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The Role of FTO and Vitamin D for the Weight Loss Effect of Roux-en-Y Gastric Bypass Surgery in Obese Patients
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology.
eSwiss Med & Surg Ctr, Interdisciplinary Obes Ctr, St Gallen, Switzerland..
eSwiss Med & Surg Ctr, Interdisciplinary Obes Ctr, St Gallen, Switzerland..
eSwiss Med & Surg Ctr, Interdisciplinary Obes Ctr, St Gallen, Switzerland..
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2015 (English)In: Obesity Surgery, ISSN 0960-8923, E-ISSN 1708-0428, Vol. 25, no 11, 2071-2077 p.Article in journal (Refereed) Published
Abstract [en]

A recent study in children demonstrated that the rs9939609 single-nucleotide polymorphism in the fat mass and obesity (FTO) gene influences prospective weight gain, however, only in those who were vitamin D-deficient. If this might also be the case for Roux-en-Y gastric bypass (RYGB), surgery-induced weight loss is however unknown. The objective of this study is to examine if the magnitude of RYGB surgery-induced weight loss after 2 years depends on patients' FTO rs9939609 genotype (i.e., TT, AT, and AA) and presurgery vitamin D status (< 50 nmol/L equals deficiency). Before and at 24 months after RYGB surgery, BMI was measured in 210 obese patients (mean BMI 45 kg/m(2), 72 % females). Serum 25-hydroxyvitamin D3 levels were also repeatedly measured. Following surgery, vitamin D was supplemented. Possible weight loss differences between genotypes were tested with multiple linear regressions. The per-allele effect of each FTO A-allele on excessive BMI loss (EBMIL) was 3 % (P = 0.02). When split by baseline status, the EBMIL of vitamin D-deficient patients carrying AA exceeded that of vitamin D-deficient patients carrying TT by similar to 14 % (P = 0.03). No such genotypic differences were found in patients without presurgery vitamin D deficiency. Post-surgery serum levels of vitamin D did not differ between groups. Our data suggest that presurgery vitamin D levels influence the size of genotype effects of FTO rs9939609 on RYGB surgery-induced weight loss in obese patients.

Place, publisher, year, edition, pages
2015. Vol. 25, no 11, 2071-2077 p.
Keyword [en]
Vitamin D, FTO, RYGB, Weight loss, Bariatric surgery
National Category
Surgery Pharmacology and Toxicology
URN: urn:nbn:se:uu:diva-266692DOI: 10.1007/s11695-015-1644-4ISI: 000362578700049PubMedID: 25724814OAI: diva2:868903
Swedish Research CouncilThe Swedish Brain FoundationNovo Nordisk
Available from: 2015-11-12 Created: 2015-11-10 Last updated: 2016-08-26Bibliographically approved
In thesis
1. The role of genetics in regulation of weight loss and food intake
Open this publication in new window or tab >>The role of genetics in regulation of weight loss and food intake
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

While obesity is a world leading health problem, the most efficient treatment option for severely obese patients is Roux-Y gastric bypass (RYGB) surgery. However, there are large inter-individual differences in weight loss after RYGB surgery. The reasons for this are not yet elucidated and the role of genetics in weight loss-regulation is still not fully understood. The main aim for this thesis was to investigate the effects of common obesity-associated genetic variants and their effect on weight loss and food intake.

We examined if the weight loss two years following RYGB surgery depends on the  FTO genotype, as well as pre-surgery vitamin D status. For FTO AA-carriers, the surgery resulted in a 3% per-allele increased excess BMI loss (EBMIL; P=0.02). When split by vitamin D baseline status, the EBMIL of vitamin D deficient patients carrying AA exceeded that of vitamin D deficient patients carrying TT by 14% (P=0.03). No such genotypic differences were found in patients without pre-surgery vitamin D deficiency.

As the influence of individual single nucleotide polymorphisms may be small, we identified a novel method to combine SNPs into a genetic risk score (GRS). Using the random forest model, SNPs with high impact on weight loss after RYGB surgery were filtered out. An up to 11% lower EBMIL with higher risk score was estimated for the GRS model (p=0.026) composed of seven BMI-associated SNPs (closest genes: MC4R, TMEM160, PTBP2, NUDT3, TFAP2B, ZNF608 and MAP2K5).

Pre-surgical hunger feelings were found to be associated with EBMIL and the SNP rs4846567. Before surgery, patients filled out the Three Factor Eating Questionnaire and were genotyped for known BMI and waist-hip ratio (WHR) associated SNPs. Patients with the lowest hunger scores had up to 32% greater EBMIL compared to the highest scoring patients (P=0.002). TT-allele carriers of rs4846567 showed a 58% lower hunger feelings. TT- carriers also showed a 51% decrease in disinhibition, but no significant impact on cognitive restraint was observed.

Due to the association of eating behaviour and weight loss, acute effects on DNA methylation in response to a food intake intervention of a standardized meal were also investigated.

After food intake, 1832 CpG sites were differentially methylated compared to the baseline after multiple testing correction. When adjusted for white blood cell fractions, 541 CpG sites remained. This may be interpreted as that the immune system is playing an active role in the response to food intake and highlights the dynamic nature of DNA-methylation.

These findings will contribute to a better care for morbidly obese patients. Post-surgical treatment may be optimized so that patients with a less favourable genetic profile may receive additional support for weight loss and weight management. This may be considered as a step in the transition towards personalized medicine.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 43 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1236
FTO, RYGB, LYPLAL1, TFEQ, Genetic Risk Score, methylation, food intake
National Category
Medical Genetics
Research subject
Bioinformatics; Medical Genetics
urn:nbn:se:uu:diva-297729 (URN)978-91-554-9617-3 (ISBN)
External cooperation:
Public defence
2016-09-09, A1:107 BMC, Husargatan 3, Uppsala, 10:00 (English)
Available from: 2016-08-19 Created: 2016-06-27 Last updated: 2016-08-26

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