Abstract
Prostaglandin (PG) F(2alpha) suppresses adipocyte differentiation by inhibiting the function of peroxisome proliferator-activated receptor gamma. However, PGF(2alpha) synthase (PGFS) in adipocytes remains to be identified. Here, we studied the expression of members of the aldo-keto reductase (AKR) 1B family acting as PGFS during adipogenesis of mouse 3T3-L1 cells. AKR1B3 mRNA was expressed in preadipocytes, and its level increased about 4-fold at day 1 after initiation of adipocyte differentiation, and then quickly decreased the following day to a level lower than that in the preadipocytes. In contrast, the mRNA levels of Akr1b8 and 1b10 were clearly lower than that level of Akr1b3 in preadipocytes and remained unchanged during adipogenesis. The transient increase in Akr1b3 during adipogenesis was also observed by Western blot analysis. The mRNA for the FP receptor, which is selective for PGF(2alpha), was also expressed in preadipocytes. Its level increased about 2-fold within 1 h after the initiation of adipocyte differentiation and was maintained at almost the same level throughout adipocyte differentiation. The small interfering RNA for Akr1b3, but not for Akr1b8 or 1b10, suppressed PGF(2alpha) production and enhanced the expression of adipogenic genes such as peroxisome proliferator-activated receptor gamma, fatty acid-binding protein 4 (aP2), and stearoyl-CoA desaturase. Moreover, an FP receptor agonist, Fluprostenol, suppressed the expression of those adipogenic genes in 3T3-L1 cells; whereas an FP receptor antagonist, AL-8810, efficiently inhibited the suppression of adipogenesis caused by the endogenous PGF(2alpha). These results indicate that AKR1B3 acts as the PGFS in adipocytes and that AKR1B3-produced PGF(2alpha) suppressed adipocyte differentiation by acting through FP receptors.
Highlights
Adipocytes are unique cells involved in the regulation of energy homeostasis [1, 2]
These results indicate that Akr1b3 was abundantly expressed in preadipocytes and that its expression and
To prove the involvement of AKR1B3-produced PGF2␣ in FP receptor-mediated suppression of adipogenesis, we measured the expression levels of adipogenic genes in 3T3-L1 cells that had been transfected with Akr1b3 siRNA and further differentiated for 8 days with or without Fluprostenol. siRNA-mediated suppression of AKR1B3 mRNA activated the transcription of Ppar␥, aP2, and Scd genes ϳ6.7, 1.7, and 1.6-fold, respectively, as compared with that in the cells transfected with negative control (NC) siRNA (Fig. 4D and inset)
Summary
Adipocytes are unique cells involved in the regulation of energy homeostasis [1, 2]. The amount of adipose tissue is altered in various conditions [3]. We show that Akr1b3 was expressed in preadipocytes and that its mRNA and protein levels were increased in the early phase of adipogenesis. More-we examined the time courses of the changes in the over, each of three Akr1b3 siRNAs suppressed the AKR1B3 expression profiles of AKR1B3, 1B8, 1B10, PPAR␥, COX-1, and protein level as compared with that of NC siRNA, the COX-2 mRNAs during differentiation of the cells.
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