Abstract: Objectives To analyze the relationship between homocysteine (Hcy) and insulin resistance in rats with intrauterine growth restriction,to discuss the possibility of affecting Hcy level by changing early diet,therely influencing insulin sensitivity,and to explore possible molecular mechanisms. Methods 1)The model of intrauterine growth retardation(IUGR) rats was established by low-protein and caloric restriction in the second and third trimester of pregnancy.IUGR newborn pups were randomly divided into dietary intervention group and non-intervention group.Lactating female rats of dietary intervention group were fed with high folate and vitamin B₁₂. Lactating female rats of non-intervention group were fed with normal diet.All of newborn pups were weaned on the 21st day after birth and then fed with normal diet to 120 days.2)On the 120th day after birth,fasting plasma gluoose(FPG),fasting insulin (FINS)and Hcy of the rats in three groups were measured.Insulin resistance index(IRI) were calculated to evaluate insulin sensitivity.The relationship between Hcy and IRI was disscussed.3)On the 120th day after birth,skeletal muscle tissues were collected from rats of the three groups,phosphatidylinositol 3-kinase(PI3K) and phosphatase and tension homologuedeleted on chromosome 10(PTEN)protein expression levels in phosphatidyl inositol 3-kinse /protein kinase B (PI3K/AKT) insulin signaling pathway were determined by using western blotting.The relationship between Hcy and protein expression was disscussed. Results 1)On the 120th day,FPG,FINS,IRI and Hcy levels in dietary intervention group were significantly lower than those in non-intervention group,but were higher than those in control group (P<0.05).2)The Hcy level of the three groups was highly positively correlated with IRI (r=0.937,P<0.05).3)On the 120th day,Hcy was negatively correlated with PI3K protein expression(r=-0.88) and positively correlated with PTEN protein expression(r=0.85) in IUGR rats,both of which were statistically significant (P<0.05). Conclusions Maternal lactation can serve as a window period for early postnatal nutrition intervention.Supplementation with folic acid and vitamin B₁₂ can reduce the Hcy level of IUGR offspring Meawhite,Hcy level is highly positively correlated with insulin resistance,and the change of Hcy is closely related to the expression of key molecules in the PI3K/AKT insulin signaling pathway in the skeletal muscle of IUGR offspring.

Key words: homocysteine, intrauterine growth retardation, insulin resistance, PI3K/AKT signaling pathway

摘要： 目的 分析同型半胱氨酸(Hcy)与宫内生长受限(IUGR)大鼠胰岛素抵抗关系,探讨改变早期膳食是否可影响Hcy水平进而影响胰岛素敏感性及可能的分子机制。方法 1)采用孕中晚期低蛋白及限制饮食的方法建立宫内发育迟缓(IUGR)大鼠模型,将新生IUGR仔鼠随机分为饮食干预组和未干预组,其中饮食干预组的哺乳期母鼠饲以高叶酸和维生素B₁₂的饲料,未干预组和对照组饲以普通饲料。三组仔鼠(饮食干预组、未干预组和对照组)均于生后21 d断奶,饲以普通饲料至生后120 d。2)测定三组仔鼠(每组各8只,雌雄各半)生后120 d空腹血浆血糖(FPG)、空腹血清胰岛素(FINS)和Hcy,计算胰岛素抵抗指数(IRI),探讨Hcy与IRI的关系。3)在生后120 d分别留取三组仔鼠的骨骼肌组织,采用Western Blotting法检测三组仔鼠骨骼肌组织骨骼肌磷脂酰肌醇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)、人第10号染色体缺失的磷酸酶及张力蛋白同源基因(PTEN)蛋白表达情况,探讨Hcy与关键分子蛋白表达的关系。结果 1)生后120 d,饮食干预组仔鼠的FPG、FINS、IRI和Hcy均显著低于未干预组,但均高于对照组,差异均有统计学意义(P＜0.05)。2)三组仔鼠的Hcy水平与IRI呈高度正相关(r=0.937,P<0.05)。3)生后120 d,Hcy与PI3K蛋白表达呈负相关(r=-0.88),与PTEN蛋白表达呈正相关(r=0.85),均具有统计学意义(P<0.05)。结论 母鼠哺乳期可作为生后早期营养干预的一个窗口期,通过补充叶酸和维生素B₁₂,可降低IUGR仔鼠成年后Hcy水平,Hcy水平与胰岛素抵抗高度正相关。PI3K/AKT胰岛素信号通路中关键分子PI3K、PTEN蛋白表达与Hcy的变化也密切相关,提示Hcy可能影响了胰岛素受体后信号传导,进而影响了胰岛素的敏感性。

关键词: 同型半胱氨酸, 宫内生长受限, 胰岛素抵抗, PI3K/AKT信号通路