Circadian transcriptome oscillations in human adipose tissue depend on napping status and link to metabolic and inflammatory pathways

Abstract

Study objectives Napping is a common habit in many countries. Nevertheless, studies about the chronic effects of napping on obesity are contradictory, and the molecular link between napping and metabolic alterations has yet to be studied. We aim to identify molecular mechanisms in adipose tissue (AT) that may connect napping and abdominal obesity. Methods In this cross-sectional study, we extracted the RNA repeatedly across 24h from cultured AT explants and performed RNA sequencing. Circadian rhythms were analyzed using 6 consecutive time points across 24 hours. We also assessed global gene expression in each group (nappers vs. non-nappers). Results With napping, there was a loss of rhythmicity in 88% of genes that showed circadian rhythmicity among non-nappers, a reduction in rhythm amplitudes of 29%, and significant phase changes from a coherent unimodal acrophase in non-nappers, towards a scattered and bimodal acrophase in nappers. Those genes that lost rhythmicity with napping were mainly involved in pathways of glucose and lipid metabolism, and of the circadian clock. Additionally, we found differential global gene expression between nappers and non-nappers with 34 genes down- and 32 genes up-regulated in nappers. The top up-regulated gene (IER3) and top down-regulated pseudogene (VDAC2P2) in nappers have been previously shown to be involved in inflammation Conclusion These new findings may have implications for our understanding of napping's effects on obesity and metabolic disorders.