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.

Context: 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.

Objective: 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.

Design: 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.

Participants: 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.

Intervention: 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.

Main Outcome Measure: Circulating clusterin levels were measured.

Results: 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.

Conclusions: 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.