EPAS1 Promotes Adipose Differentiation in 3T3-L1 Cells

Abstract

Adipose differentiation is regulated by several transcription factors, such as the CAAT/enhancer-binding protein family and peroxisome proliferator activator (PPAR) ␥2. Several recent studies have shown that the basic helix-loop-helix-PAS superfamily is also involved in the regulation of adipose differentiation. In this study, we investigated the roles played by EPAS1 (endothelial PAS domain protein 1) in adipogenesis. EPAS1, also referred to as hypoxia-inducible factor 2␣, is a transcription factor known to play essential roles in catecholamine homeostasis, vascular remodeling, and the maintenance of reactive oxygen species, and so forth. During adipose differentiation in 3T3-L1 cells, the level of EPAS1 mRNA began to increase 6 days after the induction, and EPAS1 was highly expressed in differentiated cells. To examine whether EPAS1 is involved in adipogenesis, we first isolated stable clones from 3T3-L1 cells in which we could induce the expression of an EPAS1 C-terminal deletion mutant (designated EPAS1-(1-485)) with the insect hormone. The induction of EPAS1-(1-485) allowed the cells to accumulate only minimum amounts of intracellular lipid droplets. Consistent with the morphological observations, a minimum amount of aP2 and PPAR␥2 mRNA was induced in the EPAS1-(1-485) cells. We then examined whether or not EPAS1 was able to promote adipogenesis in NIH 3T3 cells, a relatively nonadipogenic cell line. Overexpression of EPAS1 in NIH 3T3 cells induced a significant amount of lipid accumulation compared with that of the control cells in the presence of the PPAR␥ ligand. The results were also confirmed by measuring the expression of adipocyte-related genes. Adenovirus-mediated EPAS1-(1-485) expression resulted in the reduction of basal and insulin-dependent glucose transport in 3T3-L1 adipocytes. The mechanism involved the transcriptional regulation of GLUT1, GLUT4, and IRS3 expression by EPAS1. Taken together, these results suggest that EPAS1 plays several supporting roles in maintaining specific aspects of adipogenesis and adipocyte function including regulation of glucose uptake followed by lipid synthesis.

Transcriptomic Changes in Ruminal Tissue Induced by the Periparturient Transition in Dairy Cows

“…These results agree with those presented here in that during transition, cows in general are in a negative energy balance state. Similarly, EPAS1 has been shown to improve insulin sensitivity and fat homeostasis (Shimba et al, 2004) and in this study, EPAS1 was upregulated during the transition period, likely as a response to the negative energy balance described above. F2RL1 and PPAR2 are central signaling genes and originate from the signal clotting cascade in a wide variety of tissues (Reinhardt et al, 2012).…”

Macrophage HIF-2α Ameliorates Adipose Tissue Inflammation and Insulin Resistance in Obesity

“…Nevertheless, we cannot exclude the possibility that haplodeficiency of Hif-2a might suffer from systemic insulin resistance through alternative pathways. For example, it has been reported that HIF-2a is able to regulate GLUT1, GLUT4, insulin receptor substrate (IRS) 2, and IRS3 to promote insulin signaling in adipocytes and hepatocytes (33,34). In addition, HIF-2a is able to regulate the expression of several matrix metalloproteases to digest collagens (35), which would protect against fibrosis, probably by HIF-1a, in obese adipose tissue.…”

The role of oxygen availability in embryonic development and stem cell function

“…Low O 2 activates HIF-1α-ARNT heterodimers, which upregulate Dec1 gene expression; DEC1, in turn, represses PPARγ transcription and inhibits the differentiation of preadipocytes into adipocytes. HIF-2α expression is induced during adipogenesis in vivo and in vitro, but plays a distinct role from HIF-1α 48 . Therefore, O 2 availability directly controls the development of adipose tissue via HIF.…”