A special breed of mice lived up to three times longer than normal after University of Pittsburgh researchers injected them with stem cells from younger, healthy mice, according to a study being published today in the journal Nature Communications.

Working with mice that are bred to die prematurely, Pitt researchers led by Johnny Huard and Laura Niedernhofer dramatically increased the animals’ lifespans by injecting them in the abdomen with young animals’ muscle stem cells. _Post-Gazette

Keep in mind that this research was done in a special breed of mouse that is programmed to have a shorter lifespan. Additional research will be required to determine if normal ageing mice can benefit from similar treatment.

“We wanted to see if we could rescue these rapidly aging animals, so we injected stem/progenitor cells from young, healthy mice into the abdomens of 17-day-old progeria mice,” Dr. Huard said. “Typically the progeria mice die at around 21 to 28 days of age, but the treated animals lived far longer – some even lived beyond 66 days. They also were in better general health.”

As the progeria mice age, they lose muscle mass in their hind limbs, hunch over, tremble, and move slowly and awkwardly. Affected mice that got a shot of stem cells just before showing the first signs of aging were more like normal mice, and they grew almost as large. Closer examination showed new blood vessel growth in the brain and muscle, even though the stem/progenitor cells weren’t detected in those tissues.

In fact, the cells didn’t migrate to any particular tissue after injection into the abdomen.
“This leads us to think that healthy cells secrete factors to create an environment that help correct the dysfunction present in the native stem cell population and aged tissue,” Dr. Niedernhofer said. “In a culture dish experiment, we put young stem cells close to, but not touching, progeria stem cells, and the unhealthy cells functionally improved.” _MedXpress

Stem cells can conceivably be used for many purposes, in the treatment of ageing. In the case of the above research, the stem cells apparently secreted some type of hormonal growth factor which was lacking in the progeria mice.

But in future, more sophisticated uses of stem cells to treat ageing, stem cells will be used for tissue replacement, organ regeneration and replacement, humoral factor replacement, and probably other uses not yet discovered.

Al Fin Longevity

Nature’s most recent “Insight” supplement is devoted to a topic near and dear to our hearts, even when spelled with that superfluous UK “e”: Ageing. From the introductory editorial:

Ageing, the accumulation of damage to molecules, cells and tissues over a lifetime, often leads to frailty and malfunction. Old age is the biggest risk factor for many diseases, including cancer and cardiovascular and neurodegenerative diseases. … Ageing research is clearly gaining momentum, as the reviews in this Insight testify, bringing hope that at some time in the future we will be able to keep age-related diseases at bay by suppressing ageing itself.

The five reviews are all by prominent scholars — many of whose work we’ve discussed here — and cover a wide range of subjects within gerontology and biogerontology:

• The genetics of ageing, Cynthia J. Kenyon
• Lessons on longevity from budding yeast, Matt Kaeberlein
• Linking functional decline of telomeres, mitochondria and stem cells during ageing, Ergün Sahin & Ronald A. DePinho
• Neural mechanisms of ageing and cognitive decline,
  Nicholas A. Bishop, Tao Lu & Bruce A. Yankner

• Biodemography of human ageing, James W. Vaupel

As always, Nature Insight supplements are free-access, so even if you don’t have access to a university subscription, you can still read these articles.

(For a previous aging-related Nature Insight on DNA repair, see here.)

Ouroboros

The first hint comes from the Mayo Clinic’s Darren Baker. Baker has developed a way of delaying symptoms of old age in mice, and has even been able to reverse some signs of aging in already aged mice. Here’s more:

Baker has developed a way of killing all of a mouse’s senescent cells by feeding them with a specific drug. When he did that in middle age, he gave the mice many more healthy years. He delayed the arrival of cataracts in their eyes, put off the weakening of their muscles, and held back the loss of their body fat. He even managed to reverse some of these problems by removing senescent cells from mice that had already grown old. There is a lot of work to do before these results could be applied to humans, but for now, Baker has shown that senescent cells are important players in the ageing process.

Note that the mice in this study didn’t live any longer; they just spent more of their life being healthy.

Baker exploited the fact that many senescent cells rely on a protein called p16-Ink4a. He created a genetic circuit that reacts to the presence of p16-Ink4a by manufacturing an executioner: a protein called caspase-8 that kills its host cell. Caspase-8 is like a pair of scissors – it comes in two halves that only work when they unite. Baker could link the two halves together using a specific drug. By sneaking the drug into a mouse’s food, he activated the executioners, which only killed off the cells that have lots of p16-Ink4a. Only the senescent ones get the chop.

Baker tested out this system in a special strain of genetically engineered mice that age very quickly. It worked. The senescent cells disappeared, and that substantially delayed the onset of muscle loss, cataracts, and fat loss. Typically, around half of these mice show signs of muscle loss by five months of age. Without their senescent cells, only a quarter of them showed the same signs at ten months. Their muscle fibres were larger, and they ran further on treadmills. Even old mice, whose bodies had started to decline, showed improvements. _Discover

Another look at this research from the Economist:

Dr Baker genetically engineered a group of mice that were already quite unusual. They had a condition called progeria, meaning that they aged much more rapidly than normal mice. (A few unfortunate humans suffer from a similar condition.) The extra tweak he added to the DNA of these mice was a way of killing cells that produce P16INK4A. He did this by inserting into the animals’ DNA, near the gene for P16INK4A, a second gene that was, because of this proximity, controlled by the same genetic switch. This second gene, activated whenever the gene for P16INK4A was active, produced a protein that was harmless in itself, but which could be made deadly by the presence of a particular drug. Giving a mouse this drug, then, would kill cells which had reached their Hayflick limits while leaving other cells untouched. Dr Baker raised his mice, administered the drug, and watched.

The results were spectacular. Mice given the drug every three days from birth suffered far less age-related body-wasting than those which were not. They lost less fatty tissue. Their muscles remained plump (and effective, too, according to treadmill tests). And they did not suffer cataracts of the eye. They did, though, continue to experience age-related problems in tissues that do not produce P16INK4A as they get old. In particular, their hearts and blood vessels aged normally (or, rather, what passes for normally in mice with progeria). For that reason, since heart failure is the main cause of death in such mice, their lifespans were not extended.

The drug, Dr Baker found, produced some benefit even if it was administered to a mouse only later in life. Though it could not clear cataracts that had already formed, it partly reversed muscle-wasting and fatty-tissue loss. Such mice were thus healthier than their untreated confrères. _Economist

This research will require replication and a great deal of clarification, before it moves from mice to larger mammals such as humans. But it opens up a number of possible avenues of research.

The second hint of likely means to achieve healthier long lives, is research done in fruit flies at the Salk Institute, in southern California.

Although it is a well-documented fact that restricting calories during daily food intake is the easiest strategy to extend life spans for both humans and animals, little is known about biological mechanisms underlying this phenomenon.

…”Fruit flies and humans have a lot more in common than most people think,” said Leanne Jones, an Associate Professor at Salk’s Laboratory of Genetics and a lead scientist on the project, “There is a tremendous amount of similarity between a human small intestine and the fruit fly intestine.”

The researchers found that boosting the activity of dPGC-1, the Fruit Fly version of the gene, resulted in greater numbers of mitochondria and more energy-production in flies; the same phenomenon is seen in organisms on calorie restricted diets.

When the activity of the gene was accelerated in stem and progenitor cells of the intestine, which serve to replenish intestinal tissues, these cellular changes correspond with better health and longer lifespan.

The flies lived between 20 and 50 percent longer, depending on the method and extent to which the activity of the gene was altered. _ibtimes

The fruit fly research suggests that not only healthier long lives are possible, but “longer long” lives are possible as well.

The approach taken by the SENS Foundation involves using multiple approaches to extending healthy lifespan. Destroying senescent cells — such as Darren Baker is learning to do — is one of the main approaches that SENS is following. Improving the function of mitochondria is another of the main tactics of SENS.

As humans in advanced societies are putting less and less energy into raising children, and putting more and more energy into raising themselves, thoughts of increased longevity and lifespan are coming more into the mainstream of respectability. The main limitation to further research into life extension is — as always — funding. But even with unlimited funding, moving the research from animal models into human therapeutics would take a matter of decades.

Al Fin Longevity

Directions for making proteins are encoded in the DNA sequences of genes, which reside on chromosomes in the nucleus of each cell. But for proteins to be made, a gene’s DNA code must be copied, or transcribed, onto mRNA molecules, which migrate from the nucleus and into the cytoplasm where the cell’s protein-making machinery is located. For as long as it exists, an mRNA molecule can act as a template for making copies of a protein. So scientists have long suspected that cells must have ways for degrading mRNAs when, for example, a protein starts accumulating to harmful levels. “The cell somehow decides to destroy its mRNA on cue, but nobody knew how this happens,” said Dr. Singer. _EinsteinNews

Scientists at Albert Einstein College of Medicine recently made a basic discovery in the control of messenger RNA lifespan, which may help to unlock one of the important doors to understanding.

When genes are transcribed, a part of the gene called the promoter region has the job of switching on the gene so that DNA will be copied into mRNA. The Einstein scientists found that the promoter regions of the SWI5 and CLB2 genes do something else as well: they recruit a protein called Dbf2p, which jumps onto mRNA molecules as they’re being synthesized.

These mRNAs—transcribed from the SWI5 and CLB2 genes and bearing the Dbf2p protein—make their journey from the nucleus into the cytoplasm. Here a protein called Dbf20p joins Dbf2p aboard the mRNA molecules—and the two proteins together call for the molecules’ precipitous decay.

“Our findings indicate that genes making proteins whose levels must be carefully controlled contain promoter regions that sentence their mRNA molecules to death even as the mRNA is being born,” said Dr. Singer. “The promoter regions do that by ‘marking’ the newly made mRNA with the protein Dbf2p—the common factor between mRNA synthesis and its ultimate decay. Dbf2p stays attached to the mRNA from its birth and then, responding to a signal indicating that no more protein should be made, orders mRNA’s destruction.” _EinsteinNews

You see, as long as the messenger RNA stays around in the cytoplasm, it will keep binding to ribosomes, and continue to produce its protein. This is not what the cell wants, in general, since the relative quantities of different proteins are maintained in a healthy balance.

The application of this discovery to life extension is not immediately apparent to the casual reader. And yet as we come to understand the build-up of imbalances within cells which accompany the ageing process, we are likely to find multiple ways in which this particular system can go wrong, and contribute to degenerative changes.

The better we understand this complex dance of molecules, the better will be our solutions to the problems that occur when the complex system begins to break down. Eventually, we will probably want to re-design some of these sub-systems in ways to make them more robust.

PDF of actual study, published in Cell

Al Fin Longevity

The ongoing study of current cognitive enhancers such as those in the table above, have given us scattered hints as to what future therapies might offer. Here is a short list of possible future targets for cognitive therapies:

Among targets under investigation, cholinergic receptors have received much attention with several nicotinic agonists (α7 and α4β2) actively in clinical trials for the treatment of AD, CIAS and attention deficit hyperactivity disorder (ADHD). Both glutamatergic and serotonergic (5-HT) agonists and antagonists have profound effects on neurotransmission and improve cognitive function in preclinical experiments with animals; some of these compounds are now in proof-of-concept studies in humans. Several histamine H3 receptor antagonists are in clinical development not only for cognitive enhancement, but also for the treatment of narcolepsy and cognitive deficits due to sleep deprivation because of their expression in brain sleep centers. Compounds that dampen inhibitory tone (e.g., GABAA α5 inverse agonists) or elevate excitatory tone (e.g., glycine transporter inhibitors) offer novel approaches for treating diseases such as schizophrenia, AD and Down syndrome. In addition to cell surface receptors, intracellular drug targets such as the phosphodiesterases (PDEs) are known to impact signaling pathways that affect long-term memory formation and working memory. Overall, there is a genuine need to treat cognitive deficits associated with many neuropsychiatric conditions as well as an increasingly aging population. _Source

It is important for us, at the outset, to take as realistic a viewpoint toward the possibility of meaningful cognitive enhancement as possible. The Likelihood of Cognitive Enhancement (Lynch et al 2011 PDF) is a useful introduction to many of the practical issues that need to be faced from the very beginning of this enterprise. Cognitive Enhacement: Promises and Perils (Hyman 2011 PDF) is a less technical introduction to the topic, perhaps more accessible to most laymen.

Cognitive Enhancement as a Pharmacotherapy Target for Stimulant Addiction (Sofuoglu 2010) looks at the use of cognitive enhancers as possible treatments for cocaine and methamphetamine addictions. Long term and heavy use of these drugs leads to cognitive deficits which make it even more difficult for a person to stop using these drugs and lead a “normal” life. The restoration of cognitive function is likely to provide a certain amount of “mental fortification” to allow at least some addicts to turn away from the dead end lifestyle. Similarly, restoration of cognitive function in persons suffering from age-related neurodegeneration is more likely to allow the person to participate in normal social interaction, and to undertake some level of responsibility, and perhaps productive activity.

Emerging Pharmacotherapies for Neurodevelopmental Disorders (Wetmore et Garner 2010) looks at the use of cognitive enhancers for persons who suffer from neurodevelopmental disorders such as Down’s Syndrome, Fragile X, autism, etc. Given the overlap of mechanisms between some of the cognitive deficits in developmental disorders and ageing-related cognitive deficits, some of the coming developments in this area of pharmacotherapy should also prove quite helpful for treating age-related dementias.

As more is learned about the time-course of dysfunction in NDDs [neurodevelopmental disorders], targeting of therapies to the existing brain state may be improved. Moreover, individuals with NDDs have multiple cognitive and behavioral disabilities, and a particular drug therapy may improve only a subset of cognitive functions. Thus, a combination of complementary drugs may offer the most benefit by addressing deficits in attention, arousal, information processing, or depression.
…
The NDDs discussed here are phenotypically diverse yet linked by common mechanisms of dysfunction, including abnormal gene dosage, imbalance among neurotransmitter systems, and local protein translation (Fig. 2). A particular NDD can be caused by mutations in multiple genes, underscoring the convergence of dysfunction in key biochemical pathways. _Source

Finally, I would like to append to this entry some material from an earlier Al Fin article, which provides a few hints of future drug targets, as well as links to related material:

AMPAkines
CREB
PDE Inhibitors(4,10)
Nicotinic Alpha-7 agonists
mGluR antagonists
5HT6 antagonists

Frontrunners in the pharmaceutical race for smarter, better memory drugs include Memory Pharmaceuticals, Cortex Pharmaceuticals, Saegis Pharmaceuticals, Helicon, Lilly, Pfizer, Wyeth, Merck, Sention and many others. The precedent of approving drugs for erectile dysfunction (ED)–a lifestyle drug–suggests that smart drugs will eventually be approved for drooping memories as well.

Further Reading:

Molecules for Memory

Nootropics

Smart Drugs: What Are the Prospects?

Shaping the Brain with Smart Drugs (Gazzaniga)

CREB and Memory (basic neuroscience)

CREB, Synapses, and Memory Disorders

Hat tip Advanced Nano and Kurzweilai.net

Al Fin Longevity

Swiss scientists have discovered that knocking out the nuclear receptor corepressor 1 (NCoR1) gene in the muscles of mice allow the animals to run farther, and faster. Knocking out the same gene in fat cells eliminated the problem of diabetes in the mice. And those are only two tissues, of the many types of tissues in a mouse’s body. I wonder if knocking out the NCoR1 gene in human muscles would create a super athlete? Knocking out a particular gene in muscle lets mice run twice as far as normal. Knocking out the same gene in fat cells allows the animals to put on weight without developing type-2 diabetes.

(more…)

(^ Index)
(<– Previous session)

Talks in this session:

1. Choy: Intracellular trafficking and processing of amyloid precursor protein
2. Kown: Age-associated decline in immune function; new role of SIRT1 in regulatory T cells
3. Pan: Regulation of p53 and ageing by SnoN
4. Grueter: Disruption of the lipid synthesis gene, DGAT1, extends longevity

Regina Choy (Berkeley; Shekman lab) — Intracellular trafficking and processing of amyloid precursor protein

The talk began with a review of the proteolytic processing of amyloid precursor protein (APP) into Aß peptides. Choy emphasized that it is important to have a balance between the amyloidogenic and non-amyloidogenic pathways – a bias toward amyloidogenesis places one at risk for Alzheimer’s disease (AD).

The big question: Where is Aß being produced inside the cells? (What are the possible intracellular sites of Aß peptide production? Where is it actually happening). The approach: study of APP trafficking. The goal: Insights into regulation of Aß production and its relationship to AD.

Building on evidence that the primary site of Aß is the endosome, Choy performed RNAi knockdowns of the endosomal sorting machinery (ESCRT complexes as well as the ATPase VPS4). Knockdown of early components in endosomal sorting result in decreased Aß production, but knocking down the later components or VPS4 results in an increase in Aß production. Together with immunofluorescence results, these findings suggest that Aß production happens after APP leaves the early endosome. Surprisingly, however, APP does not colocalize with early endosome markers in the VPS4 knockdown – in fact, it ends up getting rerouted to the TGN. This raises the possibility that Aß production may happen after APP recycles through the TGN.

More beautiful immunofluorescence data followed, bolstering the recycling hypothesis and leading Choy to conclude in favor of a model in which the primary site of Aß production is in the TGN.

Hye-Sook Kown (Gladstone; Ott lab) — Age-associated decline in immune function; new role of SIRT1 in regulatory T cells

Regulatory T cells (Treg) maintain immune tolerance, i.e., they stop the rest of the immune system from attacking the body. They accomplish this by suppressing differentiation of naive cells and the activation of effector cells. This, in turn, helps to prevent autoimmune disease and graft rejection. However, Treg cells increase their activity during aging, which might make elderly people more susceptible to infection.

Treg activity is regulated by FoxP3, which is in turn modified by acetylation that is regulated by SIRT1. Kown used mass spec to identify the specific acetylation sites on FoxP3; she found three, and raising specific antibodies against the acetylated peptides.

Inhibition of SIRT1, a deacetylase, enhances acetylation of FoxP3 at a specific site in both Jurkat T cells and mouse inducible Treg (iTreg) cells. The acetylated protein is stabilized and active, promoting Treg differentiation and survival in a variety of cell culture and in vivo assays.

Thus, by downregulating the activity of Treg cells, SIRT1 promotes a more active immune system: lower iTreg activity promotes increased differentiation of naive T cells and activation of Th1, Th2 and Th17 effector cells. In older people where SIRT1 levels are lower, higher Treg activity may result in a less responsive immune system and higher susceptibility to infection.

In questions, I asked whether SIRT1 inhibition could therefore be used to prevent autoimmune disease – the short answer is “yes”; this has advantages over expanding Treg populations ex vivo, which sometimes results in loss of FoxP3 expression.

Deng Pan (Berkeley; Luo lab) — Regulation of p53 and ageing by SnoN

Starts off with a review of the cancer-aging hypothesis, i.e., the idea that the anticancer activity of tumor suppressors like p53 have a cost: apoptosis and senescence of damaged cells ultimately reduces the regenerative capacity of tissues, contributing to age-related decline in tissue function.

Pan has focused on SnoN, an inhibitor of TGFß/Smad signaling, using a knock-in mouse in which SnoN can no longer bind the Smad promoter. Using this system, he demonstrated that SnoN can function as a tumor suppressor by activating p53-dependent senescence.

SnoN can interact with the PML-p53 pathway; the SnoN protein is a component of PML-nuclear bodies, which in turn activate p53. There are several ways to activate p53: stabilization (i.e., preventing ubiquitination); antiprepression, and promoter-specific activation. How specifically is SnoN activating p53?

Using pulldown assays, Pan showed that SnoN can directly bind to p53, in a manner that does not depend on PML. This binding stabilizes p53, probably because SnoN competes with Mdm2 (which ubiquitinates p53, targeting it for destruction). The working model is that SnoN is a stress transducer that communicates information about cellular stress to the p53 pathway.

The knock-in mice showed premature aging-related phenotypes, including kyphosis and hair loss, as well as higher levels of senescent and apoptotic cells.

Carrie Grueter (Gladstone; Farese lab) — Disruption of the lipid synthesis gene, DGAT1, extends longevity

Given how much we know about fat and lifespan, it is perhaps surprising that very few longevity studies have focused on mice with modified lipid metabolism. To remedy this omission, Carrie Grueter has been studying the effect of the DGAT1 (diacylglycerol O-acyltransferase) knockout on phenotypes including lifespan. (DGAT is involved in triglyceride synthesis.)

Hypothesis: Leanness, with a concomitant improvement in metabolism, will extend longevity.

DGAT-deficient mice use more oxygen than wildtype siblings, but do not consume proportionally more food. The knockout mice are protected from the age-related increase in fat mass, as well as age-related increases in inflammation. (Not surprising since abdominal fat is associated with chronic inflammation.) The knockouts exhibit decreased serum IGF-I levels.

The payoff: DGAT knockouts live 25% longer than wildtype. There’s a cost: according to Grueter’s data, DGAT-KO have trouble lactating and therefore have decreased fecundity. Furthermore, the knockouts are bad at surviving short-term calorie restriction: half the mice fail to survive a 48-hour fast, probably because their core body temperatures plummet in the absence of stored fat to burn – the lethality can be rescued by group-housing the mice with wildtype animals or by raising the temperature to 30°C.

So in sum, the hypothesis enumerated above seems to hold, at least when calories are abundant – but when times are tough, it’s nice to have a little bit of extra padding.

(Next session –>)

Ouroboros

BRAIN shrinkage in people with Alzheimer’s disease can be reversed in some cases - by jolting the degenerating tissue with electrical impulses. Moreover, doing so reduces the cognitive decline associated with the disease. _NS

This approach is worth pursuing further. It is too invasive to be used on a wide scale, but it is likely that there will be no shortage of volunteers for the procedure. What is learned from this research can be used to devise less invasive approaches which will be more appropriate for use in larger populations.

In the meantime, research into the use of pharmaceuticals, growth factors, and stem cell therapies for Alzheimer’s will continue.

Al Fin Longevity

In older patients without apparent cardiovascular disease, the number of cardiac myocytes declines, while residual myocytes enlarge. Concurrently, there is an increase in elastic and collagenous tissue in all parts of the interstitial matrix and conduction system with advancing age. (more…)

A decline in glucose tolerance with age is a common finding that leads to an increased incidence of type 2 diabetes (T2DM) in the elderly. By age 60, 18.3% of persons have diabetes. Nearly 50% of individuals with T2DM are over the age of 65 years. (more…)