OBJECTIVETo understand the influence of angiotensin converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and beta3-adrenergic receptor (beta3-AR) gene Trp64Arg polymorphism on fetal growth and neonatal insulin sensitivity.

METHODSTotally 296 newborn infants were selected into our study and divided into 2 groups according to gestational age and birth weight: adequate-for-gestational-age (AGA) group (222 cases) and small-for-gestational-age (SGA) group (74 case). Serum glucose and insulin were examined in the morning of the 3rd day before milk. Insulin sensitivity was evaluated by homeostasis model assessment (HOMA) equation. beta3-AR gene Trp64Arg polymorphism and ACE gene I/D polymorphism (202 cases) were analysed using polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) technique. Gestational age, birth weight, birth weight percentage, serum glucose, insulin and HOMA-IR were compared among different genotype groups. Statistical analysis was performed with the SPSS 10.0 software.

RESULTSNo significant difference was found between the serum glucose level of SGA group (4.03 +/- 1.05 mmol/L) and AGA group (4.05 +/- 1.14 mmol/L), P = 0.008. The serum insulin level (converted into Ln) of SGA group (2.262 +/- 0.746) was significantly higher than that of AGA group (1.757 +/- 0.805), P < 0.001. The HOMA-IR (also converted into Ln) level of SGA group (0.217 +/- 0.367) was also significantly higher than that of AGA group (0.001 +/- 0.378), P < 0.001. In the SGA group beta3-AR gene Arg64 allele carriers had higher serum insulin and HOMA-IR level (both changed to Ln, 2.654 +/- 0.701, 0.371 +/- 0.338) compared with noncarriers (2.074 +/- 0.698, 0.143 +/- 0.360), P < 0.05. The ACE gene DD genotype carriers had higher serum insulin and HOMA-IR level (both were converted into Ln, 2.19 +/- 0.91, 0.51 +/- 1.01) compared with II (1.77 +/- 0.85, 0.02 +/- 0.93) and ID genotype group (1.77 +/- 0.83, 0.05 +/- 0.91), P < 0.05. The ACE gene DD carriers had lower birth weight percentage compared with II and ID genotype group, P < 0.05. When both genes' polymorphisms were taken into account, the newborns who had both DD genotype and Arg64 allele had obviously higher serum insulin level (Ln, 2.560 +/- 1.160) than the neonates who had only one of the polymorphisms mentioned above (1.970 +/- 0.821, 1.992 +/- 0.706) and the neonates who had neither of the two polymorphisms (1.683 +/- 0.832), P < 0.05. The newborns who had both DD genotype and Arg64 allele also had significantly higher HOMA-IR level (Ln, 1.042 +/- 1.315) than the neonates who had only one of the polymorphisms mentioned above (0.247 +/- 0.710, 0.230 +/- 0.890) and the neonates who had neither of the two polymorphisms (-0.053 +/- 0.924), P < 0.05.

CONCLUSIONNewborns SGA had impaired insulin sensitivity. beta3-AR gene Trp64Arg polymorphism and ACE gene I/D polymorphism are important factors that may connect IUGR with insulin resistance syndrome in adulthood.