Pregnancy

Late but Not Early Gestational Maternal Growth Hormone Treatment Increases Fetal Adiposity in Overnourished Adolescent Sheep

Abstract
In the overnourished adolescent sheep, maternal tissue synthesis is promoted at the expense of placental growth and leads to a major decrease in lamb birth weight at term. Maternal growth hormone (GH) concentrations are attenuated in these pregnancies and we have recently demonstrated that exogenous GH administration throughout the period of placental proliferation stimulates uteroplacental and fetal development at day 81 of gestation. The present study aimed to determine whether these effects persist to term and to establish whether GH influences fetal growth and body composition by increasing placental size or by altering maternal metabolism. Adolescent recipient ewes were implanted with singleton embryos on day 4 post- oestrus. Three groups of ewes offered a high (H) dietary intake were either injected twice daily with recombinant bovine GH (bGH) from day 35 to 65 (H + early GH) or day 95 to 125 (H + late GH) of gestation or remained untreated (H). A fourth moderate intake group acted as optimally nourished controls (C). Pregnancies were either terminated at day 130 of gestation (n=6 / group) or allowed to progress to term (n= 8-10 / group). GH administration elevated maternal GH, insulin, glucose and non-esterified fatty acid (NEFA) concentrations during the defined treatment windows, while urea concentrations were decreased. At day 130, bGH treatment reduced maternal adiposity score, the percentage fat in the carcass, internal fat depots and leptin concentrations, predominantly in the H + late GH group. Placental weight was lower in H versus C dams but independent of bGH treatment. In contrast fetal weight was elevated by late GH treatment and these fetuses had higher relative carcass fat content, perirenal fat mass and liver glycogen concentrations than all other groups. Fetal perirenal fat leptin mRNA expression and circulating fetal leptin concentrations were not significantly altered by maternal nutritional intake or bGH. In pregnancies proceeding to term, the duration of gestation, fetal placental mass and lamb birth weight were reduced in H compared with C dams but were not significantly affected by bGH treatment. In conclusion, exogenous bGH has profound effects on maternal endocrinology, metabolism and body composition when administered during both early and late pregnancy. Treatment during late pregnancy has a modest effect on fetal growth independent of placental size and a profound effect on fetal adiposity, which may have implications beyond the fetal period.

Key words: Mechanisms of Hormone Action • Pregnancy • Conceptus • Growth hormone • Placenta

This article has been cited by other articles:

				C. D Wright, R. J Orbus, T. R H Regnault, and R. V Anthony Effects of early gestation GH administration on placental and fetal development in sheep J. Endocrinol., July 1, 2008; 198(1): 91 - 99. [Abstract] [Full Text] [PDF]

				R. G Lea, P. Wooding, I. Stewart, L. T Hannah, S. Morton, K. Wallace, R. P Aitken, J. S Milne, T. R Regnault, R. V Anthony, et al. The expression of ovine placental lactogen, StAR and progesterone-associated steroidogenic enzymes in placentae of overnourished growing adolescent ewes Reproduction, April 1, 2007; 133(4): 785 - 796. [Abstract] [Full Text] [PDF]