The Changes Of IGF-â…¡ And Growth-Associated Factors In Small For Gestational Age Infants

PART One:The Role of IGF-Ⅱ and Methylation Regulation In Small for Gestational Age InfantsObjectives:Low birth weight is associated with an increased risk of adverse outcome in many diseases in adult life. The imprinted genes, Insulin-like growth factor Ⅱ (IGF-Ⅱ) and H19played important roles in fetal and postnatal growth. We investigated the role of IGF-Ⅱ and the differentially methylated regions (DMR) status in small for gestational age (SGA) infants after birth. Methods:Plasma IGF-Ⅱ, IGF2receptor (IGF2R), IGF-and IGF binding protein (IGFBP3) were measured within24-48hours after birth in150newborn babies, including30term appropriate for gestational age (AGA),30term SGA,30term large for gestational age (LGA),30preterm AGA and30preterm SGA infants. H19and IGF-Ⅱ mRNA level were quantified by fluorescence quantitative PCR. Methylation status of HI9DMR and IGF2DMR2were assessed by using methylation specific PCR (MSP) in these infants. Plasma IGF-Ⅱ, IGF2R, IGF-Ⅰ and IGFBP3were measured by ELISA in different AGA infants (≤30,31-33,34-36,37-39,40-42weeks) and term AGA infants at different days (D1, D7, D14, D21, D28). Results:Plasma IGF-Ⅱ level after birth was lower in both term SGA (435.1±33.82vs620.4±44.79, P=0.002) and LGA infants (483.7±33.8vs620.42±44.79, P=0.018) compared to term AGA infants. There was no difference in IGF-Ⅱ level between preterm SGA and preterm AGA (P=0.182). Plasma IGF-Ⅱ level after birth was lower in term SGA compared with preterm SGA infants (435.11±33.82vs619.07±44.58, P=0.002). There was a significant difference in IGF-Ⅱ mRNA between preterm SGA and preterm AGA infants (P=0.024) as well as between term SGA and preterm SGA infants (P=0.029). H19DMR and IGF2DMR2maintained the differential methylation status seen in most other tissues. The level of H19DMR methylation was higher in both term SGA (P=0.044) and term LGA infants (P=0.027) compare to term AGA infants. There was significant difference of H19DMR methylation between preterm SGA and preterm AGA infants as well (P=0.044). The level of IGF2DMR2methylation was higher in term SGA than preterm SGA infants (P=0.037). There was no significant change in IGF-Ⅱ between different gestational age infants, although the levels of IGF-Ⅱ and IGF-Ⅰ increased gradually during neonatal period. IGF-Ⅱ was at highest level in all these growth factors measured after birth. Conclusions:IGF-Ⅱ was associated with birth weight and expressed at high level which may continue to play an important role after birth. The methylation level of H19DMR is opposite to the level of IGF-Ⅱ in term infants after birth, which suggested the methylation of H19DMR may be involved in controlling IGF-Ⅱ expression. PART Two:Ghrelin and Obestatin Levels with Polymorphisms of the Ghrelin/Obestatin Gene in Small for Gestational Age InfantsObjectives:The preproghrelin (ghrelin/obestatin) gene encodes two peptides, ghrelin and obestatin, which have opposite effects on development and energy balance. We investigated the role of ghrelin and obestatin with polymorphisms of preproghrelin in small for gestational age (SGA) infants. Methods:Plasma ghrelin, obestatin and leptin were measured after birth in150newborn babies, including30term appropriate for gestational age (AGA),30term SGA,30term large for gestational age (LGA),30preterm AGA and30preterm SGA infants. The same factors were measured by ELI S A in different AGA infants (<30,31-33,34-36,37-39,40-42weeks) and term AGA neonates at different days (D1, D7, D14, D21, D28). Three single nucleotide polymorphisms (SNPs)(Arg51Gln, Leu72Met, Gln90Leu) were measured by TaqManTM technology in496neonates admitted from Jan. in2009to Dec. in2010including150neonates above. Results:The levels of ghrelin, obestatin and leptin were lower during neonatal period. There was no difference in ghrelin between any groups. Plasma obestatin was higher in term SGA compared with term LGA (213.46±15.62vs166.33±10.02, P=0.014) as well as term SGA with late preterm SGA (P=0.026). The level of obestatin was higher in preterm SGA infants at D7than at D1(P=0.008). Howerer, the level of leptin was higher in preterm SGA infants at D1than D7(P=0.002) as well as preterm AGA infants at D1than D7(P=0.013). There were no significant changes of ghrelin, obestatin and leptin between different gestational age infants. The level of obestatin increased gradually during the neonatal period. However, the ghrelin/obestatin ratio and leptin levels decreased during the same time. There was no significant difference in Arg51Gln, Leu72Met, Gln90Leu genotypes and allele frequency between term SGA and term AGA neonates as well as preterm SGA and preterm AGA neonates. Conclusions:The level of ghrelin, obestatin and leptin were lower after birth. There were opposite changes of obestatin and leptin in SGA at different days, which suggested they may be involved in growth after birth. There were no ghrelin/obestatin polymorphisms which might contribute to SGA infants. The role of all these factors on development need to be further investigated.