Background: Fat mobilization in adipose tissue (AT) has a specific timing. However, circadian rhythms in the activity of the major enzyme responsible for fat mobilization, hormone-sensitive lipase (HSL), have not been demonstrated in humans.
Objective: To analyze in a cross-sectional study whether there is an endogenous circadian rhythm in HSL activity in human AT ex vivo and whether rhythm characteristics are related to food timing or fasting duration.
Methods: Abdominal AT biopsies were obtained from 18 severely obese participants (age: 46 ± 11 years; body mass index 42 ± 6 kg/m2) who underwent laparoscopic gastric bypass. Twenty-four-hour rhythms of HSL activity and LIPE (HSL transcript in humans) expression in subcutaneous AT were analyzed together with habitual food timing and night fasting duration.
Results: HSL activity exhibited a circadian rhythm (P = .023) and reached the maximum value at circadian time 16 (CT) that corresponded to around midnight (relative local clock time. Similarly, LIPE displayed a circadian rhythm with acrophase also at night (P = .0002). Participants with longer night fasting duration >11.20 hours displayed almost double the amplitude (1.91 times) in HSL activity rhythm than those with short duration (P = .013); while habitual early diners (before 21:52 hours) had 1.60 times higher amplitude than late diners (P = .035).
Conclusions: Our results demonstrate circadian rhythms in HSL activity and may lead to a better understanding of the intricate relationships between food timing, fasting duration and body fat regulation.
Keywords: insulin; lipolysis; obesity; time-restricting eating.
© Endocrine Society 2020. All rights reserved. For permissions, please e-mail: email@example.com.