Acid/Alkaline Balance and Muscle/Protein Optimization – Is There a Relationship Between the Two?

In the previous five newsletters three have been about the health risk of low grade, chronic metabolic acidosis, primarily related to a low potassium/high acid-based diet and two have been about the importance of muscle and dietary protein optimization.  While, in these newsletters, I was writing about the subjects in isolation, is there, in fact, a relationship between the two?  This question occurred to me as I was reading the recently published paper “Alkalinization with potassium bicarbonate improves glutathione status and protein kinetics in young volunteers during 21-day bed rest” by Biolo et al (1), which I will review shortly.  However, the topic of the relationship between protein/muscle status and acid/alkaline balance was so interesting to me that I decided to do a literature search and see if I could find additional publications on the subject.  Fortunately, to my delight, I found several other papers, many of which I am going to also review in this forum.

MUSCLE, PROTEIN, AND ACID/ALKALINE BALANCE – AN OVERVIEW

Where I would like to begin is with the overview paper “Control of muscle protein kinetics by acid-base balance” by Caso and Garlick (2).  The first quote I would like to feature strongly suggests that acidosis has a very negative impact on protein status:

“Acidosis has been shown to have a detrimental impact on body protein metabolism and to promote negative nitrogen balance, protein wasting, loss of body weight and stunted growth.”

What is the mechanism of this impact?  The authors continue:

“Acidosis can…induce protein wasting by inhibiting protein synthesis, stimulating protein degradation or by promoting a combination of the two processes.”

In addition:

“The results have consistently shown that metabolic acidosis stimulates the degradation of whole-body protein and promotes amino acid oxidation.”

As a result, as you might expect, loss of muscle mass is an inevitable outcome:

“Accelerated protein degradation is therefore an important contributor to muscle wasting in conditions associated with acidosis.”

What is the actual cellular mechanism that leads to loss of protein with acidosis?  It is a mechanism I have discussed in previous newsletters in relation to loss of muscle mass with sarcopenia, activation of what is known as the ubiquitin-proteosome pathway:

“The effects on protein degradation have been shown to result from a stimulation of the ATP-dependent ubiquitin-proteasome pathway – one of the major enzyme systems for proteolysis – by acidosis.  Stimulation of proteolysis by acidosis is associated with activation of the ubiquitin-proteosome pathway at the transcriptional level and appears to be dependent on the concomitant presence of glucocorticoid hormones, which may represent important mediators of the proteolytic response.”

Before continuing, please note again the last sentence of the above quote that mentions “glucocorticoid hormones.”  As I have discussed so often in past newsletters and lectures in relation to chronic illness and allostatic load principles, metabolic stressors, in actuality, never act in isolation.  Rather, there are systems-based interactions where, in this case, metabolic acidosis is a stressful situation, which leads to increased production of cortisol, which, in turn, leads to increased acidosis and loss of protein via the ubiquitin-proteasome pathway – one of many vicious metabolic circles we so commonly see in chronically ailing patients.

Caso and Garlick (2) continue their discussion by pointing out that acidosis not only stimulates protein breakdown but inhibits protein synthesis:

“…the catabolic effects of acidosis on muscle have generally been believed to be mainly a consequence of a stimulation of proteolysis.  However, more recent studies have shown that acidosis not only stimulates protein degradation but can also depress protein synthesis in muscle.”

Are all muscles affected in the same way by acidosis?

The authors point out that the answer to this question is no:

“…different muscles are not affected by acidosis to the same extent and that the inhibitory response may depend on the specific muscle composition.  In particular, oxidative muscle containing predominately slow-twitch fibers may be less affected by the depressive effects of acidosis.  This relative sensitivity of different muscles to acidosis is similar to their relative sensitivities to nutritional and hormonal stimuli.”

An example of slow twitch muscles are the gluteal muscles.  Fast twitch muscles are the hamstrings.

The next quote provides more detail on the involvement of glucocorticoids in acidosis induced muscle/protein loss:

“The inhibition of protein synthesis by acidosis could be triggered by a direct effect of lowered pH on muscle and/or be indirectly elicited through the action of other mediators, such as hormones.  For example, glucocorticoids, which have been implicated in the catabolic effect of acidosis on muscle by enhancing protein degradation, may also play an important role in mediating the effect of acidosis on protein synthesis.”

If acidosis leads to loss of protein and muscle, would it follow that alkalosis would lead to gains in protein synthesis and muscle mass?

Caso and Garlick (2) indeed answer this question, as you might expect, in the affirmative:

“The inhibition of protein synthesis by acidosis leads to the logical question: does alkalosis stimulate?  There is one study that suggests that this might indeed be so.  Vosswinkel et al. studied intensive care patients with head trauma.  These patients were hyperventilated, resulting in respiratory alkalosis.  Measurements of muscle protein synthesis were made while they were alkalotic, and again 24 h after cessation of hyperventilation, when their arterial pH had returned to normal and their hemoglobin saturation was maintained at a normal level.  The rate of muscle protein synthesis during alkalosis was significantly higher than that measured at normal pH, suggesting the possibility that alkalosis stimulates muscle protein synthesis.”

Based on the above, as I suggested in the recent newsletter where I discussed the paper by Sebastian et al (3), it may be best, in terms of protein and muscle optimization, to maintain a somewhat alkaline physiology by means which include an alkaline diet high in potassium-containing foods.

Caso and Garlick (2) continue their paper with the following overview statement:

“There is increasing evidence that acidosis promotes muscle protein loss, both by enhancing protein degradation and by inhibiting protein synthesis.  This evidence suggests that maintenance of normal pH in those pathological conditions that are associated with acidosis will help to preserve muscle mass and thereby improve the health and well-being of these patients.”

Then, they end with a fascinating comment about the idea that maintaining an alkaline state may not only be valuable with illness in terms of optimizing protein and muscle mass but may also be useful in a preventive scenario:

“Finally, a recent meta-analysis has shown that dairy cattle given diets with a higher cation-anion difference have higher blood pH and also have greater milk yield.  This suggests the possibility that the effects of acid-base balance on protein synthesis and degradation might have significance for the maintenance of protein balance in health, as well as in pathological states.”

(A higher cation-anion difference indicates a more alkaline state)

SPECIFIC RESEARCH EVIDENCE THAT AN ACID STATE INCREASES PROTEIN BREAKDOWN AND AN ALKALINE STATE DECREASES IT

Does specific research evidence exist in human studies that support the contention made in the above discussion?  What follows is an overview of several studies that suggest the answer is yes.  The first study is both interesting and somewhat unique in that it does not examine the impact of alkalinization on protein/muscle status but the impact of acidification.  In “Ammonium chloride-induced acidosis increases protein breakdown and amino acid oxidation in humans” by Reaich et al (4), seven healthy subjects were supplemented with ammonium chloride, an acidifier, for five days.  As a result of this intervention, plasma levels of several amino acids increased with acidosis, indicating increased breakdown of protein-based structures:

“Plasma levels of the amino acids threonine, serine, asparagine, citrulline, valine, leucine, ornithine, lysine, histidine, arginine, and hydroxyproline increased significantly with the induction of acidosis.”

Before continuing, please note again that hydroxyproline was one of the amino acids that increased in the plasma upon acidification.  As most of you know, hydroxyproline is a protein found primarily in bone, indicating that acidification not only compromised muscle health but bone health also.  With the above results in mind, the authors concluded:

“These results confirm that acidosis in humans is a catabolic factor stimulating protein degradation and amino acid oxidation.”

The next two studies I will be reviewing both discuss the impact of supplementation of the alkalizing agent potassium bicarbonate on protein/muscle metabolism.  In “Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women” by Frassetto et al (5), the authors introduce their study with the following overview comments:

“In disorders that cause chronic metabolic acidosis, protein degradation in skeletal muscle is accelerated, increasing the production of nitrogen (N) end products that are eliminated in the urine, thereby inducing negative N balance.  This disturbance of N metabolism apparently results directly from the acidosis, not from its cause or from other sequelae of the underlying acidosis-producing disorder, because it occurs with widely differing acidosis-producing conditions, and it is reversible by administration of alkali, which corrects the acidosis but not its cause.”

Their next statement is quite interesting because it supports the contention I have long made in this forum that most metabolic imbalances we see in chronically ailing patients are actually allostatic phenomena where the body is trying to do the right thing.  However, the metabolic imbalance continues too long leading to catabolic physiology, or allostatic load:

“Acidosis-induced proteolysis appears to be an acid-base homeostatic mechanism.  By releasing increased amounts of amino acids, in particular glutamine, which is used by the kidney for synthesis of ammonia, the kidney can increase the excretion of acid (as ammonium) in the urine, thereby mitigating the severity of the acidosis.”

Before continuing, please recall that many chronically ill patients are highly deficient in glutamine, often necessitating somewhat large amounts of glutamine supplementation.  With the above quote in mind, I hope you can now see why chronically ill, acidotic patients become so depleted in glutamine.  The body is trying to use glutamine stores to reduce acidity.

Next, Frassetto et al (5) discuss the mechanics of the study.  Briefly, 14 healthy postmenopausal women aged 51-77 years were supplemented with potassium bicarbonate for 18 days.  The findings of the study are as follows:

“The findings of the present study indicate that in healthy postmenopausal women: 1) reducing the diet net acid load from normal to nearly zero with exogenous base (KHCO3) significantly reduces blood acidity and increases the plasma bicarbonate concentration, indicating that the unsupplemented normal diet acid load was significantly perturbing systemic acid-base equilibrium, causing a low grade metabolic acidosis; 2) correction of the diet-dependent metabolic acidosis causes a significant reduction in urinary N excretion, comprising nearly equal reductions in urinary ammonia and urea excretion; and 3) this N-sparing effect is reversed by withholding the exogenous base.”

The next quote I would like to feature from this paper expands upon the discussion above as to why acidosis leads to protein catabolism:

“Metabolic acidosis induces N wasting in part by directly increasing the rate of protein degradation in skeletal muscle without commensurately increasing the rate of protein synthesis.  That proteolytic effect has been attributed to two acidosis-induced disturbances in skeletal muscle cells: stimulation of an ATP- and ubiquitin-dependent proteolytic pathway and enhancement of the oxidation of proteolytically released branched chain amino acids (valine, leucine, and isoleucine), preventing their reuptake for protein synthesis.  Nonbranched chain amino acids, especially glutamine, released into the circulation in increased supply, are made available to the kidney for the generation and excretion of ammonium, thereby eliminating muscle N and precluding its reuse for protein synthesis.”

Frassetto et al (5) conclude their paper with this bottom-line overview conclusion:

“We believe that the most straightforward interpretation of the findings in this study is this.  KHCO3 administration reduced the net endogenous acid production and corrected the preexisting low grade metabolic acidosis, raising urine pH and reducing the total rate of renal ammonia production.  As a consequence, both the excretion of ammonia in the urine and the delivery of ammonia to the systemic circulation via the renal vein decreased.  The reduction in urinary ammonia contributed directly to the improvement in N balance.  The reduction in ammonia delivery to the systemic circulation via the renal vein in addition contributed indirectly to improvement in N balance by limiting substrate (viz. ammonia) available for hepatic urea production, thereby reducing external loss of N as urinary urea.  In addition, by correcting the preexisting low grade metabolic acidosis, KHCO3 decreased the pretreatment rate of muscle proteolysis, thereby limiting the availability of amino acids for both urea and ammonia production, further contributing to the improvement in N balance.”

The second potassium bicarbonate supplementation study I would like to feature considers the impact of supplementation on a macroscopic, organ-based perspective.  In “Impact of supplementation with bicarbonate on lower-extremity muscle performance in older men and women” by Dawson-Hughes et al (6) 171 healthy men and women aged 50 years and older were evaluated.  The specifics of the study are as follows:

“In this 3-month, double-blind, placebo-controlled trial, subjects were randomized in blocks of four within sex and age (50-64 and 65 and older) strata to treatment with potassium bicarbonate, sodium bicarbonate, potassium chloride, or placebo.”

The results of the study are in the quote below.  Interestingly, a positive impact was only seen with women:

“Supplementation with bicarbonate for 3 months was well tolerated and had favorable results on selected measures of muscle performance in the women but not the men.  The greatest benefit of bicarbonate treatment was observed in lower body double leg press peak power output (at 70% I-RM) which increased by 13% relative to the control group.”

In addition:

“In the women, significant improvements while on bicarbonate were also noted in other power measurements, double leg press 40% and in knee extension 70%, and in one endurance measure, knee extension at 240o.”

Why did men demonstrate different results?  The authors theorize:

“The reason why we did not detect an effect of bicarbonate on muscle performance in the men is uncertain, but dose in relation to body size may have been a factor.”

What was the impact on nitrogen excretion?  Dawson-Hughes et al (6) point out:

“Treatment with bicarbonate significantly lowered nitrogen excretion in the women in our study.  This finding confirms the previous observation in 14 healthy postmenopausal women studied on metabolic diets that ingestion of a neutralizing dose of potassium bicarbonate significantly reduced nitrogen excretion.”

In the next quote the authors offer their suggestion as to the mechanism of the reported effects:

“The mechanism(s) by which alkali affected muscle in this study are not certain.  A possible mechanism may involve facilitating removal of hydrogen ions from muscle.  During exercise, lactic acid is generated in muscle, and the accumulation of hydrogen ions in muscle is known to impair force generation and other aspects of muscle function.  Extracellular acidosis inhibits hydrogen ion efflux from muscle in dogs.  Alkali is thought to promote the efflux of hydrogen ions from muscle cells by creating greater buffering capacity in the extracellular fluid.  We might speculate that use of bicarbonate to correct the mild metabolic acidosis commonly present in older men and women may facilitate muscle performance in elders with usual levels of activity.”

Dawson-Hughes et al (6) conclude their paper with the following statement:

“In conclusion, while it will never be a substitute for exercise, oral administration of bicarbonate modestly improved lower-extremity peak muscle power and endurance and reduced nitrogen excretion over a 3-month period in healthy older women.”

ALKALINIZATION AND GLUTATHIONE

Now I would like to do an in depth review of the study mentioned in the beginning of this newsletter that was the inspiration of my examination of the relationship between acid/alkaline balance and protein metabolism, “Alkalinization with potassium bicarbonate improves glutathione status and protein kinetics in young volunteers during 21-day bed rest” by Biolo et al (1).  The first quote I would like to feature from this paper discusses the relationship between intracellular pH and redox balance:

“Changes in intracellular pH can…affect redox balance.  Glutathione (a glycine-cysteine-glutamic acid tripeptide) is the most important non-enzymatic, intracellular antioxidant.  Its concentration is particularly abundant in the liver and erythrocytes where it acts as a local and systemic antioxidant agent.  Models of hyperlactacidemia and hyperketonemia showed that acidosis can induce reactive oxygen species (ROS) formation, leading to glutathione depletion.  Conversely, alkalinization may attenuate oxidative damage and prevent glutathione reduction (depletion).”

The study design involved eight male volunteers aged 27 ± 3 years who had a BMI of 24.4 ±  0.7 kg/m2.  One group of four did bed rest, standard nutrition, plus potassium bicarbonate (BRKB) and the other group of four did bed rest and standard nutrition only.  The actual time of supplementation or no supplementation depending on the group was 21 days.

What were the findings of the study?  The authors comment:

“In the present study, we have evaluated in healthy young male volunteers, the effects of 3 weeks of oral potassium bicarbonate supplementation during experimental bed rest, on whole body protein and erythrocyte glutathione kinetics, according to a crossover experimental design.  We found that treatment with potassium bicarbonate during bed rest, as compared to bed rest with no supplementation, improved whole body protein kinetics and increased intracellular glutathione availability by lowering the utilization of this antioxidant molecule.”

The actual amount of increase in glutathione due to potassium bicarbonate supplementation was about 5%.  Why?  The authors hypothesize:

“Because the pool of glutathione is turning over quickly, an increase in erythrocyte glutathione could stem from: 1) a higher synthesis rate, 2) a decreased utilization rate, or 3) the two-process combined.”

What did Biolo et al (1) conclude:

“These results indicate that treatment with potassium bicarbonate during bed rest causes a lower glutathione utilization, while increasing its availability as an antioxidant.”

In addition:

“…we can speculate that mild alkalinization could down-regulate free radical production and decrease antioxidant requirement.  This hypothesis is supported by the fact that, in our study, changes of the glutathione fractional turnover rate were inversely related with modifications in urinary pH.  Our results are in agreement with previous observations showing down-regulation and up-regulation of glutathione availability by acidosis and alkalosis, respectively.”

Before continuing, please note the valuable clinical pearl in the above quote.  As we all know, determining glutathione availability using traditional functional medicine testing procedures can be quite costly.  Biolo et al (1) suggest that a simple first morning urinary pH can be an excellent indicator of glutathione availability.

The next quote I would like to feature will have significance to those of you who are familiar with organic acids testing.  As those of you who utilize this assay may recall, elevated levels of pyroglutamic acid are a good indicator of increased glutathione breakdown.  With the above in mind, Biolo et al (1) point out that, since glutamate is one of the constituents of glutathione, a high ratio of pyroglutamic acid to glutamate would suggest that there is less glutathione per se, primarily due to increased glutathione breakdown.  In addition, they found that alkalinization tended to decrease the ratio suggesting that alkalinization decreases glutathione breakdown and increases glutathione production:

“Glutathione is catabolized and re-synthesized through the gamma-glutamyl cycle.  Pyroglutamic acid is the product of glutathione catabolism and the immediate precursor of glutamate for glutathione re-synthesis.  The ratio between pyroglutamic acid and glutamate is therefore an index of glutathione turnover through the gamma-glutamyl cycle.  In agreement with kinetic results, we found that the ratio between pyroglutamic acid and glutamate tended to decrease following alkalinization.”

Then, in agreement with research discussed above, the authors state the following:

“In agreement with previous studies, we have observed a significant improvement of whole body protein balance in the postabsorptive state following alkali treatment.”

What about dosing?  What is the impact of a specific dose of potassium bicarbonate on a specific amount of lean body mass?  Biolo et al (1) suggest:

“Treatment with 90 mmol x d-1 potassium bicarbonate could potentially spare 18 g x d-1 of lean body mass in bed resting subjects, which would amount to about 350 g over the 21 days of the study period.  This estimation is in agreement with the results of a previous study obtained using the same potassium bicarbonate dose in post-menopausal women.”

(90 mmol of potassium bicarbonate is equal to about 3600 mg of potassium)

A separate and equally interesting aspect of the Biolo et al (1) study considered the impact of acid/alkaline balance on the polyunsaturated fatty acid (PUFA) content in red cell membranes:

“We found that 3-weeks of bed rest, with or without potassium bicarbonate supplementation, can modify PUFA composition of erythrocyte membranes independently from dietary lipid intake.”

More specifically:

“Bed rest without bicarbonate supplementation independently increased arachidonic and the ratio between arachidonic and eicosapentaenoic acid leading to a proinflammatory pattern, which may have contributed to metabolic alterations associated with muscle unloading, as already shown in our previous investigation.”

What was the impact of alkalinization with potassium bicarbonate on the pattern mentioned in the above quote?  The authors point out:

“The present study showed that alkalinization during bed rest increased the sum of n-3 PUFA and the n-3-to-n-6 PUFA ratio in cell membranes leading to an anti-inflammatory pattern, as compared to bed rest with no bicarbonate supplementation.”

The final quote of the study summarizes all the study findings:

“In the present study, we demonstrated that alkali supplementation significantly improved selected aspects of protein kinetics, glutathione status and cell membrane PUFA in a human model of muscle disuse atrophy.  Positive effects of alkalinization have been demonstrated in other clinical conditions of muscle catabolism such as ageing and chronic kidney disease.  Alkali diets have been associated with similar metabolic benefits to those shown with bicarbonate supplementation.  Thus, in clinical conditions characterized by inactivity, oxidative stress and inflammation, alkalinization could be a useful adjuvant therapeutic strategy.”

SOME FINAL THOUGHTS

As most of you know from my writings and lectures, in contrast to a large portion of the functional medicine community that seems to be increasingly enamored with complicated and sometimes expensive assessment and treatment modalities, especially when considering core metabolic issues such as PUFA balance, protein, and glutathione metabolism, I seek to pursue the opposite direction.  This is why I was so glad to discover the studies featured in this monograph.  From an assessment standpoint, as demonstrated above, we can learn a great deal about patients’ protein, glutathione, and PUFA status with tools as simple as a first morning urine pH.  Furthermore, significant corrections in imbalances of all three can be accomplished with simple and inexpensive alkalinization modalities, even in non-exercisers.  For me, having attended many lectures that advocate sometimes both very complicated and expensive lab tests to assess these three major metabolic issues and equally expensive and complicated corrective measures, this information on the relationship between these three and acid/alkaline balance is truly a welcome breath of fresh air.

Moss Nutrition Report #285 – 05/01/2019 – PDF Version

REFERENCES

  1. Biolo G et al. Alkalinization with potassium bicarbonate improves glutathione status and protein kinetics in young volunteers during 21-day bed rest. Clin Nutr. 2019;38:652-9.
  2. Caso G & Garlick PJ. Control of muscle protein kinetics by acid-base balance. Curr Opin Clin Nutr Metab Care. 2005;8(1):73-6.
  3. Sebastian A et al. An evolutionary perspective on the acid-base effects of diet. In: Gennari FJ et al, ed. Acid-Base Disorders and Their Treatment Boca Raton: Taylor & Francis; 2005:241-92.
  4. Reaich D et al. Ammonium chloride-induced acidosis increases protein breakdown and amino acid oxidation in humans. Am J Physiol. 1992;263(4):E735-9.
  5. Frassetto L et al. Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women. J Clin Endocrinol Metab. 1997;82(1):254-9.
  6. Dawson-Hughes B et al. Impact of supplementation with bicarbonate on lower-extremity muscle performance in older men and women. Osteoporosis International. 2010;21(7):1171-9.