The antihypertensive effect of arginine

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at increased risk of stroke, heart disease and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Reducing dietary salt is effective in lowering blood pressure in salt-sensitive individuals. Insulin resistance and altered glucose metabolism are common features of hypertension in humans and animal models, with or without salt sensitivity. Altered glucose metabolism leads to increased formation of advanced glycation end products. Insulin resistance is also linked to oxidative stress, and alterations in the nitric oxide pathway and renin angiotensin system. A diet rich in protein containing the semiessential amino acid, arginine, and arginine treatment, lowers blood pressure in humans and in animal models. This may be due to the ability of arginine to improve insulin resistance, decrease advanced glycation end products formation, increase nitric oxide, and decrease levels of angiotensin II and oxidative stress, with improved endothelial cell function and decreased peripheral vascular resistance. The Dietary Approaches to Stop Hypertension (DASH) study demonstrated that the DASH diet, rich in vegetables, fruits and low-fat dairy products; low in fat; and including whole grains, poultry, fish and nuts, lowered blood pressures even more than a typical North American diet with similar reduced sodium content. The DASH diet is rich in protein; the blood pressure-lowering effect of the DASH diet may be due to its higher arginine-containing protein, higher antioxidants and low salt content.     

Antioxidants in the Treatment of Hypertension

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance and glucose intolerance are common features of hypertension in humans and in animal models. Altered glucose metabolism leads to an increased production of the reactive aldehyde, methylglyoxal. Methylglyoxal binds sulfhydryl and amino groups of proteins forming conjugates/advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular calcium channels, enzymes, and tissue proteins leading to increased oxidative stress. These alterations impair endothelial function leading to an increase in intracellular free calcium, peripheral vascular resistance, and hypertension. Supplementation with antioxidants, including vitamin C, E, or B6, thiols such as lipoic acid and cysteine, and the quinone enzyme Q10, have been shown to lower blood pressure in animal models and humans with essential hypertension. The Dietary Approaches to Stop Hypertension (DASH) studies demonstrated that a well-balanced diet, rich in these nutrients, was effective in lowering blood pressure. These antioxidants may achieve their antihypertensive effects by reducing aldehyde conjugate/AGE formation and oxidative stress, by improving insulin resistance and endothelial function, or by normalizing calcium channels and peripheral vascular resistance. In essential hypertension, deficiencies of antioxidants may exist or a higher than normal amount may be required to correct metabolic abnormalities. Dietary supplementation with antioxidants may be a beneficial, inexpensive, first-line alternate treatment modality for hypertension.     

High-fat diet enhances visceral advanced glycation end products, nuclear O-Glc-Nac modification, p38 mitogen-activated protein kinase activation and apoptosis

High-fat diet intake often leads to obesity, insulin resistance and hypertension, which present a common and detrimental health problem. However, precise mechanism underlying tissue damage due to high-fat diet-induced obesity has not been carefully elucidated. The present study was designed to examine the effect of high-fat diet intake on visceral advanced glycation end products (AGEs) formation, nuclear O-Glc-NAc modification and apoptosis in heart, liver and kidney. Adult male Sprague-Dawley weight-matched rats were fed for 12 weeks with a high-fat diet (45% kcal from fat) or an isocaloric low-fat diet (10% kcal from fat). High-fat diet feeding significantly elevated body weight. Blood pressure and heart rate were comparable between the two rat groups. Competitive enzyme-linked immunosorbent assay showed significantly elevated serum AGE levels, visceral AGE formation, caspase-3 activation and cytoplasmic DNA fragmentation in heart and liver but not kidney samples of high-fat diet fed rats compared with those from low-fat diet fed group. Western blot analysis further revealed that high-fat diet feeding induced overt nuclear O-Glc-NAc modification and p38 mitogen-activated protein kinase activation in heart and liver although not in kidney samples of the high-fat diet-fed rats. Collectively, our results indicated that high-fat diet intake is associated with obesity accompanied by elevated serum and visceral AGEs, visceral post-translational nuclear O-Glc-NAcylated modification and apoptosis, which may contribute to high-fat diet-induced tissue damage.     

晚期糖基化终末产物受体在心血管疾病中的研究进展

晚期糖基化终末产物受体(RAGE)属于细胞表面免疫球蛋白超家族中的一员,广泛表达于人体内皮细胞、平滑肌细胞、系膜细胞、心肌细胞、单核巨噬细胞和神经元细胞等。RAGE不仅参与炎症反应,还与糖尿病慢性并发症的发生、发展,类风湿性关节炎,肿瘤的侵袭和转移,阿尔茨海默病,慢性肾病等有关。现主要论述其在心血管疾病中的作用。     

Attenuation of hypertension development by aminoguanidine in spontaneously hypertensive rats: role of methylglyoxal

BACKGROUND: Methylglyoxal (MG), a metabolite of glucose, and MG-induced advanced glycation endproducts (AGEs) are causatively associated with vascular complications of diabetes mellitus. We have previously reported elevated levels of MG and MG-induced AGEs in spontaneously hypertensive rats (SHR). The purpose of this study was to investigate the causative role of MG and MG-induced AGEs in the pathogenesis of hypertension in SHR. METHODS: Young SHR were treated with an AGE inhibitor, aminoguanidine, for 9 weeks. HPLC was used to determine plasma and aortic MG and reduced glutathione levels. The MG-induced AGEs, N epsilon-carboxyethyl-lysine (CEL) and argpyramidine, in the aorta were determined by immunohistochemistry. Vascular relaxation of small mesenteric arteries was measured using myograph. RESULTS: Chronic treatment with aminoguanidine attenuated age-dependent blood pressure (BP) increase in SHR. Plasma and aortic MG levels, and aortic levels of MG-induced AGEs, were significantly reduced after aminoguanidine treatment, which were comparable to those from age-matched Wistar Kyoto rats. Free radical level was significantly lowered, whereas reduced glutathione level was significantly increased by aminoguanidine treatment in the aortic tissues from SHR. Moreover, aminoguanidine therapy prevented the morphologic damage of vascular tissues in SHR and restored the endothelium-dependent relaxation to acetylcholine. Chronic aminoguanidine treatment also increased aortic endothelial nitric oxide synthase expression and reduced inducible nitric oxide synthase expression. CONCLUSIONS: The MG and MG-induced AGEs contribute to the pathogenesis of hypertension by altering the redox balance, causing vascular eutrophic inward remodeling, and inducing endothelial dysfunction in SHR.     

Glycated albumin modifies platelet adhesion and aggregation responses

A diabetic vasculature is detrimental to cardiovascular health through the actions of advanced glycation end products (AGEs) on endothelial cells and platelets. Platelets activated by AGEs agonize endothelial responses promoting cardiovascular disease (CVD) development. While it has been established that AGEs can alter platelet functions, little is known about the specific platelet pathways that AGEs modify. Therefore, we evaluated the effects of AGEs on specific salient platelet pathways related to CVDs and whether the effects that AGEs elicit are dependent on glycation extent. To accomplish our objective, platelets were incubated with reversibly or irreversibly glycated albumin. A time course for adhesion and aggregation agonist receptor expression was assessed. Optical platelet aggregometry was used to confirm the functional activity of platelets after AGE exposure. In general, platelets subjected to glycated albumin had a significantly enhanced adhesion and aggregation potential. Furthermore, we observed an enhancement in dense body secretion and intracellular calcium concentration. This was especially prevalent for platelets exposed to irreversibly glycated albumin. Additionally, functional aggregation correlated well with receptor expression, suggesting that AGE-induced altered receptor sensitivity translated to altered platelet functions. Our findings indicate that under diabetic vascular conditions platelets become more susceptible to activation and aggregation due to an overall enhanced receptor expression, which may act to promote CVD development.     

高级糖基化终末产物的合成及其与疾病的关系

高级糖基化终末产物(advanced glycation end products,AGEs)是由蛋白或者脂质暴露于还原糖中而形成的一组复杂且具有异质性的物质.该物质可通过内源性或外源性途径形成,大体可分为6种.AGEs可在不同种类的细胞内累积,影响细胞内及细胞外的结构和功能,同时它还可以通过和细胞表面的受体作用,通过信号传导,引发一系列的病理生理过程.AGEs沉积在细胞内,影响细胞功能,导致糖尿病血管并发症的发生.AGEs还与各种肿瘤的生物学特性相关,它可以修饰热休克蛋白27或者与AGEs受体相结合来影响肿瘤细胞的生长和浸润.AGEs的抑制物,如OPB-9195,可抑制这一系列病理生理过程.     

Antihypertensive effects of dietary protein and its mechanism

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at increased risk of stroke, heart disease and kidney failure. Both genetic and lifestyle factors, particularly diet, have been attributed an important role in the development of hypertension. Reducing dietary sugar and salt intake can help lower blood pressure; similarly, adequate protein intake may also attenuate hypertension. Observational, cross-sectional and longitudinal epidemiological studies, and controlled clinical trials, have documented significant inverse associations between protein intake and blood pressure. Human and animal studies have shown that specific amino acids within proteins may have antihypertensive effects. Cysteine, glutathione (a tripeptide), glutamate and arginine attenuate and prevent alterations that cause hypertension including insulin resistance, decreased nitric oxide bioavailability, altered renin angiotensin system function, increased oxidative stress and formation of advanced glycation end products. Leucine increases protein synthesis in skeletal muscle and improves insulin resistance by modulating hepatic gluconeogenesis. Taurine and tryptophan attenuate sympathetic nervous system activity. Soy protein helps lower blood pressure through its high arginine content and antioxidant activity exhibited by isoflavones. A diet containing an ample amount of protein may be a beneficial lifestyle choice for individuals with hypertension; one example is the Dietary Approaches to Stop Hypertension (DASH) diet, which is low in salt and saturated fat; includes whole grains, lean meat, poultry, fish and nuts; and is rich in vegetables, fruits and low-fat dairy products, which are good sources of antioxidant vitamins, minerals and fibre. Including an adequate supply of soy in the diet should also be encouraged.     

Glycation and cardiovascular disease in diabetes: A perspective on the concept of metabolic memory

Epidemiological studies have suggested that cumulative diabetic exposure, namely prolonged exposure to chronic hyperglycemia, contributes to the increased risk of cardiovascular disease (CVD) in diabetes. The formation and accumulation of advanced glycation end‐products (AGEs) have been known to progress under hyperglycemic conditions. Because AGEs‐modified collagens are hardly degraded and remain in diabetic vessels, kidneys and the heart for a long time, even after glycemic control has been achieved, AGEs could become a marker reflecting cumulative diabetic exposure. Furthermore, there is a growing body of evidence that an interaction between AGEs and the receptor for AGEs (RAGE) plays a role in the pathogenesis of CVD. In addition, AGEs induce the expression of RAGE, thus leading to sustained activation of the AGEs–RAGE axis in diabetes. Herein we review the pathological role of the AGEs–RAGE axis in CVD, focusing particularly on the phenomenon of metabolic memory, and discuss the potential clinical usefulness of measuring circulating and tissue levels of AGEs accumulation to evaluate diabetic macrovascular complications.     

Controlling the receptor for advanced glycation end‐products to conquer diabetic vascular complications

Diabetic vascular complications, such as cardiovascular disease, stroke and microangiopathy, lead to high rates of morbidity and mortality in patients with long‐term diabetes. Extensive intracellular and extracellular formation of advanced glycation end‐products (AGE) is considered a causative factor in vascular injuries in diabetes. Receptor‐dependent mechanisms are involved in AGE‐induced cellular dysfunction and tissue damage. The receptor for AGE (RAGE), originally an AGE‐binding receptor, is now recognized as a member of pattern‐recognition receptors and a pro‐inflammatory molecular device that mediates danger signals to the body. Previous animal studies have shown RAGE dependent of diabetic vascular injuries. Prophylactic and therapeutic strategies focusing on RAGE and its ligand axis will be of great importance in conquering diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00191.x, 2012)     

Low levels of soluble receptor for advanced glycation end products in non-ST elevation myocardial infarction patients

BACKGROUND:

Interaction of the receptors for advanced glycation end products (RAGEs) with advanced glycation end products (AGEs) results in expression of inflammatory mediators (tumor necrosis factor-alpha [TNF-α] and soluble vascular cell adhesion molecule-1 [sVCAM-1]), activation of nuclear factor-kappa B and induction of oxidative stress – all of which have been implicated in atherosclerosis. Soluble RAGE (sRAGE) acts as a decoy for the RAGE ligand and is protective against atherosclerosis.

OBJECTIVES:

To determine whether levels of serum sRAGE are lower, and whether levels of serum AGEs, TNF-α and sVCAM-1 are higher in non-ST elevation myocardial infarction (NSTEMI) patients than in healthy control subjects; and whether sRAGE or the ratio of AGEs to sRAGE (AGEs/sRAGE) is a predictor/biomarker of NSTEMI.

METHODS:

Serum levels of sRAGE, AGEs, TNF-α and sVCAM-1 were measured in 46 men with NSTEMI and 28 age- and sex-matched control subjects. Angiography was performed in the NSTEMI patients.

RESULTS:

sRAGE levels were lower, and levels of AGEs, TNF-α, sVCAM-1 and AGEs/sRAGE were higher in NSTEMI patients than in control subjects. sRAGE levels were negatively correlated with the number of diseased coronary vessels, serum AGEs, AGEs/sRAGE, TNF-α and sVCAM-1. The sensitivity of the AGEs/sRAGE test is greater than that of the sRAGE test, while the specificity and predictive values of the sRAGE test are greater than those of the AGEs/sRAGE test for identifying NSTEMI patients.

CONCLUSIONS:

Serum levels of sRAGE were low in NSTEMI patients, and were negatively correlated with extent of lesion, inflammatory mediators, AGEs and AGEs/sRAGE. Both sRAGE and AGEs/sRAGE may serve as biomarkers/predictors for identifying NSTEMI patients.     

慢阻肺急性加重期患者血浆晚期糖基化终末产物和sRAGE研究

目的研究分析慢性阻塞性肺疾病(慢阻肺)患者血浆中晚期糖基化终末产物(AGEs)和可溶性糖基化终末产物受体(sRAGE)的水平及与慢阻肺患者肺功能的关系。方法选取河北省承德县医院收治的120例慢阻肺患者(慢阻肺组)、50例健康人群(对照组),分别检测两组的血浆AGEs、sRAGE及肺功能等指标。结果慢阻肺组患者的血浆中AGEs(36.25±2.98)ug/m L显著的高于对照组的(28.94±2.31)ug/m L,sRAGE为(338.41±194.26)pg/m L显著的低于对照组的(871.50±226.49)pg/m L且差异均具有统计学意义(P0.05)。慢阻肺组患者血浆AGEs与患者的FEV1%呈显著的负相关关系(r=-0.594,P=0.0000.001);慢阻肺组患者血浆sRAGE与患者的FEV1%呈显著的正相关关系(r=0.552,P=0.0000.001)。结论慢阻肺患者血浆中AGEs、sRAGE水平发生显著的改变,AGEs与患者的肺功能呈负相关性、sRAGE与患者的肺功能呈正相关关系。     

晚期糖基化终末产物与纤维化

晚期糖基化终末产物形成增多是糖尿病的重要特征。目前多个研究显示，其在糖尿病并发症中的发生、发展起了重要作用。晚期糖基化终末产物能促进肾脏、血管、腹膜等组织纤维化。其促纤维化作用可通过直接修饰细胞外基质、促进细胞外基质分泌、促进致纤维化细胞因子的产生、促进间质细胞转化及抑制细胞外基质降解等环节实现。本文对晚期糖基化终末产物的促纤维化作用进行综述。     

Signalling pathways involved in retinal endothelial cell proliferation induced by advanced glycation end products: inhibitory effect of gliclazide

Aim:  We have previously demonstrated that advanced glycation end products (AGEs) stimulate bovine retinal endothelial cell (BREC) proliferation through induction of vascular endothelial growth factor (VEGF) production by these cells. We have also shown that gliclazide, a sulfonylurea which decreases oxidative stress, inhibits this effect. The aim of the present study was to characterize the signalling pathways involved in AGE-induced BREC proliferation and VEGF production and mediating the inhibitory effect of gliclazide on these biological events.
Methods:  BRECs were treated or not treated with AGEs in the presence or absence of gliclazide, antioxidants, protein kinase C (PKC), mitogen-activated protein kinase (MAPK) or nuclear factor-κB (NF-κB) inhibitors. BREC proliferation was assessed by measuring [³H]-thymidine incorporation into DNA. Activation of PKC, MAPK and NF-κB signal transduction pathways and determination of VEGF expression were assessed by Western blot analysis using specific antibodies. MAPK activity was also determined by an in vitro kinase assay.
Results:  Treatment of BRECs with AGEs significantly increased cell proliferation and VEGF expression. AGEs induced PKC-β translocation, extracellular signal-regulated protein kinase 1/2 and NF-κB activation in these cells. Pharmacological inhibition of these signalling pathways abolished AGE effects on cell proliferation and VEGF expression. Exposure of BRECs to gliclazide or antioxidants such as vitamin E or N -acetyl- l -cysteine resulted in a significant decrease in AGE-induced activation of PKC-, MAPK- and NF-κB-signalling pathways.
Conclusions:  Our results demonstrate the involvement of PKC, MAPK and NF-κB in AGE-induced BREC proliferation and VEGF expression. Gliclazide inhibits BREC proliferation by interfering with these intracellular signal transduction pathways.     

AGE-RAGE系统在糖尿病视网膜病变中的作用

糖尿病视网膜病变(DR)的发病机制至今尚未完全阐明。晚期糖基化终末产物(AGEs)的形成参与糖尿病视网膜病变的发生、发展,它们能与AGEs受体(RAGE)相互作用,并通过一系列分子机制导致视网膜周细胞缺失,诱发炎性反应以及新生血管的形成。因此,抑制AGEs形成或阻断AGEs与其受体相互作用可能延缓糖尿病视网膜病变的发生、发展。本文就AGEs形成、AGE-RAGE系统在DR中的作用和DR的药物治疗等作一综述。     

Association between serum levels of soluble receptor for advanced glycation end products and circulating advanced glycation end products in type 2 diabetes

Aims/hypothesis Activation of the receptor for advanced glycation end products (RAGE, also known as AGE-specific receptor [AGER]) has been implicated in the development of diabetic vascular complications. Blockade of RAGE using a soluble form of the receptor (sRAGE) suppressed vascular hyperpermeability and atherosclerosis in animal models. Since little is known about the regulation of endogenous sRAGE levels, we determined whether serum sRAGE is influenced by circulating AGEs and the severity of nephropathy in type 2 diabetic patients.Materials and methods We recruited 150 healthy control and 318 diabetic subjects. Diabetic subjects were subdivided into those with proteinuria, microalbuminuria or normoalbuminuria. Serum sRAGE was assayed by ELISA and serum AGEs by competitive ELISA using a polyclonal rabbit antiserum raised against AGE-RNase.Results Diabetic subjects had higher sRAGE (1,029.5 pg/ml [766.1–1,423.0] interquartile range vs 1,002.6 [726.5–1,345.3], p<0.05) and AGEs (4.07±1.13, SD, unit/ml vs 3.39±1.05, p<0.01) than controls. Proteinuric subjects had the highest sRAGE levels and there was a significant trend between the severity of nephropathy and sRAGE (p=0.01). In diabetic subjects, serum log(sRAGE) correlated with AGEs (r=0.27, p<0.001), log(plasma creatinine) (r=0.31, p<0.001), log(urine AER) (r=0.24, p<0.01) and log(triglycerides) (r=0.15, p<0.01). On stepwise linear regression analysis, AGEs and creatinine levels were the main independent determinants of sRAGE concentration.Conclusions/interpretation Serum sRAGE levels and circulating AGEs are associated with the severity of nephropathy in type 2 diabetic patients. Prospective studies are required to determine whether endogenous sRAGE potentially influences the development of diabetic vascular complications.     

Involvement of the TAGE-RAGE system in non-alcoholic steatohepatitis: Novel treatment strategies

Non-alcoholic fatty liver disease (NAFLD) is a major cause of liver disease around the world. It includes a spectrum of conditions from simple steatosis to non-alcoholic steatohepatitis (NASH) and can lead to fibrosis, cirrhosis, liver failure, and/or hepatocellular carcinoma. NAFLD is also associated with other medical conditions such as obesity, diabetes mellitus (DM), metabolic syndrome, hypertension, insulin resistance, hyperlipidemia, and cardiovascular disease (CVD). In diabetes, chronic hyperglycemia contributes to the development of both macro- and microvascular conditions through a variety of metabolic pathways. Thus, it can cause a variety of metabolic and hemodynamic conditions, including upregulated advanced glycation end-products (AGEs) synthesis. In our previous study, the most abundant type of toxic AGEs (TAGE); i.e., glyceraldehyde-derived AGEs, were found to make a significant contribution to the pathogenesis of DM-induced angiopathy. Furthermore, accumulating evidence suggests that the binding of TAGE with their receptor (RAGE) induces oxidative damage, promotes inflammation, and causes changes in intracellular signaling and the expression levels of certain genes in various cell populations including hepatocytes and hepatic stellate cells. All of these effects could facilitate the pathogenesis of hypertension, cancer, diabetic vascular complications, CVD, dementia, and NASH. Thus, inhibiting TAGE synthesis, preventing TAGE from binding to RAGE, and downregulating RAGE expression and/or the expression of associated effector molecules all have potential as therapeutic strategies against NASH. Here, we examine the contributions of RAGE and TAGE to various conditions and novel treatments that target them in order to prevent the development and/or progression of NASH.     

AGEs对心肌微血管内皮细胞血管新生和管腔形成的影响

目的: 观察糖基化终产物（advanced glycation end products,AGEs）对心肌微血管内皮细胞(cardiac microvascular endothelial cells,CMECs)增殖能力、迁移能力,以及血管新生和管腔形成的作用和影响。方法: 以不同浓度（100、200和400 mg/L）的AGEs作用于CMECs 48 h,分别采用MTT比色法检测细胞的增殖能力;用Transwell法检测细胞的迁移能力;用毛细血管管腔结构形成试验检测AGEs对血管新生的影响。结果: CMECs在以不同浓度（100、200及400 mg/L）的AGEs作用48 h后,MTT比色法检测显示,吸光值（分别为0.1195±0.0049、0.1422±0.0058及0.1783±0.0220）明显高于对照组（0.0955±0.0161,P<0.05,P<0.01）;Transwell法检测细胞数［分别为(24.89±6.234)、(32.89±6.990)及(55.56±10.27)个］均高于对照组［（13.89±4.622）个,P<0.05,P<0.01］;管样结构的长度［分别为(3.261±0.7016)、(4.737±1.129)及(6.687±1.308)mm/mm2］均高于对照组［(2.089±0.6723)mm/mm2,P<0.05,P<0.01］。结论: AGEs可以促进CMECs血管新生和管腔结构的形成,且与其浓度呈正相关。     

A systematic review of antiglycation medicinal plants

Background and objectivesThe present review shows a list of anti-glycation plants with their anti-glycation activity mechanisms that can attract the attention of pharmacologist for further scientific research towards finding better remedy for diabetic complications.MaterialsGoogle scholar, Pubmed, Web of Science and Scopus were searched. The terms were advanced glycation end products (AGEs), medicinal plants, antiglycation products.Resultsplants that studied in this review inhibit glycation in several possible mechanisms. Some of these plants inhibit the production of shiff base and amadori products. The others inhibit the generation of amadori products in the advanced phase. Some others blocked the aggregation of AGEs and some plants have antioxidant activity and reduce AGEs formation by preventing oxidation of amadori product and metal-catalyzed glucoxidation.ConclusionThis review can help pharmacologist to find antiglycation natural substance that can be useful in treatment of diabetic complications.     

晚期糖基化终末产物及其受体在原发性高血压中的作用机制

近年来研究发现晚期糖基化终末产物（advanced glycation end products,AGEs）在原发性高血压的发生、发展过程中起着一定的病理作用,AGEs主要通过直接修饰蛋白、结合受体RAGE并激活信号转导通路两条作用途径来发挥效应。此外AGEs—RAGE还与肾素-血管紧张素系统、氧化应激三者构成正反馈环路,共同参与了原发性高血压的进程。相信随着对AGEs—RAGE作剧机制及药物干预的进一步研究,抗AGEs的治疗策略将有望成为防治高血压及其并发症的新方向。