Mitochondria and the Methuselah Chimera

The ‘three parent’ baby born this September is making global headlines, as it should being a most remarkable event. The baby has the DNA from the sperm of its father and the DNA from the nucleus of its mother, so far so normal. However the egg from which baby developed was from a third party. This egg had its nucleus removed and replaced with the ‘mother’s’. Left behind in the cell were the mitochondria and as mitochondria are semi-autonomous self-replicating organelles within the cell they have their own DNA. This means, in short, that baby has DNA from three sources and a great deal of fuss is being made of this genetic hybrid.

The procedure is to cure diseases inherited from the mother’s mitochondria (sperm provide no mitochondria when they fertilise an egg) which are very nasty debilitating conditions so hopefully, this baby will thrive and live a long happy life. All of the earlier experiments with mice have given no reasons to sound the alarm and indeed the data indicate intriguingly that the chimera live longer, healthier lives than their conventional  cousins1.

As mentioned in previous blogs 2, 3 not all mitochondria are created equal. Some, as found in birds and bats are particularly efficient, producing fewer free radicals and delivering high outputs suitable for the flying life. The payback seems to be longer lives (pigeons 20 yrs, parrot 80 yrs, Little Brown bat 30 years) when compared to similar sized mammals ( rats 3 years, mice 2 years): oh to have such mitochondria in my cells.

Maybe this is not so fanciful. We know that inter mammal mitochondrial populations can coexist from of all things panda breeding programs in China4 using rabbit and panda embro hybrids . Essentially, in summary, depending on circumstances the rabbit and panda mitochondria in embryos replicate competitively in their micro-ecosystem and one or the other eventually dominates. They don’t self-destruct or do anything radical, they just swim about doing what mitochondria do and presumably negotiate with the nucleus for the spare parts that it provides to keep them running.

It’s should be clear where this post is going. The labs with the expertise to create chimera in mice could have a go at creating a mouse with bat mitochondria. I know bats are not flying mice and that they branched into an order of their own 50 million years ago... but they are placental mammals and are no more distantly related to mice than the above mentioned rabbit and panda work. Mitochondria don’t seem to produce violent antigenic signalling on the surface of their host cells.

In any case, it is worth a shot,  what if you could make a three parent mouse with bat mitochondria, what if it lived for five years instead of the normal two to three years? This would set fire to gerontology. Nobel prizes in 2022 anyone?

1. Roberts, Michelle (2016-09-27). "First 'three person baby' born using new method".BBC News. Retrieved 2016-09-28.

2) Super-Geriatrics and Mitochondria

3) Mitophagy and rejuvenation: a possible mechanism.

4)Biol Reprod. 2002 Aug;67(2):637-42.Interspecies implantation and mitochondria fate of panda-rabbit cloned embryos.

Chen DY1, Wen DC, Zhang YP, Sun QY, Han ZM, Liu ZH, Shi P, Li JS, Xiangyu JG, Lian L, Kou ZH, Wu YQ, Chen YC, Wang PY, Zhang HM.

Super-Geriatrics and Mitochondria

How to live to 100

It has always been a puzzle that some people age more slowly than others. Mortality data for humankind consistently shows that as first-world people start to die off in their (nowadays) late sixties a sub-population emerges in the over seventies that are destined to go on into their nineties and well beyond. Recent medical advances have blurred the distinction somewhat as it can prolong the lives of many who only twenty years ago would have died by three score and ten years; nevertheless the sub-population dubbed ‘super-geriatrics’ is still evident.

Unfortunately, having emerged from the pack as it were, super-geriatrics are too old to breed and thus are prevented from passing on their genes with the benefit of  late-life hindsight. However, I am increasingly of the opinion that super-geriatrics may be ‘made’ as much as  ‘born’ and this blog is an attempt to say why.

It is (as usual for me) all about the role of mitochondria in ageing. It is text-book conventional today to regard mitochondria as ‘ex-organisms’, organelles, a stance which whilst acknowledging their once free living existence sees mitochondria now as fully a component of the cell. I see them differently, fully as organisms that exist in an ecology provided the by cell. They reproduce, proliferate and are destroyed by their ‘environment’ which means they, like any other organism are subject to selective pressures. Like many symbionts and parasites mitochondria have outsourced functions that are either redundant or that can be taken care of by their host-environment but this does not mean that the rules of environmental selective pressures do not apply.

There is evidence to support my eco-mito view. The selection of some mitochondria over others within the population resident in a cell is well documented and is recounted in a previous blog ( Mitophagy). In fact the very existence of a reproducing population which includes sub-populations with different characteristics is the stuff of natural selection.

So this brings me to the central theme of this post. How do you live longer than the norm? A seminal paper in 1936 on post-weaned rats started the ball rolling for the longevity effects of calorie restriction in youth ( btw it just makes you thin if you try it when older!) which was supported by data obtained for humans in post war europe. It works for nematodes too. As yet no explanation for this effect has gained any real traction, but low calorie intake includes reducing free-radical damage is a standard if unconvincing old chestnut.

My thoughts now are that super-geriatrics, apart from being basically well made, have had a selection pressure applied to their mitochondria in adolescence which results in them acquiring for life a set of the best mitochondria. This is not so fanciful if one knows that this kind of thing happens to bat mitochondria once the cub takes up the very demanding flying lifestyle rather than the mouse like existence. Small bats live for ten years or more compared to the two years of mice...they have better mitochondria.

It’s not so fanciful either knowing that selective mitophagy caused by urolithins  increases the life span of nematode worms by 20%.  Finally,  in human adolescents it has been recently shown that they consume fewer calories at rest at one point in their development which puts them in today’s food rich world in danger of getting fat. Surely this means that their mitochondria are throttled back and consuming less oxygen and shunting off excess food into fat.  

All of the above is indicative of a population of ‘organisms’ that adapts to selective pressures. Therefore the question posed as to what make a super-geriatric reduces to ‘what happened to the super-geriatrics when they were young?’

One proposition would be that at a certain point they were subject to calorie restriction, not in the sense of being starved (which would induce torpor) or malnourished but  occurring maybe at a point of very high physical activity. The skinny over active youth.

The trouble with this approach is that this scenario would be commonplace ( or rather before screen time and childhood obesity was commonplace) and if it were the whole story we would be overrun with centenarians. A second proposition is that they were also subject to some hormetic challenge analogous to the effect of urolithins on nematodes referred to above and in previous blog...but what?

Could it be fever? , injury? poisoning? radiation? anoxia through altitude? Japan has the most centenarians, please don’t let it be as a result of radiation exposure in their thirties. In any case I am stuck even for a wild speculation. Any article with ‘tips’ for an old age are hopelessly unenlightening, but at least I know when and where to look for clues.

Mitophagy and rejuvenation: a possible mechanism

Mitophagy is the destruction of mitochondria within a cell by specialised  ‘garbage disposal’ units called lysosomes. ‘Selective mitophagy’ is the destruction of malfunctioning, defective or simply aged mitochondria.  Selective mitophagy is a hot topic today. As long ago as 1978 in my postgraduate days we demonstrated that in senescent rats a significant subpopulation of  mitochondria were present in aged livers which were not found when similar aged livers were caused to regenerate following partial hepatectomy1.

Since then it has become accepted from multiple studies that old, damaged, usually enlarged mitochondria inhabit senescent cells and are responsible in signalling the multivarious chain reaction of events that precipitate cell death. This process called apoptosis is now regarded as a partial blessing in old age as a clearing out of the redundant burdensome poorly performing cells but I am more interested in the problem of  weeding out the old, poor functioning mitochondria leaving the ‘younger’ to proliferate and predominate? This is, to all intents and purposes, nothing less than rejuvenation … the holy grail of gerontology.

The selection of mitochondria for their ‘fitness’ is not unknown. Small mammals such as rats and mice have typically short life spans ( 2-3yrs in captivity) and we are accustomed to thinking that size matters with regard to mammal longevity: mice, dogs, cats, apes, humans, elephants are roughly in order of mass and lifespan. But how we should  envy the Pigeon; it has a body mass not greater than a rat but a life span of over twenty years... and don’t get me started on Parrots who hold the record at 92 yrs. Pigeons, like most birds have very good mitochondria compared to our own. They produce fewer reactive oxidative species (R.O.S) and basically are just more efficiently coupled2.

However there are flying mammals too; furry flying mice-sized creatures known as bats. You guessed it, they have long life spans ( >10yrs) and yes they have good mitochondria too. They are not born with these bird-like mitochondria though. Before they fly theirs are much as they would be in any small mammal but after they fly it’s a different story. It’s hard not to conclude that there was a selection process for the best going on here3.

We are not likely to be able to subject our systems to the energetic stress of flying in order to weed out the less efficient mitochondria, it would kill us,  but maybe there are other ways?

Recent fascinating work on the urolithins (related to the tannins and other phenolics in red wines)  from pomegranate seeds I think provides not only some clues but also possible mechanism for selective mitophagy. Urolithin A has been shown to extend the life of  the simple nematodes and the mechanism is believed to be the result of selective mitophagy4.  But how?

How do you label a mitochondrion for destruction? Old, degenerating mitochondria have many ways of signalling their approaching end but these apoptotic signals mean the end of the cell too.

We need to label the mitochondria for destruction without tripping the death chain reactions.

In a previous blog ‘Mitochondrial morphology and Ageing.’5, I put forward a long cherished point of view that enlarged senescent mitochondria were that way in order to maintain their threshold membrane potential against a background of reduced e-/H+ throughput, and increased leaks across the membrane. I used an electronics model of the mitochondrion as capacitor with voltage, current, capacitance and leakage as normal parameters. Basically if you reduce surface area (capacitance) you can maintain the threshold voltage (membrane potential) in the face of lower throughput ( current) and back flow due to dielectric leakage.

In other words the old mitochondria are working but don’t push them as they are close to the edge.

With this in mind look at the urolithin molecule from pomegranates:

It’s a poly-phenol as is the molecule below:

This is rotenone, a potent inhibitor of mitochondria,

which prevents electron flow past Complex I.

It is in many ways ( see bottom left rings) very similar to urolithin.

Or may be you prefer your molecules simpler?

This is DNP (di-nitro phenol) a potent de-coupler of mitochondria.

Both of these molecules are severe toxins. Rotenone is used as a pesticide and scarily  and sometimes fatally DNP can be used by those seeking to lose fat weight!

Rotenone (in my electronics analogue) would decrease the current flow through the capacitor and DNP would increase the leak to ground. In either case a mitochondrial capacitor struggling to maintain its threshold membrane potential would be badly compromised.

Maybe then the signal for mitophagy is the blinking on and off of the threshold membrane potential, a kind of ‘drowning not waving’ signal to the lysosomes that these mitochondria are not up to the job. This kind of mechanism clearly would work well as the young bat took to flying and the less fit mitochondria failed to keep up.

Unlike in the bat where ‘stress’ is extreme energetic demand,  urolithin mediated selection is being achieved by a hormetic mechanism. A ‘little poison does you good’?

I think that this is the most promising of avenues to explore with regard to rejuvenating mitochondrial populations and thereby rejuvenating the organism. Humans cannot regenerate organs as can an old rat its liver, we cannot (when old) survive extreme energetic stress therefore hormesis seems like a good bet. But what is the best hormesis for mitochondrial rejuvenation… now there’s a question.

1. PhD Thesis: Biochemistry of Ageing in Rat Liver Mitochondria: p 165-170:awarded July 1980: online Jan 2016
2. Oxygen, The Molecule that made the World: Nick Lane 2002 Oxford University Press pp255-257

3. Urolithin A induces mitophagy and prolongs lifespan in C. elegans and increases muscle function in rodents, Nature Medicine 22,879–888, (2016)

4. Ann N Y Acad Sci. 2004 Jun;1019:506-8.Testing the free radical theory of aging in bats. Brunet Rossinni AK

5. Mitochondrial morphology and Ageing: January 2015 Spannermans Edublog www.spannerman2.co.uk

Brexit and Homo.semi-sapiens

I have been meaning to write on this topic for a very long time. As a teacher, a biologist and a computer scientist the process we call reasoning is always to the fore, whether delivering a biology module on ethology, discussing  fuzzy logic and AI or marking scripts and wondering what on earth is passing for ‘reasoning’ in the minds of my students. The recent ‘Brexit’ referendum brought it all together for me … just how does homo-semi-sapiens reason?

Artificial Intelligence or AI has had spectacular gains over the past decade or so. It started with IBM’s ‘Deep-Blue’ defeat of Gary Kasparov at chess in 1996 before retiring in 1997 after winning a controversial rematch. 20 years later Google’s computer beat the current world champion at GO! The latter board game was levels of magnitude less ‘logical’ and predictable than chess and regarded as more intuitive and complex. So much for board games. I struggle to play either so would stand no chance against a computer’s intelligence.

Next up in the real world the BBC recently reported a US AI defence system successfully outplayed incoming attack jet fighters by basically outfighting them with its own interceptors. So much for war then. I am not able to fly a jet, real or virtual, and I know little of strategic war routines having not been trained in the military so I must defer to the computers once again.

The question for me is not how smart is AI and how smart can be the very smartest humans but ‘just how dumb are humans, really?’

If we take our mammal cousins, the field mice, and look at their ‘thinking’ in the context of the life choices they have on rising in the morning. They have very little body mass and so have little  food reserve. They cannot go without food for very long so each day they look for food. But they also need to reproduce for the species to survive and to do this they must look for a mate rather than forage for food. This is risky as they may, find a mate and then starve or fail to find a mate and starve.

How do they make this life and death choice?  Well, very detailed study showed that they use a very simple algorithm which is ‘I ate well yesterday so I can look for a mate today’. That’s it!

This simple algorithmic approach to reasoning is widespread in the animal kingdom and are inferred from observed behaviours. This is why it belongs to the field known as ethology which is the study of animal behaviour. These algorithms are known to the higher primate homo-sapiens and we call them ‘rules of thumb’. Rules of thumb abound today, after all if you want to improve something then measure it.  So here then is building block No1 in human reasoning

Reasoning method Number 2 was explained to me on BBC Radio 4 many years ago when a politician was describing ‘thematic reasoning’ which at the time was new to me and a revelation. Essentially things, issues, people, whatever, are ascribed a virtue, that is ‘good’ or ‘bad’. To whit an often repeated 1990’s experiment is to ask the general public which of the following processes were most responsible for global warming: electricity generated by coal fired stations, oil fired, gas fired or nuclear powered?  Invariably the order was, worst=nuclear, best=gas.

It’s simple to understand their mistake. Global warming = a v bad thing; nuclear power = a bad thing ( this is 1990s post Chernobyl), bad begets bad so the conclusions are linked by theme. Apparently according to my radiophonic mentor all politicians understand this and are taught it at politician school which explains a lot...see referendum debates, invasion of Iraq etc etc.

Finally we have reasoning Number 3. It’s called magic. James George Frazer’s famous book ‘The Golden Bough; a study in magic and religion’ in the late nineteenth century does it for me. To cut a long story short, belief systems developed that introduced new ways of reasoning. They were/are characterised by rituals and symbols and embodied principles. The latter include an association inferring cause and effect, eg the Rooster crows just before sunrise ergo the sun’s rise is caused by the Rooster's crow. This is broadly called sympathetic magic the other main type is contact based and is called contagion. So for example the baptising of a baby with holy water is an example of contagious magic replete with symbolism and iconography.

So far so bad for homo-semi-sapiens. What about higher levels of reason? The kind of thing you get from education.

Take for example conditional statements, ‘if I do this, that will happen’. Every teacher knows by experience that students can have their minds trained so as to make correct conclusions using the conditional so long as they are given the initial knowledge conditions and the rules of the game. This is certainly the start of logical thought and in itself an educational achievement but ask also the same teachers (and setters of exams) what success they will have with double conditions. Eg, ‘ if this occurs then that will occur and then the other will occur as a result’...the nested ‘if’ of computing.  Most students cannot do this.

Putting it all together, Homo-semi-sapiens in a developed society will have access to ‘rules of thumb’, thematic constructs, magical thinking and one step conditions.

The famous thinker Scott Adam’s seminal 20th century work ‘Dilbert: Thriving on Stupidity in the 21st Century’ describes this beautifully and is still elaborating his ideas today in his latest comic strips where engineer Wally is nominated for a Nobel prize for his AI humanoid; aka a block of wood.

Homo-semi-sapiens is on the march today aided by the connectivity of social media which allows for self-referencing and reinforcement.  Authority is challenged as never before as ‘priest classes’ lose their grip unable to explain to their audience what is in effect  unexplainable and resorting to using reason that is in common use (as described above).

It is ironic that we debate the capabilities of AI systems when the ‘I’ systems in general use are so primitive. Maybe if we wish to produce realistic AI systems we should start with our own protocols.

Am I being patronising to semi-sapiens? Maybe once I could have been intimidated into being less scornful. However the Brexit referendum has removed all such inhibitions.

Ions and Mitochondria: repair or die

A restored classic car may look and run well but it’s not fresh off the production line. It will have been repaired  umpteen times, and it is not about to be thrashed around the track … except maybe on special occasions. Such is the nature of the rejuvenated.

This analogy serves well enough to illustrate the current thinking in the pursuit of longevity and the preservation of youth.  From the cosmetic (a respray), the physiological fitness plan (new suspension and bearings) to the subcellular diet-related (an engine overhaul), all cases of  ‘rejuvenation’  are synonyms for repair.  I am interested in repairing biochemical engines, which in the case of aging organisms means mitochondria.

To get started I need to set out some ground rules regarding my picture of mitochondria. A picture I have set out in previous posts. To me they are tiny electronic devices. They can conduct electrons and physically separate charges to create potential differences measured in volts.  Their membranes have low dielectric constants and large surface areas so can store charge as does a capacitor and like capacitors they leak a little charge too. Finally, they can (controllably) collapse their charge-gradient and transform that energy into chemical form … or else they can be ‘shorted out’  releasing their energy as heat.

Or, in biochemical jargon:  the process of oxidative phosphorylation and electron transport  generates a membrane potential and a proton gradient, the energy of which is used to synthesise ATP unless it is ‘uncoupled’ by something that makes the inner membrane permeable to positive ions.

My ‘electronic’ mitochondria reduce biochemical complexities to simpler axioms which include making sure that voltage and capacitance remain high and charge leakage remains low.  

To do this we must:

1. Keep the processes that separate charge going flat out.
2. Maintain the dielectric integrity of the membranes.
3. Maintain the surface area of the mitochondria and hence its capacitance
4. Stop leaks.

It has been known for a long time that stimulating the mitochondria by feeding them their favorite food 1 (acetyl units) and transporting them using a the so-called carnitine shunt using the food supplement acyl-carnitine peps up the activity of the electron transport chain. Ditto foods like malic acid and citric acid speed up the citric acid cycle. Such supplements address the first point in the list above but all will be wasted if the other points are not. ‘Revving up in neutral’ will generate heat but not a lot of action.

As we age mitochondria change,  a proportion of them become larger with fewer christae 2, They leak proteins more easily 3,4 and eventually depolarise completely leaking the fatal Cytochrome C which leads ultimately to cell death. I also proposed that larger mitochondria are an adaptive response to reduce capacitance in order to maintain  the threshold membrane potential for ATP synthesis. But what to do about this?

In a previous blog I referred to my work showing that Cytochrome C leakage was reduced in rats fed a diet high in cholesterol.4 Cholesterol rich membranes also have a higher dielectric constant than cholesterol depleted membranes. This is a start, a repair of sorts but what we really need is something to:

a) purge from the cell inefficient and downright dangerous larger mitochondria struggling to maintain their membrane potential against a backdrop of increasing leakiness.

b) plug the leaks.

When the Cats come out.

Metal cations are positively charged metal atoms and cells use different ion gradients to power various energetic processes such as nervous conduction (Sodium and Potassium (Na+, K+), kidney function (Na+, K+ and H+), mitochondrial energy production (Proton H+) and muscle contraction (Calcium Ca++).

But what about the physiological effects of other cations, cations not normally present in high quantities in the food we eat?  Specifically  I mean very small cations that can, could, or do interfere with the ions above by virtue of their small radius and ability to get into cells and bind to membranes.  That is cations small enough and rare enough to be ‘mistaken’ for the usual suspects.

My short list comprises: Lithium, Beryllium, Boron, Aluminium and Germanium ( Li+ Be++, B+++, Al+++, Ge++) on the basis of their ionic radii shown in the Periodic Table5.

Yes, all are poisonous (very)  all are very small and they all affect mitochondria causing them to enlarge and uncouple. Germanium induces mitochondrially mediated apoptosis6; aluminium caused an increase in mitochondrial free radical (ROS) production7; beryllium uncouples and cause them to swell.

Two of them though, in low doses, bizarrely increased the lifespan of short lived organisms8,9. These are Lithium and Boron, now that is interesting. Lithium increased the autophagy ( absorption) of enlarged dysfunctional mitochondria and another author10 speculated that ion channels were blocked by the unusual ion helping to reduce charge leakage and maintain membrane potential when he found enhanced mitochondrial activity in human brain tissue.

Boron also decreased the size of the mitochondrial population making them more elliptical. The experimental animals were: C elegans (a nematode worm) and Drosophila (a fruit fly).

I am intrigued. Plugging leaks and culling the weak would be close to top of my list of repairs to mitochondria. A lot more pieces of the jigsaw need to be found but in the meantime what food would benefit me most according to the repair schedule set out in this blog.

I would get my dietary cholesterol or its precursor squalene from foods naturally rich in it such as oily fish, seafood and olive oil.  Of foods with a high lithium content, pistachio nuts are prominent and for boron, walnuts and dark greens like kale. For a boost in activity I would make sure I got my fructose, malic acid or citric acid from fresh fruit. Ok that looks quite a lot like the perfect Mediterranean diet...I wonder why they live so long and have such low rates of dementia?

1)Ann N Y Acad Sci. 2004 Nov;1033:108-16.Delaying the mitochondrial decay of aging with acetylcarnitine. Ames BN1, Liu J.

2) Antioxid Redox Signal. 2010 Feb 15; 12(4): 503–535. Mitochondrial Turnover and Aging of Long-Lived Postmitotic Cells: The Mitochondrial–Lysosomal Axis Theory of AgingAlexei Terman,1 Tino Kurz,2 Marian Navratil,3 Edgar A. Arriaga,3 and Ulf T. Brunk2

3) AGE-DEPENDENT RELEASE OF MATRIX PROTEINS FROM RAT-LIVER MITOCHONDRIA

Author(s): SPENCER, JA; HORTON, AA  EXPERIMENTAL GERONTOLOGY  Volume: 13   Issue: 3-4   Pages: 227-&   DOI: 10.1016/0531-5565(78)90016-5  Published: 1978

4) Differential Effect of Digitonin on Liver Mitochondria from Old and Mature Rat  Spencer, John A.; Horton, Alan A. BIOCHEMICAL SOCIETY TRANSACTIONS  Volume: 7   Pages: 673-675   DOI: 10.1042/bst0070673   Part: 4   Published:AUG 1979

5) http://ch301.cm.utexas.edu/section2.php?target=atomic/bonding/ionic-radii.html

6) Neurosci Lett. 2006 Feb 27;395(1):18-22. Epub 2005 Nov 9.Cochlear damage due to germanium-induced mitochondrial dysfunction in guinea pigs.Yamasoba T1, Goto Y, Komaki H, Mimaki M, Sudo A, Suzuki M.

7) Aluminum induces neurotoxicity by altering mitochondria of brain cells

Thursday, January 30, 2014 by: Thomas Henry

Tags: aluminum, neurotoxicity, neuron mitochondria

8) Effects of lithium on age-related decline in mitochondrial turnover and function in Caenorhabditis elegans. Tam ZY1, Gruber J2, Ng LF3, Halliwell B3, Gunawan R4.

9) Biull Eksp Biol Med. 1990 May;109(5):492-4.[Morphometric characteristics of hepatocyte mitochondria during internal administration of boron-containing water].Korolev IuN, Panova LN, Zhukotskiĭ AV, Butusova NN, Kogan EM.

10) Lithium-induced enhancement of mitochondrial oxidative phosphorylation in human brain tissueMaurer IC1, Schippel P, Volz HP.J Gerontol A Biol Sci Med Sci. 2014 Jul;69(7):810-20. doi: 10.1093/gerona/glt210. Epub 2014 Jan 7