Biological Fountain of Youth

March 27, 2015

By Medical Discovery News

The Biological Fountain of Youth

Over 500 years ago, Ponce de Leon landed in Florida as part of his search for the fountain of youth – magical waters that reverse aging, prevent illness, and grant immortality. He never found it, and neither has anyone else. While immortality is still impossible, we have come a long way in understanding the aging process.

We do not know the precise mechanism of aging, but there are some fundamental processes in our bodies that begin to change and this can drive aging. There are several theories of aging under intense scientific investigation.

A widely accepted theory of aging today is called evolutionary senescence, which mainly hinges on the concept of mutation accumulation. As we age, our cells accumulate mutations in our genetic material or DNA, which affects the ability of our cells to replicate and our tissues to regenerate. Also, some of our genes are designed to enhance reproduction early in life, but can cause problems later. Since genes can only be passed on during reproduction, which generally occurs earlier in life, genes that have negative effects later in life are not removed from the population – we are stuck with them! A good example is a gene called p53, which controls the fate of damaged cells by preventing their replication or directing them to die. This is important in preventing cancer in young people, but it may negatively impact our ability to replace aging cells in tissues as we grow older.

Another widely discussed theory centers on the maintenance of our genomes. As we get older, we accumulate damage to our DNA, which affects cellular function and our ability to renew tissues in the body. In a sense, this is a high mileage effect. Take for example the production of free radical molecules. These highly reactive molecules are normally produced in mitochondria, which use oxygen to produce cellular energy, a process that creates free radical molecules as a by-product. These free radical molecules lead to oxidative damage of DNA and other cellular components.

There is also evidence the neuroendocrine system (hormones that affect neurological function) influences aging. For example, a reduction in hormone levels can lead to a lengthening of life, at least in experimental animals. We are beginning to suspect that the insulin-related hormonal pathway may play a significant role in aging, at least in mice. Mutations that reduce the amount of this circulating hormone extend life.

A relatively new model of aging involves the replication of chromosomes as cells divide. When cells replicate, specialized structures at the ends of chromosomes called telomeres are shortened. Shortened telomeres are linked to decreased viability and increased cancer risk. Cells whose telomeres reach a critical length can no longer divide and are described as senescent.

We are expanding our understanding of how aging occurs. The search for a modern-day fountain of youth will require a great deal of dedicated work by biomedical scientists to safely improve and extend human life.

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Thinking with your Stomach

May 31, 2013

By Medical Discovery News

“The way to a man’s heart is through his stomach.” New research might amend this common proverb to “the way to a man’s brain is through his stomach.” An article in the “New Scientist” argues that the enteric nervous system (ENS), found in the tissues of the gastrointestinal (GI) tract, functions as a second brain of sorts.

Spanning the mouth to anus, the GI system is approximately 30 feet long and can be divided into the upper (esophagus, stomach, and duodenum) and lower (large and small intestine) tracts. This is where digestion occurs, providing metabolic functions and energy to the body. With this complex role, it is not hard to imagine why it needs its own nervous system.

Like the brain, the ENS consists of different types of neurons as well as glial cells, which provide support and protection for the neurons. The human ENS contains upward of 500 million neurons and an equal number of glial cells, more than all of those in a rodent’s brain. However, the human brain contains 90 billion neurons. The ENS communicates with the brain to control unconscious or autonomic processes, like peristalsis, the wave-like motions that push food through the GI tract. 

To accomplish this, the ENS produces hormones and neurotransmitters much like the brain. In fact, the ENS produces as much dopamine (which triggers feelings of reward and pleasure) as the brain and most of the serotonin (which controls mood, appetite, and sleep) within the body.

So, if the ENS truly acts as a second brain, then the GI system can affect a person’s moods and sense of wellbeing. The ENS causes this by transmitting signals to the brain through the vagus nerve. This makes sense, since people typically feel good after enjoying a meal. For example, when rich foods are digested they release fatty acids. The gut detects this, prompting the ENS to send certain signals to the brain. According to brain imaging studies, the brain then releases pleasurable sensations, altering a person’s mood. So it’s no wonder that people crave rich, fatty foods!

On the other hand, people usually eat differently when stressed. Stress can lead to the production of a GI hormone called ghrelin, which causes feelings of hunger and leads to a reduction of anxiety and depression. In experiments, mice subjected to stress sought out fatty foods, which elevated the production of ghrelin. The link between chronic stress and obesity is then a no-brainer.

The main function of the ENS is to monitor the digestion of food and identify threats in what is eaten, such as toxins or infections. So, perhaps listening to the stomach when it comes to choosing meals isn’t all bad. After all, that’s the second brain at work.

The Moral Molecule

By Medical Discovery News

Aug. 4, 2012

Will politicians on Capital Hill ever be able to work together again? Though that may seem to call for a miracle, a mere hormone might do the trick. A recent study suggests a tiny hormone, oxytocin, causes feelings of trust and generosity in humans and other mammals.

Oxytocin is primarily known for its role in childbirth and breastfeeding. As a woman goes into labor, the hormone induces uterine contractions to speed up delivery. It then stimulates the body to release breast milk when an infant begins nursing.

Beyond these physiological functions, increased levels of oxytocin enhance bonding between a mother and her child. It also plays a role in pair bonding, sexual behavior, and even the ability to form normal social attachments.

Recent studies by Paul D. Zak, chair of economics at Claremont Graduate University in California, present oxytocin as an even more intriguing hormone. He calls it the “moral molecule,” and said it explains why some people give freely while others are stingy.

In a series of double blind experiments, Zak and his colleagues compared trusting behavior between a group of people who were administered oxytocin intranasally against a control group given a placebo. The two groups were each asked to play a trust game with money. Each person was given $12. The “investor” has the option to give any amount of their money to a “trustee.” Any amount given to the trustee was immediately tripled. So, a trustee could end up with a maximum of $48. The trustee could then choose to transfer back to the investor any or all of that money.

The results revealed that 45 percent of those who received the oxytocin displayed maximal trust by giving the trustee all $12 while only 21 percent of the control subjects did so. People in the oxytocin group who did not give the full amount still consistently gave away more of their money than the control group. These results suggest oxytocin affects behavior associated with trust, along with its other roles in social attachments and affiliation.

What’s striking about Zak’s experiment is that when he did the studies without administering oxytocin, the trustees who were generously given money, gave generously back. And blood samples showed their oxytocin levels shot up simply because they felt trusted, and in return displayed trust. In other words, oxytocin levels can surge from something as simple as a massage, prayer, singing, and other activities that foster social connections.

But this one hormone does not work in isolation. Human behavior is influenced by other hormones and past experiences. For example, in certain situations, a surge of testosterone would compete with the effects of oxytocin.

Going on the theory that oxytocin is central to a person’s ability to socially connect, scientists have already begun testing its effect on people with autism. Initial results are positive, paving the way for research on oxytocin’s effects on other social dysfunction disorders such as depression and schizophrenia.

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