Type 1 Diabetic Neuropathy and C-peptide

The most common microvascular diabetic complication, diabetic peripheral polyneuropathy (DPN), affects type 1 diabetic patients more often and more severely. In recent decades, it has become increasingly clear that perpetuating pathogenetic mechanisms, molecular, functional, and structural changes and ultimately the clinical expression of DPN differ between the two major types of diabetes. Impaired insulin/C-peptide action has emerged as a crucial factor to account for the disproportionate burden affecting type 1 patients. C-peptide was long believed to be biologically inactive. However, it has now been shown to have a number of insulin-like glucoseindependent effects. Preclinical studies have demonstrated dose-dependent effects on Na⁺,K⁺-ATPase activity, endothelial nitric oxide synthase (eNOS), and endoneurial blood flow. Furthermore, it has regulatory effects on neurotrophic factors and molecules pivotal to the integrity of the nodal and paranodal apparatus and modulatory effects on apoptotic phenomena affecting the diabetic nervous system. In animal studies, C-peptide improves nerve conduction abnormalities, prevents nodal degenerative changes, characteristic of type 1 DPN, promotes nerve fiber regeneration, and prevents apoptosis of central and peripheral nerve cell constituents. Limited clinical trials have confirmed the beneficial effects of C-peptide on autonomic and somatic nerve function in patients with type 1 DPN. Therefore, evidence accumulates that replacement of C-peptide in type 1 diabetes prevents and even improves DPN. Large-scale food and drug administration (FDA)-approved clinical trials are necessary to make this natural substance available to the globally increasing type 1 diabetic population.     

Nerve Growth Factor and Diabetic Neuropathy

Neuropathy is one of the most debilitating complications of both type 1 and type 2 diabetes, with estimates of prevalence between 50–90% depending on the means of detection. Diabetic neuropathies are heterogeneous and there is variable involvement of large myelinated fibers and small, thinly myelinated fibers. Many of the neuronal abnormalities in diabetes can be duplicated by experimental depletion of specific neurotrophic factors, their receptors or their binding proteins. In experimental models of diabetes there is a reduction in the availability of these growth factors, which may be a consequence of metabolic abnormalities, or may be independent of glycemic control. These neurotrophic factors are required for the maintenance of the neurons, the ability to resist apoptosis and regenerative capacity. The best studied of the neurotrophic factors is nerve growth factor (NGF) and the related members of the neurotrophin family of peptides. There is increasing evidence that there is a deficiency of NGF in diabetes, as well as the dependent neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) that may also contribute to the clinical symptoms resulting from small fiber dysfunction. Similarly, NT3 appears to be important for large fiber and IGFs for autonomic neuropathy. Whether the observed growth factor deficiencies are due to decreased synthesis, or functional, e.g. an inability to bind to their receptor, and/or abnormalities in nerve transport and processing, remains to be established. Although early studies in humans on the role of neurotrophic factors as a therapy for diabetic neuropathy have been unsuccessful, newer agents and the possibilities uncovered by further studies should fuel clinical trials for several generations. It seems reasonable to anticipate that neurotrophic factor therapy, specifically targeted at different nerve fiber populations, might enter the therapeutic armamentarium.     

Inflammation: Therapeutic Targets for Diabetic Neuropathy

There are still no approved treatments for the prevention or of cure of diabetic neuropathy, and only symptomatic pain therapies of variable efficacy are available. Inflammation is a cardinal pathogenic mechanism of diabetic neuropathy. The relationships between inflammation and the development of diabetic neuropathy involve complex molecular networks and processes. Herein, we review the key inflammatory molecules (inflammatory cytokines, adhesion molecules, chemokines) and pathways (nuclear factor kappa B, JUN N-terminal kinase) implicated in the development and progression of diabetic neuropathy. Advances in the understanding of the roles of these key inflammatory molecules and pathways in diabetic neuropathy will facilitate the discovery of the potential of anti-inflammatory approaches for the inhibition of the development of neuropathy. Specifically, many anti-inflammatory drugs significantly inhibit the development of different aspects of diabetic neuropathy in animal models and clinical trials.     

The Role of the Axonal Cytoskeleton in Diabetic Neuropathy

The neuropathy associated with diabetes includes well documented impairment of axonal transport, a reduction in axon calibre and a reduced capacity for nerve regeneration. All of those aspects of nerve function rely on the integrity of the axonal cytoskeleton. Alterations in the axonal cytoskeleton in experimental diabetes include an insulin-dependent non-enzymatic glycation of actin that is reflected in increased glycation of platelet actin in the clinical situation. There is a reduced synthesis of mRNA for the isoforms of tubulin that are associated with nerve growth and regeneration and an elevated non-enzymatic glycation of peripheral nerve tubulin in both diabetic patients and diabetic animals. mRNAs for neurofilament proteins are selectively reduced in the diabetic rat and the post-translational modification of at least one of the neurofilament proteins is altered. There is some evidence that altered expression of isoforms of protein kinases may contribute to these changes.     

交感皮肤反应在糖尿病周围神经病变诊断中的应用

糖尿病周围神经病变（Diabetic Peripheral Neuropathy,DPN）是糖尿病最常见的并发症之一。由于目前DPN发病机制不清楚、治疗效果不理想,故早诊断、早治疗显得至关重要。有研究指出交感神经皮肤反应（Sympathetic Skin Response,SSR）可作为评价2型糖尿病患者早期周围植物神经功能状态的指标。本文对SSR应用于DPN临床诊断中的检测技术、观测参数进行综述,发现多数研究中指出,在临床应用中SSR波形、波幅以及潜伏期指标的异常率常受到多种因素的影响、会发生很大波动,而电位曲线下面积减少值相对稳定。据此笔者建议在DPN早期临床诊断中以SSR电位曲线下面积减少作为关键参数,辅助参考SSR波形、波幅以及潜伏期指标进行诊断。     

An Early Diagnostic Tool for Diabetic Peripheral Neuropathy in Rats

The skin’s rewarming rate of diabetic patients is used as a diagnostic tool for early diagnosis of diabetic neuropathy. At present, the relationship between microvascular changes in the skin and diabetic neuropathy is unclear in streptozotocin (STZ) diabetic rats. The aim of this study was to investigate whether the skin rewarming rate in diabetic rats is related to microvascular changes and whether this is accompanied by changes observed in classical diagnostic methods for diabetic peripheral neuropathy. Computer-assisted infrared thermography was used to assess the rewarming rate after cold exposure on the plantar skin of STZ diabetic rats’ hind paws. Peripheral neuropathy was determined by the density of intra-epidermal nerve fibers (IENFs), mechanical sensitivity, and electrophysiological recordings. Data were obtained in diabetic rats at four, six, and eight weeks after the induction of diabetes and in controls. Four weeks after the induction of diabetes, a delayed rewarming rate, decreased skin blood flow and decreased density of IENFs were observed. However, the mechanical hyposensitivity and decreased motor nerve conduction velocity (MNCV) developed 6 and 8 weeks after the induction of diabetes. Our study shows that the skin rewarming rate is related to microvascular changes in diabetic rats. Moreover, the skin rewarming rate is a non-invasive method that provides more information for an earlier diagnosis of peripheral neuropathy than the classical monofilament test and MNCV in STZ induced diabetic rats.     

光子中医信息疗法治疗糖尿病周围神经病变的临床研究

目的:观察光子中医信息疗法对糖尿病周围神经病变患者的临床疗效。方法:将60例符合入选标准的患者,以1∶1的比例随机分配到治疗组(光子中医信息疗法联合药物组)、对照组(药物组),两组患者均给予糖尿病基础治疗,对照组加甲钴胺口服,每次500μg,每日3次,疗程4周;治疗组在对照组的基础上配合光子中医信息疗法,隔日照射1次,每周3次,6次为1疗程,共2个疗程。治疗前后分别对两组患者的中医临床症状、神经症状体征进行评定,并测定周围神经传导速度及观察血糖变化情况,进行综合疗效评估。结果:治疗组的临床综合疗效明显优于对照组,两组的总有效率比较有显著性差异(P<0.05)。治疗组在中医症状改善、周围神经症状及体征改善、提高周围神经传导速度方面均优于对照组,组间比较均具有显著性差异(P<0.05)。治疗后治疗组空腹血糖、餐后血糖、糖化血红蛋白与治疗前比较均明显降低(P<0.01),对照组治疗前后比较及治疗后组间比较均无显著性差异(P>0.05)。结论:光子中医信息疗法联合药物组相对于药物组在改善DPN患者的临床症状、周围神经症状及体征、神经的传导速度等方面均有良好的优势,同时具有一定的辅助降糖趋势。     

神经传导速度对糖尿病痛性周围神经病的诊断价值

目的:探讨糖尿病痛性周围神经病的神经传导特点及神经传导速度在糖尿病痛性周围神经病中的诊断价值.方法:对18例痛性周围神经病患者进行病史采集及神经系统查体.采用肌电诱发电位仪,测定患者的正中神经、尺神经、胫神经、腓总神经及腓肠神经的运动感觉神经传导速度.结果:18例患者中男性13例,女性5例.年龄40-89岁.主要表现为双足烧灼样、针刺样、过电样疼痛.神经系统查体:针刺觉减弱7例,痛觉过敏3例,音叉震动觉减弱12例,跟腱反射减弱/消失15例.18例患者中有14例神经传导速度检查结果异常,腓肠神经感觉神经检查结果异常率高,83.3％,对诊断有帮助.结论:糖尿病痛性周围神经病变出现疼痛症状时已经存在大纤维受累,故神经传导速度异常阳性率高.神经传导速度不能早期发现糖尿病痛性周围神经病,探索一种简单易行的早期筛查方法意义重大.     

Slow Axonal Transport Impairment of Cytoskeletal Proteins in Streptozociti-Induced Diabetic Neuropathy

The impairment of slow axonal transport of cytoskeletal proteins was studied in the sciatic nerves of streptozocin-diabetic rats. [35S]Methionine was unilaterally injected into the fourth lumbar ganglion and spinal cord, to label the sensory and motor axons, respectively, and then the polymerized elements of the cytoskeleton and the corresponding soluble proteins were analyzed separately. In addition, the pellet/supernatant ratio for tubulin and actin was also assessed. Our results indicate that the velocity of slow component a (SCa) of axonal transport, particularly that of neurofilaments, was strongly reduced (by 60%) in sensory axons. At the same time, a decreased pellet/supernatant ratio of tubulin, possibly owing to a depolymerization of stable microtubules, was also observed. The transport of slow component b (SCb) of axonal transport was also impaired, but the extent of this impairment could not be precisely evaluated. In contrast, motor axons showed little or no impairment of both SCa and SCb at the time studied, a result suggesting a delayed development of the neuropathy in motor axons.     

Sildenafil Ameliorates Long Term Peripheral Neuropathy in Type II Diabetic Mice

Diabetic peripheral neuropathy is a common complication of long-standing diabetes mellitus. To mimic clinical trials in which patients with diabetes enrolled have advanced peripheral neuropathy, we investigated the effect of sildenafil, a specific inhibitor of phosphodiesterase type 5 enzyme, on long term peripheral neuropathy in middle aged male mice with type II diabetes. Treatment of diabetic mice (BKS.Cg-m+/+Lepr^db/J, db/db) at age 36 weeks with sildenafil significantly increased functional blood vessels and regional blood flow in the sciatic nerve, concurrently with augmentation of intra-epidermal nerve fiber density in the skin and myelinated axons in the sciatic nerve. Functional analysis showed that the sildenafil treatment considerably improved motor and sensory conduction velocities in the sciatic nerve and peripheral thermal stimulus sensitivity compared with the saline treatment. In vitro studies showed that mouse dermal endothelial cells (MDE) cultured under high glucose levels exhibited significant down regulation of angiopoietin 1 (Ang1) expression and reduction of capillary-like tube formation, which were completely reversed by sildenafil. In addition, incubation of dorsal root ganglia (DRG) neurons with conditioned medium harvested from MDE under high glucose levels suppressed neurite outgrowth, where as conditional medium harvested from MDE treated with sildenafil under high glucose levels did not inhibit neurite outgrowth of DRG neurons. Moreover, blockage of the Ang1 receptor, Tie2, with a neutralized antibody against Tie2 abolished the beneficial effect of sildenafil on tube formation and neurite outgrowth. Collectively, our data indicate that sildenafil has a therapeutic effect on long term peripheral neuropathy of middle aged diabetic mice and that improvement of neurovascular dysfunction by sildenafil likely contributes to the amelioration of nerve function. The Ang1/Tie2 signaling pathway may play an important role in these restorative processes.     

Diabetic Peripheral Neuropathy: Role of Reactive Oxygen and Nitrogen Species

The prevalence of diabetes has reached epidemic proportions. There are two forms of diabetes: type 1 diabetes mellitus is due to auto-immune-mediated destruction of pancreatic β-cells resulting in absolute insulin deficiency and type 2 diabetes mellitus is due to reduced insulin secretion and or insulin resistance. Both forms of diabetes are characterized by chronic hyperglycemia, leading to the development of diabetic peripheral neuropathy (DPN) and microvascular pathology. DPN is characterized by enhanced or reduced thermal, chemical, and mechanical pain sensitivities. In the long-term, DPN results in peripheral nerve damage and accounts for a substantial number of non-traumatic lower-limb amputations. This review will address the mechanisms, especially the role of reactive oxygen and nitrogen species in the development and progression of DPN.     

踝肱指数与糖尿病周围神经病变及中医证候积分的相关性

目的：探讨踝肱指数（ABI）与糖尿病周围神经病变及中医证候积分的相关性。方法：选取我院内分泌科收治辩证以气阴两虚 为证型的糖尿病患者66 例，根据踝肱指数实验将患者分为ABI降低组（0.9>ABI>0.5）和ABI 正常组(1.4>ABI>0.9)。记录患者神 经病变症状尼龙丝检查以及中医症候评分，分析ABI与糖尿病周围神经病变及中医证候积分的相关性。结果：ABI降低组的糖尿 病周围神经病变的患病率高于ABI正常组（P<0.05）。ABI 降低组发麻、针刺感症状的发生率高于ABI 正常组，且有统计学差异 （P<0.05）。ABI降低组10 g尼龙丝检查异常者多于ABI正常组，差异显著（P<0.05）。ABI降低组的感觉振动阈值高于ABI正常组 （P<0.05）。ABI数值与中医证候积分呈负向直线相关（P<0.05）。结论：糖尿病患者ABI数值与糖尿病周围神经病变和中医证候积 分具有相关性。     

22例糖尿病视神经病变综合治疗的疗效观察

目的：总结诊断及治疗糖尿病性视神经病变（diabeticopticneuropathy,DON）的临床经验,为本病的治疗和预防提供依据。方法：回顾性研究22例糖尿病视神经痛变的发病特点,在接受治疗的患者中严格控制血糖,应用复方樟柳碱注射液病侧颞浅动脉旁皮下注射,口服或静脉滴注活血化瘀药物,并口服维生素B1、维生素B2、肌苷片等营养视神经的药物,同时给予全身检查,包括对高血压、糖尿病等全身疾病的治疗,观察经综合治疗前后的视力、眼底、视野改变及眼底荧光血管造影（fundusfluoresceinall-giography,FFA）的特点等。结果：接受治疗的患者共有22例（29只眼）,治愈10例（12只眼）;好转7例（10只眼）,总有效率为79．3％。结论：糖尿病性视神经病变的及时正确诊断、系统的综合治疗,可有效提高视力,扩大视野。     

22 例糖尿病视神经病变综合治疗的疗效观察

摘要目的：总结诊断及治疗糖尿病性视神经病变（diabetic optic neuropathy,DON）的临床经验,为本病的治疗和预防提供依据。方 法：回顾性研究22 例糖尿病视神经病变的发病特点,在接受治疗的患者中严格控制血糖,应用复方樟柳碱注射液病侧颞浅动脉 旁皮下注射,口服或静脉滴注活血化瘀药物,并口服维生素B1、维生素B2、肌苷片等营养视神经的药物,同时给予全身检查,包括 对高血压、糖尿病等全身疾病的治疗,观察经综合治疗前后的视力、眼底、视野改变及眼底荧光血管造影（fundus fluorescein angiography, FFA）的特点等。结果：接受治疗的患者共有22 例（29 只眼）,治愈10 例（12 只眼）;好转7 例（10 只眼）,总有效率为 79.3%。结论：糖尿病性视神经病变的及时正确诊断、系统的综合治疗,可有效提高视力,扩大视野。     

Role of T-Type Ca2+ Channels in Painful Diabetic Neuropathy

Neurophysiology - Numerous investigations implicate pronounced changes in the functioning of T-type Ca2+ channels localized on the somata of primary nociceptor units in the development and...     

Facial Sweating after Food: A New Sign of Diabetic Autonomic Neuropathy

Facial sweating during eating (gustatory sweating) has been observed for the first time in a group of diabetics, and is considered to be a feature of the autonomic neuropathy which affected them all. The sweating, which was sometimes very severe, was produced by many foodstuffs, cheese being the most powerful stimulus. Atropine inhibited sweating stimulated by eating cheese, and oral anticholinergic drugs effectively eliminated the symptoms. These bizarre symptoms are probably due to abnormal nerve regeneration occurring as a consequence of the spontaneous autonomic neuropathy.