The present invention is drawn to a gene comprising a polynucleotide encoding a polypeptide composed of an amino acid sequence represented by SEQ ID NO: 1; a gene expression product produced through expression of the gene; a recombinant expression vector including the gene; a host cell (transformant) harboring the recombinant expression vector; a protein composed of an amino acid having an amino acid sequence represented by SEQ ID NO: 1; a therapeutic or preventive composition for hypoglycemia containing as an active ingredient the above-mentioned gene or protein; and an antibody capable of binding to the protein. Through use of the gene or an expression product thereof of the present invention, it is possible to elucidate the pathology of diabetes and develop drugs for treatment and prevention of diabetes via a new action mechanism.