© Copyright 2009 by the American Association for Clinical Chemistry LOX Index, a Novel Predictive Biochemical Marker for Coronary Heart Disease and Stroke Nobutaka Inoue, Tomonori Okamura, Yoshihiro Kokubo, Yoshiko Fujita, Yuko Sato, Mamoru Nakanishi, Kazuki Yanagida, Akemi Kakino, Shin Iwamoto, Makoto Watanabe, Sayoko Ogura, Kazunori Otsui, Haruo Matsuda, Kagehiro Uchida, Ryo Yoshimoto, and Tatsuya Sawamura April © Copyright 2010 by the American Association for Clinical Chemistry Journal Club

© Copyright 2009 by the American Association for Clinical Chemistry Introduction  High LDL-C and low HDL-C are associated with the risk for coronary heart disease (CHD)  However, dyslipidemia has a much weaker relationship to the risk of stroke than CHD  Stroke mortality is higher than CHD in Japan

© Copyright 2009 by the American Association for Clinical Chemistry Introduction (cont)  Oxidized LDL Explains many aspects of biological response to LDL Is accumulated in atheroma Associates with the risk of metabolic syndrome

© Copyright 2009 by the American Association for Clinical Chemistry Introduction (cont)  LOX-1 A receptor for (oxidatively) modified LDL From animal studies; thought to be involved in the pathogenesis of endothelial dysfunction, atherosclerosis, and myocardial infarction

© Copyright 2009 by the American Association for Clinical Chemistry Question  What do you think is the better method to measure cholesterol-related parameters, if determination of LDL cholesterol concentration is ineffective for risk stratification?

© Copyright 2009 by the American Association for Clinical Chemistry Materials and Methods  Study Population 2295 community-dwelling participants (1094 men and 1201 women) in Japan without past history of CHD or stroke A mean 11-year follow-up period

© Copyright 2009 by the American Association for Clinical Chemistry Materials and Methods (cont)  Endpoint First event of stroke or CHD, i.e., myocardial infarction, coronary artery bypass surgery, or angioplasty Sudden deaths of unknown origin, which occurred within 24 hours

© Copyright 2009 by the American Association for Clinical Chemistry Figure 1. To detect modified LDL including oxidized LDL, a receptor-based assay, which measures binding activity rather than absolute amount of certain epitopes, was performed. Measurement of sLOX-1 might assess expression level of LOX-1. Materials and Methods (cont) sLOX-1 Determine both LOX-1 ligand containing ApoB (LAB) and sLOX-1 concentrations in sera collected from the participants at the start of follow-up. Receptor-based assay Measurement of receptor LOX-1 ligand (LAB)

© Copyright 2009 by the American Association for Clinical Chemistry Question  What would be a good strategy for risk stratification of CHD and stroke, if you have measured LOX-1 ligand and sLOX-1?

© Copyright 2009 by the American Association for Clinical Chemistry Results a Data are mean (SD) unless noted otherwise. b Hypertension was defined as systolic blood pressure > 140 mmHg, diastolic blood pressure > 90 mmHg, or use of antihypertensive agents. c Diabetes was defined as fasting serum glucose > 7.0 mmol/L (126 mg/dL), use of antidiabetic agents, or both. d Alcohol drinking was defined as consuming at least 1 drink per week. LAB quartilessLOX-1 quartiles LAB: LOX-1 ligand containing ApoB sLOX-1: soluble LOX-1 released from plasma membrane

© Copyright 2009 by the American Association for Clinical Chemistry Results Model 1 adjusted for age, sex, BMI, smoking, drinking, hypertension, diabetes, and use of lipid-lowering agents; model 2 as model 1 with the addition of non-HDL cholesterol. LAB quartiles LAB: LOX-1 ligand containing ApoB High LAB confers an increased risk of ischemic stroke.

© Copyright 2009 by the American Association for Clinical Chemistry Results Model 1 adjusted for age, sex, BMI, smoking, drinking, hypertension, diabetes, and use of lipid-lowering agents; model 2 as model 1 with the addition of non- HDL cholesterol. LOX index (x10 6 ) quartiles Low LOX index is associated with lower risk of ischemic stroke. High LOX index is a risk of CHD. LOX index = LAB x sLOX-1

© Copyright 2009 by the American Association for Clinical Chemistry Question  The authors have recently reported that there was no association between low density lipoprotein cholesterol (LDL-C) and the incidence of ischemic stroke in the same cohort.  Why could LOX index predict the risk of ischemic stroke, while LDL-C cholesterol could not?

© Copyright 2009 by the American Association for Clinical Chemistry Discussion  Experiments Indicate LOX index measured by activity-based assay successfully predicted the risk of ischemic stroke The hazard ratio was >3, as large as that for hypertension LOX index also predicted the risk of CHD

© Copyright 2009 by the American Association for Clinical Chemistry Discussion (cont)  Hypothesis LOX-1 ligand might have a role in promoting ischemic stroke that is not conferred by LDL-C alone LOX-1 promotes thrombosis in animal models, which can cause ischemic stroke

© Copyright 2009 by the American Association for Clinical Chemistry Discussion (cont)  Clinical Implications LOX index appears to supply the missing link between ischemic stroke and cholesterol-related parameters LOX index might be used as a therapeutic index in prophylaxis of stroke and CHD LOX-1 antagonist therapy might be effective in preventing ischemic stroke and CHD

© Copyright 2009 by the American Association for Clinical Chemistry Discussion (cont)  Take-Home Message LOX index predicts the risk of ischemic stroke as strongly as hypertension does