Nuclear receptor subfamily 1 group D member 1 (NR1D1 or REV-ERBα) is a crucial element of the circadian clock’s transcriptional and translational feedback loop. Understanding its expression in humans is critical for elucidating its role in circadian rhythms and metabolic processes, and in finding potential links to various pathologies. In a longitudinal survey, we examined REV-ERBα expression at 08:00 using a real-time polymerase chain reaction (qRT-PCR) in blood mononuclear cells from Arctic native and non-native residents during equinoxes and solstices. REV-ERBα expression exhibited a pronounced seasonality, peaking at the summer solstice, and reaching a nadir at the winter solstice in both natives and non-natives, with a relatively higher summer peak in natives. After adjusting for age, sex, and body mass index, the amount and timing of light exposure, the amount of physical activity, and indigeneity emerged as significant predictors of REV-ERBα expression.

In Arctic residents, blood lipids fluctuate seasonally in response to changes in light exposure (LE) patterns. This study investigates which aspects of LE (timing, dynamic range, and duration) are related to lipid profiles. We analyzed actigraphy data measuring LE and blue light exposure (BLE) along with blood determinations from 27 residents across different seasons. We assessed circadian parameters of melatonin in a subset of participants. We found that features of BLE and melatonin significantly predicted lipids: An earlier BLE acrophase was associated with higher HDL-C (β = −0.246, p = 0.013). Nighttime BLE was positively associated with TC (β = 0.290, p = 0.008) and LDL-C (β = 0.253, p = 0.025). The normalized circadian amplitude of BLE was inversely associated with the TG/HDL ratio (β = −0.384, p < 0.001). Finally, earlier melatonin was associated with lower TG/HDL (β = 0.464, p = 0.007). Results remained significant after adjusting for co-factors of photoperiod duration, age, sex, and indigeneity. These findings suggest that patterns of LE (circadian light hygiene) could be a way to improve cardiovascular health.

In Arctic residents, blood lipids fluctuate seasonally in response to changes in light exposure (LE) patterns. This study investigates which aspects of LE (timing, dynamic range, and duration) are related to lipid profiles. We analyzed actigraphy data measuring LE and blue light exposure (BLE), along with blood determinations from 27 residents across different seasons. We assessed circadian parameters of melatonin in a subset of participants. We found that features of BLE and melatonin significantly predicted lipids: An earlier BLE acrophase was associated with higher HDL-C (β = –0.246, p = 0.013). Nighttime BLE was positively associated with TC (β = 0.290, p = 0.008) and LDL-C (β = 0.253, p = 0.025). The normalized circadian amplitude of BLE was inversely associated with the TG/HDL ratio (β = –0.384, p < 0.001). Finally, earlier melatonin was associated with lower TG/HDL (β = 0.464, p = 0.007). Results remained significant after adjusting for co-factors of photoperiod duration, age, sex, and indigeneity. These findings suggest that patterns of LE (circadian light hygiene) could be a way to improve cardiovascular health.

Nuclear receptor subfamily 1 group D member 1 (NR1D1 or REV-ERBα) is a crucial element of the circadian clock's transcriptional and translational feedback loop. Understanding its expression in humans is critical for elucidating its role in circadian rhythms and metabolic processes, and finding potential links to various pathologies. In a longitudinal survey we examined REV-ERBα expression at 08:00 using real-time polymerase chain reaction (qRT-PCR) in blood mononuclear cells from Arctic native and non-native residents during equinoxes and solstices. REV-ERBα expression exhibited pronounced seasonality, peaking at the summer solstice and reaching a nadir at the winter solstice in both natives and non-natives with relatively higher summer peak in natives. After adjusting for age, sex, and body mass index, amount and timing of light exposure, amount of physical activity and indigeneity emerged as significant predictors of REV-ERBα expression.

Circadian light exposure influences cardiometabolic health, yet the extent to which genetic variation modifies this relationship remains unclear. We investigated whether the MTNR1B rs10830963 genotype was associated with differences in blue-light exposure (BLE) patterns and blood lipid profiles in 63 Arctic residents (35 G-allele carriers) measured around the winter solstice and spring equinox. Participants were grouped by genotype (CC homozygotes vs. G-allele carriers) and contributed week-long actigraphy data analyzed using time-resolved analyses, mixed-effects models, and cosinor modeling. Genotype group differences across seasons were observed in light-hygiene indices, including the normalized amplitude of BLE (NA BLE) and the nocturnal excess index of BLE (NEI). G-allele carriers also exhibited a less favorable lipid profile, with higher morning low-density lipoprotein cholesterol (LDL-C), TG/HDL-C ratio, and Castelli Risk Index I, together with lower HDL-C when the two seasons were considered together. Overall, a larger NA BLE was associated with lower TG, TG/HDL-C ratio, and Castelli Risk Index I, and higher HDL-C, with these associations more evident in G-allele carriers. Time-resolved analyses further showed that associations between morning fasting lipid values and 24 h BLE, assessed across 30 min exposure bins within each season, were rhythmically patterned and more evident in G-allele carriers, with descriptively later acrophases. These findings suggest that MTNR1B rs10830963 may be associated with differences in the relationship between seasonal light exposure and lipid metabolism in Arctic residents.

Circadian light exposure influences cardiometabolic health, yet the extent to which genetic variation modifies this relationship remains unclear. We investigated whether MTNR1B rs10830963 genotype modulates blue-light exposure (BLE) patterns and blood lipid profiles in 63 Arctic residents (35 G-carriers) measured around the winter solstice and spring equinox. Participants were stratified by genotype (CC homozygotes vs. G-allele carriers) and contributed weeklong actigraphy data undergoing time-resolved analyses, mixed-effects and cosinor modeling. Genotype-dependent seasonal changes were observed in light-hygiene indices, including the normalized amplitude of BLE (NA BLE) and the nocturnal excess index of BLE (NEI). G-allele carriers also exhibited a less favorable lipid profile, with higher morning LDL-C, TG/HDL-C ratio, and Castelli risk index I, together with lower HDL-C in both seasons. A larger NA BLE was associated with lower TG, TG/HDL-C ratio, and Castelli index, and higher HDL-C, with stronger associations in G-allele carriers. Time-resolved analyses further showed that associations between morning fasting lipid values and 24-h BLE, assessed across 30-min exposure bins within each season, were rhythmically patterned and more pronounced in G-allele carriers, with later acrophases. These findings suggest that MTNR1B rs10830963 modifies the link between seasonal light exposure and lipid metabolism in Arctic residents.