Synergistic Suppression of Early Phase of Adipogenesis by Microsomal PGE Synthase-1 (PTGES1)-Produced PGE2 and Aldo-Keto Reductase 1B3-Produced PGF2α

Abstract

We recently reported that aldo-keto reductase 1B3-produced prostaglandin (PG) F2α suppressed the early phase of adipogenesis. PGE2 is also known to suppress adipogenesis. In this study, we found that microsomal PGE2 synthase (PGES)-1 (mPGES-1; PTGES1) acted as the PGES in adipocytes and that PGE2 and PGF2α synergistically suppressed the early phase of adipogenesis. PGE2 production was detected in preadipocytes and transiently enhanced at 3 h after the initiation of adipogenesis of mouse adipocytic 3T3-L1 cells, followed by a quick decrease; and its production profile was similar to the expression of the cyclooxygenase-2 (PTGS2) gene. When 3T3-L1 cells were transfected with siRNAs for any one of the three major PTGESs, i.e., PTGES1, PTGES2 (mPGES-2), and PTGES3 (cytosolic PGES), only PTGES1 siRNA suppressed PGE2 production and enhanced the expression of adipogenic genes. AE1-329, a PTGER4 (EP4) receptor agonist, increased the expression of the Ptgs2 gene with a peak at 1 h after the initiation of adipogenesis. PGE2-mediated enhancement of the PTGS2 expression was suppressed by the co-treatment with L-161982, a PTGER4 receptor antagonist. Moreover, AE1-329 enhanced the expression of the Ptgs2 gene by binding of the cyclic AMP response element (CRE)-binding protein to the CRE of the Ptgs2 promoter; and its binding was suppressed by co-treatment with L-161982, which was demonstrated by promoter luciferase and chromatin immunoprecipitation assays. Furthermore, when 3T3-L1 cells were caused to differentiate into adipocytes in medium containing both PGE2 and PGF2α, the expression of the adipogenic genes and the intracellular triglyceride level were decreased to a greater extent than in medium containing either of them, revealing that PGE2 and PGF2α independently suppressed adipogenesis. These results indicate that PGE2 was synthesized by PTGES1 in adipocytes and synergistically suppressed the early phase of adipogenesis of 3T3-L1 cells in cooperation with PGF2α through receptor-mediated activation of PTGS2 expression.

Prostaglandins as PPARγModulators in Adipogenesis

“…The increased production of PGF 2 α and PGE 2 in the early phase of adipogenesis is a consequence of the elevated expression of the COX-2 gene [61]. PGF 2 α forms a positive feedback loop that coordinately suppresses the early phase of adipogenesis through the increased production of antiadipogenic PGF 2 α and PGE 2 , both of which inhibit PPAR γ function.…”

“…Moreover, when the cells are caused to differentiate into adipocytes in medium containing both PGF 2 α and PGE 2 , the expression of the adipogenic genes is decreased to a greater extent than when the cells are cultured in a medium containing either of them. Thus, PGE 2 and PGF 2 α synergistically suppress the early phase of adipogenesis through a self-amplifying loop, triggered by PGF 2 α -FP receptor and PGE 2 -EP4 receptor couplings and activation of the COX-2 gene expression in 3T3-L1 cells [61]. …”

Expression of Genes Related to Prostaglandin Synthesis or Signaling in Human Subcutaneous and Omental Adipose Tissue: Depot Differences and Modulation by Adipogenesis

“…The findings of higher expression of COX-1, AKR1B1, PTGES3, PTGIS, and PTGDS in omental versus subcutaneous adipose tissue as well as higher expression of COX-1, COX-2, AKR1B1, PTGES, and PTGDS in omental versus subcutaneous cultured preadipocytes are consistent with these results. Several studies previously established that the two COXs are the rate-limiting enzymes in the synthesis of PG [ 11 , 16 ]. In our study, higher expression of COX isoforms in visceral fat may explain depot differences in PG synthesis.…”

“…The expression of PTGES has been previously investigated in adipocytes [ 45 , 48 ], but the specific isoform involved in the production of PGE 2 has never been clearly identified in human adipose tissue. Fujimori et al recently demonstrated that PTGES is responsible for PGE 2 synthesis in 3T3-L1 cells [ 16 ]. Hétu and Riendeau demonstrated that expression of PTGES was greatly decreased in murine obese tissues, whereas PTGES2 and PTGES3 expression showed minor or no changes [ 48 ].…”

“…Three forms of PGE synthase have been identified, including cytosolic PGE synthase (cPGES), which is constitutively and ubiquitously expressed [ 14 ], and the two membrane-bound PGE synthases (mPGES-1 and mPGES-2) [ 14 , 15 ]. Fujimori et al demonstrated that mPGES-1 acts as the main PGE 2 synthase in 3T3-L1 cells [ 16 ]. PGF 2 α is synthesized by enzymes of the aldo-keto reductase (AKRs) family through various pathways [ 17 , 18 ].…”