Intraindividual variations in lipoprotein (a) levels and factors related to these changes

Lp(a) levels are genetically determined and remain stable without major changes throughout lives. However, when an individual's Lp(a) levels are observed over a one-year period, they show spontaneous variation. The rate of intraindividual variation in Lp(a) was observed in 16 patients with hypertension, hyperlipidemia and/or glucose intolerance in a chronic stable state who regularly visited the hospital clinic once a month, at least 10 times during the year, and in whom a total of 42 blood and clinical chemistry tests including serum lipids, Lp(a) and apoproteins were performed. The rate of annual intraindividual variation of Lp(a) averaged out as 16.6%. The rate was 18.8% for isoform S4 (n = 10), 18.6% for S3 (n = 3), and although small in number of subjects, other isoforms showed minor variation rates. There was a significant negative correlation between the rate of variation (y%) and LP(a) level (xmg/dl) r = -0.605, p < 0.05, y = -0.461 x +29.8). Therefore, when Lp(a) was high, the rate of variation (SD%) was low. This was consistent with the finding that the rates of variation were low for isoforms S2, S3S4 and F, whose molecular weights were low, accompanied by high Lp(a) levels. On the other hand, when the relationship between Lp(a) level and the amount of variation (SD mg/dl) was examined, there was no correlation between the two, since the amounts of variation were almost constant at a level of 3.8 mg/dl, regardless of Lp(a) level. The annual variation of Lp(a) level was found to be related to three groups of factors based on comparison of the variations among WHO phenotypes of hyperlipidemias, univariate correlation analysis with the clinical parameters tested, and multivariate analysis: the first group of factors was related to structure and metabolism of very low-density lipoprotein such as triglycerides, phospholipids, apo C-II, C-III, E, A-II and uric acid; the second group was related to thrombosis centering on platelets; and the third group involved those in the acute phase reactions represented by 1 hr and 2 hr erythrocyte sedimentation rates.