Can Medicine Ever Extend the Human Lifespan?

Will it ever be possible to increase the human lifespan by slowing down aging? Could medical science ever accomplish this or is it so improbable as to be unworthy of research? Is there anything available now that can slow the aging process? If such a thing were available would you take it? What about the claims by the manufacturers of nutritional supplements that some of their products have an effect on aging? Are any of them valid?

The Aging Process
The search for a single cause of aging has been replaced by the view of aging as an extremely complex, multifactorial process. It is very likely that several processes simultaneously interact and that more than one of the prevailing explanations of aging may be simultaneously true.

The free radical theory of aging states that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an outer shell. Most biologically-relevant free radicals are highly reactive and react chemically with the biological structures with which they come in contact. For most biological structures, free radical damage is closely associated with oxidative damage. Strictly speaking, the free radical theory is only concerned with free radicals such as superoxide ( O2- ), but it has since been expanded to encompass oxidative damage from other reactive oxygen species such as hydrogen peroxide (H2O2), or peroxynitrite (OONO-). Denham Harman first proposed the free radical theory of aging in the 1950s, and in the 1970s extended the idea to implicate mitochondrial production of reactive oxygen species. Oxygen radical absorbance capacity (ORAC) is a method of measuring antioxidant content of biological samples. Studies at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston suggest that consuming fruits and vegetables with a high ORAC value may help slow the aging process in both body and brain. Other research has shown that in middle-aged rats, foods with a high ORAC value can reduce loss of long-term memory and learning ability, maintain the ability of brain cells to respond to stimuli (thought to decrease with age) and protect blood vessels against oxygen damage.

Another component of aging is cross-linking. Cross-linking as an aging mechanism was first proposed in 1942 by Johan Bjorksten. He applied this theory to aging diseases such as sclerosis, a declining immune system and the most obvious example of cross-linking, loss of elasticity in the skin. Collagen is one of the most common proteins found in the skin, tendons, ligaments, bone and cartilage. Collagen and elastin proteins are highly susceptible to an internal chemical reaction within the body called glycation. This is a reaction that takes place between free amino groups in proteins and a sugar such as glucose, resulting in the cross-linking of protein fibers, the loss of elasticity and changes in the dermis associated with the aging process. In young people there are few cross-links and the fibers are free to move up and down. The collagen stays soft and pliable. With age however the number of cross-links increase, causing the skin to shrink and become less soft and pliable. It is thought that these cross-links also begin to obstruct the passage of nutrients and waste between cells.

Other major theories of aging include the DNA damage theory of aging, the immunologic theory, the inflammation theory, etc.

Some nutritional supplements available today:

Resveratrol
Resveratrol is a member of a group of plant compounds called polyphenols. These compounds are thought to have antioxidant properties, protecting the body against the kind of damage linked to increased risk for conditions such as cancer and heart disease. Resveratrol is found in the skin of red grapes, but other sources include peanuts and berries. Resveratrol works by acting on the SIRT1 gene, a gene that is believed to control the function and longevity of cells.

In 2003, Howitz and David Sinclair reported that resveratrol significantly extends the lifespan of the yeast Saccharomyces cerevisiae. Sinclair later reported that resveratrol also prolongs the lifespan of the worm, Caenorhabditis elegans, and the fruit fly, Drosophila melanogaster. In 2007, a different group of researchers were able to reproduce Sinclair's results with C. elegans, but other groups could not achieve consistent increases in lifespan of D. melanogaster, other flies, or C. elegans. The first demonstration of life extension by resveratrol supplementation in a vertebrate was obtained in 2006. In a short-lived fish, Nothobranchius furzeri, with a median life span of nine weeks, a maximal dose of resveratrol increased the median lifespan by 56%.

Carnosine
Carnosine is a substance produced naturally by the body. Classified as a dipeptide (a compound made up of two linked amino acid molecules), carnosine is highly concentrated in muscle tissue and in the brain. Laboratory research on cell life indicates that L-Carnosine has the ability to rejuvenate cells approaching old age, restoring normal appearance and extending cellular life span. In fact it can actually recover old cells to approximately 90 percent of its original youthful state. This appears to be done mainly through anti-glycalation and anti-oxidation.

Benfotiamine
Benfotiamine is a slightly altered derivative of vitamin B1, thiamine. It may slow down the progress of one of the components of the aging process.

In the recent years, the role of advanced glycation end products (AGEs) has been increasingly discussed in skin aging, and the potential of anti-AGE strategies has received high interest from pharmaceutical companies for the development of novel anti-aging cosmeceutical compounds. Glycation is the result of typically covalent bonding of a protein or lipid molecule with a sugar molecule, such as fructose or glucose. Glycation occurs when the sugar molecules permanently attach to collagen present in the skin and other parts of the body. At the point of attachment, there is a small mechanism creating inflammation. In addition to inflammation, glycation also causes cross-linking in our collagen, making it stiff and inflexible where it was once soft and supple.This extensive cross-linking of collagen causes the loss of skin elasticity.Healthy collagen strands normally slide over one another, which keeps skin elastic. If a young person smiles or frowns, creating lines in the face, the skin will snap back and be smooth again when he stops smiling or frowning. But the skin does not snap back out in a person whose collagen has been crosslinked from years of eating sugar and the wrong carbs. Those deep grooves remain, because that is where the sugar molecules have attached to collagen, making the fibers stiff and inflexible.

Benfotiamine blocks destructive biochemical pathways that enable high blood sugar levels to damage nerves and small blood vessels. Benfotiamine also inhibits the formation of advanced glycation end products in both diabetic and normal aging organisms. Glycation not only causes kidney, nerve, and retinal damage in diabetics, but is also a significant contributory factor in cardiovascular disease and other aging disorders in adults without diabetes.

NAD
Researchers say a major component of aging in mammals may be reversible and the key is the chemical nicotinamide adenine dinucleotide, abbreviated NAD+, a coenzyme found in all living cells. It facilitates cell communication. Researchers from a joint project of the University of New South Wales and Harvard University in America found that the tissue of two-year-old mice given the NAD-producing compound for just one week resembled that of six-month-old mice. They also found that young mice given the same compound became "supercharged" in some ways, suggesting that the technique could have benefits for young, healthy humans as well.

The researchers are now looking at the longer-term outcomes of the NAD-producing compound in mice and how it affects the mouse as a whole, including whether it will give the mice a longer, healthier life. The researchers hope to start clinical trials on humans late in 2014.

“There’s clearly much more work to be done here, but if those results stand, then aging may be a reversible condition, if it is caught early,” says Professor David Sinclair. The team's study is published in the journal "Cell."


Is any of this valid or is it just wishful thinking? Will medicine ever be able to slow aging? How about reversing aging?