Study on the mitochondrial DNA mutations in familial diabetes mellitus in Chinese population / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To 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.</p><p><b>METHODS</b>Seven 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.</p><p><b>RESULTS</b>In 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.</p><p><b>CONCLUSION</b>The 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.</p>

Prevalence and clinical characteristics of the mitochondrial tRNA(Leu(UUR)) gene 3243 A to G mutation in familial diabetes mellitus in Chinese population / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study the prevalence and clinical characteristics of the A to G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene in familial diabetes in Shanghai, Jiangsu and Zhejiang Province of China.</p><p><b>METHODS</b>The mt3243 A to G mutation in 770 randomly selected, unrelated probands of diabetic pedigrees were screened by PCR-RFLP technique and PCR-direct sequencing. Genetic and clinical analyses were further performed in the probands and their family members.</p><p><b>RESULTS</b>Thirteen diabetic patients (13/770, 1.69%) with mt3243 A to G mutation were detected. Eleven diabetic patients and 8 normal glucose tolerance (NGT) first-degree relatives of these 13 probands were also found bearing the mutation. Seventeen patients were associated with sensory hearing loss. In the 24 patients harboring the mutation, the majority had lower body mass index (BMI), 18 showed typical maternal inheritance, 15 had sensory hearing loss, 13 had insulin resistance and 14 required insulin therapy due to secondary failure to oral hypoglycemic agents.</p><p><b>CONCLUSION</b>The mutation of mt3243 A to G in the mitochondrial tRNA(Leu(UUR)) gene is an important cause of diabetes in Shanghai, Jiangsu and Zhejiang Province of China. Mitochondrial gene mutation diabetes (MDM) is clinically characterized by early onset, emaciation, maternal inheritance, sensorineural hearing loss, and lower islet beta cell function, and some have insulin resistance.</p>

The genetic and clinical characteristics of transcription factor 1 gene mutations in Chinese diabetes / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the genetic and clinical features of mutations and sequence variations of the transcription factor 1 gene (TCF1, HNF-1A) in Chinese with familial early-onset and/or multiplex diabetes mellitus.</p><p><b>METHODS</b>All ten exons of the TCF1 gene were screened, including exon and intron junctions, by direct sequencing method in 341 unrelated Chinese subjects, including 80 healthy controls and 261 probands of early-onset and/or multiplex diabetes pedigrees.</p><p><b>RESULTS</b>Five mutations were found in all. Four of the 5 different TCF1 mutations were newly identified novel mutations(T82M, Q130H, G253G, P353fsdelACGGGCCTGGAGC), mean body mass index of mutation carriers was 21.9 kg/m (2), and insulin secretion was impaired in the mutation carriers. In this study, the maturity-onset diabetes of the young type III (MODY3) only accounted for 3% of Chinese early-onset diabetes. Moreover, eleven substitutions were identified in 261 probands. Of them, three variants IVS1-8 (G-->A), IVS1 -128 (T-->G ) and IVS2+21 (G-->A) were not observed in 80 healthy controls and one of them IVS1-8 (G-->A) was not reported previously and the two promoter variants co-segregated with diabetes.</p><p><b>CONCLUSION</b>TCF1 gene is not a common cause of early-onset and/or multiplex diabetes among Chinese patients.</p>

Prevalence and clinical characteristics of the A to G variant at position 12026 of the mitochondrial ND4 gene in familial diabetes mellitus in Chinese population / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To assess the prevalence of the A to G variant at nucleotide 12026 (mt12026) of the mitochondrial NADH-dehydrogenase subunit 4 (ND4) gene in familial diabetes mellitus in Chinese population.</p><p><b>METHODS</b>The authors screened 770 randomly selected, unrelated probands of diabetic pedigrees, and 309 controls with normal glucose tolerance for the variant by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and PCR-direct-sequencing.</p><p><b>RESULTS</b>The mt12026 A --> G variant was detected in 28 diabetic patients (3.63%) and 9 controls (2.91%). The frequency of the variant mt12026 A --> G was not statistically different between diabetic patients and controls. Moreover, clinical characteristics such as age, body mass index (BMI), and insulin resistant index were not different between diabetic patients with and without the mt12026 mutation.</p><p><b>CONCLUSION</b>The mt12026 A --> G variant is a mitochondrial gene polymorphism in Chinese population, and it is unlikely that the mutation is in itself the cause of diabetes.</p>