title: Early treatment of the pregnant guinea pig with IGFs promotes placental transport and nutrient partitioning near term.
abstract: Appropriate partitioning of nutrients between the mother and conceptus is a major determinant of pregnancy success, with placental transfer playing a key role. Insulin-like growth factors (IGFs) increase in the maternal circulation during early pregnancy and are predictive of fetal and placental growth. We have previously shown in the guinea pig that increasing maternal IGF abundance in early to midpregnancy enhances fetal growth and viability near term. We now show that this treatment promotes placental transport to the fetus, fetal substrate utilization, and nutrient partitioning near term. Pregnant guinea pigs were infused with IGF-I, IGF-II (both 1 mg.kg-1.day-1) or vehicle subcutaneously from days 20-38 of pregnancy (term=69 days). Tissue uptake and placental transfer of the nonmetabolizable radio analogs [3H]methyl-D-glucose (MG) and [14C]aminoisobutyric acid (AIB) in vivo was measured on day 62. Early pregnancy exposure to elevated maternal IGF-I increased placental MG uptake by>70% (P=0.004), whereas each IGF increased fetal plasma MG concentrations by 40-50% (P<0.012). Both IGFs increased fetal tissue MG uptake (P<0.048), whereas IGF-I also increased AIB uptake by visceral organs (P=0.046). In the mother, earlier exposure to either IGF increased AIB uptake by visceral organs (P<0.014), whereas IGF-I also enhanced uptake of AIB by muscle (P=0.044) and MG uptake by visceral organs (P=0.016) and muscle (P=0.046). In conclusion, exogenous maternal IGFs in early pregnancy sustainedly increase maternal substrate utilization, placental transport of MG to the fetus, and fetal utilization of substrates near term. This was consistent with the previously observed increase in fetal growth and survival following IGF treatment.
authors.affiliation: Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA, Australia 5005.
authors.forename: Amanda N
authors.initials: AN
authors.lastname: Sferruzzi-Perri
authors.forename: Julie A
authors.initials: JA
authors.lastname: Owens
authors.forename: Prue
authors.initials: P
authors.lastname: Standen
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Taylor
authors.forename: Gary K
authors.initials: GK
authors.lastname: Heinemann
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Robinson
authors.forename: Claire T
authors.initials: CT
authors.lastname: Roberts
mesh_terms: D000621:Aminoisobutyric Acids / Q000493:pharmacokinetics; D000818:Animals; D001692:Biological Transport; D005260:Female; D020567:Fetal Weight / Q000187:drug effects; D005502:Food; D005865:Gestational Age; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects / Q000196:embryology; D008098:Litter Size / Q000187:drug effects; D008431:Maternal-Fetal Exchange / Q000187:drug effects*; D008757:Methylglucosides / Q000493:pharmacokinetics; D010920:Placenta / Q000033:anatomy & histology / Q000187:drug effects / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects; D013002:Somatomedins / Q000494:pharmacology*; D047929:Term Birth
chemical_list: D000621:Aminoisobutyric Acids; D008757:Methylglucosides; D013002:Somatomedins; C027020:methylglucoside