| 1. |
- Walters, R G, et al.
(författare)
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A new highly penetrant form of obesity due to deletions on chromosome 16p11.2.
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 463:7281, s. 671-5
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Tidskriftsartikel (refereegranskat)abstract
- Obesity has become a major worldwide challenge to public health, owing to an interaction between the Western 'obesogenic' environment and a strong genetic contribution. Recent extensive genome-wide association studies (GWASs) have identified numerous single nucleotide polymorphisms associated with obesity, but these loci together account for only a small fraction of the known heritable component. Thus, the 'common disease, common variant' hypothesis is increasingly coming under challenge. Here we report a highly penetrant form of obesity, initially observed in 31 subjects who were heterozygous for deletions of at least 593 kilobases at 16p11.2 and whose ascertainment included cognitive deficits. Nineteen similar deletions were identified from GWAS data in 16,053 individuals from eight European cohorts. These deletions were absent from healthy non-obese controls and accounted for 0.7% of our morbid obesity cases (body mass index (BMI) >or= 40 kg m(-2) or BMI standard deviation score >or= 4; P = 6.4 x 10(-8), odds ratio 43.0), demonstrating the potential importance in common disease of rare variants with strong effects. This highlights a promising strategy for identifying missing heritability in obesity and other complex traits: cohorts with extreme phenotypes are likely to be enriched for rare variants, thereby improving power for their discovery. Subsequent analysis of the loci so identified may well reveal additional rare variants that further contribute to the missing heritability, as recently reported for SIM1 (ref. 3). The most productive approach may therefore be to combine the 'power of the extreme' in small, well-phenotyped cohorts, with targeted follow-up in case-control and population cohorts.
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| 2. |
- Palmer, C. N. A., et al.
(författare)
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Paradoxical Lower Serum Triglyceride Levels and Higher Type 2 Diabetes Mellitus Susceptibility in Obese Individuals with the PNPLA3 148M Variant
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:6
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Tidskriftsartikel (refereegranskat)abstract
- Background: Obesity is highly associated with elevated serum triglycerides, hepatic steatosis and type 2 diabetes (T2D). The I148M (rs738409) genetic variant of patatin-like phospholipase domain-containing 3 gene (PNPLA3) is known to modulate hepatic triglyceride accumulation, leading to steatosis. No association between PNPLA3 I148M genotype and T2D in Europeans has been reported. Aim of this study is to examine the relationship between PNPLA3 I148M genotypes and serum triglycerides, insulin resistance and T2D susceptibility by testing a gene-environment interaction model with severe obesity. Methods and Findings: PNPLA3 I148M was genotyped in a large obese cohort, the SOS study (n = 3,473) and in the Go-DARTS (n = 15,448), a T2D case-control study. Metabolic parameters were examined across the PNPLA3 I148M genotypes in participants of the SOS study at baseline and at 2- and 10-year follow up after bariatric surgery or conventional therapy. The associations with metabolic parameters were validated in the Go-DARTS study. Serum triglycerides were found to be lower in the PNPLA3 148M carriers from the SOS study at baseline and from the Go-DARTS T2D cohort. An increased risk for T2D conferred by the 148M allele was found in the SOS study (O.R. 1.09, 95% C.I. 1.01-1.39, P = 0.040) and in severely obese individuals in the Go-DARTS study (O. R. 1.37, 95% C.I. 1.13-1.66, P = 0.001). The 148M allele was no longer associated with insulin resistance or T2D after bariatric surgery in the SOS study and no association with the 148M allele was observed in the less obese (BMI<35) individuals in the Go-DARTS study (P for interaction = 0.002). This provides evidence for the obesity interaction with 148M allele and T2D risk in a large-scale cross-sectional and a prospective interventional study. Conclusions: Severely obese individuals carrying the PNPLA3 148M allele have lower serum triglyceride levels, are more insulin resistant and more susceptible to T2D. This study supports the hypothesis that obesity-driven hepatic lipid accumulation may contribute to T2D susceptibility.
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| 3. |
- Falchi, M., et al.
(författare)
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Low copy number of the salivary amylase gene predisposes to obesity
- 2014
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 46:5, s. 492-497
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Tidskriftsartikel (refereegranskat)abstract
- Common multi-allelic copy number variants (CNVs) appear enriched for phenotypic associations compared to their biallelic counterparts. Here we investigated the influence of gene dosage effects on adiposity through a CNV association study of gene expression levels in adipose tissue. We identified significant association of a multi-allelic CNV encompassing the salivary amylase gene (AMY1) with body mass index (BMI) and obesity, and we replicated this finding in 6,200 subjects. Increased AMY1 copy number was positively associated with both amylase gene expression (P = 2.31 × 10-14) and serum enzyme levels (P < 2.20 × 10-16), whereas reduced AMY1 copy number was associated with increased BMI (change in BMI per estimated copy =-0.15 (0.02) kg/m 2; P = 6.93 × 10-10) and obesity risk (odds ratio (OR) per estimated copy = 1.19, 95% confidence interval (CI) = 1.13-1.26; P = 1.46 × 10-10). The OR value of 1.19 per copy of AMY1 translates into about an eightfold difference in risk of obesity between subjects in the top (copy number > 9) and bottom (copy number < 4) 10% of the copy number distribution. Our study provides a first genetic link between carbohydrate metabolism and BMI and demonstrates the power of integrated genomic approaches beyond genome-wide association studies. © 2014 Nature America, Inc. All rights reserved.
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| 4. |
- Moustafa, J. S. E., et al.
(författare)
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Novel association approach for variable number tandem repeats (VNTRs) identifies DOCK5 as a susceptibility gene for severe obesity
- 2012
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 21:16, s. 3727-3738
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Tidskriftsartikel (refereegranskat)abstract
- Variable number tandem repeats (VNTRs) constitute a relatively under-examined class of genomic variants in the context of complex disease because of their sequence complexity and the challenges in assaying them. Recent large-scale genome-wide copy number variant mapping and association efforts have highlighted the need for improved methodology for association studies using these complex polymorphisms. Here we describe the in-depth investigation of a complex region on chromosome 8p21.2 encompassing the dedicator of cytokinesis 5 (DOCK5) gene. The region includes two VNTRs of complex sequence composition which flank a common 3975 bp deletion, all three of which were genotyped by polymerase chain reaction and fragment analysis in a total of 2744 subjects. We have developed a novel VNTR association method named VNTRtest, suitable for association analysis of multi-allelic loci with binary and quantitative outcomes, and have used this approach to show significant association of the DOCK5 VNTRs with childhood and adult severe obesity (P-empirical 8.9 10(8) and P 3.1 10(3), respectively) which we estimate explains approximate to 0.8 of the phenotypic variance. We also identified an independent association between the 3975 base pair (bp) deletion and obesity, explaining a further 0.46 of the variance (P-combined 1.6 10(3)). Evidence for association between DOCK5 transcript levels and the 3975 bp deletion (P 0.027) and both VNTRs (P-empirical 0.015) was also identified in adipose tissue from a Swedish family sample, providing support for a functional effect of the DOCK5 deletion and VNTRs. These findings highlight the potential role of DOCK5 in human obesity and illustrate a novel approach for analysis of the contribution of VNTRs to disease susceptibility through association studies.
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| 5. |
- Dongiovanni, P., et al.
(författare)
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Transmembrane 6 Superfamily Member 2 Gene Variant Disentangles Nonalcoholic Steatohepatitis From Cardiovascular Disease
- 2015
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Ingår i: Hepatology. - : Ovid Technologies (Wolters Kluwer Health). - 0270-9139 .- 1527-3350. ; 61:2, s. 506-514
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Tidskriftsartikel (refereegranskat)abstract
- Excess hepatic storage of triglycerides is considered a benign condition, but nonalcoholic steatohepatitis (NASH) may progress to fibrosis and promote atherosclerosis. Carriers of the TM6SF2 E167K variant have fatty liver as a result of reduced secretion of very-low-density lipoproteins (VLDLs). As a result, they have lower circulating lipids and reduced risk of myocardial infarction. In this study, we aimed to assess whether TM6SF2 E167K affects liver damage and cardiovascular outcomes in subjects at risk of NASH. Liver damage was evaluated in 1,201 patients who underwent liver biopsy for suspected NASH; 427 were evaluated for carotid atherosclerosis. Cardiovascular outcomes were assessed in 1,819 controls from the Swedish Obese Subjects (SOS) cohort. Presence of the inherited TM6SF2 E167K variant was determined by TaqMan assays. In the liver biopsy cohort, 188 subjects (13%) were carriers of the E167K variant. They had lower serum lipid levels than noncarriers (P<0.05), had more-severe steatosis, necroinflammation, ballooning, and fibrosis (P<0.05), and were more likely to have NASH (odds ratio [OR]: 1.84; 95% confidence interval [CI]: 1.23-2.79) and advanced fibrosis (OR, 2.08; 95% CI: 1.20-3.55), after adjustment for age, sex, body mass index, fasting hyperglycemia, and the I148M PNPLA3 risk variant. However, E167K carriers had lower risk of developing carotid plaques (OR, 0.49; 95% CI: 0.25-0.94). In the SOS cohort, E167K carriers had higher alanine aminotransferase ALT and lower lipid levels (P<0.05), as well as a lower incidence of cardiovascular events (hazard ratio: 0.61; 95% CI: 0.39-0.95). Conclusions: Carriers of the TM6SF2 E167K variant are more susceptible to progressive NASH, but are protected against cardiovascular disease. Our findings suggest that reduced ability to export VLDLs is deleterious for the liver. (Hepatology 2015;61:506-514)
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| 6. |
- Gabrielsson, Britt, 1957, et al.
(författare)
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Molecular characterization of a local sulfonylurea system in human adipose tissue.
- 2004
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Ingår i: Molecular and cellular biochemistry. - 0300-8177 .- 1573-4919. ; 258:1-2, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- ATP-sensitive potassium (KATP) channels are present in many cell types and link cellular metabolism to the membrane potential. These channels are heterooctamers composed of two subunits. The sulfonylurea receptor (SUR) subunits are targets for drugs that are inhibitors or openers of the KATP channels, while the inwardly rectifying K+ (Kir) subunits form the ion channel. Two different SUR genes (SUR1 and SUR2) and two different Kir6.x genes (Kir6.1 and Kir6.2) have been identified. In addition, isoforms of SUR2, SUR2A and SUR2B, have been described. We have previously performed expression profiling on pooled human adipose tissue and found high expression of SUR2. Others have reported expression of SUR1 in human adipocytes. The aim of this study was to characterize the expression of the sulfonylurea receptor complex components in human adipose tissue. RT-PCR analysis, verified by restriction enzyme digestions and DNA sequencing, showed that SUR2B, Kir6.1 and alpha-endosulfine, but not SUR1, SUR2A or Kir6.2, are expressed in human adipose tissue. Real-time RT-PCR showed that SUR2B was expressed at higher levels in subcutaneous compared with omental adipose tissue in paired biopsies obtained from seven obese men (p < 0.05). Analysis of tissue distribution showed that SUR2B expression in adipose tissue was lower than that in muscle, similar to that in heart and liver, while the expression in pancreas was lower. The effect of caloric restriction was tested in obese men (n = 10) treated with very low calorie diet for 16 weeks, followed by a gradual reintroduction of ordinary food for 2 weeks. Biopsies were taken at week 0, 8 and 18. There was no consistent effect of weight reduction on SUR2B or Kir6.1 expression. We conclude that the necessary components for a local sulfonylurea system are expressed in human adipose tissue and that the sulfonylurea receptor complex in this tissue is composed of SUR2B and Kir6.1. The expression of SUR2B was higher in subcutaneous compared with omental adipose tissue and was not affected by weight loss.
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| 7. |
- Gummesson, Anders, 1973, et al.
(författare)
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Relations of Adipose Tissue Cell Death-Inducing DFFA-like Effector A Gene Expression to Basal Metabolic Rate, Energy Restriction and Obesity: Population-based and Dietary Intervention Studies.
- 2007
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 92:12, s. 4759-65
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Tidskriftsartikel (refereegranskat)abstract
- Context: Cell death-inducing DFFA-like effector A (CIDEA) could be a potential target for the treatment of obesity via the modulation of metabolic rate, based on the findings that CIDEA inhibits the brown adipose tissue uncoupling process in rodents. Objective: To investigate the putative link between CIDEA and basal metabolic rate in humans, and to further elucidate the role of CIDEA in human obesity. Design: We have explored CIDEA gene expression in adipose tissue in two different human studies: A cross-sectional and population-based study assessing body composition and metabolic rate (Mölndal Metabolic study, n=92), and a longitudinal intervention-study of obese subjects treated with a very low calorie diet (VLCD study, n=24). Results: The CIDEA gene was predominantly expressed in adipocytes as compared to other human tissues. CIDEA gene expression in adipose tissue was inversely associated with basal metabolic rate independently of body composition, age and gender (p=0.014). VLCD induced an increase in adipose tissue CIDEA expression (p<0.0001) with a subsequent decrease in response to refeeding (p<0.0001). Reduced CIDEA gene expression was associated with a high body fat content (p<0.0001) and with high insulin levels (p<0.01). No dysregulation of CIDEA expression was observed in individuals with the metabolic syndrome when compared with BMI-matched controls. In a separate sample of VLCD-treated subjects (n=10), uncoupling protein 1 expression was reduced during diet (p=0.0026) and inversely associated with CIDEA expression (p=0.0014). Conclusion: The findings are consistent with the concept that CIDEA plays a role in adipose tissue energy expenditure.
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| 8. |
- Karlsson, C, et al.
(författare)
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Effects of growth hormone treatment on the leptin system and on energy expenditure in abdominally obese men.
- 1998
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Ingår i: European journal of endocrinology / European Federation of Endocrine Societies. - 0804-4643. ; 138:4, s. 408-14
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Tidskriftsartikel (refereegranskat)abstract
- The present study has examined the short- and long-term effects of growth hormone (GH) treatment on the leptin system and energy expenditure. Thirty male individuals with abdominal obesity were randomised to GH or placebo treatment in a 9-month, double-blind study. The dose of GH was 9.5 microg/kg, administered subcutaneously every evening. Serum leptin concentrations were measured by a human leptin RIA. Total RNA was isolated from adipose tissue biopsies and leptin mRNA levels were determined by a semi-quantitative reverse transcriptase-PCR assay. Body composition was determined by potassium-40 and the basal metabolic rate (BMR) was measured by a computerised, ventilated, open-hood system. As compared with placebo, an overall decrease in serum leptin concentrations as assessed by the area under the curve (AUC) (P < 0.05) and an increase in BMR (AUC, P < 0.05) were observed during GH treatment. The overall GH-induced changes were due to marked changes in serum leptin concentrations and BMR after 6 weeks of treatment. After 9 months of GH treatment there was a significant reduction in body fat (BF) while serum leptin concentrations and BMR did not differ from baseline values. Leptin mRNA levels did not change over the study period. We speculate that long-term GH treatment induces a new energy balance steady state with decreased BF stores. The effects of GH on the leptin system is suggested to be of importance for the maintenance of a lower BF mass.
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| 9. |
- Sarzynski, M. A., et al.
(författare)
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Changes in Uric Acid Levels following Bariatric Surgery Are Not Associated with SLC2A9 Variants in the Swedish Obese Subjects Study
- 2012
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- Context and Objective: Obesity and SLC2A9 genotype are strong determinants of uric acid levels. However, data on SLC2A9 variants and weight loss induced changes in uric acid levels are missing. We examined whether the changes in uric acid levels two- and ten-years after weight loss induced by bariatric surgery were associated with SLC2A9 single nucleotide polymorphisms (SNPs) in the Swedish Obese Subjects study. Methods: SNPs (N = 14) identified by genome-wide association studies and exonic SNPs in the SLC2A9 gene locus were genotyped. Cross-sectional associations were tested before (N = 1806), two (N = 1664) and ten years (N = 1201) after bariatric surgery. Changes in uric acid were compared between baseline and Year 2 (N = 1660) and years 2 and 10 (N = 1172). A multiple testing corrected threshold of P = 0.007 was used for statistical significance. Results: Overall, 11 of the 14 tested SLC2A9 SNPs were significantly associated with cross-sectional uric acid levels at all three time points, with rs13113918 showing the strongest association at each time point (R-2 = 3.725.2%, 3.9 x 10-(22)<= p <= 7.7 x 10(-11)). One SNP (rs737267) showed a significant association (R-2 = 0.60%, P = 0.002) with change in uric acid levels from baseline to Year 2, as common allele homozygotes (C/C, N = 957) showed a larger decrease in uric acid (-61.4 mu mol/L) compared to minor allele carriers (A/X: -51.7 mu mol/L, N = 702). No SNPs were associated with changes in uric acid from years 2 to 10. Conclusions: SNPs in the SLC2A9 locus contribute significantly to uric acid levels in obese individuals, and the associations persist even after considerable weight loss due to bariatric surgery. However, we found little evidence for an interaction between genotype and weight change on the response of uric acid to bariatric surgery over ten years. Thus, the fluctuations in uric acid levels among the surgery group appear to be driven by the weight losses and gains, independent of SLC2A9 genotypes. Citation: Sarzynski MA, Jacobson P, Rankinen T, Carlsson B, Sjostrom L, et al. (2012) Changes in Uric Acid Levels following Bariatric Surgery Are Not Associated with SLC2A9 Variants in the Swedish Obese Subjects Study.
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| 10. |
- Walley, A J, et al.
(författare)
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Differential coexpression analysis of obesity-associated networks in human subcutaneous adipose tissue.
- 2012
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 1476-5497 .- 0307-0565. ; 36:1, s. 137-147
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Tidskriftsartikel (refereegranskat)abstract
- Objective:To use a unique obesity-discordant sib-pair study design to combine differential expression analysis, expression quantitative trait loci (eQTLs) mapping and a coexpression regulatory network approach in subcutaneous human adipose tissue to identify genes relevant to the obese state.Study design:Genome-wide transcript expression in subcutaneous human adipose tissue was measured using Affymetrix U133 Plus 2.0 microarrays (Affymetrix, Santa Clara, CA, USA), and genome-wide genotyping data was obtained using an Applied Biosystems (Applied Biosystems; Life Technologies, Carlsbad, CA, USA) SNPlex linkage panel.Subjects:A total of 154 Swedish families ascertained through an obese proband (body mass index (BMI) >30kgm(-2)) with a discordant sibling (BMI>10kgm(-2) less than proband).Results:Approximately one-third of the transcripts were differentially expressed between lean and obese siblings. The cellular adhesion molecules (CAMs) KEGG grouping contained the largest number of differentially expressed genes under cis-acting genetic control. By using a novel approach to contrast CAMs coexpression networks between lean and obese siblings, a subset of differentially regulated genes was identified, with the previously GWAS obesity-associated neuronal growth regulator 1 (NEGR1) as a central hub. Independent analysis using mouse data demonstrated that this finding of NEGR1 is conserved across species.Conclusion:Our data suggest that in addition to its reported role in the brain, NEGR1 is also expressed in subcutaneous adipose tissue and acts as a central 'hub' in an obesity-related transcript network.
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