Aim: This case–control study aimed to examine impairments in glucose metabolism in non-diabetic carriers of the mitochondrial mutation m.3243A>G by evaluating insulin secretion capacity and sensitivity. Methods: Glucose metabolism was investigated in 23 non-diabetic m.3243A>G carriers and age-, sex-and BMI-matched healthy controls with an extended 4-h oral glucose tolerance test (OGTT). Insulin sensitivity index and acute insulin response were estimated on the basis of the OGTT. This was accompanied by examination of body composition by dual-energy X-ray absorptiometry (DXA), maximum aerobic capacity and a Recent Physical Activity Questionnaire (RPAQ). Results: Fasting p-glucose, s-insulin and s-c-peptide levels did not differ between m.3243A>G carriers and controls. Insulin sensitivity index (BIGTT-S 1) was significantly lower in the m.3243A>G carriers, but there was no difference in the acute insulin response between groups. P-lactate levels were higher in carriers throughout the OGTT. VO 2max, but not BMI, waist and hip circumferences, lean and fat body mass%, MET or grip strength, was lower in mutation carriers. BIGTT-S 1 remained lower in mutation carriers after adjustment for multiple confounding factors including VO 2max in regression analyses. Conclusions: Glucose metabolism in m.3243A>G carriers was characterized by reduced insulin sensitivity, which could represent the earliest phase in the pathogenesis of m.3243A>G-associated diabetes.
- Insulin resistance
- Mitochondrial DNA point mutation m.3243A>G
- Mitochondrial dysfunction
- Monogenic diabetes