胰岛素受体底物1表达及其酪氨酸磷酸化与妊娠期糖尿病患者胰岛素抵抗的关系

目的探讨骨骼肌组织中胰岛素受体底物1（IRS-1）表达及其酪氨酸磷酸化与妊娠期糖尿病发生胰岛素抵抗的关系。方法采用蛋白印迹法（western blot）及免疫沉淀法检测22例妊娠期糖尿病患者（妊娠期糖尿病组）、22例正常妊娠妇女（正常妊娠组）及13例正常非孕妇女（正常非孕组）骨骼肌组织中IRS-1蛋白表达水平及其酪氨酸磷酸化程度;采用放射免疫法及葡萄糖氧化酶法检测各组妇女空腹胰岛素（FINS）及空腹血糖（FPG）水平,并采用稳态模型法计算胰岛素抵抗指数（HOMA—IR）。结果（1）妊娠期糖尿病组FPG、FINS、HOMA—IR分别为（5．6±0．8）mmol／L、（15．4±5．1）mU／L、1．2±0．5,正常妊娠组分别为（4．4±0．5）mmol／L、（10．6±3．1）mU／L、0．8±0．3,两组间各指标分别比较,差异均有统计学意义（P〈0．01）;正常非孕组FINS、HOMA—IR分别为（7．6±2．3）mU／L、0．5±0．3,分别与正常妊娠组比较,差异均有统计学意义（P〈0．01）。（2）妊娠期糖尿病组IRS．1蛋白表达水平为0．64±0．11,明显低于正常妊娠组的0．81±0．13,两组分别比较,差异均有统计学意义（P〈0．01）;正常非孕组IRS-1蛋白表达水平为0．83±0．12,与正常妊娠组比较,差异无统计学意义（P〉0．05）。（3）妊娠期糖尿病组基础及胰岛素刺激后的IRS-1酪氨酸磷酸化程度分别为0．35±0．12及0．48±0．14,均低于正常妊娠组的0．38±0．13及0．66±0．12,两组分别比较,差异均有统计学意义（P〈0．01）;正常妊娠组胰岛素刺激后的IRS．1酪氨酸磷酸化程度明显低于正常非孕组的0．85±0．09（P〈0．01）。（4）妊娠期糖尿病组IRS-1蛋白表达水平和胰岛素刺激后的酪氨酸磷酸化程度与HOMA-IR呈明显负相关（r=-0．613,-0．632;P〈0．01）;正常妊娠组胰岛素刺激后酪氨酸磷酸化程度与HOMA—IR呈明显负相关（r=-0．526,P〈0．05）。结论骨骼肌组织中IRS-1蛋白表达及其酪氨酸磷酸化程度异常,是妊娠期糖尿病患者发生胰岛素抵抗的分子机制之一。

Relationship between tyrosine phosphorylation and protein expression of insulin receptor substrate-1 and insulin resistance in gestational diabetes mellitus

OBJECTIVE: To study the relationship between tyrosine phosphorylation (TP) and protein expression of insulin receptor substrate-1 (IRS-1) and insulin resistance in patients with gestational diabetes mellitus (GDM). METHODS: IRS-1 expression and TP in skeleton muscle tissue were determined by Western blot and immunoprecipitation in women with GDM (GDM group, n=22), normal pregnant women (normal pregnancy group, n=22) and normal nonpregnant women (normal nonpregnant group, n=13). Fasting plasma glucose (FPG) and fasting insulin (FINS) were measured by oxidase assay and immunoradioassay. RESULTS: (1) The levels of FPG, FINS, and insulin resistance index were calculated according to homeostasis model assessment HOMA-IR; (5.6 +/- 0.8) mmol/L, (15.4 +/- 5.1) mU/L, and 1.2 +/- 0.5] in GDM group were significantly higher than those in normal pregnancy group (4.4 +/- 0.5) mmol/L, (10.6 +/- 3.1) mU/L, and 0.8 +/- 0.3; P<0.01]. The levels of FINS and HOMA-IR in normal pregnancy group were significantly higher than those in normal nonpregnant group (7.6 +/- 2.3) mU/L and 0.5 +/- 0.3; P<0.01]. (2) The level of IRS-1 protein expression in GDM group (0.64 +/- 0.11) was lower than that in normal pregnancy group (0.81 +/- 0.13; P<0.01). (3) TP with and without insulin stimulation (0.48 +/- 0.14, and 0.35 +/- 0.12) decreased in GDM group, compared with normal pregnancy group (0.66 +/- 0.12, and 0.38 +/- 0.13; P<0.01). TP with insulin stimulation in normal pregnancy group was lower than that in normal nonpregnant group (0.85 +/- 0.09; P<0.01). (4) Protein expression and TP with insulin stimulation of IRS-1 was negatively related to HOMA-IR in GDM group (r=- 0.613, -0.632; P<0.01), and TP with insulin stimulation was negatively related to HOMA-IR in normal pregnancy group (r=-0.526, P<0.05). CONCLUSION: Changes in protein expression and tyrosine phosphorylation of IRS-1 in skeletal muscle may be one of the molecular mechanisms leading to insulin resistance in patients with GDM.