Differences in the results and interpretation of oxidized LDL cholesterol by two ELISA assays--an evaluation with samples from the PIOstat study.
BACKGROUND
The oxidized LDL-particles (oxLDL) are considered to be an important driving factor in the pathophysiology of arteriosclerosis. Few methods exist today to directly determine oxLDL in human plasma. We evaluated the plausibility of results derived from a new ELISA (Immundiagnostik, Bensheim, Germany) in comparison to a different ELISA test (Mercodia, Uppsala, Sweden).


METHODS
Samples from a previous prospective, randomized study comparing the effects of pioglitazone with simvastatin on chronic systemic inflammation were measured at baseline and endpoint with both tests. Both drugs are known to have a decreasing effect on circulating small dense oxLDL levels.


RESULTS
In total, 84 patients without diabetes mellitus were included into this analysis (45 female, 39 male, age(mean +/- SD): 58+/- 8 years). With the Mercodia ELISA, a decrease in oxLDL was seen with simvastatin only (Mean +/- SD: 54.2 +/- 12.5 U/L at baseline vs. 42.9 +/- 12.9 U/L at endpoint; p < 0.001, pioglitzone: 53.8 +/- 13.2 U/L vs. 54.3 +/- 15.254 U/L, n.s.). In contrast, a decrease of oxLDL was observed with the new ELISA for both drugs (simvastatin 65.1 +/- 21.8 ng/mL vs. 52.7 +/- 19.8 ng/mL; pioglitazone: 72.8 +/- 26.1 ng/ml vs. 57.9 +/- 22.1 ng/ml, p < 0.01 vs. baseline in both cases).


CONCLUSIONS
Determination of oxLDL with the Mercodia method lead to lower results and detected only the changes with simvastatin. While statins decrease the overall number of oxLDL particles, pioglitazone predominantly changes the size and LDL composition leading to larger particles with lower oxidation. In our study, the Immundiagnostik ELISA but not the competitive method confirmed the expected efficacy of PPARgamma-activation in decreasing the oxidation of LDL particles.
Pfützner
Andreas
A
IKFE-Institute for Clinical Research and Development, Mainz, Germany. AndreasP@ikfe.de
Efstrathios
Karagiannis
K
Löbig
Mirjam
M
Armbruster
Franz Paul
FP
Hanefeld
Markolf
M
Forst
Thomas
T
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism; D008078:Cholesterol, LDL / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D007249:Inflammation / Q000097:blood / Q000276:immunology*; D007328:Insulin / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood*; D008297:Male; D008875:Middle Aged; D000077205:Pioglitazone; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D019821:Simvastatin / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology*
D001786:Blood Glucose; D008078:Cholesterol, LDL; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007004:Hypoglycemic Agents; D007328:Insulin; D008077:Lipoproteins, LDL; D045162:Thiazolidinediones; C099252:oxidized low density lipoprotein; D002097:C-Reactive Protein; D019821:Simvastatin; D000077205:Pioglitazone