The Role of FTO and Vitamin D for the Weight Loss Effect of Roux-en-Y Gastric Bypass Surgery in Obese Patients.
BACKGROUND
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).


METHODS
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.


RESULTS
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 ~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.


CONCLUSIONS
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.
Department Neuroscience, Functional Pharmacology, Uppsala University, Box 593, 751 24, Uppsala, Sweden. marcus.bandstein@neuro.uu.se.
Marcus
M
Bandstein
Interdisciplinary Obesity Center, eSwiss Medical & Surgical Center, St. Gallen, Switzerland. bernd.schultes@stephanshorn.ch.
Bernd
B
Schultes
Interdisciplinary Obesity Center, eSwiss Medical & Surgical Center, St. Gallen, Switzerland. barbara.ernst@stephanshorn.ch.
Barbara
B
Ernst
Interdisciplinary Obesity Center, eSwiss Medical & Surgical Center, St. Gallen, Switzerland. martin.thurnheer@stephanshorn.ch.
Martin
M
Thurnheer
Department Neuroscience, Functional Pharmacology, Uppsala University, Box 593, 751 24, Uppsala, Sweden. helgi.schioth@neuro.uu.se.
Helgi B
HB
Schiöth
Department Neuroscience, Functional Pharmacology, Uppsala University, Box 593, 751 24, Uppsala, Sweden. christian.benedict@neuro.uu.se.
Christian
C
Benedict
D000328:Adult; D000071516:Alpha-Ketoglutarate-Dependent Dioxygenase FTO; D000713:Anastomosis, Roux-en-Y; D019587:Dietary Supplements; D005260:Female; D015390:Gastric Bypass; D005838:Genotype; D006801:Humans; D008297:Male; D009767:Obesity, Morbid / Q000097:blood / Q000150:complications / Q000235:genetics / Q000601:surgery*; D020641:Polymorphism, Single Nucleotide / Q000502:physiology; D011184:Postoperative Period; D011446:Prospective Studies; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000235:genetics; D015431:Weight Loss / Q000235:genetics
D011506:Proteins; D014807:Vitamin D; D000071516:Alpha-Ketoglutarate-Dependent Dioxygenase FTO; C526492:FTO protein, human
Bariatric surgery; FTO; RYGB; Vitamin D; Weight loss