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- Claussnitzer, M., et al.
(författare)
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FTO Obesity Variant Circuitry and Adipocyte Browning in Humans
- 2015
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Ingår i: New England Journal of Medicine. - 0028-4793. ; 373:10, s. 895-907
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Genomewide association studies can be used to identify disease-relevant genomic regions, but interpretation of the data is challenging. The FTO region harbors the strongest genetic association with obesity, yet the mechanistic basis of this association remains elusive. We examined epigenomic data, allelic activity, motif conservation, regulator expression, and gene coexpression patterns, with the aim of dissecting the regulatory circuitry and mechanistic basis of the association between the FTO region and obesity. We validated our predictions with the use of directed perturbations in samples from patients and from mice and with endogenous CRISPR-Cas9 genome editing in samples from patients. Our data indicate that the FTO allele associated with obesity represses mitochondrial thermogenesis in adipocyte precursor cells in a tissue-autonomous manner. The rs1421085 T-to-C single-nucleotide variant disrupts a conserved motif for the ARID5B repressor, which leads to derepression of a potent preadipocyte enhancer and a doubling of IRX3 and IRX5 expression during early adipocyte differentiation. This results in a cell-autonomous developmental shift from energy-dissipating beige (brite) adipocytes to energy-storing white adipocytes, with a reduction in mitochondrial thermogenesis by a factor of 5, as well as an increase in lipid storage. Inhibition of Irx3 in adipose tissue in mice reduced body weight and increased energy dissipation without a change in physical activity or appetite. Knockdown of IRX3 or IRX5 in primary adipocytes from participants with the risk allele restored thermogenesis, increasing it by a factor of 7, and overexpression of these genes had the opposite effect in adipocytes from nonrisk-allele carriers. Repair of the ARID5B motif by CRISPR-Cas9 editing of rs1421085 in primary adipocytes from a patient with the risk allele restored IRX3 and IRX5 repression, activated browning expression programs, and restored thermogenesis, increasing it by a factor of 7. Our results point to a pathway for adipocyte thermogenesis regulation involving ARID5B, rs1421085, IRX3, and IRX5, which, when manipulated, had pronounced pro-obesity and anti-obesity effects. (Funded by the German Research Center for Environmental Health and others.)
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- Jordan, Jens, et al.
(författare)
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Joint scientific statement of the European Association for the Study of Obesity and the European Society of Hypertension: obesity and early vascular ageing.
- 2015
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Ingår i: Journal of Hypertension. - 1473-5598. ; 33:3, s. 425-434
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Tidskriftsartikel (refereegranskat)abstract
- Current cardiovascular risk scores do not include obesity or fat distribution as independent factors, and may underestimate risk in obese individuals. Assessment of early vascular ageing (EVA) biomarkers including arterial stiffness, central blood pressure, carotid intima-media thickness and flow-mediated vasodilation may help to refine risk assessment in obese individuals in whom traditional cardiovascular risk scores and factors suggest no need for specific medical attention. A number of issues need to be addressed before this approach is ready for translation into routine clinical practice. Methodologies for measurements of vascular markers need to be further standardized and less operator-dependent. The utility of these nontraditional risk factors will also need to be proven in sufficiently large and properly designed interventional studies. Indeed, published studies on vascular markers in obesity and weight loss vary in quality and study design, are sometimes conducted in small populations, use a variety of differing methodologies and study differing vascular beds. Finally, current vascular measurements are still crude and may not be sufficient to cover the different aspects of EVA in obesity.
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