Endothelium-dependent vasodilatation is mediated by release of nitric oxide formed by constitutively expressed endothelial nitric oxide synthase (ecNOS). We explored the distribution of polymorphism ecNOS4a/b in 549 subjects with, and 153 without, coronary artery disease in relation to smoking. In current and ex-cigarette smokers, but not nonsmokers, there was a significant excess of homozygotes for the rare ecNOS4a allele in patients with severely stenosed arteries, compared with those with no or mild stenosis. This genotype was also associated with a history of myocardial infarction. This smoking-dependent excess coronary risk in ecNOS4a homozygotes is consistent with predisposition to endothelial dysfunction.
Genome scans of bipolar disorder (BPD) have not produced consistent evidence for linkage. The rank-based genome scan meta-analysis (GSMA) method was applied to 18 BPD genome scan data sets in an effort to identify regions with significant support for linkage in the combined data. The two primary analyses considered available linkage data for "very narrow" (i.e., BP-I and schizoaffective disorder-BP) and "narrow" (i.e., adding BP-II disorder) disease models, with the ranks weighted for sample size. A "broad" model (i.e., adding recurrent major depression) and unweighted analyses were also performed. No region achieved genomewide statistical significance by several simulation-based criteria. The most significant P values (<.01) were observed on chromosomes 9p22.3-21.1 (very narrow), 10q11.21-22.1 (very narrow), and 14q24.1-32.12 (narrow). Nominally significant P values were observed in adjacent bins on chromosomes 9p and 18p-q, across all three disease models on chromosomes 14q and 18p-q, and across two models on chromosome 8q. Relatively few BPD pedigrees have been studied under narrow disease models relative to the schizophrenia GSMA data set, which produced more significant results. There was no overlap of the highest-ranked regions for the two disorders. The present results for the very narrow model are promising but suggest that more and larger data sets are needed. Alternatively, linkage might be detected in certain populations or subsets of pedigrees. The narrow and broad data sets had considerable power, according to simulation studies, but did not produce more highly significant evidence for linkage. We note that meta-analysis can sometimes provide support for linkage but cannot disprove linkage in any candidate region.
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