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Stronger muscles for newborn babies
A frequent and significant problem in neonates is poor growth following premature birth. "A condition for which causes, optimal management and long-term consequences are still not completely understood," says Marta Fiorotto PhD, associate professor of pediatrics-nutrition and of molecular physiology and biophysics at the USDA/ Children's Nutrition Research Center at Baylor College of Medicine and Texas Children's Hospital.
"It is important to know how muscles are affected in the fetus because we need muscles to breathe, to eat and swallow and to move," Fiorotto adds. "If those muscles are compromised in any way during fetal development, those functions are also likely to be compromised in the newborn baby and affect his or her growth." Her paper is published in the Journal of Endocrinology.
"Lack of proper nutrition, a form of stress, in an expectant woman raises the levels of cortisol in her blood," says Fiorotto, also director of the Mouse Metabolic Research Unit at the USDA/ARS Children's Nutrition Research Center at Baylor and Texas Children's Hospital. But is it the lack of proper nutrition during pregnancy itself or the exposure to increased levels of glucocorticoids that affect fetal growth?
Dr. Ganga Gokulakrishnan, a neonatologist at Texas Children's Hospital and assistant professor at Baylor College of Medicine working with Dr. Fiorotto, investigates how glucocorticoids affect the growth of fetal muscles in the rat.
"You can think of a muscle as a bundle of uncooked spaghetti; each spaghetti is a fiber - a single muscular cell - with many nuclei in a matrix of protein," Gokulakrishnan explains. "The number of fibers is already determined by birth and does not increase during postnatal life. So, postnatally, muscles grow by adding both more protein and more nuclei to the fibers. Nuclei are added by muscle stem cells — also called satellite cells — that divide and fuse with the fibers. These muscle stem cells drive muscle growth during fetal development. After puberty, however, the muscles stop accumulating nuclei and grow by adding only protein to the fibers."
"We were surprised at the magnitude of impairment we observed in the replication of satellite cells in the muscles of fetal rats exposed to glucocorticoids," said Gokulakrishnan. "Taking all the results together, we found that the effect of glucocorticoids on fetal muscle growth is quite complex; it depends on the duration, the level of glucocorticoids and the time during pregnancy when it occurs."
"However, our results from the current study indicate that treating rats with a dose of glucocorticoids that mimics more severe food restriction affects the reserve of satellite cells, the accumulation of nuclei in the fibers, and therefore, muscle growth," Gokulakrishnan said.
The health of future generations starts with the health of the mother.
Gokulakrishnan continues: "Conditions such as stress or malnutrition are factors that could be identified and mitigated by prenatal care. Once again emphasizing the importance of a proper diet and antenatal care for all pregnant mothers."
Received 9 August 2016; Received in final form 12 December 2016; Accepted 17 January 2017;
Xiaoyan Chang and Ryan Fleischmann at Baylor also contributed to this work.
This work is a publication of the USDA/ARS Children's Nutrition Research Center and the Department of Pediatrics at Baylor College of Medicine.
Is it the lack of proper nutrition during pregnancy, or the exposure to