-
Alcohol Research & Health : the Journal... 2001The daily light-dark cycle governs rhythmic changes in the behavior and/or physiology of most species. Studies have found that these changes are governed by a biological... (Review)
Review
The daily light-dark cycle governs rhythmic changes in the behavior and/or physiology of most species. Studies have found that these changes are governed by a biological clock, which in mammals is located in two brain areas called the suprachiasmatic nuclei. The circadian cycles established by this clock occur throughout nature and have a period of approximately 24 hours. In addition, these circadian cycles can be synchronized to external time signals but also can persist in the absence of such signals. Studies have found that the internal clock consists of an array of genes and the protein products they encode, which regulate various physiological processes throughout the body. Disruptions of the biological rhythms can impair the health and well-being of the organism.
Topics: Alcoholism; Animals; Biological Clocks; Circadian Rhythm; Gene Expression; Humans; Sleep Disorders, Circadian Rhythm; Sleep Stages; Suprachiasmatic Nucleus
PubMed: 11584554
DOI: No ID Found -
Molecular Cell Sep 2018Age-associated changes to the mammalian DNA methylome are well documented and thought to promote diseases of aging, such as cancer. Recent studies have identified... (Review)
Review
Age-associated changes to the mammalian DNA methylome are well documented and thought to promote diseases of aging, such as cancer. Recent studies have identified collections of individual methylation sites whose aggregate methylation status measures chronological age, referred to as the DNA methylation clock. DNA methylation may also have value as a biomarker of healthy versus unhealthy aging and disease risk; in other words, a biological clock. Here we consider the relationship between the chronological and biological clocks, their underlying mechanisms, potential consequences, and their utility as biomarkers and as targets for intervention to promote healthy aging and longevity.
Topics: Aging; Animals; Biological Clocks; Cellular Senescence; CpG Islands; DNA Methylation; Epigenesis, Genetic; Humans; Longevity
PubMed: 30241605
DOI: 10.1016/j.molcel.2018.08.008 -
Nutrients Aug 2020Breastfeeding is considered the most optimal mode of feeding for neonates and mothers. Human milk changes over the course of lactation in order to perfectly suit the...
BACKGROUND
Breastfeeding is considered the most optimal mode of feeding for neonates and mothers. Human milk changes over the course of lactation in order to perfectly suit the infant's nutritional and immunological needs. Its composition also varies throughout the day. Circadian fluctuations in some bioactive components are suggested to transfer chronobiological information from mother to child to assist the development of the biological clock. This review aims to give a complete overview of studies examining human milk components found to exhibit circadian variation in their concentration.
METHODS
We included studies assessing the concentration of a specific human milk component more than once in 24 h. Study characteristics, including gestational age, lactational stage, sampling strategy, analytical method, and outcome were extracted. Methodological quality was graded using a modified Newcastle-Ottawa Scale (NOS).
RESULTS
A total of 83 reports assessing the circadian variation in the concentration of 71 human milk components were included. Heterogeneity among studies was high. The methodological quality varied widely. Significant circadian variation is found in tryptophan, fats, triacylglycerol, cholesterol, iron, melatonin, cortisol, and cortisone. This may play a role in the child's growth and development in terms of the biological clock.
Topics: Adult; Biological Clocks; Breast Feeding; Circadian Rhythm; Female; Humans; Infant; Infant Nutritional Physiological Phenomena; Infant, Newborn; Lactation; Male; Milk, Human
PubMed: 32759654
DOI: 10.3390/nu12082328 -
Aging Cell Oct 2020Epigenetic clocks, developed using DNA methylation data, have been widely used to quantify biological aging in multiple tissues/cells. However, many existing epigenetic...
Epigenetic clocks, developed using DNA methylation data, have been widely used to quantify biological aging in multiple tissues/cells. However, many existing epigenetic clocks are weakly correlated with each other, suggesting they may capture different biological processes. We utilize multi-omics data from diverse human tissue/cells to identify shared features across eleven existing epigenetic clocks. Despite the striking lack of overlap in CpGs, multi-omics analysis suggested five clocks (Horvath1, Horvath2, Levine, Hannum, and Lin) share transcriptional associations conserved across purified CD14+ monocytes and dorsolateral prefrontal cortex. The pathways enriched in the shared transcriptional association suggested links between epigenetic aging and metabolism, immunity, and autophagy. Results from in vitro experiments showed that two clocks (Levine and Lin) were accelerated in accordance with two hallmarks of aging-cellular senescence and mitochondrial dysfunction. Finally, using multi-tissue data to deconstruct the epigenetic clock signals, we developed a meta-clock that demonstrated improved prediction for mortality and robustly related to hallmarks of aging in vitro than single clocks.
Topics: Aging; Biological Clocks; Epigenomics; Female; Humans; Male
PubMed: 32930491
DOI: 10.1111/acel.13229 -
Cancer Letters Feb 2022The circadian clock is an essential timekeeper that controls, for humans, the daily rhythm of biochemical, physiological, and behavioral functions. Irregular performance... (Review)
Review
The circadian clock is an essential timekeeper that controls, for humans, the daily rhythm of biochemical, physiological, and behavioral functions. Irregular performance or disruption in circadian rhythms results in various diseases, including cancer. As a factor in cancer development, perturbations in circadian rhythms can affect circadian homeostasis in energy balance, lead to alterations in the cell cycle, and cause dysregulation of chromatin remodeling. However, knowledge gaps remain in our understanding of the relationship between the circadian clock and cancer. Therefore, a mechanistic understanding by which circadian disruption enhances cancer risk is needed. This review article outlines the importance of the circadian clock in tumorigenesis and summarizes underlying mechanisms in the clock and its carcinogenic mechanisms, highlighting advances in chronotherapy for cancer treatment.
Topics: Circadian Clocks; Humans; Incidence; Neoplasms
PubMed: 34906624
DOI: 10.1016/j.canlet.2021.12.006 -
Immunology Dec 2020We here introduce a Review Series focussing on the important influences circadian rhythms have on immune responses. The three reviews in this series, expertly curated by...
We here introduce a Review Series focussing on the important influences circadian rhythms have on immune responses. The three reviews in this series, expertly curated by Rachel Edgar, discuss how the cyclic oscillations in our cellular clock affect the innate and adaptive immune response, and how interactions with the intestinal microbiota, themselves subject to daily oscillations, also influence immune responses. As we understand more about these mechanisms, by which chronobiology contributes to immunology, it is becoming increasingly clear that they have important functions in maintaining health, influence autoimmunity and may contribute to the effectiveness of vaccinations.
Topics: Adaptive Immunity; Animals; Autoimmunity; Biological Clocks; Circadian Rhythm; Gastrointestinal Microbiome; Humans; Immunity, Innate; Vaccination; Vaccines
PubMed: 33245151
DOI: 10.1111/imm.13284 -
Nutricion Hospitalaria Sep 2013Chronobiology is a word derived from three Greek stems: kronos for time, bios for life and logos for study. From microarrays studies, now it is accepted that 10-30% of... (Review)
Review
Chronobiology is a word derived from three Greek stems: kronos for time, bios for life and logos for study. From microarrays studies, now it is accepted that 10-30% of the human genome is under the control of circadian molecular clocks. This implies that most behavioral, physiological and biochemical variables display circadian rhythms in their expression. In its simplest form, circadian clocks are composed of a set of proteins that generate self-sustained circadian oscillations. The molecular clock comprises two transcription factors, CLOCK and BMAL1, whereas PERs and CRYs are responsible for the negative limb. One of the most important questions related to the circadian system and obesity, was to elucidate if adipose tissue displayed circadian rhythmicity or whether it had an internal peripheral clock. Our group of research has provided an overall view of the internal temporal order of circadian rhythms in human adipose tissue. A new concept related to illness is Chronodisruption (CD). It is defined as a relevant disturbance of the internal temporal order of physiological and behavioral circadian rhythms. In our modern society, CD may be common in several conditions such as jet lag, shift work, light at night, or social jet lag. In addition clock gene polymorphisms and aging may have also chronodisruptive effects. Our group has also demonstrated that Obesity and CD are also highly interconnected. With the help of chronobiology we can reach a new view of obesity considering not only "what" are the factors involved in obesity, but also "when" these factors are produced.
Topics: Adipose Tissue; Biological Clocks; Epigenesis, Genetic; Humans; Metabolism; Obesity
PubMed: 24010751
DOI: 10.3305/nh.2013.28.sup5.6926 -
Genome Biology and Evolution Oct 2016The molecular clock is a valuable and widely used tool for estimating evolutionary rates and timescales in biological research. There has been considerable progress in... (Review)
Review
The molecular clock is a valuable and widely used tool for estimating evolutionary rates and timescales in biological research. There has been considerable progress in the theory and practice of molecular clocks over the past five decades. Although the idea of a molecular clock was originally put forward in the context of protein evolution and advanced using various biochemical techniques, it is now primarily applied to analyses of DNA sequences. An interesting but very underappreciated aspect of molecular clocks is that they can be based on genetic data other than DNA or protein sequences. For example, evolutionary timescales can be estimated using microsatellites, protein folds, and even the extent of recombination. These genome features hold great potential for molecular dating, particularly in cases where nucleotide sequences might be uninformative or unreliable. Here we present an outline of the different genetic data types that have been used for molecular dating, and we describe the features that good molecular clocks should possess. We hope that our article inspires further work on the genome as an evolutionary timepiece.
Topics: Animals; Biological Clocks; Evolution, Molecular; Genome; Humans
PubMed: 27604881
DOI: 10.1093/gbe/evw220 -
Industrial Health Sep 2019The master clock of the biological rhythm, located in the suprachiasmatic nucleus of the anterior hypothalamus, synchronizes the molecular biological clock found in... (Review)
Review
The master clock of the biological rhythm, located in the suprachiasmatic nucleus of the anterior hypothalamus, synchronizes the molecular biological clock found in every cell of most peripheral tissues. The human circadian rhythm is largely based on the light-dark cycle. In night shift workers, alteration of the cycle and inversion of the sleep-wake rhythm can result in disruption of the biological clock and induce adverse health effects. This paper offers an overview of the main physiological mechanisms that regulate the circadian rhythm and of the health risks that are associated with its perturbation in shift and night workers. The Occupational Physician should screen shift and night workers for clinical symptoms related to the perturbation of the biological clock and consider preventive strategies to reduce the associated health risks.
Topics: Circadian Clocks; Circadian Rhythm; Humans; Light; Occupational Medicine; Sleep; Work Schedule Tolerance
PubMed: 30799323
DOI: 10.2486/indhealth.2018-0173 -
Dialogues in Clinical Neuroscience Dec 2012Biological functions occur at many different frequencies, and each has its healthy and pathological ranges, patterns, and properties. Physiology, biochemistry, and...
Biological functions occur at many different frequencies, and each has its healthy and pathological ranges, patterns, and properties. Physiology, biochemistry, and behavior are not only organized at the morphological level in cells and organs, but separated or coordinated in time for minimal interference and optimal function. One of the most important temporal frameworks is that of the 24-hour day-night cycle, and its change in day length with season. Robust circadian rhythms are important for mental and physical well-being. Though rhythms have been long neglected as irrelevant (in spite of the high prevalence of sleep disorders in nearly every psychiatric illness), we now have tools to document rhythm disruption and, through better understanding of underlying molecular and physiological mechanisms, to develop therapeutic applications. Light as the major synchronizing agent of the biological clock is becoming a treatment option not only for winter depression but other, nonseasonal forms, as well as an adjunct in optimizing sleep-wake cycles, daytime alertness, cognition, and mood in many neuropsychiatric illnesses. Melatonin is the signal of darkness and promotes sleep onset. Manipulation of sleep (wake therapy, phase advance) has yielded the most rapid, nonpharmacological antidepressant effect known, and combinations (with light, medication) provide long-lasting response. Thus, by analogy, new molecules to augment synchronization or mimic changes occuring during night-time wakefulness may yield novel treatments. This issue on biological rhythms contains articles on a variety of different frequencies not included in the usual definition of chronobiology, but which open up interesting approaches to time and illness.
Topics: Animals; Biological Clocks; Circadian Rhythm; Humans
PubMed: 23393412
DOI: 10.31887/DCNS.2012.14.4/awjustice