URINARY DESMOSINE, ELASTOLYSIS, AND LUNG-DISEASE

Desmosine is an amino acid specific to elastin. Animal studies suggest that urinary desmosine (UD) represents endogenus elastin degradation. Therefore, UD has previously been used to investigate endogenous elastolysis, but was not elevated in subjects with chronic obstructive airways disease (COAD), although accelerated pulmonary elastolysis is thought to contribute to COAD. We have investigated whether this reflects large day-to-day and between-subject variation in UD and whether, in man, dietary desmosine contributes significantly to that in urine. Mean 24-hour UD output (over 5 consecutive days) from 10 asymptomatic subjects (5 males) was higher in males than females ( 77.4 ± 9.6 and 40.2 ± 5.0 nmol 24 hours, respectively; mean ± SD, P < .001), but not significantly different when expressed in terms of creatinine (μg desmosine/100 mg creatinine: males, 2.5 ± 0.4; females, 3.1 ± 0.8; mean ± SD). The lowest between-subject variation was observed when the mean of 5 days' 24-hour UD values was analyzed on the basis of gender (coefficient of variation [CV], 12.5%); when gender was not considered, the least between-subject variation was found for the mean of 5 days' desmosine/creatinine analysis (CV, 24.5%). Approximately 1% of dietary desmosine (ingested as [3H]elastin and [3H] desmosine) was excreted in the urine within 24 hours, contributing approximately 15% of UD while on a normal diet. Although ingestion of a low elastin diet (< 1 10 desmosine/24 hours than a normal diet) resulted in lower within-subject variation in 24-hour UD excretion (mean CV decreased from 31.5% to 20.2%), the between-subject CV and UD levels did not alter. In a pilot study of subjects with bacterial pneumonia developing (1) in a normal lung (n = 3; 7 days' urine), and (2) in chronic lung disease (n = 3; 7 days' urine), elevated 24-hour UD was observed in two subjects (μg desmosine/100 mg creatinine, 7.3 ± 0.75 and 6.5 ± 1.9; mean ± SD). In subjects with α1-proteinase inhibitor (α1PI) deficiency (n = 1, 18 days' urine; n = 11, 1 days' urine), only one 24-hour urine sample contained elevated μg desmosine/100 mg creatinine (5.44). Further studies are required on the use of UD as an index of in vivo elastolysis for clinical purposes. © 1991.