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Effects of Twinning and Periconceptional Undernutrition on Late-Gestation Hypothalamic-Pituitary-Adrenal Axis Function in Ovine Pregnancy

The Liggins Institute (C.W.H.R., M.H.O., E.B.T., A.L.J., J.E.H., F.H.B.), University of Auckland, Private Bag 92019, Auckland, New Zealand; and Department of Basic Animal and Veterinary Science (S.M.H.), University of Copenhagen, DK-1870 Frederiksberg C, Denmark

Address all correspondence and requests for reprints to: Dr. Frank Bloomfield, Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand. E-mail: f.bloomfield{at}auckland.ac.nz.

The relationships between reduced size at birth, increased activity of the hypothalamic-pituitary-adrenal (HPA) axis, and increased risk of disease in adulthood are well described in singletons but are much less clear in twins. This may be because the physiological processes underlying reduced size at birth are different in singletons and twins. Periconceptional undernutrition can cause altered activity of the fetal and postnatal HPA axis without altering size at birth. However, the independent effects of periconceptional undernutrition and twinning on activity of the maternal and fetal HPA axes are not well described. We therefore studied maternal and fetal HPA axis function during late gestation in twin and singleton sheep pregnancies, either undernourished around conception or fed ad libitum. We found that twinning led to suppressed baseline HPA axis function and decreased adrenal sensitivity to ACTH stimulation but increased fetal pituitary ACTH response both to direct stimulation by CRH (ACTH area under the curve response: 29.7 ± 2.2 vs. 17.1 ± 1.6 ng/min·ml, P < 0.01) and to decreased cortisol negative feedback. In contrast, periconceptional undernutrition resulted in a decreased pituitary response (ACTH area under the curve response: 19.4 ± 1.6 vs. 26.1 ± 2.2 ng/min·ml, P = 0.02) but no difference in adrenal response. Thus, the HPA axis function of twin sheep fetuses in late gestation is very different from that of control and undernourished singletons. If the HPA axis is an important mediator between fetal adaptations and adult disease, these data may help explain why the relationship between fetal growth and postnatal physiology and disease risk is inconsistent in twins.

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				C. W. H. Rumball, J. E. Harding, M. H. Oliver, and F. H. Bloomfield Effects of twin pregnancy and periconceptional undernutrition on maternal metabolism, fetal growth and glucose-insulin axis function in ovine pregnancy J. Physiol., March 1, 2008; 586(5): 1399 - 1411. [Abstract] [Full Text] [PDF]