Adiponectin is an adipokine with a role in both endocrine and inflammatory axes. As with other circulating biomarkers, temporal variation in circulating levels means the reliability of a single, isolated measurement of adiponectin as an indicator of a subject’s baseline status has been questioned.
Similarly, vitamin D, interleukin-6 (IL-6), and cortisol are hormones with both inflammatory and endocrine functions. No published data exists on the temporal relationship between adiponectin and IL-6, vitamin D and cortisol in a control population.
Eighteen (8 men 10 women) healthy control subjects. Serial, hourly serum measurements of total and HMW adiponectin, IL-6, vitamin D and cortisol over a 12 hr period from 0600hrs to 1800hrs.
Within-subject hourly variability (CV) was demonstrated for total adiponectin (5.6 – 57.89%), HMW adiponectin (5.92 – 53.76%), IL-6 (24.1 – 88%), 25-hydroxyvitamin D3 (4.1 – 16.33%), 1,25-hydroxyvitamin D3 (8.48 – 28.72%), total cortisol (4.9 – 65%), free cortisol (57 – 141%) and ACTH (11 – 217%).
There was an increase in total group mean (SD) IL-6 levels over the sampling period from 2.09 (1.53) to 4.92 (5.10) pg/ml and a decrease in total group mean total cortisol (416 (127) to 129 (51) nmol/L), free cortisol (20.3 (12.7) to 2.4 (1.3) nmol/L) and ACTH (41.5 (68.8) to 14.13 (6.4) ng/L).
HMW adiponectin negatively correlated with IL-6 (estimate -0.069, p=0.036) and positively correlated with blood oxygen saturation (estimate 0.0026, p=0.038).
Total adiponectin positively correlated with 25-hydroxyvitamin D3 (estimate 0.071, p=0.006).
This preliminary investigation confirmed the existence of marked ultradian variability in adiponectin and additional measured biomarkers, supporting the use of caution in the interpretation of a single measured value taken in health.
With current interest in manipulating these biomarkers to correct perturbations in both the endocrine and inflammatory axes, further investigation to elucidate their relationship in health is warranted.