Clinical correlation between frequent risk factors of diabetic nephropathy and serum sialic acid

Background: It has been recently established that serum sialic acid is a potent cardiovascular and renal risk factor in the general population and elevated in diabetic type 2 patients. This study was designed to assess the coexistence of frequently documented risk factors of diabetic nephropathy with serum sialic acid. Methods: A total of 100 diabetic patients (50 with and 50 without nephropathy) aged 47.56 ± 10.68 (mean ± SD) years attending several diabetic clinics in the private sector in Karachi were included after informed consent was obtained. Systolic and diastolic blood pressures were recorded by standard mercury sphygmomanometer. Fasting blood samples were collected for estimations of blood glucose, HbA1c, serum urea, creatinine and sialic acid levels. Results: Serum sialic acid, glucose, HbA1c, urea and creatinine levels were increased significantly (P<0.01) in patients with diabetic nephropathy compared to diabetic patients without nephropathy. Regression and correlation analysis showed a significant positive correlation between serum sialic acid and fasting blood glucose, HbA1c, serum urea and creatinine levels. Body Mass Index and blood pressure were also significantly higher in diabetic patients with diabetic nephropathy compared to those without nephropathy. Fifty four percent of diabetic nephropathy patients were smokers compared with 41% of patients in the control group (diabetic patients without nephropathy). Conclusion: It is concluded that elevated serum sialic acid level is strongly associated with the presence of nephropathy, a microvascular complications of diabetes. As there is a significant unvaried link between serum sialic acid and diabetic nephropathy, consideration of sialic acid as potent disease marker for diabetic nephropathy is justified. (Int J Diabetes Metab 14: 138-142, 2006) Introduction Serum or plasma sialic acid (N-acetyl neuraminic acid), an inflammatory marker, has recently been shown to be a strong predictor of cardiovascular mortality. Several general population studies and those carried out in diabetic patients with complications have pointed to serum sialic acid as a marker of inflammation in cardiovascular disease. Sialic acid is released from the terminal oligosaccharide chains of some glycoproteins and glycolipids in the acute phase of inflammation. Diabetes mellitus is a chronic metabolic disorder that can lead to severe cardiovascular, renal, neurologic and retinal complications. Diabetic nephropathy affects more than 30% of type 1 diabetic patients and it is a leading cause of end stage renal disease. A number of risk factors have been associated with the metabolic syndrome, including hypertension, poor glycemic control, central obesity, smoking, dyslipidemia and glycated end products. Serum sialic acid is a newly established potential risk factor for the development of macroand microvascular complications of diabetes. The current study was designed to investigate the significance of serum sialic acid as a major risk factor in the ______________________________ Received on: 3/5/06 Accepted on: 30/11/06 Correspondence to: Dr. Tabassum Mahboob, Department of Biochemistry, University of Karachi, Karachi – 75270, Pakistan, Email: [email protected], [email protected] development of diabetic nephropathy and to observe the clinical relationship of serum sialic acid with other markers of diabetic nephropathy. Subjects and Methods A total of 100 previously diagnosed type 2 diabetic patients, (50 with and 50 without nephropathy) attending several diabetic clinics in the private sector in Karachi were included in the present study after informed consent was obtained. The selection criteria was based on WHO criteria. Their mean age was 47.56 ± 10.68 years. Patients suffering from type 1 diabetes mellitus, gestational diabetes and any known mental illness, macrovascular disease prior to diagnosis of type 2 diabetes, or the patients who refused to participate in the study were excluded. Fifty healthy subjects with no known history of hyperglycemia and renal disease were included as control. A previously structured questionnaire was used to record the demographic features of all subjects. Height and weight were noted for BMI (Body Mass Index=weight in kg/height in m). BMI from 20.0 to 29.9 was considered overweight and >30.0 was considered as obese. Blood pressure was measured with a standard mercury sphygmomanometer while the patient was sitting after resting for 10 min. Hypertension was defined as blood pressure ≥ 140/90 mm Hg. Patients were classified as smokers if they smoked more than one cigarette a day. Clinical correlation between frequent risk factors of diabetic nephropathy and serum sialic acid 139 Table 1: Biochemical parameters in diabetic patients with and without nephropathy as compared to control. Parameters Control Diabetic patients Diabetic nephropathy patients Serum sialic acid (mmol/L) 1.72 ± 0.36 1.95 ± 1.25* 2.21 ± 0.37* Blood glucose (mmol/L) 5.4 ± 0.5 9.0 ± 3.9* 11.9 ± 3.4* HbA1c (%) 4.6 ± 1.6 7.3 ± 2.0* 9.3 ± 1.9* Serum urea (mmol/L) 10.6 ± 2.6 10.7 ± 1.9 19.4 ± 4.9* Serum creatinine (μmol/L) 107.7 ± 48.8 112.8 ± 38.4 198.3 ± 29.9* Values are Mean ± SD P<0.01 as compared to control subjects Table 2: Physical parameters in diabetic patients with and without nephropathy as compared to control. Parameters Control Diabetic patients Diabetic nephropathy patients Systolic BP (mm Hg) 123.8 ± 8.2 125.3 ± 6.3 149.0 ± 16.7*