Intranasal insulin decreases circulating cortisol concentrations during early sleep in elderly humans

Publication date: Available online 14 March 2017
Source:Neurobiology of Aging
Author(s): Matthias Thienel, Ines Wilhelm, Christian Benedict, Jan Born, Manfred Hallschmid
Aging is associated with increases in hypothalamic-pituitary-adrenal (HPA) axis activity that can predispose to metabolic and cognitive impairments. We investigated in elderly and young subjects whether intranasal insulin administration to the human brain reduces early-sleep nadir concentrations of adrenocorticotropin (ACTH) and cortisol, i.e., indicators of baseline HPA axis activity. In within-subject comparisons, intranasal insulin (160 IU) or placebo was administered to 14 elderly (mean age 70.0 years) and 30 young (23.6 years) healthy subjects before bedtime. Sleep was polysomnographically assessed and blood samples were repeatedly collected. Elderly compared to young participants displayed increased early-sleep cortisol concentrations (P < 0.04) and reductions in slow wave and REM sleep (P < 0.001). Insulin administration reduced cortisol levels between 2300 h and 0020 h in the elderly (P = 0.03) but not young participants (P = 0.56; P = 0.003 for interaction). Findings indicate that central nervous insulin acts as an inhibitory signal in basal HPA axis activity regulation and suggest that intranasal insulin may normalize sleep-associated stress axis activity in older age.



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