Dim light melatonin onset following simulated eastward travel is earlier in young males genotyped as PER3^5/5 than PER3^4/4

ABSTRACT

Inter-individual variability exists in recovery from jetlag following travel across time zones. Part of this variation may be due to genetic differences at the variable number tandem repeat (VNTR) polymorphism of the PERIOD3 (PER3) gene as this polymorphism has been associated with chronotype and sleep, as well as sensitivity to blue light on melatonin suppression. To test this hypothesis we conducted a laboratory-based study to compare re-entrainment in males genotyped as PER3^4/4 (n = 8) and PER3^5/5 (n = 8) following simulated eastward travel across six time zones. The recovery strategy included morning blue-enriched light exposure and appropriately-timed meals during the first 24 h after simulated travel. Dim light melatonin onset (DLMO), sleep characteristics, perceived sleepiness levels (Stanford Sleepiness Scale), and resting metabolic parameters were measured during constant routine periods before and after simulated travel. While DLMO time was similar between the two groups prior to simulated eastward travel (p = .223), it was earlier in the PER3^5/5 group (17h23 (17h15; 17h37)) than the PER3^4/4 group (18h05 (17h53; 18h12)) afterwards (p = .046). During resynchronisation, perceived sleepiness and metabolic parameters were similar to pre-travel in both groups but sleep was more disturbed in the PER3^5/5 group (total sleep time: p = .008, sleep efficiency: p = .008, wake after sleep onset: p = .023). The PER3 VNTR genotype may influence the efficacy of re-entrainment following trans-meridian travel when blue-enriched light exposure is incorporated into the recovery strategy on the first day following travel.

KEYWORDS:

• Phase shift
• blue light
• circadian rhythm
• jetlag
• PER3 VNTR polymorphism

Acknowledgements

We are grateful to the participants for their time and commitment. The authors would like to thank former members of the Rhythms and Blooms Laboratory Dr Eric Banda, Dr Rob Henst, Dr Rageema Joseph, Chenjerai Muchapirei, Nyambura Shawa and the late Denford Banga, as well as Prof Vicki Lambert, Mrs Hendriena Victor and Dr Jacolene Kroff for their assistance with this study. We are grateful to Granny Goose Duvets, A1 Furnishers and Plumstead Electrical in Cape Town for their sponsorship of bedding, beds and lighting respectively.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07420528.2022.2139184

Additional information

Funding

This work was supported by research bursaries to LK from the University of Cape Town (UCT)’s International/Refugee Scholarship and the Molecular & Cell Biology Department’s Equity Development Programme as well as the UCT Research Associate grant. The experimental work was funded by UCT URC Research Development grants to LCR and DER, and a UCT start-up grant to DER.