The Effect of Maternal Starvation on Plasma Insulin-Like Growth Factor I Concentrations in the Late Gestation Ovine Fetus

Abstract

ABSTRACT. In view of the suggested relationship between substrate availability, fetal growth and circulating fetal IGF-I concentrations, we investigated the effect of maternal starvation on plasma IGF-I levels in the late gestation ovine fetus. Ten fetuses aged 125-130 d gestation were sampled daily from indwelling arterial catheters. Ewes were starved for 72 h. Starvation was terminated with an intravenous infusion of 10% glucose to the ewe. Food was then replaced 4 h later. Fetal IGF-I concentrations fell from 176.1 2 15.2 ng/mL before starvation to 124.5 f 10.3 ng/mL after 72 h starvation (p < 0.05, n = 10). The fall in IGF-I concentrations was reversed by 4 h of maternal glucose infusion. In five fetuses, where samples were obtained 24 h after terminating the starvation, fetal IGF-I concentrations were comparable to those seen before starvation (180.0 + 37.7 ng/mL). This study demonstrates that acute maternal starvation causes a reversible decrease in fetal plasma IGF-I levels. These studies suggest that nutrient and in particular glucose availability is a significant determinant of fetal IGF-I secretion and support the hypothesis that IGF-I may play a role in the regulation of fetal growth. (Pediatr Res 27: 401-404, 1990) Abbreviations GH, growth hormoneThe role of IGF in fetal life remains speculative. However, limited evidence suggests that IGF-I may have an important role in the regulation of fetal growth. IGF-I levels in umbilical cord blood at delivery have been shown to correlate with birth wt in a number of species including the rat (1, 2), rabbit (3), sheep (4), cow (5), and man (6-8). Studies in the fetal guinea pig (9) and fetal sheep (10, 11) have demonstrated that chronic alterations in placental function leading to fetal growth retardation result in decreases in fetal IGF-I levels. Such studies suggest that substrate availability may play a role in regulating fetal IGF-I secretion and that IGF-I may be an endocrine regulator of fetal growth. T o further elucidate the role of nutritional factors in the acute regulation of fetal IGF secretion we investigated the effects of maternal starvation and refeeding on plasma IGF-I levels in the late gestation ovine fetus. MATERIALS AND METHODSAnimals and surgical procedures. Romney ewes time mated with Suffolk rams provided fetuses of known gestational ages for these studies. At 125-1 30 d gestation (term = 145 f 3 d) ewes were brought into the laboratory and allowed 4-5 to become acclimatized to laboratory conditions before undergoing surgery. Fetal vascular surgery was performed under sterile conditions using halothane anaesthetic. Vascular catheters were inserted into the fetal femoral artery and vein and into the maternal tarsal artery and vein to obtain regular blood samples. Fetus and mother were allowed 5 d postoperative recovery before commencing the experiment. Ewes were fed a mixture of chaffed hay, lucerne, and barley ad libitum with water freely available.Experimental protocol. Blood samples were collected in sterile preheparinized syringes...

Maternal undernutrition alters triiodothyronine concentrations and pituitary response to GnRH in fetal sheep

“…The absence of an effect of nutrition on fetal profiles of IGF-I and insulin contrasts with previous reports involving acute undernutrition/starvation during pregnancy (Schreiner et al 1980, Bassett et al 1990. This difference in response between experiments probably reflects the difference in the pattern of undernutrition, and highlights the different effects of acute and chronic undernutrition.…”

Nutritional Regulation of Circulating Insulin-like Growth Factors (IGFs) and Their Binding Proteins in the Ovine Fetus.

“…The circulating IGF-I levels in the fetus showed a similar response to maternal fasting as that seen in postnatal animals [19,20]. This was also observed in rat and other ovine maternal/fetal models [30][31][32].…”

Effects of placental insufficiency on the ovine fetal renin-angiotensin system

“…Acute hypoxia has been reported to stimulate the circulating RAS, although nothing is known about its effects on the fetal intrarenal RAS (Wood, 1995). Placental restriction also causes fetal hypoglycaemia (Phillips et al 1997), which is also associated with low levels of insulin-like growth factor-1 (IGF-1) levels (Bassett et al 1990;Owens et al 1994;Kind et al 1995). We have recently shown that exogenous infusions of IGF-1 stimulate the activity of the circulating RAS (Marsh et al 1998) and activate renin gene expression and synthesis (A.…”