Reproducibility and persistence of neural and adrenal autoantibodies in diabetic autonomic neuropathy

Emerging Roles for MicroRNAs in Diabetic Microvascular Disease: Novel Targets for Therapy

Chronic, low-grade systemic inflammation and impaired microvascular function are critical hallmarks in the development of insulin resistance. Accordingly, insulin resistance is a major risk factor for type 2 diabetes and cardiovascular disease. Accumulating studies demonstrate that restoration of impaired function of the diabetic macro- and microvasculature may ameliorate a range of cardiovascular disease states and diabetes-associated complications. In this review, we focus on the emerging role of microRNAs (miRNAs), noncoding RNAs that fine-tune target gene expression and signaling pathways, in insulin-responsive tissues and cell types important for maintaining optimal vascular homeostasis and preventing the sequelae of diabetes-induced end organ injury. We highlight current pathophysiological paradigms of miRNAs and their targets involved in regulating the diabetic microvasculature in a range of diabetes-associated complications such as retinopathy, nephropathy, wound healing, and myocardial injury. We provide an update of the potential use of circulating miRNAs diagnostically in type I or type II diabetes. Finally, we discuss emerging delivery platforms for manipulating miRNA expression or function as the next frontier in therapeutic intervention to improve diabetes-associated microvascular dysfunction and its attendant clinical consequences.

The Role of MicroRNAs in Diabetic Complications-Special Emphasis on Wound Healing

Overweight and obesity are major problems in today’s society, driving the prevalence of diabetes and its related complications. It is important to understand the molecular mechanisms underlying the chronic complications in diabetes in order to develop better therapeutic approaches for these conditions. Some of the most important complications include macrovascular abnormalities, e.g., heart disease and atherosclerosis, and microvascular abnormalities, e.g., retinopathy, nephropathy and neuropathy, in particular diabetic foot ulceration. The highly conserved endogenous small non-coding RNA molecules, the micro RNAs (miRNAs) have in recent years been found to be involved in a number of biological processes, including the pathogenesis of disease. Their main function is to regulate post-transcriptional gene expression by binding to their target messenger RNAs (mRNAs), leading to mRNA degradation, suppression of translation or even gene activation. These molecules are promising therapeutic targets and demonstrate great potential as diagnostic biomarkers for disease. This review aims to describe the most recent findings regarding the important roles of miRNAs in diabetes and its complications, with special attention given to the different phases of diabetic wound healing.

Neuropatia autonômica: uma complicação de alto risco no diabetes melito tipo 1

O acometimento patológico do sistema nervoso no diabetes melito é muito amplo e, freqüentemente, bastante grave. A prevalência de neuropatia diabética atinge níveis elevados com a evolução temporal do diabetes, chegando, geralmente, a freqüências acima de 50% de lesão neurológica em diferentes grupos de pacientes analisados em nosso meio e no exterior. A lesão neurológica nesta situação patológica é extensa no organismo humano diabético, envolvendo amplamente todo o sistema nervoso periférico nos seus componentes sensitivo-motor e autonômico: com clínica característica e concordante com as hipóteses patogênicas de natureza metabólica e/ou microvascular. O sistema nervoso autonômico é o elemento fundamental na regulação da função da maior parte dos sistemas ou órgãos no organismo, portanto, a sua lesão pode trazer importantes alterações para as funções cardiovascular, respiratória, digestiva, urinária e genital, podendo influir na função vital de alguns desses órgãos ou sistemas. Este artigo aborda as alterações decorrentes da lesão do sistema nervoso autonômico, especialmente nos pacientes diabéticos tipo 1, procurando dimensionar o risco de morbimortalidade.

Prevalence of autoantibodies to autonomic nervous tissue structures in Type 1 diabetes mellitus

AIMS

The pathogenesis of diabetic autonomic neuropathy is multifactorial, but recent studies have suggested a link between the presence of autoantibodies to nervous tissue structures and severe, symptomatic autonomic neuropathy. The present study was designed to examine the true prevalence of these autoantibodies in a large clinic-based population of Type 1 diabetic patients compared to nondiabetic controls.

METHODS

The presence of complement fixing autoantibodies to vagus nerve (CF-VN), sympathetic ganglion (CF-SG) and adrenal medulla (CF-ADM) was assessed by immunofluorescence in a large cohort of patients (n = 394) of varying duration of Type 1 DM (median 28 years, range 6 months to 73 years) and 160 age and sex-matched nondiabetic control subjects.

RESULTS

All three autoantibodies were frequently detected in Type 1 DM (CF-VN, 22.1%; CF-SG, 30.7%; CF-ADM, 13.2%) but only rarely in healthy control subjects (4.4%, 4.4% and 3.1%, respectively; P < 0.0005 for all). There was no association between any of the autoantibodies and retinopathy (fundoscopy), peripheral somatic neuropathy (biothesiometry) or nephropathy (urinary albumin-creatinine ratio).

CONCLUSIONS

Our results on this large cohort establish the extensive presence of autonomic nervous tissue autoantibodies in Type 1 DM. Their role in reflecting, causing or predicting autonomic neuropathy remains to be determined.

Autonomic neuropathies

A limited autonomic neuropathy may underlie some unusual clinical syndromes, including the postural tachycardia syndrome, pseudo-obstruction syndrome, heat intolerance, and perhaps chronic fatigue syndrome. Antibodies to autonomic structures are common in diabetes, but their specificity is unknown. The presence of autonomic failure worsens prognosis in the diabetic state. Some autonomic neuropathies are treatable. Familial amyloid polyneuropathy may respond to liver transplantation. There are anecdotal reports of acute panautonomic neuropathy responding to intravenous gamma globulin. Orthostatic hypotension may respond to erythropoietin or midodrine.

Metabolic neuropathies

A large epidemiological study has documented that one-third of diabetic patients have peripheral neuropathy. Diabetes duration, poor glycaemic control, smoking and hypertension are all independent predictors of the incidence of diabetic polyneuropathy. High prevalence of autonomic dysfunctions, both sympathetic and parasympathetic, has been found in patients with nonalcoholic chronic liver disease. The pathogenesis of metabolic neuropathy is unclear; even immunologic factors might play a role in the development of diabetic autonomic neuropathy. No specific treatments are available for these neuropathies. Correction of metabolic derangement is fundamental, as shown by the amelioration of peripheral nerve function obtained after successful simultaneous pancreas-kidney transplantation. The therapeuthic potentials of neurotrophins for the prevention and treatment of diabetic neuropathy have to be confirmed in future studies.

Serum from patients with type 2 diabetes with neuropathy induces complement-independent, calcium-dependent apoptosis in cultured neuronal cells

We hypothesized that sera from type 2 diabetic patients with neuropathy contains an autoimmune immunoglobulin that promotes complement-independent, calcium-dependent apoptosis in neuronal cell lines. Neuronal cells were cultured in the presence of complement-inactivated sera obtained from patients with type 2 diabetes with and without neuropathy and healthy adult control patients. Serum from diabetic patients with neuropathy was associated with a significantly greater induction of apoptosis, compared to serum from diabetic patients without neuropathy and controls. In the presence of calcium channel antagonists, induction of apoptosis was reduced by approximately 50%. Pretreatment of neuronal cells with serum from diabetic patients with neuropathy was associated with a significant increase in elevated K+-evoked cytosolic calcium concentration. Serum-induced enhancement in cytosolic calcium and calcium current density was blocked by treatment with trypsin and filtration of the serum using a 100,000-kd molecular weight filter. Treatment with an anti-human IgG antibody was associated with intense fluorescence on the surface of neuronal cells exposed to sera from patients with type 2 diabetes mellitus with neuropathy. We conclude that sera from type 2 diabetic patients with neuropathy contains an autoimmune immunoglobulin that induces complement-independent, calcium-dependent apoptosis in neuronal cells.