A. Riveracoll et al., CIRCADIAN RHYTHMIC VARIATIONS IN SERUM CONCENTRATIONS OF CLINICALLY IMPORTANT LIPIDS, Clinical chemistry, 40(8), 1994, pp. 1549-1553
Twenty-five apparently healthy adults (13 men and 12 women), mean age
29.5 years (SD 3.6 years), served as subjects in a 24-h study conducte
d in Barcelona (Spain) in spring of 1990. Six blood samples were colle
cted from each subject at 4-h intervals over a 24-h period, beginning
at 1000. The oral temperature was measured at 2-h intervals to facilit
ate an independent biological time reference. The serum concentrations
of apolipoprotein (ape) A-I, apo B, cholesterol, high- and low-densit
y lipoprotein cholesterol, and triglyceride were measured. The circadi
an rhythms of these quantities were studied with use of a periodic fun
ction resulting from the sum of two cosine functions of 24 and 12 h. F
or serum concentrations of apo A-I and apo B, only the 24- or 12-h com
ponents, respectively, were significant. However, the other quantities
studied were significantly affected by both rhythmic components. The
maximum daily rhythmic variation ranged from 5% (with respect to the d
aily mean) for apo A-I to 63% for triglyceride concentration. In all c
ases except triglyceride, the daily maximum values were measured in th
e afternoon samples, near the time of maximum oral temperature.