Despite an increase in lipid oxidation ( P < @ ) , testosterone therapy had no effect on insulin sensitivity or mRNA levels of genes involved in mitochondrial biogenesis ( PPARGC@A , PRKAA@ , and PRKAG@ ) , OxPhos ( NDUFS@ , ETFA , SDHA , UQCRC@ , and COX@B ) , or lipid metabolism ( ACADVL , CD@ , CPT@B , HADH , and PDK@ ) .