Decreased endogenous secretory advanced glycation end product receptor in type 1 diabetic patients: its possible association with diabetic vascular complications

OBJECTIVE: The binding of advanced glycation end products (AGEs) to their receptor (RAGE) plays an important role in the development of diabetic vascular complications. In the present study, we examined circulating endogenous secretory RAGE (esRAGE) levels in subjects with type 1 diabetes and explored the possible association between esRAGE levels and the severity of diabetic vascular complications. RESEARCH DESIGN AND METHODS: Circulating esRAGE levels in serum were examined in 67 Japanese type 1 diabetic patients (22 men and 45 women, age 24.0 +/- 4.4 years [means +/- SD]) and 23 age-matched healthy nondiabetic subjects (10 men and 13 women aged 24.9 +/- 1.4 years). Daily urinary albumin excretion, the presence of retinopathy, and intima-media thickness (IMT) of the carotid artery were also evaluated. We further explored the association between esRAGE levels and severity of diabetic vascular complications. RESULTS: Circulating esRAGE levels were significantly lower in subjects with type 1 diabetes than in nondiabetic subjects (0.266 +/- 0.089 vs. 0.436 +/- 0.121 ng/ml, respectively, P < 0.0001) and was inversely correlated with HbA(1c) (A1C) levels (r = -0.614, P < 0.0001). In addition, multivariate regression analysis demonstrated that A1C was an independent risk factor for a low esRAGE value. Furthermore, circulating esRAGE levels were inversely correlated with carotid IMT (r = -0.325, P = 0.0017) and was one of the independent risk factors for IMT thickening. Furthermore, there was a significant difference (P = 0.0124) in esRAGE levels between patients without retinopathy (0.286 +/- 0.092 ng/ml) and those with retinopathy (0.230 +/- 0.074 ng/ml). CONCLUSIONS: Circulating esRAGE levels were significantly lower in type 1 diabetic patients than in nondiabetic subjects and were inversely associated with the severity of some diabetic vascular complications.     

氧化应激和糖基化终末产物在2型糖尿病心肌病变中的作用及其相关性

目的研究氧化应激因素和糖基化终末产物(AGEs)在2型糖尿病(T2DM)心肌病变(DCM)的作用及其相关性。方法选择泰安地区的T2DM患者78例,根据超声心动图、冠状动脉造影等情况,分为单纯T2DM组40例,DCM组38例,另选取正常对照组(NC)40例。测定超氧化物歧化酶(SOD)、丙二醛(MDA)、一氧化氮(NO)以及谷胱甘肽过氧化物酶(GHS-PX)等氧化应激指标和糖基化终末产物(AGEs),进行数据统计,并进行相关性分析。结果 T2DM组SOD、NO、GHS-PX较NC组均明显下降,MDA、AGEs则较NC组均明显升高;而DCM组较T2DM组SOD、GHS-PX明显下降,MDA、AGEs明显升高,差异均有统计学意义(P<0.01),而血清NO水平T2DM组较NC组下降,DCM组再次升高,且高于NC组,差异均有统计学意义(P<0.01)。结论氧化应激因素和AGEs在DCM的进展中均有重要作用,促进DCM的发生和发展,且二者之间有相关性,SOD的下降和MDA的升高是AGEs的独立相关因素。     

糖尿病前期患者晚期糖基化终末产物受体与氧化应激的关系

目的 通过测定糖耐量正常者、糖尿病前期及糖尿病患者血浆可溶性晚期糖基化终末产物受体(sRAGE)、内源性分泌型晚期糖基化终末产物受体(esRAGE)及氧化应激的水平,探讨糖尿病前期血浆sRAGE、esRAGE水平的变化与氧化应激的相关性,为深入了解糖尿病前期血管并发症的发病机制提供依据.方法 研究对象均行75 g标准口服葡萄糖耐量实验(OGTT)和胰岛素释放试验,按血糖水平分为糖耐量正常(NGT)组、糖尿病前期(Pre-DM)组、糖尿病(DM)组,采用酶联免疫吸附检测(ELISA)法检测血浆sRAGE、esRAGE、8-异前列腺素F2α(8-isoPGF2α);硫代巴比妥酸(TBA)法测定丙二醛(MDA),羟胺法测定超氧物岐化酶(SOD),比色法测定血浆总抗氧化能力(TAOC).结果 Pre-DM组和DM组的sRAGE、esRAGE、SOD水平明显低于NGT组,Pre-DM组和DM组的8-iso-PGF2α、MDA水平明显高于NGT组,差异均有统计学意义(P＜0.05);Pre-DM组和NGT组的TAOC水平明显高于DM组(P＜0.05);血浆esRAGE水平与sRAGE、TAOC呈正相关(r=0.39、0.64,P＜0.05),与MDA呈负相关(r =-0.45,P＜0.05),与年龄、体质量指数(BMI)、收缩压、舒张压、空腹血糖、空腹胰岛素、糖化血红蛋白、甘油三酯、低密度脂蛋白、高密度脂蛋白、8-iso PGF2α无明显相关性(P＜0.05).结论 糖尿病前期患者已发生sRAGE、esRAGE及氧化应激水平的改变,sRAGE、esRAGE在机体氧化应激与抗氧化防御平衡间可能发挥重要作用.     

Corneal advanced glycation end products increase in patients with proliferative diabetic retinopathy

OBJECTIVE: To evaluate corneal advanced glycation end product (AGE) fluorescence in patients with diabetes and in healthy control subjects. RESEARCH DESIGN AND METHODS: Corneal autofluorescence was measured in 26 eyes of 26 patients with type 2 diabetes (mean age 57.0 years; mean disease duration 12.2 years; mean HbA1c 7.1%) and 13 eyes of 13 healthy age-matched control subjects (mean age 57.9 years). The patients with type 2 diabetes were divided into the following groups: patients without diabetic retinopathy (DR), patients without proliferative diabetic retinopathy (PDR), and patients with PDR. Corneal autofluorescence was measured by fluorophotometry with the wavelength that is characteristic of AGE fluorescence (excitation and emission 360-370 nm and 430-450 nm, respectively). We defined peak corneal autofluorescence levels as corneal AGE fluorescence values. We compared the corneal AGE fluorescence values in the four groups. RESULTS: In the PDR group (11.9 +/- 3.9 arbitrary units [mean +/- SD]), the corneal AGE fluorescence values were significantly higher compared with the control subjects (6.9 +/- 1.3 arbitrary units), the patients without DR (7.4 +/- 2.1 arbitrary units), and the patients without PDR (6.9 +/- 2.2 arbitrary units) (P < 0.05). CONCLUSIONS: We found that corneal AGEs may increase in patients with diabetes and PDR compared with control subjects, patients without DR, and patients without PDR. In the patients with PDR, increased corneal AGEs may play a role in diabetic keratopathy.     

脂质体槲皮素对糖尿病大鼠视网膜糖基化终产物生成及受体表达的影响

目的观察脂质体槲皮素（LQ）对糖尿病（DM）大鼠视网膜糖基化终产物（AGEs）生成及受体（RAGEmRNA）表达的影响。方法采用蒸发-高压均质法制备LQ悬浊液,链脲佐菌素（STZ）法诱导DM大鼠模型,并随机分为DM模型组、LQ低、中、高剂量及氨基胍灌胃组;连续给药12周后,免疫荧光法、RT—PCR方法分别检测DM大鼠视网膜中AGEs沉积情况及RAGEmRNA的表达。结果与DM模型组结果（AGEs：0．922±0．005;RAGEmRNA：1．192±0．098）比较,LQ各组及氨基胍组视网膜中AGEs沉积减少,RAGEmRNA表达也降低（P〈0．05）,以LQ中剂量组（AGEs：0．734±0．007;RAGEmRNA：0．724±0．028）降低最为明显（P〈0．01）。结论LQ可通过有效减少DM大鼠视网膜中AGEs的沉积,下调RAGEmRNA的表达。     

Association between acute-phase reactants and advanced glycation end products in type 2 diabetes

OBJECTIVE: Type 2 diabetes is associated with chronic low-grade inflammation, but the underlying mechanism(s) is not well understood. Because in vitro studies have shown that advanced glycation end products (AGEs) can trigger inflammatory responses, the present study has investigated whether serum concentration of AGEs is an important determinant of circulating levels of inflammatory markers, like C-reactive protein (CRP), in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Diabetic patients (n = 210) and healthy control subjects (n = 110) of similar BMI were recruited. Serum AGEs were assayed by competitive enzyme-linked immunosorbent assay using a polyclonal rabbit anti-sera raised against AGE-RNase. Plasma high-sensitivity CRP was measured by an immunoturbidimetric assay and interleukin (IL)-6 by enzyme-linked immunosorbent assay. RESULTS: Serum AGEs were increased in diabetic patients compared with control subjects (4.24 +/- 0.88 vs. 3.15 +/- 0.81 unit/ml, respectively, P < 0.01). Both plasma CRP (1.55 [0.81-2.95] vs. 0.88 mg/dl [0.51-1.89], respectively, P < 0.01; median [interquartile range]) and IL-6 (0.80 [0.68-0.97] vs. 0.69 pg/ml [0.48-0.84], respectively, P < 0.01) were also higher in diabetic patients than in control subjects. In the diabetic patients, log(CRP) correlated with AGEs (r = 0.22, P = 0.002) and with log(IL-6) (r = 0.29, P < 0.001). Forward stepwise linear regression analysis showed that BMI, log(IL-6), and AGEs were significant independent determinants of log(CRP) in the diabetic patients, accounting for 17, 12, and 10% of the variation in log(CRP), respectively. CONCLUSIONS: Serum concentration of AGEs is increased in patients with diabetes and is an independent determinant of plasma CRP levels. Subclinical inflammation in these patients may therefore be partly due to activation of the inflammatory response by AGEs.     

Benfotiamine prevents macro- and microvascular endothelial dysfunction and oxidative stress following a meal rich in advanced glycation end products in individuals with type 2 diabetes

OBJECTIVE: Diabetes is characterized by marked postprandial endothelial dysfunction induced by hyperglycemia, hypertriglyceridemia, advanced glycation end products (AGEs), and dicarbonyls (e.g., methylglyoxal [MG]). In vitro hyperglycemia-induced MG formation and endothelial dysfunction could be blocked by benfotiamine, but in vivo effects of benfotiamine on postprandial endothelial dysfunction and MG synthesis have not been investigated in humans until now. RESEARCH DESIGN AND METHODS: Thirteen people with type 2 diabetes were given a heat-processed test meal with a high AGE content (HAGE; 15.100 AGE kU, 580 kcal, 54 g protein, 17 g lipids, and 48 g carbohydrates) before and after a 3-day therapy with benfotiamine (1,050 mg/day). Macrovascular flow-mediated dilatation (FMD) and microvascular reactive hyperemia, along with serum markers of endothelial disfunction (E-selectin, vascular cell adhesion molecule-1, and intracellular adhesion molecule-1), oxidative stress, AGE, and MG were measured during both test meal days after an overnight fast and then at 2, 4, and 6 h postprandially. RESULTS: The HAGE induced a maximum reactive hyperemia decrease of -60.0% after 2 h and a maximum FMD impairment of -35.1% after 4 h, without affecting endothelium-independent vasodilatation. The effects of HAGE on both FMD and reactive hyperemia were completely prevented by benfotiamine. Serum markers of endothelial dysfunction and oxidative stress, as well as AGE, increased after HAGE. These effects were significantly reduced by benfotiamine. CONCLUSIONS: Our study confirms micro- and macrovascular endothelial dysfunction accompanied by increased oxidative stress following a real-life, heat-processed, AGE-rich meal in individuals with type 2 diabetes and suggests benfotiamine as a potential treatment.     

Serum level of endogenous secretory receptor for advanced glycation end products and other factors in type 2 diabetic patients with mild cognitive impairment

OBJECTIVE

Determine the serum levels of endogenous secretory receptor for advanced glycation end products (esRAGEs) in patients with type 2 diabetes and mild cognitive impairment (MCI) and in control patients with type 2 diabetes but no MCI, and examine the relationship of esRAGE and MCI with other clinical factors.

RESEARCH DESIGN AND METHODS

A total of 101 patients with type 2 diabetes who were hospitalized in the Department of Endocrinology at Fujian Provincial Hospital between January 2010 and January 2011 were enrolled. There were 58 patients with MCI and 43 patients without MCI (control). Serum levels of esRAGE were measured using an enzyme-linked immunosorbent assay (ELISA). Other clinical parameters were also measured.

RESULTS

Type 2 diabetic patients with MCI had a longer duration of diabetes; elevated HbA_1c, total cholesterol (CHOL), LDL cholesterol (LDL-C), triglyceride (TG), intima-media thickness, C-reactive protein (CRP), and brachial-ankle pulse wave velocity (ba-PWV); and lower ankle brachial index (ABI) and esRAGE relative to the control group. Among patients with MCI, the Montreal Cognitive Assessment (MoCA) score was positively correlated with serum esRAGE but negatively correlated with CHOL. Spearman rank correlation analysis indicated that esRAGE was positively correlated with MoCA score and ABI but negatively correlated with ba-PWV, CHOL, TG, and CRP in all subjects.

CONCLUSIONS

Our results suggest that esRAGE may be a potential protective factor for dyslipidemia, atherosclerosis, and MCI in patients with type 2 diabetes.The condition of mild cognitive impairment (MCI) was first described in 1999 as a common disorder of aging adults that increases the risk for dementia and Alzheimer disease (AD) (1). Patients with MCI progress into dementia at an annual rate of 15.0% (1). There are approved treatments for AD, but not for MCI, although numerous clinical trials are investigating treatments for both conditions (2). The high worldwide prevalence of MCI, AD, and dementia points to the need to understand the pathogenesis of these disorders.The elevated serum glucose of patients with diabetes leads to nonenzymatic glycosylation of lipids and proteins and formation of advanced glycation end products (AGEs) (3). The accumulation of AGEs and their binding to receptors for AGE (RAGEs) on the plasma membrane triggers a series of reactions implicated in the development of disorders, such as diabetes complications and AD (4). In recent years, the endogenous soluble receptor for AGE (esRAGE) has been identified as a tissue-specific, soluble, alternative splicing isoform of RAGE that is primarily present in circulation (5). The cell-protecting function of esRAGE is attributed to its ability to capture extracellular AGEs (6).In the current study, we measured serum esRAGE levels in adult patients with type 2 diabetes and MCI and in a control group with type 2 diabetes but no MCI, and examined the association of esRAGE with clinical factors.     

Advanced glycation end products, oxidant stress and vascular lesions

The formation of advanced glycation end products (AGEs) is observed in conditions such as diabetes mellitus and ageing, both associated with vascular disorders. AGEs form by the interaction of an aldose with NH₂ of proteins, and the subsequent Amadori rearrangement leads to complex molecules. The heterogeneous class of AGE molecules is found in plasma, cells and tissues and accumulates in the vessel wall and the kidney. AGE reactions can generate reactive oxygen intermediates (ROIs), which can act as signal mediators and can be deleterious for molecules or cells. The AGEs and ROI-induced cellular dysfunctions can interfere with the gene expression of peptides and cytokines regulating cell proliferation and vascular functions. The interaction of AGEs with the AGE receptor (RAGE) is followed by a series of intracellular modifications that may be involved in the development of atherosclerosis. An attempt to minimize AGE formation and to limit ROI production by an appropriate therapy may result in the reduction or slowing of vascular disease in patients with diabetes mellitus.     

阿托伐他汀对2型糖尿病鼠主动脉糖基化终末产物受体基因表达的影响

目的观察阿托伐他汀对2型糖尿病(GK)大鼠动脉壁糖基化终末产物受体(RAGE)基因表达的影响,探讨阿托伐他汀抗糖尿病动脉粥样硬化作用的潜在机制。方法健康雄性Wistar大鼠5只作为正常对照组,GK大鼠随机分为糖尿病对照组(5只)和糖尿病阿托伐他汀治疗组(4只,每日1次阿托伐他汀20mg/kg灌胃)。各组均采用高脂饮食喂养。12周后,采用透射电镜观察主动脉壁超微结构,定量RT-PCR测定主动脉RAGE和单核细胞趋化蛋白-1(MCP-1)的表达。结果与正常对照组比较,糖尿病对照组主动脉RAGE和MCP-1表达明显升高,而阿托伐他汀治疗能够降低RAGE和MCP-1的表达。主动脉RAGE表达水平与MCP-1表达水平呈显著正相关(r=0.482,P=0.031)。透射电镜下糖尿病大鼠动脉可见超微结构的改变。结论 RAGE表达在2型糖尿病早期动脉粥样硬化形成过程中明显上调,阿托伐他汀可通过下调RAGE的表达抗动脉粥样硬化的形成。     

一氧化氮及血液净化治疗对糖尿病肾病患者血浆晚期糖基化终产物水平的影响

目的　观察不同血液净化治疗方法及血浆一氧化氮 (NO)对终末期糖尿病肾病 (DN)患者血浆晚期糖基化终产物 (AGEs)的影响。方法　终末期DN患者应用不同血液净化方式治疗 2个月 ,应用荧光分光光度法检测血浆AGEs水平 ;应用α -萘胺显色分光光度计比色法测定血浆中NO浓度。结果　随着肾功能的恶化 ,DN患者的血浆AGEs水平逐渐升高 ,二者呈明显正相关 (r=0 .781)。血液透析 (HD)治疗后AGEs水平变化不明显。单次血液透析滤过 (HDF)使血浆AGEs水平明显降低 (P <0 .0 1) ,治疗两个月后AGEs水平无明显变化。血浆AGEs的水平与NO水平成正相关 (r =0 .5 97)。结论　终末期DN患者血浆AGEs水平受血糖和肾功能双方面的影响 ,其中肾功能对其影响较大。HDF可以有效清除AGEs,但不能有效控制AGEs的透析前水平。未见NO对AGEs在体内有明确的抑制作用。     

Serum levels of advanced glycation end products are increased in patients with type 2 diabetes and coronary heart disease.

OBJECTIVE: To investigate whether serum levels of advanced glycation end products (AGEs) and the glycoxidation product Nepsilon-(carboxymethyl)lysine (CML) are increased in patients with type 2 diabetes compared with nondiabetic control subjects and whether levels of AGEs and/or CML differ in patients with type 2 diabetes with or without coronary heart disease (CHD). RESEARCH DESIGN AND METHODS: Serum levels of AGEs and CML were measured with an immunoassay in 32 men and 21 women aged 59.3+/-6.2 years (means +/- SD) with type 2 diabetes for 7.3 + 3.1 years and in 17 men and 17 women aged 56.2+/-4.2 years without diabetes. Of the patients with diabetes, 18 had CHD. RESULTS: The serum levels of AGEs and CML were significantly increased in patients with type 2 diabetes compared with nondiabetic control subjects (median [5th-95th percentile]: AGEs 7.4 [4.4-10.9] vs. 4.2 [1.6-6.4] U/ml, P < 0.0001; CML 15.6 [5.6-29.9] vs. 8.6 [4.4-25.9] U/ml, P < 0.0001). The median level of AGEs but not CML was significantly increased in patients with type 2 diabetes and CHD compared with patients without CHD (8.1 [6.4-10.9] vs. 7.1 [3.5-9.8] U/ml, P = 0.03). There were significant positive correlations between serum levels of AGEs and CML in both patients and control subjects. CONCLUSIONS: Levels of AGEs and CML were significantly increased in patients with type 2 diabetes compared with nondiabetic control subjects, and levels of AGEs but not CML were significantly higher in patients with type 2 diabetes and CHD than in patients without diabetes. These results may indicate a role for non-CML AGEs in the development of macrovascular disease in patients with type 2 diabetes.     

吡哆胺对体外晚期糖基化及其终产物形成的抑制作用

目的体外观察吡哆胺对晚期糖基化和晚期糖基化终产物(AGEs)形成的抑制作用。方法应用牛血清白蛋白-葡萄糖试验和N-乙酰-甘氨酰-赖氨酸甲基酯-核糖两种体外试验,观察吡哆胺对糖基化反应及AGEs形成的抑制效果。结果牛血清白蛋白-葡萄糖试验显示,吡哆胺对糖基化反应具有明显抑制效果。在50 mmol/L和200 mmol/L葡萄糖浓度下,当吡哆胺浓度为50 mmol/L时,相对抑制率均在50%以上。200 mmol/L吡哆胺对糖基化的抑制作用最强,其相对抑制率分别达到92.12%和86.73%。N-乙酰-甘氨酰-赖氨酸甲基酯-核糖试验证明,吡哆胺能明显抑制晚期糖基化产物AGEs的形成。随着吡哆胺剂量的增大,吡哆胺对AGEs形成的抑制作用明显增强。结论吡哆胺对体外晚期糖基化反应和AGEs形成有明显抑制作用。