Diagnosing and managing diabetic somatic and autonomic neuropathy

Orthostatic Hypotension Promotes the Progression From Mild Cognitive Impairment to Dementia in Type 2 Diabetes Mellitus

CONTEXT

In type 2 diabetes mellitus (T2DM), orthostatic hypotension (OH) is associated with cognition, but the mechanisms governing the link between OH and cognition are still unclear.

OBJECTIVE

We sought to analyze Alzheimer's disease (AD) biomarkers and the part of complement proteins in modulating the association of OH with cognitive impairment and examine whether OH could accelerate the clinical progression of mild cognitive impairment (MCI) to dementia in T2DM.

METHODS

We recruited patients with T2DM with MCI and collected general healthy information and blood samples. Complement proteins of astrocyte-derived exosomes were isolated and AD biomarkers of neuronal cell-derived exosomes isolated were quantified by enzyme-linked immunosorbent assay. Cognitive assessments were performed at patient enrollment and follow-up.

RESULTS

Mediation analysis showed that the influence of OH on cognition in T2DM was partly mediated by baseline AD biomarkers and complement proteins. Cox proportional-hazards regression proved the OH group had a higher risk of developing dementia compared to the T2DM without OH group.

CONCLUSION

In T2DM with MCI patients, AD biomarkers and complement proteins mediate the effects of OH on cognitive impairment and OH may be a risk factor of progression from MCI to dementia in T2DM.

Corneal Confocal Microscopy Predicts Cardiovascular and Cerebrovascular Events and Demonstrates Greater Peripheral Neuropathy in Patients with Type 1 Diabetes and Foot Ulcers

OBJECTIVE

In this study, we evaluate small and large nerve fibre pathology in relation to diabetic foot ulceration (DFU) and incident cardiovascular and cerebrovascular events in type 1 diabetes (T1D).

METHODS

A prospective observational study was conducted on people with T1D without diabetic peripheral neuropathy (DPN) (n = 25), T1D with DPN (n = 28), T1D with DFU (n = 25) and 32 healthy volunteers. ROC analysis of parameters was conducted to diagnose DPN and DFU, and multivariate Cox regression analysis was performed to evaluate the predictive ability of corneal nerves for cardiac and cerebrovascular events over 3 years.

RESULTS

Corneal nerve fibre length (CNFL), fibre density (CNFD) and branch density (CNBD) were lower in T1D-DPN and T1D-DFU vs. T1D (all p < 0.001). In ROC analysis, CNFD (sensitivity 88%, specificity 87%; AUC 0.93; p < 0.001; optimal cut-off 7.35 no/mm2) and CNFL (sensitivity 76%, specificity 77%; AUC 0.90; p < 0.001; optimal cut-off 7.01 mm/mm2) had good ability to differentiate T1D with and without DFU. Incident cardiovascular events (p < 0.001) and cerebrovascular events (p < 0.001) were significantly higher in T1D-DPN and T1D-DFU. Corneal nerve loss, specifically CNFD predicted incident cardiovascular (HR 1.67, 95% CI 1.12 to 2.50, p = 0.01) and cerebrovascular (HR 1.55, 95% CI 1.06 to 2.26, p = 0.02) events.

CONCLUSIONS

Our study provides threshold values for corneal nerve fibre metrics for neuropathic foot at risk of DFU and further demonstrates that lower CNFD predicts incident cardiovascular and cerebrovascular events in T1D.

Diabetic autonomic neuropathy: a clinical update

Diabetic autonomic neuropathy is an under-recognised complication of diabetes and the prediabetic state. A wide range of manifestations can be seen due to involvement of cardiovascular, gastrointestinal, genitourinary, sudomotor and neuroendocrine systems. Cardiac autonomic neuropathy is the most dreaded complication carrying significant mortality and morbidity. Early detection and control of diabetes and other cardiovascular risk factors is the key to treat and prevent progression of autonomic neuropathy. Recently, a new entity of treatment-induced neuropathy (TIND) of diabetes mellitus causing autonomic neuropathy is being increasingly recognised.

Altered Amyloid-β and Tau Proteins in Neural-Derived Plasma Exosomes of Type 2 Diabetes Patients with Orthostatic Hypotension

BACKGROUND

Emerging evidence suggests a role for orthostatic hypotension (OH) in contributing to the progression of Alzheimer's disease (AD). The exosomes in the blood can reflect the pathological changes in the brain.

OBJECTIVE

To investigate whether neural-derived plasma exosomes pathogenic proteins of AD levels are associated with OH in diabetes mellitus (DM) patients.

METHODS

There were 274 subjects without dementia included in the study: 81 control participants (controls), 101 normotensive patients with DM without OH, and 92 patients with DM and neurogenic OH (DMOH). Neural-derived exosomal proteins were measured by ELISA kits for amyloid-β (Aβ) and tau.

RESULTS

The neural-derived exosome levels of Aβ42, total tau (T-tau), and tau phosphorylated at threonine 181 (P-T181-tau) in the DM with OH group were higher than those in the DM and control groups. Multivariable linear regression analysis showed that the presence of OH in patients with DM was associated with elevated exosomal Aβ42 (β= 0.172, p = 0.018), T-tau (β= 0.159, p = 0.030), and P-T181-tau (β= 0.220, p = 0.003) levels after adjustment for age, sex, APOE ɛ4, duration of type 2 diabetes, HbA1c, and cardiovascular risk factors. Furthermore, the levels of Aβ42, T-tau, and P-T181-tau in neural-derived exosomes were correlated with HIF-1α levels and the drop in mean cerebral blood flow velocity from the supine to upright position.

CONCLUSION

The presence of OH in DM patients was independently associated with elevated the Aβ42, T-tau, and P-T181-tau levels in neural-derived plasma exosomes. Cerebral hypoperfusion from DM with OH are likely candidate mechanisms.

Prevalence and risk factors for diabetic neuropathy and painful diabetic neuropathy in primary and secondary healthcare in Qatar

Aims/Introduction

This study determined the prevalence and risk factors for diabetic peripheral neuropathy (DPN) and painful DPN (pDPN) in patients with type 2 diabetes in primary healthcare (PHC) and secondary healthcare (SHC) in Qatar.

Materials and Methods

This was a cross‐sectional multicenter study. Adults with type 2 diabetes were randomly enrolled from four PHC centers and two diabetes centers in SHC in Qatar. Participants underwent assessment of clinical and metabolic parameters, DPN and pDPN.

Results

A total of 1,386 individuals with type 2 diabetes (297 from PHC and 1,089 from SHC) were recruited. The prevalence of DPN (14.8% vs 23.9%, P = 0.001) and pDPN (18.1% vs 37.5%, P < 0.0001) was significantly lower in PHC compared with SHC, whereas those with DPN at high risk for diabetic foot ulceration (31.8% vs 40.0%, P = 0.3) was comparable. The prevalence of undiagnosed DPN (79.5% vs 82.3%, P = 0.66) was comparably high, but undiagnosed pDPN (24.1% vs 71.5%, P < 0.0001) was lower in PHC compared with SHC. The odds of DPN and pDPN increased with age and diabetes duration, and DPN increased with poor glycemic control, hyperlipidemia and hypertension, whereas pDPN increased with obesity and reduced physical activity.

Conclusions

The prevalence of DPN and pDPN in type 2 diabetes is lower in PHC compared with SHC, and is attributed to overall better control of risk factors and referral bias due to patients with poorly managed complications being referred to SHC. However, approximately 80% of patients had not been previously diagnosed with DPN in PHC and SHC. Furthermore, we identified a number of modifiable risk factors for PDN and pDPN.

Clinical spectrum and diagnosis of diabetic neuropathies

Neuropathy is the most prevalent microvascular complication of diabetes mellitus; it encompasses distal symmetric polyneuropathy, autonomic neuropathy, radiculoplexus neuropathy, mononeuropathy, and treatment-induced neuropathy. The prevalence rate of diabetic neuropathy in Korea was reported to be approximately 43%, which is similar to rates in other countries. However, the precise pathogenic mechanism underlying diabetic neuropathy is still obscure, and many clinical trials have failed to develop methods to prevent or reduce the progression of diabetic neuropathy. Nevertheless, early diagnosis and proper management of diabetic neuropathy are essential to alleviate disabling symptoms and to improve the quality of life of patients. This review discusses clinical manifestations and classification of diabetic neuropathies, bedside neurological examination, and electrophysiological tests.

Toxic Peripheral Neuropathies: Agents and Mechanisms

Toxic peripheral neuropathies are an important form of acquired polyneuropathy produced by a variety of xenobiotics and different exposure scenarios. Delineating the mechanisms of neurotoxicants and determining the degenerative biological pathways triggered by peripheral neurotoxicants will facilitate the development of sensitive and specific biochemical-based methods for identifying neurotoxicants, designing therapeutic interventions, and developing structure-activity relationships for predicting potential neurotoxicants. This review presents an overview of the general concepts of toxic peripheral neuropathies with the goal of providing insight into why certain agents target the peripheral nervous system and produce their associated lesions. Experimental data and the main hypotheses for the mechanisms of selected agents that produce neuronopathies, axonopathies, or myelinopathies including covalent or noncovalent modifications, compromised energy or protein biosynthesis, and oxidative injury and disruption of ionic gradients across membranes are presented. The relevance of signaling between the main components of peripheral nerve, that is, glia, neuronal perikaryon, and axon, as a target for neurotoxicants and the contribution of active programmed degenerative pathways to the lesions observed in toxic peripheral neuropathies is also discussed.