Autoimmunity in diabetic autonomic neuropathy: does the immune system get on your nerves?

Association of autoimmunity to autonomic nervous structures with nerve function in patients with type 1 diabetes: a 16-year prospective study

OBJECTIVE We prospectively evaluated the association between autoimmunity to autonomic nervous structures and autonomic neuropathy in type 1 diabetes in relation to clinical variables. RESEARCH DESIGN AND METHODS A cohort of 112 patients with type 1 diabetes was prospectively followed from adolescence (T0) to approximately 4 (T4) and 16 (T16) years later. Standard cardiovascular (CV) tests and neurological examination were performed and related to the presence of circulating antibodies (Ab) to autonomic nervous structures detected at T0 and T4. Quality of life was assessed by a diabetes-specific questionnaire. RESULTS Sixty-six patients (59% of the cohort) were reexamined at T16 (age 31.4 ± 2 years; disease duration 23.4 ± 3.7 years). Nineteen had circulating Ab to autonomic structures. Prevalence of abnormal tests and autonomic symptoms were higher in Ab-positive (68 and 26%, respectively) than Ab-negative (32 and 4%) patients (P < 0.05). Among Ab-positive patients, the relative risk (RR) of having at least one altered CV test was 5.77 (95% CI 1.56-21.33), and an altered deep breathing (DB) test (<15 bpm) was 14.65 (2.48-86.46). Previous glycemic control was the only other predictor (RR 1.06 [1.002-1.13]/mmol/mol HbA1c increase). Presence of Ab carried over a 68% probability of developing an altered CV test; absence of Ab carried a 91% probability of not having an altered DB test and an 89% probability of not having an altered Valsalva ratio. Autonomic neuropathy was independently associated with worse quality of life. CONCLUSIONS Circulating Ab to autonomic structures are associated with the development of autonomic dysfunction in young diabetic patients independent of glycemic control.

Biology of diabetic neuropathy

More than half of all patients with diabetes develop neuropathic disorders affecting the distal sensory and/or motor nerves, or autonomic or cranial nerve functions. Glycemic control can decrease the incidence of neuropathy but is not adequate alone to prevent or treat the disease. This chapter introduces diabetic neuropathy with a morphological description of the disease then describes our current understanding of metabolic and molecular mechanisms that contribute to neurovascular dysfunctions. Key mechanisms include glucose and lipid imbalances and insulin resistance that are interconnected via oxidative stress, inflammation, and altered gene expression. These complex interactions should be considered for the development of new treatment strategies against the onset or progression of neuropathy. Advances in understanding the combined metabolic stressors and the novel study of epigenetics suggest new therapeutic targets to combat this morbid and intractable disease affecting millions of patients with type 1 or type 2 diabetes.

Humoral autoimmunity in type 1 diabetes: prediction, significance, and detection of distinct disease subtypes

Type 1 diabetes mellitus (T1D) is an autoimmune disease encompassing the T-cell-mediated destruction of pancreatic β cells and the production of autoantibodies against islet proteins. In humoral autoimmunity in T1D, the detection of islet autoantibodies and the examination of their associations with genetic factors and cellular autoimmunity constitute major areas in both basic research and clinical practice. Although insulin is a key autoantigen and may be primus inter pares in importance among T1D autoantigens, an abundant body of research has also revealed other autoantigens associated with the disease process. Solid evidence indicates that autoantibodies against islet targets serve as key markers to enroll newly diagnosed T1D patients and their family members in intervention trials aimed at preventing or halting the disease process. The next challenge is perfecting mechanistic bioassays to be used as end points for disease amelioration following immunomodulatory therapies aimed at blocking immune-mediated β-cell injury and, in turn, preserving β-cell function in type 1 diabetes mellitus.

A novel unbiased proteomic approach to detect the reactivity of cerebrospinal fluid in neurological diseases

Neurodegenerative diseases, such as multiple sclerosis represent global health issues. Accordingly, there is an urgent need to understand the pathogenesis of this and other central nervous system disorders, so that more effective therapeutics can be developed. Cerebrospinal fluid is a potential source of important reporter molecules released from various cell types as a result of central nervous system pathology. Here, we report the development of an unbiased approach for the detection of reactive cerebrospinal fluid molecules and target brain proteins from patients with multiple sclerosis. To help identify molecules that may serve as clinical biomarkers for multiple sclerosis, we have biotinylated proteins present in the cerebrospinal fluid and tested their reactivity against brain homogenate as well as myelin and myelin-axolemmal complexes. Proteins were separated by two-dimensional gel electrophoresis, blotted onto membranes and probed separately with biotinylated unprocessed cerebrospinal fluid samples. Protein spots that reacted to two or more multiple sclerosis-cerebrospinal fluids were further analyzed by matrix assisted laser desorption ionization-time-of-flight time-of-flight mass spectrometry. In addition to previously reported proteins found in multiple sclerosis cerebrospinal fluid, such as αβ crystallin, enolase, and 14-3-3-protein, we have identified several additional molecules involved in mitochondrial and energy metabolism, myelin gene expression and/or cytoskeletal organization. These include aspartate aminotransferase, cyclophilin-A, quaking protein, collapsin response mediator protein-2, ubiquitin carboxy-terminal hydrolase L1, and cofilin. To further validate these findings, the cellular expression pattern of collapsin response mediator protein-2 and ubiquitin carboxy-terminal hydrolase L1 were investigated in human chronic-active MS lesions by immunohistochemistry. The observation that in multiple sclerosis lesions phosphorylated collapsin response mediator protein-2 was increased, whereas Ubiquitin carboxy-terminal hydrolase L1 was down-regulated, not only highlights the importance of these molecules in the pathology of this disease, but also illustrates the use of our approach in attempting to decipher the complex pathological processes leading to multiple sclerosis and other neurodegenerative diseases.

Different types of chronic inflammatory demyelinating polyneuropathy have a different clinical course and response to treatment

Chronic inflammatory demyelinating polyneuropathy (CIDP) can occur in association with other systemic diseases such as diabetes mellitus (DM) and IgG or IgA monoclonal gammopathy of undetermined significance (MGUS). Whether CIDP that is idiopathic (I-CIDP) or associated with diabetes (CIDP-DM) or MGUS (CIDP-MGUS) differ in clinical presentation, laboratory features, response to treatment, and long-term outcome is unclear, as is the relationship between these coexisting diseases and CIDP. In order to clarify this issue, we began a prospective follow-up study. Thirty-one consecutive patients with untreated CIDP, fulfilling the most restrictive diagnostic criteria, were enrolled over 18 months. Among the patients, 16 were diabetic, 7 had a MGUS, and 8 had an idiopathic CIDP. All patients were treated with IVIg, and the responders were treated again if they relapsed. In all three groups, improvement occurred after treatment. At the end of the follow-up, there was no difference in clinical conditions between groups, but a significant difference existed in the number of relapses and of IVIg administrations. CIDP-DM is a more severe disease, but with a significantly better response to IVIg and fewer relapses, than the other types that we studied.

Foot temperature in diabetic polyneuropathy: innocent bystander or unrecognized accomplice?

AIM

To explore mechanisms by which temperature could influence the pathogenesis and symptoms of diabetic polyneuropathy.

METHODS

We conducted a literature review attempting to identify mechanisms by which diabetic polyneuropathy could be affected by temperature.

RESULTS

Cooling can theoretically hasten the progression of diabetic polyneuropathy through several different mechanisms. Specifically, cooling can enhance neuronal ischaemia, increase formation of reactive oxygen species, slow axonal transport, increase protein kinase C activity, and interfere with immune function. Short-term temperature fluctuations (both warming and cooling) can initiate and exacerbate neuropathic pain by causing neuronal hyperexcitability and functional deafferentation. Although normal fluctuations of distal extremity temperature may be sufficient for these effects, impaired thermoregulation may make the distal extremities more susceptible to temperature extremes. Eventually, a 'vicious cycle' may ensue, resulting in neuronal deterioration with further disruption of temperature regulation. Limited epidemiological data suggest a higher prevalence of diabetic polyneuropathy in populations living in colder locations, supporting our hypothesis.

CONCLUSIONS

Variations in foot temperature may play an important but as yet unrecognized role in the development and symptoms of diabetic polyneuropathy. Further basic and clinical research exploring this concept could help elucidate the natural history of diabetic polyneuropathy and lead to novel therapeutic strategies.

Strategies for managing the diabetic patient

Diabetes mellitus is now classified as either 'type 1' (failure of endogenous insulin production) or 'type 2' ('insulin resistance') and can be diagnosed if fasting blood glucose is >6.1 mmol/l (110mg/dl) on two separate occasions or there is unequivocal hyperglycaemia with acute metabolic decompensation or obvious symptoms. The prevalence of the disease is rising and may be as great as 12-14% in western populations aged over 40 years. Diabetes is complicated by micro- and macrovascular consequences of chronically elevated blood glucose concentrations, and diabetic patients are over-represented in hospital populations, particularly among patients requiring surgical interventions. It is associated with increased perioperative mortality and morbidity. Evidence is now accumulating that intensive glycaemic monitoring and the administration of insulin infusions to achieve tight glycaemic control are associated with an improvement of both perioperative mortality and morbidity.

Long-term outcome after gastrectomy for intractable diabetic gastroparesis

AIMS

To examine the long-term outlook for patients with intractable vomiting from diabetic gastroparesis who underwent major gastric surgery.

METHODS

Of 18 patients with problems from vomiting referred to the King's Diabetes Centre during the years 1994-2000, seven were considered to suffer irreversible symptoms not alleviated by protracted periods of medical treatment. They were all Type 1 Caucasian diabetic women, mean age 32 years (range 28-37 years) with multiple symptoms of severe autonomic neuropathy. They underwent major gastric surgery comprising 70% gastric resection including pylorus and antrum, with a 60-cm Roux-en-Y loop of jejunum to prevent reflux gastritis.

RESULTS

The vomiting was relieved in six of the seven patients almost immediately after surgery and during review up to more than 6 years post-operatively. There have been no serious relapses, resulting in considerable improvement in quality of life. Unfortunately, three of the patients developed renal failure, two of them needing renal support treatments 2 and 3 years after successful gastrectomy. One patient died suddenly 5 months after successful surgery and one 3 months after starting dialysis.

CONCLUSIONS

Major gastric surgery can, after careful patient selection, effectively relieve distressing vomiting from severe gastroparesis and give a greatly improved quality of life to a small group of seriously disadvantaged patients where risk of subsequent renal failure is high and where life expectancy is poor.

Peripheral neuropathy does not invariably coexist with autonomic neuropathy in diabetes mellitus

Background: Peripheral somatic and autonomic neuropathies are the most common types of diabetic polyneuropathy. Although duration and degree of hyperglycemia are considered to be risk factors for both autonomic and peripheral neuropathy, recent studies have raised the question of a different development and natural history of these neuropathies in diabetes. In addition, a few studies have investigated the relationship between chronic painful and autonomic neuropathy. The aim of this study was to investigate to what extent autonomic and peripheral neuropathy coexist, as well as whether painful neuropathy is more common in diabetic patients with autonomic neuropathy. Methods: Subjects with type 1 (n=52; mean age 31.7 years) and type 2 diabetes (n=53; mean age 54.5 years) were studied. Evaluation of peripheral neuropathy was based on clinical symptoms (neuropathic symptom score), signs (neuropathy disability score), and quantitative sensory testing (vibration perception threshold). Assessment of autonomic neuropathy was based on the battery of standardized cardiovascular autonomic function tests. Results: Prevalence rates of pure autonomic and of pure peripheral neuropathy in patients with type 1diabetes were 28.8 and 13.5%, respectively. The respective rates in patients with type 2 diabetes were 20.7% (P=0.33 vs. type 1 diabetes) and 20.7% (P=0.32). Peripheral and autonomic neuropathy coexisted in 28.8% of type 1 and in 45.3% of type 2 diabetic subjects (P=0.08). Prevalence rates of chronic painful neuropathy in subjects with type 1 diabetes, with and without autonomic neuropathy, were 16.6 and 22.7%, respectively (P=0.85) and in type 2 diabetic subjects 20 and 22.2%, respectively (P=0.58). Multivariate analysis after adjustment for age, sex, blood pressure, duration of diabetes, HBA(1c), and presence of retinopathy or microalbuminuria showed that neither the indices of peripheral nerve function (neuropathic symptom score, neuropathy disability score, vibration perception threshold) nor the presence of peripheral neuropathy or chronic painful neuropathy are associated with the presence of autonomic neuropathy in individuals with either type 1 or type 2 diabetes. Conclusions: Peripheral and autonomic neuropathies do not invariably coexist in diabetes. In addition, chronic painful neuropathy may be present irrespective of the presence of autonomic neuropathy.

Dissociated sensory loss in diabetic autonomic neuropathy

AIMS

Clinical observation has led to the idea that there might be a distinctive form of selective sensory and autonomic neuropathy affecting patients with Type 1 diabetic mellitus with severe symptomatic autonomic neuropathy (Type 1-DAN) and this study was conducted to evaluate the presence of such a neuropathy in Type 1-DAN.

METHODS

Nineteen Type 1 diabetic patients presenting for treatment of severe symptomatic autonomic neuropathy were examined (all had > or = 2 autonomic symptoms; age 39.3 +/- 10.2 years; duration of disease 25.6 +/- 10.5 years). For comparison, 19 Type 1 diabetic patients with neuropathic foot ulcers (age 44.5 +/- 6.6 years; duration of disease 26.7 +/- 9.2 years), 14 clinically uncomplicated Type 1 diabetic patients (age 39.9 +/- 5.6 years; duration of disease 22.9 +/- 9.3 years) and 16 non-diabetic healthy people as controls (age 39.3 +/- 10.7 years) were also examined. Results The large fibre modalities (light touch and vibration perception) were better preserved in the Type 1-DAN group than in the foot ulcer group. Thus, light touch sensation was normal in 11 out of 19 Type 1-DAN patients compared to only three out of 19 foot ulcer patients (P < 0.01), and vibration perception was 24.9 +/- 15.0 V and 40.5 +/- 7.9 V, respectively (P < 0.002) with some of the Type 1-DAN patients in the normal range. In contrast, the small fibre modalities, thermal perception and autonomic function, were grossly abnormal in both groups (hot thermal perception 14.1 +/- 2.5 degrees C and 12.6 +/- 3.7 degrees C; cold thermal perception 13.8 +/- 2.7 degrees C and 10.9 +/- 4. 7 degrees C; heart rate variation 2.9 +/- 1.5 beats/min and 4.8 +/- 4.0 beats/min, respectively).

CONCLUSIONS

There is indeed a subgroup of Type 1 diabetic neuropathy patients who suffer from severe autonomic symptoms associated with a selective small fibre sensory and autonomic loss with relatively preserved large fibre sensory modalities.

Qualitative and quantitative studies of autoantibodies to phospholipids in diabetes mellitus

Diabetes mellitus is associated with vascular and neurological complications. We have investigated the presence of antibodies to phospholipids and to phospholipid binding plasma proteins in blood samples collected from 68 clinically and biochemically characterized type I and type II diabetic patients and from 252 healthy blood donor controls. Each sample was analysed for antibodies to three phospholipids (cardiolipin, phosphatidylserine and phosphatidylethanolamine), the antibody isotypes (IgA, IgG and IgM), and whether antibody activity was plasma protein-dependent. Patients were considered to have anti-phospholipid antibodies when one or more of these 18 tests was found above predetermined control values. The results of these experiments revealed an increased incidence of anti-phospholipid antibodies in diabetic patients compared with control subjects. The incidence of IgA isotype to phosphatidylethanolamine was higher than the incidence of other isotypes to other phospholipids, and their reactivities were independent of phospholipid-associated proteins. In addition, these antibody findings were studied for associations with prothrombin degradation products, activated factor VII and activated protein C, and with the incidence of diabetic complications. The anti-phosphatidylethanolamine antibody association with proliferative retinopathy was significant.

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.