Systemic imbalance of TGF-β isoforms in patients with various manifestations of diabetic retinopathy

Abstract

Transforming growth factor-β (TGF-β) is a group of structurally similar multifunctional regulatory proteins that exhibit pleiotropy in various tissues of the body. Considering that TGF-β isoforms show tropism to various cells, and in diabetic retinopathy both a neurodegenerative process and damage to microvessels can be simultaneously realized, we believe that the study of the content of TGF-β1, TGF-β2, and TGF-β3 in patients with various manifestations of diabetic retinopathy (DR) is relevant. The aim of the study was to determine the levels of TGF-β1, TGF-β2, and TGF-β3 in the blood serum in patients with neurodegenerative and vascular manifestations of diabetic retinopathy against the background of type 2 diabetes mellitus. The study involved 80 patients diagnosed with type 2 diabetes mellitus and 30 healthy volunteers. Based on ophthalmoscopy and optical coherence tomography (OCT), patients with type 2 diabetes mellitus were divided into 4 groups: Group 1 (n = 12) – patients without vascular symptoms of fundus DR and without OCT signs of retinal neurodegeneration; Group 2 (n = 28) – patients without vascular symptoms of fundus DR and the presence of OCT signs of retinal neurodegeneration; Group 3 (n = 10) – patients with vascular symptoms of non-proliferative DR and without OCT signs of retinal neurodegeneration; and Group 4 (n = 30) – patients with vascular symptoms of non-proliferative DR and the presence of OCT signs of retinal neurodegeneration. The serum content of TGF-β1 in all groups was within the reference values throughout the study. The serum concentration of TGF-β2 in all groups was higher in comparison with the control group. The content of TGF-β3 in the blood serum of patients with neurodegenerative manifestations of diabetic retinopathy (groups 2 and 4) was significantly lower than the reference values. A more pronounced deficiency was observed in group 4, whose patients had both vascular and neurodegenerative signs of DR. The presented study showed the presence of a systemic imbalance in the levels of TGF-β1, TGF-β2, and TGF-β3 in vascular and neuronal manifestations of diabetic retinopathy. The results obtained confirm the data that changes in the production of cytokines from the TGF-β family in one pathological process can be multidirectional.