铬酵母对糖尿病小鼠的降血糖作用研究

富铬酵母是啤酒酵母与无机三价铬（Cr）在一定的条件下生成的，其有机铬的含量较高。铬被认为是哺乳动物必须的微量元素，作为葡萄糖耐量因子（GTF）的活性成分协同胰岛素参与糖、脂肪、蛋白质和核酸的代谢，并协助胰岛素维持正常的糖耐量。糖尿病患者体内铬常处于缺乏状态，故有人尝试用补铬的方法治疗糖尿病。本实验旨在研究铬酵母对实验性糖尿病小鼠血糖的影响。     

铬与糖尿病

铬，作为一种与糖尿病密切相关的微量元素正日益被人们所重视，含铬保健食品也为糖尿病人逐渐熟悉，不少病人将强化铬食品纳入自己的食谱，甚至直接食用铬化物。那么，铬对糖尿病有无治疗作用呢？铬是一种过渡元素，在自然界中多以金属铬、三价铬、六价铬的形式存在，食物中大多为三价铬，含量较低，吸收率也偏低。铬参与构成葡萄糖耐量因子，这是一种由铬、尼克酸、谷氨酸、甘氨酸、含硫氨基酸等构成的化合物，有促进胰岛素的作用。其作用方式可能是含铬的葡萄糖耐量因子在细胞膜的硫氢基和胰岛素分子A链的两个二硫键之间形成一个稳定的桥，使胰岛素充分发挥作用，维持血糖浓度。此外，铬还参与脂质代谢，维持血清胆固醇水平。缺铬可出现不明原因的体重下降、外周神经炎、葡萄糖耐量受损等症状。研究表明，因缺铬而造成糖耐量受损者，补充铬后可使葡萄糖清除率恢复正常，体重增加。而对于糖尿病人，虽然经化验铬明显低于正常人，补铬后效果并不显著，其糖耐量、脂质水平、血浆胰岛素水平等均无明显变化。仅有一例报道糖尿病人补充铬量达每日６００微克，糖耐量有一定的改善，但此剂量已超过目前中国营养学会推荐的成人可耐受最高摄入量５００微克／日。虽然三价铬毒性较低，但亦有一定致癌性，长期过量...     

三价铬离子对2型糖尿病疗效观察

据文献报道 ,从猪胃中提取一种称为“葡萄糖耐量因子”的化合物 ,能够恢复大鼠受损的葡萄糖耐量 ,并由此确定铬是动物营养的必需微量元素。给葡萄糖耐量受损的营养不良儿童口服三氯化铬补充物 ,发现葡萄糖清除率有所改善[1 ] 。为了了解三价铬离子治疗 2型糖尿病的疗效。作者对 11例 2型糖尿病患者进行补充三价铬离子治疗 ,现报告如下。对象与方法1　对象　 2型糖尿病 2 2例 ,其中男 14例 ,女 8例 ,平均年龄 5 7岁 ;所有患者空腹血糖 >7 10± 1 30mmol L ,餐后 2小时血糖 >8 2 9± 1 6 3mmol L。随机分为铬离子组 (n =11)和对照组 (n =11)…     

三价铬的生理作用

1959年,Schwarz.K和Mertz.W首次发现三价铬是葡萄糖耐量因子(GlucoseTolerance Fector,简称GTF)的重要组成部分。一、对糖和脂代谢的作用对大鼠附睾脂肪组织、肝线粒体、膈肌及眼晶体的研究提示,三价铬与胰岛素具有协同作用。动物及人类缺铬均以糖耐量受损为主要特点,补充三价铬可以改善。三价铬也可以改善糖尿病人的症状,减少胰岛素的用量。     

高效液相色谱法测定保健食品中吡啶甲酸铬含量

随着近年来对铬元素的深入研究 ,认为三价铬是人体必需的微量营养元素 ,是葡萄糖耐量因子 (GTF)的重要组成成分。机体内的葡萄糖耐量因子和胰岛素是维持血糖浓度平衡系统的两种重要活性物质 ,作为葡萄糖耐量因子组成成分的三价铬 ,可通过激活胰岛素和细胞膜的二硫键活性 ,提高人体对葡萄糖的耐受量和胰岛素与其特异性受体相结合 ,刺激组织对葡萄糖的摄取 ,增加对葡萄糖的吸收。人体在铬缺乏时会使糖代谢紊乱 ,血胰岛素升高 ,胰岛素亲和力降低 ,α -细胞敏感性减弱 ,胰岛素受体数目减少 ,最终导致糖耐量异常和糖尿病发生。人体缺铬与长期食…     

FIA-化学发光法测定血铬的研究

铬在人体中的重要作用已有论述〔1、2〕。已知三价铬作为葡萄糖耐量因子 (Glucose Tolerance Factor)的组成部加强胰岛素的作用〔3〕。三价铬参与脂代谢〔4〕。而铬在人体含量极微 ,测定困难较大 ,国内外多用原子吸收法、同位素源激发 X射线荧光法、二氨苯基脲测定法。本文通过对铬 (VI)——亚铁氰化钾——鲁米诺化学发光反应的研究 ,建立了一个灵敏度高、操作简便、价格低廉的分析方法。其原理是 :铬 (VI)氧化亚铁氰化钾生成铁氰化钾 ,铁氰化钾与碱性鲁米诺溶液作用产生化学发光 ,溶液中铬的含量用相对发光强度的峰高定量。1　试验部分…     

铬的代谢和葡萄糖耐量因子的研究

从铬的代谢论述了铬的吸收、分布、排泄，对必需微量元素铬在体内的含量和分布，结合糖尿病的治疗，对葡萄糖耐量因子（ＧＴＦ）和低分子含铬化合物的研究进展，为研究生物活性铬提供了提取和分析鉴定方法。     

葡萄糖、胰岛素对饮食铬补充的反应

有学者通过非随机研究发现，饮食补充三价铬对Ⅱ型糖尿病的治疗及其高危人群血糖的控制是具有吸引力的选择。测定健康人群、糖耐量异常人群和Ⅱ型糖尿病患者补铬对葡萄糖、胰岛素浓度的影响，并进行系统性回顾调查和随机性临床试验(RCTs)的汇总(meta)分析。研究结论为，RCTs表明铬不能影响非糖尿病人群的葡萄糖、胰岛素的浓度，而对糖尿病患者的研究尚无结论。在高危人群中进行铬与葡萄糖、胰岛素和糖化血红蛋白的关系的临床随机试验是有必要的。     

铬的安全性与毒理学研究进展

由于铬缺乏与2型糖尿病、心血管疾病以及神经系统紊乱等疾病有关,而适量补铬可改善葡萄糖耐量、预防动脉粥样硬化,并增强机体免疫功能。因此,铬作为营养强化剂的安全性研究备受关注。动物实验和人体研究对摄入吡啶甲酸铬及其他三价铬的安全性进行了评价。从非致癌性毒性、潜在致癌性以及生物蓄积性等方面对该领域的研究进展作一综述。     

富铬酵母调节血糖血脂的作用

成人体内含铬５～１０ｍｇ，三价铬为葡萄耐量因子ＧＴＦ之主要成分。成人每日膳食中适宜的铬摄入量为５０～２００ｕｇ，天津市民每日膳食中约含铬４０～８０ｕｇ。缺铬可以导致糖尿病、高血脂症，并影响蛋白质与ＲＮＡ合成，目前，国内外有人制成富含三价铬的富铬酵母，可以降低Ⅱ型糖尿病患者血糖及血浆胰岛素，又可降低高血脂患者的ＴＣ，ＴＧ，ＬＤＬ－Ｃ，并升高ＨＤＬ－Ｃ；动物实验亦表明，可使动脉粥样硬化大鼠动脉内皮细胞     

Glucose and insulin responses to dietary chromium supplements: a meta-analysis

BACKGROUND: Several authors, mostly on the basis of nonrandomized studies, have suggested dietary trivalent chromium supplementation as an attractive option for the management of type 2 diabetes and for glycemic control in persons at high risk of type 2 diabetes. OBJECTIVE: The study aimed to determine the effect of chromium on glucose and insulin responses in healthy subjects and in individuals with glucose intolerance or type 2 diabetes. DESIGN: The study design was a systematic review and meta-analysis of randomized clinical trials (RCTs). RESULTS: The authors identified 20 reports of RCTs assessing the effect of chromium on glucose, insulin, or glycated hemoglobin (Hb A(1c)). This review summarizes data on 618 participants from the 15 trials that reported adequate data: 193 participants had type 2 diabetes and 425 were in good health or had impaired glucose tolerance. The meta-analysis showed no association between chromium and glucose or insulin concentrations among nondiabetic subjects. A study of 155 diabetic subjects in China showed that chromium reduced glucose and insulin concentrations; the combined data from the 38 diabetic subjects in the other studies did not. Three trials reported data on Hb A(1c): one study each of persons with type 2 diabetes, persons with impaired glucose tolerance, and healthy subjects. The study of diabetic subjects in China was the only one to report that chromium significantly reduced Hb A(1c). CONCLUSIONS: Data from RCTs show no effect of chromium on glucose or insulin concentrations in nondiabetic subjects. The data for persons with diabetes are inconclusive. RCTs in well-characterized, at-risk populations are necessary to determine the effects of chromium on glucose, insulin, and Hb A(1c).     

Lack of effect of dietary chromium supplementation on glucose tolerance, plasma insulin and lipoprotein levels in patients with type 2 diabetes

Chromium is essential for the regulation of insulin action, thereby influencing carbohydrate and lipid metabolism. An uncontrolled pilot study was designed to measure the habitual daily intake of chromium in a group of healthy individuals with type 2 diabetes and to monitor the effect of daily supplementation with high chromium yeast on glucose tolerance, plasma insulin and lipoproteins. Twelve free-living adults with type 2 diabetes underwent a glucose tolerance test (GTT) on recruitment, at 4 weeks (after a 7-d duplicate diet collection) and at 12 weeks (following 8 weeks daily supplementation with 100 micrograms of chromium). Urine samples were collected on the day before and the day of each GTT. Blood samples were taken at half hourly intervals for 3 hours during the GTT and the plasma glucose, cholesterol, triglyceride, HDL, LDL and insulin concentration measured. The chromium content of diets and urine samples was determined. Fasting glucose concentrations and glucose area under the curve profiles did not alter significantly post supplementation with the chromium rich yeast. No significant changes in insulin and lipoprotein concentrations were observed. The results of this study do not support the hypothesis that individuals with type 2 diabetes benefit from yeast-based chromium supplements (100 micrograms/day).     

Serum chromium does not predict glucose tolerance in late pregnancy

BACKGROUND: Chromium is an essential element in human nutrition. Serum concentrations of chromium are not well characterized during pregnancy or in gestational diabetes mellitus. OBJECTIVE: The objective of this study was to determine whether low plasma chromium concentrations (< or =3 nmol/L) are associated with altered glucose, insulin, or lipid concentrations during pregnancy. DESIGN: The study was conducted prospectively and took place at the medical obstetric clinic of a tertiary referral hospital. Seventy-nine women with abnormal results of a 50-g glucose challenge test in the third trimester of pregnancy were studied. All women had a formal 75-g oral-glucose-tolerance test, and fasting insulin, lipid, and chromium concentrations were determined. Chromium was measured by graphite furnace atomic absorption spectrometry. RESULTS: The median chromium concentration was 2 nmol/L (95% CI: 0, 12). There were no significant differences in age, plasma glucose, insulin, lipids, calculated insulin resistance, or calculated ss cell function between women with normal and those with abnormal (< or =3 nmol/L) chromium concentrations. CONCLUSIONS: Plasma chromium during pregnancy does not correlate with glucose intolerance, insulin resistance, or serum lipids. Plasma chromium concentrations may not accurately reflect tissue stores of chromium. Several trials showed a beneficial effect of chromium supplementation on glucose tolerance, insulin, and lipids. A method for assessing body chromium stores is required to allow further study.     

Efficacy of chromium supplementation in athletes: emphasis on anabolism.

As the biologically active component of glucose tolerance factor (GTF), the essential trace mineral chromium is now being marked to athletes. GTF potentiates insulin activity and is responsible for normal insulin function. Thus, insulin's effects on carbohydrate, fat, and protein metabolism are dependent upon the maintenance of adequate chromium stores. Due to excessive chromium loss and marginal chromium intake, athletes may have an increased requirement for chromium. Therefore, in some circumstances the dietary supplementation of a chromium compound may be efficacious. The restoration and maintenance of chromium stores via supplementation would promote optimal insulin efficiency, necessary for high-level athletic performance. However, potential anabolic effects of enhanced insulin function would likely be marginal, and reports of short-term anabolic increases from the supplementation of an organic chromium compound need to be confirmed.     

The role of chromium in nutrition and therapeutics and as a potential toxin

Since the 1950s it has been known that chromium is important for the expression of glucose tolerance and that in chromium deficiency the use of glucose is impaired. Chromium has been recognized as an essential nutrient since the finding of low-molecular-weight chromium as a biological modifier of insulin action and the clinical demonstration of deficiency associated with glucose intolerance that responded to the administration of chromium. The major impediment to the use of orally administered chromium is poor absorption of trivalent chromium in its inorganic form. Trivalent chromium is more available in yeast and, more recently, as chromium picolinate for oral absorption. The widespread use of these supplements has resulted in controversy regarding chromium's role as a nutrient, its use for treatment of insulin resistance, and its potential toxicity. This report reviews the evidence for the potential toxicity of chromium supplements in contrast with its usefulness as a nutrient or therapeutic agent in the treatment or prevention of insulin resistance.     

Supplemental-chromium effects on glucose, insulin, glucagon, and urinary chromium losses in subjects consuming controlled low-chromium diets

The effects of low-chromium diets containing chromium in the lowest quartile of normal intake on glucose tolerance and related variables in 11 females and 6 male subjects were evaluated. Subjects with glucose concentration greater than 5.56 mmol/L but less than 11.1 mmol/L 90 min after an oral-glucose challenge were designated as the hyperglycemic group and the remainder, the control group. Glucose tolerance and circulating insulin and glucagon of the hyperglycemic group all improved during chromium supplementation (200 micrograms/d) whereas those of the control group were unchanged. Glucose and insulin concentrations 60 min after the oral-glucose challenge and the sum of the 0-90 min and 0-240 min glucose values were all significantly lower after chromium supplementation in the hyperglycemic group. These data demonstrate that consumption of diets in the lowest 25% of normal chromium intake lead to detrimental effects on glucose tolerance, insulin, and glucagon in subjects with mildly impaired glucose tolerance.     

Chromium (III)-ion enhances the utilization of glucose in type-2 diabetes mellitus

INTRODUCTION: The prevalence of the type 2 diabetes mellitus is still growing. Although the occurrence of insulin resistance is quite frequent in the whole population, diabetes not always develops because for a time the compensating mechanism avoids it. In a frequent variation of type-2 diabetes the disease is not the result of an alteration in the insulin receptor or the glucose transporter, but a genetically determined defect of the postreceptorial intracellular signaling mechanism plays a role in its occurrence. There have been investigations for decades to find out more about the role of chromium (III) ions in glucose metabolism and in the prevention of type-2 diabetes. It has also been investigated if chromium substitution can prevent or treat those forms of diabetes where chromium deficiency is suspected to be in the background of the disorder. AIM: The aim of our present investigation is to test the role of chromium (III) compounds in glucose metabolism that are known from literature. The authors examined the effect of oral chromium supplementation on antidiabetic treatment. Chromium supplementation was applied for 6 months. METHODS: Before, through and after the investigation changes in the patient's carbohydrate and lipid metabolism were followed by laboratory tests. RESULTS: At the end of our examination the cholesterin level significantly, the HbA1c level close to the significant value decreased. Due to their results the authors presume that chromium (III) compounds may be effective in the treatment of patients' with decreased glucose tolerance or type-2 diabetes mellitus as a supplement to their therapy.     

Nutritional factors influencing the glucose/insulin system: chromium.

Chromium (Cr) improves the glucose/insulin system in subjects with hypoglycemia, hyperglycemia, diabetes and hyperlipemia with no detectable effects on control subjects. Chromium improves insulin binding, insulin receptor number, insulin internalization, beta cell sensitivity and insulin receptor enzymes with overall increases in insulin sensitivity. There have been several studies involving Cr supplementation of subjects with NIDDM and/or lipemia and most have reported beneficial effects of Cr on the glucose/insulin system. In a recent study, Chinese subjects with NIDDM were divided into three groups of 60 subjects and supplemented with placebo, 100 or 500 micrograms of Cr as chromium picolinate 2 times per day for 4 months. Improvements in the glucose/insulin system were highly significant in the subjects receiving 500 micrograms twice per day with less or no significant improvements in the subjects receiving 100 micrograms twice per day after 2 and 4 months. In summary, Cr is involved in the control of the glucose/insulin system and the amount, and likely form of chromium, are critical when evaluating the role of chromium in this system.     

Clinical and biochemical aspects of chromium deficiency

The essentiality of chromium (Cr) in animal and human nutrition is now well accepted. In animals, Cr deficiency can cause a diabetic-like state, impaired growth, elevated blood lipids, increased aortic plaque formation, and decreased fertility and longevity. The ability of Cr to potentiate insulin sensitivity has considerable experimental support. In the human, Cr deficiency has been demonstrated unequivocally in only one clinical situation, patients on total parenteral nutrition without added Cr. In such patients, impaired glucose tolerance, hyperglycemia, relative insulin resistance, peripheral neuropathy, and a metabolic encephalopathy have been noted with reversal of the clinical phenomena by Cr repletion. Many studies have been performed to determine whether Cr deficiency may be important in other clinical conditions, namely, diabetes mellitus, pregnant and parous women, and the aged population. Available data indicate that Cr supplementation can improve glucose metabolism in glucose intolerant individuals and decrease the total/HDL cholesterol ratio regardless of the status of glucose tolerance. However, whether Cr supplementation has long-term health benefits is unknown. Further, despite many tantalizing observations, it is still unclear whether Cr deficiency, latent or overt, is common in any human situation other than generalized malnutrition and total parenteral nutrition without added Cr. Technical uncertainties in the analysis of Cr, Cr contamination of food by the use of stainless steel processing equipment and eating utensils, and the lack of a clinically feasible test for Cr deficiency continue to impede progress in Cr research. Nevertheless, there is considerably more clarity as to plasma and urine Cr levels, food and tissue Cr content, and metabolic pathways of Cr metabolism than existed a decade ago. It is expected that progress will accelerate, since critical questions can now be addressed regarding the role of Cr in human nutrition.     

Chromium deficiency, glucose intolerance, and neuropathy reversed by chromium supplementation, in a patient receiving long-term total parenteral nutrition.

A white female, now age 40 and receiving total parenteral nutrition for more than 5 years, developed unexpected 15% weight loss after 3 1/2 years of regimen, together with peripheral neuropathy confirmed by nerve conduction measurements. An intravenous glucose tolerance test showed that the fractional rate (K) had decreased to 0.89%/min (normal greater than 1.2). There was observed during this glucose infusion a borderline normal insulin response with a fall in plasma free fatty acids and in plasma leucine. During daily infusion of well over 400 g of glucose, the respiratory quotient was 0.66. Chromium balance was negative. Chromium levels were, in blood 0.55 ng/ml (normal 4.9 to 9.5) and in hair 154 to 175 ng/g (normal greater than 500). Regular insulin daily (45 micron) in the infusate nearly maintained euglycemia but despite this, and even with further glucose intake to restore weight loss, intravenous glucose tolerance test (K) and respiratory quotient were unchanged. Administration of insulin was then stopped and 250 microng of Cr added to the daily total parenteral nutrition infusate for 2 weeks. After this the intravenous glucose tolerance test (K) and respiratory quotient became normal (1.35 and 0.78, respectively). Over the next 5 months insulin was not needed and glucose intake had to be reduced substantially to avoid overweight. In this period nerve conduction and well-being returned to normal. With a maintenance addition of chromium to the total parenteral nutrition infusate (tentatively this addition is 20 microng/day) the patient has remained well for 18 months (to July 1976). These results suggest that relatively isolated chromium deficiency in man, hitherto poorly documented, causes 1) glucose intolerance, 2) inability to utilize glucose for energy, 3) neuropathy with normal insulin levels, 4) high free fatty acid levels and low respiratory quotient and, 5) abnormalities of nitrogen metabolism.