Smaller circadian amplitude predicts elevated leptin in Arctic residents, independent of photoperiod
The reduced amplitude of circadian rhythms in wrist temperature, physical activity, and light exposure is independently associated with elevated morning leptin levels in residents of the Arctic, regardless of the extreme seasonal changes in day length, according to a new study in Chronobiology International.
The finding suggests that circadian rhythm weakness, rather than photoperiod itself, is a key driver of metabolic risk in high-latitude environments, and that a common variant in the CLOCK gene (rs1801260, or CLOCK 3111) sharply amplifies this effect.
What they found
Gubin and colleagues studied 64 Arctic residents across seasons with contrasting photoperiods, using wrist actigraphy to measure circadian amplitudes of wrist temperature (WTA), physical activity (PAA), and light exposure alongside morning blood leptin concentrations and CLOCK 3111 genotyping.
In fully adjusted multivariate models:
- Wrist temperature amplitude was negatively associated with leptin (beta = -0.344), a blunted temperature rhythm predicted higher leptin.
- Physical activity amplitude showed a similar negative association (beta = -0.323).
- Sleep efficiency was also inversely related to leptin (beta = -0.265).
- A larger normalized amplitude of blue light exposure was associated with both increased WTA (beta = 0.256) and lower leptin (beta = -0.171).
All associations held after adjustment for photoperiod, age, sex, and indigeneity.
The CLOCK 3111 polymorphism strongly moderated the wrist temperature-leptin relationship. Among TT homozygotes, the correlation was strongly negative (r = -0.509), while among CC carriers, a non-significant trend toward a positive association was observed (r = 0.282), a statistically significant difference (p = 0.021). For TT individuals, a wrist temperature amplitude below 1 degree C carried a nearly four-fold higher odds of morning leptin exceeding 13 ng/mL (OR = 3.93, 95% CI: 1.69-9.17) compared to those with an amplitude above 1.5 degrees C.
Why it matters
Leptin is a key regulator of appetite and energy expenditure, and elevated levels are associated with leptin resistance and metabolic dysfunction. In Arctic and sub-Arctic regions, where extreme photoperiods challenge circadian entrainment, the ability to maintain robust circadian rhythms may be a critical metabolic buffer.
The finding that CLOCK 3111 genotype can stratify risk, TT carriers with low wrist temperature amplitude had an odds ratio of nearly 4 for elevated leptin, opens the possibility of using simple actigraphy-based circadian measures combined with genotyping for targeted metabolic risk screening in high-latitude populations and shift workers.
Limits
The study sample (n=64) is modest, and the leptin threshold of 13 ng/mL was exploratory. The cross-sectional design cannot establish causation, circadian disruption may drive leptin elevation, or metabolic state may alter circadian amplitude. Replication in larger, longitudinal cohorts is needed.
Bottom line
Smaller circadian amplitudes of wrist temperature, physical activity, and blue light exposure predict elevated morning leptin in Arctic residents, independent of photoperiod. The CLOCK 3111 TT genotype sharply amplifies the risk, identifying a potentially actionable circadian-metabolic phenotype.
Source: Gubin D, et al. Circadian amplitude and CLOCK 3111 polymorphism predict morning leptin in Arctic residents, independent of photoperiod. Chronobiol Int. 2026 Jun 29:1-14. DOI: 10.1080/07420528.2026.2693222