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Nephron. 2001 Aug;88(4):307-12.

Urinary copper excretion in type 2 diabetic patients with nephropathy.

Author information

1
Department of Geriatric Medicine, Akita University School of Medicine, Akita, Japan. grtitoh@doc.med.akita-u.ac.jp

Abstract

BACKGROUND/AIMS:

The aim of this study was to examine the relationship between the degree of urinary copper excretion and stages of diabetic nephropathy.

METHODS:

Copper, ceruloplasmin and albumin concentrations were measured in serum and urine samples from 41 type 2 diabetic outpatients with different stages of nephropathy and from 10 healthy controls. The copper/albumin and copper/ceruloplasmin ratios in serum and urine were determined. Furthermore, we examined whether free copper ions are dissociated from ceruloplasmin under various pH conditions.

RESULTS:

Urinary copper concentrations significantly increased only in macroalbuminuric patients. The copper/ceruloplasmin and copper/albumin ratios in urine were consistently greater than those in serum which were not different between patients and healthy controls except the copper/albumin ratio in macroalbuminuric patients. The ratios in urine decreased in parallel with the progression of nephropathy. Copper was found to be released from ceruloplasmin under acidic conditions.

CONCLUSION:

Urinary copper excretion in healthy controls may be the result of dissociation from the albumin-copper complex of serum during its passage through the kidney. In diabetic patients with advanced nephropathy, urinary copper excretion may be due to dissociations from both copper-albumin and ceruloplasmin-copper complexes filtered through the damaged glomerulus. Overloading of urinary copper to damaged renal tubules may play some roles in the progression of nephropathy in patients with advanced nephropathy.

PMID:
11474224
DOI:
10.1159/000046013
[Indexed for MEDLINE]

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