Association of TCF7L2 rs7903146 (C/T) Polymorphism with Type 2 Diabetes Mellitus in a Chinese Population: Clinical Characteristics and Ethnic Context

<b>Background/Objectives</b>: The <i>transcription factor 7-like 2</i> (<i>TCF7L2</i>) rs7903146 polymorphism has been strongly associated with type 2 diabetes mellitus (T2DM) in various populations; however, its impact on different ethnic groups is not fully understood. Given the distinct minor allele frequency in Chinese populations, this study aimed to analyze the association of rs7903146 with the risk of T2DM in a Han Chinese cohort and its relationship with relevant clinical parameters. <b>Methods</b>: We conducted a case-control study including 600 patients with type 2 diabetes mellitus (T2DM) and 511 sex-matched non-diabetic controls of Han Chinese descent. The <i>TCF7L2</i> rs7903146 (C/T) polymorphism was genotyped using a TaqMan™ SNP assay. Clinical parameters, including body mass index (BMI), fasting plasma glucose, hemoglobin A1c, lipid profile, and high-sensitivity C-reactive protein (hs-CRP), were compared between genotypes. Logistic regression analyses were performed under a dominant genetic model (CT/TT vs. CC), adjusting for age, sex, systolic and diastolic blood pressure, BMI, and smoking status. Subgroup analyses were conducted by sex, BMI category, age at diagnosis, and family history of T2DM. Given the exploratory nature of this study and the low frequency of the TT genotype, no formal correction for multiple testing was applied. <b>Results</b>: Frequencies of the CT and TT genotypes were higher in the diabetic group (<i>p</i> = 0.045) and were significantly associated with an increased risk of T2DM under a dominant genetic model (adjusted OR = 2.24, <i>p</i> = 0.025). Individuals with CT/TT genotypes had elevated fasting glucose and hs-CRP levels; these genotypes were also linked to higher BMI in the female T2DM patients. The T allele frequency varied across ethnic groups, being lowest in East Asians and highest in Latin (Brazilian/mixed ancestry) populations. Mechanistically, the T allele may contribute to T2DM via altered <i>TCF7L2</i> expression, impaired insulin secretion, inflammation, and metabolic dysregulation. <b>Conclusions</b>: The <i>TCF7L2</i> rs7903146 T allele was associated with an increased risk of T2DM and higher fasting glucose and hs-CRP levels in this Han Chinese cohort. The CT/TT genotypes were also associated with higher BMI in the female T2DM patients. While the findings are consistent with the known effects of this variant in other populations, mechanistic hypotheses such as the involvement of inflammatory or metabolic pathways remain hypothetical and warrant further functional validation.