ABSTRACT
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-S1) 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. VO2max, but not BMI, waist and hip circumferences, lean and fat body mass%, MET or grip strength, was lower in mutation carriers. BIGTT-S1 remained lower in mutation carriers after adjustment for multiple confounding factors including VO2max 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.
ABSTRACT
Mitochondrial dysfunction is associated with several clinical manifestations including diabetes mellitus (DM), neurological disorders, renal and hepatic diseases, and myopathy. Although mitochondrial dysfunction is associated with increased bone resorption and decreased bone formation in mouse models, effects of alterations in mitochondrial function on bone remodeling and mass have not been investigated in humans. We recruited 45 carriers (29 females, 16 males) with the m.3243A>G mutation and healthy controls matched for gender, age, height, and menopausal status. DXA and HRpQCT scans were performed, and bone turnover markers (BTMs) P1NP and CTX were measured. Cases and controls were well matched except for body weight, which was lower in cases (63.6 ± 18.1 kg versus 74.6 ± 14.8 kg, p < 0.01), and manifest DM was present in 25 of 45 cases (none in controls). Bone scans showed lower BMD at the lumbar spine, total hip, and femoral neck in cases. Mean lumbar spine, total hip, and femoral neck T-scores were -1.5, -1.3, and -1.6 in cases, respectively, and -0.8, -0.3, and -0.7 in controls (all p < 0.05). The m.3243A>G mutation was associated with lower BMD, cortical but not trabecular density, cortical thickness, and estimated bone strength. Furthermore, BTMs were lower in the m.3243A>G group before but not after adjustment for DM. The mitochondrial point mutation m.3243A>G was associated with decreased bone mass and strength. Although the coexistence of DM may have influenced bone turnover, the bone phenotype observed in m.3243A>G cases appeared to mirror age-related deterioration in bone, suggesting that mitochondrial dysfunction may cause a premature aging of bone. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.
