OBJECTIVETo assess the prevalence of mutations or variants of the mitochondrial DNA (mtDNA) in familial diabetes mellitus in Chinese population, and to explore the relationship between mtDNA mutations or variants and diabetes.

METHODSSeven hundred and seventy randomly selected, unrelated probands of diabetes pedigrees and 309 controls over 60 years of age with normal glucose tolerance were recruited. PCR-RFLP and PCR-direct sequencing were applied to the screening of mtDNA mutations or variants, including the mutations at nucleotides 3243, 3256 in tRNALeu region, 12258 in tRNASer region, 14709 in tRNAGlu region, 8296, 8344, 8363 in tRNALys region, 3316, 3394, 3426 in ND1 region and 12026 in ND4 region.

RESULTSIn the diabetic group, 13 (1.69%) had mt3243 A>G mutation, 9(1.17%) had tRNAGlu 14709 T>C variant, 17 (2.21%) carried mt3316 G>A variant, 18 (2.34%) had mt3394 T>C variant, and 28 (3.63%) harbored the 12026 A>G variant. In the control group, the 14709, 3316, 3394, 12026 variants were detected in 5(1.62%), 5(1.62%), 6(1.94%), and 9(2.91%) subjects respectively. The 3256, 8296, 8344, 8363, 3426 and 12258 point mutations were not detected both in the diabetic patients and the controls. In the diabetic group, we found two double mutations, one was A3243G and T3394C, the other was A3243G and A12026G. Except that the A3243G mutation was only observed in the diabetic group, the frequencies of the other variants mentioned above were not statistically different between the diabetic and control groups. Moreover, clinical characteristics such as age of onset, BMI, and insulin resistance index were not different between diabetic patients with and without the variants.

CONCLUSIONThe tRNA (LeuUUR) 3243 A>G mutation may be the major cause of diabetes, representing 1.69% of the familial diabetes mellitus in Chinese. The other variants may be polymorphisms in this population, and the mutations not detected in our studied population may not be common contributors to diabetes mellitus in Chinese.