Single-cell RNA sequencing of preadipocytes reveals the cell fate heterogeneity induced by melatonin

Obesity is a global epidemic health disorder and associated with several diseases. Body weight-reducing effects of melatonin have been reported; however, no investigation toward examining whether the beneficial effects of melatonin are associated with preadipocyte heterogeneity has been reported. In this study, we profiled 25 071 transcriptomes of normal and melatonin-treated preadipocytes using scRNA-seq. By tSNE analysis, we present a cellular-state landscape for melatonin-treated preadipocytes that covers multiple-cell subpopulations, defined as cluster 0 to cluster 13. Cluster 0 and cluster 1 were the largest components of normal and melatonin-treated preadipocytes, respectively. G0S2, an inhibitor of adipose triglyceride lipase (ATGL), was significantly upregulated in cluster 0 and downregulated in cluster 1. We redefined cluster 0 as the G0S2-positive cluster (G0S2(+)) and cluster 1 as the G0S2-negative cluster (G0S2(-)). Through pseudotime analysis, the G0S2(-) cluster cell differentiation trajectory was divided into three major structures, that is, the prebranch, the lipid catabolism branch, and the cell fate 2 branch. In vitro, G0S2 knockdown enhanced the expression levels of ATGL, BAT markers and fatty acid oxidation-related genes, but inhibited C/EBP alpha and PPAR gamma expression. In vivo, knockdown of G0S2 reduced the body weight gain in high-fat-fed mice. The beneficial effects of the G0S2(-) cell cluster in promoting lipolysis and inhibiting adipogenesis are dependent on two major aspects: first, downregulation of the G0S2 gene in the G0S2(-) cluster, resulting in activation of ATGL, which is responsible for the bulk of triacylglycerol hydrolase activity; and second, upregulation of FABP4 in the G0S2(-) cluster, resulting in inhibition of PPAR gamma and further reducing adipogenesis.