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Biological Rhythms

Expression of clock genes in rheumatoid arthritis

Circadian rhythms are controlled and generated by the biological clock located in the hypothalamic suprachiasmatic nucleus (SCN). This “master clock” is synchronized to 24 h by various environmental factors, primarily the dark-light-cycle but also by regularly occurring social processes, motor activity and food intake. Patients with rheumatoid arthritis (RA) show modulated circadian rhythms of inflammatory cytokines and cortisol, which may be associated with a modified expression of clock genes.