Serum Adiponectin as a Diagnostic Marker of Nephropathy among Patients with Type 2 Diabetes Mellitus: A Cross-sectional Study

Introduction: Diabetic Nephropathy (DN) is the leading cause of End-Stage Renal Disease (ESRD) among Type 2 Diabetes Mellitus (T2DM) patients and it is a diagnosed by laboratory investigation like albuminuria. Albuminuria is a conventional and not a sensitive, specific marker for diagnosis of nephropathy. Additionally some of the patients shows advanced renal pathological changes without albuminuria and some of the patients with microalbuminuria revert back to normoalbuminuria. However, there is need for early detection, sensitive and specific marker for nephropathy. Serum adiponectin is an adipocytokine synthesised from adipose tissue, liver, kidney, heart, salivary glands. This has physiological properties like antidiabetic, antioxidative and anti-inflammatory properties beneficial for particularly in patient with T2DM. Adiponectin activates Adenosine Mono Phosphate (AMP) Kinase and Nicotinamide Adenine Dinucleotide Phosphate (NADPH) pathways results in improve insulin sensitivity and preventing albumin excretion in urine. Increased adiponectin levels are beneficial to patients with T2DM and its complications.Aim: To determine serum adiponectin levels for the prediction of early onset of nephropathy in patients with T2DM.Materials and Methods: This cross-sectional study was conducted from March 2018 to May 2019 at the Department of Biochemistry and Endocrine at the Basaveshwara Medical University Hospital and Research Centre in Karnataka, India, with a total of 120 subjects. Out of the 120 subjects, 80 were T2DM subjects and 40 were age, gender and BMI matched controls (group 1). Eighty T2DM subjects were further categorised into two groups based on urinary Albumin-to-Creatinine Ratio (ACR) levels, such as 40 T2DM with normoalbuminuria [(Group 2), Urine ACR: <30 mg/g], and 40 T2DM with microalbuminuria, [(Group 3) urinary ACR: 30-299 mg/g]. Comparisons were made between groups based on socio-demographic and clinical parameters. Pearson's correlation was used to test the relationship between estimated Glomerular Filtration Rates (eGFR), Glycated Haemoglobin (HbA1c), urine ACR, and serum adiponectin. The Receiver Operating Characteristic (ROC) curve was used to test the sensitivity and specificity of a marker for nephropathy. The Statistical Package for the Social Sciences (SPSS) version 20.0 and Medcalc Software were used to analyse data.Results: The mean values of serum adiponectin were significantly higher in patients with T2DM 11.92 +/- 3.86 when compared to controls 3.84 +/- 1.98. The serum adiponectin had a significantly very high positive correlation with HbA1c, urinary ACR r=0.726, 0.642, p-value=0.0001 and also a significantly very high negative correlation with estimated glomerular filtration rate, r =-0.399, p-value=0.0001 was observed. In ROC analysis serum adiponectin was found to be proportionately elevated in T2DM with normoalbuminuria and it was statistically significant, with a sensitivity of 92.5% and specificity of 87.50, p-value=0.0001. The urinary ACR also has shown significance with low sensitivity of 62.5% and specificity of 80%, p-value=0.0250.Conclusion: The serum adiponectin might be a sensitive and specific marker to predict the early onset of nephropathy in T2DM patients and therefore can be used as a diagnostic marker for DN. These concentrations were positively correlated with urinary ACR and negatively correlated with eGFR.