Effect of TCF7L2 on the relationship between lifestyle factors and glycemic parameters: a systematic review.

BACKGROUND: Among candidate genes related to type 2 diabetes (T2DM), one of the strongest genes is Transcription factor 7 like 2 (TCF7L2), regarding the Genome-Wide Association Studies. We aimed to conduct a systematic review of the literature on the modification effect of TCF7L2 on the relation between glycemic parameters and lifestyle factors. METHODS: A systematic literature search was done for relevant publications using electronic databases, including PubMed, EMBASE, Scopus, and Web of Science, from January 1, 2000, to November 2, 2021. RESULTS: Thirty-eight studies (16 observational studies, six meal test trials, and 16 randomized controlled trials (RCTs)) were included. Most observational studies had been conducted on participants with non-diabetes showing that TCF7L2 modified the association between diet (fatty acids and fiber) and insulin resistance. In addition, findings from meal test trials showed that, compared to non-risk-allele carriers, consumption of meals with different percentages of total dietary fat in healthy risk-allele carriers increased glucose concentrations and impaired insulin sensitivity. However, ten RCTs, with intervention periods of less than ten weeks and more than one year, showed that TCF7L2 did not modify glycemic parameters in response to a dietary intervention involving different macronutrients. However, two weight loss dietary RCTs with more than 1-year duration showed that serum glucose and insulin levels decreased and insulin resistance improved in non-risk allele subjects with overweight/obesity. Regarding artichoke extract supplementation (ALE), two RCTs observed that ALE supplementation significantly decreased insulin concentration and improved insulin resistance in the TT genotype of the rs7903146 variant of TCF7L2. In addition, four studies suggested that physical activity levels and smoking status modified the association between TCF7L2 and glycemic parameters. However, three studies observed no effect of TCF7L2 on glycemic parameters in participants with different levels of physical activity and smoking status. CONCLUSION: The modification effects of TCF7L2 on the relation between the lifestyle factors (diet, physical activity, and smoking status) and glycemic parameters were contradictory. PROSPERO REGISTRATION NUMBER: CRD42020196327.

Is the metabolic syndrome inversely associates with butter, non-hydrogenated- and hydrogenated-vegetable oils consumption: Tehran lipid and glucose study.

AIM: The aim of this study was to investigate the association between hydrogenated- (HVOs) and non-hydrogenated vegetable oils (non-HVOs) and butter and the metabolic syndrome (MetS) after 3-years of follow-up in adults. METHODS: This study was conducted between 2006-2008 and 2009-2011 within the framework of the Tehran Lipid and Glucose Study, on 1582 adults, aged 19-84 years. Intakes of HVOs, non-HVOs and butter were assessed by a validated semi-quantitative food frequency questionnaire. Based on the consumption of food rich in fat including HVOs, non-HVOs and butter, participants were categorized to consumers and non-consumers. RESULTS: Of 1582 participants during a 3-year follow-up, 15.2% developed MetS. Non-consumption of butter was associated with lower MetS risk compared with its consumption. Among consumers of food rich in fat, intake of HVOs and butter were associated with an increased risk of MetS; ORs in the final multivariate model were 2.70 (95% CI: 1.52-4.78) for HVOs and 2.03 (95% CI: 1.20-3.41) for butter, in the highest, compared to the lowest category of dietary intakes. Intake of non-HVOs was not associated with risk of MetS. CONCLUSIONS: Consumption of HVOs and butter were positively associated with an increase risk of MetS.

Combined effect of unsaturated fatty acids and saturated fatty acids on the metabolic syndrome: Tehran lipid and glucose study.

AIMS: The aim of this study was to investigate whether the background intakes of total dietary fat, monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) modulate the effects of dietary saturated fatty acids (SFA) on metabolic syndrome (MetS). MATERIAL AND METHODS: This population-based cross-sectional study was conducted on a representative sample of 4,677 adults, aged 19 to 84 years. MetS was defined according to the ATP III criteria. RESULTS: Median intakes of SFA, MUFA and PUFA were 9.5, 9.6 and 5.6% of total energy. High SFA intakes were associated with higher prevalence of MetS, in both individuals with higher and lower median intakes of total fat, MUFA and PUFA. CONCLUSIONS: Our findings indicate that SFA intakes were positively associated with the prevalence of MetS, independent of total dietary fat, MUFA and PUFA intake.

Association between interaction and ratio of ω-3 and ω-6 polyunsaturated fatty acid and the metabolic syndrome in adults.

OBJECTIVE: To investigate the association of the intakes of ω-3 (including α-linolenic acid [ALA], eicosapentaenoic acid [EPA] plus docosahexaenoic acid [DHA]) and ω-6 polyunsaturated fatty acids (PUFAs), the interaction, and the ratio of these PUFAs with the metabolic syndrome (MetS) in adults. METHODS: This cross-sectional study was conducted in a random sample of participants (n = 2451, 19-84 y old) in the Tehran Lipid Glucose Study. Dietary intake was assessed using a validated semiquantitative food-frequency questionnaire. Anthropometric characteristics, blood pressure, and fasting plasma concentrations of glucose and lipids were measured. The MetS was defined according to the Adult Treatment Panel III guidelines. RESULTS: Among the PUFAs, the ALA and ω-6 PUFA intakes were inversely associated with the MetS. Subjects in the highest quartile of ALA and ω-6 fatty acid intakes had a 38% (odds ratio 0.62, 95% confidence interval 0.41-0.95) and a 0.47% (odds ratio 0.53, 95% confidence interval 0.31-0.89) lower prevalence of MetS, respectively, compared with those in the lowest quartile. The dietary ratio of ω-6 to ω-3 fatty acids was not associated with the MetS. When the interaction between ALA and ω-6 fatty acid was assessed, the ALA intake was associated with a lower prevalence of the MetS, without modification by the ω-6 PUFA intake. Subjects with at least the median ALA intake (1084 mg/d) had a lower prevalence of the MetS, irrespective of an ω-6 PUFA intake lower or higher than the median compared with subjects with intakes below the median for both. CONCLUSION: The ALA intake was inversely associated with the MetS, irrespective of the background intake of ω-6 PUFAs, in adults.