Chronic cAMP activation induces adipocyte browning through discordant biphasic remodeling of transcriptome and chromatin accessibility

• Main Authors: Jisun So (Author), Solaema Taleb (Author), Jamie Wann (Author), Olivia Strobel (Author), Kyungchan Kim (Author), Hyun Cheol Roh (Author)
• Format: Book
• Published: Elsevier, 2022-12-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 2212-8778; 10.1016/j.molmet.2022.101619
• Keywords: Beige adipocyte; Transcriptome; Epigenome; NFIL3; Cellular reprogramming; Obesity; Internal medicine; RC31-1245
• Source: Molecular Metabolism, Vol 66, Iss , Pp 101619- (2022)

Objective: Adipose tissue thermogenesis has been suggested as a new therapeutic target to promote energy metabolism for obesity and metabolic disease. Cold-inducible thermogenic adipocytes, called beige adipocytes, have attracted significant attention for their potent anti-obesity activity in adult humans. In this study, we identified the mechanisms underlying beige adipocyte recruitment, so-called adipocyte browning, by different stimuli. Methods: We generated a new adipocyte cell line with enhanced browning potentials and determined its transcriptomic and epigenomic responses following cAMP (forskolin, FSK) versus PPARγ activation (rosiglitazone). We performed time-course RNA-seq and compared the treatments and in vivo adipocyte browning. We also developed an improved protocol for Assay for Transposase Accessible Chromatin-sequencing (ATAC-seq) and defined changes in chromatin accessibility in a time course. The RNA-seq and ATAC-seq data were integrated to determine the kinetics of their coordinated regulation and to identify a transcription factor that drives these processes. We conducted functional studies using pharmacological and genetic approaches with specific inhibitors and shRNA-mediated knockdown, respectively. Results: FSK, not rosiglitazone, resulted in a biphasic transcriptomic response, resembling the kinetics of in vivo cold-induced browning. FSK promoted tissue remodeling first and subsequently shifted energy metabolism, concluding with a transcriptomic profile similar to that induced by rosiglitazone. The thermogenic effects of FSK were abolished by PPARγ antagonists, indicating PPARγ as a converging point. ATAC-seq uncovered that FSK leads to a significant chromatin remodeling that precedes or persists beyond transcriptomic changes, whereas rosiglitazone induces minimal changes. Motif analysis identified nuclear factor, interleukin 3 regulated (NFIL3) as a transcriptional regulator connecting the biphasic response of FSK-induced browning, as indicated by disrupted thermogenesis with NFIL3 knockdown. Conclusions: Our findings elucidated unique dynamics of the transcriptomic and epigenomic remodeling in adipocyte browning, providing new mechanistic insights into adipose thermogenesis and molecular targets for obesity treatment.