Lipid-binding proteins and lipoprotein lipase activity in human skeletal muscle: influence of physical activity and gender

The protein and mRNA levels of several muscle lipid-binding proteins and the activity and mRNA level of muscle lipoprotein lipase (mLPL) were investigated in healthy, nonobese, nontrained (NT), moderately trained, and endurance-trained (ET) women and men. FAT/CD36 protein level was 49% higher (P<0.05) in women than in men, irrespective of training status, whereas FAT/CD36 mRNA was only higher (P<0.05) in women than in men in NT subjects (85%). Plasma membrane-bound fatty acid binding protein (FABP(pm)) content was higher in ET men compared with all other groups, whereas training status did not affect FABP(pm) content in women. FABP(pm) mRNA was higher (P<0.05) in NT women than in FT women and NT men. mLPL activity was not different between gender, but mLPL mRNA was 160% higher (P<0.001) in women than in men. mLPL activity was 48% higher (P<0.05) in ET than in NT subjects, irrespective of gender, in accordance with 49% higher (P<0.05) mLPL mRNA in ET than in NT subjects. A 90-min exercise bout induced an increase (P<0.05) in FAT/CD36 mRNA (similar to 25%) and FABP(pm) mRNA (similar to 15%) levels in all groups. The present study demonstrated that, in the NT state, women had higher muscle mRNA levels of several proteins related to muscle lipid metabolism compared with men. In the ET state, only the gender difference in mLPL mRNA persisted. FAT/CD36 protein in muscle was higher in women than in men, irrespective of training status. These findings may help explain gender differences in lipid metabolism and, furthermore, suggest that the balance between gene transcription, translation, and possibly breakdown of several proteins in muscle lipid metabolism depend on gender.