Aims/hypothesis: We examined whether age of type 2 diabetes onset is related to mitochondrial DNA content in peripheral blood monocytes (PBMCs).
Methods: PBMCs were isolated from 65 patients with type 2 diabetes. To minimise age as a confounder, only patients aged >or=50 years were studied. Sample mitochondrial DNA (mtDNA) content was determined by amplification of the mitochondrial gene CYT-B (also known as MT-CYB) and adjusted for single-copy nuclear control genes (36B4 [also known as RPLPO] and GAPDH).
Results: Age of diabetes onset ranged from 25 to 69 years. There was a significant positive relationship between age of diabetes onset in quartiles and mtDNA content for the whole group (p = 0.02 for trend). When stratified by the presence of diabetes complications, a strong positive relationship was observed between age of diagnosis and mtDNA content for participants without diabetic complications (r = 0.7; p = 0.0002), but not for those with complications (r = -0.04; p = 0.8). Multivariate analysis confirmed age of onset and complication status as independent determinants. There was co-linearity between age of onset and disease duration, with similar relationships also seen between duration and mtDNA content.
Conclusions/interpretation: An earlier age of type 2 diabetes onset is associated with a lower PBMC mtDNA content, but only in patients without diabetes complications. This may reflect a differing biology of PBMC mtDNA in those with early-onset diabetes and those who are prone to complications. PBMC mtDNA depletion may accelerate diabetes onset; however the independent effect of diabetes duration remains to be evaluated.