Antagonistic Pleiotropy and Free Radicals in Skin Tissue
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Antagonistic pleiotropy is a term used to describe the results of a trait or mechanism that is beneficial in youth but then causes harm in later life. Evolutionary processes appear to select such traits due to their impact on early reproductive success, and that is one of the reasons why we age. Here, researchers illustrate this point while investigating one of the many roles played by free radicals in mammalian tissues:

When scientists bred mice that produced excess free radicals that damaged the mitochondria in their skin, they expected to see accelerated aging across the mouse lifespan - additional proof of the free radical theory of aging. Instead, they saw a surprising benefit in young animals: accelerated wound healing due to increased epidermal differentiation and re-epithelialization. Free radicals are especially reactive atoms or groups of atoms that have one or more unpaired electrons. They are produced in the body as a by-product of normal metabolism and can also be introduced from an outside source, such as tobacco smoke, or other toxins. Free radicals can damage cells, proteins and DNA by altering their chemical structure. Excessive amounts of free radicals are known to cause cellular damage that leads to aging, but in some mouse models and human studies lowering free radicals with antioxidants have not always conferred the expected benefits.

While increased free radical production showed benefit in younger animals, the mice paid a price over time. Mitochondrial damage from excess free radicals caused some of the skin cells to go into senescence - they stopped dividing and started accumulating. Over time the energy available to the epidermal stem cells was depleted - the stem cells simply became too scarce and the mice showed expected signs of aging, thin skin and poor wound healing. "In this case, we found unexpected pleotropic effects, mechanisms that benefit us when we're young cause problems as we age." Mitochondrial stress caused by the increase in free radicals also forced the skin cells in the younger animals to differentiate faster than normal, further depleting the pool of stem cells available to renew the skin over time. "This is not a simple process. It may be that nature used free radicals to optimize skin health, but because this process is not deleterious to the organism until later in life, past its reproductive age, there was no need to evolve ways to alter this mechanism." There could be one practical implication of the study: taking large amounts of anti-oxidants might have deleterious effects, at least in the skin.


Age-Related Increase in Clearance Time for Amyloid Protein
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The amyloid associated with Alzheimer's disease builds up with age, and much more so in people eventually diagnosed with Alzheimer's. Many lines of evidence indicate that the underlying problem is one of slowly failing clearance of amyloid proteins: various systems and mechanisms falter with age due the accumulation of cell and tissue damage. Until amyloid proteins gather in large enough numbers to form lasting clumps, their presence are fairly dynamic, created and cleared on a timescale of hours. Researchers here provide direct evidence of slower clearance rates in older people:

The greatest risk factor for Alzheimer's disease is advancing age. After 65, the risk doubles every five years, and 40 percent or more of people 85 and older are estimated to be living with the devastating condition. Researchers have identified some of the key changes in the aging brain that lead to the increased risk. The changes center on amyloid beta 42, a main ingredient of Alzheimer's brain plaques. The protein, a natural byproduct of brain activity, normally is cleared from the brain before it can clump together into plaques. Scientists long have suspected it is a primary driver of the disease. "We found that people in their 30s typically take about four hours to clear half the amyloid beta 42 from the brain. In this new study, we show that at over 80 years old, it takes more than 10 hours." The slowdown in clearance results in rising levels of amyloid beta 42 in the brain. Higher levels of the protein increase the chances that it will clump together to form Alzheimer's plaques.

For the study, the researchers tested 100 volunteers ages 60 to 87. Half had clinical signs of Alzheimer's disease, such as memory problems. Plaques had begun to form in the brains of 62 participants. The subjects were given detailed mental and physical evaluations, including brain scans to check for the presence of plaques. The researchers also studied participants' cerebrospinal fluids using a technology known as stable isotope-linked kinetics (SILK), which allowed the researchers to monitor the body's production and clearance of amyloid beta 42 and other proteins.

In patients with evidence of plaques, the researchers observed that amyloid beta 42 appears to be more likely to drop out of the fluid that bathes the brain and clump together into plaques. Reduced clearance rates of amyloid beta 42, such as those seen in older participants, were associated with clinical symptoms of Alzheimer's disease, such as memory loss, dementia and personality changes. Scientists believe the brain disposes of amyloid beta in four ways: by moving it into the spine, pushing it across the blood-brain barrier, breaking it down or absorbing it with other proteins, or depositing it into plaques. "Through additional studies like this, we're hoping to identify which of the first three channels for amyloid beta disposal are slowing down as the brain ages. That may help us in our efforts to develop new treatments."


Further Investigation of the Endoplasmic Reticulum in Aging
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Researchers here outline recent discoveries relating to changes in the endoplasmic reticulum inside cells that occur over the course of aging. All cellular machinery falters with age due to accumulating damage, and the primary goal of the research community remains to catalog and fully understand these changes, with doing something about coming it a distant second where it is a focus at all. The endoplasmic reticulum is the site of protein synthesis, and since all cellular machinery is built out of proteins, it is not unreasonable to look for links between changes in the endoplasmic reticulum - and its many component parts - and the disruption of proteostasis in aging. In older tissues there are many more broken and misfolded proteins, and this may turn out to have as much to do with issues in production as with issues in quality control and damage repair.

Each cell consists of different compartments. One of them is the endoplasmic reticulum (ER). Here, proteins which are then secreted e.g. into the bloodstream, such as insulin or antibodies of the immune system, mature in an oxidative environment. A type of quality control, so-called redox homoeostasis, ensures that the oxidative milieu is maintained and disulphide bridges can form. Disulphide bridges form and stabilise the three-dimensional protein structure and are thus essential for a correct function of the secretory proteins, e.g. those migrating into the blood. Researchers have now shown that the ER loses its oxidative power in advanced age, which shifts the reducing/oxidising equilibrium - redox for short - in this compartment. This leads to a decline in the capacity to form the disulphide bridges that are so important for correct protein folding. As a consequence, many proteins can no longer mature properly and become unstable.

Although, it was already known that increased protein misfolding occurs with the progression of ageing, it was not known whether the redox equilibrium is affected. Likewise, it was not known that the loss of oxidative power in the ER also affects the equilibrium in another compartment of the cell: in reverse, namely, the otherwise protein-reducing cytosol becomes more oxidising during ageing, which leads to the known oxidative protein damage such those caused by the release of free radicals. "Up to now, it has been completely unclear what happens in the endoplasmic reticulum during the ageing process. We have now succeeded in answering this question." At the same time, the scientists were able to show that there is a strong correlation between protein homoeostasis and redox equilibrium. "This is absolutely new and helps us to understand why secretory proteins become unstable and lose their function in advanced age and after stress. This may explain why the immune response declines as we get older. We gained a lot of insight, but have also learned that ageing is much more complex than previously assumed." Thus, for example, the mechanism of the signal transduction of protein folding stress to the redox equilibrium - both within the cell from one compartment to another and also between two different tissues - remains completely unclear.


Engineered Microbes as Programmable Medical Tools
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Entirely artificial medical nanorobots will one day exist to augment or greatly improve on functions presently carried out by cellular machinery. Long before then, however, we will see the widespread use of modified cells and bacteria, altered to form programmable tools such as drug manufactories that travel to where they are needed and take the appropriate actions in response to local circumstances.

A successful microbial diagnostic or therapeutic agent must to able to detect a particular signal with high fidelity, integrate this signal through precise intracellular circuitry, and respond to this signal at the appropriate level. Researchers have recently described genetic tools that allow the commensal bacterial species B. thetaiotaomicron to efficiently perform all three of these functions. Notably, they show that circuits integrating signal detection, genetic memory, and CRISPR interefence function as expected when engineered B. thetaiotaomicron is introduced into the gut microbiome of mice.

In the future, one can imagine the use of these mechanisms to tightly regulate the expression of different genes in a biosynthetic gene cluster for a small molecule therapeutic (e.g., an antibiotic), engineered in a microbiome-derived Bacteroides strain. The in vivo expression of this gene cluster could be controlled by the level of a carbohydrate administered in the diet, or preferably, by a specific small molecule produced by the target pathogen itself. Decoupling of the synthesis and secretion of the small molecule (e.g., to reach an effective local therapeutic dose) can be achieved by putting the export machinery under the control of an inducible circuit that responds only to high intracellular levels of the small molecule, or by engineering a time delay between the synthesis and secretion of the molecule. Once the therapeutic effect has been achieved (e.g., the elimination of a pathogen), CRISPR interference can be used to knock down residual expression of the therapeutic genes or to eliminate the chassis itself by targeting an essential gene. This final step could be triggered by a second signal administered in diet, or by the absence of the pathogen-derived small molecule. This entire series of events could be recorded on memory switches and read through analysis of the Bacteroides genome in host feces, providing timely snapshots of what is happening in vivo.

Although it is still early days for its approval, using engineered commensal microbes to produce therapeutic molecules may be preferred over using oral or systemic drugs for several reasons. First, commensals naturally occupy specific niches in the gastrointestinal tract, allowing drug delivery to a very defined site. Subsequently, the dosage needed to obtain a local therapeutic effect would be much lower than needed if orally administered, and many adverse effects could in turn be eliminated. Second, because the production of a therapeutic molecule can be precisely controlled in engineered bacteria, long-term control of diseases can be achieved using a single organism that produces the drug only when needed. Last, using an engineered bacterium to produce and deliver one or more therapeutic molecules could provide an economical alternative to the costly production, formulation, distribution, and storage of drugs. This is even more applicable in the cases where a drug is specially formulated or administered via intramuscular or subcutaneous injection to avoid degradation in the stomach.


The Organoid Stage of the Tissue Engineering Revolution
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The first stage for commercially useful tissue engineering is testing and further research, and that is actually well underway. Tissue sections for test and research purposes don't have to be large, and therefore the big problem of how to generate suitable blood vessel networks doesn't have to be solved yet. So researchers have been building organoids and other small sections of tissue, gaining experience and refining techniques. The first tissue types were being sold years ago by companies such as Organovo, and these days many more are being added at an accelerating pace by competing research and development groups. This is a staging ground for the near future construction of organs to order, built from scratch from a patient's own cells:

Efforts to grow stem cells into rudimentary organs have taken off. Using carefully timed chemical cues, researchers around the world have produced three-dimensional structures that resemble tissue from the eye, gut, liver, kidney, pancreas, prostate, lung, stomach and breast. These bits of tissue, called organoids because they mimic some of the structure and function of real organs, are furthering knowledge of human development, serving as disease models and drug-screening platforms, and might eventually be used to rescue damaged organs. "It's probably the most significant development in the stem-cell field in the last five or six years."

The current crop of organoids isn't perfect. Some lack key cell types; others imitate only the earliest stages of organ development or vary from batch to batch. So researchers are toiling to refine their organoids -- to make them more complex, more mature and more reproducible. Still, biologists have been amazed at how little encouragement cells need to self-assemble into elaborate structures. "It doesn't require any super-sophisticated bioengineering. We just let the cells do what they want to do."

Biologists know that their mini-organs are still a crude mimic of their life-sized counterparts. But that gives them something to aim for. "The long-term goal is that you will be able to replicate more and more of the functionality of a human organ." Already, the field has brought together developmental biologists, stem-cell biologists and clinical scientists. Now the aim is to build more-elaborate organs -- ones that are larger and that integrate more cell types. Even today's rudimentary organoids are facilitating discoveries that would have been difficult to make in an animal model, in which the molecular signals are hard to manipulate.


Slowing Aging By Restricting Cryptic Transcription
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Researchers have demonstrated slower aging in yeast by increasing H3K36 methylation, which has the effect of restricting certain forms of transcription, the first step in the process of gene expression whereby proteins are generated from their genetic blueprints. It is worth noting that many ways to slow aging in laboratory species, including calorie restriction, have broad effects on observed patterns of transcription, and there is a still a long way to go towards a complete understanding of everything that is taking place in these portions of cellular biochemistry.

Gene expression is regulated by chemical modifications on chromatin - histone proteins tightly associated with DNA. Certain chemical groups on histones allow DNA to open up, and others to tighten it. These groups alter how compact DNA is in certain regions of the genome, which in turn, affect which genes are available to be made into RNA (a process called transcription) and eventually proteins. Researchers have pinpointed specific histone modifications that not only are altered during aging, but also directly determine longevity. "In this study, we found that a type of abnormal transcription dramatically increases in aged cells and that its reduction can prolong lifespan. This longevity effect is mediated through an evolutionarily conserved chemical modification on histones. This is the first demonstration that such a mechanism exists to regulate aging."

In yeast, aging is measured by the number of times a mother cell divides to form daughters before it stops. This number - a mean of 25 divisions - is under tight control and can be either reduced or increased by altering histone modifications, as the researchers found. They showed that when fewer chemical groups of a certain type attach to yeast histones, the abnormal transcription greatly increases in old cells. In contrast, the team found that in yeast strains with a certain enzyme deletion, this abnormal transcription is reduced and lifespan is extended by about 30 percent.

The results reveal that lack of sustained histone H3K36 methylation is commensurate with increased cryptic transcription in a subset of genes in old cells and with shorter life span. In contrast, deletion of the K36me2/3 demethylase Rph1 increases H3K36me3 within these genes, suppresses cryptic transcript initiation, and extends life span. "We show that this aging phenomenon is conserved, as cryptic transcription also increases in old worms. We propose that epigenetic misregulation in aging cells leads to loss of transcriptional precision that is detrimental to life span, and, importantly, this acceleration in aging can be reversed by restoring transcriptional fidelity. We have started investigating whether such a longevity pathway can also be demonstrated in mammalian cells. However, these investigations are confounded by the complexity of the genome in more advanced organisms. One of our long-term goals is to design drugs that can help retain these beneficial histone modifications and extend healthy lifespan in humans."


Targeting an Improvement in Protein Quality Control
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A range of research efforts aim at finding ways to improve or enhance the activity of cellular maintenance mechanisms involved in ensuring quality control. Proteins are the building blocks of cell machinery but constantly become damaged or misfolded, which can then cause harm through incorrect function. Thus cells work hard to clear out, break down, and recycle these problem molecules, but all of these mechanisms decline with aging; based on what we know to date, this happens because the repair machinery itself is vulnerable to forms of damage or can be negatively impacted by reactions to damage taking place in other processes, just like the rest of a cell.

So far there is little concrete progress towards therapies based on enhanced protein quality control, though a variety of genetic alterations that extend life in laboratory animals are shown to include enhanced quality control as a part of their effects. I would expect some candidate therapies to emerge in the years ahead, however, as the interest in moving in that direction certainly exists:

Impairment of "protein quality control" in neurons is associated with the etiology and pathogenesis of neurodegenerative diseases. The worn-out products of cell metabolism should be safely eliminated via the proteasome, autophago-lysosome and exocytosis. Insufficient activity of these degradation mechanisms within neurons leads to the accumulation of toxic protein oligomers, which represent a starting material for development of neurodegenerative proteinopathy.

The spectrum of CNS linked proteinopathies is particularly broad and includes Alzheimer's disease (AD), Parkinson's disease (PD), Lewy body dementia, Pick disease, Frontotemporal dementia, Huntington disease, Amyotrophic lateral sclerosis and many others. Although the primary events in etiology and pathogenesis of sporadic forms of these diseases are still unknown, it is clear that aging, in connection with decreased activity of ubiquitin proteasome system, is the most significant risk factor.

We discuss the pathogenic role and intracellular fate of the candidate molecules associated with onset and progression of AD and PD, the protein tau and α-synuclein in context with the function of ubiquitin proteasome system. We also discuss the possibility whether or not the strategies focused to re-establishment of neuroproteostasis via accelerated clearance of damaged proteins in proteasome could be a promising therapeutic approach for treatment of major neurodegenerative diseases.


Supercentenarian Research Study
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A number of ongoing research programs aim to collect more data on the biochemistry and genetics of the oldest of old people, and here is an example of one of them. I don't believe that these efforts contribute greatly towards building meaningful treatments for aging, for all the same reasons that trying to build calorie restriction mimetic drugs is a dead end: the underlying causes of aging are known, the damage that produces degeneration and loss of function, and researchers should be focused on repairing it to extend healthy life by decades, not on exploring comparatively small differences in how the body adapts to high levels of damage, or how to eke out a few more years while in a diminished and dysfunctional state. From a purely academic perspective, the study of natural variations in human aging is a good way to learn more about the fine details of how exactly aging progresses at the cellular level, however. Just don't expect this to have practical results beyond the production of new knowledge.

Supercentenarians are very rare, very precious individuals, who have lived to at least 110 years of age. Surviving decades longer than their peers -- often in far better health -- supercentenarians may hold the keys to protection from disease, decline, and early death. Our researchers are engaged in an extensive, international study of individuals demonstrating increased or extreme resistance to devastating, age-related diseases -- such as cancer, cardiovascular disease, diabetes, Alzheimer's disease, Parkinson's disease, organ failure, immune system failure, and neurodegeneration -- as well as the illness and injury caused by bone and muscle deterioration, dementia, loss of mobility, and cognitive decline. Supercentenarians have avoided the vast majority of these age-related illnesses, and the study of the protective mechanisms that have ensured their survival may lead to the discovery and development of new treatments and therapies, bringing the good health and great longevity of supercentenarians to the rest of us.

There is a great deal of research to support the theory that supercentenarians' longevity is hereditary. The siblings of supercentenarians are up to 17 times more likely to survive to age 100 than the siblings of non-supercentenarians. Many of these individuals also enjoy increased and lifelong resistance to disease, suffering far less age-related morbidity. Studies reveal a strong link between inherited traits and healthy longevity, as well as mechanisms that protect against a wide variety of illnesses. The careful study of supercentenarians and their families can provide unparalleled insights into the mechanisms of health, aging, and disease.


Towards Better Cryoprotectants, With an Eye on Thawing
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Below find an interesting discussion of one research program aimed at producing a better class of cryoprotectant that enables tissue thawing without damage. The organ storage and cryonics industries have many of the same technical goals: how to preserve complex tissues for the long term at low temperatures while enabling a safe thaw at the far side of storage. Some research companies straddle both industries, such as 21st Century Medicine. The enemy here is ice, as it is crystallization that destroys cells and structures in straight freezing. If near-future thawing is not a concern, then many varieties of cryoprotectant compounds are useful. When infused into tissue the result is vitrification rather than freezing, with minimal ice crystal formation and preservation of even very fine-scale cellular structures, such as synapses and other aspects of brain structure thought to hold the data of the mind.

To date there are very few examples of the successful thaw and use of a vitrified organ, even in the laboratory. It is research programs such as the one noted here that may help to change this state of affairs. Given better cryoprotectants and significant use of long-term organ storage in medicine, one would hope that the public will become more accepting of cryonics as an end of life choice, a shot at living again to see a better future for those who will age to death prior to the advent of rejuvenation therapies.

Researchers have synthesised a polymer that limits ice crystal growth in frozen red blood cells as they thaw. The polymer is set to pave the way for similar synthetic structures that mimic the properties of natural antifreeze proteins. During cryopreservation, cells and tissues are stored at sub-zero temperatures and thawed before use. However, frozen cells can be damaged as they defrost. When ice melts, it can refreeze into larger crystals that puncture cells from the outside. This process, called recrystallisation, is especially damaging for organs and blood bags, which defrost over a long time. "'If you directly freeze cells they don't survive due to ice-induced damage, and the traditional solution is to add antifreeze solvents. Although these work, they involve complex preparation procedures, and transfusing large volumes of solvent is not desirable. Alternatives to the conventional cryoprotectants are urgently required as the fields of regenerative medicine and tissue engineering continue to advance."

Unlike proteins, which need to be extracted or expressed in microorganisms, polymers are more accessible, processable, tunable and cheaper. Researchers modified an already available polymer called a polyampholyte, which is composed of monomers with both positively and negatively charged groups. The polymer functions outside the cells, so it can be washed-off after thawing. This may explain its good compatibility with red blood cells. Up to 60% red blood cell recovery after freezing was observed during slow thawing when the new polymer was used, and this increased to 80% when the cells were thawed quickly. Notably, the polymer was capable of inhibiting ice recrystallisation by 50%.

The mechanism by which the synthesised polymer inhibits ice recrystallisation is still not clear. Although it has been assumed for many years that macromolecules had to bind directly to ice crystal faces to inhibit growth, their work supports the idea that binding to ice crystals is not essential. "It seems that they somehow disrupt the rate exchange of water molecules between ice crystals, via the quasi liquid layer, although we do not have direct evidence for this at the moment. As to why the ampholyte structure works, we are not sure, but we are thinking that it might be a semi-rigid polymer due to charged interactions along the backbone, which helps. Cheap, non-toxic, degradable polymers that inhibit ice recrystallisation may become attractive non-permeating additives for cryopreservation of red blood cells if these boost cell recovery by more than 80% and allow for prolonged post-thaw storage."


Suggesting the Correlation Between Intelligence and Longevity is Mostly Genetic
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Researchers building on twin study data are suggesting that the well-known correlation between greater intelligence and a little additional longevity is mostly genetic in nature, not a matter of more intelligent people making better lifestyle choices, or tending to be wealthier, or any of the other social or economic factors that are associated with both intelligence and longevity. The size of the effect due to intelligence is small, but a demonstration of it being due to genetics is not the result I would have expected based on past data on human longevity. To date I'm aware of little other research to back this point of view. For one of them, you might look at a paper from a few years back that suggests learning and longevity in bees are both influenced by the same underlying mechanisms of robustness in biological systems, their resistance to stress.

The tendency of more intelligent people to live longer has been shown, for the first time, to be mainly down to their genes. By analysing data from twins, researchers found that 95 per cent of the link between intelligence and lifespan is genetic. They found that, within twin pairs, the brighter twin tends to live longer than the less bright twin and this was much more pronounced in fraternal (non identical) twins than in identical twins. Studies that compare genetically identical twins with fraternal twins - who only share half of their twin's DNA - help distinguish the effects of genes from the effects of shared environmental factors such as housing, schooling and childhood nutrition.

"We know that children who score higher in IQ-type tests are prone to living longer. Also, people at the top of an employment hierarchy, such as senior civil servants, tend to be long-lived. But, in both cases, we have not understood why. Our research shows that the link between intelligence and longer life is mostly genetic. So, to the extent that being smarter plays a role in doing a top job, the association between top jobs and longer lifespans is more a result of genes than having a big desk. However, it's important to emphasise that the association between intelligence and lifespan is small. So you can't, for example, deduce your child's likely lifespan from how he or she does in their exams this summer. It could be that people whose genes make them brighter also have genes for a healthy body. Or intelligence and lifespan may both be sensitive to overall mutations, with people with fewer genetic mutations being more intelligent and living longer. We need to continue to test these ideas to understand what processes are in play."