FABP4 Concentrations Quantified in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR), a progressive and serious stage of diabetic retinopathy (DR) due to retinal ischemia, is characterized by neovascularization (NV), vitreous hemorrhaging (VH) and tractional retinal detachment (TRD), all of which are major causes of blindness in patients with diabetes mellitus (DM).

Fatty acid-binding proteins (FABPs) that act as intracellular lipid chaperones are a group of molecules that coordinate lipid responses in cells. Among the currently known FABPs, the FABP4, known as adipocyte FABP (A-FABP) or aP2, is expressed in both adipocytes and macrophages, and can be detected in most bodily fluids.

Scientists specializing in Ophthalmology at the Sapporo Medical University School of Medicine (Sapporo, Japan) and their colleagues recruited 20 PDR patients (mean age 63.27 ± 11.9 years; 10 males and 10 females), and 20 non-DR patients (mean age 69.2 ± 9.1 years; eight males and 12 females). Body height and weight measurements, blood pressure measurements and the collection of peripheral blood specimens for a complete blood count and biochemical analyses were performed.

The team performed biochemistry measurements of the vitreous concentrations of FABP4 (V-FABP4) or vascular endothelial growth factor A (V-VEGFA) and several blood chemistry analyses including plasma glucose levels, hemoglobin A1c (HbA1c), creatinine (Cr), blood urea nitrogen (BUN), uric acid, aspartate transaminase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), lipid profiles, including total cholesterol and triglycerides, high-sensitivity C-reactive protein (hsCRP) and estimated glomerular filtration rate (eGFR). The concentrations of V-FABP4 (ng/mg protein) or V-VEGFA (pg/mg protein) were determined by enzyme-linked immunosorbent assay for FABP4 (Biovendor R&D, Modrice, Czech Republic) or human VEGFA (Fuji film Wako. Co., Osaka, Japan), respectively.

The investigators reported that the levels of V-FABP4 and V-VEGFA were significantly higher in PDR patients than in non-PDR patients with a high positive correlation between them. The findings were not affected by body mass index values and the presence of vitreous hemorrhaging. Among the clinical parameters, V-FABP4 correlated positively with creatinine and negatively with age and aspartate transaminase (AST) levels, while V-VEGFA correlated positively with fasting plasma glucose and hemoglobin A1c (HbA1c) levels, but negatively with AST. Multiple regression analyses indicated that V-VEGFA, or V-FABP4, AST and HbA1c were independent predictors of V-FABP4 or V-VEGFA, respectively. Both were negatively correlated, but more evident in V-FABP4, with the optic nerve head (ONH) ocular blood flow.

The authors concluded that the concentrations of both V-FABP4 and V-VEGFA were substantially elevated in eyes with PDR, and a significantly higher positive correlation was observed between them. However, correlation analyses and stepwise multiple regression analyses for V-FABP and V-VEGFA strongly suggested that both factors were independently regulated, suggesting that V-FABP4 might also be involved in the pathogenesis of PDR. The study was published on June 11, 2021 in the journal Scientific Reports.

Related Links:
Sapporo Medical University School of Medicine
Biovendor R&D
Fuji film Wako. Co