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Circadian lipid synthesis in brown fat maintains murine body temperature during chronic cold.

ABSTRACT: Ambient temperature influences the molecular clock and lipid metabolism, but the impact of chronic cold exposure on circadian lipid metabolism in thermogenic brown adipose tissue (BAT) has not been studied. Here we show that during chronic cold exposure (1 wk at 4 °C), genes controlling de novo lipogenesis (DNL) including Srebp1, the master transcriptional regulator of DNL, acquired high-amplitude circadian rhythms in thermogenic BAT. These conditions activated mechanistic target of rapamycin 1 (mTORC1), an inducer of Srebp1 expression, and engaged circadian transcriptional repressors REV-ERB? and ? as rhythmic regulators of Srebp1 in BAT. SREBP was required in BAT for the thermogenic response to norepinephrine, and depletion of SREBP prevented maintenance of body temperature both during circadian cycles as well as during fasting of chronically cold mice. By contrast, deletion of REV-ERB? and ? in BAT allowed mice to maintain their body temperature in chronic cold. Thus, the environmental challenge of prolonged noncircadian exposure to cold temperature induces circadian induction of SREBP1 that drives fuel synthesis in BAT and is necessary to maintain circadian body temperature during chronic cold exposure. The requirement for BAT fatty acid synthesis has broad implications for adaptation to cold.

SUBMITTER: Adlanmerini M

PROVIDER: S-EPMC6744860 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Circadian lipid synthesis in brown fat maintains murine body temperature during chronic cold.

Adlanmerini Marine M Carpenter Bryce J BJ Remsberg Jarrett R JR Aubert Yann Y Peed Lindsey C LC Richter Hannah J HJ Lazar Mitchell A MA

Proceedings of the National Academy of Sciences of the United States of America 20190826 37

Ambient temperature influences the molecular clock and lipid metabolism, but the impact of chronic cold exposure on circadian lipid metabolism in thermogenic brown adipose tissue (BAT) has not been studied. Here we show that during chronic cold exposure (1 wk at 4 °C), genes controlling de novo lipogenesis (DNL) including <i>Srebp1</i>, the master transcriptional regulator of DNL, acquired high-amplitude circadian rhythms in thermogenic BAT. These conditions activated mechanistic target of rapam ...[more]

PMID: 31451658

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Project description:ContextThe contribution of brown adipose tissue (BAT) to the energy balance in humans exposed to sustainable cold has not been completely established, partially because of measurement limitations of both BAT activity and energy expenditure (EE).ObjectiveThe objective of the study was to characterize the role of BAT activation in cold-induced thermogenesis (CIT).DesignThis study was a single-blind, randomized crossover intervention.SettingThe study was conducted at the National Institutes of Health Clinical Center.Study participantsThirty-one healthy volunteers participated in the study.InterventionsThe intervention included mild cold exposure.Main outcomesCIT and BAT activation were the main outcomes in this study.MethodsOvernight EE measurement by whole-room indirect calorimeter at 24 °C or 19 °C was followed by 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography (PET) scan. After 36 hours, volunteers crossed over to the alternate study temperature under identical conditions. BAT activity was measured in a 3-dimensional region of interest in the upper torso by comparing the uptake at the two temperatures.ResultsTwenty-four volunteers (14 males, 10 females) had a complete data set. When compared with 24 °C, exposure at 19 °C resulted in increased EE (5.3 ± 5.9%, P < .001), indicating CIT response and mean BAT activity (10.5 ± 11.1%, P < .001). Multiple regression analysis indicated that a difference in BAT activity (P < .001), age (P = .01), and gender (P = .037) were independent contributors to individual variability of CIT.ConclusionsA small reduction in ambient temperature, within the range of climate-controlled buildings, is sufficient to increase human BAT activity, which correlates with individual CIT response. This study uncovers for the first time a spectrum of BAT activation among healthy adults during mild cold exposure not previously recognized by conventional PET and PET-computed tomography methods. The enhancement of cold-induced BAT stimulation may represent a novel environmental strategy in obesity treatment.

Dataset Information

Circadian lipid synthesis in brown fat maintains murine body temperature during chronic cold.

Publications

Circadian lipid synthesis in brown fat maintains murine body temperature during chronic cold.

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