HEALTH AND AGING TEXTBOOK NOTES
¾ Sohal and Weindruch (1996) argue that the concentration of free radicals (and thus cell damage) increase with
age, because (a) more free radicals are generated in aging cells, (b) there appears to be a decrease in the ability
of the cell to generate antioxidants, and (c) cellular mechanisms become less efficient.
¾ Aging cells also accumulate waste matter called lipofuscin, a dark mixture of lipoproteins and various waste
¾ Lipofuscin is found in nearly all cell types, from heart muscle cells to neurons, and increases with age.
¾ One recent finding suggests that there may be different types of lipofuscin, one on which may be associated
¾ Accumulation of lipofuscin may be a biomarker for metabolic rate, because it reflects oxidation and thus the
production of free radicals.
Heat Shock Proteins
¾ There are many different types of cellular repair mechanisms, which can be considered aging decelerators. The
most important of these for the aging process may be heat shock proteins (Hsps).
¾ They play a major role in protecting cells from nearly every kind of stressor, from radiation to infection to
¾ In addition to protecting cells against the effects of stress, they also are important in promoting healthy cell
growth and proliferation.
¾ Small Hsps protect cells from stress oxidative processes by regulating enzymatic processes necessary for repair
¾ They also play a major role in the inflammatory process.
¾ Hsps are one of the mechanisms that control inflammation. If they cannot repair a cell, they may help the cell to
¾ In apoptosis, a cell systematically dismantles and repackages itself and is readily reabsorbed by the surrounding
cells. But in necrosis, the cell ruptures spewing toxic chemicals and distress signals, leading to an increase in
the inflammatory process.
¾ Thus, Hsps may aid in the healing process by dismantling damage cells, or they may contribute to chronic
¾ To function, organisms must maintain a certain level of homeostasis, that is, stability in intra- and extracellular
environmental conditions, such as pH balance, blood pressure, heart rate, temperature, and electrolyte and fluid
¾ Homeostasis requires communication among the various organ systems and is largely regulated by the
autonomic nervous system via the neuroendocrine system.
¾ There is good evidence to suggest that as we age, it becomes harder to maintain homeostasis.
¾ Problems in homeostasis regulation may be due to one of three factors:
1) There may be a decline in the production of hormones or other type of regulatory peptides. Ovarian
decrease in estrogen production is a good example of this.
2) The target organs may become less responsive, due either to fewer receptors for neuroendocrine
signals or to degradation in the functioning of receptor sites on cell surfaces.
3) The target organ may synthesize less than optimal amounts of its product, due either to fewer secretory
cells or less efficient production.
¾ A number of illnesses commonly associated with aging reflect these problems in homeostasis, such as
orthostatic hypertension and diabetes.
¾ One of the earliest theories of aging was the simple wear-and-tear theory ± that is, with continual use, our
organs and joints simply wear out.
¾ For most organ systems, this early theory does not hold.
¾ The one exception to this adage appears to be skeletal joints. One of the causes of osteoarthritis is wear and tear
on the joints, and it is nearly universal in late life.
¾ However, it is also true that total bed rest in the elderly can result in stiffened, immobile joints (contracture), as
well as problems with a host of other systems.