For instance, the free radical theory of aging is under "re-evaluation," while DR as a golden standard for prolonging life span and ameliorating the effects of aging is also under debate. Critical Issues: This review article pays special attention to highlight the link between DR and oxidative stress in both aging and age-related diseases. We discuss in particular DR's capability to counteract the consequences of oxidative stress and the molecular mechanisms involved in these processes. Future Directions: Although DR is undoubtedly beneficial, several considerations must be taken into account when designing the best dietary intervention. Use of intermittent fasting, daily food reduction, or DR mimetics? Future research should unravel the pros and cons of all these processes. Antioxid. Redox Signal. 34, 421-438.
Asunto(s)
Restricción Calórica , Estrés Oxidativo , Envejecimiento , Animales , Dieta , Susceptibilidad a Enfermedades , Metabolismo Energético , Humanos , Longevidad , Mitocondrias/metabolismo , Oxidación-Reducción , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Alzheimer's disease (AD) is the most common form of dementia worldwide, characterized by a progressive decline in a variety of cognitive and non-cognitive functions. The amyloid beta protein cascade hypothesis places the formation of amyloid beta protein aggregates on the first position in the complex pathological cascade leading to neurodegeneration, and therefore AD might be considered to be a protein-misfolding disease. The Ubiquitin Proteasome System (UPS), being the primary protein degradation mechanism with a fundamental role in the maintenance of proteostasis, has been identified as a putative therapeutic target to delay and/or to decelerate the progression of neurodegenerative disorders that are characterized by accumulated/aggregated proteins. The purpose of this study was to test if the activation of proteasome in vivo can alleviate AD pathology. Specifically by using two compounds with complementary modes of proteasome activation and documented antioxidant and redox regulating properties in the 5xFAD transgenic mice model of AD, we ameliorated a number of AD related deficits. Shortly after proteasome activation we detected significantly reduced amyloid-beta load correlated with improved motor functions, reduced anxiety and frailty level. Essentially, to our knowledge this is the first report to demonstrate a dual activation of the proteasome and its downstream effects. In conclusion, these findings open up new directions for future therapeutic potential of proteasome-mediated proteolysis enhancement.
Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/genética , Animales , Modelos Animales de Enfermedad , Ratones , Ratones Transgénicos , Fenotipo , Complejo de la Endopetidasa ProteasomalRESUMEN
Maintaining the cholesterol homeostasis is essential for normal CNS functioning. The enzyme responsible for elimination of cholesterol excess from the brain is cholesterol 24-hydroxylase (Cyp46). Since cholesterol homeostasis is disrupted following brain injury, in this study we examined the effect of right sensorimotor cortex suction ablation on cellular and temporal pattern of Cyp46 expression in the rat brain. Increased expression of Cyp46 at the lesion site at all post injury time points (2, 7, 14, 28 and 45 days post injury, dpi) was detected. Double immunofluorescence staining revealed colocalization of Cyp46 expression with different types of glial cells in time-dependent manner. In ED1(+) microglia/macrophages Cyp46 expression was most prominent at 2 and 7 dpi, whereas Cyp46 immunoreactivity persisted in reactive astrocytes throughout all time points post-injury. However, during the first 2 weeks Cyp46 expression was enhanced in both GFAP(+) and Vim(+) astrocytes, while at 28 and 45 dpi its expression was mostly associated with GFAP(+) cells. Pattern of neuronal Cyp46 expression remained unchanged after the lesion, i.e. Cyp46 immunostaining was detected in dendrites and cell body, but not in axons. The results of this study clearly demonstrate that in pathological conditions, like brain injury, Cyp46 displayed atypical expression, being expressed not only in neuronal cells, but also in microglia and astrocytes. Therefore, injury-induced expression of Cyp46 in microglial and astroglial cells may be involved in the post-injury removal of damaged cell membranes contributing to re-establishment of the brain cholesterol homeostasis.
Asunto(s)
Lesiones Encefálicas/enzimología , Neuroglía/metabolismo , Esteroide Hidroxilasas/genética , Activación Transcripcional , Animales , Astrocitos , Colesterol , Colesterol 24-Hidroxilasa , Hemostasis , Cinética , Masculino , Microglía , Neuroglía/patología , Ratas , Ratas Wistar , Esteroide Hidroxilasas/fisiología , Factores de TiempoRESUMEN
Alzheimer's disease patients (AD), as well as AD transgenic mice, are characterized by increased frailty. Furthermore, the assessment of frailty status represents a feasible approach for detecting individuals prone to develop more severe form of AD and for measuring the outcome of existing and putative AD therapeutics. The 5xFAD mouse is one of the widely used transgenic animal models of AD, but frailty in this model is scantly investigated. We used two validated mouse frailty assessment tools: phenotypic frailty score (FS) and clinical frailty index (FI) to investigate age- and sex- related differences in frailty status in 5xFAD mice. These tools measure different age-related deficits and do not necessarily identify the same subpopulations as frail. We detected a significant increase in frailty with age in both sexes, although females were surprisingly less frail than males. Depending on the tools used, a notable difference in frailty status was detected, with frailty index and frailty score identifying different mice as frail. These results warrant great caution when choosing the frailty tool and point to the need for further adaptation of frailty measurements in mouse models of AD.
Asunto(s)
Enfermedad de Alzheimer/fisiopatología , Modelos Animales de Enfermedad , Fragilidad/diagnóstico , Ratones , Factores de Edad , Animales , Variación Biológica Poblacional , Indicadores de Salud , Humanos , Ratones Transgénicos , Proyectos de Investigación , Factores SexualesRESUMEN
Expression profiles of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), apolipoprotein E (ApoE) and cholesterol 24S-hydroxylase (CYP46), proteins involved in cholesterol biosynthesis, transport and excretion from the CNS, were analyzed in the rat cortex, hippocampus and cerebellum as a function of aging (624 months) and in response to long-term dietary restriction (DR). Age-related increases for all three mRNAs were observed, with the highest induction found for Cyp46 in the cortex and hippocampus of 24-month-old animals. DR maintained stable levels of Cyp46, HMGR, and ApoE mRNAs during aging, exhibiting an attenuating effect on age-related changes through specific temporal and regional pattern. Neither age nor DR had any prominent effects at the protein level, except for Cyp46 and ApoE protein levels in the hippocampus and cerebellum, respectively. Overall, the changes in the cerebellum were different from those in the cortex and hippocampus. Our results demonstrated a modulatory effect of DR on agerelated changes of CYP46, HMGR, and ApoE and suggest that the anti-aging effect of DR is in part mediated though transcriptional modulation of cholesterol metabolism genes in the rat brain.
Asunto(s)
Envejecimiento/metabolismo , Encéfalo/metabolismo , Restricción Calórica , Colesterol/metabolismo , Metabolismo de los Lípidos/genética , Factores de Edad , Envejecimiento/genética , Animales , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Peso Corporal , Cerebelo/metabolismo , Corteza Cerebral/metabolismo , Colesterol 24-Hidroxilasa , Hipocampo/metabolismo , Homeostasis , Hidroximetilglutaril-CoA Reductasas/genética , Hidroximetilglutaril-CoA Reductasas/metabolismo , Masculino , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Esteroide Hidroxilasas/genética , Esteroide Hidroxilasas/metabolismo , Transcripción Genética , Regulación hacia ArribaRESUMEN
Increased evidence suggests that dysregulation of cholesterol metabolism may be a key event contributing to progression of multiple sclerosis (MS). Using an experimental autoimmune encephalomyelitis (EAE) model of MS we revealed specific changes in the mRNA and protein expression of key molecules involved in the maintaining of cholesterol homeostasis in the rat spinal cord: 3-hydroxy-3-methylglutaryl-coenzyme-A reductase (HMGCR), apolipoprotein E (ApoE) and cholesterol 24-hydroxylase (CYP46A1) during the course of disease. The presence of myelin lipid debris was seen only at the peak of EAE in demyelination loci being efficiently removed during the recovery period. Since CYP46A1 is responsible for removal of cholesterol excess, we performed a detailed profiling of CYP46A1 expression and revealed regional and temporal specificities in its distribution. Double immunofluorescence staining demonstrated CYP46A1 localization with neurons, infiltrated macrophages, microglia and astrocytes in the areas of demyelination, suggesting that these cells play a role in cholesterol turnover in EAE. We propose that alterations in the regulation of cholesterol metabolism at the onset and peak of EAE may add to the progression of disease, while during the recovery period may have beneficial effects contributing to the regeneration of myelin sheath and restoration of neuronal function.
Asunto(s)
Colesterol/metabolismo , Encefalomielitis Autoinmune Experimental/etiología , Encefalomielitis Autoinmune Experimental/metabolismo , Metabolismo de los Lípidos/genética , Médula Espinal/metabolismo , Transcriptoma , Animales , Astrocitos/inmunología , Astrocitos/metabolismo , Biomarcadores , Colesterol 24-Hidroxilasa/genética , Colesterol 24-Hidroxilasa/metabolismo , Enfermedades Desmielinizantes/genética , Enfermedades Desmielinizantes/metabolismo , Modelos Animales de Enfermedad , Progresión de la Enfermedad , Encefalomielitis Autoinmune Experimental/patología , Expresión Génica , Macrófagos/inmunología , Macrófagos/metabolismo , Macrófagos/patología , Microglía/inmunología , Microglía/metabolismo , Microglía/patología , Esclerosis Múltiple/etiología , Esclerosis Múltiple/metabolismo , Esclerosis Múltiple/patología , Neuronas/metabolismo , Fenotipo , Ratas , Índice de Severidad de la Enfermedad , Médula Espinal/patologíaRESUMEN
Proper function of lysosomes is particularly important in neurons, as they cannot dilute accumulated toxic molecules and aggregates by cell division. Thus, impairment of lysosomal function plays an important role in neuronal degeneration and in the pathogenesis of numerous neurodegenerative diseases. In this work we analyzed how inhibition and/or loss of the major lysosomal proteases, the cysteine cathepsins B and L (CtsB/L), affects lysosomal function, cholesterol metabolism and degradation of the key Alzheimer's disease (AD) proteins. Here, we show that cysteine CtsB/L, and not the aspartyl cathepsin D (CtsD), represent a major lysosomal protease(s) that control lysosomal function, intracellular cholesterol trafficking and AD-like amyloidogenic features. Intriguingly, accumulation of free cholesterol in late endosomes/lysosomes upon CtsB/L inhibition resembled a phenotype characteristic for the rare neurodegenerative disorder Niemann-Pick type C (NPC). CtsB/L inhibition and not the inhibition of CtsD led to lysosomal impairment assessed by decreased degradation of EGF receptor, enhanced LysoTracker staining and accumulation of several lysosomal proteins LC3II, NPC1 and NPC2. By measuring the levels of NPC1 and ABCA1, the two major cholesterol efflux proteins, we showed that CtsB/L inhibition or genetic depletion caused accumulation of the NPC1 in lysosomes and downregulation of ABCA1 protein levels and its expression. Furthermore, we revealed that CtsB/L are involved in degradation of the key Alzheimer's proteins: amyloid-ß peptides (Aß) and C-terminal fragments of the amyloid precursor protein (APP) and in degradation of ß-secretase (BACE1). Our results imply CtsB/L as major regulators of lysosomal function and demonstrate that CtsB/L may play an important role in intracellular cholesterol trafficking and in degradation of the key AD proteins. Our findings implicate that enhancing the activity or levels of CtsB/L could provide a promising and a common strategy for maintaining lysosomal function and for preventing and/or treating neurodegenerative diseases.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Proteínas Amiloidogénicas/metabolismo , Catepsina B/metabolismo , Catepsina L/metabolismo , Colesterol/metabolismo , Lisosomas/metabolismo , Enfermedad de Niemann-Pick Tipo C/metabolismo , Animales , Células CHO , Catepsina B/antagonistas & inhibidores , Catepsina L/antagonistas & inhibidores , Línea Celular Tumoral , Cricetulus , Homeostasis , ProteolisisRESUMEN
Over 60% of people aged over 65 are affected by multiple morbidities, which are more difficult to treat, generate increased healthcare costs and lead to poor quality of life compared to individual diseases. With the number of older people steadily increasing this presents a societal challenge. Age is the major risk factor for age-related diseases and recent research developments have led to the proposal that pharmacological interventions targeting common mechanisms of ageing may be able to delay the onset of multimorbidity. Here we review the state of the knowledge of multimorbidity, appraise the available evidence supporting the role of mechanisms of ageing in the development of the most common age-related diseases and assess potential molecules that may successfully target those key mechanisms.
Asunto(s)
Envejecimiento/genética , Envejecimiento/metabolismo , Envejecimiento/patología , Anciano , Anciano de 80 o más Años , HumanosRESUMEN
Maintaining cholesterol homeostasis in the brain is vital for its proper functioning. While it is well documented that dietary restriction modulates the metabolism of cholesterol peripherally, little is known as to how it can affect cholesterol metabolism in the brain. The present study was designed to elucidate the impact of long-term dietary restriction on brain cholesterol metabolism. Three-month-old male Wistar rats were exposed to long-term dietary restriction until 12 and 24 months of age. The concentrations of cholesterol, its precursors and metabolites, and food-derived phytosterols were measured in the serum, cortex, and hippocampus by gas chromatography/mass spectrometry. Relative changes in the levels of proteins involved in cholesterol synthesis, transport, and degradation were determined by Western blot analysis. Reduced food intake influenced the expression patterns of proteins implicated in cholesterol metabolism in the brain in a region-specific manner. Dietary restriction decreased the concentrations of cholesterol precursors, lanosterol in the cortex, and lanosterol and lathosterol in the hippocampus at 12 months, while the level of desmosterol was elevated in the hippocampus at 24 months. The concentrations of cholesterol and 24(S)-hydroxycholesterol remained unaffected. Food-derived phytosterols were significantly lower after dietary restriction in both the cortex and hippocampus at 12 and 24 months. These findings provide new insight into the effects of dietary restriction on cholesterol metabolism in the brain, lending further support to its neuroprotective effect.
Asunto(s)
Envejecimiento/metabolismo , Corteza Cerebral/metabolismo , Colesterol/metabolismo , Dieta con Restricción de Proteínas/métodos , Hipocampo/metabolismo , Animales , Estudios de Seguimiento , Masculino , Ratas , Ratas Wistar , Factores de TiempoRESUMEN
The objective of this study was to examine the effects of aging and long-term dietary restriction (DR) on the level of amyloid precursor protein (APP) and presenilin-1 (PS-1), proteins that are critically involved in Alzheimer's disease. Changes in mRNA and protein expression were assessed by real-time PCR and western blot analysis during aging and long-term DR in the cortex and hippocampus of 6-, 12-, 18-, and 24-month-old rats. Prominent regional changes in expression were observed in response to aging and DR. Although the hippocampus displayed significant alterations in APP mRNA and protein expression and no significant changes in PS-1 expression, an opposite pattern was observed in the cortex. DR counteracted the age-related changes in APP mRNA expression in both structures of old animals. The observed DR-induced increase in mRNA levels in the hippocampus was accompanied by an increase in the level of full-length protein APP. These results indicate that although both structures are very sensitive to aging, a specific spatial pattern of changes in APP and PS-1 occurs during aging. Furthermore, these findings provide evidence that DR can affect APP and PS-1 expression in a manner consistent with its proposed 'antiaging' effect.
Asunto(s)
Envejecimiento/metabolismo , Precursor de Proteína beta-Amiloide/biosíntesis , Restricción Calórica , Corteza Cerebral/metabolismo , Hipocampo/metabolismo , Presenilina-1/biosíntesis , ARN Mensajero/biosíntesis , Animales , Corteza Cerebral/patología , Hipocampo/patología , Masculino , Ratas , Ratas WistarRESUMEN
Neurotrophins are established molecular mediators of neuronal plasticity in the adult brain. We analyzed the impact of aging on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) protein isoforms, their receptors, and on the expression patterns of multiple 5' exon-specific BDNF transcripts in the rat cortex and hippocampus throughout the life span of the rat (6, 12, 18, and 24 months of age). ProNGF was increased during aging in both structures. Mature NGF gradually decreased in the cortex, and, in 24-month-old animals, it was 30% lower than that in adult 6-month-old rats. The BDNF expression did not change during aging, while proBDNF accumulated in the hippocampus of aged rats. Hippocampal total BDNF mRNA was lower in 12-month-old animals, mostly as a result of a decrease of BDNF transcripts 1 and 2. In contrast to the region-specific regulation of specific exon-containing BDNF mRNAs in adult animals, the same BDNF RNA isoforms (containing exons III, IV, or VI) were present in both brain structures of aged animals. Deficits in neurotrophin signaling were supported by the observed decrease in Trk receptor expression which was accompanied by lower levels of the two main downstream effector kinases, pAkt and protein kinase C. The proteolytic processing of p75NTR observed in 12-month-old rats points to an additional regulatory mechanism in early aging. The changes described herein could contribute to reduced brain plasticity underlying the age-dependent decline in cognitive function.
Asunto(s)
Envejecimiento/genética , Factor Neurotrófico Derivado del Encéfalo/genética , Corteza Cerebral/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica , Hipocampo/crecimiento & desarrollo , Factores de Crecimiento Nervioso/genética , Precursores de Proteínas/genética , Envejecimiento/metabolismo , Animales , Western Blotting , Factor Neurotrófico Derivado del Encéfalo/biosíntesis , Corteza Cerebral/metabolismo , Hipocampo/metabolismo , Inmunohistoquímica , Factores de Crecimiento Nervioso/biosíntesis , Precursores de Proteínas/biosíntesis , ARN Mensajero/genética , Ratas , Ratas Wistar , Reacción en Cadena en Tiempo Real de la Polimerasa , Transcripción GenéticaRESUMEN
Brain aging is related to the numerous structural and functional changes including decreased synaptic plasticity. The beneficial effects of dietary restriction (DR) are well known but insufficiently investigated at the level of plasticity-related markers. Therefore, the aim of this study was to examine the expression profiles of proteins structurally and functionally related to synapses-growth-associated protein 43 (GAP-43), synaptophysin (SPH) and alpha-synuclein (alpha-Syn), in the course of aging and in response to long-term DR. The mRNA and protein levels of three presynaptic proteins were assessed by Real Time RT-PCR and Western blotting in the cortex and hippocampus of young (6-month-old), middle-aged (12-month-old), aged (18-month-old) and old (24-month-old) male Wistar rats fed ad libitum and exposed to DR starting from 6 months of age. We observed that long-term DR modulated age-related transcriptional changes by maintaining stable mRNAs levels in the cortex. No major age-related changes of the protein levels were observed in the cortex, while the specific temporal decline was detected in the hippocampus for all three proteins. The SPH levels were decreased across lifespan (0.8-, 0.8- and 0.6-fold change at 12, 18 and 24 months), while the significant decrease of GAP-43 and alpha-Syn protein was detected at 24 months of age (0.6- and 0.7-fold decrease, respectively). Long-term DR eliminated this decline by increasing GAP-43, SPH and alpha-Syn protein levels (1.7-, 1.7- and 1.6-fold, respectively) thus reverting protein levels to the values measured in 6-month-old animals.Specific pattern of changes observed in the hippocampus identifies this structure as more vulnerable to the processes of aging and with a more pronounced response to the DR effects. The observed DR-induced stabilization of the levels of three presynaptic proteins indicates the beneficial effect of DR on age-related decline in the capacity for synaptic plasticity.