Autonomic and Somatic Nerve Functions in Type 2 Diabetes Mellitus Patients: Electrophysiological Aspects

Evaluating Diagnostic Ultrasound of the Vagus Nerve as a Surrogate Marker for Autonomic Neuropathy in Diabetic Patients

Background and Objectives: Diagnostic ultrasound of the vagus nerve has been used to examine different polyneuropathies, and it has been suggested to be useful as a marker of autonomic dysfunction in diabetic patients. Materials and Methods: We analyzed the cross-sectional area (CSA) of the right vagus nerve of 111 patients with type 2 diabetes in comparison to 104 healthy adults and 41 patients with CIDP (chronic inflammatory demyelinating polyneuropathy). In the diabetes group, sympathetic skin response (SSR) was measured as an indicator for autonomic neuropathy. Carotid intima-media thickness (CIMT) was measured as a surrogate for atherosclerosis. Clinical symptoms of polyneuropathy were assessed using the Neuropathy Symptom Score and the Neuropathy Disability Score. Results: In total, 61.3% of the diabetes patients had clinical signs of polyneuropathy; 23.4% had no SSR at the feet as an indicator of autonomic neuropathy. Mean vagus nerve CSA did not differ in patients with and without diabetic polyneuropathy or in diabetic patients with and without SSR at the feet. No significant correlation was found between vagus nerve CSA and CIMT or SSR parameters in diabetic patients. Mean CSA of the right vagus nerve was slightly larger in diabetic patients (p = 0.028) and in patients with CIDP (p = 0.015) than in healthy controls. Conclusions: Effect sizes and mean differences were rather small so that a reliable diagnosis cannot be performed based on the vagus nerve measurement of a single person alone. Vagus nerve CSA seems not suitable as an indicator of autonomic dysfunction or cardiovascular risk in diabetic patients.

Research for correlation between heart rate variability parameters and bone mineral density in patients of type 2 diabetes mellitus

PURPOSE

The relationship of CAN and BMD, fracture risk is still unclear in T2DM. The aim of the present study is to investigate the correlation between heart rate variability (HRV) and BMD in T2DM.

METHODS

The study included 276 patients with T2DM aged ≥ 50 years, and Cardiovascular Autonomic Reflex Tests (CARTs) were applied to divide patients into two groups: CAN ( ±). 24 h Ambulatory ECG was assessed for HRV, BMD was measured by dual-energy X-ray bone densitometry, and FRAX scores were calculated for 10-year hip fracture risk (HF¹) and major osteoporotic fracture risk (MOF). Adjusted regression analysis was performed to investigate influence factors for BMD and fracture risk. ROC curve was used to analyze the optimal cut-off point of LF/HF for screening osteoporosis.

RESULTS

Baseline data showed significant differences in the duration of T2DM, insulin resistance index (HOMA-IR), 25-hydroxyvitamin D[25(OH)D], femoral neck BMD, hip BMD, lumbar BMD, HF¹, and MOF between the CAN ( +) and CAN (-) groups. The proportion of patients with osteoporosis increased as the degree of CAN lesion increased. Correlation analysis showed that LF/HF was significantly correlated with BMD, especially with hip (r = - 0.534, p < 0.001). Regression analysis showed that LF/HF was a risk factor for reduced BMD and increased fracture risk. The optimal cut-point value for LF/HF to predict osteoporosis by ROC curve analysis was 3.17.

CONCLUSIONS

CAN is associated with reduced BMD and increased fracture risk in patients with T2DM, and LF/HF may have the potential to be a predictor of diabetic osteoporosis and have some clinical value in early diagnosis of diabetic osteoporosis and non-traumatic fractures in T2DM.