Clock genes expression in intensive care unit patients

Abstract

In the present study, we tried to document alterations of some circadian rhythms in intensive care unit (ICU) patients. The genes involved in the generation and regulations of the physiological circadian rhythms have been now identified in several species, including human beings. Patients in ICUs often develop symptoms of circadian rhythm disorders. The effect of coma or surgery on the biological clock remains unknown. The present study determines the 24-h expression of clock genes: Per(s), Clock, Bmal1, and CRY1, in peripheral blood leucocytes. Plasma melatonin concentration was also measured in five comatose and 10 non-comatose patients. Cosinor and student's t-test were used as statistical tools to test inter-group differences in the obtained time series. The Per(s) gene mRNA exhibits a circadian expression in comatose patients, while the rhythmicity of some studied genes disappeared in non-comatose patients. The 24-h profiles of melatonin in both groups were greatly disturbed. These results suggest that surgical stress and intensive care environment affect the peripheral clock as well as the endogenous hormones in humans.

Keywords:

• circadian rhythms
• clock genes
• intensive care unit
• melatonin
• peripheral blood leucocytes