Diabetic neuropathies are the most prevalent chronic complications of diabetes. This heterogeneous group of conditions affects different parts of the nervous system and presents with diverse clinical manifestations. The early recognition and appropriate management of neuropathy in the patient with diabetes is important for a number of reasons: 1. Diabetic neuropathy is a diagnosis of exclusion. Nondiabetic neuropathies may be present in patients with diabetes and may be treatable by specific measures. 2. A number of treatment options exist for symptomatic diabetic neuropathy. 3. Up to 50% of diabetic peripheral neuropathies may be asymptomatic. If not recognized and if preventive foot care is not implemented, patients are at risk for injuries to their insensate feet. 4. Recognition and treatment of autonomic neuropathy may improve symptoms, reduce sequelae, and improve quality of life. Among the various forms of diabetic neuropathy, distal symmetric polyneuropathy (DSPN) and diabetic autonomic neuropathies, particularly cardiovascular autonomic neuropathy (CAN), are by far the most studied (1–4). There are several atypical forms of diabetic neuropathy as well (1–4). Patients with prediabetes may also develop neuropathies that are similar to diabetic neuropathies (5–10). Table 1 provides a comprehensive classification scheme for the diabetic neuropathies. View this table: Table 1 Classification for diabetic neuropathies Due to a lack of treatments that target the underlying nerve damage, prevention is the key component of diabetes care. Screening for symptoms and signs of diabetic neuropathy is also critical in clinical practice, as it may detect the earliest stages of neuropathy, enabling early intervention. Although screening for rarer atypical forms of diabetic neuropathy may be warranted, DSPN and autonomic neuropathy are the most common forms encountered in practice. The strongest available evidence regarding treatment pertains to these forms. This Position Statement is based on several recent technical reviews, to which the reader is referred for detailed discussion …

Preceding the joint meeting of the 19th annual Diabetic Neuropathy Study Group of the European Association for the Study of Diabetes (NEURODIAB) and the 8th International Symposium on Diabetic Neuropathy in Toronto, Canada, 13–18 October 2009, expert panels were convened to provide updates on classification, definitions, diagnostic criteria, and treatments of diabetic peripheral neuropathies (DPNs), autonomic neuropathy, painful DPNs, and structural alterations in DPNs.

OBJECTIVE To assess, in the general diabetic population, 1) the prevalence of painful neuropathic symptoms; 2) the relationship between symptoms and clinical severity of neuropathy; and 3) the role of diabetes type, sex, and ethnicity in painful neuropathy. RESEARCH DESIGN AND METHODS Observational study of a large cohort of diabetic patients receiving community-based health care in northwest England (n = 15,692). Painful diabetic neuropathy (PDN) was assessed using neuropathy symptom score (NSS) and neuropathy disability score (NDS). RESULTS Prevalence of painful symptoms (NSS ≥5) and PDN (NSS ≥5 and NDS ≥3) was 34 and 21%, respectively. Painful symptoms occurred in 26% of patients without neuropathy (NDS ≤2) and 60% of patients with severe neuropathy (NDS >8). Adjusted risk of painful neuropathic symptoms in type 2 diabetes was double that of type 1 diabetes (odds ratio [OR] = 2.1 [95% CI 1.7–2.4], P < 0.001) and not affected by severity of neuropathy, insulin use, foot deformities, smoking, or alcohol. Women had 50% increased adjusted risk of painful symptoms compared with men (OR = 1.5 [1.4–1.6], P < 0.0001). Despite less neuropathy in South Asians (14%) than Europeans (22%) and African Caribbeans (21%) (P < 0.0001), painful symptoms were greater in South Asians (38 vs. 34 vs. 32%, P < 0.0001). South Asians without neuropathy maintained a 50% increased risk of painful neuropathy symptoms compared with other ethnic groups (P < 0.0001). CONCLUSIONS One-third of all community-based diabetic patients have painful neuropathy symptoms, regardless of their neuropathic deficit. PDN was more prevalent in patients with type 2 diabetes, women, and people of South Asian origin. This highlights a significant morbidity due to painful neuropathy and identifies key groups who warrant screening for PDN.

The epidemiology and natural history of diabetic neuropathy (DN) remain poorly defined, partly because of poor patient selection and the variable criteria for what constitutes a diagnosis of DN. These aspects, as well as the pathogenesis of DN, will be covered in detail in this review. Studies have confirmed the major contribution of prolonged hyperglycemia in the etiopathogenesis of neuropathy and neuropathic pain (7–9,10), and this and other putative mechanisms will be discussed.

Background— Inflammation in adipose tissue has been implicated in vascular dysfunction, but the local mechanisms by which this occurs are unknown. Methods and Results— Small arteries with and without perivascular adipose tissue were taken from subcutaneous gluteal fat biopsy samples and studied with wire myography and immunohistochemistry. We established that healthy adipose tissue around human small arteries secretes factors that influence vasodilation by increasing nitric oxide bioavailability. However, in perivascular fat from obese subjects with metabolic syndrome (waist circumference 111±2.8 versus 91.1±3.5 cm in control subjects, P <0.001; insulin sensitivity 41±5.9% versus 121±18.6% in control subjects, P <0.001), the loss of this dilator effect was accompanied by an increase in adipocyte area (1786±346 versus 673±60 μm ² , P <0.01) and immunohistochemical evidence of inflammation (tumor necrosis factor receptor 1 12.4±1.1% versus 6.7±1%, P <0.001). Application of the cytokines tumor necrosis factor receptor-α and interleukin-6 to perivascular fat around healthy blood vessels reduced dilator activity, resulting in the obese phenotype. These effects could be reversed with free radical scavengers or cytokine antagonists. Similarly, induction of hypoxia stimulated inflammation and resulted in loss of anticontractile capacity, which could be rescued by catalase and superoxide dismutase or cytokine antagonists. Incubation with a soluble fragment of adiponectin type 1 receptor or inhibition of nitric oxide synthase blocked the vasodilator effect of healthy perivascular adipose tissue. Conclusions— We conclude that adipocytes secrete adiponectin and provide the first functional evidence that it is a physiological modulator of local vascular tone by increasing nitric oxide bioavailability. This capacity is lost in obesity by the development of adipocyte hypertrophy, leading to hypoxia, inflammation, and oxidative stress.