肌醇有益于哪些方面

肌醇在体内的作用非常广泛，它在构建细胞膜的过程中是必不可少的，三磷酸肌醇参与细胞钙离子信号的调控，是体内多种激素，包括胰岛素、促甲状腺激素（TSH）、促卵泡生成素（FSH）等的第二信使。

Myo-肌醇增强葡萄糖摄取，减少脂肪组织中游离脂肪酸的释放[1]。D-手性肌醇增强糖原合酶活性，在糖原沉积较多的组织，比如肝脏或骨骼肌中，D-手性肌醇的可用性会显著增加。D-手性肌醇还可以增加IRS2、PI3K和AKT的mRNA和蛋白质表达，上调P-AKT蛋白的水平，下调GSK3β蛋白的水平，所有这些都是胰岛素和其他激素信号转导的关键参与者。通过这些机制，Myo-肌醇和D-手性肌醇可以发挥胰岛素增敏作用，从而降低胰岛素需求[2]。

补充肌醇可以增加胰岛素敏感性，有助于改善空腹血糖和餐后血糖控制[19-20]，它可能有助于预防或治疗糖尿病，对一些与糖代谢相关的疾病可能发挥有益的治疗作用，包括代谢综合征，超重，肥胖以及妊娠糖尿病[3-6]。

一项研究中，比较了肥胖PCOS myo-Ins与d-chiro-Ins联合治疗的体重减轻，与单独饮食相比，治疗会加速体重减轻[3]。相关试验证明[4,5]，myo-Ins可以降低GDM发生率，改善妊娠期血糖、血脂和胰岛素抵抗参数，以及在GDM较晚发展时减少对胰岛素治疗的需求。另一项小型研究表明[6]，肌醇可能有助于治疗绝经后妇女的代谢综合征。当用肌醇治疗时，患有代谢综合征的女性舒张压下降了 11%，甘油三酯下降了 20%，高密度脂蛋白胆固醇增加了22%。

荟萃分析显示，怀孕期间补充肌醇可能会降低妊娠糖尿病和相关分娩并发症的发生率[7-9]。

在几乎所有存在胰岛素抵抗的情况下，肌醇代谢物的尿液排泄增加，这在一定程度上表明，胰岛素抵抗的人由于排泄率增加而处于相对肌醇缺乏的状态。

很多的影像学证据都表明，抑郁症患者大脑中肌醇的浓度比较低，相反，在双相情感障碍患者中躁狂和轻躁狂发作的患者中发现肌醇水平升高[10]，这些发现表明肌醇可能在情绪障碍的发病机制中发挥作用。

肌醇的治疗活性可能与5-羟色胺或去甲肾上腺素受体的调节以及对信号转导途径的影响有关。事实上，从文献中提供的数据来看，肌醇是肌醇磷酸肌醇 （IPP）循环的前体，IPP循环及其衍生的第二信使参与多种受体系统，包括去甲肾上腺素能受体（α-1）、5-羟色胺能受体、胆碱能受体和多巴胺能受体（D1）。

在一些小型人体试验中发现，肌醇可能对治疗抑郁症[11]，惊恐障碍[12-14]，强迫症[15]，经前焦虑障碍[16,17]是有益的。

在Levine等人对抑郁期的重度抑郁症（MDD）和双向情感障碍（BD）患者进行的一项研究中，给予12 g肌醇4周，结果显示与安慰剂组相比，肌醇治疗组的HDRS评分显著降低[11]。Nemets等人[17]和Gianfranco等人[16]进行的两项临床试验表明，与安慰剂相比，肌醇单一疗法的疗效呈上升趋势。一项小型研究调查了肌醇对20名恐慌症患者的影响。在每天服用18克剂量的肌醇4周后，与一组未给予肌醇的个体相比，接受肌醇治疗的人每周惊恐发作平均减少2.4次[14]。关于惊恐障碍药物干预的初步结果得出结论，肌醇具有抗惊恐特性，可能是治疗惊恐障碍的有效化合物[12,13]。

由于肌醇的亲水性，低浓度的肌醇无法通过血脑屏障，因此，要将肌醇运输到中枢神经系统，需要高于12 g/d的剂量[18]。此外，一些常用作抗抑郁的药物可能会降低中枢神经系统中肌醇的浓度，比如锂和丙戊酸钠，补充肌醇有助于降低这些药物产生的一些副作用。

作为第二信使，肌醇对于甲状腺激素合成也至关重要的，肌醇消耗或肌醇依赖性TSH信号通路受损可能导致某些甲状腺疾病的发展。

许多临床研究表明，用肌醇加硒治疗后，伴有或不伴有自身免疫性甲状腺炎的亚临床甲减患者的TSH水平显着降低，抗甲状腺自身抗体下降。补充肌醇似乎对甲状腺良性结节的管理也有好处，可能有助于减少结节的大小。

在甲状腺细胞中，TSH剂量依赖性地刺激肌醇磷酸盐形成，PIP2级联反应和cAMP级联反应控制甲状腺激素的合成。在甲状腺中，肌醇代谢的失衡会损害甲状腺激素的生物合成、储存和分泌。具体来说，MYO通过PLC依赖性肌醇磷酸盐Ca2+/DAG途径调节甲状腺细胞中 过氧化氢介导的碘化，导致过氧化氢生成增加，这是碘有机化和甲状腺激素生物合成的关键步骤。不同的是，TSH活性诱导的cAMP级联反应更多地参与细胞生长和分化以及甲状腺激素分泌。因此，MYO肌醇在甲状腺生理学中起着至关重要的作用，因为它在TSH调节碘化中发挥作用，并且增加甲状腺细胞对TSH的敏感性。

一些相关研究发现，肌醇也具有一定的抗癌作用，这与它的另一个特性有关。动物来源的肌醇主要以游离形式或磷脂酰肌醇存在，但在植物性食品中，肌醇优先以六磷酸肌醇（InsP6）的形式存在，六磷酸肌醇也叫做植酸。

植酸长期以来被认为是一种抗营养物质，因为它会干扰营养吸收。就癌症而言，植酸和肌醇可能会以更共生的方式发挥作用。InsP6和myo-Ins的抗癌作用机制，粗略总结为这几方面：

InsP6参与细胞周期控制，具有细胞抑制和细胞毒作用[29,30]。

InsP6通过诱导癌症中的细胞凋亡[31]以及抑制肿瘤细胞分泌血管内皮生长因子（VEGF），从而影响新血管生成[32]。

InsP6具有抗氧化作用，可以减少活性氧介导的致癌作用，减少细胞损伤[33]。

IP6和myo-Ins可以增加p53的肿瘤抑制活性[34]，显著降低P13K的表达和AKT的激活，这是参与细胞生长的分子途径[35,36]。

InsP6和肌醇还调节肿瘤微环境中的免疫系统和免疫抑制，增加体外杀伤细胞活性[37,38]。

myo-Ins还参与调节Wnt/β-连环蛋白通路，有助于下调不同炎症标志物[39]。

在结肠和乳腺肿瘤以及转移性纤维肉瘤的动物模型中观察到IP6联合肌醇的协同抗癌作用[40-42]。

虽然补充肌醇对于改善胰岛素抵抗的作用是很多研究证实的，但是也有一些证据表明，有25%-75%的myo-Ins治疗患者可能仍对治疗耐药[43]。大多数对myo-Ins治疗耐药的患者是肥胖女性[44]。因此，肥胖状态、胰岛素抵抗的存在、高雄激素血症、肌醇生物利用度的差异肯定是与肌醇抵抗相关的潜在风险因素，因为它们可能会损害myo-Ins口服生物利用度。

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