In the liver, clock genes are proposed to drive metabolic rhythms. These gene rhythms are driven by the suprachiasmatic nucleus (SCN) mainly by food intake and via autonomic and hormonal pathways. Forced activity during the normal rest phase, induces also food intake, thus neglecting the signals of the SCN, leading to conflicting time signals to target tissues of the SCN. The present study explored in a rodent model of night-work the influence of food during the normal sleep period on the synchrony of gene expression between clock genes and metabolic genes in the liver. Male Wistar rats were exposed to forced activity for 8 h either during the rest phase (day) or during the active phase (night) by using a slow rotating wheel. In this shift work model food intake shifts spontaneously to the forced activity period, therefore the influence of food alone without induced activity was tested in other groups of animals that were fed ad libitum, or fed during their rest or active phase. Rats forced to be active and/or eating during their rest phase, inverted their daily peak of Per1, Bmal1 and Clock and lost the rhythm of Per2 in the liver, moreover NAMPT and metabolic genes such as Pparα lost their rhythm and thus their synchrony with clock genes. We conclude that shift work or food intake in the rest phase leads to desynchronization within the liver, characterized by misaligned temporal patterns of clock genes and metabolic genes. This may be the cause of the development of the metabolic syndrome and obesity in individuals engaged in shift work.

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. P hysiology and behavior of all mammals is organized in an alternating pattern of rest and activity cycles, whereby the endogenous and light-induced daily neuronal activity of the suprachiasmatic nucleus (SCN) signals rest in nocturnal rodents and activity in diurnal primates, such as humans (1, 2). Restricting food access to a short and predictable episode during the rest phase changes this behavioral pattern, such that an animal becomes active and for up to several hours anticipates the upcoming feeding event. This food anticipatory activity (FAA) is even exhibited without the known circadian oscillator, the SCN (3), and thus may rely on a different circadian pacemaker.In search of the location of this so-called "food entrained oscillator" (FEO), two recent studies have claimed that its position is within the dorsomedial nucleus of the hypothalamus (DMH) (4, 5). The designation of the DMH as master clock for food entrainment is, however, controversial because some groups reported unimpaired FAA despite large lesions of the DMH (6, 7); others have shown that lesions of the DMH disturb and diminish the intensity of FAA (6). The possible participation of other brain structures in FAA is evident from studies that demonstrate modulation of neuronal activity and induction of clock-gene rhythmicity in hypothalamic and limbic structures by feeding schedules (8-11). Thus, it has been suggested that FAA depends on a multioscillatory system comprised of a complex and redundant neuronal netwo...

The hexane, acetone and methanol extracts of Calophyllum brasiliense leaves were fractionated following a three bioassay guide: high HIV-1 RT inhibition, low cytotoxicity on MT2 cells and high inhibition of HIV-1 IIIb/LAV replication. This led to the isolation of three anti HIV-1 dipyranocoumarins: calanolides A and B and soulattrolide. In contrast, other isolated compounds such as apetalic acid, isoapetalic acid, a structural isomer of isoapetalic acid, friedelin, canophyllol and amentoflavone were devoid of HIV-1 RT inhibitory activity. Calanolide C was also obtained as a natural product and showed moderate inhibitory properties.

No abstract

The suprachiasmatic nucleus (SCN) drives circadian rhythms in behavioral and physiological variables, including the inflammatory response. Shift work is known to disturb circadian rhythms and is associated with increased susceptibility to develop disease. In rodents, circadian disruption due to shifted light schedules (jet lag) induced increased innate immune responses. To gain more insight into the influence of circadian disruption on the immune response, we characterized the inflammatory response in a model of rodent shift work and demonstrated that circadian disruption affected the inflammatory response to lipopolysaccharide (LPS) both in vivo and in vitro. Since food consumption is a main disturbing element in the shift work schedule, we also evaluated the inflammatory response to LPS in a group of rats that had no access to food during their working hours. Our results demonstrated that the shift work schedule decreased basal TNF-α levels in the liver but not in the circulation. Despite this, we observed that shift work induced increased cytokine response after LPS stimulation in comparison to control rats. Also, Kupffer cells (liver macrophages) isolated from shift work rats produced more TNF-α in response to in vitro LPS stimulation, suggesting important effects of circadian desynchronization on the functionality of this cell type. Importantly, the effects of shift work on the inflammatory response to LPS were prevented when food was not available during the working schedule. Together, these results show that dissociating behavior and food intake from the synchronizing drive of the SCN severely disturbs the immune response.

BackgroundLight at night creates a conflicting signal to the biological clock and disrupts circadian physiology. In rodents, light at night increases the risk to develop mood disorders, overweight, disrupted energy metabolism, immune dysfunction and cancer. We hypothesized that constant light (LL) in rats may facilitate tumor growth via disrupted metabolism and increased inflammatory response in the host, inducing a propitious microenvironment for tumor cells.MethodsMale Wistar rats were exposed to LL or a regular light-dark cycle (LD) for 5 weeks. Body weight gain, food consumption, triglycerides and glucose blood levels were evaluated; a glucose tolerance test was also performed. Inflammation and sickness behavior were evaluated after the administration of intravenous lipopolysaccharide. Tumors were induced by subcutaneous inoculation of glioma cells (C6). In tumor-bearing rats, the metabolic state and immune cells infiltration to the tumor was investigated by using immunohistochemistry and flow cytometry. The mRNA expression of genes involved metabolic, growth, angiogenes and inflammatory pathways was measured in the tumor microenvironment by qPCR. Tumor growth was also evaluated in animals fed with a high sugar diet.ResultsWe found that LL induced overweight, high plasma triglycerides and glucose levels as well as reduced glucose clearance. In response to an LPS challenge, LL rats responded with higher pro-inflammatory cytokines and exacerbated sickness behavior. Tumor cell inoculation resulted in increased tumor volume in LL as compared with LD rats, associated with high blood glucose levels and decreased triglycerides levels in the host. More macrophages were recruited in the LL tumor and the microenvironment was characterized by upregulation of genes involved in lipogenesis (Acaca, Fasn, and Pparγ), glucose uptake (Glut-1), and tumor growth (Vegfα, Myc, Ir) suggesting that LL tumors rely on these processes in order to support their enhanced growth. Genes related with the inflammatory state in the tumor microenvironment were not different between LL and LD conditions. In rats fed a high caloric diet tumor growth was similar to LL conditions.ConclusionsData indicates that circadian disruption by LL provides a favorable condition for tumor growth by promoting an anabolic metabolism in the host.Electronic supplementary materialThe online version of this article (10.1186/s12885-017-3636-3) contains supplementary material, which is available to authorized users.

Variations in circulating corticosterone (Cort) are driven by the paraventricular nucleus of the hypothalamus (PVN), mainly via the sympathetic autonomic nervous system (ANS) directly stimulating Cort release from the adrenal gland and via corticotropin-releasing hormone targeting the adenohypophysis to release adrenocorticotropic hormone (ACTH). Cort feeds back through glucocorticoid receptors (GRs). Here we show in male Wistar rats that PVN neurons projecting to the adrenal gland do not express GRs, leaving the question of how the ANS in the PVN gets information about circulating Cort levels to control the adrenal. Since the arcuate nucleus (ARC) shows a less restrictive blood–brain barrier, expresses GRs, and projects to the PVN, we investigated whether the ARC can detect and produce fast adjustments of circulating Cort. In low Cort conditions (morning), local microdialysis in the ARC with type I GR antagonist produced a fast and sustained increase of Cort. This was not observed with a type II antagonist. At the circadian peak levels of Cort (afternoon), a type II GR antagonist, but not a type I antagonist, increased Cort levels but not ACTH levels. Antagonist infusions in the PVN did not modify circulating Cort levels, demonstrating the specificity of the ARC to give Cort negative feedback. Furthermore, type I and II GR agonists in the ARC prevented the increase of Cort after stress, demonstrating the role of the ARC as sensor to modulate Cort release. Our findings show that the ARC may be essential to sense blood levels of Cort and adapt Cort secretion depending on such conditions as stress or time of day.

Circadian disruption is associated with metabolic disturbances such as hepatic steatosis (HS), obesity and type 2 diabetes. We hypothesized that HS, resulting from constant light (LL) exposure is due to an inconsistency between signals related to food intake and endocrine-driven suprachiasmatic nucleus (SCN) outputs. Indeed, exposing rats to LL induced locomotor, food intake and hormone arrhythmicity together with the development of HS. We investigated whether providing temporal signals such as 12-h food availability or driving a corticosterone plus melatonin rhythm could restore rhythmicity and prevent the metabolic disturbances under LL conditions in male rats. Discrete metabolic improvements under these separate treatments stimulated us to investigate whether the combination of hormone treatment together with mealtime restriction (12-h food during four weeks) could prevent the metabolic alterations. LL exposed arrhythmic rats, received daily administration of corticosterone (2.5 µg/kg) and melatonin (2.5 mg/kg) in synchrony or out of synchrony with their 12-h meal. HS and other metabolic alterations were importantly ameliorated in LL-exposed rats receiving hormonal treatment in synchrony with 12-h restricted mealtime, while treatment out of phase with meal time did not. Interestingly, liver bile acids, a major indication for HS, were only normalized when animals received hormones in synchrony with food indicating that disrupted bile acid metabolism might be an important mechanism for the HS induction under LL conditions. We conclude that food-elicited signals, as well as hormonal signals, are necessary for liver synchronization and that HS arises when there is conflict between food intake and the normal pattern of melatonin and corticosterone.