Short-term variability of biomarkers of proteinase activity in patients with emphysema associated with type Z alpha-1-antitrypsin deficiency

Abstract

Background: The burden of proteinases from inflammatory cells in the lung of subjects with type Pi ZZ of alpha-1-antitrypsin deficiency is higher than in those without the deficiency. Cross-sectional studies have shown increased levels of biomarkers of extracellular matrix degradation in vivo. Longitudinal variability of these biomarkers is unknown but desirable for clinical studies with proteinase inhibitors.

Methods: We measured three different types of biomarkers, including desmosines, elastase-formed fibrinogen fragments and heparan sulfate epitope JM403, in plasma and urine for a period of 7 weeks in a group of 12 patients who participated in a placebo-controlled study to assess the safety of a single inhalation of hyaluronic acid.

Results: Effect of study medication on any of the biomarkers was not seen. Baseline desmosines in plasma and urine correlated with baseline CO diffusion capacity (R = 0.81, p = 0.01 and R = 0.65, p = 0.05). Mean coefficient of variation within patients (CVi) for plasma and urine desmosines was 18.7 to 13.5%, respectively. Change in urinary desmosine levels correlated significantly with change in plasma desmosine levels (R = 0.84, p < 0.01). Mean CVi for fibrinogen fragments in plasma was 20.5% and for JM403 in urine was 27.8%. No correlations were found between fibrinogen fragments or JM403 epitope and desmosines.

Conclusion: We found acceptable variability in our study parameters, indicating the feasibility of their use in an evaluation of biochemical efficacy of alpha-1-antitrypsin augmentation therapy in Pi Z subjects.

Figure 1

Plasma desmosines levels (median ± quartels presented as box together with minimal and maximal values) determined on samples collected on indicated days from the patients. Values of plasma desmosines in healthy individuals (n = 15) range between 40 and 60 μg/l, mean 43 ± 3 μg/l (mean ± SD, reference 16).

Figure 2

Urine desmosines levels (median ± quartels) determined on samples collected on indicated days from the study patients. Ten healthy individuals had mean values of 22.70 ± 1.66 μg/g creatinine (mean ± SD, reference 14).

Figure 3

Plasma fibrinogen fragments generated by PMN (PMN-FDP) determined on samples collected on indicated days from the study patients (median ± quartels). Ten healthy individuals had mean values of 35 ± 12 ng/ml (mean ± SD, reference 11).

Figure 4

Urine JM403 values corrected for urine creatinine concentration on samples collected on indicated days from the study patients. Individual values are shown to appreciate the differences between patients. Values are expressed as Units/mg creatinine. One unit is defined as the amount of JM403 epitope present on 1 microgram kidney heparan sulfate. Sample on Day 9 of patient X is missing because he forgot to collect the sample. The top line of asterixes represents data from a patient that also had stable chronic pancreatitis, a condition not known to be associated with type Z alpha-1-antitrypsin deficiency. The other patient with normal values had no other known conditions and had a stable lung function for the past 15 years as measured in our clinic.

Figure 5

Change in plasma desmosines level and change in urine desmosines level during the 44 days of the study assessed for each of the 12 participating patients. Spearman's rank correlation coefficient between individual change in plasma and urine desmosines is 0.84 (P < 0.01).