White fat cells (white adipose tissue) in the human body exhibit circadian rhythms affecting critical metabolic functions, according to a new study from the University of Surrey, UK.
Christou et al conducted the first ever analysis of circadian rhythms in human fat taken from people isolated from daily environmental changes. Image credit: Bruce Blaus, Blausen.com / CC BY 3.0.
Circadian rhythms are approximately 24-hour changes governed by the body’s internal clocks.
Misalignment of these internal clocks with each other and the environment is believed to be a major contributor to obesity and poor health.
“Tissues made up of fat cells don’t just store excess energy, they are active metabolic tissues, full of their own rhythms,” said study lead author Dr. Jonathan Johnston, a researcher in the Faculty of Health and Medical Sciences at the University of Surrey.
“This is the first time that we have been able to identify such rhythms in human fat.”
“This provides us with more information about how human metabolism changes across the day and possibly why the body processes foods differently during day and night.”
In the study, seven participants underwent regulated sleep-wake cycles and meal times before entering the lab, where they maintained this routine for a further three days.
They then experienced a 37-hour ‘constant routine’ during which time they did not experience daily changes in light-dark, feed-fast and sleep-wake cycles.
Biopsies of fat tissue were taken at six hourly intervals and then followed by an analysis of gene expression.
Dr. Johnston and colleagues identified 727 genes in the fat tissue that express their own circadian rhythm, many carrying out key metabolic functions.
A clear separation in gene rhythms was identified with approximately a third peaking in the morning and two thirds in the evening.
Morning-peaking transcripts were associated with regulation of gene expression and nucleic acid biology (vital for cell functioning), while evening-peaking transcripts associated with redox activity and organic acid metabolism.
These rhythms, which are independent of external factors such as light and feeding, demonstrate that genes within fat cells naturally complete their functions at different times during the day which could impact on metabolic processes.
The findings were published in the journal Scientific Reports.
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Skevoulla Christou et al. 2019. Circadian regulation in human white adipose tissue revealed by transcriptome and metabolic network analysis. Scientific Reports 9, article number: 2641; doi: 10.1038/s41598-019-39668-3
