The relationship between serum apelin level and different grades of diabetic nephropathy in type 2 diabetic patients

Background
Diabetic nephropathy (DN) is the leading cause of renal failure. Diabetic patients with microalbuminuria typically progress to proteinuria and overt DN. Similar to other microvascular complications of diabetes, there are strong associations between glucose control (as measured using HbA1c) and the risk of developing DN. Apelin (APLN), a peptide first isolated from bovine stomach tissue extracts, is the endogenous ligand for the G-protein-coupled APJ receptor that is expressed at the surface of some cell types. APLN and APJ are widely expressed in homogenates from animal organs in a pattern shared with angiotensinogen and the angiotensin receptor. APLN is widely distributed in the central nervous system and periphery, especially in the heart, kidney, lung, and mammary glands. The APLN–APJ system may be involved in the pathogenesis of DN, which may play a renoprotective role partially by antagonizing the angiotensin II–ATIR pathway.
Aim
The aim of this study was to investigate the relation between serum APLN and different grades of DN in type 2 diabetic patients.
Patients and methods
This study was conducted on 150 diabetic patients and 20 controls selected from the inpatient department and outpatient clinics of the Internal Medicine Department in Menoufia University Hospital. The selected participants were divided into four groups: group 1 included 20 healthy controls; group 2 included 50 type 2 diabetes mellitus (T2DM) patients with normoalbuminuria; group 3 included 50 T2DM patients with microalbuminuria; and group 4 included 50 T2DM patients with macroalbuminuria. Members of the study groups were subjected to thorough history taking with special emphasis on age, sex, and duration of diabetes mellitus. Investigations included liver profile, complete blood count, fasting and 2 h postprandial plasma glucose, glycosylated hemoglobin (HbA1c), complete urine analysis, kidney function tests (blood urea nitrogen and serum creatinine), urine albumin/creatinine ratio, estimated glomerular filtration rate, and serum APLN.
Results
Serum APLN was significantly higher in group 4 compared with the other groups, in group 3 compared with groups 1 and 2, and in group 2 compared with group 1. There was a significant positive correlation between serum APLN and serum creatinine, urine albumin/creatinine ratio, and HbA1c. Further, there was a significant negative correlation between serum APLN and estimated glomerular filtration rate in the studied diabetic patients. There was no correlation between serum APLN and BMI in diabetic patients.
Conclusion
From this study, we can conclude that serum APLN is significantly higher in patients with DN compared with diabetic patients without nephropathy, and there is a positive correlation between serum apelin and the degree of DN. Thus, APLN may play an important role in the development of DN.