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DNA damage and the capacity to repair damaged DNA have been associated with the pathogenesis of several diseases such as cancer. While it is well known that external mutagenic agents can induce DNA damage, less is known about endogenous contributors to genomic instability. The aim of this study was to investigate whether excess body weight as a physiological factor and vital exhaustion as a psychological factor would be associated with basal levels of DNA damage as well as DNA repair capacity.In a cross-sectional between-subject design we recruited 53 apparently healthy men within the normal to non-obese overweight range (mean BMI: 25.2 ± 0.5) who were either vitally exhausted (VE) (VE-score ≥ 10) or non-exhausted (VE-score ≤ 3). Vital exhaustion was assessed using the Maastricht Vital Exhaustion Questionnaire. We assessed DNA damage and repair in terms of strand breaks in PBMCs by means of the automated Fluorimetric Detection of Alkaline Unwinding (FADU) assay. DNA repair capacity was assessed by repeatedly measuring the amount of intact DNA up to 90 min after standardized X-irradiation of the cells.General linear models revealed that elevated levels of basal DNA damage (β=-0.34, p=0.013, f=0.33) as well as impaired capacity to repair damaged DNA (F(1/50)=5.40, p=0.024, f=0.33) with increasing BMI, but not with vital exhaustion (p's ≥ 0.63).Our findings point to DNA integrity impairments with increasing BMI, already in the overweight range, and suggest impaired DNA repair as a potential underlying molecular mechanism. In contrast, the psychological factor vital exhaustion was not associated with DNA damage or DNA repair capacity.

In mammals, biological rhythms synchronize physiological and behavioral processes to the 24-h light–dark (LD) cycle. At the molecular level, self-sustaining processes, such as oscillations of transcription–translation feedback loops, control the circadian clock, which in turn regulates a wide variety of cellular processes, including gene expression and cell cycle progression. Furthermore, previous studies reported circadian oscillations in the repair capacity of DNA lesions specifically repaired by nucleotide excision repair (NER). However, it is so far only poorly understood if DNA repair pathways other than NER are under circadian control, in particular base excision and DNA strand break repair. In the present study, we analyzed potential day and night variations in the repair of DNA lesions induced by ionizing radiation (i.e., mainly oxidative damage and DNA strand breaks) in living mouse splenocytes using a modified protocol of the automated FADU assay. Our results reveal that splenocytes isolated from mice during the light phase (ZT06) displayed higher DNA repair activity than those of the dark phase (ZT18). As analyzed by highly sensitive and accurate qPCR arrays, these alterations were accompanied by significant differences in expression profiles of genes involved in the circadian clock and DNA repair. Notably, the majority of the DNA repair genes were expressed at higher levels during the light phase (ZT06). This included genes of all major DNA repair pathways with the strongest differences observed for genes of base excision and DNA double strand break repair. In conclusion, here we provide novel evidence that mouse splenocytes exhibit significant differences in the repair of IR-induced DNA damage during the LD cycle, both on a functional and on a gene expression level. It will be interesting to test if these findings could be exploited for therapeutic purposes, e.g. time-of-the-day-specific application of DNA-damaging treatments used against blood malignancies.