Ruth Loos and colleagues report results of a large genome-wide association study for body mass index. They identify 18 new loci associated with this trait, some of which map near key hypothalamic regulators of energy balance. Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ∼2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10−8), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation.

Timothy Frayling, Joel Hirschhorn, Peter Visscher and colleagues report a meta-analysis of genome-wide association studies for adult height in 253,288 individuals. They identify 697 variants in 423 loci significantly associated with adult height and find that these variants cluster in pathways involved in growth and together explain one-fifth of the heritability for this trait. Using genome-wide data from 253,288 individuals, we identified 697 variants at genome-wide significance that together explained one-fifth of the heritability for adult height. By testing different numbers of variants in independent studies, we show that the most strongly associated ∼2,000, ∼3,700 and ∼9,500 SNPs explained ∼21%, ∼24% and ∼29% of phenotypic variance. Furthermore, all common variants together captured 60% of heritability. The 697 variants clustered in 423 loci were enriched for genes, pathways and tissue types known to be involved in growth and together implicated genes and pathways not highlighted in earlier efforts, such as signaling by fibroblast growth factors, WNT/β-catenin and chondroitin sulfate–related genes. We identified several genes and pathways not previously connected with human skeletal growth, including mTOR, osteoglycin and binding of hyaluronic acid. Our results indicate a genetic architecture for human height that is characterized by a very large but finite number (thousands) of causal variants.

Erik Ingelsson and colleagues report a large-scale genome-wide meta-analysis for associations to the extremes of anthropometric traits, including body mass index, height, waist-to-hip ratio and clinical obesity. They identify four loci newly associated with height and seven loci newly associated with clinical obesity and find overlap in the genetic structure and distribution of variants identified for these extremes of the trait distributions and for the general population. Approaches exploiting trait distribution extremes may be used to identify loci associated with common traits, but it is unknown whether these loci are generalizable to the broader population. In a genome-wide search for loci associated with the upper versus the lower 5th percentiles of body mass index, height and waist-to-hip ratio, as well as clinical classes of obesity, including up to 263,407 individuals of European ancestry, we identified 4 new loci (IGFBP4, H6PD, RSRC1 and PPP2R2A) influencing height detected in the distribution tails and 7 new loci (HNF4G, RPTOR, GNAT2, MRPS33P4, ADCY9, HS6ST3 and ZZZ3) for clinical classes of obesity. Further, we find a large overlap in genetic structure and the distribution of variants between traits based on extremes and the general population and little etiological heterogeneity between obesity subgroups.

Essential hypertension is a multifactorial disorder and is the main risk factor for renal and cardiovascular complications. The research on the genetics of hypertension has been frustrated by the small predictive value of the discovered genetic variants. The HYPERGENES Project investigated associations between genetic variants and essential hypertension pursuing a 2-stage study by recruiting cases and controls from extensively characterized cohorts recruited over many years in different European regions. The discovery phase consisted of 1865 cases and 1750 controls genotyped with 1M Illumina array. Best hits were followed up in a validation panel of 1385 cases and 1246 controls that were genotyped with a custom array of 14 055 markers. We identified a new hypertension susceptibility locus (rs3918226) in the promoter region of the endothelial NO synthase gene (odds ratio: 1.54 [95% CI: 1.37–1.73]; combined P =2.58 · 10 ⁻¹³ ). A meta-analysis, using other in silico/de novo genotyping data for a total of 21 714 subjects, resulted in an overall odds ratio of 1.34 (95% CI: 1.25–1.44; P =1.032 · 10 ⁻¹⁴ ). The quantitative analysis on a population-based sample revealed an effect size of 1.91 (95% CI: 0.16–3.66) for systolic and 1.40 (95% CI: 0.25–2.55) for diastolic blood pressure. We identified in silico a potential binding site for ETS transcription factors directly next to rs3918226, suggesting a potential modulation of endothelial NO synthase expression. Biological evidence links endothelial NO synthase with hypertension, because it is a critical mediator of cardiovascular homeostasis and blood pressure control via vascular tone regulation. This finding supports the hypothesis that there may be a causal genetic variation at this locus.

To assess possible relationships between endogenous ouabain, sodium balance and blood pressure. This review concerns the structure of endogenous ouabain, circulating levels of this steroid in various disorders of fluid and electrolyte balance, recent evidence for the association of endogenous ouabain with human hypertension, the influence of sodium and volume factors on ouabain-induced hypertension, and possible mechanisms for the hypertensinogenic activity of ouabain. The human circulation contains a closely related isomer of ouabain of putative adrenocortical origin. Elevated circulating levels of this 'endogenous ouabain' are common but not universal in physiologic and pathologic states associated with positive sodium balance or high blood pressure, or both. In the absence of adrenal hyperfunction, elevating circulating levels of endogenous ouabain appear to be secondary to impaired renal clearance. Prolonged elevation of circulating ouabain in the rat induces sustained hypertension. This model exhibits normal plasma renin activity, increased levels of ouabain in the hypothalamus, pituitary, and kidney, and responds to angiotensin converting enzyme inhibitor. In rats with normal kidney function, ouabain-induced hypertension is primarily sodium-insensitive although maneuvers that hinder renal sodium excretion augment the pressor effect of this steroid. Prolonged administration of ouabain into the brain ventricles augments sympathetic nervous system activity and induces sustained hypertension. These observations lead us to propose the following hypothesis. Among Caucasian patients with essential hypertension, a large fraction have elevated circulating levels of endogenous ouabain, possibly caused by an inherited or acquired renal defect in clearance of this steroid. In these patients, and in rats with ouabain-induced hypertension, increased local generation of, or increased target organ sensitivity to, angiotensin II, or both, may contribute critically to heightened vasoconstriction and a sustained increase in blood pressure. Investigations of the efferent pressor mechanisms and the renal handling of endogenous ouabain are novel approaches to the etiology and therapy of several common cardiovascular disorders.