Low-molecular-weight proteinuria in insulin-dependent diabetes mellitus: a study of the urinary excretion of beta 2-microglobulin and retinol-binding protein in alkalinized patients with and without microalbuminuria.
The urinary excretion of two low-molecular-weight proteins (beta 2-microglobulin and retinol-binding protein) was measured in 12 insulin-dependent diabetic patients with persistent microalbuminuria and an equal number with normal albumin excretion; reference ranges for the excretion of beta 2-microglobulin (beta 2M) and retinol-binding protein (RBP) were also obtained in 40 non-diabetic subjects. To ensure the stability of beta 2M in urine a urinary pH greater than or equal to 7 was achieved by giving oral sodium bicarbonate. beta 2M and RBP excretion was significantly higher in the diabetics than in the controls (p less than 0.01), but no higher in microalbuminuric than non-albuminuric diabetics. In the diabetics as a group a significant correlation was found between the excretion of beta 2M and RBP (r = 0.53, p less than 0.01), but more patients had an abnormal excretion of beta 2M than RBP (p less than 0.001). No significant correlation was found between the urinary excretion of either low-molecular-weight protein and duration of diabetes, insulin dose, HbA1, urinary glucose excretion or systemic blood pressure. Measured under appropriate alkaline conditions beta 2M appears to be more sensitive than RBP in detecting an abnormality of the renal proximal tubule which may be an early feature of diabetic renal involvement not characterized by microalbuminuria; microalbuminuria may have glomerular and tubular components.
Watts
G F
GF
Department of Chemical Pathology and Metabolic Disorders, United Medical School, Guy's Hospital, London, UK.
Powell
M
M
Rowe
D J
DJ
Shaw
K M
KM
D000293:Adolescent; D000328:Adult; D000419:Albuminuria / Q000209:etiology / Q000652:urine; D003922:Diabetes Mellitus, Type 1 / Q000150:complications* / Q000652:urine; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D011507:Proteinuria / Q000209:etiology*; D012177:Retinol-Binding Proteins / Q000652:urine*; D001613:beta 2-Microglobulin / Q000652:urine*
D012177:Retinol-Binding Proteins; D001613:beta 2-Microglobulin