孕鼠叶酸缺乏对子鼠胰岛素样生长因子系统甲基化的影响

Effects of maternal folate deficiency on the methylation of insulin-like growth factor system in the offspring rats

目的观察孕期叶酸缺乏对胎鼠生长发育及胰岛素样生长因子(IGF)系统甲基化的影响。方法将22只Sprague-Dawley雌鼠随机分为叶酸缺乏组(n=12)和正常对照组(n=10),分别喂养叶酸缺乏饲料和普通饲料,2周后与雄鼠交配,两组各8只雌鼠成功受孕,于怀孕第20天对孕鼠剖腹取胎,每组取32只胎鼠测量其头尾长、体重。两组分别另取8只胎鼠,采用ELISA法对其脑、肝脏组织中的叶酸、IGF-1、胰岛素样生长因子结合蛋白(IGFBP)-3水平进行检测。两组分别另取3只胎鼠,使用全基因组甲基化测序方法检测其脑、肝脏组织IGF系统的甲基化情况。同时采用ELISA法对两组孕鼠血清IGF-1、IGFBP-3水平进行检测。结果叶酸缺乏组胎鼠头尾长、体重较正常对照组降低(P<0.05);叶酸缺乏组孕鼠血清IGF-1、IGFBP-3与胎鼠脑、肝脏组织中的叶酸、IGFBP-3水平均低于正常对照组(P<0.05);叶酸缺乏组胎鼠脑组织中IGF-1R、IGF-2R、IGFBP-2、IGFBP-5、IGFBP-6、IGFBP-7的甲基化水平均高于正常对照组(P<0.05);而在肝脏组织中,相比于正常对照组,叶酸缺乏组胎鼠IGF-1R、IGF-2R、IGFBP-3、IGFBP-5甲基化水平增加,IGF-2甲基化水平则下降(P<0.05)。结论孕鼠叶酸缺乏会影响胎鼠宫内的生长发育,其机制可能与胰岛素生长因子系统的甲基化异常有关。

Objective To study the effects of maternal folate deficiency on fetal growth and development and the methylation profiles of insulin-like growth factor system in the offspring rats. Methods Twenty-two Sprague-Dawley female rats were randomly assigned to two groups： a folate deficient group（n=12） and a control group（n=10）. They were fed with folate deficient and normal diet respectively. Dams were mated after 2 weeks of feeding. Eight female rats from each group were pregnant. On the 20 th day of gestation, the fetuses were delivered by caesarean section. Thirty-two fetal rats from each group were randomly selected and the body length and weight were measured. Eight fetal rats from each group were randomly selected and ELISA was used to measure the level of folate content, IGF-1 and IGFBP-3 in the fetal brain and liver. Three fetal rats from each group were randomly selected and methylated DNA immunoprecipitation sequencing（Me DIP-Seq） was used to detect the methylation level of insulin-like growth factor system in the fetal brain and liver. ELISA was used to measure the level of IGF-1 and IGFBP-3 in the maternal serum from both groups. Results The mean fetal length and weight were lower in the folate deficient group than in the control group（P0.05）. The levels of IGF-1 and IGFBP-3 in the maternal serum, as well as folate content and IGFBP-3 in the fetal brain and liver were significantly lower in the folate deficient group than in the control group（P0.05）. The methylation levels of IGF-1R, IGF-2R, IGFBP-2, IGFBP-5, IGFBP-6 and IGFBP-7 in the fetal brain were higher in the folate deficient groupthan in the control group（P0.05）. The methylation levels of IGF-1R, IGF-2R, IGFBP-3 and IGFBP-5 in the fetal liver were higher in the folate deficient group than in the control group. The methylation of IGF-2 gene showed a significant reduction in the folate deficient group（P0.05）. Conclusions Maternal folate deficiency may cause retardation of growth and development of the offspring, which is possibly associated with the changes of methylation profiles of insulin-like growth factors.