Influence of sleep deprivation on plasma ghrelin levels in healthy subjects

• Published in: Experimental and Clinical Endocrinology & Diabetes
• Main Authors: Dzaja, A, Schuld, A, Uhr, M, Yassouridis, A, Pollmächer, T
• Format: Conference Proceeding
• Language: German
• Published: 01.10.2003
• ISSN: 0947-7349; 1439-3646
• DOI: 10.1055/s-2003-817579

Introduction: It is well established that the regulation of sleep, wakefulness and circadian rhythmicity are tightly coupled to neuroendocrine networks, the regulation of feeding and metabolism. Ghrelin is a recently discovered orexigenic peptide which promotes NREM sleep in humans. Plasma ghrelin levels increase between meals, but also in subjects fasted over night during the early morning hours. It is unknown so far if sleep itself affects ghrelin levels or whether circadian networks are involved. Methods: Nine healthy male volunteers (age 28±1.22 years, BMI 22.8±1.79) took part in the present study after written informed consent had been obtained. The study protocol had been approved by an independent Ethics Committee. Each subject, in a randomized order, underwent twice a 24-hour protocol starting at 07.30h. Subjects remained throughout in a semi-recumbent position in a clinical sleep research center. Illumination was below 100 lux. Standardized breakfast, lunch and dinner were served at fixed time points (07.30, 12.00, 19.00h). Water was available ad libitum. After dinner, until the next morning, no food was available. During one of the 24-hour protocols subjects slept between 2300 and 0700 hours, whereas during the other protocol they were kept awake by social interaction throughout the night. Polygraphic recordings of EEG, EOG and EMG were performed continuously. Blood samples were collected by a through-the-wall technique and assayed for ghrelin levels hourly in duplicate using a commercially available radioimmunoassay (Phoenix Pharmaceuticals, CA, U.S.A.). Data were analyzed statistically by analysis of variance (general linear model, GLM incorporated in SPSS) with condition as between-subject factor and time as within-subject factor. Results: In the sleep condition subjects showed a normal nocturnal sleep between 2300 and 0700 hours. Throughout the day and during the sleep deprivation schedule no major lapses into sleep (>5min) occurred. Ghrelin plasma levels showed the established relationship to meals, i.e. levels increased prior to every meal and sharply declined thereafter. During sleep ghrelin levels displayed an initial increase followed by a decline towards morning awakening. In contrast, during the sleep deprivation condition ghrelin levels increased steadily to a plateau and did not decrease prior to breakfast again. Conclusion: We conclude that an early increase of ghrelin levels during sleep and a decline in the morning hours are related to sleep itself, because overnight wakefulness coincides with steadily increasing ghrelin levels.