Hyperlipid by Petro Dobromylskyj
25 May 2020You need to get calories from somewhere, should it be from carbohydrate or fat?
I thought I would just take a break from trying to simplify the Protons electron transport chain as regards ultra low fat diets and talk about sensitivity and specificity of serology tests for a break.
People may have noticed I'm quite keen on serology and am rather less than enthusiastic about PCR for test, track and trace in a situation where the SARS-CoV-2 virus is present throughout the country, as it is here in the UK. Stupid is as stupid does.
However, serology is not quite as straight forward as I might like either.
There are a number of serology tests coming on to the market, and many have a 100% sensitivity and 98% specificity. It difficult to express how phenomenally accurate these test are. If I submit a blood sample for some routine analysis I accept that 95% for these sorts of accuracy assessments is pretty good, we're dealing with biological systems, there is room for grey zones.
So presently serology has a 100% sensitivity. That means it will always pick up seropositive people. If you have antibodies, this test will find them. Always. Getting a negative needs some thought.
This is addressed by specificity. A 98% specificity means that a negative on the test will be correct 98 times out of 100. If the test says you don't have antibodies, it is also most likely correct, a one in fifty error rate there.
It is difficult to over emphasise quite how good these values for sensitivity and specificity are for a lab test. They are very, very good.
At detecting antibodies.
If antibodies are found in a healthy person it is, with a test this good, pretty well certain that they have been exposed to the disease and, in the absence of illness, that they are immune. Or at least they were at the time of exposure.
Sadly human immune systems can be recalcitrant in cooperating with serology.
The Royal College of Pathologists short presentation on serology is now up on Youtube
The COVID 19 pandemic: testing – serological diagnostics for COVID 19
and here is a screenshot from just after 18 minutes in:
The dotted red line is the lower limit of the serology assay used. All of the patients have had known, absolutely certain, clinical disease. If you use a serology test which is 100% sensitive and 98% specific, you will pick up everyone over the red dashed line. A negative result will be correct 98% of the time. That is what a highly sensitive, highly specific test does. To put that in a more visually clear image here is another screenshot:
Again, below the red dotted line you will be classified as seronegative, you are seronegative. That does not mean that you have not been exposed. It doesn't matter how good your test is. The test cannot see below the red line, above the red line the test is phenomenal. This not a problem with the test, the test is not for exposure/recovery from the disease. It is just for antibodies above a certain level. This is the limit of serology testing, it is undermined by the ability to recover from this infection without seroconverting. It happens, it's on the graphs. It's not the test's fault.
To a large extent recovery without seroconversion suggest that the innate immune system is at work (or you are simply unable to become infected) and that would fit nicely with the reports suggesting that hyperglycaemia over 10mmol/l is bad news and hyperglycaemia below 10mmol/l gives a slightly better outlook in severely ill patients. Hyperglycaemia is a good way of suppressing the innate immune system.
Passthecream put an interesting link in the comments of the last serology post which suggests the innate immune system is also adaptive, it remembers, no antibodies needed...
Adaptation in the Innate Immune System and Heterologous Innate Immunity
Sadly, at our rudimentary level of understanding of the immune system, we are in no position to assess whether a given person might be seronegative but still immune.
Having said all of this, it's worth remembering that being seropositive without having being ill suggests you are immune. It's interesting to see the WHO position on this. The WHO currently suggests that there is no evidence that having antibodies confers immunity.
That is interesting and absolutely, currently, technically correct. Thus far seropositive people have never been challenge-tested with virulent virus, so there can be no evidence that antibodies are protective (try getting that one through ethics committee review!). It is theoretically possible that a person could have been exposed to virulent virus, have never been ill, have developed antibodies, and yet is still be susceptible to the virus. You can imagine that this might be the case.
Well, actually, I can't.
So, if you are the head of an ITU in a UK district general hospital in London and you find you are one of those lucky people who are solidly IgG seropositive without ever having been ill, what would you do as regards PPE for yourself?
As the WHO says, there is no evidence that being seropositive is protective, as yet. But for antibodies produced in vivo, by someone who was never unwell, for these antibodies not to be protective would have to be a first of a kind as regards immunology (vaccine induced seropositivity is a whole different ball game).
I love this guy:
COVID-19: ICU care, long-term effects and immunity with Dr Richard Breeze
(Hat tip to Unknown for the link and no, Breeze didn't use any PPE while treating the large wave of COVID-19 patients which passed through Lewisham District General Hospital's upgraded ITU)
Knowledge over protocol. He also strikes me as the sort of person who might look at a patient on a ventilator who was developing barotrauma because "protocol" suggest "Xml/kg" as the "correct" tidal volume setting and who might reach over and reduce (gasp) the tidal volume setting. Just my guess. Or avoid intubated ventilation if at all possible (which was what they did).
You have to contrast this with the hospital managers who discharged SARS-CoV-2 positive patients in to unprotected nursing homes because "it's protocol".
I get the impression that good medics (and there are some excellent ones out there) don't seem to be the sort of people that become the politico-medics who guide the government...
Aside: I just can't get over Dr Breeze working without PPE. Sort of thing I might have done under the circumstances. I can't believe it was allowed nowadays!
For your enjoyment I have simplified this graph from
Hyperinsulinemia Drives Diet-Induced Obesity Independently of Brain Insulin Production
out of Jim Johnson's lab:
down to this graph (at great effort) to show only the mice on standard chow:
These are the insulin responses to an IP glucose tolerance test at a year of age in mice which have been fed on good quality chow all of their lives. The mice in the top curve are phenotypically normal in their insulin response to glucose, the mice in the lower curve have had three out of four of their insulin genes knocked out. They weigh the same.
We all know from the Surwit posts that the normal insulin exposure mice have an 11% decrease in median lifespan compared to low insulin exposed mice, Jim Johnson's lab again.
None of us is in a position to have our insulin genes partially silenced from before birth, but we do have a choice as to how much insulin we expose ourselves to, based on our dietary choices.
What we need to know is what the insulin response to a given meal might be if we were to try to imitate the partial insulin gene knockout mice. Very few studies have provided this sort of information but the current pre print from Hall et al does just this. Here is the graph
The red curve is from a group of people fed a single meal of a mildly ketogenic diet. With insulin peaking between 20 and 30micoU/ml this is quite similar to the value in mice with reduced insulin gene load, those pan out at around the 22microU/ml mark (don't you wish everyone just used picomoles all the time? Well, I do). Or you can eat low fat, plant based and choose to expose yourself to over 100microU/ml of insulin. Doing this you might still lose a little weight (another post, eventually), you might lose a little fat but you also might lose a few years of lifespan as the insulin drives ageing with its associated chronic diseases.
How many years? If the median lifespan for humans is around 70-80 years and we are talking about an 11% reduction that gives us a ballpark of just under a decade lost. As a thought experiment.
PBLF, plant based low fat. ABLC, animal based low carbohydrate.
There is no choice.
Total aside: I really hope that Hall keeps the title of this paper unchanged in the version which eventually gets published. It's a single sentence of prose which encapsulates what is wrong with nutrition research. It is absolutely, totally factually accurate, while being completely selective in its choice of factual content to give an absolutely misleading impression. As a declaration of bias it is unbeatable. I love it.
I guess everyone knows about this pre-print
A plant-based, low-fat diet decreases ad libitum energy intake compared to an animal-based, ketogenic diet: An inpatient randomized controlled trial
There is a wealth of data to enjoy and a lot to say from the Protons and insulin point of view but just a brief look gives us equal weight loss, equal fat loss and the sort of changes in fat free mass you would expect from likely shifts in glycogen and its associated water:
Clearly the extra 600kcal eaten under ketogenic conditions did nothing to blunt fat loss, much as we would expect from the low carb perspective. The extra calories did not evaporate, they were lost through increased energy expenditure, especially during sleep and while sedentary:
These people have uncoupled metabolism during the period of eating the ketogenic diet, they generate heat. As measured within the limits of indirect calorimetry. You could argue about a greater faecal, urinary or breath mediated loss of calories too but that's less important than a measured equivalent weight loss despite higher, extremely accurately measured caloric intake.
That's all pretty boring.
What is really, really interesting is the equivalent spontaneous weight loss under the period of high carbohydrate intake. Over the years I've looked at the carbosis vs ketosis for potential mechanisms and this study may go some way to clarifying what is going on. The very low fat eating certainly does not limit the penetration of either glucose nor insulin past the liver. Both spike systemically after every meal. But still there is spontaneous weight loss due to a suppressed appetite.
Under low fat eating less "waste" heat is generated, metabolism is coupled. Tightly coupled metabolism means people needed less calories. The subjects, under very low fat eating, lost weight without any biochemical markers of inadequate calories. Just as they did under ketogenic eating.
That's really interesting. With data, lots of it including important things like the effect of a typical meal on blood glucose, insulin and lactate. Plenty to work with. Needs a lot of thinking about.
BTW does this sound like a metabolic advantage to ketogenic eating? Rhetorical question, 24h energy expenditure combined with utterly accurate food intake measurements tells us something...
Just a one liner-ish type post.
I had the privilege of listening-in to one of the weekly Royal College of Pathologist webinars on the SARS-CoV-2 virus, this one on serology testing. These webinars are really fantastic, they are given as a 15 minute presentation by a scientist at the top of their field, in the complete absence of political interference or the sort of financial pressures applied to produce a 100% specific, 98% sensitive serology test to make billions of dollars for a commercial company. They have spent their careers as coronavirus "enthusiasts". The presentations are by pathologists, for pathologists. They are technical and utterly honest (as far as I can tell).
So. There are three types of people in the world. If you have had SARS-CoV-2, confirmed by PCR, have been seriously unwell, hospitalised, needed supplementary oxygen and been considered for a respirator/ITU admission then the chances are good that you will be solidly seropositive for SARS-CoV-2 on a blood sample in recovery. I would suggest that your medical history might be quite a big hint in this direction, which might render the use of the serology test under these circumstances somewhat superfluous.
The second type of person has also had SARS-CoV-2, confirmed by PCR test, been clearly unwell but not so unwell as to need any hospital admission for management. With the best possible testing using multiple different antibodies and different test techniques these people are very, very difficult to detect on a serology basis. Many will be negative on serology within the limits of what we have available now and what will be developed commercially. That is worth thinking about.
The third type of person has never been ill, has never been PCR tested, has no idea whether they have been exposed to SARS-CoV-2 or not. These are the apparently healthy population, the sort of people John Ioannidis sampled in Santa Clara County.
Of the 3300 people Ioannidis tested, 2.5-4.2% turned out to be sero-positive. Listening to the RCPath webinar on the problems of serology testing in mildly unwell people (let alone those apparently never unwell) this implies that the values from Ioannidis might well be the absolute, rock bottom, tip of the iceberg minimum. Exposure has probably been much, much higher in this still healthy population.
I find that rather hopeful.
It is difficult to describe how badly I feel that the COVID-19 pandemic has been managed here in the UK. I don't make political posts on the blog (or anywhere else) but the level of utter incompetence of our current government is breathtaking. I suppose a different administration could have done worse, but that's hard to imagine.
TLDR: A "healthy", complex carbohydrate, low glycaemic index diet appears to markedly shorten the median lifespan of mice when compared to a diet of maltodextrin/sucrose with hydrogenated coconut oil, irrespective of obesity or insulin gene dose.
This is the second excellent paper from Jim Johnson's lab:
Reduced Circulating Insulin Enhances Insulin Sensitivity in Old Mice and Extends Lifespan
It is slightly different from the 2012 paper as these mice are full knockout for the Ins1 gene and this time it is the Ins2 gene that is present as a full complement or at half knockout, to adjust the insulin gene dosage.
The study was never intended to compare the two diets, the diets were simply intended to provide a fairly normal insulin environment using a rodent chow against an high insulin environment generated by a Surwit type diet. It was the insulin exposure which was the focus of the study.
But, ultimately, the study did compare the two diets and in some detail.
Just to summarise the diets. Both had 4% of calories as PUFA, primarily linoleic acid. The 5LJ5 chow used a slow release carbohydrate (as uncooked ground wheat) combined with a little extra protein from soybean meal. The D12330 (Surwit type) diet was the usual hydrogenated coconut oil with maltodextrin/sucrose plus casein as the sole protein source.
Maximum individual longevities came out as expected, with the 5LJ5 coming out best and the low insulin gene dose conferring benefit to both diets.
These are the mean lifespans of the four longest lived mice in each group (top decile) as shown by the open circles/squares on the bar chart, taken from the end stage of the survival curves as shown here:
That's relatively unexciting and no one would be surprised by it.
What surprised me was the longevity advantage to the Surwit diet groups when assessed at median life span. Not only did the Surwit groups both do a great deal better than the chow groups at median lifespan but there was only a very small improvement (about 3%) obtained by reducing insulin exposure. In fact the normal gene-dose, obese, high insulin-exposure Surwit diet group (purple) had a longer median lifespan compared to the reduced insulin-exposure group that was on chow. Which was better again than that of the ordinary mice fed on chow.
If we simply ignore the reduced insulin exposure groups we can also suggest, based on these data, that the unmodified Surwit diet produces a median longevity gain in the order of 16% over a top-of-the-range excellently formulated lab animal breeding chow.
If the Surwit diet was a drug it would knock spots off of metformin, rapamycin, ethanol, caffeine or glucosamine for median lifespan extension. These mostly gain around 10% in median life span extension.
I accept that, for the four mice which made it in to extreme old age, there is a small disadvantage to the Surwit diet, but this only becomes apparent at those lifespans at over 750 days of age, out of a max of just over 900 days.
A quick look round the literature shows us that feeding a 60% fat diet where the PUFA content comes out at around 15% of total calories (high PUFA lard as the fat source), combined with Surwit-like levels of maltodextrin/sucrose, is a catastrophe. As in this one using TD.06414.
At the risk of speculating; there may be a host of problems triggered by a wheat/soybean based diet which do not appear to occur with a casein/saturated fat based diet, certainly until extreme old age is achieved. Or there could be some specific advantage to a highly saturated fat based diet which over rides the problems provided by maltodextrin/sucrose. Lots of possibilities, no obvious answers!