The present invention refers to the use of an antisense DNA oligonucleotide for the messenger RNA of the PGC-la protein, useful as drug for the treatment of diabetes mellitus, insulin resistance and metabolic syndrome. More specifically, the present invention deals with a compound used as drug, through enteral or parenteral route, preferably, with the property of inhibiting the protein expression peroxisome proliferator-activated receptor alpha Coactivator 1 (PGC-la) leading to the reduction of the blood glucose levels. It deals, therefore, with a pharmacological compound that promotes, in diabetic and insulin-resistant individuals, improvement of the glucose serum levels, increase of the plasmatic insulin concentration and reduction of insulin resistance. The present invention presents a more effective control of the glucose levels and acts beneficially on other complications associated to the Diabetes and obesity conditions, according to tests performed in animal models. In this manner, the principal advantage of the present invention over others alike already existing in the market is the effectiveness that controls blood glucose levels and the fact of acting beneficially on other complications that accompany the disease.