Prevalence and clinical characteristics of mitochondrial tRNAleu(UUR) nt 3243 A-->G and nt 3316 G-->A mutations in Chinese patients with type 2 diabetes.

Seven hundred and sixteen randomly selected, unrelated patients with type 2 diabetes were screened for mutations using a PCR-RFLP technique to assess the prevalence of the A-G mutation at position 3243 of the mitochondrial (mt) tRNAleu(UUR) gene in type 2 diabetes in the Chinese population. Three individuals with this mutation were identified, representing approximately 0.4% of the type 2 diabetes patients screened. Further screening of the first-degree relatives of these three patients identified another four affected carriers. In comparison with type 2 diabetic patients without the mutation, these seven carriers of the mt 3243 mutation had; (1) had an earlier onset of diabetes (38.0+/-10.1 vs. 53.4+/-10.0 year, P<0.001); (2) a lower body mass index (BMI) (19.5+/-2.0 vs. 24.9+/-10.9, P<0.0001); and (3) and lower post-challenge insulin levels (area under the curve of insulin levels during the OGTT, 2946+/-1647.2 vs. 7469+/-6647.7, P<0.01). In addition, the same 716 patients with type 2 diabetes, as well as 181 controls with normal glucose tolerance, were screened for a newly described mt 3316 G-A mutation. This mutation was found in 16 patients with type 2 diabetes (2.2%) and five controls (2.7%). Therefore, the frequency of the mutation was not significantly different in the patients and controls. Moreover, the clinical characteristics such as the age of the onset of diabetes, the BMI, and insulin levels were not significantly different between the diabetic patients with the mt 3316 G-A mutation and those without. This shows that the mt 3316 G-A mutation is a polymorphism unrelated to diabetes.