Reversal of experimental diabetic neuropathy by VEGF gene transfer

The pathogenetic basis for diabetic neuropathy has been enigmatic. Using two different animal models of diabetes, we have investigated the hypothesis that experimental diabetic neuropathy results from destruction of the vasa nervorum and can be reversed by administration of an angiogenic growth factor. Nerve blood flow, as measured by laser Doppler imaging or direct detection of a locally administered fluorescent lectin analogue, was markedly attenuated in rats with streptozotocin-induced diabetes, consistent with a profound reduction in the number of vessels observed. A severe peripheral neuropathy developed in parallel, characterized by significant slowing of motor and sensory nerve conduction velocities, compared with nondiabetic control animals. In contrast, 4 weeks after intramuscular gene transfer of plasmid DNA encoding VEGF-1 or VEGF-2, vascularity and blood flow in the nerves of treated animals were similar to those of nondiabetic control rats; constitutive overexpression of both transgenes resulted in restoration of large and small fiber peripheral nerve function. Similar experiments performed in a rabbit model of alloxan-induced diabetes produced comparable results. These findings support the notion that diabetic neuropathy results from microvascular ischemia involving the vasa nervorum and suggest the feasibility of a novel treatment strategy for patients in whom peripheral neuropathy constitutes a secondary complication of diabetes.     

HSV-mediated gene transfer of vascular endothelial growth factor to dorsal root ganglia prevents diabetic neuropathy

We examined the utility of herpes simplex virus (HSV) vector-mediated gene transfer of vascular endothelial growth factor (VEGF) in a mouse model of diabetic neuropathy. A replication-incompetent HSV vector with VEGF under the control of the HSV ICP0 promoter (vector T0VEGF) was constructed. T0VEGF expressed and released VEGF from primary dorsal root ganglion (DRG) neurons in vitro, and following subcutaneous inoculation in the foot, expressed VEGF in DRG and nerve in vivo. At 2 weeks after induction of diabetes, subcutaneous inoculation of T0VEGF prevented the reduction in sensory nerve amplitude characteristic of diabetic neuropathy measured 4 weeks later, preserved autonomic function measured by pilocarpine-induced sweating, and prevented the loss of nerve fibers in the skin and reduction of neuropeptide calcitonin gene-related peptide and substance P in DRG neurons of the diabetic mice. HSV-mediated transfer of VEGF to DRG may prove useful in treatment of diabetic neuropathy.     

Angiopoietin-1 gene transfer improves impaired wound healing in genetically diabetic mice without increasing VEGF expression

Ang-1 (angiopoietin-1) improves the ineffective angiogenesis and impaired wound healing in diabetes; however, the mechanism underlying this positive effect is still far from being completely understood. In the present study, we investigated whether rAAV (recombinant adeno-associated virus)-Ang-1 gene transfer could improve wound repair in genetically diabetic mice (db+/db+) and the mechanism(s) by which it causes new vessel formation. An incisional skin-wound model in diabetic and normoglycaemic mice was used. After the incision, animals received rAAV-LacZ or rAAV-Ang-1 in the wound edge. After 7 and 14 days, wounds were used to (i) confirm Ang-1 gene transfer, (ii) assess histologically the healing process, (iii) evaluate wound-breaking strength, and (iv) study new vessel formation by PECAM-1 (platelet/endothelial cell adhesion molecule-1) immunostaining. Finally, we investigated VEGF (vascular endothelial growth factor) mRNA and protein levels, eNOS (endothelial NO synthase) expression and VEGFR-1 and VEGFR-2 (VEGF receptor-1 and -2 respectively) immunostaining. The efficiency of Ang-1 gene transfer was confirmed by increased mRNA and protein expression of the protein. rAAV-Ang-1 significantly improved the healing process, stimulating re-epithelization and collagen maturation, increasing breaking strength and significantly augmenting the number of new vessels, as indicated by PECAM-1 immunostaining. However, Ang-1 gene transfer did not modify the decrease in VEGF mRNA and protein expression in diabetic mice; in contrast, Ang-1 increased eNOS expression and augmented nitrate wound content and VEGFR-2 immunostaining and protein expression. Ang-1 gene transfer did not change vascular permeability. Similar results were obtained in normoglycaemic animals. In conclusion, our results provide strong evidence that Ang-1 gene transfer improves the delayed wound repair in diabetes by inducing angiogenesis in a VEGF-independent manner.     

Biotin for diabetic peripheral neuropathy

Biotin in high doses was given for 1-2 years to three diabetic patients suffering from severe diabetic peripheral neuropathy. Within 4-8 weeks there was a marked improvement in clinical and laboratory findings. It is suggested that in diabetes may exist a deficiency, inactivity or unavailability of Biotin, resulting in disordered activity of biotin-dependent enzyme, pyruvate carboxylase, leading to accumulation of pyruvate and/or depletion of aspartate, both of which play a significant role in nervous system metabolism. Based on our good results, regular biotin administration could be suggested for every diabetic patient for the prevention and management of peripheral neuropathy although extensive randomised clinical trials are required.     

Adenovirus-mediated VEGF(165) gene transfer enhances wound healing by promoting angiogenesis in CD1 diabetic mice

It has been previously shown that vascular endothelial growth factor (VEGF) plays a central role in promoting angiogenesis during wound repair and that healing-impaired diabetic mice show decreased VEGF expression levels. In order to investigate the potential benefits of gene therapy with growth factors on wound repair, a replication-deficient recombinant adenovirus vector carrying the human VEGF(165) gene (AdCMV.VEGF(165)) was topically applied on excisional wounds of streptozotocin-induced diabetic mice. Treatment with AdCMV.VEGF(165) significantly accelerated wound closure when compared with AdCMV.LacZ-treated, as well as saline-treated control mice, by promoting angiogenesis at the site of injury. Our findings suggest that AdCMV.VEGF(165) may be regarded as a therapeutic tool for the treatment of diabetic ulcers.     

Peripheral diabetic neuropathy

Diabetic neuropathy is a common complication of diabetes mellitus with significant morbidity and mortality. Hyperglycemia with its secondary metabolic, vascular, and enzymatic consequences is most likely to be the predominant cause. The clinical manifestations includes a wide range of somatic and autonomic syndromes. Painful diabetic neuropathy may require symptomatic treatment. The precise role of therapies such as continuous subcutaneous insulin therapy and aldose reductase inhibitors remains to be clarified.     

Partial prevention of cisplatin-induced neuropathy by electroporation-mediated nonviral gene transfer

Cisplatin-induced sensory peripheral neuropathy is the dose-limiting factor for cisplatin chemotherapy. We describe the preventive effect of NT-3 delivery, using direct gene transfer into muscle by in vivo electroporation in a mouse model of cisplatin-induced neuropathy. Cisplatin-induced neuropathy was produced by weekly injections of cisplatin (five injections). Two doses of plasmid DNA encoding murine NT-3 (pCMVNT-3) were tested (5 and 50 microg/animal/injection). Cisplatin-treated mice were given two intramuscular injections. The first injection of pCMVNT-3 was given 2 days before the first injection of cisplatin and the second injection 2 weeks later. Six weeks after the start of the experiment, measurement of NT-3 levels (ELISA) demonstrated significant levels both in muscle and plasma. We observed a smaller cisplatin-related increase in the latency of the sensory nerve action potential of the caudal nerve in pCMVNT-3-treated mice than in controls (p < 0.0001). Mean sensory distal latencies were not different between the 5- and 50- microg/animal/injection groups. Treatment with gene therapy induced only a slight muscle toxicity and no general side effects. Therefore, neurotrophic factor delivery by direct gene transfer into muscle by electroporation is of potential benefit in the prevention of cisplatin-induced neuropathy and of peripheral neuropathies in general.     

F波对糖尿病周围神经病的早期评估

背景F波最短潜伏期和传导速度已广泛应用于各种神经病变的检测.然而,F波的其他参数的意义和诊断评估价值较少见报道,其对提高糖尿病周围神经病早期评估敏感性如何?目的探讨F波各参数在糖尿病周围神经病的早期评估意义.设计以2型糖尿病患者和健康人为研究对象的病例-对照研究.单位武汉大学人民医院神经科和内分泌科病房和门诊.对象糖尿病组为1999-01/2000-12武汉大学人民医院神经科和内分泌科就诊的2型糖尿病患者106例,男64例,女42例,平均(55±13)岁;糖尿病平均病程(10.2±4.8)年.正常对照组为75例健康志愿者,男45例,女30例,平均年龄(54±12)岁.两组间年龄、腿长匹配(P＞0.05).干预以Nicolet-VikingⅣ肌电图仪,对糖尿病组和对照组胫神经进行F波测定;同时记录M波.主要观察指标①2型糖尿病患者和正常人F波最短潜伏期(Fmin)、时限(Fdur)、波幅(Famp)和面积(Farea);M波负峰波幅(Mamp)和面积(Marea)的差异.②有无神经病变及不同病变程度2型糖尿病患者异常胫神经F波分布情况.结果①对照组Fmin上限(Y)与腿长(X)的函数关系为y=12.3+48.8X2.②无神经病变患者组(n=30)Fdur增宽8例(异常率27%)、Fmin延长4例(13%)、F/Marea增大2例.③与对照组比较,有神经病变患者组(n=76)Fmin延长,F/Mamp及F/Marea增大(P均＜0.01).④轻型DPN亚组与重型比较,Fdur异常率显著高(96%和21%,P＜0.01);Fmin异常率低(51%和76%,P＜0.05);其余参数无显著性差异(P＞0.05).结论①F波(尤其是Fdur)可作为早期诊断糖尿病周围神经病的敏感指标,并可发现亚临床糖尿病周围神经病.②糖尿病周围神经病患者的近、远端神经均可受累,近端损害可早于远端.     

Clinical diagnosis of diabetic polyneuropathy with the diabetic neuropathy symptom and diabetic neuropathy examination scores

OBJECTIVE: To evaluate the discriminative power of the Diabetic Neuropathy Symptom (DNS) and Diabetic Neuropathy Examination (DNE) scores for diagnosing diabetic polyneuropathy (PNP), as well as their relation with cardiovascular autonomic function testing (cAFT) and electro-diagnostic studies (EDS). RESEARCH DESIGN AND METHODS: Three groups (matched for age and sex) were selected: 24 diabetic patients with neuropathic foot ulcers (DU), 24 diabetic patients without clinical neuropathy or ulcers (DC), and 21 control subjects without diabetes (C). In all participants, the DNS and DNE scores were assessed and cAFT (heart rate variability [HRV], baroreflex sensitivity [BRS]), and EDS were performed (Nerve Conduction Sum [NCS] score; muscle fiber conduction velocity: fastest/slowest ratio [F/S ratio]). RESULTS: Both the DNS and the DNE scores discriminated between the DU and DC groups significantly (P < 0.001). The DNE score even discriminated between DC and C (P < 0.05). Spearman's correlation coefficients between both DNS and DNE scores and cAFT (HRV -0.42 and -0.44; BRS -0.30 and -0.29, respectively) and EDS (NCS 0.51 and 0.62; F/S ratio 0.44 and 0.62, respectively) were high. Odds ratios were calculated for both DNS and DNE scores with cAFT (HRV 4.4 and 5.7; BRS 20.7 and 14.2, respectively) and EDS (NCS 5.6 and 16.8; F/S ratio 7.2 and 18.8, respectively). CONCLUSIONS: The DNS and DNE scores are able to discriminate between patients with and without PNP and are strongly related to cAFT and EDS. This further confirms the strength of the DNS and DNE scores in diagnosing diabetic PNP in daily clinical practice.     

Dextromethorphan and diabetic neuropathy

OBJECTIVE: To review the use of dextromethorphan for the treatment of painful diabetic neuropathy. DATA SOURCES: MEDLINE and EMBASE searches for studies using dextromethorphan to manage diabetic neuropathy were conducted from 1966 to 1999 and 1980 to 1999, respectively. DATA SYNTHESIS: Peripheral neuropathy is a common manifestation of diabetic patients. Many classes of medications have been investigated to treat this condition, including N-methyl-D-aspartate inhibitors. A review of studies using dextromethorphan to manage diabetic neuropathy was performed. CONCLUSIONS: There are insufficient safety and efficacy data to justify the use of dextromethorphan for treating painful diabetic neuropathy. Further clinical trials are needed.     

Pharmacotherapy of painful diabetic neuropathy

The scope of this review is to describe the epidemiology, physiology, symptomatology, and treatment of diabetic painful neuropathy, which is a common complication of diabetes with significant morbidity. This article focuses on treatment options. Various clinical trials of several classes of medications (eg, antidepressants, anticonvulsants, and topical medications) and alternative treatments (eg, acupuncture, electrostimulation, magnets) are reviewed. Physicians have a large panel of medications that can be used effectively solely or in combination at their disposal. However, a number of these treatments have significant side effects, which are noted, that limit their use. As the understanding of the pathophysiologic mechanisms of diabetic neuropathy improves, new medications are under investigation, which are reviewed in this article. There is great hope that the future may hold treatments that would prevent nerve damage.