Fat mass-and obesity-associated (FTO) gene variant is associated with obesity: longitudinal analyses in two cohort studies and functional test.

Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, USA.
Diabetes (Impact Factor: 7.9). 11/2008; 57(11):3145-51. DOI: 10.2337/db08-0006
Source: PubMed

ABSTRACT To examine the longitudinal association of fat mass-and obesity-associated (FTO) variant with obesity, circulating adipokine levels, and FTO expression in various materials from human and mouse.
We genotyped rs9939609 in 2,287 men and 3,520 women from two prospective cohorts. Plasma adiponectin and leptin were measured in a subset of diabetic men (n = 854) and women (n = 987). Expression of FTO was tested in adipocytes from db/db mice and mouse macrophages.
We observed a trend toward decreasing associations between rs9939609 and BMI at older age (>or=65 years) in men, whereas the associations were constant across different age groups in women. In addition, the single nucleotide polymorphism (SNP) rs9939609 was associated with lower plasma adiponectin (log[e]--means, 1.82 +/- 0.04, 1.73 +/- 0.03, and 1.68 +/- 0.05 for TT, TA, and AA genotypes, respectively; P for trend = 0.02) and leptin (log[e]--means, 3.56 +/- 0.04, 3.63 +/- 0.04, and 3.70 +/- 0.06; P for trend = 0.06) in diabetic women. Adjustment for BMI attenuated the associations. FTO gene was universally expressed in human and mice tissues, including adipocytes. In an ancillary study of adipocytes from db/db mice, FTO expression was approximately 50% lower than in those from wild-type mice.
The association between FTO SNP rs9939609 and obesity risk may decline at older age. The variant affects circulating adiponectin and leptin levels through the changes in BMI. In addition, the expression of FTO gene was reduced in adipocytes from db/db mice.

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    ABSTRACT: Background: The fat mass and obesity-associated (FTO) single nucleotide polymorphisms (SNPs; rs1421085, rs17817449, rs9939609, rs8050136) and macronutrient intake (carbohydrate, protein, fat, total calories) are associated with body mass index (BMI). However, the mechanism for this relationship has not been fully elucidated. Objective: This study examined whether macronutrient intake mediates the association between FTO SNPs and BMI. Design: Baseline cross-sectional data from the Atherosclerosis Risk in Communities (ARIC) study of whites (n = 10,176) and African Americans (n = 3641) aged 45 to 64 years were analyzed. Results: In linear regression models with BMI as the dependent variable, FTO SNPs were significantly associated with higher BMI after adjusting for covariates. The addition of energy-adjusted macronutrients attenuated the FTO effect estimates, indicating partial mediation. In whites, β ranged from 0.40 (95% confidence interval [CI], 0.20, 0.60) for rs17817449 heterozygous carriers to 0.93 (95% CI, 0.64, 122) for rs8050136 homozygous carriers; for African Americans rs17817449 homozygous carriers β was 0.65 (95% CI, 0.03, 1.27). In models with macronutrient intake as the dependent variable, all FTO SNPs were associated with higher protein intake for homozygous carriers after adjusting for BMI and other covariates. Among whites, β ranged from 1.44 (95% CI, 0.51, 2.37) for rs8050136 to 1.73 (95% CI, 0.85, 2.61) for rs17817449; among African American rs8050136 homozygous carriers β was 2.46 (95% CI, 0.77, 4.14). In mediation analysis, in whites only, FTO high-risk alleles were associated with higher BMI partly through their small effects on carbohydrate and protein intake. Conclusions: These findings suggest that in adults, the relationship between FTO variants and BMI is not primarily through mediation of food intake.
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    ABSTRACT: Fat mass and obesity-associated (FTO) gene was found to be associated with energy homeostasis in mammals, yet the function of chicken FTO is less clear. In this study, chicken embryo fibroblast cells (DF-1) were transiently transfected to over-express (FTO(+)) or to knockdown (FTO(-)) the chicken FTO gene and were used for the functional analysis. FTO expression was significantly augmented in FTO(+) cells while depressed in FTO(-) cells (P<0.05). FTO(+) cells had significantly lower glucose yet higher lactic acid (LD) concentrations (P<0.05) in the culture media, which was associated with significantly up-regulated (P<0.05) mRNA expression of the rate-limiting gluconeogenic enzymes, glucose-6-phosphatase (G6PC) and the phosphoenolpyruvate carboxykinase-mitochondrial (PEPCK-m). The protein content and enzyme activity of G6PC were also significantly higher (P<0.05) in FTO(+) cells. Moreover, CCAAT/enhancer-binding protein-beta (C/EBP-beta) and cAMP responsive element binding protein 1 (CREB1), which were found to transcriptionally regulate the expression of G6PC, were increased at the level of both mRNA (P<0.05) and protein (P<0.05) in FTO(+) cells. ChIP analysis revealed significantly higher (P<0.05) binding of C/EBP-beta and phospho-CREB1 to G6PC gene promoter in FTO(+) cells. In addition, the interaction of FTO and C/EBP-beta was significantly enhanced (P<0.05) in FTO(+) cells. Opposite changes in G6PC expression and regulation were observed in FTO(-) cells. Our results indicate that chicken FTO regulates gluconeogenesis in DF-1 cells through enhanced transcriptional regulation of G6PC gene by C/EBP-beta and phospho-CREB1. Copyright © 2014 Elsevier Inc. All rights reserved.
    Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 10/2014; 179C:149-156. DOI:10.1016/j.cbpa.2014.10.003 · 2.37 Impact Factor

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