Morning Enzymatic Activity of DPP-4 Is Differentially Altered by Sleep Loss in Women and Men

No study to date has investigated whether the activity of circulating dipeptidyl peptidase 4 (DPP-4) is affected by sleep loss. DPP-4 is an enzyme that catalyzes a variety of important physiological processes in humans by cleavage of, e.g., the incretin hormones glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (1). Both chronic sleep loss and an increased activity of DPP-4 have been implicated in the development of several diseases, including type 2 diabetes (1–4). Twenty-five normal-weight healthy adults (aged 18–28 years; 13 women, using oral monophasic contraceptives) participated in two in-laboratory experimental conditions separated by about 1 week: one night of regular sleep (scheduled 2230–0630) and one night of total sleep loss, in a counterbalanced order. In the morning (∼0730), fasting blood samples were taken to measure the enzymatic activity of DPP-4, as previously described (3). The effects of sleep loss on DPP-4 activity were examined by using a linear mixed model (restricted maximum likelihood method; scaled identity as covariance matrix) with the fixed factors experimental condition (sleep/total sleep deprivation) and sex (women/men), as well as their interaction. All participants gave written informed consent, and the study was approved by the regional ethics review board …