SERUM LEVELS OF ADIPOCYTE FATTY ACID BINDING PROTEIN 4 AND RETINOL BINDING PROTEIN 4 AS BIOMARKERS FOR EARLY DETECTION OF DIABETIC NEPHROPATHY IN TYPE 2 DIABETES

Background: Adipocyte fatty acid binding protein 4(A-FABP4) and retinol binding protein 4(RBP4) are recently discovered adipokines, which are members of lipocalin family. Both adipokines have been proposed to be important markers for metabolic syndrome and diabetes mellitus . Diabetic nephropathy is a leading cause of chronic kidney disease in patient starting renal replacement therapy and is associated with increased cardiovascular mortality . Objective: To study serum A-FABP4 and RBP4 levels in patients with type 2 DM with different stages of diabetic nephropathy and to investigate whether serum A-FABP4 and RBP4 could be used as biomarkers-in single or combination-for early detection of diabetic nephropathy.
Subjects and methods: 60 subjects were included in this study ,they were divided into six groups according urinary albumin excretion(UAE) and glomerular filtration rate (GFR) Group 1 (Control group) consists of 10 patients who are normo-albuminuric with normal GFR . Group 2 consists of 10 patients who are normoalbuminuric with increased GFR>120 Group 3 consists of 10 patients who are microalbuminuric i.e. UAE 30-300 mg/day. Group 4 consists of 10 patients who are macroalbuminuric i.e. UAE ≥ 300 mg/day without renal impairment (normal creatinine and GFR > 90 ml/min/1.73m²). Group 5 consists of 10 patients who are macroalbuminuric with renal impairment and declining GFR <90 ml/min/1.73m². Group 6 consists of 10 patients who are end-stage renal disease (GFR <15 ml/min/1.73m²). Measurement of serum AFABP4 , serum RBP4 , UAE, GFR were done for every subject
Results: There was significant increase in the serum level of AFABP4 and RBP4 among different stages of diabetic nephropathy and there was significant difference between microalbuminuric group and normoalbuminuric group so both biomarkers can be used for early detection of diabetic nephropathy. Both AFABP4 and RBP4 correlated positively with UAE and negatively with GFR. Conclusion: High circulating AFABP4 and RBP4 concentrations were demonstrated in early diabetic nephropathy in type 2 DM. AFABP4 and RBP4 increased significantly with the progression of diabetic nephropathy. Large scale multicenter and prospective studies are necessary to gather a definitive support that these adipokines might be directly involved in early detection of diabetic nephropathy and in impairment of kidney function in type 2 DM.