Does Vitamin D deficiency play a role in peripheral neuropathy in Type 2 diabetes?

An update on vitamin D and B deficiency in the pathogenesis and treatment of diabetic neuropathy: a narrative review

Diabetic peripheral neuropathy (DPN) is highly prevalent and affects up to 50% of patients with diabetes. Painful neuropathic symptoms may occur in a third of patients with diabetes and is a major cause of sleep disturbance, morbidity and poor quality of life. Effective treatment of DPN remains a major challenge as current therapeutic options have a number of undesirable side effects and only provide a partial response to neuropathic pain. Furthermore, there are a lack of treatments that modulate the natural history of DPN. A growing body of evidence suggests that vitamin B and vitamin D may have analgesic effects and neuroprotective benefits in DPN. This narrative review explores the role of these vitamins in DPN. Given their limited side effects, further mechanistic studies and good quality randomized controlled trials of their putative analgesic ability are required to define the role of vitamin B and D in DPN.

Body mass index and vitamin D level in carpal tunnel syndrome patients

Background

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper extremity. The aim of this study is to evaluate the body mass index (BMI) and vitamin D levels in CTS patients.

Methods

The current study was conducted at Zagazig University Hospitals. It included 50 CTS patients and 50 controls. Clinical assessment was carried out to exclude symptoms and signs of neuropathy. Laboratory investigations including vitamin D levels, glycosylated hemoglobin, liver, and kidney function were carried out for every participant. All patients underwent electrodiagnostic study and completed Boston questionnaire to assess their pain sum score, symptom severity (SSS), and functional status (FSS).

Results

Patients had significantly higher BMI and lower vitamin D levels compared to controls (p = 0.003 and p = 0.001, respectively). Those with severe CTS had a significantly higher BMI and lower vitamin D levels than the others (p = 0.03 and p = 0.01 respectively). No significant difference was found between CTS subgroups regarding the SSS, while a higher significant FSS and pain sum score were reported in the severe CTS patients compared to the other two groups (p = 0.01 and p = 0.04 respectively). A significant negative correlation was detected between vitamin D levels and both of BMI, and Boston pain sum scores (p = 0.01 and p = 0.03 respectively). Also, an inverse correlation was detected between vitamin D levels and both of SSS and FSS (p = 0.14, p = 0.06). Furthermore, a significant positive and negative correlation between vitamin D levels and both of conduction velocity and distal motor latency respectively was observed (p = 0.02 and p = 0.01 respectively).

Conclusions

Carpal tunnel syndrome was significantly associated with hypovitaminosis D especially in patients with higher BMI. This highlights the importance of vitamin D supplements and weight loss regimes to minimize the severity of their pain.

Diabetic Peripheral Neuropathy: Epidemiology, Diagnosis, and Pharmacotherapy

PURPOSE

Diabetic peripheral neuropathy (DPN) is the commonest cause of neuropathy worldwide, and its prevalence increases with the duration of diabetes. It affects approximately half of patients with diabetes. DPN is symmetric and predominantly sensory, starting distally and gradually spreading proximally in a glove-and-stocking distribution. It causes substantial morbidity and is associated with increased mortality. The unrelenting nature of pain in this condition can negatively affect a patient's sleep, mood, and functionality and result in a poor quality of life. The purpose of this review was to critically review the current literature on the diagnosis and treatment of DPN, with a focus on the treatment of neuropathic pain in DPN.

METHODS

A comprehensive literature review was undertaken, incorporating article searches in electronic databases (EMBASE, PubMed, OVID) and reference lists of relevant articles with the authors' expertise in DPN. This review considers seminal and novel research in epidemiology; diagnosis, especially in relation to novel surrogate end points; and the treatment of neuropathic pain in DPN. We also consider potential new pharmacotherapies for painful DPN.

FINDINGS

DPN is often misdiagnosed and inadequately treated. Other than improving glycemic control, there is no licensed pathogenetic treatment for diabetic neuropathy. Management of painful DPN remains challenging due to difficulties in personalizing therapy and ascertaining the best dosing strategy, choice of initial pharmacotherapy, consideration of combination therapy, and deciding on defining treatment for poor analgesic responders. Duloxetine and pregabalin remain first-line therapy for neuropathic pain in DPN in all 5 of the major published guidelines by the American Association of Clinical Endocrinologists, American Academy of Neurology, European Federation of Neurological Societies, National Institute of Clinical Excellence (United Kingdom), and the American Diabetes Association, and their use has been approved by the US Food and Drug Administration.

IMPLICATIONS

Clinical recognition of DPN is imperative for allowing timely symptom management to reduce the morbidity associated with this condition.

Is Hypovitaminosis D Related to Incidence of Type 2 Diabetes and High Fasting Glucose Level in Healthy Subjects: A Systematic Review and Meta-Analysis of Observational Studies

There is evidence that vitamin D status is associated with type 2 diabetes. Many observational studies have been performed investigating the relationship of vitamin D status and circulating biomarkers of glycemic regulation. To find out whether this association holds, we conducted a systematic review and meta-analysis of cross sectional and longitudinal studies. We searched Pubmed, Medline and Embase, all through June 2017. The studies were selected to determine the effect of vitamin D on the parameters of glucose metabolism in diabetic and non-diabetic subjects. Correlation coefficients from all studies were pooled in a random effects meta-analysis. The risk of bias was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. We found significant inverse relationship of vitamin D status with glycemic level in both diabetic (r = -0.223, 95% CI = -0.184 to -0.261, p = 0.000) and non-diabetic (r = -0.073, 95% CI = -0.052 to -0.093, p = 0.000) subjects. This meta-analysis concludes that hypovitaminosis D is associated with increased risk of hyperglycemia both in diabetic and non-diabetic subjects. A future strategy for the prevention of impaired glycemic regulation could be individualized supplementation of vitamin D.

Vitamin D-Binding Protein Clearance Ratio Is Significantly Associated with Glycemic Status and Diabetes Complications in a Predominantly Vitamin D-Deficient Population

INTRODUCTION

Studies have shown increased urine excretion of vitamin D-binding protein (VDBP) in patients with diabetic nephropathy (DN) resulting from postulated mechanisms linked to renal tubular damage. In this study, we evaluate the utility of VDBP clearance ratio as a novel determinant of glycemic status, DN, and other diabetes-associated complications.

METHODS

Levels of vitamin D, HbA1c, serum, urine concentrations of VDBP, and creatinine were measured in 309 subjects. The ratio of urine microalbumin to creatinine was determined to categorize subjects as normoalbuminuric (NAO), microalbuminuric (MIA), and macroalbuminuric (MAA). The VDBP clearance ratio was calculated.

RESULTS

Mean VDBP clearance ratios in NAO, MIA, and MAA were 0.7, 4, and 15, respectively. Significant positive correlations of VDBP clearance ratio were found with age, WC, SBP, DBP, TG, glucose, HbA1c, urine VDBP, urine microalbumin, and urine microalbumin/creatinine, and a significant negative correlation was found with the steady-state estimate of beta cell function (B%). Receiver operating curve (ROC) analyses of the use of VDBP clearance ratio for detection of albumin status shows a value of 0.81 for the area under the curve.

CONCLUSIONS

The strong associations of VDBP clearance ratio with glycemic control and diabetes-associated complications suggest that this index could play a wider role in detection and/or pathogenesis and complications of diabetes.

Non-musculoskeletal benefits of vitamin D

The aim of this study is to determine and critically evaluate the plausible relationships of vitamin D with extra-skeletal tissues in humans. Severe vitamin D deficiency results in rickets in children and osteomalacia in adults; these beneficial effects in the musculoskeletal system and certain physiological functions are well understood. Nevertheless, mounting reports support additional beneficial effects of vitamin D, outside the musculoskeletal system. This review explores the recent advances in knowledge about the non-skeletal effects of vitamin D. Peer-reviewed papers were extracted from research databases using key words, to assess correlations between vitamin D and extra-skeletal diseases and conditions. As per the guidelines of the Preferred Reporting Items for Systematic Reviews (PRISMA); general interpretations of results are included; taking into consideration the broader evidence and implications. This review summarizes current knowledge of the effects of vitamin D status on extra-skeletal tissues with special attention given to relationships between vitamin D status and various diseases commonly affecting adults; the effects of intervention with vitamin D and exposure to sunlight. Evidence suggests that vitamin D facilitates the regulation of blood pressure; and cardiac; endothelial; and smooth muscle cell functions; playing an important role in cardiovascular protection. In addition; 1,25(OH)₂D improves immunity; subdues inflammation; and reduces the incidence and severity of common cancers; autoimmune diseases and infectious diseases. Almost all adequately powered; epidemiological and biological studies that use; adequate doses of vitamin D supplementation in D-deficient populations have reported favorable outcomes. These studies have concluded that optimizing 25(OH)D status improves the functionality of bodily systems; reduces comorbidities; improves the quality of life; and increases survival. Although accumulating evidence supports biological associations of vitamin D sufficiency with improved physical and mental functions; no definitive evidence exists from well-designed; statistically powered; randomized controlled clinical trials. Nevertheless, most studies point to significant protective effects of vitamin D in humans when the minimum 25(OH)D serum level exceeds 30ng/mL and is maintained throughout the year.

Vitamin D levels in subjects with or without chronic kidney disease among Veterans with diabetes in North East United States

AIM

To evaluate the prevalence of vitamin D deficiency and its relation to diabetes and kidney disease in Veterans residing in the North East United States (VISN 2).

METHODS

In this retrospective study, we used data from the computerized patient record system at Stratton Veterans Administration Medical Center at Albany, NY (VHA) for those patients who had 25-hydroxyvitamin D levels and 1,25 (OH) vitamin D levels measured between 2007 and 2010. We collected demographic information including age, sex, body mass index and race; clinical data including diabetes, hypertension and CAD; and laboratory data including calcium, creatinine and parathyroid hormone (PTH) (intact). Vitamin D deficiency is defined as a serum 25-hydroxyvitamin D level of less than 20 ng/mL (50 nmol/L), and insufficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng/mL (50 to 75 nmol/L).

RESULTS

Data was available for approximately 68000 subjects. We identified 64144 subjects for analysis after exclusion of duplicates. Among them, 27098 had diabetes. The mean age of subjects with diabetes was 68 ± 11 with a mean body mass index (BMI) of 32 ± 7 and duration of diabetes of 5.6 ± 3.2 years. The mean 25 (OH) vitamin D level among subjects with diabetes was 27 ± 11.6. There was no significant difference in 25 (OH) vitamin D levels between subjects with diabetes and glomerular filtration rate (e-GFR) < 60 compared to those with e-GFR ≥ 60. As expected, subjects with e-GFR < 60 had significantly lower 1,25 (OH) vitamin D levels and significantly elevated PTH-intact. Of the 64144 subjects, 580 had end-stage renal disease. Of those, 407 had diabetes and 173 did not. Vitamin D levels in both groups were in the insufficiency range and there was no significant difference irrespective of presence or absence of diabetes. Subjects with vitamin D levels less than 20 ng/mL had a higher BMI and elevated PTH, and higher HbA1C levels compared to those with vitamin D levels more than 20 ng/mL.

CONCLUSION

We conclude that we need to keep a close eye on vitamin D levels in subjects with mild chronic kidney disease as well as those with moderate control of diabetes.

The effect of vitamin D supplementation on pain, quality of life, and nerve conduction studies in women with chronic widespread pain

The aim of this study was to investigate the effects of vitamin D supplementation on pain, quality of life, and nerve conduction studies (NCSs) in women with chronic widespread pain (CWP) diagnosed with Vitamin D insufficiency. Thirty-three female participants with CWP and vitamin D insufficiency were included in this open-label trial. They were evaluated by routine NCSs in upper and lower limbs, pain scales, and the Nottingham Health Profile before and 8 weeks after starting vitamin D supplementation therapy. The P-value was adjusted to account for the number of comparisons performed in each assessment. After 8 weeks of treatment, participants reported significantly lower pain scores (P=0.000). The total Nottingham Health Profile score and subscores for pain, emotional reactions, and physical activity domains were significantly lower (0.000≤P≤0.008). However, no statistically significant changes in NCSs were detected, except trends toward increases in the amplitudes of left median and ulnar sensory nerve potentials and a decrease in the distal latency of the right median sensory potential (0.01≤P≤0.04). Vitamin D supplementation therapy decreased pain and increased quality of life without significantly affecting nerve conduction in patients with CWP.

The association between vitamin D level and diabetic peripheral neuropathy in patients with type 2 diabetes mellitus: An update systematic review and meta-analysis

AIM

Recently, increasing studies have been carried out to explore the association between vitamin D level and the development of diabetic peripheral neuropathy (DPN) in patients with diabetes mellitus (DM). However, because of the shortcoming in study design and sample size, there is still no clear conclusion. We performed this meta-analysis to examine the exact impact of vitamin D deficiency on DPN in type 2 diabetic patients.

METHODS

Various databases were searched to identify the potential articles which explored the association between vitamin D level and diabetic peripheral neuropathy in type 2 diabetes. We pooled OR to assess the correlation between vitamin D deficiency and DPN using the random-effects model. The standardized mean difference (SMD) with 95% CI of vitamin D was also calculated to evaluate the vitamin D level between DPN and non DPN in T2DM.

RESULTS

There was obvious heterogeneity in those included ten studies (I² = 94.1%, Cochran Q test P < 0.001) using mean and standard deviation (SD) of vitamin D level. In Caucasian, vitamin D level was significantly lower in DPN patients compared with diabetic patients without DPN (SMD = -0.56, I² = 16.9%). In Asian, the pooled OR value of vitamin D deficiency was 1.22 (95%CI: 1.17-1.27). Sensitivity analysis showed one study had great influence on this meta-analysis and it still existed after excluded that one. There was no evidence of public bias in meta analysis as showed in Begg test and Egger test.

CONCLUSION

This meta-analysis indicates that vitamin D deficiency is associated with the generation and development of DPN in Caucasian with T2DM, and in Asian, diabetic patients with vitamin D deficiency are 1.22 times to suffer from DPN compared with normal vitamin D level. Vitamin D supplementation is urgently needed to prevent the development of DPN in T2DM.

Lack of Definite Association of Vitamin D Deficiency with Diabetic Neuropathy. Investigation in Greek and in Bangladeshi Patients

AIM

Determination of the 25(OH) vitamin D levels in Greek-born and in Bangladeshi immigrant patients in Greece with diabetes with and without polyneuropathy.

MATERIALS AND METHODS

The method for the detection and staging of polyneuropathy proposed by Dyck, 1988 was used.

RESULTS

A total of 111 Bangladeshi immigrants and 101 Greek diabetic patients took part in the study. Vitamin D levels were significantly lower in Bangladeshi than in Greek diabetic patients, and were significantly lower in Greek patients with small-fiber neuropathy. In Bangladeshi patients, there was no statistically significant difference in the subgroup of patients with polyneuropathy in comparison to those without polyneuropathy.

CONCLUSION

The association of vitamin D deficiency only with a small number of Greek patients with exclusively small-fiber neuropathy does not allow us to draw a definite conclusion on the role of vitamin D in the pathogenesis of diabetic neuropathy.

Vitamin D and diabetes mellitus: Causal or casual association?

The incidence of both type 2 and type 1 diabetes mellitus has been increasing worldwide. Vitamin D deficiency, or the awareness of its prevalence, has also been increasing. Vitamin D may have a role in the pathogenic mechanisms predisposing to type 2 diabetes by modulating insulin resistance and/or pancreatic β-cell function. Vitamin D status or elements involved in its activation or transport may also be involved in the development of type 1 diabetes mellitus through immunomodulatory role . Based on these observations a potential association between vitamin D and diabetes has been hypothesized. In this review we discuss up to date evidence linking vitamin D with the development of diabetes. Moreover, the role of vitamin D supplementation in the prevention of both types of diabetes is analysed together with its role in improving glycemic control in diabetic patients. We also address the potential role of vitamin D deficiency in the development of macro- and microvascular complications in diabetes. Finally, we provide recommendation for Vitamin D therapy in diabetes in view of current evidence and highlight areas for potential future research in this area.

Vitamin D deficiency increases the risk of peripheral neuropathy in Chinese patients with type 2 diabetes

BACKGROUND

Vitamin D deficiency was reported to be associated with diabetic peripheral neuropathy. But the association in Chinese population and the screening value of vitamin D deficiency for diabetic peripheral neuropathy were unknown.

METHODS

A total of 861 patients with type 2 diabetes were recruited in this cross-sectional study. Vitamin D deficiency was defined as serum circulating 25-hydroxyvitamin D(25(OH)D) level < 20 ng/mL. Peripheral neuropathy was evaluated by neurological symptoms, neurological signs, neurothesiometer and electromyogram.

RESULTS

The patients with diabetic peripheral neuropathy had significantly lower serum 25(OH)D concentration (15.59 ± 7.68 ng/mL) and higher prevalence of vitamin D deficiency (80%) than patients with signs of diabetic peripheral neuropathy (17.66 ± 7.50 ng/mL; 64.5%) and non-DPN patients (18.35 ± 6.60; 61.7%) (all p < 0.01). Spearman's correlation analysis showed that serum circulating 25(OH)D level was closely associated with DPN (r = 0.121) and signs of DPN (r = 0.111) (both p < 0.01). After adjusting for all potential confounders, VDD was still linked with increased risk of DPN [odds ratio 2.59 (1.48-4.53)] (p < 0.01). Logistical regression analysis further revealed that VDD was an independent risk factor for DPN (β = 0.88) (p < 0.01). Receiver operating characteristic analysis indicated that serum 25(OH)D < 17.22 ng/mL hinted the signs of DPN and serum 25(OH)D < 16.01 ng/mL predicted the occurrence of DPN (both p < 0.01).

CONCLUSIONS

Vitamin D deficiency is an independent risk factor for diabetic peripheral neuropathy and may be a potential biomarker for peripheral neuropathy in Chinese patients with type 2 diabetes. Copyright © 2016 John Wiley & Sons, Ltd.

Vitamin D and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) has become a significant global health care problem and its reported incidence is increasing at an alarming rate. Despite the improvement in therapy and development of new drugs, treatment still remains insufficient especially due to the associated side effects of most available drugs. Efforts are continuing toward disease prevention and search for safer drugs. Conflicting evidence is associating low levels of vitamin D in the body to T2DM and as such studies have been conducted to test the effect of vitamin D levels on incidence of diabetes, diabetic control as well as diabetic complications.Despite the conflicting evidence, vitamin D replacement seems to have some beneficial effect on the many aspects of diabetes: incidence, control and complications. Further long term and more convincing controlled trials are required in order to draw firmer conclusions on this beneficial role of vitamin D treatment on T2DM.

Improvement in Neuropathy Specific Quality of Life in Patients with Diabetes after Vitamin D Supplementation

OBJECTIVE

To assess the effect of vitamin D supplementation on neuropathy specific quality of life (NeuroQoL) in patients with painful diabetic neuropathy.

METHODS

This prospective, open label study was conducted between June 2012 and April 2013. Patients with symptomatic diabetic neuropathy were given a single dose of 600,000 IU intramuscular vitamin D, and NeuroQol was assessed at baseline and at five follow-up visits every 4 weeks.

RESULTS

Of 143 participants, 41.3% were vitamin D deficient (vitamin D < 20 ng/ml). Treatment with vitamin D resulted in a significant increase in 25(OH)D (P < 0.0001) and a significant improvement in the NeuroQoL subscale score for emotional distress (P = 0.04), with no significant change in the other NeuroQoL domains of painful symptoms and paresthesia, loss of temperature and touch sensation, unsteadiness, limitation in daily activities, and interpersonal problems. There was a significant reduction in patient perception about foot problems on QoL of "quite a lot" (P < 0.05) and "very much" (P < 0.0001) with a significant reduction in the baseline response of having a "poor" QoL from 5.2% to 0.7% (P < 0.0001) and an increase in the response of an "excellent QoL" from 1.5% to 7.4% (P < 0.0001).

CONCLUSION

Vitamin D is effective in improving quality of life in patients with painful diabetic neuropathy.

Vitamin D Insufficiency is Associated with Reduced Parasympathetic Nerve Fiber Function in Type 2 Diabetes

OBJECTIVE

Vitamin D insufficiency is prevalent in subjects with type 2 diabetes mellitus (T2DM) and is associated with peripheral neuropathy. However, there are little data regarding vitamin D status in patients with cardiovascular autonomic neuropathy. Our objective was to evaluate the association of cardiovascular autonomic function, 25-hydroxyvitamin D (25[OH]D) insufficiency (i.e., levels <30 ng/mL), and multiple metabolic parameters in subjects with T2DM.

METHODS

We examined 50 individuals with T2DM. Cardiovascular autonomic function (i.e., parasympathetic function) was assessed by RR-variation during deep breathing (i.e., mean circular resultant [MCR] and expiration/inspiration [E/I] ratio). Metabolic parameters included measures of adiposity, glycemic control, insulin resistance, calcium metabolism, and 25(OH)D.

RESULTS

Participants with 25(OH)D insufficiency (n = 26) were younger (66 ± 9 vs. 60 ± 10 years, P<.05), more insulin resistant, had a higher body mass index (BMI) and lower adiponectin levels. The MCR (39.5 ± 26.3 vs. 27.6 ± 17.2, P<.01) and E/I ratio (1.21 ± 0.17 vs. 1.15 ± 0.09, P<.01) were lower for those with 25(OH)D insufficiency after controlling for age. A stepwise selection procedure regressing MCR and E/I ratio on a number of metabolic parameters resulted in a model identifying age and 25(OH)D insufficiency as significant determinants for both measures. The interaction of age x 25(OH)D insufficiency was also included (MCR model, R2 = 0.491, P<.001; E/I ratio, R2 = 0.455, P<.001). Neither glycemic control nor other metabolic parameters were selected.

CONCLUSION

Our results suggest that 25(OH)D insufficiency is associated with reduced parasympathetic function, with a stronger association in younger persons with T2DM. Studies are needed to determine if vitamin D supplementation into the sufficient range could prevent or delay the onset of cardiovascular autonomic dysfunction.

The association of vitamin D with inflammatory cytokines in diabetic peripheral neuropathy

[Purpose] The effects of vitamin D on the circulating levels of IL-17 and IL-13 were investigated in patients with diabetic peripheral neuropathy, patients with diabetes mellitus type 2 without neuropathy, and healthy controls. [Subjects and Methods] A single-blind controlled clinical study was performed, including70 type 2 diabetic patients with or without diabetic peripheral neuropathy and 33 healthy volunteer controls. The 25(OH)D levels were evaluated using ultra-performance liquid chromatography, and IL-17 and IL-13 levels were assessed using enzyme-linked immunosorbent assays. [Results] The 25(OH) vitamin D concentration was lower in diabetic peripheral neuropathy patients than in diabetes mellitus patients without neuropathy and healthy controls. Similarly, 25(OH)D levels were lower in diabetes mellitus patients than healthy controls. IL-17 and IL-13 levels were higher in diabetes mellitus patients than in controls. Additionally, IL-13 levels were higher in diabetic peripheral neuropathy patients than in diabetes mellitus patients without neuropathy. These differences were statistically significant. There was a significant positive correlation between 25(OH)D and IL-13,and a negative correlation between 25(OH)D andIL-17 in the diabetic and diabetic neuropathy groups. [Conclusion] Vitamin D is a potential modifiable risk factor for diabetic peripheral neuropathy and may regulate inflammatory mediators, e.g., IL-17 and IL-13.

Evaluation of vitamin D levels in women with carpal tunnel syndrome

Studies suggest that vitamin D has a role in neuroprotection. We investigated whether vitamin D status is associated with carpal tunnel syndrome. Vitamin D levels were compared between carpal tunnel syndrome women (n = 135) and healthy control women (n = 135) or patients with other upper limb conditions (n = 135). There were no differences in vitamin D levels between the patients with carpal tunnel syndrome and the controls. However, women with carpal tunnel syndrome younger than 50 years old had significantly lower vitamin D levels than age-matched healthy control women (P = 0.023) or patients with other upper limb conditions (P = 0.035). When women with carpal tunnel syndrome and healthy control women were pooled, the incidence of carpal tunnel syndrome was higher in vitamin D deficient women than in non-deficient women, especially in those younger than 50 years. This study suggests a potential link between vitamin D status and the occurrence of carpal tunnel syndrome in women younger than 50 years but causation is not established.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic Level III.

A high thyroid stimulating hormone level is associated with diabetic peripheral neuropathy in type 2 diabetes patients

AIM

The association between thyroid stimulating hormone (TSH) and type 2 diabetes mellitus (T2DM) is well known. However, whether TSH is related to diabetic peripheral neuropathy (DPN) has not been studied. The aim of this study was to explore the relationship between TSH and DPN in Chinese patients with T2DM.

METHODS

In this cross-sectional study, 605 patients with T2DM were enrolled. Subclinical hypothyroidism (SCH) was defined as an elevated TSH level (>4.0mIU/L) and a normal free thyroxine level. DPN was evaluated by neurological symptoms, neurological signs, and electromyogram.

RESULTS

Serum TSH levels were significantly higher in DPN and signs of DPN compared with non-DPN T2DM patients (both P<0.01).The prevalence of DPN and signs of DPN in SCH subjects was higher than that in euthyroid subjects (both P<0.01). Spearman's correlation analysis showed that the serum TSH level was positively associated with DPN (r=0.172, P<0.01). A significant independent association between TSH and DPN was found by multiple logistic regression analysis after adjusting for potential confounding variables [odds ratio (OR)=1.365, P<0.01]. The patients were sequentially assigned to quartiles according to TSH level. Compared with quartile 1, patients in quartile 2 (P<0.01), quartile 3 (P=0.01), and quartile 4 (P<0.01) had a higher risk of DPN. Receiver-operating characteristic curve analysis revealed that the optimal cutoff point of TSH to indicate DPN was 3.045mIU/L in men and 2.94mIU/L in women.

CONCLUSION

TSH level is independently associated with DPN in Chinese population with T2DM. A high serum TSH level may be a potential risk factor for DPN.

Wherefore Art Thou, O Treatment for Diabetic Neuropathy?

As of March 2016, we continue to advocate the diagnosis of diabetic neuropathy using a simple foot examination or monofilament, which identifies only those with severe neuropathy and hence risk of foot ulceration. Given the fact that the 5-year mortality rate of diabetic patients with foot ulceration is worse than that of most common cancers, surely we should be identifying patients at an earlier stage of neuropathy to prevent its progression to a stage with such a high mortality? Of course, we lament that there is no licensed treatment for diabetic neuropathy. Who is to blame? As researchers and carers, we have a duty of care to our patients with diabetic neuropathy. So, we have to look forward not backwards, and move away from our firmly entrenched views on the design and conduct of clinical trials for diabetic neuropathy. Relevant organizations such as Neurodiab, the American Diabetes Association and the Peripheral Nerve Society have to acknowledge that they cannot continue to endorse a bankrupt strategy. The FDA needs an open and self-critical dialogue with these organizations, to give pharmaceutical companies at least a fighting chance to deliver effective new therapies for diabetic neuropathy.

Vitamin D and Diabetic Complications: True or False Prophet?

Vitamin D deficiency is now recognized as a condition of increasing prevalence worldwide. Vitamin D has an established role in calcium and bone metabolism; however, more recently associations with vitamin D deficiency and risk of developing diabetes, diabetes complications, and cardiovascular disease have all been acknowledged. The vitamin D receptor is ubiquitously expressed, and experimental, in vitro, and in vivo studies strongly suggest a role in regulating the transcription of multiple genes beyond calcium homeostasis. These include antiproliferative, immunomodulatory, angiogenic, inhibition of the renin-angiotensin-aldosterone system, and neurotrophic factor expression. Observational studies report a strong association between vitamin D deficiency and cardiovascular and metabolic disorders; however, there remains a paucity of large long-term randomized clinical trials showing a benefit with treatment. An increasing body of literature suggests a possible pathogenetic role of vitamin D in the long-term complications of diabetes and vitamin D deficiency may also exacerbate symptoms of painful diabetic peripheral neuropathy. It remains unknown if supplementation of vitamin D to normal or non-deficient levels alters pathogenetic processes related to diabetic microvascular complications. With the high prevalence of vitamin D deficiency in patients with diabetes and putative mechanisms linking vitamin D deficiency to diabetic complications, there is a compelling argument for undertaking large well-designed randomized controlled trials of vitamin D supplementation.

Low serum vitamin D occurs commonly among multiple myeloma patients treated with bortezomib and/or thalidomide and is associated with severe neuropathy

PURPOSE

Previous studies have shown that low serum vitamin D levels have been associated with many skeletal and non-skeletal disorders. We studied the relationship between 25-hydroxyvitamin D (25D) levels and motor and sensory peripheral neuropathy (PN) among multiple myeloma (MM) patients who have been treated with bortezomib and/or thalidomide.

METHODS

We performed a study of 111 MM patients who had received at least one of these two agents for at least 12 weeks by correlating physical exam/neurologic assessment findings with patient self-assessment responses.

RESULTS

The median age of study patients was 66 years (range 42-89 years) and 54 % were males. 25D levels were determined, and complete history and physical and neurologic examinations were performed at the same study visit. In addition, study subjects completed questionnaires regarding symptoms related to motor and sensory PN. Overall, patients had a median serum 25D level of only 32 ng/ml; 42 % of patients were considered either 25D-deficient (<20.0 ng/mL; 16 % of patients) or 25D-insufficient (20.0-29.9 ng/mL; 26 %). Notably, we found that 25D-deficient MM patients were more likely to have severe PN (>grade 2) of both motor (p = 0.0415) and sensory (p = 0.0086) types although the overall incidence of PN was not higher in this patient population.

CONCLUSION

These results show that the severity of peripheral neuropathy is associated with lower vitamin D levels and provides the rationale for monitoring vitamin D for myeloma patients especially those receiving drugs associated with the development of peripheral neuropathy.

Non-linear contribution of serum vitamin D to symptomatic diabetic neuropathy: A case-control study

AIMS

Vitamin D deficiency has recently been speculated to be associated with increased risk of diabetes neuropathy (DN). The aim of this study was to evaluate the odds of symptomatic DN across serum vitamin D levels.

METHODS

All patients with DM were assessed using diabetic neuropathy symptoms and diabetic neuropathy examination score. Overall, 150 cases with DN and 600 controls were included. Serum 25-hydroxyvitamin D (25-OH-D) was measured to determine vitamin D status.

RESULTS

A non-linear association between 25-OH-D and suffering from symptomatic DN was observed which was extracted after stratifying the ORs across different serum 25-OH-D levels. When compared to individuals with 25-OH-D of 30-40 ng/mL, patients with deficient (<20 ng/mL) vitamin D levels had higher odds of having symptomatic DN (OR: 2.04, 95%CI: 0.99-4.02, P=0.054). Participants with vitamin D values of greater than 40 ng/mL were also more likely to exhibit symptomatic DN (fully adjusted OR: 4.29, 95%CI: 1.59-11.55).

CONCLUSIONS

We hypothesize a non-linear contribution of serum vitamin D to symptomatic DN occurrence, which emphasizes that administration of vitamin D should be monitored and evaluated more carefully, especially in patients with diabetes.

Vitamin D for the treatment of painful diabetic neuropathy

OBJECTIVE

To assess the effect of high-dose vitamin D in patients with painful diabetic neuropathy.

METHODS

A single intramuscular dose of 600 000 IU vitamin D was administered, and the effects on metabolic parameters and neuropathic pain assessed over 20 weeks.

RESULTS

143 participants with predominantly type 2 diabetes, aged 52.31±11.48 years, with a Douleur Neuropathique 4 (DN4) score (3.0±1.8), total McGill pain score (21.2±14.9), and Short Form McGill Pain Questionnaire (SFMPQ) score (2.1±0.9), were enrolled. The baseline 25-hydroxyvitamin D (25(OH)D) level was 31.7±23.3 ng/mL and 58 (40.5%) patients showed evidence of vitamin D deficiency (25(OH)D<20 ng/mL). Intramuscular administration of vitamin D resulted in a significant increase in 25(OH)D (46.2±10.2 ng/mL, p<0.0001) and a reduction in positive symptoms on the DN4 (p<0.0001), total pain score (p<0.0001), and SFMPQ (p<0.0001).

CONCLUSIONS

Treatment with a single intramuscular dose of 600 000 IU of vitamin D in patients with painful diabetic neuropathy is associated with a significant decrease in the symptoms of painful diabetic neuropathy.

TRIAL REGISTRATION NUMBER

BIDE-12/2014.

Risk Factors and Comorbidities in Diabetic Neuropathy: An Update 2015

Distal symmetric sensorimotor polyneuropathy (DSPN) is the most common neurological manifestation in diabetes. Major risk factors of DSPN include diabetes duration, hyperglycemia, and age, followed by prediabetes, hypertension, dyslipidemia, and obesity. Height, smoking, insulin resistance, hypoinsulinemia, and others represent an additional risk. Importantly, hyperglycemia, hypertension, dyslipidemia, obesity, and smoking are modifiable. Stringent glycemic control has been shown to be effective in type 1, but not to the same extent in type 2 diabetes. Antilipidemic treatment, especially with fenofibrate, and multi-factorial intervention have produced encouraging results, but more experience is necessary. The major comorbidities of DSPN are depression, autonomic neuropathy, peripheral arterial disease, cardiovascular disease, nephropathy, retinopathy, and medial arterial calcification. Knowledge of risk factors and comorbidities has the potential to enrich the therapeutic strategy in clinical practice as part of the overall medical care for patients with neuropathy. This article provides an updated overview of DSPN risk factors and comorbidities.

The relationship between microvascular complications and vitamin D deficiency in type 2 diabetes mellitus

BACKGROUND

Vitamin D deficiency is reported as a possible risk factor for the development of diabetes in several epidemiologic studies. In this study, we investigated the frequency of 25-OH vitamin D deficiency in type 2 diabetes mellitus and the relationship between 25-OH vitamin D deficiency and the prevalence of microvascular complications.

METHODS

In this retrospective study, we evaluated the medical records of 557 patients with type 2 diabetes admitted to the Endocrinology Outpatient Clinic from January to March 2010 and 112 healthy controls randomly selected from individuals admitted to the hospital for a check-up and who had a laboratory result for serum 25-OH vitamin D concentrations at screening. The levels of 25-OH vitamin D in patients with type 2 diabetes and the relationship between 25-OH vitamin D deficiency and microvascular complications were investigated.

RESULTS

No significant difference in serum 25-OH vitamin D concentrations was observed between the diabetic and control groups. No correlation was observed between HbA1C and serum 25-OH vitamin D levels. Serum 25-OH vitamin D levels were lower in diabetic patients with nephropathy, and patients not using any medication, i.e., those treated with dietary changes alone, had a higher prevalence of nephropathy.

CONCLUSION

Vitamin D deficiency is more common in diabetic patients with nephropathy. When microvascular complications were evaluated, vitamin D levels were found to be lower in patients in whom these complications were more severe. Vitamin D deficiency is therefore associated with microvascular complications in diabetic patients.

Serum 25-hydroxyvitamin D levels and peripheral neuropathy in patients with type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Vitamin D is a multifunctional pro-hormone and has widespread actions in human body. Several studies showed a possible association between vitamin D deficiency and diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes, but no definite conclusion was available.

METHODS

A systematic review and meta-analysis was performed to comprehensively assess the association between serum 25-hydroxyvitamin D [25(OH)D] levels and DPN in patients with type 2 diabetes. Data from eligible studies were pooled using meta-analysis.

RESULTS

Six studies that involved a total of 1,484 type 2 diabetic patients were finally included into the meta-analysis. Meta-analysis showed that there were obviously decreased serum 25(OH)D levels in DPN patients [weighted mean difference (WMD) = -6.36 ng/ml, 95 % confidence interval (95 % CI) -8.57 to -4.14, P < 0.00001]. Vitamin D deficiency was also significantly associated with increased risk of DPN in patients with type 2 diabetes [odds ratio (OR) 2.88, 95 % CI 1.84-4.50, P < 0.00001]. Meta-analysis of three studies with adjusted estimates showed that vitamin D deficiency was independently associated with increased risk of DPN in patients with type 2 diabetes (OR 2.68, 95 % CI 1.67-4.30, P < 0.0001). Sensitivity analysis showed that there was no obvious change in the pooled estimates.

CONCLUSION

Vitamin D is involved in the development of DPN in type 2 diabetic patients, and vitamin D deficiency is very likely to be associated with DPN in type 2 diabetic patients. Further studies are needed to validate the association between vitamin D deficiency and DPN.

High glucose upregulates CYP24A1 expression which attenuates the ability of 1,25(OH)2D3 to increase NGF secretion in a rat Schwann cell line RSC96

Vitamin D deficiency or insufficiency is an independent risk factor for diabetic peripheral neuropathy (DPN), but the relationship between 1,25(OH)2D3 and DPN remains unknown. We found that 1,25(OH)2D3 stimulated the secretion of nerve growth factor (NGF) in rat Schwann cell line RSC96, but ability of 1,25(OH)2D3 to increase NGF protein was impaired under high glucose conditions. High glucose upregulated the expression of CYP24A1 protein, which catalyzes the conversion of 1,25(OH)2D3 into inactive products, further impairing the ability of 1,25(OH)2D3 to upregulate NGF secretion in Schwann cells. Inhibition of CYP24A1 protein expression ameliorated the secretion of NGF in response to 1,25(OH)2D3. The findings of this study suggest that CYP24A1 protein plays an important role in the relationship between DPN and 1,25(OH)2D3.

Decreased serum vitamin D levels are associated with diabetic peripheral neuropathy in a rural area of Turkey

Data examining the association between vitamin D and diabetic peripheral neuropathy are limited. This study investigated the serum levels of vitamin D, vitamin D-binding protein (VDBP), and vitamin D receptor (VDR) in diabetics in the Yozgat region of Turkey, and assessed their relationships with diabetic peripheral neuropathy. 69 diabetic patients and 49 age- and sex-matched control subjects were enrolled in this clinical prospective study. All the diabetics underwent conventional sensory and motor nerve conduction studies, and diabetic peripheral neuropathy was confirmed or ruled out according to the electromyography findings and Douleur Neuropathique 4 questions. Serum vitamin D, VDBP and VDR levels were measured using commercial enzyme-linked immunosorbent assay kits. The serum vitamin D levels (p = 0.001) were significantly lower, while the VDR levels (p = 0.003) were higher, in diabetics than in controls. The serum VDBP levels were similar in both groups (p > 0.05). The serum vitamin D levels were significantly lower in diabetics with diabetic peripheral neuropathy than in those without (p = 0.032), whereas the serum VDBP and VDR levels were similar in these two groups (p > 0.05). The lower serum vitamin D levels in diabetics, especially in those with peripheral neuropathy, may suggest a neurotrophic effect of vitamin D.

Serum 25-hydroxyvitamin D: a predictor of macrovascular and microvascular complications in patients with type 2 diabetes

OBJECTIVE

People with diabetes frequently develop vascular disease. We investigated the relationship between blood 25-hydroxyvitamin D (25OH-D) concentration and vascular disease risk in type 2 diabetes.

RESEARCH DESIGN AND METHODS

The relationships between blood 25OH-D concentration at baseline and the incidence of macrovascular (including myocardial infarction and stroke) and microvascular (retinopathy, nephropathy, neuropathy, and amputation) disease were analyzed with Cox proportional hazards models and logistic regression in an observational study of patients in the 5-year Fenofibrate Intervention and Event Lowering in Diabetes trial.

RESULTS

A total of 50% of the patients had low vitamin D concentrations, as indicated by median blood 25OH-D concentration of 49 nmol/L. These patients with a blood 25OH-D concentration <50 nmol/L had a higher cumulative incidence of macrovascular and microvascular events than those with levels ≥50 nmol/L. Multivariate analysis, stratified by treatment and adjusted for relevant confounders, identified blood 25OH-D concentration as an independent predictor of macrovascular events. A 50 nmol/L difference in blood 25OH-D concentration was associated with a 23% (P = 0.007) change in risk of macrovascular complications during the study, and further adjustments for seasonality, hs-CRP, and physical activity level had little impact. The unadjusted risk of microvascular complications was 18% (P = 0.006) higher during the study, though the excess risk declined to 11-14% and lost significance with adjustment for HbA1c, seasonality, or physical activity.

CONCLUSIONS

Low blood 25OH-D concentrations are associated with an increased risk of macrovascular and microvascular disease events in type 2 diabetes. However, a causal link remains to be demonstrated.

Lower levels of 25-hydroxyvitamin D3 are associated with a higher prevalence of microvascular complications in patients with type 2 diabetes

OBJECTIVE

Low levels of serum 25-hydroxyvitamin D [25(OH)D] are commonly found in type 2 diabetes. We examined whether there is an association between circulating 25(OH)D concentrations and the presence of microvascular complications in people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied 715 outpatients with type 2 diabetes who regularly attended our clinic. Participants were evaluated for the presence of microvascular complications (namely retinopathy and/or nephropathy) by clinical evaluation, fundus examination, urine examination and biochemical tests. Serum 25(OH)D levels were also measured for each participant.

RESULTS

Hypovitaminosis D (ie, a serum 25(OH)D level <30 ng/mL) was found in 75.4%, while deficiency (ie, a 25(OH)D level <20 ng/mL) was found in 36.6% of these patients. Serum 25(OH)D levels decreased significantly in relation to the severity of either retinopathy or nephropathy or both. In multivariate logistic regression analysis, lower 25(OH)D levels were independently associated with the presence of microvascular complications (considered as a composite end point; OR 0.758; 95% CI 0.607 to 0.947, p=0.015). Notably, this association remained significant even after excluding those with an estimated glomerular filtration rate <60 mL/min/1.73 m(2).

CONCLUSIONS

We found an inverse and independent relationship between circulating 25(OH)D levels and the prevalence of microvascular complications in patients with type 2 diabetes. However, vitamin D may be simply a marker and causality cannot be implied from our cross-sectional study. Whether vitamin D supplementation in patients with type 2 diabetes may have beneficial effects on the risk of microvascular complications remains to be investigated.

Prospective evaluation of the effect of short-term oral vitamin d supplementation on peripheral neuropathy in type 2 diabetes mellitus

OBJECTIVE

We aimed to assess the efficacy of short-term oral vitamin D supplementation on peripheral neuropathy in patients with type 2 diabetes.

MATERIALS AND METHODS

This prospective, placebo-controlled trial included 112 type 2 diabetic patients with diabetic peripheral neuropathy (DPN) and vitamin D [25(OH)D] deficiency. Patients were sequentially assigned to a treatment group (n = 57) and a placebo group (n = 55). DPN was assessed using a neuropathy symptom score (NSS), a neuropathy disability score (NDS) and a nerve conduction study (NCS). Vitamin D status was determined by measuring the serum total 25(OH)D concentration. Patients received either oral vitamin D3 capsules or starch capsules once weekly for 8 weeks. The primary outcome was changes in NSS and NDS from baseline. The secondary outcome was changes in the NCS result.

RESULTS

Serum 25(OH)D concentrations significantly improved after oral vitamin D supplementation in the treatment group when compared to the placebo group (32.8 ± 23.7 vs. 1.1 ± 3.6, p < 0.0001). Similarly, the improvement in NSS values was significantly greater in the treatment group than in the placebo group (-1.49 ± 1.37 vs. -0.20 ± 0.59, p < 0.001). No improvement was observed for NDS and NCS between the 2 groups after treatment.

CONCLUSION

Short-term oral vitamin D3 supplementation improved vitamin D status and the symptoms of neuropathy in patients with type 2 diabetes.

Is there an association between diabetic neuropathy and low vitamin D levels?

In the past few years, the effects of vitamin D that go beyond its relationship with bone metabolism have come into the focus of scientific attention. Research concerning diabetes and its complications has become a public health priority. An increasing number of reports link vitamin D deficiency to diabetes; however, so far, there has only been limited and contradictory data available on the correlation between diabetic peripheral neuropathy and vitamin D. Studies of people with type 2 diabetes confirmed the relationship between vitamin D deficiency and neuropathy incidence as well as the severity of the symptoms caused by neuropathy. The latest studies are also suggesting a relationship between the incidence of plantar ulcers and vitamin D deficiency.

Hypovitaminosis D in widespread pain: its effect on pain perception, quality of life and nerve conduction studies

The aim of the study was to investigate the effects of hypovitaminosis D on pain, quality of life (QoL) and nerve conduction studies (NCSs) in patients with chronic widespread pain (CWP). We randomly selected 83 female patients with CWP according to their vitamin D levels in this cross-sectional study. Patients were divided into two groups as sufficient vitamin D level (above 20 ng/ml) and deficient vitamin D level (below 20 ng/ml, hypovitaminosis D). Various pain scales and Nottingham Health Profile (NHP) were used. NCSs were also done. In patients with hypovitaminosis D, there were significantly higher pain scores for all scales (p value range 0.002-0.027). The subscale and total NHP scores were significantly higher in hypovitaminosis D group (p = 0.048-0.001) except social isolation subscale (p = 0.553). Vitamin D levels were in negative correlation with right and left median and/or ulnar motor nerve amplitudes, left tibial motor amplitude. This study confirm that hypovitaminosis D is related with higher pain intensity and lower QoL scores in patients with CWP when compared with control group. Additionally, we identified for the first time that there were negative correlations between vitamin D levels and some findings of NCSs.

[Vitamin D and neuropathy]

Diabetes is a widespread disease and, therefore, studies dealing with diabetes and its complications are very important for public health. Numerous reports link vitamin D deficiency to the increased risk of diabetes mellitus and complications such as neuropathy. However, there are limited and conflicting data available on vitamin D deficiency in patients with diabetic peripheral neuropathy. Studies in type 2 diabetics confirmed the relationship between vitamin D deficiency and incidence of neuropathy. Recent reports suggest a relationship between the incidence of plantar ulcers and vitamin D deficiency.

Musculoskeletal pain: should physicians test for vitamin D level?

AIM

The aim of this study was to evaluate vitamin D levels using a reliable method in patients with regional and generalized musculoskeletal (MSK) pain in comparison to healthy controls.

METHODS

A consecutive prospective case control cohort was recruited. Patients with generalized MSK pain, for example, fibromyalgia (FM), and regional MSK pain, for example, nonspecific low back pain (LBP) and knee osteoarthritis (OA) were screened for 25 hydroxy-vitamin D [25(OH)D₃ ] levels over a period of 9 months in a hospital-based setting.

RESULTS

One hundred and twenty-four patients and 82 age-sex matched controls were evaluated. The mean age for patients was 41.71 ± 13.86 years. Of the 124 patients, 118 (95%) were female, 77 (62.6%) had FM, 18 (14.6%) had LBP and 28 (22.8%) had knee OA. All patients had normal muscle power; 83.7% of females wore long garments, 11.4% wore veils, 95.5% had sun exposure < 10 min/day and 58.5% were multiparaous; 7.3% were strict vegetarians, 45.5% took inadequate dairy products. The mean calcium, parathyroid hormone, alkaline phosphatase and albumin levels were within normal limits for all study subjects. The vitamin D level was deficient in all patients. There was no statistical difference between the mean vitamin D values of the patients and controls, 27.61 ± 13.06 and 25.82 ± 15.06 nmol/L respectively, (P = 0.368).

CONCLUSION

Our findings suggest that it is unlikely that measuring vitamin D will be of diagnostic value in the routine assessment of regional and generalized MSK pain.

The study of serum vitamin d and insulin resistance in chinese populations with normal glucose tolerance

Objectives. The aim of this study was to investigate the relationship between serum vitamin D and insulin resistance in Chinese subjects without diabetes mellitus. Methods. Serum 25(OH)D was measured in 897 individuals with normal glucose tolerance (NGT). Oral glucose tolerance tests (OGTTs) were conducted to exclude cases with diabetes, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT). Metabolic parameters were measured and compared between the highest and lowest 25(OH)D quartiles. The relationship between serum 25(OH)D and homeostatic model assessment-insulin resistance (HOMA-IR) was analyzed. Results. Indexes, such as HOMA-IR, FINS, and SBP, were negatively correlated with serum 25(OH)D concentrations. Compared with the lowest quartile, individuals in the highest group had decreased Lg (HOMA-IR), Lg (FINS), and SBP. Pearson correlation analyses showed that serum 25(OH)D was negatively associated with age, BMI, Lg (HOMA-IR), and Lg (FINS). Multivariate linear regression analysis confirmed the negative correlation of Lg (HOMA-IR) and 25(OH)D. Conclusions. This study showed that serum 25(OH)D could be regarded as an independent predictor of insulin resistance for subjects without diabetes mellitus in China. Adequate vitamin D supplementation may improve multiple metabolic disturbances.

Putative corneal neuralgia responding to vitamin d supplementation

A patient with putative corneal neuralgia was incidentally discovered to have hypovitaminosis D. Supplementation of vitamin D appears to have led to a resolution of the patient's pain, whereas other efforts to treat the patient were unsuccessful.

Role of vitamin d in cardiometabolic diseases

Vitamin D deficiency is a highly prevalent condition. Low vitamin D levels have long been associated with bone diseases, such as rickets in children and osteomalacia and osteoporosis in adults. However, it has become apparent in recent years that adequate vitamin D levels are also important for optimal functioning of many organs and tissues throughout the body, including the cardiovascular system. Evolving data indicate that vitamin D deficiency is associated with an increased risk of cardiovascular disease (CVD). Studies have shown that low vitamin D levels are associated with hypertension, diabetes, metabolic syndrome, left ventricular hypertrophy, and chronic vascular inflammation, all of which are risk factors for CVD. This paper reviews the definition and pathophysiology of vitamin D deficiency, clinical evidence linking vitamin D and CVD risk, diabetes and its complications, and metabolic syndrome.

Reversal of the Symptoms of Diabetic Neuropathy through Correction of Vitamin D Deficiency in a Type 1 Diabetic Patient

Vitamin D deficiency has been associated with both type 1 and type 2 diabetes as well as both the microvascular and macrovascular complications of diabetes. Vitamin D deficiency has been shown to be more common in diabetic patients who have symptoms of distal symmetrical polyneuropathy. In addition, vitamin D deficiency has been associated with a lower pain threshold which increases when vitamin D deficiency is corrected. Herein, I describe a type 1 diabetic patient with neuropathic symptoms so severe that he could not work and for which he needed narcotics for pain management and whose symptoms improved dramatically with correction of the vitamin D deficiency. To my knowledge, this is the first report of an improvement in severe symptoms of diabetic neuropathy with correction of vitamin D deficiency in a single patient.

The impact of 1,25-dihydroxy vitamin D3 on the expressions of vascular endothelial growth factor and transforming growth factor-β₁ in the retinas of rats with diabetes

AIMS

To define whether 1,25-dihydroxy vitamin D3 (1,25-(OH)₂ D₃) can protect diabetic retinopathy and to investigate its impact on the expressions of vascular endothelial growth factor (VEGF) and transforming growth factor-β₁ (TGF-β₁) in the retinas of rats with diabetes.

METHODS

Male Sprague-Dawley (SD) rats were divided into normal control group, 1,25-(OH)₂ D₃ group and diabetes group. The rats in 1,25-(OH)₂ D₃ group and diabetes group were established to type 2 diabetes model with high-fat and high-sugar diet and streptozotocin (STZ). Meanwhile, the rats of 1,25-(OH)₂ D₃ group were treated with 1,25-(OH)₂ D₃. After 13 weeks, morphological changes of retinal tissues were observed under microscopes after hematoxylin-eosin staining. VEGF and TGF-β₁ expressions in the retinal tissues were detected with immunohistochemistry staining.

RESULTS

Pathological examination showed an appearance of edema and disordered arrangement of retinal tissues in diabetes group, but milder pathological changes in 1,25-(OH)₂ D₃ group. VEGF and TGF-β₁ expressions of both diabetes group and 1,25-(OH)₂ D₃ group significantly increased (P<0.05), but those of 1,25-(OH)₂ D₃ group were significantly lower than diabetes group (P<0.05).

CONCLUSION

1,25-(OH)₂ D₃ had partially protective effect on diabetic retinopathy of diabetic rats, the mechanism of which might inhibit VEGF and TGF-β₁ expressions in the retinal tissues.

Electroencephalography to assess motor control during balance tasks in people with diabetes

BACKGROUND

Balance is sensed through peripheral and central receptors and mediated by central control through the brain and spinal cord. Although some evidence exists as to the areas of the brain involved and how processing of data occurs in young individuals, nothing has been published on people with diabetes. The purpose of this study was to examine the electroencephalogram (EEG) during common sensorimotor and balance training tasks and to relate these to task difficulty.

SUBJECTS AND METHODS

Postural sway and EEG change of alpha, beta, and sigma wave bands were measured in 17 young subjects, 10 older subjects, and 10 subjects with diabetes during eight progressively more difficult balance tasks with eyes open and closed, feet in tandem or apart, and on foam or a firm surface.

RESULTS

EEG power of beta and sigma wave bands showed significant increases on the cortical and parietal areas of the brain relative to the control tasks when eyes were open (P<0.05). The cortical involvement decreased as the task became more difficult with vision and somatosensory information reduced, whereas that of the parietal area increased with task difficulty. The greatest increase was in subjects with diabetes, and the least was in younger people. Individuals with diabetes had increased sigma and beta EEG power in all regions of the brain examined with increased complexity of the balance task.

CONCLUSIONS

This study demonstrated cortical and parietal involvement in static balance tasks commonly used in sensorimotor training. The results support the proposal that there was increased subcortical control with increase in task difficulty in the young subjects, but in subjects with diabetes, there was a major increase in activity across the brain.