Circulating Clusterin (Apolipoprotein J) Levels Do Not Have Any Day/Night Variability and Are Positively Associated with Total and LDL Cholesterol Levels in Young Healthy Individuals

Abstract

Clusterin has been associated with several pathologies, including cardiovascular disease and neoplasias. However, little is known about its physiology and its association with metabolic and anthropometric parameters in humans. The aim of the study was to examine whether circulating clusterin levels exhibit a day/night variation pattern and whether clusterin is associated with anthropometric and metabolic parameters. Study A was a frequent sampling study to evaluate potential periodicity in clusterin secretion. Study B was an observational study to evaluate the cross-sectional and prospective associations of clusterin with anthropometric and metabolic parameters. Study A participants were healthy males (n = 6) and females (n = 6), aged 22.3 ± 3.1 and 22.8 ± 3.4 yr, respectively. Study B participants were 186 healthy males aged 18.4 ± 0.14 yr. Ninety-one of the study B subjects were studied again 2 yr later and clusterin's associations with change of anthropometric and metabolic parameters were thus investigated prospectively. Samples in study A were collected every 15 min during an overnight admission, and subsequently pooled every hour. Samples in study B were collected during a screening visit. Circulating clusterin levels were measured. In study A, spectral domain and cosinor regression analysis failed to reveal any day/night variation pattern. In study B, clusterin was positively correlated with total and low-density lipoprotein cholesterol (r = 0.23, P = 0.002; and r = 0.20, P = 0.005). Baseline clusterin did not predict change of any anthropometric, biochemical, or metabolic parameters prospectively. We report for the first time that circulating clusterin does not have a day/night variation pattern in healthy young individuals. Clusterin levels are associated with total and low-density lipoprotein cholesterol cross-sectionally but do not predict short-term changes in metabolic parameters in healthy young males.