No Influence of the Fat Mass and Obesity-Associated Gene rs9939609 Single Nucleotide Polymorphism on Blood Lipids in Young Males

Associations of the obesity gene FTO variant with complications and comorbidities in patients with type 1 diabetes

BACKGROUND AND AIMS

Because FTO gene is connected with the risk of obesity, cardiovascular disease and hypertension, as well as type 2 diabetes, we hypothesize that the rs9939609 FTO polymorphism may affect type 1 diabetes (T1D) complications and comorbidities.

METHODS

We have investigated the associations of the FTO gene variant with the T1D and its complications and comorbidities, as well as the serum levels of pro- and anti-inflammatory markers and lipid profiles.

RESULTS

The key results of our study are as follows: (1) the rs9939609 FTO polymorphism does not predispose individuals to T1D; (2) AA genotype is associated with an increased risk of overweight and obesity, retinopathy, hypertension, dyslipidemia and celiac disease; (3) AT genotype is associated with a decreased risk of retinopathy and celiac disease, whereas TT genotype is connected with decreased risk of dyslipidemia; (4) the FTO rs9939609 polymorphism affects the inflammatory status as well as lipid profile in T1D patients.

CONCLUSIONS

Our results, for the first time, comprehensively indicate that the rs9939609 FTO polymorphism could be considered a genetic marker for increased susceptibility to T1D complications and comorbidities as well as suggests importance of FTO-mediated pathways in their etiology.

NEFA Dynamics in Adults With Severe Obesity and Insulin Resistance: No Coupling to the rs9939609 FTO Risk Allele

Context

The FTO gene is highly expressed in adipose tissues; however, whether nonesterified fatty acids (NEFA) dynamics are impacted by FTO has not been rigorously tested for in a uniformly obese study population comprising both sexes.

Objective

To test for associations of the rs9939609 FTO risk allele with NEFA suppression.

Methods

We investigated 97 subjects with severe obesity but without diabetes, having genotype TT (n = 32), AT (n = 31), or AA (n = 34) in a cross-sectional observation study. NEFA suppression was assessed from a low-dose hyperinsulinemic euglycemic clamp with glucose-tracer as well as from the response to a standardized meal. Insulin sensitivity was assessed by hepatic and total insulin sensitivity measurements in the clamp and by the Matsuda index during the meal. Variables of possible importance for NEFA dynamics were primarily assessed by linear regression.

Results

No genotype associations with fasting or suppressed NEFA were found, whether in the clamp or meal situation (P > .7 for all comparisons). Independent of genotype, higher fasting concentrations of NEFA and larger NEFA suppression were found in female compared with male subjects. Fasting NEFA or degree of suppression were not associated with total fat mass or body mass index. The respiratory quotient was negatively associated with NEFA suppression.

Conclusion

In a gender-mixed adult population of obese individuals, an FTO obesity-risk allele did not affect fasting NEFA nor suppression thereof. These negative results on NEFA dynamics appear strengthened by the documentation of gender influence and associations with parameters reflective of insulin resistance.

Association between the FTO rs9939609 single nucleotide polymorphism and dietary adherence during a 2-year caloric restriction intervention: Exploratory analyses from CALERIE™ phase 2

Caloric restriction (CR) improves markers of aging in humans; but it is not known if the fat mass and obesity-associated gene (FTO) rs9939609 single nucleotide polymorphism (SNP), which is associated with appetite and energy intake, influences adherence to prolonged CR. Utilizing data from the two-year Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE™) phase 2 randomized controlled trial, we tested whether the FTO rs9939609 SNP was associated with adherence to CR in healthy adults without obesity. As secondary aims, we assessed whether the FTO rs9939609 SNP was associated with changes in body composition, biomarkers of aging, and eating behaviors. Participants were randomized into either a CR group that targeted a 25% reduction in energy intake compared to the habitual energy intake at baseline, or an ad libitum (AL) control group. Participants were genotyped for the FTO rs9939609 SNP. Dietary adherence was determined through changes in energy intake using doubly labeled water and changes in body composition at baseline, month 12, and month 24 in both the CR and AL condition. Weight, body composition, resting metabolic rate (RMR), adiponectin, insulin, leptin, and eating behaviors were measured at the same timepoints. A total of 144 participants (91 CR and 53 AL, age: 38.6 ± 7.1 years; body mass index: 25.3 ± 1.7 kg/m²) were studied. Of these, 27 were homozygous for the 'obesity-risk' A allele (AA), while 44 were homozygous for the T allele (TT) and 73 were heterozygotes (AT). By design, the CR group exhibited greater percent CR compared to the AL group during the trial (P < 0.01), but no genotype-by-treatment interaction was observed for change in energy intake or percent CR (P ≥ 0.40). The FTO rs9939609 SNP was also negligibly associated with change in most other endpoints (P ≥ 0.13), though AAs showed a reduction in RMR adjusted for body composition change over the 24 months relative to TTs (genotype-by-treatment interaction: P = 0.03). In a two-year CR intervention delivered to healthy individuals without obesity, the FTO rs9939609 SNP was not associated with adherence to CR and did not alter improvements in most aging biomarkers.