Aging theories cover the physiological, genetic, biochemical properties of a typical organism, and the way these properties change with time. Theories of genetic dealing with the identity of aging obesity genes, accumulation of errors in the genetic machinery, programmed senescence, and telomeres theory. Biochemical theories are concerned with generation of free radicals, the rate of living, energy metabolism, and the health of mitochondria. While Theory of Physiological deal most entirely with the endocrine system and the purpose of hormones in governing the rate of cellular aging.
Running a cell is a complex affair. RNA (Ribonucleic Acid) and proteins have to be synthesized on a regular basis to maintain and run the cell’s machinery. Protein production, either for enzymes or structural materials, occurs in a two-step process: transcription of the gene to produce mRNA, followed by translation of the message to protein produce. For cells that are actively dividing, a third step, replication of the DNA, precedes the other two. Errors can occur all along the way; when they do, defective genes, mRNA, and proteins are produced. The error catastrophe theory, first proposed in the 1960s, suggests that over time, the number of errors build up to a catastrophic level leading to the death of the cell and, possibly, the entire organism.
Soon after this theory was proposed, many scientists conducted experiments that attempted to force a buildup of errors to see how the cells would cope with it. Bacteria were grown on a medium containing defective amino acid sequence to maximize the error frequency of protein synthesis. Similar experiments were conducted on fruit flies (Drosophila) and mice, both of which were given food containing defective amino acid sequence. To everyone’s surprise, these experiments had no effect on the bacteria’s or animal’s health, vigor, or human life span. Somehow the cells were able to avoid an error catastrophe. Today we understand why those experiments failed: Cells have elaborate repair systems and strategies that detect and destroy defective molecules. If a defective protein is synthesized, it is quickly broken down and replaced with a normal copy. Only in cases where the repair systems have been damaged would an error catastrophe occur, which then cause a Werner’s syndrome disease.
In its original formulation, the error catastrophe theory focused on protein synthesis, which apparently can tolerate a high error frequency. Consequently, many scientists began to wonder if errors in the genome, or possibly a defective regulation of the genes, might be responsible for the aging process. After all, cells avoid an error catastrophe at the translational level because they can always try again with a fresh mRNA from a good gene. But if the genes themselves are damaged, or programmed for senescence, the outcome would be a gradual decline in cell vigor and the eventual death of the organism.
