Circadian biology in astronauts—space missions disrupt circadian genes and melatonin

Key Findings

🌙 Evening People Show Higher Heart Disease Risk in 104 Shift Workers

• Evening chronotype shift workers had significantly higher visceral fat (12.8 vs 8.90), blood pressure (137.0 vs 127.6 mmHg), and LDL cholesterol (4.00 vs 3.40 mmol/L) compared to morning types

• All shift workers showed elevated body fat (31.7% vs 22.7%), blood pressure, and cholesterol compared to day workers

• The combination of shift work and evening preference created the worst metabolic profile

🧠 Sleep Deprivation Damages Gut Health Through Clock Gene Disruption

• Chronic sleep deprivation in mice reduced intestinal barrier proteins and triggered gut inflammation through disrupted Nr1d1 (a key clock gene)

• Fecal transplants from sleep-deprived mice caused intestinal inflammation in healthy recipients, proving the gut microbiome's role

• Taurine supplementation restored Nr1d1 expression and repaired intestinal barrier function

👶 Preschoolers' Bedtimes Closely Track Their Internal Clocks

• In 49 children aged 3-6 years, melatonin onset occurred an average of 35 minutes before bedtime, with 18% going to bed before their biological clock was ready

• For every hour later that melatonin onset occurred, bedtime and sleep onset were 28-33 minutes later respectively

• Children with later internal clocks scored higher on evening chronotype measures

💊 Steroid Medication Disrupts Body Clocks in Healthy Men

• Prednisolone (12.5mg twice daily for 5 days) eliminated normal morning-evening variations in four clock genes (BMAL1, NPAS2, PER3, REV-ERB-β) in both fat and muscle tissue

• The drug increased nighttime glucose levels by 67% and raised nighttime blood pressure from 116 to 123 mmHg

• Sleep efficiency dropped from 87% to 84% during treatment

🌅 Morning Labor Inductions Lead to Faster Deliveries

• Analysis of 2,367 pregnant women showed morning labor inductions were 1.5 hours faster for healthy women and 7 hours faster for those with gestational diabetes

• Mouse studies revealed oxytocin receptors follow daily rhythms controlled by the BMAL1 clock gene

• Diabetic mice and those lacking BMAL1 showed reduced uterine response to oxytocin

🧬 Key Clock Gene Controls Normal 24-Hour Rhythms

• Mice lacking REV-ERB nuclear receptors showed dramatically shortened circadian periods due to overproduction of NPAS2 and CLOCK proteins

• This effect occurred consistently across different tissues (brain and liver), showing it's a fundamental cellular mechanism

• REV-ERB proteins normally act as brakes on the circadian system, preventing it from running too fast