The invention provides not only a smooth muscle growth inhibitory composition and a composition for inhibiting expression of adhesion molecules in vascular endothelial cells, each comprising the adipose tissue-specific secretory factor apM1 as an active ingredient, but also a method for diagnosis of arteriosclerosis which comprises assaying apM1 in a sample, an antibody against apM1, and a diagnostic kit for arteriosclerosis which comprises the antibody as an active component, all of which contribute to the elucidation of obesity-related genes and corresponding expression products which are useful for the etiologic exploration and establishment of therapeutic modalities for various obesity-related diseases, particularly arteriosclerosis inclusive of angina pectoris and myocardial infarction. By utilizing the information thus obtained, therapeutic and diagnostic methods for various diseases can be established.