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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 -
Biomedicine & Pharmacotherapy =... Jan 2023The circadian clock regulates many key physiological processes such as the sleep-wake cycle, hormone release, cardiovascular health, glucose metabolism and body... (Review)
Review
The circadian clock regulates many key physiological processes such as the sleep-wake cycle, hormone release, cardiovascular health, glucose metabolism and body temperature. Recent evidence has suggested a critical role of the circadian system in controlling bone metabolism. Here we review the connection between bone metabolism and the biological clock, and the roles of these mechanisms in bone loss. We also analyze the regulatory effects of clock-related genes on signaling pathways and transcription factors in osteoblasts and osteoclasts. Additionally, osteocytes and endothelial cells (ECs) regulated by the circadian clock are also discussed in our review. Furthermore, we also summarize the regulation of circadian clock genes by some novel modulators, which provides us with a new insight into a potential strategy to prevent and treat bone diseases such as osteoporosis by targeting circadian genes.
Topics: Circadian Rhythm; Endothelial Cells; Biological Clocks; Transcription Factors; Osteoclasts
PubMed: 36423544
DOI: 10.1016/j.biopha.2022.114019 -
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 -
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 -
Frontiers in Endocrinology 2023Physical activity represents a potent, non-pharmacological intervention delaying the onset of over 40 chronic metabolic and cardiovascular diseases, including type 2... (Review)
Review
Physical activity represents a potent, non-pharmacological intervention delaying the onset of over 40 chronic metabolic and cardiovascular diseases, including type 2 diabetes, coronary heart disease, and reducing all-cause mortality. Acute exercise improves glucose homeostasis, with regular participation in physical activity promoting long-term improvements in insulin sensitivity spanning healthy and disease population groups. At the skeletal muscle level, exercise promotes significant cellular reprogramming of metabolic pathways through the activation of mechano- and metabolic sensors, which coordinate downstream activation of transcription factors, augmenting target gene transcription associated with substrate metabolism and mitochondrial biogenesis. It is well established that frequency, intensity, duration, and modality of exercise play a critical role in the type and magnitude of adaptation; albeit, exercise is increasingly considered a vital lifestyle factor with a critical role in the entrainment of the biological clock. Recent research efforts revealed the time-of-day-dependent impact of exercise on metabolism, adaptation, performance, and subsequent health outcomes. The synchrony between external environmental and behavioural cues with internal molecular circadian clock activity is a crucial regulator of circadian homeostasis in physiology and metabolism, defining distinct metabolic and physiological responses to exercise unique to the time of day. Optimising exercise outcomes following when to exercise would be essential to establishing personalised exercise medicine depending on exercise objectives linked to disease states. We aim to provide an overview of the bimodal impact of exercise timing, i.e. the role of exercise as a time-giver () to improve circadian clock alignment and the underpinning clock control of metabolism and the temporal impact of exercise timing on the metabolic and functional outcomes associated with exercise. We will propose research opportunities that may further our understanding of the metabolic rewiring induced by specific exercise timing.
Topics: Humans; Diabetes Mellitus, Type 2; Homeostasis; Acclimatization; Circadian Clocks; Exercise
PubMed: 36875451
DOI: 10.3389/fendo.2023.987208 -
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