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circadian

In reference to biologic rhythms with a cycle of about 24 hours. Physiology: - the suprachiasmatic nucleus acts as the central pacemaker for the human circadian system - when the retina processes wavelengths of light typically emitted by the sun, a series of signal transduction eventactivate expression of circadian genes within the suprachiasmatic nucleus - liver, muscles, fat tissue, beta cells, & the gut may have circadian clocks of their own - timing of food may synchronize may synchronize these peripheral circadian clocks - glucose metabolism is tied to a circadian rhythm & influenced by food timing - healthy individuals process sugar from nighttime meals more slowly than they process comparable morning meals - when peripheral circadian oscillators are not in sync withthe central oscillator, deranged metabolism occurs with weight gain & development of glucose intolerance - restricted eating to a period of 10-12 hours each day has benefits in glycemic control & weight reduction Pathology: - evening chronotype (a circadian preference to go to sleep late at night) may be associated with an unhealthy lifestyle & increased risk of type-2 diabetes [7] - disrupted circadian rhythms in cognitively normal adults linked to higher subsequent amyloid-beta PET burden [8] - link stronger in APOE4 carriers Genetics: - human myocardium biopsy samples found that time of day affected expression of nearly 300 genes [5] Comparative biology: - 43% of protein-coding genes in mice show circadian variation Pharmacology: - > 50% of the 100 best-selling drugs in the U.S. target products of genes with circadian periodicity Notes: - mobile smartphone application that helps patients understand their body's rhythms while contributing to research [3] - Nobel Prize in Physiology or Medicine 2017 for work on the molecular mechanisms of circadian rhythm [4]

Related

chronotype; night owl; early bird circadian clock oscillator

General

periodicity

References

  1. Zhang R et al. A circadian gene expression atlas in mammals: Implications for biology and medicine. Proc Natl Acad Sci U S A 2014 Nov 11; 111:16219 PMID: 25349387 http://www.pnas.org/content/111/45/16219
  2. Kuehn BM Resetting the Circadian Clock Might Boost Metabolic Health. JAMA. Published online March 15, 2017. PMID: 28296999 http://jamanetwork.com/journals/jama/fullarticle/2612679
  3. myCircadianClock http://mycircadianclock.org/
  4. The Nobel Prize in Physiology or Medicine 2017 Jeffrey C. Hall, Michael Rosbash, Michael W. Young https://www.nobelprize.org/nobel_prizes/medicine/laureates/2017/press.html
  5. Montaigne D, Marechal X, Modine T et al Daytime variation of perioperative myocardial injury in cardiac surgery and its prevention by Rev-Erb alpha antagonism: a single-centre propensity-matched cohort study and a randomised study. The Lancet. Oct 26, 2017 PMID: 29107324 http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(17)32132-3/fulltext
  6. Allada R, Bass J Circadian Mechanisms in Medicine. N Engl J Med 2021; 384:550-561 PMID: 33567194 https://www.nejm.org/doi/full/10.1056/NEJMra1802337
  7. Kianersi S et al. Chronotype, unhealthy lifestyle, and diabetes risk in middle-aged U.S. women: A prospective cohort study. Ann Intern Med 2023 Sep 12 PMID: 37696036 https://www.acpjournals.org/doi/10.7326/M23-0728
  8. George J Alzheimer's Amyloid Tied to Circadian Disruption Earlier in Life. Sleep fragmentation may be an Alzheimer's risk factor, data suggest. MedPage Today June 24, 2024 . https://www.medpagetoday.com/neurology/alzheimersdisease/110799 - Nguyen Ho PT, Hoepel SJW, Rodriguez-Ayllon M et al Sleep, 24-Hour Activity Rhythms, and Subsequent Amyloid-beta Pathology. JAMA Neurol. Published online June 24, 2024. PMID: 38913396 https://jamanetwork.com/journals/jamaneurology/fullarticle/2820395