Epigenetic Alterations
Your genome is more than a long sequence of DNA letters. DNA strands are wound around spools of protein called histones, and both DNA and histones can have various chemical handles, cranks, and levers attached to them to help turn genes on or off. These handles, cranks, and levers comprise your epigenome.
Your epigenome changes as you age--levers are lost, added inappropriately, or shifted around. As a result, precise coordination of gene activity can be compromised. One particularly well-studied group of molecules than influence the epigenome is the sirtuins, molecules that remove one type of epigenetic handle. Interestingly, your epigenome can be modified by diet, other lifestyle factors, and pharmaceuticals.
Evidence that the epigenome affects aging comes mostly from the study of yeast, worms, and flies. However, dietary restriction in mice slows epigenetic changes, and when mice are made deficient in one of the seven mouse sirtuins, they show signs of accelerated aging. Moreover, when that same sirtuin is superabundant, male mice live longer.