Association Of The Mitochondrial DNA T14783C And A15235G Variants With Type 2 Diabetes Mellitus

Type2 diabetes mellitus (T2DM) is a genetically heterogeneous disorder characterized by chronic hyperglycemia, which is affected by complex interaction between genetic and environmental factors. To explore the genetic etiology of type 2 diabetes, obesity and hypertension in Dalian population, we studied the association between T14873C and A15235G polymorphisms in mtDNA CYB gene and T2DM, obesity and hypertension.Objective: The present study included 153 T2DM patients and 198 unrelated non-diabetic controls recruited from Dalian. The diabetic patients consisted of 61 patients coming from T2DM families, 64 sporadic patients coming from diabetic census in Dalian supported by National 95 Project, and 28 patients coming from Dalian Centre Hospital from 2004 to 2006. Among these patients, there were 71 men and 82 female, and their average age was 56.56±13.62 years. The non-diabetic controls consisted of 104 men and 95 female with fasting glucose level less than 5.6 mmol/L or 2-h plasma glucose less than 7.8 mmol/L after glucose load, no other endocrinopathic disease and no diabetic family history, their average age was 50.31±10.59 years Furthermore, the diabetic patients were divided into diabetic with obesity subgroup and diabetic without obesity subgroup according to the criteria of Asia-Pacific. After collecting blood samples and extracting genomic DNA from their peripheral blood leucocytes.Methods we designed the primers according to the CYB gene sequence to amplify the 589-bp fragment spanning T14783C and A15235G polymorphisms. The PCR products were then digested withrestriction enzyme VspI and Dpn I at 37oC overnight, respectively. Subsequently, the digestion products were separated with 8% SDS-PAGE to identify different genotypes. The genotypic distributions and frequencies in T2DM and non-diabetes groups were analyzed, and these differences were also analyzed between diabetes with obesity and without obesity groups. Statistical analyses were performed usingχ~2 test, and a P value < 0.05 was considered to be statistically significant.Results1. mtDNA T14783C variant1.1 The frequencies of 14783C allele were 60.1% in diabetes group and 59.1% in non-diabetes group, respectively. There was no significant difference between diabetes and non-diabetes groups (χ~2 = 0.039, P=0.844).1.2 The frequencies of 14783C allele were 61.3% in diabetes with obesity group and 59.0% in diabetes without obesity group, respectively. There was no significant difference between these two groups (χ~2 = 0.089, P=0.766).1.3 The frequencies of 14783C allele were 62.5% in hypertension group and 58.8% in non-hypertension group, respectively. There was no significant difference between hypertension and non-hypertension groups (χ~2 = 0.207, P=0.649).2. mtDNA A15235G variant2.1 The frequencies of 15235G allele were 2.6% in diabetes group and 4.0% in non-diabetes group, respectively. There was no significant difference between diabetes and non-diabetes groups (χ~2 =0.532 ,P=0.303).2.2 The frequencies of 15235G allele were 2.6% in diabetes with obesity group and2.6% in diabetes without obesity group, respectively. There was no significant difference between these two groups (χ~2 = 0.002, P=0.968).2.3 The frequencies of 15235G allele were 3.57% in hypertension group and 2.1% in non-hypertension group, respectively. There was no significant difference between hypertension and non-hypertension groups (χ~2 = 0.318, P=0.573).Conclusions mtDNA T14783C and A15235G variants are not associated with T2DM, diabetes with obesity and hypertension in Dalian population.