Association Of The Mitochondrial DNA A3537G,A4824G,A5351G Variant With Type 2 Diabetes Mellitus

Type 2 diabetes mellitus is charaterized as a heterogeneous disease and a multifactorial diaorder in which variants in mitochondial DNA (mtDNA) could play a role. While diabetes is a major feature in certain mtDNA diasease, pathogenic mtDNA mutations have only been identified in a tiny minority of diabeteics. We used PCR-RFLP and haplotype analysis to detect the A3537G, A4824G, A5351G variant of mtDNA in 145 patients with type 2 diabetes mellitus (T2DM) and 334 control subjects with normal glucose tolerance without family history of T2DM in Dalian area Han nationality people in order to investigate the association of the mitochondrial DNA A3537G, A4824G and A5351G variant with T2DM.Objective To investigate the association of the mitochondrial DNA A3537G, A4824G and A5351G variant with T2DM.Methods Case group include 145 patients with T2DM(63 men and 82 women, mean age 56.56±13.62 yrs) and control group include 334 normal glucose tolerance subjects with fasting glucose less than 5.6 mmol/L and OGTT glucose less than 7.8 mmol/L (188 men and 146 women, mean age 52.31±10.59 yrs) in Dalian Han nationality were selected. Then control group was separated into overweight subgroup (BMI≥24kg/m2) and non-overweight subgroup (BMI < 24kg/m2). Mitochondrial DNA was isolated from peripheral blood cell according to standard procedures. Sense and anti-sense primers of the three SNPs were designed according to the sequence of mtDNA , 557bp, 658bp, 505bp fragments of polymerase chain reaction spanning the A3537G, A4824G and A5351G single nucleotidepolymorphism was amplified, respectively. The PCR products were digested with restriction enzyne AluI,BstEII,HhaI for 12 hours, respectively. The genotypes were read after separation of the digested products with 8% SDS-PAGE. Different distribution in genotypes between T2DM and non-diabetetic subjects was analyzed. We analyzed the haplotypes that the three SNPs composed with the HaploView software.Results: 1. The prevalence of mitochondrial DNA A4824G variant was lower in case group than in control group: 4.1%(6/145) vs 10.2%(34/334) (χ2 = 4.82, P = 0.03). However the prevalence of A3537G[1.4%(2/145) vs 4.2%(14/334)] and A5351G variant [4.8%(7/145) vs 2.1%(7/334)] did not reach a significant difference between the two groups (P>0.05). People with the 4824A could increase the risk of occurrence of T2DM (OR = 2.63, 95% CI: 1.08～10.71), but 4824G could decrease the risk (OR = 0.38, 95% CI: 0.16～0.66).2. The prevalence of A3537G,A4824G and A5351G variant in overweight subgroup and non-overweight subgroups was 0.6%(1/154) vs 4.4%(6/180), 8.4%(13/154) vs 12.2%(22/180) and 3.2%(5/154) vs 5.0%(9/180), respectively. The prevalence of the 3 SNPs did not reach a significant difference between the two subgroups (P>0.05).3. The frequencies of 3537-4824-5351 AAA and AGA haplotype in case group and control group were 0.897 vs 0.841 and 0.041 vs 0.096, which have a significant difference between the two groups (P<0.05).Conclusions:1. mtDNA A4824G polymorphism may be associated with T2DM, and A4824G variant may play a protective role in the development of T2DM.2. mtDNA A3537, A5351G polymorphism may not be associated with T2DM.3. mtDNA A3537G,A4824G,A5351G polymorphism may not be associated with overweight.4. There may be susceptible sites of T2DM in this 1.8kb area of 3537-5351, which may be the A4824G mutation or other sites that around the A4824G.