Mitochondrial genome copy number increases in the hearth of aged mice

To identify potential markers of aging, we compared the expression of a set of genes involved in mitochondrial activity in heart, skeletal muscle and brain of young and aged mice. By RT-qPCR, we analysed the transcription of cyclooxygenase-1 (COX-1), cytochrome-b (Cytb), peroxisome proliferator–activated-receptor-gamma-coactivator-1α (PGC-1α), sirt-1, sirt-2, sirt-3, sirt-6, manganese superoxide dismutase (MnSOD), UnCoupling Proteins-2 (UCP2), F3-contactin (F3-con), Ranbp17 and TNF-α in two groups of 24, 4-months-old, and 7, 22-month-old, mice. Furthermore, we analysed the relative amount of mitochondrial genome in the same tissues by qPCR. Transcription of many of these genes shows significant variations between young and old, in a tissue-specific way. While most of our observations are in agreement with the literature, in hearth, unexpectedly, even though the transcriptional activity of most genes is significantly decreased, the copy number of mitochondrial genome is noticeably increased. The meaning of this finding is worth further investigation. Blood analyses indicate an inflammatory and oxidative status in old vs. young displayed by higher concentration of haptoglobin and ROMt and lower concentration of SOD.