Imaging Modalities for Assessing the Vascular Component of Diabetic Retinal Disease: Review and Consensus for an Updated Staging System

Purpose

To review the evidence for imaging modalities in assessing the vascular component of diabetic retinal disease (DRD), to inform updates to the DRD staging system.

Design

Standardized narrative review of the literature by an international expert workgroup, as part of the DRD Staging System Update Effort, a project of the Mary Tyler Moore Vision Initiative. Overall, there were 6 workgroups: Vascular Retina, Neural Retina, Systemic Health, Basic and Cellular Mechanisms, Visual Function, and Quality of Life.

Participants

The Vascular Retina workgroup, including 16 participants from 4 countries.

Methods

Literature review was conducted using standardized evidence grids for 5 modalities: standard color fundus photography (CFP), widefield color photography (WFCP), standard fluorescein angiography (FA), widefield FA (WFFA), and OCT angiography (OCTA). Summary levels of evidence were determined on a validated scale from I (highest) to V (lowest). Five virtual workshops were held for discussion and consensus.

Main Outcome Measures

Level of evidence for each modality.

Results

Levels of evidence for standard CFP, WFCP, standard FA, WFFA, and OCTA were I, II, I, I, and II respectively. Traditional vascular lesions on standard CFP should continue to be included in an updated staging system, but more studies are required before they can be used in posttreatment eyes. Widefield color photographs can be used for severity grading within the area covered by standard CFPs, although these gradings may not be directly interchangeable with each other. Evaluation of the peripheral retina on WFCP can be considered, but the method of grading needs to be clarified and validated. Standard FA and WFFA provide independent prognostic value, but the need for dye administration should be considered. OCT angiography has significant potential for inclusion in the DRD staging system, but various barriers need to be addressed first.

Conclusions

This study provides evidence-based recommendations on the utility of various imaging modalities for assessment of the vascular component of DRD, which can inform future updates to the DRD staging system. Although new imaging modalities offer a wealth of information, there are still major gaps and unmet research needs that need to be addressed before this potential can be realized.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Report From the 2022 Mary Tyler Moore Vision Initiative Diabetic Retinal Disease Clinical Endpoints Workshop

The Mary Tyler Moore Vision Initiative Diabetic Retinal Disease (DRD) Clinical Endpoints Workshop was held on October 22, 2022 to accelerate progress toward establishment of useful clinical and research endpoints and development of new therapeutics that have important relevance across the full spectrum of DRD pathology. More than 90 patient representatives, clinicians, scientists, funding and regulatory agencies, diagnostic, therapeutic and biotech industry representatives discussed the needs for new diagnostic and therapeutic approaches to prevent and restore retinal neurovascular unit integrity. Phase I of the MTM Vision Initiative plans, notably updating the DRD staging system and severity scale, establishing a human ocular biorepository and resource, and clinical endpoints and biomarker development and validation, was emphasized.

The effect of surgical weight loss on diabetes complications in individuals with class II/III obesity

AIMS/HYPOTHESIS

The aim of this study was to determine the effect of bariatric surgery on diabetes complications in individuals with class II/III obesity (BMI > 35 kg/m2).

METHODS

We performed a prospective cohort study of participants with obesity who underwent bariatric surgery. At baseline and 2 years following surgery, participants underwent metabolic phenotyping and diabetes complication assessments. The primary outcomes for peripheral neuropathy (PN) were a change in intra-epidermal nerve fibre density (IENFD, units = fibres/mm) at the distal leg and proximal thigh, the primary outcome for cardiovascular autonomic neuropathy (CAN) was a change in the expiration/inspiration (E/I) ratio, and the primary outcome for retinopathy was a change in the mean deviation on frequency doubling technology testing.

RESULTS

Among 127 baseline participants, 79 completed in-person follow-up (age 46.0 ± 11.3 years [mean ± SD], 73.4% female). Participants lost a mean of 31.0 kg (SD 18.4), and all metabolic risk factors improved except for BP and total cholesterol. Following bariatric surgery, one of the primary PN outcomes improved (IENFD proximal thigh, +3.4 ± 7.8, p<0.01), and CAN (E/I ratio -0.01 ± 0.1, p=0.89) and retinopathy (deviation -0.2 ± 3.0, p=0.52) were stable. Linear regression revealed that a greater reduction in fasting glucose was associated with improvements in retinopathy (mean deviation point estimate -0.7, 95% CI -1.3, -0.1).

CONCLUSIONS/INTERPRETATION

Bariatric surgery may be an effective approach to reverse PN in individuals with obesity. The observed stability of CAN and retinopathy may be an improvement compared with the natural progression of these conditions; however, controlled trials are needed.

Frontiers in diabetic retinal disease

Diabetic retinal disease (DRD) remains a leading cause of vision loss and blindness globally. Although treatments can be effective when given at vision-threatening stages of DRD, there is a lack of knowledge about the earliest mechanisms leading to the development of clinically evident DRD. Recent advances in retinal imaging methods for patients with diabetes allow a more precise and granular characterization of the different stages of DRD than is provided by the classic Diabetic Retinopathy Severity Scale based on fundus photographs. In addition, recent clinical studies have yielded more information on how to adjust blood glucose levels, lipid levels and blood pressure to minimize the risk of DRD. Given the incomplete success of current therapies, there is a critical need for better understanding of the mechanisms underlying DRD and novel treatment targets that address the entire neurovascular retina. Moreover, the causes for interindividual variability in the development of DRD in patients with similar glycemic history and other metabolic factors are not yet clarified either. Finally, greater focus on patients' experience with visual disabilities and treatment effects should be addressed in research in this field.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

mTORC1 regulates high levels of protein synthesis in retinal ganglion cells of adult mice

Mechanistic target of rapamycin (mTOR) and mTOR complex 1 (mTORC1), linchpins of the nutrient sensing and protein synthesis pathways, are present at relatively high levels in the ganglion cell layer (GCL) and retinal ganglion cells (RGCs) of rodent and human retinas. However, the role of mTORCs in the control of protein synthesis in RGC is unknown. Here, we applied the SUrface SEnsing of Translation (SUnSET) method of nascent protein labeling to localize and quantify protein synthesis in the retinas of adult mice. We also used intravitreal injection of an adeno-associated virus 2 vector encoding Cre recombinase in the eyes of mtor- or rptor-floxed mice to conditionally knockout either both mTORCs or only mTORC1, respectively, in cells within the GCL. A novel vector encoding an inactive Cre mutant (CreΔC) served as control. We found that retinal protein synthesis was highest in the GCL, particularly in RGC. Negation of both complexes or only mTORC1 significantly reduced protein synthesis in RGC. In addition, loss of mTORC1 function caused a significant reduction in the pan-RGC marker, RNA-binding protein with multiple splicing, with little decrease of the total number of cells in the RGC layer, even at 25 weeks after adeno-associated virus-Cre injection. These findings reveal that mTORC1 signaling is necessary for maintaining the high rate of protein synthesis in RGCs of adult rodents, but it may not be essential to maintain RGC viability. These findings may also be relevant to understanding the pathophysiology of RGC disorders, including glaucoma, diabetic retinopathy, and optic neuropathies.

A validated analysis pipeline for mass spectrometry-based vitreous proteomics: new insights into proliferative diabetic retinopathy

Background

Vitreous is an accessible, information-rich biofluid that has recently been studied as a source of retinal disease-related proteins and pathways. However, the number of samples required to confidently identify perturbed pathways remains unknown. In order to confidently identify these pathways, power analysis must be performed to determine the number of samples required, and sample preparation and analysis must be rigorously defined.

Methods

Control (n = 27) and proliferative diabetic retinopathy (n = 23) vitreous samples were treated as biologically distinct individuals or pooled together and aliquoted into technical replicates. Quantitative mass spectrometry with tandem mass tag labeling was used to identify proteins in individual or pooled control samples to determine technical and biological variability. To determine effect size and perform power analysis, control and proliferative diabetic retinopathy samples were analyzed across four 10-plexes. Pooled samples were used to normalize the data across plexes and generate a single data matrix for downstream analysis.

Results

The total number of unique proteins identified was 1152 in experiment 1, 989 of which were measured in all samples. In experiment 2, 1191 proteins were identified, 727 of which were measured across all samples in all plexes. Data are available via ProteomeXchange with identifier PXD025986. Spearman correlations of protein abundance estimations revealed minimal technical (0.99–1.00) and biological (0.94–0.98) variability. Each plex contained two unique pooled samples: one for normalizing across each 10-plex, and one to internally validate the normalization algorithm. Spearman correlation of the validation pool following normalization was 0.86–0.90. Principal component analysis revealed stratification of samples by disease and not by plex. Subsequent differential expression and pathway analyses demonstrated significant activation of metabolic pathways and inhibition of neuroprotective pathways in proliferative diabetic retinopathy samples relative to controls.

Conclusions

This study demonstrates a feasible, rigorous, and scalable method that can be applied to future proteomic studies of vitreous and identifies previously unrecognized metabolic pathways that advance understanding of diabetic retinopathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09328-8.

Diminished retinal complex lipid synthesis and impaired fatty acid β-oxidation associated with human diabetic retinopathy

BACKGROUND

This study systematically investigated circulating and retinal tissue lipid determinants of human diabetic retinopathy (DR) to identify underlying lipid alterations associated with severity of DR.

METHODS

Retinal tissues were retrieved from postmortem human eyes, including 19 individuals without diabetes, 20 with diabetes but without DR, and 20 with diabetes and DR, for lipidomic study. In a parallel study, serum samples from 28 American Indians with type 2 diabetes from the Gila River Indian Community, including 12 without DR, 7 with mild nonproliferative DR (NPDR), and 9 with moderate NPDR, were selected. A mass-spectrometry–based lipidomic platform was used to measure serum and tissue lipids.

RESULTS

In the postmortem retinas, we found a graded decrease of long-chain acylcarnitines and longer-chain fatty acid ester of hydroxyl fatty acids, diacylglycerols, triacylglycerols, phosphatidylcholines, and ceramide(NS) in central retina from individuals with no diabetes to those with diabetes with DR. The American Indians’ sera also exhibited a graded decrease in circulating long-chain acylcarnitines and a graded increase in the intermediate-length saturated and monounsaturated triacylglycerols from no DR to moderate NPDR.

CONCLUSION

These findings suggest diminished synthesis of complex lipids and impaired mitochondrial β-oxidation of fatty acids in retinal DR, with parallel changes in circulating lipids.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00340678.

FUNDING

This work was supported by NIH grants R24 DK082841, K08DK106523, R03DK121941, P30DK089503, P30DK081943, P30DK020572, P30 EY007003; The Thomas Beatson Foundation; and JDRF Center for Excellence (5-COE-2019-861-S-B).

Proteomic Analyses of Vitreous in Proliferative Diabetic Retinopathy: Prior Studies and Future Outlook

Vitreous fluid is becoming an increasingly popular medium for the study of retinal disease. Numerous studies have demonstrated that proteomic analysis of the vitreous from patients with proliferative diabetic retinopathy yields valuable molecular information regarding known and novel proteins and pathways involved in this disease. However, there is no standardized methodology for vitreous proteomic studies. Here, we share a suggested protocol for such studies and outline the various experimental and analytic methods that are currently available. We also review prior mass spectrometry-based proteomic studies of the vitreous from patients with proliferative diabetic retinopathy, discuss common pitfalls of these studies, and propose next steps for moving the field forward.

Insulin-like growth factor-2 regulates basal retinal insulin receptor activity

The retinal insulin receptor (IR) exhibits basal kinase activity equivalent to that of the liver of fed animals, but unlike the liver, does not fluctuate with feeding and fasting; it also declines rapidly after the onset of insulin-deficient diabetes. The ligand(s) that determine basal IR activity in the retina has not been identified. Using a highly sensitive insulin assay, we found that retinal insulin concentrations remain constant in fed versus fasted rats and in diabetic versus control rats; vitreous fluid insulin levels were undetectable. Neutralizing antibodies against insulin-like growth factor 2 (IGF-2), but not insulin-like growth factor 1 (IGF-1) or insulin, decreased IR kinase activity in normal rat retinas, and depletion of IGF-2 from serum specifically reduced IR phosphorylation in retinal cells. Immunoprecipitation studies demonstrated that IGF-2 induced greater phosphorylation of the retinal IR than the IGF-1 receptor. Retinal IGF-2 mRNA content was 10-fold higher in adults than pups and orders of magnitude higher than in liver. Diabetes reduced retinal IGF-2, but not IGF-1 or IR, mRNA levels, and reduced IGF-2 and IGF-1 content in vitreous fluid. Finally, intravitreal administration of IGF-2 (mature and pro-forms) increased retinal IR and Akt kinase activity in diabetic rats. Collectively, these data reveal that IGF-2 is the primary ligand that defines basal retinal IR activity and suggest that reduced ocular IGF-2 may contribute to reduced IR activity in response to diabetes. These findings may have importance for understanding the regulation of metabolic and prosurvival signaling in the retina.

Integrative Biology of Diabetic Retinal Disease: Lessons from Diabetic Kidney Disease

Diabetic retinal disease (DRD) remains the most common cause of vision loss in adults of working age. Progress on the development of new therapies for DRD has been limited by the complexity of the human eye, which constrains the utility of traditional research techniques, including animal and tissue culture models-a problem shared by those in the field of kidney disease research. By contrast, significant progress in the study of diabetic kidney disease (DKD) has resulted from the successful employment of systems biology approaches. Systems biology is widely used to comprehensively understand complex human diseases through the unbiased integration of genetic, environmental, and phenotypic aspects of the disease with the functional and structural manifestations of the disease. The application of a systems biology approach to DRD may help to clarify the molecular basis of the disease and its progression. Acquiring this type of information might enable the development of personalized treatment approaches, with the goal of discovering new therapies targeted to an individual's specific DRD pathophysiology and phenotype. Furthermore, recent efforts have revealed shared and distinct pathways and molecular targets of DRD and DKD, highlighting the complex pathophysiology of these diseases and raising the possibility of therapeutics beneficial to both organs. The objective of this review is to survey the current understanding of DRD pathophysiology and to demonstrate the investigative approaches currently applied to DKD that could promote a more thorough understanding of the structure, function, and progression of DRD.

Visual Field Changes Over 5 Years in Patients Treated With Panretinal Photocoagulation or Ranibizumab for Proliferative Diabetic Retinopathy

Importance

Preservation of peripheral visual field (VF) is considered an advantage for anti-vascular endothelial growth factor agents compared with panretinal photocoagulation (PRP) for treatment of proliferative diabetic retinopathy. Long-term data on VF are important when considering either treatment approach.

Objective

To further evaluate changes in VF throughout 5 years among eyes enrolled in the Protocol S clinical trial, conducted by the DRCR Retina Network.

Design, Setting, and Participants

Post hoc analyses of an ancillary study within a multicenter (55 US sites) randomized clinical trial. Individuals with eyes with proliferative diabetic retinopathy enrolled in Protocol S were included. Data were collected from February 2012 to February 2018. Analysis began in June 2018.

Interventions

Panretinal photocoagulation or intravitreous injections of 0.5-mg ranibizumab. Diabetic macular edema, whenever present, was treated with ranibizumab in both groups. Panretinal photocoagulation could be administered to eyes in the ranibizumab group when failure or futility criteria were met.

Main Outcomes and Measures

Mean change in total point score on VF testing with the Humphrey Field Analyzer 30-2 and 60-4 test patterns.

Results

Of 394 eyes enrolled in Protocol S, 234 (59.4%) were targeted for this ancillary study. Of these, 167 (71.4%) had VF meeting acceptable quality criteria at baseline (median [interquartile range] age, 50 [43-58] years; 90 men [53.9%]). At 5 years, 79 (33.8%) had results available. The mean (SD) change in total point score in the PRP and ranibizumab groups was -305 (521) dB and -36 (486) dB at 1 year, respectively, increasing to -527 (635) dB and -330 (645) dB at 5 years, respectively (P = .04). After censoring VF results after PRP treatments in the ranibizumab group, the 5-year mean change in total point score was -201 (442) dB. In a longitudinal regression analysis of change in total point score including both treatment groups, laser treatment was associated with a mean point decrease of 208 (95% CI, 112-304) dB for the initial PRP session, 77 (95% CI, 21-132) dB for additional PRP sessions, and 325 (95% CI, 211-439) dB for endolaser. No association was found between change in point score and the number of ranibizumab injections during the previous year (-9 per injection [95% CI, -22 to 3]).

Conclusions and Relevance

The limited data available from Protocol S suggest that there are factors besides PRP associated with VF loss in eyes treated for proliferative diabetic retinopathy. Further clinical research is warranted to clarify the finding.

Trial Registration

ClinicalTrials.gov identifier: NCT01489189.

Randomized Safety and Feasibility Trial of Ultra-Rapid Cooling Anesthesia for Intravitreal Injections

PURPOSE

To test the safety and preliminary efficacy of rapid, nonpharmacologic anesthesia via cooling for intravitreal injections.

DESIGN

Single-center, randomized phase 1 dose-ranging safety study (ClinicalTrials.gov identifier, NCT02872012).

PARTICIPANTS

Adults 18 years of age or older with a diagnosis of exudative macular degeneration or diabetic macular edema requiring bilateral anti-vascular endothelial growth factor therapy were included.

METHODS

A handheld device was developed to provide anesthesia via cooling to a focal area on the surface of the eye before intravitreal treatment (IVT). In 22 patients undergoing bilateral IVT, 1 eye was randomized to receive standard of care (SOC) lidocaine-based anesthesia and the other eye received cooling-anesthesia at 1 of 5 different temperatures and cooling times. Subjective pain was assessed via the visual analog scale (VAS; range, 1-10) at 2 time points: (1) immediately after IVT and (2) 4 hours after IVT. Treated eyes were assessed for ocular safety 24 hours after IVT.

MAIN OUTCOME MEASURES

We determined the occurrence of adverse events in eyes treated with cooling anesthesia. Mean VAS pain scores immediately after IVT and 4 hours after IVT in eyes receiving cooling anesthesia were compared with eyes receiving SOC.

RESULTS

A total of 44 eyes were treated, 22 with cooling anesthesia and 22 with SOC. No dose-related toxicity was found with cooling anesthesia. Mild, transient adverse events were recorded in 32% of patients treated with cooling anesthesia versus 44% of patients receiving SOC. The mean±standard error of the mean (SEM) VAS pain scores immediately after intravitreal injection were 2.3 ± 0.4 for patients receiving SOC and 2.2 ± 0.6 in patients receiving -10° C cooling anesthesia (P = 0.8). Mean±SEM pain scores 4 hours after injection were 1.6 ± 0.4 for SOC and 1.2 ± 0.5 in the combined -10° C arms (P = 0.56). Total mean±SEM procedure time was 124 ± 5 seconds for patients treated with cooling anesthesia versus 395 ± 40 seconds for SOC (P < 0.0001).

CONCLUSIONS

Ultra-rapid cooling of the eye for anesthesia was well tolerated, with -10° C treatment resulting in comparable levels of anesthesia to SOC with a reduction in procedure time.

Density-based classification in diabetic retinopathy through thickness of retinal layers from optical coherence tomography

Diabetic retinopathy (DR) is a severe retinal disorder that can lead to vision loss, however, its underlying mechanism has not been fully understood. Previous studies have taken advantage of Optical Coherence Tomography (OCT) and shown that the thickness of individual retinal layers are affected in patients with DR. However, most studies analyzed the thickness by calculating summary statistics from retinal thickness maps of the macula region. This study aims to apply a density function-based statistical framework to the thickness data obtained through OCT, and to compare the predictive power of various retinal layers to assess the severity of DR. We used a prototype data set of 107 subjects which are comprised of 38 non-proliferative DR (NPDR), 28 without DR (NoDR), and 41 controls. Based on the thickness profiles, we constructed novel features which capture the variation in the distribution of the pixel-wise retinal layer thicknesses from OCT. We quantified the predictive power of each of the retinal layers to distinguish between all three pairwise comparisons of the severity in DR (NoDR vs NPDR, controls vs NPDR, and controls vs NoDR). When applied to this preliminary DR data set, our density-based method demonstrated better predictive results compared with simple summary statistics. Furthermore, our results indicate considerable differences in retinal layer structuring based on the severity of DR. We found that: (a) the outer plexiform layer is the most discriminative layer for classifying NoDR vs NPDR; (b) the outer plexiform, inner nuclear and ganglion cell layers are the strongest biomarkers for discriminating controls from NPDR; and (c) the inner nuclear layer distinguishes best between controls and NoDR.

mTORC1 and mTORC2 expression in inner retinal neurons and glial cells

The retina is one of the most metabolically active tissues, yet the processes that control retinal metabolism remains poorly understood. The mTOR complex (mTORC) that drives protein and lipid biogenesis and autophagy has been studied extensively in regards to retinal development and responses to optic nerve injury but the processes that regulate homeostasis in the adult retina have not been determined. We previously demonstrated that normal adult retina has high rates of protein synthesis compared to skeletal muscle, associated with high levels of mechanistic target of rapamycin (mTOR), a kinase that forms multi-subunit complexes that sense and integrate diverse environmental cues to control cell and tissue physiology. This study was undertaken to: 1) quantify expression of mTOR complex 1 (mTORC1)- and mTORC2-specific partner proteins in normal adult rat retina, brain and liver; and 2) to localize these components in normal human, rat, and mouse retinas. Immunoblotting and immunoprecipitation studies revealed greater expression of raptor (exclusive to mTORC1) and rictor (exclusive for mTORC2) in normal rat retina relative to liver or brain, as well as the activating mTORC components, pSIN1 and pPRAS40. By contrast, liver exhibits greater amounts of the mTORC inhibitor, DEPTOR. Immunolocalization studies for all three species showed that mTOR, raptor, and rictor, as well as most other known components of mTORC1 and mTORC2, were primarily localized in the inner retina with mTORC1 primarily in retinal ganglion cells (RGCs) and mTORC2 primarily in glial cells. In addition, phosphorylated ribosomal protein S6, a direct target of the mTORC1 substrate ribosomal protein S6 kinase beta-1 (S6K1), was readily detectable in RGCs, indicating active mTORC1 signaling, and was preserved in human donor eyes. Collectively, this study demonstrates that the inner retina expresses high levels of mTORC1 and mTORC2 and possesses active mTORC1 signaling that may provide cell- and tissue-specific regulation of homeostatic activity. These findings help to define the physiology of the inner retina, which is key for understanding the pathophysiology of optic neuropathies, glaucoma and diabetic retinopathy.

The Prevalence and Determinants of Cognitive Deficits and Traditional Diabetic Complications in the Severely Obese

OBJECTIVE

To determine the prevalence of cognitive deficits and traditional diabetic complications and the association between metabolic factors and these outcomes.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional study in severely obese individuals before bariatric surgery. Lean control subjects were recruited from a research website. Cognitive deficits were defined by the National Institutes of Health (NIH) Toolbox (<5th percentile for lean control subjects). Cardiovascular autonomic neuropathy (CAN) was defined by an expiration-to-inspiration (E-to-I) ratio of <5th percentile for lean control subjects. Retinopathy was based on retinal photographs and nephropathy on the estimated glomerular filtration rate (<60 mg/dL) and/or the albumin-to-creatinine ratio (ACR) (≥30 mg/g). NIH Toolbox, E-to-I ratio, mean deviation on frequency doubling technology testing, and ACR were used as sensitive measures of these outcomes. We used multivariable linear regression to explore associations between metabolic factors and these outcomes.

RESULTS

We recruited 138 severely obese individuals and 46 lean control subjects. The prevalence of cognitive deficits, CAN, retinopathy, and nephropathy were 6.5%, 4.4%, 0%, and 6.5% in lean control subjects; 22.2%, 18.2%, 0%, and 6.1% in obese participants with normoglycemia; 17.7%, 21.4%, 1.9%, and 17.9% in obese participants with prediabetes; and 25.6%, 31.9%, 6.1%, and 16.3% in obese participants with diabetes. Waist circumference was significantly associated with cognitive function (-1.48; 95% CI -2.38, -0.57) and E-to-I ratio (-0.007; 95% CI -0.012, -0.002). Prediabetes was significantly associated with retinal function (-1.78; 95% CI -3.56, -0.002).

CONCLUSIONS

Obesity alone is likely sufficient to cause cognitive deficits but not retinopathy or nephropathy. Central obesity is the key metabolic risk factor.

Treated PDR Reveals Age-Appropriate Vision Deterioration But Distorted Retinal Organization

Purpose

We determined the progression of visual function, macular structure, and quality of life in patients with regressed proliferative diabetic retinopathy (PDR) after panretinal photocoagulation (PRP).

Methods

In this prospective study, 22 patients who underwent PRP for PDR and 11 age-matched control participants underwent examinations at baseline and after 5 years. Visual acuity, contrast sensitivity, reading acuity, frequency doubling perimetry, Humphrey field analyzer, and dark adaptation were measured. The Low Luminance Questionnaire and National Eye Institute Vision Function Questionnaire-25 were administered. Macular spectral-domain optical coherence tomography was taken.

Results

After 5 years, patients who had previously undergone PRP for PDR (18.4 ± 7.9 years previously) showed significant deterioration in contrast sensitivity, reading acuity, frequency doubling perimetry 24-2 pattern standard deviation, and Humphrey field analyzer 10-2 foveal sensitivity, which were equivalent to age-related decreases in control participants. They revealed no further impairment in vision-related activities on questionnaires. In contrast with controls, their maculas showed pathologic disorganization of the retinal layers, especially the nerve fiber layer, which were thicker and constituted a greater proportion of the overall retinal thickness than the norm and associated with impaired vision.

Conclusions

Patients with treated PDR had age-related decreases in vision, but stable quality of life. Prior injuries from the diabetes and, possibly, laser treatment led to substantial disruption in the retinal structure, which may explain the loss of vision.

Translational Relevance

Despite PRP treatment, patients with regressed PDR had pathologic progression of the nerve fiber layer; further investigation may identify a new therapeutic target to reverse the visual deficits.

Increased lipogenesis and impaired β-oxidation predict type 2 diabetic kidney disease progression in American Indians

BACKGROUNDIn this study, we identified the lipidomic predictors of early type 2 diabetic kidney disease (DKD) progression, which are currently undefined.METHODSThis longitudinal study included 92 American Indians with type 2 diabetes. Serum lipids (406 from 18 classes) were quantified using mass spectrometry from baseline samples when iothalamate-based glomerular filtration rate (GFR) was at least 90 mL/min. Affymetrix GeneChip Array was used to measure renal transcript expression. DKD progression was defined as at least 40% decline in GFR during follow-up.RESULTSParticipants had a mean age of 45 ± 9 years and median urine albumin/creatinine ratio of 43 (interquartile range 11-144). The 32 progressors had significantly higher relative abundance of polyunsaturated triacylglycerols (TAGs) and a lower abundance of C16-C20 acylcarnitines (ACs) (P < 0.001). In a Cox regression model, the main effect terms of unsaturated free fatty acids and phosphatidylethanolamines and the interaction terms of C16-C20 ACs and short-low-double-bond TAGs by categories of albuminuria independently predicted DKD progression. Renal expression of acetyl-CoA carboxylase-encoding gene (ACACA) correlated with serum diacylglycerols in the glomerular compartment (r = 0.36, and P = 0.006) and with low-double-bond TAGs in the tubulointerstitial compartment (r = 0.52, and P < 0.001).CONCLUSIONCollectively, the findings reveal a previously unrecognized link between lipid markers of impaired mitochondrial β-oxidation and enhanced lipogenesis and DKD progression in individuals with preserved GFR. Renal acetyl-CoA carboxylase activation accompanies these lipidomic changes and suggests that it may be the underlying mechanism linking lipid abnormalities to DKD progression.TRIAL REGISTRATIONClinicalTrials.gov, NCT00340678.FUNDINGNIH R24DK082841, K08DK106523, R03DK121941, P30DK089503, P30DK081943, and P30DK020572.

Reading deficits in diabetic patients treated with panretinal photocoagulation and good visual acuity

PURPOSE

Patients with proliferative diabetic retinopathy (PDR) treated with panretinal photocoagulation (PRP) can have abnormal visual functioning that may be missed by Snellen visual acuity alone. We investigated reading deficits in patients treated with PRP for PDR using the Minnesota reading (MNREAD) test.

METHODS

Thirty patients treated with PRP and 15 controls underwent best-corrected visual acuity (BCVA), the MNREAD, frequency doubling perimetry (FDP), and fundus photography. Panretinal photocoagulation (PRP)-treated subjects were compared to controls on MNREAD results by two-sample t-tests and Wilcoxon tests and Pearson correlations were used to assess the association between performance on MNREAD and other central visual function tests within PRP subjects.

RESULTS

Panretinal photocoagulation (PRP)-treated patients had reduced MNREAD acuity (p < 0.0001) and increased critical print size (p = 0.01) compared to controls but not a significantly reduced maximum reading speed (p = 0.06). Logmar MNREAD acuity was strongly positive correlated with logMAR BCVA (r = 0.58, p = 0.0098) and strongly negatively correlated with FDP foveal threshold (r = -0.63, p = 0.0030). Maximum reading speed was positively correlated with FDP foveal threshold (r = 0.57, p = 0.0143) and FDP mean deviation (r = 0.51, p = 0.0432). Visual acuity did not correlate with the sensitivities on the FDP.

CONCLUSION

The MNREAD test reveals that PRP reduces reading ability and other aspects of macular function, and thus provides new understanding of how vision-related quality of life is impaired. These findings may lead to improved means to evaluate and enhance vision following treatment for PDR.

Five-Year Outcomes of Panretinal Photocoagulation vs Intravitreous Ranibizumab for Proliferative Diabetic Retinopathy: A Randomized Clinical Trial

Importance

Ranibizumab is a viable treatment option for eyes with proliferative diabetic retinopathy (PDR) through 2 years. However, longer-term results are needed.

Objective

To evaluate efficacy and safety of 0.5-mg intravitreous ranibizumab vs panretinal photocoagulation (PRP) over 5 years for PDR.

Design, Setting, and Participants

Diabetic Retinopathy Clinical Research Network multicenter randomized clinical trial evaluated 394 study eyes with PDR enrolled February through December 2012. Analysis began in January 2018.

Interventions

Eyes were randomly assigned to receive intravitreous ranibizumab (n = 191) or PRP (n = 203). Frequency of ranibizumab was based on a protocol-specified retreatment algorithm. Diabetic macular edema could be managed with ranibizumab in either group.

Main Outcomes and Measures

Mean change in visual acuity (intention-to-treat analysis) was the main outcome. Secondary outcomes included peripheral visual field loss, development of vision-impairing diabetic macular edema, and ocular and systemic safety.

Results

The 5-year visit was completed by 184 of 277 participants (66% excluding deaths). Of 305 enrolled participants, the mean (SD) age was 52 (12) years, 135 (44%) were women, and 160 (52%) were white. For the ranibizumab and PRP groups, the mean (SD) number of injections over 5 years was 19.2 (10.9) and 5.4 (7.9), respectively; the mean (SD) change in visual acuity letter score was 3.1 (14.3) and 3.0 (10.5) letters, respectively (adjusted difference, 0.6; 95% CI, -2.3 to 3.5; P = .68); the mean visual acuity was 20/25 (approximate Snellen equivalent) in both groups at 5 years. The mean (SD) change in cumulative visual field total point score was -330 (645) vs -527 (635) dB in the ranibizumab (n = 41) and PRP (n = 38) groups, respectively (adjusted difference, 208 dB; 95% CI, 9-408). Vision-impairing diabetic macular edema developed in 27 and 53 eyes in the ranibizumab and PRP groups, respectively (cumulative probabilities: 22% vs 38%; hazard ratio, 0.4; 95% CI, 0.3-0.7). No statistically significant differences between groups in major systemic adverse event rates were identified.

Conclusions and Relevance

Although loss to follow-up was relatively high, visual acuity in most study eyes that completed follow-up was very good at 5 years and was similar in both groups. Severe vision loss or serious PDR complications were uncommon with PRP or ranibizumab; however, the ranibizumab group had lower rates of developing vision-impairing diabetic macular edema and less visual field loss. Patient-specific factors, including anticipated visit compliance, cost, and frequency of visits, should be considered when choosing treatment for patients with PDR. These findings support either anti-vascular endothelial growth factor therapy or PRP as viable treatments for patients with PDR.

Trial Registration

ClinicalTrials.gov Identifier: NCT01489189.

New insights into the mechanisms of diabetic complications: role of lipids and lipid metabolism

Diabetes adversely affects multiple organs, including the kidney, eye and nerve, leading to diabetic kidney disease, diabetic retinopathy and diabetic neuropathy, respectively. In both type 1 and type 2 diabetes, tissue damage is organ specific and is secondary to a combination of multiple metabolic insults. Hyperglycaemia, dyslipidaemia and hypertension combine with the duration and type of diabetes to define the distinct pathophysiology underlying diabetic kidney disease, diabetic retinopathy and diabetic neuropathy. Only recently have the commonalities and differences in the metabolic basis of these tissue-specific complications, particularly those involving local and systemic lipids, been systematically examined. This review focuses on recent progress made using preclinical models and human-based approaches towards understanding how bioenergetics and metabolomic profiles contribute to diabetic kidney disease, diabetic retinopathy and diabetic neuropathy. This new understanding of the biology of complication-prone tissues highlights the need for organ-specific interventions in the treatment of diabetic complications.

Patient-Reported Outcomes Reveal Impairments Not Explained by Psychophysical Testing in Patients With Regressed PDR

Purpose

We evaluated the correlations between visual deficits and patient-reported symptoms in patients with regressed proliferative diabetic retinopathy (PDR) to determine whether there is a psychophysical basis for vision-related impairments.

Methods

Visual acuity, reading acuity, contrast sensitivity, frequency doubling perimetry (FDP), Humphrey field analyzer (HFA), and dark adaptation assessed visual function. The National Eye Institute Vision Function Questionnaire-25 (NEI VFQ-25) and Low Luminance Questionnaire (LLQ) assessed quality of life.

Results

We recruited 30 adults who received panretinal photocoagulation (PRP) for PDR and 15 control subjects; 22 diabetic and 11 control participants completed a second evaluation 5 years later. Visual acuity of the worse-seeing eyes tended to correlate better with NEI VFQ-25 and LLQ than did the acuity of the better-seeing eyes. Other vision measures were generally not associated with either questionnaire, especially responses related to driving ability and mental health. Visual acuity only detected subnormal performance in 43% to 45% of patients, while FDP 24-2, HFA 60-4, and LLQ detected abnormal performance in >80% of patients.

Conclusions

Poor visual acuity may explain some vision-related impairments in daily function. However, many patients with regressed PDR have normal acuity but reduced visual field and poor quality of life. In these patients, their reported symptoms were not fully explained by visual acuity or any psychophysical tests alone.

Translational Relevance

Visual acuity is a poor indicator of overall visual function in people with regressed PDR. In clinical settings, visual field tests and patient-reported outcomes may provide more comprehensive assessments of their functional deficits than visual acuity.

Identification of population characteristics through implementation of the Comprehensive Diabetic Retinopathy Program

Background

Diabetic retinopathy is the most common cause of blindness in working-age adults. Characteristics of patients with diabetes presenting to a retina subspecialty clinic have not been adequately studied, limiting our ability to risk stratify patients with diabetic retinopathy. Our goal is to describe an innovative program that collects structured, longitudinal data on patients with diabetes in a retina clinic, and identifies population characteristics to define patient risk stratification.

Methods

Demographics, body-mass index, blood pressure, hemoglobin A_1c, smoking history, diabetes type, diabetes duration, kidney disease history, and diagnosis codes were collected on all patients with diabetes at the Kellogg Eye Center retina clinic. A mixed effects negative binomial regression was then performed to assess visit frequency as a function of these variables. Visit frequency was used as a marker for cost of care. A subgroup of patients was surveyed about knowledge of diabetes management goals and barriers to better self-management.

Results

There were 2916 patients in the cohort with 1014 in the subgroup. The cohort was predominantly Caucasian (74.5%), with a mean age of 64 years (range 13–99) and a relatively even distribution of sex (53.2% men). The mean maximum hemoglobin A_1c was 8.0% (range 4.3–15.7%), and 57.1% had a diagnosis of diabetic retinopathy. Patients averaged 3.9 visits (range 1–27) during the 18-month study period. Blood pressure and duration of diabetes were positively associated with visit frequency (p < 0.0001, p < 0.0001, respectively). Of the surveyed patients, 87.6% knew their goal hemoglobin A_1c, while only 45.9% identified the correct blood pressure goal. The most common reported barrier to better self-management was “it’s just not working” (47.1%).

Conclusions

Implementation of this program enables the creation of a longitudinal dataset on patients with diabetes. Resulting data can be used to improve quality of care provided to patients at a retina clinic. The findings suggest considerable healthcare resources are being directed to a small patient population. This enhanced understanding of characteristics of patients with diabetes will improve efforts to preserve vision and utilize health system resources efficiently.

Disorganization of Retinal Inner Layers (DRIL) and Neuroretinal Dysfunction in Early Diabetic Retinopathy

Purpose

To elucidate the relationship between disorganization of retinal inner layers (DRILs) and retinal function in diabetic patients without diabetic retinopathy (DR) and with nonproliferative DR, but without diabetic macular edema (DME).

Methods

Fifty-seven participants with diabetes mellitus (DM) and 18 healthy controls underwent comprehensive ophthalmic examination, fundus photography, and spectral-domain optical coherence tomography. Scans of the fovea were evaluated for the presence of DRIL. Retinal function was evaluated using Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, the quick contrast sensitivity function (qCSF) on the AST Sentio Platform, short-wavelength automated perimetry (SWAP), standard automated perimetry (SAP), and frequency doubling perimetry (FDP). ANOVA and Kruskal-Wallis were used to compare retinal function in subjects with and without DRIL. Tukey-Kramer test and Wilcoxon were used for post hoc analysis.

Results

DRIL was identified in 9 of 57 diabetic subjects. DRIL subjects had higher body mass index and longer diabetes duration compared to diabetic subjects without DRIL (P = 0.03 and P = 0.009, respectively). Subjects with DRIL had reduced ETDRS visual acuity (P = 0.003), contrast sensitivity function (P = 0.0003), and SAP performance (PSD, P < 0.0001) compared to controls and diabetic subjects without DRIL. Structural analysis revealed inner retinal thinning, and some outer retinal thinning, associated with DRIL.

Conclusions

Diabetic subjects with DRIL have reduced retinal function compared to those without DRIL, and defective retinal lamination may be an early cellular consequence of diabetes responsible for this in some patients. Following further longitudinal studies, DRIL may be a readily available and reliable structural biomarker for reduced retinal function in early diabetic neuroretinal disease.

Risk Factors for Retinopathy in Type 1 Diabetes: The DCCT/EDIC Study

OBJECTIVE

The Diabetes Control and Complications Trial (DCCT) demonstrated that intensive therapy reduced the development and progression of retinopathy in type 1 diabetes (T1D) compared with conventional therapy. The Epidemiology of Diabetes Interventions and Complications (EDIC) study observational follow-up showed persistent benefits. In addition to glycemia, we now examine other potential retinopathy risk factors (modifiable and nonmodifiable) over more than 30 years of follow-up in DCCT/EDIC.

RESEARCH DESIGN AND METHODS

The retinopathy outcomes were proliferative diabetic retinopathy (PDR), clinically significant macular edema (CSME), and ocular surgery. The survival (event-free) probability was estimated using the Kaplan-Meier method. Cox proportional hazards models assessed the association between risk factors and subsequent risk of retinopathy. Both forward- and backward-selection approaches determined the multivariable models.

RESULTS

Rate of ocular events per 1,000 person-years was 12 for PDR, 14.5 for CSME, and 7.6 for ocular surgeries. Approximately 65%, 60%, and 70% of participants remained free of PDR, CSME, and ocular surgery, respectively. The greatest risk factors for PDR in descending order were higher mean HbA_1c, longer duration of T1D, elevated albumin excretion rate (AER), and higher mean diastolic blood pressure (DBP). For CSME, risk factors, in descending order, were higher mean HbA_1c, longer duration of T1D, and greater age and DBP and, for ocular surgeries, were higher mean HbA_1c, older age, and longer duration of T1D.

CONCLUSIONS

Mean HbA_1c was the strongest risk factor for the progression of retinopathy. Although glycemic control is important, elevated AER and DBP were other modifiable risk factors associated with the progression of retinopathy.

Proteomic Analysis of Early Diabetic Retinopathy Reveals Mediators of Neurodegenerative Brain Diseases

Purpose

Current evidence suggests that retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy. Our main goal was to examine whether, in the diabetic human retina, common proteins and pathways are shared with brain neurodegenerative diseases.

Methods

A proteomic analysis was performed on three groups of postmortem retinas matched by age: nondiabetic control retinas (n = 5), diabetic retinas without glial activation (n = 5), and diabetic retinas with glial activation (n = 5). Retinal lysates from each group were pooled and run on an SDS-PAGE gel. Bands were analyzed sequentially by liquid chromatography-mass spectrometry (LC/MS) using an Orbitrap Mass Spectrometer.

Results

A total of 2190 proteins were identified across all groups. To evaluate the association of the identified proteins with neurological signaling, significant signaling pathways belonging to the category “Neurotransmitters and Other Nervous System Signaling” were selected for analysis. Pathway analysis revealed that “Neuroprotective Role of THOP1 in Alzheimer's Disease” and “Unfolded Protein Response” pathways were uniquely enriched in control retinas. By contrast, “Dopamine Degradation” and “Parkinson's Signaling” were enriched only in diabetic retinas with glial activation. The “Neuregulin Signaling,” “Synaptic Long Term Potentiation,” and “Amyloid Processing” pathways were enriched in diabetic retinas with no glial activation.

Conclusions

Diabetes-induced retinal neurodegeneration and brain neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases, share common pathogenic pathways. These findings suggest that the study of neurodegeneration in the diabetic retina could be useful to further understand the neurodegenerative processes that occur in the brain of persons with diabetes.

Blood Pressure Is Associated with Receiving Intravitreal Anti-Vascular Endothelial Growth Factor Treatment in Patients with Diabetes

PURPOSE

Intravitreal anti-vascular endothelial growth factor (VEGF) injections are used commonly in the treatment of diabetic retinopathy (DR), but the need for treatment and frequency of administration vary considerably among patients. There is no way to predict which patients will require treatment and how frequently injections will be needed. This study aimed to identify factors associated with receiving anti-VEGF injections and the number of treatments received in an 18-month period in patients with diabetes.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Two thousand nine hundred sixteen patients with diabetes treated at the Kellogg Eye Center Retina Clinic from June 1, 2016, through December 31, 2017.

METHODS

Retrospective analysis was performed with institutional review board approval using data collected from diabetic patients treated at the retina clinic at the Kellogg Eye Center. Logistic regression was used to identify demographic and medical factors associated with receiving at least 1 injection. Negative binomial regression was used to model the number of anti-VEGF injections.

MAIN OUTCOME MEASURES

Receiving at least 1 anti-VEGF injection and the number of anti-VEGF injections received during the study period.

RESULTS

Systolic blood pressure and a diagnosis of DR were associated significantly with receiving an injection. A history of kidney disease was associated positively with the number of injections received. Type 1 diabetes was associated negatively with receiving an injection and the number of injections. Current hemoglobin A1c level was not associated with either receiving an injection or the number of injections.

CONCLUSIONS

Elevated blood pressure is associated significantly with the need for treatment with anti-VEGF injections in patients with diabetes, and a diagnosis of type 1 diabetes is associated negatively with both receiving treatment and the number of injections. Of note, current glycemic control is not associated significantly with either outcome measure. To our knowledge, these associations have not been previously reported, and imply that factors that confer risk for DR development may not be the same that confer risk for treatment.

Neurodegeneration in diabetic retinopathy: does it really matter?

The concept of diabetic retinopathy as a microvascular disease has evolved, in that it is now considered a more complex diabetic complication in which neurodegeneration plays a significant role. In this article we provide a critical overview of the role of microvascular abnormalities and neurodegeneration in the pathogenesis of diabetic retinopathy. A special emphasis is placed on the pathophysiology of the neurovascular unit (NVU), including the contributions of microvascular and neural elements. The potential mechanisms linking retinal neurodegeneration and early microvascular impairment, and the effects of neuroprotective drugs are summarised. Additionally, we discuss how the assessment of retinal neurodegeneration could be an important index of cognitive status, thus helping to identify individuals at risk of dementia, which will impact on current procedures for diabetes management. We conclude that glial, neural and microvascular dysfunction are interdependent and essential for the development of diabetic retinopathy. Despite this intricate relationship, retinal neurodegeneration is a critical endpoint and neuroprotection, itself, can be considered a therapeutic target, independently of its potential impact on microvascular disease. In addition, interventional studies targeting pathogenic pathways that impact the NVU are needed. Findings from these studies will be crucial, not only for increasing our understanding of diabetic retinopathy, but also to help to implement a timely and efficient personalised medicine approach for treating this diabetic complication.

Developmental and light regulation of tumor suppressor protein PP2A in the retina

Protein phosphatases are a group of universal enzymes that are responsible for the dephosphorylation of various proteins and enzymes in cells. Cellular signal transduction events are largely governed by the phosphorylation of key proteins. The length of cellular response depends on the activation of protein phosphatase that dephosphorylates the phosphate groups to halt a biological response, and fine-tune the defined cellular outcome. Dysregulation of these phosphatase(s) results in various disease phenotypes. The retina is a post-mitotic tissue, and oncogenic tyrosine and serine/ threonine kinase activities are important for retinal neuron survival. Aberrant activation of protein phosphatase(s) may have a negative effect on retinal neurons. In the current study, we characterized tumor suppressor protein phosphatase 2 (PP2A), a major serine/ threonine kinase with a broad substrate specificity. Our data suggest that PP2A is developmentally regulated in the retina, localized predominantly in the inner retina, and expressed in photoreceptor inner segments. Our findings indicate that PKCα and mTOR may serve as PP2A substrates. We found that light regulates PP2A activity. Our studies also suggest that rhodopsin regulates PP2A and its substrate(s) dephosphorylation. PP2A substrate phosphorylation is increased in mice lacking the A-subunit of PP2A. However, there is no accompanying effect on retina structure and function. Together, our findings suggest that controlling the activity of PP2A in the retina may be neuroprotective.

Approach for a Clinically Useful Comprehensive Classification of Vascular and Neural Aspects of Diabetic Retinal Disease

The Early Treatment Diabetic Retinopathy Study (ETDRS) and other standardized classification schemes have laid a foundation for tremendous advances in the understanding and management of diabetic retinopathy (DR). However, technological advances in optics and image analysis, especially optical coherence tomography (OCT), OCT angiography (OCTa), and ultra-widefield imaging, as well as new discoveries in diabetic retinal neuropathy (DRN), are exposing the limitations of ETDRS and other classification systems to completely characterize retinal changes in diabetes, which we term diabetic retinal disease (DRD). While it may be most straightforward to add axes to existing classification schemes, as diabetic macular edema (DME) was added as an axis to earlier DR classifications, doing so may make these classifications increasingly complicated and thus clinically intractable. Therefore, we propose future research efforts to develop a new, comprehensive, and clinically useful classification system that will identify multimodal biomarkers to reflect the complex pathophysiology of DRD and accelerate the development of therapies to prevent vision-threatening DRD.

Shared and distinct lipid-lipid interactions in plasma and affected tissues in a diabetic mouse model

Lipids are ubiquitous metabolites with diverse functions; abnormalities in lipid metabolism appear to be related to complications from multiple diseases, including type 2 diabetes. Through technological advances, the entire lipidome has been characterized and researchers now need computational approaches to better understand lipid network perturbations in different diseases. Using a mouse model of type 2 diabetes with microvascular complications, we examined lipid levels in plasma and in renal, neural, and retinal tissues to identify shared and distinct lipid abnormalities. We used correlation analysis to construct interaction networks in each tissue, to associate changes in lipids with changes in enzymes of lipid metabolism, and to identify overlap of coregulated lipid subclasses between plasma and each tissue to define subclasses of plasma lipids to use as surrogates of tissue lipid metabolism. Lipid metabolism alterations were mostly tissue specific in the kidney, nerve, and retina; no lipid changes correlated between the plasma and all three tissue types. However, alterations in diacylglycerol and in lipids containing arachidonic acid, an inflammatory mediator, were shared among the tissue types, and the highly saturated cholesterol esters were similarly coregulated between plasma and each tissue type in the diabetic mouse. Our results identified several patterns of altered lipid metabolism that may help to identify pathogenic alterations in different tissues and could be used as biomarkers in future research into diabetic microvascular tissue damage.

Diabetic retinopathy: research to clinical practice

BACKGROUND

Diabetic Retinopathy (DR) is a leading cause of visual impairment in the United States. The CDC estimates that the prevalence of DR will triple from 2005 to 2050.

MAIN BODY

The report summarizes major past advances in diabetes research and their impact on clinical practice. Current paradigms and future directions are also discussed.

CONCLUSIONS

DR is a leading cause of visual impairment in the US. Significant progress has been made in the understanding and treatment of DR, but rising prevalence demands innovative approaches to management in the future.

Multidimensional Functional and Structural Evaluation Reveals Neuroretinal Impairment in Early Diabetic Retinopathy

Purpose

To test whether quantitative functional tests and optical coherence tomography (OCT)-defined structure can serve as effective tools to diagnose and monitor early diabetic neuroretinal disease.

Methods

Fifty-seven subjects with diabetes (23 without diabetic retinopathy [no DR], 19 with mild nonproliferative diabetic retinopathy [mild NPDR], 15 with moderate to severe [moderate NPDR]), and 18 controls underwent full ophthalmic examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), e-ETDRS (Early Treatment Diabetic Retinopathy Study) acuity, and the quick contrast sensitivity function (qCSF) method. Perimetry testing included short-wavelength automated perimetry (SWAP), standard automated perimetry (SAP), frequency doubling perimetry (FDP), and rarebit perimetry (RBP).

Results

ETDRS acuity and RBP were not sensitive for functional differences among subjects with diabetes. AULCSF, a metric of qCSF, was reduced in diabetics with moderate compared to mild NPDR (P = 0.03), and in subjects with no DR compared to controls (P = 0.04). SWAP and SAP mean deviation (MD) and foveal threshold (FT) were reduced in moderate compared to mild NPDR (SWAP, MD P = 0.002, FT P = 0.0006; SAP, MD P = 0.02, FT P = 0.007). FDP 10-2 showed reduced MD in moderate compared to mild NPDR (P = 0.02), and FDP 24-2 revealed reduced pattern standard deviation (PSD) in mild NPDR compared to no DR (P = 0.02). Structural analysis revealed thinning of the ganglion cell layer and inner plexiform layer (GCL+IPL) of moderate NPDR subjects compared to controls. The thinner GCL+IPL correlated with impaired retinal function.

Conclusions

This multimodal testing analysis reveals insights into disruption of the neuroretina in diabetes and may accelerate the testing of novel therapies.

A proposal for early and personalized treatment of diabetic retinopathy based on clinical pathophysiology and molecular phenotyping

This paper presents a new approach to the prevention and treatment of early stage diabetic retinopathy before vision is severely impaired. This approach includes two major steps. The first step is to understand the mechanisms of vision impairment and classify diabetic retinopathy on the basis of pathophysiologic adaptations, rather than on the presence of advanced pathologic lesions, as defined by current clinical practice conventions. The second step is to develop patient-specific molecular diagnoses of diabetic retinopathy so that patients can be treated based on their individual characteristics, a process analogous to the individualized diagnosis and treatment of cancer patients. This step is illustrated by proteomic analysis of vitreous fluid that reveals evidence of neuroretinal degeneration and inflammation, as well as vascular proliferation. Together, these steps may lead to improved means to preserve vision in the ever-increasing number of patients with diabetes worldwide.

Ophthalmic Screening Patterns Among Youths With Diabetes Enrolled in a Large US Managed Care Network

Importance

Ophthalmic screening to check for diabetic retinopathy (DR) is important to prevent vision loss in persons with diabetes. The American Academy of Ophthalmology recommends that ophthalmic screening for DR occur beginning at 5 years after initial diabetes diagnosis for youths with type 1 diabetes; the American Diabetes Association recommends screening of youths with type 2 diabetes at the time of initial diagnosis. To our knowledge, it is unknown to what extent youths with diabetes obtain eye examinations in accordance with these guidelines.

Objective

To assess the rate of obtaining ophthalmic examinations and factors associated with receipt of eye examinations for youths with diabetes.

Design, Setting, and Participants

This retrospective, longitudinal cohort study examined youths 21 years or younger with newly diagnosed diabetes enrolled in a US managed care network from January 1, 2001, through December 31, 2014.

Main Outcomes and Measures

Kaplan-Meier survival curves estimated the time from initial diabetes diagnosis to first eye examination by an ophthalmologist or optometrist. Multivariable Cox proportional hazards regression models identified factors associated with receiving an ophthalmic examination after initial diabetes diagnosis.

Results

Among 5453 youths with type 1 diabetes (median age at initial diagnosis, 11 years; interquartile range, 8-15 years; 2972 male [54.5%]; 4505 white [82.6%]) and 7233 youths with type 2 diabetes (median age at initial diagnosis, 19 years; interquartile range, 16-22 years; 1196 male [16.5%]; 5052 white [69.9%]), 64.9% of patients with type 1 diabetes and 42.2% of patients with type 2 diabetes had undergone an eye examination by 6 years after initial diabetes diagnosis. Black youths (1367 [10.8%] of the sample) had an 11% and Latino youths (1450 [11.4%] of the sample) had an 18% decreased hazard of undergoing an eye examination by 6 years compared with white youths (black youths: adjusted hazard ratio [HR], 0.89; 95% CI, 0.79-0.99; Latino youths: HR, 0.82; 95% CI, 0.73-0.92). As household net worth increased, youths were increasingly more likely to undergo an eye examination by 6 years after initial diabetes diagnosis (net worth of ≥$500 000 vs <$25 000: HR, 1.50; 95% CI, 1.34-1.68).

Conclusions and Relevance

Despite possessing health insurance, many youths with diabetes are not receiving eye examinations by 6 years after initial diagnosis to monitor for DR. These data suggest that adherence to clinical practice guidelines is particularly challenging for racial minorities and youths from less affluent families.

Safety and Feasibility of Quantitative Multiplexed Cytokine Analysis From Office-Based Vitreous Aspiration

Purpose

The goals of this study were to evaluate the safety of office-based vitreous sampling, and determine the utility of these samples with multiplex cytokine analysis.

Methods

Vitreous samples were collected from office-based needle aspiration and the rate of adverse events during follow-up was reviewed. The vitreous cytokine concentrations in a subset of patients with diabetic macular edema (DME) were analyzed using a 42 plex-cytokine bead array. These results were compared with vitreous cytokine concentrations in proliferative diabetic retinopathy (PDR) and controls (macular hole, epiretinal membrane, symptomatic vitreous floaters) from pars plana vitrectomy.

Results

An adequate volume of vitreous fluid (100–200 μL) was obtained in 52 (88%) of 59 office-based sampling attempts. The average length of follow-up was 300 days (range, 42–926 days). There were no complications, including cataract, retinal tear or detachment, and endophthalmitis. Two patients (3%) had posterior vitreous detachments within 3 months. Vitreous cytokine concentrations were measured in 44 patients: 14 controls, 13 with DME, and 17 with PDR. The concentration of ADAM11, CXCL-10, IL-8, and PDGF-A were higher in PDR compared with controls and DME. The concentration of IL-6 was higher in PDR compared with controls, but not compared with DME.

Conclusions

Office-based vitreous aspiration is safe and yields high-quality samples for multiplex vitreous cytokine analysis. Significant elevations of vitreous cytokines were found in PDR compared with DME and controls, including the novel finding of elevated ADAM11. As such, office-based aspiration is a safe and effective means to identify vitreous factors associated with vitreoretinal disease.

Incidence and Risk Factors for Developing Diabetic Retinopathy among Youths with Type 1 or Type 2 Diabetes throughout the United States

PURPOSE

Despite the increasing prevalence of type 2 diabetes mellitus (T2DM) among children and adolescents, little is known about their risk of developing diabetic retinopathy (DR). We sought to identify risk factors for DR in youths with diabetes mellitus, to compare DR rates for youths with type 1 diabetes mellitus (T1DM) and those with T2DM, and to assess whether adherence to DR screening guidelines promoted by the American Academy of Ophthalmology, American Academy of Pediatrics, and American Diabetes Association adequately capture youths with DR.

DESIGN

Retrospective observational longitudinal cohort study.

PARTICIPANTS

Youths aged ≤21 years with newly diagnosed T1DM or T2DM who were enrolled in a large US managed-care network.

METHODS

In this study of youths aged ≤21 years with newly diagnosed T1DM or T2DM who were under ophthalmic surveillance, we identified the incidence and timing of DR onset. Kaplan-Meier survival curves assessed the timing of initial diagnosis of DR for participants. Multivariable Cox proportional hazard regression modeling identified factors associated with the hazard of developing DR. Model predictors were age and calendar year at initial diabetes mellitus diagnosis, sex, race/ethnicity, net worth, and glycated hemoglobin A1c fraction (HbA1c).

MAIN OUTCOME MEASURES

Hazard ratios (HRs) with 95% confidence intervals (CIs) for developing DR.

RESULTS

Among the 2240 youths with T1DM and 1768 youths with T2DM, 20.1% and 7.2% developed DR over a median follow-up time of 3.2 and 3.1 years, respectively. Survival curves demonstrated that youths with T1DM developed DR faster than youths with T2DM (P < 0.0001). For every 1-point increase in HbA1c, the hazard for DR increased by 20% (HR = 1.20; 95% CI 1.06-1.35) and 30% (HR = 1.30; 95% CI 1.08-1.56) among youths with T1DM and T2DM, respectively. Current guidelines suggest that ophthalmic screening begin 3 to 5 years after initial diabetes mellitus diagnosis, at which point in our study, >18% of youths with T1DM had already received ≥1 DR diagnosis.

CONCLUSIONS

Youths with T1DM or T2DM exhibit a considerable risk for DR and should undergo regular screenings by eye-care professionals to ensure timely DR diagnosis and limit progression to vision-threatening disease.

Impaired Retinal Vasoreactivity: An Early Marker of Stroke Risk in Diabetes

Diabetes is a common cause of small vessel disease leading to stroke and vascular dementia. While the function and structure of large cerebral vessels can be easily studied, the brain's microvasculature remains difficult to assess. Previous studies have demonstrated that structural changes in the retinal vessel architecture predict stroke risk, but these changes occur at late disease stages. Our goal was to examine whether retinal vascular status can predict cerebral small vessel dysfunction during early stages of diabetes. Retinal vasoreactivity and cerebral vascular function were measured in 78 subjects (19 healthy controls, 22 subjects with prediabetes, and 37 with type-2 diabetes) using a new noninvasive retinal imaging device (Dynamic Vessel Analyzer) and transcranial Doppler studies, respectively. Cerebral blood vessel responsiveness worsened with disease progression of diabetes. Similarly, retinal vascular reactivity was significantly attenuated in subjects with prediabetes and diabetes compared to healthy controls. Subjects with prediabetes and diabetes with impaired cerebral vasoreactivity showed mainly attenuation of the retinal venous flicker response. This is the first study to explore the relationship between retinal and cerebral vascular function in diabetes. Impairment of venous retinal responsiveness may be one of the earliest markers of vascular dysfunction in diabetes possibly indicating subsequent risk of stroke and vascular dementia.

The neurovascular unit and the pathophysiologic basis of diabetic retinopathy

PURPOSE

To relate the concept of the retinal neurovascular unit and its alterations in diabetes to the pathophysiology of diabetic retinopathy.

METHODS

Case illustrations and conceptual frameworks are presented that illustrate adaptive and maladaptive "dis-integration" of the retinal neurovascular unit with the progression of diabetes.

RESULTS

Retinopathy treatment should address pathophysiologic processes rather than pathologic lesions as is current practice.

CONCLUSIONS

Future improvements in the treatment of diabetic retinopathy requires deeper understanding of the cellular and molecular changes induced by diabetes, coupled with the use of quantitative phenotyping methods that assess the pathophysiologic processes.

Tissue-specific metabolic reprogramming drives nutrient flux in diabetic complications

Diabetes is associated with altered cellular metabolism, but how altered metabolism contributes to the development of diabetic complications is unknown. We used the BKS db/db diabetic mouse model to investigate changes in carbohydrate and lipid metabolism in kidney cortex, peripheral nerve, and retina. A systems approach using transcriptomics, metabolomics, and metabolic flux analysis identified tissue-specific differences, with increased glucose and fatty acid metabolism in the kidney, a moderate increase in the retina, and a decrease in the nerve. In the kidney, increased metabolism was associated with enhanced protein acetylation and mitochondrial dysfunction. To confirm these findings in human disease, we analyzed diabetic kidney transcriptomic data and urinary metabolites from a cohort of Southwestern American Indians. The urinary findings were replicated in 2 independent patient cohorts, the Finnish Diabetic Nephropathy and the Family Investigation of Nephropathy and Diabetes studies. Increased concentrations of TCA cycle metabolites in urine, but not in plasma, predicted progression of diabetic kidney disease, and there was an enrichment of pathways involved in glycolysis and fatty acid and amino acid metabolism. Our findings highlight tissue-specific changes in metabolism in complication-prone tissues in diabetes and suggest that urinary TCA cycle intermediates are potential prognostic biomarkers of diabetic kidney disease progression.

Insulin-like growth factor 1 rescues R28 retinal neurons from apoptotic death through ERK-mediated BimEL phosphorylation independent of Akt

Insulin-like growth factor 1 (IGF-1) can provide long-term neurotrophic support by activation of Akt, inhibition of FoxO nuclear localization and suppression of Bim gene transcription in multiple neuronal systems. However, MEK/ERK activation can also promote neuron survival through phosphorylation of BimEL. We explored the contribution of the PI3K/Akt/FoxO and MEK/ERK/BimEL pathways in IGF-1 stimulated survival after serum deprivation (SD) of R28 cells differentiated to model retinal neurons. IGF-1 caused rapid activation of Akt leading to FoxO1/3-T32/T24 phosphorylation, and prevented FoxO1/3 nuclear translocation and Bim mRNA upregulation in response to SD. IGF-1 also caused MAPK/MEK pathway activation as indicated by ERK1/2-T202/Y204 and Bim-S65 phosphorylation. Overexpression of FoxO1 increased Bim mRNA expression and amplified the apoptotic response to SD without shifting the serum response curve. Inhibition of Akt activation with LY294002 or by Rictor knockdown did not block the protective effect of IGF-1, while inhibition of MEK activity with PD98059 prevented Bim phosphorylation and blocked IGF-1 protection. In addition, knockdown of Bim expression was protective during SD, while co-silencing of FoxO1 and Fox03 expression had little effect. Thus, the PI3K/Akt/FoxO pathway was not essential for protection from SD-induced apoptosis by IGF-1 in R28 cells. Instead, IGF-1 protection was dependent on activation of the MEK/ERK pathway leading to BimEL phosphorylation, which is known to prevent Bax/Bak oligomerization and activation of the intrinsic mitochondrial apoptosis pathway. These studies demonstrate the requirement of the MEK/ERK pathway in a model of retinal neuron cell survival and highlight the cell specificity for IGF-1 signaling in this response.

Occludin S490 Phosphorylation Regulates Vascular Endothelial Growth Factor-Induced Retinal Neovascularization

Occludin is a transmembrane tight junction protein that contributes to diverse cellular functions, including control of barrier properties, cell migration, and proliferation. Vascular endothelial growth factor (VEGF) induces phosphorylation of occludin at S490, which is required for VEGF-induced endothelial permeability. Herein, we demonstrate that occludin S490 phosphorylation also regulates VEGF-induced retinal endothelial cell proliferation and neovascularization. Using a specific antibody, phospho-occludin was located in centrosomes in endothelial cell cultures, animal models, and human surgical samples of retinal neovessels. Occludin S490 phosphorylation was found to increase with endothelial tube formation in vitro and in vivo during retinal neovascularization after induction of VEGF expression. More important, expression of occludin mutated at S490 to Ala, completely inhibited angiogenesis in cell culture models and in vivo. Collectively, these data suggest a novel role for occludin in regulation of endothelial proliferation and angiogenesis in a phosphorylation-dependent manner. These findings may lead to methods of regulating pathological neovascularization by specifically targeting endothelial cell proliferation.