Mertz W
U.S. Department of Agriculture, Beltsville Human Nutrition Research Center, MD 20705.
J Nutr. 1993 Apr;123(4):626-33. doi: 10.1093/jn/123.4.626.
This review summarizes the results of 15 controlled studies supplementing defined Cr(III) compounds to subjects with impaired glucose tolerance. Three of these (3-4 mumol Cr/d for > 2 mo) produced no beneficial effects: serum glucose, insulin and lipid concentrations remained unchanged. The remaining 12 interventions improved the efficiency of insulin or the blood lipid profile of subjects (ranging from malnourished children and healthy middle-aged individuals to insulin-requiring diabetics). In addition, three cases of impaired glucose tolerance after long-term total parenteral alimentation responding to Cr supplementation have been reported. Chromium potentiates the action of insulin in vitro and in vivo; maximal in vitro activity requires a special chemical form, termed Glucose Tolerance Factor and tentatively identified as a Cr-nicotinic acid complex. Its complete structural identification is a major challenge to chromium research. The development and validation of a procedure to diagnose chromium status is the second challenge. Such a test would allow the assessment of incidence and severity of deficiency in the population and the selection of deficiency in the population and the selection of chromium-responsive individuals. The third challenge is the definition of chromium's mode of action on parameters of lipid metabolism that have been reported from some studies but not others. Future research along these lines might establish whether chromium deficiency is a factor in the much discussed "Syndrome X" of insulin resistance.
本综述总结了15项对照研究的结果，这些研究对糖耐量受损的受试者补充了特定的三价铬化合物。其中三项研究（每天补充3 - 4微摩尔铬，持续超过2个月）未产生有益效果：血糖、胰岛素和血脂浓度均未改变。其余12项干预措施改善了受试者的胰岛素效能或血脂状况（受试者范围从营养不良的儿童、健康的中年个体到需要胰岛素治疗的糖尿病患者）。此外，还报告了3例长期全胃肠外营养后糖耐量受损但补充铬后有反应的病例。铬在体外和体内均可增强胰岛素的作用；体外最大活性需要一种特殊的化学形式，称为葡萄糖耐量因子，初步确定为铬 - 烟酸复合物。其完整的结构鉴定是铬研究的一项重大挑战。开发和验证一种诊断铬状态的方法是第二项挑战。这样的测试将有助于评估人群中铬缺乏的发生率和严重程度，并筛选出铬缺乏个体和对铬有反应的个体。第三项挑战是明确铬对脂质代谢参数的作用方式，一些研究报告了这种作用，但另一些研究未报告。沿着这些方向的未来研究可能会确定铬缺乏是否是备受讨论的胰岛素抵抗“X综合征”的一个因素。
