Endoneurial localisation of microvascular damage in human diabetic neuropathy

Shear wave elastography of tibial nerve in patients with diabetic peripheral neuropathy-A cross-sectional study

OBJECTIVE

To explore the role of shear wave elastography of the tibial nerve as a potential ultrasonographic method for the diagnosis of tibial neuropathy in patients with type 2 diabetes.

MATERIALS AND METHODS

This cross-sectional study included 50 subjects each in case (patients with diabetic tibial neuropathy diagnosed on the basis of clinical features and nerve conduction study) and control groups (non-diabetic non-neuropathic healthy volunteers). The exclusion criteria included the presence of type 1 diabetes, a known history of neuropathy from other causes except for type 2 diabetes, or a history of leg or ankle fracture. Cross-sectional area and shear wave velocity values of the tibial nerve were measured in both groups. Demographic details and body mass index were obtained in both groups and additionally, the duration of type 2 diabetes and HbA1c values in the case group were also noted. Wilcoxon Mann-Whitney U test was used to compare these variables in study groups. ROC curve analysis provided additional findings.

RESULTS

Tibial nerve stiffness was significantly higher in the case group (p-value < 0.001). The study groups did not significantly differ in the Cross-sectional area of the tibial nerve (p-value 0.57). The case group exhibited a higher frequency of loss of the fascicular pattern of the tibial nerve (40% vs 18%, p-value 0.027). Duration of diabetes mellitus and HbA1c values did not significantly affect Shear wave velocity values in the case group. At the cut-off value of Shear wave velocity of 3.13 m/s, sensitivity and specificity to diagnose diabetic peripheral neuropathy were 94% and 88% respectively.

CONCLUSION

Increased nerve stiffness is seen in patients with diabetic peripheral neuropathy. Shear wave elastography might prove as a novel noninvasive technology for screening/early diagnosis of diabetic peripheral neuropathy.

Cutaneous changes in diabetic patients: Primed for aberrant healing?

Cutaneous manifestations affect most patients with diabetes mellitus, clinically presenting with numerous dermatologic diseases from xerosis to diabetic foot ulcers (DFUs). Skin conditions not only impose a significantly impaired quality of life on individuals with diabetes but also predispose patients to further complications. Knowledge of cutaneous biology and the wound healing process under diabetic conditions is largely limited to animal models, and studies focusing on biology of the human condition of DFUs remain limited. In this review, we discuss the critical molecular, cellular, and structural changes to the skin in the hyperglycaemic and insulin-resistant environment of diabetes with a focus specifically on human-derived data. Elucidating the breadth of the cutaneous manifestations coupled with effective diabetes management is important for improving patient quality of life and averting future complications including wound healing disorders.

Reactive Hyperemia and Cardiovascular Autonomic Neuropathy in Type 2 Diabetic Patients: A Systematic Review of Randomized and Nonrandomized Clinical Trials

Objective: This work aimed to determine the relationship between the autonomic nervous system and reactive hyperemia (RH) in type 2 diabetes patients with and without cardiovascular autonomic neuropathy (CAN). Methodology: A systematic review of randomized and nonrandomized clinical studies characterizing reactive hyperemia and autonomic activity in type 2 diabetes patients with and without CAN was performed. Results: Five articles showed differences in RH between healthy subjects and diabetic patients with and/or without neuropathy, while one study did not show such differences between healthy subjects and diabetic patients, but patients with diabetic ulcers had lower RH index values compared to healthy controls. Another study found no significant difference in blood flow after a muscle strain that induced reactive hyperemia between normal subjects and non-smoking diabetic patients. Four studies measured reactive hyperemia using peripheral arterial tonometry (PAT); only two found a significantly lower endothelial-function-derived measure of PAT in diabetic patients than in those without CAN. Four studies measured reactive hyperemia using flow-mediated dilation (FMD), but no significant differences were reported between diabetic patients with and without CAN. Two studies measured RH using laser Doppler techniques; one of them found significant differences in the blood flow of calf skin after stretching between diabetic non-smokers and smokers. The diabetic smokers had neurogenic activity at baseline that was significantly lower than that of the normal subjects. The greatest evidence revealed that the differences in RH between diabetic patients with and without CAN may depend on both the method used to measure hyperemia and that applied for the ANS examination as well as the type of autonomic deficit present in the patients. Conclusions: In diabetic patients, there is a deterioration in the vasodilator response to the reactive hyperemia maneuver compared to healthy subjects, which depends in part on endothelial and autonomic dysfunction. Blood flow alterations in diabetic patients during RH are mainly mediated by sympathetic dysfunction. The greatest evidence suggests a relationship between ANS and RH; however, there are no significant differences in RH between diabetic patients with and without CAN, as measured using FMD. When the flow of the microvascular territory is measured, the differences between diabetics with and without CAN become evident. Therefore, RH measured using PAT may reflect diabetic neuropathic changes with greater sensitivity compared to FMD.

Peripheral Neuropathy in Diabetes Mellitus: Pathogenetic Mechanisms and Diagnostic Options

Diabetic neuropathy (DN) is one of the main microvascular complications of both type 1 and type 2 diabetes mellitus. Sometimes, this could already be present at the time of diagnosis for type 2 diabetes mellitus (T2DM), while it appears in subjects with type 1 diabetes mellitus (T1DM) almost 10 years after the onset of the disease. The impairment can involve both somatic fibers of the peripheral nervous system, with sensory-motor manifestations, as well as the autonomic system, with neurovegetative multiorgan manifestations through an impairment of sympathetic/parasympathetic conduction. It seems that, both indirectly and directly, the hyperglycemic state and oxygen delivery reduction through the vasa nervorum can determine inflammatory damage, which in turn is responsible for the alteration of the activity of the nerves. The symptoms and signs are therefore various, although symmetrical painful somatic neuropathy at the level of the lower limbs seems the most frequent manifestation. The pathophysiological aspects underlying the onset and progression of DN are not entirely clear. The purpose of this review is to shed light on the most recent discoveries in the pathophysiological and diagnostic fields concerning this complex and frequent complication of diabetes mellitus.

Reduced macula microvascular densities may be an early indicator for diabetic peripheral neuropathy

Purpose: To assess the alteration in the macular microvascular in type 2 diabetic patients with peripheral neuropathy (DPN) and without peripheral neuropathy (NDPN) by optical coherence tomography angiography (OCTA) and explore the correlation between retinal microvascular abnormalities and DPN disease. Methods: Twenty-seven healthy controls (42 eyes), 36 NDPN patients (62 eyes), and 27 DPN patients (40 eyes) were included. OCTA was used to image the macula in the superficial vascular complex (SVC) and deep vascular complex (DVC). In addition, a state-of-the-art deep learning method was employed to quantify the microvasculature of the two capillary plexuses in all participants using vascular length density (VLD). Results: Compared with the healthy control group, the average VLD values of patients with DPN in SVC (p = 0.010) and DVC (p = 0.011) were significantly lower. Compared with NDPN, DPN patients showed significantly reduced VLD values in the SVC (p = 0.006) and DVC (p = 0.001). Also, DPN patients showed lower VLD values (p < 0.05) in the nasal, superior, temporal and inferior sectors of the inner ring of the SVC when compared with controls; VLD values in NDPN patients were lower in the nasal section of the inner ring of SVC (p < 0.05) compared with healthy controls. VLD values in the DVC (AUC = 0.736, p < 0.001) of the DPN group showed a higher ability to discriminate microvascular damage when compared with NDPN. Conclusion: OCTA based on deep learning could be potentially used in clinical practice as a new indicator in the early diagnosis of DM with and without DPN.

Is diabetes the risk factor for poor neurological recovery after cervical spine surgery? A review of the literature

The poor prognosis of cervical spine surgery is mainly manifested as poor neurological recovery and the presence of new upper extremity dysfunction that promotes significant psychological and physiological burdens on patients. Many factors influence the prognosis of cervical spine surgery, including the age of patients, the time and mode of surgery, and the surgical technique used. However, in clinical studies, it has been observed that patients with diabetes have a higher probability of poor prognosis after surgery. Therefore, we review the pathophysiology of diabetic neuropathies and discuss its impact on cervical nerve system function, especially in cervical nerve roots and upper limb peripheral nerve conduction.

Whole plantar nerve conduction study: A new tool for early diagnosis of peripheral diabetic neuropathy

AIMS

Peripheral neuropathy (PN) affects two-thirds of type 2 diabetes patients (T2DM). According to diabetic PN length-dependent pattern, neurophysiological evaluation of foot-sole nerves might increase NCS diagnostic sensitivity, hence allowing early diagnosis of PN. Thus, we aim to assess the ability of whole plantar nerve (WPN) conduction in diabetic PN early diagnosis.

METHODS

This is a single center prospective observational cohort study on 70 T2DM patients referred to Internal Medicine Unit of A.O.U. "Luigi Vanvitelli" between October 2019/October 2020. Primary endpoint was WPN efficacy assessment in PN early detection. As secondary, we evaluated (i) a potential cut-off of SNAPs amplitude by WPN and (ii) WPN diagnostic accuracy vs. gold-standard distal sural nerve conduction.

RESULTS

ROC curve analysis allowed to establish two potential cut-offs for people aged ≤60 years (AUROC: 0.83, 95%CI: 0.69-0.96, p < 0.001) and ≤60 years (AUROC: 0.76, 95%CI: 0.59-0.93, p = 0.017). In depth, we fixed a cut-off of WPN-SNAP amplitude of 4.55 μV and 2.65 μV, respectively, with subsequent 48 patients classified as PN-T2DM.

CONCLUSIONS

Our data support WPN conduction study reliability in characterizing the most distal sensory nerve fibers at lower limbs. Thus, WPN may represent an extremely useful diagnostic tool for diabetic PN early detection.

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.

The effect of a topical combination of clonidine and pentoxifylline on post-traumatic neuropathic pain patients: study protocol for a randomized, double-blind placebo-controlled trial

BACKGROUND

First-line pharmacotherapy for neuropathic pain entails the use of systemic antidepressants and anticonvulsants. These drugs are not optimally effective and poorly tolerated, especially for older patients with comorbid conditions. Given the high number of such patients, there is a need for a greater repertoire of safer and more effective analgesics. Clonidine and pentoxifylline are vasodilator agents that work synergistically to enhance tissue perfusion and oxygenation. The topical administration of these drugs, individually and in combination, has shown anti-nociceptive properties in rodent models of neuropathic pain. A topically-administered combination of clonidine and pentoxifylline also effectively reduced the intensity of both spontaneous and evoked pain in healthy volunteers with experimentally-induced neuropathic pain. The next step in advancing this formulation to clinical use is the undertaking of a phase II clinical study to assess its efficacy and safety in neuropathic pain patients.

METHODS/DESIGN

This is a study protocol for a randomized, double-blind, placebo-controlled, phase II clinical trial with a cross-over design. It is a single-centered, 5-week study that will enroll a total of 32 patients with post-traumatic peripheral neuropathic pain. Patients will be treated topically with either a combination of clonidine and pentoxifylline or placebo for a period of 2 weeks each, in randomly assigned order across patients, with an intervening washout period of 1 week. The primary outcome measures of the study are the intensity of spontaneous pain recorded daily in a pain diary with a visual analog scale, and the degree of mechanical allodynia evoked by a brush stimulus. The secondary outcome measures of the study include scores of pain relief and change in the area of punctate hyperalgesia. This trial has been prospectively registered with ClinicalTrials.gov on November 1, 2017. ClinicalTrials.gov Identifier: NCT03342950 .

DISCUSSION

The analgesic use of topical treatment with clonidine and pentoxifylline in combination has not been investigated in post-traumatic neuropathic pain. This study could generate the first evidence for the efficacy and safety of the formulation in alleviating pain in patients with neuropathic pain. Furthermore, this trial will provide objective grounds for the investigation of other agents that enhance tissue oxygenation in the topical treatment of peripheral neuropathic pain.

TRIAL REGISTRATION

This trial has been registered with ClinicalTrials.gov owned by NIH's US National Library of Medicine. ClinicalTrials.gov NCT03342950 . Registered on November 1, 2017 (trial was prospectively registered).

PROTOCOL VERSION AND IDENTIFIERS

This is protocol version 5, dated June 2018. McGill University Health Center (MUHC) Reaseach Ethics Board (REB) identification number: TTNP 2018-3906.

Microvascular Dysfunction in Diabetes Mellitus and Cardiometabolic Disease

This review takes an inclusive approach to microvascular dysfunction in diabetes mellitus and cardiometabolic disease. In virtually every organ, dynamic interactions between the microvasculature and resident tissue elements normally modulate vascular and tissue function in a homeostatic fashion. This regulation is disordered by diabetes mellitus, by hypertension, by obesity, and by dyslipidemia individually (or combined in cardiometabolic disease), with dysfunction serving as an early marker of change. In particular, we suggest that the familiar retinal, renal, and neural complications of diabetes mellitus are late-stage manifestations of microvascular injury that begins years earlier and is often abetted by other cardiometabolic disease elements (eg, hypertension, obesity, dyslipidemia). We focus on evidence that microvascular dysfunction precedes anatomic microvascular disease in these organs as well as in heart, muscle, and brain. We suggest that early on, diabetes mellitus and/or cardiometabolic disease can each cause reversible microvascular injury with accompanying dysfunction, which in time may or may not become irreversible and anatomically identifiable disease (eg, vascular basement membrane thickening, capillary rarefaction, pericyte loss, etc.). Consequences can include the familiar vision loss, renal insufficiency, and neuropathy, but also heart failure, sarcopenia, cognitive impairment, and escalating metabolic dysfunction. Our understanding of normal microvascular function and early dysfunction is rapidly evolving, aided by innovative genetic and imaging tools. This is leading, in tissues like the retina, to testing novel preventive interventions at early, reversible stages of microvascular injury. Great hope lies in the possibility that some of these interventions may develop into effective therapies.

[Causes, spectrum, and treatment of the diabetic neuropathy]

BACKGROUND

Half of all diabetics are affected by a diabetic neuropathy. Microangiopathy, dysfunctional Schwann cell interactions, accumulation of toxic metabolites, and inflammatory processes all contribute to nerve damage.

OBJECTIVE

Overview and perspectives of the pathophysiology as well as the current and future treatment implications.

METHODS

Literature search (1990-2020).

RESULTS

Clinically predominant are sensory and autonomic symptoms; however, muscle weakness can occur as well. Complications such as unrecognized myocardial infarctions and the diabetic foot syndrome are potentially life-threatening and can cause major disability. The pathophysiology of neuropathies in type 1 and type 2 diabetes mellitus differs due to additional risk factors of the metabolic syndrome. To reduce the risk of neuropathy, an intensive insulin therapy is superior compared to the conventional insulin therapy. Oral antidiabetic drugs should be chosen based on individual risk profiles. Metformin can cause an iatrogenic vitamin B12 deficiency. In the treatment of neuropathic pain, the calcium channel blocker pregabalin has the highest recommendation level. The tricyclic antidepressant amitriptyline is considered to be equally effective, but it is contraindicated in autonomic dysregulation and cognitive impairment. Alternatively, the serotonin-norepinephrine reuptake inhibitor duloxetine is approved for the symptomatic treatment of diabetic neuropathies. Controversially discussed medications include alpha-lipoic acid, epalrestat, and L‑serine.

CONCLUSION

The diabetic neuropathy is frequent and causes severe complications. A good understanding of the underlying pathophysiology can contribute to the development of novel treatment strategies in the future.

Vitamin D and Its Potential Interplay With Pain Signaling Pathways

About 50 million of the U.S. adult population suffer from chronic pain. It is a complex disease in its own right for which currently available analgesics have been deemed woefully inadequate since ~20% of the sufferers derive no benefit. Vitamin D, known for its role in calcium homeostasis and bone metabolism, is thought to be of clinical benefit in treating chronic pain without the side-effects of currently available analgesics. A strong correlation between hypovitaminosis D and incidence of bone pain is known. However, the potential underlying mechanisms by which vitamin D might exert its analgesic effects are poorly understood. In this review, we discuss pathways involved in pain sensing and processing primarily at the level of dorsal root ganglion (DRG) neurons and the potential interplay between vitamin D, its receptor (VDR) and known specific pain signaling pathways including nerve growth factor (NGF), glial-derived neurotrophic factor (GDNF), epidermal growth factor receptor (EGFR), and opioid receptors. We also discuss how vitamin D/VDR might influence immune cells and pain sensitization as well as review the increasingly important topic of vitamin D toxicity. Further in vitro and in vivo experimental studies will be required to study these potential interactions specifically in pain models. Such studies could highlight the potential usefulness of vitamin D either alone or in combination with existing analgesics to better treat chronic pain.

Relationship between impaired parasympathetic vasodilation and hyposalivation in parotid glands associated with type 2 diabetes mellitus

We examined the relationship between hemodynamics in the three major salivary glands and salivary secretion in urethane-anesthetized and sympathectomized type 2 diabetic and nondiabetic rats via laser speckle imaging and by collecting the saliva. Lingual nerve stimulation elicited rapid increases in glandular blood flow and induced salivary secretion from the three glands in both diabetic and nondiabetic rats. In the parotid gland, the magnitude of blood flow increase and salivary secretion was significantly lower in the diabetic rats when compared with the nondiabetic rats; however, this was not observed in the other glands. Although the intravenous administration of acetylcholine increased blood flow in the parotid gland in a dose-dependent manner, the response was significantly lower in the diabetic rats when compared with the nondiabetic rats. Similarly, mRNA expression levels of M1 and M3 muscarinic acetylcholine receptors in the parotid gland were relatively lower in the diabetic rats compared with the nondiabetic rats. Our results indicate that type 2 diabetes impairs parasympathetic vasodilation and salivary secretion in the parotid gland and suggest that disturbances in the cholinergic vasodilator pathway may contribute to the underlying mechanisms involved in the disruption of parasympathetic nerve-mediated glandular vasodilation.

Diabetic neuropathies influence recovery from hip-fracture surgery in older persons with diabetes

BACKGROUND/OBJECTIVES

To explore the impact of diabetic peripheral neuropathy (DPN) on the recovery of older persons with diabetes mellitus (DM) after hip-fracture surgery.

DESIGN, SETTING, PARTICIPANTS

Secondary data for this study came from a clinical trial on the effectiveness of a DM-specific care model for 176 older persons (age ≥ 60) with DM over 2 years following hip-fracture surgery at a medical center in Taiwan. In the original trial, the experimental group (n = 88) received DM-specific care comprising diabetes care plus subacute care, and the control group (n = 88) received only usual care.

MEASUREMENTS

DPN was assessed using the Michigan Neuropathy Screening Instrument. Outcomes of self-care ability in activities of daily living (ADL), health-related quality of life (HRQoL), and depressive symptoms were assessed 1, 3, 6, 12, 18, 24 months following hospital discharge using the Chinese Barthel Index and Chinese-version instrumental ADL (IADL) scale; the SF-36 Taiwan version; and the Chinese-version Geriatric Depression Scale, short form, respectively.

RESULTS

After controlling for covariates, participants with DPN had 8.38 fewer points in ADL performance, 0.49 fewer points in IADL performance, and 2.33 fewer points in the physical component summary (PCS) of HRQoL than participants without DPN at 3 months following discharge. During the first year following discharge, the rate of improvement increased less for PCS (β = -0.45, p < 0.05), but more for the mental component summary (β = 0.49, p < 0.05) for those with DPN than for those without. During the second year, the rate of decline in physical function-related HRQoL increased slightly more for those with DPN than for those without (β = 0.03, p < 0.05).

CONCLUSION

DPN adversely affected ADL performance, IADL performance, and physical function-related health outcomes for older persons recovering from hip-fracture surgery. These results suggest that older patients with DM recovering from hip-fracture surgery should be assessed and managed for DPN.

Coaching of lifestyle recommendations improves sensory neurophysiological parameters in neuropathies related to glycemic disorder or metabolic syndrome. A pilot study

OBJECTIVES

Metabolic abnormalities, such as, glycemic disorders and metabolic syndrome (GDMS) are one of the main causes of peripheral neuropathies. The objective of this study was to evaluate the impact of adding specific coaching care (CC) to standard care (SC) of therapeutic education based on lifestyle recommendations for neuropathies associated with GDMS.

METHODS

This prospective randomized study included two groups of four patients (SC vs. CC) with examiners blinded to group allocation. The SC group had one day of therapeutic education on lifestyle measures (physical activity and diet recommendations) followed by only one phone call of reinforcement. The CC group received an additional weekly phone call of reinforcement for 3 months. Clinical, biological and neurophysiological variables were compared between the two groups at baseline and for the percentage of change at 3 months.

RESULTS

All patients (4 men and 4 women) had diabetes or pre-diabetes, which was associated with metabolic syndrome in 5 cases. There was no difference on any variable at baseline, but at 3 months, Mann-Whitney test showed a difference (P=0.0008) between the two groups regarding the sensory neurophysiological variable, which deteriorated in the SC group (median: -6.0%) and improved in the CC group (median: +12.4%). No significant difference was observed between the two groups for the other variables at 3 months.

CONCLUSION

The weekly coaching of recommendations for lifestyle measures over a period of three months allows an improvement of GDMS neuropathies, at least in terms of sensory aspects, as evidenced by neurophysiological assessments.

Stain-free LED scanning lifetime imaging system for diabetes modified tissue matrices

In contrast to labor intensive and destructive histological techniques, intrinsic autofluorescence lifetimes of extra cellular matrix proteins can provide label-free imaging of tissue modifications in diseases, including the diabetic ulcers. However, decoupling the complex mixture of tissue fluorophores requires costly and complicated fluorescent lifetime instrumentation. Furthermore, a list of autofluorescent and fluorogenic proteins must be characterized to profile their changes during disease progression. Towards these goals, an imaging system based on frequency domain light-emitting diode (LED) modulation was designed and demonstrated, using off-the-shelf components in a low complexity design. The system was operated by coupling and imaging fluorescence intensities using a pair of objectives. The system's scanning and signal acquisition performances were optimized with respect to etendues. To study fluorescent proteins in diabetic ulcers, lifetimes from purified and pentosidine modified collagen I, collagen III, and elastin were measured. Pentosidine measurements showed a decrease in autofluorescent lifetimes while elevated collagen III in diabetic ulcers showed increased lifetimes. These lifetimes, plus future protein measurements enabled by our system, can serve as standards for developing a biophotonic model of diabetic ulcers. As a proof-of-concept, a 3 cm × 3 cm diabetic foot ulcer was imaged using the developed system. Phasor analysis was applied to aid the interpretation of lifetime images. As a result, a compact biophotonic imaging system targeting diabetic tissue was achieved, towards making the technique accessible for clinical histology.

The association between renal function and neurological diseases in type 2 diabetes: a multicenter nationwide cross-sectional study

BACKGROUND

The evidence for an association between renal function and neurological diseases among type 2 diabetes mellitus (T2DM) patients, particularly in the Asian population, is limited. This study aimed to assess the association between glomerular filtration rate (GFR) and various neurological diseases among T2DM patients in Thailand using a nationwide patient sample.

METHODS

We conducted a nationwide cross-sectional study based on the DM/HT study of the Medical Research Network of the Consortium of Thai Medical Schools. This study evaluated adult T2DM patients receiving care at public Thailand hospitals in the year 2014. GFR was categorized into ≥60, 30-59, and < 30 mL/min/1.73 m². Neurological diseases studied included ischemic stroke/transient ischemic attack (TIA), hemorrhagic stroke, dementia, all cerebrovascular disease, and peripheral neuropathy. Multivariate logistic regression was performed to assess the association between GFR and neurological diseases.

RESULTS

A total of 30,423 T2DM patients with available GFR data were included in the analysis. The mean GFR was 68.18 ± 26.45 mL/min/1.73 m². The prevalence of ischemic stroke/TIA, hemorrhagic stroke, dementia, any cerebrovascular diseases and peripheral neuropathy were 2.9%, 0.3%, 0.1%, 3.2%, and 3.1%, respectively. Patients with GFR of 30-59 and <30 mL/min/1.73 m² were significantly associated with increased rates of ischemic stroke/TIA, any cerebrovascular diseases, and peripheral neuropathy when compared with patients with GFR of ≥60 mL/min/1.73 m². This association remained significant after adjustment for potential confounders.

CONCLUSION

Decreased GFR was associated with increased ischemic stroke/TIA, all cerebrovascular diseases, and peripheral neuropathy. GFR should be monitored in diabetic patients for neurological disease awareness and prevention.

Microangiopathy-A Potential Contributing Factor to Idiopathic Polyneuropathy: A Mini Review

Chronic idiopathic axonal polyneuropathy (CIAP) is a slowly progressive predominantly sensory axonal polyneuropathy. The prevalence of CIAP increases with age. The pathogenic cause of CIAP is unknown although there are several prevailing etiological hypotheses. In this mini review, we focus on the hypothesis of disturbed microcirculation in the vasa nervorum of peripheral nerves as a pathogenic cause of CIAP. There is an association between CIAP and metabolic risk factors. Furthermore, the phenotype of CIAP resembles diabetic neuropathy both clinically and electrophysiologically. In sural nerve biopsies from patients with diabetes mellitus, structural abnormalities indicating microangiopathy in the endoneurial microvessels are well documented. Similarly, sural microvessel abnormalities have been shown in patients with atherosclerotic non-diabetic peripheral vascular disease. However, the reported histopathological alterations of microvasculature in sural nerves of CIAP patients are inconsistent. Two studies report microangiopathic changes in CIAP sural nerves comparable with those found in patients with diabetic neuropathy. Conversely, another recent study showed no significant differences in the microangiopathic parameters in the endoneurial microvessels in the sural nerve biopsies from CIAP patients compared to controls without polyneuropathy. However, this CIAP patient group was younger compared to the patient groups in the other two studies. A general limitation with the published morphological studies are that different methods have been used in the assessment of microangiopathy, and there is also a risk of subjectivity in the results. Immunohistochemistry studies of sural nerves with verification of microangiopathy using specific biomarkers would be of great interest to develop.

The relationship between neutrophil-to-lymphocyte ratio and diabetic peripheral neuropathy in Type 2 diabetes mellitus

To explore the relationship between neutrophil-to-lymphocyte ratio (NLR) and diabetic peripheral neuropathy (DPN) in type 2 diabetes mellitus.A total of 557 newly diagnosed Type 2 Diabetes Mellitus (T2DM) patients were recruited, including 397 T2DM patients without complication (DM group) as well as 160 T2DM patients complicated with DPN (DPN group). Student t test, Mann-Whitney U test, or χ test was applied to the data of the 2 groups, including the levels of neutrophils and lymphocytes as well as the NLR values of peripheral blood and other biochemistry indexes; Pearson correlation analysis was used to calculate the correlation of NLR and detected factors; risk factors of DPN were estimated via logistic regression analysis and multivariate analysis.The values of triglyceride (TG), neutrophils, fasting insulin, urinary albumin, and 2 hour postglucose in DPN group were significantly higher than those of the DM group, whereas the number of lymphocytes of DPN group was considerably lower than that of the DM group (P < .05 respectively); NLR values were remarkably higher in DPN group compared with those of DM group (2.58 ± 0.50 vs 2.18 ± 0.61, P < .001); logistic regression analysis showed that NLR (P = .002, OR = 4.960, 95% CI = 1.843-13.349) was a risk factor of DPN. Multivariate logistic regression analysis showed that DPN was independently related to NLR (P = .002, OR = 4.960, 95% CI = 1.843-13.349). The ROC curve analysis confirmed that the optimal cut-off point, specificity, and sensitivity in diagnosing DPN by NLR were 2.13%, 48.1%, and 81.3% respectively.Our results showed that NLR is significantly correlated with DPN, which suggested that NLR may be an independent risk factor of DPN.

MR Micro-Neurography and a Segmentation Protocol Applied to Diabetic Neuropathy

The aim of this study was to assess with MRI morphometric ultrastructural changes in nerves affected by diabetic peripheral neuropathy (DPN). We used an MR micro-neurography imaging protocol and a semiautomated technique of tissue segmentation to visualize and measure the volume of internal nerve components, such as the epineurium and nerve fascicles. The tibial nerves of 16 patients affected by DPN and of 15 healthy volunteers were imaged. Nerves volume (NV), fascicles volume (FV), fascicles to nerve ratio (FNR), and nerves cross-sectional areas (CSA) were obtained. In patients with DPN the NV was increased and the FNR was decreased, as a result of an increase of the epineurium (FNR in diabetic neuropathy 0,665; in controls 0,699, p = 0,040). CSA was increased in subjects with DPN (12,84 mm² versus 10,22 mm², p = 0,003). The FV was increased in patients with moderate to severe DPN. We have demonstrated structural changes occurring in nerves affected by DPN, which otherwise are assessable only with an invasive biopsy. MR micro-neurography appears to be suitable for the study of microscopic changes in tibial nerves of diabetic patients.

[Clinical features and diagnosis of diabetic polyneuropathy]

Diabetic polyneuropathy (DPN) is a serious complication of diabetes that leads to early disability in patients if late diagnosed. There has been a lot of research into pathophysiological mechanisms of nerve fiber damage and risk factors for neurological complications of diabetes. Early diagnosis of the latter is quite a challenge and, thus, the problem of finding more reliable diagnostic modalities is rather pressing. In this review, an interdisciplinary approach to the said problem, high-end diagnostic methods, and clinical features of DPN are described.

Study of Autophagy and Microangiopathy in Sural Nerves of Patients with Chronic Idiopathic Axonal Polyneuropathy

Twenty-five percent of polyneuropathies are idiopathic. Microangiopathy has been suggested to be a possible pathogenic cause of chronic idiopathic axonal polyneuropathy (CIAP). Dysfunction of the autophagy pathway has been implicated as a marker of neurodegeneration in the central nervous system, but the autophagy process is not explored in the peripheral nervous system. In the current study, we examined the presence of microangiopathy and autophagy-related structures in sural nerve biopsies of 10 patients with CIAP, 11 controls with inflammatory neuropathy and 10 controls without sensory polyneuropathy. We did not find any significant difference in endoneurial microangiopathic markers in patients with CIAP compared to normal controls, though we did find a correlation between basal lamina area thickness and age. Unexpectedly, we found a significantly larger basal lamina area thickness in patients with vasculitic neuropathy. Furthermore, we found a significantly higher density of endoneurial autophagy-related structures, particularly in patients with CIAP but also in patients with inflammatory neuropathy, compared to normal controls. It is unclear if the alteration in the autophagy pathway is a consequence or a cause of the neuropathy. Our results do not support the hypothesis that CIAP is primarily caused by a microangiopathic process in endoneurial blood vessels in peripheral nerves. The significantly higher density of autophagy structures in sural nerves obtained from patients with CIAP and inflammatory neuropathy vs. controls indicates the involvement of this pathway in neuropathy, particularly in CIAP, since the increase in density of autophagy-related structures was more pronounced in patients with CIAP than those with inflammatory neuropathy. To our knowledge this is the first report investigating signs of autophagy process in peripheral nerves in patients with CIAP and inflammatory neuropathy.

Mechanisms of diabetic neuron damage: Molecular pathways

Diabetic polyneuropathy (DPN) is a common but intractable degenerative disorder of peripheral neurons. DPN first results in retraction and loss of sensory terminals in target organs such as the skin, whereas the perikarya (cell bodies) of neurons are relatively preserved. This is important because it implies that regrowth of distal terminals, rather than neuron replacement or rescue, may be useful clinically. Although a number of neuronal molecular abnormalities have been examined in experimental DPN, several are prominent: loss of structural proteins, neuropeptides, and neurotrophic receptors; upregulation of "stress" and "repair" proteins; elevated nitric oxide synthesis; increased AGE-RAGE signaling, NF-κB and PKC; altered neuron survival pathways; changes of pain-related ion channel investment. There is also a role for abnormalities of direct signaling of neurons by insulin, an important trophic factor for neurons that express its receptors. While evidence implicating each of these pathways has emerged, how they link together and result in neuronal degeneration remains unclear. However, several offer interesting new avenues for more definitive therapy of this condition.

Updates in diabetic peripheral neuropathy

Diabetes has become one of the largest global health-care problems of the 21 ^st century. According to the Centers for Disease Control and Prevention, the population prevalence of diabetes in the US is approaching 10% and is increasing by 5% each year. Diabetic neuropathy is the most common complication associated with diabetes mellitus. Diabetes causes a broad spectrum of neuropathic complications, including acute and chronic forms affecting each level of the peripheral nerve, from the root to the distal axon. This review will focus on the most common form, distal symmetric diabetic polyneuropathy. There has been an evolution in our understanding of the pathophysiology and the management of diabetic polyneuropathy over the past decade. We highlight these new perspectives and provide updates from the past decade of research.

Impact of Diabetic Complications on Balance and Falls: Contribution of the Vestibular System

Diabetes causes many complications, including retinopathy and peripheral neuropathy, which are well understood as contributing to gait instability and falls. A less understood complication of diabetes is the effect on the vestibular system. The vestibular system contributes significantly to balance in static and dynamic conditions by providing spatially orienting information. It is noteworthy that diabetes has been reported to affect vestibular function in both animal and clinical studies. Pathophysiological changes in peripheral and central vestibular structures due to diabetes have been noted. Vestibular dysfunction is associated with impaired balance and a higher risk of falls. As the prevalence of diabetes increases, so does the potential for falls due to diabetic complications. The purpose of this perspective article is to present evidence on the pathophysiology of diabetes-related complications and their influence on balance and falls, with specific attention to emerging evidence of vestibular dysfunction due to diabetes. Understanding this relationship may be useful for screening (by physical therapists) for possible vestibular dysfunction in people with diabetes and for further developing and testing the efficacy of interventions to reduce falls in this population.

Peripheral sensory neuropathy is associated with altered postocclusive reactive hyperemia in the diabetic foot

OBJECTIVE

This study examined whether the presence of peripheral sensory neuropathy or cardiac autonomic deficits is associated with postocclusive reactive hyperemia (reflective of microvascular function) in the diabetic foot.

RESEARCH DESIGN AND METHODS

99 participants with type 2 diabetes were recruited into this cross-sectional study. The presence of peripheral sensory neuropathy was determined with standard clinical tests and cardiac autonomic function was assessed with heart rate variation testing. Postocclusive reactive hyperemia was measured with laser Doppler in the hallux. Multiple hierarchical regression was performed to examine relationships between neuropathy and the peak perfusion following occlusion and the time to reach this peak.

RESULTS

Peripheral sensory neuropathy predicted 22% of the variance in time to peak following occlusion (p<0.05), being associated with a slower time to peak but was not associated with the magnitude of the peak. Heart rate variation was not associated with the postocclusive reactive hyperemia response.

CONCLUSIONS

This study found an association between the presence of peripheral sensory neuropathy in people with diabetes and altered microvascular reactivity in the lower limb.

Diabetic neuropathic pain: Physiopathology and treatment

Diabetic neuropathy is a common complication of both type 1 and type 2 diabetes, which affects over 90% of the diabetic patients. Although pain is one of the main symptoms of diabetic neuropathy, its pathophysiological mechanisms are not yet fully known. It is widely accepted that the toxic effects of hyperglycemia play an important role in the development of this complication, but several other hypotheses have been postulated. The management of diabetic neuropathic pain consists basically in excluding other causes of painful peripheral neuropathy, improving glycemic control as a prophylactic therapy and using medications to alleviate pain. First line drugs for pain relief include anticonvulsants, such as pregabalin and gabapentin and antidepressants, especially those that act to inhibit the reuptake of serotonin and noradrenaline. In addition, there is experimental and clinical evidence that opioids can be helpful in pain control, mainly if associated with first line drugs. Other agents, including for topical application, such as capsaicin cream and lidocaine patches, have also been proposed to be useful as adjuvants in the control of diabetic neuropathic pain, but the clinical evidence is insufficient to support their use. In conclusion, a better understanding of the mechanisms underlying diabetic neuropathic pain will contribute to the search of new therapies, but also to the improvement of the guidelines to optimize pain control with the drugs currently available.

Mechanisms of diabetic neuropathy: Schwann cells

As ensheathing and secretory cells, Schwann cells are a ubiquitous and vital component of the endoneurial microenvironment of peripheral nerves. The interdependence of axons and their ensheathing Schwann cells predisposes each to the impact of injury in the other. Further, the dependence of the blood-nerve interface on trophic support from Schwann cells during development, adulthood, and after injury suggests these glial cells promote the structural and functional integrity of nerve trunks. Here, the developmental origin, injury-induced changes, and mature myelinating and nonmyelinating phenotypes of Schwann cells are reviewed prior to a description of nerve fiber pathology and consideration of pathogenic mechanisms in human and experimental diabetic neuropathy. A fundamental role for aldose-reductase-containing Schwann cells in the pathogenesis of diabetic neuropathy, as well as the interrelationship of pathogenic mechanisms, is indicated by the sensitivity of hyperglycemia-induced biochemical alterations, such as polyol pathway flux, formation of reactive oxygen species, generation of advanced glycosylation end products (AGEs) and deficient neurotrophic support, to blocking polyol pathway flux.

Pathology of human diabetic neuropathy

Pathologic study of a disease provides insights into the precise mechanisms and targets of damage and may provide insights into new therapies. The main targets in diabetic neuropathy are myelinated and unmyelinated fibers as dysfunction and damage to them explains the symptoms of painful neuropathy and the major end points of foot ulceration and amputation as well as mortality. Demyelination and axonal degeneration are established hallmarks of the pathology of human diabetic neuropathy and were derived from pioneering light and electronmicroscopic studies of sural nerve biopsies in the late 1960s and early 1970s. Additional abnormalities, which are relevant to the pathogenesis of human diabetic neuropathy, include pathology of the microvessels and extracellular space. Intraepidermal and sudomotor nerve quantification in skin biopsies provides a minimally invasive means for the detection of early nerve damage. Studies of muscle biopsies are limited and show significant alterations in the expression of neurotrophins, but limited changes in muscle fiber size and capillary density.

Magnetic resonance imaging of the central nervous system in diabetic neuropathy

Diabetic 'peripheral' neuropathy (DPN) is one of the common sequelae to the development of both type-1 and type-2 diabetes mellitus. Neuropathy has a major negative impact on quality of life. Abnormalities in both peripheral vasculature and nerve function are well documented and, in addition, evidence is emerging regarding changes within the central nervous system (CNS) that are concomitant with the presence of DPN. The often-resistant nature of DPN to medical treatment highlights the need to understand the role of the CNS in neuropathic symptomatology and progression, as this may modulate therapeutic approaches. Advanced neuroimaging techniques, especially those that can provide quantitative measures of structure and function, can provide objective markers of CNS status. With that comes great potential for not only furthering our understanding of involvement of the CNS in neuropathic etiology but also most importantly aiding the development of new and more effective, targeted, analgesic interventions.

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 effects of Ginkgo biloba extract (GBe) on axonal transport microvasculature and morphology of sciatic nerve in streptozotocin-induced diabetic rats

To evaluate the protective effects ofGinkgo biloba extract (GBe) which has antioxidant activity against peripheral neuropathy due to diabetes mellitus, slow axonal transport and morphology of sciatic nerve including endoneurial microvessels were examined in 12 rats with diabetes mellitus induced by streptozotocin (STZ, 60mg/kg, b.w., i.p.). Six of the diabetic rats were treated with 0.1 % of GBe for 6 weeks from one week after the STZ injection. Serum glucose and lipid peroxide levels in GBe-treated diabetic rats were significantly lower than those in untreated diabetic rats (p<0.01, respectively), though the serum glucose level was higher than that in the control rats. L-[(35)S] methionine pulse radiolabeling with subsequent gel fluorography demonstrated that mean velocities (Vmean) of actin and β-tubulin, i.e. slow component b (SCb) transport in untreated diabetic rats were significantly lower than those in control rats (p<0.05, respectively); mean diameter of axons in the former rats was significantly smaller than that in the latter (p<0.01). Vmean of actin transport in GBe-treated diabetic rats was significantly faster than that in untreated diabetic rats (p<0.05). Vmean of slow axonal transport was significantly correlated with mean diameter of axons in the three groups of rats combined (p<0.01). On electron microscopy, severe altered endoneurial microvessels decreasing in luminal area together with endothelial cell degeneration or hypertrophy, pericyte debris and basement membrane thickening were observed in untreated diabetic rats; on the other hand these findings were less prominent in the diabetic rats treated with GBe. It is suggested that GBe treatment may protect disturbed slow axonal transport and pathological alterations of peripheral nerve with abnormal endoneurial microvasculature from diabetes mellitus by antioxidant activity.

Advances in the epidemiology, pathogenesis and management of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) affects up to 50% of patients with diabetes and is a major cause of morbidity and increased mortality. Its clinical manifestations include painful neuropathic symptoms and insensitivity, which increases the risk for burns, injuries and foot ulceration. Several recent studies have implicated poor glycaemic control, duration of diabetes, hyperlipidaemia (particularly hypertryglyceridaemia), elevated albumin excretion rates and obesity as risk factors for the development of DPN. Although there is now strong evidence for the importance of nerve microvascular disease in the pathogenesis of DPN, the risk factors for painful DPN are not known. However, emerging evidence regarding the central correlates of painful DPN is now afforded by brain imaging. The diagnosis of DPN begins with a careful history of sensory and motor symptoms. The quality and severity of neuropathic pain if present should be assessed using a suitable scale. Clinical examination should include inspection of the feet and evaluation of reflexes and sensory responses to vibration, light touch, pinprick and the 10-g monofilament. Glycaemic control and addressing cardiovascular risk is now considered important in the overall management of the neuropathic patient. Pharmacological treatment of painful DPN includes tricyclic compounds, serotonin-norepinephrine reuptake inhibitors (e.g. duloxetine), anticonvulsants (e.g. pregabalin), opiates, membrane stabilizers, the antioxidant alpha lipoic acid and others. Over the past 7 years, new agents with perhaps less side effect profiles have immerged. Management of patients with painful neuropathy must be tailored to individual requirements and will depend on the presence of other co-morbidities. There is limited literature with regard to combination treatment.

Central nervous system involvement in diabetic neuropathy

Diabetic neuropathy is a chronic and often disabling condition that affects a significant number of individuals with diabetes. Long considered a disease of the peripheral nervous system, there is now increasing evidence of central nervous system involvement. Recent advances in neuroimaging methods detailed in this review have led to a better understanding and refinement of how diabetic neuropathy affects the central nervous system. Recognition that diabetic neuropathy is, in part, a disease that affects the whole nervous system is resulting in a critical rethinking of this disorder, opening a new direction for further research.

Aldose reductase deficiency improves Wallerian degeneration and nerve regeneration in diabetic thy1-YFP mice

This study examined the role of aldose reductase (AR) in diabetes-associated impaired nerve regeneration using thy1-YFP (YFP) mice. Sciatic nerves of nondiabetic and streptozotocin-induced diabetic AR(+/+)YFP and AR(-/-)YFP mice were transected after 4 weeks of diabetes. Wallerian degeneration and nerve regeneration were evaluated at 1 and 2 weeks postaxotomy by fluorescence microscopy. Motor nerve conduction velocity recovery and regenerating nerve morphometric parameters were determined at 10 and 20 weeks, respectively. There was no difference in the extent of Wallerian degeneration, size of regenerating stump, motor nerve conduction velocity recovery, or caliber of regenerating fibers between nondiabetic AR(+/+)YFP and AR(-/-)YFP mice. In diabetic AR(+/+)YFP mice, Wallerian degeneration was delayed, associated with slower macrophage invasion and abnormal vascularization. Those mice had smaller regenerating stumps, slower motor nerve conduction velocity, and smaller regenerating fibers compared with nondiabetic mice. These features of impaired nerve regeneration were largely attenuated in diabetic AR(-/-)YFP mice. Retarded macrophage invasion and vascularization associated with Wallerian degeneration were normalized in diabetic AR(-/-)YFP mice. These results indicate that AR plays an important role in diabetes-associated impaired nerve regeneration, in part by affecting vascularization and macrophage invasion during Wallerian degeneration. The thy1-YFP mice are valuable tools for further investigation of the mechanism of diabetes-associated nerve regeneration.

Vibration perception threshold and the law of mobility in diabetic mellitus patients

BACKGROUND

Diabetic neuropathy is a family of nerve disorders with progressive loss of nerve function in 15% of diabetes mellitus (DM) subjects. Vibration Perception Threshold (VPT) is one of the modalities of testing loss of protective sensation. Law of mobility for VPT is well known for normal subjects, but not for diabetic subjects. This is a pilot study to evaluate and plot the law of mobility for VPT among DM subjects.

METHODS

We used biothesiometer to find the VPT of several areas in upper and lower extremities for normal and diabetic subjects. VPT of normal and diabetic subjects for different foot areas from proximal to distal is evaluated for 30 subjects. All the subjects are screened for peripheral artery occlusive disease with ankle brachial pressure index (0.9 or above). VPT values of different areas are arranged in a proximal to distal order for the analysis.

RESULTS

VPT values monotonically decrease from proximal to distal areas. Vierodt's law of mobility holds well for normal subjects in both feet areas. The law of mobility does not hold good for the DM subjects in one or both feet areas.

CONCLUSIONS

The VPT value of diabetic subjects reveals that the law of mobility do not holds good for diabetic subjects in foot areas. Though the number of subjects is small, all the subjects defied the law.

Diabetes-related microvascular and macrovascular diseases in the physical therapy setting

Physical therapists commonly treat people with diabetes for a wide variety of diabetes-associated impairments, including those from diabetes-related vascular disease. Diabetes is associated with both microvascular and macrovascular diseases affecting several organs, including muscle, skin, heart, brain, and kidneys. A common etiology links the different types of diabetes-associated vascular disease. Common risk factors for vascular disease in people with diabetes, specifically type 2 diabetes, include hyperglycemia, insulin resistance, dyslipidemia, hypertension, tobacco use, and obesity. Mechanisms for vascular disease in diabetes include the pathologic effects of advanced glycation end product accumulation, impaired vasodilatory response attributable to nitric oxide inhibition, smooth muscle cell dysfunction, overproduction of endothelial growth factors, chronic inflammation, hemodynamic dysregulation, impaired fibrinolytic ability, and enhanced platelet aggregation. It is becoming increasingly important for physical therapists to be aware of diabetes-related vascular complications as more patients present with insulin resistance and diabetes. The opportunities for effective physical therapy interventions (such as exercise) are significant.

Endothelial and neural regulation of skin microvascular blood flow in patients with diabetic peripheral neuropathy: effect of treatment with the isoform-specific protein kinase C beta inhibitor, ruboxistaurin

PURPOSE

This article aims to study the effects of ruboxistaurin (RBX) on skin microvascular blood flow (SkBF) and evaluate the relationship between endothelial and neural control of SkBF in patients with diabetic peripheral neuropathy (DPN).

METHODS

We studied 11 placebo- and 9 RBX (32 mg/day)-treated patients who participated in a 1-year, double-masked, randomized, Phase 3 study of RBX for treatment of DPN sensory symptoms. Patients had type 1 or type 2 diabetes, a detectable sural sensory nerve action potential, and Neuropathy Total Symptom Score-6 (NTSS-6) >6 points. SkBF was measured by laser Doppler velocimetry, combined with iontophoresis of acetylcholine and sodium nitroprusside, at baseline, 3 months, and 1 year. Sensory symptoms and electrophysiology were also evaluated during the study. The relationship between endothelial and neural control of SkBF at baseline was assessed using linear regression.

RESULTS

No significant differences (RBX vs. placebo) were demonstrable for post-iontophoresis SkBF [fold increase from basal state (1 year): endothelium-dependent, 3.6 vs. 8.6; endothelium-independent, 3.7 vs. 2.0; C fiber-mediated, 1.7 vs. 2.0; P>.05] or sensory symptoms [NTSS-6 total score (1 year): 7.7 vs. 6.0 points; P=.4]. There were also no significant between-group differences in nerve conduction parameters, except for placebo peroneal nerve conduction velocity, which demonstrated a statistically significant improvement of unknown clinical importance (Z=2.1; P=.034). At baseline, C fiber-mediated vasodilatation correlated well with endothelium-dependent vasodilation (r=.7, P<.01) but not with endothelium-independent vasodilatation (r=-.1, P=.7).

CONCLUSIONS

RBX demonstrated no effect on SkBF or sensory symptoms after 1 year in this cohort. The correlation between C fiber-mediated and endothelium-dependent SkBF at baseline suggests that improving endothelial function could affect the microcirculation not only locally but also via the neurovascular arcade.

Endoneurial microvascular pathology in feline diabetic neuropathy

Endoneurial capillaries in nerve biopsies from 12 adult diabetic cats with varying degrees of neurological dysfunction were examined for evidence of microvascular pathology and compared to nerves obtained at necropsy from 7 adult non-diabetic cats without clinical evidence of neurological dysfunction. As reported previously [Mizisin, A.P., Nelson, R.W., Sturges, B.K., Vernau, K.M., LeCouteur, R.A., Williams, D.C., Burgers, M.L., Shelton, G.D., 2007. Comparable myelinated nerve pathology in feline and human diabetes mellitus. Acta Neuropathol. 113, 431-442.], the diabetic cats had elevated glycosylated hemoglobin and serum fructosamine levels, decreased motor nerve conduction velocity and compound muscle action potential (CMAP) amplitude, and markedly decreased myelinated nerve fiber densities. Compared to non-diabetic cats, there was a non-significant 26% increase in capillary density and a significant (P<0.009) 45% increase in capillary size in diabetic cats. Capillary luminal size was also significantly (P<0.001) increased, while an index of vasoconstriction was significantly decreased (P<0.001) in diabetic cats compared to non-diabetic controls. No differences in endothelial cell size, endothelial cell number or pericyte size were detected between non-diabetic and diabetic cats. In diabetic cats, basement membrane thickening, seen as a reduplication of the basal lamina, was significantly (P<0.0002) increased by 73% compared to non-diabetic controls. Regression analysis of either myelinated nerve fiber density or CMAP amplitude against basement membrane size demonstrated a negative correlation with significant slopes (P<0.03 and P<0.04, respectively). These data demonstrate that myelinated nerve fiber injury in feline diabetic neuropathy is associated with microvascular pathology and that some of these changes parallel those documented in experimental rodent and human diabetic neuropathy.

Diabetes mellitus and the peripheral nervous system: manifestations and mechanisms

Diabetes targets the peripheral nervous system with several different patterns of damage and several mechanisms of disease. Diabetic polyneuropathy (DPN) is a common disorder involving a large proportion of diabetic patients, yet its pathophysiology is controversial. Mechanisms considered have included polyol flux, microangiopathy, oxidative stress, abnormal signaling from advanced glycation endproducts and growth factor deficiency. Although some clinical trials have demonstrated modest benefits in disease stabilization or pain therapy in DPN, robust therapy capable of reversing the disease is unavailable. In this review, general aspects of DPN and other diabetic neuropathies are examined, including a summary of recent therapeutic trials. A particular emphasis is placed on the evidence that the neurobiology of DPN reflects a unique yet common and disabling neurodegenerative disorder.

Abnormal levels of serum antielastin antibodies in children with diabetes mellitus type 1

Antibodies to alpha-elastin (elastin breakdown product) and elastin sequences devoid of cross-linked regions (linear elastin) are found in the serum of all human subjects and correlate with their respective serum peptide levels. The aim of this study was to determine if the serum level of antielastin antibodies (AEAbs) differs between type 1 diabetic children and nondiabetic children. Enzyme-linked immunosorbent assay was used to measure the levels of immunoglobulin (Ig)G and IgM AEAbs in the sera of 45 diabetic children (mean age 12.8 +/- 3.2 years, diabetes duration 5.3 +/- 3.6 years). Twenty-two children presented with vascular complications (group 1), whereas 23 displayed no vascular complications (group 2). The controls were 18 healthy children (mean age 11.9 +/- 2.3 years). Diabetic patients showed statistically significant higher levels of IgM alpha-AEAbs (0.82 +/- 0.26 vs 0.61 +/- 0.14, p = .0013) than the control group. In group 1, alpha-AEAbs showed statistically significant higher level than controls: IgG (0.86 +/- 0.42 vs 0.59 +/- 0.12; p = .0109) and IgM (0.88 +/- 0.24 vs 0.61 +/- 0.14; p = .0001). IgM antilinear elastin antibodies (ALEAbs) in group 1 were significantly lower than in controls (0.462 +/- 0.191 vs 0.652 +/- 0.127; p = .0009). IgG alpha-AEAbs showed correlation with microalbuminuria (r = -.26; p = .05) and IgM ALEAbs correlated with microalbuminuria (r = -.32; p = .035). IgG alpha-AEAbs correlated with neuropathy (r = -.32; p = .035). Group 1 patients displayed a correlation between IgG ALEAbs and retinopathy (r = -.48; p = .023) and IgM ALEAbs and microalbuminuria (r = .52; p = .014). Levels of AEAbs and ALEAbs can serve as immunologic markers of the extent of elastin degradation. These markers may provide a tool to study elastin metabolism and a potential clinical role for AEAbs in the pathogenesis and development of vascular complications in diabetic children.

The role of PPARs in the microvascular dysfunction in diabetes

There is a major defect in skin blood flow (SkBF) in people with type 2 diabetes (T2DM). This defect is associated with relatively normal nitric oxide (NO) production in the skin. The abnormal blood flow cosegregates with hypertension, dyslipidemia, abnormal fatty acid composition, a proinflammatory state, and insulin resistance. Since these covariates are an integral part of the insulin resistance syndrome, we examined the effects of the thiazoledindiones (TZDs) as insulin sensitizers for their ability to correct the abnormal blood flow. The PPARgamma rosiglitazone improved NO production to normal levels, but had a small effect on SKBF. In contrast, pioglitazone had a small effect on skin neurovascular function but a dramatic effect on reducing nitrosative stress. These effects do not appear to be due to the insulin sensitizing properties of these compounds but are associated with a reduction in indices of inflammation, hemodilution, and are likely to be due to one of the many "vascular" effects of TZDs. The role of inflammation in the disordered neurovascular function in diabetes cannot be underplayed and the possible contribution of PPARalpha agonists to alter the inflammatory state needs to be explored further. Since blood flow regulation is mediated by mechanisms other than NO, such as prostaglandins and endothelial derived hyperpolarizing factor, which, in turn, are compromised by the inflammatory state, we anticipate that activation of both the PPARgamma as well as PPARalpha should ameliorate the disordered blood flow in type 2 diabetes. While it now appears that the PPARs may have a major role to play in protection from macrovascular disease, their contribution to amelioration of the microvascular defects in type 2 diabetes has fallen short of spectacular success. In this respect, the combinations of PPARalpha, PPARbeta and PPARgamma may better serve the unique requirements for improving the microvascular defect in diabetes.

Diabetic neuropathies: features and mechanisms

Diabetic neuropathies include both focal neuropathies and diffuse polyneuropathy. Polyneuropathy, the most common of the diabetic neuropathies excluding focal entrapment, has not yet been explained by a single disease mechanism despite intensive investigation. A number of abnormalities appear to cascade into a 'vicious cycle' of progressive microvascular disease associated with motor, sensory and autonomic fiber loss. These abnormalities include excessive polyol (sugar alcohol) flux through the aldose reductase pathway, functional and structural alterations of nerve microvessels, nerve and ganglia hypoxia, oxidative stress, nonspecific glycosylation of axon and microvessel proteins, and impairment in the elaboration of trophic factors critical for peripheral nerves and their ganglia. While an initiating role for nerve ischemia in the development of polyneuropathy has been proposed, the evidence for it can be questioned. The role of sensory and autonomic ganglia in the development of polyneuropathy has had relatively less attention despite the possibility that they may be vulnerable to a variety of insults, particularly neurotrophin deficiency. Superimposed on the deficits of polyneuropathy is the failure of diabetic nerves to regenerate as effectively as nondiabetics. Polyneuropathy has not yet yielded to specific forms of treatment but a variety of new trials addressing plausible hypotheses have been initiated. This review will summarize some of the clinical, pathological and experimental work applied toward understanding human diabetic neuropathy and will emphasize ideas on pathogenesis.

The diabetic neuropathies

BACKGROUND

Diabetes remains the most common cause of neuropathy in the United States and is a significant source of morbidity and mortality, accounting for substantial suffering and billions of dollars in health care expenditures each year.

REVIEW SUMMARY

Our insight into the pathophysiology of the diabetic neuropathies has increased considerably over the last decade. aided by advances in the basic science of diabetes itself. A wide variety of potential mechanisms for nerve injury in diabetes has been identified, including the polyol pathway of glucose metabolism, oxidative nerve injury, the deposition of advanced glycosylation end products within the nerve and the effects of vascular insufficiency, among others. Diabetic neuropathy may take a variety of clinical forms beyond the well-known distal symmetric neuropathy, many of which are often misdiagnosed or overlooked entirely, sometimes with serious consequences for the patient. Proper therapy after diagnosis is also critical and may include not only primary management, but also treatment of painful diabetic neuropathy through an expanding repertoire of increasingly effective pharmacologic agents. Though primary treatment trials have not yet provided effective therapies, ongoing and future trials offer continuing promise.

CONCLUSIONS

The diabetic neuropathies are exceedingly common, but often improperly diagnosed and incompletely treated. A proper understanding of the mechanisms underlying these diseases and the clinical recognition of their various forms is highly important as appropriate primary and symptomatic management can substantially reduce the morbidity and mortality associated with these disorders.