Large-fiber dysfunction in diabetic peripheral neuropathy is predicted by cardiovascular risk factors

Comprehensive Assessment of Neuropathy and Metabolic Parameters in Type 1 Diabetic Patients with or Without Using Continuous Glucose Sensors

The present study was conducted in type 1 diabetic (T1DM) patients to evaluate the metabolic and glycemic control as well as the manifestations of neuropathy. The impact of continuous glucose monitoring (CGM) on the measured parameters was also analyzed. A total of 61 T1DM patients (age: 42.5 ± 1.8 years, DM duration: 22.8 ± 1.6 years, mean ± SE) participated in the study. In total, 24 patients had CGM sensors and 37 did not. Cardiovascular autonomic neuropathy was assessed using cardiovascular reflex tests. Peripheral sensory function was evaluated by a Neurometer and calibrated tuning fork on the upper and lower limbs. Metabolic status was characterized by the determination of triglycerides, high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol, and glycated haemoglobin (HbA1c). A positive correlation was found between HbA1c and triglyceride levels (r = 0.28, p < 0.05). CGM users and non-users differed in triglyceride (0.9 ± 0.1 vs. 1.24 ± 0.12 mmol/L, p < 0.05), HDL cholesterol (1.7 ± 0.1 vs. 1.4 ± 0.1 p < 0.05 mmol/L), and HbA1c (7.5 ± 0.2 vs. 8.3 ± 0.3%, p < 0.05) levels as well. Significant differences were found for the Valsalva ratio, Neurometer, and calibrated tuning fork results between CGM users and non-users. This study found a significant correlation between HbA1c and triglyceride levels in T1DM. CGM use resulted in improved metabolic parameters and less autonomic and sensory nerve damage. As a novel finding, CGM is presumed to prevent both micro-, and macrovascular complications and, by this way, potentially reducing mortality rates.

Association between phase angle and diabetic peripheral neuropathy in Type 2 diabetes patients

BACKGROUND

Diabetic peripheral neuropathy (DPN), the very prevalent microvascular complication of type 2 diabetes mellitus (T2DM), severely threatens the quality of life of diabetic patients. Thus, prevention of DPN is extremely important for public health, and the identification of potential biomarkers may help with early prevention. Our work determined the association between phase angles (PhAs) and the risk of DPN in T2DM patients.

MATERIALS AND METHODS

This cross-sectional study recruited 697 T2DM patients from the Third Affiliated Hospital of Soochow University. All patients were divided into the non-diabetic peripheral neuropathy group and diabetic peripheral neuropathy group, and the DPN group was further divided into low, medium, and high diabetic foot ulcer risk groups according to vibration perception threshold results. Using univariate and multivariate logistic regression analyses continuously, the relationship between PhAs (arms, legs, trunk, and whole body) and the risk of DPN were evaluated. Further analysis was conducted on different subgroups of the study population.

RESULTS

After adjusting for the potential covariates, multivariate logistic regression analyses indicated that PhAs of the arms, legs, and whole body correlated inversely with the risk of DPN. However, the PhA of the trunk had no significant correlation with DPN. According to the stratified subgroup analysis, the negative association between PhA of the whole body and the risk of DPN remained significant in the sex and BMI group except for participants with BMI ≥ 28 kg/m².

CONCLUSIONS

For the first time, PhAs were acknowledged to be independently associated with DPN. Further exploration is needed to explain the findings.

The impact of obstructive sleep apnea treatment on microvascular complications in patients with type 2 diabetes: a feasibility randomized controlled trial

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with an increased risk of diabetes-related complications. Hence, it is plausible that continuous positive airway pressure (CPAP) could have a favorable impact on these complications. We assessed the feasibility of conducting a randomized control trial in patients with type 2 diabetes and OSA over 2 years.

METHODS

We conducted an open-label multicenter feasibility randomized control trial of CPAP vs no CPAP in patients with type 2 diabetes and OSA. Patients with resting oxygen saturation < 90%, central apnea index > 15 events/h, or Epworth Sleepiness Scale ≥ 11 were excluded. OSA was diagnosed using a multichannel portable device (ApneaLink Air, ResMed). The primary outcome measures were related to feasibility and the secondary outcomes were changes in various clinical and biochemical parameters related to diabetes outcomes.

RESULTS

Eighty-three (40 CPAP vs 43 no CPAP) patients were randomly assigned, with a median (interquartile range) follow-up of 645 (545, 861) days. CPAP compliance was inadequate, with a median usage of approximately 3.5 hours/night. Early CPAP use predicted longer-term compliance. The adjusted analysis showed a possible favorable association between being randomly assigned to CPAP and several diabetes-related end points (chronic kidney disease, neuropathy, and quality of life).

CONCLUSIONS

It was feasible to recruit, randomly assign, and achieve a high follow-up rate over 2 years in patients with OSA and type 2 diabetes. CPAP compliance might improve by a run-in period before randomization. A full randomized control trial is necessary to assess the observed favorable association between CPAP and chronic kidney disease , neuropathy, and quality of life in patients with type 2 diabetes.

CLINICAL TRIAL REGISTRATION

Registry: ISRCTN; Name: The impact of sleep disorders in patients with type 2 diabetes; URL: https://www.isrctn.com/ISRCTN12361838; Identifier: ISRCTN12361838.

CITATION

Makhdom EA, Maher A, Ottridge R, et al. The impact of obstructive sleep apnea treatment on microvascular complications in patients with type 2 diabetes: a feasibility randomized controlled trial. J Clin Sleep Med. 2024;20(6):947-957.

Biomarkers and signaling pathways of diabetic nephropathy and peripheral neuropathy: possible therapeutic intervention of rutin and quercetin

Diabetic nephropathy and peripheral neuropathy are the two main complications of chronic diabetes that contribute to high morbidity and mortality. These conditions are characterized by the dysregulation of multiple molecular signaling pathways and the presence of specific biomarkers such as inflammatory cytokines, indicators of oxidative stress, and components of the renin-angiotensin system. In this review, we systematically collected and collated the relevant information from MEDLINE, EMBASE, ELSEVIER, PUBMED, GOOGLE, WEB OF SCIENCE, and SCOPUS databases. This review was conceived with primary objective of revealing the functions of these biomarkers and signaling pathways in the initiation and progression of diabetic nephropathy and peripheral neuropathy. We also highlighted the potential therapeutic effectiveness of rutin and quercetin, two plant-derived flavonoids known for their antioxidant and anti-inflammatory properties. The findings of our study demonstrated that both flavonoids can regulate important disease-promoting systems, such as inflammation, oxidative stress, and dysregulation of the renin-angiotensin system. Importantly, rutin and quercetin have shown protective benefits against nephropathy and neuropathy in diabetic animal models, suggesting them as potential therapeutic agents. These findings provide a solid foundation for further comprehensive investigations and clinical trials to evaluate the potential of rutin and quercetin in the management of diabetic nephropathy and peripheral neuropathy. This may contribute to the development of more efficient and comprehensive treatment approaches for diabetes-associated complications.

Diabetic Sensorimotor Polyneuropathy: An Overview on Epidemiology, Risk Factors, Classification, Diagnosis, and Treatment

Diabetic distal symmetric sensorimotor polyneuropathy (DSPN) is a common complication of diabetes with devastating consequences. Hyperglycaemia is the major aetiological factor, while emerging data demonstrate that cardiometabolic risk factors also contribute to its development. Diagnosis of DSPN involves interview of medical and neurological history, foot inspection, and sensory and motor function examination with specific tests such as temperature and pinprick perception for small nerve fibers, and vibration and light touch assessments for large nerve fibers. Management includes optimised glycaemic control, treatment of cardiovascular risk factors, and symptomatic treatment aiming at improving life quality. This article provides an overview on epidemiology, risk factors, classification, diagnosis and current treatment of DSPN.

MACHINE LEARNING ANALYSIS OF THE UK BIOBANK REVEALS PROGNOSTIC AND DIAGNOSTIC IMMUNE BIOMARKERS FOR POLYNEUROPATHY AND NEUROPATHIC PAIN IN DIABETES

AIMS

We assessed the health data of 11,047 people with diabetes in the UK Biobank to rank 329 risk factors for diabetic polyneuropathy (DPN) and DPN with chronic neuropathic pain without a priori assumption.

METHODS

The Integrated Disease Explanation and Risk Scoring (IDEARS) platform applies machine learning algorithms to multimodal data to determine individual disease risk, and rank risk factor importance using mean SHapley Additive exPlanations (SHAP) score.

RESULTS

IDEARS models showed discriminative performances with AUC > 0.64. Lower socioeconomic status, being overweight, poor overall health, cystatin C, HbA1C, and immune activation marker, C-reactive protein (CRP), predict DPN risk. Neutrophils and monocytes were higher in males and lymphocytes lower in females with diabetes that develop DPN. Neutrophil-to-Lymphocyte Ratio (NLR) was increased and IGF-1 levels decreased in people with type 2 diabetes that later develop DPN. CRP was significantly elevated in those with DPN and chronic neuropathic pain compared to DPN without pain.

CONCLUSIONS

Lifestyle factors and blood biomarkers predict the later development of DPN and may relate to DPN pathomechanisms. Our results are consistent with DPN as a disease involving systemic inflammation. We advocate for the use of these biomarkers clinically to predict future DPN risk and improve early diagnosis.

Hypertension the 'Missed Modifiable Risk Factor' for Diabetic Neuropathy: a Systematic Review

Diabetes and hypertension stand as the major non-infectious diseases affecting 34.2 million and 1.28 billion people respectively. The literature on the impact of diabetes on hypertension and vice versa is evolving. The major objectives of this review were to compile the evolving literature establishing the role of hypertension in diabetic neuropathy, derive the exact mechanisms for its pathogenesis, and describe evidence-based precise individualized management of diabetic neuropathy in patients having diabetes complicated by hypertension. A systematic review was conducted by searching databases of PubMed, Embase, and Scopus covering the literature from inception to 2022. We included all observational and experimental studies, including both human and animal studies looking into the correlation between diabetic neuropathy and hypertension. Hypertension poses to be the leading modifiable risk factor for the development of diabetic neuropathy, especially distal symmetrical polyneuropathy, producing abnormal nerve conduction parameters and increased vibration perception threshold in patients with diabetes mellitus. Thus, we advocate that good glycemic control in patients with diabetes needs to be supported with strict blood pressure control for preventing and delaying the onset of diabetic neuropathy.

The co-existence of sensory and autonomic neuropathy in type 1 diabetes with and without pain

AIMS

To investigate the co-existence of diabetic peripheral neuropathy (DPN), painful diabetic peripheral neuropathy (PDPN), and cardiac autonomic neuropathy (CAN) and to establish a model to predict CAN based on peripheral measurements.

METHODS

Eighty participants (20 type 1 diabetes (T1DM) + PDPN, 20 T1DM + DPN, 20 T1DM-DPN (without DPN), and 20 healthy controls (HC)) underwent quantitative sensory testing, cardiac autonomic reflex tests (CARTs), and conventional nerve conduction. CAN was defined as ≥ 2 abnormal CARTs. After the initial analysis, the participants with diabetes were re-grouped based on the presence or absence of small (SFN) and large fibre neuropathy (LFN), respectively. A prediction model for CAN was made using logistic regression with backward elimination.

RESULTS

CAN was most prevalent in T1DM + PDPN (50%), followed by T1DM + DPN (25%) and T1DM-DPN and HC (0%). The differences in prevalence of CAN between T1DM + PDPN and T1DM-DPN/HC were significant (p < 0.001). When re-grouping, 58% had CAN in the SFN group and 55% in the LFN group, while no participants without either SFN or LFN had CAN. The prediction model had a sensitivity of 64%, a specificity of 67%, a positive predictive value of 30%, and a negative predictive value of 90%.

CONCLUSION

This study suggests that CAN predominantly co-exists with concomitant DPN.

Corneal Confocal Microscopy Identifies People with Type 1 Diabetes with More Rapid Corneal Nerve Fibre Loss and Progression of Neuropathy

There is a need to accurately identify patients with diabetes at higher risk of developing and progressing diabetic peripheral neuropathy (DPN). Fifty subjects with Type 1 Diabetes Mellitus (T1DM) and sixteen age matched healthy controls underwent detailed neuropathy assessments including symptoms, signs, quantitative sensory testing (QST), nerve conduction studies (NCS), intra epidermal nerve fiber density (IENFD) and corneal confocal microscopy (CCM) at baseline and after 2 years of follow-up. Overall, people with type 1 diabetes mellitus showed no significant change in HbA1c, blood pressure, lipids or neuropathic symptoms, signs, QST, neurophysiology, IENFD and CCM over 2 years. However, a sub-group (n = 11, 22%) referred to as progressors, demonstrated rapid corneal nerve fiber loss (RCNFL) with a reduction in corneal nerve fiber density (CNFD) (p = 0.0006), branch density (CNBD) (p = 0.0002), fiber length (CNFL) (p = 0.0002) and sural (p = 0.04) and peroneal (p = 0.05) nerve conduction velocities, which was not related to a change in HbA1c or cardiovascular risk factors. The majority of people with T1DM and good risk factor control do not show worsening of neuropathy over 2 years. However, CCM identifies a sub-group of people with T1DM who show a more rapid decline in corneal nerve fibers and nerve conduction velocity.

Magnetic Resonance Neurography Reveals Smoking-Associated Decrease in Sciatic Nerve Structural Integrity in Type 2 Diabetes

Objective

It is controversially discussed in how far smoking contributes to diabetic polyneuropathy (DPN) in type 2 diabetes (T2D). Diffusion-weighted magnetic resonance neurography (MRN) at 3 Tesla has been shown to provide objective values for structural nerve integrity in patients with T2D. The aim of this study was to investigate the contribution of cigarette smoking on structural nerve integrity in T2D.

Methods

This cross-sectional prospective cohort study investigated the structural integrity of the sciatic nerve in 10 smokers, 40 never-smokers, and 20 ex-smokers with T2D and 10 healthy control subjects, using diffusion tensor imaging MRN at 3 Tesla and semi-automated nerve fiber tracking. Results were correlated with clinical, electrophysiological, and serological data.

Results

The sciatic nerve’s fractional anisotropy (FA), a parameter for structural nerve integrity, was significantly lower in smokers with T2D when compared to controls (p = 0.002) and never-smokers (p = 0.015), and lower in ex-smokers when compared to controls (p = 0.015). In addition, sciatic nerve radial diffusivity, a marker of myelin damage, was increased in smokers versus controls and never-smokers (p = 0.048, p = 0.049, respectively). Furthermore, FA in T2D patients was negatively correlated with clinical and electrophysiological markers of DPN. FA also showed negative correlations with the pulse wave velocity, a marker of arterial stiffness and associated microangiopathy, in controls (r = −0.70; p = 0.037), never-smokers (r = −0.45; p = 0.004), ex-smokers (r = −0.55; p = 0.009), and a similar trend in smokers (r = −0.63; p = 0.076). Negative correlations were found between FA and skin auto-fluorescence, a marker of tissue advanced glycation end product accumulation and therefore long-term glycemic stress in T2D, in never-smokers (r = −0.39; p = 0.020) and smokers (r = −0.84; p = 0.004), but not in ex-smokers (r = −0.07; p = 0.765).

Conclusion

The findings indicate that smoking contributes to sciatic nerve damage in T2D, potentially worsening DPN due to glycemic stress and less microangiopathy-associated myelin damage in active smokers, while angiopathic effects predominate in ex-smokers. To stop smoking may therefore pose a promising preventive measure to slow the progression of DPN in T2D.

Diabetic neuropathy: A narrative review of risk factors, classification, screening and current pathogenic treatment options (Review)

Diabetic neuropathy (DN) is a frequent complication of diabetes mellitus (DM) with severe consequences as it progresses and influences all human body systems. This review discusses the risk factors for DN, the main characteristics of the clinical forms of DN, the screening methods and the current therapeutic options. Distal symmetric DN is the primary clinical form, and DM patients should be screened for this complication. The most important treatment of DN remains good glucose control, generally defined as HbA1c ≤7%. Symptomatic treatment improves life quality in diabetic patients. Pharmacological agents such as alpha (α)-lipoic acid and benfotiamine have been validated in several studies since they act on specific pathways such as increased oxidative stress (α-lipoic acid exerts antioxidant effects) and the excessive production of advanced glycosylation products (benfotiamine may inhibit their production via the normalization of glucose). Timely diagnosis of DN is significant to avoid several complications, including lower limb amputations and cardiac arrhythmias.

Non-glucose risk factors in the pathogenesis of diabetic peripheral neuropathy

In this review, we consider the diverse risk factors in diabetes patients beyond hyperglycemia that are being recognized as contributors to diabetic peripheral neuropathy (DPN). Interest in such alternative mechanisms has been encouraged by the recognition that neuropathy occurs in subjects with metabolic syndrome and pre-diabetes and by the reporting of several large clinical studies that failed to show reduced prevalence of neuropathy after intensive glucose control in patients with type 2 diabetes. Animal models of obesity, dyslipidemia, hypertension, and other disorders common to both pre-diabetes and diabetes have been used to highlight a number of plausible pathogenic mechanisms that may either damage the nerve independent of hyperglycemia or augment the toxic potential of hyperglycemia. While pathogenic mechanisms stemming from hyperglycemia are likely to be significant contributors to DPN, future therapeutic strategies will require a more nuanced approach that considers a range of concurrent insults derived from the complex pathophysiology of diabetes beyond direct hyperglycemia.

Troponin T Parallels Structural Nerve Damage in Type 2 Diabetes: A Cross-sectional Study Using Magnetic Resonance Neurography

Clinical studies have suggested that changes in peripheral nerve microcirculation may contribute to nerve damage in diabetic polyneuropathy (DN). High-sensitivity troponin T (hsTNT) assays have been recently shown to provide predictive values for both cardiac and peripheral microangiopathy in type 2 diabetes (T2D). This study investigated the association of sciatic nerve structural damage in 3 Tesla (3T) magnetic resonance neurography (MRN) with hsTNT and N-terminal pro-brain natriuretic peptide serum levels in patients with T2D. MRN at 3T was performed in 51 patients with T2D (23 without DN, 28 with DN) and 10 control subjects without diabetes. The sciatic nerve's fractional anisotropy (FA), a marker of structural nerve integrity, was correlated with clinical, electrophysiological, and serological data. In patients with T2D, hsTNT showed a negative correlation with the sciatic nerve's FA (r = -0.52, P < 0.001), with a closer correlation in DN patients (r = -0.66, P < 0.001). hsTNT further correlated positively with the neuropathy disability score (r = 0.39, P = 0.005). Negative correlations were found with sural nerve conduction velocities (NCVs) (r = -0.65, P < 0.001) and tibial NCVs (r = -0.44, P = 0.002) and amplitudes (r = -0.53, P < 0.001). This study is the first to show that hsTNT is a potential indicator for structural nerve damage in T2D. Our results indirectly support the hypothesis that microangiopathy contributes to structural nerve damage in T2D.

Foot ulceration and its association with mortality in diabetes mellitus: a meta-analysis

BACKGROUND

Diabetic foot ulcers portend an almost twofold increase in all-cause mortality compared with diabetes on its own.

AIM

To investigate the association between diabetic foot ulcers and risk of death.

METHODS

We performed a meta-analysis of all observational studies investigating the association between diabetic foot ulcers and all-cause mortality. Risk ratios and risk differences were pooled in a random-effects model. The I² statistic was used to quantify heterogeneity between studies.

RESULTS

Altogether, we identified 11 studies that reported 84 131 deaths from any cause in 446 916 participants with diabetes during a total of 643 499 person-years of follow-up. The crude event rate for all-cause mortality in individuals with diabetes who did not develop foot ulceration was 22% lower at 181.5 deaths (per 1000 person-years) than in those who developed foot ulcers (230.8 per 1000 person-years). Diabetic foot ulceration was associated with an increased risk of all-cause mortality (pooled relative risk 2.45, 95% CI 1.85-2.85). We did not observe any tangible differences in risk of all-cause mortality from diagnosis in studies reporting a mean duration of follow-up of ≤3 years (relative risk 2.43, 95% CI 2.27-2.61) or >3 years (relative risk 2.26, 95% CI 2.13-2.40) years. Funnel plot inspection revealed no significant publication bias among studies included in this meta-analysis.

CONCLUSIONS

Our study shows an excess rate of all-cause mortality in people with diabetic foot ulceration when compared to those without foot ulceration. It is imperative that early interventions to prevent foot ulceration and modify cardiovascular disease risk factors are put in place to reduce excess mortality.

Cardiovascular Autonomic Neuropathy and Distal Symmetric Sensorimotor Polyneuropathy: These Two Diabetic Microvascular Complications do not Invariably Co-Exist

Background:

Cardiovascular autonomic neuropathy (CAN) and distal symmetrical sensorimotor polyneuropathy (DSPN) are serious microvascular complications of diabetes mellitus (DM). Their simultaneous development remains disputable. The aim of the present study was to examine the correlation between CAN and the presence/severity of DSPN in DM.

Methods:

Subjects with type 1 (group A: n=51; mean age 40.4 years) and type 2 DM (group B: n=153; mean age 64.6 years) were studied. Evaluation of DSPN was based on neuropathy disability score. Assessment of CAN was based on the battery of 4 standardized cardiovascular autonomic function tests.

Results:

In group A, patients with moderate/severe DSPN exhibited a 12-fold higher likelihood of CAN in univariate analysis (p=0.035). However, significance was lost after adjustment for gender, age, DM duration, and haemoglobin A1c. In group A, likelihood for CAN did not correlate with the presence of mild DSPN in univariate and multivariate analysis. In group B, likelihood of CAN was similar in patients with mild and in those with moderate/severe DSPN compared with patients without DSPN in univariate and multivariate analysis. In between group comparison CAN was similarly distributed in the 2 groups (p for interaction=0.367), in patients with no, mild and moderate/severe DSPN.

Conclusion:

CAN does not always co-exist with degrees of DSPN, ranging from mild to moderate/ severe and is similarly distributed in T1DM and T2DM patients with mild and moderate/severe DSPN and in patients without DSPN.

Correlation of cardiac autonomic neuropathy with small and large peripheral nerve function in type 2 diabetes mellitus

AIMS

To analyse the correlation of cardiac autonomic neuropathy (CAN), sympathetic and parasympathetic dysfunction with the different diagnostic tools for large and small peripheral nerve fibres in type 2 diabetes mellitus (T2DM).

METHODS

We included 153 T2DM subjects (92 men) with mean age of 64.4 years. CAN, as well as sympathetic and parasympathetic dysfunction were diagnosed by the Ewing's cardiovascular reflex tests. Vibration perception threshold (VPT), monofilament, Ipswich Touch test, automated sural nerve conduction study and neuropathy disability score (NDS) evaluated large and small peripheral nerve fibre function.

RESULTS

CAN (adjusted odds ratio [aOR]: 44.57), parasympathetic (aOR: 18.40) and sympathetic dysfunction (aOR: 5.50) correlated with measures of small fibre function evaluated by pinprick sensation and temperature perception. Among tools for large nerve fibres, positive correlation was shown between: (1) CAN and abnormal VPT (aOR: 16.78), (2) parasympathetic dysfunction and abnormal VPT (aOR: 39.47).

CONCLUSIONS

CAN and parasympathetic dysfunction correlate with peripheral neuropathy, especially when the latter is assessed through VPT and measures of small fibre function as evaluated by pinprick sensation and temperature perception. The latter additionally correlate with sympathetic nervous system impairment.

Association between serum uric acid and large-nerve fiber dysfunction in type 2 diabetes: a cross-sectional study

Background

Large-nerve fiber dysfunction, as assessed by vibration perception threshold (VPT) predicts risks of ulceration, amputation, and mortality in diabetes. Serum uric acid (UA) is closely associated with various metabolic disorders, especially diabetes. Thus, we sought to investigate the clinical relevance of UA to large-nerve fiber dysfunction, among patients with type 2 diabetes (T2D).

Methods

Medical records of consecutive patients with T2D who were admitted to Beijing Friendship Hospital Pinggu Campus between May 2014 and December 2016 were collected. Data for the 824 eligible patients included in the final analysis were extracted using a structured form. A VPT value ≥15 in either foot was defined as abnormal. We compared the clinical characteristics between patients with abnormal VPT and those with normal VPT (VPT value <15 in both feet) in the overall population and in gender subgroups. Logistic regression analysis was performed to explore the association of abnormal VPT with UA level. One-way analysis of variance was used to compare VPT values across four UA quartiles.

Results

UA levels were significantly lower in T2D patients with abnormal VPT than in those with normal VPT (294.5 ± 84.0 vs. 314.9 ± 92.8 μmol/L, P < 0.01), especially among male patients (311.7 ± 85.2 vs. 336.9 ± 89.6 μmol/L, P < 0.01). From the logistic regression analysis, hyperuricemia (males >420 μmol/L; females >360 μmol/L) was associated with a reduced risk of abnormal VPT (odds ratio [OR], 0.60; 95% confidence interval [CI], 0.39–0.91; P < 0.05). This association was robust in male patients (OR, 0.43; 95% CI, 0.24–0.76; P < 0.01) but not in female patients (OR, 0.92; 95% CI, 0.47–1.82; P = 0.816), even after adjustment for confounding factors. For the younger male subgroup (age <65 years), VPT values decreased as the UA level increased (P for trend = 0.002), but this trend was not significant in older male subgroup (age ≥65 years; P for trend = 0.400).

Conclusions

Low serum UA levels showed a significant association with an increased risk of large-nerve fiber dysfunction in male patients with T2D, but not in female patients with T2D. In addition, in only the younger subgroup of male patients (<65 years), lower levels of UA also correlated with higher VPT values.

Hypertension Contributes to Neuropathy in Patients With Type 1 Diabetes

BACKGROUND

Diabetic peripheral neuropathy (DPN) can lead to foot ulceration and amputation. There are currently no disease-modifying therapies for DPN. The aim of this study was to determine if hypertension contributes to DPN in patients with type 1 diabetes mellitus (T1DM).

METHODS

Subjects with T1DM (n = 70) and controls (n = 78) underwent a comprehensive assessment of DPN.

RESULTS

Hypertension was present in 40 of 70 T1DM subjects and 20 of 78 controls. Hypertension was associated with abnormal nerve conduction parameters (P = 0.03 to <0.001), increased vibration perception threshold (P = 0.01) and reduced corneal nerve fiber density and length (P = 0.02) in subjects with T1DM. However, after adjusting for confounding factors only tibial compound motor action potential and nerve conduction velocity were associated with hypertension (P = 0.03) and systolic blood pressure (P < 0.01 to <0.0001). Hypertension had no effect on neuropathy in subjects without diabetes.

CONCLUSIONS

This study shows that hypertension is associated with impaired nerve conduction in T1DM. It supports previous small trials showing that angiotensin-converting enzyme inhibitors improve nerve conduction and advocates the need for larger clinical trials with blood pressure lowering agents in DPN.

Association of Serum Cholesterol Levels With Peripheral Nerve Damage in Patients With Type 2 Diabetes

IMPORTANCE

Lowering serum cholesterol levels is a well-established treatment for dyslipidemia in patients with type 2 diabetes (T2D). However, nerve lesions in patients with T2D increase with lower serum cholesterol levels, suggesting that lowering serum cholesterol levels is associated with diabetic polyneuropathy (DPN) in patients with T2D.

OBJECTIVE

To investigate whether there is an association between serum cholesterol levels and peripheral nerve lesions in patients with T2D with and without DPN.

DESIGN, SETTING, AND PARTICIPANTS

This single-center, cross-sectional, prospective cohort study was performed from June 1, 2015, to March 31, 2018. Observers were blinded to clinical data. A total of 256 participants were approached, of whom 156 were excluded. A total of 100 participants consented to undergo magnetic resonance neurography of the right leg at the Department of Neuroradiology and clinical, serologic, and electrophysiologic assessment at the Department of Endocrinology, Heidelberg University Hospital, Heidelberg, Germany.

EXPOSURES

Quantification of the nerve's diameter and lipid equivalent lesion (LEL) load with a subsequent analysis of all acquired clinical and serologic data with use of 3.0-T magnetic resonance neurography of the right leg with 3-dimensional reconstruction of the sciatic nerve.

MAIN OUTCOMES AND MEASURES

The primary outcome was lesion load and extension. Secondary outcomes were clinical, serologic, and electrophysiologic findings.

RESULTS

A total of 100 participants with T2D (mean [SD] age, 64.6 [0.9] years; 68 [68.0%] male) participated in the study. The LEL load correlated positively with the nerve's mean cross-sectional area (r = 0.44; P < .001) and the maximum length of a lesion (r = 0.71; P < .001). The LEL load was negatively associated with total serum cholesterol level (r = -0.41; P < .001), high-density lipoprotein cholesterol level (r = -0.30; P = .006), low-density lipoprotein cholesterol level (r = -0.33; P = .003), nerve conduction velocities of the tibial (r = -0.33; P = .01) and peroneal (r = -0.51; P < .001) nerves, and nerve conduction amplitudes of the tibial (r = -0.31; P = .02) and peroneal (r = -0.28; P = .03) nerves.

CONCLUSIONS AND RELEVANCE

The findings suggest that lowering serum cholesterol levels in patients with T2D and DPN is associated with a higher amount of nerve lesions and declining nerve conduction velocities and amplitudes. These findings may be relevant to emerging therapies that promote an aggressive lowering of serum cholesterol levels in patients with T2D.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.

Optimization of Surgical Outcome in Lower Extremity Nerve Decompression Surgery

BACKGROUND

There is still debate regarding whether the surgical release of entrapped lower extremity nerves reduces complaints of associated neuropathy and results in gain of sensory function. The aim of this study was to investigate which factors are associated with a favorable surgical outcome, by follow-up of patients previously participating in a randomized controlled trial.

METHODS

The authors evaluated the 5-year follow-up of diabetic patients previously participating in the Lower Extremity Nerve Entrapment Study (LENS). Visual analogue pain scores, satisfaction, complaints, quality of life (i.e., 36-Question Short-Form Health Survey and EuroQol 5 Dimensions instrument), sensory function, and incident ulceration and amputation were assessed. Differences between patients who underwent unilateral versus bilateral decompressions were investigated.

RESULTS

Thirty-one of the original 42 LENS participants were measured, of which eight patients underwent additional decompression of the contralateral leg, after 12-month LENS follow-up. At 5 years, bilateral surgical patients (n = 8) had significantly lower pain scores and higher quality of life compared with unilateral surgical patients (n = 23), were younger, had a lower age when diagnosed with diabetes, and had a lower body mass index at baseline. Pain scores of the additional decompressed leg decreased in a manner similar to that of the initial decompressed leg during follow-up. Patients with severe preoperative sensory loss did worse; 41.2 percent of the LENS Follow-Up Study subjects underwent or considered undergoing contralateral surgery.

CONCLUSION

The authors' results suggest that the beneficial effects of lower extremity nerve decompression surgery are reserved for a select group of patients, of which preoperative nerve damage, age, duration of diabetes, and body mass index are important effect modifiers.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

A model of chronic diabetic polyneuropathy: benefits from intranasal insulin are modified by sex and RAGE deletion

Human diabetic polyneuropathy (DPN) is a progressive complication of chronic diabetes mellitus. Preliminary evidence has suggested that intranasal insulin, in doses insufficient to alter hyperglycemia, suppresses the development of DPN. In this work we confirm this finding, but demonstrate that its impact is modified by sex and deletion of RAGE, the receptor for advanced glycosylation end products. We serially evaluated experimental DPN in male and female wild-type mice and male RAGE null (RN) mice, each with nondiabetic controls, during 16 wk of diabetes, the final 8 wk including groups given intranasal insulin. Age-matched nondiabetic female mice had higher motor and sensory conduction velocities than their male counterparts and had lesser conduction slowing from chronic diabetes. Intranasal insulin improved slowing in both sexes. In male RN mice, there was less conduction slowing with chronic diabetes, and intranasal insulin provided limited benefits. Rotarod testing and hindpaw grip power offered less consistent impacts. Mechanical sensitivity and thermal sensitivity were respectively but disparately changed and improved with insulin in wild-type female and male mice but not RN male mice. These studies confirm that intranasal insulin improves indexes of experimental DPN but indicates that females with DPN may differ in their underlying phenotype. RN mice had partial but incomplete protection from underlying DPN and lesser impacts from insulin. We also identify an important role for sex in the development of DPN and report evidence that insulin and AGE-RAGE pathways in its pathogenesis may overlap.

Relationship between sensorimotor peripheral nerve function and indicators of cardiovascular autonomic function in older adults from the Health, Aging and Body Composition Study

BACKGROUND

Age-related peripheral nervous system (PNS) impairments are highly prevalent in older adults. Although sensorimotor and cardiovascular autonomic function have been shown to be related in persons with diabetes, the nature of the relationship in general community-dwelling older adult populations is unknown.

METHODS

Health, Aging and Body Composition participants (n=2399, age=76.5±2.9years, 52% women, 38% black) underwent peripheral nerve testing at the 2000/01 clinic visit. Nerve conduction amplitude and velocity were measured at the peroneal motor nerve. Sensory nerve function was assessed with vibration detection threshold and monofilament (1.4-g/10-g) testing at the big toe. Symptoms of lower-extremity peripheral neuropathy were collected by self-report. Cardiovascular autonomic function indicators included postural hypotension, resting heart rate (HR), as well as HR response to and recovery from submaximal exercise testing (400m walk). Multivariable modeling adjusted for demographic/lifestyle factors, medication use and comorbid conditions.

RESULTS

In fully adjusted models, poor motor nerve conduction velocity (<40m/s) was associated with greater odds of postural hypotension, (OR=1.6, 95% CI: 1.0-2.5), while poor motor amplitude (<1mV) was associated with 2.3beats/min (p=0.003) higher resting HR. No associations were observed between sensory nerve function or symptoms of peripheral neuropathy and indicators of cardiovascular autonomic function.

CONCLUSIONS

Motor nerve function and indicators of cardiovascular autonomic function remained significantly related even after considering many potentially shared risk factors. Future studies should investigate common underlying processes for developing multiple PNS impairments in older adults.

Association of SUDOSCAN Values with Vibration Perception Threshold in Chinese Patients with Type 2 Diabetes Mellitus

AIMS/INTRODUCTION

SUDOSCAN has been proved to be an efficient method in detecting diabetic microvascular complications. In this study, we determine to detect the possible relationship between vibration perception threshold (VPT) and cardiac autonomic neuropathy (CAN) values produced by SUDOSCAN.

MATERIALS AND METHODS

A total of 920 Chinese patients with T2DM were enrolled in the study. Spearman correlation analysis and multivariate regression analysis were performed to determine the relation between CAN and VPT values. Mean VPT values across the CAN value tertiles were analyzed stratified by HbA1c status.

RESULTS

In the study, we discovered a relatively high correlation between CAN value and both VPT values from dorsal feet and toes. Multivariate regression analyses also showed a significant relation between VPT and CAN values after adjusting all covariates. The mean value of VPT decreased across the SUDOSCAN-CAN value quartiles in both groups, and it was higher in patients with HbA1C > 9% than in patients with HbA1C < 9% across all quartiles of the SUDOSCAN-CAN except for the VPT mean in the low quartile of the SUDOSCAN-CAN value.

CONCLUSIONS

All these results suggested that SUDOSCAN-CAN result was associated with VPT value which indicated a probable link between VPT value and cardiovascular autonomic dysfunction.

Peripheral and Autonomic Neuropathy in South Asians and White Caucasians with Type 2 Diabetes Mellitus: Possible Explanations for Epidemiological Differences

Objectives. To compare the prevalence of diabetic peripheral neuropathy (DPN) and that of cardiac autonomic neuropathy (CAN) between South Asians and White Caucasians with type 2 diabetes and to explore reasons for observed differences. Methods. A cross-sectional study of casually selected South Asian and White Caucasian adults attending a hospital-based diabetes clinic in the UK. DPN and CAN were assessed using the Michigan Neuropathy Screening Instrument (MNSI) and heart rate variability testing, respectively. Results. Patients (n = 266) were recruited (47.4% South Asians). DPN was more common in White Caucasians compared to South Asians (54.3% versus 38.1%, p = 0.008). Foot insensitivity as assessed by 10 g monofilament perception was more common in White Caucasians (43.9% versus 23.8%, p = 0.001). After adjustment for confounders, White Caucasians remained twice as likely to have DPN as South Asians, but the impact of ethnicity became nonsignificant after adjusting for adiposity measures or height. No difference in prevalence of standardized CAN test abnormalities was detected between ethnicities. Skin microvascular assessment demonstrated that South Asians had reduced heating flux but preserved acetylcholine response. Conclusions. South Asians with type 2 diabetes have fewer clinical signs of DPN compared to White Caucasians. Differences in adiposity (and its distribution) and height appear to explain these differences.

Endothelial Dysfunction as a Link Between Cardiovascular Risk Factors and Peripheral Neuropathy in Diabetes

CONTEXT

Cardiovascular risk factors are well-known predictors of the development of diabetic peripheral neuropathy (DPN), which has traditionally been considered as a manifestation of diabetes-associated microangiopathy. Because endothelial dysfunction is strongly associated with all cardiovascular risk factors, we hypothesized that it may be a link between cardiovascular risk factors and DPN.

OBJECTIVE

The primary objective of this study was to test whether endothelial dysfunction is a predictor of DPN.

DESIGN AND SETTING

This is a cross-sectional analysis of a cohort composed of patients followed at the Microcirculatory Laboratory, Beth Israel Deaconess Medical Center.

PATIENTS

Participants with diabetes without DPN (n = 192) and with DPN (n = 166), subjects with prediabetes (n = 75), and nondiabetic controls (n = 59) were included.

INTERVENTIONS

Endothelial function was assessed with flow-mediated dilation (FMD) of the brachial artery. Inflammatory cytokines and biomarkers of endothelial function (soluble intercellular and vascular cell adhesion molecules) were quantified using a multiplex bead-based immunoassay. Neurological assessment included the neuropathy disability score (NDS).

MAIN OUTCOME MEASURE

The relationship between FMD and NDS assessed using multiple linear regression.

RESULTS

In addition to already known risk factors of DPN, FMD was strongly associated with NDS (β = -0.24; P < .001). Sensitivity analysis that removed FMD from the model provided similar results for soluble intercellular cell adhesion molecule-1, another biomarker of endothelial function. Confirmatory factor analysis further showed that endothelial dysfunction is a significant mediator between glycosylated hemoglobin and diabetes duration and diabetic complications.

CONCLUSIONS

This study shows that endothelial dysfunction occurs early in the pathophysiology of diabetes and is a link between cardiovascular risk factors and DPN.

Increased Mortality in Diabetic Foot Ulcer Patients: The Significance of Ulcer Type

Diabetic foot ulcer (DFU) patients have a greater than twofold increase in mortality compared with nonulcerated diabetic patients. We investigated (a) cause of death in DFU patients, (b) age at death, and (c) relationship between cause of death and ulcer type. This was an eleven-year retrospective study on DFU patients who attended King's College Hospital Foot Clinic and subsequently died. A control group of nonulcerated diabetic patients was matched for age and type of diabetes mellitus. The cause of death was identified from death certificates (DC) and postmortem (PM) examinations. There were 243 DFU patient deaths during this period. Ischaemic heart disease (IHD) was the major cause of death in 62.5% on PM compared to 45.7% on DC. Mean age at death from IHD on PM was 5 years lower in DFU patients compared to controls (68.2 ± 8.7 years versus 73.1 ± 8.0 years, P = 0.015). IHD as a cause of death at PM was significantly linked to neuropathic foot ulcers (OR 3.064, 95% CI 1.003-9.366, and P = 0.049). Conclusions. IHD is the major cause of premature mortality in DFU patients with the neuropathic foot ulcer patients being at a greater risk.

An association of large-fibre peripheral nerve dysfunction with non-invasive measures of liver fibrosis secondary to non-alcoholic fatty liver disease in diabetes

AIM

To examine for an association of elevated lower-limb vibration perception threshold (VPT) with NAFLD fibrosis.

METHODS

Two cohorts from a tertiary diabetes centre were studied - Cohort 1, n=456 with type 1 or 2 diabetes, and Cohort 2, n=106 with type 2 diabetes mellitus. All underwent a detailed assessment, including VPT measurement. Cohort 2 also had liver ultrasound and transient elastography (TE). NAFLD Fibrosis Score (NFS) was calculated for all with available data. Follow-up VPT measurements on participants in Cohort 1 to 2014 were also collected if available.

RESULTS

Adjusted risk of higher VPT category (≥25V but <50V, or ≥50V, c.f. < 25V) was greater for high-risk NFS in both cohorts (Cohort 1, OR 2.22 [95% CI 1.24-3.98, p=0.007] and Cohort 2, OR 4.51 [95% CI 1.08-18.87], p=0.039) and higher liver stiffness measurement (LSM) by TE in Cohort 2 (OR for each unit natural log increase in LSM of 2.42 (95% CI 1.13-5.19), p=0.023). In Cohort 1, in those with VPT<50V and complete data, those with higher NFS had greater odds of increasing VPT category after 2.2 (IQR 1.5-2.9) years.

CONCLUSIONS

Higher VPT associates with markers of liver fibrosis due to NAFLD in diabetes mellitus.

The Effect of Cigarette Smoking on Diabetic Peripheral Neuropathy: A Systematic Review and Meta-Analysis

OBJECTIVE

Studies suggest that smoking may be a risk factor for the development of microvascular complications such as diabetic peripheral neuropathy (DPN). The objective of this study was to assess the relationship between smoking and DPN in persons with type 1 or type 2 diabetes.

RESEARCH DESIGN AND METHODS

A systematic review of the PubMed, Embase, and Cochrane clinical trials databases was conducted for the period from January 1966 to November 2014 for cohort, cross-sectional and case-control studies that assessed the relationship between smoking and DPN. Separate meta-analyses for prospective cohort studies and case-control or cross-sectional studies were performed using random effects models.

RESULTS

Thirty-eight studies (10 prospective cohort and 28 cross-sectional) were included. The prospective cohort studies included 5558 participants without DPN at baseline. During follow-up ranging from 2 to 10 years, 1550 cases of DPN occurred. The pooled unadjusted odds ratio (OR) of developing DPN associated with smoking was 1.26 (95% CI 0.86-1.85; I(2) = 74%; evidence grade: low strength). Stratified analyses of the prospective studies revealed that studies of higher quality and with better levels of adjustment and longer follow-up showed a significant positive association between smoking and DPN, with less heterogeneity. The cross-sectional studies included 27,594 participants. The pooled OR of DPN associated with smoking was 1.42 (95% CI 1.21-1.65; I(2) = 65%; evidence grade: low strength). There was no evidence of publication bias.

CONCLUSIONS

Smoking may be associated with an increased risk of DPN in persons with diabetes. Further studies are needed to test whether this association is causal and whether smoking cessation reduces the risk of DPN in adults with diabetes.

Cardiovascular disease predicts diabetic peripheral polyneuropathy in subjects with type 2 diabetes: A 10-year prospective study

BACKGROUND

The relationship between cardiovascular disease and diabetic peripheral neuropathy is mainly sustained by data retrieved from cross-sectional studies focused on cardiovascular risk factors. We aimed to assess the presence of cardiovascular disease as a risk factor for developing diabetic peripheral neuropathy in a type 2 diabetes mellitus population.

METHOD

A 10-year prospective, primary care, multicentre study in a randomly selected cohort. Cardiovascular disease presence included stroke, coronary artery disease and/or peripheral ischaemia. Diabetic peripheral neuropathy diagnosis was based on clinical neurological examination as well as the neuropathy symptoms score and nerve conduction studies.

RESULTS

Three hundred and ten (N=310) patients were initially recruited. Two-hundred and sixty seven (N=267) patients were included in the study. Diabetic peripheral neuropathy cumulative incidence was 18.3% (95% confidence intervals 14.1-23.4; N=49). Diabetic peripheral neuropathy development was significantly more frequent in participants presenting with cardiovascular disease at baseline (P=0.01). In the final logistic regression analysis, the presence of cardiovascular disease remained associated with an increased risk for diabetic peripheral neuropathy (odds ratio 2.32, 95% confidence intervals 1.03-5.22) in addition to diabetes duration and low density lipoprotein-cholesterol levels.

CONCLUSIONS

In our series, type 2 diabetes mellitus patients with cardiovascular disease at baseline present with an increased risk of developing diabetic peripheral neuropathy at 10 years of follow-up. Our results suggest that measures aimed at the prevention, control and treatment of cardiovascular disease can also help prevent diabetic peripheral neuropathy development.

Risks and benefits of statin use in young people with type 1 diabetes

Cardiovascular disease (CVD) is the primary cause of mortality in patients with type 1 diabetes (T1D). Despite advances in the management of microvascular complications of T1D, there is a lack of similar progress in reduction of macrovascular complications. Dyslipidemia is one of the major contributory factors for macrovascular complications in T1D, but the literature suggests significant under-treatment of this risk factor in children and adolescents with diabetes. Statins have shown to be both effective and safe in young people with familial hypercholesterolemia and adults with diabetes mellitus, but the role for statins in children and adolescent with T1D remains unclear and controversial. In this review, we will summarize the risks and benefits of statin use in young people with T1D.

Relationship between platelet volume indices with macrovascular and peripheral neuropathy complications in type 2 diabetic patients

BACKGROUND

The relationship of platelet volume indices including mean platelet volume (MPV) and platelet distribution width (PDW) with carotid intima-media thickness (IMT) as well as vibration perception threshold (VPT) was investigated in type 2 diabetic patients.

METHODS

A total of 500 type 2 diabetic patients (298 male, 202 female) were enrolled. Clinical and laboratory data were collected from hospital records.

RESULTS

Both MPV and PDW were significantly associated with carotid IMT, after adjustment for confounding factors including age, systolic blood pressure, total cholesterol and creatinine (0.833 ± 0.029 mm vs. 0.955 ± 0.030 mm; 0.839 ± 0.029 mm vs. 0.955 ± 0.030 mm; P = 0.0015 and P = 0.022, respectively). Agreed with carotid IMT analysis results, significant association was found between PDW and VPT as tertiles (15.760 ± 1.091V vs 20.187 ± 1.094V, P = 0.016). In multivariable analysis, both MPV and PDW were significantly associated with VPT (P = 0.021 and P = 0.007, respectively). However, only PDW, but not MPV, was significantly associated with carotid IMT (P = 0.002).

CONCLUSIONS

These findings implied the predictive value of platelets volume indices in vascular and peripheral neuropathy complications in type 2 diabetes.

Red blood cell distribution width and diabetes-associated complications

AIM

Red blood cell distribution width (RDW) is a marker of cardiovascular morbidity and mortality. However, there is little data on the relationship between RDW and diabetes-associated complications. The aim was to investigate whether there is any association between RDW, nephropathy, neuropathy and peripheral arterial disease (PAD) in a type 2 diabetic population.

METHODS

This study included 196 diabetic patients with proliferative diabetic retinopathy. All subjects were investigated for diabetic nephropathy, diabetic neuropathy and PAD. Participants underwent 24-h blood pressure monitoring and were analysed for markers of the metabolic syndrome, inflammation, and insulin resistance.

RESULTS

57% of the participants had diabetic nephropathy, 46% had diabetic neuropathy while 26% had PAD. No significant association was found between RDW, diabetic neuropathy and PAD (p=NS). However, RDW was strongly associated with diabetic nephropathy (p=0.006), even following adjustment for potential confounding variables. Multivariate logistic regression analysis showed RDW (odds ratio [OR] 1.64, 95% confidence interval [CI] 1.15-2.35, p=0.006), estimated glomerular filtration rate (OR 0.98, 95% CI 0.96-0.99, p<0.001), night-time diastolic blood pressure (OR 1.07, 95% CI 1.03-1.11, p=0.001) and erythrocyte sedimentation rate (OR 1.03, 95% CI 1.004-1.05, p=0.019) to be independently associated with diabetic nephropathy.

CONCLUSIONS

This is the first study to report lack of association between RDW, neuropathy and PAD in subjects with type 2 diabetes mellitus. More importantly, RDW was shown to be significantly associated with diabetic nephropathy in a type 2 diabetic population with advanced proliferative retinopathy independent of traditional risk factors, including diabetes duration and glycaemic control.

Vibration perception threshold in relation to postural control and fall risk assessment in elderly

PURPOSE

This study investigates (i) the potential discriminative role of a clinical measure of peripheral neuropathy (PN) in assessing postural performance and fall risk and (ii) whether the integration of a simple screening vibration perception threshold (VPT) for PN in any physical (fall risk) assessment among elderly should be recommended, even if they do not suffer from DM.

METHOD

One hundred and ninety-five elderly were entered in a four-group model: DM with PN (D+; n = 75), DM without PN (D-; n = 28), non-diabetic elderly with idiopathic PN (C+; n = 31) and non-diabetic elderly without PN (C-; n = 61). Posturographic sway parameters were captured during different static balance conditions (AMTI AccuGait, Watertown, MA). VPT, fall data, Mini-Mental State Examination and Clock Drawing Test were registered. Two-factor repeated-measures ANOVA was used to compare between groups and across balance conditions.

RESULTS

The groups with PN demonstrated a strikingly comparable, though bigger sway, and a higher prospective fall incidence than their peers without PN.

CONCLUSIONS

The indication of PN, irrespective of its cause, interferes with postural control and fall incidence. The integration of a simple screening for PN (like bio-thesiometry) in any fall risk assessment among elderly is highly recommended. Implications for Rehabilitation The indication of peripheral neuropathy (PN), irrespective of its cause, interferes with postural control and fall incidence. Therefore, the integration of a simple screening for PN (like bio-thesiometry) in any fall risk assessment among elderly is highly recommended. It might be useful to integrate somatosensory stimulation in rehabilitation programs designed for fall prevention.

Cell therapy for diabetic neuropathy using adult stem or progenitor cells

Diabetic neuropathy (DN) is the most common and disabling complication of diabetes that may lead to foot ulcers and limb amputations. Despite widespread awareness of DN, the only effective treatments are glucose control and pain management. A growing body of evidence suggests that DN is characterized by reduction of vascularity in peripheral nerves and deficiency in neurotrophic and angiogenic factors. Previous studies have tried to introduce neurotrophic or angiogenic factors in the form of protein or gene for therapy, but the effect was not significant. Recent studies have shown that bone marrow (BM)-derived stem or progenitor cells have favorable effects on the repair of cardiovascular diseases. Since these BM-derived stem or progenitor cells contain various angiogenic and neurotrophic factors, these cells have been attempted for treating experimental DN, and turned out to be effective for reversing various manifestations of experimental DN. These evidences suggest that cell therapy, affecting both vascular and neural components, can represent a novel therapeutic option for treatment of clinical DN.

Hypertension-induced peripheral neuropathy and the combined effects of hypertension and diabetes on nerve structure and function in rats

Diabetic neuropathy includes damage to neurons, Schwann cells and blood vessels. Rodent models of diabetes do not adequately replicate all pathological features of diabetic neuropathy, particularly Schwann cell damage. We, therefore, tested the hypothesis that combining hypertension, a risk factor for neuropathy in diabetic patients, with insulin-deficient diabetes produces a more pertinent model of peripheral neuropathy. Behavioral, physiological and structural indices of neuropathy were measured for up to 6 months in spontaneously hypertensive and age-matched normotensive rats with or without concurrent streptozotocin-induced diabetes. Hypertensive rats developed nerve ischemia, thermal hyperalgesia, nerve conduction slowing and axonal atrophy. Thinly myelinated fibers with supernumerary Schwann cells indicative of cycles of demyelination and remyelination were also identified along with reduced nerve levels of myelin basic protein. Similar disorders were noted in streptozotocin-diabetic rats, except that thinly myelinated fibers were not observed and expression of myelin basic protein was normal. Superimposing diabetes on hypertension compounded disorders of nerve blood flow, conduction slowing and axonal atrophy and increased the incidence of thinly myelinated fibers. Rats with combined insulinopenia, hyperglycemia and hypertension provide a model for diabetic neuropathy that offers an opportunity to study mechanisms of Schwann cell pathology and suggests that hypertension may contribute to the etiology of diabetic neuropathy.

Quantitative vibration perception threshold in assessing diabetic neuropathy: is the cut-off value lower for Indian subjects? [Q-VADIS Study]

AIMS

The aim was to compute a normative data of VPT [Vibration Perception Threshold], compare results of VPT among type 2 diabetes patients with and without neuropathy, validate VPT taking NDS [Neuropathy Disability Scores] as gold standard and suggest a cut off value for the Indian population.

MATERIALS AND METHODS

A clinic based case-control study was conducted at Nightingale Hospital (NH) in Kolkata for 2 months duration. Fifty type 2 diabetes patients (who were detected with by fasting plasma glucose or on medication) reporting at OPD (Out Patent Department) were randomly selected and informed consent was obtained. The age range was 20-65 years and other common causes of neuropathy were excluded. Same number of control patients without diabetes and reporting at the same hospital during the study period in the similar age range were selected.

RESULTS

The normative data of VPT for mean of 4 sites (malleoli and great toe) was 11.3±4.9mV. The VPT value was significantly higher among diabetic patients with neuropathy compared to non-neuropathic and non-diabetic patients. Considering NDS score as gold standard lowering the cutoff value of VPT from 25mV to 20mV increased the sensitivity from 50% to 62.5% in detecting diabetic neuropathy compared to NDS taken as a gold standard.

CONCLUSIONS

It was found that lowering the cut off value of VPT in Indian population increased the sensitivity of the test to detect diabetic neuropathy without hampering the specificity. There is however no indication that a lower cut off VPT value is justified as of now.

Small fibre dysfunction, microvascular complications and glycaemic control in type 1 diabetes: a case-control study

AIMS/HYPOTHESIS

The aim of this study was to determine the influence of microvascular disease on C-fibre function in patients with type 1 diabetes of moderate duration.

METHODS

The axon-reflex flare area induced on the dorsum of the foot by local skin heating to 47 °C was measured with a laser Doppler imager (LDI) in sex-, age- and height-matched groups with type 1 diabetes, with and without microvascular disease (MV+ and MV-, respectively) and in healthy controls (HC). Each group consisted of 24 individuals and all were free from clinical neuropathy (neuropathy disability score <3 and Toronto clinical neuropathy score <5).

RESULTS

LDI flare (LDIflare) was reduced in MV+ compared with HC (5.1 ± 1.8 vs 10.0 ± 3.1 cm², p < 0.0001) and MV- groups (9.9 ± 2.9 cm², p < 0.0001). MV- and HC groups did not differ. There was no difference in diabetes duration between MV- and MV+ groups (17.5 ± 5.7 and 20.1 ± 5.2 years, p = 0.21) nor current HbA(1c) (MV- 8.0 ± 1.2% [64 ± 10 mmol/mol]; MV+ 8.0 ± 0.9% [64 ± 9 mmol/mol], p = 0.53); neither variable correlated with flare size. In contrast, duration-averaged HbA(1c) was higher in the MV+ group (8.6 ± 0.9% [70 ± 9 mmol/mol] vs 7.6 ± 0.6% [60 ± 7 mmol/mol], p < 0.001) and correlated with LDIflare size (r = -0.50, p < 0.001). Triacylglycerols were higher in MV+ compared with MV- (1.23 ± 0.121 vs 0.93 ± 0.7 mmol/l, p = 0.04), but other metabolic variables did not differ between the groups.

CONCLUSIONS/INTERPRETATION

We have shown that glycaemic burden and the presence of microvascular complications are associated with small fibre dysfunction in type 1 diabetes.

Diabetic peripheral neuropathy in type 2 diabetes mellitus in Korea

Diabetic peripheral neuropathy (DPN), a common and troublesome complication in patients with type 2 diabetes mellitus (T2DM), contributes to a higher risk of diabetic foot ulcer and lower limb amputation. These situations can negatively impact the quality of life of affected individuals. Despite its high prevalence and clinical importance, most diabetes mellitus patients not only do not recognize the presence of diabetic neuropathy, but also do not report their symptoms to physicians or other health care providers. Therefore, DPN is usually under diagnosed and undertreated. For early detection and appropriate intervention for DPN, a careful history, physical with neurologic examination, and prompt treatment are needed in T2DM patients.

Vibrotactile sense in patients with diabetes and carpal tunnel syndrome

AIM

To evaluate vibration perception thresholds of patients with and without diabetes, before and after surgical carpal tunnel release.

METHODS

In a prospective study, 35 consecutive patients with diabetes and carpal tunnel syndrome were age and gender matched with 31 patients without diabetes having idiopathic carpal tunnel syndrome. Preoperatively, 6, 12 and 52 weeks after surgery, the vibration perception threshold of the index and little finger (median and ulnar nerve, respectively) was measured at seven different frequencies (8, 16, 32, 64, 125, 250 and 500 Hz).

RESULTS

At several frequencies, patients with diabetes and carpal tunnel syndrome demonstrated significantly impaired vibration perception thresholds of both the index and the little finger, before as well as after carpal tunnel release, compared with patients without diabetes with idiopathic carpal tunnel syndrome. After surgery, the overall sensibility index improved for the index finger [patients with diabetes and carpal tunnel syndrome (0.79 to 0.91, P < 0.001), patients without diabetes with idiopathic carpal tunnel syndrome (0.91 to 0.96, P > 0.05)] as well as for the little finger [patients with diabetes and carpal tunnel syndrome (0.82 to 0.90, P < 0.008), patients without diabetes with idiopathic carpal tunnel syndrome (0.95 to 0.99, P < 0.05)]. For the index finger, the sensibility index improved to a significantly higher degree for patients with diabetes and carpal tunnel syndrome not having signs of peripheral neuropathy (0.83 to 0.95, P < 0.001) compared with those with neuropathy (0.74 to 0.84, P < 0.02). Vibration perception threshold correlates with age of both patients with diabetes and carpal tunnel syndrome and patients without diabetes with idiopathic carpal tunnel syndrome, while no relationship was found based on duration of diabetes.

CONCLUSIONS

Vibrotactile sense is significantly impaired in patients with diabetes before and after carpal tunnel release compared with patients without diabetes. However, patients with diabetes obtained significant recovery of vibration perception threshold, particularly those without peripheral neuropathy.

Corneal confocal microscopy detects improvement in corneal nerve morphology with an improvement in risk factors for diabetic neuropathy

AIM

We have assessed whether corneal confocal microscopy can be used to detect alterations in nerve morphology following an improvement in risk factors associated with diabetic neuropathy.

METHODS

Twenty-five patients with diabetes with mild to moderate neuropathy and 18 control subjects underwent corneal confocal microscopy to quantify corneal nerve fibre (density, branch density, length and tortuosity) at baseline and after 24 months from first visit. This was not planned as an intervention trial and was simply an observational follow-up.

RESULTS

At baseline, nerve fibre density (18.8 ± 2.1 vs. 46.0 ± 3.8 number/mm(2), P = 0.001), nerve branch density (6.9 ± 1.5 vs. 35.6 ± 6.7 number/mm(2), P < 0.0001), nerve fibre length (8.3 ± 0.9 vs. 13.5 ± 0.8 mm/mm(2), P < 0.0001) and nerve fibre tortuosity (19.8 ± 1.6 vs. 22.7 ± 2.2, P < 0.05) were significantly lower in patients with diabetes than in control subjects. At follow-up, glycaemic control (HbA(1c) 64 ± 3 to 58 ± 2 mmol/mol, P = 0.08), total cholesterol (4.9 ± 0.2 to 4.2 ± 0.2 mmol/l, P = 0.01), systolic blood pressure (145.8 ± 4.9 to 135.9 ± 3.7 mmHg, P = 0.09) and diastolic blood pressure (77.8 ± 2.7 to 70.8 ± 2.5, P = 0.03) improved. Nerve fibre density (24.1 ± 2.0, P = 0.05), nerve branch density (11.1 ± 1.3, P < 0.01) and nerve fibre tortuosity (22.6 ± 1.5, P = 0.05) increased significantly, with no change in nerve fibre length (8.4 ± 0.5). Improvement in nerve fibre density correlated significantly with the improvement in HbA(1c) (r = -0.51, P = 0.008). Via four multifactorial regressions, this confirms the negative association between HbA(1c) and nerve fibre density (P = 0.02).

CONCLUSIONS

This study shows that corneal confocal microscopy may be employed in longitudinal studies to assess progression of human diabetic neuropathy and also supports the hypothesis that improvements in risk factors for diabetic neuropathy, in particular HbA(1c) , may lead to morphological repair of nerve fibres.

Diabetic neuropathy: cellular mechanisms as therapeutic targets

In patients with diabetes, nerve injury is a common complication that leads to chronic pain, numbness and substantial loss of quality of life. Good glycemic control can decrease the incidence of diabetic neuropathy, but more than half of all patients with diabetes still develop this complication. There is no approved treatment to prevent or halt diabetic neuropathy, and only symptomatic pain therapies, with variable efficacy, are available. New insights into the mechanisms leading to the development of diabetic neuropathy continue to point to systemic and cellular imbalances in metabolites of glucose and lipids. In the PNS, sensory neurons, Schwann cells and the microvascular endothelium are vulnerable to oxidative and inflammatory stress in the presence of these altered metabolic substrates. This Review discusses the emerging cellular mechanisms that are activated in the diabetic milieu of hyperglycemia, dyslipidemia and impaired insulin signaling. We highlight the pathways to cellular injury, thereby identifying promising therapeutic targets, including mitochondrial function and inflammation.

Association between Diabetic Polyneuropathy and Cardiovascular Complications in Type 2 Diabetic Patients

BACKGROUND

Diabetes mellitus is a major independent risk factor for cardiovascular disease (CVD), but high cardiovascular risk in diabetes mellitus patients is not completely explained by clustering traditional risk factors. Recently, associations between diabetic polyneuropathy (DPN) and macrovasculopathy have been suggested. We aimed to assess associations between DPN and cardiovascular complications in type 2 diabetic patients.

METHODS

Microvascular and cardiovascular complications were evaluated in 1,041 type 2 diabetic patients.

RESULTS

In patients with DPN, the age, prevalence of hypertension, diabetes duration, systolic blood pressure, pulse pressure, and hemoglobin glycation (HbA1c) levels were significantly higher, while the high density lipoprotein cholesterol (HDL-C) levels were lower than in those without DPN. The prevalence of CVD was higher in patients with DPN. In multivariate analysis, DPN was independently associated with CVD (odds ratio, 1.801; 95% confidence interval, 1.009 to 3.214).

CONCLUSION

Our results showed that DPN was associated with a high prevalence of cardiovascular disease in type 2 diabetic patients, but further studies are needed to investigate the causative nature of associations between DPN and CVD.

Screening for the high-risk foot of ulceration: tests of somatic and autonomic nerve function

Diabetic foot ulcers affect almost 5% of the patients with diabetes and carry a huge physical, emotional, and financial burden. Almost 80% of amputations in patients with diabetes are preceded by a foot ulcer. The need for simple screening methods for prevention of foot ulcers and amputations is indisputable. Simple tests such as monofilament, tuning fork, vibration perception threshold determination, ankle reflexes, and pinprick sensation alone or in combination have been studied prospectively and can be used for identification of patients at risk. Newer tests examining sudomotor dysfunction and skin dryness have been introduced in recent years. In cross-sectional studies sudomotor dysfunction assessed by either sympathetic skin response or NEUROPAD™ (Miro Verbandstoffe GmbH, Wiehl-Drabenderhöhe, Germany) testing has been consistently associated with foot ulceration. In addition, NEUROPAD™ testing is simple, reproducible, and widely available and has a high sensitivity for the diagnosis of clinical or subclinical diabetic polyneuropathy. Prospective studies are required to establish whether sudomotor dysfunction can predict foot ulcers and if simple methods assessing sudomotor dysfunction (eg, NEUROPAD™ testing) can be included in the screening tests for the prevention of this complication.