Biovariability of plasma adiponectin.

BACKGROUND

Adiponectin is a cytokine produced by adipose tissue with insulin sensitising and anti-atherosclerotic effects. Low plasma adiponectin levels are used as a marker of the metabolic syndrome and incipient type 2 diabetes.

METHODS

We carried out a series of studies to determine the short- and long-term variability of plasma adiponectin levels, including diurnal and post-prandial changes. These investigations also included examining the effect of frozen storage on plasma adiponectin levels.

RESULTS

A nested study in 10 overweight subjects with the metabolic syndrome and 10 age- and sex-matched controls showed intra-subject variation in adiponectin levels over a 30-day period of 12.2% and 18.8%, respectively, equivalent to reference change values of 1.7 and 3.6 microg/mL. In non-obese subjects, plasma adiponectin levels varied minimally over a 15-month period (baseline, 8.3+/-2.9 microg/mL vs. +15 months, 8.2+/-3.0 microg/mL, p=0.95) and showed only minor diurnal and post-prandial changes (pre-meal, 8.2+/-3.0 microg/mL vs. 3 h post-prandial, 8.3+/-3.1 microg/mL, p=0.60). The adiponectin assay had an intra-assay variation of 8.8%, with storage at -30 degrees C for 33 months or three cycles of freezing and thawing having no discernible effect on adiponectin levels.

CONCLUSIONS

These results demonstrate that plasma adiponectin levels have relatively low biovariability and that adiponectin can be sampled fasting or non-fasting to provide a reliable marker of insulin resistance and incipient type 2 diabetes.