Sunday, March 31, 2013

TCA rap

From Bert. Not advocating carb consumption but I can see that electron transferring flavoprotein dehydrogenase would need some serious effort to rap... So enjoy glycolysis and the TCA:

Click-able, sorted!

Ta Bert. I enjoyed.


Now if I can get Ryan started on beta oxidation. Hmmmm....

Wednesday, March 20, 2013

Sta'ins, CoQ, diabetes and Dr Andreas Eenfeldt's link

I'm not very conscientious about reading many blogs as I don't really have time to look after my own blog properly, but I will occasionally flick through the links from Stan's site and I felt that Dr Andreas Eenfeldt's link to the official Swedish data sheet for simvastatin was rather excellent. Via Google translation:

"Diabetes is a possible side effect. This is more likely if you have high blood sugar and high blood fat levels, are overweight and have high blood pressure. Your doctor will monitor you while you are taking this medicine."

Statins deplete CoQ. This means that for every electron carried from any input, NADH or FADH2, down the ETC there will be less CoQ available in the redox couple and the CoQH2 levels will be relatively high. An highly reduced CoQ couple (ie low CoQ per unit CoQH2) will drive reverse electron flow through complex I and generate superoxide. Insulin resistance. Diabetes.

I suspect that EVERYONE on a statin will step their insulin resistance up by an amount proportional to the CoQ depletion. Everyone. Just a few will cross the arbitrary boundaries between "normality", "impaired glucose tolerance" and "diabetes".

Hyperglycaemia doesn't care about labels or boundaries. You get it, you suffer.

Obviously this rather nasty side effect can be COMPLETELY avoided by putting the statin script in the bin.

If you are going to take simvastatin anyway then some coenzyme Q10 might ameliorate some of the damage you have chosen to do to yourself.


Let them eat fat: Ron Rosenbaum

Dave Lull fwded me this link. I don't know who Ron Rosenbaum is, but he sure as hell talks some sense.

For when the link goes down I've put the text on to the odds and sods blog here.


Tuesday, March 19, 2013

Protons: Aside to T cells

Just because I like it. This is obscure. We can ignore the upper section as this is quite specific to T cells (which the paper is all about). What I love is the consideration that mitochondrial glycerol-3-phosphate dehydrogenase (marked as GPD2), sitting on the outer surface of the mitochondria, is very likely to be driving reverse electron flow through complex I to generate free radicals. Something I would avoid, personally (except perhaps in my T cells).

The bit I love is the big red outline arrow from QH2 going to the left towards complex I.

The whole mechanism and specific purpose here is linked to activation of the drive for T cells to divide, a free radical mediated phenomenon through NF-kappaB. What interests me at the moment is what might happen to a cell which cannot divide when mG3Pdh is driven, say by hyperglycaemia acting on a neuron... Lots of papers to wade through on this.


Saturday, March 16, 2013

Protons: Meet the glycerol 3 phosphate shuttle

The next thing we have to think about is the glycerol 3 phosphate shuttle. This is a route in to the electron transport chain for cytoplasmic NADH, directly from the cytoplasm, no complex I involved.

There are two glycerol 3 phosphate dehydrogenases which make up the shuttle, just to confuse matters. Free in the cytosol there is cytosolic G3P dehydrogenase, which actually uses NADH to add a pair of hydrogens to a glycolysis intermediate (dihydroxyacetone phosphate) to form G3P.

The other G3P dehydrogenase really does dehydrogenate G3P, back to dihydroxyacetone phosphate. But this second G3P dehydrogenase is embedded in the outer surface of the inner mitochondrial membrane. And it contains an FAD/FADH2 moiety which takes these two hydrogens and uses them to reduce the CoQ couple, feeding electrons in to the electron transport chain.

So we are putting electrons from cytosolic NADH directly in to the ETC through FADH2. From the outside. And pumping no protons.

The G3P shuttle is very, very important.

In healthy cells the signal to reject excess calories picks on glucose, in the form of the development of insulin resistance, mediated by superoxide generated at complex I of the mitochondria. At iron sulphur cluster N-1a. The most simple way of doing this is to oxidise fully saturated fats (mmmmm, butter), generate a lot of FADH2, post a few electrons the wrong way through complex I and shut down glucose acceptance by the cell.

You can make glucose act as if it were butter through the G3P shuttle.

Think what happens if you are a Taterhead, just finishing your 4th plate of plain boiled, unsalted, unseasoned, unpeeled spuds.

Your FFAs, especially palmitate, are through the floor. Your glucose, given its own way, would be through the roof. Insulin is demanding that all cells accept glucose because no one wants a blood glucose of 30mmol/l. There is a shedload of NADH in both the cytoplasm and in the mitochondrial matrix. Electrons are pouring down the ETC but, in your post spud-prandial insulin induced stupor, you are not exactly sprinting to the gym.

You have to stop the supply of NADH pouring through complex I but, unless the NADH level is over three times the NAD+ level in mitochondria, you are not exactly going to get an electron on to N-1a excepting when there is a markedly reduced CoQ couple and a strong membrane potential. In the absence of palmitic acid (you're pigging out on fat-free spuds, don't forget) you need mitochondrial G3P dehydrogenase to pour electrons on to the CoQ couple, which allow the insulin/glucose induced membrane potential to push electrons back up the ETC to N-1a. And then SHUT DOWN THE BLOODY GLUCOSE SUPPLY.

You might just be able to do the same to deal with excess insulin. If insulin (from exogenous injection or an insulinoma) is allowing a free fall of glucose in to the cell and the cell really doesn't want all of this metabolic substrate, it has to say no. It was quite a while ago now but we have discussed insulin induced insulin resistance. Here's a possible metabolic mechanism. And the mechanism would kick in when the G3P shuttle goes in to overdrive, not when glucose becomes too low. Back to when we had the discussions about the Somogyi overswing... It's just a mimic of pigging out on spuds but without the spuds.

But the queen of insulin resistance generators is, of course, fructose. Fructose free falls through glycolysis to levels that the cells really cannot expect to use immediately. Of course a lot of it gets off loaded as lactate but there is still way more pyruvate than a cell can reasonably be expected to oxidise immediately. I consider this effect to be dose related. Eating the occasional apple might not kill you (gasp, there, I said it) but three Big Gulps per day probably has you well on your way.

Answer to fructose exposure is to shut down glucose supply to a level which compensates for the calories coming through from fructose. There can be no easier way than to reduce the CoQ couple using an FADH2 input. G3P dehydrogenase does this directly from the cytoplasm. It, like electron transferring flavoprotein dehydrogenase, is what I would describe as "complex II -like" in its action.

This smacks of physiological regulation to me.

Things get slightly more pathological where hyperglycaemia is overcoming insulin resistance. Or overcoming absolute insulin deficiency, as Sonksen and Sonksen pointed out. I'll come back to this in future posts.

There is quite a lot of support for this concept in Pubmed but here is an abstract I particularly enjoyed. Anyone thinking of indulging in a bit of Taterism should have a read first. A real giggle while you boil your spuds.

The wild type mice were funniest. For your delectation:

"The high carbohydrate diet induced hyperglycaemia, hyperinsulinaemia, and islet hyperplasia in the wild-type [mice]"

Oh, for the love of Taterism, does anyone remember the discussion of Barnard's victims and their progression of diabetes under a low sugar, high complex carbohydrate diet? Well, mice are not so different from people! In people we call this Taterism. Well, some of us do.

And look at the tweaked physiology in the same abstract. If you knock out mG3P dehydrogenase (ie you eliminate this "complex II-like" FADH2 reduction of the CoQ couple) you get increased insulin sensitivity (no reverse electron flow as there is no FADH2 route in to the ETC except complex II and we're not feeding fat).

Is this a good or a bad state to be in? That depends on degree and whether you are happy to push far more electrons down your ETC than you could possibly have a use for. An interesting question. I'm not in the queue to trial a mG3P dehydrogenase inhibitor (actually, it's called diazoxide and it does seem to help). Not eating carbs seems a rather safer bet.

[BTW if anyone has this high carb paper it would be nice to know which mice they used and what the diet was actually made of... Ta.]

Edit: Got it, many thanks Paul and Purposelessness. End edit

Which leads straight on to neurons.


Thursday, March 14, 2013

Protons: NAD+/NADH some more

This is an interesting paper (from George I think). There are a stack of caveats about it, but the core findings appear to hold water.

They are dealing with cancer cell lines (ie cancer cells which are immortal and live in tissue culture) which have lost complex I of the electron transport chain. These cells have elevated levels of NADH per unit NAD+, ie their NAD+/NADH ratio is low. Obviously NADH is high because there is no complex I to oxidise it back down to NAD+. Any NAD+ which gets converted to NADH simply stays there as NADH.

Glycolysis continues to generate NADH and the TCA generates more NADH because that's all you can do with acetyl CoA (pax complex II derived FADH2), barring the scenario we looked at in a previous post.

You can manipulate the NAD+/NADH ratio.

It doesn't seem to matter whether you manipulate the absolute NADH levels down or the absolute NAD+ levels upwards and it doesn't seem to matter how you manipulate either level. Having excess NADH combined with relatively depleted NAD+ makes these cancers very much more aggressive in terms of metastasis. It's fascinating to see terms like Ki67 bandied around as aggression markers, we are just starting to use Ki67 clinically to try to assess to seriousness of that almost invariable "Grade 2" score assigned to the vast majority of mast cell tumours which get as far as histopathology. Are they a good Grade 2 or a bad Grade 2? Scoring cancer aggression is not the easiest thing to do and Ki67 looks interesting for those of us who have to manage mast cell tumours with a scalpel and/or a tyrosine kinase inhibitor. Anyway, back to the paper:

The paper brings up Ndi1, a fascinating little enzyme stolen from yeasts and engineered in to cancer cells. Ndi1 is a rather small, relatively simple enzyme which inserts itself in to the inner surface of the inner mitochondrial membrane and happily converts mitochondrial matrix NADH to NAD+ in a process linked to reducing the CoQ couple, but it pumps no protons in the process. It bypasses the broken complex I completely, skipping electrons straight from NADH to CoQ while effectively lowering NADH and raising NAD+. And it tames the cancer's metastatic behaviour.

Compare this Ndi1 route in to the ETC to the FADH2 route in from fat metabolism, which uses electron-transferring-flavoprotein dehydrogenase, and also reduces the CoQ without pumping any protons.

The two produce rather similar effects. Ndi1 is essentially making NADH behave like an FADH2 based input to the CoQ couple. Ndi1 may be more effective because it is purely focused on relieving the excess NADH and could, theoretically, completely normalise the NAD+/NADH ratio, whereas running metabolism on fat will only bias electron supply to FADH2 without stopping some NADH generation.

Both mice and cell cultures are being run on glucose in this paper. If all that matters is the NADH to NAD+ ratio, what might happen on a diet which intrinsically generates less NADH? An interesting but un-asked question.

Perhaps you might not need that Ndi1 enzyme inserted in to your inner mitochondrial membrane?

The very simple converse approach, similar to giving B3 as used by Hoffer, was to add an NAD+ precursor to the drinking water. I can see that this might well be effective in raising NAD+ but the thought of long term megadosing on any nutrient to achieve this effect is beyond what I might personally want to do. I might change my mind if I had cancer.

I do think that is very interesting in its own right, but it leads on to a host of other questions. In fact there are too many questions for a simple thread. It's particularly interesting to think about what an excess of NADH to NAD+ signifies to a cell. This strikes me as a core decision making signal about a cell's future. How this ties in with superoxide production from complex I, or the lack of it when complex I is dysfunctional, is also related. Couple that with the fact that high levels of NADH providing substrates (pyruvate, malate or glutamate) massively increase superoxide generation when FADH2 generating substrates (succinate) are simultaneously provided to isolated mitochondria from normal tissues. The whole area looks to have lots of potential for working out what is going on at the primary switching point of the electron transport chain.

That looks OK but life is never quite that simple....

It's very interesting to note that there are now several publications from this group which are pretty convincing that many breast cancers, in vivo, have hyperactive mitochondria and perform oxphos to a very high level to support their aggressive growth pattern. Including both increased expression of the genes for complex I components and the enhanced ability (in mitochondria from fresh frozen human surgical breast cancer biopsies) to process large amounts of NADH to NAD+. Certainly compared to both non neoplastic surrounding epithelial cells and most especially compared to the surrounding stromal cells (mostly fibroblasts).

The results from the two groups are both very convincing and utterly incompatible.


To square the circle you get some help from this paper which suggest that at least one of the cell lines used in Santidrian's study are, in fact, melanoma derived cells, not breast cancer cells at all. In terms of aggressive phenotype most clinicians might be significantly more concerned about melanoma vs breast adenocarcinoma. I would anyway.

You may have to be married to a pathologist to realise quite how difficult it is to differentiate highly malignant cell types as both their genes and their appearance seem to eventually degenerate or evolve in to some sort of identical "cancer cell".

That seems to be the point being made by this chap.

So whether MDA-MB-435 cells are melanoma cells or breast cancer cells, they are degenerate/evolved enough to be indistinguishable from either family of cancer of origin and may well be behaviourally indistinguishable too.

The logical explanation is that MDA-MB-435 cells represent a more advanced cancer development than the still rather "normal" cells in routine surgical patients, most of the cells from which will be running on oxphos fueled by manipulating their surround fibroblasts (which will be running on glycolysis, with shut down mitochondria) to donate large amounts of TCA substrates to their controlling cancer cells

Aside: You still have a massive fuel source for cancer cells based on glycolysis here, it's just moved from the cancer cells themselves to the surrounding fibroblasts. But the down side is that while you might starve the fibroblasts by running on low glucose and high FFAs (they have lost their mitochondria) you still have active cancer cells willing to use ketones, FFAs or lactate through their very active mitochondrial electron transport chains... End depressing aside.

I really like this idea of degrees of degeneration as a possible explanation for the irreconcilable results. Again, you might need to be married to a pathologist to appreciate the phenomenal importance of fibroblasts in coming to a histopathological diagnosis about many cancer families. Fibroblasts are VERY important. Metabolic coupling may well be why.

Not sure whether to go on to mitochondria in Parkinsons or have a break and look at this whole concept of metabolic coupling between cancer cells and fibroblasts. The two subjects are vaguely convergent, eventually.


Protons: Back to N-1a and a nice quote

Eureka moment when I tripped over this gem by Vinogradov

"The redox potential of one binuclear [FeS] center (N-1a) is so negative that it can not be reduced by NADH"

Couple this with this group's conclusion:

"These results lead us to propose a model of thermodynamic control of mitochondrial ROS production which suggests that the ROS-generating site of complex I is the Fe-S centre N-1a".

You can't reduce N-1a to generate superoxide using NADH at "normal" concnetrations. The easiest way you can generate superoxide at N-1a is by reverse electron flow through complex 1 under conditions of a strong membrane potential and a high FADH2 input, in this case using succinate. Very satisfying. They also point out that, if you can get the NAD+/NADH ratio high enough you can get it far enough from its electrical mid point to pass electrons "down gradient" to N-1a. At ratios of less than about 3 parts NADH to one part NAD+ the transfer is uphill and isn't going to happen. As they say:

"...the reduction of the *ROS site [they consider that it is probably N-1a] is regulated by the NADH/NAD+ ratio rather than the NADH level (eqns 7 and 8)..."

which sort of takes us back to B3 and some cancer cells which have probably lost N-1a so fail to develop insulin resistance, ie they don't limit their energy generation to their needs. They also develop metastatic aggressiveness in proportion to their elevated NADH:NAD+ ratio (even if they expressed it as a reduced NAD+/NADH ratio!). I wrote that post a while ago, time to check it and hit publish...


BTW Vinogradov pointed out in his review paper that very few labs have the massively expensive and complex gear to look at this sort of redox research and both of the papers discussed here are from groups who know each other, Vinogradov being thanked for reading through the manuscript of the second paper. But I think they are correct.