Skeletal Muscle Myofiber Development in Non-Human Primate Offspring Deprived of Estrogen in Utero

Introduction: We previously showed that baboon offspring born to mothers deprived of estrogen during the second half of gestation exhibited insulin resistance prior to and after the onset of puberty. Moreover, the size of skeletal muscle myofibers and the number of microvessels important for delivery of insulin/glucose to myofibers were lower in near-term fetuses deprived of estrogen during pregnancy, and myofiber capillarization remained reduced in post-pubertal offspring deprived of estrogen in utero. However, it remains to be determined whether skeletal muscle size is restored to normal in animals deprived of estrogen in utero after the onset of puberty/gonadal estrogen production. Methods: To answer this question, the current study quantified the size and number of slow and fast fibers in biopsies of vastus lateralis skeletal muscle obtained from post-pubertal female baboon offspring 9–12 years old, born to mothers who were untreated (n = 7) or treated during the second half of gestation with letrozole (n = 6; suppressed maternal and fetal estrogen by >90%) or letrozole plus estradiol benzoate (n = 3). Results: Results indicated that skeletal muscle slow and fast fiber growth in female offspring appeared to occur by hypertrophy and that respective size of fibers after the onset of puberty was similar in offspring born to mothers who were untreated or deprived of estrogen in utero. Conclusions: Postnatal myofiber hypertrophy likely reflects the impact of the pubertal surge in and continued exposure of offspring myofibers to ovarian estrogen and is restored to normal in post-pubertal female offspring deprived of estrogen in utero.