The total activity of PGC-1α was found to be decreased in skeletal muscle-specific AdipoR1-deficient mice to one-fourth that seen in normal mice, with decreases also found in mitochondrial mass and function and in proportion of type I muscle fibers, which led not only to decreased exercise endurance but to impaired glucose tolerance and insulin resistance at the organism-level (56). This evidence concerns the gene ADIPOR1 and Insulin resistance.