Prospective assessment of autonomic and peripheral nerve function in adolescents with diabetes

Vibrotactile sense might improve over time in paediatric subjects with type 1 diabetes-A mid-term follow-up using multifrequency vibrometry

AIM

Impaired vibrotactile sense, mirroring diabetic peripheral neuropathy, is present among children and adolescents with type 1 diabetes. This study aims to re-examine the vibrotactile sense of paediatric type 1 diabetes subjects in order to evaluate any alterations in the vibrotactile sense over time.

METHODS

A VibroSense Meter I device was used to determine the vibrotactile perception thresholds (VPTs) for seven frequencies from the pulp of index and little fingers and for five frequencies from metatarsal heads one and five on the sole of the foot, of 37 children and adolescents with type 1 diabetes, previously examined in a larger cohort. Subjects were followed up after a median time of 30 months. Z-scores of VPTs were calculated using previously collected normative data.

RESULTS

Vibrotactile perception thresholds improved over time at low frequencies (especially 16 Hz) on the foot, while not being statistically significant different on the rest of the frequencies, either on hand or foot. VPTs were not correlated with HbA1c.

CONCLUSION

A mid-term follow-up of vibrotactile sense in paediatric subjects with type 1 diabetes shows a conceivable normalization of previously impaired vibrotactile sense on some frequencies on the foot, indicating that vibrotactile sense might fluctuate over time.

Diabetic neuropathy in children and youth: New and emerging risk factors

Pediatric neuropathy attributed to metabolic dysfunction is a well-known complication in children and youth with type 1 diabetes. Moreover, the rise of obesity and in particular of type 2 diabetes may cause an uptick in pediatric neuropathy incidence. However, despite the anticipated increase in neuropathy incidence, pathogenic insights and strategies to prevent or manage neuropathy in the setting of diabetes and obesity in children and youth remain unknown. Data from adult studies and available youth cohort studies are providing an initial understanding of potential diagnostic, management, and preventative measures in early life. This review discusses the current state of knowledge emanating from these efforts, with particular emphasis on the prevalence, clinical presentation, diagnostic approaches and considerations, and risk factors of neuropathy in type 1 and type 2 diabetes in children and youth. Also highlighted are current management strategies and recommendations for neuropathy in children and youth with diabetes. This knowledge, along with continued and sustained emphasis on identifying and eliminating modifiable risk factors, completing randomized controlled trials to assess effectiveness of strategies like weight loss and exercise, and enhancing awareness to support early detection and prevention, are pertinent to addressing the rising incidence of neuropathy associated with diabetes and obesity in children and youth.

Peripheral nerve disease secondary to systemic conditions in children

This review is an overview of systemic conditions that can be associated with peripheral nervous system dysfunction. Children may present with neuropathic symptoms for which, unless considered, a causative systemic condition may not be recognized. Similarly, some systemic conditions may be complicated by comorbid peripheral neuropathies, surveillance for which is indicated. The systemic conditions addressed in this review are critical illness polyneuropathy, chronic renal failure, endocrine disorders such as insulin-dependent diabetes mellitus and multiple endocrine neoplasia type 2b, vitamin deficiency states, malignancies and reticuloses, sickle cell disease, neurofibromatosis, connective tissue disorders, bowel dysmotility and enteropathy, and sarcoidosis. In some disorders presymptomatic screening should be undertaken, while in others there is no benefit from early detection of neuropathy. In children with idiopathic peripheral neuropathies, systemic disorders such as celiac disease should be actively excluded. While management is predominantly focused on symptomatic care through pain control and rehabilitation, some neuropathies improve with effective control of the underlying etiology and in a small proportion a more targeted approach is possible. In conclusion, peripheral neuropathies can be associated with a diverse range of medical conditions and unless actively considered may not be recognized and inadequately managed.

Prevalence of Diabetic Neuropathy in Young Adults with Type 1 Diabetes and the Association with Insulin Pump Therapy

AIMS

The aim was to investigate the prevalence of diabetic sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN) in a Danish population of young adults with type 1 diabetes (T1D) using both established and novel measuring modalities. Furthermore, to investigate the association between continuous subcutaneous insulin infusion (CSII) treatment and these complications.

MATERIALS AND METHODS

CAN was assessed by cardiovascular autonomic reflex tests. DSPN was assessed not only by perception of light touch and pain, vibration perception threshold (VPT), Brief Pain Inventory (BPI), and Michigan Neuropathy Screening Instrument questionnaires but also by novel modalities: electrochemical skin conductance (ESC), sural nerve conduction velocity (SNCV), and sural nerve amplitude potential (SNAP).

RESULTS

The study comprised 156 young adults with a mean age of 22 years (standard deviation 1.6). The prevalence of CAN and early CAN was 9% and 28.1%, respectively. Subclinical DSPN was 55.1% and confirmed DSPN was 2.6%. Prevalence of abnormal SNAP was 23.8%, SNCV was 37.1%, ESC on the hands and feet was 4% and 8%, respectively, VPT was 1.3%, and BPI questionnaire was 1.9%. No association was found between CSII treatment and the measures of DSPN and CAN.

CONCLUSION

DSPN and CAN are prevalent in young adults with T1D with no association found with CSII treatment. The use of novel measuring modalities identified a higher number of subjects with DSPN compared with established measures. Screening for diabetic neuropathy in young adults may be beneficial to detect and prevent nerve damages at early stages.

Cardiac autonomic function in children with type 1 diabetes

Cardiovascular autonomic neuropathy (CAN) is a major complication of type 1 diabetes (T1D). This study aimed to evaluate cardiac autonomic nervous system (ANS) function in children with T1D and its relation to different demographic, clinical and laboratory variable. This cross-sectional study included 60 children with T1D (mean age = 15.1 ± 3.3 years; duration of diabetes = 7.95 ± 3.83 years). The following 8 non-invasive autonomic testing were used for evaluation: heart rate at rest and in response to active standing (30:15 ratio), deep breathing and Valsalva maneuver (indicating parasympathetic function); blood pressure response to standing (orthostatic hypotension or OH), sustained handgrip and cold; and heart rate response to standing or positional orthostatic tachycardia syndrome or POTs (indicating sympathetic function). None had clinically manifest CAN. Compared to healthy children (5%), 36.67% of children with T1D had ≥ 2 abnormal tests (i.e., CAN) (P = 0.0001) which included significantly abnormal heart rate response to standing (POTs) (P = 0.052), active standing (30:15 ratio) (P = 0.0001) and Valsalva maneuver (P = 0.0001), indicating parasympathetic autonomic dysfunction, and blood pressure response to cold (P = 0.01), indicating sympathetic autonomic dysfunction. 54.55, 27.27 and 18.18% had early, definite and severe dysfunction of ANS. All patients had sensorimotor peripheral neuropathy. The longer duration of diabetes (> 5 years), presence of diabetic complications and worse glycemic control were significantly associated with CAN.

CONCLUSIONS

The study concluded that both parasympathetic and sympathetic autonomic dysfunctions are common in children with T1D particularly with longer duration of diabetes and presence of microvascular complications. What is Known: • Cardiovascular autonomic neuropathy (CAN) is a major complication of type 1 diabetes (T1D). • Limited studies evaluated CAN in children with T1D. What is New: • CAN is common in children with T1D. • Cardiac autonomic functions should be assessed in children with T1D particularly in presence of microvascular complications.

High Prevalence and Incidence of Diabetic Peripheral Neuropathy in Children and Adolescents With Type 1 Diabetes Mellitus: Results From a Five-Year Prospective Cohort Study

BACKGROUND

In this prospective cohort study, we investigated the prevalence of diabetic peripheral neuropathy at baseline and after five years of follow-up in children and adolescents with type 1 diabetes mellitus using both measurements of nerve conduction velocity and clinical neurological examination.

METHODS

A total of 38 patients who underwent insulin pump or intensive insulin therapy were included. The subjects averaged 12.6 ± 2.4 years of age and their diabetes duration averaged 5.6 ± 3.2 years. All patients underwent a detailed physical, neurological, and electrophysiological examination, as well as laboratory testing at their annual checkup.

RESULTS

At baseline, the prevalence of diabetic peripheral neuropathy diagnosed using neurological examination was 13.2%, whereas nerve conduction velocity testing revealed diabetic peripheral neuropathy in 31.6%, highlighting a high prevalence of subclinical diabetic peripheral neuropathy. During follow-up, there was a strong increase in the prevalence of clinically diagnosed diabetic peripheral neuropathy, which reached 34.2% (P = 0.039) after five years; the proportion of patients with subclinical diabetic peripheral neuropathy even reached 63.2% (P = 0.002). The most significant changes in electrophysiological parameters were observed in the tibial sensory nerve (P = 0.001).

CONCLUSIONS

The prevalence of diabetic peripheral neuropathy in children and adolescents with type 1 diabetes mellitus was high, and there was a rapid increase in the prevalence of diabetic peripheral neuropathy during a five-year follow-up interval. Importantly, our data show that a mere clinical evaluation is not sensitive enough to diagnose diabetic peripheral neuropathy in these patients. Nerve conduction velocity measurement, which is regarded as the gold standard for the assessment of diabetic peripheral neuropathy, should be applied more broadly.

Heart rate variability in pubertal girls with type 1 diabetes: its relationship with glycaemic control, insulin resistance and hyperandrogenism

OBJECTIVE

To examine the association between glycaemic control, insulin resistance and hyperandrogenism on cardiac autonomic function in peripubertal girls with type 1 diabetes.

DESIGN

Prospective, clinic-based study of 125 girls with diabetes and 46 age-matched nondiabetic girls.

MEASUREMENTS

Heart rate variability (HRV) parameters derived from a 10-min ECG recording using LabChart Pro were as follows: standard deviation of mean NN intervals (SDNN), where NN = adjacent QRS complexes; root mean squared difference of successive NN intervals (RMSSD) - estimates of overall HRV; and low-/high-frequency (LF:HF) ratio - an estimate of the sympathovagal balance. Androgens and sex hormone binding globulin (SHBG) were measured in girls with diabetes, and free androgen index (FAI) calculated. HRV and anthropometry were measured in nondiabetic controls.

RESULTS

Adolescents with diabetes (median age 15·1 years [13·3-16·0], diabetes duration 7·0 years [4·6-10·0] and median HbA1c 8·4% [7·5-9·3]) had higher HR and lower HRV compared with controls. Using multivariate models in the diabetes group, higher HR was associated with higher HbA1c, total daily dose insulin/kg body weight and systolic BP standard deviation scores (SDS), whilst reduced HRV was associated with higher HbA1c (SDNN, RMSSD and LF:HF ratio), lower SHBG (SDNN and RMSSD) and higher weight SDS (LF:HF ratio). Higher FAI was associated with higher HR and reduced HRV measures in the univariate analyses only.

CONCLUSIONS

In adolescent girls with diabetes, reduced HRV parameters are associated with worse glycaemic control, lower SHBG and higher weight SDS. SHBG should be considered in the cardiac risk models for this population.

Autonomic neuropathy in young people with type 1 diabetes: a systematic review

Autonomic neuropathy is an under-recognized complication of diabetes, although it affects multiple organ systems and has widespread clinical manifestations including orthostatic hypotension, exercise intolerance, gastroparesis, diarrhea, constipation, and urinary incontinence. The most severe consequences include hypoglycemia unawareness and cardiovascular dysfunction. Autonomic neuropathy is also implicated in sudden unexplained deaths in otherwise healthy young people--the ‘dead in bed syndrome’. In adults, cardiovascular autonomic neuropathy is an independent predictor of mortality, predominantly due to cardiovascular disease, nephropathy, and hypoglycemia. While overt autonomic neuropathy is rare in childhood and adolescence, subclinical signs of autonomic dysfunction are common, and can be found soon after diabetes diagnosis. Risk factors for autonomic neuropathy in young people include diabetes duration, poor glycemic control, and presence of aldose reductase gene (AKR1B1) polymorphisms, specifically the Z-2/Z-2 genotype. Autonomic dysfunction is accelerated by puberty.

Continued reduction in the prevalence of retinopathy in adolescents with type 1 diabetes: role of insulin therapy and glycemic control

OBJECTIVE

To examine trends in microvascular complications in adolescents with type 1 diabetes between 1990 and 2009 in Sydney, Australia.

RESEARCH DESIGN AND METHODS

We used analysis of complications in 1,604 adolescents (54% female, aged 12-20 years, median duration 8.6 years), stratified by four time periods using Generalized Estimation Equations as follows: T1 (1990-1994), T2 (1995-1999), T3 (2000-2004), and T4 (2005-2009). Early retinopathy was detected using seven-field fundal photography, albumin excretion rate (AER) using timed overnight urine collections, and albumin-to-creatinine ratio (ACR) and peripheral nerve function using thermal and vibration threshold.

RESULTS

Retinopathy declined (53, 38, 23, and 12%; P < 0.001), as did borderline elevation of AER/ACR (45, 30, 26, and 30%; P < 0.001) and microalbuminuria (8, 4, 3, and 3%; P = 0.006). Multiple daily injections (MDI)/continuous subcutaneous insulin infusion (CSII) use increased (17, 54, 75, and 88%; P < 0.001), median HbA(1c) decreased (9.1, 8.9, 8.5, and 8.5%; P < 0.001), and severe hypoglycemia was unchanged (6, 8, 10, and 7%; P = 0.272). Retinopathy was associated with diabetes duration (odds ratio [OR] 1.12 [95% CI 1.08-1.17]), age (1.13 [1.06-1.20]), HbA(1c) (1.16 [1.08-1.25]), systolic blood pressure (BP) SDS (1.31 [1.16-1.48]), socioeconomic disadvantage (1.42 [1.04-1.95]), and 1 to 2 injections per day (vs. MDI/CSII; 1.35 [1.05-1.73]); borderline AER/ACR with male sex (1.32 [1.02-1.70]), age (1.19 [1.12-1.26]), HbA(1c) (1.18 [1.08-1.29]), weight SDS (1.31 [1.21-1.53]), insulin dose per kilograms (1.64 [1.13-2.39]), 1 to 2 injections per day (1.41 [1.08-1.84]), and socioeconomic disadvantage (1.68 [1.23-2.31]); and microalbuminuria with age (1.14 [1.01-1.29]), HbA(1c) (1.20 [1.05-1.37]), diastolic BP SDS (1.76 [1.26-2.46]), and 1 to 2 injections per day (1.95 [1.11-3.41]).

CONCLUSIONS

The decline in retinopathy supports contemporary guidelines that recommend lower glycemic targets and use of MDI/CSII in children and adolescents with type 1 diabetes.

A 5-yr follow-up nerve conduction study for the detection of subclinical diabetic neuropathy in children with newly diagnosed insulin-dependent diabetes mellitus

OBJECTIVE

To investigate the changes of peripheral nerve conduction in children with insulin-dependent diabetes mellitus (IDDM) prospectively from diagnosis and to know how those results were related to clinical risk factors.

METHODS

A total of 37 patients (14 males and 23 females) aged 3-19 yr (mean 12.0 ± 3.7) with newly diagnosed IDDM underwent bilateral nerve conduction studies (NCS) of median, ulnar, posterior tibial, peroneal, and sural nerves annually for 5 yr.

RESULTS

In all, 12 patients (32.4%) showed electrophysiological evidence of polyneuropathy in at least two different nerves including the sural nerve at the diagnosis of IDDM; 20 patients (54%) had multiple (≥2) abnormalities in parameters of NCS. The most common abnormal parameters at the diagnosis were conduction velocities of peroneal motor and sural nerves. In sequential NCS over 5 yr, the percentage of abnormal nerve conduction velocities rose except within the sural nerve. Poor metabolic control, height, duration of diabetes, and older age of onset were related to the changes of parameters of NCS over 5 yr. Among those risk factors, the duration of diabetes and sustained hyperglycemia affected the parameters of NCS more frequently than others.

CONCLUSIONS

Children with IDDM frequently have nerve conduction abnormalities without clinical neuropathy at initial diagnosis. The frequency of abnormalities of any attribute of nerve conduction increased over the 5 yr follow-up. The duration of diabetes and poor glycemic control proved to be more important risk factors over 5 yr as related to the development of subclinical neuropathy.

Autonomic function testing in children and adolescents with diabetes mellitus

Cardiac autonomic neuropathy (CAN) is a common complication in type 1 diabetes mellitus (T1DM) and associated with an increased mortality. Early detection of CAN would be desirable for a better individual risk stratification. The aim of this study was to determine whether autonomic dysfunction can be diagnosed in young patients with a recent history of T1DM. Autonomic function was assessed in 20 pediatric patients with T1DM, aged 10-19 yr, and a control group of 136 non-diabetic patients using four cardiorespiratory reflexes: heart rate and blood pressure response in standing position, deep breathing, and Valsalva maneuver. Furthermore, power spectral analyses of the low- and high-frequency band of heart rate variability (HRV) and baroreflex sensitivity (BRS) were tested with the non-invasive Task force monitor (CNSystems, Graz, Austria). Cardiorespiratory reflexes were pathologic for at least one item in 75% of the diabetic and 60% in the healthy control group. A reduced BRS was always combined with abnormal HRV. We found this pattern in 30% of diabetic patients and never in the control group. In patients with impaired BRS, mean hemoglobin A1c (HbA1c) was 7.7% and duration of diabetes 6.5 yr. This did not differ from the overall value of the diabetic group: HbA1c level 8.4% and diabetes duration 7.3 yr. In conclusion, signs of autonomic dysfunction are not uncommon in an early stage of diabetes in young patients. Classical cardiorespiratory reflexes seem to be less specific than HRV and BRS as testing methods.

Diabetes mellitus en niños y adolescentes: complicaciones crónicas y enfermedades asociadas

Diabetes is one of the most common chronic diseases. Type 1, or autoimmune, diabetes accounts for more than 95 % of cases in children and adolescents. Chronic hyperglycemia per se is responsible for the development of several microvascular (retinopathy, nephropathy, neuropathy) and macrovascular complications (ischemic heart disease, cerebrovascular disease, and peripheral vascular disease). Other autoimmune diseases are also more frequent in type 1 diabetic patients. The present review aims to provide an update on some recent advances in this field to aid early detection of these complications and prevent or delay their progression through improved metabolic control.

Autoantibody-mediated Bladder Dysfunction in Type 1 Diabetes

Bladder dysfunction is a common complication of diabetic autonomic neuropathy; however, its cause remains uncertain. We have recently identified a novel IgG autoantibody (Ab) in patients with type 1 diabetes that acts as an agonist at the dihydropyridine (DHP) site of L-type voltage-gated calcium channels (VGCC), disrupting neuronal regulation of visceral smooth muscle. In the present study, passive transfer to mice of IgG from patients with type 1 diabetes was used to investigate the role of anti-VGCC Abs in mediating diabetic bladder dysfunction. Injection of mice with diabetic immunoglobulin (IgG) with anti-VGCC activity induced features of an overactive bladder, including phasic detrusor contractions and a loss of bladder wall compliance. The bladder overactivity is mimicked by the DHP agonist Bay K8644, reversed by the DHP antagonist nicardipine, but is insensitive to the motor nerve blocker tetrodotoxin, indicating that the anti-VGCC Ab acts at the level of the bladder detrusor itself. This study reports the first evidence of Ab-mediated bladder dysfunction in type 1 diabetes, which may be part of a wider spectrum of smooth muscle and cardiac abnormalities.

Contemporary Australian outcomes in childhood and adolescent type 1 diabetes: 10 years post the Diabetes Control and Complications Trial

The reporting of the results of the Diabetes Control and Complications Trial in 1993 has led to a major reappraisal of management practices and outcomes in type 1 diabetes in children and adolescents. A considerable body of outcome data has been generated from Australia in this post-Diabetes Control and Complications Trial era relating to incidence, metabolic control, growth, hypoglycaemia, microvascular and macrovascular complications, cognition, behaviour and quality of life. These data are important in planning future management strategies and resource allocation and as a basis for future research.

Prevalence of diabetes complications in adolescents with type 2 compared with type 1 diabetes

OBJECTIVE

To compare the prevalence of diabetes complications and their risk factors in youth with type 1 versus type 2 diabetes.

RESEARCH DESIGN AND METHODS

We performed a comparative clinic-based study of 1,433 patients with type 1 diabetes and 68 patients with type 2 diabetes aged <18 years from New South Wales, Australia. Retinopathy was assessed by seven-field stereoscopic retinal photography; albumin excretion rate from three consecutive, timed, overnight urine collections; peripheral neuropathy by thermal and vibration threshold; and autonomic neuropathy by pupillometry. HbA(1c) (A1C) and lipids were measured in all patients and C-peptide in patients with type 2 diabetes.

RESULTS

In patients with type 1 versus type 2 diabetes, median (interquartile range) age was 15.7 years (13.9-17.0) and 15.3 years (13.6-16.4), respectively (P = 0.2), whereas median diabetes duration was 6.8 years (4.7-9.6) and 1.3 years (0.6-3.1), respectively (P < 0.0001). Retinopathy was significantly more common in patients with type 1 diabetes (20 vs. 4%, P = 0.04), while microalbuminuria and hypertension were significantly less common (6 and 16% in type 1 diabetes vs. 28 and 36% in type 2 diabetes). Rates of peripheral and autonomic neuropathy were similar (27 and 61% in type 1 diabetes vs. 21 and 57% in type 2 diabetes). In multivariate analyses, microalbuminuria was significantly associated with older age (odds ratio 1.3 [95% CI 1.2-1.5], P < 0.001) and systolic hypertension (3.63 [2.0-6.3], P < 0.001) in type 1 diabetes, while only higher A1C (1.7 [1.3-2.9], P = 0.002) was significant in patients with type 2 diabetes.

CONCLUSIONS

Youth with type 2 diabetes have significantly higher rates of microalbuminuria and hypertension than their peers with type 1 diabetes, despite shorter diabetes duration and lower A1C. The results of this study support recommendations for early complications screening and aggressive targeting of glycemic control in patients with type 2 diabetes.

Muscle weakness and foot deformities in diabetes: relationship to neuropathy and foot ulceration in caucasian diabetic men

OBJECTIVE

To examine the relationships among muscle weakness, foot deformities, and peroneal and tibial nerve conduction velocity in diabetic and nondiabetic men.

RESEARCH DESIGN AND METHODS

A neuropathic and foot evaluation was undertaken in 10 nondiabetic control subjects (group C) and in 36 consecutive diabetic patients attending Diabetes Centre clinics, including 10 diabetic control subjects (group D), 15 diabetic neuropathic patients (group DN), and 11 diabetic patients with a history of ulceration (group DU). Neuropathy was defined as a peroneal motor nerve conduction <40 m/s. Muscle weakness was assessed in seven intrinsic and seven extrinsic muscles of the foot using a semiquantitative score (max score per muscle = 3). Foot deformities were assessed using a foot deformity score (max score = 3). A higher score indicated increased muscle weakness or more severe foot deformities. Muscle weakness and foot deformities were assessed without prior knowledge of patient and neuropathy status.

RESULTS

Peroneal and tibial nerve conduction velocity were associated with weakness in muscles innervated by, respectively, the peroneal and tibial nerve (r = -0.70 and r = -0.51, P < 0.01) and foot deformities (r = -0.60 and r = -0.59, P < 0.001). The DN and DU groups had more weakness in intrinsic and extrinsic muscles compared with the C and D groups. Muscles innervated by the tibial nerve had a greater proportional muscle weakness than those innervated by the peroneal nerve in the DN and DU groups. The DN and DU patients had more foot deformities (median food deformity score [interquartile range]) (3 [2-3] and 2 [2-3]) compared with D and C patients (0 [0-0.75] and 0 [0-0]).

CONCLUSIONS

Important relationships have been shown between motor nerve conduction deficit and muscle weakness; however, it is still not clear whether abnormal nerve function, leading to a decrease in muscle strength, could be responsible for the development of foot deformities.

Disruption of intestinal motility by a calcium channel-stimulating autoantibody in type 1 diabetes

BACKGROUND & AIMS

Autonomic neuropathy, including gastrointestinal dysfunction, is a common complication of type 1 diabetes; however, its cause is uncertain. This study aimed to test whether functional autoantibodies cause the gastrointestinal dysfunction.

METHODS

We used isolated mouse colon undergoing colonic migrating motor complex (MMC) activity to test for autoantibodies that disrupt colonic motility. Purified immunoglobulin G (IgG) from patients with type 1 diabetes or from controls was tested either in vitro or after passive transfer. Pharmacological studies of the interaction between the IgG and L-type calcium channel activator (Bay K8644) and inhibitors (nicardipine and verapamil) were performed. The effect of IgG on nerve-evoked contraction of the vas deferens longitudinal smooth muscle was also assessed.

RESULTS

MMC activity was disrupted by IgG (0.2 mg/mL) from 8 of 16 patients with type 1 diabetes but not by control IgG. Passive transfer of diabetic IgG to mice also disrupted MMCs, showing access to the antigen in vivo. The acute effect of the autoantibody was mimicked by the dihydropyridine agonist, Bay K8644 (2-10 nmol/L), and both Bay K8644 and the autoantibody competitively inhibited the effect on MMC contraction of the dihydropyridine antagonist, nicardipine. Diabetic IgG, but not control IgG, altered the nerve-evoked contractile activity of vas deferens smooth muscle effects mimicked by Bay K8644.

CONCLUSIONS

A novel functional autoantibody that activates smooth muscle L-type calcium channels at the dihydropyridine binding site is produced specifically by patients with type 1 diabetes and may mediate gastrointestinal and autonomic dysfunction in these patients.

Cardiovascular autonomic reactivity is decreased in adolescents with Type 1 diabetes

AIMS

To characterize autonomic nervous system function by means of the heart rate and blood pressure responses to various stimuli in relation to pubertal maturation in patients with Type 1 diabetes mellitus (DM).

METHODS

One hundred out of 138 eligible patients at the Out-patient Diabetes Clinic and 100 healthy control subjects were examined in terms of cardiovascular parameters at rest, during deep breathing and when standing. Heart rate variability was analysed with time domain,frequency domain and fractal dimension parameters. Tanner pubertal staging was performed before the examinations.

RESULTS

The time domain parameters of heart rate variability at rest or during standing did not significantly differ between the patients and controls in total or at pubertal stages. In the spectral analysis of heart rate variability the very low frequency band was decreased in the patients during standing (P = 0.023).The increase in the very low frequency (P = 0.013)and low frequency (P = 0.031) spectral powers upon changing from a supine position to standing was attenuated in the patients in total, while no significant differences were observed within the Tanner pubertal stages between patients and controls. Heart rate variability during deep breathing was decreased in the patients with distal polyneuropathy (P = 0.006).

CONCLUSIONS

Although cardiovascular integrity is in the main well preserved in adolescent patients with Type 1 DM, these patients are prone to attenuated autonomic nervous system reactivity.

Peripheral nerve function is increasingly impaired during puberty in adolescents with type 1 diabetes

OBJECTIVE

To evaluate the impact of puberty on peripheral nerve function in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Of 138 eligible patients with type 1 diabetes, 100 patients (age >9 years and diabetes duration >2 years) attending an outpatient diabetes clinic and 100 age- and sex-matched healthy control subjects took part in this cross-sectional study. Peripheral motor and sensory nerve conduction tests, cardiovascular reflex tests on the autonomic nervous system, and measurements of vibration-perception threshold (VPT) were performed.

RESULTS

Nerve conduction velocity (NCV) in the distal motor and sensory nerves, the motor nerve distal latency, and the sensory nerve action potential (SNAP) amplitude were impaired in the adolescent patients with type 1 diabetes. The deterioration in motor NCV, H-reflex latency, and SNAP amplitude became more conspicuous in late puberty and postpuberty and was related to poor metabolic control. A total of 10 patients had distal diabetic polyneuropathy (DP) neurophysiologically, and these patients had significantly lower heart-rate variation in the deep breathing test than the other patients. Three of the patients with DP had peripheral neurological signs or symptoms. A slight difference in the VPT between the patients and control subjects was observed after puberty.

CONCLUSIONS

Increasing subclinical motor nerve impairment can be detected during late puberty and after puberty, and sensory NCV and SNAP amplitude are reduced in adolescents with type 1 diabetes. Poor metabolic control during puberty appears to induce deteriorating peripheral neural function in young patients with type 1 diabetes.

A 6-year nationwide cohort study of glycaemic control in young people with type 1 diabetes. Risk markers for the development of retinopathy, nephropathy and neuropathy. Danish Study Group of Diabetes in Childhood

The study aimed to identify risk markers (present at the start of the study in 1989) for the occurrence and progression of microvascular complications 6 years later (in 1995) in a Danish nationwide cohort of children and adolescents with Type 1 diabetes (average age at entry 13.7 years). Probabilities for the development of elevated albumin excretion rate (AER), retinopathy, and increased vibration perception threshold (VPT) could then be estimated from a stepwise logistic regression model. A total of 339 patients (47% of the original cohort) were studied. Sex, age, diabetes duration, insulin regimen and dose, height, weight, HbA(1c), blood pressure, and AER were recorded. In addition, information on retinopathy, neuropathy (VPT), and anti-hypertensive treatment was obtained at the end of the study. HbA(1c) (normal range 4.3-5.8, mean 5.3%) and AER (upper normal limit <20 microg min(-1)) in two, timed overnight urine collections were analysed centrally. Eye examination was performed by two-field fundus photography. Determination of VPT was assessed by biothesiometry. Increased AER (> or =20 microg min(-1)) was found in 12.8% of the patients in 1995, and risk markers for this were increased AER and high HbA(1c), in 1989 (both p<0.001). Retinopathy was present in 57.8% of patients in 1995, for which the risk markers were long duration of diabetes (p<0.0001), age (p<0.01), and high HbA(1c) (p<0.0001) in 1989. Elevated VPT (>6.5 V) was found in 62.5% of patients in 1995, for which the risk markers were male sex (p<0.05), age (p<0.0001), and increased AER (p<0.05) in 1989. This study confirms that hyperglycaemia plays a major role for the development of microvascular complications in kidneys and eyes, and emphasises the need for optimal glycaemic control in children and adolescents with Type 1 diabetes.

Autonomic neuropathy: diagnosis and impact on health in adolescents with diabetes

Symptomatic autonomic neuropathy and abnormal cardiovascular autonomic tests are associated with increased mortality due to vascular disease and increased risk of sudden deaths. Intensive therapy in the DCCT caused a significant risk reduction of developing autonomic nerve abnormalities at five years only in the Primary Prevention Group (4 vs. 9%). At the Royal Alexandra Hospital for Children, the prevalence of cardiovascular reflex abnormalities is 28%. Over 5 years, we have found no increase in the rate of single cardiovascular abnormalities and a low rate of persistence. Two or more abnormalities developed in 5%. Repeated measures of pupillary function showed a significant increase in abnormalities and a higher level of persistently abnormal tests. Spectral analysis and 24-hour BP monitoring may detect autonomic dysfunction at earlier stages but longitudinal studies are not yet available.

Autonomic nerve function in adolescents with Type 1 diabetes mellitus: relationship to microalbuminuria

AIMS

Thirty adolescent patients with Type 1 diabetes mellitus and microalbuminuria were studied for evidence of early autonomic neuropathy.

METHODS

Using tests involving cardiovascular and pupillary reflexes, the adolescents were compared with a normoalbuminuric group of patients with diabetes, who were matched for age, sex, puberty and duration of diabetes.

RESULTS

There was an increased prevalence of autonomic nerve dysfunction in the patients with microalbuminuria. These patients had higher resting heart rates (86 beats/min in the microalbuminuric group vs. 77 beats/min in normoalbuminuric controls, P = 0.002), and impaired pupillary dilatation in darkness (pupillary diameter % 56.5% vs. 62.5%, P = 0.003). Patients with microalbuminuria also had poorer long term glycaemic control (mean HbA1C 8.7% vs. 7.8%, P = 0.002) and higher blood pressures (systolic 125 vs. 116 mmHg, P = 0.001; diastolic 69 vs. 62 mmHg, P = 0.0001; mean arterial pressure 90 vs. 83 mmHg, P = 0.002) than those with normal urinary albumin excretion.

CONCLUSIONS

Microalbuminuria and autonomic nerve dysfunction co-exist in patients with Type 1 DM. Longitudinal studies will determine whether these findings have implications for the identification of patients at higher risk of progression of early renal complications.

Subclinical neuropathy in type I diabetic children

OBJECTIVES

Small and large, somatic and autonomic nerve fibre functions were neurophysiologically evaluated in 33 asymptomatic neurologically free type I diabetic children and 69 age-matched healthy controls.

METHODS

The evaluation of large and small somatic nerve fibre function was performed by conventional nerve conduction studies, thermal specific and thermal pain sensitivity tests, as well as autonomic nerve fibre functions by sympathetic skin response and R-R interval variation assessment.

RESULTS

A significant difference was established between the healthy and the diabetic group. Neurophysiologically determined subclinical neuropathy was found in 87% of type I diabetic children. The majority of abnormal recordings were found on the lower limbs. The dysfunction of the somatic motor large nerve fibre type in the lower limbs was altered in 57% of patients, somatic sensory large in 39%, somatic sensory small in 45%, and sympathetic in 45%. The leading abnormal measure was a delayed sympathetic skin response on the foot (42% of diabetic children) followed by a reduced amplitude of sural nerve action potential (36%). The whole spectrum of recordings showed scattered involvement of nerve functions. There was no selective susceptibility of nerve fibre types exposed to a noxious factor.

CONCLUSION

A complex neurophysiological assessment, including standard nerve conduction studies as well as psychophysical examination and autonomic nerve function tests, evaluating the function of small and large nerve fibres, is recommended for evaluating the subclinical neuropathy in asymptomatic type I diabetic children.

Auditing paediatric diabetes care and the impact of a specialist nurse trained in paediatric diabetes

AIMS

To define outcome measures for auditing the clinical care of children and adolescents with insulin dependent diabetes mellitus (IDDM) and to assess the benefit of appointing a dedicated paediatric trained diabetes specialist nurse (PDSN).

METHODS

Retrospective analysis of medical notes and hospital records. Glycaemic control, growth, weight gain, microvascular complications, school absence, and the proportion of children undergoing an annual clinical review and diabetes education session were assessed. The effect of the appointment of a PDSN on the frequency of hospital admission, length of inpatient stay, and outpatient attendance was evaluated.

RESULTS

Children with IDDM were of normal height and grew well for three years after diagnosis, but grew suboptimally thereafter. Weight gain was above average every year after diagnosis. Glycaemic control was poor at all ages with only 16% of children having an acceptable glycated haemoglobin. Eighty five per cent of patients underwent a formal annual clinical review, of whom 16% had background retinopathy and 20% microalbuminuria in one or more samples. After appointing the PDSN the median length of hospital stay for newly diagnosed patients decreased from five days to one day, with 10 of 24 children not admitted. None of the latter was admitted during the next year. There was no evidence of the PDSN affecting the frequency of readmission or length of stay of children with established IDDM. Non-attendance at the outpatient clinic was reduced from a median of 19 to 10%.

CONCLUSIONS

Outcome measures for evaluating the care of children with IDDM can be defined and evaluated. Specialist nursing support markedly reduces the length of hospital stay of newly diagnosed patients without sacrificing the quality of care.