Impact of anti-VEGF treatment on development of proliferative diabetic retinopathy in routine clinical practice.

BACKGROUND: This study evaluated impact of anti-vascular endothelial growth factor (VEGF) treatment on proliferative diabetic retinopathy (PDR) development among patients with non-proliferative diabetic retinopathy (NPDR) in US real-world clinical practice. METHODS: This was a retrospective analysis of electronic medical records (Vestrum Health; January 2013 to June 2019) of eyes with baseline NPDR, without DME, and naïve to anti-VEGF treatment at index DR diagnosis. Eyes that received anti-VEGF and/or laser treatment over the course of study before development of PDR constituted the treated cohort while the remaining including those treated with laser constituted the anti-VEGF naïve cohort. Survival analysis via Kaplan-Meier method evaluated time to DME and PDR development by baseline NPDR severity, with anti-VEGF treatment as censoring variable. Baseline factors affecting PDR development were analyzed using Cox multivariable regression, censoring for anti-VEGF treatment. RESULTS: Among anti-VEGF-naive eyes, cumulative incidence of DME in eyes with mild (n = 70,050), moderate (n = 39,116), and severe NPDR (n = 10,692) at baseline was 27.1%, 51.2%, and 60.6%. Multivariable regression analysis identified baseline NPDR severity as the most significant predictor of PDR development over 48 months (hazard ratio [HR] [95% confidence interval {CI}] of 2.69 (2.65-2.72) for moderate vs mild NPDR and 6.51 (6.47-6.55) for severe vs mild NPDR). Cumulative incidence (95% CI) of PDR was 7.9% (7.4%-8.3%), 20.9%, (20.0%-21.7%) and 46.8% (44.4%-49.2%) over 48 months in eyes with mild, moderate, and severe NPDR at baseline, respectively. Among treated eyes with baseline severe NPDR, cumulative incidence of PDR at 48 months was 50.1% in eyes treated with laser (n = 546; HR [95% CI] vs no treatment: 0.8 [0.7-1.0]), 27.4% in eyes treated with anti-VEGF (n = 923; HR [95% CI]: 0.4 [0.4-0.5]), and 25.6% in eyes treated with anti-VEGF plus laser (n = 293; HR [95% CI]: 0.5 [0.4-0.7]) compared with 49.9% in eyes with no treatment (n = 8930). CONCLUSIONS: DME and PDR development rates increased with increasing baseline NPDR severity. Approximately half of anti-VEGF‒naive eyes with severe NPDR progressed to PDR within 4 years in US clinical practice. The progression rate from severe NPDR to PDR was approximately halved with anti-VEGF versus no treatment.

Accuracy of Artificial Intelligence in Estimating Best-Corrected Visual Acuity From Fundus Photographs in Eyes With Diabetic Macular Edema.

Importance: Best-corrected visual acuity (BCVA) is a measure used to manage diabetic macular edema (DME), sometimes suggesting development of DME or consideration of initiating, repeating, withholding, or resuming treatment with anti-vascular endothelial growth factor. Using artificial intelligence (AI) to estimate BCVA from fundus images could help clinicians manage DME by reducing the personnel needed for refraction, the time presently required for assessing BCVA, or even the number of office visits if imaged remotely. Objective: To evaluate the potential application of AI techniques for estimating BCVA from fundus photographs with and without ancillary information. Design, Setting, and Participants: Deidentified color fundus images taken after dilation were used post hoc to train AI systems to perform regression from image to BCVA and to evaluate resultant estimation errors. Participants were patients enrolled in the VISTA randomized clinical trial through 148 weeks wherein the study eye was treated with aflibercept or laser. The data from study participants included macular images, clinical information, and BCVA scores by trained examiners following protocol refraction and VA measurement on Early Treatment Diabetic Retinopathy Study (ETDRS) charts. Main Outcomes: Primary outcome was regression evaluated by mean absolute error (MAE); the secondary outcome included percentage of predictions within 10 letters, computed over the entire cohort as well as over subsets categorized by baseline BCVA, determined from baseline through the 148-week visit. Results: Analysis included 7185 macular color fundus images of the study and fellow eyes from 459 participants. Overall, the mean (SD) age was 62.2 (9.8) years, and 250 (54.5%) were male. The baseline BCVA score for the study eyes ranged from 73 to 24 letters (approximate Snellen equivalent 20/40 to 20/320). Using ResNet50 architecture, the MAE for the testing set (n = 641 images) was 9.66 (95% CI, 9.05-10.28); 33% of the values (95% CI, 30%-37%) were within 0 to 5 letters and 28% (95% CI, 25%-32%) within 6 to 10 letters. For BCVA of 100 letters or less but more than 80 letters (20/10 to 20/25, n = 161) and 80 letters or less but more than 55 letters (20/32 to 20/80, n = 309), the MAE was 8.84 letters (95% CI, 7.88-9.81) and 7.91 letters (95% CI, 7.28-8.53), respectively. Conclusions and Relevance: This investigation suggests AI can estimate BCVA directly from fundus photographs in patients with DME, without refraction or subjective visual acuity measurements, often within 1 to 2 lines on an ETDRS chart, supporting this AI concept if additional improvements in estimates can be achieved.

Anti-vascular endothelial growth factor dosing frequency and visual outcomes in macular oedema following branch retinal vein occlusion.

OBJECTIVES: To determine the relationship between treatment frequency with intravitreal anti-vascular endothelial growth factor (anti-VEGF) agents and visual acuity (VA) outcomes in eyes with macular oedema (MO) secondary to branch retinal vein occlusion (BRVO) in US clinical practice. METHODS: Study eyes that initiated anti-VEGF injections between January 2012 and May 2016 were followed for ≥1 year in a retrospective analysis of medical records (Vestrum Health database). Eyes were analysed in 2 cohorts by treatment duration (years 1 and 2) and then in 2 subcohorts by injection frequency (≤6 or ≥7 injections/year). RESULTS: Among 3099 eyes with MO secondary to BRVO, 1197 (38.6%) received ≤6 injections (mean injections, 4.6; baseline mean VA, 53 letters) and 1902 (61.4%) received ≥7 injections through 1 year (mean injections, 8.8; baseline mean VA, 52 letters). At year 1, mean VA gain from baseline was 10.4 versus 13.9 letters in eyes receiving ≤6 versus ≥7 injections (p < 0.001). At year 2, mean VA in eyes receiving ≤6 (n = 42) versus ≥7 injections (n = 227) was 64 versus 68 letters, respectively (p = 0.19). Mean VA change between the start and end of year 2 in eyes receiving ≥7 injections in year 1 and ≤6 in year 2 differed significantly from that of eyes receiving ≥7 injections in both years (-3.0 vs 0.7 letters, respectively; p < 0.001). CONCLUSIONS: In routine clinical practice, more frequent dosing with anti-VEGF agents was associated with greater visual benefits in eyes with MO secondary to BRVO.

Longitudinal Quantitative Ultrawide-field Fluorescein Angiography Dynamics in the RUBY Diabetic Macular Edema Study.

OBJECTIVE: The purpose of this study was to evaluate the longitudinal change in quantitative ultrawide-field angiographic (UWFA) parameters and correlate them with functional outcomes and spectral domain-OCT metrics. DESIGN: This study is a post hoc analysis of the phase II RUBY study: a prospective, randomized trial of patients with diabetic macular edema (DME) treated with either intravitreal aflibercept injection (IAI) or combined IAI/nesvacumab (antiangiopoietin 2 mAb). SUBJECTS: Subjects with DME that underwent UWFA across all treatment groups (n = 44). METHODS: A machine learning-enabled feature extraction system generated panretinal quantitative UWFA metrics, including leakage, ischemia, and microaneurysm (MA) burden. Zonal assessments were performed corresponding to the macula, midperiphery, and far periphery. MAIN OUTCOME MEASURES: Changes in ischemic area and index (proportion of nonperfusion in analyzable retina), leakage area and index (proportion of leakage in analyzable retina), and MA count at baseline, week 12, week 24, and week 36 were analyzed. Spectral-domain-OCT quantitative metrics, such as central subfield thickness, ellipsoid zone (EZ) integrity parameters, intraretinal fluid (IRF) volume, and subretinal fluid (SRF) volume were extracted via a machine learning-enhanced OCT feature extraction platform and analyzed. Additionally, the effect of these changes on best-corrected visual acuity (BCVA) was evaluated. RESULTS: Mean panretinal leakage index, zonal leakage area, and panretinal MA count improved significantly between baseline and week 36. Panretinal ischemic index decreased between baseline and week 36, with some aspects showing significant improvement. Mean BCVA significantly improved from baseline to week 36. There was a significant inverse correlation between change in BCVA and change in macular leakage area. A direct correlation was observed between both baseline macular leakage area and panretinal leakage index with IRF volume, SRF volume, and EZ disruption on OCT. CONCLUSIONS: Assessment of UWFA parameters demonstrates a significant improvement in panretinal leakage index, leakage area, and MA burden in eyes treated with IAI with or without nesvacumab. A numeric reduction in panretinal ischemic index and area was noted. The analysis also shows the critical association of leakage with visual and OCT features. This highlights the potential role of UWFA in disease burden assessment, with leakage parameters serving as a primary end point. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Functional outcomes of sustained improvement on Diabetic Retinopathy Severity Scale with intravitreal aflibercept in the VISTA and VIVID trials.

AIMS: To assess time to, cumulative incidence of, and functional benefit of achieving sustained ≥2-step Diabetic Retinopathy Severity Scale (DRSS) improvement in diabetic macular oedema (DMO). METHODS: Post hoc analysis of VISTA/VIVID including eyes with DMO treated with intravitreal aflibercept injections (IAI), 2 mg q4 weeks (2q4, n = 250) or q8 weeks after 5 monthly doses (2q8, n = 249), or laser control (n = 249). Changes from baseline in best-corrected visual acuity (BCVA) and central subfield thickness (CST) were evaluated in sustained (≥2 consecutive visits) DRSS subgroups (≥1-step worsening, no change, ≥2-step improvement). RESULTS: Time to sustained ≥2-step DRSS improvement was shorter for both the IAI 2q4 and IAI 2q8 groups versus laser (both log-rank p < 0.001). Cumulative incidences of sustained ≥2-step DRSS improvement with IAI 2q4 and IAI 2q8 versus laser were 40.0% and 42.8% versus 15.5% (both p < 0.001) through week 100. Mean differences (95% CI) in BCVA gains from baseline at weeks 52 and 100 between eyes with sustained ≥2-step DRSS improvement versus sustained ≥1-step DRSS worsening were -3.0 (-8.9, 2.9) and 6.2 (0.2, 12.2) letters with laser, and 4.2 (0.8, 7.6) and 4.9 (1.3, 8.4) letters with IAI combined, respectively. Difference (95% CI) in CST reduction was significantly greater only with IAI combined at week 100 (-83.0 [-140.8, -25.3]). Correlations between BCVA and CST changes were weak. CONCLUSIONS: DMO eyes treated with IAI achieved sustained ≥2-step DRSS improvement significantly earlier and more frequently versus laser. This improvement was associated with greater BCVA gains, independent of CST reductions. TRIAL REGISTRATION: ClinicalTrials.gov ( https://clinicaltrials.gov/ ) identifiers: NCT01363440 and NCT01331681 .

Time to Resolution of Diabetic Macular Edema after Treatment with Intravitreal Aflibercept Injection or Laser in VISTA and VIVID.

OBJECTIVE: To assess the relationship between baseline factors and time to diabetic macular edema (DME) resolution. DESIGN: Post hoc analysis of VISTA and VIVID. PARTICIPANTS: Eyes with baseline central subfield thickness (CST) of ≥ 290 µm. INTERVENTION: Eyes were treated with intravitreal aflibercept injection (IAI) 2 mg (n = 558; every 4 weeks or every 8 weeks after 5 monthly doses) or laser control (n = 274). The effect of baseline factors on the time to DME resolution (CST < 290 µm) was assessed in univariable and multivariable models and further evaluated by the Kaplan-Meier method. MAIN OUTCOME MEASURES: Time to and cumulative incidence of DME resolution. RESULTS: Eyes treated with IAI had a 2.5-fold higher DME resolution rate, with median time of 33.0 weeks (95% confidence interval [CI], 28.1-40.0), compared with DME resolution not being achieved in 50% of eyes treated with laser control. Multivariable analysis demonstrated that a lower DME resolution rate was associated with a thicker baseline CST (hazard ratio [HR] [95% CI] per 100-µm CST increase, 0.79 [0.72-0.86]) and better baseline best-corrected visual acuity (BCVA) (HR [95% CI] per 5-letter increase, 0.87 [0.83-0.92]) with IAI. Tertiles of increasing CST (T1CST ≤ 419 µm; T2CST > 419 to ≤ 541; T3CST > 541) were associated with longer median times to DME resolution (20.1, 39.1, and 49.1 weeks, respectively; P < 0.001 for T2CST and T3CST versus T1CST) and lower cumulative incidence of events (HR, 1.0, 0.6, and 0.6, respectively; P < 0.001 for T2CST and T3CST versus T1CST) with IAI. Tertiles of increasing BCVA (T1BCVA ≤ 57 letters; T2BCVA > 57 to ≤ 66; T3BCVA >66) were associated with longer median times to DME resolution (28.4, 31.7, and 44.1 weeks, respectively; P < 0.05 for T3BCVA versus T1BCVA) and lower cumulative incidence of events (HR, 1.0, 0.9, and 0.8, respectively; P < 0.05 for T3BCVA versus T1BCVA) with IAI. No other baseline factor was associated with the time to DME resolution. CONCLUSIONS: The median time to DME resolution was 33 weeks among IAI-treated eyes. A thicker baseline CST and better baseline BCVA in the IAI group were associated with a longer time to and a lower rate of DME resolution.

INCIDENCE OF NEW DIABETIC MACULAR EDEMA IN FELLOW EYES OF PATIENTS IN THE VISTA AND VIVID STUDIES.

PURPOSE: To characterize diabetic macular edema (DME) incidence in fellow eyes of patients treated for DME in the study eye. METHODS: This post hoc analysis of VISTA/VIVID data evaluated fellow eyes without DME at baseline through Week 100. Diabetic macular edema presence in the fellow eye was inferred by investigator-reported DME adverse events and use of DME treatments. RESULTS: Over 100 weeks, 44.9%, 44.2%, and 42.9% of fellow eyes developed DME in the intravitreal aflibercept injection 2 mg every 4 weeks (n = 245), intravitreal aflibercept injection 2 mg every 8 weeks (n = 258), and laser control (n = 252) groups, respectively. Mean time to DME development in combined treatment groups was ∼6 months. Multivariable regression analysis confirmed patients with shorter diabetes duration (hazard ratio per 10-year decrease, 1.16; 95% confidence interval, 1.03-1.30; P = 0.0160) and thicker baseline study eye central subfield thickness (hazard ratio per 10- µ m increase, 1.01; 95% confidence interval, 1.01-1.02; P = 0.0002) were at higher risk of developing DME in the fellow eye. CONCLUSION: Among patients with DME in one eye at baseline, almost half developed DME in the fellow eye over 2 years. Shorter duration of diabetes and thicker study eye central subfield thickness were predictors of DME development in the fellow eye.

Correlation between change in central subfield thickness and change in visual acuity in macular edema due to retinal vein occlusion: post hoc analysis of COPERNICUS, GALILEO, and VIBRANT.

PURPOSE: Assess correlation between change in central subfield thickness (CST) and change in best-corrected visual acuity (BCVA) in eyes with macular edema due to retinal vein occlusion (RVO) that received intravitreal aflibercept injections (IAI). METHODS: Post hoc analysis of COPERNICUS and GALILEO trials for CRVO and VIBRANT trial for BRVO with relationships determined using Pearson correlation coefficient. RESULTS: In COPERNICUS, correlations (r) between change in CST and change in BCVA from baseline at weeks 12, 24, 52, and 100 were -0.36 (95% CI: -0.52, -0.18; P < 0.001), -0.38 (95% CI: -0.53, -0.20; P < 0.001), -0.44 (95% CI: -0.58, -0.27; P < 0.001), and -0.41 (95% CI: -0.56, -0.23; P < 0.001), respectively. CST changes accounted for only 21% of the variance in BCVA changes; every 100-µm decrease in CST was associated with a 2.1-letter increase in BCVA (P = 0.003). Similar findings were noted for GALILEO (r, -0.45 to -0.23) and VIBRANT (r, -0.36 to -0.32) trials. CONCLUSION: In eyes treated with IAI for macular edema due to RVO, correlation between change in CST and change in BCVA was weak to moderate. While change in CST may be helpful in determining the need for anti-VEGF therapy, these findings do not support using changes in CST as a surrogate for changes in visual acuity outcomes.

Correlation of Change in Central Subfield Thickness and Change in Visual Acuity in Neovascular AMD: Post Hoc Analysis of VIEW 1 and 2.

PURPOSE: Determine correlation between change in central subfield thickness (CST) and change in best-corrected visual acuity (BCVA) in neovascular age-related macular degeneration receiving anti-vascular endothelial growth factor agents. DESIGN: A post hoc analysis of VIEW 1 and 2 randomized clinical trials. METHODS: This analysis included participants randomized to ranibizumab 0.5 mg every 4 weeks (Rq4), intravitreal aflibercept injection 2 mg every 4 weeks (2q4), and intravitreal aflibercept injection 2 mg every 8 weeks after 3 monthly doses (2q8) to week 52, followed by capped as-needed (at least every 12 weeks) dosing to week 96. Relationship between changes in CST and BCVA was determined using Pearson correlation coefficient. RESULTS: Of 1815 eyes, 595 were assigned to the Rq4, 613 to 2q4, and 607 to 2q8 arms. Correlations (95% confidence intervals [CI]) at weeks 12, 52, and 96 were -0.08 (95% CI, -0.17 to 0.00), -0.05 (95% CI, -0.14 to 0.04), and -0.15 (95% CI, -0.24 to -0.06) for Rq4; -0.13 (95% CI, -0.21 to -0.04), -0.06 (95% CI, -0.14 to 0.03) and -0.04 (95% CI, -0.13 to 0.05) for 2q4, and -0.04 (95% CI, -0.12 to 0.05), -0.01 (95% CI, -0.09 to 0.08), and -0.01 (95% CI, -0.10 to 0.09) for 2q8. Linear regression analysis adjusted for relevant baseline factors showed CST changes accounted for 11% of BCVA changes. Every 100 µm decrease in CST was associated with a 0.3 letter decrease (P = .25) at week 52 and a 0.14 letter decrease (P = .69) at week 96. CONCLUSIONS: Weak or no correlation was found between changes in CST and BCVA with either agent or regimen, suggesting changes in CST should not be used as a surrogate for visual acuity outcomes in neovascular age-related macular degeneration.

Effects of Repeated Intravitreal Aflibercept Injection on the Corneal Endothelium in Patients With Age-Related Macular Degeneration: Outcomes From the RE-VIEW Study.

PURPOSE: The effects of repeated intravitreal aflibercept injection (IAI) on the corneal endothelium were studied in patients with unilateral neovascular age-related macular degeneration. METHODS: RE-VIEW was a phase 4, open-label, single-arm, multicenter study. Patients received IAI every 8 weeks after 3 monthly doses. Slit-lamp biomicroscopy was performed at all study visits. The central corneal endothelial health was evaluated by specular microscopy in the treated versus untreated fellow eyes at baseline and weeks 24 and 52. RESULTS: No slit-lamp abnormalities were noted in 154 enrolled patients (eyes). Baseline versus 52-week mean (±SD) endothelial morphometric values (n = 118) for the treated versus untreated fellow eyes were respectively as follows: endothelial cell density was 2410 ± 364 versus 2388 ± 384 cells/mm at baseline and remained unchanged at 2401 ± 353 versus 2376 ± 364 cells/mm at 52 weeks (P = 0.87); the coefficient of variation was 33.5 ± 4.4% versus 34.0 ± 5.0% at baseline and remained unchanged at 34.2 ± 4.7% versus 34.1 ± 4.9% at 52 weeks (P = 0.18); the percentage of hexagonal cells was 59.5 ± 5.8% versus 59.6 ± 6.4% at baseline and remained unchanged at 59.5 ± 6.0% versus 59.5 ± 5.8% at 52 weeks (P = 0.96). CONCLUSIONS: Repeated IAI for 52 weeks had no apparent corneal endothelial toxicity noted on specular microscopy in patients treated for neovascular age-related macular degeneration.

Microperimetric assessment of retinal sensitivity in eyes with diabetic macular edema from a phase 2 study of intravitreal aflibercept.

PURPOSE: To evaluate retinal sensitivity in patients with diabetic macular edema who received intravitreal aflibercept injection (IAI) or laser. METHODS: A substudy included 46 patients from DA VINCI (a randomized, double-masked Phase 2 study) receiving either laser, 0.5 mg IAI every 4 weeks, 2 mg IAI every 4 weeks, 2 mg IAI every 8 weeks after 3 monthly doses (2q8), or 2 mg IAI as-needed after 3 monthly doses for 52 weeks. Retinal sensitivity was measured in one (central), five (one central and four inner), and eight (four inner and four outer) optical coherence tomography subfields. RESULTS: Mean best-corrected visual acuity improvement in the subgroup at Week 52 was 3.3 letters with laser and ranged from 5.4 to 16.3 letters in the IAI groups. Retinal sensitivity of laser patients at Week 52 was comparable with baseline in the central optical coherence tomography subfield but decreased in the five and eight optical coherence tomography subfields. Compared with laser, retinal sensitivity significantly increased with IAI in the 2q8 and pooled IAI groups in the 5 and 8 optical coherence tomography subfields at Week 52 (P < 0.05). CONCLUSION: Intravitreal aflibercept injection improved best-corrected visual acuity and retinal sensitivity in this subgroup of patients. Laser may cause a deterioration of macular function that is not detectable with best-corrected visual acuity testing.

Nitric oxide, endothelin-1, and superoxide production in arterial bypass grafts.

In this study, basal and thrombin-stimulated release of nitric oxide and endothelin-1 in the internal mammary artery and the radial artery were measured, together with superoxide radicals generated after anoxia and reoxygenation. Arterial segments were obtained from patients undergoing coronary bypass operations. Quantification of nitric oxide was performed by measuring the stable oxidation products of nitric oxide. Endothelin levels were measured by an enzyme immunoassay kit, and the superoxides were measured by lucigenin-enhanced chemiluminescence. Basal and stimulated release of nitric oxide from the internal mammary artery is significantly higher than that in the radial artery. On the other hand, basal release of endothelin-1 is less in the internal mammary artery than in the radial artery, but similar after stimulation. In our study, the quantity of superoxide radicals produced by the internal mammary artery was greater than that produced by the radial artery. Our results show that there are differences between these 2 arteries in regard to production of nitric oxide, endothelin-1, and superoxide radicals. These differences may have a role in the process of atherogenesis and may contribute to long-term patency of arterial bypass grafts. These results may also explain the mechanism of radial artery graft spasm in coronary artery surgery and may constitute a basis for future pharmacological and clinical improvements for successful surgical application.

ESR and cell culture studies on free radical-scavenging and antioxidant activities of isoflavonoids.

Isoflavonoids are thought to be the biologically active components in soy that play a role in the prevention of coronary heart disease and breast and prostate cancer. Mechanisms to explain how isoflavonoids mediate beneficial effects have not yet been clearly established. This study was undertaken to investigate the free radical-scavenging and antioxidant activities of various structure-related isoflavonoids including genistein, daidzein, biochanin A, and genistin in a cell-free and an endothelial cell model system. Electron spin resonance spectroscopy and spin trapping techniques were applied to evaluate the ability of isoflavonoids to scavenge hydroxyl, superoxide, nitric oxide, diphenylpicrylhydrazyl, galvinoxyl, and lipid-derived radicals. All isoflavonoids tested had no significant scavenging effects on the aforementioned radicals in concentrations up to 1.0 mM. However, at a physiologically achievable concentration of 5 nM, both genistein and daidzein slightly increased intracellular-reduced glutathione levels approximately by 10 and 30%, respectively, in human endothelial cells, whereas cellular alpha-tocopherol and uric acid remained unchanged by the isoflavonoid treatments. Present data indicate that free radical-scavenging activities of the isoflavonoids tested probably do not substantially contribute to their antioxidant properties. The ability of genistein and daidzein to increase cellular GSH (reduced glutathione) might be important for their action in biological system.

R-alpha-lipoic acid action on cell redox status, the insulin receptor, and glucose uptake in 3T3-L1 adipocytes.

The insulin signaling pathway has been reported to mediate R-alpha-lipoic acid- (R-LA-)-stimulated glucose uptake into 3T3-L1 adipocytes and L6 myotubes. We investigated the role of the thiol antioxidant dihydrolipoic acid (DHLA) and intracellular glutathione (GSH) in R-LA-stimulated glucose transport and explored the hypothesis that R-LA could increase glucose uptake into 3T3-L1 adipocytes in an oxidant-mimetic manner. R-LA pretreatment of 3T3-L1 cells stimulated glucose transport at early time points (30 min - 6 h), whereas it inhibited glucose uptake at later time points. Analysis of the oxidized and reduced content of LA in cells and medium showed that >90% of lipoic acid present was in its oxidized form. Furthermore, all oxidized forms of LA (S-, R-, and racemic LA) stimulated glucose uptake, whereas the reduced form, dihydrolipoic acid, was ineffective. Intracellular GSH levels were not changed at the early time points (before 12 h), while longer preincubation (24 - 48 h) of cells with R-LA significantly increased intracellular GSH. Pretreatment of adipocytes with R-LA increased intracellular peroxide levels at early time points (30 min - 6 h), after which it was decreased (12 - 48 h). R-LA also increased tyrosine phosphorylation of immunoprecipitated insulin receptors from 3T3-L1 adipocytes. These results indicate that (i) 3T3-L1 adipocytes have a low capacity to reduce R-LA and the oxidized form of lipoic acid is responsible for stimulating glucose uptake, (ii) R-LA modulates glucose uptake by changing the intracellular redox status, and (iii) the insulin receptor is a potential cellular target for R-LA action.