Urinary-peptide excretion by patients with and volunteers without diabetes

Kimberley Strong, T.M. Osicka, W.D. Comper

    Research output: Contribution to journalArticle

    38 Citations (Scopus)

    Abstract

    Large quantities of peptides (1-4 g) are excreted in human urine each day. In this study we sought to analyze how peptide excretion varies with increasing albuminuria associated with diabetes, as well as to characterize the size distribution of albumin-derived peptides in urine from volunteers without diabetes and from patients with macroalbuminuria and diabetes. We detected albumin-derived peptides by injecting tritiated albumin intravenously into human volunteers and patients with diabetes. Urine was collected after 24 hours and fractionated on a size-exclusion column. This fractionation revealed peptides with molecular weights ranging from 300 to 500 Da in volunteers without diabetes. The albumin-derived peptides were of higher molecular weight in the urine of a patient with macroalbuminuria and diabetes. The molecular-weight distribution of the peptides derived from tritiated albumin peptides was paralleled by the distribution of all protein peptides (including albumin) as determined with the use of the Biuret protein assay or absorbance at 214 nm. We determined peptide-excretion rates by filtering urine from patients with diabetes through a 10,000 Da molecular-weight-cutoff membrane and then measuring the filtrate with the use of the Biuret assay. This analysis revealed that the peptide-excretion rate increased with increasing total protein excretion, regardless of whether the patient demonstrated normoalbuminuria or microalbuminuria. Among patients with macroalbuminuria, the peptide-excretion rate leveled off and even decreased in the face of an increasing albumin concentration or protein-excretion rate. This study confirms that albumin-derived and protein-derived peptides exist at high concentrations in urine. Although peptide-excretion rates are maintained at similar levels up to macroalbuminuric states, the relative proportion of peptide excretion is significantly reduced compared with total protein.
    Original languageEnglish
    Pages (from-to)239-246
    JournalJournal of Laboratory and Clinical Medicine
    Volume145
    Issue number5
    DOIs
    Publication statusPublished - 2005

    Fingerprint

    Medical problems
    Volunteers
    Peptides
    Albumins
    Urine
    Biuret
    Molecular Weight
    Proteins
    Molecular weight
    Assays
    Albuminuria
    Distillation columns
    Molecular weight distribution
    Fractionation

    Cite this

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    Urinary-peptide excretion by patients with and volunteers without diabetes. / Strong, Kimberley; Osicka, T.M.; Comper, W.D.

    In: Journal of Laboratory and Clinical Medicine, Vol. 145, No. 5, 2005, p. 239-246.

    Research output: Contribution to journalArticle

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