Circulating Bone morphogenetic protein 9 (BMP9) as a new biomarker for noninvasive stratification of nonalcoholic fatty liver disease and metabolic syndrome.

Nonalcoholic fatty liver disease (NAFLD) is closely related to metabolic syndrome (MetS). Bone morphogenetic protein 9 (BMP9) is an essential factor in glucose, lipid and energy metabolism. This study aims to investigate whether BMP9 can serve as a serological marker for the severity of NAFLD or MetS. Blood samples, clinical data and FibroTouch test were collected from consecutively recruited 263 individuals in Shanghai East hospital. All the participants were divided into three groups: the healthy controls, nonalcoholic fatty liver (NAFL) group and nonalcoholic steatohepatitis (NASH) at-risk group according to the results of FibroTouch test and liver function. Serum BMP9 levels were measured by enzyme-linked immunosorbent assay. Serum BMP9 levels were positively correlated with transaminase, triglyceride, fasting plasma glucose, glycated hemoglobin (HbA1c) and uric acid while it showed a downward trend as the increasing number of MetS components. Furthermore, it differentiated NASH at-risk (58.13 ± 2.82 ng/L) from the other groups: healthy control (70.32 ± 3.70 ng/L) and NAFL (64.34 ± 4.76 ng/L) (p < 0.0001). Controlled attenuation parameter of liver fat and liver stiffness measurement were negatively correlated with BMP9 levels, while high-density lipoprotein levels were positively correlated. The risk of developing NAFLD increased along with elevated serum BMP9 and BMI, and a significantly higher risk was observed in men compared to women. BMP9 should be considered a protective factor for the onset and development of NAFLD, as well as a promising biomarker for the severity of the NAFLD and MetS.