Metabolism of albumin and fibrinogen in type 1 (insulin-dependent) diabetes mellitus.

The metabolism of albumin and fibrinogen was studied in 24 long-term diabetic Type 1 (insulin-dependent) patients, using a double tracer technique. The patients were divided into three groups according to their urinary albumin excretion. Group 1 had normal albumin excretion (less than 30 mg/24 h), group 2 had persistent microalbuminuria (30-300 mg/24 h), and group 3 had clinical nephropathy (greater than 300 mg/24 h). Eight normal persons served as control subjects. Except for slightly lower distribution fractions of both proteins (intravascular mass/total mass), group 1 did not differ from normal subjects. In groups 2 and 3 the relative catabolism of albumin was increased, as denoted by an increase in the fractional catabolic rate. Albumin synthesis was unaltered, resulting in lower plasma concentrations and lower intravascular and total body masses of albumin. Oppositely, fibrinogen synthesis was augmented, leading to an increase in plasma fibrinogen concentration and total fibrinogen body mass, in spite of increased catabolism. The fractional catabolic rates were unaltered. The study demonstrates that long-term diabetic patients with normal urinary albumin excretion have normal albumin and fibrinogen metabolism, but that grave alterations in plasma protein metabolism are present in patients with only slightly increased urinary albumin excretion.