Soluble protein hormones are key regulators of a number of metabolic processes, including food intake and insulin sensitivity. We have used a signal sequence trap to identify genes that encode secreted or membrane-bound proteins in Psammomys obesus, an animal model of obesity and type 2 diabetes (T2D). Using this signal sequence trap, we identified the chemokine chemerin as being a novel adipokine. Gene expression of chemerin and its receptor, chemokine-like receptor 1 (CMKLR1), was significantly higher in adipose tissue of obese and type 2 diabetic P. obesus compared with lean, normoglycemic P. obesus. Fractionation of P. obesus adipose tissue confirmed that chemerin was predominantly expressed in adipocytes, whereas CMKLR1 was expressed in both adipocytes and stromal-vascular cells of adipose tissue. In 3T3-L1 adipocytes, chemerin was markedly induced during differentiation, whereas CMKLR1 was down-regulated during differentiation. Serum chemerin levels were measured by ELISA in human plasma samples from 114 subjects with T2D and 142 normal glucose tolerant controls. Plasma chemerin levels were not significantly different between subjects with T2D and normal controls. However, in normal glucose tolerant subjects, plasma chemerin levels were significantly associated with body mass index, circulating triglycerides, and blood pressure. Here we report, for the first time, that chemerin is an adipokine, and circulating levels of chemerin are associated with several key aspects of metabolic syndrome.

To further understanding of the genetic basis of type 2 diabetes (T2D) susceptibility, we aggregated published meta-analyses of genome-wide association studies (GWAS) including 26,488 cases and 83,964 controls of European, East Asian, South Asian, and Mexican and Mexican American ancestry. We observed significant excess in directional consistency of T2D risk alleles across ancestry groups, even at SNPs demonstrating only weak evidence of association. By following up the strongest signals of association from the trans-ethnic meta-analysis in an additional 21,491 cases and 55,647 controls of European ancestry, we identified seven novel T2D susceptibility loci. Furthermore, we observed considerable improvements in fine-mapping resolution of common variant association signals at several T2D susceptibility loci. These observations highlight the benefits of trans-ethnic GWAS for the discovery and characterisation of complex trait loci, and emphasize an exciting opportunity to extend insight into the genetic architecture and pathogenesis of human diseases across populations of diverse ancestry.

Quantitative differences in gene expression are thought to contribute to phenotypic differences between individuals. We generated genome-wide transcriptional profiles of lymphocyte samples from 1,240 participants in the San Antonio Family Heart Study. The expression levels of 85% of the 19,648 detected autosomal transcripts were significantly heritable. Linkage analysis uncovered >1,000 cis-regulated transcripts at a false discovery rate of 5% and showed that the expression quantitative trait loci with the most significant linkage evidence are often located at the structural locus of a given transcript. To highlight the usefulness of this much-enlarged map of cis-regulated transcripts for the discovery of genes that influence complex traits in humans, as an example we selected high-density lipoprotein cholesterol concentration as a phenotype of clinical importance, and identified the cis-regulated vanin 1 (VNN1) gene as harboring sequence variants that influence high-density lipoprotein cholesterol concentrations.

The European Union, the UK National Institute for Health Research, the Wellcome Trust, the UK Medical Research Council, Action on Hearing Loss, the UK Biotechnology and Biological Sciences Research Council, the Oak Foundation, the Economic and Social Research Council, Helmholtz Zentrum Munchen, the German Research Center for Environmental Health, the German Federal Ministry of Education and Research, the German Center for Diabetes Research, the Munich Center for Health Sciences, the Ministry of Science and Research of the State of North Rhine-Westphalia, and the German Federal Ministry of Health.

We carried out a genome wide association study of type-2 diabetes (T2D) amongst 20,119 people of South Asian ancestry (5,561 with T2D); we identified 20 independent SNPs associated with T2D at P<10−4 for testing amongst a further 38,568 South Asians (13,170 with T2D). In combined analysis, common genetic variants at six novel loci (GRB14, ST6GAL1, VPS26A, HMG20A, AP3S2 and HNF4A) were associated with T2D (P=4.1×10−8 to P=1.9×10−11); SNPs at GRB14 were also associated with insulin sensitivity, and at ST6GAL1 and HNF4A with pancreatic beta-cell function respectively. Our findings provide additional insight into mechanisms underlying T2D, and demonstrate the potential for new discovery from genetic association studies in South Asians who have increased susceptibility to T2D.