Diurnal rhythm of circulating nicotinamide phosphoribosyltransferase (Nampt/visfatin/PBEF): impact of sleep loss and relation to glucose metabolism.

CONTEXT

Animal studies indicate that nicotinamide phosphoribosyltransferase [Nampt/visfatin/pre-B-cell colony-enhancing factor (PBEF)] contributes to the circadian fine-tuning of metabolic turnover. However, it is unknown whether circulating Nampt concentrations, which are elevated in type 2 diabetes and obesity, display a diurnal rhythm in humans.

OBJECTIVE

Our objective was to examine the 24-h profile of serum Nampt in humans under conditions of sleep and sleep deprivation and relate the Nampt pattern to morning postprandial glucose metabolism.

INTERVENTION

Fourteen healthy men participated in two 24-h sessions starting at 1800 h, including either regular 8-h-night sleep or continuous wakefulness. Serum Nampt and leptin were measured in 1.5- to 3-h intervals. In the morning, plasma glucose and serum insulin responses to standardized breakfast intake were determined.

MAIN OUTCOME MEASURES

Under regular sleep-wake conditions, Nampt levels displayed a pronounced diurnal rhythm, peaking during early afternoon (P < 0.001) that was inverse to leptin profiles peaking in the early night. When subjects stayed awake, the Nampt rhythm was preserved but phase advanced by about 2 h (P < 0.05). Two-hour postprandial plasma glucose concentrations were elevated after sleep loss (P < 0.05), whereas serum insulin was not affected. The relative glucose increase due to sleep loss displayed a positive association with the magnitude of the Nampt phase shift (r = 0.54; P < 0.05).

CONCLUSIONS

Serum Nampt concentrations follow a diurnal rhythm, peaking in the afternoon. Sleep loss induces a Nampt rhythm phase shift that is positively related to the impairment of postprandial glucose metabolism due to sleep deprivation, suggesting a regulatory impact of Nampt rhythmicity on glucose homeostasis.