Plays a role in the regulation of the early stage of white and brown preadipocyte cell differentiation. Promotes adipogenic commitment of preadipocytes by increasing gene expression of the transcription factor PPARG in a BMP4-dependent signaling pathway. Homodimer. Secreted by adipose precursor cells (PubMed:28052263). Not detected in the nucleus (By similarity). Expressed in brain. Expressed in neurons. Expressed in adipose precursor cells in epididymal white adipose tissue (at protein level). Strongly expressed in adipose precursor cells. Weakly expressed in adipocytes. Expressed in embryo in subcutaneous white adipose tissue from 16.5 days post coitum (dpc) to 4 days postnatal (P4). Expressed early in pups in visceral epididymal white adipose tissue at 4 days postnatal (P4) and strongly decreases from P7 to P56 (at protein level). Up-regulated is response to high-fat feeding (at protein level) (PubMed:28052263). Up-regulated by the transcription factor PPARG in a BMP4-signaling dependent manner. Up-regulated during adipocyte differentiation. N-glycosylated. N-linked glycosylation on Asn-35 and Asn-175 is critical for secretion but not for preadipocyte cell differentiation activity. Truncated N-terminus.