Browning of white adipose tissue has been proven to be a potential target to fight against obesity and its metabolic commodities, making the exploration of molecules involved in browning process important. Among those browning agents reported recently, FGF21 play as a quite promising candidate for treating obesity for its obvious enhancement of thermogenic capacity in adipocyte and significant improvement of metabolic disorders in both mice and human. However, whether other members of fibroblast growth factor (FGF) family play roles in adipose thermogenesis and obese development is still an open question. Here, we examined the mRNA expression of all FGF family members in three adipose tissues of male C57BL/6 mice and found that FGF9 is highly expressed in adipose tissue and decreased under cold stress. Furthermore, FGF9 treatment inhibited thermogenic genes in the process of beige adipocytes differentiation from stromal vascular fraction (SVF) in a dose-dependent manner. Similar results were obtained with FGF9 overexpression. Consistently, knockdown of FGF9 in SVF cells by using lentiviral shRNA increased thermogenic genes in differentiated beige adipocytes. RNA sequencing analysis revealed a significant increment of hypoxia-inducible factor (HIF) pathway in the early stage of beige adipocytes differentiation under FGF9 treatment, which was validated by real-time PCR. FGF9 expression was increased in subcutaneous WAT of obese human and mice. This study shows that adipose-derived FGF9 play as an inhibitory role in the browning of white adipocytes. Activation of hypoxia signaling at early stage of adipose browning process may contribute to this anti-thermogenic effect of FGF9.
Supplementary Figure 1. A-H, mRNA level of adipogenic genes in response to different FGF9 treatment during white adipogenesis. I-J, mRNA level of FGF9 in full-differentiated mice SVF isolated from iWAT (I) and eWAT (J) in response to CL316243.
Supplementary Figure 2. A Cluster images of global sample distribution and relationships analyzed by t-distributed stochastic neighbor embedding. B-D, Volcano plots of differential genes in response to FGF9 treatment. E, Differential genes induced by FGF9 at the very beginning of differentiation stage (Day 0). F, Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis based on the downregulated genes in Fig. 5H. G, KEGG pathway enrichment analysis based on consistently downregulated genes in day 1 and day 2 after differentiation.