Unacylated ghrelin, leptin, and appetite display diurnal rhythmicity in lean adults

Iain Templeman, Harry A Smith, Jean-Philippe Walhin, Benita Middleton, Javier T Gonzalez, Leonidas G Karagounis, Jonathan D Johnston, James A Betts

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Constant routine and forced desynchrony protocols typically remove the effects of behavioural/environmental cues to examine endogenous circadian rhythms, yet this may not reflect rhythms of appetite regulation in the real world. It is therefore important to understand these rhythms within the same subjects under controlled diurnal conditions of light, sleep and feeding. Ten healthy adults (9M/1F, Mean ±SD: age: 30 ± 10 y; BMI: 24.1 ± 2.7 kg·m-2) rested supine in the laboratory for 37 hours. All data were collected during the final 24 hours of this period (i.e. 0800 - 0800 h). Participants were fed hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 2200-0700 h. Hourly blood samples were collected throughout the 24-h period. A diurnal rhythm in mean plasma unacylated ghrelin concentration was identified (p=0.04), with the acrophase occurring shortly after waking (08:19 h), falling to a nadir in the evening with a relative amplitude of 9%. Plasma leptin concentration also exhibited a diurnal rhythm (p<0.01), with the acrophase occurring shortly after lights-out (00:32 h) and the lowest concentrations at midday. The amplitude for this rhythm was 25%. Diurnal rhythms were established in all dimensions of appetite except for sweet preference (p=0.29), with both hunger (21:03) and prospective food consumption (19:55) reaching their peak in the evening before falling to their nadir shortly after waking. Under controlled diurnal conditions, simultaneous measurement of leptin, unacylated ghrelin, and subjective appetite over a 24-hour period revealed rhythmicity in appetite regulation in lean, healthy humans.

Original languageEnglish
JournalJournal of Applied Physiology
Early online date11 Mar 2021
Publication statusE-pub ahead of print - 11 Mar 2021

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