Stimulation of fat storage by prostacyclin and selective agonists of prostanoid IP receptor during the maturation phase of cultured adipocytes

Abstract

We have previously shown that cultured adipocytes have the ability to biosynthesize prostaglandin (PG) I 2 called alternatively as prostacyclin during the maturation phase by the positive regulation of gene expression of PGI synthase and the prostanoid IP receptor. To clarify how prostacyclin regulates adipogenesis, we investigated the effects of prostacyclin and the specific agonists or antagonists for the IP receptor on the storage of fats during the maturation phase of cultured adipocytes. Exogenous PGI 2 and the related selective agonists for the IP receptor including MRE-269 and treprostinil rescued the storage of fats attenuated by aspirin, a cyclooxygenase inhibitor. On the other hand, selective antagonists for IP such as CAY10441 and CAY10449 were effective to suppress the accumulation of fats as GW9662, a specific antagonist for peroxisome proliferator-activated receptor (PPAR)c. Thus, pro-adipogenic action of prostacyclin can be explained by the action mediated through the IP receptor expressed at the maturation stage of adipocytes. Cultured adipocytes incubated with each of PGI 2 and MRE-269 together with troglitazone, an activator for PPARc, exhibited additively higher stimulation of fats storage than with either compound alone. The combined effect of MRE-269 and troglitazone was almost abolished by coincubation with GW9662, but not with CAY10441. Increasing concentrations of troglitazone were found to reverse the inhibitory effect of CAY10441 in a dose-dependent manner while those of MRE-269 failed to rescue adipogenesis suppressed by GW9662, indicating the critical role of the PPARc activation as a downstream factor for the stimulated adipogenesis through the IP receptor. Treatment of cultured adipocytes with cell permeable stable cAMP analogues or forskolin as a cAMP elevating agent partly restored the inhibitory effect of aspirin. However, excess levels of cAMP stimulated by forskolin attenuated adipogenesis. Supplementation with H-89, a cell permeable inhibitor for protein kinase A (PKA), had no effect on the promoting action of PGI 2 or MRE-269 along with aspirin on the storage of fats, suggesting that the promotion of adipogenesis mediated by the IP receptor does not require the PKA activity.

Metabolic Regulation in Adipocytes by Prostanoid Receptors

“…Activation of the IP receptor by agonists was suggested to enhance fat storage during the maturation phase of adipocyte cultures of ob1771 or 3T3-L1 cells. 28,29) Moreover, diet-induced obesity (DIO) was suppressed in mice deficient in PGI synthase or the IP receptor. 30,31) On the other hand, the PGF 2α -FP pathway was reported to attenuate adipocyte differentiation in 3T3-L1 cells and MSCs.…”

Prostacyclin: A major prostaglandin in the regulation of adipose tissue development

“…Prostacyclin can mediate its effect on dormant adipose precursor cells and mature adipocytes by both autocrine and paracrine modes for the development of adipose tissues in the presence of proper hormonal milieu (Negrel et al, ). Natural prostacyclin has a very short lifespan chemically, but can exert its pro‐adipogenic effect through IP in an autocrine manner before its spontaneous degradation in the maturation medium (Khan et al, ). Besides, the paracrine adipogenic features of PGI 2 have also been noticed in the presence of angiotensin‐II.…”

“…Adipocyte differentiation can be characterized by sequential expressions of specific genes and demonstration of phenotypical changes of preadipocytes, which include gaining a spherical shape and filling up with lipid droplets (Gregoire et al, 1998;Moreno-Navarrete & Fernández-Real, 2012;Prokesch, Hackl, Hakim-Weber, Bornstein, & Trajanoski, 2009). 3T3-L1 and Ob1771 have been used profoundly along with some other adipocytes for the studying the involvement of prostacyclin in adipogenesis in the last few decades (Aubert et al, 2000;Borglum, Pedersen, Ailhaud, Negrel, & Richelsen, 1999;Catalioto, Gaillard, Maclouf, Ailhaud, & Negrel, 1991;Khan et al, 2016;Rahman et al, 2014). 3T3-L1 cells were developed from the Swiss 3T3 cell line, which originated from disaggregated 17-19-day-old Swiss 3T3 mouse embryos (Gregoire et al, 1998;Moreno-Navarrete & Fernández-Real, 2012).…”

“…However, the terminal differentiation can also be prompted via the activation of Epac 1 linking with Akt/PKB pathway activating PPARγ. Akt/PKB: protein kinase B; cAMP: cyclic adenosine monophosphate; COX: cyclooxygenase; Epac 1: exchange proteins directly activated by cAMP 1; G protein: GTP (Guanosine-5′-triphosphate) binding protein; PGIS: prostacyclin synthase; PKA: protein kinase A; PPARγ: peroxisome proliferator-activated receptor γ lifespan chemically, but can exert its pro-adipogenic effect through IP in an autocrine manner before its spontaneous degradation in the maturation medium (Khan et al, 2016). Besides, the paracrine adipogenic features of PGI 2 have also been noticed in the presence of angiotensin-II.…”

“…The possibility of PGI 2 to regulate the gene expression of PPARγ through the IP receptor might be considered as an interesting area to conduct some future research (Khan et al, 2016;Mei et al, 2002).…”