Disturbance of Circadian Rhythms Extensively Affects Blood Biochemical Parameters and Serum miRNA Profiles

Background: Circadian clock plays a critical role in synchronizing the inner molecular, metabolic and physiological processes to the environmental cues with a period of 24 h. Misalignment in the circadian rhythms leads to decreased adaptation and performance and increased risk of associated disorders. The non-24-h schedules and shift schedules are commonly used in maritime operations, both of which could result in disturbance of circadian rhythms.Methods: In this study, we recruited volunteers and conducted two experiments: in one experiment 15 subjects followed an 8-h on and 4-h off schedule (non-24-h schedule), and in the second experiment 12 subjects followed a 3-d rotary schedule with consecutive shift in sleep time (phase-changing schedule). The serum/blood biochemical variables were measured and the serum miRNAs of the volunteers in the second experiment were subjected to transcriptomic miRNA sequencing.Results: The results show both of the schedules caused comprehensive changes in the blood/serum biochemical variables. Notably, significant elevation in serum phosphate was observed in both experiments: 1.210 ± 0.141 in control and 1.330 ± 0.117 in recovery (P = 0.014) in the first experiment and 1.193 ± 0.152 in control and 1.343 ± 0.099 in recovery (P = 0.007) in the second experiment. In addition, a subset of serum miRNAs targeting genes involved in circadian rhythms, sleep homeostasis, phosphate metabolism and multiple critical physiological processes or pathways were identified in the second experiments.Conclusions: This study reveals that non-24-h and shift schedules lead to changes in a large spectrum of blood/serum biochemical variables due to circadian misalignment. Schedules with frequent shift may cause remarkable changes in serum miRNAs which are involved in multiple physiological pathways. These findings would help understand the deleterious effects of shift schedules and develop optimized strategy to enhance welfare and performance of the shift workers.