Evaluation of blood interleukin levels and their correlations in the patients with diabetic retinopathy with mild and moderate cognitive impairment

Abstract

Systemic immunological disorders are associated with various geriatric conditions, including cognitive dysfunction. However, in patients with diabetic retinopathy, the changes of blood interleukin profile were studied without considering the severity of cognitive impairment. The aim of this study was to analyze blood plasma levels and intercorrelations of interleukins in the patients with diabetic retinopathy accompanied by mild and moderate cognitive impairment. Fifty-four elderly patients with diabetic retinopathy and mild cognitive impairment, and 62 patients with diabetic retinopathy and moderate cognitive disorders underwent inpatient examination and treatment at the Tambov branch of the S. Fedorov Center of Eye Microsurgery over 2021-2022. The interleukins contents in blood plasma were studied by enzyme immunoassay using the Protein Contour kit, including IL-1α, IL-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12, IL-17, IL-18. The diagnostics of diabetic retinopathy was based on comprehensive ophthalmological examination, according to the Clinical recommendations of the Society of the Russian Association of Ophthalmologists «Diabetes mellitus: diabetic retinopathy, diabetic macular edema». Cognitive functions were assessed according to a valid Mini- Mental-State-Examination scale. It has been shown that the patients with diabetic retinopathy and moderate cognitive impairment have a significantly increased level of all the studied proinflammatory interleukins, as compared to similar cohort with diabetic retinopathy accompanied by a mild cognitive impairment. In mild cognitive disorders, the content of IL-6 in blood plasma was higher (24.4±2.1 pg/mL versus 5.1±0.8 pg/mL, p < 0.001). Development of moderate cognitive impairment in the patients with diabetic retinopathy was also accompanied by a statistically significant increase of plasma IL-8 to 36.7±3.5 pg/mL versus 10.5±2.3 pg/mL with mild cognitive impairment; IL-17, to 21.9±1.8 pg/mL versus 8.5±1.1 pg/mL, respectively. Concentrations of anti-inflammatory interleukins in blood plasma of the patients with diabetic retinopathy and moderate cognitive dysfunction were significantly decreased, i.e., IL-4 to 2.1±0.3 pg/mL versus 3.4±0.5 pg/mL in cases of mild mental deterioration; IL-10, to 8.7±0.5 pg/mL versus 15.4±1.3 pg/mL, respectively. A sufficient correlation was shown between the levels of systemic interleukins and moderate cognitive disorders in the patients with diabetic retinopathy. For the proinflammatory interleukins in cases of moderate cognitive impairment, an inverse correlations with IL-1β (r = -0.336; p = 0.021), IL-6 (r = -0.584; p = 0.019), IL-8 (r = -0.469; p = 0.006), and with IL-17 (r = -0.348; p = 0.018) were shown. The content of IL-4 and IL-10 in blood plasma of the patients with diabetic retinopathy correlated with moderate cognitive impairment at a significant level of r = +0,407 (p = 0.016) and r = +0.359 (p = 0.008), respectively. In mild cognitive impairment, the correlations with fewer numbers of interleukins were revealed, i.e., IL-1β, IL-6, IL-8 and IL-10, and exhibit weaker connections, except of IL-6 (a moderate connection level). Development of moderate cognitive impairment among the patients with diabetic retinopathy may be caused by increase in IL-1β, IL-6, IL-8, IL-17, and a decrease in IL-10.