Inflammatory Tear Cytokine Levels May Vary According to Diabetic Severity

Diabetes and the severity of progression affect the tear concentrations of IL-1RA, IL-8, and TNF-α inflammatory cytokines, according to a study published in Experimental Eye Research. 

Researchers enrolled 90 participants (52% women) in a cross-sectional study and stratified them into 4 groups: control group participants (n=20; mean age, 46.05 years), patients with diabetes without retinopathy (n=20; mean age, 47.75 years), patients with diabetes and non-proliferative diabetic retinopathy (NPDR; n=25; mean age, 52.04 years), and patients with proliferative diabetic retinopathy (PDR; n=25; mean age, 52.92 years). All participants with diabetes were diagnosed as having type 2.

Approximately 50 μL of basal tears were collected from each participant at the same time of day (from 9 AM to 11 AM) to prevent diurnal variations in cytokine concentrations. The samples were immediately frozen at -70 ° C to prevent structural changes in the peptides and sent to the laboratory. 

According to the report, patients with diabetes had higher TNF-α (437.5 vs 233.4 ng/L) and IL-8 (291.0 vs 234.8) concentrations compared with control individuals (P =.001 for both). TNF-α concentration was higher among patients with NPDR compared with patients with diabetes and no retinopathy (P =.026) and lower among patients with PDR compared with patients with NPDR (P =.028). All subgroups with diabetes had a higher mean IL-8 concentration compared with control group participants, but statistical significance remained only between patients with PDR compared with patients with diabetes and no diabetic retinopathy (P=.028) following the intensification of retinal involvement.

Control group participants had higher IL-IRA concentrations compared with participants with diabetes (622.8 vs 278.6 ng/L; P =.001)

“Tear values of various inflammatory mediators (TNF-α, IL-8, IL-1RA), changes in patients with diabetes, and onset and severity of retinopathy may be monitored by assessing the tear concentrations of these cytokines,” according to researchers.

Study limitations include the evaluation of a limited number of cytokines, lack of access to laboratory tests, and a single center design.