Table of Contents

Textbooks list proteins, nucleic acids and lipids as the building blocks of life. But how important are these species relative to one another? Imagine spending a day in B, the world’s life sciences capital. On a crisp sunny morning you mosey up and down the streets, admiring the views. Tall expensive buildings rise skywards, so high they remind you of reverence-instilling cathedral ceilings, designed to make us lift our heads to look up to Heaven. Those shiny new high-rises provide a great unobstructed view of the skyline, and are filled to the brim with top Scientists, tirelessly striving to push the frontiers of biology beyond that horizon.

1880s were the last years of Vincent Van Gogh’s short life. Just like at the beginning of his painting career a decade earlier, he still could not afford to buy the essentials, neither for work, nor for personal use. Luckily for us, he faced no dilemmas in making choices - being barely able to scrape together the absolute minimum to sustain his work simply meant giving up on his own basic needs. This was not lost on Jeanne Calment (the jovial French longevity record holder who reached the age of 122), who a hundred years later recounted seeing a scruffy looking Van Gogh pop in to buy some canvas in her family shop in Arles.

We will talk about how lipid peroxidation affects the living brain, and what can be done to mitigate the problem, in later sections. However, the dead brain probably belongs in this non-biological introductory chapter, so here we go: Oil paintings and linoleum (just like aging and disease) both rely on lipid peroxidation. But Alexandra Morton-Hayward of Oxford University is concerned with a more macabre outcome of the same process. Of all our organs, the brain tissue, a soft, squiggly-squirmy gel-like mass that fills up our decision-making cockpits, seems least suitable for long term preservation... Essentially, our dead brain can self-immortalize by turning into a linoleum oil painting of itself.

When the first life-forms appeared on Earth about 3.5 billion years ago, nitrogen was likely the main ingredient of the atmosphere. 2.5-2 billion years ago in the late Archean, the Great Oxygenation Event started, and the levels of atmospheric oxygen, produced by anaerobic photosynthesizing cyanobacteria, began to rise. The bugs used solar energy to split water, generating reducing hydrogen to be used in biosynthesis, and puffing out toxic molecular oxygen as waste to make sure it would not kill them.

Electrons, released amply by fuel-burning mitos, are supposed to be passed on along the respiratory chain in a precise step-by-step fashion, gradually releasing bits of energy in a piece-meal way. But enzymes are not perfect, and even a 99.9% efficient enzyme would still make 0.1% errors. That’s only one error per 1000 cycles but imagine how many of those each enzyme performs per day...

If you think that this has nothing to do with you because you do not fly often, are not a member of a nuclear sub crew, live far away from the nearest nuclear power station, do not have a radon-filled cellar, and harbour no plans to relocate to Mars, here is the rub: ionizing radiation fills the universe, and daily ionizing particles and rays collide with molecules of about 1% of our cells, so whatever number of cells we are made of, - somewhere between 36 to 100 trillion - the number of hits is still astronomically large.

Even cobalt can be more active than iron in the Fenton reaction, so do not overdose on your Vitamin B12 supplements. Injecting cobalt in animals led to damage consistent with hydroxyl radical formation – and this was not known in the early 1960s, when dishwashers became a kitchen staple. A thin film of detergent left on washed dishes and glassware is a pretty nasty thing to ingest... but unexpectedly the residual detergent on the glass surface compromised beer foam formation.

We cannot make PUFAs, yet our cells cannot survive without them. But why? No one knows. Even the nature itself may not, as some of us suspect it assembles its clockwork mechanisms blindly. PUFAs are not always abundant in food, so nature goes an extra mile to preserve them in species from cephalopods to vertebrates.

Linoleic acid (LIN) is my least favourite PUFA, but some major distortions in LIN supply and abundance, causing a lot of global problems, need to be covered. LIN was isolated from linseed oil (hence the name) in Justus von Liebig’s lab in 1844... The emergence of LIN corresponded to the arrival of seeds, through flowering plants (angiosperms: most trees, grasses, vines and shrubs).

The idea of quantum effects in consciousness is speculative. We are focusing here on biological phenomena which so far failed to be explained in any other way. And leading the way is the hard problem of consciousness, which overlaps with concepts of conscious free will and is the subject of vast literature. Reducing this arcane math-replete field to a Twitter style outline, the first proposal of QM algorithms being involved in cognition seems to have come from Efim Liberman in the USSR.

The long-standing mystery of the visual processes in the eye, as mentioned in George Wald’s Nobel Prize lecture in 1967, was that the events following the photoactivation of rhodopsin, namely the transduction of visual excitation, were too slow to explain visual reception. It should take substantially longer for a visual signal to get from the retina to visual cortex based on the speed of the spike travelling along neuronal membranes...

Various metaphors can be used to describe the concept of chemical or nuclear chain reactions (CR). A domino effect, matchsticks set aflame in a matchbox, an avalanche, a snowball effect... My favourite analogy formed based on the alleged reports by British pilots during the Falklands war. There are million-strong colonies of penguins in the Southern Atlantic... In 1982, several Royal Air Force pilots reported penguins staring, with curiosity, at fighter jets taking off... The first rows would then start falling on their backs like dominoes, pushing on the neighbours and so on.

Having spread through the PUFA membranes like wildfire, frying them from within and destroying the barrier function, eventually the lipid peroxidation (LPO) chains cool off. The trouble, however, is just beginning. Oxidized PUFAs are unstable and rapidly break down through multiple pathways, many not well understood, reducing them to smithereens. Dozens of fragments are generated, some inert (like isoPs or alkanes), but many more highly reactive, hence toxic.

Cells must have polyunsaturated fatty acids (PUFA) in their membranes. The PUFA composition of many cells is tightly controlled, irrespective of the dietary intake, except in cases of severe deficiency. And antioxidants cannot stop the lipid peroxidation (LPO), and sometimes they make the matters worse. So lipid peroxidation always festers in the background. Many LPO products cross-link with other biomolecules forming difficult-to-remove conjugates, which gradually accumulate.

Many other chemicals can also cause lipid peroxidation (LPO). The ill-famed MPTP, a by-product in illegal manufacturing of synthetic opioids, was discovered when young drug addicts mysteriously started developing rapid onset Parkinsonism. MPTP is a rare case of a bioactive compound which in research went from humans to mice, and not the other way round.

A provoking conclusion follows from inspecting the examples above. In many pathologies – neurological, retinal, metabolic, inflammatory, and age-related, - lipid peroxidation (LPO) is likely one of the drivers. Almost all neurological disorders, main indications (AD, PD, TBI, etc), and orphan (rare) diseases (FA, INAD, ALS, etc) have an LPO component, detectable at very early stages of the disease.

Just when we thought we understood the lipid peroxidation (LPO) process fairly well… Kazuo Miyashita at the Hokkaido University has been baffled by his observations for years. The ease of polyunsaturated fatty acid (PUFA) peroxidation is linked to the number of bis-allylic positions between the double bonds, from which hydrogen atoms are abstracted by ROS.

It is 4 pm, going on 5. Happens 24 times per day, somewhere on Earth. Time to enjoy a spot of tea. The hot amber brew is poured into the teacup, and you reach out for, - well, wait a minute, aspartame is a methyl ester, and methanol is poison... so your hand changes tack, and instead of the small sweetener pellets you pick a lump of sugar... The swirling liquid dissolves the lump, but it also provides aeration. And that’s where the things may take an unexpected turn…

To measure the progress of a disease, or the efficiency of treatments, an easily detectable “biomarker”, that correlates with disease severity, is a very useful (and potentially lucrative) thing to have. A fertile ground for research, the biomarker field has churned out thousands of candidates, but only a couple hundred made it into the clinic.

Stir fry cooking often involves setting a hearty quantity of overheated PUFA-rich “vegetable” oil in a wok on fire. Flames engulf the bowl from both sides, helping to sustain a runaway LPO process. So massive and brutal the ensuing PUFA damage is that some of you may find it disturbing... Indeed, “vegetable” oil in food is the new smoking! And it gets worse…

As the Cat in the Hat, a big connoisseur of all things fishy, would have put it, if the smell isn’t swell, well, that’s a tell, that the fish oil’s not necessarily well. Fish oil can be bad in several ways. Oxidation of PUFAs can be really fast. A UCLA professor John Edmond, who sadly passed away in 2022, recalled that in response to his scepticism about the speed of PUFA peroxidation in air, his PhD supervisor had him smear a small glob of fish oil onto a microscope slide surface...

The pressure of natural selection has always been rather simple. Mature fast to reach reproductive stage before the predators get you. Quickly build strength and weight to survive childhood, then outcompete others to reproduce. Our food preferences evolved to support this... Some adaptations that would help to reach the Goal early in life could actually be detrimental later in life…

As you are working your way through your coffee, a bowl of porridge, and this chapter, - here is a disclaimer. The suggestions below, based strictly on metabolic input, ignoring the social aspects, are not claiming any medical, nutritional or health benefits. Just the well-being of your precious PUFA stock...

Our eye is not built to last. It is the only organ where some cells survive the entire lifespan from the time we are born. As retinal cells are mostly formed by about age one, continuous body growth is associated with stretching and distortion of the retina. The evolution might be too optimistic when pinning hope on the resilience of eye tissues, which are exposed to light and have the highest oxygen levels after lungs.

We have already mulled over the main elements of the evil that will befall the brain over its lifespans. The neurons are full of PUFAs, oxygen and metals, all the necessary prerequisites for the chain reaction, so the brain is the hot spot for LPO. The way the neurons store information means that most brain nerve cells last a lifetime and cannot renew themselves by dividing.

The number and type of mitos varies hugely, depending on the cell type, from tens to thousands. The large numbers should not be too shocking considering there are peripheral neurons more than a metre long. Extending Nick Lane’s epigraph, to a large degree the problems with mitos stem from the contract they themselves signed with PUFAs. As mitos pack a lot of PUFAs, iron and oxygen, we basically have a large depot of tiny live grenades that keep exploding in every cell…

The roller-coaster journey of a neuronal signal, sometimes referred to as a “spike”, generated by a peripheral pain receptor in response to, say, a toe cut, proceeds through the spinal cord, to the thalamus sorting station for redirecting to various pain perception areas of the brain. It travels across multiple synaptic junctions and more than 1.5 metres of neuronal membranes.

Other channels important in pain sensation and hyperalgesia can also be modulated by the LPO products. Methylglyoxal has been shown to drive hyperalgesia by reacting with a sodium channel. In diabetic neuropathy patients, methylglyoxal above a certain threshold concentration in plasma was associated with pain.

While honing his insect brain surgery skills... Gero Miesenböck, the father of a widely adopted optogenetics technique, now in charge of Centre for Neural Circuits and Behaviour at Oxford, must have gotten to know every one of approximately 123,456 Drosophila’s neurons up close and personal. Deep understanding of voltage-gated cationic channels in neuronal membranes helped him to make an astonishing observation…

To understand these body-wide lipid transport systems, think mayonnaise. Nature has sorted out carrying insoluble lipids in blood by emulsifying the fats. Hydrophobic triglycerides and cholesterol esters (“the olive oil”) are wrapped around by amphiphilic PLs, free cholesterol and various apolipoproteins (“the yolk, vinegar and mustard”). Small intestine and liver are “the blender”.

These and many other consequences of the population-wide addiction to “vegetable” oils reduce lifespans. Not only does seed oil consumption exacerbate the CVD incidence and outcome (while reducing cholesterol – yet another argument in favour of PUFAs and LPO in the CVD pathology). It ruins the omega balance…

Icebergs and glaciers do not lend themselves well to photo sessions. Pictures fail to capture what is clear only when directly looking at the real thing – the floes emanate this unearthly, alien-blue light from within. The situation is even more complicated for warm-blooded humans. The soft rosy glow coming off the healthy radiant youthful flesh is now accompanied by a myriad of balmy hues and cues...

While the inner organs are exposed to oxygen levels which are orders of magnitude below the atmospheric, our skin is facing a constant 21% oxygen onslaught, day in day out, dressed or naked. And with so much molecular oxygen sloshing about, its insidious relatives ozone and singlet oxygen will sure turn up as well.

Consider a popular idiom, “to smell blood”. Predators are attracted to the odour of blood, while it is often aversive to the prey species. But blood itself has no smell, so what is going on? Well, you are actually smelling the Fenton reaction! When exposed to oxygen in air, iron in hemoglobin generates ROS, which oxidize PUFAs in red blood cells into lipid peroxides that decompose into volatile secondary products.

As discussed above, the trifecta of PUFA, metals and oxygen make very uncomfortable bedfellows, even in the dark. Now imagine what would happen if for a good measure some light were shone upon that bed. Skin-penetrating UV and visible light may be strong enough to “radicalize” water molecules and UV can break up H2O2 into hydroxyl radicals.

The number of people who have hired someone to deposit unknown chemicals under their skin steadily grows. Typically, people get inked to make sure their tattoos are visible to others, so naturally this often overlaps with beach time and sun exposure. From the LPO perspective, several things should concern us here…

Test yourself with a cryptic crossword, designed by an anonymous science-funding body: Q: A novel cutting-edge multi-$ Bn technology. A: Colloidal chemistry…

Year 2012 saw the second shot on goal. Enter the Ferroptosis* cell death modality, the brainchild of professor Brent Stockwell. “Ferroptosis: an iron-dependent form of nonapoptotic cell death” was the title that did the trick. Cited 12,000 times.

Often, the events start with a knock on a cellular door. The caller could be a calcium ion, an LPO product, glutamate, LPS, an eicosanoid, a cytokine, acetylcholine, or many other things. A lipase – say, cPLA2, - peers through the peephole, and acknowledges the caller by latching on to the endoplasmic reticulum membrane.

Life coexisted with LPO long enough to learn how toxic the oxidation products are. Animals evolved to recognize the telltale signs and respond, trying to mitigate the problem. We saw multiple recognition mechanisms for oxidized PUFAs. So carefully is the PUFA oxidation status monitored, that essentially any oxidatively modified PUFA would be flagged up as a distress signal.

Lest I digress too far from the main track: LPO plays the major role in the senescence pathways. Oxidized PUFAs and LPO products are elevated in senescent cells, and senescence is strongly associated with LPO and in particular with its most toxic offspring, the reactive carbonyl species.

The minimum viable product concept, prioritizing quick software release and doing things on the cheap versus excessive refinement, is not a Silicon Valley invention. It is 3.5 billion years older, as evolution only develops things to the state of being “good enough”. Thus, even though there is no “aging gene” that turns on to turn us off, the imperfections are essentially encoded into enzymes.

There is a sweet spot for the optimal ROS and antioxidant levels, both exceeding or falling short of which would be detrimental. Metals have their goldilocks zone too, - think anaemia and hemochromatosis. Similar to oxygen, iron is both essential, and harmful, for life.

Everywhere in the body, - in lipid bilayers of cells and organelles, in lipid droplets and lipoprotein particles, - wherever there are PUFAs, - one can see the meandering trajectories of LPO chains, ceaselessly crawling or darting, day in, day out, through the membranes, leaving destruction in their wake. Oxidizing PUFAs, churning out toxic agents, spilling pro-inflammatory molecules.

Age pigments are like routers in a large house, ensuring the wi-fi signal is always strong. If for whatever reason the LPO dwindles – they make sure it is rekindled, by virtue of their photosensitizing properties and high transition metal content. But growing steadily, and the older the faster, the lipofuscin deposits gradually clog up and suffocate cells.

There are some paradoxical observations, where deficiency in antioxidant defences is associated with increased lifespan, with examples from popular fly, worm and rodent workhorse biological models. This was observed for both natural antioxidants such as peroxiredoxins and GSH-related machinery, as well as for vit E.

Staring down the barrel of aging, we see the relentless onslaught of LPO, with the newly minted reactive carbonyl species rank and file marching forward day and night. We may not be aware, but our body is certainly mindful of the clear and present danger.

Biochemistry deals with interactions of valence electrons occupying the outermost layers of electron shells in atoms. Nuclear chemistry focuses on reactions that happen inside atoms. The latter are more violent as there is more energy “stored” in nuclei than in electrons. An interesting phenomenon emerges at the overlap of the two chemistries…

As discussed in ch.2.6, the slowest, rate-limiting step of the LPO process is the abstraction of hydrogen from the CH2 moieties located between two double bonds. Because C-D bonds are more resistant to breaking compared to C-H bonds, replacing the hydrogen atoms of these CH2 groups with deuteriums would reduce the rate of abstraction, slowing down the LPO process.

Significant effort was made trying to understand the protective effect of low D-PUFA levels. Ned Porter, the key authority on LPO from the Vanderbilt University, measured the IE on the chain oxidation of D-LIN and D-LNN in organic solvents. In presence of vit E, the IE for D-LIN chain oxidation was found to be 23.

That the protective effect of D-PUFAs varies from moderate through substantial to strong is not unexpected, as different pathologies may have LPO involved to a different degree. What is surprising is the scope of conditions in which LPO plays a role, - and can be reduced by D-PUFAs. This speaks to the common denominator status of the LPO.

At the advanced stages of AD, chunks of brain degrade and disappear, as the liquid-filled, gaping voids become clearly visible on the brain scans. Sadly, it is only in quantum mechanics that the information cannot be lost. The disappeared neurons take with them the memories, and the identity, irreversibly depriving the affected individuals of self. At that stage, it is too late to interfere.

Making lipid membranes more resilient, with all the positive downstream effects, is where the D-PUFAs may help cells just to stay in the same place – that is, in the same age. And for this method of prevention, we don’t even need an ounce: a gramme per day may do, to keep the LPO and inflammaging away…