Metformin suppresses pro-inflammatory cytokines in vitreous of diabetes patients and human retinal vascular endothelium

Metformin is a traditional anti-hyperglycemic medication that has recently been shown to benefit vascular complications of diabetes via an anti-inflammatory mechanism other than glycemic control. This study aims to test the hypothesis that metformin suppresses diabetic retinopathy (DR) associated intraocular inflammation. Human vitreous from control and proliferative diabetic retinopathy (PDR) patients with or without long-term metformin treatment (> 5 years) were collected for multiple inflammatory cytokines measurements with a cytokine array kit. The vast majority of the measurable cytokines in PDR vitreous has a lower level in metformin group than non-metformin group. Although the p values are not significant due to a relatively small sample size and large deviations, the 95% confidence interval (CI) for the mean difference between the two groups shows some difference in the true values should not be neglected. Using quantitative ELISA, soluble intercellular adhesion molecule -1 (ICAM-1) and monocyte chemoattractant protein -1 (MCP-1) presented with significantly lower concentrations in metformin group versus non-metformin group. Metformin group also has significantly less up-regulated cytokines and diminished positive correlations among the cytokines when compared to non-metformin group. Possible role of AMP-activated protein kinase (AMPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in metformin’s anti-inflammatory effects were studied in human retinal vascular endothelial cells (hRVECs) cultured in normal glucose (NG) and high glucose (HG) conditions. Metformin inhibited HG-induced ICAM-1, IL-8, and MCP-1 via AMPK activation, whereas pharmacological AMPK inhibition had no effect on its inhibition of NF-κB p65, sICAM-1, and tumor necrosis factor-α (TNF-α). Metformin-induced suppression of the inflammatory cytokines could also be mediated through its direct inhibition of NF-κB, independent of AMPK pathway. This is a proof-of-concept study that found metformin treatment was associated with reduced inflammatory responses in vitreous of diabetes patients and retinal vascular endothelial cells, supporting the rationale for using metformin to treat DR at an early stage.

Pyramidal Inflammatory Deposits of the Retinal Pigment Epithelium and Outer Retina in Ocular Syphilis

PURPOSE

To evaluate the role of OCT in the diagnosis of uveitis secondary to syphilis.

DESIGN

Consecutive, retrospective case series.

PARTICIPANTS

All patients 18 years of age or older with ocular syphilis from 2 tertiary referral centers.

METHODS

All patients who were diagnosed with intermediate uveitis, posterior uveitis, or panuveitis secondary to syphilis were included in the study (40 patients representing a total of 62 eyes) to identify important imaging features to aid in diagnosis. Patients underwent confirmatory serologic testing, OCT imaging, and dilated examination by a uveitis specialist.

MAIN OUTCOME MEASURE

Hyperreflective retinal lesions on OCT.

RESULTS

The mean age of the study population was 42.9 ± 12.16 years. Forty-five percent of the eyes included in this study harbored hyperreflective pyramidal lesions of the outer retina and retinal pigment epithelium on OCT. Fifty-four percent of eyes with these imaging findings did not show a placoid retinal lesion on examination. Sixty-eighty percent of the described outer retinal lesions on OCT resolved after treatment for syphilis. Visual acuity ranged from normal (20/20) to no light perception, with a mean of 20/43 at diagnosis, and improved significantly to a mean visual acuity of 20/26 after treatment (P < 0.05). Vision-threatening complications were seen in less than 5% of eyes and included both treatable and irreversible causes of vision loss, including retinal detachment, cystoid macular edema, and optic neuropathy.

CONCLUSIONS

Patients treated for uveitis secondary to syphilis achieve good visual recoveries. Outer retinal lesions seen on OCT are common and can serve as an additional imaging finding of the disease.