The relationship between dopamine and renalase in type 2 diabetic patients with and without diabetic nephropathy

Abstract

Background: Diabetes clustered with hypertension and nephropathy is the commonest cause of end stage renal disease. Dopamine, an ancestral catecholamine, is involved in the regulation of sodium homeostasis and blood pressure. Renalase metabolises circulating catecholamines and is thought to regulate blood pressure. This study aimed to assess the relationship between dopamine and renalase in type 2 diabetic patients with and without diabetic nephropathy. Methods: This study was conducted on 80 subjects. Group 1 included 10 healthy subjects as controls, group 2 included 60 type 2 diabetic patients with normal or increased albumin excretion rate (AER) and group 3 included 10 type 2 diabetic patients on maintenance hemodialysis (HD). Thorough clinical assessment and laboratory investigations included estimation of serum levels of fasting glucose (FSG), creatinine, urea, calcium, phosphorus, cholesterol (total and high and low-density lipoprotein) and triglycerides. Urinary albumin/creatinine ratio (ACR) was estimated to assess AER and plasma dopamine and serum renalase were estimated. Results: There were no significant differences in the mean dopamine levels between the three studied groups. Renalase level was significantly higher in HD patients than controls and other diabetic patients. Diabetic patients with increased AER had significantly higher systolic blood pressure, serum creatinine and renalase levels than diabetic patients with normal AER. Diabetic patients with increased serum creatinine ≥ 1.5 mg/dl had significantly longer duration of diabetes and higher systolic and diastolic blood pressures. They also had significantly higher AER, FSG, dopamine and renalase levels than diabetic patients with serum creatinine < 1.5 mg/dl. ACR was positively correlated with duration of diabetes, systolic and diastolic blood pressure and serum creatinine and negatively correlated with the use of angiotensin converting enzyme inhibitors or angiotensin receptor blockers. Renalase was positively correlated with diastolic blood pressure, ACR, serum creatinine, phosphorus and dopamine Conclusion: Serum levels of renalase are increased in type 2 diabetic patients with renal dysfunction. Renalase levels may be increased to compensate for the increase in dopamine level. The higher renalase level in HD patients may be due to much lower renalase clearance, higher production or slower degradation in these patients.