Supplementary Material for: Evaluation of the Associations of <b><i>GC</i></b> and <b><i>CYP2R1</i></b> Genes and Gene-Obesity Interactions with Type 2 Diabetes Risk in a Chinese Rural Population

<b><i>Introduction:</i></b> Group-specific component (<i>GC</i>) and cytochrome P450 family 2 subfamily R member 1 (<i>CYP2R1</i>) gene polymorphisms and obesity have been associated with an increased risk for development of type 2 diabetes mellitus (T2DM) in Asian populations. <b><i>Objective:</i></b> This study assessed the associations of interactions between <i>GC</i> gene variants and <i>CYP2R1</i> gene variants and between genes and obesity with T2DM risk. <b><i>Methods:</i></b> A study that included 2,271 subjects was performed. Eight single nucleotide polymorphisms in the <i>GC</i> and <i>CYP2R1</i> genes were genotyped. Interaction analysis was performed using rs7041 in the <i>GC</i> gene and rs1993116 in the <i>CYP2R1</i> gene. The effects of multiplicative and additive gene-gene and gene-environment interactions on T2DM risk were assessed. <b><i>Results:</i></b> The T2DM risk was significantly associated with being overweight/obese, abdominal obesity, rs7041, and rs1993116. A significant additive interaction between rs1993116 and rs7041 was associated with T2DM. In addition, there was a significant multiplicative interaction between rs7041 and body mass index (BMI) associated with elevated blood glucose levels, and at a higher BMI (&gt;28.47), the G allele carrier showed a stronger effect than the TT genotype. <b><i>Conclusions:</i></b> The interactions between <i>GC</i> rs7041-<i>CYP2R1</i> rs1993116 and <i>GC</i> rs7041-BMI may explain the mechanisms by which these factors increase the risk of T2DM development.