Association of dietary fibre with type 2 diabetes risk is modified by transcription factor 7 like 2 genotype in men with impaired fasting glucose: the T2D-GENE study

Dietary fibre helps prevent type 2 diabetes (T2D), but the effect could be affected by a risk allele T of the transcription factor 7 like 2 (TCF7L2) gene. We investigated the effects of a group-based, 3-year T2D-GENE diet and exercise intervention on dietary fibre intake and if fibre intake was associated with T2D risk and plasma glucose parameters. We also investigated if the TCF7L2 rs7903146 genotype modified the effects of fibre. A 3-year lifestyle intervention with Finnish men having impaired fasting glucose, aged 50-75 years. We measured fibre intake with 4-day food records (FR) and used plasma alkylresorcinol measurements for fibre intake validation. The participants (n = 558) were categorised into low (<3 g/MJ) and high (≥3 g/MJ) fibre intake group. We measured glucose parameters with a 2-h oral glucose tolerance test and stratified participants by the TCF7L2 genotype. The intervention increased the proportion of participants with fibre intake ≥3 g/MJ (45 % at baseline vs. 64 % at the end of the intervention, p < 0.001). Higher fibre intake associated with lower risk for T2D in all participants (hazard ratio [HR] 0.46 (95 % confidence interval [CI] 0.23; 0.94), adjusted with age, body mass index, exercise, smoking, alcohol consumption, saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid intake), especially in the TCF7L2 rs7903146 risk allele carriers (HR 0.06 (95 % CI 0.01; 0.36), the adjusted model). The increase of fasting plasma glucose and glucose area under the curve and the decrease of disposition index were attenuated in the T allele carriers with fibre intake of ≥3 g/MJ as compared to the participants not reaching the fibre target (p = 0.01, p = 0.012, p = 0.013, respectively). Group-based lifestyle intervention increased dietary fibre intake. Higher fibre intake benefited especially the risk allele carriers in TCF7L2 rs7903146 gene. T2D-GENE study was registered at clinicaltrials.gov as NCT02709057.