Circadian clock control of endocrine factors

Gamble, Karen L.; Berry, Ryan; Frank, Stuart J.; Young, Martin E.

doi:10.1038/nrendo.2014.78

Cited by 371 publications

(296 citation statements)

References 152 publications

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“…Thus, the hGH1 transcript profile has the appearance of a classic clock-controlled gene with a peak and trough that are 12 h apart under light and dark conditions (49). By contrast, mGH RNA levels showed no significant oscillation over the same 26-h period.…”

Section: Discussionmentioning

confidence: 99%

Evidence for a Circadian Effect on the Reduction of Human Growth Hormone Gene Expression in Response to Excess Caloric Intake

Vakili¹,

Jin

Cattini

2016

Journal of Biological Chemistry

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Rhythmicity of biological functions is fundamental for optimal adaptations to environmental cues. Growth hormone (GH) is a major metabolic homeostatic factor that is secreted with a circadian pattern, but whether it is synthesized rhythmically is unknown. We used transgenic mice containing the human (h) GH gene (hGH1) locus to investigate the rhythmicity of hGH synthesis and secretion and to show that RNA and secreted protein levels oscillate over a 24-h cycle. Analysis of hGH1 promoter sequences revealed an enhancer motif (E-box) element that binds the circadian transcriptional machinery (Bmal1 and Clock). Furthermore, Bmal1/Clock were able to transactivate the hGH1 promoter, and mutation of this E-box element adversely affected basal activity after gene transfer. The ability of Bmal1 to bind the hGH1 promoter region containing the E-box element was confirmed in the hGH1 transgenic mouse pituitary in situ. Occupancy was reduced in mice fed a high fat diet during the light (inactive) stage of the daily cycle in mice and corresponded to a decrease in hGH1 RNA levels. The decreases in occupancy and RNA levels were not seen, however, during the dark (active) stage. A chromatin loop required for efficient postnatal hGH1 expression was negatively affected by the high fat diet in the light but not dark stage similar to the pattern observed with Bmal1 association with the promoter region. This is the first evidence that hGH synthesis follows a diurnal rhythm and of dynamic associations of the circadian machinery with a component of a chromosomal structure of the hGH1 locus that is essential for efficient expression.

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Section: Discussionmentioning

confidence: 99%

Evidence for a Circadian Effect on the Reduction of Human Growth Hormone Gene Expression in Response to Excess Caloric Intake

Vakili¹,

Jin

Cattini

2016

Journal of Biological Chemistry

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“…Insulin sensitivity decreases throughout the day and into the night (37). This is, in part, due to the circadian rhythm of insulin secretion and the insulinimpeding action of growth hormone, the pulsatile concentrations of which increase at night.…”

Section: Circadian Biologymentioning

confidence: 99%

Metabolic Effects of Intermittent Fasting

2017

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The objective of this review is to provide an overview of intermittent fasting regimens, summarize the evidence on the health benefits of intermittent fasting, and discuss physiological mechanisms by which intermittent fasting might lead to improved health outcomes. A MEDLINE search was performed using PubMed and the terms "intermittent fasting," "fasting," "time-restricted feeding," and "food timing." Modified fasting regimens appear to promote weight loss and may improve metabolic health. Several lines of evidence also support the hypothesis that eating patterns that reduce or eliminate nighttime eating and prolong nightly fasting intervals may result in sustained improvements in human health. Intermittent fasting regimens are hypothesized to influence metabolic regulation via effects on (a) circadian biology, (b) the gut microbiome, and (c) modifiable lifestyle behaviors, such as sleep. If proven to be efficacious, these eating regimens offer promising nonpharmacological approaches to improving health at the population level, with multiple public health benefits.

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“…The molecular genesis of circadian rhythms by the SCN and peripheral oscillators involves transcription-translation feedback loops (15)(16)(17). This system is entrained to the solar day by external photic (i.e., the light/dark cycle) and nonphotic (e.g., nutrient intake) inputs (15)(16)(17). Causal evidence for an independent and important impact of the endogenous circadian system on glucose metabolism comes from animal and human studies.…”

mentioning

confidence: 99%

“…Most species have evolved an endogenous circadian timing system that optimally times physiological variations and behaviors relative to the 24-h environmental cycle (15)(16)(17). The mammalian circadian system is composed of a central pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus along with circadian oscillators in virtually all tissues and organs of the body, also referred to as peripheral oscillators (15)(16)(17).…”

mentioning

confidence: 99%

“…The mammalian circadian system is composed of a central pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus along with circadian oscillators in virtually all tissues and organs of the body, also referred to as peripheral oscillators (15)(16)(17). The molecular genesis of circadian rhythms by the SCN and peripheral oscillators involves transcription-translation feedback loops (15)(16)(17). This system is entrained to the solar day by external photic (i.e., the light/dark cycle) and nonphotic (e.g., nutrient intake) inputs (15)(16)(17).…”

mentioning

confidence: 99%

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Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans

Morris

Yang

Garcia

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

335

329

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Glucose tolerance is lower in the evening and at night than in the morning. However, the relative contribution of the circadian system vs. the behavioral cycle (including the sleep/wake and fasting/ feeding cycles) is unclear. Furthermore, although shift work is a diabetes risk factor, the separate impact on glucose tolerance of the behavioral cycle, circadian phase, and circadian disruption (i.e., misalignment between the central circadian pacemaker and the behavioral cycle) has not been systematically studied. Here we show-by using two 8-d laboratory protocols-in healthy adults that the circadian system and circadian misalignment have distinct influences on glucose tolerance, both separate from the behavioral cycle. First, postprandial glucose was 17% higher (i.e., lower glucose tolerance) in the biological evening (8:00 PM) than morning (8:00 AM; i.e., a circadian phase effect), independent of the behavioral cycle effect. Second, circadian misalignment itself (12-h behavioral cycle inversion) increased postprandial glucose by 6%. Third, these variations in glucose tolerance appeared to be explained, at least in part, by different mechanisms: during the biological evening by decreased pancreatic β-cell function (27% lower earlyphase insulin) and during circadian misalignment presumably by decreased insulin sensitivity (elevated postprandial glucose despite 14% higher late-phase insulin) without change in early-phase insulin. We explored possible contributing factors, including changes in polysomnographic sleep and 24-h hormonal profiles. We demonstrate that the circadian system importantly contributes to the reduced glucose tolerance observed in the evening compared with the morning. Separately, circadian misalignment reduces glucose tolerance, providing a mechanism to help explain the increased diabetes risk in shift workers.circadian disruption | shift work | night work | glucose metabolism | diabetes I n healthy humans, there is a strong time-of-day variation in glucose tolerance, with a peak in the morning and a trough in the evening and night (1-6). Understanding the underlying mechanisms of the day/night variation in glucose tolerance is important for diurnally active individuals as well as shift workers, who are at increased risk for developing type 2 diabetes (7-9). The endogenous circadian system and circadian misalignment (i.e., misalignment between the endogenous circadian system and 24-h environmental/behavioral cycles) have been shown to affect glucose metabolism (4,(10)(11)(12)(13)(14). However, the relative and separate importance of the endogenous circadian system and circadian misalignment-after accounting for behavioral cycle effects (including the sleep/wake, fasting/feeding, and physical inactivity/activity cycles, etc.)-on 24-h variation in glucose tolerance is not well understood.Most species have evolved an endogenous circadian timing system that optimally times physiological variations and behaviors relative to the 24-h environmental cycle (15-17). The mammalian circadian system is comp...

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Circadian clock control of endocrine factors

Cited by 371 publications

References 152 publications

Evidence for a Circadian Effect on the Reduction of Human Growth Hormone Gene Expression in Response to Excess Caloric Intake

Evidence for a Circadian Effect on the Reduction of Human Growth Hormone Gene Expression in Response to Excess Caloric Intake

Metabolic Effects of Intermittent Fasting

Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans

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