Abstract
<p>Adiponectin is a beneficial adipocyte-secreted hormone, which circulates in a variety of multimeric forms termed low and high molecular weight (LMW/HMW). Effectiveness of clinical therapeutic trials which target adiponectin rely on accurate determination of circulating total and HMW adiponectin levels but the accuracy may be influenced by variations in sample handling processes. The aim of this pilot study was to investigate the effects of delayed processing of blood samples on the concentration of total and HMW adiponectin.</p><p>Materials and Methods: Fasting blood samples were collected for analysis of total and HMW adiponectin concentrations in EDTA plasma and serum from eight healthy participants. Samples were centrifuged post 15 min storage at 4<sup>o</sup>C as the comparative ‘ideal’ method or after up to 72 h of refrigerated storage or 6 h at room temperature. Total and HMW adiponectin concentrations were measured by ELISA.</p><p>Results: Under ideal handling conditions measurements of total and HMW adiponectin concentrations were significantly higher in serum than in plasma (mean difference: -1.3 µg/mL [95% CI: -1.6, -1.0], p&lt;0.001; and, -0.6 µg/mL [95% CI: -0.7, -0.5], p&lt;0.001, respectively). Storage of blood samples at 4<sup>o</sup>C for 72 h resulted in significant reductions in concentration of total adiponectin in serum (mean difference: -1.4 µg/mL [95% CI: -2.0, -0.8], p=0.001) and HMW adiponectin in plasma (mean difference: -0.6 µg/mL [95%CI: -0.9, -0.2], p=0.007), compared with ideal conditions. Further analysis of serum samples showed a significant decrease in total adiponectin concentration after 6 h storage at 4<sup>o</sup>C (mean difference: -1.4 µg/mL [95% CI: -2.0, -0.8], p=0.001) compared with ideal conditions.</p><p>Conclusions: Delayed processing of samples may have differential effects on the concentration of total and HMW adiponectin in serum or plasma. Larger studies are warranted for clinical intervention trials.</p>
Highlights
Optimised and standardised handling processes and conditions for blood collection and sample storage for accurate “true” concentration estimation of analytes are essential for accurate clinical decisions
Storage of blood samples at 4oC for 72 h resulted in significant reductions in concentration of total adiponectin in serum and high molecular weight (HMW) adiponectin in plasma, compared with ideal conditions
Further analysis of serum samples showed a significant decrease in total adiponectin concentration after 6 h storage at 4oC compared with ideal conditions
Summary
Optimised and standardised handling processes and conditions for blood collection and sample storage for accurate “true” concentration estimation of analytes are essential for accurate clinical decisions. Adiponectin has insulin-sensitising, anti-atherogenic, anti-inflammatory, anti-neoplastic and cerebroprotective properties (Hickman & Whitehead, 2012) It undergoes post-translational modification and multimerisation prior to secretion (Simpson & Whitehead, 2010) and circulates in multimers termed low molecular weight (LMW; trimer and hexamer) and high molecular weight (HMW; 12- to 18mers) (Hickman & Whitehead, 2012; Tsao, 2013). We hypothesise that variation in serum or plasma separation from cells post storage at different temperature and length of time may effect the concentration of adiponectin in serum and plasma This pilot study aimed to investigate the stability of total and HMW adiponectin in EDTA plasma and serum samples, stored for 6 h and 72 h at 4°C and 6 h at room temperature (RT), measured using commercially available enzyme-linked immunosorbent assays (ELISAs) that detect monomeric or HMW adiponectin
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