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Studies on the effectiveness of maternal dietary creatine to protect the fetal musculature from birth asphyxia
thesisposted on 2017-02-21, 23:09 authored by LaRosa, Domenic Anthony
Birth asphyxia is a significant problem, responsible for ~1.2 million deaths each year worldwide. Those who survive often suffer from a myriad of health issues including brain damage, manifesting as cerebral palsy (CP), respiratory insufficiency, and cardiovascular collapse. Although the majority of research is directed towards reducing the brain injury that results from birth asphyxia, the multi-organ effects observed in surviving neonates are of equal importance. Furthermore, the motor deficits observed in babies and children with CP, traditionally thought to be neural in origin, may have a muscular component which has not been investigated. Using our spiny mouse model of birth asphyxia, we previously reported damage to the brain and kidney, as well as structural and functional deficits in the diaphragm muscle. These deficits were prevented by supplementing the maternal diet with 5% creatine from mid-pregnancy. However, the effect of this model on the heart, as well as the potential involvement of the skeletal muscle in the motor deficits observed in this model have not been examined. Furthermore, the long-term effects of this exposure on all three muscle types are unknown. In these studies, pregnant spiny mice were fed control or 5% creatine-supplemented diet for the second half of pregnancy, and fetuses were delivered by caesarean section with or without 7.5 min of in-utero asphyxia. Surviving pups were raised by a cross-foster dam for 24 hours or 33±2 days of age when heart, diaphragm and hindlimb skeletal muscle were obtained for ex-vivo functional assessment, and for structural and molecular analyses. The major findings of this study were that, like the diaphragm, the hindlimb skeletal muscle exhibited significant structural changes immediately after birth asphyxia including a reduction in muscle fibre size in all three-muscle fibre types and a reduction in oxidative capacity. There were also significant reductions in fatigue resistance in male offspring, assessed ex-vivo at 24 h of age. We found persistent structural changes in the diaphragm and hindlimb skeletal muscles, including alterations in fibre type proportions, reductions in fibre size and decreased oxidative capacity. These changes corresponded to substantial functional deficits, with birth asphyxia animals exhibiting significantly reduced fatigue resistance in the diaphragm at 1 month of age and reduced aerobic endurance, assessed using the accelerating Rotarod test. Lastly, this model caused no significant short- or long-term molecular, structural or functional changes in the heart. Finally, we report that in the case of the hindlimb and diaphragm muscle, maternal creatine supplementation completely prevented all structural and functional changes observed in the immediate neonatal period and into later life. Furthermore, creatine did not result in any significant changes to normal muscle structure or function, thus highlighting this harmless dietary supplement as a potentially lifesaving preventative treatment for birth asphyxia induced muscular injury, and strengthening the body of evidence supporting the clinical translation of creatine for prevention of birth asphyxia in human pregnancy.