scholarly journals Nutrition and the circadian system

2016 ◽  
Vol 116 (3) ◽  
pp. 434-442 ◽  
Author(s):  
Gregory D. M. Potter ◽  
Janet E. Cade ◽  
Peter J. Grant ◽  
Laura J. Hardie
Keyword(s):  
Environmental Changes ◽  
Time Of Day ◽  
Circadian System ◽  
Suprachiasmatic Nuclei ◽  
Peripheral Tissues ◽  
Physiological Processes ◽  
Nutritional Science ◽  
High Fat Diets ◽  
Nutritional Compounds ◽  
Fat Diets

AbstractThe human circadian system anticipates and adapts to daily environmental changes to optimise behaviour according to time of day and temporally partitions incompatible physiological processes. At the helm of this system is a master clock in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. The SCN are primarily synchronised to the 24-h day by the light/dark cycle; however, feeding/fasting cycles are the primary time cues for clocks in peripheral tissues. Aligning feeding/fasting cycles with clock-regulated metabolic changes optimises metabolism, and studies of other animals suggest that feeding at inappropriate times disrupts circadian system organisation, and thereby contributes to adverse metabolic consequences and chronic disease development. ‘High-fat diets’ (HFD) produce particularly deleterious effects on circadian system organisation in rodents by blunting feeding/fasting cycles. Time-of-day-restricted feeding, where food availability is restricted to a period of several hours, offsets many adverse consequences of HFD in these animals; however, further evidence is required to assess whether the same is true in humans. Several nutritional compounds have robust effects on the circadian system. Caffeine, for example, can speed synchronisation to new time zones after jetlag. An appreciation of the circadian system has many implications for nutritional science and may ultimately help reduce the burden of chronic diseases.

Abstract P199: Circadian Contributions To Blood Pressure Variation Under Constant Conditions

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Gabrielle F Gloston ◽  
Annie E Ensor ◽  
Samarth Patel ◽  
Rebecca Williams ◽  
Courtney M Peterson ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Body Temperature ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Core Body Temperature ◽  
Circadian System ◽  
External Factors ◽  
Future Research ◽  
Physiological Processes ◽  
Core Body

The circadian clock is an endogenous biological timekeeper that responds to environmental changes and governs various physiological processes over a 24-hour cycle. Blood pressure (BP) variation is thought to be controlled by the circadian clock, but few studies have examined circadian control of BP in humans. Moreover, it is unknown whether nighttime BP dipping is driven by the circadian system or by external factors. We investigated whether the circadian system drives 24-hour rhythms in BP, including nighttime BP dipping, using a 30-hour constant routine (CR) protocol. The CR protocol controls for external factors, allowing circadian rhythms to be isolated and measured, by having participants lie in a semi-recumbent posture in dim light (<10 lux) at a constant temperature, consume isocaloric snacks every 2 hours, and maintain wakefulness. To measure the BP rhythm, ambulatory BP was measured every 30 minutes (SpaceLabs 90227), and to measure the central circadian rhythm, core body temperature was measured every 10 seconds using an ingestible, wireless sensor (HQInc Core Body Temperature Wireless Data Record and Sensor). To date, 17 normotensive African American participants (13 females and 4 males), with a mean age of 37 (± 11.3) years and body mass index (BMI) of 32.5 kg/m 2 , have completed the study. Approximately 59% of participants (10 of 17) had non-dipping systolic BP at screening, defined as a <10% decrease in mean systolic BP from daytime to nighttime. Under constant conditions, 94% of participants (16 of 17) had a non-dipping BP phenotype. Median systolic BP dipping was 0.8% for females and 2.2% for males. There was a robust rhythm in participants’ core body temperature but not BP, suggesting that the circadian clock may not contribute substantially to a nighttime decrease in BP in normotensive African Americans. Instead, the non-dipping BP phenotype is likely more so a result of behavioral and/or physiological sleep-related processes. Future research and interventions for non-dipping BP may need to target these underlying behavioral and physiological processes.

scholarly journals Circadian Variation in Placental and Hepatic Clock Genes in Rat Pregnancy

Endocrinology ◽  
2011 ◽  
Vol 152 (9) ◽  
pp. 3552-3560 ◽  
Author(s):  
Michaela D. Wharfe ◽  
Peter J. Mark ◽  
Brendan J. Waddell
Keyword(s):  
Clock Genes ◽  
Fetal Liver ◽  
Circadian Variation ◽  
Time Of Day ◽  
Peripheral Tissues ◽  
Clock Gene Expression ◽  
Physiological Processes ◽  
Maternal Liver ◽  
Physiological Adaptations ◽  
Circadian Patterns

Clock genes drive circadian rhythms in a range of physiological processes both centrally and in peripheral tissues such as the liver. The aims of this study were to determine whether the two functionally-distinct zones of the rat placenta (junctional and labyrinth) differentially express clock genes and, if so, whether these exhibit circadian patterns. Rats were sampled from d 21 of pregnancy (term = d 23) and from diestrus I of the estrous cycle. Adult liver (all animals), fetal liver, and placental zones (pregnant animals) were collected at 0800, 1400, 2000, and 0200 h. Both zones of the rat placenta expressed all seven canonical clock genes (Clock, Bmal1, Per1, Per2, Per3, Cry1, and Cry2), but there were marked zonal differences and, unlike in maternal liver, circadian variation in placenta was limited. Similarly, placental expression of Vegf varied with zone but not time of day. Pregnancy also led to marked changes in hepatic clock gene expression, with peak levels of Per1, Cry1, and Cry2 all reduced, Per3 increased, and circadian variation in Clock expression lost. All clock genes were expressed in fetal liver, but there was less circadian variation than in maternal liver. Similarly, fetal corticosterone levels remained stable across the day, whereas maternal corticosterone showed clear circadian variation. In conclusion, our data show that the rat placenta expresses all canonical clock genes in a highly zone-specific manner but with relatively little circadian variation. Moreover, pregnancy alters the expression and circadian variation of clock genes in maternal liver, possibly contributing to maternal physiological adaptations.

scholarly journals Phosphorylation and Circadian Molecular Timing

2020 ◽  
Vol 11 ◽  
Author(s):  
Andrea Brenna ◽  
Urs Albrecht
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Circadian System ◽  
Post Translational Modifications ◽  
Physiological Processes ◽  
Clock Proteins ◽  
Protein Components ◽  
Response To Environmental Change ◽  
External Stimuli

Endogenous circadian rhythms are biological processes generated by an internal body clock. They are self-sustaining, and they govern biochemical and physiological processes. However, circadian rhythms are influenced by many external stimuli to reprogram the phase in response to environmental change. Through their adaptability to environmental changes, they synchronize physiological responses to environmental challenges that occur within a sidereal day. The precision of this circadian system is assured by many post-translational modifications (PTMs) that occur on the protein components of the circadian clock mechanism. The most ancient example of circadian rhythmicity driven by phosphorylation of clock proteins was observed in cyanobacteria. The influence of phosphorylation on the circadian system is observed through different kingdoms, from plants to humans. Here, we discuss how phosphorylation modulates the mammalian circadian clock, and we give a detailed overview of the most critical discoveries in the field.

scholarly journals Slowpoke functions in circadian output cells to regulate rest:activity rhythms

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0249215
Author(s):  
Daniela Ruiz ◽  
Saffia T. Bajwa ◽  
Naisarg Vanani ◽  
Tanvir A. Bajwa ◽  
Daniel J. Cavanaugh
Keyword(s):  
Time Of Day ◽  
Circadian System ◽  
Activity Rhythms ◽  
Behavioral Rhythms ◽  
Neuronal Populations ◽  
Physiological Processes ◽  
Multiple Components ◽  
A Cell ◽  
Central Clock ◽  
Rhythmic Behaviors

The circadian system produces ~24-hr oscillations in behavioral and physiological processes to ensure that they occur at optimal times of day and in the correct temporal order. At its core, the circadian system is composed of dedicated central clock neurons that keep time through a cell-autonomous molecular clock. To produce rhythmic behaviors, time-of-day information generated by clock neurons must be transmitted across output pathways to regulate the downstream neuronal populations that control the relevant behaviors. An understanding of the manner through which the circadian system enacts behavioral rhythms therefore requires the identification of the cells and molecules that make up the output pathways. To that end, we recently characterized theDrosophilapars intercerebralis (PI) as a major circadian output center that lies downstream of central clock neurons in a circuit controlling rest:activity rhythms. We have conducted single-cell RNA sequencing (scRNAseq) to identify potential circadian output genes expressed by PI cells, and used cell-specific RNA interference (RNAi) to knock down expression of ~40 of these candidate genes selectively within subsets of PI cells. We demonstrate that knockdown of theslowpoke(slo) potassium channel in PI cells reliably decreases circadian rest:activity rhythm strength. Interestingly,slomutants have previously been shown to have aberrant rest:activity rhythms, in part due to a necessary function ofslowithin central clock cells. However, rescue ofsloin all clock cells does not fully reestablish behavioral rhythms, indicating that expression in non-clock neurons is also necessary. Our results demonstrate thatsloexerts its effects in multiple components of the circadian circuit, including PI output cells in addition to clock neurons, and we hypothesize that it does so by contributing to the generation of daily neuronal activity rhythms that allow for the propagation of circadian information throughout output circuits.

Non-Fasting Factor VII Coagulant Activity (FVII:C) Increased by High-Fat Diet

1994 ◽  
Vol 71 (06) ◽  
pp. 755-758 ◽  
Author(s):  
E M Bladbjerg ◽  
P Marckmann ◽  
B Sandström ◽  
J Jespersen
Keyword(s):  
High Fat Diet ◽  
Fat Content ◽  
Factor Vii ◽  
Amidolytic Activity ◽  
High Fat ◽  
Low Fat Diet ◽  
Increased Risk ◽  
Coagulant Activity ◽  
High Fat Diets ◽  
Fat Diets

SummaryPreliminary observations have suggested that non-fasting factor VII coagulant activity (FVII:C) may be related to the dietary fat content. To confirm this, we performed a randomised cross-over study. Seventeen young volunteers were served 2 controlled isoenergetic diets differing in fat content (20% or 50% of energy). The 2 diets were served on 2 consecutive days. Blood samples were collected at 8.00 h, 16.30 h and 19.30 h, and analysed for triglycerides, FVII coagulant activity using human (FVII:C) or bovine thromboplastin (FVII:Bt), and FVII amidolytic activity (FVIPAm). The ratio FVII:Bt/FVII:Am (a measure of FVII activation) increased from fasting levels on both diets, but most markedly on the high-fat diet. In contrast, FVII: Am (a measure of FVII protein) tended to decrease from fasting levels on both diets. FVII:C rose from fasting levels on the high-fat diet, but not on the low-fat diet. The findings suggest that high-fat diets increase non-fasting FVII:C, and consequently may be associated with increased risk of thrombosis.

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