PIIANP and HELIXII diurnal variation.
OBJECTIVE: Serum levels of procollagen type IIA N-terminal propeptide (sPIIANP) and type-II collagen helical peptide (sHELIXII) biomarkers were evaluated for variation diurnally and with physical activity and food in participants with osteoarthritis (OA) of the knee. METHODS: Forty participants with OA of at least one knee were admitted overnight to the General Clinical Research Center for serial serum sampling. Samples were obtained on the evening (6-8 pm) of Day 1 (T3, n=40); prior to rising (8 am) from bed (T0, n=40); 1 h after rising (9 am) without food consumption (T1a, n=20); 1-2 h after rising (9-10 am) with food consumption (T1, n=40); and additionally at noon, 4 h after rising (T2, n=20). sPIIANP and sHELIXII were measured by enzyme-linked immunosorbent assay. Results were analyzed using non-parametric Freidman's test with Dunn's post-hoc multiple comparison test. RESULTS: Normalized mean concentrations for sPIIANP and sHELIXII increased significantly from T0 to T1 (P<0.05). CONCLUSIONS: This is the first study to demonstrate diurnal variation of these collagen-II biomarkers in individuals with knee OA. These results suggest that serum sampling for these markers should be standardized for purposes of clinical trials.
Quintana, DJ; Garnero, P; Huebner, JL; Charni-Ben Tabassi, N; Kraus, VB
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