and luteinizing hormone may then stimulate ovarian cytochrome P450c17 activity.
二、胰岛素抵抗与PCOS
胰岛素及其受体的结构
❖ 胰岛素是胰腺Langerhans小岛上的β-细胞产生多 肽，由A链(21AAs)和B链(30AAs)构成。
胰岛素抵抗的机理(1)
❖ 受体与胰岛素的结合或者受体亲和力无改变
❖ 50% PCOS-ser : IR 酪氨酸磷酸化 或 IR 丝 氨酸磷酸化
❖ 50% PCOS-nl: IR下游信号传导受阻 (IRS-1 的磷酸化； PI3-K的活性 ）
胰岛素抵抗的机理（2）
Figure 9. The tyrosine-phosphorylated IR phosphorylates intracellular substrates, such as IR substrate (IRS)-1 and IRS-2, initiating signal transduction and the plieotropic actions of insulin. The activation of PI3-K (PI3-kinase) by tyrosinephosphorylated IRS-1 appears to be the pathway for insulin-mediated glucose transport. The Ras-MAP kinase pathway appears to regulate cell growth and glycogen synthesis.
Basal autophosphorylation is increased and there is minimal further insulinstimulated phosphorylation in the PCOS-ser b-subunits. The high basal phosphorylation represents phosphoserine, and phosphotyrosine content does not increase in response to insulin in the PCOS-ser b-subunits.
FIG.2. a normal (control), a PCOS woman with normal insulin-stimulated tyrosine phosphorylation (PCOS-nl) and a PCOS woman with high basal autophosphorylation on serine residues (PCOS-ser); S-serine, Y-tyrosine.
对患有PCOS的绝经后妇女，PCOS 及葡萄糖不耐 受的研究显示 PCOS-相关的胰岛素抵抗使患 NIDDM的危险显著增加。
雄激素能引起胰岛素抵抗?
❖降低雄激素水平不能完全恢复胰岛素敏感性。 ❖雄激素不引起或引起轻度胰岛素抵抗。
高胰岛素血症能引起高雄激素血症？
❖在PCOS病人，高胰岛素血症能增加雄激素水平。
胰岛素抵抗与多囊卵巢综合征
北京大学深圳医院生殖医学中心 李蓉
背景
❖ 1921年，Achard 和 Their首先发现糖代谢异 常与高雄激素血症有关;
❖ 1935年， Stein and Leventhal首先提出 PCOS;
❖ 1976年，Kahn 和同事发现高雄激素血症、胰 岛素抵抗和黑棘皮症有关;
❖胰岛素通过IR直接介导，而不是占据了IGF-I 受体。 ❖类固醇合成异常。 ❖降低胰岛素水平却未改变高雄激素 的异常。
FIG. 6 A single factor that causes serine phosphorylation of the IR and serine phosphorylation of P450c17, the key regulatory enzyme controlling androgen biosynthesis, could produce both the insulin resistance and the hyperandrogenism characteristic of PCOS. It is also possible that the insulin resistance and the reproductive abnormalities reflect separate genetic defects and that the insulin resistance unmasks the syndrome in genetically susceptible women. Recent studies suggest that insulin acting through its own receptor augments steroidogenesis and LH release. Androgens amplify the associated insulin resistance.
Figure 1. Possible Mechanisms of Insulin Stimulation of Ovarian Cytochrome P450c17 Activity and Androgen production. In theca cells, insulin may directly stimulate (plus signs) ovarian cytochrome P450c17 , resulting in increased 17 -hydroxylase and, to a lesser extent, 17,20-lyase activity. This would lead to increased production of androstenedione, which is then converted to testosterone by the enzyme 17 -reductase. Alternatively or in conjunction with this, insulin may stimulate ovarian androgen production indirectly by enhancing the amplitude of serum luteinizing hormone (LH) pulses,
一、胰岛素与卵巢功能的关系
❖胰岛素通过IGF-1受体刺激卵巢分泌雌激素，雄激素及 孕酮(细胞色素 p-450c 17α 17 α-羟化酶 )
❖胰岛素抑制肝脏分泌SHBG 雄激素的效应 ❖胰岛素抑制肝脏合成 IGFBP-1 IGF-1的效应 ❖同 Gn相互作用 ❖抑制卵泡的凋亡 闭锁 ❖上调 IGF-1受体
胰岛素抵抗的机理（3）
IR 丝氨酸磷酸化因子 IR 酪氨酸激酶抑制因子
膜糖蛋白 PC-1/TNF-a
抑制 IRigure 14. Insulin resistance in 50% of PCOS women appears to be secondary to a cell membrane-associated factor, presumably a serine/threonine kinase, that serine-phosphorylates the IR-inhibiting signaling. Serine phosphorylation of IRS-1 appears to be the mechanism for TNF -mediated insulin resistance. The membrane glycoprotein PC-1 also inhibits IR kinase activity, but it does not cause serine phosphorylation of the receptor. These are examples of a recently appreciated mechanism for insulin resistance secondary to factors regulating the receptor’s tyrosine kinase activity.
❖ 1980年，Burghen 首先提出PCOS与高雄激素 血症、高胰岛素血症有关;
Figure 2. Section of a polycystic ovary with multiple subscapular follicular cysts and stromal hypertrophy (left panel). At higher power (x100) islands of luteinized theca cells are visible in the stroma (right panel). This morphological change is called stromal hyperthecosis and appears to be directly correlated with circulating insulin levels.
FIG. 3. a striking increase in phosphoserine content and a marked decrease in insulin-stimulated phosphotyrosine content after mixing hIR with PCOS-ser lectin eluates as compared with mixing hIR with control lectin eluates or in the absence of mixing.
胰岛素受体α-亚单位
胰岛素受体β-亚单位的酪氨酸位点磷酸化