Many factors affect how fast one ages. Poor lifestyle choices such as poor diet, lack of exercise, and substance abuse can affect how rapidly one ages. However, a new study has found that genes passed down from your mother may affect your aging process; thus, if mom lived—or is living to—a ripe old age, you may follow in her footsteps. Researchers affiliated with the Karolinska Institute in Sweden and the Max Planck Institute for Biology of Ageing in Germany reported their findings on August 21 in the journal Nature.
The researchers not that aging is due to an accumulation of various types of damage to one’s cells. Mitochondria are small structures within the cells, which are often termed the powerhouses of the cells because they break down sugars to produce cellular energy. Mitochondrial dysfunction has long been considered to be important in this process. The researchers note that substantial sequence variation exists in mammalian mitochondrial DNA, and the high mutation rate is counteracted by different mechanisms that decrease maternal transmission of mutated mitochondrial DNA. However, despite these protective mechanisms, it is becoming increasingly clear that low-level mitochondrial DNA heteroplasmy is quite common and often inherited in humans. (Mitochondrial DNA heteroplasmy is the presence of a mixture of more than one type of mitochondrial DNA within a cell or individual.)
The researchers developed a series of mouse mutants to investigate the extent to which inherited mitochondrial DNA mutations can contribute to aging. They bred the mice with varying degrees of these mutations, and then estimated their aging rates by measuring fitness characteristics such as weight, fertility, and red blood cell count. They found that maternally transmitted mitochondrial DNA mutations could induce a mild increase in aging in the mice. In addition, maternally transmitted mitochondrial DNA mutations could produce reduced fertility in mice that are heterozygous for the mitochondrial mutator allele (PolgAwt/mut) and aggravate premature ageing phenotypes in mitochondrial DNA mutator mice (PolgAmut/mut). (Heterozygosity refers to a genetic disorder is present on only one of a chromosome pair. An allele is one of two or more variants of a gene.) The investigators also discovered an unexpected finding: a combination of maternally transmitted and somatic (within the body) mitochondrial DNA mutations also leads to stochastic (unpredictable) brain malformations.
The authors wrote that their findings demonstrate that a pre-existing mutation load will not only allow somatic mutagenesis to create a critically high total mitochondrial DNA mutation load sooner but will also increase the expansion of mitochondrial mutations as the cells divide. They note that their findings suggest that maternally transmitted mitochondrial DNA mutations may have a similar role in aggravating aspects of normal human ageing. They cautioned, however, that additional research is required to support this theory.