New insights into the pathogenesis of diabetic neuropathy

The pathophysiology of diabetic foot: a narrative review

An aging population and changes in dietary habits have increased the incidence of diabetes, resulting in complications such as diabetic foot ulcers (DFUs). DFUs can lead to serious disabilities, substantial reductions in patient quality of life, and high financial costs for society. By understanding the etiology and pathophysiology of DFUs, their occurrence can be prevented and managed more effectively. The pathophysiology of DFUs involves metabolic dysfunction, diabetic immunopathy, diabetic neuropathy, and angiopathy. The processes by which hyperglycemia causes peripheral nerve damage are related to adenosine triphosphate deficiency, the polyol pathway, oxidative stress, protein kinase C activity, and proinflammatory processes. In the context of hyperglycemia, the suppression of endothelial nitric oxide production leads to microcirculation atherosclerosis, heightened inflammation, and abnormal intimal growth. Diabetic neuropathy involves sensory, motor, and autonomic neuropathies. The interaction between these neuropathies forms a callus that leads to subcutaneous hemorrhage and skin ulcers. Hyperglycemia causes peripheral vascular changes that result in endothelial cell dysfunction and decreased vasodilator secretion, leading to ischemia. The interplay among these four preceding pathophysiological factors fosters the development and progression of infections in individuals with diabetes. Charcot neuroarthropathy is a chronic and progressive degenerative arthropathy characterized by heightened blood flow, increased calcium dissolution, and repeated minor trauma to insensate joints. Directly and comprehensively addressing the pathogenesis of DFUs could pave the way for the development of innovative treatment approaches with the potential to avoid the most serious complications, including major amputations.

On the effects of diabetes mellitus on the mechanical properties of DRG sensory neurons and their possible relation with diabetic neuropathy

Diabetic neuropathy (DN) is one of the principal complications of diabetes mellitus (DM). Dorsal root ganglion (DRG) neurons are the primary sensory neurons that transduce mechanical, chemical, thermal, and pain stimuli. Diabetes-caused sensitivity alterations and presence of pain are due to cellular damage originated by persistent hyperglycemia, microvascular insufficiency, and oxidative and nitrosative stress. However, the underlying mechanisms have not been fully clarified. The present work addresses this problem by hypothesizing that sensitivity changes in DN result from mechanotransduction-system alterations in sensory neurons; especially, plasma membrane affectations. This hypothesis is tackled by means of elastic-deformation experiments performed on DGR neurons from a murine model for type-1 DM, as well a mathematical model of the cell mechanical structure. The obtained results suggest that the plasma-membrane fluidity of DRG sensory neurons is modified by the induction of DM, and that this alteration may correlate with changes in the cell calcium transient that results from mechanical stimuli.

Protective Effects of PACAP in a Rat Model of Diabetic Neuropathy

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide with a widespread occurrence and diverse effects. PACAP has well-documented neuro- and cytoprotective effects, proven in numerous studies. Among others, PACAP is protective in models of diabetes-associated diseases, such as diabetic nephropathy and retinopathy. As the neuropeptide has strong neurotrophic and neuroprotective actions, we aimed at investigating the effects of PACAP in a rat model of streptozotocin-induced diabetic neuropathy, another common complication of diabetes. Rats were treated with PACAP1-38 every second day for 8 weeks starting simultaneously with the streptozotocin injection. Nerve fiber morphology was examined with electron microscopy, chronic neuronal activation in pain processing centers was studied with FosB immunohistochemistry, and functionality was assessed by determining the mechanical nociceptive threshold. PACAP treatment did not alter body weight or blood glucose levels during the 8-week observation period. However, PACAP attenuated the mechanical hyperalgesia, compared to vehicle-treated diabetic animals, and it markedly reduced the morphological signs characteristic for neuropathy: axon–myelin separation, mitochondrial fission, unmyelinated fiber atrophy, and basement membrane thickening of endoneurial vessels. Furthermore, PACAP attenuated the increase in FosB immunoreactivity in the dorsal spinal horn and periaqueductal grey matter. Our results show that PACAP is a promising therapeutic agent in diabetes-associated complications, including diabetic neuropathy.

Clinical study of diabetic peripheral neuropathy screening by retinal vascular geometric parameters

To investigate the relationship between geometrical changes of retinal vessels and diabetic peripheral neuropathy (DPN), and to determine the effectiveness of retinal vascular geometry analysis and vibration perception threshold (VPT) for DPN assessment. Type 2 diabetes patients (n = 242) were categorized by stage of DPN. VPT and fundus photography was performed to obtain retinal vascular geometry parameters. The risk factors for DPN and the correlation between DPN stages were analyzed. The efficiency of the retinal vascular geometric parameters obtained with VPT as a diagnostic tool for DPN was examined. Stages of DPN showed a linear correlation with VPT (r = 0.818), central retinal vein equivalent (CRVE) (r = 0.716), and fractal dimension arterioles (DFa) (r = - 0.769). VPT, CRVE, DFa, and fractal dimension veins (DFv) showed high sensitivity (80%, 55%, 82%, and 67%, respectively) and specificity (92%, 93%, 82%, and 80%, respectively) for DPN diagnosis. Good agreement was observed between combined use of geometric parameters (CRVE, DFa and DFv) and VPT (Kappa value 0.430). The detection rate of DPN with combined use of geometric parameters of retinal vessels (64.88%) was significantly higher than that with use of VPT (47.52%). Retinal vascular geometry changes demonstrated significant correlation with DPN severity. VPT, CRVE, DFa, and DFv may provide insights for understanding DPN.

Treatment of Diabetic Neuropathy with A Novel PAR1-Targeting Molecule

Diabetic peripheral neuropathy (DPN) is a disabling common complication of diabetes mellitus (DM). Thrombin, a coagulation factor, is increased in DM and affects nerve function via its G-protein coupled protease activated receptor 1 (PAR1). Methods: A novel PAR1 modulator (PARIN5) was designed based on the thrombin PAR1 recognition site. Coagulation, motor and sensory function and small fiber loss were evaluated by employing the murine streptozotocin diabetes model. Results: PARIN5 showed a safe coagulation profile and showed no significant effect on weight or glucose levels. Diabetic mice spent shorter time on the rotarod (p < 0.001), and had hypoalgesia (p < 0.05), slow conduction velocity (p < 0.0001) and reduced skin innervation (p < 0.0001). Treatment with PARIN5 significantly improved rotarod performance (p < 0.05), normalized hypoalgesia (p < 0.05), attenuated slowing of nerve conduction velocity (p < 0.05) and improved skin innervation (p <0.0001). Conclusion: PARIN5 is a novel pharmacological approach for prevention of DPN development, via PAR1 pathway modulation.

A study of nerve conduction velocity in diabetic patients and its relationship with tendon reflexes (T-Reflex)

Background and Objective:

Neuropathy is one of the most common complications of diabetes mellitus. Neuropathy can cause sensory deficit, neurological disorder, organ ulcers, osteomyelitis, and amputation. Therefore, neurological examinations, determining the nerve conduction velocity and performing sensory and motor tests are important for timely diagnosis and treatment. The present study aimed to investigate the nerve conduction velocity in diabetic patients and its relationship with tendon reflexes.

Materials and Methods:

The present study was observational-cross sectional research carried out on 77 diabetic patients who admitted to the EMG / NCV Department of Shariati Hospital in the academic year 1996-1997. In all patients, the medical history of the patient (age, duration of diabetes, gender and age of onset of diabetes), neurological examination, nerve conduction velocity, heat test, vibration test, tendon reflexes, D.L and Amplitude were examined and recorded. Finally, the raw data obtained was entered into the IBM SPSS Statistics software and the important relationships between these variables were analyzed. Moreover, in present study, the statistical significance level (P-value) was considered less than 0.05.

Results:

The present study was conducted on a population consisting of 48 women and 29 men with diabetes. The age range of participants was 14-70 years old with an average age of 50.506 ± 7.50. The results of present study showed that the participants with clinical neuropathy (11.2 ± 7.2) had significantly longer duration of diabetes than the normal group and those participants with sub-clinical neuropathy (P-value = 0.12). Statistical analyses indicated that increase in age, increase in the duration of diabetes and the gender of male significantly made the nerve conduction velocity abnormal. The analysis of the response to neural reflexes indicated that the ratio of neurological disorders in the five nerves of the ankle and knee was generally higher in the abnormal group (the patients with nerve conduction disorder) compared to the normal (the patients with normal nerve conduction) and in some cases, such as the ulnar motor nerve of ankle (P-value = 0.010), and the ulnar motor nerve of knee motor (P-value = 0.002) and also in the peroneal motor nerve of knee (P-value = 0.003) and the sural sensory nerve of knee (P-value = 0.003), increase in neurological disorders was significant.

Conclusion:

Increase in age, increase in the duration of diabetes and the gender of male can significantly make the nerve conduction velocity abnormal. (www.actabiomedica.it)

The role of thrombin in the pathogenesis of diabetic neuropathy

Diabetic neuropathy is common and disabling despite glycemic control. Novel neuroprotective approaches are needed. Thrombin and hypercoagulability are associated with diabetes and nerve conduction dysfunction. Our aim was to study the role of thrombin in diabetic neuropathy. We measured thrombin activity by a biochemical assay in streptozotocin (STZ)-induced diabetic neuropathy in male Sprague-Dawley rats. Neuropathy severity was assessed by thermal latency and nerve conduction measures. Thermal latencies were longer in diabetic rats, and improved with the non-specific serine-protease inhibitor Tosyl-L-lysine-chloromethyl ketone (TLCK) treatment (p<0.01). The tail nerve of diabetic rats showed slow conduction velocity (p˂0.01), and interestingly, increased thrombin activity was noted in the sciatic nerve (p˂0.001). Sciatic nodes of Ranvier and the thrombin receptor, protease activated receptor 1 (PAR1) reactivity showed abnormal morphology in diabetic animals by immunofluorescence staining (p<0.0001). Treatment of diabetic animals with either the specific thrombin inhibitor, N-alpha 2 naphtalenesulfonylglycyl alpha-4 amidino-phenylalaninepiperidide (NAPAP) or TLCK preserved normal conduction velocity, (p˂0.01 and p = 0.01 respectively), and prevented disruption of morphology (p˂0.05 and p˂0.03). The results establish for the first time an association between diabetic neuropathy and excessive activation of the thrombin pathway. Treatment of diabetic animals with thrombin inhibitors ameliorates both biochemical, structural and electrophysiological deficits. The thrombin pathway inhibition may be a novel neuroprotective therapeutic target in the diabetic neuropathy pathology.

A Study of Nerve Conduction Velocity in Diabetic Patients and its Relationship with Tendon Reflexes (T-Reflex)

BACKGROUND

Neuropathy is one of the most common complications of diabetes mellitus. Neuropathy can cause the sensory deficit, neurological disorder, limb ulcers, osteomyelitis, and amputation. Therefore, neurological examinations, determining the nerve conduction velocity and performing sensory and motor tests are important for timely diagnosis and treatment.

AIM

The present study aimed to investigate the nerve conduction velocity in diabetic patients and its relationship with tendon reflexes.

MATERIAL AND METHODS

The present study was observational-cross sectional research carried out on 77 diabetic patients who were admitted into the EMG/NCV Department of Shariati Hospital in the academic year 1996-1997. In all patients, the medical history of the patient (age, duration of diabetes, gender and age of onset of diabetes), neurological examination, nerve conduction velocity, heat test, vibration test, tendon reflexes, D.L and Amplitude were examined and recorded. Finally, the raw data obtained were entered into the IBM SPSS Statistics software, and the important relationships between these variables were analysed. Moreover, in the present study, the statistical significance level (P-value) was considered less than 0.05.

RESULTS

The present study was conducted on a population consisting of 48 women and 29 men with diabetes. The age range of participants was 14-70 years old with an average age of 50.506 ± 7.50. The results of present study showed that the participants with clinical neuropathy (11.2 ± 7.2) had a significantly longer duration of diabetes than the normal group and those participants with sub-clinical neuropathy (P-value = 0.12). Statistical analyses indicated that increase in age, increase in the duration of diabetes and the gender of male significantly made the nerve conduction velocity abnormal. The analysis of the response to neural reflexes indicated that the ratio of neurological disorders in the five nerves of the ankle and knee was generally higher in the abnormal group (the patients with nerve conduction disorder) compared to the normal (the patients with normal nerve conduction) and in some cases, such as the ulnar motor nerve of ankle (P-value = 0.010), and the ulnar motor nerve of knee motor (P-value = 0.002) and also in the peroneal motor nerve of knee (P-value = 0.003) and the sural sensory nerve of knee (P-value = 0.003), increase in neurological disorders was significant.

CONCLUSION

Increase in age, increase in the duration of diabetes, and the male gender can significantly increase the risk of abnormal nerve conduction velocity.

Effectiveness and feasibility of nailfold microcirculation test to screen for diabetic peripheral neuropathy

AIMS

The nailfold microcirculation index (MI) is a non-invasive, objective, and highly sensitive blood capillary detection method. This study evaluated the diagnostic efficiency of the nailfold MI relative to the more subjective vibration perception threshold (VPT) examination for early diagnostic screening of diabetic peripheral neuropathy (DPN).

METHODS

From February 2015 to February 2016, 227 diabetes mellitus patients and 39 healthy individuals were enrolled. Each subject underwent the MI test and the VPT examination.

RESULTS

MI was more closely associated with DPN than age, diabetic duration, smoking, drinking, systolic pressure, serum creatinine, 24-h urinary protein, hypoxia-inducible factor-1α (HIF1A), vascular endothelial growth factor (VEGF), the VEGF receptors Flt-1 and Flt-4, ankle branchial index (ABI), DPN, or DPN stage (OR=11.819). Both the MI and VPT closely correlated with age, diabetic duration, serum creatinine, 24-h urinary protein, HIF1A, VEGF, Flt-1, Flt-4, ABI, DPN, and DPN stage. By the receiver operating characteristic (ROC) curve, the MI diagnostic cutoff point was 2.56, where the corresponding Youden's index was maximum and the area under ROC curve was 0.943. The diagnostic efficiency of MI and VPT were similar. MI and VPT indicated similar percentages of diabetic patients with DPN at the most severe stage, while MI achieved a higher diagnostic rate for the earliest stages.

CONCLUSIONS

The nailfold MI is a feasible method for clinical early diagnostic screening of DPN in diabetic patients, and is more objective and reliable than VPT.

Pedobarography as a clinical tool in the management of diabetic feet in New Zealand: a feasibility study

Background

The peripheral complications of diabetes mellitus remain a significant risk to lower-limb morbidity. In New Zealand, risk of diabetes, comorbidity and lower-limb amputation are highly-differential between demographic groups, particularly ethnicity. There is growing and convincing evidence that the use of pedobarography – or plantar pressure measurement – can usefully inform diabetic foot care, particularly with respect to the prevention of re-ulceration among high-risk patients.

Methods

For the current feasibility study, we embedded pedobarographic measurements into three unique diabetic foot clinic settings in the New Zealand context, and collected pedobarographic data from n = 38 patients with diabetes using a platform-based (Novel Emed) and/or in-shoe-based system (Novel Pedar). Our aim was to assess the feasibility of incorporating pedobarographic testing into the clinical care of diabetic feet in New Zealand.

Results and Conclusions

We observed a high response rate and positive self-reported experience from participants. As part of our engagement with participants, we observed a high degree of lower-limb morbidity, including current ulceration and chronic foot deformities. The median time for pedobarographic testing (including study introduction and consenting) was 25 min. Despite working with a high-risk population, there were no adverse events in this study. In terms of application of pedobarography as a clinical tool in the New Zealand context, the current feasibility study leads us to believe that there are two avenues that deserve further investigation: a) the use of pedobarography to inform the design and effectiveness of offloading devices among high-risk diabetic patients; and b) the use of pedobarography as a means to increase offloading footwear and/or orthoses compliance among high-risk diabetic patients. Both of these objectives deserve further examination in New Zealand via clinical trial.

Electronic supplementary material

The online version of this article (doi:10.1186/s13047-017-0205-6) contains supplementary material, which is available to authorized users.

Demographics, Pharmacoeconomics, Assessment, and Treatment of Pain in the Elderly

The burden of pain in the elderly population of our society is observed by the greater numbers of the aged who suffer from pain as compared to their younger counterparts. The elderly present difficult challenges for pain clinicians in terms of the ability to assess for pain, amid other medical and pain problems, due to cognitive, sensory, and functional impairment. Treatment with pharmaceuticals may be altered by the impact of aging. Finally, the elderly suffer financial restraints that often prevent optimal treatment of pain even if pain is identified. Principles of pain management in the elderly are reviewed in the context of special attention to assessment tools for the elderly, the evaluation of comorbid factors in the presentation of pain, and pharmacokinetic/pharmacodynamic concerns in the aging. Pharmacologic and nonpharmacologic treatment strategies are described relative to the elder.

Vascular Impairment of Epineurial Arterioles of the Sciatic Nerve: Implications for Diabetic Peripheral Neuropathy

This article reviews the impact of diabetes and its treatment on vascular function with a focus on the reactivity of epineurial arterioles, blood vessels that provide circulation to the sciatic nerve. Another focus is the relationship between the dysregulation of neurovascular function and diabetic peripheral neuropathy. Diabetic peripheral neuropathy is a debilitating disorder that occurs in more than 50 percent of patients with diabetes. The etiology involves metabolic, vascular, and immunologic pathways besides neurohormonal growth factor deficiency and extracellular matrix remodeling. In the light of this complex etiology, an effective treatment for diabetic peripheral neuropathy has not yet been identified. Current opinion postulates that any effective treatment for diabetic peripheral neuropathy will require a combination of life style and therapeutic interventions. However, a more comprehensive understanding of the factors contributing to neurovascular and neural dysfunction in diabetes is needed before such a treatment strategy can be developed. After reading this review, the reader should have gained insight into the complex regulation of vascular function and blood flow to the sciatic nerve, and the impact of diabetes on numerous elements of vascular reactivity of epineurial arterioles of the sciatic nerve.

Mitochondrial transcription factor A regulation of mitochondrial degeneration in experimental diabetic neuropathy

Oxidative stress-induced mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage in peripheral neurons is considered to be important in the development of diabetic neuropathy. Mitochondrial transcription factor A (TFAM) wraps mtDNA and promotes mtDNA replication and transcription. We studied whether overexpression of TFAM reverses experimental peripheral diabetic neuropathy using TFAM transgenic mice (TFAM Tg) that express human TFAM (hTFAM). Levels of mouse mtDNA and the total TFAM (mouse TFAM + hTFAM) in the dorsal root ganglion (DRG) increased by approximately twofold in the TFAM Tg mice compared with control (WT) mice. WT and TFAM Tg mice were made diabetic by the administration of streptozotocin. Neuropathy end points were motor and sensory nerve conduction velocities, mechanical allodynia, thermal nociception, and intraepidermal nerve fiber density (IENFD). In the DRG neurons, mtDNA copy number and damage to mtDNA were quantified by qPCR, and TFAM levels were measured by Western blot. Mice with 16-wk duration of diabetes developed motor and sensory nerve conduction deficits, behavioral deficits, and intraepidermal nerve fiber loss. All of these changes were mostly prevented in diabetic TFAM Tg mice and were independent of changes in blood parameters. Mice with 16 wk of diabetes had a 40% decrease in mtDNA copy number compared with nondiabetic mice (P < 0.01). Importantly, the mtDNA copy number in diabetic TFAM Tg mice reached the same level as that of WT nondiabetic mice. In comparison, there was upregulation of mtDNA and TFAM in 6-wk diabetic mice, suggesting that TFAM activation could be a therapeutic strategy to treat peripheral neuropathy.

Beneficial effects of levobupivacaine regional anaesthesia on postoperative opioid induced hyperalgesia in diabetic mice

Background

Diabetic neuropathy is one of the most common complications of diabetes and causes various problems in daily life. The aim of this study was to assess the effect of regional anaesthesia on post surgery opioid induced hyperalgesia in diabetic and non-diabetic mice.

Methods

Diabetic and non-diabetic mice underwent plantar surgery. Levobupivacaine and sufentanil were used before surgery, for sciatic nerve block (regional anaesthesia) and analgesia, respectively. Diabetic and non-diabetic groups were each randomly assigned to three subgroups: control, no sufentanil and no levobupivacaine; sufentanil and no levobupivacaine; sufentanil and levobupivacaine. Three tests were used to assess pain behaviour: mechanical nociception; thermal nociception and guarding behaviours using a pain scale.

Results

Sufentanil, alone or in combination with levobupivacaine, produced antinociceptive effects shortly after administration. Subsequently, sufentanil induced hyperalgesia in diabetic and non-diabetic mice. Opioid-induced hyperalgesia was enhanced in diabetic mice. Levobupivacaine associated to sufentanil completely prevented hyperalgesia in both groups of mice.

Conclusion

The results suggest that regional anaesthesia can decrease opioid-induced hyperalgesia in diabetic as well as in non-diabetic mice. These observations may be clinically relevant for the management of diabetic patients.

Neuropeptides: metabolism to bioactive fragments and the pharmacology of their receptors

The proteolytic processing of neuropeptides has an important regulatory function and the peptide fragments resulting from the enzymatic degradation often exert essential physiological roles. The proteolytic processing generates, not only biologically inactive fragments, but also bioactive fragments that modulate or even counteract the response of their parent peptides. Frequently, these peptide fragments interact with receptors that are not recognized by the parent peptides. This review discusses tachykinins, opioid peptides, angiotensins, bradykinins, and neuropeptide Y that are present in the central nervous system and their processing to bioactive degradation products. These well-known neuropeptide systems have been selected since they provide illustrative examples that proteolytic degradation of parent peptides can lead to bioactive metabolites with different biological activities as compared to their parent peptides. For example, substance P, dynorphin A, angiotensin I and II, bradykinin, and neuropeptide Y are all degraded to bioactive fragments with pharmacological profiles that differ considerably from those of the parent peptides. The review discusses a selection of the large number of drug-like molecules that act as agonists or antagonists at receptors of neuropeptides. It focuses in particular on the efforts to identify selective drug-like agonists and antagonists mimicking the effects of the endogenous peptide fragments formed. As exemplified in this review, many common neuropeptides are degraded to a variety of smaller fragments but many of the fragments generated have not yet been examined in detail with regard to their potential biological activities. Since these bioactive fragments contain a small number of amino acid residues, they provide an ideal starting point for the development of drug-like substances with ability to mimic the effects of the degradation products. Thus, these substances could provide a rich source of new pharmaceuticals. However, as discussed herein relatively few examples have so far been disclosed of successful attempts to create bioavailable, drug-like agonists or antagonists, starting from the structure of endogenous peptide fragments and applying procedures relying on stepwise manipulations and simplifications of the peptide structures.

Correlation of adherence to the 2012 Infectious Diseases Society of America practice guidelines with patient outcomes in the treatment of diabetic foot infections in an outpatient parenteral antimicrobial programme

AIM

To evaluate adherence to the 2012 Infectious Diseases Society of America practice guidelines for the management of patients with diabetic foot infections and to determine an association between adherence and clinical outcome.

METHODS

A retrospective chart review was performed to evaluate the management and clinical outcomes of patients with diabetic foot infections treated with outpatient parenteral antimicrobial therapy between 1 January 2011 and 30 June 2012 at Wishard Health Services/Eskenazi Health. Adherence to individual Infectious Diseases Society of America diabetic foot infection treatment guideline recommendations was measured, and then assessed in relation to clinical outcome.

RESULTS

A total of 57 patients (61% male, mean age 54 years) with moderate to severe diabetic foot infection met the inclusion criteria. None of the treatment courses of these patients adhered to all the Infectious Diseases Society of America guideline recommendations. The recommendations most frequently adhered to were consultation of appropriate multidisciplinary teams (n=54, 94.7%) and performance of diagnostic imaging (n=52, 89.5%). The recommendations least frequently adhered to were diabetic foot wound classification scoring on admission (n=0, 0%), appropriate culture acquisition (n=12, 21.2%), surgical intervention when indicated (n=32, 46.2%) and appropriate empiric antibiotic selection (n=34, 59.7%). Of 56 patients, 52 (92.9%) experienced clinical cure at the end of outpatient parenteral antimicrobial therapy compared with 34 of 53 patients (64%) at 6 months after the completion of therapy. Adherence to individual guidelines was not associated with clinical outcome. Patients who experienced treatment failure were more likely to have severe diabetic foot infection or peripheral neuropathy.

CONCLUSIONS

Adherence to the Infectious Diseases Society of America diabetic foot infection guideline recommendations was found to be suboptimal in the present study. The effect of adhering to individual Infectious Diseases Society of America diabetic foot infection recommendations on clinical outcome needs to be investigated.

Adults with diabetic peripheral neuropathy exhibit impairments in multitasking and other executive functions

BACKGROUND AND PURPOSE

Diabetic peripheral neuropathy (DPN) contributes to functional impairment, and there is growing evidence that neuropsychological factors also influence physical function. We compared cognitive and executive function in adults with DPN with an age-matched comparison group, and examined the relationships between DPN, executive function, and physical function.

METHODS

Twenty subjects with DPN and 20 comparison subjects were assessed. Diabetic peripheral neuropathy was quantified via the Michigan Neuropathy Screening Instrument and nerve conduction velocity testing. Subjects were administered Beck's Depression Inventory, the Mini-Mental Status Examination, and the Timed Up and Go (TUG) test. Each participant also completed a battery of 7 executive function tasks, including the Cognitive Timed Up and Go (cTUG) test, in which a concurrent mental subtraction task was added to the standard TUG test.

RESULTS

The DPN group demonstrated poorer letter fluency (34.2 ± 11.6 words vs 46.2 ± 12.2 words; P = 0.001), category fluency (47.0 ± 8.1 words vs 56.3 ± 8.5 words; P = 0.003), and Rey-Osterrieth scores (25.9 ± 4.3 points vs 31.7 ± 2.4 points; P < 0.001), and took longer to complete both the TUG (10.3 ± 2.8 seconds vs 5.9 ± 1.0 seconds; P < 0.001) and cTUG (13.0 ± 5.8 seconds vs 6.9 ± 1.6 seconds; P < 0.001). Poorer global cognitive performance and greater depression symptoms were significantly related to each other (r = -0.46; P = 0.04) and to slower TUG times (r = -0.53; P = 0.02; and r = 0.54; P = 0.02, respectively).

DISCUSSION AND CONCLUSIONS

Verbal, visuospatial, and multitasking measures of executive function may be impaired in adults with DPN. Future research should examine how these and other cognitive and psychological factors, such as depression, affect physical function in this population.

Diabetic neuropathy part 1: overview and symmetric phenotypes

Diabetes is the most common cause of neuropathy in United States and neuropathies are the most common complication of diabetes mellitus, affecting up to 50% of patients with type 1 and type 2 diabetes mellitus. Symptoms usually include numbness, tingling, pain, and weakness. Dizziness with postural changes can be seen with autonomic neuropathy. Metabolic, vascular, and immune theories have been proposed for the pathogenesis of diabetic neuropathy. Axonal damage and segmental demyelination can be seen with diabetic neuropathies. Management of diabetic neuropathy should begin at the initial diagnosis of diabetes and mainly requires tight and stable glycemic control.

The effects of chromium picolinate and chromium histidinate administration on NF-κB and Nrf2/HO-1 pathway in the brain of diabetic rats

The objective of this experiment was to investigate the effects of supplemental chromium picolinate (CrPic) and chromium histidinate (CrHis) on nuclear factor-kappa B (NF-κB p65) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling pathway in diabetic rat brain. Nondiabetic (n = 45) and diabetic (n = 45) male Wistar rats were either not supplemented or supplemented with CrPic or CrHis via drinking water to consume 8 μg elemental chromium (Cr) per day for 12 weeks. Diabetes was induced by streptozotocin injection (40 mg/kg i.p., for 2 weeks) and maintained by high-fat feeding (40 %). Diabetes was associated with increases in cerebral NF-κB and 4-hydroxynonenal (4-HNE) protein adducts and decreased in cerebral nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor, alpha (IκBα) and Nrf2 levels. Both Cr chelates were effective to decrease levels of NF-κB and 4-HNE protein adducts and to increase levels of IκBα and Nrf2 in the brain of diabetic rats. However, responses of these increases and decreases were more notable when Cr was supplemented as CrHis than as CrPic. In conclusion, Cr may play a protective role in cerebral antioxidant defense system in diabetic subjects via the Nrf2 pathway by reducing inflammation through NF-κB p65 inhibition. Histidinate form of Cr was superior to picolinate form of Cr in reducing NF-κB expression and increasing Nrf2 expression in the brain of diabetic rats.

Emerging therapy for diabetic neuropathy: cell therapy targeting vessels and nerves

Diabetic neuropathy (DN), the most common complication of diabetes, frequently leads to foot ulcers and may progress to limb amputations. Despite continuous increase in incidence, there is no clinical therapy to effectively treat DN. Pathogenetically, DN is characterized by reduced vascularity in peripheral nerves and deficiency in angiogenic and neurotrophic factors. We will briefly review the pathogenetic mechanism of DN and address the effects and the mechanisms of cell therapies for DN. To reverse the changes of DN, studies have attempted to deliver neurotrophic or angiogenic factors for treatment in the form of protein or gene therapy; however, the effects turned out to be very modest if not ineffective. Recent studies have demonstrated that bone marrow (BM)-derived cells such as mononuclear cells or endothelial progenitor cells (EPCs) can effectively treat various cardiovascular diseases through their paracrine effects. As BM-derived cells include multiple angiogenic and neurotrophic cytokines, these cells were used for treating experimental DN and found to reverse manifestations of DN. Particularly, EPCs were shown to exert favorable therapeutic effects through enhanced neural neovascularization and neuro-protective effects. These findings clearly indicate that DN is a complex disorder with pathogenetic involvement of both vascular and neural components. Studies have shown that cell therapies targeting both vascular and neural elements are shown to be advantageous in treating DN.

The effect of exercise on neuropathic symptoms, nerve function, and cutaneous innervation in people with diabetic peripheral neuropathy

Although exercise can significantly reduce the prevalence and severity of diabetic complications, no studies have evaluated the impact of exercise on nerve function in people with diagnosed diabetic peripheral neuropathy (DPN). The purpose of this pilot study was to examine feasibility and effectiveness of a supervised, moderately intense aerobic and resistance exercise program in people with DPN. We hypothesized that the exercise intervention can improve neuropathic symptoms, nerve function, and cutaneous innervation.

METHODS

A pre-test post-test design was used to assess change in outcome measures following participation in a 10-week aerobic and strengthening exercise program. Seventeen subjects with diagnosed DPN (8 males/9 females; age 58.4±5.98; duration of diabetes 12.4±12.2 years) completed the study. Outcome measures included pain measures (visual analog scale), Michigan Neuropathy Screening Instrument (MNSI) questionnaire of neuropathic symptoms, nerve function measures, and intraepidermal nerve fiber (IENF) density and branching in distal and proximal lower extremity skin biopsies.

RESULTS

Significant reductions in pain (-18.1±35.5 mm on a 100 mm scale, P=.05), neuropathic symptoms (-1.24±1.8 on MNSI, P=.01), and increased intraepidermal nerve fiber branching (+0.11±0.15 branch nodes/fiber, P=.008) from a proximal skin biopsy were noted following the intervention.

CONCLUSIONS

This is the first study to describe improvements in neuropathic and cutaneous nerve fiber branching following supervised exercise in people with diabetic peripheral neuropathy. These findings are particularly promising given the short duration of the intervention, but need to be validated by comparison with a control group in future studies.

Explorative study on diabetes neuropathy among type II diabetic patients in Universiti Sains Malaysia Hospital

OBJECTIVE

The aim of this study was to determine risk factors and prevalence of diabetic neuropathy (DN) among type II diabetic patients in Malaysian hospital setting.

SUBJECTS AND METHODS

a observational prospective longitudinal follow up study design was selected, total no of respondents were 1077 type 2 diabetes mellitus outpatients recruited via attended the diabetes clinics at Hospital Universiti Sains Malaysia (HUSM) in Kelantan. The diagnosis of neuropathy was confirmed by nerve conduction studies. Logistic regression analysis was used to assess the independent variables that affect the development of neuropathy.

RESULTS

The prevalence of nephropathy is 54.3%. Longitudinal logistic regression identified four predictive variables on the development and progression of diabetic neuropathy that are: duration of diabetes, retinopathy, HbA1c at second visit, and creatinine clearance third visit.

CONCLUSION

Findings of this study show high prevalence of diabetic neuropathy. HbA1c and creatinine clearance are two modifiable risk factors for the development of diabetic neuropathy.

The dipeptide Phe-Phe amide attenuates signs of hyperalgesia, allodynia and nociception in diabetic mice using a mechanism involving the sigma receptor system

Background

Previous studies have demonstrated that intrathecal administration of the substance P amino-terminal metabolite substance P_1-7 (SP_1-7) and its C-terminal amidated congener induced antihyperalgesic effects in diabetic mice. In this study, we studied a small synthetic dipeptide related to SP_1-7 and endomorphin-2, i.e. Phe-Phe amide, using the tail-flick test and von Frey filament test in diabetic and non-diabetic mice.

Results

Intrathecal treatment with the dipeptide increased the tail-flick latency in both diabetic and non-diabetic mice. This effect of Phe-Phe amide was significantly greater in diabetic mice than non-diabetic mice. The Phe-Phe amide-induced antinociceptive effect in both diabetic and non-diabetic mice was reversed by the σ₁ receptor agonist (+)-pentazocine. Moreover, Phe-Phe amide attenuated mechanical allodynia in diabetic mice, which was reversible by (+)-pentazocine. The expression of spinal σ1 receptor mRNA and protein did not differ between diabetic mice and non-diabetic mice. On the other hand, the expression of phosphorylated extracellular signal-regulated protein kinase 1 (ERK1) and ERK2 proteins was enhanced in diabetic mice. (+)-Pentazocine caused phosphorylation of ERK1 and ERK2 proteins in non-diabetic mice, but not in diabetic mice.

Conclusions

These results suggest that the spinal σ₁ receptor system might contribute to diabetic mechanical allodynia and thermal hyperalgesia, which could be potently attenuated by Phe-Phe amide.

Impaired sensory nerve function and axon morphology in mice with diabetic neuropathy

Diabetes is the most prevalent metabolic disorder in the United States, and between 50% and 70% of diabetic patients suffer from diabetes-induced neuropathy. Yet our current knowledge of the functional changes in sensory nerves and their distal terminals caused by diabetes is limited. Here, we set out to investigate the functional and morphological consequences of diabetes on specific subtypes of cutaneous sensory nerves in mice. Diabetes was induced in C57Bl/6 mice by a single intraperitoneal injection of streptozotocin. After 6-8 wk, mice were characterized for behavioral sensitivity to mechanical and heat stimuli followed by analysis of sensory function using teased nerve fiber recordings and histological assessment of nerve fiber morphology. Diabetes produced severe functional impairment of C-fibers and rapidly adapting Aβ-fibers, leading to behavioral hyposensitivity to both mechanical and heat stimuli. Electron microscopy images showed that diabetic nerves have axoplasm with more concentrated organelles and frequent axon-myelin separations compared with control nerves. These changes were restricted to the distal nerve segments nearing their innervation territory. Furthermore, the relative proportion of Aβ-fibers was reduced in diabetic skin-nerve preparations compared with nondiabetic control mice. These data identify significant deficits in sensory nerve terminal function that are associated with distal fiber loss, morphological damage, and behavioral hyposensitivity in diabetic C57Bl/6 mice. These findings suggest that diabetes damages sensory nerves, leading to functional deficits in sensory signaling that underlie the loss of tactile acuity and pain sensation associated with insensate diabetic neuropathy.

The impact of diabetes on the outcomes of surgical and nonsurgical treatment of patients in the spine patient outcomes research trial

STUDY DESIGN

A secondary analysis comparing diabetic patients with nondiabetic patients enrolled in the Spine Patient Outcomes Research Trial (SPORT).

OBJECTIVE

To compare surgical outcomes and complications between diabetic and nondiabetic spine patients.

SUMMARY OF BACKGROUND DATA

Patients with diabetes are predisposed to comorbidities that may confound the diagnosis and treatment of patients with spinal disorders.

METHODS

Baseline characteristics and outcomes of 199 patients with diabetes were compared with those of the nondiabetic population in a total of 2405 patients enrolled in the Spine Patient Outcomes Research Trial for the diagnoses of intervertebral disc herniation (IDH), spinal stenosis (SpS), and degenerative spondylolisthesis (DS). Primary outcome measures include the 36-Item Short Form Health Survey (SF-36) Health Status questionnaire and the Oswestry Disability Index.

RESULTS

Patients with diabetes were significantly older and had a higher body mass index than nondiabetic patients. Comorbidities, including hypertension, stroke, cardiovascular disease, and joint disease, were significantly more frequent in diabetic patients than in nondiabetic patients. Patients with diabetes and IDH did not make significant gains in pain and function with surgical intervention relative to diabetic patients who underwent nonoperative treatment. Diabetic patients with SpS and DS experienced significantly greater improvements in pain and function with surgical intervention when compared with nonoperative treatment. Among those who had surgery, nondiabetic patients with SpS achieved marginally significantly greater gains in function than their diabetic counterparts (SF-36 physical function, P = 0.062). Among patients who had surgery for DS, diabetic patients did not have as much improvement in pain or function as did the nondiabetic population (SF-36 bodily pain, P = 0.003; physical function, P = 0.002). Postoperative complications were more prevalent in patients with diabetes than in nondiabetic patients with SpS (P = 0.002). There was an increase in postoperative (P = 0.028) and intraoperative (P = 0.029) blood replacement in DS patients with diabetes.

CONCLUSION

Diabetic patients with SpS and DS benefited from surgery, though older SpS patients with diabetes have more postoperative complications. IDH patients with diabetes did not benefit from surgical intervention.

The effect of substance P1-7 amide on nociceptive threshold in diabetic mice

We previously demonstrated that intrathecal treatment with substance P metabolite substance P(1-7) induced anti-hyperalgesia in diabetic mice. In the present study, we have used a synthetic analog of this peptide, the substance P(1-7) amide, showing higher binding affinity than the native heptapeptide, for studies of the tail-flick response in diabetic and non-diabetic mice. Intrathecal injection of substance P(1-7) amide produced prolongation of the tail-flick latency in both diabetic and non-diabetic mice, an effect that was more pronounced in diabetic mice than non-diabetic mice. Moreover, the observed antinociceptive potency of the substance P(1-7) amide was higher in both diabetic and non-diabetic mice in comparison with the native substance P(1-7). The antinociceptive effect of substance P(1-7) amide was reversed by naloxone but not by the selective opioid receptor antagonist β-funaltrexamine, naltrindole or nor-binaltorphimine, selective for the μ-, δ- or κ-opioid receptor, respectively. In addition, the antinociceptive effect induced by substance P(1-7) amide was partly reversed by the σ(1) receptor agonist (+)-pentazocine, suggesting a possible involvement of the σ(1) receptor for the action of this peptide. These results suggest that the actions of substance P(1-7) amide mimic the effects of the native substance P fragment but with higher potency and that the mechanisms for its action may involve the σ(1) receptor system.

The Etiopathogenesis of the Diabetic Foot: An Unrelenting Epidemic

Diabetes mellitus is a metabolic disease that is associated with hyperglycemia affecting various organ systems of the body. One of the most dreaded complications of this disease is the diabetic foot. The diabetic foot is the end result of multiple causal pathways, which include peripheral neuropathy and vascular disease. The problem is compounded by the increased incidence of infection. This article deals with the various pathogenic pathways associated with the development of the diabetic foot.

Feasibility and effectiveness of a pilot health promotion program for adults with type 2 diabetes: lessons learned

PURPOSE

The purpose of this pilot study was to assess the feasibility and effectiveness of an intense health promotion program in older adults with diabetes. The program combined individually prescribed and supervised exercise with nutrition and education programs on glycemic control and aerobic fitness.

METHODS

Various recruitment and retention strategies were analyzed for effectiveness. Out of 28 potential subjects assessed for eligibility, 6 subjects with type 2 diabetes (2 male and 4 female; all white; age, 60.2 +/- 4.7 years) participated in the 10-week intervention. Aerobic and resistance exercise was performed on alternate days (3-4 days per week), with individualized nutrition counseling and diabetes health education sessions once weekly. The primary outcome measures were aerobic fitness and glycemic control (A1C), and secondary outcome measures included body mass index (BMI), self-efficacy, and symptoms of neuropathy. Changes in outcomes were assessed using descriptive statistics and paired t test analysis (alpha = .05).

RESULTS

Following the intervention, subjects had improvements that approached significance in A1C and pain, with significant improvements in self-efficacy.

CONCLUSIONS

A systematic approach to analysis of feasibility revealed issues with recruitment and retention that would need to be addressed for future studies or clinical implementation of this program. However, for the subset of subjects who did complete the intervention, adherence was excellent, and satisfaction with the program was confirmed by exit interview comments. Following participation in this pilot health promotion program, subjects had meaningful improvements in glycemic control, pain, and self-efficacy.

Engineered zinc finger protein-mediated VEGF-a activation restores deficient VEGF-a in sensory neurons in experimental diabetes

OBJECTIVE

The objectives of the study were to evaluate retrograde axonal transport of vascular endothelial growth factor A (VEGF-A) protein to sensory neurons after intramuscular administration of an engineered zinc finger protein activator of endogenous VEGF-A (VZ+434) in an experimental model of diabetes, and to characterize the VEGF-A target neurons.

RESEARCH DESIGN AND METHODS

We compared the expression of VEGF-A in lumbar (L)4/5 dorsal root ganglia (DRG) of control rats and VZ+434-treated and untreated streptozotocin (STZ)-induced diabetic rats. In addition, axonal transport of VEGF-A, activation of signal transduction pathways in the DRG, and mechanical sensitivity were assessed.

RESULTS

VEGF-A immunoreactivity (IR) was detected in small- to medium-diameter neurons in DRG of control rats. Fewer VEGF-A-IR neurons were observed in DRG from STZ-induced diabetic rats; this decrease was confirmed and quantified by Western blotting. VZ+434 administration resulted in a significant increase in VEGF-A protein expression in ipsilateral DRG, 24 h after injection. VEGF-A was axonally transported to the DRG via the sciatic nerve. VZ+434 administration resulted in significant activation of AKT in the ipsilateral DRG by 48 h that was sustained for 1 week after injection. VZ+434 protected against mechanical allodynia 8 weeks after STZ injection.

CONCLUSIONS

Intramuscular administration of VZ+434 increases VEGF-A protein levels in L4/5 DRG, correcting the deficit observed after induction of diabetes, and protects against mechanical allodynia. Elevated VEGF-A levels result from retrograde axonal transport and are associated with altered signal transduction, via the phosphatidylinositol 3'-kinase pathway. These data support a neuroprotective role for VEGF-A in the therapeutic actions of VZ+434 and suggest a mechanism by which VEGF-A exerts this activity.

Cardiac innervation and sudden cardiac death

The heart is extensively innervated and its performance is tightly controlled by the nervous system. Cardiac innervation density varies in diseased hearts leading to unbalanced neural activation and lethal arrhythmia. Diabetic sensory neuropathy causes silent myocardial ischemia, characterized by loss of pain perception during myocardial ischemia, which is a major cause of sudden cardiac death in diabetes mellitus (DM). Despite its clinical importance, the mechanisms underlying the control and regulation of cardiac innervation remain poorly understood.We found that cardiac innervation is determined by the balance between neural chemoattractants and chemorepellents within the heart. Nerve growth factor (NGF), a potent chemoattractant, is induced by endothelin-1 upregulation during development and is highly expressed in cardiomyocytes. By comparison, Sema3a, a neural chemorepellent, is highly expressed in the subendocardium of early stage embryos, and is suppressed during development. The balance of expression between NGF and Seme3a leads to epicardial-to-endocardial transmural sympathetic innervation patterning. We also found that downregulation of cardiac NGF leads to diabetic neuropathy, and that NGF supplementation rescues silent myocardial ischemia in DM. Cardiac innervation patterning is disrupted in Sema3a-deficient and Sema3a-overexpressing mice, leading to sudden death or lethal arrhythmias. The present review focuses on the regulatory mechanisms underlying cardiac innervation and the critical role of these processes in cardiac performance.

Evaluation of the efficacy of pulsed electromagnetic field in the management of patients with diabetic polyneuropathy

AIM

The study was carried out to evaluate and compare the effect of low power, low frequency pulsed electromagnetic field (PEMF) of 600 and 800 Hz, respectively, in management of patients with diabetic polyneuropathy.

SETTINGS AND DESIGNS

The study was a randomized controlled trial performed in Guru Nanak Dev University and Medical College, Amritsar, India with different subject experimental design.

MATERIALS AND METHODS

Thirty subjects within an age group of 40-68 years with diabetic polyneuropathy stages N1a, N1b, N2a were randomly allocated to groups 1, 2, 3 with 10 subjects in each. Group 1 and 2 were treated with low power 600 and 800-Hz PEMF for 30 min for 12 consecutive days. Group 3 served as control on usual medical treatment of diabetic polyneuropathy (DPN). The subjects with neuropathy due to any cause other than diabetes were excluded. The pain and motor nerve conduction parameters (distal latency, amplitude, nerve conduction velocity) were assessed before and after treatment.

STATISTICAL ANALYSIS

Related t-test and unrelated t-test were used for data analysis.

RESULTS

Significant reduction in pain and statistically significant (P<0.05) improvement in distal latency and nerve conduction velocity were seen in experimental group 1 and 2.

CONCLUSIONS

Low-frequency PEMF can be used as an adjunct in reducing neuropathic pain as well as for retarding the progression of neuropathy in a short span of time.

Predisposing factors for critical illness polyneuromyopathy in a multidisciplinary intensive care unit

OBJECTIVE

To investigate risk factors of critical illness polyneuromyopathy (CIPM) in a general multidisciplinary intensive care unit (ICU).

PATIENTS AND METHODS

Prospective observational study in a 28-bed university multidisciplinary ICU. Four hundred and seventy-four (323 M/151 F, age 55 +/- 19) consecutive patients were prospectively evaluated. All patients were assigned admission Acute Physiology and Chronic Health Evaluation (APACHE II; 15 +/- 7) and Sequential Organ Failure Assessment (SOFA; 6 +/- 3) scores and were subsequently evaluated for newly developed neuromuscular weakness. Other potential causes of new-onset weakness after ICU admission were excluded before CIPM was diagnosed.

RESULTS

Forty-four (23.8%) of 185 patients developed generalized weakness that met the criteria for CIPM. Patients with CIPM had higher APACHE II (18.9 +/- 6.6 vs 15.6 +/- 6.4, P = 0.004) and SOFA scores (8.4 +/- 2.9 vs 7.1 +/- 2.9, P = 0.013). According to multivariate logistic regression analysis, the following risk factors were independently associated with the development of CIPM: severity of illness at the time of ICU admission, administration of aminoglycoside antibiotics and high blood glucose levels. Analysis according to severity of illness stratification revealed the emergence of Gram (-) bacteremia as the most important independent predisposing factor for CIPM development in less severely ill patients.

CONCLUSIONS

CIPM has a high incidence in the ICU setting. Our study revealed the association of aminoglycosides, hyperglycemia and illness severity with CIPM development, as well as the association between Gram (-) bacteremia and development of CIPM in less severely ill patient population.

Clinical and nerve conduction studies in female patients with diabetic dermopathy

This study aims to assess the clinical and electrophysiological characteristics of diabetic polyneuropathy (PNP) in female patients. We investigated clinical and electrophysiological features in 175 female patients with diabetes mellitus to compare those with PNP only, diabetic dermopathy (DD), or diabetic foot (DF). Among clinical features, the loss of deep tendon reflexes, the presence of negative sensory symptoms, superficial sensory loss, and the loss of vibration sense were more common in DD patients than PNP patients. As compared with DD patients, the presence of skin atrophy, superficial and positive sensory symptoms were more common in DF patients. Neuropathic symptom and disability scores were significantly higher in DD and DF patients than PNP patients. In the electrophysiological studies, the only significant difference was observed in the mean distal latencies for ulnar nerves, which were longer in DD patients as compared with PNP patients, but similar between DD and DF patients. All other parameters failed to show significant difference among patients, though values for DD patients lied in between PNP and DF patients. Carpal tunnel syndrome was present in 45% of PNP patients, 63.8% of DD patients, and 50% of DF patients (P = 0.031). Our results suggest that female patients with diabetic dermopathy might have a more severe sensorial neuropathy than patients without these skin lesions.

Muscle fiber conduction abnormalities in early diabetic polyneuropathy

OBJECTIVE

Diabetic polyneuropathy (PNP) has been proposed to be a primary disorder of sensory nerves. At an early stage motor nerve conduction velocity (MNCV) and muscle strength remain preserved due to compensatory mechanisms (axonal sprouting, reinnervation). We evaluated the use of invasive muscle fiber conduction velocity (MFCV) measurements as a method to detect muscle fiber denervation atrophy, as an early sign of motor axonal loss in diabetes mellitus (DM).

METHODS

Twelve selected male patients (8 type 1, 4 type 2; mean age 35.8 years, SD 10.6), without any sign of micro- or macroangiopathy, were studied by systematic clinical and neurophysiological testing including MFCV estimation.

RESULTS

Hand-held dynamometry was normal in all subjects. There were no signs of recent denervation by concentric needle EMG in any of the patients. Sensory nerve conduction velocity (SNCV) was abnormal in 6 subjects, MFCV in 6 subjects (5 had also low SNCV). The ratio of fastest/slowest muscle fibers in MFCV was correlated to SNCV of sural nerve (-.59, p < .05), but not to MNCV.

CONCLUSIONS

Half of the clinically asymptomatic DM subjects showed sensory involvement together with MFCV abnormalities, despite normal needle EMG and force.

SIGNIFICANCE

MFCV estimation offers a sensitive method in detecting early signs of motor axonal dysfunction in DM.

Induction of abnormal proliferation by nonmyelinating schwann cells triggers neurofibroma formation

Recent evidence suggests that alterations in the self-renewal program of stem/progenitor cells can cause tumorigenesis. By utilizing genetically engineered mouse models of neurofibromatosis type 1 (NF1), we demonstrated that plexiform neurofibroma, the only benign peripheral nerve sheath tumor with potential for malignant transformation, results from Nf1 deficiency in fetal stem/progenitor cells of peripheral nerves. Surprisingly, this did not cause hyperproliferation or tumorigenesis in early postnatal period. Instead, peripheral nerve development appeared largely normal in the absence of Nf1 except for abnormal Remak bundles, the nonmyelinated axon-Schwann cell unit, identified in postnatal mutant nerves. Subsequent degeneration of abnormal Remak bundles was accompanied by initial expansion of nonmyelinating Schwann cells. We suggest abnormally differentiated Remak bundles as a cell of origin for plexiform neurofibroma.

Peripheral neuropathy in patients with diabetes mellitus presenting as Bell's palsy

The aim of this study is to evaluate the peripheral nerves in diabetes mellitus with or without peripheral facial paralysis (PFP). A total of 49 diabetic patients with PFP within the last year (23 females, mean age 60.3 +/- 9.3), and 83 diabetic patients without PFP (41 females, mean age 59.5 +/- 9.9) were enrolled. The neurological examination, eye-blinking response, needle EMG and electrophysiological parameters of peripheral nerves were evaluated. The neuropathic pain, other positive and negative sensory symptoms were statistically more frequent in controls than the PFP group, while no difference was noted in total neuropathy score. Sural sensorial nerve action potential amplitudes were same in both groups, but median nerve amplitudes were significantly lower in the PFP group. It is suggested that PFP is not a part of multifocal neuropathy in diabetes mellitus. However, at least some parts of the nerve conduction studies were involved, focal neuropathies were more frequent while sensory neuropathies with small nerve fiber involvement were less frequent in diabetes patients with PFP.

Emerging role of mitogen-activated protein kinases in peripheral neuropathies

Among the different families of intracellular molecules that can be modulated during cell damage and repair, mitogen-activated protein kinases (MAPKs) are particularly interesting because they are involved in several intracellular pathways activated by injury and regeneration signals. Despite most of the studies have been performed in non-neurological models, recently a causal role for MAPKs has been postulated in central nervous system disorders. However, also in some peripheral neuropathies, MAPK changes can occur and these modifications might be relevant in the pathogenesis of the damage as well as during regeneration and repair. In this review, the current knowledge on the role of MAPKs in peripheral neuropathies will be discussed.

Clinical and electrophysiological correlations in type 2 diabetes mellitus at diagnosis

The purpose of this study was to evaluate, in newly diagnosed type 2 diabetes mellitus (DM): (1) the prevalence and staging of peripheral neuropathy, as well as its possible relationship with metabolic profile; (2) the clinical value of both the Diabetic Neuropathy Index (DNI) and the Diabetic Neuropathy Score (DNS), and their reciprocal concordance, as a screening method for neuropathy. Thirty-nine newly diagnosed DM subjects underwent: neurological examination, nerve conduction studies (NCS), quantitative sensory system and cardiovascular autonomic function assessments. Peripheral neuropathy was observed in 72% of the subjects (its staging was similar to that of patients with longer disease history), while another 10% of them showed a borderline neuropathy. The Deep Breathing test was abnormal in 28% of the patients; postural hypotension was found in 6%. The same proportion (82%) of subjects who scored positively on the DNI showed altered NCS, while the quantitative sensory system assessments had a low sensitivity in order to detect the neuropathy. No correlation was found between metabolic indexes and DNI/DNS parameters. The high prevalence of peripheral and autonomic function alterations suggests that each newly diagnosed diabetic subject should be screened for neuropathy by the DNI, to reduce the negative prognostic influence of this complication.

Effect of the aldose reductase inhibitor fidarestat on experimental diabetic neuropathy in the rat

AIMS/HYPOTHESIS

Fidarestat, an aldose reductase inhibitor (ARI), has been reported to improve clinical symptoms and nerve conduction deficits in human diabetic neuropathy. We evaluated the dose-dependency and some of the mechanisms of the drug action in experimental diabetic neuropathy (EDN).

METHODS

Control rats and rats with EDN were fed on normal pellets or pellets containing 0.00066% (1 mg/kg) or 0.00263% (4 mg/kg) fidarestat for 10 weeks. We evaluated the effect of fidarestat on nerve blood flow (NBF), electrophysiology, and sorbitol and fructose content in sciatic nerve in control and diabetic rats. For detection of oxidative stress in peripheral nerve, we measured sciatic nerve reduced glutathione (GSH) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunolabelling of dorsal root ganglion (DRG) neurons.

RESULTS

NBF, compound muscle action potential and amplitude of C-potential were significantly improved in diabetic rats fed on the diet supplemented with fidarestat. Fidarestat suppressed the increase in sorbitol and fructose, normalised GSH in sciatic nerve, and reduced the number of 8-OHdG-positive cells in DRG.

CONCLUSIONS/INTERPRETATION

Fidarestat improves neuropathy, presumably via an improvement in oxidative stress. This study supports a role for fidarestat in the treatment of diabetic neuropathy.

Nerve Growth Factor Is Critical for Cardiac Sensory Innervation and Rescues Neuropathy in Diabetic Hearts

BACKGROUND

Molecular mechanisms regulating the cardiac sensory nervous system remain poorly understood. Cardiac sensory nerve impairment causes silent myocardial ischemia, a main cause of sudden death in diabetes mellitus (DM). The present study focused on the roles of nerve growth factor (NGF) in the regulation of the cardiac sensory nervous system and analyzed the mechanism of silent myocardial ischemia in DM.

METHODS AND RESULTS

We screened neurotrophic factors and found that cardiac sensory nerves developed in parallel with NGF synthesized in the heart. Cardiac nociceptive sensory nerves that were immunopositive for calcitonin gene-related peptide, dorsal root ganglia (DRG), and the dorsal horn were markedly retarded in NGF-deficient mice, whereas cardiac-specific overexpression of NGF rescued these deficits. DM was induced with streptozotocin in wild-type and transgenic mice overexpressing NGF in the heart. Downregulation of NGF, calcitonin gene-related peptide-immunopositive cardiac sensory denervation, and atrophic changes in DRG were observed in DM-induced wild-type mice, whereas these deteriorations were reversed in DM-induced NGF transgenic mice. Cardiac sensory function, measured by myocardial ischemia-induced c-Fos expression in DRG, was also downregulated by DM in the wild-type mice but not in NGF transgenic mice. Direct gene transfer of NGF in the diabetic rat hearts improved impaired cardiac sensory innervation and function, determined by electrophysiological activity of cardiac afferent nerves during myocardial ischemia.

CONCLUSIONS

These findings demonstrate that the development and regulation of the cardiac sensory nervous system are dependent on NGF synthesized in the heart and that DM-induced NGF reduction causes cardiac sensory neuropathy.

Resource use among patients with diabetes, diabetic neuropathy, or diabetes with depression

BACKGROUND

Diabetes is often associated with complications and comorbidities. The purpose of this research is to compare medical resources used by patients with the following diagnoses: diabetes mellitus (DM), diabetic neuropathy (DN), and diabetes mellitus combined with comorbid depression (DD).

METHODS

Adult patients who were diagnosed with DM, DN, or DD were included in the study. There were 55,972 patients in the DM cohort, 2,146 in the DN, and 2,379 in the DD. P values for comparisons between the three mutually exclusive cohorts were conducted using the Tukey-Kramer method. Cost comparisons among the cohorts were conducted using a stepwise multivariate regression that controlled for patient characteristics and comorbid conditions.

RESULTS

Individuals in the DM or DN cohorts were generally more likely to use antidiabetic medications than patients in the DD group. Those diagnosed with DN or DD generally used more pain medications than individuals in the DM cohort. The DM cohort had significantly lower diabetes-related total medical costs ($1,297 v $5,125, p < 0.0001) and lower total medical costs ($4,819 v $24,765, p < 0.0001) than the DN cohort. The DM cohort also had significantly lower diabetes-related total medical costs ($1,297 v $3,264, p < 0.0001) as well as significantly lower total medical costs ($4,819 v $19,298, p < 0.0001) than the DD cohort.

CONCLUSION

Results from this study indicated significant differences in demographic characteristics, comorbidities, and medication use among individuals diagnosed with DM, DN, or DD. These differences translated into significant cost differences. Patients diagnosed with DN or DD had higher diabetes-related costs than patients diagnosed with DM.

New developments in diabetic neuropathy

PURPOSE OF REVIEW

Diabetic neuropathy is a debilitating consequence of type 1 and 2 diabetes. Hyperglycemia disrupts the normal function of neurons and their supporting glia at multiple levels. The complexity of this complication, combined with difficulties of delivering therapy to sensory, sympathetic and parasympathetic neurons, contributes to the intractability of this serious diabetic complication. This review summarizes recent reviews examining the state of research on and treatment of diabetic neuropathy and highlights areas of clinical and basic research that may yield new diagnostic and treatment options.

RECENT FINDINGS

Recent reviews summarize the effects of hyperglycemia on the peripheral nervous system as well as diagnosis and treatment of patients with diabetic neuropathy. Advances in the analysis of intraepidermal fiber densities could shorten the time course of clinical trials and extend data analyses to include sympathetic as well as sensory information. Unchecked glucose-mediated oxidative stress and advanced glycation endproduct signaling through receptors for advanced glycation endproducts are implicated in diabetic neuropathy and may serve as new therapeutic targets.

SUMMARY

The best efforts of countless investigators have yet to find effective treatments either to stop the progression of axonal degeneration and cell death or regrow damaged axons. Basic research into the prevention of oxidative stress caused by excess glucose as well as the prevention of advanced glycation endproduct/receptor for advanced glycation endproduct signaling may offer new therapeutic targets. The use of skin biopsies may aid in early detection of both sensory and autonomic neuropathy, and perhaps in the case of patients with type 2 diabetes, diagnose neuropathy prior to the onset of symptoms.

Electrophysiological findings of peripheral neuropathy in newly diagnosed type II diabetes mellitus

This study was aimed at assessing the electrophysiological signs of peripheral neuropathy in diabetes mellitus (DM) type II patients at diagnosis. Nerve conduction studies (NCS) of median, ulnar, peroneal, tibial and sural nerves were performed in 39 newly diagnosed DM subjects and compared to those of 40 healthy controls. Metabolic indices were also investigated. Electrophysiological alterations were found in 32 (82%) of the DM patients, and more than half of them (62.2%) showed multiple (two to five) abnormal parameters. Because most of the subjects (84.4%) had from two to five nerves involved, these alterations were widespread in the seven nerves evaluated. Forty-two percent of the patients had NCS alterations suggestive of distal median mononeuropathy, implying that metabolic factors in DM make the median nerve more susceptible to focal entrapment. A reduced sensory nerve action potential (SNAP) amplitude was observed in the median nerve in 70% of the patients, in the ulnar in 69% and in the sural nerve only in 22%. In the presence of a decrease in the SNAP amplitude of the ulnar or median nerve, the SNAP amplitude of the sural nerve was normal in 82 or 80% of the subjects, respectively. This finding may be in keeping with a distal involvement of the sensory fibres, as explored by routine median or ulnar NCS. No correlation was found between metabolic indices and NCS parameters. In conclusion, a high percentage of newly diagnosed DM patients show signs of neuropathy, and upper limb nerve sensory NCS seem to be more sensitive in detecting it than lower limb NCS.

Potential risk factors for diabetic neuropathy: a case control study

Background

Diabetes mellitus type II afflicts at least 2 million people in Iran. Neuropathy is one of the most common complications of diabetes and lowers the patient's quality of life. Since neuropathy often leads to ulceration and amputation, we have tried to elucidate the factors that can affect its progression.

Methods

In this case-control study, 110 diabetic patients were selected from the Shariati Hospital diabetes clinic. Michigan Neuropathic Diabetic Scoring (MNDS) was used to differentiate cases from controls. The diagnosis of neuropathy was confirmed by nerve conduction studies (nerve conduction velocity and electromyography). The multiple factors compared between the two groups included consumption of angiotensin converting enzyme inhibitors (ACEI), blood pressure, serum lipid level, sex, smoking, method of diabetes control and its quality.

Results

Statistically significant relationships were found between neuropathy and age, gender, quality of diabetes control and duration of disease (P values in the order: 0.04, 0.04, < 0.001 and 0.005). No correlation was found with any atherosclerosis risk factor (high BP, hyperlipidemia, cigarette smoking).

Conclusion

In this study, hyperglycemia was the only modifiable risk factor for diabetic neuropathy. Glycemic control reduces the incidence of neuropathy, slows its progression and improves the diabetic patient's quality of life. More attention must be paid to elderly male diabetic patients with poor diabetes control with regard to regular foot examinations and more practical education.