The participants in the case group had a longer duration of T2DM (p < 0.001) and hypertension (p = 0.0058), a higher systolic blood pressure (p < 0.001), a larger waist circumference (p < 0.001), a higher prevalence of diabetic neuropathy (p < 0.001) and DR (p < 0.001), and higher levels of glucose (p < 0.001), HbA1c (p < 0.001), cystatin C (p < 0.001), triglycerides (p = 0.0123), and albumin–creatinine ratio in all three samples (p < 0.001) in comparison with the control group. The gene discussed is CST3; the disease is type 2 diabetes mellitus.