Tuesday, April 21, 2015

Redox balance, the pentose phosphate pathway, and adrenal function

In my last blog I went over some of the science linking thiamine deficiency to altered adrenal function, dysautonomia, and how that relates to adrenal fatigue and it's symptoms.  In this blog we begin looking at mechanisms by which thiamine impacts adrenal function.  The first mechanism deals with the pentose phosphate pathway as well as the folate cycle.

Cellular redox balance

Before we get in to the specifics of how the pentose phosphate pathway and folate/methylation cycles affect adrenal function, we need to discuss something called redox balance.  Redox reactions involve the passing of electrons between molecules and are normally coupled with one another.  Reduction involves a molecule gaining an electron while oxidation involves a molecule losing an electron.  In order for one molecule to gain an electron, one must give up an electron, hence the pairing. 

You may be familiar with free radicals and antioxidants.  Free radicals are molecules that have an unpaired electron in their outer shell.  This makes them unstable so they "steal" electrons from other molecules.  By stealing an electron, a free radical becomes more stable and is reduced while the other molecule becomes unstable and is oxidized.  Antioxidants donate an electron to free radicals to prevent healthy tissues from becoming oxidized, but when they reduce free radicals they become oxidized and unstable themselves.
Based on the above information, we can call free radicals oxidizing agents and antioxidants reducing agents.  Redox balance refers to the reactive state of the cell.  A cell with a higher percentage of oxidizing agents will favor oxidation while a cell with a higher percentage of reducing agents will favor reduction.   In addition, certain redox pairs exist in different ratios since they function as coenzymes in metabolic pathways.  This is important because many biochemical reactions are dependent on cellular redox balance and this balance will dictate the direction of the pathway as each side of the coenzyme pair causes the reaction to go in a different direction.

Think of it this way.  Often times, when a molecule comes to a metabolic crossroads, it encounters 2 enzymes that will direct it in opposing directions.  Each one of these enzymes is dependent on a cofactor for activation.  If the reduced cofactor is present in higher concentrations, the enzyme dependent on the reduced coenzyme will become active while the one dependent on the oxidized cofactor will be more dormant.  This will direct the molecule down that enzymes pathway and oxidize the cofactor, increasing the chances that the next one of those molecules will go in the other direction.  However, these cofactors are used in so many different reactions that it's possible to "lock" the cellular pathway to favor oxidation or reduction if the redox balance favors one or the other.

The three primary coenzyme redox pairs are FAD/FADH2, NAD+/NADH and NADP+/NADPH; noted as oxidizing agent/reducing agent.  Since cells tend to maintain a very high ratio of NAD+:NADH(Approximately 700 in mammalian tissues), this coezyme pair favors oxidation while the very low NADP+:NADPH ratio in cells(.005) favors reduction.  This allows cells to perform both oxidation and reduction depending on whether the enzyme in the reaction prefers NAD+/NADH as the coenzyme pair or NADP+/NADPH.  In addition, some of these pairs work together as coenzymes, passing electrons between one another.  FAD/FADH2 often work in concert with NADP+/NADPH as cofactors for certain enzymes, many of which are involved in adrenal function. To keep it simple, for the purposes of this blog, we will focus on NADP+/NADPH.  Keep in mind, as mentioned above, that once NADPH is used in a reaction it becomes NADP+, and vice versa.  We use the term redox balance because when one side of the pair goes down the other goes up.

NADPH and cellular redox balance

NADPH is a very interesting molecule.  It's used in cells to provide reducing power to promote anabolic reactions as well as function as an electron donor to glutathione.  Glutathione functions as the primary cellular antioxidant and exists in a reduced (GSH) and oxidized (GSSG) form.  When GSH encounters a free radical, it donates an electron with the help of selenium to stabilize the free radical and becomes GSSG, its oxidized, inactive form.  NADPH, in concert with riboflavin(FAD), then converts GSSG back in to the active GSH.  This process converts NADPH to NADP+.
This cycle occurs over and over again in your cells as they encounter free radicals.  Therefore, a high level of free radicals in the cell will shift the redox balance towards oxidation.  However, as you may notice on the left side of the diagram, we have yet to discuss how NADP+ gets converted back to NADPH so that it can reactivate GSSG to GSH again and promote a more reductive cellular environment.  This is where the pentose phosphate pathway comes in.  The oxidative phase of the pentose phosphate pathway converts NADP+ to NADPH to help maintain a reductive state(More NADPH in relation to NADP+).

The non-oxidative phase supports this process by converting products of the oxidative phase back in to glucose 6-phosphate to create more NADPH via the enzymes transaldolase and thiamine dependent transketolase.  For every molecule of glucose 6-phosphate, the pentose phosphate pathway can create 2 NADPH from NADP+ using only the oxidative phase while using both phases yields 12 NADPH provided there is enough thiamine to maintain transketolase activity.  Keep in mind, when looking at redox balance, this means that the oxidative phase increases the number of NADPH by 2 and also decreases the number of NADP+ by 2 while the non-oxidative branch changes each by 12, a 24 point swing in redox balance in favor of NADPH.

Redox balance, specifically NADP+:NADPH, relates to adrenal function because biosynthesis of glucocorticoids, as well as most steroid hormonse, is dependent on NADPH(1).  This could help explain why thiamine deficiency has such an impact on adrenal function because thiamine, specifically thiamine diphosphate, is necessary to get the full NADPH recharging effect of the pentose phosphate pathway.  Additionally, NADP+ favors the conversion of cortisol to cortisone, a weaker glucorticoid, while NADPH favors the opposite conversion.  A redox balance that favors oxidation in the adrenal glands, therefore, can have a negative impact on adrenal function by creating more cortisone than cortisol.  It's interesting to note that cortisol is also capable of binding to the mineralocorticoid receptor while cortisone is not.  This would negatively impact electrolyte balance by increasing sodium loss in the urine, a common casuative factor in adrenal fatigue symptoms.

While we have focused on the pentose phosphate pathway for NADPH production because it provides the greatest contribution, there are other ways NADPH can be produced.  One newly discovered and very interesting pathway involves the folate cycle, so if you have an MTHFR mutation, you may want to strap in.

Tuesday, April 14, 2015

The importance of addressing thiamine status in adrenal fatigue

In my last blog I discussed the multi-system symptomology of adrenal fatigue and used the analogy of a home heating system to describe how one may address the underlying causes of adrenal fatigue.  The analogy identified 3 components of your home heating system that may be the problem.
  1. The thermostat isn't set properly or doesn't sense the temperature
  2. The ignitor doesn't turn the gas in to heat
  3. The gas flow is off or obstructed
In this analogy, properly setting the thermostat involves changing your lifestyle to address how your brain perceives stress while fixing gas flow is increasing carbohydrate or caloric intake.  Both of these components are important factors to consider and most people do a good job at addressing them.  Addressing the ignitor, on the other hand, is another story.  I would consider addressing the ignitor as addressing nutritional deficiencies.  One nutritional deficiency that has some pretty solid science behind it is thiamine deficiency.  Most people are quick to address vitamin C, magnesium, D3 and other deficiencies with large doses of vitamins or multivitamins while ignoring something that may be as, if not more, important.  Let's take a look how thiamine may play a role in adrenal fatigue.

Thiamine 101

Every living organism on the planet, from bacteria to plants to animals, requires thiamine.  Certain bacteria and plants can synthesize thiamine on their own but animals require thiamine in their diet.  Thiamine is found in a variety of foods including yeast, lean pork, grains, legumes, and certain seeds.  Liver also contains a large amount of thiamine as most animals, including humans, have high stores of thiamine in the liver and red blood cells.

Thiamine is absorbed from the jejunum and ileum from food that is digested or, in some cases, via production by resident gut bacteria.  In fact, of the 3 identified human enterotypes, enterotype 2 has a large proportion of thiamine generating bacteria making hosts with that enterotype less likely to experience thiamine deficiency(1).  There are also bacteria that bind thiamine or create thiaminases, enzymes that degrade thiamine.  Humans absorb a high percentage of low dose thiamine but a gradual decline in the percentage of thiamine absorbed occurs at levels above 5 mg.  Thiamine is absorbed by intestinal cells as thiamine diphosphate but is converted in to free thiamine and released in to the bloodstream.    In the blood, it circulates as free thiamine and only becomes active when it is phosphorylated.  The most active form of thiamine is thiamine diphopshate although it seems thiamine triphosphate has some important, not well defined roles in the nervous system.

Humans store between 25-30mg of thaimine, much less than other animals.  Due to thiamine being a water soluble nutrient, depletion can occur in 14-18 days.  Under deficient thiamine intake, different organs lose thiamine at different rates.  Of utmost importance, the brain and central nervous system hold on to thiamine much longer than other organs.  This is likely due to the brains reliance on oxidative glucose metabolism and the role thiamine dependent enzymes play in that process.  The limbic system, an area of the brain responsible for emotion that also contains the hypothalamus, is typically hit very hard by thiamine deficiency.  It's of interest to note for our purposes that the hypothalamus is the H in the HPA axis. 

Cellular roles of thiamine

Thiamine has several roles in cellular glucose metabolism as it functions as a cofactor for various enzyme complexes.  The pyruvate dehydrogenase(PDH) and alpha ketoglutarate dehydrogenase(a-KGDH) enzyme complexes are important thiamine dependent enzyme complexes that help liberate energy from glucose in the citric acid cycle of mitochondria.  During glycolysis in the cytosol, glucose is converted in to 2 pyruvate molecules that enter the mitochondria.  Inside the mitochondria, pyruvate is converted in to acetyl CoA by the PDH complex so that it can enter the citric acid cycle.  This step requires thiamine diphosphate as a coenzyme.  This is important for 2 reasons.  In neurons, acetyl CoA comes predominantly from glucose and is necessary for the synthesis of the neurotransmitter acetylcholine, which we will cover later.  Secondly, in all cell types, insufficient thiamine decreases PDH activity and lactate accumulates in the cell and pours out in to the circulation.  Blood lactate is known to be elevated in Type 2 diabetics(2) and high blood lactate levels induce insulin resistance in skeletal muscle(3).

The role of a-KGDH in the citric acid cycle is also of importance as this enzyme complex is necessary for the synthesis of the neurotransmitters GABA, glutamate, and aspartate.  Furthermore, the altered glucose metabolism that accompanies a deficiency in the activity of PDH and a-KGDH can lead to mitochondrial damage and eventual cell death(4).

Another area of glucose metabolism where thiamine is important is the pentose phosphate pathway.  The pentose phopshate pathway is an anabolic pathway of glucose metabolism that creates NADPH or R5P based on cellular needs.  For a more thorough look at this process, check out this blog.  Understanding the pentose phosphate pathway is crucial for understanding hormonal balance and how adrenal function can be affected by thiamine deficiency so I urge you to check that blog out.

The thiamine dependent enzyme in the pentose phosphate pathway that's important is called transketolase.  Transketolase allows the products of  the non-oxidative pathway of the pentose phosphate pathway to be recycled in to glycolysis for generation of energy, to be converted in to glucose 6 phosphate to re-enter the oxidative phase of the pentose phosphate pathway to generate NADPH, or it can work in reverse and convert glycolytic intermediates in to ribose 5 phosphate, a necessary component of DNA and RNA.

This diagram shows the function of transketolase, abbreviated as Tkt.  Note how transketolase allows the products of the pentose phosphate pathway to move back in to glycolysis or feed back in to the pentose phosphate pathway.  One could look at it as transketolase preventing metabolic dead ends in the pentose phosphate pathway that aren't really dead ends at all.  Without transketolase, these products may accumulate and enter pathways that lead to glyoxal and methylglyoxal formation that eventually lead to advanced glycations endproducts(AGEs).  Thiamine has been shown to decrease formation of these troublesome substrates(5, 6) and the primary mechanism is through increased transketolase activity(5, 7) re-routing precursors back in to the pentose phosphate pathway and away from glyoxal formation.

Research on thiamine deficiency and adrenal function

Given the ethical challenges that inducing a thiamine deficiency in humans would raise, much of the data on the effect of thiamine deficiency on adrenal function comes from studies in rats.  One study showed that inducing thiamine deficiency in rats led to hyperstimulation of the zona fasciculata of the adrenal glands in 2 weeks causing increased corticosterone output followed by complete exhaustion in 4 weeks(8). Corticosterone is the chief glucocorticoid in rats whereas cortisol fills that role in humans.  While this is obviously an extreme example of thiamine deficiency and its effect on the adrenal gland, it does underscore the importance of thiamine in adrenal function.

Another study in rats found thiamine deficiency elevated corticosterone levels and depressed the aldosterone response to sodium deprivation(9).  Aldosterone is released by the adrenal glands when sodium levels drop, causing the kidney to recycle sodium back in to the bloodstream.  This is interesting because many of the symptoms associated with adrenal fatigue relate to an electrolyte imbalance, specifically a decrease in the sodium:potassium ratio.  A decrease in aldosterone under low sodium intake would induce the same set of symptoms.  Many people with adrenal fatigue notice an improvement in their symptoms with increased salt intake.

A study in humans found thiamine injections prevented functional adrenal gland exhaustion during and after surgical stress(10).  Again, it's hard to extraploate this data to otherwise healthy individuals, but it does show a general effect of thiamine on adrenal gland function.  Other studies in humans, particularly alcoholics, show biochemical lesions in the brain of people who are thiamine deficient.  This is likely due to decreased a-KGDH activity and impaired carbohydrate metabolism(11).  Since these lesions manifest themselves in the limbic system of the brain, they likely have an effect on adrenal function via an altered emotional state as well as damage to the hypothalamus.

It is apparent that thiamine is important for proper adrenal function.  The question now becomes what are the mechanisms by which thiamine deficiency can lead to adrenal dysfunction.  We'll tackle that after the break.

Redox balance, the pentose phosphate pathway, and adrenal function

Thursday, April 2, 2015

The multi-system symptomology of adrenal fatigue: Is thiamine deficiency at play?

People with adrenal fatigue tend to have symptomology that ranges across many body systems.  While these systems likely affect one another due to the fact that they must work in concert with one another to help us adapt to our environment and are controlled by the autonomic nervous system, it's an assumption that one system is throwing the others out of whack.  While this may be true, there is the potential that what we are seeing in adrenal fatigue isn't just one system throwing other systems off, but all systems being thrown off by a deficiency in a nutrient that they all rely on for proper function. 

Dr. Derrick Lonsdale, MD has written many articles on dysautonomia, dysfunction of the autonomic nervous system, which is the defining characteristic of adrenal fatigue.  He points to dysfunction in oxidative carbohydrate metabolism as the primary cause of dysautonomia(1).  He discusses the early stages of beriberi, a disease of thiamine deficiency, as the prototypical example of dysautonomia(2, 3).  His perspective is coming from the Standard America Diet and it's reliance on processed carbohydrate as being causative in thiamine deficiency.

It is interesting to note that beriberi was discovered as being caused by an imbalance between the level of dietary carbohydrate and thiamine.  In 19th century Japan, beriberi was extremely common in the Japanese Navy and the culprit was eventually determined to be diet related.  Rice that has been polished, white rice, is stripped of its thiamine content while leaving the carbohydrate levels intact.  Cadets who had relied solely on white rice were far more likely to experience beriberi than cadets fed a more varied diet.  This led to the discovery of accessory nutrients, aka vitamins, that were necessary for proper cellular metabolism.

It is assumed in modern medicine that the only people who experience thiamine deficiency are alcoholics or the malnourished.  Dr. Lonsdale and his co-workers have published multiple case studies showing thiamine deficiency as a product of micronutrient deficiency brought on by excess processed carbohydrate consumption.  Dr. Lonsdale calls this high calorie malnutrition.  These people are neither alcoholics nor malnourished by macronutrient standards.  Many of these people are told that their symptomns are in their head by their mainstream doctor, and when they are tested for thiamine deficiency by Dr. Lonsdale they are shown to be deficient because a mainstream doctor isn't on the look out for thiamine deficiency.  Thiamine defiency is known to affect the limbic system very hard.  The limbic system is an area of the brain responsible for emotion, adrenaline flow, motivation, long-term memory, and contains the hypothalamus: the H in the HPA axis,.

The symptomology of these case studies closely reflects autonomic dysfunction, similar to the early stages of beriberi(3), and are corrected by increased thiamine intake.  As mentioned above, thiamine needs are known to be dependent on carbohydrate intake, but the question is are they dependent simply on carbohydrate intake or are they also dependent on how much a person relies on oxidative carbohydrate metabolism for their physical activity?

In people on the Standard American Diet, high intake of processed carbohydrate in the absence of adequate thiamine presents as a thiamine deficiency because they are forcing glucose in to their cells which increases their need for the nutrients needed to efficiently oxidize glucose.  While these people may meet the RDA for thiamine, these RDAs were likely determined based on a lower consumption of carbohydrate.  Eating larger doses of carbohydrate with the same level of thiamine may actually reflect deficiency as cells are unable to oxidize the level of carbohydrate contained in the diet.  In addition, higher levels of free radicals brought on by hyperglycemia may require higher thiamine intake to produce NADPH in the pentose phosphate pathway for reduction of these free radicals via reduction of glutathione(We will cover this in the next blog).  Another problem is that people with insulin resistance and type 2 diabetes have dysregulated thiamine status evidenced by a 75% reduction in plasma thiamine levels in comparison to controls(4), most likely due to thiamine loss in the urine.  It's also interesting to note that these people also tend to be sedentary, so muscle stores of thiamine are likely to be fairly low as well.

Participating in intense exercise that relies on these same glycolytic pathways should cause the same problem.  Compounding the issue is that people doing this who also eschew grains and legumes are eliminating 2 of the better sources of thiamine in the diet.  One could probably meet thiamine needs with other food sources, particularly liver, the question is are you?  If a person is already at marginal thiamine status from insulin resistance or random bouts of hyperglycemia and they cut out 2 significant sources of thiamine, deficiency seems likely.  One has to question what would happen if a person with Type 2 diabetes/insulin resistance went from eating the Standard American Diet with already low to marginal thiamine status to cutting out grains and legumes from their diet and exercising intensely.  Sounds like a recipe for autonomic dysfunction, aka adrenal fatigue.

Hopefully this blog has put thaimine on your radar screen, particularly if you plan to undertake a diet such as the Paleo diet, which I hope you do.  A nutrient dense diet that limits processed food is universally considered the optimal human diet.  However, one has to be sure to meet thiamine requirements as well as not overdo the intense exercise portion of the lifestyle right off the bat.  Before you go out to the store and buy regular old thiamine, let me save you the time, if you already have adrenal fatigue it's not going to work.  Don't worry, we'll get to that later.  In the next blog we will look at the science of how thiamine deficiency affects adrenal function.

The importance of addressing thiamine status in adrenal fatigue

Thursday, March 26, 2015

"Adrenal Fatigue", intense exercise and the Paleo diet

Adrenal Fatigue, or the more aptly named HPA axis dysfunction, has seemingly taken the online world by storm.  There are countless support groups, online lifestyle programs, and dietary interventions aimed at preventing adrenal fatigue, but so far we have a fairly limited knowledge of what adrenal fatigue is.  Sure, there is the general notion that as people light the candle at both ends too frequently their autonomic nervous system goes haywire, but what is truly causing it to go haywire?  Are we dealing with a situation where a person's perception of stress has gone wonky, are they exhausting the adrenals to the point they no longer have the raw materials to make cortisol when they experience stress, or is something interfering with the signal?

Honestly, I don't know that everyone experiences the same thing, but looking at biology and the stress response can give us clues to what is considered the most common pathway to adrenal fatigue in the Paleo world: overexercise and nutritional deficiency.  When you look at the symptomology of adrenal fatigue, you get a picture of the systems that are affected:
  • Electrolyte balance
    • Hypotension, dizziness, headaches, frequent urination, cramps
  • Immune system
    • Frequent respiratory infections, prolonged length of infection, parasitic infections
  • Digestive disturbances
    • IBS, loose stools, gas/bloating, parasitic infections
  •  Blood glucose control
    • Low or high blood glucose, irritability, fatigue/low energy
  • Neurological
    • Muscle twitching, heart palpitations/arrythmias, brain fog
  • Hormonal
    • Thyroid issues, sex hormone issues, irritability
While this is merely a small list of the things that people with adrenal fatigue experience, we can use it to look for commonalities between these systems and compare them to some of the things we may expect to see in a person who decides to cut out certain foods from their diet and partake in intense exercise modalities.  This allows us to identify some factors, particularly nutritional, that could be playing a causative role in adrenal fatigue.  Ironically enough, some of these same factors may predispose sedentary over-eaters to the exact same symptoms.

The typical culprit framed for the intense exercise/Paleo diet link to adrenal fatigue is low carbohydrate consumption, but upon further research, I believe other factors related to the type of carbohydrate to be at play.  Many also indicate a link between low carbohydrate intake in general and low thyroid output, but  I don't really feel this link is entirely comprehensive as well.  I do believe carbohydrates, or rather, carbohydrate metabolism, is a central player in this phenomenon.  Where I part ways with this line of thought is when the solution is throwing carbohydrates at the problem.  I believe that merely throwing carbohydrates at the problem can make it much worse if you look at the way cells work.

Understanding cells

Before we move further, it's important to understand how your cells work. All of your cells are constantly interacting with their environment by identifying environmental conditions and performing the biological function that they are programmed to do under those environmental condition via your genes.  For example, when the beta cells in your pancreas identify an increase in blood glucose, they secrete the hormone insulin in to your bloodstream which causes other cells in the body to take in glucose.  Most biological functions occur in this manner, a manner similar to the way the heating system in your house adjusts the temperature.

The thermostat in your house is programmed to the desired temperature and when it senses the temperature drop below that point, it signals your furnace to increase the heat.  An ignitor in your furnace turns on and gas is blown past the ignitor which turns it in to a flame that can distribute heat through the heating duct.  Failure in the system can occur if:
  1. The thermostat doesn't sense the temperature or is improperly programmed
  2. The ignitor fails to turn on, preventing the conversion of fuel to fire
  3. The gas flow doesn't turn on or is obstructed.
This analogy holds for the microscopic physiology of the cell as well as what's happening during adrenal fatigue.  Things like lowering stress, getting better sleep, meditating, and other ways of manipulating lifestyle are, in essence, changing the setting of the thermostat.  Specific enzymes and their cofactors that perform functions within the HPA axis as well as other, related, systems are the ignitor which can be handled with nutritional supplementation.  Finally, the gas flow can be looked at as energy in the system and is most often related to carbohydrate consumption.  While I feel most programs meant to deal with adrenal fatigue take care of resetting the thermostat and increasing gas flow, most fail to address the failed ignitor.

Over-stoking your furnace

While I see no harm and much benefit to changing the setting of the thermostat through meditation, proper exercise, and good stress management, I don't feel the problem is truly being addressed by simply doing these things.  Stress is unavoidable, and it's my opinion that being able to deal with high levels of stress from time to time is important.  I don't feel simply removing all of the stress in one's life is in the best interest of the individual.

On the other side of the equation, simply increasing carbohydrate consumption can be disastrous if not done properly.  There is a lot of clinical evidence supporting this notion and the refeeding syndrome is simply the clinical manifestation of what happens when you increase gas flow in your furnace without addressing the ignitor.  Going back to the furnace analogy, imagine if the heating system in your house kept calling for gas and the gas kept flowing but the ignitor didn't turn on.  Your house would quickly fill up with gas, a far from ideal situation.  In the refeeding syndrome, introducing carbohydrates before all of the nutrients/cofactors needed to utilize carbohydrates properly have been restored leads to symptoms of vitamin deficiency and electrolyte imbalance(1, 2).  In other words, your heating system is filling your house up with gas, not heat.  Bad idea.

A better approach to dealing with this issue is to adjust the thermostat by bringing stress back to a manageable level through lifestyle change, fix the ignitor by replenishing the enzymes and cofactors that are necessary to kick it on, and then gradually increase carbohydrates to a level that is suitable to your activity level.  The first and third parts are easy, but what are the important steps in fixing the ignitor?  The immediate thought is to simply begin supplementing with vitamins and minerals, but it's not as simple as that.  Unfortunately, this is the direction most people go in and progress drags along slowly for several reasons.

First, many of the things you do in everyday life impact nutrient status, and you are going to have to avoid or cut back on some of these things to restart your ignitor.  If you have adrenal fatigue, you are likely avoiding some of these things but may be doing others.  Second, There are multiple steps in getting nutrients in to cells that become an issue.  This includes absorption, maintaining high levels in the bloodstream, and getting them in to your cells.  While there are many nutrients that are important in restarting your ignitor, there is a large amount of scientific evidence linking one specific nutrient to all of the systems mentioned above, and strong evidence that a deficiency in this nutrient quickly induces stage 1, followed by stage 2, adrenal fatigue.  Deficiency in this nutrient is highly dependent on carbohydrate intake, and deficiency can occur both in people who exercise too intensely and don't ingest enough carbohydrates as well as people who eat tons of carbohydrates while living a sedentary lifestyle.  We will cover that nutrient and all of the ins and outs of it, after the jump.

Next Blog

Monday, February 16, 2015

The Pentose Phosphate Pathway: The missing link between hormonal imbalances and carbohydrate metabolism?

I've taken a bit of time away from blogging because I've been swamped with clients and wanted to spend what free time I have reading.  I've come across some very interesting stuff that I believe plays a significant role in hormonal balance that no one is covering so I'll do my best to break it down in to digestible information.

Anabolic carbohydrate metabolism

When people think of carbohydrate metabolism, they immediately think of glycolysis and maybe even the citric acid cycle.  Both of these reactions are catabolic, they are oxidative processes that make ATP through the breakdown of glucose.  However, there is another pathway of glucose metabolism called the pentose phosphate pathway that is anabolic in nature.  The function of the pentose phosphate pathway is to produce reducing equivalents to power anabolic reactions, to produce ribose 5 phosphate(R5P) for the synthesis of DNA, and to help shuffle carbons between sugars so that they can be utilized again.  But why is this important?  Let's take a look.

Anaerobic glycolysis is the breakdown of glucose in the cytosol of cells.  The first step uses ATP to make glucose 6 phosphate(G6P) which can either continue along the pathway of glycolysis to make ATP or be directed through the pentose phosphate pathway to produce reducing equivalents and/or R5P.  The path that G6P takes is ultimately dictated by cellular needs.  To make this uber-confusing I'll post the steps of both pathways below.

It's not really important that you focus on the steps so much as the parallel pathways that glucose metabolism can take based on cellular needs.  Depending on cell type, there are different levels of pentose phosphate pathway activity.  Cells that are exposed to high levels of oxidative stress, that produce hormones, and that have a high turnover rate tend to have more flux through the pentose phosphate pathway.  But why?

The 2 phases of the pentose phosphate pathway

There are 2 phases of the pentose phosphate pathway, an oxidative phase and a non-oxidative phase, both shown below.

The oxidative phase of the pentose phosphate pathway

The oxidative phase reduces 2 nicotinamide adenine dinucleuotide phosphates (NADP+) to 2 NADPH, the reduced form.  This is important for 2 reasons.  First, NADPH is needed to convert oxidized glutathione to its reduced form.  Everyone and their mother who is trying to optimize health is likely taking some form of supplement or eating foods that promote glutathione production.  Glutathione is known as the master antioxidant as it goes around donating electrons to free radicals before they can react with cellular structures.  The problem is, once glutathione does this it's converted to its oxidized form which can no longer donate electrons.  In this form, glutathione is essentially worthless until NADPH reduces it back to the active form.  This converts NADPH back to NADP+ where the oxidative phase of the pentose phosphate pathway can swing back in and produce more NADPH.  For this reason, any cell that is subject to high levels of oxidative stress such as red blood cells and liver cells has a very active pentose phopshate pathway.  The figure below illustrates the process by which NADPH reduces oxidized glutathione.

Note that selenium is needed in order for glutathione to reduce free radicals and NADPH and riboflavin are needed to reduce oxidized glutathione back to its active form.  Without NADPH, glutathione remains inactive, something you most certainly do not want.  The pentose phosphate pathway is the primary way in which our cells make NADPH for this purpose.

In addition, cells of the immune system used NADPH to kill foreign pathogens through a process called the respiratory burst.  A decrease in the ratio of NADPH:NADP+ ratio will compromise the immune system and provide an environment where pathogens can evade killing by phagocytosis.

The next reason that the oxidative phase is important is because reducing power is needed for all anabolic processes.  This includes the biosynthesis of hormones, so there are high levels of pentose phosphate activity in the adrenal and sex glands.  With insufficient reducing power in the form of NADPH, hormonal balance can be thrown out of whack.  This includes the adrenal and sex hormones as well as the the thyroid, but for a different reason.  Several reversible hormonal conversions are dependent on the ratio of NADPH to NADP+ including:

                                                    DHEA                     <---->  Androstenediol
                                                    Androstenedione   <---->  Testosterone
                                                    Estrone                   <---->  Estradiol
                                                    Cortisone               <---->  Cortisol

NADPH causes the conversions to go from left to right while NADP+ causes them to go from right to left.  So what does this mean?  NADPH will convert androstenedione to testosterone while NADP+ will convert testosterone to androstenedione.  In other words, reduced flux through the oxidative arm of the pentose phosphate pathway will negatively impact testosterone levels in men because there will be more NADP+ than NADPH which favors androstenedione over testosterone.

I am not expert on women's hormonal issues, but given the fact that estrone is the predominant form of estrogen in postmenopausal women while estradiol is the predominant form in women of reproductive age, I'll go out on a limb and say this conversion is likely detrimental.

On the adrenal side of things, reduced flux through the oxidative arm of the pentose phosphate pathway will negatively impact cortisol levels by favoring cortisone production.  Since cortisol has greater glucocorticoid activity and cortisone has no mineralocorticoid activity, this can have a pretty significant effect on glucose levels, inflammation, and electrolyte balance.

Since these hormonal conversions occur in the endoplasmic reticulum(ER) of cells, the ratio of NADPH:NADP+ within the ER can have a pretty significant effect on hormonal balance.  Reduced flux through the pentose phosphate pathway and high levels of oxidative stress are 2 factors that can decrease this ratio leading to poor hormonal balance.

With the thyroid, the proposed mechanism by which reduced flux through the oxidative arm of the pentose phosphate pathway may negatively impact hormone production is through a reduction in glutathione function.  The thyroid relies on hydrogen peroxide, a free radical, for thyroid hormone synthesis.  Without sufficient levels of reduced glutathione to keep this in check, the thyroid can become damaged, inflamed, and thyroid function can become compromised.

The non-oxidative phase of the pentose phosphate pathway

The non-oxidative arm of the pentose phosphate pathway is also important, especially in tissues with high rates of cell turnover.  The non-oxidative arm of the pentose phosphate pathway essentially interconverts sugars in to different forms.  One of those sugars, R5P, is necessary for DNA production. Cells with high turnover rates such as epithelial cells in the gut are dependent on sufficient flux through the non-oxidative arm to produce enough DNA for replication.  The non-oxidative arm also gives the pentose phosphate pathway flexibility.  By interconverting sugars, the non-oxidative arm can create sugars that can re-enter glycolysis to generate pyruvate or feed back in to the oxidative arm to create more NADPH.

The non-oxidative arm allows the pentose phosphate pathway and glycolytic pathways to work synergistically to meet cell needs.  There are essentially 4 modes of pentose phosphate pathway activity that can be used to increase energy levels, increase reducing power, provide building blocks for DNA, or a combination of these functions.

Figure 20.24. Four Modes of the Pentose Phosphate Pathway.  
The yield of each mode is:

Mode 1-6 G6P makes 5 R5P
Mode 2-1 G6P makes 1 R5P and 2 NADPH
Mode 3 -1 G6P makes 12 NADPH
Mode 4-3 G6P make 6 NADPH, 8 ATP, & 5 pyruvate and NADH which can be used to create more ATP

As you can see, carbohydrate metabolism is a lot more than simply breaking down glucose to use for energy.  Carbohydrate metabolism also has anabolic effects via the pentose phosphate pathway.  Decreased flux through the pentose phosphate pathway can increase oxidative stress and negatively impact hormonal balance and cellular reproduction.  There is compelling scientific evidence that altered flux through the pentose phosphate pathway may be at the root of adrenal dysfunction, increased inflammation, and some gut pathologies including SIBO.  In addition, many metabolic consequences of Type 2 diabetes can alter flux through the pentose phosphate pathway and there are many blood markers we see in Type 2 diabetes that indicate this.  If there is enough demand I may pull some of that stuff out, so read, like, and share.

Thursday, November 20, 2014

Why your crash diet last New years set you up for this years failure

It's that time of year again.  It's the time of year where people say, "Screw it, I'll get back on the wagon after New Years!"  This statement is followed by unfettered food consumption and little to no physical activity for 6 weeks followed by a crash diet and Tasmanian Devil levels of physical activity to work off what was put on over the holidays, not to mention the other 5 lbs you gained prior to the binge.  What people fail to realize is that their failure was sealed long before they decided to throw caution to the wind and see how many holiday cookies they could eat without getting up on Thanksgiving day.

It's should come as no surprise to anyone that as we get older, our metabolism slows down.  What may come as a surprise to most people, if not all, is that research shows that the crash diet you participated in last year probably jeopardized your chance at success this year.  Hormones controlling everything from appetite to how much energy you burn take a hit from low calorie dieting, and the negative effect 10 weeks of low calorie dieting has on many of these hormones persists for a year or more(1).

This is one of the many reasons I tell people to stay away from anything like the Isagenix or Medifast programs, short-term results for long-term failure.  If you are wondering how I jumped from a low calorie diet to either one of these programs, it's because the low calorie diet in the study above used essentially the same program, Optifast.  They all follow the same template, consume 3-5 of our supplements per day, eat little to no food, and watch the fat melt away.  What's even more disappointing is that these programs often tout that they are perfectly healthy since they provide 100% of the RDI(Reference daily intake) for micronutrients while also creating a caloric deficit.  This may not be the case.

A small study looking at serum and intracellular micronutrient levels in obese people losing weight on the Optifast system paints a starkly different picture.  The study followed obese people after following the Optifast 52 plan for 3 months and through 26 weeks of follow-up.  It's not surprising that the diet of the participants before the study did not meet the RDI for several micronutrients and many were, therefore, found to have insufficient serum and intracellular levels of multiple micronutrients.  What is surprising is that after 3 months of low calorie dieting with shakes that did meet or exceed the RDI of all essential micronutrients, more of the subjects experienced micronutrient deficiencies and some of the micronutrient deficiencies grew worse, particularly Vitamin C, selenium, iron, zinc, and lycopene(2).  That doesn't seem very healthy to me.
Some of this can be explained by increased nutrient demand due to weight loss.  However, if scientists are a little fuzzy on the micronutrient needs of people participating in a weight loss program, how well read up do you think the person who sold you this product is on the topic?  Keep in mind Optifast is only administered by "qualified healthcare providers", which is basically code for someone with an MD who knows nothing about diet.  Do you really think the guy at the gym who is schlepping this stuff to you based solely on his personal experience with it has any idea if it's healthy for you?

Interestingly, the participants in the second study who were able to maintain the fat loss through follow up were able to improve these deficiencies as they began eating real food.  If they were able to maintain the weight loss eating real food, why not just start there and not risk long term hormonal dsyregulation due to the low calorie diet?  The first study we looked at showed this altered hormonal state lasts a year and, unfortunately, follow up in this study only lasted 26 weeks.  Who knows if that weight loss was maintained or not?  Maybe this holiday season would be better spent with sane levels of holiday food consumption and high levels of physical activity followed by a nutritious whole food diet at a slight caloric deficit and intelligently programmed exercise?

Thursday, November 13, 2014

Fibrolmyaglia and Non-celiac Gluten Sensitivity: Two peas in a pod?

Some newer research looking at remission in fibromyalgia recently caught my eye for a few reasons.  First, I worked on a clinical trial in fibromyalgia at the University of Pennsylvania a few years back and formed several opinions on what I thought may be predisposing factors to the syndrome.  Second, over the course of the last few years I have expanded my knowledge on gut health and gut bacteria to the point where I keep coming back to my thoughts on fibromyalgia and many of the things I thought were potential contributing factors.  This new study renewed my interest because it may be shedding light on potential lifestyle modifications that can send fibromyalgia in to remission.

Before I go in depth in to the research, I have to point out that you really cannot make very many hard scientific conclusions based on this information.  For one, this data is merely a short communication pinpointing clinical findings of the use of a gluten free diet in people with fibromyalgia.  Secondly, this wasn't a random sample of people with fibromyalgia.  These people were selected based on certain criteria, specifically that they did not have Celiac disease, they had intraepithelial lymphocytosis, and their symptoms improved on a gluten free diet.  While this very specific set of symptoms makes it hard to generalize these results to everyone with fibromyalgia, they honestly make this data far more interesting.

In Fibromyalgia and non-celiac gluten sensitivity: a description with remission of fibromyalgia, physicians in Madrid, Spain chronicle their success at putting patients with fibromyalgia in to remission with a gluten free diet.  The study followed 20 patients who met the above criteria of the study and who were willing to try a gluten free diet.  The results found all patients had improvement in their pain with 15 of the 20 patients having complete remission of their pain.  Fatigue, depression, migraines and GI symptoms all improved with pain and 2 people with psoriatic arthritis and spondylarthritis, 2 autoimmune conditions, saw remission of those conditions as well.

This data is interesting or a few reasons.  First, all but one of the patients had some sort of digestive tract abnormality/issue, and the patient who didn't was the patient who had been diagnosed with fibromyalgia for the shortest period of time(3 years).  Indigestion, IBS, constipation, and GERD were the most commonly reported digestive issues.  Oral aphthae was also an interesting finding in 2 of the patients.  Oral aphthae is essentially recurrent canker sores in the mouth.  I've always thought this condition was a barometer of total GI health, and the presence of immune cells in the intestine provide support for this notion.

Next, none of the patients had villous atrophy, a flattening of the villi associated with Celiac disease, but all had intraepithelial lymphocytosis.  This isn't a finding because this was part of the inclusion criteria, but it provides significant evidence for the existence of non-celiac gluten sensitivity.  Intraepithelial lymphocytosis essentially means something is triggering intestinal inflammation, but it cannot be assumed that gluten is the specific cause just because there is inflammation.  Resolution of the problem via a gluten free diet and re-occurence of symptoms in 7 people who reintroduced gluten indicate gluten may be one of, if not the causative factor.  The picture below illustrates the stages of progression from normal small intestinal tissue to the damaged villi seen in Celiac disease.

Notice how the normal tissue on the left has projections, called villi, that erode over time in to flat tissue.  This is villous atrophy and is caused by intraepithelial lymphocytosis, which is illustrated by the little black dots that slowly infiltrate the intestinal tissue gradually from left to right.  As the villi become flattened, a person's ability to absorb nutrients is decreased and they may eventually become deficient in one or several nutrients.  In addition, inflammation can dump in to the circulation and cause problems elsewhere in the body.  This is where it gets interesting.

For the most part, it has always been assumed that forming antibodies to something called tissue transglutaminase has been the cause of problems outside of the gut due to ingestion of gluten.  In Celiac disease, it is believed that tissue transglutaminase binds with gluten and the immune system recognizes this complex as foreign.  From there it has been assumed that the immune system mistakes other body tissues as foreign because tissue transglutaminase is found in every cell in the body, but the patients in this study were not forming antibodies to tissue transglutaminase.  Therefore, this data does not support the notion that antibodies to tissue transglutaminase is the issue in fibromyalgia, at least not in those who fit the inclusion criteria in this study.  So what could be causing the pain?

Interestingly enough, inflammation is known to induce the release of something called nerve growth factor.  Nerve growth factor(NGF) has many functions in the body, in response to inflammation that role is to attempt to reduce it under certain circumstances.  NGF is produced locally in tissues but can also be produced by cells of the GI tract and may circulate throughout the body to help maintain homeostasis(1).  However, continually assaulting the body with a food that increases inflammation, in this case gluten, will cause more (NGF) to be produced.

Another one of NGFs functions is that it increases pain sensitivity both acutely and chronically in an inflammatory state(2, 3, 4) and administration of anti-NGF drugs reverses this increased sensitivity rapidly(5, 6).  Notably, the biggest finding in this short communication is that removal of gluten from the diet of these patients reduced or eliminated their widespread pain.  Below is an illustration of the tender points known to be extremely sensitive to touch in people with fibromyalgia.

People with fibromyalgia have an extreme sensitivity to touch in these areas, the slightest brush to the area can cause tremendous pain.  In the study I was part of, we directly measured the amount of pressure with a dolorimeter and the difference in pain tolerance between someone with fibromyalgia and someone without it is pretty striking.  However, these areas tend to be tender for most people indicating that they may have a greater supply of nerve endings than the surrounding tissue.  Fascia, a body-wide matrix of connective tissue that runs throughout muscle tissue, is richly innervated with pain receptors.  Therefore, it is tempting to hypothesize that the fascia may be involved in the widespread pain associated with fibromyalgia.  A recent study found pain receptors in the fascia to be highly prone to the pain sensitizing effects of NGF, and that effect lasted up to 2 weeks(7).

When I worked on the AT101 clinical study on fibromyalgia at UPENN, researchers elsewhere were looking at levels of something called Substance P in the cerebrospinal fluid of people with fibromyalgia as a way to diagnose the syndrome as it is elevated in patients with fibromyalgia.  In an interesting twist of fate, Substance P levels in cerebrospinal fluid appear to be tied to cerebrospinal NGF levels and cerebrospinal NGF levels have been shown to be 4x higher in people with primary fibromyalgia than in healthy controls and 2x higher than people with other pain conditions(8).

I have yet to find anything on how blood levels of NGF relate to levels of NGF in cerebrospinal fluid, and NGF appears to play a dual role in inflammation, acting as pro-inflammatory or anti-inflammatory depending on the situation.  However, in LPS induced sepsis, NGF appears to have a pro-inflammatory role(9) and this state is similar to what one would experience in non-celiac gluten sensitivity with bacteria from inside the intestine leaking in to the bloodstream due to a leaky gut.  Whether NGF functions as pro- or anti-inflammatory is irrelevant, however, since an increase in NGF that accompanies inflammation likely induces increased sensitivity to pain, the hallmark of fibromyalgia.

I would love to go more in depth with the science aspect in this blog, but it gets rather dry.  The take-home message is that a gluten free diet is a potential therapeutic approach that most people with fibromyalgia likely don't use to their advantage.  Even in those who have tried it, the results are variable and can take some time.  I've worked with people to eliminate gluten and it's hard enough to get them to go without it for a week, let alone for several months.

In the short communication discussed in this blog, some patients saw quick relief over the course of a few months while others took much longer and the results came along much more slowly.  I have a feeling this may have had to do with how damaged their GI tract was as well as how strictly they followed the diet or whether they ate foods that may have cross-reactivity with gluten or that the person is reacting to separately.  Even a small dose of gluten can be problematic for someone who is reacting to it, and a diet containing something the body senses as foreign with a structure similar to gluten, such as oats or eggs, can have the same effect as eating gluten itself.  For more on gluten cross-reactivity go here.  A study looking at a gluten free diet found persistent intraepithelial lymphocytosis in people with Celiac disease despite a long term gluten free diet.  The offending nutrient was oats(10), which do not contain the problematic proteins associated with wheat and barley. Cross-contamination may be a potential contributing factor in this study.

Another confounding dietary issue could be the presence of small intestinal bacterial overgrowth, or SIBO.  A recent study found that 100% of the people enrolled in the study(42 out of 42) who had fibromyalgia also had SIBO(11).  We do not know if this is cause or effect, but eating a reduced FODMAP diet is likely a good idea to help normalize the gastrointestinal flora as SIBO can induce intestinal inflammation.  Finally, consumption of foods that contain or cause the release of histamine may be problematic due to the inflammatory effects of histamine..  For more information on histamine, check out this blog.

Now, to the bottom line.  If you have fibromyalgia, the autoimmune paleo protocol low in FODMAPs and histamine containing and releasing foods is likely the best dietary protocol to help calm down the immune activation in the gut.  Below are a couple of links to foods that fit the FODMAP and histamine criteria.  After a couple of weeks the hope is that the pain sensitizing effects of NGF will wear off, but it wouldn't surprise me if results took longer.  There are other strategies that have to do with exercise, stretching and physical activity that would speed up the process, but we'll save that blog for another day.

A final interesting note on this study.  The predominant theory is that once an autoimmune process starts, it will continue throughout life if the environmental trigger is reintroduced.  In other words, it would mean lifelong elimination of gluten from the diet.  However, this study does not support fibromyalgia as a classic autoimmune disease in that antibodies are not being produced, at least not to tissue transglutaminase.  In theory, this means that once the gut is healed, a person may be able to eat gluten in sane quantities provided their gut is healthy and the majority of their diet is centered on maintaining a healthy gut.  This would mean that once their gut is healed, it would be beneficial to gradually increase FODMAPs and other types of fiber to promote a more acidic GI tract and to limit inflammation, once the SIBO is cleared.  However, there is the potential that people with fibromyalgia are forming different antibodies when they ingest gluten, but I don't imagine the science will pick up on that for quite some time.

Histamine in foods

Foods low in FODMAPS