槟榔碱抑制氧化型低密度脂蛋白诱导的小鼠巨噬细胞炎症因子表达及其机制

目的 观察槟榔碱对氧化型低密度脂蛋白诱导的小鼠巨噬细胞炎症因子表达的影响,并探讨其作用机制.方法不同浓度槟榔碱(10-6、10-5、10-4和10-3moL/L)处理细胞24 h,台盼兰拒染法观察细胞活力;氧化型低密度脂蛋白诱导小鼠巨噬细胞,同时给予槟榔碱处理,采用逆转录聚合酶链反应检测肿瘤坏死因子α、白细胞介素6和细胞间黏附分子1 mRNA的表达以及过氧化体增殖物激活型受体γ mRNA的表达.结果 槟榔碱处理细胞24h后,10-3 mol/L组细胞活力下降(P<0.01),而10-6、10-5和10-4 mol/L组对细胞活力无明显影响;10-6、10-5和10-4 mol/L槟榔碱分别处理细胞24 h后,对肿瘤坏死因子α、白细胞介素6和细胞间黏附分子1 mRNA的表达无明显影响;10-6mol/L槟榔碱与氧化型低密度脂蛋白共同处理细胞24 h后,细胞肿瘤坏死因子α、白细胞介素6和细胞间黏附分子1 mRNA的表达无显著改变,而10-5和10-4mol/L槟榔碱明显抑制氧化型低密度脂蛋白诱导的小鼠巨噬细胞肿瘤坏死因子α、白细胞介素6和细胞间黏附分子1 mRNA的表达,且10-5mol/L槟榔碱使氧化型低密度脂蛋白诱导的细胞内过氧化体增殖物激活型受体γ mRNA的表达增加(P<0.01).结论 槟榔碱抑制氧化型低密度脂蛋白诱导的巨噬细胞炎症因子表达,其作用机理可能是通过过氧化体增殖物激活型受体γ起作用.     

过氧化体增殖物激活型受体γ配体抑制巨噬—泡沫细胞炎性介质和基质金属蛋白酶2的分泌

目的在证实泡沫细胞有过氧化体增殖物激活型受体γ表达的基础上,探讨其配体对巨噬细胞、泡沫细胞炎性介质和基质金属蛋白酶分泌的影响。方法体外诱导THP-1单核细胞分化为巨噬细胞,给予氧化型低密度脂蛋白进一步诱导其转变为泡沫细胞,应用逆转录聚合酶链反应检测过氧化体增殖物激活型受体γmRNA表达;过氧化体增殖物激活型受体γ配体吡格列酮干预后用Western blot检测巨噬细胞CD40蛋白的表达;用酶联免疫吸附测定法测定泡沫细胞培养上清液中白细胞介素6、肿瘤坏死因子α、基质金属蛋白酶2和9的浓度,Gelatin Zymog-raphy测定基质金属蛋白酶活性。结果巨噬细胞转化为泡沫细胞后其过氧化体增殖物激活型受体γ基因表达无显著变化。吡格列酮可显著抑制巨噬细胞CD40的表达,呈剂量依赖性;显著抑制泡沫细胞白细胞介素6、肿瘤坏死因子α和基质金属蛋白酶9的分泌(P<0.05),抑制基质金属蛋白酶9的活性,对基质金属蛋白酶2的分泌和活性无影响。结论巨噬细胞、泡沫细胞中过氧化体增殖物激活型受体γ基因表达无变化。过氧化体增殖物激活型受体γ配体从多个环节抑制致动脉粥样硬化炎性因子的分泌,减少基质金属蛋白酶的释放并抑制其活性,对防治动脉粥样硬化有利。     

过氧化体增殖物激活型受体对心肌能量代谢调控的病理生理机制

过氧化体增殖物激活型受体是调节编码脂肪酸β－氧化相关酶类基因的重要转录调节因子，在调节心肌能量代谢中发挥重要作用。心肌肥厚和心力衰竭时心肌细胞过氧化体增殖物激活型受体α的表达和转录调控活性均降低，脂肪酸β－氧化的相关酶类基因（过氧化体增殖物激活型受体α的靶基因）的表达在转录水平降低，说明过氧化体增殖物激活型受体α可能通过信号转导途径影响心肌的能量代谢。过氧化体增殖物激活型受体γ激活剂可增加心肌细胞对葡萄糖的氧化和利用，减轻心肌缺血／再灌注损伤和心肌肥厚的程度，有潜在的心脏保护作用。但仍缺乏过氧化体增殖物激活型受体γ激活剂对心肌能量代谢的调控与心脏保护作用关系的研究报道。     

高密度脂蛋白2和高密度脂蛋白3对THP-1巨噬细胞脂质蓄积及过氧化体增殖物激活型受体γ和CD36表达的影响

为探讨高密度脂蛋白2和高密度脂蛋白3对THP-1巨噬细胞过氧化体增殖物激活型受体γ和CD36表达及脂质蓄积的影响。取新鲜抗凝血浆，用超速离心术进行密度梯度离心，收集低密度脂蛋白、高密度脂蛋白2和3。将氧化型低密度脂蛋白分别与高密度脂蛋白2和3共孵育THP-1巨噬细胞，用油红O染色及高效液相分析法观测细胞内脂质蓄积程度；用逆转录聚合酶链反应检测CD36和过氧化体增殖物激活型受体γ mRNA的表达：用Westem blotting检测CD36和过氧化体增殖物激活型受体γ蛋白的表达。结果发现，与单独用氧化型低密度脂蛋白和THP-1孵育相比，用高密度脂蛋白2、高密度脂蛋白3分别与氧化型低密度脂蛋白共孵育THP-1可使细胞内脂质蓄积明显减少，过氧化体增殖物激活型受体γ mRNA及蛋白表达上调，CD36 mRNA及蛋白表达下调。而高密度脂蛋白3比高密度脂蛋白2作用更明显。结果提示，高密度脂蛋白2和3对氧化型低密度脂蛋白诱导THP-1细胞脂质蓄积有显著抑制作用，而高密度脂蛋白3的作用更强。其机制与高密度脂蛋白可以增强过氧化体增殖物激活型受体γ mRNA和蛋白表达上调及过氧化体增殖物激活型受体γ磷酸化，进而抑制过氧化体增殖物激活型受体γ的应答基因CD36 mRNA及蛋白表达有关。     

过氧化体增殖物激活型受体γ对巨噬细胞脂质蓄积及CD36表达的影响

目的观察过氧化体增殖物激活型受体γ激动剂和拮抗剂对THP-1巨噬细胞胆固醇蓄积及CD36表达的影响。方法实验分对照组、氧化型低密度脂蛋白组、Ciglitazone处理组和GW9662处理组,后两组用50 mg/L氧化型低密度脂蛋白分别与过氧化体增殖物激活型受体γ激动剂Ciglitazone(10μmol/L)及拮抗剂GW9662(10μmol/L)共同孵育24 h,高效液相色谱分析法检测细胞总胆固醇蓄积情况,RT-PCR和Western blot分别检测THP-1巨噬细胞CD36 mRNA和蛋白的表达。结果与对照组(76.28±10.36 mg/g)相比,氧化型低密度脂蛋白(121.63±13.32 mg/g)能使细胞总胆固醇含量显著增加,而Ciglitazone能使氧化型低密度脂蛋白处理的细胞总胆固醇含量进一步增加(136.23±14.78 mg/g),GW9662能使氧化型低密度脂蛋白处理的细胞总胆固醇含量减少(98.52±11.45 mg/g)。过氧化体增殖物激活型受体γ拮抗剂GW9662使巨噬细胞CD36 mRNA和蛋白的表达下调及胆固醇蓄积减少,过氧化体增殖物激活型受体γ激动剂Ciglitazone使巨噬细胞CD36 mRNA和蛋白的表达上调及胆固醇蓄积增多。结论过氧化体增殖物激活型受体γ拮抗剂使THP-1巨噬细胞胆固醇蓄积减少及氧化型低密度脂蛋白诱导的CD36表达下调。     

过氧化体增殖物激活型受体各亚型与动脉粥样硬化形成

大量资料证实转录因子过氧化体增殖物激活型受体在动脉粥样硬化形成中起重要调控作用。过氧化体增殖物激活型受体系核受体家族成员之一，作为配体活化的转录因子，最初被发现能够调节各种代谢通路。过氧化体增殖物激活型受体α、γ和β/δ各亚型的配体衍化物有60％～80％的同源性，但其配体和靶基因的特异性显著不同。过氧化体增殖物激活型受体各亚型在组成血管壁的各种细胞中均有表达，具有抗炎和潜在抗动脉粥样硬化特性。动物模型和临床研究表明活化的过氧化体增殖物激活型受体α和过氧化体增殖物激活型受体γ直接作用于血管壁，减缓动脉粥样硬化的进程。目前尚无资料证明过氧化体增殖物激活型受体β/γ激动剂在动脉粥样硬化形成中有何作用。认识过氧化体增殖物激活型受体α和过氧化体增殖物激活型受体γ激动剂的血管保护作用并在心血管病高危患者中使用，具有重要的临床价值。     

NO-1886对过氧化体增殖物激活型受体、脂蛋白脂肪酶和肿瘤坏死因子α基因表达的影响

为了探讨脂蛋白脂肪酶活化剂NO-1886对高脂高糖饮食喂养贵州小香猪过氧化物体增殖物激活型受体、脂蛋白脂肪酶及肿瘤坏死因子α表达的影响，选择雄性贵州小香猪15头，随机分为3组。正常对照组喂普通饲料；高脂高糖组喂高脂高蔗糖饲料；治疗组喂高脂高蔗糖饲料4个月后加1％NO-1886冶疗。8个月后处死动物，采用Trizol提取组织总RNA，逆转录聚合酶链反应检测过氧化体增殖物激活型受体、脂蛋白脂肪酶及肿瘤坏死因子nmRNA的表达。结果发现，正常对照组肌肉组织和肝脏过氧化体增殖物激活型受体α的表达较低。高脂高糖组肌肉组织和肝脏过氧化体增殖物激活型受体α的表达增强，NO-1886使高脂高糖喂养增强肌肉组织和肝脏过氧化体增殖物激活型受体α表达的作用减弱；在脂肪组织，治疗组脂蛋白脂肪酶的表达水平最高，分别比正常对照组和高脂高糖组高27％和20％；NO-1886抑制高脂高糖喂养小香猪脂肪组织肿瘤坏死因子α的表达。结果提示，NO-1886能促进小香猪脂肪组织脂蛋白脂肪酶的表达，显著抑制脂肪组织肿瘤坏死因子α基因表达，高调脂肪组织过氧化体增殖物激活型受体γ，减弱肝脏和肌肉过氧化体增殖物激活型受体α的表达，是NO-1886有效降低血浆游离脂肪酸和肿瘤坏死因子α水平可能的机制。     

过氧化体增殖物激活型受体γ和δ在高密度脂蛋白介导细胞胆固醇流出中的作用

为探讨过氧化体增殖物激活型受体γ和δ在高密度脂蛋白介导的细胞胆固醇流出中的作用。取新鲜抗凝血浆 ,用超速离心机进行密度梯度离心 ,收集密度为 1 .0 6 3～ 1 .2 1 0组分。U937细胞用 5 0～ 4 0 0nmol L反义过氧化体增殖物激活型受体γ和δ预处理细胞 1 2h。培养U937细胞与 0 .2 8mCi L [3H] 胆固醇乙醇液共孵育 2 4h ,15 0 0r min离心 1 0min ,收集细胞 ,PBS漂洗 2次 ,RPMI 1 6 4 0重悬细胞 ,加HDL继续培养 0～ 4 8h。液体闪烁计数仪测细胞相对放射活性。Westernblot检测过氧化体增殖物激活型受体γ和δ蛋白表达水平。不同浓度HDL处理后细胞胆固醇流出具有明显差异 ,呈剂量 -效应关系。用 1 0 0nmol L反义过氧化体增殖物激活型受体γ处理 2 4h后 ,HDL介导的细胞胆固醇流出减少 (4 5 78± 2 0 6 ) ,与对照组 (4 0 2 4± 385 )比较差别有显著性。过氧化体增殖物激活型受体γ激动剂ciglitizone预处理后 ,HDL介导的细胞胆固醇流出增加 ,用 0、2 5、5 0、1 0 0、2 0 0 μmol Lciglitizone处理的放射活性分别为 4 371± 2 4 3、386 9± 2 1 2、346 9± 2 0 9、31 5 6± 31 5和 30 2 0± 2 96。反义过氧化体增殖物激活型受体δ处理后 ,HDL介导的细胞胆固醇流出略有增加 ,处理浓度达 4 0 0nmol L时的放射活     

过氧化体增殖物激活型受体δ激动剂抑制RAW264.7细胞炎症因子的表达

目的探讨过氧化体增殖物激活型受体δ激动剂GW0742对氧化型低密度脂蛋白诱导的RAW264.7细胞单核细胞趋化蛋白1、血管细胞黏附分子1、基质金属蛋白酶9基因和蛋白表达的影响。方法构建小鼠过氧化体增殖物激活型受体δ基因干扰慢病毒载体及空病毒载体,将培养的RAW264.7细胞分为对照组、GW0742组、GW0742+过氧化体增殖物激活型受体δ干扰组以及假干扰组,各组均给予氧化型低密度脂蛋白(50mg/L)孵育24h。分别采用逆转录聚合酶链反应和蛋白免疫印迹法检测细胞中单核细胞趋化蛋白1、血管细胞黏附分子1及基质金属蛋白酶9的mRNA及蛋白表达。采用单核细胞趋化实验观察人外周血单核细胞在不同条件培养基中的趋化活性。结果GW0742组细胞中单核细胞趋化蛋白1、血管细胞黏附分子1及基质金属蛋白酶9的mRNA及蛋白表达显著低于对照组(P<0.01或P<0.05),而过氧化体增殖物激活型受体δ干扰显著削弱GW0742对单核细胞趋化蛋白1、血管细胞黏附分子1及基质金属蛋白酶9的抑制作用(P<0.01或P<0.05)。GW0742组单核细胞迁移距离小于对照组(P<0.05),而过氧化体增殖物激活型受体δ干扰能阻断GW0742...     

过氧化体增殖物激活型受体反应元件类似序列对细胞胆固醇外流的影响

目的　过氧化体增殖物激活型受体是调节脂质代谢的关键固醇类核内受体家族 ,过氧化体增殖物激活型受体反应元件调控多种与脂质代谢相关的蛋白和酶类 ,包括细胞胆固醇转运相关蛋白。探讨过氧化体增殖物激活型受体反应元件掩蔽物对细胞大胆固醇流出的影响。方法　设计的掩蔽物序列以过氧化体增殖物激活型受体α对过氧化体增殖物激活型受体的结合为基础。掩蔽物Scrambled寡核苷酸序列为ACTTGATCCCGTTTCAACTC ,寡核苷酸为TAAGGGAATCAGCAAGAGGT。培养U937细胞通过 5mg Llipofectin处理 4h ,用 0 .1～ 1μmol L掩蔽物或 1μmol L随机寡核苷酸转染。换培养基后加HDL或过氧化体增殖物激活型受体γ激动剂ciglitizone处理 2 4h。结果　过氧化体增殖物激活型受体反应元件掩蔽物寡核苷酸经质脂体介导转染细胞后可以抑制过氧化体增殖物激活型受体γ的促细胞胆固醇流出作用。由于所设计的过氧化体增殖物激活型受体反应元件掩蔽物无过氧化体增殖物激活型受体型特异性 ,因此 ,掩蔽物寡核苷酸产生的效应是各亚型过氧化体增殖物激活型受体在细胞内调控基因表达的综合效应。过氧化体增殖物激活型受体反应元件掩蔽物寡核苷酸的净效应是使细胞胆固醇流出效率降低。结论　三种过氧化体增殖物激活型受体亚型可能都参与细胞胆固     

胰岛素瘤的解剖分布特点分析

目的胰岛素瘤是最常见的胰腺神经内分泌肿瘤，因其临床表现多样，导致诊断困难。影像学诊断尤其是超声内镜(EUS)在胰岛素瘤的诊断中起着重要作用，拥有较高的敏感性和特异性。本研究拟通过明确胰岛素瘤的解剖分布特点，以期有助于提高影像学的诊断准确率和降低漏诊率，尤其是在教育和培训实践中对于EUS的学习者更具有指导价值。 方法回顾性分析解放军总医院第一医学中心病案资料数据库1993年1月至2019年11月经外科手术、病理确诊为胰岛素瘤的患者的临床资料，检索方法采取搜索术后病理诊断为"胰岛素瘤"的病例，通过查阅病例的方法，提取出胰岛素瘤的大小和解剖分布等数据，进一步分析其特点。 结果共检索到确诊为胰岛素瘤的患者116例，其中，男45例、女71例，年龄13～76岁，平均年龄(44.4±14.85)岁。胰岛素瘤单发110例(94.8%)、多发6例(5.2%)。位置分布：头颈部46例(39.7%)，单发45例、多发1例；体尾部68例(58.6%)，单发65例、多发3例；全胰腺多发2例(1.7%)。病变大小特点：最大径0.4～3.4 cm，平均大小(1.53±0.58)cm。≤1 cm 29例、>1 cm而≤1.5 cm41例、>1.5 cm而≤2.0 cm28例，≤3 cm 15例，>3 cm 3例。年龄与肿瘤的大小相关，≤44岁患者肿瘤平均大小为(1.36±0.51)cm、>44岁患者肿瘤平均大小为(1.70±0.60)cm，P<0.05。头颈部的肿瘤大于体尾部的肿瘤，头颈部肿瘤平均大小(1.66±0.63)cm，体尾部(1.42±0.52)cm，P<0.05。 结论胰岛素瘤在胰腺体尾部较头颈部更好发；绝大多数单发，但可以全胰腺多发；多数小于1.5 cm，肿瘤的大小与患者年龄和肿瘤的解剖分布相关。     

Pathogenesis of carcinoma of the papilla of Vater

Most adenomas and carcinomas of the small intestine and extrahepatic bile ducts arise in the region of the papilla of Vater. In familial adenomatous polyposis (FAP) it is the main location for carcinomas after proctocolectomy. In many cases symptoms due to stenosis lead to diagnosis at an early tumor stage. In about 80%, curative intended resection is possible. Operability is the most relevant prognostic factor. Most ampullary carcinomas resp. carcinomas of the papilla of Vater develop from adenomatous or flat dysplastic precursor lesions. They can be sited in the ampulloduodenal part of the papilla of Vater, which is lined by intestinal mucosa. They also can develop in deeper parts of the ampulla, which are lined by pancreaticobiliary duct mucosa. Intestinal-type adenocarcinoma and pancreaticobiliary-type adenocarcinoma represent the main histological types of ampullary carcinoma. Furthermore, there exist unusual types and undifferentiated carcinomas. Many carcinomas of intestinal type express the immunohistochemical marker profile of intestinal mucosa (keratin 7?, keratin 20+, MUC2+). Carcinomas of pancreaticobiliary type usually show the immunohistochemical profile of pancreaticobiliary duct mucosa (keratin 7+, keratin 20?, MUC2?). Even poorly differentiated carcinomas, as well as unusual histological types, may conserve the marker profile of the mucosa they developed from. These findings underline the concept of histogenetically different carcinomas of the papilla of Vater which develop either from intestinal- or from pancreaticobiliary-type mucosa of the papilla of Vater. Molecular alterations in ampullary carcinomas are similar to those of colorectal as well as pancreatic carcinomas, although they appear at different frequencies. In future studies, molecular alterations in ampullary carcinomas should be correlated closely with the different histologic tumor types. Consequently, the histologic classification should reflect the histogenesis of ampullary tumors from the two different types of papillary mucosa.     

Demonstration of the mechanism of action of biguanides

Summary Palmitic acid oxidation in rat diaphragm homogenate is depressed by biguanide concentrations that are still incapable of inhibiting oxidative phosphorylation. Glucose oxidation is not directly effected by the same biguanide concentrations: however, the inhibitory effect of palmitic acid on glucose oxidation is partly removed by biguanides. Inhibition of fatty acid oxidation, which accounts for most of the metabolic effects caused by these drugs, can be regarded as the fundamental mechanism of action of biguanides. There is some evidence suggesting that these drugs might interact with carnitine, thus preventing long-chain fatty acids from being transported across the mitochondrial membrane to the site of oxidation. Traduzione a cura degli AA.     

Lack of correlation of degree of villous atrophy with severity of clinical presentation of coeliac disease

BACKGROUND AND AIM: Both the clinical presentation and the degree of mucosal damage in coeliac disease vary greatly. In view of conflicting information as to whether the mode of presentation correlates with the degree of villous atrophy, we reviewed a large cohort of patients with coeliac disease. PATIENTS AND METHODS: We correlated mode of presentation (classical, diarrhoea predominant or atypical/silent) with histology of duodenal biopsies and examined their trends over time. RESULTS: The cohort consisted of 499 adults, mean age 44.1 years, 68% females. The majority had silent coeliac disease (56%) and total villous atrophy (65%). There was no correlation of mode of presentation with the degree of villous atrophy (p=0.25). Sixty-eight percent of females and 58% of males had a severe villous atrophy (p=0.052). There was a significant trend over time for a greater proportion of patients presenting as atypical/silent coeliac disease and having partial villous atrophy, though the majority still had total villous atrophy. CONCLUSIONS: Among our patients the degree of villous atrophy in duodenal biopsies did not correlate with the mode of presentation, indicating that factors other than the degree of villous atrophy must account for diarrhoea in coeliac disease.     

血吸虫童虫生长发育及其机制的研究进展

血吸虫童虫是宿主免疫系统攻击的重要靶标,包括皮肤型、肺型和肝门型童虫。宿主分子对童虫生长发育具有重要作用。童虫生长发育机制包括免疫调节、信号转导、性别发育及凋亡等。肌动蛋白、组织蛋白酶、烯醇化酶和葡萄糖基转移酶等分子为血吸虫童虫生长发育的重要分子。本文对血吸虫童虫生长发育及其机制的研究进展做一综述。     

124例耐多药结核分枝杆菌基因突变特征分析

目的对临床分离的耐多药结核分枝杆菌相关基因的突变特征进行分析。方法对124例耐多药结核分枝杆菌以及50株敏感株的耐药相关基因(包括异烟肼inh A、kat G、oxyR-ahp C间隔区以及利福平rpo B)进行序列测定,分析其基因突变情况。结果异烟肼耐药inh A基因突变率为14.5%;kat G基因突变率为70.2%(87/124),主要位于315位;oxyR-ahp C间隔区突变率为15.3%;inh A、kat G两种基因同时突变率75.0%,三种基因同时突变率为89.5%。利福平rpo B基因突变的检出率高达95.2%,突变主要发生在531、526、516位点。结论我省耐多药菌异烟肼耐药相关基因最常见突变为kat G 315、inh A C-T(-15)、axyR-ahp C间隔区(-10)C-T,利福平为rpo B531、526、516。结合MDR-TB耐药相关基因的特征分析,可以建立一种快速、准确、特异的适合于我省的检测结核菌耐多药性的新方法。     

氯硝柳胺悬浮剂的毒性评价

目的评价氯硝柳胺悬浮剂的毒性，为现场大规模应用灭螺提供依据。方法按照中华人民共和国国家标准GB 15670-1995《农药登记毒理学试验方法》和鱼类毒性试验方法进行。结果经口、经皮肤的LDso雌、雄性大鼠均>5 000 mg/kg，经呼吸道的LCso雌、雄性大鼠均>5 000mg/m3，该药经口、经皮肤、经呼吸道毒性均属微毒类药物；兔眼用药后，观察期内无不良反应，对眼无刺激性；皮肤用药后对皮肤无刺激性。与氯硝柳胺原药、氯硝柳胺乙醇胺盐原药和氯硝柳胺乙醇胺盐可湿性粉剂相比，氯硝柳胺悬浮剂对鱼急性毒性最低。结论氯硝柳胺悬浮剂属微毒类药物，对鱼的毒性低于其乙醇胺盐可湿性粉剂，适合于现场应用。     

Assessment of quality of life of parents of children with juvenile chronic arthritis

The aim of the study was to assess the quality of life (QOL) and the psychological status of parents of children with juvenile chronic arthritis (JCA). The QOL, anxiety and depression of the parents of 28 children with JCA were evaluated and compared to those of the parents of 28 healthy children. Mothers of JCA children and mothers of healthy children reported similar QOL. The reported anxiety and depression levels were similar for mothers and fathers in both groups. The parents of children with pauciarticular-type JCA reported lower QOL and higher levels of anxiety and depression than the parents of children with other types, namely polyarticular and systemic JCA. These findings may be explained by the fact that the pauciarticular patients had shorter disease duration and were less frequently seen in the outpatient clinic. The QOL of mothers of children with JCA was found to be slightly impaired in the group of children with pauciarticular JCA. Future larger studies are needed to confirm these results, as the number of subjects in the three groups was rather low. Received: 26 September 2001 / Accepted: 8 February 2002     

Numerical Simulation of the Effect of Rate of Change of Glucose on Measurement Error of Continuous Glucose Monitors

Background

A 5-day in-patient study designed to assess the accuracy of the FreeStyle Navigator® Continuous Glucose Monitoring System revealed that the level of accuracy of the continuous sensor measurements was dependent on the rate of glucose change. When the absolute rate of change was less than 1 mg•dl⁻¹•min⁻¹ (75% of the time), the median absolute relative difference (ARD) was 8.5%, with 85% of all points falling within the A zone of the Clarke error grid. When the absolute rate of change was greater than 2 mg•dl⁻¹•min⁻¹ (8% of the time), the median ARD was 17.5%, with 59% of all points falling within the Clarke A zone.

Method

Numerical simulations were performed to investigate effects of the rate of change of glucose on sensor measurement error. This approach enabled physiologically relevant distributions of glucose values to be reordered to explore the effect of different glucose rate-of-change distributions on apparent sensor accuracy.

Results

The physiological lag between blood and interstitial fluid glucose levels is sufficient to account for the observed difference in sensor accuracy between periods of stable glucose and periods of rapidly changing glucose.

Conclusions

The role of physiological lag on the apparent decrease in sensor accuracy at high glucose rates of change has implications for clinical study design, regulatory review of continuous glucose sensors, and development of performance standards for this new technology. This work demonstrates the difficulty in comparing accuracy measures between different clinical studies and highlights the need for studies to include both relevant glucose distributions and relevant glucose rate-of-change distributions.     

Study of constancy of hydrogen-consuming flora of human colon

The constancy of the hydrogen consuming flora of the human colon was studied in 15 healthy subjects via two measurements obtained 18 to 36 months apart. Hydrogen disappearance rate and the major products of H₂-consuming bacteria, methane and sulfide, were measured during incubation of fecal homogenates with excess hydrogen and sulfate. In 11/15, the hydrogen consumption rate and the predominant hydrogen-consuming pathway (methanogenesis, sulfate reduction, or neither) remained constant. However, major shifts in these pathways were observed in four subjects, with two losing and two gaining the ability to produce methane. Methanogenesis was associated with the highest hydrogen consumption rate. This study demonstrates that clinically unrecognizable, major alterations of the colonic flora occur in healthy subjects. Understanding of the factors responsible for these alterations might allow for therapeutic manipulation of the colonic flora.Supported in part by the Department of Veterans Affairs and NIDDKD RO1 DK 13309-25.