The acylated/unacylated ghrelin (AG/UAG) ratio has been reported to range from 0.02 to 0.3, suggesting biologically relevant independent regulation of each ghrelin isoform. However, AG is deacylated to UAG by esterases in blood samples, and esterase inhibition is critical for their accurate measurement.
Our hypothesis is that at least part of the variation in reported AG and UAG values is due to inconsistent sample preparation.
AG and UAG levels measured in samples collected in EDTA tubes without [E] or with the addition of AEBSF [A] after 1 day or 6 months of storage at either -20 °C or -80 °C.
Non-AEBSF plasma contained low AG and high UAG indicating rapid conversion of AG to UAG. However, AEBSF plasma, stored at -80 °C and measured at 0 and 6 months contained AG and UAG ranges of 12–350 and 17–170 pg/ml, respectively. Mean (SEM) AG/UAG ratios were 1.7(0.3) and 1.8 (0.5) at each time point with no significant effect of storage period.