Diurnal rhythm of plasma delta-sleep-inducing peptide in humans: evidence for positive correlation with body temperature and negative correlation with rapid eye movement and slow wave sleep.

This study found that plasma DSIP levels follow a diurnal rhythm and are lower during rapid eye movement sleep, but do not rise significantly during slow wave sleep.

Summary and findings

This study measured plasma delta-sleep-inducing peptide (DSIP) levels in 12 normal volunteers over 24 hours. The researchers found a diurnal rhythm with maximum levels at 1500 h and minimum at 0100 h. DSIP levels were lower during rapid eye movement sleep and somewhat lower during slow wave sleep compared to awake values.

Abstract

Since delta-sleep-inducing peptide (DSIP) was isolated in 1977, numerous reports have suggested that this nonapeptide stimulates delta-sleep [slow wave sleep (SWS)]. Although DSIP-like immunoreactivity (DSIP-LI) has been found in the serum of many animals and man, its diurnal rhythm and relation to sleep stages have not been well defined. We hypothesized that circulating levels of this putative sleep hormone would be highest at night and would probably be elevated before or during episodes of SWS. We, therefore, measured plasma DSIP-LI levels every 30 min for 24 h in 12 normal volunteers in whom we obtained simultaneous polygraphic recordings. We found a distinct diurnal rhythm for plasma DSIP-LI levels, with the maximum at 1500 h and the minimum at 0100 h. DSIP-LI levels were substantially lower in rapid eye movement sleep (P < 0.005) and somewhat lower in SWS (P < 0.05) compared to awake values. DSIP-LI levels did not rise before, during, or after a significant percentage of episodes of SWS. We found, however, that the diurnal rhythm of DSIP-LI closely followed that of body temperature with a high degree of correlation (r2 = 0.66; P < 0.0001). We conclude that endogenous elevations of circulating DSIP may be associated with suppression of slow wave and rapid eye movement sleep, and that the circadian rhythm of this peptide is coupled directly or indirectly to that of body temperature.

Limitations

Not reported in abstract.

Elsewhere in the DSIP corpus