Circadian Rhythms in Adipose Tissue Physiology

Abstract

The different types of adipose tissues fulfill a wide range of biological functions-from energy storage to hormone secretion and thermogenesis-many of which show pronounced variations over the course of the day. Such 24-h rhythms in physiology and behavior are coordinated by endogenous circadian clocks found in all tissues and cells, including adipocytes. At the molecular level, these clocks are based on interlocked transcriptional-translational feedback loops comprised of a set of clock genes/proteins. Tissue-specific clock-controlled transcriptional programs translate time-of-day information into physiologically relevant signals. In adipose tissues, clock gene control has been documented for adipocyte proliferation and differentiation, lipid metabolism as well as endocrine function and other adipose oscillations are under control of systemic signals tied to endocrine, neuronal, or behavioral rhythms. Circadian rhythm disruption, for example, by night shift work or through genetic alterations, is associated with changes in adipocyte metabolism and hormone secretion. At the same time, adipose metabolic state feeds back to central and peripheral clocks, adjusting behavioral and physiological rhythms. In this overview article, we summarize our current knowledge about the crosstalk between circadian clocks and energy metabolism with a focus on adipose physiology. © 2017 American Physiological Society. Compr Physiol 7:383-427, 2017.

Time zones of pancreatic islet metabolism

“…The circadian system and metabolic processes are intimately linked via complex behavioural, neural and endocrine pathways . Peripheral oscillators operative in liver, skeletal muscle, adipose tissue, thyroid gland, endocrine pancreas and other organs orchestrate physiological functions within these organs, adjusting them on a daily basis to the rest‐activity and feeding‐fasting cycles of the body . Genome‐wide transcriptome profiling studies of peripheral oscillators indicate that the temporal orchestration of metabolism and xenobiotic detoxification is a major purpose of circadian clocks in peripheral tissues .…”

“…5,[26][27][28][29] Peripheral oscillators operative in liver, skeletal muscle, adipose tissue, thyroid gland, endocrine pancreas and other organs orchestrate physiological functions within these organs, adjusting them on a daily basis to the rest-activity and feeding-fasting cycles of the body. [30][31][32][33] Genome-wide transcriptome profiling studies of peripheral oscillators indicate that the temporal orchestration of metabolism and xenobiotic detoxification is a major purpose of circadian clocks in peripheral tissues. 27,30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] It was recently suggested that in mouse liver circadian gene expression is controlled by rhythmic chromatin interactions between enhancers and promoters.…”

“…[30][31][32][33] Genome-wide transcriptome profiling studies of peripheral oscillators indicate that the temporal orchestration of metabolism and xenobiotic detoxification is a major purpose of circadian clocks in peripheral tissues. 27,30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] It was recently suggested that in mouse liver circadian gene expression is controlled by rhythmic chromatin interactions between enhancers and promoters. Specifically, Rev-erbα opposes functional interactions between enhancers and promoters of circadian target genes by recruitment of the NCoR-HDAC3 corepressor complex and histone deacetylation (Figure 1), suggesting that rhythmic modulation of chromatin loops controls circadian gene transcription.…”

“…The essential role of the circadian clock in the body is to ensure temporal adaptation of key metabolic processes to geophysical time changes, thus enabling anticipation of rest-activity and feedingfasting rhythms. While circadian regulation ensures the proper temporal orchestration of metabolic processes under physiological conditions in rodents and in humans (Figure 2), circadian misalignments have been associated with an increased risk of metabolic disorders, including obesity and T2D (Figure 3 30,33,68,70,[121][122][123].…”

Circadian disruption by shifting the light‐dark cycle negatively affects bone health in mice

“…1,2 There is a substantial amount of evidence demonstrating the importance of circadian rhythm in biological functions of metabolic tissues such as liver, muscle, and adipose tissue. [3][4][5] Accordingly, circadian disruption through shift work has been associated with numerous disorders related to a dysfunction in metabolic tissues, such as obesity, diabetes, and cardiovascular disease. [6][7][8] In addition, shift work has been associated with a low bone mineral density and increased fracture risk, 9,10 which are both hallmarks of the bone disease osteoporosis.…”