Effects of meal timing on changes in circulating epinephrine, norepinephrine, and acylated ghrelin concentrations: A pilot study

BACKGROUND: Timing of food intake impacts on metabolic diseases. Few data are available about post-meal changes in epinephrine (E), norepinephrine (NE), and acylated ghrelin (AG) at different times of the day. SUBJECTS AND METHODS: This randomized cross-over trial investigated E/NE/AG concentrations after identical meals consumed at 0800 or 2000 hours in 20 healthy volunteers, by standardizing diet, exercise, duration of fast, and resting. Participants randomly received the test meal at 0800 or 2000 hours, and vice versa after 1 week. Blood samples were collected before and up to 180-min post-meal, every 30 min, with participants supine, motionless, but awake. RESULTS: Median E levels increased at 30-60 min, then declined and rose again at 150 min; values at 60 min (19.0 vs. 15.0 ng/l, p = 0.03) and 180 min (25.0 vs. 11.0 ng/l, p < 0.001) were higher after the morning meals. NE rose at 30-60 min and then progressively declined; median values at 60 min (235.3 vs. 206.3 ng/l, p = 0.02) and 120 min (208.8 vs. 142.0 ng/l, p = 0.04) increased more after morning meals. AG progressively declined to increase again at 90 min after meal; median AG area-under-the-curve (AUC) values were lower at morning (7206.8 vs. 8828.3 pg/mL×h). AG-AUC was inversely associated with diet-induced thermogenesis (β = -121.6; 95% CI -201.0 to 42.2; p = 0.009 for each unit increase), while log NE-AUC was inversely associated with log-triglyceride AUC (β = -0.57; 95% CI -0.98 to 0.16; p = 0.015) in a multiple regression model, after multiple adjustments. CONCLUSIONS: In conclusion, E/NE concentrations were higher after the morning meal, while AG showed an opposite behavior. These data, although requiring confirmation in larger samples, suggest an adjunctive possible mechanism explaining the unfavorable effects of evening eating on metabolic risk.