GDF2 and non-alcoholic fatty liver: Furthermore, the concentrations of BMP9 in healthy control group, NAFL group and NASH at-risk group were 70.32 ± 3.70 ng/L, 64.34 ± 4.76 ng/L and 58.13 ± 2.82 ng/L, respectively, as shown in Fig. 1D, and significant differences were observed among all the groups (all p < 0.0001).