Despite an increase in lipid oxidation ( P < 0.05 ) , testosterone therapy had no effect on insulin sensitivity or mRNA levels of genes involved in mitochondrial biogenesis ( PPARGC1A , PRKAA2 , and PRKAG3 ) , OxPhos ( NDUFS1 , ETFA , SDHA , UQCRC1 , and COX5B ) , or lipid metabolism ( ACADVL , CD36 , CPT1B , HADH , and PDK4 ) .