Is there a connection between postprandial hyperglycemia and IGT related sensory nerve dysfunction?

BACKGROUND AND AIMS: To assess the risk factors for sensory nerve dysfunction in subjects with isolated impaired glucose tolerance (IGT). METHODS AND RESULTS: Seventy-two people with isolated IGT (WHO 1999 criteria) and 39 gender and age-matched healthy volunteers underwent detailed clinical and neurological assessment including quantitative sensory testing using the Neurometer device (current perception threshold measurement on four limbs at three different frequencies). Sensory nerve dysfunction was defined as at least two abnormalities on any frequencies on the upper or lower limbs. Sensory nerve dysfunction was more prevalent among subjects with IGT compared to controls (58.3 vs. 10.3%, OR: 11.23, 95%CI: 3.57-35.35). This association was not influenced by BMI, systolic and diastolic blood pressure, heart rate and autonomic neuropathy (multiple adjusted OR: 13.87, 95%CI: 3.18-60.58), but further adjustment for glycaemic measures abolished the association (OR: 1.58, 95%CI: 0.07-35.68). Assessing the components of glycaemic measures separately, the association between sensory nerve dysfunction and IGT was not affected by HbA1c (OR: 13.94, 95%CI: 1.84-105.5). It was, however, substantially attenuated by fasting plasma glucose (OR: 6.75, 95%CI: 1.33-34.27) while the significance was lost after adjustment for 120 min postload glucose level (OR: 3.76, 95%CI: 0.26-54.10). In the pooled population assessed, independent determinants of sensory nerve dysfunction were older age, 120 min glucose, higher height and cardiovascular autonomic neuropathy at near significance. CONCLUSIONS: Sensory nerve dysfunction amongst subjects with IGT was not explained by cardiovascular covariates, only by glycaemic measures. In addition to 120 min glucose, cardiovascular autonomic neuropathy at borderline significance, age, and height were the independent determinants of sensory nerve dysfunction.

Small-Fiber Neuropathy: A Diabetic Microvascular Complication of Special Clinical, Diagnostic, and Prognostic Importance.

Damage of small nerve fibers may lead to a large variety of clinical symptoms. Small-fiber neuropathy underlies the symptoms of painful diabetic neuropathy, which may decrease quality of life. It also contributes to the poor prognosis of diabetic neuropathy because it plays a key role in the pathogenesis of foot ulceration and autonomic neuropathy. Impairment of small nerve fibers is considered the earliest alteration in the course of diabetic neuropathy. Therefore, assessment of functional and morphological abnormalities of small nerve fibers may enable timely diagnosis. The definition, symptoms, and clinical significance of small-fiber neuropathy are considered in the present review. An apparently more complex interaction between small-fiber impairment and microcirculation is extensively discussed. Diagnostic modalities include morphometric and functional methods. Corneal confocal microscopy and punch skin biopsy are considered gold standards, but noninvasive functional tests are also diagnostically useful. However, in routine clinical practice, small-fiber neuropathy is diagnosed by its typical clinical presentation. Finally, prompt treatment should be initiated following diagnosis.

Autonomic dysfunction and circadian blood pressure variations in people with impaired glucose tolerance.

AIMS: To assess circadian blood pressure variability in people with impaired glucose tolerance and a healthy control population. METHODS: Seventy-five people with impaired glucose tolerance and 40 healthy volunteers (frequency matched on 10-year age bands and sex) underwent a detailed neurological assessment. Autonomic neuropathy was detected by the five standard cardiovascular autonomic tests and heart rate variability was characterized by the triangle index. Diurnal indices were assessed by 24-h ambulatory blood pressure monitoring. Systolic and diastolic diurnal indices were defined as: (mean daytime blood pressure - mean night-time blood pressure) × 100/mean daytime blood pressure. RESULTS: Mean 24-h systolic and diastolic blood pressure was significantly higher in the group with impaired glucose tolerance compared with the control group [126 ± 12 (mean ± SD) vs. 117 ± 10, 75 ± 7 vs. 71 ± 6 mmHg, both P < 0.05). Systolic and diastolic diurnal indices and heart rate variability triangular index were significantly lower in people with impaired glucose tolerance compared with control subjects (9.1 ± 7.8 vs. 13.2 ± 5.4, 14.5 ± 9.7 vs. 18.4 ± 7.1 mmHg, 28.0 ± 8.4 vs. 39.5 ± 9.3, all P < 0.05). Differences in mean diastolic blood pressure, heart rate variability triangular index and the frequency of non-dippers between those with impaired glucose tolerance and control subjects seemed to be independent of BMI and the presence of cardiovascular autonomic neuropathy, as simultaneous adjustment for BMI and cardiovascular autonomic neuropathy had no major effect on the results. CONCLUSION: Our data suggest that people with impaired glucose tolerance have increased diastolic blood pressure and abnormal circadian blood pressure regulation, independent of obesity and the presence of cardiovascular autonomic neuropathy.

Relationship between autonomic neuropathy and hypertension--are we underestimating the problem?

BACKGROUND: Cardiac autonomic neuropathy (CAN) is associated with significant morbidity and mortality in diabetes and the risk is even greater in those with hypertension. AIMS: The aim of our study was to investigate the relationship between CAN and 24-h blood pressure profile in normoalbuminuric patients with Type 2 diabetes mellitus. METHODS: Seventy patients with Type 2 diabetes (31 without CAN, 39 with CAN), who had no history of hypertension, and 29 healthy volunteers underwent five standard cardiovascular reflex tests to assess autonomic function and 24-h ambulatory blood pressure monitoring. RESULTS: Twenty-four-hour mean systolic blood pressure, blood pressure load and hyperbaric impact values were significantly higher in diabetic patients with CAN compared with control subjects and diabetic patients without CAN (P < 0.05). In spite of normal clinic blood pressures, 54% of diabetic subjects with CAN and 29% without CAN were hypertensive (systolic blood pressure load > 20%, P < 0.05). In the diabetes group as a whole, Valsalva ratio, postural systolic blood pressure changes and diastolic blood pressure responses during sustained handgrip correlated significantly and negatively with 24-h mean systolic blood pressure (P < 0.01, P < 0.001, P < 0.05) and blood pressure load (P < 0.05, P < 0.001, P < 0.05). CONCLUSIONS: Cardiovascular autonomic neuropathy is independently associated with hypertension in normoalbuminuric Type 2 diabetic patients with no history of hypertension. Relying on clinic blood pressures in subjects with CAN could lead to a failure to diagnose hypertension in over half of cases. All normotensive patients with CAN should be screened for hypertension using ambulatory blood pressure monitoring in order to institute early aggressive interventions to improve their long-term outlook.