昼夜节律钟调控代谢的研究进展

生理和行为的昼夜节律性调控对健康生活是必需的。越来越多的流行病学和遗传学证据显示昼夜节律的破坏与代谢紊乱性疾病相关联。在分子水平上,昼夜节律受到时钟蛋白组成的转录一翻译负反馈环的调控。时钟蛋白通过以下两种途径调节代谢：首先,时钟蛋白作为转录因子直接调节一些代谢关键步骤的限速酶和代谢相关核受体的表达,其次作为代谢相关核受体的辅调节因子来激活或抑制其转录活性。虽然时钟蛋白对代谢途径的调节导致代谢物水平呈昼夜节律振荡,但是产生的代谢物反过来又可以影响昼夜节律钟基因的表达,进而影响昼夜节律钟。深入研究昼夜节律钟与代谢的交互调节可能为治疗某些代谢紊乱性疾病提供新的治疗方案。     

Microbiota dysbiosis and barrier dysfunction in inflammatory bowel disease and colorectal cancers: exploring a common ground hypothesis

Inflammatory bowel disease (IBD) is a multifactorial disease which arises as a result of the interaction of genetic, environmental, barrier and microbial factors leading to chronic inflammation in the intestine. Patients with IBD had a higher risk of developing colorectal carcinoma (CRC), of which the subset was classified as colitis-associated cancers. Genetic polymorphism of innate immune receptors had long been considered a major risk factor for IBD, and the mutations were also recently observed in CRC. Altered microbial composition (termed microbiota dybiosis) and dysfunctional gut barrier manifested by epithelial hyperpermeability and high amount of mucosa-associated bacteria were observed in IBD and CRC patients. The findings suggested that aberrant immune responses to penetrating commensal microbes may play key roles in fueling disease progression. Accumulative evidence demonstrated that mucosa-associated bacteria harbored colitogenic and protumoral properties in experimental models, supporting an active role of bacteria as pathobionts (commensal-derived opportunistic pathogens). Nevertheless, the host factors involved in bacterial dysbiosis and conversion mechanisms from lumen-dwelling commensals to mucosal pathobionts remain unclear. Based on the observation of gut leakiness in patients and the evidence of epithelial hyperpermeability prior to the onset of mucosal histopathology in colitic animals, it was postulated that the epithelial barrier dysfunction associated with mucosal enrichment of specific bacterial strains may predispose the shift to disease-associated microbiota. The speculation of leaky gut as an initiating factor for microbiota dysbiosis that eventually led to pathological consequences was proposed as the “common ground hypothesis”, which will be highlighted in this review. Overall, the understanding of the core interplay between gut microbiota and epithelial barriers at early subclinical phases will shed light to novel therapeutic strategies to manage chronic inflammatory disorders and colitis-associated cancers.     

The Role of Circadian Clocks in Metabolic Disease

The circadian clock is a highly conserved timing system, resonating physiological processes to 24-hour environmental cycles. Circadian misalignment is emerging as a risk factor of metabolic disease. The molecular clock resides in all metabolic tissues, the dysfunction of which is associated with perturbed energy metabolism. In this article, we will review current knowledge about molecular mechanisms of the circadian clock and the role of clocks in the physiology and pathophysiology of metabolic tissues.     

生物钟在卵巢生理和病理中的作用

哺乳动物的昼夜节律是基因编码的分子钟在体内产生的一种以大约24 h为周期的生理现象,使机体的生理过程与外界环境的变化相协调,是对环境适应的一种表现.在哺乳动物中,繁殖生理功能受生物钟系统的调节.在下丘脑-垂体-卵巢(hypothalamic-pituitary-ovarian,HPO)轴的各组织中均已观察到生物钟基因的...     

Are Circadian Rhythms the Code of Hypothalamic-Immune Communication? Insights from Natural Killer Cells

Circadian rhythms in physiology and behavior are ultimately regulated at the hypothalamic level by the suprachiasmatic nuclei (SCN). This central oscillator transduces photic information to the cellular clocks in the periphery through the autonomic nervous system and the neuroendocrine system. The fact that these two systems have been shown to modulate leukocyte physiology supports the concept that the circadian component is an important aspect of hypothalamic-immune communication. Circadian disruption has been linked to immune dysregulation, and recent reports suggest that several circadian clock genes, in addition to their time-keeping role, are involved in the immune response. In this overview, we summarize the findings demonstrating that Natural Killer (NK) cell function is under circadian control. Special issue article in honor of George Fink.     

Entrainment of breast (cancer) epithelial cells detects distinct circadian oscillation patterns for clock and hormone receptor genes

Most physiological and biological processes are regulated by endogenous circadian rhythms under the control of both a master clock, which acts systemically and individual cellular clocks, which act at the single cell level. The cellular clock is based on a network of core clock genes, which drive the circadian expression of non-clock genes involved in many cellular processes. Circadian deregulation of gene expression has emerged to be as important as deregulation of estrogen signaling in breast tumorigenesis. Whether there is a mutual deregulation of circadian and hormone signaling is the question that we address in this study. Here we show that, upon entrainment by serum shock, cultured human mammary epithelial cells maintain an inner circadian oscillator, with key clock genes oscillating in a circadian fashion. In the same cells, the expression of the estrogen receptor α (ERA) gene also oscillates in a circadian fashion. In contrast, ERA-positive and -negative breast cancer epithelial cells show disruption of the inner clock. Further, ERA-positive breast cancer cells do not display circadian oscillation of ERA expression. Our findings suggest that estrogen signaling could be affected not only in ERA-negative breast cancer, but also in ERA-positive breast cancer due to lack of circadian availability of ERA. Entrainment of the inner clock of breast epithelial cells, by taking into consideration the biological time component, provides a novel tool to test mechanistically whether defective circadian mechanisms can affect hormone signaling relevant to breast cancer.Key words: circadian rhythm, clock genes, estrogen receptor alpha (ERA), breast cancer cells, entrainment, serum shock     

Sex and dosing-time dependencies in irinotecan-induced circadian disruption

Circadian disruption accelerates malignant growth; thus, it should be avoided in anticancer therapy. The circadian disruptive effects of irinotecan, a topoisomerase I inhibitor, was investigated according to dosing time and sex. In previous work, irinotecan achieved best tolerability following dosing at zeitgeber time (ZT) 11 in male and ZT15 in female mice, whereas worst toxicity corresponded to treatment at ZT23 and ZT3 in male and female mice, respectively. Here, irinotecan (50 mg/kg intravenous [i.v.]) was delivered at the sex-specific optimal or worst circadian timing in male and female B6D2F1 mice. Circadian disruption was assessed with rest-activity, body temperature, plasma corticosterone, and liver mRNA expressions of clock genes Rev-erbα, Per2, and Bmal1. Baseline circadian rhythms in rest-activity, body temperature, and plasma corticosterone were more prominent in females as compared to males. Severe circadian disruption was documented for all physiology and molecular clock endpoints in female mice treated at the ZT of worst tolerability. Conversely, irinotecan administration at the ZT of best tolerability induced slight alteration of circadian physiology and clock-gene expression patterns in female mice. In male mice, irinotecan produced moderate alterations of circadian physiology and clock-gene expression patterns, irrespective of treatment ZT. However, the average expression of Rev-erbα, Per2, and Bmal1 were down-regulated 2- to 10-fold with irinotecan at the worst ZT, while being minimally or unaffected at the best ZT, irrespective of sex. Corticosterone secretion increased acutely within 2?h with a sex-specific response pattern, resulting in a ZT-dependent phase-advance or -delay in both sex. The mRNA expressions of irinotecan clock-controlled metabolism genes Ce2, Ugt1a1, and Top1 were unchanged or down-regulated according to irinotecan timing and sex. This study shows that the circadian timing system represents an important toxicity target of irinotecan in female mice, where circadian disruption persists after wrongly timed treatment. As a result, the mechanisms underling cancer chronotherapeutics are expectedly more susceptible to disruption in females as compared to males. Thus, the optimal circadian timing of chemotherapy requires precise determination according to sex, and should involve the noninvasive monitoring of circadian biomarkers.     

Foundations of circadian medicine

The circadian clock is an evolutionarily highly conserved endogenous timing program that structures physiology and behavior according to the time of day. Disruption of circadian rhythms is associated with many common pathologies. The emerging field of circadian medicine aims to exploit the mechanisms of circadian physiology and clock–disease interaction for clinical diagnosis, treatment, and prevention. In this Essay, we outline the principle approaches of circadian medicine, highlight the development of the field in selected areas, and point out open questions and challenges. Circadian medicine has unambiguous health benefits over standard care but is rarely utilized. It is time for clock biology to become an integrated part of translational research.

The emerging field of circadian medicine implements and translates findings from clock biology to improve health. Circadian medicine has clear health benefits over standard care but is rarely used owing to a lack of systematic and mechanistic evidence and overarching concepts. This Essay explains the principles of circadian medicine and highlights future approaches to promote its dissemination.     

Circadian modulation of acute alcohol sensitivity but not acute tolerance in Drosophila

An increased understanding of the factors affecting behavioral and neurological responses to alcohol and alcohol physiology is necessary given the tremendous toll alcohol abuse and alcoholism exert on individuals and society. At the behavioral and molecular levels, the response to alcohol appears remarkably conserved from Drosophila to humans, suggesting that investigations across model species can provide insight into the identification of common modulatory factors. We investigated the interaction between the circadian clock and alcohol sensitivity, alcohol tolerance, and alcohol absorbance in Drosophila melanogaster. Using a loss-of-righting reflex (LoRR) assay, we found that flies exhibit a circadian rhythm in the LoRR, with the greatest sensitivity to alcohol occurring from mid to late night, corresponding to the flies' inactive phase. As predicted, a circadian rhythm in the LoRR was absent in circadian mutant flies and under conditions in which the circadian clock was nonfunctional. Circadian modulation of the response to alcohol was not due to circadian regulation of alcohol absorbance. Similar to other animals, Drosophila develop acute and chronic tolerance to alcohol upon repeat exposures. We found that the circadian clock did not modulate the development of acute alcohol tolerance measured as the difference in sensitivity to alcohol between na?ve and pre-exposed flies. Thus, the circadian clock modulates some, but not all, of the behavioral responses to alcohol exposure, suggesting that specific mechanisms underlie the observed circadian modulation of LoRR rather than global cellular circadian regulation. This study provides valuable new insights in our understanding of the circadian modulation of alcohol-induced behaviors that ultimately could facilitate preventative measures in combating alcohol abuse and alcoholism.     

Relationships between the Circadian System and Alzheimer's Disease-Like Symptoms in Drosophila

Circadian clocks coordinate physiological, neurological, and behavioral functions into circa 24 hour rhythms, and the molecular mechanisms underlying circadian clock oscillations are conserved from Drosophila to humans. Clock oscillations and clock-controlled rhythms are known to dampen during aging; additionally, genetic or environmental clock disruption leads to accelerated aging and increased susceptibility to age-related pathologies. Neurodegenerative diseases, such as Alzheimer''s disease (AD), are associated with a decay of circadian rhythms, but it is not clear whether circadian disruption accelerates neuronal and motor decline associated with these diseases. To address this question, we utilized transgenic Drosophila expressing various Amyloid-β (Aβ) peptides, which are prone to form aggregates characteristic of AD pathology in humans. We compared development of AD-like symptoms in adult flies expressing Aβ peptides in the wild type background and in flies with clocks disrupted via a null mutation in the clock gene period (per⁰¹). No significant differences were observed in longevity, climbing ability and brain neurodegeneration levels between control and clock-deficient flies, suggesting that loss of clock function does not exacerbate pathogenicity caused by human-derived Aβ peptides in flies. However, AD-like pathologies affected the circadian system in aging flies. We report that rest/activity rhythms were impaired in an age-dependent manner. Flies expressing the highly pathogenic arctic Aβ peptide showed a dramatic degradation of these rhythms in tune with their reduced longevity and impaired climbing ability. At the same time, the central pacemaker remained intact in these flies providing evidence that expression of Aβ peptides causes rhythm degradation downstream from the central clock mechanism.     

Circadian Modulation of Acute Alcohol Sensitivity But Not Acute Tolerance in Drosophila

An increased understanding of the factors affecting behavioral and neurological responses to alcohol and alcohol physiology is necessary given the tremendous toll alcohol abuse and alcoholism exert on individuals and society. At the behavioral and molecular levels, the response to alcohol appears remarkably conserved from Drosophila to humans, suggesting that investigations across model species can provide insight into the identification of common modulatory factors. We investigated the interaction between the circadian clock and alcohol sensitivity, alcohol tolerance, and alcohol absorbance in Drosophila melanogaster. Using a loss-of-righting reflex (LoRR) assay, we found that flies exhibit a circadian rhythm in the LoRR, with the greatest sensitivity to alcohol occurring from mid to late night, corresponding to the flies' inactive phase. As predicted, a circadian rhythm in the LoRR was absent in circadian mutant flies and under conditions in which the circadian clock was nonfunctional. Circadian modulation of the response to alcohol was not due to circadian regulation of alcohol absorbance. Similar to other animals, Drosophila develop acute and chronic tolerance to alcohol upon repeat exposures. We found that the circadian clock did not modulate the development of acute alcohol tolerance measured as the difference in sensitivity to alcohol between naïve and pre-exposed flies. Thus, the circadian clock modulates some, but not all, of the behavioral responses to alcohol exposure, suggesting that specific mechanisms underlie the observed circadian modulation of LoRR rather than global cellular circadian regulation. This study provides valuable new insights in our understanding of the circadian modulation of alcohol-induced behaviors that ultimately could facilitate preventative measures in combating alcohol abuse and alcoholism. (Author correspondence: lyons@bio.fsu.edu)     

Chronobiological aspects of obesity and metabolic syndrome

Circadian rhythms (approximately 24h) are widely characterized at molecular level and their generation is acknowledged to originate from oscillations in expression of several clock genes and from regulation of their protein products. While general entrainment of organisms to environmental light-dark cycles is mainly achieved through the master clock of the suprachiasmatic nucleus in mammals, this molecular clockwork is functional in several organs and tissues. Some studies have suggested that disruption of the circadian system (chronodisruption (CD)) may be causal for manifestations of the metabolic syndrome. This review summarizes (1) how molecular clocks coordinate metabolism and their specific role in the adipocyte; (2) the genetic aspects of and scientific evidence for obesity as a chronobiological illness; and (3) CD and its causes and pathological consequences. Finally, ideas about use of chronobiology for the treatment of obesity are discussed.     

Robust circadian rhythms in organoid cultures from PERIOD2::LUCIFERASE mouse small intestine

Disruption of circadian rhythms is a risk factor for several human gastrointestinal (GI) diseases, ranging from diarrhea to ulcers to cancer. Four-dimensional tissue culture models that faithfully mimic the circadian clock of the GI epithelium would provide an invaluable tool to understand circadian regulation of GI health and disease. We hypothesized that rhythmicity of a key circadian component, PERIOD2 (PER2), would diminish along a continuum from ex vivo intestinal organoids (epithelial ‘miniguts’), nontransformed mouse small intestinal epithelial (MSIE) cells and transformed human colorectal adenocarcinoma (Caco-2) cells. Here, we show that bioluminescent jejunal explants from PERIOD2::LUCIFERASE (PER2::LUC) mice displayed robust circadian rhythms for >72 hours post-excision. Circadian rhythms in primary or passaged PER2::LUC jejunal organoids were similarly robust; they also synchronized upon serum shock and persisted beyond 2 weeks in culture. Remarkably, unshocked organoids autonomously synchronized rhythms within 12 hours of recording. The onset of this autonomous synchronization was slowed by >2 hours in the presence of the glucocorticoid receptor antagonist RU486 (20 μM). Doubling standard concentrations of the organoid growth factors EGF, Noggin and R-spondin enhanced PER2 oscillations, whereas subtraction of these factors individually at 24 hours following serum shock produced no detectable effects on PER2 oscillations. Growth factor pulses induced modest phase delays in unshocked, but not serum-shocked, organoids. Circadian oscillations of PER2::LUC bioluminescence aligned with Per2 mRNA expression upon analysis using quantitative PCR. Concordant findings of robust circadian rhythms in bioluminescent jejunal explants and organoids provide further evidence for a peripheral clock that is intrinsic to the intestinal epithelium. The rhythmic and organotypic features of organoids should offer unprecedented advantages as a resource for elucidating the role of circadian rhythms in GI stem cell dynamics, epithelial homeostasis and disease.KEY WORDS: Circadian rhythm, Intestinal organoid, PERIOD2, R-spondin, RU486     

Sex and Dosing-Time Dependencies in Irinotecan-Induced Circadian Disruption

Circadian disruption accelerates malignant growth; thus, it should be avoided in anticancer therapy. The circadian disruptive effects of irinotecan, a topoisomerase I inhibitor, was investigated according to dosing time and sex. In previous work, irinotecan achieved best tolerability following dosing at zeitgeber time (ZT) 11 in male and ZT15 in female mice, whereas worst toxicity corresponded to treatment at ZT23 and ZT3 in male and female mice, respectively. Here, irinotecan (50?mg/kg intravenous [i.v.]) was delivered at the sex-specific optimal or worst circadian timing in male and female B6D2F1 mice. Circadian disruption was assessed with rest-activity, body temperature, plasma corticosterone, and liver mRNA expressions of clock genes Rev-erbα, Per2, and Bmal1. Baseline circadian rhythms in rest-activity, body temperature, and plasma corticosterone were more prominent in females as compared to males. Severe circadian disruption was documented for all physiology and molecular clock endpoints in female mice treated at the ZT of worst tolerability. Conversely, irinotecan administration at the ZT of best tolerability induced slight alteration of circadian physiology and clock-gene expression patterns in female mice. In male mice, irinotecan produced moderate alterations of circadian physiology and clock-gene expression patterns, irrespective of treatment ZT. However, the average expression of Rev-erbα, Per2, and Bmal1 were down-regulated 2- to 10-fold with irinotecan at the worst ZT, while being minimally or unaffected at the best ZT, irrespective of sex. Corticosterone secretion increased acutely within 2?h with a sex-specific response pattern, resulting in a ZT-dependent phase-advance or -delay in both sex. The mRNA expressions of irinotecan clock-controlled metabolism genes Ce2, Ugt1a1, and Top1 were unchanged or down-regulated according to irinotecan timing and sex. This study shows that the circadian timing system represents an important toxicity target of irinotecan in female mice, where circadian disruption persists after wrongly timed treatment. As a result, the mechanisms underling cancer chronotherapeutics are expectedly more susceptible to disruption in females as compared to males. Thus, the optimal circadian timing of chemotherapy requires precise determination according to sex, and should involve the noninvasive monitoring of circadian biomarkers. (Author correspondence: francis.levi@inserm.fr)