Diagnosis of Neuropathy and Risk Factors for Corneal Nerve Loss in Type 1 and Type 2 Diabetes: A Corneal Confocal Microscopy Study

Sustained corneal nerve loss predicts the development of diabetic neuropathy in type 2 diabetes

Introduction

This study was undertaken to investigate whether sustained rather than a single measure of corneal nerve loss was associated with the onset of diabetic peripheral neuropathy (DPN) and the progression of neuropathic symptoms and deficits in individuals with type 2 diabetes (T2D).

Methods

Participants underwent clinical, metabolic testing and assessment of neuropathic symptoms, vibration perception threshold (VPT), sudomotor function, and corneal confocal microscopy (CCM) at baseline, 1, 2, and 4-7 years. Sustained corneal nerve loss was defined as abnormal corneal nerve fiber density (CNFD, <24 fibers/mm2), corneal nerve branch density (CNBD, <21 branches/mm2), and corneal nerve fiber length (CNFL, <16 mm/mm2) persisting for ≥50% of the study duration.

Results

A total of 107 participants with a mean duration of T2D of 13.3 ± 7.3 years, aged 54.8 ± 8.5 years, underwent baseline and follow-up assessments over a median duration of 4 years, ranging from 1 to 7 years. The DPN prevalence at baseline was 18/107 (16.8%), and of the 89 participants without DPN at baseline, 13 (14.6%) developed DPN during follow-up. Approximately half of the cohort had sustained corneal nerve damage, and corneal nerve measures were significantly lower in this group than those without sustained damage (p < 0.0001). Sustained corneal nerve damage was associated with the development of DPN (p < 0.0001), a progressive loss of vibration perception (p ≤ 0.05), an increased incidence of burning pain, numbness, or a combination of both (p = 0.01-0.001), and a borderline association with progressive sudomotor dysfunction (p = 0.07). Sustained abnormal CNFL effectively distinguished between participants who developed DPN and those who did not (AUC: 76.3, 95% CI: 65.9-86.8%, p < 0.0001), while baseline and other sustained measures did not predict DPN onset.

Conclusion

Sustained abnormal CCM is associated with more severe corneal nerve damage, DPN development, and the progression of neuropathic symptoms and deficits. Regular CCM monitoring may enable the identification of those at greater risk of developing and worsening DPN who may benefit from more aggressive risk factor reduction.

Corneal confocal microscopy detects early nerve regeneration after pharmacological and surgical interventions: Systematic review and meta-analysis

Corneal confocal microscopy (CCM) is an ophthalmic imaging technique that enables the identification of corneal nerve fibre degeneration and regeneration. To undertake a systematic review and meta-analysis of studies utilizing CCM to assess for corneal nerve regeneration after pharmacological and surgical interventions in patients with peripheral neuropathy. Databases (EMBASE [Ovid], PubMed, CENTRAL and Web of Science) were searched to summarize the evidence from randomized and non-randomized studies using CCM to detect corneal nerve regeneration after pharmacological and surgical interventions. Data synthesis was undertaken using RevMan web. Eighteen studies including 958 patients were included. CCM identified an early (1-8 months) and longer term (1-5 years) increase in corneal nerve measures in patients with peripheral neuropathy after pharmacological and surgical interventions. This meta-analysis confirms the utility of CCM to identify nerve regeneration following pharmacological and surgical interventions. It could be utilized to show a benefit in clinical trials of disease modifying therapies for peripheral neuropathy.

Comprehensive assessment of ocular parameters for identifying diagnostic indicators of diabetic peripheral neuropathy

PURPOSE

To explore variations in systemic and ocular parameters among patients with diabetes, both with and without diabetic peripheral neuropathy (DPN) and to identify sensitive indicators for DPN diagnosis.

METHODS

Ninty-five patients with type 2 diabetes mellitus (T2DM) were involved in this cross-sectional study, including 49 without DPN and 46 with DPN. Ocular parameters were obtained using optical coherence tomography angiography (OCTA) and corneal confocal microscopy (CCM).

RESULT

Patients with DPN presented with significantly higher HbA1c (p < 0.05) and glycated albumin (GA, p < 0.01) levels, increased prevalence of diabetic retinopathy (DR, p < 0.05), and lower serum albumin (ALB, p < 0.01) and red blood cell (RBC, p < 0.05) levels. Ocular assessments revealed reduced corneal nerve fiber length (CNFL, p < 0.001) and enlarged foveal avascular zone (FAZ) area (p < 0.05) in DPN group. Logistic regression analysis indicated a significant association of presence of DR, RBC, GA, ALB, CNFL and DPN (p < 0.05, respectively). In the binary logistic regression for DPN risk, all three models including the presence of DR and CNFL exhibited the area under the curve (AUC) exceeding 0.8.

CONCLUSION

The study establishes a strong correlation between ocular parameters and DPN, highlighting CCM's role in early diagnosis. Combining systemic and ocular indicators improves DPN risk assessment and early management.

[Clinical profile of corneal sensitivity in diabetic patients: A case-control study]

PURPOSE

To evaluate the corneal sensitivity of black diabetic patients and identify factors associated with changes in corneal sensitivity.

METHODOLOGY

We conducted a cross-sectional comparative case-control study at the National Obesity Center of the Yaounde Central Hospital and the Djoungolo District Hospital from March 1 to July 31, 2022. Corneal sensitivity was measured using the Cochet-Bonnet esthesiometer in all diabetic patients over 18 years of age, matched for age and sex to a clinically healthy control population. Data were analyzed using SPSS version 23.0 software. A P-value of less than 5% was considered significant.

RESULTS

A total of 111 diabetic and 111 non-diabetic patients participated in the study. The mean age was 53.46±12.74 years for diabetics and 52.85±11.77 years for non-diabetics (P=0.901). The mean duration of diabetes was 6.4±5.30 years. Corneal sensitivity in diabetics was lower (44.56±9.59mm) compared to non-diabetics (53.59±6.30mm) with a statistically significant difference (P=0.000). Factors associated with decrease in corneal sensitivity in diabetics were duration of diabetes and poor glycemic control.

CONCLUSION

Decrease in corneal sensitivity related to diabetes is a complication to be systematically screened for during the ophthalmologic follow-up of diabetic patients.

Earlier diagnosis of peripheral neuropathy in primary care: A call to action

Peripheral neuropathy (PN) often remains undiagnosed (~80%). Earlier diagnosis of PN may reduce morbidity and enable earlier risk factor reduction to limit disease progression. Diabetic peripheral neuropathy (DPN) is the most common PN and the 10 g monofilament is endorsed as an inexpensive and easily performed test for DPN. However, it only detects patients with advanced neuropathy at high risk of foot ulceration. There are many validated questionnaires to diagnose PN, but they can be time-consuming and have complex scoring systems. Primary care physicians (PCPs) have busy clinics and lack access to a readily available screening method to diagnose PN. They would prefer a short, simple, and accurate tool to screen for PN. Involving the patient in the screening process would not only reduce the time a physician requires to make a diagnosis but would also empower the patient. Following an expert meeting of diabetologists and neurologists from the Middle East, South East Asia and Latin America, a consensus was formulated to help improve the diagnosis of PN in primary care using a simple tool for patients to screen themselves for PN followed by a consultation with the physician to confirm the diagnosis.

Quantitative sensory testing defines the trajectory of sensory neuropathy after severe COVID-19

AIMS

To assess sensory neuropathy development after severe COVID-19.

METHODS

Patients with severe COVID-19 underwent assessment of neuropathic symptoms, tendon reflexes, and quantitative sensory testing to evaluate vibration (VPT), cold (CPT), warm (WPT) and heat perception thresholds (HPT) within 1-3 weeks of admission and after 1-year.

RESULTS

32 participants with severe COVID-19 aged 68.6 ± 12.4 (18.8 % diabetes) were assessed. At baseline, numbness and neuropathic pain were present in 56.3 % and 43.8 % of participants, respectively. On the feet, VPT, WPT, and HPT were abnormal in 81.3 %, CPT was abnormal in 50.0 % and HPT on the face was abnormal in 12.5 % of patients. At 1-year follow-up, the prevalence of abnormal VPT (81.3 % vs 50.0 %, P < 0.01), WPT (81.3 % vs 43.8 %, P < 0.01), and HPT (81.3 % vs 50.0 %, P < 0.01) decreased, with no change in CPT (P = 0.21) on the feet or HPT on the face (P = 1.0). Only participants without diabetes recovered from an abnormal VPT, CPT, and WPT. Patients with long-COVID (37.5 %) had comparable baseline VPT, WPT and CPT with those without long-COVID (P = 0.07-0.69).

CONCLUSIONS

Severe COVID-19 is associated with abnormal vibration and thermal thresholds which are sustained for up to 1 year in patients with diabetes. Abnormal sensory thresholds have no association with long-COVID development.

Corneal characteristics of Mongolian population with type 2 diabetic peripheral neuropathy in inner Mongolia, China: an assessment using corneal confocal microscopy

OBJECTIVE

To quantify corneal nerve fiber parameters in a Mongolian population with diabetic peripheral neuropathy (DPN) by corneal confocal microscopy.

METHODS

This study conducted a comprehensive evaluation of 114 participants from Hulunbuir between January 2020 and December 2021. The participants included healthy controls, Mongolian and Han patients with type 2 diabetes mellitus. Demographic, medical, and laboratory data were collected, and neuropathy was evaluated by confocal corneal microscopy. And compare various parameters between Han and Mongolian were performed using SPSS software.

RESULTS

The average waist circumference of Mongolian diabetic patients was larger than that of Han diabetic patients (P < 0.05). The mean HbA1c of Mongolian was 9.30 (8.15, 10.30) %, and that of Han was 8.30 (7.20, 9.40) % (P = 0.023). The average values of Corneal Nerve Fiber Density (CNFD), Corneal Nerve Fiber Length (CNFL) and corneal nerve branch density (CNBD) in Mongolian diabetic patients were significantly lower than those in Han diabetic patients (P < 0.05). The correlation coefficient between CNFL and age was - 0.368. ROC results show that CNBD has a certain diagnostic value for DPN in Mongolian patients with type 2 diabetes and the optimal cut-off point value is 24.99(no./mm2), the sensitivity is 80.0%, and the specificity is 77.8%.

CONCLUSION

The corneal confocal microscopy could possibly represent a promising adjuvant technique for the early diagnosis and assessment of PDN in Mongolian T2DM patients.

Correlation Between Corneal Whorl-Like Nerve and Retinal Neurodegenerative Changes and Their Association With Microvessel Perfusion in Diabetes

Purpose

The purpose of this study was to compare the evolution of changes in the corneal nerves, retinal nerves, and cells and blood vessels at a single time point in early diabetic retinopathy (DR).

Methods

Eighty participants (60 with diabetes and 20 nondiabetic controls) were examined. DR was graded according to the International Classification of Diabetic Retinopathy. Inferior whorl length (IWL), spiral orientation, central nerve fiber length (CNFL), retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) layer thickness, global loss volume (GLV), focal loss volume (FLV) indices, superficial (sVD), and deep vessel densities (dVD) were examined.

Results

Compared with those of healthy controls, the IWL, CNFL, and FLV were decreased in the diabetic groups (P < 0.001). The IWL was significantly positively correlated with the RNFL and GCC thicknesses in the diabetic group (r = 0.248, P = 0.006 and r = 0.207, P = 0.023, respectively) and significantly negatively correlated with the FLV (r = -0.535, P < 0.001). The sVD was significantly positively correlated with the RNFL thickness (r = 0.314, P < 0.001) and negatively correlated with the GLV (r = -0.229, P = 0.012).

Conclusions

Our findings suggest a correlation between corneal whorl-like nerve plexus and retinal nerve changes in the early stages of DR and that the IWL of the cornea may be able to indicate the extent of DR. Retinal nerve changes are associated with retinal microvessel perfusion, and nerve changes may precede vessel lesions.

Decreased corneal subbasal nerve fiber length and density in diabetic dogs with cataracts using in vivo confocal microscopy

OBJECTIVE

To determine whether there is a difference in corneal sensitivity and corneal subbasal nerve plexus (CSNP) morphology in cataractous dogs with diabetes mellitus (DM) versus without DM.

ANIMALS STUDIED

Twenty six domestic dogs with cataracts of various breeds presented for phacoemulsification, 13 with DM and 13 without DM.

PROCEDURE

The inclusion criteria for the study were dogs with bilateral cataracts and no clinical evidence of corneal disease. The diabetic group had documented hyperglycemia and was currently treated with insulin. The non-diabetic group had no evidence of DM on examination and bloodwork. Complete ophthalmic examination, corneal esthesiometry, and in vivo confocal microscopy of the CSNP was performed for both eyes of each dog. The CSNP was evaluated using a semi-automated program and statistically analyzed.

RESULTS

The mean (±SD) CSNP fiber length was significantly decreased in diabetic (3.8 ± 3.0 mm/mm2 ) versus non-diabetic (6.7 ± 1.9 mm/mm2 ) dogs. Likewise, the mean (±SD) fiber density was significantly decreased in diabetic (8.3 ± 3.1 fibers/mm2 ) versus non-diabetic (15.5 ± 4.9 fibers/mm2 ) dogs. The corneal touch threshold was significantly reduced in diabetic (2.1 ± 0.8 cm) versus non-diabetic (2.8 ± 0.4 cm) dogs. There was a non-significant trend towards subclinical keratitis in diabetic (9/13) versus non-diabetic (4/13) dogs.

CONCLUSIONS

Morphological and functional abnormalities of the CSNP were present in dogs with DM, including decreased fiber length, fiber density, and corneal sensitivity. These findings are consistent with diabetic neuropathy and could contribute to clinically significant corneal complications after cataract surgery.

Exploring exercise-driven inhibition of pyroptosis: novel insights into treating diabetes mellitus and its complications

Diabetes mellitus (DM) and its complications are important, worldwide public health issues, exerting detrimental effects on human health and diminishing both quality of life and lifespan. Pyroptosis, as a new form of programmed cell death, plays a critical role in DM and its complications. Exercise has been shown to be an effective treatment for improving insulin sensitivity or preventing DM. However, the molecular mechanisms underlying the effects of exercise on pyroptosis-related diseases remain elusive. In this review, we provided a comprehensive elucidation of the molecular mechanisms underlying pyroptosis and the potential mechanism of exercise in the treatment of DM and its complications through the modulation of anti-pyroptosis-associated inflammasome pathways. Based on the existing evidence, further investigation into the mechanisms by which exercise inhibits pyroptosis through the regulation of inflammasome pathways holds promising potential for expanding preventive and therapeutic strategies for DM and facilitating the development of novel therapeutic interventions.

Occurrence of corneal sub-epithelial microneuromas and axonal swelling in people with diabetes with and without (painful) diabetic neuropathy

AIMS/HYPOTHESIS

Non-invasive in vivo corneal confocal microscopy is gaining ground as an alternative to skin punch biopsy to evaluate small-diameter nerve fibre characteristics. This study aimed to further explore corneal nerve fibre pathology in diabetic neuropathy.

METHODS

This cross-sectional study quantified and compared corneal nerve morphology and microneuromas in participants without diabetes (n=27), participants with diabetes but without distal symmetrical polyneuropathy (DSPN; n=33), participants with non-painful DSPN (n=25) and participants with painful DSPN (n=18). Clinical and electrodiagnostic criteria were used to diagnose DSPN. ANCOVA was used to compare nerve fibre morphology in the central cornea and inferior whorl, and the number of corneal sub-epithelial microneuromas between groups. Fisher's exact tests were used to compare the type and presence of corneal sub-epithelial microneuromas and axonal swelling between groups.

RESULTS

Various corneal nerve morphology metrics, such as corneal nerve fibre length and density, showed a progressive decline across the groups (p<0.001). In addition, axonal swelling was present more frequently (p=0.018) and in higher numbers (p=0.03) in participants with painful compared with non-painful DSPN. The frequency of axonal distension, a type of microneuroma, was increased in participants with painful and non-painful DSPN compared to participants with diabetes but without DSPN and participants without diabetes (all p≤0.042). The combined presence of all microneuromas and axonal swelling was increased in participants with painful DSPN compared with all other groups (p≤0.026).

CONCLUSIONS/INTERPRETATION

Microneuromas and axonal swelling in the cornea increase in prevalence from participants with diabetes to participants with non-painful DSPN and participants with painful DSPN.

Corneal Confocal Microscopy Abnormalities in Children and Adolescents With Type 1 Diabetes

OBJECTIVE

Utility of corneal confocal microscopy (CCM) in children and adolescents with type 1 diabetes mellitus (T1DM) without neuropathic symptoms or signs and minimal abnormality in large and small nerve fiber function tests remains largely undetermined. This study aimed to evaluate the performance of CCM in comparison to thermal detection thresholds (TDT) testing and nerve conduction studies (NCS) for detecting neuropathy in children with T1DM.

METHODS

A cohort of children and adolescents with T1DM (n = 51) and healthy controls (n = 50) underwent evaluation for symptoms and signs of neurological deficits, including warm detection threshold, cold detection threshold, vibration perception threshold, NCS, and CCM.

RESULTS

Children with T1DM had no or very minimal neuropathic symptoms and deficits based on the Toronto Clinical Neuropathy Score, yet NCS abnormalities were present in 18 (35%), small fiber dysfunction defined by an abnormal TDT was found in 13 (25.5%) and CCM abnormalities were present in 25 (49%). CCM was abnormal in a majority of T1DM children with abnormal TDT (12/13, 92%) and abnormal NCS (16/18, 88%). CCM additionally was able to detect small fiber abnormalities in 13/38 (34%) in T1DM with a normal TDT and in 9/33 (27%) with normal NCS.

CONCLUSION

CCM was able to detect corneal nerve loss in children with and without abnormalities in TDT and NCS.

Evaluation of Corneal Nerve Regeneration After Minimally Invasive Corneal Neurotization

PURPOSE

To evaluate the corneal nerve regeneration after minimally invasive corneal neurotization (MICN) and to further clarify the recovery patterns of sensory and trophic functions of the corneal nerves.

DESIGN

A retrospective cohort study based in the Shanghai Ninth People's Hospital.

METHODS

Eighteen patients (18 eyes) who underwent MICN for neurotrophic keratopathy due to intracranial surgery was conducted to analyze their follow-up data at 6, 12, 18, and 24 months after surgery.

RESULTS

At 12 months postoperatively, the growth of the central and peripheral corneal nerve fiber density (CNFD) was 11.47±8.56 and 14.73±8.08 n/mm 2 with subsequent improvement slowing down, and the patient's corneal epithelium defect was healed ahead of the accomplishment of corneal nerve regeneration. The number of dendritic cells also reached its peak. At 18 months postoperatively, the recovery of central and peripheral corneal sensation was 37.22±23.06 mm and 39.38±18.08 mm with no subsequent improvement, and the growth of the central and peripheral corneal nerve branch density (CNBD) was 29.69±11.05 and 43.75±1.41 n/mm 2 , with a positive and significant correlation between corneal sensation and CNBD (at central r =0.632, P <0.005; at peripheral r =0.645, P <0.005). At 24 months postoperatively, mean CNFD, CNBD, and corneal sensation recovered significantly compared with preoperative, but a few patients' corneal sensation recovered insignificantly with good CNFD recovery and poor CNBD recovery.

CONCLUSIONS

After MICN, the trophic function of the corneal nerve recovers before the sensory function, and in particular, the recovery of sensation is based on the coexistence of the corneal nerve trunk and branches.

Corneal confocal microscopy demonstrates sensory nerve loss in children with autism spectrum disorder

Autism spectrum disorder (ASD) is a developmental disorder characterized by difficulty in communication and interaction with others. Postmortem studies have shown cerebral neuronal loss and neuroimaging studies show neuronal loss in the amygdala, cerebellum and inter-hemispheric regions of the brain. Recent studies have shown altered tactile discrimination and allodynia on the face, mouth, hands and feet and intraepidermal nerve fiber loss in the legs of subjects with ASD. Fifteen children with ASD (age: 12.00 ± 3.55 years) and twenty age-matched healthy controls (age: 12.83 ± 1.91 years) underwent corneal confocal microscopy (CCM) and quantification of corneal nerve fiber morphology. Corneal nerve fibre density (fibers/mm2) (28.61 ± 5.74 vs. 40.42 ± 8.95, p = 0.000), corneal nerve fibre length (mm/mm2) (16.61 ± 3.26 vs. 21.44 ± 4.44, p = 0.001), corneal nerve branch density (branches/mm2) (43.68 ± 22.71 vs. 62.39 ± 21.58, p = 0.018) and corneal nerve fibre tortuosity (0.037 ± 0.023 vs. 0.074 ± 0.017, p = 0.000) were significantly lower and inferior whorl length (mm/mm2) (21.06 ± 6.12 vs. 23.43 ± 3.95, p = 0.255) was comparable in children with ASD compared to controls. CCM identifies central corneal nerve fiber loss in children with ASD. These findings, urge the need for larger longitudinal studies to determine the utility of CCM as an imaging biomarker for neuronal loss in different subtypes of ASD and in relation to disease progression.

Mining and Validation of Novel Hemp Seed-Derived DPP-IV-Inhibiting Peptides Using a Combination of Multi-omics and Molecular Docking

Hemp seed-derived inhibitors of dipeptidyl peptidase IV (DPP-IV) demonstrate potential as novel therapeutics for diabetes; however, their proteome and genome remain uncharacterized. We used multi-omics technology to mine peptides capable of inhibiting DPP-IV. First, 1261 and 1184 proteins were identified in fresh and dry hemp seeds, respectively. Simulated protease cleavage of dry seed proteins yielded 185,446 peptides for virtual screening to select the potential DPP-IV-inhibiting peptides. Sixteen novel peptides were selected according to their DPP-IV-binding affinity determined via molecular docking. In vitro DPP-IV inhibition assays identified the peptides LPQNIPPL, YPYY, YPW, LPYPY, WWW, YPY, YPF, and WS with half-maximal inhibitory concentration (IC₅₀) values lower than 0.5 mM, which were 0.08 ± 0.01, 0.18 ± 0.03, 0.18 ± 0.01, 0.20 ± 0.03, 0.22 ± 0.03, 0.29 ± 0.02, 0.42 ± 0.03, and 0.44 ± 0.09 mM, respectively. The dissociation constants (K_D) of the 16 peptides ranged from 1.50 × 10^-4 to 1.82 × 10^-7 M. Furthermore, Caco2 and INS-1 cell assays showed that all 16 peptides could efficiently inhibit DPP-IV activity and increase insulin and glucagon-like peptide-1 concentrations. These results demonstrate a well-established and efficient method to isolate food-derived therapeutic DPP-IV-inhibiting peptides.

Assessing Corneal Confocal Microscopy and Other Small Fiber Measures in Diabetic Polyneuropathy

BACKGROUND AND OBJECTIVES

Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes.

METHODS

In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds).

RESULTS

A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN (p ≤ 0.001, <0.001, 0.002, p < 0.001, p = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN.

DISCUSSION

CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

Jatrorrhizine ameliorates Schwann cell myelination via inhibiting HDAC3 ability to recruit Atxn2l for regulating the NRG1-ErbB2-PI3K-AKT pathway in diabetic peripheral neuropathy mice

Diabetic peripheral neuropathy (DPN) is a chronic complication associated with nerve dysfunction and uncontrolled hyperglycemia. Unfortunately, due to its complicated etiology, there has been no successful therapy for DPN. Our research recently revealed that jatrorrhizine (JAT), one of the active constituents of Rhizoma Coptidis, remarkably ameliorated DPN. This work highlighted the potential mechanism through which JAT relieves DPN using db/db mice. The results indicated that JAT treatment significantly decreased the threshold for thermal and mechanical stimuli and increased nerve conduction velocity. Histopathological analysis revealed that JAT significantly increased the number of sciatic nerve fibers and axons, myelin thickness, and axonal diameters. Additionally, JAT markedly elevated the expression of myelination-associated proteins (MBP, MPZ, and Pmp22). The screening of histone deacetylases (HDAC) determined that histone deacetylase 3 (HDAC3) is an excellent target for JAT-induced myelination enhancement. Liquid chromatography-mass spectrometry-(MS)/MS and coimmunoprecipitation analyses further confirmed that HDAC3 antagonizes the NRG1-ErbB2-PI3K-AKT signaling axis by interacting with Atxn2l to augment SCs myelination. Thus, JAT ameliorates SCs myelination in DPN mice via inhibiting the recruitment of Atxn2l by HDAC3 to regulate the NRG1-ErbB2-PI3K-AKT pathway.

Multi-omics analysis revealed the role of CYP1A2 in the induction of mechanical allodynia in type 1 diabetes

Background: Mechanical allodynia (MA) is one of the leading clinical symptoms of painful diabetic peripheral neuropathy (PDPN), which is a primary reason for non-traumatic amputations, foot ulceration, and gait abnormalities in patients with diabetes. However, the pathogenic mechanisms of MA have not yet been fully elucidated, and there is no effective treatment. This study aims to study the potential pathogenetic mechanisms of MA and to provide targets for the therapy of MA. Methods: A single intraperitoneal injection of streptozotocin induced type 1 diabetes in rat models. Subsequently, rats were divided into the control group, the diabetic group without MA, and the diabetic group with MA based on weekly behavioral assays. The differentially expressed lipids in the sciatic nerve of each group were detected using untargeted lipidomics, and the differentially expressed genes in the sciatic nerve of each group were detected by transcriptomics. The pathogenesis of MA was predicted using integrated analysis and validated by immunofluorescence staining and transmission electron microscopy. Results: Untargeted lipidomics revealed the accumulation of a more severe lipid in MA rats. Transcriptomics results suggested that differentially expressed genes in MA rats were primarily related to lipid droplets and myelin sheath. Integrated analysis results indicated that the downregulation of Cytochrome P450 1A2 (CYP1A2) expression was closely linked to lipid metabolism disorders. Immunofluorescence staining demonstrated that down-regulation of CYP1A2 expression occurred in MA rats. Transmission electron microscopy results showed that more severe lipid droplet accumulation and myelin sheath degeneration occurred in MA rats. Conclusion: Our findings imply that the downregulation of CYP1A2 expression leads to disorders of lipid metabolism and further leads to lipid droplet accumulation and myelin sheath degeneration, which might ultimately lead to the development of MA. Therefore, our study contributes to promoting the understanding of the molecular mechanisms of MA and providing potential targets for the clinical treatment of MA.

Continuous glucose monitoring reveals a novel association between duration and severity of hypoglycemia, and small nerve fiber injury in patients with diabetes

Objective

Continuous glucose monitoring (CGM) has revealed that glycemic variability and low time in range are associated with albuminuria and retinopathy. We have investigated the relationship between glucose metrics derived from CGM and a highly sensitive measure of neuropathy using corneal confocal microscopy in participants with type 1 and type 2 diabetes.

Methods

A total of 40 participants with diabetes and 28 healthy controls underwent quantification of corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL) and inferior whorl length (IWL) and those with diabetes underwent CGM for four consecutive days.

Results

CNBD was significantly lower in patients with high glycemic variability (GV) compared to low GV (median (range) (25.0 (19.0-37.5) vs 38.6 (29.2-46.9); P = 0.007); in patients who spent >4% compared to <4% time in level 1 hypoglycemia (54-69 mg/dL) (25.0 (22.9-37.5) vs 37.5 (29.2-46.9); P = 0.045) and in patients who spent >1% compared to <1% time in level 2 hypoglycemia (<54 mg/dL) (25.0 (19.8-41.7) vs 35.4 (28.1-44.8); P = 0.04). Duration in level 1 hypoglycemia correlated with CNBD (r = -0.342, P = 0.031). Duration in level 1 (181-250 mg/dL) and level 2 (>250 mg/dL) hyperglycemia did not correlate with CNFD (P > 0.05), CNBD (P > 0.05), CNFL (P > 0.05) or IWL (P > 0.05).

Conclusions

Greater GV and duration in hypoglycemia, rather than hyperglycemia, are associated with nerve fiber loss in diabetes.

A novel combination of corneal confocal microscopy, clinical features and artificial intelligence for evaluation of ocular surface pain

OBJECTIVES

To analyse various corneal nerve parameters using confocal microscopy along with systemic and orthoptic parameters in patients presenting with ocular surface pain using a random forest artificial intelligence (AI) model.

DESIGN

Observational, cross-sectional.

METHODS

Two hundred forty eyes of 120 patients with primary symptom of ocular surface pain or discomfort and control group of 60 eyes of 31 patients with no symptoms of ocular pain were analysed. A detailed ocular examination included visual acuity, refraction, slit-lamp and fundus. All eyes underwent laser scanning confocal microscopy (Heidelberg Engineering, Germany) and their nerve parameters were evaluated. The presence or absence of orthoptic issues and connective tissue disorders were included in the AI. The eyes were grouped as those (Group 1) with symptom grade higher than signs, (Group 2) with similar grades of symptoms and signs, (Group3) without symptoms but with signs, (Group 4) without symptoms and signs. The area under curve (AUC), accuracy, recall, precision and F1-score were evaluated.

RESULTS

Over all, the AI achieved an AUC of 0.736, accuracy of 86%, F1-score of 85.9%, precision of 85.6% and recall of 86.3%. The accuracy was the highest for Group 2 and least for Group 3 eyes. The top 6 parameters used for classification by the AI were microneuromas, immature and mature dendritic cells, presence of orthoptic issues and nerve fractal dimension parameter.

CONCLUSIONS

This study demonstrated that various corneal nerve parameters, presence or absence of systemic and orthoptic issues coupled with AI can be a useful technique to understand and correlate the various clinical and imaging parameters of ocular surface pain.

Mosaic vs. Single Image Analysis with Confocal Microscopy of the Corneal Nerve Plexus for Diagnosis of Early Diabetic Peripheral Neuropathy

INTRODUCTION

The assessment of the corneal nerve fibre plexus with corneal confocal microscopy (CCM) is an upcoming but still experimental method in the diagnosis of early stage diabetic peripheral neuropathy (DPN). Using an innovative imaging technique-Heidelberg Retina Tomograph equipped with the Rostock Cornea Module (HRT-RCM) and EyeGuidance module (EG)-we were able to look at greater areas of subbasal nerve plexus (SNP) in order to increase the diagnostic accuracy. The aim of our study was to evaluate the usefulness of EG instead of single image analysis in diagnosis of early stage DPN.

METHODS

This prospective study was performed on 60 patients with type 2 diabetes mellitus, classified equally into two subgroups based on neuropathy deficient score (NDS): patients without DPN (group 1) or with mild DPN (group 2). The following parameters were analysed in the two subgroups: corneal nerve fibre length (CNFL; mm/mm²), corneal nerve fibre density (CNFD; no./mm²), corneal nerve branch density (CNBD; no./mm²). Furthermore, we compared the data calculated with the novel mosaic, EG-based method with those received from single image analysis using different quantification tools.

RESULTS

Using EG we did not find a significant difference between group 1 and group 2: CNFL (16.81 ± 5.87 mm/mm² vs. 17.19 ± 7.19 mm/mm², p = 0.895), CNFD (254.05 ± 115.36 no./mm² vs. 265.91 ± 161.63 no./mm², p = 0.732) and CNBD (102.68 ± 62.28 no./mm² vs. 115.38 ± 96.91 no./mm², p = 0.541). No significant difference between the EG method of analysing the SNP and the single image analysis of 10 images per patient was detected.

CONCLUSION

On the basis of our results it was not possible to differentiate between early stages of large nerve fibre DPN in patients with type 2 diabetes mellitus via SNP analysis. To improve sensitivity and specificity of this method newer technologies are under current evaluation.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT05326958.

Corneal subbasal nerve analysis in patients with primary Sjogren's syndrome: a novel objective grading method and clinical correlations

PURPOSE

To investigate corneal sub-basal nerve morphology changes in primary Sjogren's syndrome (SS) dry eye (SSDE) patients and determine the association with disease severity at microstructural level.

METHODS

Twenty-eight eyes of 17 SSDE and 82 eyes of 47 age- and sex-matched non-SS dry eye (NSSDE) patients were included. The Ocular Surface Disease Index questionnaire (OSDI), Schirmer's test (ST), tear meniscus height (TMH), non-invasive breakup time (NIBUT), meibomian gland (MG) morphology, and ocular staining score (OSS) were assessed. In vivo confocal microscopy was performed to observe corneal sub-basal nerve morphology (length, reflectivity, width, and tortuosity). Associations between clinical features and nerve parameters were analysed.

RESULTS

SSDE patients more frequently had increased nerve reflectivity (151.12 ± 17.07 vs. 139.37 ± 14.31 grey value), width (4.45 ± 0.87 vs. 3.92 ± 0.81 μm), tortuosity (132.90 ± 8.04 vs. 129.50 ± 7.33 degree), and higher reflectivity, width, and total nerve grades than NSSDE individuals (all P < 0.05). Significant associations were found between nerve reflectivity/width and anti-SSA [OR = 1.139 (1.013-1.281)/1.802 (1.013-4.465)]/labial gland biopsy [OR = 1.046 (1.002-1.161)/1.616 (1.020-3.243)]. Higher nerve width was associated with increased OSDI [β = 0.284 (0.187-0.455)], MG score [β = 0.185 (0.109-0.300)] and OSS [β = 0.163 (0.020-0.345)], but decreased NIBUT [β =  - 0.247 (- 0.548 ~  - 0.154)]. Higher nerve total grade was associated with increased OSDI [β = 0.418 (0.157-0.793)] and OSS [β = 0.287 (0.027-0.547)], but decreased ST [β =  - 0.410 (-0.857 ~  - 0.138)].

CONCLUSIONS

Corneal nerve morphology changes associated with clinical features in SS patients. These changes may facilitate severity evaluation and management of the disease.

Corneal Confocal Microscopy as a Quantitative Imaging Biomarker of Diabetic Peripheral Neuropathy: A Review

Distal symmetric polyneuropathy (DPN), particularly chronic sensorimotor DPN, represents one of the most frequent complications of diabetes, affecting 50% of diabetic patients and causing an enormous financial burden. Whilst diagnostic methods exist to detect and monitor this condition, they have significant limitations, mainly due to their high subjectivity, invasiveness, and non-repeatability. Corneal confocal microscopy (CCM) is an in vivo, non-invasive, and reproducible diagnostic technique for the study of all corneal layers including the sub-basal nerve plexus, which represents part of the peripheral nervous system. We reviewed the current literature on the use of CCM as an instrument in the assessment of diabetic patients, particularly focusing on its role in the study of sub-basal nerve plexus alterations as a marker of DPN. CCM has been demonstrated to be a valid in vivo tool to detect early sub-basal nerve plexus damage in adult and pediatric diabetic patients, correlating with the severity of DPN. Despite its great potential, CCM has still limited application in daily clinical practice, and more efforts still need to be made to allow the dissemination of this technique among doctors taking care of diabetic patients.

Relationship between time in range and corneal nerve fiber loss in asymptomatic patients with type 2 diabetes

BACKGROUND

Corneal confocal microscopy (CCM) is a noninvasive technique to detect early nerve damage of diabetic sensorimotor polyneuropathy (DSPN). Time in range (TIR) is an emerging metric of glycemic control which was reported to be associated with diabetic complications. We sought to explore the relationship between TIR and corneal nerve parameters in asymptomatic patients with type 2 diabetes (T2DM).

METHODS

In this cross-sectional study, 206 asymptomatic inpatients with T2DM were recruited. After 7 days of continuous glucose monitoring, the TIR was calculated as the percentage of time in the glucose range of 3.9 to 10.0 mmol/L. CCM was performed to determine corneal nerve fiber density, corneal nerve branch density, and corneal nerve fiber length (CNFL). Abnormal CNFL was defined as ≤15.30 mm/mm 2 .

RESULTS

Abnormal CNFL was found in 30.6% (63/206) of asymptomatic subjects. Linear regression analyses revealed that TIR was positively correlated with CCM parameters both in the crude and adjusted models (all P   <  0.05). Each 10% increase in TIR was associated with a 28.2% (95% CI: 0.595-0.866, P  = 0.001) decreased risk of abnormal CNFL after adjusting for covariates. With the increase of TIR quartiles, corneal nerve fiber parameters increased significantly (all P for trend <0.01). The receiver operating characteristic curve indicated that the optimal cutoff point of TIR was 77.5% for predicting abnormal CNFL in asymptomatic patients.

CONCLUSIONS

There is a significant independent correlation between TIR and corneal nerve fiber loss in asymptomatic T2DM patients. TIR may be a useful surrogate marker for early diagnosis of DSPN.

Technical Report: Automatic Measurement of Corneal Nerve Fiber Area Using Versatile Software

SIGNIFICANCE

In vivo confocal microscopy has become a popular method to observe the details of corneal structures. We consider the area of corneal structures to be a versatile index and have measured the areas of various corneal structures using commercially available software.

PURPOSE

To evaluate the accuracy of software used to measure the corneal nerve fiber area.

METHODS

The corneal structures of 11 healthy volunteers were visualized using in vivo confocal microscopy. The image that most clearly depicted the corneal nerve fibers of each participant was selected for analysis. The corneal nerve fiber area was automatically measured by the software. An experienced ophthalmologist then manually measured the corneal nerve fiber area in each image assessed by the software. The Pearson correlation test was used to determine the correlation coefficient between the corneal nerve fiber areas measured automatically and those measured manually. The correlation between the corneal nerve fiber area and the participant's age was also evaluated.

RESULTS

A strong correlation was found between the corneal nerve fiber area measured automatically and the corneal nerve fiber area measured manually (r = .98, P = 2.4 × 10-7). The corneal nerve fiber area was not correlated with participant age, regardless of whether the area was measured automatically (r = -.26, P = .44) or manually (r = -.13, P = .71).

CONCLUSIONS

The software used in this study automatically measures the corneal nerve fiber area with accuracy similar to that of manual measurement by an experienced ophthalmologist. This software has potential for use in quantifying the areas of various corneal structures.

Lipids, Lipid-Lowering Therapy, and Neuropathy: A Narrative Review

Statins, or 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, are the mainstay of treatment for hypercholesterolemia as they effectively reduce LDL-C levels and risk of atherosclerotic cardiovascular disease. Apart from hyperglycemia, dyslipidemia and HDL dysfunction are known risk factors for neuropathy in people with obesity and diabetes. Although there are case reports of statin-induced neuropathy, ad hoc analyses of clinical trials and observational studies have shown that statins may improve peripheral neuropathy. However, large randomized controlled trials and meta-analyses of cardiovascular outcome trials with statins and other lipid-lowering drugs have not reported on neuropathy outcomes. Because neuropathy was not a prespecified outcome in major cardiovascular trials, one cannot conclude whether statins or other lipid-lowering therapies increase or decrease the risk of neuropathy. The aim of this review was to assess if statins have beneficial or detrimental effects on neuropathy and whether there is a need for large well-powered interventional studies using objective neuropathy end points.

The impact of sensory neuropathy and inflammation on epithelial wound healing in diabetic corneas

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, with several underlying pathophysiological mechanisms, some of which are still uncertain. The cornea is an avascular tissue and sensitive to hyperglycemia, resulting in several diabetic corneal complications including delayed epithelial wound healing, recurrent erosions, neuropathy, loss of sensitivity, and tear film changes. The manifestation of DPN in the cornea is referred to as diabetic neurotrophic keratopathy (DNK). Recent studies have revealed that disturbed epithelial-neural-immune cell interactions are a major cause of DNK. The epithelium is supplied by a dense network of sensory nerve endings and dendritic cell processes, and it secretes growth/neurotrophic factors and cytokines to nourish these neighboring cells. In turn, sensory nerve endings release neuropeptides to suppress inflammation and promote epithelial wound healing, while resident immune cells provide neurotrophic and growth factors to support neuronal and epithelial cells, respectively. Diabetes greatly perturbs these interdependencies, resulting in suppressed epithelial proliferation, sensory neuropathy, and a decreased density of dendritic cells. Clinically, this results in a markedly delayed wound healing and impaired sensory nerve regeneration in response to insult and injury. Current treatments for DPN and DNK largely focus on managing the severe complications of the disease. Cell-based therapies hold promise for providing more effective treatment for diabetic keratopathy and corneal ulcers.

Alterations in corneal epithelial dendritic cell in Sjogren's syndrome dry eye and clinical correlations

We aimed to investigate the density and morphology of corneal dendritic cells (DCs) in dry eye (DE) patients with or without Sjogren’s syndrome (SS). This study included 28 patients with Sjogren’s syndrome dry eye (SSDE), 33 patients with non-Sjogren’s syndrome dry eye (NSSDE), and 30 age and sex matched healthy volunteers. In vivo confocal microscopy (IVCM) was used to investigate density and morphology (size, dendrites, and field) of DC. Compared with NSSDE and healthy group, SSDE showed significantly higher DC density, larger DC size, more DC dendrites with larger DC field (all P < 0.001). Comparison between NSSDE and healthy group demonstrated that DC density, dendrites and field were significantly higher in NSSDE. However, there was no significant difference in DC size (P = 0.076). DC density and morphological parameters showed significant associations with the systemic severity (salivary gland biopsy and serum antibodies) and ocular surface damage. The corneal epithelium DC density and morphological alterations were obvious in SSDE, which reflected higher level of immune activation and inflammatory response in SS. Marked correlations were found between DC density/morphology and systemic/ocular severity. Dynamic assessment of corneal DC may facilitate to clarify pathogenesis, stratify patient, and tailor treatment in SS patients.

Progressive loss of corneal nerve fibers is associated with physical inactivity and glucose lowering medication associated with weight gain in type 2 diabetes

Aims/Introduction

Limited studies have identified risk factors linked to the progression of diabetic peripheral neuropathy (DPN) in type 2 diabetes. This study examined the association of risk factors with change in neuropathy measures over 2 years.

Materials and Methods

Participants with type 2 diabetes (n = 78) and controls (n = 26) underwent assessment of clinical and metabolic parameters and neuropathy using corneal confocal microscopy (CCM), vibration perception threshold (VPT), and the DN4 questionnaire at baseline and 2 year follow‐up.

Results

Participants with type 2 diabetes had a lower corneal nerve fiber density (CNFD), branch density (CNBD), and fiber length (CNFL) (P ≤ 0.0001) and a higher VPT (P ≤ 0.01) compared with controls. Over 2 years, despite a modest reduction in HbA1c (P ≤ 0.001), body weight (P ≤ 0.05), and LDL (P ≤ 0.05) the prevalence of DPN (P = 0.28) and painful DPN (P = 0.21) did not change, but there was a significant further reduction in CNBD (P ≤ 0.0001) and CNFL (P ≤ 0.05). CNFD, CNBD, and CNFL decreased significantly in physically inactive subjects (P < 0.05–0.0001), whilst there was no change in CNFD (P = 0.07) or CNFL (P = 0.85) in physically active subjects. Furthermore, there was no change in CNFD (P = 0.82), CNBD (P = 0.08), or CNFL (P = 0.66) in patients treated with glucose lowering medication associated with weight loss, whilst CNBD (P = 0.001) decreased in patients on glucose lowering medication associated with weight gain.

Conclusions

In participants with type 2 diabetes, despite a modest improvement in HbA1c, body weight, and LDL there was a progressive loss of corneal nerve fibers; except in those who were physically active or on glucose lowering medication associated with weight loss.

Heart rate-corrected QT interval: A novel diagnostic biomarker for diabetic peripheral neuropathy

AIMS/INTRODUCTION

To explore the relationship between heart rate-corrected QT (QTc) interval and diabetic peripheral neuropathy (DPN), and whether QTc interval has diagnostic utility for DPN beyond nerve conduction velocity.

MATERIALS AND METHODS

A total of 965 patients with diabetes, including 473 patients with DPN and 492 patients without DPN, underwent standard 12-lead electrocardiography and detailed assessments of peripheral neuropathy.

RESULTS

Patients with DPN had longer QTc intervals than those without. Among participants, from the first to fourth quartile of QTc interval, the proportion of patients with DPN appreciably increased and the nerve conduction velocity obviously decreased (P for trend <0.001). The univariate and multivariate analyses showed that prolonged QTc interval was closely associated with increased risk of DPN (univariable odds ratio 1.112, 95% confidence interval 1.097-1.127, P < 0.001; multivariable odds ratio 1.118, 95% confidence interval 1.099-1.137, P < 0.001). Receiver operating characteristic analysis for the diagnosis of DPN showed a greater area under the curve for QTc interval of 0.894 than the median nerve motor conduction velocity of 0.691, median nerve sensory conduction velocity of 0.664 and peroneal nerve motor conduction velocity of 0.692. The optimal cut-off point of QTc interval for DPN was 428.5 ms with sensitivity of 0.715 and specificity of 0.920 (P < 0.001). The combination of QTc interval and nerve conduction testing increased the area under the curve for the diagnosis of DPN (from 0.736 to 0.916; P < 0.001).

CONCLUSIONS

QTc interval with 428.5 ms has more reliable diagnostic utility for DPN than nerve conduction velocity, and prolonged QTc interval is closely associated with an increased risk of DPN.

Prevalence and risk factors for diabetic peripheral neuropathy, neuropathic pain and foot ulceration in the Arabian Gulf Region

Aims/Introduction

This study determined the prevalence and risk factors for diabetic peripheral neuropathy (DPN), painful DPN and diabetic foot ulceration (DFU) in patients with type 2 diabetes in secondary healthcare in Qatar, Kuwait and the Kingdom of Saudi Arabia.

Materials and Methods

Adults aged 18–85 years with type 2 diabetes were randomly enrolled from secondary healthcare, and underwent clinical and metabolic assessment. DPN was evaluated using vibration perception threshold and neuropathic symptoms and painful Diabetic Peripheral Neuropathy was evaluated using the Douleur Neuropathique 4 questionnaire.

Results

A total of 3,021 individuals were recruited between June 2017 and May 2019. The prevalence of DPN was 33.3%, of whom 52.2% were at risk of DFU and 53.6% were undiagnosed. The prevalence of painful DPN was 43.3%, of whom 54.3% were undiagnosed. DFU was present in 2.9%. The adjusted odds ratios for DPN and painful DPN were higher with increasing diabetes duration, obesity, poor glycemic control and hyperlipidemia, and lower with greater physical activity. The adjusted odds ratio for DFU was higher with the presence of DPN, severe loss of vibration perception, hypertension and vitamin D deficiency.

Conclusions

This is the largest study to date from the Middle East showing a high prevalence of undiagnosed DPN, painful DPN and those at risk of DFU in patients with type 2 diabetes, and identifies their respective risk factors.

Bioactive Compounds and Diabetes Mellitus: Prospects and Future Challenges

Diabetes mellitus is a metabolic condition that influences the endocrine framework. Hyperglycemia and hyperlipidemia are two of the most widely recognized metabolic irregularities in diabetes, just as two of the most well-known reasons for diabetic intricacies. Diabetes mellitus is a persistent illness brought about by metabolic irregularities in hyperglycemic pancreatic cells. Hyperglycemia can be brought about by an absence of insulin-producing beta cells in the pancreas (Type 1 diabetes mellitus) or inadequate insulin creation that does not work effectively (Type 2 diabetes mellitus). Present diabetes medication is directed toward directing blood glucose levels in the systemic circulation to the typical levels. Numerous advanced prescription medicines have many negative results that can bring about unexpected severe issues during treatment of the bioactive compound from a different source that is beneficially affected by controlling, adjusting metabolic pathways or cycles. Moreover, a few new bioactive medications disengaged from plants have shown antidiabetic action with more noteworthy adequacy than the oral hypoglycemic agent that specialists have utilized in clinical treatment lately. Since bioactive mixtures are collected from familiar sources, they have a great activity in controlling diabetes mellitus. This study discusses bioactive compounds and their activity to manage diabetes mellitus and their prospects. Though bioactive compound has many health beneficial properties, adequate clinical studies still need to gain large acknowledge that they are effective in the management of diabetes mellitus.

Dry eye disease, a prominent manifestation of systemic autoimmune disorders

OBJECTIVES

Dry eye disease (DED) is arguably the most frequent ocular disease encountered in ophthalmic clinical practice. DED is frequently an underestimated condition causing a significant impact on visual function and quality of life. Many systemic autoimmune diseases (SAIDs) are related to moderate to severe DED. The main objective of this review is to enhance the awareness among ophthalmologists of the potential association of an underlying SAID in a high-risk patient with DED.

METHODS

An exhaustive literature search was performed in the National Library of Medicine's Pubmed, Scopus, Web of Science, and Google Scholar databases for all English language articles published until November 2021. The main keywords included "dry eye disease" associated with autoimmune, connective tissue, endocrine, gastrointestinal, hematopoietic, vascular, and pulmonary diseases. Case reports, series, letters to the editor, reviews, and original articles were included.

RESULTS

Although DED is frequently associated with SAIDs, its diagnosis is commonly delayed or missed, producing significant complications, including corneal ulceration, melting, scleritis, uveitis, and optic neuritis resulting in severe complications detrimental to visual function and quality of life. SAID should be suspected in a woman, 30 to 60 years old with a family history of autoimmunity, presenting with DED symptoms and extraocular manifestations including arthralgias, dry mouth, unexplained weight and hair loss, chronic fatigue, heat or cold intolerance, insomnia, and mood disorders.

CONCLUSIONS

Establishing the correct diagnosis and treatment of DED associated with SAIDs is crucial to avoid its significant burden and severe ocular complications.

Corneal Confocal Microscopy to Image Small Nerve Fiber Degeneration: Ophthalmology Meets Neurology

Neuropathic pain has multiple etiologies, but a major feature is small fiber dysfunction or damage. Corneal confocal microscopy (CCM) is a rapid non-invasive ophthalmic imaging technique that can image small nerve fibers in the cornea and has been utilized to show small nerve fiber loss in patients with diabetic and other neuropathies. CCM has comparable diagnostic utility to intraepidermal nerve fiber density for diabetic neuropathy, fibromyalgia and amyloid neuropathy and predicts the development of diabetic neuropathy. Moreover, in clinical intervention trials of patients with diabetic and sarcoid neuropathy, corneal nerve regeneration occurs early and precedes an improvement in symptoms and neurophysiology. Corneal nerve fiber loss also occurs and is associated with disease progression in multiple sclerosis, Parkinson's disease and dementia. We conclude that corneal confocal microscopy has good diagnostic and prognostic capability and fulfills the FDA criteria as a surrogate end point for clinical trials in peripheral and central neurodegenerative diseases.

Diabetic Corneal Neuropathy: Pathogenic Mechanisms and Therapeutic Strategies

Diabetes mellitus (DM) is a major global public health problem that can cause complications such as diabetic retinopathy, diabetic neuropathy, and diabetic nephropathy. Besides the reporting of reduction in corneal nerve density and decrease in corneal sensitivity in diabetic patients, there may be a subsequent result in delayed corneal wound healing and increased corneal infections. Despite being a potential cause of blindness, these corneal nerve changes have not gained enough attention. It has been proposed that corneal nerve changes may be an indicator for diabetic neuropathy, which can provide a window for early diagnosis and treatment. In this review, the authors aimed to give an overview of the relationship between corneal nerves and diabetic neuropathy as well as the underlying pathophysiological mechanisms of corneal nerve fiber changes caused by DM for improved prediction and prevention of diabetic neuropathy. In addition, the authors summarized current and novel therapeutic methods for delayed corneal wound healing, nerve protection and regeneration in the diabetic cornea.

Diabetes Distal Peripheral Neuropathy: Subtypes and Diagnostic and Screening Technologies

Diabetes distal symmetrical peripheral neuropathy (DSPN) is the most prevalent form of neuropathy in industrialized countries, substantially increasing risk for morbidity and pre-mature mortality. DSPN may manifest with small-fiber disease, large-fiber disease, or a combination of both. This review summarizes: (1) DSPN subtypes (small- and large-fiber disease) with attention to clinical signs and patient symptoms; and (2) technological diagnosis and screening for large- and small-fiber disease with inclusion of a comprehensive literature review of published studies from 2015-present (N = 66). Review findings, informed by the most up-to-date research, advance critical understanding of DSPN large- and small-fiber screening technologies, including those designed for point-of-care use in primary care and endocrinology practices.

Corneal confocal microscopy for the diagnosis of diabetic peripheral neuropathy: A systematic review and meta-analysis

INTRODUCTION

Corneal confocal microscopy (CCM) is a rapid non-invasive ophthalmic imaging technique that identifies corneal nerve fiber damage. Small studies suggest that CCM could be used to assess patients with diabetic peripheral neuropathy (DPN).

AIM

To undertake a systematic review and meta-analysis assessing the diagnostic utility of CCM for sub-clinical DPN (DPN- ) and established DPN (DPN+ ).

DATA SOURCES

Databases (PubMed, Embase, Central, ProQuest) were searched for studies using CCM in patients with diabetes up to April 2020.

STUDY SELECTION

Studies were included if they reported on at least one CCM parameter in patients with diabetes.

DATA EXTRACTION

Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), and inferior whorl length (IWL) were compared between patients with diabetes with and without DPN and controls. Meta-analysis was undertaken using RevMan V.5.3.

DATA SYNTHESIS

Thirty-eight studies including ~4,000 participants were included in this meta-analysis. There were significant reductions in CNFD, CNBD, CNFL, and IWL in DPN- vs controls (P < 0.00001), DPN+ vs controls (P < 0.00001), and DPN+ vs DPN- (P < 0.00001).

CONCLUSION

This systematic review and meta-analysis shows that CCM detects small nerve fiber loss in subclinical and clinical DPN and concludes that CCM has good diagnostic utility in DPN.

Corneal Nerve Parameter Reference Values for Chinese Adults Assessed by Corneal Confocal Microscopy

BACKGROUND

Confocal corneal microscopy is an excellent new noninvasive tool for assessing diabetic peripheral neuropathy. We aimed to investigate the clinical variables associated with corneal nerve parameters and establish reference values for clinical use in healthy Chinese adults.

METHODS

The study enlisted 257 healthy volunteers (137 females and 120 males) from two clinical academic centers in China. Two experts captured and selected images of the central corneal subbasal nerve plexus at each center using the same corneal confocal microscopy instrument according to a commonly adopted protocol. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were measured using fully automated software (ACCMetrics). The correlation between clinical indicators and confocal corneal microscopy measures was determined using partial correlation. Quantile regression was used to calculate reference values and estimate the effects of clinical factors on the normative values of confocal corneal microscopy measures.

RESULTS

Females had significantly higher CNFD, CNBD, and CNFL than males. There was no correlation between age, glycated hemoglobin (HbA1c), height, weight, body mass index (BMI), and any corneal nerve fiber parameter in both sexes. In either sex, age, weight, height, BMI, and HbA1c did not affect the 0.05^th quantile values of any corneal nerve parameter.

CONCLUSIONS

This study establishes sex-adjusted reference values for corneal confocal microscopy measures in Chinese adults and provides a reference for clinical practice and research with this technique.

Loss of corneal nerves and brain volume in mild cognitive impairment and dementia

Introduction

This study compared the capability of corneal confocal microscopy (CCM) with magnetic resonance imaging (MRI) brain volumetry for the diagnosis of mild cognitive impairment (MCI) and dementia.

Methods

In this cross‐sectional study, participants with no cognitive impairment (NCI), MCI, and dementia underwent assessment of Montreal Cognitive Assessment (MoCA), MRI brain volumetry, and CCM.

Results

Two hundred eight participants with NCI (n = 42), MCI (n = 98), and dementia (n = 68) of comparable age and gender were studied. For MCI, the area under the curve (AUC) of CCM (76% to 81%), was higher than brain volumetry (52% to 70%). For dementia, the AUC of CCM (77% to 85%), was comparable to brain volumetry (69% to 93%). Corneal nerve fiber density, length, branch density, whole brain, hippocampus, cortical gray matter, thalamus, amygdala, and ventricle volumes were associated with cognitive impairment after adjustment for confounders (All P’s < .01).

Discussion

The diagnostic capability of CCM compared to brain volumetry is higher for identifying MCI and comparable for dementia, and abnormalities in both modalities are associated with cognitive impairment.

Corneal Confocal Microscopy in the Diagnosis of Small Fiber Neuropathy: Faster, Easier, and More Efficient Than Skin Biopsy?

Chronic pain may affect 30–50% of the world’s population and an important cause is small fiber neuropathy (SFN). Recent research suggests that autoimmune diseases may be one of the most common causes of small nerve fiber damage. There is low awareness of SFN among patients and clinicians and it is difficult to diagnose as routine electrophysiological methods only detect large fiber abnormalities, and specialized small fiber tests, like skin biopsy and quantitative sensory testing, are not routinely available. Corneal confocal microscopy (CCM) is a rapid, non-invasive, reproducible method for quantifying small nerve fiber degeneration and regeneration, and could be an important tool for diagnosing SFN. This review considers the advantages and disadvantages of CCM and highlights the evolution of this technique from a research tool to a diagnostic test for small fiber damage, which can be a valuable contribution to the study and management of autoimmune disease.

Corneal confocal microscopy: A useful tool for diagnosis of small fiber neuropathy in type 2 diabetes

AIM

To investigate the diagnostic utility of corneal confocal microscopy (CCM) for small fiber neuropathy in type 2 diabetes.

MATERIALS AND METHODS

There were 186 participants with type 2 diabetes enrolled in this cross-sectional research. Pure small fiber neuropathy and mixed fiber neuropathy were defined using clinical examination, electromyography, and quantitative sensory testing. Demographics and clinical data, corneal confocal microscopy parameters, and other neuropathy measures were compared among the groups. The diagnostic utility of corneal confocal microscopy for small fiber neuropathy was assessed by the receiver operating curve.

RESULTS

Of the 186 patients, 24.7% had a pure small fiber neuropathy and 17.2% of patients were diagnosed with mixed fiber neuropathy. The corneal nerve fiber density (CNFD), corneal nerve fiber branch density (CNBD), and corneal nerve fiber length (CNFL) were significantly lower in subjects with pure small fiber neuropathy compared with those without diabetic peripheral neuropathy (all P < 0.05). The receiver operating curve analysis for corneal confocal microscopy diagnosing small fiber neuropathy demonstrated the area under the curve for CNFD of 0.791, CNFL of 0.778, CNBD of 0.710.

CONCLUSIONS

Patients with type 2 diabetes with pure small fiber neuropathy showed more corneal nerve loss compared with those without diabetic peripheral neuropathy. It was revealed that corneal confocal microscopy can be a reasonable marker in the diagnosis of small fiber neuropathy in type 2 diabetes.

Corneal nerve loss as a surrogate marker for poor pial collaterals in patients with acute ischemic stroke

In patients with acute ischemic stroke, pial collaterals play a key role in limiting neurological disability by maintaining blood flow to ischemic penumbra. We hypothesized that patient with poor pial collaterals will have greater corneal nerve and endothelial cell abnormalities. In a cross-sectional study, 35 patients with acute ischemic stroke secondary to middle cerebral artery (MCA) occlusion with poor (n = 12) and moderate-good (n = 23) pial collaterals and 35 healthy controls underwent corneal confocal microscopy and quantification of corneal nerve and endothelial cell morphology. In patients with MCA stroke, corneal nerve fibre length (CNFL) (P < 0.001), corneal nerve fibre density (CNFD) (P = 0.025) and corneal nerve branch density (CNBD) (P = 0.002) were lower compared to controls. Age, BMI, cholesterol, triglycerides, HDL, LDL, systolic blood pressure, NIHSS and endothelial cell parameters did not differ but mRS was higher (p = 0.023) and CNFL (p = 0.026) and CNBD (p = 0.044) were lower in patients with poor compared to moderate-good collaterals. CNFL and CNBD distinguished subjects with poor from moderate-good pial collaterals with an AUC of 72% (95% CI 53–92%) and 71% (95% CI 53–90%), respectively. Corneal nerve loss is greater in patients with poor compared to moderate-good pial collaterals and may act as a surrogate marker for pial collateral status in patients with ischemic stroke.

Corneal nerve loss is related to the severity of painful diabetic neuropathy

Background and purpose

Previously it has been shown that patients with painful diabetic neuropathy (PDN) have greater corneal nerve loss compared to patients with painless diabetic neuropathy. This study investigated if the severity of corneal nerve loss was related to the severity of PDN.

Methods

Participants with diabetic neuropathy (n = 118) and healthy controls (n = 38) underwent clinical and neurological evaluation, quantitative sensory testing, nerve conduction testing and corneal confocal microscopy and were categorized into those with no (n = 43), mild (n = 34) and moderate‐to‐severe (n = 41) neuropathic pain.

Results

Corneal nerve fibre density (p = 0.003), corneal nerve fibre length (p < 0.0001) and cold perception threshold (p < 0.0001) were lower and warm perception threshold was higher (p = 0.002) in patients with more severe pain, but there was no significant difference in the neuropathy disability score (p = 0.5), vibration perception threshold (p = 0.5), sural nerve conduction velocity (p = 0.3) and amplitude (p = 0.7), corneal nerve branch density (p = 0.06) and deep breathing heart rate variability (p = 0.08) between patients with differing severity of PDN. The visual analogue scale correlated significantly with corneal nerve fibre density (r = −0.3, p = 0.0002), corneal nerve branch density (r = −0.3, p = 0.001) and corneal nerve fibre length (r = −0.4, p < 0.0001). Receiver operating curve analysis showed that corneal nerve fibre density had an area under the curve of 0.78 with a sensitivity of 0.73 and specificity of 0.72 for the diagnosis of PDN.

Conclusions

Corneal confocal microscopy reveals increasing corneal nerve fibre loss with increasing severity of neuropathic pain and a good diagnostic outcome for identifying patients with PDN.

Eye disorders other than diabetic retinopathy in patients with diabetes

AIM

While diabetic retinopathy is the most specific complication of chronic hyperglycaemia, numerous other ocular conditions also can involve the eyes of people with diabetes. Cataract, glaucoma, age-related macular degeneration, retinal vascular occlusion, and acute ischaemic optic neuropathy combine to impair vision in people with diabetes, especially when they are old. This report provides a critical analysis and an overview of the current knowledge of the main ocular disorders (excluding diabetic retinopathy) and their association in patients with diabetes.

METHODS

A literature search strategy was conducted for all English-language literature with a systematic review of key references until 2021.

RESULTS

Patients with diabetes have a high-to-moderate increased risk for most of the usual ocular disorders we reviewed with the exception of age-related macular degeneration. Exposure to chronic hyperglycaemia promotes the development of many eye disorders while acute glucose changes are involved in refractive disorders, diabetic papillopathy and acute cataract.

CONCLUSION

Diabetes, beyond diabetic retinopathy, increases the risk of numerous eye disorders leading to low vision with implications for daily diabetes management. Even in the absence of clearly demonstrated benefit from glucose control in all eye conditions, achieving good glycaemic control and adherence to diabetes treatment will likely help avoid an additional risk of visual impairment in people with diabetes. In perspective, interesting findings suggesting a preventive effect of metformin use on age-related macular degeneration occurrence justify further studies.

Corneal Confocal Microscopy Predicts the Development of Diabetic Neuropathy: A Longitudinal Diagnostic Multinational Consortium Study

OBJECTIVE

Corneal nerve fiber length (CNFL) has been shown in research studies to identify diabetic peripheral neuropathy (DPN). In this longitudinal diagnostic study, we assessed the ability of CNFL to predict the development of DPN.

RESEARCH DESIGN AND METHODS

From a multinational cohort of 998 participants with type 1 and type 2 diabetes, we studied the subset of 261 participants who were free of DPN at baseline and completed at least 4 years of follow-up for incident DPN. The predictive validity of CNFL for the development of DPN was determined using time-dependent receiver operating characteristic (ROC) curves.

RESULTS

A total of 203 participants had type 1 and 58 had type 2 diabetes. Mean follow-up time was 5.8 years (interquartile range 4.2-7.0). New-onset DPN occurred in 60 participants (23%; 4.29 events per 100 person-years). Participants who developed DPN were older and had a higher prevalence of type 2 diabetes, higher BMI, and longer duration of diabetes. The baseline electrophysiology and corneal confocal microscopy parameters were in the normal range but were all significantly lower in participants who developed DPN. The time-dependent area under the ROC curve for CNFL ranged between 0.61 and 0.69 for years 1-5 and was 0.80 at year 6. The optimal diagnostic threshold for a baseline CNFL of 14.1 mm/mm² was associated with 67% sensitivity, 71% specificity, and a hazard ratio of 2.95 (95% CI 1.70-5.11; P < 0.001) for new-onset DPN.

CONCLUSIONS

CNFL showed good predictive validity for identifying patients at higher risk of developing DPN ∼6 years in the future.

Lipids and peripheral neuropathy

PURPOSE OF REVIEW

Hyperlipidaemia is associated with the development of neuropathy. Indeed, a mechanistic link between altered lipid metabolism and peripheral nerve dysfunction has been demonstrated in a number of experimental and clinical studies. Furthermore, post hoc analyses of clinical trials of cholesterol and triglyceride-lowering pharmacotherapy have shown reduced rates of progression of diabetic neuropathy. Given, there are currently no FDA approved disease-modifying therapies for diabetic neuropathy, modulation of lipids may represent a key therapeutic target for the treatment of diabetic nerve damage. This review summarizes the current evidence base on the role of hyperlipidaemia and lipid lowering therapy on the development and progression of peripheral neuropathy.

RECENT FINDINGS

A body of literature supports a detrimental effect of dyslipidaemia on nerve fibres resulting in somatic and autonomic neuropathy. The case for an important modulating role of hypertriglyceridemia is stronger than for low-density lipoprotein cholesterol (LDL-C) in relation to peripheral neuropathy. This is reflected in the outcomes of clinical trials with the different therapeutic agents targeting hyperlipidaemia reporting beneficial or neutral effects with statins and fibrates. The potential concern with the association between proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor therapy and cognitive decline raised the possibility that extreme LDL-C lowering may result in neurodegeneration. However, studies in murine models and data from small observational studies indicate an association between increased circulating PCSK9 levels and small nerve fibre damage with a protective effect of PCSK9i therapy against small fibre neuropathy. Additionally, weight loss with bariatric surgery leads to an improvement in peripheral neuropathy and regeneration of small nerve fibres measured with corneal confocal microscopy in people with obesity with or without type 2 diabetes. These improvements correlate inversely with changes in triglyceride levels.

SUMMARY

Hyperlipidaemia, particularly hypertriglyceridemia, is associated with the development and progression of neuropathy. Lipid modifying agents may represent a potential therapeutic option for peripheral neuropathy. Post hoc analyses indicate that lipid-lowering therapies may halt the progression of neuropathy or even lead to regeneration of nerve fibres. Well designed randomized controlled trials are needed to establish if intensive targeted lipid lowering therapy as a part of holistic metabolic control leads to nerve fibre regeneration and improvement in neuropathy symptoms.