Salivary ghrelin response to drinks varying in protein content and quantity and association with energy intake and appetite

• Published in: Physiology & behavior 2021-12, Vol.242, p.113622-113622, Article 113622
• Main Authors: Crabtree, Daniel R., Buosi, William, Fyfe, Claire L., Horgan, Graham W., Holst, Jens J., Johnstone, Alexandra M.
• Format: Article
• Language: English
• Subjects: Adult; Appetite; Cross-Over Studies; Energy Intake; Ghrelin; Humans; Meals; Postprandial Period; Protein; Saliva
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2021.113622

•Fasted salivary ghrelin concentrations were not associated with fasted plasma ghrelin concentrations.•Postprandial changes in salivary ghrelin in response to test drinks varying in protein content and quantity were unrelated to changes in plasma ghrelin.•Salivary ghrelin was not associated with ad libitum energy intake or appetite perceptions. Salivary hormone analysis is a non-invasive alternative to blood-borne hormone analysis. The orexigenic hormone ghrelin has been detected in human saliva, though the relationship between salivary and blood-borne ghrelin and salivary ghrelin's association with energy intake (EI) and appetite remains unclear. The primary aim of this study was to compare salivary and plasma ghrelin responses to dairy breakfast drinks varying in protein content and quantity, and to determine the relationship between salivary ghrelin and EI and appetite. Participants (n = 25) consumed four test drinks, varying in protein content and quantity, on four separate days in a double-blind randomized controlled study. Salivary and plasma total ghrelin were measured at 0, 30, 60 and 120 min and appetite perceptions at 0, 30, 60, 90 and 120 min. A buffet-style test meal was presented at 120 min to measure ad libitum EI. There was no correlation between the sample means for fasted salivary and plasma ghrelin (r = 0.099, p = 0.637). Furthermore, there was no within-participant association between fasted salivary and plasma ghrelin (r = -0.041, p = 0.725). Mean bias between fasted salivary and plasma ghrelin was -448 pg/ml (95% confidence intervals (CI) = -623 – -273 pg/ml) and upper and lower limits of agreement (LOA) were 427 pg/ml and -1324 pg/ml, respectively. Variation in postprandial levels of salivary and plasma ghrelin within-participants were not associated (r = -0.004, p = 0.943). There was no significant association between EI and salivary (r = 0.003, p = 0.979) or plasma (r = -0.080, p = 0.492) ghrelin. Salivary ghrelin was not significantly correlated with composite appetite score (r = 0.023; p = 0.654), though plasma ghrelin was (r = 0.225, p