Cold-induced thermogenesis shows a diurnal variation that unfolds differently in males and females

This work was supported by the Fundacion Alfonso Martin Escudero (to B.M.T), by the Dutch Heart Foundation (2017T016 to S.K.), by the Dutch Society for Diabetes Research (NVDO; Prof. dr. J. Terpstra Award to S.K.), the Dutch Diabetes Foundation (2015.81.1808 to M.R.B.) and the Netherlands Cardiovascular Research Initiative: an initiative with support of the Dutch Heart Foundation (CVON2014-02 ENERGISE and CVON2017 GENIUS-2 to P.C.N.R.)
Context: Cold exposure mobilizes lipids to feed thermogenic processes in organs, including brown adipose tissue (BAT). In rodents, BAT metabolic activity exhibits a diurnal rhythm, which is highest at the start of the wakeful period. Objective: We investigated whether cold-induced thermogenesis displays diurnal variation in humans and differs between the sexes. Methods: This randomized crossover study included 24 young and lean male (n = 12) and female (n = 12) participants who underwent 2.5-hour personalized cooling using water-perfused mattresses in the morning (7:45 am) and evening (7:45 pm), with 1 day in between. We measured energy expenditure (EE) and supraclavicular skin temperature in response to cold exposure. Results: In males, cold-induced EE was higher in the morning than in the evening (+54% ± 10% vs +30% ± 7%; P = 0.05) but did not differ between morning and evening in females (+37% ± 9% vs +30% ± 10%; P = 0.42). Only in males, supraclavicular skin temperature upon cold increased more in morning than evening (+0.2 ± 0.1 °C vs −0.2 ± 0.2 °C; P = 0.05). In males, circulating free fatty acid (FFA) levels were increased after morning cold exposure, but not evening (+90% ± 18% vs +9% ± 8%; P < 0.001). In females, circulating FFA (+94% ± 21% vs +20% ± 5%; P = 0.006), but also triglycerides (+42% ± 5% vs +29% ± 4%, P = 0.01) and cholesterol levels (+17% ± 2% vs 11% ± 2%; P = 0.05) were more increased after cold exposure in morning than in evening. Conclusion: Cold-induced thermogenesis is higher in morning than evening in males; however, lipid metabolism is more modulated in the morning than the evening in females.
Fundacion Alfonso Martin Escudero
Netherlands Heart Foundation 2017T016 CVON2014-02 ENERGISE CVON2017 GENIUS-2
Dutch Society for Diabetes Research (NVDO)
Dutch Diabetes Foundation 2015.81.1808
Netherlands Cardiovascular Research Initiative