Aging is a complex set of processes that involve a diverse group of conditions and reactions. This is why the aging process has been challenging to define; it is also why there are multiple theories on it. However, aging processes can be divided into two groups: the amassing various degrees of damage to the cells and the genetically programmed process.
Aging Clock - Pineal Gland and other Pacemakers
Is there a centralized aging clock in humans that dictates the pace at which all bodily systems run? Yes and No... Studies have not yet found a specific central mechanism that is solely responsible for aging. However, there is a system of development. An example of this is a system that takes a single cell (zygote) and evolves it into a complex organism. Certain parts of this developmental system are not programmed to stop even after their roles in the organism's development have been finished. These systems are key to the growth and sexual maturation of the human, but without an "off switch," they seem to have several delayed side effects. In reality, these systems can harm mature adults because they behave as if the body is still developing. The result is an increased aging process that can lead to age-related disease. This means that the central aging clock could be seen as a by-product of the body's developmental systems when they do not shut off at maturity.
This rather unusual theory of development is the premise of the neuroendocrine theory of aging. Neuroendocrine refers to the fact that there is a synergy between the endocrine systems (the system which controls the body's functions via hormones) and the central nervous system. Vladimir Dilman, a well-known Russian scientist and physician-developed the neuroendocrine theory of aging in the 1950s. In the years since a large body of evidence has been developed to support his theory on aging.
The next important function that we need to understand is the idea of homeostasis. Basically, homeostasis is the way that the body maintains a proper balance of all of its systems. To be able to function in a normal manner, the body has to have its physiological framework kept within an optimal range: body temperature should be about 98.6F (37 C), blood pressure at about 120/80, blood sugar at 70-120 mg/dl and so on. Homeostasis is the way the system keeps the systems stable. If homeostasis is disrupted, the system works to bring it back to normal function. Failure to maintain homeostasis can lead to death.
Homeostasis is different at all stages of life. An example of this is that the average hemoglobin level (the molecule that moves oxygen in the blood) is about 11mg/100ml in infant males. In comparison, 10-year-olds would have a level of approximately 12mg/100ml, and adult males would have an average of 15mg/100ml. This simply means that homeostasis has to change its rate according to where the body is in the aging process.
The main function of growth is to increase homeostasis levels with the expending of more energy, growing in size, and the development of the reproductive organs. The issue at hand is that the homeostasis continues to take place event after the body reaches maturity. It continues to occur throughout the lifespan of the individual. After maturity, instead of stimulating growth, homeostasis ages you instead. This means that the developmental system turns into an aging clock as time goes on.
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An interesting question is why doesn't the developmental system in the body shut off at a certain point instead of stimulating accelerated aging after the body reaches maturity. Unfortunately, no one knows the answer to this question. The good news is that biological clocks can be speeded up or slowed if need be.
To understand an explanation of possible ways to slow down the body clock first, we need to understand some of the physiology. The hypothalamus is the part of the brain that is the mechanism that is primarily responsible for the process of homeostasis in the body. The hypothalamus continually monitors the numerous internal systems of the body. If one of the systems goes out of the appropriate range of function, then the hypothalamus sends out a message to the pituitary, the endocrine system's primary gland. The pituitary gland then transmits the signals it has received from the hypothalamus into hormonal messages to the peripheral endocrine glands such as the adrenals or the thyroid. The peripheral endocrine glands then regulate the functions of the organs and tissues.
Another key concept that needs to be understood in the discussion of the body clock is that of negative feedback (that is, with regards to feedback inhibition). For example, in the winter, the body's metabolic rate needs to go up to compensate for the colder temperature of the air. To do this, the hypothalamus sends the appropriate message to the pituitary, which in turn transmits a message to the thyroid to secrete more thyroxin (thyroxin is the hormone that raises the metabolic rate). The rise in thyroxin levels is then sensed by the hypothalamus, which in turn stops it from sending a further signal. This is how negative feedback works. Basically, it is the ability of the body's systems to end a stimulatory signal when the request has been fulfilled.
To summarize: the body needs a slow shift in homeostasis to develop. The hypothalamus is the main directing force behind that work of homeostasis. Therefore, the neuroendocrine theory of aging suggests that the hypothalamus runs the body's developmental systems until maturity, at which point it becomes an aging clock. The process of negative feedback can explain this switch-off function.
A good example of this is the sexual maturation process of women. As young girls, the ovaries produce a small amount of estrogen, but enough to trigger a negative feedback reaction from the hypothalamus. As the young woman grows older, the hypothalamus reacts less readily to the negative feedback messages, thereby stimulating the ovaries to produce a higher estrogen level. This raised level of estrogen production leads then leads to sexual maturity. Comparable processes of homeostasis occur during the maturation of all bodily systems. Sadly, after maturity, the hypothalamus doesn't react to negative feedback as quickly, resulting in further homeostatic shifts, which begin to have a negative role, leading to aging and degenerative diseases.
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The next question to look at is the actual effects of the homeostatic system on the body clock and how age-related diseases can result from this. Again, a complicated set of systems seems to be involved in this process. Age-related diseases are abnormal stress response, age-related depression, insulin excess, and syndrome X - a carbohydrate tolerance.
Energy usage is the driving force in the homeostatic shifts that cause age-related insulin excess and impaired carbohydrate tolerance. The pancreas secretes a hormone known as insulin. Insulin is secreted as a response to the body's glucose level (blood sugar), which normally rises after eating. It then assists with moving glucose, amino acids, and fats into the relevant cells, where they are either used for energy, stored, or used as structural materials. The normal pattern is that when a meal has been consumed, the food is digested and absorbed, causing the blood sugar (glucose) level to rise, thereby setting off the secretion of insulin; after about an hour, the insulin raises the blood sugar level back to its original level. As we age, the absorbency of muscle and other tissues in response to insulin declines, and the amount of insulin produced after a meal goes up. The net result is that after eating, older people have a higher level of blood sugar for a more prolonged period of time and increased levels of insulin circulating through the bloodstream. There has been a lot of debate about whether a raised muscle sensitivity to insulin causes excessive insulin secretion or vice versa. The neuroendocrine theory of aging explains that the central hypothalamic clock contributes to both factors.
Raised insulin levels and impaired glucose tolerance can raise the levels of LDL, triglycerides, and cholesterol. The higher levels of these substances can cause cell damage via glycation and cross-linking. They can also lead to salt (sodium) retention and many other problems. The aforementioned metabolic shifts often lead to the development of most age-related diseases, including heart disease, diabetes, hypertension, obesity, cancer, and lower immunity levels.
Type II diabetes (noninsulin-dependent diabetes) is the most common manifestation of glucose intolerance. Patients who have type II diabetes have raised levels of glucose despite still being able to produce insulin. In the early stages of type II diabetes, it isn't unusual for the level of insulin to be at an abnormally high level. When diabetes goes untreated, it can lead to complications that cause a speeding up of the aging process as well as degenerative diseases.
In one scientific study, insulin production and glucose tolerance was examined in Italian people over the age of 100. It was found that in these older adults, both the insulin production levels and the glucose tolerance were at the same levels as they were in adults under the age of 50 and better than those between 50 and 75. This shows that in people over 100, there is often only a minimal shift in the level of homeostasis, which could be the explanation for their advanced age.
There are many ways to raise glucose tolerance levels and prevent excessive insulin levels in the body. These effects can be brought about through exercise, weight loss, a diet high in fiber and lower in saturated fats, and a careful correction of nutrient levels. Conversely, negative effects to glucose tolerance and insulin levels can be brought on by stress, a lack of physical exercise, a diet heavy on saturated fats and low in fiber, and overeating and nutrient deficiencies.
Another key contributor to the aging process is the disruption of the stress response. The neuroendocrine theory of aging explains that the hypothalamus slowly loses its responsiveness to the feedback inhibition of corticosteroids, which are the key stress hormones in the body. Corticosteroids are created and released by the adrenal glands (the main corticosteroid in people is cortisol). There is a higher level of corticosteroid production in older people as a response to normal stresses. Older people can also have too high a level of corticosteroids in their bloodstream even when stress levels are low. This is the equivalent of living with chronic stress. This state of chronic stress is a vicious circle in which the central aging clock slowly disrupts the normal stress response, which then speeds up the clock itself. Corticosteroid excess is a key contributing factor to glucose intolerance, which slows the immune system, raises blood pressure, and can contribute to the onset of age-related diseases.
The central aging clock appears to contribute to many other age-related issues, including the production of sex hormones, abnormal appetites, and so on.
How can the aging clock be slowed down? Improving the level of sensitivity in the hypothalamus to negative feedback can slow the clock down. However, very little research has been done to date to develop practical means of slowing the aging clock. The research that has been done shows that the levels of the chemicals that transmit messages between the brain cells (neurotransmitters) in the hypothalamus are directly related to the responsiveness to the process of negative feedback. Alternatively, when neurotransmitter levels in the hypothalamus are higher than the aging clock slows down. The table below shows some of the factors that appear to affect the central aging clock.
| Speeding up of the central aging clock is related to: | Slowing down of the central aging clock is related to: |
|---|---|
| Stress; abnormal response to stress | Improving stress resistance; restoration of optimal response to stress; avoidance of intense or prolonged stress |
| Overeating, excess calories | Caloric restriction (in rodents), maintenance of ideal body weight (in humans) |
| Impaired carbohydrate tolerance | Improved carbohydrate tolerance |
| Insulin excess | Optimal insulin release |
| Depression; decreased neurotransmitter levels in the hypothalamus | Optimal emotional state, the elevation of neurotransmitter levels in the hypothalamus |
| Lack of melatonin and other pineal gland hormones | Restoration of the levels of melatonin and other pineal gland hormones |
| Free radical damage to the brain due to oxidation, ionizing radiation, or environmental toxins. | Prevention of free radical damage to the brain |
Free radicals are the chemicals in the body that have an unpaired electron. This means that they are very dangerous as they can behave in an erratic manner which can be very damaging to the effective functioning of the body.
DNA is the critical molecule of life: it is the blueprint of the creature encoded in the genes. DNA is an indispensable part of the cell. Other parts of the cells, such as proteins, lipids, and RNA, can be replaced if need be. DNA, if lost or damaged, cannot be replaced.
Cells of higher organisms like birds or mammals work slightly differently. Until the middle of the 20th century, it was believed that cells in all species could also live forever.
Certain substances that contribute to the aging process can be avoided. A good example of this is tobacco tar. Other contributory substances are not as easily avoided as they are key parts of the metabolism. The best example of this is glucose.
The majority of energy that is produced in the cells is done by the mitochondria. Cell function is dependent on the mitochondria providing energy to the rest of the system. Mitochondria are also the main factor behind free radical damage.
One of the most important defense mechanisms in the body is inflammation. It is a key to survival but at the same time appears to add to the pace of aging and the speed of the onset of degenerative diseases.
The body's metabolism produces waste regularly. The majority of bodily waste is expelled through breathing, urine, feces, and sweat. The most easily disposable waste is composed of small molecules like urea, carbon dioxide, and electrolytes.
Stress has been closely linked to the development of age-related diseases and the aging process as well. The stress response is basically a complicated adaptive reaction in the body.
There are two commonly asked questions about the lifespan of humans. The first is why does the rate of aging differ so dramatically among different species of animals? The second one is why are there more short-lived species than long-lived ones?
Wellness gurus will tell you that many herbs and supplements can slow down the aging process. But, unfortunately, the media and advertisers can't tell you much of anything.
The greater our comprehension of the aging process the more ways that scientists find to try to extend the average life span. Ironically, the most effective means of anti-aging intervention has been the same for the past 50 years; eating less!!