Evaluating the interaction of common FTO genetic variants, added sugar, and trans-fatty acid intakes in altering obesity phenotypes.

BACKGROUND AND AIMS: The results of studies on the effect of trans-fatty acids (TFAs) and added sugars on obesity are not consistent. This study aimed to investigate whether the association of changes in general and central obesity with added sugar and TFA intakes is modified by common fat mass and obesity-associated gene (FTO) polymorphisms, in isolation or in a combined-form genetic risk score (GRS). METHODS AND RESULTS: Subjects of this cohort study were selected from among adult participants of the Tehran Lipid and Glucose Study (n = 4292, 43.2% male). Dietary data were collected using a valid and reliable food frequency questionnaire. The genotypes of selected polymorphisms (rs1421085, rs1121980, and rs8050136) were determined. Genetic risk score (GRS) was calculated using the dominant weighted method. The mean age of participants was 42.6 ± 14 and 40.4 ± 13 years in men and women, respectively. FTO rs8050136 polymorphisms and TFAs have a significant interaction in changing body mass index (BMI) (P interaction = 0.01). There were no changes in waist circumference (WC) and BMI among FTO risk allele carriers, across quartiles of added sugar intake. GRS and TFA intakes significantly interacted in altering the BMI and WC; thus, a higher intake of TFAs was associated with higher changes of BMI and WC in subjects with high GRS (P trend<0.05) compared to individuals with low GRS. CONCLUSION: Our findings suggest that TFA intake can increase the genetic susceptibility of FTO SNPs to BMI or WC change.

Effect of interactions of polymorphisms in the Melanocortin-4 receptor gene with dietary factors on the risk of obesity and Type 2 diabetes: a systematic review.

AIM: To perform a systematic review of the effect of interaction between Melanocortin-4 receptor (MC4R) single nucleotide polymorphisms and diet on the development of obesity and Type 2 diabetes. BACKGROUND: Environmental factors, such as nutrient intakes or feeding behaviours, can modulate the association of polymorphism in the MC4R gene with obesity and Type 2 diabetes mellitus. METHODS: A systematic literature search was conducted in the PubMed, Scopus and Google Scholar databases, with a combination of the following keywords: Diet*, nutr*, melanocortin receptor, melanocortin 4 receptor and MC4R. To assess the quality of observational studies, we used a 12-item quality checklist, derived from the STREGA statement. RESULTS: A total of 14 articles were selected based on the inclusion and exclusion criteria. Consumption of highly salty foods and adherence to a Mediterranean dietary pattern can modulate the association between MC4R polymorphisms and the risk of obesity or Type 2 diabetes. Despite the highly contradictory results of intervention studies, after short-term lifestyle interventions, children with variant alleles of MC4R single nucleotide polymorphisms can lose more body weight, compared with non-carriers, although they may have difficulty in maintaining this weight loss in the long-term. To interpret the results of studies on adults, we need further studies. CONCLUSIONS: The interaction between MC4R genes with dietary factors plays a significant role in the development of obesity or Type 2 diabetes phenotypes. Early detection of MC4R risk alleles in individuals and modification of their diet based on these results could be an efficient strategy to prevent obesity or diabetes in these subgroups.

Metabolic syndrome profiles, obesity measures and intake of dietary fatty acids in adults: Tehran Lipid and Glucose Study.

BACKGROUND: To determine the association between fatty acid intake and the prevalence of risk factors for the metabolic syndrome. METHODS: In this population-based cross-sectional study, a sample of 2750 Tehranian subjects (44% men and 56% women) aged 20-74 years, who completed a validated food frequency questionnaire, was studied. The metabolic syndrome (MetS) was defined in accordance with the modified guidelines of the National Cholesterol Education Program Adults Treatment Panel III, and waist circumference was coded according to the newly-introduced cut-off points for Iranian adults (≥95 cm for both sexes). Metabolic risk factors across quartile categories of each type of dietary fat [total fat intake, total poly-unsaturated fatty acid (PUFA) intake, total MUFA intake, total saturated fatty acid (SFA) intake expressed as percentage of energy and quartiles of the ratio of polyunsaturated fat to saturated fat (P : S)] were compared. RESULTS: The mean (SD) ages of participants were 40.8 (14.6) and 38.6 (12.9) years, respectively, for men and women. The mean contribution of fat to energy intake was approximately 26% in men and women. A positive trend over successive quartiles of SFA intake with low-density lipoprotein-cholesterol (LDL-C) and triglyceride, as well as P/S ratio intake with high-density lipoprotein-cholesterol (HDL-C), was found. An inverse association between HDL-C with SFA and PUFA intake and a positive association with MUFA and the P/S ratio was found. A significant association of fatty acid consumption and risk of the MetS in this population was observed, except for total PUFA intake. CONCLUSIONS: Special dietary fatty acids are associated with metabolic risk factors among the Iranian population. Because of the high prevalence of cardiovascular disease and MetS, national nutrition policies must be developed accordingly for the modification of dietary fatty acid intake with respect to causation and prevention.

Fast food consumption and the risk of metabolic syndrome after 3-years of follow-up: Tehran Lipid and Glucose Study.

BACKGROUND: There are growing concern globally regarding fast food consumption and its related cardiometabolic outcomes. In this study we investigated whether fast food consumption could affect the occurrence of metabolic syndrome (MetS) after 3-years of follow-up in adults. METHODS: This longitudinal study was conducted in the framework of Tehran Lipid and Glucose Study on 1476 adults, aged 19-70 y. The usual intakes of participants were measured using a validated semi-quantitative food frequency questionnaire at baseline. Biochemical and anthropometric measurements were assessed at baseline (2006-2008) and 3 years later (2009-2011). Multiple logistic regression models were used to estimate the occurrence of the MetS in each quartile of fast food consumption. RESULTS: The mean age of participants was 37.8±12.3 y, and mean BMI was 26.0±4.5 kg/m(2) at baseline. Participants in the highest quartile of fast food consumption were younger (33.7 vs 43.4 years, P<0.01). Higher consumption of fast food was accompanied with more increase in serum triglyceride levels and triglyceride to HDL-C ratio after the 3-year follow-up. After adjustment for all potential confounding variables, the risk of metabolic syndrome, in the highest quartile of fast foods compared with the lowest, was 1.85 (95% CI=1.17-2.95). The effects of fast food consumption on the occurrence of MetS were more pronounced in younger adults (<30 years), and participants who had greater wait to hip ratio, consumed less phytochemical-rich foods or had low-fiber diet (P<0.05). CONCLUSION: We demonstrated that higher consumption of fast foods had undesirable effects on metabolic syndrome after 3-years of follow-up in Iranian adults.