RENAL URIC-ACID HANDLING IN NON-INSULIN-DEPENDENT DIABETIC-PATIENTS WITH ELEVATED GLOMERULAR-FILTRATION RATES

1. Hypouricaemia is prevalent in diabetic patients. In most of the studies, the diabetic patients had some degree of diabetic nephropathy as evidenced by a decreased glomerular filtration rate and proteinuria. Therefore we studied renal uric acid handling in a group of type II diabetic patients with elevated glomerular filtration rates. 2. Eighteen type II diabetic patients with normal kidney functions and elevated glomerular filtration rate and a group of 18 healthy, age- and weight-matched control subjects, were studied. Serum fructosamine, creatinine and uric acid levels were determined. Twenty-four hour urine collections were obtained, and microalbumin, glucose, creatinine and uric acid, were measured. 3. The creatinine clearance was higher and the serum uric acid concentration was lower in the diabetic patients (P<0.05). The 24h urinary uric acid excretion and filtered uric acid load were similar in both groups. However, the derived parameters of uric acid clearance and fractional excretion were significantly higher in the diabetic patients (P<0.002 and P<0.05, respectively). A negative correlation was apparent between serum fructosamine concentration and serum uric acid concentration (r= -0.76). A positive correlation was found between serum fructosamine concentration and fractional uric acid excretion (r=0.64) and between serum fructosamine concentration and filtered uric acid load (r=0.66). A positive correlation was found between creatinine clearance and 24h uric acid excretion (r=0.61) and between creatinine clearance and filtered uric acid load (r = 0.82). 4. It appears that the hypouricaemia and hyperuricosuria in diabetic patients are associated with an elevated glomerular filtration rate and a net tubular reabsorptive defect that may herald the development of diabetic nephropathy.