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

Parasympathetic versus sympathetic control of the cardiovascular system in young patients with type 1 diabetes mellitus

Autonomic neuropathy and cardiovascular dysregulation are common complications of the diabetes mellitus (DM). The aim of the study was to test the hypothesis that cardiovascular regulation is abnormal in young patients with type 1 DM. Patients with type 1 DM (17, 10 females, 7 males) aged 12.9-31.5 years (mean+/-SEM: 22.4+/-1.0 years) were investigated. The mean duration of DM was 12.4+/-1.2 years. The control group consisted of 17 healthy probands matched for sex and age. The length of R-R intervals was measured using telemetric system (VariaCardio TF4; Sima Media) where ECG signal (sampling frequency 1000 Hz) from thoracic belt was transferred into PC for further analysis. Systolic blood pressure (SBP) was monitored beat-to-beat using volume-clamp method by Finapres 2300 (Ohmeda). Spectral power in HF band of HRV (HRV-HF) was taken as an index of parasympathetic control and spectral power in LF band of systolic BPV (BPV-LF) as an index of sympathetic control. In young patients with type 1 DM significant reduction of spectral power in HF band of the heart rate variability was found, whereas no significant difference between DM group and control group was observed in spectral power in LF band of blood pressure variability. In conclusion, we found impaired parasympathetic control of heart rate in young patients with type 1 DM. No differences in blood vessels sympathetic control were detected using spectral analysis of BPV. We suggest that abnormalities in cardiac parasympathetic regulation precede impairment of blood vessels sympathetic control in young diabetics.

The association of aldose reductase gene (AKR1B1) polymorphisms with diabetic neuropathy in adolescents

AIMS

Variants in the aldose reductase gene (AKR1B1) have been implicated in the development of diabetic retinopathy and nephropathy, with the most convincing data identifying a (CA)(n) repeat microsatellite allele (Z-2), which has a functional role in gene expression. In this study the association between polymorphisms in the AKR1B1 gene and diabetic neuropathy was investigated.

METHODS

The pupillary response to light was used as the major outcome in this study along with abnormal hot thermal threshold. Three hundred and sixty-three adolescents underwent genotyping of the AKR1B1 gene. The microsatellite (CA)(n) repeat was sequenced and two single nucleotide polymorphisms, -106C-->T and -12C-->G, were investigated by restriction fragment length polymorphism.

RESULTS

Seventy-six percent of participants had pupillary abnormalities (45% with two, 15% with three abnormalities). Presence of the Z-2/Z-2 genotype increased the risk nearly three-fold for pupillary abnormalities [odds ratio (OR) 3.02, 95% confidence interval (CI) 1.14, 7.98). The susceptibility genotypes (Z-2/Z-2 with -106C/-106C, Z-2/Z with -106C/-106C or Z/Z with -106C/-106C) were associated with resting pupil diameter abnormalities when compared with the protective genotypes (Z+2/Z+2 or -106T/-106T) (OR 2.83, 95% CI 1.25, 6.41). The combination of Z+2/-106T reduced the risk of abnormal heat discrimination (OR 0.48, 95% CI 0.23, 0.99).

CONCLUSIONS

In this study we have shown that Z-2/Z-2 genotype is significantly associated with the development of pupillary abnormality, an early indicator of diabetic autonomic neuropathy, in adolescent Australian patients with Type 1 diabetes.

Heart rate variability in young patients with diabetes mellitus and healthy subjects explored by Poincaré and sequence plots

Autonomic neuropathy is a common complication of the diabetes mellitus (DM). The significance of its early diagnosis is very high because the mortality of the patients with this complication is elevated. Considering the effort to apply new mathematical methods to cardiac dysregulation diagnosis, the major aim of the study was to ascertain which of the new heart rate variability (HRV) parameters are different in young patients with DM type 1 compared with control group. The next aim was to assess the HRV changes during prolonged (40 min) supine rest. The heart rate was continuously recorded during supine rest in 17 young patients with DM type 1 (10 women, 7 men) aged 22.4 +/- 1.0 years (mean +/- SEM). The control group consisted of 17 healthy matched probands. The HRV (time/frequency domains, Poincare and sequence plots, sample entropy) was analysed in two intervals - T1 starting at fifth minute and T2 starting at 30th minute of supine rest. The major results of our study are: the reduced Poincare plot pattern measures in the young DM group; the lower percentage of points in the third quadrant of sequence plot (this parameter was not correlated with the mean heart rate) and significant changes in HRV during supine rest in DM group (in contrast to control subjects). In conclusion, HRV parameters based on nonlinear dynamics were able to distinguish cardiac dysregulation in young patients with DM from the control group. The percentage of points in the third quadrant of sequence plot provides information that is not dependent on mean heart rate. Poincare and sequence plots, together with the rate of HRV changes during supine rest, can provide clinically relevant information usable in diagnosis of the cardiac dysregulation.

Pupil signs of sympathetic autonomic neuropathy in patients with type 1 diabetes

OBJECTIVE

Pupillary autonomic neuropathy is considered an early sign of the development of systemic autonomic neuropathy. Sympathetic denervation is related to the duration of diabetes and the development of systemic autonomic dysfunction. We investigated pupil responsiveness to directly and indirectly acting sympathomimetics in type 1 diabetic patients with and without long-term complications, defined as cardiac autonomic neuropathy (CAN), peripheral sensomotor neuropathy, retinopathy, and nephropathy, and in healthy subjects.

RESEARCH DESIGN AND METHODS

A total of 47 randomly chosen type 1 diabetic patients and 20 healthy subjects were selected for this study. Patients were divided into groups determined by whether they had long-term diabetic complications. Pharmacological tests were performed with cocaine 4%, epinephrine 1%, and pholedrine 5% eye drops. Horizontal pupil diameter (HPD) was measured at the beginning of the pharmacological tests and at defined time points after instillation of the eye drops.

RESULTS

Statistical analysis showed a significantly smaller HPD in the patients before instillating eye drops (P = 0.011). In particular, the HPD was significantly smaller in the patient group without CAN when compared with healthy subjects (P = 0.004). Maximal cocaine reaction was diminished in the complication group (P < 0.001). Epinephrine test, visual acuity, ocular pressure, and HbA(1c) did not differ in patients with or without long-term complications. The noncomplication group showed no significant differences in pupillary responses as compared with healthy subjects. The complication group showed a smaller HPD (P = 0.022), reduced pupillary responses in the cocaine (P = 0.037) and pholedrine tests (P < 0.001), and anisocor pupil sizes after instillation of the eye drops (P = 0.034).

CONCLUSIONS

Our results clearly show that sympathetic denervation does exist in the pupil of diabetic patients and that it can be rapidly assessed using the cocaine test. These data and the results of the epinephrine test suggest a mixed pre- and postganglionic dysfunction of the sympathetic plexus. The significant smaller HPD in patients without CAN compared with that of healthy subjects could be a sign for early involvement of the pupil function before cardiac manifestation of systemic autonomic diabetic neuropathy.

Aldose reductase inhibition ameliorates pupillary light reflex and F-wave latency in patients with mild diabetic neuropathy

OBJECTIVE

The present study was conducted to investigate the effect of an aldose reductase inhibitor, epalrestat, on autonomic and somatic neuropathy at an early stage in type 2 diabetic patients by assessing the pupillary light reflex and minimum latency of the F-wave.

RESEARCH DESIGN AND METHODS

A total of 30 diabetic patients with subclinical or mild diabetic neuropathy were randomly allocated to a control group (n = 15) and epalrestat (150 mg/day) group (n = 15). After 24 weeks, the pupillary light reflex test, cardiovascular autonomic function tests, and nerve conduction study were performed.

RESULTS

The beneficial effect of epalrestat on the pupillary light reflex was observed in the minimum diameter after light stimuli (P = 0.044), constriction ratio (P = 0.014), and maximum velocity of constriction (P = 0.008). Among cardiovascular autonomic nerve functions, the ratio of the longest expiratory R-R interval to the shortest inspiratory R-R interval during deep breathing was significantly improved by epalrestat (P = 0.037). Minimum latencies of F-wave of median and tibial motor nerves were significantly shortened by epalrestat (P = 0.002 and P = 0.001, respectively); however, no significant effects were observed in motor or sensory nerve conduction velocity.

CONCLUSIONS

These observations suggest that epalrestat may have therapeutic value at the early stage of diabetic neuropathy and that the pupillary light reflex and minimum latency of F-wave may be useful indicators of diabetic neuropathy.

Early diabetes-related complications in children and adolescents with type 1 diabetes. Implications for screening and intervention

Although children and adolescents with type 1 diabetes are faced with the threat of the acute complications of hypoglycemia and ketoacidosis on a day-to-day basis, in the long-term, the microvascular and macrovascular complications of the disease place them at greatest risk for serious morbidity and earlier than expected mortality. The families of children with diabetes should be provided with information about the complications of diabetes beginning at the time of diagnosis, and this information needs to be reinforced throughout the follow-up period. Appropriate surveillance for the earliest evidence of microvascular disease should begin at the onset of puberty and after 3 to 5 years of diabetes. Therapeutic interventions, particularly excellent metabolic control, may be exceedingly effective in preventing complication onset or significantly retarding the rate of progression.