Enhanced glucose control for preventing and treating diabetic neuropathy

Retinal Failure in Diabetes: a Feature of Retinal Sensory Neuropathy

Physiologic adaptations mediate normal responses to short-term and long-term stresses to ensure organ function. Organ failure results if adaptive responses fail to resolve persistent stresses or maladaptive reactions develop. The retinal neurovascular unit likewise undergoes adaptive responses to diabetes resulting in a retinal sensory neuropathy analogous to other sensory neuropathies. Vision-threatening diabetic retinal neuropathy results from unremitting metabolic and inflammatory stresses, leading to macular edema and proliferative diabetic retinopathy, states of "retinal failure." Current regulatory strategies focus primarily on the retinal failure stages, but new diagnostic modalities and understanding of the pathophysiology of diabetic retinopathy may facilitate earlier treatment to maintain vision in persons with diabetes.

Distal Symmetric Polyneuropathy: A Review

IMPORTANCE

Peripheral neuropathy is a highly prevalent and morbid condition affecting 2% to 7% of the population. Patients frequently experience pain and are at risk of falls, ulcerations, and amputations. We aimed to review recent diagnostic and therapeutic advances in distal symmetric polyneuropathy, the most common subtype of peripheral neuropathy.

OBSERVATIONS

Current evidence supports limited routine laboratory testing in patients with distal symmetric polyneuropathy. Patients without a known cause should undergo a complete blood cell count, comprehensive metabolic panel, vitamin B12 measurement, serum protein electrophoresis with immunofixation, fasting glucose measurement, and glucose tolerance test. The presence of atypical features such as asymmetry, non-length dependence, motor predominance, acute or subacute onset, and prominent autonomic involvement should prompt a consultation with a neurologist or neuromuscular specialist. Electrodiagnostic tests and magnetic resonance imaging of the neuroaxis contribute substantial cost to the diagnostic evaluation, but evidence supporting their use is lacking. Strong evidence supports the use of tricyclic antidepressants, serotonin norepinephrine reuptake inhibitors, and voltage-gated calcium channel ligands in the treatment of neuropathic pain. More intensive glucose control substantially reduces the incidence of distal symmetric polyneuropathy in patients with type 1 diabetes but not in those with type 2 diabetes.

CONCLUSIONS AND RELEVANCE

The opportunity exists to improve guideline-concordant testing in patients with distal symmetric polyneuropathy. Moreover, the role of electrodiagnostic tests needs to be further defined, and interventions to reduce magnetic resonance imaging use in this population are needed. Even though several efficacious medications exist for neuropathic pain treatment, pain is still underrecognized and undertreated. New disease-modifying medications are needed to prevent and treat peripheral neuropathy, particularly in type 2 diabetes.

Effects of exenatide on measures of diabetic neuropathy in subjects with type 2 diabetes: results from an 18-month proof-of-concept open-label randomized study

OBJECTIVE

Experimental studies have reported potential benefit of glucagon-like peptide-1(GLP-1) receptor agonists in preventing diabetic peripheral neuropathy (DPN). We therefore performed a proof-of-concept pilot study to evaluate the effect of exenatide, a GLP-1 agonist, on measures of DPN and cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Forty-six T2D subjects (age 54±10years, diabetes duration 8±5years, HbA1c 8.2±1.3%) with mild to moderate DPN at baseline were randomized to receive either twice daily exenatide (n=22) or daily insulin glargine (n=24). The subjects, with similar HbA1c levels, were followed for 18months. The primary end point was the prevalence of confirmed clinical neuropathy (CCN). Changes in measures of CAN, other measures of small fiber neuropathy such as intra-epidermal nerve fiber density (IENFD), and quality of life were also analyzed.

RESULTS

Glucose control was similar in both groups during the study. There were no statistically significant treatment group differences in the prevalence of CCN, IENFD, measures of CAN, nerve conductions studies, or quality of life indices.

CONCLUSIONS

In this pilot study of patients with T2D and mild to moderate DPN, 18months of exenatide treatment had no significant effect on measures of neuropathy compared with glargine treatment.

Modulating Molecular Chaperones Improves Mitochondrial Bioenergetics and Decreases the Inflammatory Transcriptome in Diabetic Sensory Neurons

We have previously demonstrated that modulating molecular chaperones with KU-32, a novobiocin derivative, ameliorates physiologic and bioenergetic deficits of diabetic peripheral neuropathy (DPN). Replacing the coumarin core of KU-32 with a meta-fluorinated biphenyl ring system created KU-596, a novobiocin analogue (novologue) that showed neuroprotective activity in a cell-based assay. The current study sought to determine whether KU-596 offers similar therapeutic potential for treating DPN. Administration of 2-20 mg/kg of KU-596 improved diabetes induced hypoalgesia and sensory neuron bioenergetic deficits in a dose-dependent manner. However, the drug could not improve these neuropathic deficits in diabetic heat shock protein 70 knockout (Hsp70 KO) mice. To gain further insight into the mechanisms by which KU-596 improved DPN, we performed transcriptomic analysis of sensory neuron RNA obtained from diabetic wild-type and Hsp70 KO mice using RNA sequencing. Bioinformatic analysis of the differentially expressed genes indicated that diabetes strongly increased inflammatory pathways and that KU-596 therapy effectively reversed these increases independent of Hsp70. In contrast, the effects of KU-596 on decreasing the expression of genes regulating the production of reactive oxygen species were more Hsp70-dependent. These data indicate that modulation of molecular chaperones by novologue therapy offers an effective approach toward correcting nerve dysfunction in DPN but that normalization of inflammatory pathways alone by novologue therapy seems to be insufficient to reverse sensory deficits associated with insensate DPN.

The Metabolic Syndrome and Microvascular Complications in a Murine Model of Type 2 Diabetes

To define the components of the metabolic syndrome that contribute to diabetic polyneuropathy (DPN) in type 2 diabetes mellitus (T2DM), we treated the BKS db/db mouse, an established murine model of T2DM and the metabolic syndrome, with the thiazolidinedione class drug pioglitazone. Pioglitazone treatment of BKS db/db mice produced a significant weight gain, restored glycemic control, and normalized measures of serum oxidative stress and triglycerides but had no effect on LDLs or total cholesterol. Moreover, although pioglitazone treatment normalized renal function, it had no effect on measures of large myelinated nerve fibers, specifically sural or sciatic nerve conduction velocities, but significantly improved measures of small unmyelinated nerve fiber architecture and function. Analyses of gene expression arrays of large myelinated sciatic nerves from pioglitazone-treated animals revealed an unanticipated increase in genes related to adipogenesis, adipokine signaling, and lipoprotein signaling, which likely contributed to the blunted therapeutic response. Similar analyses of dorsal root ganglion neurons revealed a salutary effect of pioglitazone on pathways related to defense and cytokine production. These data suggest differential susceptibility of small and large nerve fibers to specific metabolic impairments associated with T2DM and provide the basis for discussion of new treatment paradigms for individuals with T2DM and DPN.

Increased aortic stiffness predicts future development and progression of peripheral neuropathy in patients with type 2 diabetes: the Rio de Janeiro Type 2 Diabetes Cohort Study

AIMS/HYPOTHESIS

Diabetic peripheral neuropathy (DPN) is a chronic microvascular complication that is strongly associated with poor glycaemic control and also with a worse prognosis. We aimed to evaluate the predictors of the development and progression of DPN in a cohort of high-risk patients with type 2 diabetes.

METHODS

In a prospective study, 477 patients with type 2 diabetes were clinically assessed for the presence of DPN at baseline and after a median follow-up of 6.2 years (range 2-10 years). Clinical laboratory data were obtained at study entry and throughout the follow-up. Aortic stiffness was assessed by the carotid-femoral pulse wave velocity (cf-PWV) at baseline. Multivariate Poisson regression analysis was used to examine independent predictors of the development/progression of DPN.

RESULTS

At baseline, 135 patients (28%) had DPN, and during follow-up 97 patients (20%) had either a new development or a worsening of DPN. Patients who showed a development or progression of DPN were taller and had a longer duration of diabetes, a greater prevalence of other microvascular complications and hypertension, greater aortic stiffness and poorer glycaemic control than patients who did not have new or progressive neuropathy. After adjustments for the baseline prevalence of DPN, the patient's age and sex, and the time interval between DPN assessments; an increased aortic stiffness (cf-PWV >10 m/s) were predictive of new/progressive DPN (incidence rate ratio 2.04, 95% CI 1.28, 3.23; p = 0.002). Other independent predictors were the mean first-year HbA1c level (p = 0.05), nephropathy (p = 0.006), arterial hypertension (p = 0.06) and height (p = 0.03).

CONCLUSIONS/INTERPRETATION

Increased aortic stiffness at baseline predicts the future development or progression of peripheral neuropathy, independent of diabetic metabolic control, suggesting a physiopathological link between macrovascular and microvascular abnormalities in type 2 diabetes.

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.

Treating Diabetic Neuropathy: Present Strategies and Emerging Solutions

Diabetic peripheral neuropathies (DPN) are a heterogeneous group of disorders caused by neuronal dysfunction in patients with diabetes. They have differing clinical courses, distributions, fiber involvement (large or small), and pathophysiology. These complications are associated with increased morbidity, distress, and healthcare costs. Approximately 50% of patients with diabetes develop peripheral neuropathy, and the projected rise in the global burden of diabetes is spurring an increase in neuropathy. Distal symmetrical polyneuropathy (DSPN) with painful diabetic neuropathy, occurring in around 20% of diabetes patients, and diabetic autonomic neuropathy (DAN) are the most common manifestations of DPN. Optimal glucose control represents the only broadly accepted therapeutic option though evidence of its benefit in type 2 diabetes is unclear. A number of symptomatic treatments are recommended in clinical guidelines for the management of painful DPN, including antidepressants such as amitriptyline and duloxetine, the γ-aminobutyric acid analogues gabapentin and pregabalin, opioids, and topical agents such as capsaicin. However, monotherapy is frequently not effective in achieving complete resolution of pain in DPN. There is a growing need for head-to-head studies of different single-drug and combination pharmacotherapies. Due to the ubiquity of autonomic innervation in the body, DAN causes a plethora of symptoms and signs affecting cardiovascular, urogenital, gastrointestinal, pupillomotor, thermoregulatory, and sudomotor systems. The current treatment of DAN is largely symptomatic, and does not correct the underlying autonomic nerve deficit. A number of novel potential candidates, including erythropoietin analogues, angiotensin II receptor type 2 antagonists, and sodium channel blockers are currently being evaluated in phase II clinical trials.

A review of the clinical utility of duloxetine in the treatment of diabetic peripheral neuropathic pain

Diabetes mellitus is a world-wide epidemic with many long-term complications, with neuropathy being the most common. In particular, diabetic peripheral neuropathic pain (DPNP), can be one of the most distressing complications associated with diabetes, leading to decreases in physical and mental quality of life. Despite the availability of many efficient medications, DPNP remains a challenge to treat, and the optimal sequencing of pharmacotherapy remains unknown. Currently, there are only three medications approved by the US Food and Drug Administration specifically for the management of DPNP. Duloxetine (DUL), a selective serotonin-norepinephrine reuptake inhibitor, is one of these. With the goal of optimizing pharmacotherapy use in DPNP population, a review of current literature was conducted, and the clinical utility of DUL described. Along with early clinical trials, recently published observational studies and pharmacoeconomic models may be useful in guiding decision making by clinicians and managed care organizations. In real-world practice settings, DUL is associated with decreased or similar opioid utilization, increased medication adherence, and similar health care costs compared with current standard of care. DUL has consistently been found to be a cost-effective option over short time-horizons. Currently, the long-term cost-effectiveness of DUL is unknown. Evidence derived from randomized clinical trials, real-world observations, and economic models support the use of DUL as a first-line treatment option from the perspective of the patient, clinician, and managed care payer.

A Genome-wide Association Study Provides Evidence of Sex-specific Involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) With Diabetic Neuropathic Pain

Neuropathic pain is defined as pain arising as a direct consequence of a lesion or a disease affecting the somatosensory system and it affects around 1 in 4 diabetic patients in the UK. The purpose of this genome-wide association study (GWAS) was to identify genetic contributors to this disorder. Cases of neuropathic pain were defined as diabetic patients with a multiple prescription history of at least one of five drugs specifically indicated for the treatment of neuropathic pain. Controls were diabetic individuals who were not prescribed any of these drugs, nor amitriptyline, carbamazepine, or nortriptyline. Overall, 961 diabetic neuropathic pain cases and 3260 diabetic controls in the Genetics of Diabetes Audit and Research Tayside (GoDARTS) cohort were identified. We found a cluster in the Chr1p35.1 (ZSCAN20-TLR12P) with a lowest P value of 2.74 × 10(- 7) at rs71647933 in females and a cluster in the Chr8p23.1, next to HMGB1P46 with a lowest P value of 8.02 × 10(- 7) at rs6986153 in males. Sex-specific narrow sense heritability was higher in males (30.0%) than in females (14.7%). This GWAS on diabetic neuropathic pain provides evidence for the sex-specific involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) with the disorder, indicating the need for further research.

Diabetic neuropathies

PURPOSE OF REVIEW

This article provides an overview for understanding the diagnosis, pathogenesis, and management of diabetic neuropathy.

RECENT FINDINGS

New information about the pathogenesis of diabetic neuropathy continues to emerge, which will lead to identifying new drug targets. It is clear that the natural history of diabetic neuropathy is changing and the rate of progression is slowing. This is likely because of a combination of earlier diagnosis, improved glycemic management, and improved control of related complications such as hyperlipidemia and hypertension. Early diagnosis is critical, and small fiber neuropathy or subclinical diabetic neuropathy may be reversed or significantly improved with appropriate intervention. The American Academy of Neurology recently published guidelines for the treatment of painful diabetic neuropathy.

SUMMARY

Diabetic neuropathy is common and can present with varied clinical presentations discussed in this article. Although treatment currently focuses on pain management, attention should be paid to potential risk factors for neuropathy. For example, glycemic control, hyperlipidemia, and hypertension should be managed with diet, exercise, and medications. Class I or II clinical studies indicate that pregabalin, duloxetine, amitriptyline, gabapentin, and opioids are effective in the management of diabetic neuropathic pain.

Pharmacological treatment of diabetic peripheral neuropathy

Pain modulation is a key treatment goal for diabetic peripheral neuropathy patients. Guidelines have recommended antidepressant, anticonvulsant, analgesic, and topical medications-both approved and off-label-to reduce pain in this population.

Longitudinal patient-oriented outcomes in neuropathy: Importance of early detection and falls

OBJECTIVE

To evaluate longitudinal patient-oriented outcomes in peripheral neuropathy over a 14-year time period including time before and after diagnosis.

METHODS

The 1996-2007 Health and Retirement Study (HRS)-Medicare Claims linked database identified incident peripheral neuropathy cases (ICD-9 codes) in patients ≥65 years. Using detailed demographic information from the HRS and Medicare claims, a propensity score method identified a matched control group without neuropathy. Patient-oriented outcomes, with an emphasis on self-reported falls, pain, and self-rated health (HRS interview), were determined before and after neuropathy diagnosis. Generalized estimating equations were used to assess differences in longitudinal outcomes between cases and controls.

RESULTS

We identified 953 peripheral neuropathy cases and 953 propensity-matched controls. The mean (SD) age was 77.4 (6.7) years for cases, 76.9 (6.6) years for controls, and 42.1% had diabetes. Differences were detected in falls 3.0 years before neuropathy diagnosis (case vs control; 32% vs 25%, p = 0.008), 5.0 years for pain (36% vs 27%, p = 0.002), and 5.0 years for good to excellent self-rated health (61% vs 74%, p < 0.0001). Over time, the proportion of fallers increased more rapidly in neuropathy cases compared to controls (p = 0.002), but no differences in pain (p = 0.08) or self-rated health (p = 0.9) were observed.

CONCLUSIONS

In older persons, differences in falls, pain, and self-rated health can be detected 3-5 years prior to peripheral neuropathy diagnosis, but only falls deteriorates more rapidly over time in neuropathy cases compared to controls. Interventions to improve early peripheral neuropathy detection are needed, and future clinical trials should incorporate falls as a key patient-oriented outcome.

Neuroprotective effects of Gymnema sylvestre on streptozotocin-induced diabetic neuropathy in rats

The application of traditional medicine for diabetes and associated complications, such as diabetic neuropathy (DN), has received increasing attention. The aim of the present study was to investigate the potential ameliorative effect of Gymnema sylvestre (Gs) in a rat model of DN. Diabetes was induced via a single intraperitoneal injection of streptozotocin (STZ; 60 mg/kg). Treatment with Gs extract (50 or 100 mg/kg/day) began two weeks following the administration of STZ and was continued for five weeks. Pain threshold behavior tests were performed subsequent to the five-week Gs treatment period. In addition, the serum levels of glucose, insulin and proinflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, were determined. Furthermore, the sciatic tissue levels of nitric oxide, thiobarbituric acid reactive substances and reduced glutathione were determined, as well as the activity levels of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. Levels of insulin-like growth factor (IGF), nerve growth factor (NGF), TNF-α, IL-1β and IL-6 were also assessed in the sciatic tissue. In addition, the sciatic nerve tissue samples were analyzed for histopathological alterations. The diabetic rats exhibited apparent reductions in the paw-withdrawal (31%; P<0.01) and tail-flick latencies (38%; P<0.05). Furthermore, the diabetic rats demonstrated an evident elevation in serum and sciatic levels of proinflammatory cytokines. Measured oxidative stress biomarkers were significantly altered in the sciatic nerve tissue of the diabetic rats. Treatment with Gs attenuated diabetes-induced modifications with regard to the levels of serum glucose, insulin and proinflammatory cytokines. In the sciatic nerve tissue, the diabetes-induced alterations in IL levels and oxidative stress biomarkers were significantly improved in the Gs-treated rats. Furthermore, the reduction in the sciatic tissue expression levels of IGF and NGF was also ameliorated by Gs treatment. Histological analysis indicated that Gs corrected the sciatic tissue in the diabetic rats. Therefore, the results demonstrated that the neuroprotective effect of Gs may be associated with the inhibitory effect on the excessive activation of inflammatory molecules and oxidative stress mediators.

Treatment of painful diabetic neuropathy

Painful diabetic neuropathy (PDN) is a debilitating consequence of diabetes that may be present in as many as one in five patients with diabetes. The objective assessment of PDN is difficult, making it challenging to diagnose and assess in both clinical practice and clinical trials. No single treatment exists to prevent or reverse neuropathic changes or to provide total pain relief. Treatment of PDN is based on three major approaches: intensive glycaemic control and risk factor management, treatments based on pathogenetic mechanisms, and symptomatic pain management. Clinical guidelines recommend pain relief in PDN through the use of antidepressants such as amitriptyline and duloxetine, the γ-aminobutyric acid analogues gabapentin and pregabalin, opioids and topical agents such as capsaicin. Of these medications, duloxetine and pregabalin were approved by the US Food and Drug Administration (FDA) in 2004 and tapentadol extended release was approved in 2012 for the treatment of PDN. Proposed pathogenetic treatments include α-lipoic acid (stems reactive oxygen species formation), benfotiamine (prevents vascular damage in diabetes) and aldose-reductase inhibitors (reduces flux through the polyol pathway). There is a growing need for studies to evaluate the most potent drugs or combinations for the management of PDN to maximize pain relief and improve quality of life. A number of agents are potential candidates for future use in PDN therapy, including Nav 1.7 antagonists, N-type calcium channel blockers, NGF antibodies and angiotensin II type 2 receptor antagonists.

Glucose regulation, cognition, and brain MRI in type 2 diabetes: a systematic review

Type 2 diabetes is associated with cognitive dysfunction and structural brain changes. Abnormalities in glucose regulation are involved in several complications related to type 2 diabetes, but their role in these cerebral complications is unclear. We systematically reviewed studies of the association between glucose regulation (glycaemia, hypoglycaemic events, insulin concentration, insulin resistance, and glucose-lowering treatment) and cognitive function and brain abnormalities on MRI in people with type 2 diabetes. The 86 papers included showed that glycaemia, particularly high HbA1c concentration and glucose variability, are negatively associated with cognitive function in people with type 2 diabetes without dementia. However, the strength of this association is weak, and HbA1c generally accounted for less than 10% of the variance in cognition. Importantly, few studies have measured long-term cerebral outcomes, such as dementia and structural brain changes on MRI, and the effect of glucose-lowering treatment on these outcomes. More randomised controlled trials are needed to establish the effect of glucose-lowering treatment on long-term cognitive function in people with type 2 diabetes.

Optimization of a cisplatin model of chemotherapy-induced peripheral neuropathy in mice: use of vitamin C and sodium bicarbonate pretreatments to reduce nephrotoxicity and improve animal health status

Background

Cisplatin, a platinum-derived chemotherapeutic agent, produces antineoplastic effects coupled with toxic neuropathic pain and impaired general health status. These side-effects complicate long term studies of neuropathy or analgesic interventions in animals. We recently demonstrated that pretreatment with sodium bicarbonate (4% NaHCO₃) prior to cisplatin (3 mg/kg i.p. weekly up to 5 weeks) was associated with improved health status (i.e. normal weight gain, body temperature, creatinine and ketone levels, and kidney weight ratio) in rats (Neurosci Lett 544:41-46, 2013). To reduce the nephrotoxic effects of cisplatin treatment in mice, we compared effects of sodium bicarbonate (4% NaHCO₃ s.c_.), vitamin C (25 mg/kg s.c_.), resveratrol (25 mg/kg s.c_.) and saline (0.9% NaCl) pretreatment on cisplatin-induced changes in animal health status, neuropathic pain and proinflammatory cytokine levels in spinal cord and kidney.

Results

Cisplatin-treated mice receiving saline pretreatment exhibited elevated ketone, creatinine and kidney weight ratios, representative of nephrotoxicity. Vitamin C and sodium bicarbonate lowered creatinine/ketone levels and kidney weight ratio whereas resveratrol normalized creatinine levels and kidney weight ratios similar to saline pretreatment. All pretreatments were associated with decreased ketone levels compared to saline pretreatment. Cisplatin-induced neuropathy (i.e. mechanical and cold allodynia) developed equivalently in all pretreatment groups and was similarly reversed by either morphine (6 mg/kg i.p.) or ibuprofen (6 mg/kg i.p.) treatment. RT-PCR showed that mRNA levels for IL-1β were increased in lumbar spinal cord of cisplatin-treated groups pretreated with either saline, NaHCO₃ or resveratrol/cisplatin-treated groups. However, IL-6 and TNF-alpha were elevated in the kidneys in all cisplatin-treated groups. Our studies also demonstrate that 60 days after the last cisplatin treatment, body weight, body temperature, kidney functions and mRNA levels have returned to baseline although the neuropathic pain (mechanical and cold) is maintained.

Conclusions

Studies employing cisplatin should include NaHCO₃ or vitamin C pretreatment to improve animal health status and reduce nephrotoxicity (lower creatinine and kidney weight ratio) without affecting the development of chemotherapy-induced neuropathy or analgesic efficacy.

Targeting intensive versus conventional glycaemic control for type 1 diabetes mellitus: a systematic review with meta-analyses and trial sequential analyses of randomised clinical trials

OBJECTIVE

To assess the benefits and harms of targeting intensive versus conventional glycaemic control in patients with type 1 diabetes mellitus.

DESIGN

A systematic review with meta-analyses and trial sequential analyses of randomised clinical trials.

DATA SOURCES

The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded and LILACS to January 2013.

STUDY SELECTION

Randomised clinical trials that prespecified different targets of glycaemic control in participants at any age with type 1 diabetes mellitus were included.

DATA EXTRACTION

Two authors independently assessed studies for inclusion and extracted data.

RESULTS

18 randomised clinical trials included 2254 participants with type 1 diabetes mellitus. All trials had high risk of bias. There was no statistically significant effect of targeting intensive glycaemic control on all-cause mortality (risk ratio 1.16, 95% CI 0.65 to 2.08) or cardiovascular mortality (0.49, 0.19 to 1.24). Targeting intensive glycaemic control reduced the relative risks for the composite macrovascular outcome (0.63, 0.41 to 0.96; p=0.03), and nephropathy (0.37, 0.27 to 0.50; p<0.00001. The effect estimates of retinopathy, ketoacidosis and retinal photocoagulation were not consistently statistically significant between random and fixed effects models. The risk of severe hypoglycaemia was significantly increased with intensive glycaemic targets (1.40, 1.01 to 1.94). Trial sequential analyses showed that the amount of data needed to demonstrate a relative risk reduction of 10% were, in general, inadequate.

CONCLUSIONS

There was no significant effect towards improved all-cause mortality when targeting intensive glycaemic control compared with conventional glycaemic control. However, there may be beneficial effects of targeting intensive glycaemic control on the composite macrovascular outcome and on nephropathy, and detrimental effects on severe hypoglycaemia. Notably, the data for retinopathy and ketoacidosis were inconsistent. There was a severe lack of reporting on patient relevant outcomes, and all trials had poor bias control.

Leptin monotherapy rescues spermatogenesis in male Akita type 1 diabetic mice

Type 1 diabetes is associated with subfertility in humans. The current treatment for type 1 diabetes, insulin monotherapy, is suboptimal to fully stabilize glycemia, potentially leading to this subfertility. Recent work has demonstrated that treatment with the energy-regulating hormone leptin, alone or in combination with insulin, can more effectively control glycemia in mouse models of type 1 diabetes. Here, we sought to determine whether the fertility defects in a type 1 diabetic mouse model, the Akita mouse, can be rescued with leptin monotherapy in the absence of any exogenous insulin. Akita homozygous mice treated with leptin alone had a larger total body size, testes, and seminal vesicles than their untreated siblings. Leptin treatment prevented testicular degeneration and rescued sperm motility to wild-type levels. Furthermore, sperm obtained from leptin-treated mice could successfully fertilize ooctyes in vitro. Despite completely rescuing spermatogenesis, the critical reproductive hormones LH and testosterone were only modestly higher than in untreated mice, indicating that a minimum threshold of these hormones must be met to maintain spermatogenesis. Cumulatively, these findings implicate the importance of leptin in maintaining fertility and support the use of leptin therapy in the treatment of type 1 diabetes.

Diabetic neuropathy: mechanisms, emerging treatments, and subtypes

Diabetic neuropathies (DNs) differ in clinical course, distribution, fiber involvement (type and size), and pathophysiology, the most typical type being a length-dependent distal symmetric polyneuropathy (DSP) with differing degrees of autonomic involvement. The pathogenesis of diabetic DSP is multifactorial, including increased mitochondrial production of free radicals due to hyperglycemia-induced oxidative stress. Mechanisms that impact neuronal activity, mitochondrial function, membrane permeability, and endothelial function include formation of advanced glycosylation end products, activation of polyol aldose reductase signaling, activation of poly(ADP ribose) polymerase, and altered function of the Na(+)/K(+)-ATPase pump. Hyperglycemia-induced endoplasmic reticulum stress triggers several neuronal apoptotic processes. Additional mechanisms include impaired nerve perfusion, dyslipidemia, altered redox status, low-grade inflammation, and perturbation of calcium balance. Successful therapies require an integrated approach targeting these mechanisms. Intensive glycemic control is essential but is insufficient to prevent onset or progression of DSP, and disease-modifying treatments for DSP have been disappointing. Atypical forms of DN include subacute-onset sensory (symmetric) or motor (asymmetric) predominant conditions that are frequently painful but generally self-limited. DNs are a major cause of disability, associated with reduced quality of life and increased mortality.

Intradermal insulin delivery: a promising future for diabetes management

The incidence of insulinopenic diabetes mellitus is constantly increasing, and in addition, approximately a third of all hyperinsulinemic diabetic patients develop insulinopenia. Optimal glycemic control is essential to minimize the risk for diabetes-induced complications, but the majority of diabetic patients fail to achieve proper long-term glucose levels even in clinical trials, and even more so in clinical practice. Compliance with a treatment regimen is likely to be higher if the procedure is simple, painless, and discreet. Thus, insulin has been suggested for nasal, gastrointestinal, and inhalation therapy, but so far with considerable downsides in effect, side effects, or patient acceptance. The stratum corneum is the main barrier preventing convenient drug administration without the drawbacks of subcutaneous injections. Recently, devices with miniaturized needles have been developed that combine the simplicity and discretion of patch-based treatments, but with the potential of peptide and protein administration. As this review describes, initial comparisons with subcutaneous administration now suggest microneedle patches for active insulin delivery are efficient in maintaining glycemic control. Hollow microneedle technology could also prove to be efficient in systemic as well as local delivery of other macromolecular drugs, such as vaccines.

Pancreas transplantation: solid organ and islet

Transplantation of the pancreas, either as a solid organ or as isolated islets of Langerhans, is indicated in a small proportion of patients with insulin-dependent diabetes in whom severe complications develop, particularly severe glycemic instability and progressive secondary complications (usually renal failure). The potential to reverse diabetes has to be balanced against the morbidity of long-term immunosuppression. For a patient with renal failure, the treatment of choice is often a simultaneous transplant of the pancreas and kidney (SPK), whereas for a patient with glycemic instability, specifically hypoglycemic unawareness, the choice between a solid organ and an islet transplant has to be individual to the patient. Results of SPK transplantation are comparable to other solid-organ transplants (kidney, liver, heart) and there is evidence of improved quality of life and life expectancy, but the results of solitary pancreas transplantation and islets are inferior with respect to graft survival. There is some evidence of benefit with respect to the progression of secondary diabetic complications in patients with functioning transplants for several years.

Intensive glucose control versus conventional glucose control for type 1 diabetes mellitus

BACKGROUND

Clinical guidelines differ regarding their recommended blood glucose targets for patients with type 1 diabetes and recent studies on patients with type 2 diabetes suggest that aiming at very low targets can increase the risk of mortality.

OBJECTIVES

To assess the effects of intensive versus conventional glycaemic targets in patients with type 1 diabetes in terms of long-term complications and determine whether very low, near normoglycaemic values are of additional benefit.

SEARCH METHODS

A systematic literature search was performed in the databases The Cochrane Library, MEDLINE and EMBASE. The date of the last search was December 2012 for all databases.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) that had defined different glycaemic targets in the treatment arms, studied patients with type 1 diabetes, and had a follow-up duration of at least one year.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, assessed studies for risk of bias, with differences resolved by consensus. Overall study quality was evaluated by the 'Grading of Recommendations Assessment, Development, and Evaluation' (GRADE) system. Random-effects models were used for the main analyses and the results are presented as risk ratios (RR) with 95% confidence intervals (CI) for dichotomous outcomes.

MAIN RESULTS

We identified 12 trials that fulfilled the inclusion criteria, including a total of 2230 patients. The patient populations varied widely across studies with one study only including children, one study only including patients after a kidney transplant, one study with newly diagnosed adult patients, and several studies where patients had retinopathy or microalbuminuria at baseline. The mean follow-up duration across studies varied between one and 6.5 years. The majority of the studies were carried out in the 1980s and all trials took place in Europe or North America. Due to the nature of the intervention, none of the studies could be carried out in a blinded fashion so that the risk of performance bias, especially for subjective outcomes such as hypoglycaemia, was present in all of the studies. Fifty per cent of the studies were judged to have a high risk of bias in at least one other category.Under intensive glucose control, the risk of developing microvascular complications was reduced compared to conventional treatment for a) retinopathy: 23/371 (6.2%) versus 92/397 (23.2%); RR 0.27 (95% CI 0.18 to 0.42); P < 0.00001; 768 participants; 2 trials; high quality evidence; b) nephropathy: 119/732 (16.3%) versus 211/743 (28.4%); RR 0.56 (95% CI 0.46 to 0.68); P < 0.00001; 1475 participants; 3 trials; moderate quality evidence; c) neuropathy: 29/586 (4.9%) versus 86/617 (13.9%); RR 0.35 (95% CI 0.23 to 0.53); P < 0.00001; 1203 participants; 3 trials; high quality evidence. Regarding the progression of these complications after manifestation, the effect was weaker (retinopathy) or possibly not existent (nephropathy: RR 0.79 (95% CI 0.37 to 1.70); P = 0.55; 179 participants with microalbuminuria; 3 trials; very low quality evidence); no adequate data were available regarding the progression of neuropathy. For retinopathy, intensive glucose control reduced the risk of progression in studies with a follow-up duration of at least two years (85/366 (23.2%) versus 154/398 (38.7%); RR 0.61 (95% CI 0.49 to 0.76); P < 0.0001; 764 participants; 2 trials; moderate quality evidence), while we found evidence for an initial worsening of retinopathy after only one year of intensive glucose control (17/49 (34.7%) versus 7/47 (14.9%); RR 2.32 (95% CI 1.16 to 4.63); P = 0.02; 96 participants; 2 trials; low quality evidence).Major macrovascular outcomes (stroke and myocardial infarction) occurred very rarely, and no firm evidence could be established regarding these outcome measures (low quality evidence).We found that intensive glucose control increased the risk for severe hypoglycaemia, however the results were heterogeneous and only the 'Diabetes Complications Clinical Trial' (DCCT) showed a clear increase in severe hypoglycaemic episodes under intensive treatment. A subgroup analysis according to the baseline haemoglobin A1c (HbA1c) of participants in the trials (low quality evidence) suggests that the risk of hypoglycaemia is possibly only increased for patients who started with relatively low HbA1c values (< 9.0%). Several of the included studies also showed a greater weight gain under intensive glucose control, and the risk of ketoacidosis was only increased in studies using insulin pumps in the intensive treatment group (very low quality evidence).Overall, all-cause mortality was very low in all studies (moderate quality evidence) except in one study investigating renal allograft as treatment for end-stage diabetic nephropathy. Health-related quality of life was only reported in the DCCT trial, showing no statistically significant differences between the intervention and comparator groups (moderate quality evidence). In addition, only the DCCT published data on costs, indicating that intensive glucose therapy control was highly cost-effective considering the reduction of potential diabetes complications (moderate quality evidence).

AUTHORS' CONCLUSIONS

Tight blood sugar control reduces the risk of developing microvascular diabetes complications. The evidence of benefit is mainly from studies in younger patients at early stages of the disease. Benefits need to be weighed against risks including severe hypoglycaemia, and patient training is an important aspect in practice. The effects of tight blood sugar control seem to become weaker once complications have been manifested. However, further research is needed on this issue. Furthermore, there is a lack of evidence from RCTs on the effects of tight blood sugar control in older patient populations or patients with macrovascular disease. There is no firm evidence for specific blood glucose targets and treatment goals need to be individualised taking into account age, disease progression, macrovascular risk, as well as the patient's lifestyle and disease management capabilities.

Therapy for diabetic neuropathy: an overview

Neuropathy is a highly prevalent complication of diabetes that is only likely to increase as the diabetic epidemic continues. Unfortunately, the only disease-modifying treatment is to address the underlying diabetes with enhanced glucose control. In patients with type 1 diabetes, improved glycemic control dramatically reduces the incidence of neuropathy. In contrast, in patients with type 2 diabetes, better glucose control has only a marginal effect on the prevention of neuropathy. However, recognition and treatment of neuropathic pain is also important. An ever expanding number of randomized, controlled clinical trials support multiple medications for the reduction of pain. This includes medications such as calcium channel agonists, tricyclic antidepressants, and selective serotonin/norepinephrine reuptake inhibitors. However, the precise order and combination of these medications remains unclear. Furthermore, several new promising medications are being developed. Overall, the cornerstones of the treatment of diabetic neuropathy are improved glycemic control and initiation of a neuropathic pain medication with high levels of evidence to support its use when pain is present.

Glucose control and diabetic neuropathy: lessons from recent large clinical trials

Diabetic peripheral and autonomic neuropathies are common complications of diabetes with broad spectrums of clinical manifestations and high morbidity. Studies using various agents to target the pathways implicated in the development and progression of diabetic neuropathy were promising in animal models. In humans, however, randomized controlled studies have failed to show efficacy on objective measures of neuropathy. The complex anatomy of the peripheral and autonomic nervous systems, the multitude of pathogenic mechanisms involved, and the lack of uniformity of neuropathy measures have likely contributed to these failures. To date, tight glycemic control is the only strategy convincingly shown to prevent or delay the development of neuropathy in patients with type 1 diabetes and to slow the progression of neuropathy in some patients with type 2 diabetes. Lessons learned about the role of glycemic control on distal symmetrical polyneuropathy and cardiovascular autonomic neuropathy are discussed in this review.

Autonomic neuropathy in diabetes mellitus

Diabetic autonomic neuropathy (DAN) is a serious and common complication of diabetes, often overlooked and misdiagnosed. It is a systemic-wide disorder that may be asymptomatic in the early stages. The most studied and clinically important form of DAN is cardiovascular autonomic neuropathy defined as the impairment of autonomic control of the cardiovascular system in patients with diabetes after exclusion of other causes. The reported prevalence of DAN varies widely depending on inconsistent definition, different diagnostic method, different patient cohorts studied. The pathogenesis is still unclear and probably multifactorial. Once DAN becomes clinically evident, no form of therapy has been identified, which can effectively stop or reverse it. Prevention strategies are based on strict glycemic control with intensive insulin treatment, multifactorial intervention, and lifestyle modification including control of hypertension, dyslipidemia, stop smoking, weight loss, and adequate physical exercise. The present review summarizes the latest knowledge regarding clinical presentation, epidemiology, pathogenesis, and management of DAN, with some mention to childhood and adolescent population.

The metabolic syndrome and neuropathy: therapeutic challenges and opportunities

The metabolic syndrome and neuropathy are common conditions, especially in the elderly, that are associated with significant morbidity. Furthermore, the metabolic syndrome is reaching epidemic proportions across the world. Current evidence supports the association of the metabolic syndrome and its individual components with neuropathy. Several clinical trials have demonstrated that treating hyperglycemia, a component of the metabolic syndrome, has a significant effect on reducing the incidence of neuropathy in those with type 1 diabetes. However, glucose control has only a marginal effect on preventing neuropathy in those with type 2 diabetes, suggesting that other factors may be driving nerve injury in these patients. Emerging evidence supports the metabolic syndrome as including risk factors for neuropathy. Interventions exist for treatment of all of the metabolic syndrome components, but only glucose control has strong evidence to support its use and is widely employed. Our understanding of the biology of metabolic nerve injury has rapidly expanded over the past several years. Mechanisms of injury include fatty deposition in nerves, extracellular protein glycation, mitochondrial dysfunction, and oxidative stress. Additionally, the activation of counter-regulatory signaling pathways leads to chronic metabolic inflammation. Medications that target these signaling pathways are being used for a variety of diseases and are intriguing therapeutic agents for future neuropathy clinical trials. As we move forward, we need to expand our understanding of the association between the metabolic syndrome and neuropathy by addressing limitations of previous studies. Just as importantly, we must continue to investigate the pathophysiology of metabolically induced nerve injury.

Chinese herbal medicine for diabetic peripheral neuropathy

BACKGROUND

Chinese herbal medicine is frequently used for treating diabetic peripheral neuropathy in China. Many controlled trials have been undertaken to investigate its efficacy.This is an update of a Cochrane review that was first published in the year 2011.

OBJECTIVES

To assess the beneficial effects and harms of Chinese herbal medicine for people with diabetic peripheral neuropathy.

SEARCH METHODS

On 14 May 2012, we searched the Cochrane Neuromuscular Disease Group Specialized Register CENTRAL (2012, Issue 4 in The Cochrane Library), MEDLINE (January 1966 to May 2012), EMBASE (January 1980 to May 2012), AMED (January 1985 to May 2012) and in October 2012, the Chinese Biomedical Database (CBM) (1979 to October 2012), Chinese National Knowledge Infrastructure Database (CNKI) (1979 to October 2012), and VIP Chinese Science and Technique Journals Database (1989 to October 2012). We searched for unpublished literature in the Chinese Conference Papers Database, and Chinese Dissertation Database (from inception to October 2012). There were no language or publication restrictions.

SELECTION CRITERIA

We included randomised controlled trials of Chinese herbal medicine (with a minimum of four weeks treatment duration) for people with diabetic peripheral neuropathy compared with placebo, no intervention, or conventional interventions. Trials of herbal medicine plus a conventional drug versus the drug alone were also included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and evaluated trial quality. We contacted study authors for additional information.

MAIN RESULTS

Forty-nine randomised trials involving 3639 participants were included. All trials were conducted and published in China. Thirty-eight different herbal medicines were tested in these trials, including four single herbs (extracts from a single herb), eight traditional Chinese patent medicines, and 26 self concocted Chinese herbal compound prescriptions. The trials reported on global symptom improvement (including improvement in numbness or pain) and changes in nerve conduction velocity. The positive results described from the 49 studies of low quality are of questionable significance. There was inadequate reporting on adverse events in the included trials. Eighteen trials found no adverse events. Two trials reported adverse events: adverse events occurred in the control group in one trial, and in the other it was unclear in which group the adverse events occurred. 29 trials did not mention whether they monitored adverse events. Conclusions cannot be drawn from this review about the safety of herbal medicines, due to inadequate reporting. Most of the trials were of very low methodological quality and therefore the interpretation of any positive findings for the efficacy of the included Chinese herbal medicines for treating diabetic peripheral neuropathy should be made with caution.

AUTHORS' CONCLUSIONS

Based on this systematic review, there is no evidence to support the objective effectiveness and safety of Chinese herbal medicines for diabetic peripheral neuropathy. No well-designed, randomised, placebo controlled trial with objective outcome measures has been conducted.

Impact of glycemic control strategies on the progression of diabetic peripheral neuropathy in the Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) Cohort

OBJECTIVE

The Bypass Angioplasty Revascularization Investigation 2 Diabetes (BARI 2D) trial demonstrated similar long-term clinical effectiveness of insulin-sensitizing (IS) versus insulin-providing (IP) treatments for type 2 diabetes on cardiovascular outcomes in a cohort with documented coronary artery disease. We evaluated the effects of randomized glycemic control strategy (IS vs. IP) on the prevalence and incidence of diabetic peripheral neuropathy (DPN).

RESEARCH DESIGN AND METHODS

DPN (defined as Michigan Neuropathy Screening Instrument [MNSI] clinical examination score>2) was assessed at baseline and yearly for 4 years. DPN prevalence and incidence were compared by intention-to-treat modeling by logistic generalized estimating equation models for prevalence and Kaplan-Meier estimates and Cox regression models for incidence rates.

RESULTS

Results are reported for 2,159 BARI 2D participants (70% males) with valid baseline and at least one follow-up MNSI score (mean age 62±9 years, mean HbA1c 7.7±1.6%, diabetes duration 10±9 years). There were no differences in the prevalence of DPN between the IS and the IP groups throughout the 4 years of follow-up. In 1,075 BARI 2D participants with no DPN at baseline, the 4-year cumulative incidence rate of DPN was significantly lower in the IS (66%) than in the IP (72%) strategy group (P=0.02), which remained significant after adjusting for the in-trial HbA1c (P=0.04). In subgroup analyses, IS strategy had a greater benefit in men (hazard ratio 0.75 [99% CI 0.58-0.99], P<0.01).

CONCLUSIONS

Among patients with type 2 diabetes followed for up to 4 years during BARI 2D, a glycemic control therapy with IS significantly reduced the incidence of DPN compared with IP therapy and may add further benefit for men.

Reconsidering nerve decompression: an overlooked opportunity to limit diabetic foot ulcer recurrence and amputation

Nerve decompression for relief of subjective diabetic sensorimotor polyneuropathy pain and numbness has been labeled of "unknown" benefit. Objective outcomes in treatment and prevention of diabetic foot complications are reviewed. There is growing evidence that plantar foot ulceration and recurrence in high-risk feet are minimized with this operation. Avoiding neuropathic and neuroischemic ulcer wounds should theoretically reduce amputations and perhaps mortality risk. Protective effects are hypothesized to act via relief of neuro-vascular entrapment, thereby improving neurally modulated tissue homeostasis factors. Nerve decompression deserves considerable research attention to understand its role in limiting foot complications. Its apparent benefits challenge the paradigm that diabetic neuropathy is a purely length-dependent axonopathy and may necessitate appreciation of superimposed nerve entrapment as an significant operant factor.

Obesity and hyperlipidemia are risk factors for early diabetic neuropathy

The Utah Diabetic Neuropathy Study (UDNS) examined 218 type 2 diabetic subjects without neuropathy symptoms, or with symptoms of<5 years, in order to evaluate risk factors for neuropathy development. Each subject completed symptom questionnaires, the Utah Early Neuropathy Scale (UENS), nerve conduction studies (NCS), quantitative sensory testing (QST) for vibration and cold detection, quantitative sudomotor axon reflex testing (QSART), and skin biopsy with measurement of intraepidermal nerve fiber density (IENFD). Those with abnormalities of≥3 were classified as having probable, and those with 1-2 as possible neuropathy. The relationship between glycemic control, lipid parameters (high density lipoprotein and triglyceride levels), blood pressure, and obesity, and neuropathy risk was examined. There was a significant relationship between the number of abnormalities among these features and neuropathy status (p<0.01). Hypertriglyceridemia, obesity and 3 or more abnormalities increased neuropathy risk (risk ratios 2.1 p<0.03, 2.9 p>0.02 and 3.0 p<0.004 respectively). Multivariate analysis found obesity and triglycerides were related to loss of small unmyelinated axons based on IENFD whereas elevated hemoglobin A1c was related to large myelinated fiber loss (motor conduction velocity). These findings indicate obesity and hypertriglyceridemia significantly increase risk for peripheral neuropathy, independent of glucose control. Obesity/hypertriglyceridemia and hyperglycemia may have differential effects on small versus large fibers.

Corneal confocal microscopy: a new technique for early detection of diabetic neuropathy

Corneal confocal microscopy (CCM) is a noninvasive method for the study of human cornea in vivo. It has increasingly been used to assess the morphology of the sub-basal corneal nerve plexus. CCM has good reproducibility and may contribute to the early diagnosis of diabetic polyneuropathy. It may also be useful to document favorable changes in nerve fiber structure early after therapeutic intervention. Corneal nerve pathology is more pronounced in patients with diabetic polyneuropathy and is associated with its clinical severity. The sensitivity and specificity of CCM for the diagnosis of polyneuropathy is moderate to high. CCM now merits further use in large longitudinal studies to provide more information on the natural history of diabetic neuropathy and effects of treatment. Moreover, there is a need for a larger normative database. Finally, technical progress is expected to enable visualization of larger corneal areas and improve nerve fiber quantification, increasing diagnostic accuracy.

Parkia speciosa Hassk.: A Potential Phytomedicine

Parkia speciosa Hassk., or stink bean, is a plant indigenous to Southeast Asia. It is consumed either raw or cooked. It has been used in folk medicine to treat diabetes, hypertension, and kidney problems. It contains minerals and vitamins. It displays many beneficial properties. Its extracts from the empty pods and seeds have a high content of total polyphenol, phytosterol, and flavonoids. It demonstrates a good antioxidant activity. Its hypoglycemic effect is reported to be attributable to the presence of β-sitosterol, stigmasterol, and stigmast-4-en-3-one. The cyclic polysulfide compounds exhibit antibacterial activity, while thiazolidine-4-carboxylic acid possesses anticancer property. The pharmacological properties of the plant extract are described in this review. With ongoing research conducted on the plant extracts, Parkia speciosa has a potential to be developed as a phytomedicine.

Whither pathogenetic treatments for diabetic polyneuropathy?

Diabetic distal symmetric polyneuropathy (DSPN) occurs in around one-third of patients with diabetes and is associated with significant morbidity and increased mortality. Diagnosis and clinical assessment of DSPN remain a challenge, not only for the physician in clinical practice but also for clinical trials. Optimal diabetes control is generally considered an essential first step in the prevention and management of DSPN. However, glycaemic control alone may be insufficient to prevent the development or progression of DSPN, especially in type 2 diabetes. Near-normoglycaemia is also difficult to achieve in a significant proportion of patients. Although considerable advances have been made in symptomatic pain management, these have not addressed the problem of sensory deficits and have no impact on the underlying pathogenesis of DSPN. There remains a lack of treatment options that effectively target the natural history of the disease. Several pathogenetic treatment approaches have been investigated, but evidence from clinical trials is limited with a number of treatments having shown disappointing results. However, some pathogenetic therapies have shown clinically relevant improvements in neuropathic endpoints in randomised controlled trials, in particular α-lipoic acid and Actovegin. These advances in DSPN disease modification need to be confirmed with further robust evidence from clinical trials together with a better understanding of the mechanisms of action of promising treatments.

Fenugreek seed extract treats peripheral neuropathy in pyridoxine induced neuropathic mice

Trigonella foenum graecum commonly known as Fenugreek exerts normoglycemic and insulinotropic effects in humans by compounds from its seed and leaf extracts. Some studies reported that treating pregnant mice with fenugreek seed could cause toxic effects on the nervous system of its pubs during developmental growth, while in some other studies neuroprotective properties were considered for it. Safety of anti-diabetic drugs for nervous system is very important because peripheral neuropathy is a common complication of diabetes and hazardous drugs could worsen it. In this study, the effect of treatment with fenugreek seed extract on the function of sciatic nerves of neuropathic mice was evaluated. Neuropathy was induced in male mice by pyridoxine intoxication. After that, animals were treated with 0.2, 2 and 20 mg/kg of hydro-alcoholic extract of fenugreek seeds for 10 days, tail flick, electrophysiological and histological assays were performed to evaluate the effect of fenugreek seed extract on function of the peripheral nerves. Our data showed that fenugreek has anti neuropathic effect and restores the function of nerve fibers. Results of electrophysiological recordings stated that the highest rate of healing was occurred in 20 mg/kg fenugreek extract treated animals. In conclusion, findings of the present study demonstrate that treatment with fenugreek seed extract can potentially facilitate healing from pyridoxine induced peripheral neuropathy in mice.

Diabetic neuropathy: one disease or two?

PURPOSE OF REVIEW

To compare and contrast the evidence for the effect of glucose control on the prevention of neuropathy in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

RECENT FINDINGS

In T1DM, multiple clinical trials have demonstrated a large benefit from enhanced glucose control, whereas the benefit in T2DM is much more modest. Epidemiologic and laboratory evidence exists to support factors other than hyperglycemia in the development of neuropathy including obesity, hypertension, dyslipidemia, inflammation, and insulin resistance.

SUMMARY

T1DM neuropathy and T2DM neuropathy are fundamentally different. In T1DM, glucose control has a large effect on the prevention of neuropathy; therefore, future efforts should continue to concentrate on this avenue of treatment. In contrast, in T2DM, glucose control has a small effect on the prevention of neuropathy; as a result, more research is needed to define the underlying mechanisms for the development of neuropathy. Understanding these mechanisms may lead to novel therapeutic approaches to prevent or treat diabetic neuropathy.