Potential negative effect of total parenteral nutrition on the human circadian clock.

When patients cannot eat on their own, total parenteral nutrition (TPN) is a clinically beneficial method of maintaining nutrition. However, many animal studies have demonstrated that circadian rhythms are strongly affected by feeding time, raising the concern that continuous TPN around the clock may have an unexpected negative impact on the circadian clock of patients. To investigate this concern, we compared clock gene expression of aged subjects with or without TPN using hair follicle cells and found that while none of the non-TPN subjects showed any obvious defects in circadian rhythms of peripheral clock gene expression, a portion of aged subjects receiving continuous TPN showed abnormal circadian rhythms in peripheral clocks. Continuous TPN around the clock may therefore potentially perturb peripheral circadian rhythms, giving rise to the proposal that TPN needs to be administered with consideration to time factors.