Interaction between hypothalamic dorsomedial nucleus and the suprachiasmatic nucleus determines intensity of food anticipatory behavior.

Food anticipatory behavior (FAA) is induced by limiting access to food for a few hours daily. Animals anticipate this scheduled meal event even without the suprachiasmatic nucleus (SCN), the biological clock. Consequently, a food-entrained oscillator has been proposed to be responsible for meal time estimation. Recent studies suggested the dorsomedial hypothalamus (DMH) as the site for this food-entrained oscillator, which has led to considerable controversy in the literature. Herein we demonstrate by means of c-Fos immunohistochemistry that the neuronal activity of the suprachiasmatic nucleus (SCN), which signals the rest phase in nocturnal animals, is reduced when animals anticipate the scheduled food and, simultaneously, neuronal activity within the DMH increases. Using retrograde tracing and confocal analysis, we show that inhibition of SCN neuronal activity is the consequence of activation of GABA-containing neurons in the DMH that project to the SCN. Next, we show that DMH lesions result in a loss or diminution of FAA, simultaneous with increased activity in the SCN. A subsequent lesion of the SCN restored FAA. We conclude that in intact animals, FAA may only occur when the DMH inhibits the activity of the SCN, thus permitting locomotor activity. As a result, FAA originates from a neuronal network comprising an interaction between the DMH and SCN. Moreover, this study shows that the DMH-SCN interaction may serve as an intrahypothalamic system to gate activity instead of rest overriding circadian predetermined temporal patterns.

Midazolam reduction with pre-operative melatonin in abdominal hysterectomy: double-blind randomized clinical trial.

INTRODUCTION: Midazolam is a benzodiazepine used for sedation, however, can cause respiratory depression and increases morbidity in patients. Melatonin is an effective alternative to manage anxiety in the perioperative period and could help to reduce the use of benzodiazepines during surgery. The aim of this clinical trial was to determine the efficacy of pre-operative sedation with a single-dose melatonin to reduce intraoperative use of midazolam in women under total abdominal hysterectomy (TAH). MATERIALS AND METHODS: This is a double-blind randomized clinical trial conducted in women over 25 years, scheduled for TAH, with American Society of Anesthesiologists Grade I or II. Each patient was randomly assigned to receive 5 mg of melatonin prolonged-release oral capsules or placebo. Midazolam use for anesthetic management was the decision of the treating anesthesiologist and sedation status was determined using the observer's assessment of alertness/sedation scale. RESULTS: In patients receiving melatonin, the use of midazolam during surgery was less than in patients receiving placebo. In addition, melatonin produces sedation 30 min after administration, the sedative effect was maintained at 60- and 90-min. Furthermore, hospital stay was shorter in patients who received melatonin (p = 0.006). CONCLUSION: Melatonin is effective for reduces intraoperative midazolam consumption and hospital stay in women undergoing TAH.

INTRODUCCIÓN: El midazolam es una benzodiazepina utilizada para la sedación, sin embargo, puede causar depresión respiratoria y aumentar la morbilidad en los pacientes. La melatonina es una alternativa eficaz para controlar la ansiedad en el período perioperatorio y podría ayudar a reducir el uso de benzodiazepinas durante la cirugía. El objetivo de este ensayo clínico fue determinar la eficacia de la sedación preoperatoria con una dosis única de melatonina para reducir el uso intraoperatorio de midazolam en mujeres sometidas a histerectomía abdominal total (HTA). MATERIAL Y MÉTODOS: Se trata de un ensayo clínico aleatorizado doble ciego realizado en mujeres mayores de 25 años, programadas para TAH, con American Society of Anesthesiologists Grado I o II. Cada paciente fue asignado al azar para recibir 5 mg de cápsulas orales de liberación prolongada de melatonina o placebo. El uso de midazolam para el manejo anestésico fue decisión del anestesiólogo tratante y el estado de sedación se determinó mediante la escala OAA/S. RESULTADOS: En las pacientes que recibieron melatonina, el uso de midazolam durante la cirugía fue menor que en las pacientes que recibieron placebo. Además, la melatonina produce sedación 30 min después de la administración, el efecto sedante se mantuvo a los 60 y 90 min. Además, la estancia hospitalaria fue más corta en los pacientes que recibieron melatonina (p = 0.006). CONCLUSIÓN: La melatonina es eficaz para reducir el consumo de midazolam intraoperatorio y la estancia hospitalaria en mujeres sometidas a HTA.

Effect of a light-darkness cycle on the body weight gain of preterm infants admitted to the neonatal intensive care unit.

The Continuous bright light conditions to which premature infants are subjected while hospitalized in Neonatal Intensive Care Units (NICU) can have deleterious effects in terms of growth and development. This study evaluates the benefits of a light/darkness cycle (LDC) in weight and early hospital discharge from the NICU. Subjects were recruited from three participating institutions in Mexico. Eligible patients (n = 294) were premature infants who were hospitalized in the low-risk and high-risk neonatal units classified as stable. The subjects randomized to the experimental group (n = 150) were allocated to LDC conditions are as follows: light from 07:00 to 19:00 and darkness (25 lx) from 19:00 to 07:00. The control group (n = 144) was kept under normal room light conditions (CBL) 24 h a day. Main outcome was weight gain and the effect of reducing the intensity of nocturnal light in development of premature infants. Infants to the LDC gained weight earlier, compared with those randomized to CBL, and had a significant reduction in length of hospital stay. These results highlight those premature infants subjected to a LDC exhibit improvements in physiological development, favoring earlier weight gain and consequently a decrease in hospital stays. ClinicalTrials.gov; 02/09/2020 ID: NCT05230706.

Development of the circadian system and relevance of periodic signals for neonatal development.

Circadian rhythms are generated endogenously with a period of approximately 24h. Studies carried out during the last decade indicate that the circadian system develops before birth, and that the suprachiasmatic nucleus, a structure that is considered the mammalian circadian clock, is present in primates from the middle of pregnancy. Recent evidence shows that the infants' circadian system is sensitive to light from very early stages of development; it has also been proposed that low-intensity lighting can regulate the developing clock. After birth there is a progressive maturation of the outputs of the circadian system with marked rhythms in sleep-wake phenomena and hormone secretion. These facts express the importance of circadian photic regulation in infants. Thus, the exposure of premature babies to light/dark cycles results in a rapid establishment of activity/rest patterns, which are in the light-dark cycle. With the continuous study of the development of the circadian system and the influence on human physiology and disease, it is anticipated that the application of circadian biology will become an increasingly important component in the perinatal care.

The pterional approach for the surgical resection of an orbital cholesteatoma: a case report.

BACKGROUND: Cholesteatomas are benign tumors mainly composed of cholesterol crystals that rarely arise within the orbit. However, orbital cholesteatomas require a complete surgical resection due to their recidivating potential. Transcranial approaches offering a broad surgical exposure of the orbital cavity have been scarcely used for the management of these tumors. Here, we provide evidence of the benefits of the pterional craniotomy for the surgical resection of orbital tumors by sharing our experience in the surgical management of a cholesteatoma of the superotemporal orbital wall. CASE PRESENTATION: A 45-year-old Hispanic man with a 2-year history of progressive proptosis of the left eye attended to our center complaining of diplopia and migraine. At his arrival, physical examination revealed ptosis, palpebral edema, and exophthalmos of the left eye, as well as the abolishment of the ipsilateral photomotor and consensual responses. Fundoscopy showed mild optic atrophy, whereas a T2-weighted magnetic resonance imaging (MRI) of the head showed a hyperintense mass arising at the superotemporal wall of the orbit that was displacing the eyeball. The tumor was resected using a pterional craniotomy without postoperative complications. The histopathological analysis of the tumor revealed a cholesteatoma. The patient recovered the functionality of the left eye with no visual sensitive deficits nor tumor recurrence 1 year after the surgery. CONCLUSIONS: Our results support the use of the pterional craniotomy as a safe procedure for the surgical resection of cholesteatomas arising at the superotemporal walls of the orbit, with low postoperative morbidity.

Altered Fos immunoreactivity in the hypothalamus after glucose administration in pre- and post-weaning malnourished rats.

The present study explored the effects of malnutrition and nutritional rehabilitation on the response to glucose in hypothalamic nuclei involved in metabolic homeostasis. Male Wistar rats were malnourished during gestation-lactation (MGL) or at weaning to 55 days (MPW). Two groups of rats were rehabilitated with a balanced diet until 90 days (MGL-R and MPW-R, respectively). After a glucose tolerance test (GTT), brains were processed for Fos immunoreactivity (Fos-IR). Both malnourished groups displayed hyperglycemia after GTT. MGL exhibited an increased number of Fos-IR neurons in the ventromedial hypothalamic nucleus (VMH), while MPW showed increased Fos-IR in the arcuate nucleus (ARC) and VMH and a decrease in the paraventricular nucleus (PVN), as compared with their controls. Nutritional rehabilitation normalized values of glucose after GTT in both groups, while low number of Fos-IR neurons remained in the ARC, PVN and VMH of MPW-R rats, indicating a deleterious, long-lasting effect after post-weaning malnutrition.

A Complete and State of the Art Pre-mortem Diagnostic Approach to Creutzfeldt-Jakob Disease: A Case Report.

Sporadic Creutzfeldt-Jakob disease (sCJD) is a fatal and rapidly progressive form of dementia caused by the spread of a prion protein within the brain. Its real incidence is unknown since its definitive diagnosis requires histopathological analysis of brain specimens. However, novel tests that detect prion proteins in cerebrospinal fluid samples, such as the real-time quaking-induced conversion (RT-QuIC) technique, now allow the pre-mortem diagnosis of sCJD. Here, we report the first case of sCJD confirmed by RT-QuIC in Latin America, providing evidence of its diagnostic performance and clinical correlation.

Chocolate for breakfast prevents circadian desynchrony in experimental models of jet-lag and shift-work.

Night-workers, transcontinental travelers and individuals that regularly shift their sleep timing, suffer from circadian desynchrony and are at risk to develop metabolic disease, cancer, and mood disorders, among others. Experimental and clinical studies provide evidence that food intake restricted to the normal activity phase is a potent synchronizer for the circadian system and can prevent the detrimental metabolic effects associated with circadian disruption. As an alternative, we hypothesized that a timed piece of chocolate scheduled to the onset of the activity phase may be sufficient stimulus to synchronize circadian rhythms under conditions of shift-work or jet-lag. In Wistar rats, a daily piece of chocolate coupled to the onset of the active phase (breakfast) accelerated re-entrainment in a jet-lag model by setting the activity of the suprachiasmatic nucleus (SCN) to the new cycle. Furthermore, in a rat model of shift-work, a piece of chocolate for breakfast prevented circadian desynchrony, by increasing the amplitude of the day-night c-Fos activation in the SCN. Contrasting, chocolate for dinner prevented re-entrainment in the jet-lag condition and favored circadian desynchrony in the shift-work models. Moreover, chocolate for breakfast resulted in low body weight gain while chocolate for dinner boosted up body weight. Present data evidence the relevance of the timing of a highly caloric and palatable meal for circadian synchrony and metabolic function.

Peripheral oscillators: the driving force for food-anticipatory activity.

Food-anticipatory activity (FAA) and especially the food-entrained oscillator (FEO) have driven many scientists to seek their mechanisms and locations. Starting our research on FAA we, possibly like many other scientists, were convinced that clock genes held the key to the location and the underlying mechanisms for FAA. In this review, which is aimed especially at discussing the contribution of the peripheral oscillators, we have put together the accumulating evidence that the clock gene machinery as we know it today is not sufficient to explain food entrainment. We discuss the contribution of three types of oscillating processes: (i) within the suprachiasmatic nucleus (SCN), neurons capable of maintaining a 24-h oscillation in electrical activity driven by a set of clock genes; (ii) oscillations in metabolic genes and clock genes in other parts of the brain and in peripheral organs driven by the SCN or by food, which damp out after a few cycles; (iii) an FEO which, we propose, is a system built up of different oscillatory processes and consisting of an as-yet-unidentified network of central and peripheral structures. In view of the evidence that clock genes and metabolic oscillations are not essential for the persistence of FAA we propose that food entrainment is initiated by a repeated metabolic state of scarcity that drives an oscillating network of brain nuclei in interaction with peripheral oscillators. This complex may constitute the proposed FEO and is distributed in our peripheral organs as well as within the central nervous system.

Trastornos circadianos del sueño / Circadian Sleep Disorders

Resumen El sistema circadiano está sincronizado al ciclo luz-oscuridad que es generado por la rotación de la tierra, asegurando que la vigilia sea durante el día y que el sueño ocurra durante la noche. Sin embargo, el ritmo de sueño-vigilia puede estar desincronizado del ciclo luz-oscuridad o desincronizado de manera endógena, dando como resultado: insomnio, fatiga y bajo rendimiento en las actividades cotidianas. Mientras que los trastornos del sueño están clasificados por la Asociación Americana de Trastornos del Sueño como: disomnias intrínsecas, disomnias extrínsecas, parasomnias o trastornos del sueño médicos/psiquiátricos. Los trastornos circadianos del sueño se han categorizado por separado, en parte para reconocer que en la mayoría de los casos la etiología de los trastornos circadianos es una mezcla de factores internos y ambientales, o por un desajuste temporal entre ambos. Los síntomas generalmente son insomnio o hipersomnia, síntomas comunes en pacientes con trastornos circadianos del sueño, aunque hay otras causas a las que pueden atribuirse y que deben excluirse antes de realizar el diagnóstico de un trastorno circadiano del sueño. En el paciente sin otra patología del sueño, un registro diario de actividades, comidas, ejercicio, siestas y la hora de acostarse es una herramienta esencial para evaluar los trastornos circadianos del sueño. Estos registros deben mantenerse durante 2 semanas o más, ya que una perturbación debida a cambios de trabajo o viajes a través de zonas horarias puede tener efectos sobre el sueño y el estado de alerta durante el día, semanas después del evento.

Abstract The circadian system is synchronized to the light-dark cycle generated by the rotation of the earth, ensuring that wakefulness is during the day and sleep occurs at night. However, the sleep-wake rhythm may be out of sync with the light-dark cycle or endogenously out of sync, resulting in insomnia, fatigue, and poor performance in activities of daily living. Sleep disorders are classified by the American Sleep Disorders Association, as intrinsic dyssomnias, extrinsic dyssomnias, parasomnias, or medical/psychiatric sleep disorders. Circadian sleep disorders have been categorized separately to recognize that in most cases the etiology of circadian disturbances is a mix of internal and environmental factors or a temporary mismatch between the two. Symptoms are usually insomnia or hypersomnia, common symptoms in patients with circadian sleep disorders although other causes can be attributed and must be excluded before a diagnosis of a circadian sleep disorder is made. In the patient without other sleep pathology, a daily record of activities, meals, exercise, naps, and bedtime is an essential tool in assessing circadian sleep disorders. These records should be kept for 2 weeks or more, as a disturbance due to job changes or travel across time zones can have effects on sleep and daytime alertness weeks after the event.

Social jet-lag potentiates obesity and metabolic syndrome when combined with cafeteria diet in rats.

BACKGROUND/OBJECTIVES: Modern lifestyle promotes shifted sleep onset and shifted wake up time between weekdays and weekends, producing a condition termed "social-jet lag." Disrupted sleep promotes increased appetite for carbohydrate and fat-rich food, which in long term leads to overweight, obesity and metabolic syndrome. In order to mimic the human situation we produced an experimental model of social-jet lag (Sj-l). With this model, we explored the link between shifted sleep time with consumption of a cafeteria diet (CafD) and the development of obesity and metabolic syndrome. SUBJECTS/METHODS: The first experiment was designed to create and confirm the model of Sj-l. Rats (n=8-10/group) were exposed to a shifted sleep time protocol achieved by placing the rats in slow rotating wheels from Monday to Friday during the first 4h of the light period, while on weekends they were left undisturbed. The second experiment (n=8-12/group) explored the combined effect of Sj-l with the opportunity to ingest CafD. All protocols lasted 12weeks. We evaluated the development of overweight and indicators of metabolic syndrome. The statistical significance for all variables was set at P<0.05. RESULTS: Sj-l alone did not affect body weight gain but induced significant changes in cholesterol in metabolic variables representing a risk factor for metabolic syndrome. Daily restricted access to CafD in the day or night induced glucose intolerance and only CafD during the day led to overweight. Sj-l combined with CafD induced overconsumption of the diet, potentiated body weight gain (16%) and promoted 5 of the criteria for metabolic syndrome including high insulin and dislipidemia. CONCLUSION: Present data provide an experimental model of social-jet lag that combined with overconsumption of CafD, and maximized the development of obesity and metabolic syndrome. Importantly, access to CafD during the night did not lead to overweight nor metabolic syndrome.

Loss of melatonin daily rhythmicity is asociated with delirium development in hospitalized older adults.

Delirium is associated with circadian rhythm disruption. In this study we have explored whether circadian variation of melatonin is an indicator for delirium. Melatonin levels were determined from the first day of hospitalization and up to three days after the onset of delirium. Patients who did not developed delirium exhibited a daily melatonin rhythm, while in patients that developed delirium, the melatonin rhythm was lost and mean melatonin levels were found decreased as early as three days before the diagnosis of delirium, indicating that on arrival to the hospital circadian melatonin disruption can be used as an indicator of delirium.

Differential role of the accumbens Shell and Core subterritories in food-entrained rhythms of rats.

Restricted feeding schedules (RFS) entrain behavioral and physiological rhythms even in suprachiasmatic nucleus ablated animals, suggesting the existence of a food-entrained oscillator. The nucleus accumbens is an important structure for the expression of motivational behaviors and because its anatomical subterritories, Shell (Acc-Sh) and Core (Acc-Co) establish connections with different functional systems, they may participate in a differential way in food-entrainment. A first experiment, explored the role of Acc-Sh and Acc-Co in food-entrainment using the immunohistochemical detection of the protein c-Fos as a transcriptional activation marker. Experiment 2 tested the differential effect of Acc-Sh and Acc-Co, NMDA excitotoxic lesions. Lesioned rats were entrained to RFS and locomotor activity and free fatty acids (FFA) concentrations were evaluated. Results data show that in the Acc-Sh there is an increase of c-Fos immunoreactivity in food-entrained rats principally during feeding, whereas c-Fos expression in the Acc-Co region was increased during feeding and also anticipating mealtime. FFA were entrained in both lesioned groups, but the basal level was lower in Core-lesion rats. All rats exhibited food anticipatory activity (FAA). However, FAA was increased in Shell-lesioned animals and was almost abolished in the Core-lesion rats. These data indicate that the accumbens nucleus is involved with behavioral and metabolic food-entrainment, and that there is a differential role between both subregions.

Enfermedad pulmonar obstructiva crónica (EPOC). Bases para el médico general / Chronic Obstructive Pulmonary Disease (COPD). Bases for the General Practitioner

Resumen La enfermedad pulmonar obstructiva crónica (EPOC) es una enfermedad crónico-degenerativa frecuente, prevenible y tratable, caracterizada por persistentes síntomas respiratorios y limitación del flujo aéreo. En 2016, el Instituto Nacional de Enfermedades Respiratorias (INER) la ubicó en el cuarto lugar en la tabla de morbi-mortalidad anual en México. Su prevalencia está directamente relacionada con la del tabaquismo; sin embargo, su desarrollo es multifactorial. Para el estudio de la EPOC es importante conocer los antecedentes de exposición a factores de riesgo y la presencia de los principales síntomas; es esencial una historia clínica bien detallada, donde se recabe la mayor cantidad de datos de todo nuevo paciente en el que se conozca o se sospeche de la enfermedad, así como una espirometría para establecer el diagnóstico. Debido a la gran variabilidad que existe entre los pacientes con EPOC, es necesario establecer tratamiento farmacológico individualizado. Los fármacos utilizados en su tratamiento reducen los síntomas, la frecuencia y la gravedad de las exacerbaciones; sin embargo, no hay ningún medicamento que modifique el deterioro a largo plazo de la función pulmonar. Por lo tanto, el conocimiento básico de este padecimiento por el médico de primer contacto es esencial para la sospecha en una etapa inicial, y así ofrecer al paciente una intervención médica inmediata. El presente trabajo tiene la finalidad de acercar al médico general una visión básica de la EPOC.

Abstract Chronic obstructive pulmonary disease (COPD) is a chronic degenerative disease. It is a frequent, preventable and treatable disease characterized by persistent respiratory symptoms and airflow limitation. The National Institute of Respiratory Diseases (INER), ranked COPD in 2016 in fourth place in the table of annual morbidity and mortality in Mexico. The prevalence of COPD is directly related to smoking; however, its development is multifactorial. For its study it is important to know of any prior exposure to risk factors and of any manifestation of the main symptoms. To make a diagnosis, a detailed clinical history, where the largest amount of data is collected from every new possible COPD patient, and a spirometry are essential. Individual pharmacological treatment is necessary due to the great variability among COPD patients. The drugs used in the treatment of COPD reduce the symptoms, the frequency and severity of exacerbations; however, there is no medication that modifies the long-term deterioration of the lung function. Therefore, a basic knowledge of this condition by the medical doctor first contacted, is essential for the suspicion of COPD in its initial stage and thus, offer the patient immediate medical intervention. The objective of the present work is to provide a basic overview of COPD to the general practitioner.

A light/dark cycle in the NICU accelerates body weight gain and shortens time to discharge in preterm infants.

BACKGROUND: Bright constant light levels in the NICU may have negative effects on the growth and development of preterm infants OBJECTIVE: The aim of this study is to evaluate the benefits of an alternating light/dark cycle in the NICU on weight gain and early discharge from the therapy in premature infants. PATIENTS AND METHODS: A randomized interventional study was designed comparing infants in the NICU of Hospital Juarez de México, exposed from birth either to an LD environment (LD, n=19) or to the traditional continuous light (LL, n=19). The LD condition was achieved by placing individual removable helmets over the infant's heads. Body weight gain was analyzed, as the main indicator of stability and the main criteria for discharge in preterm infants born at 31.73±0.31week gestational age. RESULTS: Infants maintained in an LD cycle gained weight faster than infants in LL and therefore attained a shorter hospital stay, (34.37±3.12 vs 51.11±5.29days; P>0.01). Also, LD infants exhibited improved oxygen saturation and developed a daily melatonin rhythm. CONCLUSIONS: These findings provide a convenient alternative for establishing an LD environment for preterm healthy newborns in the NICU and confirm the beneficial effects of an alternating LD cycle for growth and weight gain and for earlier discharge time. Here we provide an easy and practical alternative to implement light/dark conditions in the NICU.

Disruption of circadian rhythms due to chronic constant light leads to depressive and anxiety-like behaviors in the rat.

Depression is strongly associated with the circadian system, disruption of the circadian system leads to increased propensity to disease and to mood disorders including depression. The present study explored in rats the effects of circadian disruption by constant light on behavioral and hormonal indicators of a depressive-like condition and on the biological clock, the suprachiasmatic nucleus (SCN). Exposure to constant light for 8 weeks resulted in loss of circadian patterns of spontaneous general activity, melatonin and corticosterone. Moreover these rats exhibited anhedonia in a sucrose consumption test, and increased grooming in the open-field test, which reflects an anxiety-like condition. In the SCN decreased cellular activation was observed by c-Fos immunohistochemistry. In rats exposed to constant darkness, circadian behavioral and hormonal patterns remained conserved, however mild depressive-like indicators were observed in the anhedonia test and mild anxiety-like behaviors were observed in the open field test. Data indicate that chronic conditions of LL or DD are both disruptive for the activity of the SCN leading to depression- and anxiety-like behavior. Present results point out the main role played by the biological clock and the risk of altered photoperiods on affective behavior.

Síndrome de jet lag o cambio de zonas de tiempo / The jet lag syndrome or time-zone changes

Resumen Nuestro planeta, así como la vida que en él se desarrolla, se encuentra en constante movimiento. Los ritmos geofísicos influyen en la actividad de los organismos, de tal manera que los seres vivos han desarrollado mecanismos adaptativos para poder responder a las variaciones diarias del medio ambiente. El sistema circadiano es el responsable de responder a estas variaciones cíclicas ambientales. Cuando se modifican las señales ambientales, como en un viaje que implica atravesar varias zonas horarias, se ocasionan cambios fisiológicos que han llevado a buscar estrategias para contrarrestar los síntomas que se presentan; estas estrategias incluyen el ejercicio programado, la exposición a la luz brillante, la melatonina y la alimentación programada.

Abstract Our planet and the life that develops in it are in constant movement, therefore, the geophysical rhythms influence the activity of organisms, in such a way that living beings have developed adaptative mechanims in order to respond to the daily variations of the environment. The circadian system is responsible for responding to these cyclical environmental variations. When the environmental signals are modified, like for instance, on a trip that involves crossing several time zones, physiological changes occur. This results in searching for possible strategies to counteract the symptomatology. These strategies include scheduled exercise, exposure to a bright light, melatonin and scheduled meals.

La comida por la noche como factor inductor de obesidad / Food during the night is a factor leading to obesity

Resumen: Esta revisión tiene como objetivo presentar evidencias obtenidas mediante observaciones clínicas y modelos animales que señalan la relevancia que tiene el horario de alimentación sobre el metabolismo y el mantenimiento del peso corporal. Hallazgos recientes han puesto en evidencia que la misma cantidad de alimento ingerida durante el día o la noche afecta diferencialmente el metabolismo, lo que determina una diferencia significativa en el desarrollo del sobrepeso y la obesidad. Este conocimiento se fundamenta en el estudio del sistema circadiano, regido por el reloj biológico del hipotálamo anterior, que le transmite tiempos a todas las funciones del cuerpo, incluyendo aquellas para el gasto y el ahorro de energía. A pesar de que estos ciclos circadianos están normalmente regulados por los cambios de iluminación resultantes de la alternancia del día y la noche, los cambios metabólicos que resultan de una comida han mostrado también ser señales de tiempo que modifican el orden temporal de algunos sistemas y grupos celulares. De ello se desprende que para que el sistema circadiano funcione sincronizado, las horas de alimentación deben coincidir con los ciclos dictados por el reloj biológico. De tal manera, comer durante las horas normalmente asignadas al reposo lleva a la pérdida de coordinación de los ritmos circadianos metabólicos con respecto al reloj biológico. Esta desincronización sucede a diferentes niveles, tanto entre las células de los tejidos como en una misma célula a nivel molecular. En esta revisión se enfatizarán los efectos adversos de las comidas por la noche sobre el metabolismo energético, además se presentarán resultados recientes que describen los cambios circadianos y metabólicos a diversos niveles de regulación.

Abstract: The present review aims to present evidence obtained in clinical surveys and experimental studies that point out the relevance of meal schedules on metabolism and body weight. Recent findings indicate that in spite of ingesting equivalent amounts, food ingestion during the day or during the night can have completely different effects on metabolism determining bodyweight gain and propensity to obesity. Such findings find support in studies of the circadian rhythms, driven by a biological clock located in the anterior hypothalamus, which transmits temporal signals to the body including functions for energy balance. Circadian cycles are normally driven by the alternation of the day- night luminosity cycles, however metabolic changes resulting from food have proven to be powerful temporal signals capable of modifying de temporal order in tissues and cells. Considering the power of food elicited signals, the feeding schedule must coincide with the timing signals driven by the biological clock. Thus eating during the hours normally assigned for sleep and rest leads to a loss of coordination between metabolic rhythms and the biological clock. This circadian disruption occurs at different levels, among cells in a specific tissue as well as in the molecular processes in cells. The aim of this review is to emphasize the adverse effects that meals during the night can exhert on metabolism, we provide evidence about circadian and metabolic alterations at different regulatory levels.

Scheduled meals and scheduled palatable snacks synchronize circadian rhythms: consequences for ingestive behavior.

Food is a potent time signal for the circadian system and has shown to entrain and override temporal signals transmitted by the biological clock, the suprachiasmatic nucleus, which adjusts mainly to the daily light/dark (LD) alternation. Organisms mostly ingest food in their active period and this permits a correct coordination between the LD and the food elicited time signals with the circadian system. Under conditions when feeding opportunities are shifted to the usual resting/sleep phase, the potent entraining force of food, shifts circadian fluctuations in several tissues, organs, and brain structures toward meal time, resulting a desynchrony within the body and between the organism and the external LD cycle. The daily scheduled access to a palatable snack exerts similar changes specifically to brain areas involved in motivation and reward responses. This review describes the phenomenology of food entrainment and entrainment by a palatable snack. It suggests how scheduled feeding can lead to food addiction and how shifted feeding schedules toward the sleep phase can result in altered ingestive behavior, obesity and disturbed metabolic responses.