Increased plasminogen-activator inhibitor 1 (PAI-1) activity is a common finding in patients with coronary heart disease. Here we provide evidence for an independent, etiological role of PAI-1 in myocardial infarction. The 4G allele of a recently described common 4/5-guanine-tract (4G/5G) polymorphism in the PAI-i promoter is associated with higher plasma PAI-1 activity. The prevalence of the 4G allele is significantly higher in patients with myocardial infarction before the age of 45 than in population-based controls (allele frequencies of 0.63 vs. 0.53). Both alleles bind a transcriptional activator, whereas the 5G allele also binds a repressor protein to an overlapping binding site. In the absence of bound repressor, the basal level of PAI-i transcription is increased.

OBJECTIVEProinsulin is a precursor of mature insulin and C-peptide. Higher circulating proinsulin levels are associated with impaired β-cell function, raised glucose levels, insulin resistance, and type 2 diabetes (T2D). Studies of the insulin processing pathway could provide new insights about T2D pathophysiology.RESEARCH DESIGN AND METHODSWe have conducted a meta-analysis of genome-wide association tests of ∼2.5 million genotyped or imputed single nucleotide polymorphisms (SNPs) and fasting proinsulin levels in 10,701 nondiabetic adults of European ancestry, with follow-up of 23 loci in up to 16,378 individuals, using additive genetic models adjusted for age, sex, fasting insulin, and study-specific covariates.RESULTSNine SNPs at eight loci were associated with proinsulin levels (P < 5 × 10−8). Two loci (LARP6 and SGSM2) have not been previously related to metabolic traits, one (MADD) has been associated with fasting glucose, one (PCSK1) has been implicated in obesity, and four (TCF7L2, SLC30A8, VPS13C/C2CD4A/B, and ARAP1, formerly CENTD2) increase T2D risk. The proinsulin-raising allele of ARAP1 was associated with a lower fasting glucose (P = 1.7 × 10−4), improved β-cell function (P = 1.1 × 10−5), and lower risk of T2D (odds ratio 0.88; P = 7.8 × 10−6). Notably, PCSK1 encodes the protein prohormone convertase 1/3, the first enzyme in the insulin processing pathway. A genotype score composed of the nine proinsulin-raising alleles was not associated with coronary disease in two large case-control datasets.CONCLUSIONSWe have identified nine genetic variants associated with fasting proinsulin. Our findings illuminate the biology underlying glucose homeostasis and T2D development in humans and argue against a direct role of proinsulin in coronary artery disease pathogenesis.

Background-Apolipoprotein (apo) A-II is a major structural protein of plasma HDLs, but little is known regarding its functions. Methods and Results-To investigate the physiological role of apoA-II in humans, we screened the promoter region of the apoA-II gene for a functional polymorphism and used this polymorphism as a tool in association studies. A common, functional polymorphism in the promoter region of the apoA-II gene, a T to C substitution at position Ϫ265, was found. Electrophoretic mobility shift assays demonstrated that the Ϫ265T/C polymorphism influences the binding of nuclear proteins, whereas transient transfection studies in human hepatoma cells showed a reduced basal rate of transcription of the Ϫ265C allele compared with the Ϫ265T allele. The Ϫ265C allele was associated with decreased plasma apoA-II concentration and decreased waist circumference in healthy 50-year-old men. In addition, oral fat tolerance tests provided evidence that the Ϫ265C allele enhances postprandial metabolism of large VLDLs. Conclusions-ApoA-II appears to promote visceral fat accumulation and impair metabolism of large VLDLs.

Abstract-Plasma fibrinogen is a major risk factor for coronary heart disease, stroke, and peripheral artery disease. There is evidence that genetic variation in the ␤-fibrinogen gene contributes to the rate of synthesis of fibrinogen, but the molecular mechanism underlying the genetic heritability of the plasma fibrinogen concentration is largely unknown. We evaluated the physiological roles of 5 common nucleotide substitutions in the promoter region of the ␤-fibrinogen gene at positions Ϫ148, Ϫ249, Ϫ455, Ϫ854, and Ϫ993 from the transcriptional start site. Electrophoretic mobility shift assays revealed distinct differences in the binding characteristics of nuclear proteins between wild-type and mutant fragments of both the Ϫ455G/A and Ϫ854G/A polymorphisms, whereas no clear differences were observed for the Ϫ148C/T, Ϫ249C/T, and Ϫ993C/T sites. Transfection studies in HepG2 cells showed increased basal rates of transcription for both the G-to-A substitution at position Ϫ455 (ϩ50%, PϽ0.05) and the G-to-A substitution at Ϫ854 (ϩ51%, PϽ0.05). Additional transfection studies using proximal promoter constructs confirmed that both the Ϫ455A and Ϫ854A alleles independently enhance the basal rate of transcription of the ␤-fibrinogen gene. The rare alleles of the nonrelated Ϫ455G/A and Ϫ854G/A polymorphisms were also associated with significantly increased plasma fibrinogen levels in healthy middle-aged men. Overall, the 2 polymorphisms together explained Ϸ11% of the variation in plasma fibrinogen concentration. It is concluded that the Ϫ455G/A and Ϫ854G/A polymorphisms of the ␤-fibrinogen gene are physiologically relevant mutations with a significant impact on the plasma fibrinogen concentration.