Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes

Translation and Cross-Cultural Adaptation of the Questionnaire on Stress in Diabetic Patients (QSD-R) to Brazilian Portuguese

BACKGROUND

Diabetes mellitus is a chronic disease that can cause psychological stress. This study was conducted to perform the translation and cross-cultural adaptation of the QSD-R for diabetic patients into Portuguese (Brazil).

METHODS

This study was a cross-cultural adaptation process carried out in a public university in São Paulo, Brazil, in three stages: translation and backtranslation by two native-speaking independent professionals, analysis by a committee of specialists, and a pre-test phase.

RESULTS

The final version was created by seven experts after making semantic, idiomatic, and cultural changes to eighteen items. The results indicated a satisfactory content validation index (CVI ≥ 0.80). This version was applied to 30 patients. No item was excluded from the instrument.

CONCLUSION

The translated version of the QSD-R was considered adequate and culturally adapted for use in Brazil to enable the psychometric validation of the instrument.

Diabetes and climate change: current evidence and implications for people with diabetes, clinicians and policy stakeholders

Climate change will be a major challenge for the world's health systems in the coming decades. Elevated temperatures and increasing frequencies of heat waves, wildfires, heavy precipitation and other weather extremes can affect health in many ways, especially if chronic diseases are already present. Impaired responses to heat stress, including compromised vasodilation and sweating, diabetes-related comorbidities, insulin resistance and chronic low-grade inflammation make people with diabetes particularly vulnerable to environmental risk factors, such as extreme weather events and air pollution. Additionally, multiple pathogens show an increased rate of transmission under conditions of climate change and people with diabetes have an altered immune system, which increases the risk for a worse course of infectious diseases. In this review, we summarise recent studies on the impact of climate-change-associated risk for people with diabetes and discuss which individuals may be specifically prone to these risk conditions due to their clinical features. Knowledge of such high-risk groups will help to develop and implement tailored prevention and management strategies to mitigate the detrimental effect of climate change on the health of people with diabetes.

Dryness of Foot Skin Assessed by the Visual Indicator Test and Risk of Diabetic Foot Ulceration: A Prospective Observational Study

Research Question: Previous cross-sectional studies have shown an association between sudomotor dysfunction and diabetic foot ulceration (DFU). The aim of this prospective multicenter study was to determine the role of dryness of foot skin and of established neurological modalities in the prediction of risk for foot ulceration in a cohort of individuals with diabetes mellitus (DM). Design: The study was conducted from 2012 to 2017. A total of 308 subjects with DM without history of DFU or critical limb ischemia completed the study. Diabetic neuropathy was assessed using the neuropathy symptom score (NSS) and neuropathy disability score (NDS). In a subset of participants, vibration perception threshold (VPT) was evaluated. Dryness of foot skin was assessed by the visual indicator plaster method (IPM). The diagnostic performance of the above neurological modalities for prediction of DFU was tested by receiver operating characteristic curve (ROC) analysis. Results: During the 6-year follow-up, 55 patients (annual ulceration incidence 2.97%) developed DFU. Multivariate Cox-regression analysis after controlling for the effect of age, gender, and DM duration demonstrated that the risk (hazard ratio, 95% confidence intervals) of DFU increased significantly with either abnormal IPM (3.319, 1.460-7.545, p = 0.004) or high (≥6) NDS (2.782, 1.546-5.007, p = 0.001) or high (≥25 volts) VPT (2.587, 1.277-5.242, p = 0.008). ROC analysis showed that all neurological modalities could discriminate participants who developed DFU (p < 0.001). IPM testing showed high sensitivity (0.86) and low specificity (0.49), while high vs. low NDS and VPT showed low sensitivity (0.40 and 0.39, respectively) and high specificity (0.87 and 0.89, respectively) for identification of patients at risk for DFU. Conclusion: Dryness of foot skin assessed by the IPM predicts the development of DFU. IPM testing has high sensitivity, whereas high NDS and VPT have high specificity in identifying subjects at risk for DFU. The IPM can be included in the screening methods for identification of the foot at risk.

Assessment of sudomotor function

PURPOSE

To review the currently available literature on clinical autonomic tests of sudomotor function.

METHODS

We searched PubMED/MEDLINE for articles on technical principles and clinical applications of sudomotor tests with a focus on their drawbacks and perspectives in order to provide a narrative review.

RESULTS

The quantitative sudomotor axon reflex sweat test (QSART) is the most widely used test of sudomotor function. The technique captures pathology with low intra- and inter-subject variability but is limited by technical demands. The thermoregulatory sweat test comprises topographic sweat pattern analysis of the ventral skin surface and allows differentiating preganglionic from postganglionic sudomotor damage when combined with a small fiber test such as QSART. The sympathetic skin response also belongs to the more established techniques and is used in lie detection systems due to its high sensitivity for sudomotor responses to emotional stimuli. However, its clinical utility is limited by high variability of measurements, both within and between subjects. Newer and, therefore, less widely established techniques include silicone impressions, quantitative direct and indirect axon reflex testing, sensitive sweat test, and measurement of electrochemical skin conductance. The spoon test does not allow a quantitative assessment of the sweat response but can be used as bedside-screening tool of sudomotor dysfunction.

CONCLUSION

While new autonomic sudomotor function testings have been developed and studied over the past decades, the most were well-studied and established techniques QSART and TST remain the gold standard of sudomotor assessment. Combining these techniques allows for sophisticated analysis of neurally mediated sudomotor impairment. However, newer techniques display potential to complement gold standard techniques to further improve their precision and diagnostic value.

A model for in vivo analysis of sudomotor sympathetic C-fiber activation and human sweat gland output

Quantitative assessment of small-fiber peripheral neuropathy often involves an evaluation of the interaction between the C-fiber sudomotor nerve and local sweat rate (SR). Typically, some sort of quantitative sudomotor axon reflex test (QSART) is performed to aid in diagnosing small-fiber dysfunction. The currently used QSART demonstrates only moderate test-retest reliability and therefore limits its usefulness in tracking small-fiber dysfunction. A new experimental model to examine small C-fiber function in the skin using intradermal electrical stimulation and simultaneous monitoring of SR is proposed. Using intradermal electrical stimulation (1.5 and 2.5 mA) and varying stimulus frequency from 0.2 to 64 Hz, a quantitative relationship between the area under the SR-time curve and log₁₀ stimulus frequency is modeled using a four-parameter logistic equation, providing the following parameters: baseline, plateau, EC₅₀, and Hill slope. The model has good to excellent repeatability within the same day (ICC = 0.98), on different days at the same skin site (ICC = 0.80), and when comparing two different skin sites (ICC = 0.78) with a small bias estimate and the line of identity always lying within the 95% limits of agreement. Atropine sulfate (0.1 mg/ml) blocked 90 ± 5% of the electrically induced sweating. Overall, the model provides control over sudomotor nerve activity and a quantitative assessment of SR. Finally, the ability to reproduce the quantitative stimulus-response curve on different days allows for a robust assessment of the relationship between the activation of a sympathetic C-fiber and local SR.NEW & NOTEWORTHY A model for quantitative assessment of C-fiber function in human skin using intradermal electrical stimulation and local sweat rate measurements has been developed. This new electrically induced sweating model is nonpainful and allows for a complete stimulus-response curve plotting the area under the local sweat rate-time curve vs. the log₁₀ stimulus frequency. The model has good reproducibility and should provide a means of assessing the progression of small C-fiber peripheral neuropathy in humans.

Tool Chest

PURPOSE

The purpose of this study was to evaluate the new indicator test for sudomotor function (Neuropad) in the diagnosis of small-fiber impairment in patients with type 2 diabetes.

METHODS

This study included 123 patients with type 2 diabetes (59 men; mean age, 64.3 +/- 8.6 years; mean diabetes duration, 12 +/- 6.1 years). Sudomotor dysfunction was assessed by means of the new indicator test. Neuropathy was diagnosed by the Neuropathy Disability Score and small-fiber impairment by temperature perception (Tiptherm device) and pain perception (Neurotip).

RESULTS

The frequency of sudomotor dysfunction was significantly (P = .001) higher in patients with neuropathy (95%) than in those without neuropathy (30.2%). Sensitivity of the indicator test for neuropathy was 95%, and specificity was 69.8%. Frequency of neuropathy was significantly (P = .018) higher with the indicator test (74.8%) than with conventional clinical examination (65.4%). Sudomotor dysfunction was significantly (P = .001) more frequent in patients with small-fiber impairment (99%) than in those without small-fiber impairment (21.7%). Sensitivity for small-fiber impairment was 99%, and specificity was 78.3%. There was no difference (P = .999) in the frequency of small-fiberimpairment as diagnosed with the indicator test (80.5%) and with clinical examination (81.3%).

CONCLUSIONS

The indicator test has a very high sensitivity and specificity for small-fiber impairment in patients with type 2 diabetes.

Autonomic thermoregulatory dysfunction in neurofibromatosis type 1

Objective

Neurofibromatosis type 1 (NF1) causes neural and cutaneous disorders and reduced exercise capacity. Exercise/heat exposure increasing internal temperature must be compensated by eccrine sweat function and warmed skin vasodilation. We suspected NF1 could adversely affect eccrine sweat function and/or vascular thermoregulatory responses (VTR).

Methods

The eccrine sweat function and VTR of 25 NF1 volunteers (14 males, 11 females; 16-57 years old) were compared with 23 non-NF1 controls matched by sex, age, height and weight (CG). Sweating was induced by 1) pilocarpine 1% iontophoresis (PILO); and 2) by passive heating (HEAT) via the lower third of the legs being immersed in 42°C water for one hour. Previously established eccrine sweat function and VTR protocols were used.

Results

The NF1 group showed: a) lower sweat rate than the CG group during PILO; b) a smaller diastolic pressure decrease; and c) higher tympanic temperatures than controls during HEAT (p < 0.05).

Conclusion

Reduced sweating and vascular thermoregulatory responses suggest autonomic dysfunction in NF1 individuals.

Hyperhidrosis Prevalence and Demographical Characteristics in Dermatology Outpatients in Shanghai and Vancouver

Background

There is a wide variation in the reported prevalence of primary hyperhidrosis in the literature. Further, it is unknown if primary hyperhidrosis is a lifelong condition, or if demographical factors influence hyperhidrosis prevalence.

Objectives

This study aims to examine the prevalence of hyperhidrosis in multiple ethnic groups from two ethnically diverse cities and to determine if the prevalence of primary hyperhidrosis changes according to age, gender, ethnicity, body mass index, and geographical locations.

Methods

In total, 1010 consecutive subjects attending dermatology outpatient clinics in Shanghai Skin Disease Hospital and 1018 subjects in Skin Care Center of Vancouver General Hospital were invited to fill out a questionnaire on their presenting concerns, demographical information, and sweating symptoms. The subjects were then classified to have primary hyperhidrosis using the criteria of International Hyperhidrosis Society, late-onset hyperhidrosis, or no-hyperhidrosis. The prevalence of primary HH and late-onset HH was calculated for the entire study population and in subgroups stratified according to age of examination, sex, ethnicity, presenting diagnosis, body mass index, and specific study cities. Multivariate logistic regression analyses were performed to assess the impact of these factors on HH prevalence.

Results

The prevalence of primary hyperhidrosis is very similar in Shanghai and in Vancouver, at 14.5% and 12.3% respectively. In addition, 4.0% of subjects in Shanghai and 4.4% subjects in Vancouver suffer from late-onset HH. Primary HH has highest prevalence in those younger than 30 years of age, decreasing dramatically in later years. Caucasian subjects are at least 2.5 times more likely to develop axillary hyperhidrosis compared to Chinese subjects. Obesity does not have much influence on primary HH presentation, although it does increase significantly the development of late-onset HH. Finally, there is no major difference of hyperhidrosis between Chinese subjects in Shanghai and Vancouver.

Limitations

The data were gathered according to patients’ self-reports only and the sample size was relatively small in some groups after stratification for gender, ethnicity and age.

Conclusion

Prevalence of primary HH and late-onset HH is similar in dermatology outpatients independent of geographical locations. However, certain specific HH subtypes can show great variations according to ethnicity, age, body mass index and sex.

Body temperature regulation in diabetes

The effects of type 1 and type 2 diabetes on the body's physiological response to thermal stress is a relatively new topic in research. Diabetes tends to place individuals at greater risk for heat-related illness during heat waves and physical activity due to an impaired capacity to dissipate heat. Specifically, individuals with diabetes have been reported to have lower skin blood flow and sweating responses during heat exposure and this can have important consequences on cardiovascular regulation and glycemic control. Those who are particularly vulnerable include individuals with poor glycemic control and who are affected by diabetes-related complications. On the other hand, good glycemic control and maintenance of aerobic fitness can often delay the diabetes-related complications and possibly the impairments in heat loss. Despite this, it is alarming to note the lack of information regarding diabetes and heat stress given the vulnerability of this population. In contrast, few studies have examined the effects of cold exposure on individuals with diabetes with the exception of its therapeutic potential, particularly for type 2 diabetes. This review summarizes the current state of knowledge regarding the impact of diabetes on heat and cold exposure with respect to the core temperature regulation, cardiovascular adjustments and glycemic control while also considering the beneficial effects of maintaining aerobic fitness.

Impairments in local heat loss in type 1 diabetes during exercise in the heat

Studies show that vasomotor and sudomotor activities are compromised in individuals with Type 1 diabetes mellitus (T1DM), which could lead to impaired skin blood flow (SkBF) and sweating during heat stress. However, recent work suggests the impairments may only be evidenced beyond a certain level of heat stress.

PURPOSE

We examined T1DM-related differences in heat loss responses of SkBF and sweating during exercise performed at progressive increases in the requirement for heat loss.

METHODS

Sixteen adults (10 males and six females) with (T1DM, n = 8) and without T1DM (control, n = 8) matched for age, sex, body surface area, and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W·m in the heat (35°C and 20% relative humidity). Each rate was performed sequentially for 30 min. Local sweat rate (LSR, ventilated capsule), sweat gland activation (modified iodine paper technique), and sweat gland output were measured on the forearm, upper back, and chest, whereas SkBF (laser Doppler) was measured on the forearm and upper back.

RESULTS

Despite a similar requirement for heat loss, LSR was lower in T1DM on the forearm and chest relative to that in the control. Reductions were measured in the second (forearm: 0.68 ± 0.14 vs 0.85 ± 0.11 mg·min·cm, P = 0.004; chest: 0.58 ± 0.08 vs 0.82 ± 0.12 mg·min·cm, P = 0.046) and third exercise bouts (forearm: 0.75 ± 0.11 vs 0.98 ± 0.12 mg·min·cm, P = 0.005; chest: 0.66 ± 0.1 vs 1.02 ± 0.16 mg·min·cm, P = 0.032). Differences in forearm LSR were the result of a reduction in sweat gland output, whereas the decrease in chest LSR was due to lower sweat gland activation. SkBF did not differ between groups.

CONCLUSIONS

We show that T1DM is associated with impairments in heat dissipation during exercise in the heat, as evidenced by attenuated LSR. However, these differences are only shown beyond a certain requirement for heat loss.

Whole-body heat loss during exercise in the heat is not impaired in type 1 diabetes

PURPOSE

The objective of this study is to determine whether individuals with type 1 diabetes exhibit impairments in local and whole-body heat loss responses that could affect core temperature regulation during exercise in the heat compared with matched, nondiabetic individuals.

METHODS

Twelve otherwise healthy individuals with type 1 diabetes (HbA1c = 7.7% ± 0.3%) and 12 controls matched for age, sex, body surface area, and physical fitness cycled continuously for 60 min at a set rate of metabolic heat production (approximately 400 W) in a whole-body direct calorimeter (35°C and 20% relative humidity). Local sweat rate (ventilated capsule) was measured on the back and skin blood flow (laser Doppler velocimetry) on the forearm. Core (rectal and esophageal) and mean skin temperatures and heart rate were measured continuously. Whole-body heat exchange and change in body heat content were measured using simultaneous direct whole-body and indirect calorimetry.

RESULTS

The change (mean ± SE) in body heat content was similar between groups during exercise (diabetes, 409 ± 27 kJ; control, 386 ± 33 kJ; P = 0.584) and recovery (diabetes, -115 ± 16 kJ; control, -93 ± 24 kJ; P = 0.457). Local heat loss responses of sweating (P = 0.783) and skin blood flow (P = 0.078) as well as rectal temperature (diabetes, 37.87°C ± 0.10°C; control, 37.85°C; ± 0.13°C; P = 0.977) and heart rate (diabetes, 130 ± 9 beats·min, vs control, 126 ± 8 beats·min, P = 0.326) were comparable at the end of the exercise period.

CONCLUSION

During light-to-moderate-intensity exercise performed under conditions permitting full sweat evaporation, otherwise healthy type 1 diabetic individuals did not show impaired heat loss responses during heat exposure when compared with matched individuals without diabetes.

Correlation between sudomotor function, sweat gland duct size and corneal nerve fiber pathology in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION

To study the correlation between sudomotor function, sweat gland duct size and corneal nerve fiber pathology in type 2 diabetes.

MATERIALS AND METHODS

Sudomotor function was quantified by Neuropad test, and sweat gland duct and corneal nerve fibers were visualized by confocal microscopy in 78 patients with type 2 diabetes stratified by diabetic neuropathy and 28 control participants.

RESULTS

In patients with diabetic neuropathy, sudomotor function, as judged by the time required for complete color change of a Neuropad, was impaired compared with that of controls (P < 0.0001), thereby showing deterioration was related to the severity of diabetic neuropathy (P < 0.0001). Sweat gland ducts were smaller in patients without neuropathy than in controls (P < 0.0001), and further shrinking was seen in patients with severe diabetic neuropathy (P < 0.05). Patients without diabetic neuropathy showed reduced density and length (P < 0.001) of corneal nerve fibers and beading frequency (P < 0.0001), and increased tortuosity (P < 0.0001) compared with controls, and these changes deteriorated in patients with severe diabetic neuropathy. Sudomotor function was negatively associated with corneal nerve fibers (P < 0.002) and branches (P < 0.01), and influenced by the severity of diabetic neuropathy (P < 0.0001); sweat gland duct size correlated with serum triglycerides (P < 0.02), uric acid (P < 0.01), corneal nerve branch (P < 0.03), sudomotor function (P < 0.03) and severity of neuropathy (P < 0.03).

CONCLUSIONS

Type 2 diabetic patients had sudomotor dysfunction and smaller sweat gland ducts compared with controls. The stage of diabetic neuropathy and corneal nerve fiber pathology were independent predictors of sudomotor dysfunction, and serum triglycerides, uric acid, corneal nerve branch, stage of diabetic neuropathy and sudomotor function were predictors of sweat gland duct size.

A simple new non-invasive sweat indicator test for the diagnosis of diabetic neuropathy

A simple non-invasive indicator test (Neuropad(®)) has been developed for the assessment of sweating and, hence, cholinergic innervation in the diabetic foot. The present review summarizes current knowledge on this diagnostic test. The diagnostic ability of this test is based on a colour change from blue to pink at 10 min, with excellent reproducibility, which lends itself to patient self-examination. It has a high sensitivity (65.1-100%) and negative predictive value (63-100%), with moderate specificity (32-78.5%) and positive predictive value (23.3-93.2%) for the diagnosis of diabetic peripheral neuropathy. It also has moderate to high sensitivity (59.1-89%) and negative predictive value (64.7-91%), but low to moderate specificity (27-78%) and positive predictive value (24-48.6%) for the diagnosis of diabetic cardiac autonomic neuropathy. There are some data to suggest that Neuropad can detect early diabetic neuropathy, but this needs further evaluation. It remains to be established whether this test can predict foot ulceration and amputation, thereby contributing to the identification of high-risk patients.

Small fiber function in drug naïve patients with idiopathic restless legs syndrome

To assess whether idiopathic restless legs syndrome (RLS) is associated with small fiber abnormalities, we evaluated somatic and autonomic small fiber function in 56 patients with idiopathic RLS and 36 age-matched and sex-matched healthy controls using quantitative sensory testing and quantitative sudomotor axon reflex tests. The warm detection thresholds (WDT) of the hands (p=0.017) and feet (p=0.008) were higher in patients with RLS than in controls. Cooling detection thresholds (CDT) were higher in the feet of patients with RLS than controls (p<0.001), but CDT in the hands did not differ between groups (p=0.161). There were no significant between-group differences in total sweat volume and sweat production in the forearms, proximal legs, distal legs, and feet (p>0.1 each). These findings suggest that abnormal sensory perception in patients with idiopathic RLS may result from impairment of central somatosensory processing rather than small fiber neuropathy.

Accuracy of a Novel Non-Invasive technology based EZSCAN system for the diagnosis of diabetes mellitus in Chinese

BACKGROUND

A new simple technique based on iontophoresis technology (EZSCAN, Impeto Medical, Paris, France) has recently been developed for the screening of diabetes. In the present study, we investigated the accuracy of this system for the diagnosis of diabetes mellitus in Chinese.

METHODS

We performed the EZSCAN test in diabetic and non-diabetic subjects. EZSCAN measures electrochemical conductance (EC) at forehead, hands and feet, and derives a diabetes index with a value ranging from 0 to 100. Diabetes mellitus was defined as a plasma glucose concentration of at least 7 mmol/l at fasting or 11.1 mmol/l at 2 hours after glucose load, or as the use of antidiabetic drugs.

RESULTS

The 195 study participants (51% men, mean age 52 years) included 75 diabetic patients (use of antidiabetic drugs 81%) and 120 non-diabetic subjects. EC (micro Siemens, μSi) was significantly (P < 0.001) lower in diabetic patients at the hands (44 vs. 61) and feet (51 vs. 69) locations, but not at the forehead (15 vs. 17, P = 0.39). When a diabetes index of 40 (suggested by the manufacturer) was used as the threshold, the sensitivity and specificity for the diagnosis of diabetes mellitus was 85% and 64%, respectively. In 80 patients who underwent an oral glucose tolerance test, EC at hands and feet and the diabetes index were significantly (P < 0.001) associated with both 2-hour post-load plasma glucose and serum glycosylated haemoglobin.

CONCLUSIONS

EZSCAN might be useful in screening diabetes mellitus with reasonable sensitivity and specificity.

Clinical differentiation of primary from secondary hyperhidrosis

BACKGROUND

Hyperhidrosis (HH) is excessive sweating that may be primary (idiopathic) or secondary to medication or disease. Clinical features supporting primary or secondary etiology have not been well documented.

OBJECTIVE

To identify clinical and demographic features predictive of a diagnosis of primary versus secondary HH.

METHODS

A retrospective chart review was conducted over a 13-year period (1993-2005) of all patients (children and adults) seen at a university-based outpatient dermatology department with an International Classification of Diseases, 9th revision diagnosis code for HH (N = 415).

RESULTS

Three hundred eighty-seven patients (93.3%) had primary HH (PHH); 28 patients (6.7%) had secondary HH (SHH). SHH patients were older (39.0 ± 18.6 years vs 27.3 ± 12.3 years) with more frequent onset at age older than 25 years (55% for SHH vs12.1% for PHH; odds ratio [OR] 8.7; 95% confidence interval [CI] 3.5-21.4; P < .00001 for each). SHH was more often unilateral/asymmetric (OR: 51; 95% CI: 12.6-208), generalized (vs focal; OR: 18; 95% CI: 7.3-47.6), and present nocturnally (OR: 23.2; 95% CI: 4.3-126; P < .00001 for each). Of SHH cases, endocrine disease accounted for 57% (including diabetes mellitus [11], hyperthyroidism [4], and hyperpituitarism [1]). Neurologic disease accounted for 32% (including peripheral nerve injury [3], Parkinson's disease [2], reflex sympathetic dystrophy [2], spinal injury [1] and Arnold-Chiari malformation [1]). Malignancy (pheochromocytoma), respiratory disease, and psychiatric disease were each represented once. Compared to other secondary causes, asymmetric HH favored neurologic disease (OR: 63; 95% CI: 4.9-810); P = .0002).

LIMITATIONS

Results were obtained from a single, university-based population.

CONCLUSIONS

On the basis of these data, the diagnostic criteria for PHH were assessed statistically. Criteria include: excessive sweating of 6 months or more in duration, with 4 or more of the following: primarily involving eccrine-dense (axillae/palms/soles/craniofacial) sites; bilateral and symmetric; absent nocturnally; episodes at least weekly; onset at 25 years of age or younger; positive family history; and impairing daily activities. These criteria discriminate well between PHH and SHH (sensitivity: 0.99; specificity: 0.82; positive predictive value: 0.99; negative predictive value: 0.852) and may facilitate optimal clinical management.

A new simple method for assessing sudomotor function: relevance in type 2 diabetes

AIM

The current sudomotor function tests are too time-consuming to be used for diabetic patients in daily practice. EZSCAN is a new, patented technology that measures electrochemical skin conductance (ESC) through reverse iontophoresis and chronoamperometry. The aim of the present study was to assess the sensitivity, specificity and reproducibility of the method in type 2 diabetic patients in comparison to control subjects with no risk of diabetes.

METHODS

A total of 133 type 2 diabetic patients and 41 control subjects were tested. Participants placed their hands and feet on nickel electrodes, and an incremental low direct current was applied to the anode for 2 min. ESC was calculated from the resulting voltage and generated current. ESC diagnostic accuracy was analyzed by ROC curve modeling, and reproducibility was assessed using Bland-Altman analysis.

RESULTS

The ESC of hands and feet was significantly reduced in diabetic patients (53±16μSi and 67±14μSi, respectively) compared with control subjects (68±16μSi and 80±7μSi, respectively; P<0.0001). ESC values had a sensitivity of 75% and specificity of 100%, with an area under the ROC curve of 0.88 at a threshold of 50% on the EZSCAN scale. Coefficients of variation in hand and foot measurements were 15 and 7%, respectively.

CONCLUSION

The good sensitivity, specificity and reproducibility of EZSCAN make it a feasible alternative for assessing sudomotor dysfunction, a clinical manifestation of autonomic neuropathy in diabetic patients. The test takes<3 min to perform, and requires neither special patient preparation nor medical personnel training.

Sudomotor dysfunction is associated with foot ulceration in diabetes

AIM

To examine the relationship between sudomotor dysfunction and foot ulceration (FU) in patients with diabetes.

METHODS

Ninety patients with either Type 1 or Type 2 diabetes [30 without peripheral sensorimotor neuropathy (PN), 30 with PN but without FU and 30 with FU] were recruited in this cross-sectional study. Assessment of PN was based on neuropathy symptom score (NSS), neuropathy disability score (NDS) and vibration perception threshold (VPT). Sudomotor dysfunction was assessed using the sympathetic skin response (SSR). Cardiac autonomic nervous system activity was assessed by the battery of the classical autonomic function tests.

RESULTS

Patients with foot ulcers had longer duration of diabetes, higher values of VPT and NDS and lower values of the autonomic functions tests in comparison with the other study groups. Sudomotor dysfunction and cardiac autonomic neuropathy were significantly more common in the FU group. Multivariate logistic regression analysis after adjustment for gender, body mass index, duration of diabetes and glycated haemoglobin (HbA(1c)) demonstrated that the odds ratio (95% confidence intervals) of FU increased with measures of neuropathy such as NDS >or= 6 (10.2, 6.2-17.3) and VPT >or= 25 volts (19.8, 9.9-47.5), but was also significantly increased with absent SSR (15.3, 5.3-38.4).

CONCLUSIONS

Sudomotor dysfunction is associated with increased risk of FU and should be included in the screening tests for identification of diabetic patients at risk of ulceration.

Diabetes mellitus tipo 1 na ausência de neuropatia autonômica não altera a taxa de sudorese no exercício

A sudorese é o principal mecanismo autonômico termorregulatório na espécie humana. A taxa de sudorese (TS) durante o exercício pode ser influenciada por diversos fatores, entre eles doenças, como o diabetes mellitus tipo 1, cujos pacientes são vítimas potenciais de distúrbios termorregulatórios. Os exercícios regulares são recomendados para diabéticos e, inclusive, alguns deles tornam-se atletas. No entanto, ainda não foi medida a TS de diabéticos durante exercício progressivo até a exaustão (GXT) e comparada com a de indivíduos sadios com características antropométricas semelhantes. O presente estudo comparou a TS de sete voluntários diabéticos (DM) e sete controles (GC), semelhantes quanto à idade, gênero, composição corporal e capacidade aeróbica. Antes e após o GXT, foram medidos a gravidade específica da urina (GEU), o peso e a glicemia capilar. A TS global foi calculada dividindo-se a variação do peso pelo tempo de coleta e área de superfície corporal. A TS local do antebraço foi calculada utilizando-se a variação do peso de um filtro absorvente corrigido pela sua área e tempo de coleta. As TS locais do antebraço e da perna foram induzidas por iontoforese com pilocarpina (0,5%) no grupo DM. A freqüência cardíaca (FC) foi registrada antes, durante e após GXT. A temperatura média da pele (TMP) e as condições térmicas ambientais foram medidas durante o experimento. A glicemia capilar foi maior no DM, como o esperado. As TS global e local foram semelhantes entre os grupos, enquanto que a FC no repouso e a TMP no repouso e no exercício foram maiores no DM. Não houve diferença entre as TS do antebraço e da perna no DM com a pilocarpina. Concluiu-se que a resposta sudorípara foi semelhante entre diabéticos jovens e grupo controle durante exercício progressivo em ambiente temperado.

Use of Nanotechnology-Designed Footsock in the Management of Preulcerative Conditions in the Diabetic Foot: Results of a Single, Blind Randomized Study

The Difoprev system constituted by a sock loaded with nanocapsules containing a hydrating agent in the diabetic foot is tested. A total of 30 neuropathic outpatients with foot anhydrosis were randomized into group A, treated with the application of the sock with the nanocapsules, and group B wearing only the socks without the nanocapsules. Patients were blindly evaluated with a clinical score, hygrometry, transepidermal water loss, skin temperature, and skin hardness at baseline and after 6 weeks. No difference between the groups emerged at baseline. Although group B showed no changes at the end of the treatment, group A significantly ( P < .05) improved in all the parameters evaluated. No adverse events were recorded in both groups during the study. The use of hydrating agents carried by nanocapsules-loaded socks is safe and effective for the neuropathic diabetic foot.

Thermoregulatory sudomotor dysfunction and diabetic neuropathy develop in parallel in at-risk feet

AIMS

To establish the longitudinal relationship of foot complications to neuropathy based on a 4-year follow-up of diabetic patients stratified by sudomotor dysfunctions.

METHODS

One hundred and nineteen Type 2 diabetic patients and 36 non-diabetic subjects were initially registered in the prospective cohort study. Plantar skin temperature and sympathetic skin response (SSR) were used to monitor sympathetic mediated thermoregulation and sudomotor function. Peripheral somatic and central autonomic functions were studied using clinical, nerve conduction and cardiovascular reflex tests. At enrolment, the diabetic patients were classified into one of three groups by the progressive stages of sudomotor dysfunction: SSR+ (SSR present; 49 patients), SSR- (SSR absent; 41 patients) and at-risk group (SSR absent but with cracked skin involving partial thickness of the dermis; 29 patients).

RESULTS

The at-risk group had 13.4 times (95% confidence interval 1.4-125.7) higher plantar ulceration rates than the other two patient groups during the 4 years. Skin temperature elevation occurred in parallel with development of foot sweating problems. There were no significant differences between the three patient groups in the ratios of abnormal heart rate variation, orthostatic test and clinical neuropathy score at follow-up. After 4 years of follow-up, nerve conduction abnormalities were more frequent in the at-risk and SSR- groups than in the SSR+ group.

CONCLUSIONS

Early deterioration of small sympathetic fibres could not be quantified accurately by the clinical, somatic and autonomic tests. Assessing skin integrity and sudomotor function in at-risk individuals identifies early peripheral sympathetic neuropathy, even if the patients have no overt clinical symptoms.

Evaluation of the self-administered indicator plaster neuropad for the diagnosis of neuropathy in diabetes

OBJECTIVE

To evaluate the inter-rater reliability between patient and health care provider of the indicator plaster neuropad (IPN) in the diagnosis of peripheral neuropathy and the feasibility of the IPN.

RESEARCH DESIGN AND METHODS

A total of 156 patients with diabetes were examined. At the same visit, the IPN was evaluated by the health care provider. Afterward, the IPN with written instructions for its use and evaluation for self-testing at home were provided together with a questionnaire asking for the easiness of the IPN.

RESULTS

Neuropathy was diagnosed in 56.9% of the participants by the health care provider. The k statistic to measure overall agreement between patient and health care provider of the IPN was very good: 0.88 (95% CI 0.85-0.91). The indicated instructions and the IPN were evaluated as easy by the patients.

CONCLUSIONS

The high degree of reliability and the easiness of the IPN suggest that it is proper for self-testing for the identification of peripheral neuropathy.

Usefulness of a new indicator test for the diagnosis of peripheral and autonomic neuropathy in patients with diabetes mellitus

AIMS

The aim of the present study was to assess the performance of a new indicator test (NIT), based on the measurement of sweat production after exposure to dermal foot perspiration, in the diagnosis of both peripheral sensorimotor polyneuropathy (PSN) and autonomic neuropathy in patients with diabetes.

METHODS

One hundred and seventeen diabetic patients were examined. PSN was assessed using the neuropathy symptoms score, the neuropathy disability score and the vibration perception threshold. Cardiac autonomic neuropathy (CAN) was assessed using the battery of the four classical standardized tests proposed by Ewing et al., Diabetes Care 1985; 8: 491-498. Sudomotor dysfunction was assessed using the NIT.

RESULTS

Fifty patients (42.7%) had PSN and 44 patients (37.6%) had CAN. Of the 50 patients with PSN, 43 had a positive NIT (sensitivity 86%) and, out of the 67 patients without PSN, a negative NIT was obtained in 45 patients (specificity 67%). The positive and the negative predictive value of the NIT in detecting PSN were 66.2 and 86.5%, respectively. The sensitivity and specificity of NIT in detecting CAN was 59.1 and 46.5%, respectively. In the case of severe CAN, the sensitivity was increased to 80.9% and the specificity to 50%.

CONCLUSIONS

The NIT has good sensitivity and negative predictive value for diagnosis of PSN and can be used as a screening method for detection of this complication in patients with diabetes. In addition, the test has a low sensitivity for detection of autonomic neuropathy in patients with milder forms of CAN.

Sensitivity and specificity of a new indicator test (Neuropad) for the diagnosis of peripheral neuropathy in type 2 diabetes patients: a comparison with clinical examination and nerve conduction study

OBJECTIVE

The objective of this study was to evaluate the sensitivity and specificity of a new indicator test (Neuropad) for the diagnosis of peripheral neuropathy in type 2 diabetes patients as compared with clinical examination and nerve conduction study (NCS).

PATIENTS AND METHODS

This study included 120 type 2 diabetes patients (58 men) with a mean age of 67.3 +/- 5.9 years and a mean diabetes duration of 13.1 +/- 3.2 years. Diabetic neuropathy was diagnosed through the Neuropathy Disability Score. An NCS was performed on radial, ulnar, sural, and common and deep peroneal nerves. Patients were also examined with the new indicator test. The "time to complete color change of the test" from blue to pink was recorded. The test was considered abnormal in patients who exhibited a time to complete color change of the test exceeding 600 s in at least one foot.

RESULTS

Neuropathy was diagnosed by clinical examination in 83 (69.2%) patients. The sensitivity of the indicator test for clinical neuropathy was 95.2%, and its specificity was 67.6%. The sensitivity of NCS for clinical neuropathy was 94%, and its specificity was 62.1%. The sensitivity of the indicator test for abnormal NCS was 97.8%, and its specificity was 96.4%.

CONCLUSIONS

The new indicator test has a very high sensitivity not only for the diagnosis of clinical neuropathy but also for the diagnosis of neurophysiological neuropathy. Specificity is moderately high for the diagnosis of clinical neuropathy, while it is particularly high for the diagnosis of neurophysiological neuropathy. The indicator test has a validity comparable to that of NCS for the diagnosis of diabetic neuropathy. Finally, the time to complete color change of the test is associated with the severity of nerve conduction impairment.

Impaired glucose tolerance is associated with postganglionic sudomotor impairment

We compared quantitative sudomotor axon-reflex test responses in persons with normal and impaired glucose tolerance (IGT). Responses were significantly impaired in those with IGT, which may be indicative of early distal small fiber neuropathy.

Autonomic nerve testing predicts the development of complications: a 12-year follow-up study

OBJECTIVE

Cardiac autonomic nerve tests have predicted increased mortality in adults with diabetes, predominantly due to nephropathy, cardiac disease, and hypoglycemia. The significance of subclinical autonomic nerve test abnormalities has not been systematically studied in adolescents. We aimed to reassess an adolescent cohort, whose autonomic nervous system had been tested 12 years earlier by both pupillometry and cardiovascular tests.

RESEARCH DESIGN AND METHODS

From 1990 to 1993, adolescents with type 1 diabetes (n = 335) were assessed for autonomic neuropathy (median age 14.7 years [interquartile range 13.0-16.8], duration of diabetes 6.3 years [4.0-9.6], and A1C 8.3% [7.5-9.4]). Between 2003 and 2005, contact was made with 59% of the original group. Individual assessment 12 years later included completion of a validated hypoglycemia unawareness questionnaire (n = 123) and urinary albumin-to-creatinine ratio (n = 99) and retinal (n = 102) screening, as well as analysis of reports from external doctors (n = 35).

RESULTS

At baseline, there was no difference in age, duration of diabetes, or complications between those who participated in the follow-up phase (n = 137) and those who did not participate (n = 196). However, baseline A1C was lower in the follow-up participants (8.2 vs. 8.5% for participants vs. nonparticipants, respectively, P = 0.031). At 12 years of follow-up, 93% were aware and 7% were unaware that they had hypoglycemia; 32 (31%) had no retinopathy, but 10% required laser therapy, and 80 (81%) had no microalbuminuria. Small pupil size at baseline was independently associated with the development of microalbuminuria (odds ratio 4.36 [95% CI 1.32-14.42], P = 0.016) and retinopathy (4.83 [1.3-17.98], P = 0.019) but not with the development of hypoglycemia unawareness. There was no association with baseline cardiovascular tests and the development of complications 12 years later.

CONCLUSIONS

In this study, we found an association between baseline pupillometry tests and the presence of microalbuminuria and retinopathy at 12 years of follow-up. This suggests that pupillometry abnormalities may be early indicators of patients who are at high risk of future microvascular disease.

Sympathetic sudomotor disturbance in early type 1 diabetes mellitus is linked to lipid peroxidation

The present study was performed to determine whether increased lipid peroxidation, as assessed from malondialdehyde (MDA) excretion, is associated with deterioration in peripheral nerve function in early type 1 diabetes mellitus. These parameters were measured annually for 3 years in 36 patients who entered the study less than 2 years after the diagnosis of diabetes. Malondialdehyde excretion was 1.51 +/- 0.20 micromol/g creatinine in the controls, and 2.43 +/- 0.21, 2.39 +/- 0.22, and 1.93 +/- 0.21 micromol/g creatinine at the first, second, and third evaluations, respectively (P < .005). The increased MDA was seen only in the female participants. Malondialdehyde excretion was increased in those with high vs low hemoglobin Alc across all years (P < .05). Malondialdehyde excretion correlated negatively with sudomotor function below the waist. The mean sweat production from the 3 evaluations correlated with mean MDA excretion across all years in the proximal leg (r = -0.42, P < .005) and distal leg (r = -0.40, P < .01). Below the waist, sweating correlated with MDA (r = -0.40, P < .01) as did total sweat (r = -0.38, P < .01). The response amplitudes of the peroneal nerves correlated negatively with MDA excretion (for the mean values at the second 2 evaluations, P < .005, r = -0.45). Tests of sensory function correlated inconsistently with MDA excretion. In summary, lipid peroxidation, as assessed from malondialdehyde excretion, is associated with sudomotor dysfunction in early diabetes.

Peripheral nerve functions may deteriorate parallel to the progression of microangiopathy in diabetic patients

Our aim was to obtain information to help in the early detection of impaired nerve function and to assess the severity of diabetic symmetric polyneuropathy (DPN). Various somatic and autonomic nerve functions in 40 diabetics and 20 age-matched healthy volunteers were evaluated using six objective examinations: nerve conduction study, quantitative vibratory perception threshold, heart rate variability, Valsalva test, head-up tilt and quantitative sudomotor axonal reflex test (QSART). The diabetics were divided into three groups according to the severity of their microangiopathy. The nerve function data and level of impairment were compared between a healthy control and three diabetic groups. The relationships between nerve function data and clinical background were also examined using multivariate analysis. Results were as follows: (1) all nerve dysfunctions seemed to develop parallel to the progression of microangiopathy, (2) reduced nerve conduction velocity and elevated vibratory perception thresholds in the feet might be early detectable signs of DPN, (3) vasomotor and sudomotor sympathetic functions and cardiovagal functions seemed to deteriorate with the appearance of microangiopathy, (4) lowered compound muscle action potential seemed to appear at the advanced microangiopathic condition, (5) hypohydrosis was closely related to diabetic foot ulcers. In conclusion, nerve dysfunction in diabetics might generally progress with microangiopathy from somatic sensory nerve dysfunction to autonomic nerve dysfunction and then to somatic motor nerve dysfunction. Sympathetic sudomotor dysfunction might be a sensitive predictor of diabetic foot ulcer.

Relationship of skin temperature to sympathetic dysfunction in diabetic at-risk feet

The relationship of plantar skin temperature to diabetic neuropathy was studied using clinical, nerve conduction and autonomic evaluations. The sympathetic skin response (SSR) was found present in both feet of 25 control subjects and 29 (out of 69) diabetic patients (SSR+ group). For those diabetic patients absent with the SSR in both feet, 18 patients (at-risk group) had preulcerative skin lesions (dry and fissured skin) and 22 did not (SSR- group). The at-risk group showed significantly higher mean foot temperature (30.2+/-1.3 degrees Celsius) than the SSR- (27.9+/-1.7 degrees Celsius), the SSR+ (27.1+/-2.0 degrees Celsius) and the control group (26.8+/-1.8 degrees Celsius). The SSR- group had smaller temperature differences (7.2+/-1.7 degrees Celsius versus 8.6+/-1.6 degrees Celsius, p<0.05) and smaller normalized temperature (referencing to the forehead temperature) (0.19 versus 0.24, p<0.01) than the SSR+ group. Although the three diabetic groups had no significant differences in clinical and cardiovascular abnormalities, the at-risk group showed more nerve conduction abnormalities than the SSR- and SSR+ groups (55% versus 23% and 14%, p<0.02). This study indicated that the thermoregulatory sweating abnormality signified early sympathetic damage in diabetic feet. Assessing skin conditions and sudomotor activities should help identify small fiber neuropathy in diabetic patients with at-risk feet conditions.

Differential impairment of the sudomotor and nociceptor axon-reflex in diabetic peripheral neuropathy

It is not known whether C-fiber functional subclasses are differentially affected by diabetes mellitus or whether the patterns of C-fiber dysfunction are different between type 1 and type 2 diabetes. We therefore examined efferent sympathetic sudomotor and primary afferent nociceptor C-fiber function in diabetic patients. Acetylcholine (10%) was used to evoke C-fiber (axon-reflex)-mediated responses. The nociceptor (flare) response was measured using a laser Doppler device. The sudomotor response was quantified with silastic imprints. The nociceptor C-fiber-mediated flare response was reduced in type 2 diabetic patients (P < 0.008) but was similar to controls in type 1 diabetic patients. The sympathetic C-fiber-mediated responses, including sweat volume (P < 0.05) and the number of activated sweat glands (P = 0.003), were increased in patients with type 1 diabetes. There also was a trend toward a larger axon-reflex sweat area in patients with type 1 diabetes (P = 0.09). No differences in these sweat responses were found in patients with type 2 diabetes compared to controls. These findings suggest that the functional abnormalities in diabetic peripheral neuropathy are not homogeneous and that C-fiber subclasses are differentially affected in type 1 and 2 diabetes mellitus.

Foot temperature in diabetic polyneuropathy: innocent bystander or unrecognized accomplice?

AIM

To explore mechanisms by which temperature could influence the pathogenesis and symptoms of diabetic polyneuropathy.

METHODS

We conducted a literature review attempting to identify mechanisms by which diabetic polyneuropathy could be affected by temperature.

RESULTS

Cooling can theoretically hasten the progression of diabetic polyneuropathy through several different mechanisms. Specifically, cooling can enhance neuronal ischaemia, increase formation of reactive oxygen species, slow axonal transport, increase protein kinase C activity, and interfere with immune function. Short-term temperature fluctuations (both warming and cooling) can initiate and exacerbate neuropathic pain by causing neuronal hyperexcitability and functional deafferentation. Although normal fluctuations of distal extremity temperature may be sufficient for these effects, impaired thermoregulation may make the distal extremities more susceptible to temperature extremes. Eventually, a 'vicious cycle' may ensue, resulting in neuronal deterioration with further disruption of temperature regulation. Limited epidemiological data suggest a higher prevalence of diabetic polyneuropathy in populations living in colder locations, supporting our hypothesis.

CONCLUSIONS

Variations in foot temperature may play an important but as yet unrecognized role in the development and symptoms of diabetic polyneuropathy. Further basic and clinical research exploring this concept could help elucidate the natural history of diabetic polyneuropathy and lead to novel therapeutic strategies.

Sympathetic and parasympathetic neuropathy are frequent in both type 1 and type 2 diabetic patients

OBJECTIVE

The aim of this study was to evaluate the frequency of sympathetic versus parasympathetic neuropathy among type 1 and type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

There were 43 patients with type 1 and 17 with type 2 diabetes who were investigated. Sympathetic nerve function was assessed by measurement of the vasoconstriction (VAC) index by laser Doppler perfusion imaging of a locally heated finger followed by indirect cooling. Parasympathetic nerve function was assessed by R-R interval variation during deep breathing as measured by the expiration/inspiration (E/I) ratio. Results were expressed as age-corrected z scores in SD; VAC index >1.64 SD and E/I ratio <-1.64 SD were considered abnormal.

RESULTS

VAC index was abnormal in 40% with type 1 and 41% with type 2 diabetes, whereas the E/I ratio was abnormal in 42% with type 1 and 65% with type 2 diabetes. There was a clear association between VAC index and E/I ratio among type 1 (rs=0.525; P=0.0002) but not among type 2 (rs=0.10) diabetic patients. Among type 2 diabetic patients, the degree of dysfunction was most severe regarding parasympathetic function (P=0.0167).

CONCLUSIONS

Sympathetic and parasympathetic neuropathy were frequent in both type 1 and type 2 diabetic patients. However, there was a difference between the two types of diabetes. Sympathetic and parasympathetic nerve functions correlated in type 1 but not in type 2 diabetic patients. The explanation for this discrepancy might be that parasympathetic nerve function was most severely affected among type 2 diabetic patients.

Chemically and electrically induced sweating and flare reaction

Both thin afferent (nociceptors) and efferent (sympathetic sudomotor) nerve fibers can be activated electrically and chemically, resulting in neurogenic erythema and sweating. These reactions have been used before to assess the impairment of sympathetic and nociceptor fibers in humans. In this study, electrically induced sweating and erythema were assessed simultaneously in the foot dorsum and thigh, and were compared to chemically induced activation. Reproducible intensity-response relations (stimulation intensities 0-30 mA, 1 Hz) were obtained from 32 subjects. The steepest increase of the sweat response was induced at lower intensities as compared to that of the erythema (18.3 mA vs. 25.7 mA, p<0.01) and reached a plateau for intensities above 25 mA, suggesting lower electrical thresholds for sudomotor fibers. Maximum flare areas induced electrically with 30 mA were smaller than those evoked chemically (flare size: 4.5 cm2 vs. 10.6 cm2). In contrast, the electrically evoked sweating rate was higher than that evoked chemically (acetylcholine, or ACh; sweating rate 0.31 vs. 0.21 microl/cm2/min, p<0.01), which might be attributed to an increased effectiveness of synchronized discharge in sympathetic fibers upon electrical stimulation.

Blunted circadian variation in autonomic regulation of sinus node function in veterans with Gulf War syndrome

PURPOSE

To test the hypothesis that subtle abnormalities of the autonomic nervous system underlie the chronic symptoms reported by many Gulf War veterans, such as chronic diarrhea, dizziness, fatigue, and sexual dysfunction.

METHODS

Twenty-two ill Gulf War veterans and 19 age-, sex-, and education-matched control veterans underwent measurement of circadian rhythm of heart rate variability by 24-hour electrocardiography, ambulatory blood pressure recording, Valsalva ratio testing, sympathetic skin response evaluation, sweat imprint testing, and polysomnography. Investigators were blinded to case- or control-group status.

RESULTS

High-frequency spectral power of heart rate variability increased normally 2.2-fold during sleep in controls but only 1.2-fold in ill veterans (P <0.0001). In ill veterans as compared with controls, it was lower at night (P = 0.0006), higher during the morning (P = 0.007), but no different during the rest of the day (P = 0.8). The mean heart rate of ill veterans also declined less at night (P = 0.0002), and their corrected QT intervals tended to be longer over the full 24 hours (P = 0.07), particularly at night (P = 0.03). Blunting of the nocturnal heart rate dip in ill veterans was confirmed by 24-hour automatic ambulatory blood pressure monitoring (P = 0.05) and polysomnography (P = 0.03). These differences remained significant after adjusting for potential confounders. Cases and controls were similar on measures of sympathetic adrenergic and sudomotor function, sleep architecture, respiratory function, and circadian variation in blood pressure and body temperature.

CONCLUSION

Some symptoms of Gulf War syndrome may be due to subtle autonomic nervous system dysfunction.

Nitrosative stress, uric Acid, and peripheral nerve function in early type 1 diabetes

The present study was performed to determine whether nitric oxide overproduction is associated with deterioration in peripheral nerve function in type 1 diabetes. We measured peripheral nerve function and biochemical indicators of nitrosative stress annually for 3 years in 37 patients with type 1 diabetes. Plasma nitrite and nitrate (collectively NO(x)) were 34.0 +/- 4.9 micro mol/l in the control subjects and 52.4 +/- 5.1, 50.0 +/- 5.1, and 49.0 +/- 5.2 in the diabetic patients at the first, second, and third evaluations, respectively (P < 0.01). Nitrotyrosine (NTY) was 13.3 +/- 2.0 micro mol/l in the control subjects and 26.8 +/- 4.4, 26.1 +/- 4.3, and 32.7 +/- 4.3 in the diabetic patients (P < 0.01). Uric acid was suppressed by 20% in the diabetic patients (P < 0.001). Composite motor nerve conduction velocity for the median, ulnar, and peroneal nerves was decreased in patients with high versus low NTY (mean Z score -0.522 +/- 0.25 versus 0.273 +/- 0.22; P < 0.025). Patients with high NO(x) had decreased sweating, and those with suppressed uric acid had decreased autonomic function. In conclusion, nitrosative stress in early diabetes is associated with suppressed uric acid and deterioration in peripheral nerve function.