Abstract:Objective To study the relationship between gene polymorphisms of mitochondrial DNA (mtDNA) D-loop region and ulcerative colitis (UC). Methods The rectal mucosal tissues were taken respectively from 180 UC patients with mucosal lesions treated from January 2017 to August 2019 (UC group) and 180 physical examiners in the same period(control group). The mtDNA D-loop regions were amplified and sequenced by polymerase chain reaction (PCR) and were compared with the revised Cambridge reference sequence (rCRS) to find the mutation sites. Results In D-loop region of mtDNA, a total of 218 mutant sites and 203 mutant sites were found in UC group and control group, respectively. The incidence of more than 10% in 19 mutant sites was in both groups, and there was a statistical difference in the incidence of four mutant sites between two groups. Among them, the incidence [16520 (T→C)] in control group was significantly higher than that in UC group (χ²=6.890, P<0.01), and the incidences [ 311 (T--→CTC), 16299 (T→C) and 16320 (G→A) in UC group were significantly higher than those in control group (χ²=58.973, P<0.01;, χ²=141.917, P<0.01; χ²=20.238, P<0.01). There were no significant differences in the incidence of mutant sites among the different clinical type, the different extent of pathological changes and different severity for UC (P>0.05). Conclusion The mtDNA D-loop region in UC with high frequeny of polymorphism and high rate of mutation is related to the pathogenesis of UC, and possibly related to the reduction in activity of mitochondrial respiratory chain complexes and the lack of adenosinetriphosphate (ATP) content.