Abstract
It is well recognized that the decrease of adiponectin associated with high-fat diet and lack of exercise accounts for the onset of insulin resistance, type 2 diabetes, the metabolic syndrome, and cardiovascular disease. Our research efforts have led to the identification of adiponectin receptors, AdipoR1 and AdipoR2, with the former shown to activate AMP kinase in the liver and the latter shown to activate peroxisome proliferator-activated receptor-α signaling thereby increasing fatty acid oxidation. Again, adiponectin upregulates mitochondrial function in the skeletal muscle thereby improving glucose/lipid metabolism and insulin resistance. These findings suggested that activation of adiponectin/AdipoR signaling could represent a viable therapeutic approach to lifestyle-linked diseases associated with prevalent obesity thus contributing to healthy longevity in humans. Indeed, they have led to the successful discovery of AdipoRon, a small-molecule AdipoR-activating compound. Thus far, AdipoRon has been found not only to improve insulin resistance in mice but to prolong their lifespan shortened by high-fat diet. Additionally, our structure-based drug discovery research has led to AdipoR being identified as an entirely novel structure having a zinc iron bound within its seven-transmembrane domain as well as an opposite orientation to that of G protein-coupled receptors. It is expected that increasing insight into AdipoR signaling will facilitate the structure-based optimization of candidate small-molecule AdipoR-activating compounds for human use as well as the development of molecularly targeted and calorie-limiting/exercise-mimicking agents for lifestyle-linked diseases.