The anti-adipogenic effect of PGRN on porcine preadipocytes involves ERK1,2 mediated PPARγ phosphorylation

Recent researches indicate that PGRN is closely related to diabetes and is regarded as a novel adipokine associated with obesity development, affecting adipocyte biology. In the present study, we investigated the effects and mechanisms of PGRN on porcine preadipocytes differentiation. Porcine preadipocytes were induced to differentiation with the addition of lentivirius-expressed PGRN shRNA at the early or late stage of induction period, and in the presence or absence of recombinant PGRN protein. The effects of PGRN on adipogenic genes expression and ERK activation were investigated. At the early stage of induction, knockdown of PGRN promoted differentiation, evidenced by enhanced lipid accumulation, upregulation of adipocyte markers, as well as master adipogenic transcription factors, PPAR gamma and C/EBP alpha. While, decreasing PGRN expression at the late stage of induction (day 3) had no effect on differentiation. These results suggested that PGRN functions in the early adipogenic events. Conversely, porcine preadipocytes differentiation was impaired by MDI and recombinant PGRN protein induction, the expressions of adipocyte markers were decreased. Further studies revealed that PGRN can specifically facilitate ERK1,2 activation, and this activation can be abolished by U0126. Moreover, PPAR gamma phosphorylation at serine 112 site was increased by PGRN treatment, which could reduce the transcriptional activity of PPAR gamma. We conclude that PGRN inhibits adipogenesis in porcine preadipocytes partially through ERK activation mediated PPAR gamma phosphorylation.