Transferrinuria in type 2 diabetes: the effect of glycaemic control.

Urinary excretion rates of transferrin, albumin, N-acetyl-beta-D-glucosaminidase (NAG) and alpha-1-microglobulin (A1M) were measured in type 2 (non-insulin-dependent) diabetic patients at diagnosis and after 6 and 12 weeks treatment. Initially 21 (53%) patients had elevated transferrin excretion rates. The proportion of patients with raised transferrin excretion rates fell to 30% at 6 weeks and 20% at 12 weeks with treatment of diabetes. At diagnosis 11 (28%) patients had elevated albumin excretion rates and 10 of these had elevated transferrin excretion rates. After 6 weeks treatment only six (15%) had elevated albumin excretion rates and by 12 weeks this number had fallen to four (10%). NAG and A1M levels also fell with treatment of diabetes. There were correlations between the transferrin excretion rate and albumin excretion rate (r = 0.86, P less than 0.0001), transferrin excretion rate and NAG (r = 0.46, P less than 0.0001), and transferrin excretion rate and A1M (r = 0.55, P less than 0.0001) at each visit. There were weaker correlations between the albumin excretion rate and A1M and NAG at each visit. The correlations between the transferrin excretion rate and markers of tubular function (NAG and A1M) suggest that tubular dysfunction may play a part in renal loss of transferrin in diabetes mellitus. There were no differences in transferrin excretion rates between patients with and without evidence of complications.