Role of bone morphogenetic protein in the liver
Elevated levels of plasma homocysteine (Hcy) are believed to be involved in several health problems, including liver fibrosis. However, the mechanism of Hcy induced liver injury remains to be further investigated. Although all hepatic cell types are involved in fibrogenesis, the activation and proliferation of hepatic stellate cells (HSCs) are considered to be central events. Moreover, it is reported that bone morphogenetic proteins (BMPs) play an important role in cell proliferation, differentiation and apoptosis. In this experiment, we examined the expression of BMPs in rat liver with hyperhomocysteinemia (HHcy) and in HSC cell lines at both mRNA and protein levels. The principal findings suggest that the expression of BMP-13 was significantly reduced in the liver of rats after 4 and 12 weeks of HHcy compared with that in control. Furthermore, there were significant increase in cell proliferation and modification of HSCs after Hcy treatment. In conclusion, a long term high methionine diet can cause a reduction of BMP-13 in the liver. The reduction of BMP-13 in the liver may contribute to liver injury induced by a high methionine diet.