Polynucleotides which are produced by preadipocytes within 12 hours from the start of adipocyte differentiation induction and comprise a base sequence identical or at least 93% homologous to SEQ ID NO:1, or a base sequence identical to SEQ ID NO:9, or polynucleotides complementary to those polynucleotides, and proteins comprising an amino acid sequence identical or at least 96% homologous to the protein shown under SEQ ID NO:2 or comprising the amino acid sequence shown under SEQ ID NO:10 are provided.