Mitochondrial DNA A3243G mutation in patients with early- or late-onset type 2 diabetes mellitus in Hong Kong Chinese

BACKGROUND AND OBJECTIVES The mitochondrial DNA A to G mutation at nucleotide 3243 (mt3243) is associated with a subtype of diabetes characterized by maternal transmission and deafness. We have previously reported a 2.7% prevalence of this mutation in a cohort of young patients with either type 1 or type 2 diabetes. In this study, we aimed to confirm this finding by examining for the prevalence of this mutation in a large-scale study. SUBJECTS AND METHODS Nine hundred and six unrelated Chinese patients with type 2 diabetes and 213 nondiabetic controls were studied. The presence of mt3243 mutation was determined by polymerase chain reaction amplification and Apal digestion. RESULTS This mutation was found in four of 133 (3.0%) patients with early onset (less than or equal to 40 years) diabetes who also had a positive maternal family history, and in one of 348 (0.3%) patients with late-onset (less than or equal to 40 years) diabetes and no family history. Basal pancreatic beta-cell function, as assessed by fasting plasma C-peptide, was variable amongst mutation carriers, and did not correlate with the level of heteroplasmy of mutation. CONCLUSIONS In agreement with most studies, our results suggest that despite the high prevalence of positive maternal family history of diabetes amongst our type 2 diabetic patients, mt3243 mutation was not a major cause of diabetes in either early- or late-onset diabetic patients in Hong Kong, The role of other genetic, environmental and intrauterine factors needs further investigation.