Montag, 14. Dezember 2015

Optimizing resource use - Chronic toxicity and preclinical studies

This post is related to the idea of "Optimizing resource use by outsourcing of lifespan research" to pet owners and zoos.

What should we study? We're clueless!
We don't understand aging very well. That's the reason why we need to perform both naive screens with novel chemical matter (more on that below) as well as large, high-throughput screens with drugs that target plausible pathways. But what are the plausible pathways if we are clueless?

Well, it's not quite as bad as you may think, since we do have some basic paradigms in aging research. Bluntly put, there's for instance "anti-growth" as well as "mimic CR/dwarfism" (= which usually amounts to an "anti-growth" paradigm). The idea that diminished signalling through a multitude of growth pathways extends longevity has been shown to be true in scores of studies (just recently, ref. 1, 2).

Preclinical studies: how about worms and flies?
Preclinical safety studies presently include cell culture work in human cells as well as rodent models (usually rat) and non-rodent models. The latter often includes dogs and primates (5). From a basic science perspective, we should consider mandating chronic "safety" testing in invertebrates. This would be very useful to biogerontologists, as we can expect to find a reasonable number of life extending drugs by pure chance. On the other hand, it is not clear if such "safety" testing has any meaning for human toxicity. An alternative would be to compel companies to give out the drugs (in a blinded fashion to prevent IP problems) and for the government to perform lifespan testing. This method would work particularly well to test the already available drug libraries. (As of today no free market based incentive exists to develop anti-aging therapies. We won't consider the details here.)

Indeed thousands of failed drug candidates must exist and represent a large untapped source for biogerontology. Modern cancer drugs are particularly promising since they target various growth-related pathways. In 2015 "According to the Pharmaceutical Research and Manufacturers of America (PhRMA), 771 new drugs and vaccines are in development by US companies" just to treat cancer (6). It is difficult to find high quality lists with advanced drugs, but there's one up to date list for lung cancer (7). These lists may come in handy for "smaller" projects like the NIA's ITP. It might also be helpful to think in terms of drug targets and then prioritize the most plausible targets and drugs (8).

Samstag, 21. November 2015

Resources for biogerontologists


Suggestions for Animal husbandry

List of lifespan extension...
Genetic (1, 2). No good online resource or database available. "Lifespan Observations Database" is outdated
Other interventions

AnAGE database: lists maxLS for different species

(to be continued)


References
1. Ladiges W, Van Remmen H, Strong R, et al. Lifespan extension in genetically modified mice. Aging Cell. 2009;8(4):346–352
http://onlinelibrary.wiley.com/doi/10.1111/j.1474-9726.2009.00491.x/full

2. Liao, C. Y., & Kennedy, B. K. (2014). Mouse models and aging: longevity and progeria. Mouse Models of the Nuclear Envelopathies and Related Diseases, 109, 249-285.

Donnerstag, 19. November 2015

Cliffnotes: anti-aging effects GHRKO, what is the target tissue?

GHRKO - Growth hormone receptor knpck-out robustly extends lifespan, but how? Is it through lower IGF1, lowere GH, both and which tissue are the targets?

Very briefly, superficially:

Kopchick, Miller and others (1) have been running tests at two different sites to dig into an answer, but so far they haven't really uncovered any answers. So far they looked into liver, muscle and fat tissue.
An increase in survival and in maximal lifespan was detected in male MuGHRKO [muscle specific GHRKO] at UM mice, though not in a parallel experiment at OU and not in females at either test site. [OU, UM are the 2 different test sites/universities]
While removal of GH action in muscle of male mice results in features that are consistent with the hypothesis that blocking the anti-insulin activity of GH improved glucose homeostasis, the hypothesis that improved glucose homeostasis in MuGHRKO mice will improve lifespan remains questionable. However, we do know that removal of GHR in muscle did not shorten lifespan as discussed above. Since MuGHRKO mice were one of three lines simultaneously generated and studied by our laboratories, we can compare the effects of disrupting GHR in three insulin sensitive tissues (muscle, liver, and fat). Our previous work with liver- and fat-specific GHR gene disrupted mice indicates that lifespan does not always positively correlate with glucose homeostasis. For example, liver-specific disruption of the GHR (LiGHRKO) produces mice that have impaired glucose homeostasis [21, 22]. However, these mice have a normal lifespan as determined by two laboratories (OU and UM)[34]. Furthermore, fat-specific disruption of GHR (FaGHRKO) produces mice that have normal glucose homeostasis and these mice are short lived (List, Kopchick and Miller unpublished results at OU and UM). This suggests that other processes related to aging may have been altered (improved in LiGHRKO and impaired in FaGHRKO mice) to counteract the effect of glucose homeostasis on aging.
The authors state:
Collective data regarding muscle from MuGHRKO, global GHR−/−, Ames, and LiGHRKO mouse lines suggests that removing the indirect GH action, i.e. lowering IGF-1, may be more important in protection against musculoskeletal frailty.
Which to me doesn't quite add up (at a first glance). Another paper utilizing large, multi-site testing (2) found that IGF-1 itself has a small (but apprently real) effect on aging. For a few years now, I think, there has been mounting evidence that global GHRKO is somehow "better" than messing with IGF1 only. I recall quite clearly other controversial IGF1R papers (e.g. ref. 3).

I suppose lowered IGF1 could be more important in muscle, but on a whole body level there must be some beneficial effect of lowered GH.

References

1. Aging (Albany NY). 2015 Jul;7(7):500-12.
Removal of growth hormone receptor (GHR) in muscle of male mice replicates some of the health benefits seen in global GHR-/- mice.
List EO, Berryman DE, Ikeno Y, Hubbard GB, Funk K, Comisford R, Young JA, Stout MB, Tchkonia T, Masternak MM, Bartke A, Kirkland JL, Miller RA, Kopchick JJ.

2. Lorenzini A, Salmon AB, Lerner C, Torres C, Ikeno Y, Motch S, McCarter R, Sell C. Mice producing reduced levels of insulin-like growth factor type 1 display an increase in maximum, but not mean, life span. The journals of gerontology Series, A, Biological sciences and medical sciences. 2014;69:410–419.

3. Aging Cell. 2014 Feb;13(1):19-28. doi: 10.1111/acel.12145. Epub 2013 Sep 11.
Longevity effect of IGF-1R(+/-) mutation depends on genetic background-specific receptor activation.
Xu J1, Gontier G, Chaker Z, Lacube P, Dupont J, Holzenberger M.

Freitag, 30. Oktober 2015

Stress resistance, Proteostasis and Aging reviewed (2015)


Let's start with a brief literature review by Alper, Bronikowski and Harper 2015 (1). I have excerpted some particularly noteworthy passages.

CR does not lead to epigenetically stable programming, hence an ex vivo model of CR has been hard to come by:
Interestingly, cells grown from dietary models of life extension fail to show this correlation. More specifically, dermal fibroblasts from mice subjected to life-long caloric restriction (CR) or provided with a diet low in the essential amino acid methionine, were no more stress resistant to multiple cytotoxins relative to their normal-fed counterparts (Harper et al., 2006b). Caloric restriction is perhaps the most robust life-extending intervention known (Fontana and Partridge, 2015) while diets low in methionine have been repeatedly shown to increase longevity in both rats and mice (Perrone et al., 2013, Sun et al., 2009 and Miller et al., 2005). A clue to this apparent discrepancy comes from studies using conditioned media; or more specifically, cells exposed to media supplemented with serum collected from rodents undergoing CR are more stress resistant than are cells grown in the presence of normal media alone. This suggests the presence of specific circulating factors needed for the life extending effects of dietary restriction that are lost during the derivation and expansion of individual cell lines (de Cabo et al., 2003 and De Cabo et al., 2015).
Multi-stress resistance correlates with long lifespans but there are exceptions to the rule:

Freitag, 18. September 2015

Mitochondrial Deletions Matter in the Heart: another mosaic piece gets us closer to a solution

Here, I will discuss a recent paper by Baris, ..., Wiesner et al. (1). This work is from a Cologne group and the renowned “Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD)”.

In the discussion the authors describe their hypothesis thusly:
Tissues of aged mammals display respiratory mosaicism, i.e., few cells with severe mitochondrial dysfunction embedded into normal tissue. This was shown for heart, skeletal muscle of the limbs and extraocular muscle, substantia nigra, and liver (reviewed in Larsson, 2010). However, it was unclear whether this mosaic phenotype is responsible for causing any of the typical aging-related symptoms of organ dysfunction.

Of course, the interested reader will note that it was not at all "unclear". The evidence is certainly controversial, particularly in humans/Rhesus monkeys, but by no means non-existent. I am not a fan of overselling and plenty of data by Aiken-McKenzie and others supports the idea (c.f. ref. 3 and start from there). One should give credit when it’s due, which is what the editorial by Khrapko et al. does (2). The paper by Baris et al. while interesting is certainly not any more definitive than the data we already have. However, it does clarify some controversy surrounding the TWINKLE KO model of accelerated deletion accumulation.

Dienstag, 21. Juli 2015

Drug approvals - more good news from Pharma

More than two years ago I blogged about an upturn in drug approvals. Although, there were concerns this might be a temporary fluke, so far the trend has continued. Let's just hope that drug prices do not rise all that much in the future, since 2014 has been the year of biologics and orphan drugs, not exactly known to be cheap. (Note: In 2013, 7 out of 10 best-selling drugs were biologics.)

Drug approvals (New Molecular Entity + Biologics, ref. 1, 2) increased from the low 20s from the years past.
2007: <20
2012: 39
2013: 27
2014: 41
2015: 45 (edit: updated data)
2016: 22 (edit: updated data)

What's the link to biogerontology?
First of all, the pace of pharma research indicates whether we are capable of addressing challenging diseases or if they are intractable for some reason. Second, aging is one of the most challenging diseases or disease-causing conditions and the first, primitive drugs to treat it may well be small molecules. Since development of these anti-aging drugs will require the help of pharma at some point, it's good to see the business thriving again.

1. http://pharmamkting.blogspot.co.at/2014/12/43-of-new-drug-approvals-in-2014-were.html
2. http://cen.acs.org/articles/93/i5/Year-New-Drugs.html

FDA:
http://www.fda.gov/Drugs/DevelopmentApprovalProcess/DrugInnovation/ucm429247.htm

EDIT: Added new data

Dienstag, 14. Juli 2015

Aspirin and Ethics - a brief reflection

When I was reading current literature on Aspirin I found this gem (emphasis mine):

"Once-daily, low-dose aspirin did not significantly reduce the risk of the composite outcome of cardiovascular death, nonfatal stroke, and nonfatal myocardial infarction among Japanese patients 60 years or older with atherosclerotic risk factors...
[Hence] The [JPPP] study was terminated early by the data monitoring committee after a median follow-up of 5.02 years (interquartile range, 4.55–5.33) based on likely futility...We plan to conduct further analyses to establish whether aspirin had beneficial effects in particular subgroups of patients or if there were beneficial effects with respect to cancer prevention."

Is this the ethics committee-equivalent of first shoot, then ask questions? Why would you kill the study for futility before conducting a full analysis including cancer? I know that there are confounding issues if cancer was only a secondary endpoint, but at some point something must have gone ridiculously wrong, be it initial study design or the decision by the ethics committee. Perhaps, we are just dealing with sloppy writing, the monitoring committee knowing that cancer was unchanged, and the authors hoping that a signal will emerge now or in the future. Something isn't quite right here.

Either way, it'd be a travesty if there turns out to be a signal, yet the trial (n~14 000) was stopped precociously.

1. Ikeda, Yasuo, Kazuyuki Shimada, Tamio Teramoto, Shinichiro Uchiyama, Tsutomu Yamazaki, Shinichi Oikawa, Masahiro Sugawara, et al. 2014. “Low-Dose Aspirin for Primary Prevention of Cardiovascular Events in Japanese Patients 60 Years or Older with Atherosclerotic Risk Factors: A Randomized Clinical Trial.” JAMA 312 (23): 2510–20. doi:10.1001/jama.2014.15690.

Freitag, 26. Juni 2015

How not to run a lifespan study

Every biogerontologist should have a poster on the wall with the following paper:

Spindler SR. Review of the literature and suggestions for the design of rodent survival studies for the identification of compounds that increase health and life span. Age (Dordr). 2011 Mar 22. [Epub ahead of print]

Why do I care about other people's research so much? One could obviously quip: Why does it matter if people run badly designed lifespan studies? Isn't it up to the principal investigator (PI) to decide if they want to screw with taxpayer and grant money? Well, first of all, I don't think that people run these weak studies on purpose, but I do believe they should know better. It's the PI's job to be on top of current research practise. Admittedly, the mouse facility may be out of your control, but if you cannot guarantee high quality, why would you commit to a 4-year lifespan study? The main issue I have with these weak studies is that they waste more than the money of a single research group or a grant. They also lead to unnecessary follow-up research. Let me give a few examples.

Resveratrol research produced a lot of unwarranted hype that was later defused by the NIA's ITP, yet how many research dollars were spent to do so? The initial study by Sinclair fell into a common trap: methodically weak (2), but not terrible enough to rule it out as a waste of a biogerontologist's time. Due to the hype, it produced a lot of unnecessary follow-up work. Soon afterwards, for reasons completely beyond me, Resveratrol was granted three "slots" in the ITP study at varying doses (a slot here is one whole lifespan study, there are 3-5 slots available per year). Instead, we could have studied something more productive, but hype and perhaps politics got in the way.

Another type of "methodically weak, but not terrible" research plagues the fields of autophagy, glycation and aging. These studies are good enough so there is little grant money to repeat what seems like a redundant study, but weak enough to cast doubt on the results (no replication, crypto-CR,  short-lived controls). To quote myself:
Autophagy 
I am not exactly sure what is holding back the field. However, there are 2 promising interventional studies in mice, or perhaps, I should say only two. ATG5 overexpression (7a) in somewhat short-lived strain and hepatic rejuvenation by the Cuervo lab (7b). Unfortunately, Dr. Cuervo has never responded to my inquiries about extending and reproducing her work.
Advanced Glycation Endproducts  
Again, I am not exactly sure what is holding back the field. Since the failure of Alagebrium (around 2013) and some promising studies by Vlassara (around 2007, ref. 9) there has been a dearth of relevant proof of principle studies. I have not kept up with the field, but it seems to have shifted towards diabetes and mechanistic understanding. All in all, I do believe the field may deliver some breakthroughs, but it will take time. Meanwhile reduction of dietary AGEs may provide modest benefits (we don't really know).

Verdict
I really fear that mediocre lifespan studies can stunt the development of whole fields, or as in the case of Resveratrol, completely derail the research. Multiple factors affect mouse lifespan and some are outside of our control (e.g. sporadic infections), but overall husbandry is often inadequate. Researchers need to stay strong and demand better mouse facilities!

References
1. Spindler SR. Review of the literature and suggestions for the design of rodent survival studies for the identification of compounds that increase health and life span. Age (Dordr). 2011 Mar 22. [Epub ahead of print] PubMed PMID: 21424790.

2. Nature. 2006 Nov 16;444(7117):337-42. Epub 2006 Nov 1.
Resveratrol improves health and survival of mice on a high-calorie diet.
Baur JA1, Pearson KJ, Price NL, Jamieson HA, Lerin C, Kalra A, Prabhu VV, Allard JS, Lopez-Lluch G, Lewis K, Pistell PJ, Poosala S, Becker KG, Boss O, Gwinn D, Wang M, Ramaswamy S, Fishbein KW, Spencer RG, Lakatta EG, Le Couteur D, Shaw RJ, Navas P, Puigserver P, Ingram DK, de Cabo R, Sinclair DA.
Problems: All mice unhealthy (fed a high-fat diet), no maxLS reported. It is not even so much a weak study; it's simply inadequate as an aging study.

Samstag, 20. Juni 2015

Optimizing resource use by outsourcing of lifespan research

Is it possible to outsource lifespan studies to laypeople (who are supported by professionals)? The idea may seem far-fetched to some of you, but in the end it would amount to a "pragmatic trial"; which is certainly an accepted study design. This type of study is generally less rigorous but considerably more realistic than a classic RCT (3).
It should be easy to get pet-owners to participate since life span testing on animals it at worst ethically neutral and most probably a net positive for the animals. Obviously, drugs and interventions designed to extend the lifespan will be minimally invasive and have a high risk/benefit ratio. Sine qua non. And since all animals age, enrolling them in such a trial would be beneficial for them; like enrolling cancer patients in a cancer trial.

Outsourcing of lifespan studies to pet owners
The idea seems ingenious and abstruse at the same time (1), but these days it has reached the mainstream. As we have discussed, Kaeberlein and others have suggested to test rapamycin for late-life rejuvenation in dogs. The advantage is obvious. As a researcher you can save on housing facilities, animal food, doctor visits and drugs (loving pet owners visit the veterinarian themselves), caretaker costs, taxes, toys, accessories, "environmental enrichment". On the other hand, you still have to pay drug costs, additional vet visits (e.g. specialized tests), recruitment, administrative costs and the salaries of the involved researchers. As it turns out, all the latter costs are quite high. Kaeberlein mentioned costs in the range of 10^5 to 10^6$for his study. Additionally, you have to cope with the added problem of heterogeneity (every pet owner behaves somewhat differently) and lack of training (these people are not trained technicians or health professionals).

Outsourcing of lifespan studies to zoos?
There are more than a thousand zoos world-wide by a conservative estimate (2), perhaps closer to 5000. I see no reason why those places could not conduct lifespan studies, if pet owners can. So far, I think I'm the first person to propose this study design. The idea is simple, one could for instance, mimic a cluster randomized trial (4). The advantages over individual pet-owners are lower heterogeneity in husbandry, availability of primates, better access to trained professionals, improved record-keeping, etc. It's difficult to think of a disadvantage, except that it's harder to recruit Zoos for altruistic reasons than pet-owners.
Edit: I briefly brought the idea up at an aging conference I attended and felt little optimism. I think the concern is that husbandry is worse in practice than one would assume and the aggressive use of euthanasia precludes an aging study. It seems no zoo wants to keep elderly animals that might look unhealthy (even if they are not suffering). This is an important concern, I agree, and it remains to be seen if my idea is feasible.

General ethics of animal keeping
There are concerns that keeping animals is unethical per se. (Some would even argue that all animal research is useless [5b]. They are wrong.) Husbandry is often criticized, especially in Zoos (5). I am sure this can be improved and it is necessary to do so. But is it unethical to keep well-husbanded animals? In the case of many animals the answer is, definitely not. The reason should be self-evident to any loving pet-owners and right now I don't want to delve into the details. Just to mention, an interesting argument for the ethics of keeping lab mice for longevity research is that they live longer, healthier and more peaceful lives in captivity than in the wild (6). At some point, I will probably do a longer post on research ethics in animal studies.

References
1. I became aware of this idea perhaps 5 years ago. It was championed (maybe even invented) by Edouard D. and other people from longecity/imminst.
http://www.longecity.org/

2. http://www.statisticbrain.com/zoo-statistics/

3. Patsopoulos, N. A. (2011). A pragmatic view on pragmatic trials. Dialogues in clinical neuroscience, 13(2), 217.

4. Donner, A., & Klar, N. (2004). Pitfalls of and controversies in cluster randomization trials. American Journal of Public Health, 94(3), 416-422.

5a. http://www.captiveanimals.org/news/2010/03/10-facts-about-zoos
5b. http://www.isthmus.com/archive/isthmus-35/june-4-2004-inside-the-monkey-house/
(not yet read in full)

6. Suckow, M.A., Stevens, K.A., Wilson, R.P., 2012. The Laboratory Rabbit, Guinea Pig, Hamster, and Other Rodents. Academic Press.
Note: The deer mouse (Peromysces), for instance, lives 8 years in captivity but only ~1 year in the wild.
I cannot find the data for M. musculus but it looks very similar from what I recall.

Samstag, 13. Juni 2015

What's hot in Aging Research? (2015 List)

I. Which interventions could produce a life-extension breakthrough in the next decade or so? (Short Term breakthroughs)
II. Which interventions hold promise, but are a little more speculative? (Mid Term breakthroughs)

Starting from now, I would like to review this question annually or every two years. In my analysis I'll include interventions, drugs, diets, etc. that could have a large and meaningful effect on aging or any of the major age-related diseases. From a methodological point, the answer must consider: A. effect sizes and B. plausibility (how advanced is the science?). Aspirin is an example of an intervention with high plausibility, but small effect size, since the effects are limited to cancer prevention. In fact, even if Aspirin reduced cancer incidence by 10-50% this would only result in 1 or 2 years added to the average human lifespan.

The answer to this question is personal opinion to some extent. To be as objective as possible I tried to track down reviews highlighting "important" research (3-6).

Mittwoch, 13. Mai 2015

The oxidative stress theory of aging - concepts and limitations

What do we know about the involvement of oxidative stress in disease?
Definitely not enough. The speakers at MiP-School London reminded us that researchers use the term "ROS" as explanation to hide behind with little explanatory value. Berry Halliwell (3,4) and Mike Murphy (6) gave fascinating talks on this topic. I would like to add a more biogerontologic perspective.

A deep mechanistic understanding of how ROS regulate lifespan might be called for, but I don't think we should over-emphasize detailed understanding in the field of aging as a whole. Gerontology is difficult. There are enough basic questions still unanswered. (Is calorie restriction a universal mechanism? Are current models of mouse lifespan extension redundant/convergent? etc.)

Historically, progress has come from rather crude phenotypic screens. Calorie-restriction was discovered before the Second World War, using mice without fancy molecular biology. To me, the whole Interventions Testing Programme is one big, naive phenotypic screen (readout = dead mice). The rationale for some of the tested compounds is almost cringe-worthy. Guess what? It's the most successful programme in the world, yielding multiple promising leads. Particularly, Rapamycin. To propose a test of rapamycin as a CR-mimetic we do not need to understand the underlying biology in any detail. Unsurprisingly, the first data on the mTOR pathway was generated using simple phenotypic screens in yeast and 6 years after the rapamycin lifespan study in mice, we still do not understand the mTOR pathway very well. The big invention by the ITP, and others like Spindler, were perfect animal husbandry combined with a modicum of understanding.

Given how little we understand about aging, the naive phenotypic screen will remain a worthwhile strategy. Knowing "just enough" is often quite useful. However, the naive approach to the oxidative stress theory of aging has produced conflicting results. Is it time to re-consider some of the basics?

Samstag, 4. April 2015

NIA's intervention testing program (ITP) - where does the journey take us now?

While this paper briefly outlines the history of the "intervention testing program", trying to find life extending drugs in mice, I want to comment on a tangential paragraph. As is known to anyone following the literature, the ITP identified rapamycin as the first drug to robustly extend maximum life span. Now the question arises how best to translate this data to humans? One important step will certainly be a long term study in long-lived animals.

And there exists an ingenious proposal for such a project (1, 2):

Matt Kaeberlein and Daniel Promislow at the University of Washington ... have been considering the potential value of a study in dogs living freely in the same environmental conditions as humans. They propose a small trial using 60 pet dogs that typically have life spans of 8–10 years, 30 of which would receive rapamycin and 30 would not. The trial would be started at 6 years of age, and the dogs would be monitored for cardiac function and other aging phenotypes such as development of type 2 diabetes and cancer until death. Such a study might reveal whether rapamycin retards aging per se, or acts principally by reducing late-life disease, but a larger study will probably be necessary to establish this unequivocally.

This basically outsources the lab work to pet owners. The idea is obviously brilliant, though, not completely novel. I have myself briefly collaborated on a project trying to get this done with mice. One of the biggest hurdles is getting enough people to participate - since such study must be large due to increased heterogeneity inherent to its design. Thus coordinating such a project through a university or some other body that is able to promote it makes sense. It goes without saying that large scale roll-out of this study type could save billions of dollars at virtually no cost.

The dog project by Kaeberlein is open to donations (3). Curiously, his wordpress page layout is even uglier than my blog. Unbelievable!

1. Age (Dordr). 2015 Apr;37(2):9761. doi: 10.1007/s11357-015-9761-5. Epub 2015 Mar 1.
NIA's intervention testing program at 10 years of age.
Warner HR

2. Hayden EC (2014) Pet dogs set to test anti-aging drug. Nature 514: 546

3. http://dogagingproject.com/help-us/

Samstag, 28. März 2015

Is complex I the culprit? Is it as easy as that?


Rapamycin, complex I and mitochondrial ROS
Despite plenty of controversy there is ample support for the mitochondrial free radical theory of aging. Here, I want to highlight some recent findings implicating complex I in mtROS production and aging.
Two recent papers (2, 4), Fok and Miwa, both find subtle reductions of specific complex I subunits after rapamycin treatment using *omic approaches. Miwa using proteomics and Fok using transcriptomics. Miwa et al. also showed decreased complex I and superoxide production after calorie restriction and reductions of complex I in a longer vs a shorter-lived strain. These changes were most pronounced in the matrix arm of complex I. Fok (4) studied chronic rapamycin feeding using transcriptomics ("Illumina Mouse Ref8 microarray") and found:
"The majority of the transcripts that change in complex I and II transcripts decrease while complex III, IV, and V transcripts that change increase in chronic Rapa-fed female and Rapa-2 male mice."

Mittwoch, 18. März 2015

Don't judge the primate studies of Calorie Restriction if you haven't read them!

I despair when non-expert scientists and intelligent lay people unknowingly spread misinformation about calorie restriction (CR). Not long ago I had to read again that the primate studies somehow refute CR. The reality, however, is more nuanced than that. Do not forget: misinformation can jeopardize public understanding and acceptance of research.

I will echo Ingram and Roth on this topic and use this post as a future reference. Both were involved (principal investigators, I believe) with the CR primate studies. (emphasis mine)
The long-term study of rhesus monkeys at the University of Wisconsin reported significantly reduced morbidity and mortality in those monkeys maintained on 30% CR from adult ages (7–14 years of age) compared to controls (Colman et al., 2009 and Colman et al., 2014). In contrast, a report from the long-term study of rhesus monkeys from the NIA that we initiated in 1987 found no evidence of improved survival in monkeys initiated on 30% CR from young ages (2–6 years) or older ages (14–21 years) (Mattison et al., 2012). Differences in the design of these studies, particularly the dietary composition, are now being investigated to uncover reasons for the different outcomes. Even if the conclusion is ultimately that CR does not significantly extend lifespan in rhesus monkeys, there is ample evidence from these studies to demonstrate improved health and function at older ages in monkeys on CR. 
Better yet not judge any of data, if your understanding comes only from popular science articles. I welcome comments by everyone, including lay people, as long as they are informed. I'll briefly mention another controversy for the sake of completeness:

Addendum: Does CR work in wild-derived or heterogenous mice?
This is important since these mice are more representative of healthy animals than, say, gluttonous black 6 mice. As in primates, I think the preponderance of evidence says "yes". A recent paper on the "yes"-side of the equation includes a review of other studies as well (2). This includes the negative study by Liao, Rikke et al. and Harper et al. with wild-derived mice.

1. Ageing Res Rev. 2015 Mar;20C:46-62. doi: 10.1016/j.arr.2014.11.005. Epub 2014 Dec 19.
Calorie restriction mimetics: Can you have your cake and eat it, too?
Ingram DK, Roth GS.

2. J Gerontol A Biol Sci Med Sci. 2010 Dec;65(12):1275-84. doi: 10.1093/gerona/glq155. Epub 2010 Sep 5.
Life extension by diet restriction and N-acetyl-L-cysteine in genetically heterogeneous mice.
Flurkey K1, Astle CM, Harrison DE.

Samstag, 14. März 2015

Senescence the gift that keeps on giving: dasatanib and quercetin to the rescue?

I wanted to highlight the recent paper by the Kirkland group (1), despite the press it has already gotten, since it is indeed deserving of praise. Starting last summer I developed an interest in the field of senescence since senescence was a focus of the "Neurobiology and Neuroendocrinology of Aging conference" in Bregenz, which I attended, and some of my colleagues work on it. The field does not cease to amaze us with promising data.

Why does senescence matter? Briefly, senescent cells accumulate in aging non-human primates (2), impede tissue function (1), and are reduced in long-lived mutant mice (3). Further, progeroid phenotypes can be alleviated by removing senescent cells (4), although, I do not quite trust models of accelerated aging and prefer other types of evidence (1, 2, 3).


Accumulation of senescent cells in baboon skin (2)
The majority of 53BP1 foci (62 ± 7.7%) colocalized with telomeric DNA, thus classifying them as TIFs … The frequency of TIF-positive nuclei increased exponentially with age, reaching a value of 15 to 20% in very old animals

Right now we are basically waiting for the (definitely already ongoing) lifespan studies, based on genetic (4) or pharmacologic (1) senescent cell ablation, to be published in Nature/Science so that we can start developing human therapies. And I do expect them to be successful. In the meantime Kirkland & co will continue publishing amuse bouches studies.
Given the paucity of data available, even though the evidence appears strong, I wonder if human studies will commence before the lifespan studies in rodents finish? All bets are off: in principle the data is promising enough to pursue pilot trials, similarly to parabiosis, but ethics boards tend to be painfully slow and conservative.


Dienstag, 10. März 2015

Safety of testosterone: I stand corrected, at least in the short-term

"Two Studies Suggest Testosterone Might Not Increase Risks of Cardiovascular Events"
http://www.medscape.com/viewarticle/841098

I predicted testoserone would lead to an elevated risk of cardiovascular events based on animal data and a recent tesosterone study that was terminated due to apparent adverse effects (ref. 1, TOM study). An older interventional study also hinted at harmful effects of testosterone (2). There was some reason to think that testosterone could explain the increased mortality of males (H. Sapiens and in some other species, see [3] for a discussion).
The new studies presented this later week at the ACC cast some doubt on those previous concerns. In the first study, Dr Zuber Ali (Aurora Health Care, Milwaukee, WI) and colleagues studied 7245 men, mean age 54 years, prescribed testosterone-replacement therapy for low testosterone (<300 ng/dL). The mean follow-up period was 1.78 years. Cardiovascular risk factors were documented in many patients, with 41% having dyslipidemia and 34% having hypertension. In the multivariate analysis, there was no increased risk of acute MI, stroke, or death at 3 years among the testosterone-treated patients compared with the untreated patients.

The short follow-up is worrying, but apparently a recent meta-analysi did not find any risk either. The last time I checked another study, the "T trial", with n=800 participants was still ongoing. We will see what this one shows.

Conclusions
Testosterone may be safer in the short-term to mid-term than we thought, but this does not rule out harmful effects in the long term (c.f. ref. 3).

References
1. Basaria S, Coviello AD, Travison TG, et al. Adverse events associated with testosterone administration. N Engl J Med 2010; DOI:10.1056/NEJMoa1000485.

2. HAMILTON J.B, & MESTLER G.E. (1969) Mortality and survival: A comparison of eunuchs with intact men and women in a mentally retarded population. J. Gerontol. 24:395

3. http://arc.crsociety.org/read.php?2,112565,112602#msg-112602

EDIT: Data added, TOM study corrected

Mittwoch, 4. März 2015

Rapalogs and Rapamycin in the healthy?

I admit that I was skeptical at first whether the immunosuppressant rapamycin could ever be used in healthy people. A number of recent findings have changed my opinion, of which I will discuss a few (1, 3). Since I saw an enthusiastic talk by Arlan Richardson on the safety of rapamycin in animal models of age-related diseases, I have been warming up to this idea. In any case, there are three "solutions" to the major side-effect of immunosuppression: 1. design more selective rapalogs (is this possible?), 2. micro-dosing without immunosuppression may be enough to shift mTOR activity towards a healthier, lower level in vivo, 3. accepting the potential trade-offs: a 5-10% increase in life-expectancy would compare favorably to mild immunosuppression, for instance.

Study I. Familial adenomatous polyposis is a condition that leads to a massive increase in colorectal cancer incidence and it is caused by APC mutations. Rapalogs (Rapamycin analogs) have been approved for some cancers and now Faller et al. (1) found that rapamycin can protect APC deficient mice from cancer.

Mittwoch, 4. Februar 2015

Two inspiring Stories suggest how to do better Science: Parabiosis and Super Resolution Microscopy


Parabiosis
Nature has a fascinating background story on this type of research (6), but other reviews are recommended as well (7). Parabiosis was invented in the 19th century and became popular around the 1970s before interest waned again. Then some 10 years ago it was rediscovered by the biogerontology community. What I would like to emphasize is that the ebb and flow in research interest isn't uncommon. One has to wonder how many other gems are there to be found in papers from 1900-1960?
An example that I recall is research on medial calcification, which was pioneered by Blumenthal and Lansing. Although, interest in (medial) calcification has steadily risen, few studies have revisited the exact pathology they described and the idea to tackle this pathology is rather new (1).

Freitag, 30. Januar 2015

Recent advances in cancer treatment: immune checkpoint therapy, electromagnetic therapy

From time to time I like to highlight biomedical advances that caught my interest. Here are two recent examples:

Immune checkpoint therapies were first applied to advanced melanoma and, as far as I know, they were the first treatment to significantly improve the prognosis of this once intractable cancer (1, 3):
...immune checkpoint antibodies are clinically active in a variety of malignancies, including those not traditionally classified as immunogenic, such as non-small-cell lung cancer (NSCLC)....
Anti-CTLA-4 agents: ipilimumab and tremelimumab...
the number of long-term survivors exceeded the number of patients with objective responses (ORs)...immune-based therapies may generate a sustained antitumour effect in a subset of patients, long after completion of active therapy
Antitumour responses with immunotherapies are heterogenous: responses may be mixed or delayed, lesions may enlarge before shrinking, lesions may remain stable or slowly regress over time. These responses can be potentially explained by T-cell activation and tumoral infiltration by immune cells, as well as intra-patient heterogeneity of tumour–host interactions.
I always thought that a vaccine type immunotherapy would be first to market, but it turned out differently. According to a talk by James Allison I recently went to, longer term data will become available soon.

Freitag, 23. Januar 2015

The comparative study of the "mito-free radical theory of aging" hit a brick wall.

Put another way, it's all about the money

Not long ago a colleague and I briefly discussed and summarised the most recent evidence regarding fatty acid (membrane) composition and aging. Importantly, mitochondrial fatty acid composition along with reduced mitochondrial ROS production in long-lived species is one of the major pillars of the "mito-free radical theory of aging" derived from comparative studies.
I would like to emphasize a few additional key points. For a broader state of the art review, the reader is refered to the literature (5, 6). Not long ago I noticed a letter by Barja (1), discussing a major headache for anyone doing comparative biology of aging. One way of putting his idea is as follows:

Samstag, 10. Januar 2015

The Tithonus Fallacy explained: The example of Nordihydroguaiaretic Acid (NDGA)

The Tithonus fallacy has been outlined elsewhere (1). Basically, it's the belief that an extension of lifespan will lead to an extension of frailty and suffering. Why this is wrong, as a rule, is obvious to a biogerontologist but not to a layperson: The diseases of aging and their underlying molecular pathologies are aging. A large extension of maximum lifespan is impossible without a delay of diseases.The 'area-under-the-curve' of health will always increase, so to say.

Border cases are substances or interventions which lead to modest changes in lifespan, particulary changes in mean lifespan. Rapamycin was assumed a potential case, but this has been refuted (2). Conceivably, lifespan may be extended somewhat by delaying a specific disease at the cost of health. Think, for instance, of a badly designed chemotherapy protocol. A substance or "longevity mutation" might also decrease the rate of aging while having some other terrible side-effects. One -- still highly speculative -- example is human dwarfism. While dwarf mice live longer than their mates, this disease is associated with (intellectual) disability and suffering in humans, yet could modestly extend lifespan in people as well (3).