Autoantibodies against sympathetic ganglia and evidence of cardiac sympathetic dysinnervation in newly diagnosed and long-term IDDM patients

Review: Autonomic neuropathy: a marker of cardiovascular risk

Cardiac autonomic neuropathy (CAN) represents a serious complication as it carries an approximately five-fold risk of mortality in patients with diabetes just as in those with chronic liver diseases. The high mortality rate may be related to silent myocardial infarction, cardiac arrhythmias, cardiovascular and cardiorespiratory instability and to other causes not yet explained. Resting tachycardia due to parasympathetic damage may represent one of the earliest signs. Typical findings referring to autonomic dysfunction may include exercise intolerance, orthostatic hypotension and cardiac dysfunction to rest or exercise. Severe autonomic neuropathy may be responsible for spontaneous respiratory arrest and unexplained sudden death. A relationship between the presence and/or severity of CAN and corrected QT interval prolongation is well documented. Better understanding of the prognostic importance of autonomic neuropathy followed the use of simple non-invasive cardiovascular reflex tests. These most commonly include heart rate variation in response to deep breathing, standing, the Valsalva maneouvre and blood pressure response to standing and sustained handgrip. Near normoglycaemia is now generally accepted as the primary approach to the prevention of diabetic neuropathy, but is not achievable in most patients. Our experience of the use of the antioxidant alpha-lipoic acid in the treatment of cardiac autonomic neuropathy is described.

Type 1 diabetes and cardiovascular disease

The presence of cardiovascular disease (CVD) in Type 1 diabetes largely impairs life expectancy. Hyperglycemia leading to an increase in oxidative stress is considered to be the key pathophysiological factor of both micro- and macrovascular complications. In Type 1 diabetes, the presence of coronary calcifications is also related to coronary artery disease. Cardiac autonomic neuropathy, which significantly impairs myocardial function and blood flow, also enhances cardiac abnormalities. Also hypoglycemic episodes are considered to adversely influence cardiac performance. Intensive insulin therapy has been demonstrated to reduce the occurrence and progression of both micro- and macrovascular complications. This has been evidenced by the Diabetes Control and Complications Trial (DCCT) / Epidemiology of Diabetes Interventions and Complications (EDIC) study. The concept of a metabolic memory emerged based on the results of the study, which established that intensified insulin therapy is the standard of treatment of Type 1 diabetes. Future therapies may also include glucagon-like peptide (GLP)-based treatment therapies. Pilot studies with GLP-1-analogues have been shown to reduce insulin requirements.

Cardiovascular autonomic neuropathies as complications of diabetes mellitus

Diabetic autonomic neuropathies are a heterogeneous and progressive disease entity and commonly complicate both type 1 and type 2 diabetes mellitus. Although the aetiology is not entirely understood, hyperglycaemia, insulin deficiency, metabolic derangements and potentially autoimmune mechanisms are thought to play an important role. A subgroup of diabetic autonomic neuropathy, cardiovascular autonomic neuropathy (CAN), is one of the most common diabetes-associated complications and is ultimately clinically important because of its correlation with increased mortality. The natural history of CAN is unclear, but is thought to progress from a subclinical stage characterized by impaired baroreflex sensitivity and abnormalities of spectral analysis of heart rate variability to a clinically apparent stage with diverse and disabling symptoms. Early diagnosis of CAN, using spectral analysis of heart rate variability or scintigraphic imaging techniques, might enable identification of patients at highest risk for the development of clinical CAN and, thereby, enable the targeting of intensive therapeutic approaches. This Review discusses methods for diagnosis, epidemiology, natural history and potential causes and consequences of CAN.

Autoantibodies to autonomic nerves associated with cardiac and peripheral autonomic neuropathy

OBJECTIVE

This study examines whether autonomic nerve autoantibodies (ANabs) are associated with development of autonomic neuropathy using a prospective study design.

RESEARCH DESIGN AND METHODS

A group of type 1 diabetic patients were followed prospectively with regard to autonomic nerve function on four occasions. At the third examination, 41 patients were tested for ANabs (complement-fixing autoantibodies to the sympathetic ganglion, vagus nerve, and adrenal medulla), and the results were related to cardiac autonomic nerve function (heart rate variation during deep breathing [expiration/inspiration ratio] and heart-rate reaction to tilt [acceleration and brake index]) and to peripheral sympathetic nerve function (vasoconstriction after indirect cooling [vasoconstriction index]).

RESULTS

ANabs were detected in 23 of 41 (56%) patients at the third examination. Compared with patients without ANabs (ANabs-), patients with ANabs (ANabs+) showed significantly higher frequencies of at least one abnormal cardiac autonomic nerve function test at the third examination (17 of 23 [74%] vs. 7 of 18 [39%]; P = 0.03) and fourth examination (15 of 21 [71%] vs. 4 of 16 [25%]; P < 0.01). In contrast, there was no similar difference at the first or second examination. The relative risk for ANabs(+) patients to develop cardiac autonomic neuropathy at follow-up was 7.5 (95% CI 1.72-32.80). The vasoconstriction index was more abnormal in ANabs+ than in ANabs- patients at the fourth examination (median 1.40 [interquartile range 1.58] vs. 0.35 [2.05]; P = 0.01).

CONCLUSIONS

ANabs were associated with future development of cardiac and peripheral autonomic neuropathy in diabetic patients, implying an etiological relationship between nervous tissue autoimmunity and these diabetes complications.

Autonomic dysfunction in rheumatic diseases

Patients who have rheumatic diseases often present with dysfunctions that are related to the autonomic nervous system (ANS) and are due to peripheral autonomic neuropathy or central changes. This article describes the prevalence of autonomic dysfunctions in patients who have rheumatic diseases. In the second part of this article, another form of ANS dysfunction-complex regional pain syndromes-is demonstrated. Clinically, these syndromes are characterized by pain (spontaneous, hyperalgesia, allodynia); active movement disorders, including an increased physiologic tremor, abnormal regulation of blood flow and sweating, edema of skin and subcutaneous tissues; and trophic changes of skin, appendages of skin, and subcutaneous tissues. In conclusion, this discussion shows that alterations of the ANS occur in rheumatic and related diseases, that these alterations may be involved in the pathogenesis of these diseases, and that we need more refined methods to study the changes that are related to the ANS.

Islet-infiltrating B-cells in nonobese diabetic mice predominantly target nervous system elements

B-cells accumulate in pancreatic islets during the autoimmune response that precedes the onset of type 1 diabetes. However, the role and antigenic specificity of these cells remain a mystery. To elucidate the antigenic repertoire of islet-infiltrating B-cells in type 1 diabetes, we generated hybridoma cell lines of islet-infiltrating B-cells from nonobese diabetic (NOD) mice and NOD mice expressing a diabetogenic T-cell receptor (8.3-NOD). Surprisingly, characterization of the tissue specificity of the antibodies secreted by these cells revealed that a predominant fraction of these hybridomas produce antibodies specific for the pancreatic nervous system. Similar results were obtained with B-cell hybridomas derived from mild insulinic lesions of diabetes-resistant (NOD x NOR)F1 and 8.3-(NOD x NOR)F1 mice. Immunoglobulin class analyses further indicated that most islet-derived hybridomas had arisen from B-cells that had undergone immunoglobulin class switch recombination, suggesting that islet-associated B-cells are involved in active, T-helper-driven immune responses against local antigenic targets. This is the first evidence showing the existence of a predominant active B-cell response in situ against pancreatic nervous system elements in diabetogenesis. Our data are consistent with the idea that this B-cell response precedes the progression of insulitis to overt diabetes, thus strongly supporting the idea that pancreatic nervous system elements are early targets in type 1 diabetes.

Non-obese diabetic mice rapidly develop dramatic sympathetic neuritic dystrophy: a new experimental model of diabetic autonomic neuropathy

To address the pathogenesis of diabetic autonomic neuropathy, we have examined the sympathetic nervous system in non-obese diabetic (NOD) and streptozotocin (STZ)-induced diabetic mice, two models of type 1 diabetes, and the db/db mouse, a model of type 2 diabetes. After only 3 to 5 weeks of diabetes, NOD mice developed markedly swollen axons and dendrites ("neuritic dystrophy") in the prevertebral superior mesenteric and celiac ganglia (SMG-CG), similar to the pathology described in diabetic STZ- and BBW-rat and man. Comparable changes failed to develop in the superior cervical ganglia of the NOD mouse or in the SMG-CG of non-diabetic NOD siblings. STZ-induced diabetic mice develop identical changes, although at a much slower pace and to a lesser degree than NOD mice. NOD-SCID mice, which are genetically identical to NOD mice except for the absence of T and B cells, do not develop diabetes or neuropathology comparable to diabetic NOD mice. However, STZ-treated NOD-SCID mice develop severe neuritic dystrophy, evidence against an exclusively autoimmune pathogenesis for autonomic neuropathy in this model. Chronically diabetic type 2 db/db mice fail to develop neuritic dystrophy, suggesting that hyperglycemia alone may not be the critical and sufficient element. The NOD mouse appears to be a valuable model of diabetic sympathetic autonomic neuropathy with unambiguous, rapidly developing neuropathology which corresponds closely to the characteristic pathology of other rodent models and man.

Neuropathology and pathogenesis of diabetic autonomic neuropathy

Autonomic neuropathy is a significant complication of diabetes resulting in increased patient morbidity and mortality. A number of studies, which have shown correspondence between neuropathologic findings in experimental animals and human subjects, have demonstrated that axonal and dendritic pathology in sympathetic ganglia in the absence of significant neuron loss represents a neuropathologic hallmark of diabetic autonomic neuropathy. A recurring theme in sympathetic ganglia, as well as in the pot-ganglionic autonomic innervation of various end organs, is the involvement of distal portions of axons and nerve terminals by degenerative or dystrophic changes. In both animals and humans, there is a surprising selectivity of the diabetic process for subpopulations of autonomic ganglia, nerve terminals within sympathetic ganglia and end organs, from end organ to end organ, and between vascular and other targets within individual end organs. Although the involvement or autonomic axons in somatic nerves may reflect an ischemic pathogenesis, the selectivity of the diabetic process confounds simple global explanations of diabetic autonomic neuropathy as the result of diminished blood flow with resultant tissue hypoxia. A single unifying pathogenetic hypothesis has not yet emerged from clinical and experimental animal studies, and it is likely that diabetic autonomic neuropathy will be shown to have multiple causative mechanisms, which will interact to result in the variety of presentations of autonomic injury in diabetes. Some of these mechanisms will be shared with aging changes in the autonomic nervous system. The role of various neurotrophic substances and the polyol pathway in the pathogenesis and treatment of diabetic neuropathy likely represents a two-edged sword with both salutary and exacerbating effects. The basic neurobiologic process underlying the diabetes-induced development of neuroaxonal dystrophy, synaptic dysplasia, defective axonal regeneration, and alterations in neurotrophic substance may be mechanistically related.

Cardiac sympathetic dysinnervation in Type 2 diabetes mellitus with and without ECG-based cardiac autonomic neuropathy

To evaluate the presence and extent of global and regional distributions of cardiac sympathetic dysinnervation in Type 2 diabetes mellitus I-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy was applied to 15 Type 2 (noninsulin-dependent) diabetic patients with ECG-based cardiac autonomic neuropathy (> or = two of five age-related cardiac reflex tests abnormal) and 15 clinically comparable Type 2 diabetic patients without ECG-based cardiac autonomic neuropathy. Myocardial perfusion abnormalities were excluded by 99 m-Tc-methoxyisobutylisonitrile (99 m-MIBI) scintigraphy. Both in Type 2 diabetic patients with and without, ECG-based autonomic neuropathy, only one patient (7%) was found to have a normal homogeneous uptake of I-123-MIBG compared to 14 patients (93%) with a reduced I-123-MIBG uptake. The uptake of I-123-MIBG in the posterior myocardium of diabetic patients was smaller than in the anterior, lateral, and septal myocardium (P< .001, P< .001, P< .001, respectively). Diabetic patients with ECG-based cardiac autonomic neuropathy demonstrated a more pronounced reduction of the posterior I-123-MIBG myocardial uptake than diabetic patients without (P< .01). The mean global and the anterior, lateral, septal, and apical myocardial I-123-MIBG uptake was comparable between the two groups. The uptake of the posterior myocardial region correlated with all indices of heart rate variation at rest and during deep breathing. A correlation between global or regional myocardial I-123-MIBG uptake and QT interval was not observed. The study demonstrates that cardiac sympathetic dysinnervation is common in Type 2 diabetes mellitus both with and without ECG-based cardiac autonomic neuropathy. In Type 2 diabetes mellitus, the posterior myocardium is predominantly affected and the extent of dysinnervation is more pronounced in the presence of ECG-based cardiac autonomic neuropathy.

Diabetes causes an early reduction in autonomic ganglion blood flow in rats

Impaired blood flow to peripheral nerve trunks makes a major contribution to the neuropathic complications of diabetes mellitus. Comparatively little attention has been paid to perfusion abnormalities for the cell bodies of origin of the autonomic and sensory nerves, although they are severely affected in diabetic neuropathy. The aim was to examine the time course of changes in superior cervical ganglion (SCG) perfusion in streptozotocin-induced diabetic rats. Ganglion blood flow, measured by hydrogen clearance microelectrode polarography, was approximately 70 ml min(-1) 100 g(-1). One week of diabetes caused a 46% perfusion deficit, which was maintained (54%) over 24 weeks. Thus, an early, profound, and long-lived reduction in ganglion perfusion may deleteriously affect neural cell body function and could contribute to autonomic neuropathy.

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.

Cardiac sympathetic denervation in early stages of amyotrophic lateral sclerosis demonstrated by 123I-MIBG-SPECT

Involvement of the autonomic cardiac nervous system in early stages of amyotrophic lateral sclerosis (ALS) was evaluated in 40 patients. I-123-metaiodobenzylguanidine-single photon emission computed tomography (MIBG-SPECT) and heart rate variability (HRV) yielded information about sympathetic and parasympathetic innervation of the heart. MIBG-SPECT is a sensitive diagnostic method for demonstration of early cardiac sympathetic denervation. Both sympathetic and parasympathetic dysfunction was observed in 16 (40%) out of 40 patients. Mean cardiac MIBG uptake as demonstrated by the heart/mediastinum ratio was significantly reduced in all ALS patients in comparison with controls (P<0.01). The global MIBG-SPECT score was clearly abnormal in 29% and slightly abnormal in 22% of patients. HRV was diminished in 6 of 38 patients, 4 of whom having an abnormal MIBG-SPECT score as well. The presented results indicate that ALS patients with mild to moderate impairment may have evidence of postganglionic sympathetic adrenergic cardiac or cardiovagal denervation. To our knowledge, this is the first study indicating possible postganglionic sympathetic denervation in ALS. The original concept of ALS as an isolated degeneration of motor neurons seems to extend to a more widespread understanding of the disease which possibly represents different entities.

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.

Three-year follow-up on scintigraphically assessed cardiac sympathetic denervation in patients with long-term insulin-dependent (type I) diabetes mellitus

Scintigraphy using I-123-metaiodobenzylguanidine (I-123-MIBG) and Tc-99m-methoxyisobutylisonitrile (Tc-99m-MIBI) allows assessment of the cardiac sympathetic innervation and the myocardial perfusion. To investigate the natural history of cardiac sympathetic denervation in long-term diabetic patients without myocardial perfusion defects, global and regional I-123-MIBG and Tc-99m-MIBI uptake was determined (score 1-6; 1 = normal uptake, 6 = no uptake) in 22 patients with insulin-dependent (type I) diabetes mellitus (IDDM) at 3-year follow-up. All patients were treated with intensive insulin therapy and HbA1c was 8.0% +/- 1.0% at entry compared with 7.9% +/- 1.1% at follow-up. Cardiac sympathetic denervation (I-123-MIBG uptake score > 2), initially observed in 18 patients, was detectable in 21 patients at follow-up. The global myocardial I-123-MIBG uptake score deteriorated in eight patients, remained unchanged in 11 and improved in three patients. The changes in mean global I-123-MIBG uptake score (3.5 +/- 1.0 versus 3.8 +/- 0.8) were not significant. Reduction of the anterior, lateral, posterior, septal, and apical I-123-MIBG uptake did not progress significantly during follow-up. The mean uptake score of the posterior myocardial region (4.7 +/- 0.8) was smaller than the uptake score of the anterior (3.0 +/- 1.1, p = 0.001), lateral (3.2 +/- 0.9, p < 0.001) and septal (4.1 +/- 1.1, p < 0.05) myocardial regions. At follow-up, moderate myocardial perfusion defects (global Tc-99m-MIBI uptake score = 3) were detectable in four patients. Our study demonstrates that scintigraphically assessed cardiac sympathetic denervation does neither significantly regress nor progress on the average in a group of long-term IDDM patients during a 3-year follow-up. Thus, it is concluded that cardiac sympathetic abnormalities are a persistent, yet frequent phenomenon in long-term IDDM patients.