Effect of NGF and neurotrophin-3 treatment on experimental diabetic autonomic neuropathy

Peripheral neuropathy is a significant complication of diabetes resulting in increased patient morbidity and mortality. Deficiencies of neurotrophic substances (e.g. NGE NT-3, and IGF-I) have been proposed as pathogenetic mechanisms in the development of distal symmetrical sensory diabetic polyneuropathy, and salutary effects of exogenous NGF administration have been reported in animal models. In comparison, relatively little is known concerning the effect of NGF on experimental diabetic sympathetic autonomic neuropathy. We have developed an experimental animal model of diabetic autonomic neuropathy characterized by the regular occurrence of pathologically distinctive dystrophic axons in prevertebral sympathetic ganglia and ileal mesenteric nerves of rats with chronic streptozotocin (STZ)-induced diabetes. Treatment of STZ-diabetic rats for 2-3 months with pharmacologic doses of NGF or NT-3, neurotrophic substances with known effects on the adult sympathetic nervous system, did not normalize established neuroaxonal dystrophy (NAD) in diabetic rats in the prevertebral superior mesenteric ganglia (SMG) and ileal mesenteric nerves as had pancreatic islet transplantation and IGF-I in earlier experiments. NGF treatment of control animals actually increased the frequency of NAD in the SMG. New data suggests that, in adult sympathetic ganglia. NGF may contribute to the pathogenesis of NAD rather than its amelioration, perhaps as the result of inducing intraganglionic axonal sprouts in which dystrophic changes are superimposed. NT-3 administration did not alter the frequency of NAD in diabetic animals, although it resulted in a significant decrease in NAD in control SMG. Although deficiencies of neurotrophic substances may represent the underlying pathogenesis of a variety of experimental neuropathies, delivery of excessive levels of selected substances may produce untoward effects.     

Neurotrophic factors and diabetic peripheral neuropathy

Recent evidence from animal models of diabetes and human diabetic subjects suggests that the reduced availability of neurotrophic factors may contribute to the pathogenesis of diabetic peripheral neuropathy (DPN). Of these proteins, nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin (NT-3) and NT-4/5 appear to be important for the development and maintenance of peripheral neurons, but others, including insulin-like growth factors (IGFs), may also be involved. Studies with NGF, NT-3, IGF-I and IGF-II both in vitro and in animal models of neuropathies (including DPN) suggest that these factors ameliorate nerve degeneration. Recombinant human NGF is the first neurotrophic factor to enter clinical trials for DPN and is currently being tested in two phase III studies.     

Diabetic neuropathy: models, mechanisms and mayhem.

Rational treatment of diabetic polyneuropathy depends upon establishing its cause, which is at present unknown. A number of animal models of diabetes have been examined and although abnormalities are detectable in the peripheral nervous system they do not duplicate the degenerative neuropathy encountered in the human. The relevance of these abnormalities is therefore uncertain, although they may reflect the earlier changes in man. For human neuropathy, it is likely that vascular lesions or an abnormal susceptibility to mechanical injury are responsible for focal neuropathies. The evidence that ischaemia and hypoxia are responsible for the diffuse sensory neuropathy and autonomic polyneuropathy is still equivocal and it is often difficult to establish whether the vascular changes are primary or secondary. Metabolic explanations, such as sorbitol accumulation in nerve, have not so far been adequately validated by responses to treatment. The manifestations of diabetic neuropathy are complex and a single explanation should not be sought.     

Botulinum toxin and painful peripheral neuropathies: what should be expected?

Botulinum toxin type A (BTX-A) is a potent neurotoxin that blocks acetylcholine release from presynaptic nerve terminals by cleaving the SNARE complex. BTX-A has been reported to have analgesic effects independent of its action on muscle tone. The most robust results have been observed in patients with neuropathic pain. Neuropathic pain due to peripheral lesions has been the most widely studied. BTX-A has shown its efficacy on pain and allodynia in various animal models of inflammatory neuropathic pain. The only randomized, double-blind, placebo-controlled trial in patients with focal painful neuropathies due to nerve trauma or postherpetic neuralgia demonstrated significant effects on average pain intensity from 2 weeks after the injections to 14 weeks. Most patients reported pain during the injections, but there were no further local or systemic side effects. The efficacy of BTX-A in painful peripheral neuropathies has been more recently studied. Results were positive in the only study in an animal model of peripheral neuropathy. One study in patients with diabetic painful peripheral neuropathy demonstrated a significant decrease in Visual Analog Scale. In conclusion, one session of multiple intradermal injection of BTX-A produces long-lasting analgesic effects in patients with focal painful neuropathies and diabetic neuropathic pain, and is particularly well tolerated. The findings are consistent with a reduction of peripheral sensitisation, the place of a possible central effect remaining to define. Further studies are needed to assess some important issues, i.e. BTX-A efficacy in patients with small fiber neuropathies and the relevance of early and repeated injections. Future studies could also provide valuable insights into pathophysiology of neuropathic pain.     

How to assess new drugs for neuropathies: advances in trial design and methodology

PURPOSE OF REVIEW: New randomized controlled trials are very much needed to improve the outcome in patients with a variety of peripheral neuropathies. A relatively low incidence of immune-mediated neuropathies such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy and multifocal motor neuropathy, and slow progression in diabetic or hereditary neuropathies may hinder a rapid inclusion and may lead to undesirable extended trial duration. RECENT FINDINGS: Some recent randomized controlled trials use modern trial methodology. Identification of prognostic factors, stratification for important variables at randomization, and the selection of appropriate outcome measurements using a modern clinimetric approach may contribute to a more proper randomized controlled trial design for trials that can be conducted within a limited time frame. SUMMARY: Modern trial methodology and the appropriate use of outcome measurements may improve the quality and reduce the numbers of patients needed in randomized controlled trials in patients with peripheral neuropathies.     

Experimentally induced autonomic neuropathy: beneficial effect of a systemic ACTH4-9 analogue on oculomotor nerve regeneration

While the regenerating capacity of peripheral nerves has been the subject of intensive study, little is known about the regenerative capacity of the autonomic nervous system. Using an animal model, where the pupil diameter of the eye in the rat serves as a parameter of autonomic function, we studied whether systemic treatment with the neuropeptide Org 2766, a synthetic ACTH4-9, analogue, facilitates the functional recovery of parasympathetic nerve fibres after transection, and after a crush lesion of the oculomotor nerve. By simply photographing the rat's pupil under standardised conditions, we show that sectioning the oculomotor nerve leads to an immediate mydriasis, followed by spontaneous regeneration in 30 days. Systemic treatment with an ACTH4-9 analogue had no effect on the rate or quality of recovery. However, systemic treatment with an ACTH4-9 analogue after a crush lesion of the oculomotor nerve (spontaneous regeneration time 16 days) did enhance the speed of recovery of the parasympathetic nerve fibres in the oculomotor nerve, especially in the initial stages of regeneration. We conclude that the animal model used in this study is valuable for studying the regenerative capacity of the autonomic nervous system and the influence of neurotrophic peptides on autonomic neuropathies. Evidence is presented that synthetic ACTH4-9 analogue exerts beneficial neurotrophic effects, not only in peripheral sensorimotor neuropathies but also in autonomic neuropathies.     

Ocular neuropathy in peripheral neuropathies

Ocular movements and coordination require complex and integrated functions of somatic and autonomic nervous systems. Neurological disorders affecting these nervous systems may cause ocular dysfunction involving extraocular muscles and pupils. In this article, the prevalence, clinical presentations, and management of ocular neuropathy related to certain peripheral neuropathies, including diabetic neuropathy, Guillain–Barré syndrome (GBS), chronic inflammatory neuropathies, human immunodeficiency virus (HIV)‐associated neuropathy, and hereditary neuropathies, are examined in detail. Muscle Nerve 46: 681–686, 2012     

Neurotrophic factors: basis for their clinical application

Neurotrophic factors are molecules that regulate neuronal survival, nervous system plasticity and many other physiological functions of neuronal and glial cells, as well as some non-neuronal tissues. They have been involved in the etiopathogenesis of some neurodegenerative disorders, and some of them have been proposed as potential treatments for these diseases on the basis of in vitro experiments and animal models. The main neurotrophic factor families with potential therapeutic applications include the family of neurotrophins (NGF, BDNF or NT-3), GDNF and related neurotrophic factor, CNTF and the members of the IGF family. Some of these molecules have already been tested in clinical trials with contradictory results. One of the major challenges to their clinical use is the difficulty to deliver them into the central nervous system. Nevertheless, solid rational exists for the possible use of neurotrophic factors in the treatment of Alzheimer's and Parkinson's diseases, peripheral neuropathies or amyotrophic lateral sclerosis. This review compiles the essential aspects of neurotrophic factors and the current studies of their clinical relevance and therapeutic potentialities. Future directions for further research are also discussed.     

Disorders of the autonomic nervous system: Part 1. Pathophysiology and clinical features

Autonomic dysfunction may result from diseases that affect primarily either the central nervous system or the peripheral autonomic nervous system. The most common pathogenesis of disturbed autonomic function in central nervous system diseases is degeneration of the intermediolateral cell columns (progressive autonomic failure) or disease or damage to descending pathways that synapse on the intermediolateral column cells (spinal cord lesions, cerebrovascular disease, brainstem tumors, multiple sclerosis). The peripheral autonomic nervous system may be damaged in isolation in the acute and subacute autonomic neuropathies or in association with a generalized peripheral neuropathy. The peripheral neuropathies most likely to cause severe autonomic disturbance are those in which small myelinated and unmyelinated fibers are damaged in the baroreflex afferents, the vagal efferents to the heart, and the sympathetic efferent pathways to the mesenteric vascular bed. Acute demyelination of the sympathetic and parasympathetic nerves in the Guillain-Barré syndrome may also cause acute autonomic dysfunction. Although autonomic disturbances may occur in other types of peripheral neuropathy, they are rarely clinically important.     

Paraneoplastic peripheral neuropathies

Paraneoplastic peripheral neuropathies constitute a heterogeneous group of conditions. A link between the tumor and the neuropathy has been demonstrated in a subgroup only. Definite paraneoplastic neuropathies correspond to neuropathies associated with antibodies reacting with antigens common to the peripheral nervous system and the cancer. Neuropathies associated with anti-Hu antibodies are the most frequent and consist mainly in subacute sensory neuronopathy. Sensory or sensory-motor neuropathies with anti-CV2 antibodies are less frequent. The link between the cancer and the neuropathy is less clear in the other forms. The frequency of cancer in this group varies from 1 to 18 p.cent.These neuropathies include inflammatory demyelinating neuropathies, neuropathy and vasculitis, lower motor neurone diseases, and autonomic neuropathies. Occasionally, the neuropathy improves with treatment of the tumor. Recent data suggest that gangliosides may be the target of the immune process in neuropathies associated with melanoma.     

Selektive Immunadsorption bei neurologischen Komplikationen eines systemischen Lupus erythematodes

Vasculitis of the nervous system is a rare cause of multifocal neurologic symptoms and may involve both the central and peripheral nervous systems. Typical symptoms include headache, encephalopathy with cognitive impairment and psychotic symptoms, epileptic seizures, and peripheral neuropathies. Here we report the case of a 71-year-old female presenting with Raynaud's syndrome and paresthesia of the feet. Several weeks later she was admitted to our hospital with a status epilepticus and complex partial seizures. On admission she had mild aphasia, distal paresis of the arms without sensory deficits, and disorientation with hallucinations. Cerebral MRI revealed small, multifocal infarctions in several arterial territories. Multiple cerebral artery stenoses were detected by ultrasound. Examination of the CSF was unremarkable. Serologic tests for autoimmune disorders detected Ro antibodies compatible with systemic lupus erythematosus or Sj?gren's syndrome. A sural nerve biopsy revealed ischemic axonal neuropathy. During administration of i.v. methylprednisolone, the symptom progression stopped but dosages could not be tapered due to severe CNS symptoms (mental decline, disorientation, aphasia, hallucinations). Slow but sustained clinical improvement was achieved by immunoadsorption over 3 weeks followed by a combined high-dose immunosuppressive treatment with cyclophosphamide and prednisolone that paralleled a reduction in anti-Ro titers and normalization of cerebral blood flow velocities as detected by repeated transcranial Doppler sonography. Systemic vasculitis may present with multiple neurologic and psychiatric symptoms due to involvement of the central and peripheral nervous systems. After excluding systemic infection, immunosuppressive therapy should be started early. In our case a combination of high-dose methylprednisolone, immunoadsorption with elimination of Ro antibodies, and cyclophosphamide led to the patient's recovery.     

Acquired inflammatory demyelinating polyneuropathies: clinical and electrodiagnostic features

The acquired demyelinating polyneuropathies include acute (AIDP, Guillain-Barré syndrome, GBS) and chronic (CIDP, dysproteinemic) forms which differ primarily in their temporal profile. They are inflammatory-demyelinating diseases of the peripheral nervous system and likely have an immunologic pathogenesis. Although these neuropathies usually have a characteristic presentation, the electromyographer plays a central role in their recognition, since the demyelinating component of the neuropathy, which greatly reduces the differential diagnosis, is often first identified in the electromyography laboratory. In AIDP, the electromyographer, in addition to establishing the diagnosis, can sometimes predict the prognosis. Recognition of the chronic and dysproteinemic forms of acquired demyelinating polyneuropathy is important since they are treatable. The dysproteinemic forms also may be associated with occult systemic disorders that also may require treatment, independent of the neuropathy.     

Human Recombinant Nerve Growth Factor Replaces Deficient Neurotrophic Support in the Diabetic Rat

Manipulation of neurotrophic support is a developing strategy for new therapy aimed at neurodegenerative diseases. This study demonstrates reduced content and retrograde transport of endogenous nerve growth factor (NGF) in sciatic nerve of diabetic rats. There were also reductions in the diabetic rats in NGF protein and mRNA in skin and muscle of the hindlimb. These deficits correlated with reductions in substance P and calcitonin gene-related peptide–both products of NGF-influenced genes in primary afferents. These manifestations of deficient neurotrophic support were corrected by intensive insulin treatment and surmounted by administration of exogenous human recombinant NGF in a dose-related manner. Impaired neurotrophic support may, therefore, participate in the pathogenesis of diabetic and other peripheral neuropathies.     

Diabetic peripheral neuropathies: their cost to patient and society and the value of knowledge of risk factors for development of interventions

Diabetic peripheral neuropathies are a variety of syndromes which affect sensory, autonomic and motor nerve function. The commonest form, distal symmetric sensory polyneuropathy, is a major risk factor for foot ulceration, which may eventually lead to lower limb amputation. By 2010, it is estimated that globally 220 million people will have diabetes, and epidemiological studies estimate that more than 50% of diabetic patients with a 25-year history will develop diabetic peripheral neuropathies. In 1986, the USA expenditure for care of these neuropathies was estimated at $240 million, and, as the incidence of diabetes is predicted to increase, this cost is likely to escalate. Risk factors associated with diabetic peripheral neuropathy need to be identified so that interventions can be devised. Recombinant nerve growth factor, a putative treatment for diabetic peripheral neuropathies, is currently being evaluated in phase III trials for this indication.     

Polyneuropathy associated with neurofibromatosis

INTRODUCTION: We review the literature on the spectrum of polyneuropathies associated with neurofibromatosis 1 (NF1) and 2 (NF2). BACKGROUND: Symptomatic neuropathies in NF1 are rarer than in NF2, but constitute a potentially severe complication associated with frequent morbidity related to the neuropathy itself, spinal cord compression or peripheral nerve sheath tumor malignant degeneration. Neuropathies are typically observed in young men with subcutaneous neurofibromas (NF1) or cutaneous schwannomas (NF2) and are characterized by a chronic slowly worsening sensorimotor polyneuropathy of the lower limbs. In NF1, demyelinating neuropathy may occur alone or in association with axonal features, whereas in NF2, axonal neuropathies are reported. Large multinodular roots and nerves, which can be easily detected by limb MRI, are characteristic features of NF1-associated polyneuropathies. PERSPECTIVES AND CONCLUSION: Although an associated pathogenic factor may reveal an asymptomatic neuropathy, patients should be monitored carefully because of the increased morbidity and mortality related to the significant proportion of malignant nerve-sheath tumors in these patients with NF1.     

Biological actions of nerve growth factor in the peripheral nervous system

Since the discovery of nerve growth factor (NGF), its role in the physiology/pathophysiology of nerve function has been under intense investigation. More recently, the potential of recombinant human NGF (rhNGF) as a putative treatment for peripheral neuropathies, in particular diabetic polyneuropathy and HIV-associated sensory neuropathy, is being explored. In animal models of diabetes, depletion of endogenous NGF levels has been demonstrated in foot skin and skeletal muscle; these levels reduce further with increasing disease duration. Preclinical studies in animal models of diabetes have shown that administration of NGF can reverse or alleviate impairment in nerve function.     

Animal Models of Peripheral Neuropathies

Peripheral neuropathies are common neurological diseases, and various animal models have been developed to study disease pathogenesis and test potential therapeutic drugs. Three commonly studied disease models with huge public health impact are diabetic peripheral neuropathy, chemotherapy-induced peripheral neuropathy, and human immunodeficiency virus-associated sensory neuropathies. A common theme in these animal models is the comprehensive use of pathological, electrophysiological, and behavioral outcome measures that mimic the human disease. In recent years, the focus has shifted to the use of outcome measures that are also available in clinical use and can be done in a blinded and quantitative manner. One such evaluation tool is the evaluation of epidermal innervation with a simple skin biopsy. Future clinical trials will be needed to validate the translational usefulness of this outcome measure and validation against accepted outcome measures that rely on clinical symptoms or examination findings in patients.     

Tumor necrosis factor-alpha antagonists and neuropathy

Tumor necrosis factor (TNF)-alpha plays an important role in many aspects of immune system development, immune-response regulation, and T-cell-mediated tissue injury. The evidence that TNF-alpha, released by autoreactive T cells and macrophages, may contribute to the pathogenesis of immune-mediated demyelinating neuropathies is reviewed. TNF-alpha antagonists (infliximab, etanercept, adalimumab) are indicated for the treatment of advanced inflammatory rheumatic and bowel disease, but these drugs can induce a range of autoimmune diseases that also attack the central and peripheral nervous systems. Case histories and series report on the association between anti-TNF-alpha treatment and various disorders of peripheral nerve such as Guillain-Barré syndrome, Miller Fisher syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy with conduction block, mononeuropathy multiplex, and axonal sensorimotor polyneuropathies. The proposed pathogeneses of TNF-alpha-associated neuropathies include both a T-cell and humoral immune attack against peripheral nerve myelin, vasculitis-induced nerve ischemia, and inhibition of signaling support for axons. Most neuropathies improve over a period of months by withdrawal of the TNF-alpha antagonist, with or without additional immune-modulating treatment. Preliminary observations suggest that TNF-alpha antagonists may be useful as an antigen-nonspecific treatment approach to immune-mediated neuropathies in patients with a poor response to, or intolerance of, standard therapies, but further studies are required.     

Chemotherapy-induced neuropathy

Abstract Neurotoxic side effects of cancer therapy are second in frequency to hematological toxicity. Unlike hematological side effects that can be treated with hematopoietic growth factors, neuropathies cannot be treated and protective treatment strategies have not been effective. For the neurologist, the diagnosis of a toxic neuropathy is primarily based on the case history, the clinical and electrophysiological findings, and knowledge of the pattern of neuropathy associated with specific agents. In most cases, toxic neuropathies are length‐dependent, sensory, or sensorimotor neuropathies often associated with pain. The platinum compounds are unique in producing a sensory ganglionopathy. Neurotoxicity is usually dependent on cumulative dose. Severity of neuropathy increases with duration of treatment and progression stops once drug treatment is completed. The platinum compounds are an exception where sensory loss may progress for several months after cessation of treatment (“coasting”). As more effective multiple drug combinations are used, patients will be treated with several neurotoxic drugs. Synergistic neurotoxicity has not been extensively investigated. Pre‐existent neuropathy may influence the development of a toxic neuropathy. Underlying inherited or inflammatory neuropathies may predispose patients to developing very severe toxic neuropathies. Other factors such as focal radiotherapy or intrathecal administration may enhance neurotoxicity. The neurologist managing the cancer patient who develops neuropathy must answer a series of important questions as follows: (1) Are the symptoms due to peripheral neuropathy? (2) Is the neuropathy due to the underlying disease or the treatment? (3) Should treatment be modified or stopped because of the neuropathy? (4) What is the best supportive care in terms of pain management or physical therapy for each patient? Prevention of toxic neuropathies is most important. In patients with neuropathy, restorative approaches have not been well established. Symptomatic and other management are necessary to maintain and improve quality of life.     

Pathologic findings in nerve and muscle biopsies from 47 women with silicone breast implants.

OBJECTIVE: To describe the pathologic findings in 47 consecutively received nerve and muscle biopsies from patients with silicone breast implants (SBI). BACKGROUND: The controversial proposal that systemic illness may result from SBI includes diseases of the central and peripheral nervous system. METHODS: All of the biopsies were processed in full according to current standard methodologies in nerve and muscle pathology. Myelinated fiber histograms were prepared in 40 of the 47 cases. RESULTS: Eight of the 47 nerves showed pathologic changes likely to be symptomatic: 7 with an axonal neuropathy, including 1 with a granulomatous neuritis and myositis and 1 with diabetic neuropathy, and the eighth with a hypertrophic onion bulb neuropathy. Eleven showed minor morphologic or morphometric alterations of uncertain clinical significance. The remaining 28 nerve biopsies were normal, including 1 in which the accompanying muscle showed an inflammatory myopathy typical of polymyositis. CONCLUSIONS: These findings represent the largest set of reported pathologic data derived from women with SBI. Within this highly selected cohort of women with SBI, the majority of the biopsies were normal, and in 9 of 47 diverse abnormalities were detected including axonal and demyelinating neuropathies and inflammatory myopathies. These findings do not support a consistent association between SBI and any neuropathologic entity.