Diabetic neuropathy

Pleiotrophin induces formation of functional neovasculature in vivo

Pleiotrophin (PTN) is a heparin-binding growth/differentiation inducing cytokine that shares 50% amino acid sequence identity and striking domain homology with Midkine (MK), the only other member of the Ptn/Mk developmental gene family. The Ptn gene is expressed in sites of early vascular development in embryos and in healing wounds and its constitutive expression in many human tumors is associated with an angiogenic phenotype, suggesting that PTN has an important role in angiogenesis during development and in wound repair and advanced malignancies. To directly test whether PTN is angiogenic in vivo, we injected a plasmid to express PTN into ischemic myocardium in rats. Pleiotrophin stimulated statistically significant increases in both normal appearing new capillaries and arterioles each of which had readily detectable levels of the arteriole marker, smooth muscle cell alpha-actin. Furthermore, the newly formed blood vessels were shown to interconnect with the existent coronary vascular system. The results of these studies demonstrate directly that PTN is an effective angiogenic agent in vivo able to initiate new vessel formation that is both normal in appearance and function. The data suggest that PTN signals the more "complete" new blood vessel formation through its ability to stimulate different functions in different cell types not limited to the endothelial cell.

Spinal orexin-1 receptors mediate anti-hyperalgesic effects of intrathecally-administered orexins in diabetic neuropathic pain model rats

Orexin-A and orexin-B are endogenous ligands of orexin receptors that contain orexin-1 and orexin-2. Activation of the orexinergic system can produce antinociceptive effects in acute inflammatory, mono-neuropathic, and postoperative pain animal models, though the effects of orexins on diabetic neuropathic pain have not been previously investigated. In this study, we studied the anti-hyperalgesic effects of intrathecally administered orexins in a streptozotocin-induced diabetic rat. First, dose-dependent effects were investigated by measuring hind paw withdrawal thresholds in response to noxious-heat and punctate stimuli, after which orexin levels in the cerebrospinal fluid of diabetic rats were measured and compared with those of normal rats using a radioimmunoassay method. The functional role of spinal orexin-1 receptors with the anti-hyperalgesic effects of orexins was also investigated using intrathecal pretreatment with SB-334867, a selective orexin-1 receptor antagonist. Intrathecally administered orexins produced an antinociceptive effect in diabetic rats, however, not in normal rats, though the orexin levels in the cerebrospinal fluid of diabetic rats were similar to those in normal rats. In addition, the anti-hyperalgesic effects of orexins were significantly inhibited by pretreatment with SB-334867. These findings demonstrate that the anti-hyperalgesic effects of orexins in diabetic rats are unlikely due to any direct effect by the supplement on decreased endogenous orexins in the cerebrospinal fluid and that orexin-1 receptors in the spinal cord may be involved in the modulation of nociceptive transmission in diabetic neuropathy. We conclude that the spinal orexinergic system may be a possible target for elucidating the mechanisms of diabetes-induced hyperalgesia.

Endocrine interventions in the ICU

Patients with critical illness, particularly those who depend on intensive care for a prolonged period of time, have a high morbidity and mortality. The acute and chronic phases of critical illness are associated with distinct endocrine alterations. Acute endocrine adaptations to the severe stress of critical illness, comprising an activated anterior pituitary function, have been selected by nature and can, as such, be considered as beneficial for surviving. These adaptations disappear or wane during the prolonged phase of critical illness. In this phase there is a reduced pulsatile secretion of different anterior pituitary hormones and the so-called "wasting syndrome" occurs. This prolonged endocrine/metabolic stress response is quite different from the acute response and may, to some extent, no longer be adaptive. Intervention within the endocrine system, however, remains highly controversial, as it is difficult to differentiate between beneficial adaptations and harmful abnormalities and to outline strategies for therapy. Insulin infusion titrated to maintain normoglycemia may be a notable exception, as this intervention has been proven to increase survival and reduce morbidity of surgical intensive care patients. Treatment of "relative adrenal failure" with hydrocortisone also appears to improve the outcome of patients with septic shock, but diagnostic and dosing issues still remain unresolved. Although extensive research has shown that infusion of hypothalamic-releasing peptides is able to restore physiological hormonal patterns within the somatotropic, thyrotropic, and gonadal axes and, thereby, to generate a controlled anabolic response, further research is needed to investigate whether such interventions actually improve the outcome of critical illness.

Changing the Natural History of Diabetic Neuropathy: Incidence of Ulcer/Amputation in the Contralateral Limb of Patients With a Unilateral Nerve Decompression Procedure

The natural history of diabetes neuropathy is progressive and irreversible loss of sensibility in the feet, leading to ulceration and/or amputation in 15% of patients. The prevalence of neuropathy is more than 50% in those who have been diabetic for 20 years. Decompression of the tibial and peroneal nerves in those with diabetic neuropathy improves sensation in 70% of patients. The impact of this surgery on the development of ulcers and amputations in both the operated and the contralateral, nonoperated limb was evaluated in a retrospective analysis of 50 patients with diabetes a mean of 4.5 years (range, 2-7 years) from the date of surgery. No ulcers or amputations occurred in the index limb of these patients. In contrast, there were 12 ulcers and 3 amputations in 15 different patients in contralateral limbs. This difference was significant at P < 0.001. It is concluded that decompression of lower extremity nerves in diabetic neuropathy changes the natural history of this disease, representing a paradigm shift in health care costs.

Evaluation of SET--a new device for the measurement of pain perception in comparison to standard measures of diabetic neuropathy

BACKGROUND

Early detection of sensory impairment and loss of protective pain sensation is of major importance for the prevention of neuropathic foot ulceration. The aim of our study was to evaluate a new handheld device (SET, a prototype developed by Dr. W. Henniges, Zülpich, Germany) for measurement of pain perception, in comparison with established methods for diagnosis of diabetic neuropathy.

METHODS

Sixty-one patients with diabetes mellitus (13 type 1, 48 type 2; 42 men, 19 women; mean +/- SD age 61.6 +/- 11.6 years) received measurement of pain perception threshold using the new SET device and a measurement of light touch sensation, temperature sensation, and vibration sensation by the use of standard clinical devices. In addition, warm, cold, heat pain and vibration perception thresholds were determined by the use of a computer-based peltier thermode and a vibration stimulator (TSA 2001, Medoc, Ramat Yishai, Israel).

RESULTS

Using the new SET device, patients with sensory impairment showed significantly elevated pain perception thresholds at the dorsum of the foot (P < 0.001), while only a trend towards higher measurements could be observed at the plantar aspect of the foot. A significant correlation could be observed between plantar and dorsal measuring sites (r = 0.78, P < 0.0001) and between both feet (r = 0.85, P < 0.0001). Compared with other qualities of sensory dysfunction, pain perception measurement with the SET device provided the highest sensitivity (pain = 0.82; vibration = 0.61; temperature = 0.42; light touch = 0.11).

CONCLUSIONS

Measurement of pain perception threshold using the SET device is an easy and reliable method for identifying patients with impaired small nerve fiber function.

Diagnosis, epidemiology and pathogenesis of diabetes mellitus: an update for psychiatrists

BACKGROUND

Diabetes mellitus is a complex metabolic disorder characterised by persistent hyperglycaemia. The prevalence of diabetes is increased in people with schizophrenia.

AIMS

To provide an update of current thinking in diabetes for practising psychiatrists.

METHOD

Literature review.

RESULTS

Diabetes is a costly condition in individual, social and economic terms, and the global burden of diabetes is increasing in most populations. The insidious onset and asymptomatic nature of diabetes results in many people remaining undiagnosed and at great risk of developing life-threatening vascular complications. Lifestyle and pharmacological interventions can reduce incident diabetes and delay its progression.

CONCLUSIONS

Public health policies are urgently required to encourage people to follow a healthy lifestyle. Primary prevention strategies for diabetes should target individuals at especially high risk of developing type 2 diabetes, including those with severe mental illness.

Pressure and the diabetic foot: clinical science and offloading techniques

Diabetic foot ulceration is a common, yet in many cases an eminently preventable, complication that affects 1 in 20 patients with diabetes. Risk factors for ulceration include insensitivity (secondary to somatic neuropathy), high foot pressures, callus formation (a consequence of sympathetic neuropathy and high foot pressures), deformities (such as claw feet, prominent metatarsal heads, etc.), peripheral vascular disease, and most importantly, a past history of ulceration. None of these factors alone causes ulceration; thus, early identification and amelioration of these factors is a primary aim in foot ulcer prevention. A number of therapeutic approaches may help reduce ulcer incidence: these include therapeutic footwear, hosiery, and, potentially, liquid silicone injected under high-pressure areas. In the management of neuropathic ulcers, pressure relief is of the utmost importance, and total contact casting remains the "gold standard" means of achieving such pressure redistribution. The successful management of diabetic foot ulceration depends on a team approach, remembering that ulcers should heal if (1) the arterial circulation is intact, (2) pressure relief is achieved and maintained over the ulcer, and (3) infection is appropriately treated.

The value of motor and somatosensory evoked potentials in evaluation of cervical myelopathy in the presence of peripheral neuropathy

STUDY DESIGN

Patterns and rates of motor-evoked potential (MEP) and somatosensory-evoked potential (SEP) abnormalities were evaluated in 9 patients with combined cervical cord compression and diabetic neuropathy and 15 patients with asymptomatic cervical cord compression. The results were compared with those of 8 patients with pure cervical myelopathy and 7 patients with pure diabetic neuropathy.

OBJECTIVE

To assess the efficacy of MEPs and SEPs in the evaluation of cervical myelopathy in the presence of peripheral neuropathy.

SUMMARY OF BACKGROUND DATA

Previous studies have demonstrated a high sensitivity of MEPs and SEPs in documenting a functional involvement of motor and somatosensory pathways in pure or preclinical cervical myelopathy. However, there have been no detailed reports on MEPs and SEPs in cervical cord compression associated with peripheral neuropathy.

METHODS

Central somatosensory conduction was assessed by median and tibial SEPs using peak-to-peak and onset-to-onset methods. Central motor conduction was measured by MEPs and F-waves elicited from upper and lower limb muscles in response to transcranial magnetic stimulation, magnetic stimulation of cervical motor roots, and electrical stimulation of peripheral nerves.

RESULTS

MEPs were more sensitive than SEPs in detecting central conduction impairments in patients with either pure or preclinical or combined forms of cervical myelopathy. The rate of MEP abnormalities suggesting the corticospinal tract involvement in the combined cervical cord compression-neuropathy group did not differ significantly from that in the asymptomatic cervical cord compression group but was lower than in the pure cervical myelopathy group. Combined MEP and SEP analysis improved the test sensitivity in detecting clinically "silent" cervical cord dysfunctions.

CONCLUSIONS

MEPs associated with SEPs are a valuable tool for assessing the presence and severity of cervical cord involvement in combined cervical cord compression and peripheral neuropathy lesions.

Severe and disabling diabetic autonomic neuropathy: a case report

We report a case of a woman with several and severe disabling manifestations of autonomic neuropathy in whom reasonable quality of life was established by combining continuous insulin infusion, jejunal feeding, colostomy and bladder self-catheterisation. We discuss the prevalence rates, pathophysiology, management and prognosis of this disabling condition.

VEGF: a critical player in neurodegeneration

VEGF is a prototype angiogenic factor, but recent evidence indicates that this growth factor also has direct effects on neural cells. Abnormal regulation of VEGF expression has now been implicated in several neurodegenerative disorders, including motoneuron degeneration. This has stimulated an increasing interest in assessing the therapeutic potential of VEGF as a neuroprotective agent for such neurodegenerative disorders.

VEGF: a critical player in neurodegeneration

VEGF is a prototype angiogenic factor, but recent evidence indicates that this growth factor also has direct effects on neural cells. Abnormal regulation of VEGF expression has now been implicated in several neurodegenerative disorders, including motoneuron degeneration. This has stimulated an increasing interest in assessing the therapeutic potential of VEGF as a neuroprotective agent for such neurodegenerative disorders.

Up-regulation of spinal muscarinic receptors and increased antinociceptive effect of intrathecal muscarine in diabetic rats

Spinally administered muscarinic receptor agonists or acetylcholinesterase inhibitors produce effective pain relief. Intrathecal injection of a small dose of neostigmine produces a profound antiallodynic effect in rats with diabetic neuropathy. However, the mechanisms of increased antinociceptive effect of cholinergic agents on diabetic neuropathic pain are not clear. In the present study, we tested the hypothesis that spinal muscarinic receptors are up-regulated in diabetes. The withdrawal threshold of the hindpaw in response to noxious heat and pressure stimuli was determined in streptozotocin-induced diabetic and age-matched normal rats. Muscarine-stimulated guanosine 5'-O-(3-[35S]thio)triphosphate ([35S]GTPgammaS) binding was used to assess the change of functional muscarinic receptors in the spinal cord in diabetes. The [3H]AF-DX 384 membrane binding was performed to determine the number and affinity of spinal cord M2 muscarinic receptors in normal and diabetic rats. We found that the antinociceptive effect of intrathecal 2 to 12 mug muscarine in diabetic animals was potentiated significantly compared with that in normal animals. The maximal muscarine-stimulated [35S]GTPgammaS binding was 112.5 +/- 8.3% in normal rats and 168.8 +/- 12.1% (P < 0.05) in diabetic rats. Although the KD value (2.9 nM) was similar in both groups, the Bmax of [3H]AF-DX 384 membrane binding was significantly higher in diabetic than in normal rats (255.2 +/- 5.9 versus 165.9 +/- 3.5 fmol/mg protein, P < 0.05). Collectively, these data strongly suggest that the muscarinic receptor is up-regulated in the dorsal spinal cord in diabetic rats. This finding probably accounts for the increased efficacy of the antinociceptive effect of intrathecal muscarinic agonists in diabetic neuropathic pain.

Paracrine control of vascularization and neurogenesis by neurotrophins

The neuronal system plays a fundamental role in the maturation of primitive embryonic vascular network by providing a paracrine template for blood vessel branching and arterial differentiation. Furthermore, postnatal vascular and neural regeneration cooperate in the healing of damaged tissue. Neurogenesis continues in adulthood although confined to specific brain regions. Following ischaemic insult, neural staminal cells contribute towards the healing process through the stimulation of neurogenesis and vasculogenesis. Evidence indicates that nerves and blood vessels exert a reciprocal control of their own growth by paracrine mechanisms. For instance, guidance factors, including vascular endothelial growth factor A (VEGF-A) and semaphorins, which share the ability of binding neuropilin receptors, play a pivotal role in the tridimensional growth pattern of arterial vessels and nerves. Animal models and clinical studies have demonstrated a role of VEGF-A in the pathogenesis of ischaemic and diabetic neuropathies. Further, supplementation with VEGF-A ameliorates neuronal recovery by exerting protective effects on nerves and stimulating reparative neovascularization. Human tissue kallikrein, a recently discovered angiogenic and arteriogenic factor, accelerates neuronal recovery by stimulating the growth of vasa nervorum. Conversely, the neurotrophin nerve growth factor, known to regulate neuronal survival and differentiation, is now regarded as a stimulator of angiogenesis and arteriogenesis. These results indicate that angiogenesis and neurogenesis are paracrinally regulated by growth factors released by endothelial cells and neurons. Supplementation of these growth factors, alone or in combination, could benefit the treatment of ischaemic diseases and neuropathies.

Optimal blood glucose control during 18 years preserves peripheral nerve function in patients with 30 years' duration of type 1 diabetes

OBJECTIVE

To assess the association between 18 years of mean HbA(1c) and nerve conduction parameters of the lower limb in patients with type 1 diabetes of 30 years' duration.

RESEARCH DESIGN AND METHODS

HbA(1c) has been examined prospectively since 1982 in a group of 39 patients with type 1 diabetes. Mean age at baseline was 25 years (range 18-40) with 12 years' disease duration. The mean age at diagnosis of diabetes was 12.5 years. Nerve function of lower limbs was assessed at baseline, after 8 years, and after 18 years.

RESULTS

A total of 23 men and 16 women were studied. Mean age was 43 years. Mean HbA(1c) was 8.2% (range 6.6-11.3) during 18-year follow-up. Nerve conduction velocity (NCV) and nerve action potential amplitude (NAPA) at the last examination were significantly associated with mean HbA(1c) (P < 0. 05). From 1982 to 1999, there was a significant reduction in nerve function in patients with mean HbA(1c) >or=8.4% (highest tertile). For example, the mean NCV in the tibial nerve was reduced from 47 to 31 m/s (P < 0.01). The number of nerves with NCV (P < 0.01) and NAPA (P = 0.01) reduced to below the reference level in each patient was also significantly associated to mean HbA(1c). No significant associations were found between nerve function parameters, sex, disease duration, blood pressure, serum cholesterol, microalbuminuria, or smoking.

CONCLUSIONS

The present study shows that mean HbA(1c) is a strong predictor of nerve function. Mean HbA(1c) <8.4% over 18 years was associated with near-normal nerve function.

Effect of various nerve decompression procedures on the functions of distal limbs in streptozotocin-induced diabetic rats: further optimism in diabetic neuropathy

It is known that diabetic neuropathy is the result of endoneurial edema caused by various biochemical reactions triggered by hyperglycemia. This sequence of events can cause cessation of circulation at the perineurial level, or the tough layer, which is not resilient enough to spread intraneural pressure. Internal and external limiting structures create a double crush phenomenon to the nerve structure. Decompression of the nerve trunk at separate levels is one of the adjuncts to the overall treatment plan for diabetic neuropathy. In this study, the right sciatic nerves of 30 rats with streptozotocin-induced diabetes were used; three groups were created. In the control group, the sciatic nerves were explored and dissected only. In group II, tarsal tunnel release was performed and accompanied by epineurotomy of the sciatic nerve and its peroneal and tibial extensions. In group III, in addition to the procedures performed in group II, perineural sheaths, exposed through the epineurotomy sites at both the peroneal and tibial nerves, were incised for decompression of the fascicles. Improvement in diabetic neuropathy was evaluated by using footprint parameters. The last print length values, estimated according to the 38-month measurements, were 26.1 +/- 0.12 mm in the control group, 23.2 +/- 0.07 mm in group II, and 22.2 +/- 0.1 mm in group III. The toe spread and intermediate toe spread values of the groups were parallel to improvements in print lengths throughout the study. The best improvement was observed in the perineurotomy group. Finally, an electron microscopic study revealed variable degenerative changes in all groups, but they were milder in groups II and III. This experimental study reveals that adding internal decompression to external release doubled the effect in reducing derangement in the sciatic nerves of the rats and, in the authors' opinion, offers cause for further optimism in the treatment of diabetic neuropathy.

Corneal confocal microscopy: a non-invasive surrogate of nerve fibre damage and repair in diabetic patients

AIMS/HYPOTHESIS

The accurate detection, characterization and quantification of human diabetic neuropathy are important to define at risk patients, anticipate deterioration, and assess new therapies. Corneal confocal microscopy is a reiterative, rapid, non-invasive in vivo clinical examination technique capable of imaging corneal nerve fibres. The aim of this study was to define the ability of this technique to quantify the extent of degeneration and regeneration of corneal nerve fibres in diabetic patients with increasing neuropathic severity.

METHODS

We scanned the cornea and collected images of Bowman's layer (containing a rich nerve plexus) from 18 diabetic patients and 18 age-matched control subjects.

RESULTS

Corneal nerve fibre density (F(3)=9.6, p<0.0001), length (F(3)=23.8, p<0.0001), and branch density (F(3)=13.9, p<0.0001) were reduced in diabetic patients compared with control subjects, with a tendency for greater reduction in these measures with increasing severity of neuropathy.

CONCLUSION/INTERPRETATION

Corneal confocal microscopy is a rapid, non-invasive in vivo clinical examination technique which accurately defines the extent of corneal nerve damage and repair and acts as a surrogate measure of somatic neuropathy in diabetic patients. It could represent an advance to define the severity of neuropathy and expedite assessment of therapeutic efficacy in clinical trials of human diabetic neuropathy.

Static magnetic field therapy for symptomatic diabetic neuropathy: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To determine if constant wearing of multipolar, static magnetic (450G) shoe insoles can reduce neuropathic pain and quality of life (QOL) scores in symptomatic diabetic peripheral neuropathy (DPN).

DESIGN

Randomized, placebo-control, parallel study.

SETTING

Forty-eight centers in 27 states.

PARTICIPANTS

Three hundred seventy-five subjects with DPN stage II or III were randomly assigned to wear constantly magnetized insoles for 4 months; the placebo group wore similar, unmagnetized device.

INTERVENTION

Nerve conduction and/or quantified sensory testing were performed serially.

MAIN OUTCOME MEASURES

Daily visual analog scale scores for numbness or tingling and burning and QOL issues were tabulated over 4 months. Secondary measures included nerve conduction changes, role of placebo, and safety issues. Analysis of variance (ANOVA), analysis of covariance (ANCOVA), and chi-square analysis were performed.

RESULTS

There were statistically significant reductions during the third and fourth months in burning (mean change for magnet treatment, -12%; for sham, -3%; P<.05, ANCOVA), numbness and tingling (magnet, -10%; sham, +1%; P<.05, ANCOVA), and exercise-induced foot pain (magnet, -12%; sham, -4%; P<.05, ANCOVA). For a subset of patients with baseline severe pain, statistically significant reductions occurred from baseline through the fourth month in numbness and tingling (magnet, -32%; sham, -14%; P<.01, ANOVA) and foot pain (magnet, -41%; sham, -21%; P<.01, ANOVA).

CONCLUSIONS

Static magnetic fields can penetrate up to 20mm and appear to target the ectopic firing nociceptors in the epidermis and dermis. Analgesic benefits were achieved over time.

Polyol pathway and diabetic peripheral neuropathy

This chapter critically examines the concept of the polyol pathway and how it relates to the pathogenesis of diabetic peripheral neuropathy. The two enzymes of the polyol pathway, aldose reductase and sorbitol dehydrogenase, are reviewed. The structure, biochemistry, physiological role, tissue distribution, and localization in peripheral nerve of each enzyme are summarized, along with current informaiton about the location and structure of their genes, their alleles, and the possible links of each enzyme and its alleles to diabetic neuropathy. Inhibitors of pathway enzyme and results obtained to date with pathway inhibitors in experimental models and human neuropathy trials are updated and discussed. Experimental and clinical data are analyzed in the context of a newly developed metabolic odel of the in vivo relationship between nerve sorbitol concentration and metabolic flux through aldose reuctase. Overall, the data will be interpreted as supporting the hypothesis that metabolic flux through the polyol pathway, rather than nerve concentration of sorbitol, is the predominant polyol pathway-linked pathogeneic factor in diabetic preipheral nerve. Finally, key questions and future directions for bsic and clinical research in this area are considered. It is concluded that robust inhibition of metabolic flux through the polyol pathway in peripheral nerve will likely result in substantial clinical benefit in treating and preventing the currently intractable condition of diabetic peripheral neuropathy. To accomplish this, it is imperative to develop and test a new generation of "super-potent" polyol pathway inhibitors.

Neuropathology and pathogenesis of diabetic autonomic neuropathy

Autonomic neuropathy is a significant complication of diabetes resulting in increased patient morbidity and mortality. A number of studies, which have shown correspondence between neuropathologic findings in experimental animals and human subjects, have demonstrated that axonal and dendritic pathology in sympathetic ganglia in the absence of significant neuron loss represents a neuropathologic hallmark of diabetic autonomic neuropathy. A recurring theme in sympathetic ganglia, as well as in the pot-ganglionic autonomic innervation of various end organs, is the involvement of distal portions of axons and nerve terminals by degenerative or dystrophic changes. In both animals and humans, there is a surprising selectivity of the diabetic process for subpopulations of autonomic ganglia, nerve terminals within sympathetic ganglia and end organs, from end organ to end organ, and between vascular and other targets within individual end organs. Although the involvement or autonomic axons in somatic nerves may reflect an ischemic pathogenesis, the selectivity of the diabetic process confounds simple global explanations of diabetic autonomic neuropathy as the result of diminished blood flow with resultant tissue hypoxia. A single unifying pathogenetic hypothesis has not yet emerged from clinical and experimental animal studies, and it is likely that diabetic autonomic neuropathy will be shown to have multiple causative mechanisms, which will interact to result in the variety of presentations of autonomic injury in diabetes. Some of these mechanisms will be shared with aging changes in the autonomic nervous system. The role of various neurotrophic substances and the polyol pathway in the pathogenesis and treatment of diabetic neuropathy likely represents a two-edged sword with both salutary and exacerbating effects. The basic neurobiologic process underlying the diabetes-induced development of neuroaxonal dystrophy, synaptic dysplasia, defective axonal regeneration, and alterations in neurotrophic substance may be mechanistically related.

Current and Future Strategies for the Management of Diabetic Neuropathy

Diabetic neuropathy is common, related to increased morbidity and mortality, and has no effective treatment at present. Interventions based on putative pathways thought to contribute to damage and repair of nerve fibres have yielded little success to date. Pain is a potentially debilitating manifestation of diabetic neuropathy and has many potential sites of origin and, hence, modulation. Its cause is unclear and it does not respond well to traditional pain therapies, proposed to mediate their benefits via multiple peripheral and central mechanisms. A better understanding of the mechanisms leading to nerve fibre degeneration and regeneration as well as pain has recently resulted in the development of a more targeted approach to the treatment of diabetic neuropathy. Thus, specific NMDA receptor antagonists and more specific neuronal serotonin and norepinephrine (noradrenaline) uptake inhibitors offer promise in the treatment of painful diabetic neuropathy. A number of treatments which include the aldose reductase inhibitors and neurotrophins have failed to reach the clinical arena. However, the antioxidant alpha-lipoic acid, as well as compounds which correct vascular dysfunction and hence neuropathy, such as ACE inhibitors and protein kinase C-beta inhibitors, have demonstrated more success.

Treatment of symptomatic diabetic neuropathy

Painful diabetic neuropathy is a common and particularly unpleasant long-term complication of diabetes that affects a significant minority of patients with distal polyneuropathy. After exclusion of other causes of neuropathic pain, attention should be focused on achieving optimal and stable glycaemic control avoiding flux of blood glucose levels, which have been shown to aggravate pain. Most patients will require pain control therapy and whilst the tricyclic drugs remain a first-line approach, their use is often hampered by predictable but troublesome side effects. Gabapentin, the only agent specifically licensed for the treatment of neuropathic pain in the United Kingdom, is useful in diabetic neuropathy and is generally better tolerated than the tricyclics. Additionally, other pharmacological and non-pharmacological pain management approaches may be useful. Patient education has a significant role to play in the avoidance of late neurological complications.

Clinical potential of insulin therapy in critically ill patients

Stress of critical illness is often accompanied by hyperglycaemia, whether or not the patient has a history of diabetes mellitus. This has been considered to be part of the adaptive metabolic response to stress. The level of hyperglycaemia in patients with acute myocardial infarction (MI) or stroke upon admission to the hospital has been related to the risk of adverse outcome. However, until recently, there was no evidence of a causal relationship and thus stress-induced hyperglycaemia was only treated with exogenous insulin when it exceeded 12 mmol/L (220 mg/dL). In patients with known diabetes, even higher levels were often tolerated. Recently, new data became available in support of another approach. In this review, we focus on the new evidence and the clinical aspects of managing hyperglycaemia with insulin in critically ill patients, drawing a parallel with diabetes management. Particularly, the 'Diabetes and Insulin-Glucose infusion in Acute Myocardial Infarction (DIGAMI) study' and the 'insulin in intensive care study' have provided novel insights. The DIGAMI study showed that in patients with diabetes, controlling blood glucose levels below 12 mmol/L for 3 months after acute MI improves long-term outcome. In the recent study of predominantly surgical intensive care patients, the majority of whom did not previously have diabetes, it was shown that an even tighter control of blood glucose with exogenous insulin, aiming for normoglycaemia, dramatically improved outcome. Indeed, in this large prospective, randomised, controlled study, 1548 intensive care patients had been randomly allocated to either the conventional approach, with insulin infusion started only when blood glucose levels exceeded 12 mmol/L, or intensive insulin therapy, with insulin infused to maintain blood glucose at a level of 4.5-6.1 mmol/L (80-110 mg/dL). Intensive insulin therapy reduced intensive care mortality by more than 40% and also decreased a number of morbidity factors including acute renal failure, polyneuropathy, ventilator-dependency and septicaemia. Future studies will be needed to further unravel the mechanisms that explain the beneficial effects of this simple and cost-saving intervention. Although available evidence supports implementation of intensive insulin therapy in surgical intensive care, the benefit for other patient populations, such as patients on medical intensive care units or hospitalised patients who do not require intensive care but who do present with stress-induced hyperglycaemia, remains to be investigated.

Local sympathetic denervation in painful diabetic neuropathy

This study assessed whether painful diabetic neuropathy is associated with abnormal sympathetic nervous function in the affected limbs. Nine patients with diabetes (four men, five women; age 61 +/- 7 years) and painful peripheral neuropathy of the feet, but without evidence of generalized autonomic neuropathy, underwent intravenous infusion of tritiated norepinephrine (NE) and sampling of arterial and venous blood in both feet and in one arm to quantify the rate of entry of NE into the local venous plasma (NE spillover). In the same patients, positron emission tomography (PET) scanning after intravenous injection of the sympathoneural imaging agent 6-[(18)F]fluorodopamine was used to visualize sympathetic innervation and after intravenous [(13)N]ammonia to visualize local perfusion. The results were compared with those in the feet of normal volunteers and in an unaffected foot of patients with unilateral complex regional pain syndrome (CRPS). In addition, neurochemical results obtained in painful diabetic neuropathy were compared with those obtained in diabetic control patients with painless neuropathy and diabetic control patients without neuropathy. Local arteriovenous difference in plasma NE levels (DeltaNE(AV)) and NE spillover in the arms did not differ across the groups. However, DeltaNE(AV) in the feet was significantly less in the group with painful diabetic neuropathy than in the control groups. Also NE spillover in the feet tended to be lower in painful neuropathy. DeltaNE(AV) of diabetic control patients without neuropathy (n = 6) resembled values in the control groups without diabetes, whereas patients with painless diabetic neuropathy (n = 6) had evidence suggesting partial loss of sympathetic innervation. PET scanning revealed decreased flow-corrected 6-[(18)F]fluorodopamine-derived radioactivity in patients with painful diabetic neuropathy, compared with values in normal volunteers and patients with CRPS. The results provide neurochemical and neuroimaging evidence for regionally selective sympathetic denervation in the painful feet of patients with diabetic neuropathy.

Focal and multifocal neuropathies

The focal and multifocal neuropathies affect only a minority of patients with diabetes; however, they form a major clinical problem in terms of diagnosis, development of significant symptoms and signs, and often inadequate therapy. Diagnosis requires accurate and detailed clinical history and neurologic examination combined with targeted neurophysiologic tests, which differ considerably from those carried out in day-to-day practice. Because of their relatively infrequent occurrence, treatment is not evidence based.

Vascular and neuronal effects of VEGF in the nervous system: implications for neurological disorders

Vascular endothelial growth factor (VEGF) was originally discovered as an endothelial-specific growth factor. While the predominant role of this growth factor in the formation of new blood vessels (angiogenesis) is unquestioned, recent observations indicate that VEGF also has direct effects on neurons and glial cells, and stimulates their growth, survival and axonal outgrowth. Because of these pleiotropic effects, VEGF has now been implicated in several neurological disorders both in the preterm infant (leukomalacia) and the adult (stroke, neurodegeneration, cerebral and spinal trauma, ischemic and diabetic neuropathy, nerve regeneration). A challenge for the future is to unravel to what extent the effect of VEGF in these disorders relates to its angiogenic activity or direct neurotrophic effect.

Clinical protocol: Phase I trial to evaluate the safety of H5.020CMV.PDGF-B for the treatment of a diabetic insensate foot ulcer

Most patients with chronic wounds fail to heal in a reasonable period of time. Despite considerable advances in elucidating the molecular basis of wound repair, attempts at developing new therapies have been disappointing. In fact, in the few studies where cytokine growth factors have been efficacious, their effect has been dramatically less than would have been predicted from animal studies. We hypothesize that platelet-derived growth factor-BB, a growth factor associated with wound healing, when produced in large quantities within the wound bed due to adenovirus mediated gene overexpression by the cells of the wound bed will dramatically enhance wound healing. Simply stated, we plan to insure the delivery of the growth factor by using gene therapy techniques so that cells locally involved in the wound healing process will temporarily increase their production of platelet-derived growth factor-BB. We present the first step in the series of human investigations to test this hypothesis which is a phase I clinical trial. Our proposed study is designed to assess local and systemic toxicity, and the feasibility of using the maximum tolerated dose of H5.020CMV.PDGF-b associated with in vivo platelet-derived growth factor-BB gene transduction via an intraulcer injection of H5.020CMV.PDGF-b in patients with a diabetic insensate foot ulcer.

Angiogenesis in cancer and other diseases

Pathological angiogenesis is a hallmark of cancer and various ischaemic and inflammatory diseases. Concentrated efforts in this area of research are leading to the discovery of a growing number of pro- and anti-angiogenic molecules, some of which are already in clinical trials. The complex interactions among these molecules and how they affect vascular structure and function in different environments are now beginning to be elucidated. This integrated understanding is leading to the development of a number of exciting and bold approaches to treat cancer and other diseases. But owing to several unanswered questions, caution is needed.

Maintenance of the long-term effectiveness of tramadol in treatment of the pain of diabetic neuropathy

OBJECTIVE

The objective of this study was to evaluate the efficacy and safety of tramadol in a 6-month open extension following a 6-week double-blind randomized trial.

RESEARCH DESIGN AND METHODS

Patients with painful diabetic neuropathy who completed the double-blind study were eligible for enrollment in an open extension of up to 6 months. All patients received tramadol 50-400 mg/day. Self-administered pain intensity scores (scale 0-4; none to extreme pain) and pain relief scores (scale -1-4; worse to complete relief) were recorded the first day of the open extension (last day of the double-blind phase) and at 30, 90, and 180 days.

RESULTS

A total of 117 patients (56 former tramadol and 61 former placebo) entered the study. On the first day of the study, patients formerly treated with placebo had a significantly higher mean pain intensity score (2. 2+/-1.02 vs. 1.4+/-0.93, P<0.001) and a lower pain relief score (0. 9+/-1.43 vs. 2.2+/-1.27, P<0.001) than former tramadol patients. By Day 90, both groups had mean pain intensity scores of 1.4, which were maintained throughout the study. Mean pain relief scores (2. 4+/-1.09 vs. 2.2+/-1.14) were similar after 30 days in the former placebo and former tramadol groups, respectively and were maintained for the duration of the study. Four patients discontinued therapy due to ineffective pain relief; 13 patients discontinued due to adverse events. The most common adverse events were constipation, nausea, and headache.

CONCLUSIONS

Tramadol provides long-term relief of the pain of diabetic neuropathy.

Can diabetic neuropathy be prevented by angiotensin-converting enzyme inhibitors?

The incidence of diabetes and its complications is increasing to staggering proportions. Presently the WHO estimates an overall prevalence of 130 million, but by 2025 there will be 300 million individuals with diabetes mellitus. The incidence of diabetic neuropathy approaches 50% in most diabetic populations; there is no treatment, and its consequences in the form of foot ulceration and amputation are financially punishing for health care providers. Attempts to develop treatments have faltered for want of an understanding of the aetiology of diabetic neuropathy. As a consequence, 1999 saw the demise of two further compounds: recombinant growth factor by Roche-Genentech and the aldose reductase inhibitor zopolrestat, by Pfizer, both had reached phase III clinical trials. They joined an impressive list of at least 30 other compounds which have reached phase III clinical trials and failed to establish efficacy. The need to establish a viable treatment for human diabetic neuropathy is absolutely paramount. To provide a rational answer as to whether angiotensin-converting enzyme (ACE) inhibitors can prevent human diabetic neuropathy, two major issues need addressing: 1) Does vascular dysfunction cause human diabetic neuropathy? 2) Can ACE inhibitors ameliorate diabetic vascular dysfunction and hence neuropathy? Epidemiological studies support a strong association between neuropathy, retinopathy and nephropathy. Microangiopathy is deemed as the root cause of both nephropathy, and retinopathy and mounting evidence provides support for a vascular basis of diabetic neuropathy. ACE inhibitors appear to correct many of the abnormalities associated with the vascular dysfunction found in diabetes. Thus effective ACE inhibition impacts very positively on cardiovascular outcomes in patients with ischaemic heart disease, particularly in diabetic patients. ACE inhibition also prevents the development and progression of incipient and established diabetic nephropathy and delays progression of background retinopathy. Quinapril improves measures of diabetic autonomic neuropathy. Our recent study has demonstrated a significant improvement in peripheral neuropathy following 12 months of treatment with the ACE inhibitor trandolapril.

Clinico-pathological features of postural hypotension in diabetic autonomic neuropathy

We report the clinico-pathological features and management of a 49-year-old male with a 30-year history of Type 1 diabetes mellitus who had nephropathy (proteinuria 1.81 g/24 h, creatinine 136 micromol/l), proliferative retinopathy and severe somatic and autonomic neuropathy. A sural nerve biopsy demonstrated marked myelinated fibre loss with unmyelinated fibre degeneration and regeneration combined with extensive endoneurial microangiopathy. The management of the patient's blood pressure problems (supine hypertension) and symptomatic postural hypotension is discussed.

Structural abnormalities do not explain the early functional abnormalities in the peripheral nerves of the streptozotocin diabetic rat

The streptozotocin (STZ)-diabetic rat, the most commonly employed model of experimental diabetic neuropathy, is characterised by a reduction in nerve conduction velocity, pain threshold and blood flow. Whether or not structural abnormalities underlie these functional abnormalities is unclear. 10 adult male Sprague-Dawley STZ-diabetic rats (diabetes duration 27 d) and 10 age-matched (23 wk) control animals were studied. Motor nerve conduction velocity (m s(-1)) was significantly reduced in diabetic (41.31 +/- 0.8) compared with control (46.15 +/- 1.5) animals (P < 0.001). The concentration of sciatic nerve glucose (P < 0.001), fructose (P < 0.001) and sorbitol (P < 0.001) was elevated, and myoinositol (P < 0.001) was reduced in diabetic compared with control animals. Detailed morphometric studies demonstrated no significant difference in fascicular area, myelinated fibre density, fibre and axon areas as well as unmyelinated fibre density and diameter. Endoneurial capillary density, basement membrane area and endothelial cell profile number did not differ between diabetic and control animals. However, luminal area (P < 0.03) was increased and endothelial cell area (P < 0.08) was decreased in the diabetic rats. We conclude there is no detectable structural basis for the reduction in nerve conduction velocity, pain threshold or blood flow, observed in the streptozotocin diabetic rat.