Influence of Insulin-Like Growth Factor I and Nutrition During Phases of Postnatal Growth in Very Preterm Infants

Abstract

Pronounced growth restriction (GR) occurs after very preterm birth. The interaction between IGF-I, nutritional intake, and growth was evaluated prospectively in 64 infants with a mean (SD) GA of 25.7 (1.9) wk. Blood sampling of IGF-I and measurements of weight, length, and head circumference were performed weekly until discharge. Daily calculation of nutritional intake was performed. Standard deviation scores (SDSs) for growth parameters defined two growth phases: GR phase (birth until lowest SDS) and catch-up (CU) phase (lowest SDS until 35 gestational weeks). IGF-I concentrations during the first postnatal weeks were low and increased at 30 wk GA, irrespective of GA at birth, coinciding with initiation of CU growth. Concentrations of IGF-I were positively associated with change in weight SDS during the GR phase, p ϭ 0.001 and CU phase, p ϭ 0.004 -0.027. Protein and energy intake were not associated with change in SDS weight during the GR phase as opposed to the CU phase (p Ͻ 0.001, respectively). Nutritional intake did not correlate to concentrations of IGF-I before 30 wk GA. IGF-I is associated with growth at an earlier postnatal age than nutrient intake and the effect of nutrition on levels of IGF-I may be restricted to the period of established CU growth. T he maximum growth rate of the fetus is reached in the middle of pregnancy, where it is approximately three times higher than at term (1). Fetal growth rate is to a large extent determined by placental capacity of delivering nutrients to the fetus, whereas genetic influence seems to play a less important role. Placental function depends on the maternal nutritional state and the intrauterine endocrine environment. At preterm birth, the fetal-placental interaction is interrupted, which has an impact on continued extrauterine growth capacity. Postnatal growth retardation occurs almost inevitably after preterm birth and has been associated with decreased brain volumes and impaired neurodevelopmental outcome (2,3). Although attempts are made to optimize postnatal nutritional intakes in preterm infants, these are still commonly suboptimal according to intrauterine requirements (4). Increased postnatal nutritional intake has been shown to improve growth rate in very LBW infants (5), although a recent study could not demonstrate any apparent effect of hyperalimentation on subsequent postnatal growth in very preterm infants (6).IGF-I is an important fetal growth factor, which is essential for the developing brain (7). Concentrations of fetal IGF-I are closely related to placental transfer of glucose where fetal glucose increases insulin secretion, which in turn stimulates fetal IGF-I production (8). Fetal levels of IGF-I may also be regulated by an interaction at the feto-maternal placental interface (9). The disruption of placental nutrient supply after birth is followed by a rapid decrease in postnatal levels of IGF-I, suggesting a low endogenous production (10). While term infants restore their IGF-I levels within the first postnatal weeks, very prete...

Bone and fat mass in relation to postnatal levels of insulin-like growth factors in prematurely born children at 4 y of age

“…Circulating IGF-I has also been suggested to regulate adipose tissue growth and the differentiation of preadipocytes into adipocytes (18). The influence or effect of IGF-II has been more difficult to establish, though IGF-II mutations seem to affect lean mass and fat mass distribution in pigs (19).Circulating IGF-I and IGFBP-3 reflect the short-term growth velocity in very-low-birth-weight infants (20,21). In healthy pregnancies, cord serum IGF-I levels are related more to the size of the skeleton than to the degree of mineralization (17).…”

“…Circulating IGF-I and IGFBP-3 reflect the short-term growth velocity in very-low-birth-weight infants (20,21). In healthy pregnancies, cord serum IGF-I levels are related more to the size of the skeleton than to the degree of mineralization (17).…”

Dietary proteins and IGF I levels in preterm infants: determinants of growth, body composition, and neurodevelopment

“…In line with that, Okuma et al found that IGF I levels were associated with white matter organization (42). Interestingly, mean IGF I concentration was positively correlated to neurodevelopmental outcome during a period, from 30 to 35 wk postmenstrual age, when a surge in IGF I levels occurred and infants started growing after a phase of postnatal growth restriction (14,39). This may suggest that IGF I has to reach a certain level before it can enhance neurodevelopmental outcome.…”

“…Until term age, these infants IGF I levels' are also positively correlated with their preceding as well as their subsequent weight gain, indicating higher previous as well as higher subsequent growth rate in those infants with higher IGF I levels (14).…”

“…After preterm birth, IGF I levels slowly increase (14). Meanwhile, infants born at term show a quick surge in IGF-I levels (15).…”