title: Daily quadratic trend in basal monocyte expressed HSP72 in healthy human subjects.
abstract: The inducible human stress protein heat shock protein 72 (HSP72) performs vital roles within the body at rest and during periods of stress. Recently it was shown over a 24 h period that basal HSP72 followed a diurnal variation. However, these results and previous literature demonstrate noticeable inter-subject variation in basal HSP72 expression. The notion of intra/inter-day variation in basal HSP72 expression has not been explored in detail. Basal monocyte expressed HSP72 was determined every 3 h, over a 9 h period in 12 healthy male subjects (20.2 +/- 1.9 years, 178.7 +/- 5.6 cm, 75.1 +/- 6.0 kg) within a temperature controlled laboratory. A significant quadratic trend was observed for time (F = 26.0, P = 0.001, partial eta(2) = 0.74), where HSP72 decreased between 0800 and 1100 hours (P < 0.001) and then increased between 1100 and 1400 hours (P = 0.015). The main effect for day (F = 2.6, P = 0.14) and the day x time interaction effect (F = 3.9, P = 0.08) were not significant. There was no correlation between serum and monocyte expressed HSP72, with no significant effect for time (F = 2.0, P = 0.21) in serum HSP72 expression. The results support findings by others that basal monocyte expressed HSP72 follows a diurnal variation which incorporates a quadratic trend, which is not compromised by any significant daily variation and that serum HSP72 expression has no endogenous circadian rhythm. The significant quadratic trend in basal monocyte HSP72 expression shown here highlights the need to tightly control variables, such as timing of sample collection, as it is known basal values influence the magnitude of HSP72 expression post-stressor/intervention.
authors.affiliation: Department of Sport, Health and Exercise Science, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Lee
authors.initials: L
authors.lastname: Taylor
authors.forename: Adrian W
authors.initials: AW
authors.lastname: Midgley
authors.forename: Bryna
authors.initials: B
authors.lastname: Chrismas
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Madden
authors.forename: Rebecca V
authors.initials: RV
authors.lastname: Vince
authors.forename: Lars R
authors.initials: LR
authors.lastname: McNaughton
mesh_terms: D002940:Circadian Rhythm; D050884:HSP72 Heat-Shock Proteins / Q000097:blood*; D006801:Humans; D008297:Male; D009000:Monocytes / Q000378:metabolism*; D012016:Reference Values
chemical_list: D050884:HSP72 Heat-Shock Proteins