Abstract: Objective To investigate the influence of adding folic acid and vitamin B12 in maternal lactation on the expression of phosphatidylinositol 3-kinase(PI3K)in phosphatidyl inositol 3-kinse /protein kinase B (PI3K/AKT) insulin signaling pathway,and to analyze the relationship between the changes in the expression of the main molecules and the change in insulin resistance. Methods 1)To establish the model of insulin resistance index (IUGR) rats by low-protein (LP) and caloric restriction in the second and third trimester of pregnancy.IUGR newborn pups were randomly divided into IUGR intervention group and IUGR without intervention group.Lactating female rats of the intervention group were fed with high folate and vitamin B12 in the diet; Lactating female rats of without intervention group were fed normal diet.All of newborn pups were weaned at the 21st day after birth and then fed with normal diet to 120 days.2)On the 21st,60th and 120th day after birth,fasting plasma glucose (FPG) and fasting insulin (FINS) of the three groups were tested.IRI were calculated to evaluate insulin sensitivity.3)On the 21st,60th and 120th day after birth,skeletal muscle tissues were collected from rats of the three groups,phosphatidylinositol 3-kinase(PI3K) gene and protein expression levels were determined by using quantitative RT-PCR and western blotting. Results 1)Birth weights of LP offspring[(4.44±0.58)g] were significantly lower than those of NP ones[(7.03±0.56)g] (t=15.75,P<0.05).The incidence of IUGR in LP was 93.33%.2)On the 21st day after birth,FPG,FINS and IRI of the three groups showed no significant difference.On the 60th and the 120th day,FPG,FINS and IRI of IUGR in the intervention group were significantly lower than those of IUGR in non-intervention group,but were higher than those of the control group (all P <0.05).3)On the 21st,60th and 120th day,the levels of PI3K mRNA and protein expression were highest in the NP group and were lowest in IUGR without intervention group.They appeared significant difference in three groups(all P<0.05).4)On the 60th and 120th day,both IRI levels of IUGR without intervention group and the intervention group had a negative correlation with PI3K (both P<0.05). Conclusion Adding folic acid and vitamin B12 in maternal lactation has an impact on the expression of PI3K in IUGR rats,and these changes are closely correlated with insulin resistance.

Key words: intrauterine growth retardation, insulin resistance, folic acid, vitamin B12, PI3K

摘要： 目的 探讨母鼠哺乳期补充叶酸和维生素B12对宫内生长受限(IUGR)仔鼠骨骼肌磷脂酰肌醇3激酶的蛋白激酶B(PI3K/AKT)胰岛素信号通路中关键分子磷脂酰肌醇3激酶( PI3K)表达的影响,并分析PI3K分子表达的改变与胰岛素抵抗的关系。方法 1)采用孕中晚期低蛋白及限制饮食的方法建立IUGR大鼠模型,将新生IUGR仔鼠随机分为IUGR干预组和IUGR未干预组,其中IUGR干预组的哺乳期母鼠饲以高叶酸和维生素B12的饲料(叶酸和维生素B12含量比普通饲料提高4倍),IUGR未干预组和对照组的哺乳期母鼠饲以正常标准饲料。三组仔鼠均于生后21 d断奶,饲以正常标准饲料至生后120 d。2)测定对照组、IUGR未干预组及IUGR干预组(每组各8只,雌雄各半)在生后21、60 d及120 d空腹血浆血糖(FPG)、空腹血清胰岛素(FINS),计算胰岛素抵抗指数(IRI)。3)在生后21、60 d和120 d分别留取3组仔鼠的骨骼肌组织,采用Real-Time PCR和Western Blotting法检测三组仔鼠骨骼肌组织中PI3K mRNA和蛋白表达情况。结果 1)低蛋白组仔鼠平均出生体重[(4.44±0.58)g]低于对照组[(7.03±0.56) g],差异有统计学意义(t=15.75,P<0.05),低蛋白组仔鼠中IUGR发生率为93.3%。2)生后21 d,三组仔鼠FPG、FINS和IRI差异均无统计学意义(P>0.05);生后60 d和120 d,IUGR干预组仔鼠的FPG、FINS和IRI均显著低于IUGR未干预组,但均高于对照组,差异均有统计学意义(P值均＜0.05)。3)生后21 d、60 d和120 d,三组仔鼠PI3K mRNA和蛋白表达水平均在对照组最高,IUGR干预组次之,IUGR未干预组最低,差异均有统计学意义(P值均＜0.05)。4)生后60 d和120 d,IUGR未干预和干预组仔鼠IRI与PI3K蛋白表达均呈负相关(P值均<0.05)。结论 母鼠哺乳期补充叶酸和维生素B12,影响了IUGR仔鼠骨骼肌PI3K/AKT胰岛素信号通路中关键分子PI3K的蛋白表达,且这些变化与胰岛素抵抗密切相关。

关键词: 宫内生长受限, 胰岛素抵抗, 叶酸, 维生素B12, PI3K