α-葡萄糖苷酶抑制剂的研究及应用

概述α-葡萄糖苷酶抑制剂的化学结构特点、作用机制、制备途径与临床应用情况。临床上常用的降糖药阿卡波糖、伏格列波糖、米格列醇为一类微生物来源的α-葡萄糖苷酶抑制剂,其与寡糖结构类似,因此可竞争性地与α-葡萄糖苷酶结合,阻滞寡糖水解成单糖,从而降低餐后血糖峰值。并且某些α-葡萄糖苷酶抑制剂还具有抗HIV活性。     

中药提取物对鼠肠α-葡萄糖苷酶抑制作用的研究

目的 评估中药提取物对鼠肠α-葡萄糖苷酶的抑制作用.方法 从治疗糖尿病的中药方剂中选出常用的54味中药,水煎煮及煎煮后残渣以70％乙醇提取,各提取物进行α-葡萄糖苷酶体外抑制活性试验,探讨其对鼠肠α-葡萄糖苷酶的抑制作用,并与阳性对照药物阿卡波糖比较.结果 与阿卡波糖相比,桑枝等9味中药水煎煮液乙醇提取物对鼠肠α-葡萄糖苷酶的抑制作用显著,其中马齿笕、桑葚,桑枝和桑白皮这4味中药水煎煮液乙醇提取物对鼠肠α-葡萄糖苷酶抑制作用较强,抑制率分别为81.45％、72.35％、62.72％和63.93％,相应的阿卡波糖的抑制率为39.56％.结论 中药水煎煮液乙醇提取物对鼠肠α-葡萄糖苷酶有较好的抑制作用,对新型降糖中成药品种开发具有很好的参考价值.     

甲壳低聚糖对α-葡萄糖苷酶活性的影响及降血糖作用

目的探讨甲壳低聚糖对α-葡萄糖苷酶活性的影响及降糖效果。方法在体外建立标准酶反应体系,分别加入6%甲壳低聚糖50,100,150,200,250,300μl,用4-硝基酚-α-D呋喃葡萄糖苷法测定酶活性;再建立加有6%阿卡波糖200μl的酶反应体系,测定酶活性;以250 mg/(kg.d)剂量灌胃,观察其对实验性糖尿病大鼠空腹及餐后血糖的影响。结果甲壳低聚糖对α-葡萄糖苷酶具有明显抑制作用,抑制效果接近于阿卡波糖;甲壳低聚糖能显著降低糖尿病大鼠空腹及餐后血糖。结论甲壳低聚糖可能具有阿卡波糖样的降血糖作用。     

用固定化酶筛选模型从天然产物中筛选α-葡萄糖苷酶抑制剂

目的:用固定化酶筛选模型从天然产物中筛选α-葡萄糖苷酶抑制剂.方法:把α-葡萄糖苷酶固定化,模拟其在体内小肠壁上的情况,建立固定化酶筛选模型,先用α-葡萄糖苷酶抑制剂阿卡波糖对该模型进行验证,然后用该筛选模型对2种天然产物-虎杖水溶性部位和广西血竭甲醇溶液进行筛选.结果:阿卡波糖对固定化α-葡萄糖苷酶和游离α-葡萄糖苷酶的IC50分别为0.413 mg·mL-1和0.126 mg·mL,虽然固定化酶被阿卡波糖抑制的IC50值是游离酶的3.3倍,但固定化酶筛选模型更准确地反映阿卡波糖的体内作用.虎杖水溶性部位和广西血竭的甲醇溶液对固定化α-葡萄糖苷酶的IC50分别为0.224 mg·mL-1和5.5 μg·mL-1.结论:该筛选模型能很好的进行体外α-葡萄糖苷酶抑制剂的筛选,其筛选结果和文献报道相符.     

微生物来源的α-葡萄糖苷酶抑制剂国内外生产情况及市场分析

由于生活水平的提高,糖尿病的发病率日益上升,其已成为人类健康的三大杀手之一,为其寻求高效的治疗药物,已成为当今的主流话题.自从发现阿卡波糖,α-葡萄糖苷酶抑制剂作为一种新型的降糖药物出现在人类面前,并且在治疗糖尿病,尤其是针对2型糖尿病有独特的优势.本文通过对微生物来源的α-葡萄糖苷酶抑制剂类药物的调研,了解阿卡波糖、伏格列波糖和米格列醇3种α-葡萄糖苷酶抑制剂当今市场情况,运用SWOT分析方法预测其市场前景,期望能为相关企业生产经营方向的选择、医院临床用药及政府指导性定价等提供导向.     

糖尿病的治疗药物进展

随着人们对糖尿病基础研究的深入，已开发出αk葡萄糖苷抑制剂、胰岛素增敏剂、胰岛素分泌促进剂、醛糖还原酶抑制剂及抗肿瘤坏死因子—α药物等。本文介绍了伏格列波糖、阿卡波糖、吡格列酮、罗格列酮、瑞格列奈等，临床使用或临床研究的新型抗糖尿病药物。     

卡博平——第一个国产阿卡波糖制剂

卡博平由华东医药集团公司生产,于2002年6月获国家新药证书。卡博平,正式名称为阿卡波糖片。阿卡波糖是一种α-糖苷酶抑制剂,它通过竞争性地抑制小肠内壁上参与碳水化合物降解的α-葡萄糖苷酶的活性,延迟碳水化合物的分解消化,延缓肠内葡萄糖的吸收,控制餐后血糖浓度的升高,同时也降低糖化血红蛋白的水平。它是Frommer等人于70年代初从放线菌Actinoplanesu-     

葛根素对α-葡萄糖苷酶抑制作用机理的探讨

目的探讨葛根素对α-葡萄糖苷酶的抑制作用机理。方法取40只雄性小鼠,分为5组:对照组、阿卡波糖对照组、葛根素(2.5、5.0、10)μM,每组8只,采用酶抑制动力学方法,研究葛根素对α-葡萄糖苷酶的抑制作用和抑制动力学,并用分光光度计测定葛根素对小鼠血糖含量变化的影响。结果葛根素是一种可逆的竞争型α-葡萄糖苷酶抑制剂[半抑制浓度IC50为(4.32±0.42)μM],抑制常数Ki为(0.41±0.09)μM;与阳性对照阿卡波糖对比,葛根素能够明显的抑制大鼠血糖水平的增长。结论葛根素作为一个α-葡萄糖苷酶抑制剂,诱导了酶活性的降低,对调节血糖水平起到重要作用,为临床降血糖提供了理论基础。     

蒲桃不同药用部位乙醇提取物对α-葡萄糖苷酶和α-淀粉酶活性的抑制作用研究

目的:比较蒲桃不同药用部位(根、茎、叶、种子、花和果肉)乙醇提取物对α-葡萄糖苷酶、α-淀粉酶活性的抑制作用。方法:以半数抑制浓度(IC50)为评价指标,阿卡波糖为阳性对照,采用体外抑制模型方法评价蒲桃不同药用部位乙醇提取物对α-葡萄糖苷酶(酵母菌源和小鼠小肠源)和α-淀粉酶活性的抑制作用,并采用酶促动力学与Lineweaver-Burk双倒数法分析作用最强的药用部位对α-葡萄糖苷酶和α-淀粉酶活性的抑制类型。结果:蒲桃不同药用部位乙醇提取物对酵母菌源α-葡萄糖苷酶活性抑制作用的强弱顺序为蒲桃种子>蒲桃茎>蒲桃叶>蒲桃根>蒲桃花>蒲桃果肉>阿卡波糖,对小鼠小肠源α-葡萄糖苷酶活性抑制作用的强弱顺序为蒲桃种子>蒲桃茎>蒲桃根>蒲桃叶>蒲桃花>蒲桃果肉>阿卡波糖,对α-淀粉酶活性抑制作用的强弱顺序为阿卡波糖>蒲桃种子>蒲桃茎>蒲桃根>蒲桃叶>蒲桃果肉>蒲桃花。其中,蒲桃种子乙醇提取物对酵母菌源α-葡萄糖苷酶、小鼠小肠源α-葡萄糖苷酶和α-淀粉酶活性的抑制作用[IC50分别为(6.64±0.24)、(32.77±2.46)和(41.18±1.63)μg/m L]显著强于其他药用部位,并且对α-葡萄糖苷酶活性的抑制作用显著强于阿卡波糖[对酵母菌源α-葡萄糖苷酶和小鼠小肠源α-葡萄糖苷酶的IC50分别为(2 833.33±5.48)、(1 304.21±6.45)μg/m L](P<0.05),但其对α-淀粉酶活性的抑制作用不及阿卡波糖[IC50为(27.27±1.24)μg/mL](P<0.05)。酶促动力学研究结果表明,蒲桃种子乙醇提取物对α-葡萄糖苷酶、α-淀粉酶的抑制作用均为可逆竞争性抑制类型。结论:在蒲桃根、茎、叶、种子、花和果肉等不同部位中,以蒲桃种子对α-葡萄糖苷酶、α-淀粉酶活性的抑制作用最强,具有开发成辅助降糖的药品或保健食品的价值。     

知名药师解答“三高”用药

(接上期)59.常用的α葡萄糖苷酶抑制药有哪些?其各自的特点与用法、用量如何?①阿卡波糖(拜糖平):本品的优点是能降低餐后血糖,安全且不增加胰岛素分泌,降糖作用较弱,适用于心血管     

Efficacy of gut lavage,hemodialysis, and hemoperfusion in the therapy of paraquat or diquat intoxication

Clinical and in vitro investigations were carried out to test the efficacy of gut lavage, hemodialysis, and hemoperfusion in the treatment of poisoning with paraquat or diquat. In a patient suffering from diquat intoxication 130 times more diquat was removed by gut lavage 30 h after ingestion than was removed by complete aspiration of the gastric contents.Determination of in vitro clearances for paraquat and diquat by hemodialysis showed that, at serum concentrations of 1–2 ppm, such as are frequently encountered in poisoning in man, toxicologically relevant quantities of herbicide cannot be removed from the body. At a concentration of 20 ppm, on the other hand, hemodialysis proved to be effective, the clearance being 70 ml/min at a blood flow rate of 100 ml/min. The efficacy of hemoperfusion with coated activated charcoal was on the whole better. Especially at concentrations around 1–2 ppm, the clearance values for hemoperfusion were some 5–7 times higher than those for hemodialysis.In a patient suffering from paraquat poisoning, both hemodialysis as well as hemoperfusion were carried out. The in vitro results could be confirmed: At serum concentrations of paraquat less than 1 ppm no clearance could be obtained by hemodialysis while by hemoperfusion with activated charcoal quite high clearance values were measured and the serum level dropped down to zero.

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Zusammenfassung Klinische Untersuchungen und Laboratoriumsversuche wurden durchgeführt, um die Wirksamkeit von Darmspülung, Hämodialyse und Hämoperfusion bei Paraquat- und Deiquat-Vergiftungen zu prüfen.Bei einem Patienten wurde 30 Std nach Deiquat-Aufnahme durch Darmspülung 130mal mehr Deiquat entfernt als durch vollständige Aspiration des Mageninhaltes. In vitro-Versuche ergaben, daß bei Blutserumkonzentrationen von 1–2 ppm, die bei Vergiftungen oft gemessen werden, durch Hämodialyse keine toxikologisch relevanten Paraquat- oder Deiquat-Mengen entfernt werden können. Dagegen erwies sich die Hämodialyse bei 20 ppm und einer Blutumlaufgeschwindigkeit von 100 ml/min mit einer Clearance von 70 ml/min als wirksam. Die Hämoperfusion mit beschicheter Aktivkohle war in diesen Versuchen aber eindeutig überlegen, denn insbesondere bei Konzentrationen um 1–2 ppm waren die Clearance-Werte 5–7mal höher als bei der Hämodialyse.Die in vitro-Ergebnisse wurden bei einem Patienten mit einer Paraquat-Vergiftung bestätigt: Bei Konzentrationen unter 1 ppm war die Hämodialyse wirkungslos, während durch Hämoperfusion relativ hohe Clearance-Werte erreicht wurden, so daß der Serumspiegel rasch unter die Nachweisgrenze abfiel.

     

Aquatic Insects and Trace Metals: Bioavailability,Bioaccumulation, and Toxicity

Abstract

The uptake of metals from food and water sources by insects is thought to be additive. For a given metal, the proportions taken up from water and food will depend both on the bioavailable concentration of the metal associated with each source and the mechanism and rate by which the metal enters the insect. Attempts to correlate insect trace metal concentrations with the trophic level of insects should be made with a knowledge of the feeding relationships of the individual taxa concerned. Pathways for the uptake of essential metals, such as copper and zinc, exist at the cellular level, and other nonessential metals, such as cadmium, also appear to enter via these routes. Within cells, trace metals can be bound to proteins or stored in granules. The internal distribution of metals among body tissues is very heterogeneous, and distribution patterns tend to be both metal and taxon specific. Trace metals associated with insects can be both bound on the surface of their chitinous exoskeleton and incorporated into body tissues. The quantities of trace meals accumulated by an individual reflect the net balance between the rate of metal influx from both dissolved and particulate sources and the rate of metal efflux from the organism. The toxicity of metals has been demonstrated at all levels of biological organization: cell, tissue, individual, population, and community. Much of the literature pertaining to the toxic effects of metals on aquatic insects is based on laboratory observations and, as such, it is difficult to extrapolate the data to insects in nature. The few experimental studies in nature suggest that trace metal contaminants can affect both the distribution and the abundance of aquatic insects. Insects have a largely unexploited potential as biomonitors of metal contamination in nature. A better understanding of the physico-chemical and biological mechanisms mediating trace metal bioavailability and exchange will facilitate the development of general predictive models relating trace metal concentrations in insects to those in their environment. Such models will facilitate the use of insects as contaminant biomonitors.     

Alzheimer’s disease – current trends in basic and clinical research. Highlights from the 16th ECNP

Advances in the molecular biological knowledge of neuronal nicotinic acetylcholine receptors (nAChRs) have led to a growing interest by the pharmaceutical industry in the development of novel compounds that selectively modulate nAChR function. The ability of (-)-nicotine, an activator of nAChRs, to enhance attentional aspects of cognition in animals and humans, to exert neuroprotective and anxiolytic-like effects, and presumably to mediate the negative correlation between smoking and Alzheimer's (and Parkinson's) Disease, has focused interest on the potential therapeutic utility of modulators of nAChR function for treatment of some of the deficits associated with these progressive, neurodegenerative conditions. Numerous compounds are known which activate nAChRs and which might serve as lead compounds toward the development of such agents. The pharmacologic diversity of neuronal nAChR subtypes suggests the possibility of developing selective compounds which would have more favourable side-effect profiles than existing agents. This broader class of agents, collectively called cholinergic channel modulators (ChCMs), is anticipated to encompass compounds which would have more favourable side-effect profiles than existing agents, which generally exhibit low selectivity. This selectivity may be achieved by preferentially activating some subtypes of nAChRs (i.e., Cholinergic Channel Activators, ChCAs) or inhibiting the function of other subtypes (Cholinergic Channel Inhibitors, ChCIs). An overview of the biology of nAChRs and the rationale for the use of ChCMs for the treatment of dementia related to neurodegenerative diseases are presented, followed by a discussion of lead compounds and compounds under consideration for clinical evaluation.     

2-(Acetoxyphenyl)-(Z)-styryl sulfides as cyclooxygenase inhibitors

2-(Acetoxyphenyl)-(Z)-styryl sulfides are described as selective cyclooxygenase-2 (COX-2) inhibitors, useful for treating inflammation and COX-2-mediated disorders including neoplasia. 2-(Acetoxyphenyl)-(Z)-styryl sulfide is claimed to be the most potent COX inhibitor in the series with a COX-2 selectivity ratio of 33. This compound is also claimed to be superior to celecoxib (Celebrex^®, Pfizer) in inhibiting cell growth of colorectal carcinoma cells. In this evaluation, the COX inhibitory activity of this compound is compared to that previously disclosed for diarylheterocycles and 2-(acetoxyphenyl)alkyl sulfides. The validity of the DLD-1 cell line in the growth inhibition studies is questioned based on recent literature reports indicating the lack of COX-2 expression in this cell line.     

Sleep-disordered breathing with chronic opioid use

Chronic opioid use for pain relief or as substitution therapy for illicit drug abuse is prevalent in our societies. In the US, retail distribution of methadone and oxycodone has increased by 824 and 660%, respectively, between 1997 and 2003. μ-Opioids depress respiration and deaths related to illicit and non illicit chronic opioid use are not uncommon. Since 2001 there has been an emerging literature that suggests that chronic opioid use is related to central sleep apnoea of both periodic and non-periodic breathing types, and occurs in ～ 30% of these subjects. The clinical significance of these sleep-related abnormalities are unknown. This review addresses the present knowledge of control of ventilation mechanisms during wakefulness and sleep, the effects of opioids on ventilatory control mechanisms, the sleep-disordered breathing found with chronic opioid use and a discussion regarding the future research directions in this area.     

Drug targets for cognitive enhancement in neuropsychiatric disorders

The investigation of novel drug targets for treating cognitive impairments associated with neurological and psychiatric disorders remains a primary focus of study in central nervous system (CNS) research. Many promising new therapies are progressing through preclinical and clinical development, and offer the potential of improved treatment options for neurodegenerative diseases such as Alzheimer's disease (AD) as well as other disorders that have not been particularly well treated to date like the cognitive impairments associated with schizophrenia (CIAS). Among targets under investigation, cholinergic receptors have received much attention with several nicotinic agonists (α7 and α4β2) actively in clinical trials for the treatment of AD, CIAS and attention deficit hyperactivity disorder (ADHD). Both glutamatergic and serotonergic (5-HT) agonists and antagonists have profound effects on neurotransmission and improve cognitive function in preclinical experiments with animals; some of these compounds are now in proof-of-concept studies in humans. Several histamine H3 receptor antagonists are in clinical development not only for cognitive enhancement, but also for the treatment of narcolepsy and cognitive deficits due to sleep deprivation because of their expression in brain sleep centers. Compounds that dampen inhibitory tone (e.g., GABA_A α5 inverse agonists) or elevate excitatory tone (e.g., glycine transporter inhibitors) offer novel approaches for treating diseases such as schizophrenia, AD and Down syndrome. In addition to cell surface receptors, intracellular drug targets such as the phosphodiesterases (PDEs) are known to impact signaling pathways that affect long-term memory formation and working memory. Overall, there is a genuine need to treat cognitive deficits associated with many neuropsychiatric conditions as well as an increasingly aging population.