Genome-wide association studies for blood lipids. A great start but a long way to go

Trends in the incidence and mortality of coronary heart disease in asian pacific region: the Singapore experience

The rates of coronary heart disease are lower in Asia than in developed countries. Singapore has undergone rapid urbanization over the past several decades. In the several decades between the 1960s and 1980s, a rapid increase in the rates of ischemic heart disease was observed, to the extent that Singapore exhibits one of the highest rates of mortality from cardiovascular disease in the Asia-Pacific region, higher even than the rates in North America. Rates of cardiovascular disease have now stabilized, and are declining. This is, a pattern that has been observed in many developed countries. Increased life expectancy has resulted in an epidemiologic transition that has seen chronic non-communicable diseases replace malnutrition and infections as the major causes of mortality. At the same time, there have been changes in nutrient intake and physical activity as well as rapid increases in the levels of several cardiovascular risk factors including obesity, hypertension, hyperlipidemia, diabetes mellitus and systemic inflammation. Furthermore, when present, there is a lack of awareness and sub-optimal treatment of these risk factors. In addition to the changes in environmental exposures related to socio-economic development, it does appear that specific populations are particularly prone to the development of cardiovascular disease and its risk factors. In particular, Asian Indians experience a high rate of coronary heart disease and diabetes mellitus. Emerging data suggests that Chinese may be particularly prone to the adverse effects of obesity in relation to insulin resistance and inflammation. A concerted effort to change lifestyles to prevent the development of coronary heart disease risk factors, and to improve awareness and treatment of risk factors when then develop, is required to halt the epidemic of coronary heart disease that is occurring in Asia.

Integrated approaches to functionally characterize novel factors in lipoprotein metabolism

PURPOSE OF REVIEW

To discuss if and how the combined analysis of large-scale datasets from multiple independent sources benefits the mapping of novel genetic elements with relevance to lipoprotein metabolism and allows for conclusions on underlying molecular mechanisms.

RECENT FINDINGS

Genome-wide association studies (GWAS) have identified numerous genomic loci associated with plasma lipid levels and cardiovascular disease. Yet, despite being highly successful in mapping novel loci the GWAS approach falls short to systematically extract functional information from genomic data. With the aim to complement GWAS for a better insight into disease mechanisms and identification of the most promising targets for drug development, a number of high-throughput functional genomics strategies have now been applied. These include computational approaches, consideration of gene-gene and gene-environment interactions, as well as unbiased gene-expression analyses in relevant tissues. For a limited number of loci, mechanistic insight has been gained through in-vitro and in-vivo studies by knockdown and overexpression of candidate genes.

SUMMARY

The integration of GWAS data with existing functional genomics strategies has contributed to ascertain the relevance of a number of novel factors for lipoprotein biology and disease. However, technologies are warranted that provide a more systematic insight into the molecular function and pathogenic relevance of promising candidate genes.

Genetic determinants of lipid homeostasis

Circulating levels of blood lipids are heritable risk factors for atherosclerosis and heart disease, and are the target of therapeutic intervention. Studies of monogenic disorders and - more recently - genome-wide association studies have identified several important genetic determinants of blood lipid levels. These have the potential to provide new drug targets to alter blood lipid levels and may improve prediction of cardiovascular disease. Better functional validation of lipid loci is required to clarify the biological role of proteins encoded by specific genomic regions and understand how they influence lipid metabolism and confer disease risk.

Inclusion and exclusion in nutrigenetics clinical research: ethical and scientific challenges

BACKGROUND/AIMS

There are compelling reasons to ensure the participation of ethnic minorities and populations of all ages worldwide in nutrigenetics clinical research. If findings in such research are valid for some individuals, groups, or communities, and not for others, then ethical questions of justice--and not only issues of methodology and external validity--arise. This paper aims to examine inclusion in nutrigenetics clinical research and its scientific and ethical challenges.

METHODS

In total, 173 publications were identified through a systematic review of clinical studies in nutrigenetics published between 1998 and 2007. Data such as participants' demographics as well as eligibility criteria were extracted.

RESULTS

There is no consistency in the way participants' origins (ancestry, ethnicity, or race) and ages are described in publications. A vast majority of the studies identified was conducted in North America and Europe and focused on 'white' participants. Our results show that pregnant women (and fetuses), minors, and the elderly (≥ 75 years old) remain underrepresented.

CONCLUSION

Representativeness in nutrigenetics research is a challenging ethical and scientific issue. Yet, if nutrigenetics is to benefit whole populations and be used in public and global health agendas, fair representation as well as clear descriptions of participants in publications are crucial.

Lipoprotein association studies: taking stock and moving forward

PURPOSE OF REVIEW

Over the last year, huge progress has been made using SNP arrays to identify genes associated with lipid traits.

RECENT FINDINGS

The single genome-wide association studies (GWASs) may have reached a limit in identifying novel genes, but there has been tremendous progress from collaborative consortia examining pooled data from GWASs, often employing SNP imputation. For example, the Global Lipid Consortium reported that 56 of the 95 lipid-associated loci were novel to the pooled analysis from over 100 000 individuals. Complementary to this, a gene-centric approach, such as the 50K IBC HumanCVD chip, which provides deep coverage of approximately 2100 genes, has had success in ascertaining independently acting variants and helped us to move a step closer to identify functional variants. Yet irrespective of the platform used, for each trait, the percentage variance explained by these genes remains in the order of approximately 10-12% and it is still unclear to what extent rare mutations, identified by resequencing or exome sequencing approaches, or gene × gene and gene × environment studies, might boost this.

SUMMARY

GWAS-identified novel lipid-related loci highlight new pathways in lipid metabolism and may provide innovative drug targets. Furthermore, the use of lipid gene scores, over and above a single lipid measure, may have clinical utility.