Abstract: Disclosed are a substance and a pharmaceutical product inhibiting activation of a G protein-coupled receptor.

Abstract: An object of the invention is to provide a pharmaceutical composition and a kit therefor for the lowering of elevated blood sugar level associated with diabetes and for the prevention of the elevation of blood sugar level. The invention provides a pharmaceutical composition containing a ligand (agonist or antagonist) for a GT01 polypeptide, particularly a free fatty acid as a GT01 polypeptide-specific ligand, or a GT01 gene or the GT01 polypeptide, for treating the hyperglycemia associated with diabetes, and a kit therefor. The invention also provides a ligand specific for the GT01 polypeptide, and a screening method exerting an influence on the binding of the specific ligand to the GT01 polypeptide.