When you’re in certain states of physical stress—if you have diabetes or heart disease—mitochondria can malfunction and cells won’t receive enough energy. This can affect brain function, because the neurons don’t have enough energy to fire. Your muscles may be weaker. The liver, heart, and kidneys—all organs that consume mass quantities of energy—suffer. One way to tell if cells are under major stress is to examine their mitochondrial DNA copy numbers, which tell us how hard the body is working to produce additional mitochondria to supplement the ones that are weary and damaged.
