エッセイ集
スポーツ/アスリート
Sport performance and ingestion of BCAA
Due to absence of standardized models to evaluate the impact of a diet component on athletic performance, as well as due to plethora of confounding factors (gender, age, previous training, basal diet, altitude, liquid intake …); controversy remains about the effect of key amino acid groups on sport performance. Branched-chain amino acids (BCAA), arginine and glutamine are the most frequently evaluated amino acids. A brief look at the recent findings from four different sport categories tells a lot…
Among recent studies, researchers in Taiwan few well-trained handball players of both genders with app. 12 g BCAA and 3 g arginine before training sessions on two consecutive days. BCAA and arginine supplementation improved performance in handball sprints on the second consecutive day of simulated handball game www.ncbi.nlm.nih.gov/pubmed/25803783.
In athletes trained for strength performance, BCAA (20 g) administered acutely before and following intensive gym training attenuated a drop in power-producing ability. The apparent significant effects on functional strength suggested that BCAA made for an effective ergogenic aid for athletes who required augmented recovery following intensive exercise www.ncbi.nlm.nih.gov/pubmed/26853239.
In trained endurance cyclists, 12 g of BCAA given daily for several weeks before and during long-term cycling trainings had broad positive effects on select body compositions, performance, and immune variables. Specifically, this chronic BCAA supplementation improved not only sprint performance variables, and protected lean body mass, but also blunted the neutrophil response to intense cycling training, thus benefiting immune function during a prolonged cycling season www.ncbi.nlm.nih.gov/pubmed/26553453. Very similar effects were observed in a study that used a combination of BCAA and glutamine in active rowers www.ncbi.nlm.nih.gov/pubmed/25202189 .
Not all clinical tests revealed produced positive effects of BCAA in exercise and some older studies suffered with problems of design and interpretation. Yet, the summarized clinical evidence from the last decade points to a strong positive correlation between performance/recovery on one hand and BCAA intake on the other. The optimal dose of BCAA (10 – 20g?) remains unclear and there are too many variables to make this conclusion stronger and applicable to all sub-groups of sports-men and -women.
スクワット前及び遅発性筋肉痛前における分岐鎖アミノ酸の補給
本研究では、特にトレーニングをしていない健康な若年女性12例により、スクワット運動で引き起こされる遅発性筋肉痛（DOMS）に対する分岐鎖アミノ酸（BCAA）補給の効能を調べた。
実験は交差二重盲検試験によりおこなわれた。
運動セッションの日の朝、参加者はスクワットをおこなう前にBCAA（イソロイシン：ロイシン：バリン＝1:2.3:1.2）またはデキストリンを100mg/kg（体重）摂取した。
運動は20スクワット＝1セットとする7セットで構成され、各セットの間隔を3分とした。
実験の2日目と3日目に遅発性筋肉痛（DOMS）のピークが認められたが、BCAAを摂取した側ではプラセボを摂取した側よりも痛みの度合いは低かった。
最大随意等尺性収縮が起こっている間の脚筋力を運動（第3日）の2日後に測定したところ、BCAAを摂取した側ではプラセボを摂取した側にみられた筋力の低下が80％に抑制された。
血漿BCAA濃度はプラセボ側では運動後に減少したが、BCAA側では運動の2時間後に上昇した。
プラセボ側では運動により血清ミオグロビン濃度が上昇したが、BCAA側では上昇しなかった。
双方のスクワット運動後、好中球の活性化の指標として血漿エラスターゼの濃度は増えたようにみえたが、プラセボ側においてのみエラスターゼ値の有意な変化がみられた。
これらの結果は、BCAAの補給により筋肉の損傷が抑えられることを示している。
高齢者/シニア
Age and amino acids
Maintaining muscle mass and physical function is fundamental to promoting health and independence with age. It has particular relevance for the prevention of falls, fracture and disability which may have life-threatening implications for elderly individuals. The identification of effective nutritional treatments for age-related sarcopenia (age-dependent loss of muscle mass) represents an ongoing challenge.
We have already discussed here that essential amino acids (EAA) and especially leucine could be of benefit to an aging individual, especially considering a positive balance of costs and benefits of EAA. A recent clinical work published after our LinkedIn summary (see here, in August 2015) has compared the efficacy of EAAs enriched with different amounts of leucine on muscle mass and physical performance in elderly men and women. In line with our assumptions, the authors hypothesized that an increase in the proportion of leucine in a modified mixture of EAAs would be of greater benefit than a standard mixture of EAAs or a placebo. For study itself; see: www.ncbi.nlm.nih.gov/pubmed/26081485
The authors found that twice-daily supplementation of EAAs containing 20% or 40% leucine improved the key aspects of functional status and at the higher level improved lean tissue mass. Since elderly rarely care about their muscle mass, the improvement in functionality is the key message. Among the tricky points of the study was the app. 79% adherence, indicating that the taste and texture could be a hurdle when implementing leucine-rich EAA diet for elderly people. This point aside, the referenced study further confirmed prophylactic role of EAAs and in particular leucine for the treatment of sarcopenia. Twice-daily supplementation with 0.21 g/kg/day EAAs (with 40% content of leucine) alongside a diet providing adequate protein is the best recommendation nutritional science can right now provide…
Branched-Chain Amino Acids in elderly
Sarcopenia, the gradual loss of lean muscle mass associated with middle- and especially high-age, contributes to the fragility of an aging person. There is no clear consensus on how to blunt the process, but it is reasonable to claim that absence of chronic disease in a combination with physical activity and a healthy diet rich high-quality protein are the key factors.
Because the anabolic capacity of skeletal muscle decreases with age and there is no apparent harm associated with protein intake above the Recommended Dietary Allowance (RDA, the current RDA is 0.83 g protein/kg body weight/day), high protein diets were already proposed for elderly adults (Wolfe, Br J Nutr 2012;108:S88-S93).
However, the quality of long-term ingested dietary protein in terms of essential amino acids content, and especially leucine content, comes up as more important than quantity of the protein eaten (Paddon-Jones, Exp Gerontol. 2006;41(2):215-219).
Leucine and the two other branched-chain amino acids (BCAA) belong to the most studied group of amino acids with respect to muscular functions in both young and elderly humans. The unique role of leucine as the trigger of muscle synthesis is well studied (e.g. Valerio, Aging 2011;3:464-478). Clinical data support leucine central role in muscle protein synthesis, nitrogen provision for synthesis of other amino acids, as well as its role as an insulin stimulant.
Importantly, the beneficial effects of leucine were identified in both young and elderly humans. Among others, Koopman and colleagues reported that ingesting whey protein and 13 g leucine following physical activity resulted in similar increases in muscle strength/mass and body protein balance in young and eldely men (Koopman, Am J Clin Nutr 2006;84:623-632). Similar results, in addition to an enhanced rate of skeletal muscle synthesis, were obtained with another larger group of elderly adults supplementing for two weeks their normal diet with 12 g leucine per day (Casperson, Clin Nutr. 2012;31(4):512-519).
A different approach often used in clinical research involves the administration of a mixture of all nine essential amino acids in addition to extra high leucine doses. From a summary of all comparable trials, one could deduce that the minimum dose of leucine to stimulate muscle growth and strength in the elderly was at least 3 g leucine (i.e., Paddon-Jones, Curr Opin Clin Nutr Metab Care 2009;12:86-90).
It is also of value to note that leucine and BCAA mixtures have been reported to exert beneficial effects on body weight and body fat control in middle-aged individuals (Qin, J Nutr 2011;141:249-254). These epidemiological data on the importance of leucine in body weight management were further supported by interventional findings (i.e., Zanchi, Med Hypotheses 2012;79:883-888).
Taken together, clinical results have been very promising and demonstrated the key role of leucine and other branched-chain amino acids (BCAA) in tackling muscle loss in elderly, although it is important to note that physical activity, glucose metabolism and background intake of dietary protein are also very important factors.
Amino acids nutritional supplement formulations for elder people health; a suggestion for a different investigation approach
Amino acids are well known to exhibit significant health boost effects when taken in optimum quantities and their lack has been correlated with various negative effects including psychological disturbances, loss of muscular and bone mass, and others. Of special attention is the positive effect that they may provoke on specific population groups that suffer from known health problems, such as elderly people. Several studies have been published on the subject, and major guidelines are presented here.
In relevant research works, different amino acids have been supplied to patients at different combinations, contents and rates. Such recipes include any of the following amino acids:
– L-Leucine
– L-Lysine
– L-Isoleucine
– L-Valine
– L-Threonine
– L-Cysteine
– L-Histidine
– L-Phenylalanine
– L-Methionine
– L- Tyrosine
and others. Supplying amino acids as nutritional supplements has been proved to increase health of elderly people in terms of reducing mild depression and increasing muscle strength. Long term effects should also be investigated since it is possible that they could reveal other improvements related to energy transfer, organ functionality, improvement of cardio vascular status, and others.
Up to now, most studies have focused on multi amino acids mixtures, trying to simulate a ‘complete’ nutritional approach effect on the health of older people. However, the opposite approach might provide a better and more efficient way to investigate specific effects of essential amino acids on health of older people. Different studies have revealed the synergistic effects of amino acids, but single amino acids effects are well established as well. A viable and promising technique would be to investigate combinations of amino acids in increasing number of components, thus advancing to the next greater group of amino acids only when conclusions are reached for a specific combination. Such a work would be based on probabilities theory and potential calculations of a number of given amino acids. Different methodologies exist to investigate such processes, for example Monte Carlo statistical approaches. Working with such methodologies can lead to better understanding of published experimental results and better estimations on health improvement of older people.
Optimization of nutritional supplements composition is less likely to be successful when a large number of amino acids are utilized simultaneously. On the other hand, an additive technique, starting at a low number of amino acids can provide significant advances in the search for such optimum formulations. The methodology of addition should follow a ‘gradient’ measurement of effects, focusing on the largest changes towards required properties. Using published results on low numbers of components can increase the rate of this trial and error procedure. An important advantage of such a technique is that masking effects can be avoided, since addition of components is a step by step procedure. A similar approach would be characterized as reducing the components of a mixture of numerous components to investigate the effects of each compound in the mixture. Both techniques are expected to be used in a larger extend by the scientific community.
その他
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Correlation of plasma amino acids to obesity and cardiovascular disease: what they don’t mean
Several clinical studies published during the last five years reported a positive correlation between blood level of branched-chain amino acids (BCAA; leucine, isoleucine, valine) and metabolic disorders, mainly obesity and cardiovascular disease. Among others, see: www.ncbi.nlm.nih.gov/pubmed/19356713 or www.ncbi.nlm.nih.gov/pubmed/20173117. Other case-control observational studies found positive associations between cardiovascular disease and a score of other amino acids measured at baseline. See, www.ncbi.nlm.nih.gov/pubmed/23242195.
What does it all mean? There are twenty protein-building amino acids present in our body and circulating in our blood. It is therefore not surprising that synthesis or breakdown of some amino acids may go up (down) during a long-term observational study in specific sub-populations. Does such a correlation indicate causative effects linking the intake of the said amino acids to some metabolic diseases? It definitively does not, as reasoned below in 4 steps applied to the case of BCAA, which are the best studied group of amino acids in that respect.
1. Interventional clinical studies indicated that BCAA improve metabolic health and even benefit a specifically susceptible group of patients with heart failure. See, www.ncbi.nlm.nih.gov/pubmed/25287287 and www.ncbi.nlm.nih.gov/pubmed/24925377.
2. Patients with obesity and/or cardiovascular disease were reported to have somehow elevated plasma levels of BCAA (see references in the 1st paragraph).
3. Dietary intake of BCAA (from foods or dietary supplements) does not correlate to plasma BCAA levels (see, www.ncbi.nlm.nih.gov/pubmed/26277881).
4. People with metabolic syndrome have a decreased capacity to break-down BCAA in the adipose tissue. Consequently, BCAA may accumulate in plasma of such subgroups of patients, when compared to healthy population (see, www.ncbi.nlm.nih.gov/pubmed/22560213).
As a conclusion; above points 1 – 4 demonstrate that, (A) BCAA circulating in the blood do not serve as biomarkers of their dietary intake, and (B) plasma BCAA may serve as one of the biomarkers for metabolic diseases, because cardiovascular pathologies and obesity influence BCAA break-down and overall homeostasis. -
Theory on dietary essential amino acids and LDL
Dr. Kummerow, an honorary professor of biosciences at the University of Illinois, made his original discovery on causal relationship between low-density lipoprotein (LDL), cholesterol and dietary level of essential amino acids already more than 50 years ago (see, J Nutr. November 1961;75:319-329).
LDL is well known as the “bad cholesterol” and its increase in blood circulation is considered as one of the key indicators of heart disease. However, Dr. Kummerow claims that a high LDL is “only” a consequence of a diet lacking in essential amino acids.
As a simple background, the key protein component of LDL is apolipoprotein B, which serves to bind the lipoprotein particles to LDL-specific receptors on the cell surfaces. The LDL particles are used as a structural component of cell membranes or converted to steroid hormones. Apoliprotein B is the major protein in all lipoproteins, except high density lipoprotein (HDL; the good one).
In his research spanning 5 decades, Dr. Kummerow noticed that apoliprotein B inversely depended on dietary supply of the amino acid tryptophan. He further speculated that a high LDL level indicated a lack of essential amino acids, mainly tryptophan, in our diet. There is an interesting consequence of this thinking, because the current medical practitioners advice patients to avoid foods that are rich in tryptophan, for example eggs, turkey, nuts.
Should we believe Dr. Kummerow? Well, since he will be soon a healthy 102-old man, perhaps we should, especially as he advice concerns tryptophan which is also needed to prevent cases of mild depression and improve sleep (besides being an irreplaceable component of proteins).
Finally, some of other general ideas Dr. Kummerow holds are worth noticing. For example, “…A diet low in dietary cholesterol and in fats that raise blood cholesterol will not provide long-term prevention of coronary heart disease. Protein from animal products normally needs to be in the diet because this contains all the essential amino acids and essential fatty acids, and has the best biological value. Reducing dietary cholesterol intake to a level at or below 200 mg a day will result in a less nutritious diet for most people. A diet low in dietary cholesterol and cholesterol-raising fats is likely to be deficient in protein, vitamins and minerals.”
wphna.org/wp-content/uploads/2015/01/WN-2015-06-01-02-72-78-Idea-Fred-Kummerow-My-diet-JF.pdf -
Essential amino acids and hyperlipidemia
An increased level of blood lipids is one of the risk factors for cardiovascular disease. Current medical classification schemes and treatment levels for hyperlipidemia emphasize the pharmaceutical use of statins as the preferred class of drugs to lower elevated low density lipoprotein cholesterol. There are other drug classes to augment or perhaps substitute for statins, such as fibrates and niacin. Indeed, research has raised the question whether or not the current guidelines are sufficiently inclusive and effective. New guidelines are expected to be released in the near future, but in the meantime, physicians are facing insecurity when advising patients on how to lower dangerous low density lipoprotein cholesterol.
In that respect, it is worthwhile to notice that simple dietary supplementation with essential amino acids (EAA) could lower plasma triglyceride and improve glucose metabolism in humans. In a clinical study conducted with elderly a few years back, circulating TG concentrations were reduced ~20% from the starting value, while total caloric intake was not significantly affected by the EAA supplements ingested daily over 16 weeks. (www.ncbi.nlm.nih.gov/pubmed/19041223 ). The most recent clinical study was conducted in subjects who were 50 years or older and had a documented plasma plasma triglycerides elevated at >150 mg/dL. The outcome of the study further showed that a dietary supplementation of leucine-enriched EAA, in a combination with phytosterols, promoted favorable reductions of blood lipids in individuals with hyperlipidemia (www.ncbi.nlm.nih.gov/pubmed/26726312 ).
Since elevating dietary intake of EAA is relatively simple and affordable, one could only hope that such an intervention would be incorporated into new medical classification schemes and treatment levels for hyperlipidemia. This is especially true when considering that lysine-enriched EAA, perhaps in combination with arginine, also substantially increase lean body mass, improve strength as well as physical function compared to baseline values in elderly individuals. (see, www.ncbi.nlm.nih.gov/pubmed/18294740) -
Safety profile of amino acids Part 2
In last week’s post, I wrote that traditional toxicology does not describe the safety of ingested amino acids in any reliable manner. I also came to the conclusion that we did not know much about the tolerability of high amino acid doses, despite their wide use in medical foods and sport supplements. This is also due to the use of experimental animals to answer toxicological questions that are primarily rooted in human physiology and metabolism.
ICAAS members have stepped up and devoted effort to testing the safety of key amino acids DIRECTLY in humans. This original research effort focused on leucine, the amino acid frequently added to sport supplements, and proteins. Indeed, research studies conducted in the last 15 years have confirmed that leucine has functions that go beyond being an essential nutrient. In respect to skeletal muscle, the key leucine function is the ability to promote protein synthesis via activation of the mammalian target of rapamycin (mTOR) pathway (for those interested in the newest efficacy studies: www.ncbi.nlm.nih.gov/pubmed/25772815).
In the ICAAS-sponsored clinical study of leucine safety, the scientists aimed to determine the upper “metabolic limit” to oxidize excess dietary leucine fed to adult volunteers www.ncbi.nlm.nih.gov/pubmed/23077191. They measured excretion of carbon-labeled leucine in response to gradually increasing loads of orally ingested leucine. The key experimental hypothesis was that the labeled leucine will be excreted in parallel to the increasing leucine intake, because the body will be effectively dealing with the dietary excess. If an increment in leucine ingestion does not lead to an increase in excreted leucine (breakpoint), one could assume that the body has lost the metabolic capacity to deal with the dietary excess. Indeed, such a breakpoint was found at a dose of 555 mg of leucine per kg body weight (approx. 44 g of leucine in an 80 kg human). This led the authors and others (www.ncbi.nlm.nih.gov/pubmed/23096009) to propose 55 mg leucine/kg/day as the true upper limit. Note that the proposed limit is substantially higher than the average leucine intake from food (approx. 6 g per day) and shows a huge safety margin for leucine used in supplements, as we predicted earlier.
The same approach is being applied to elderly people (due to the high importance of leucine in preserving muscle mass in the elderly, which will be our topic next week). Preliminary data presented during this spring’s “Experimental Biology” meeting indicated that age had no substantial impact on our ability to process amino acids, and thus, on the safety factors.
Similar to the above conclusion about leucine, a clinical study conducted in Japan in healthy women found that another essential amino acid, tryptophan (a popular sleep aid), can be ingested safely up to 5.0 g per day (www.ncbi.nlm.nih.gov/pubmed/23616514). This is very relevant considering that typical doses of tryptophan for sleep quality improvement or in stress reduction are 0.5 – 1.0 g per person.
ICAAS is soon expecting data on arginine and methionine safety. Scientists at Texas A&M University who conducted pre-testing of arginine safety in pigs (www.ncbi.nlm.nih.gov/pubmed/25655382) concluded in their peer-reviewed article that, “…results indicate that dietary supplementation with arginine (up to 630 mg/kg body weight/day) is safe in pigs for at least 91 days. Our findings help guide clinical studies to determine the safety of long-term oral administration of arginine to humans”. This dose would correspond to almost 50 g of arginine eaten by an 80 kg human daily for three months, which is again a very high margin considering that you are probably consuming only 4 – 5 g of arginine from your daily diet. By this October, we will have this margin confirmed (or not) from a clinical study.
Taken together: (a) even if safety studies are not the “hottest” medical research area, ICAAS is proactively devoting resources in order to establish a framework for the evaluation of amino acid safety; (b) presently available data document a huge safety margin for most amino acids that would be practically impossible to breach via normal dietary means. Amino acids are effective substances, and it seems that we can use them SAFELY to supplement our diet in specific situations.
So, why worry about upper limits for amino acids? Indeed, ICAAS recommends to those involved in regulating, researching, and using amino acids to concentrate much more on the quality and specifications of amino acids than on their dose-limits. This aspect can be discussed again in the near future. -
Safety profile of amino acids Part 1
Amino acids have been present in our food supply since the origin of the human species. Nine amino acids that our body cannot synthetize must be ingested daily from food to avoid negative influences on the immune system, growth or even the quality of our skin. For those nine amino acids, dietary requirements (minimum safety limits) have been established by the World Health Organization and the Food & Agriculture Organization of the UN in 2007.
www.who.int/nutrition/publications/nutrientrequirements/WHO_TRS_935/en/
The maximum safe limits for amino acids in general, however are a still disputed. We ingest substantial amounts with our daily diet (for example, based on the Dietary Reference Intakes (1994) published by National Academies Press in 2001, a person on a typical western diet daily ingests more than 5 grams of leucine and lysine each). One could therefore assume that a human body has the capacity to deal with an increased intake, even if taken for specific supplemental needs (for example, lysine to prevent recurrent herpes, leucine to enhance skeletal muscle recovery or arginine to support the cardiovascular system).
How much is “too much”, though? How much would override our innate capacity to deal with high intakes?
Traditional toxicological approaches are not helpful in respect of these questions. Those approaches had been developed to evaluate new, artificially created ingredients or medicines and relay heavily on rodent studies. In a simple way, a toxicologist would feed a growing rat for thirteen consecutive week on a diet supplemented with a given amino acid at levels ranging from 1 to 5 % (as a portion of the overall diet) and search for the maximum dose which would not yet cause any pathology (a so-called NOAEL dose). Since rats are not people, the expert then would use a “safety factor” (usually a number between 100 and 300) to divide the NOAEL dose and to establish “Acceptable Daily Intake” (ADI) for humans. So, if a substance had an ADI equal to1 gram per day, you would have to eat 100 grams of that substance every day for 13 weeks before reaching the equivalent dose that had triggered a problem in rats!
This approach has been tried with a few amino acids. Interestingly, the ADI for many of the studied essential amino acids were determined to be at levels that were comparable to minimum dietary requirements for the same amino acids! For example, the minimum dietary requirement for leucine in an adult with body weight of 70 kg is roughly 2.2 gram per day, while the ADI for leucine was indicated at 2.3 gram per day.
(http://www.ncbi.nlm.nih.gov/pubmed/15204732).
So, the “upper limit” was practically equal to what you really needed to ingest to keep your body healthy! Clearly, this approach did not work. Using traditional toxicology to study the safety of substances which have been in our body, environment and food for millennia does not seem to be effective.
In addition, Dietary Reference Intake data point to a substantial spread of amino acid intakes among the US population (the best studied population in this respect). For example, the mean daily intake of an essential amino acid tryptophan in the US adult population was 0.9 gram, but 1% of the population took as much as 2.1 grams per day – and no harm has been reported from those intakes (on the contrary, a high tryptophan intake correlated with positive mood and quality of sleep). For another essential amino acid, lysine, the mean daily intake was 5.3 grams and the highest daily intake (1% of population) was as much as 12.6 grams.
One could try to consider historic intake data from those population groups that are characterized with the highest intakes and, if no evidence of harm was reported, consider those levels as appropriate upper limits for population as a whole. But, is this truly so simple? Can infants or frail elderly take as much as a healthy teenager? On the other hand, what about those sub-groups who choose to use very high doses occasionally (let’s say more than 3 grams of tryptophan daily to improve sleep, http://www.ncbi.nlm.nih.gov/pubmed/3097693) ?
We do not really know how to fully answer those questions.
However, there is a medical area which perhaps could offer assistance, because amino acids have been used in medical elemental diets and even intravenous infusions since the late 1950s (amino acids are the building blocks of proteins and are generally more easily ingestible than complete protein). Not only have they been used, but also applied at very high doses in traumatic events, when the body was losing nitrogen and essential nutrients rapidly. Post-operative states are a typical example. So, there are historic data from the use of nine essential, as well as some non-essential (glutamine, arginine, alanine) amino acids. For example, a healthy American ingests about 4.2 grams of arginine every day from her or his diet, but a patient may receive an infusion with 25.0 grams to save her life! Another example, patients with liver cirrhosis triggered by chronic alcohol intake were requested to take 12.0 grams of supplemental branched chain amino acids for 3 years and no harm was reported (http://www.ncbi.nlm.nih.gov/pubmed/16206505). On the contrary, many patients were saved specifically because they were receiving high doses of branched-chain amino acids! So, can we take the patient data in the cases where very high doses of free amino acids were applied and extend them to healthy population en masse?
I am repeating myself, but we do not know how to fully answer even this question.
For the above reasons, ICAAS members and ICAAS scientific advisors have invested substantial efforts and money to proactively come up with safety evaluation systems that would rely on the direct testing of amino acid safety in humans and those evaluations have already confirmed that the most frequently used supplemental amino acids are very safe and well tolerated. This will be the subject of our next post. -
Computational biology tools in Amino acids and bone cell metabolism; an opportunity for advances
Numerous works have dealt with the relationship between protein intake and origin and bone mass loss rates. It can be identified that published works in the period 1990-2005 mostly supported that animal protein intake amount was correlated to increased bone mass loss rates, in contrast to plant protein intake case. Most works in the following decade however have suggested that increased animal protein intake was correlated with higher bone mass densities and lower bone mass loss rates. However, research works on amino acids effects on bone cell metabolism are scarce. The few works on specific amino acids effect on bone mass loss rates are quite revealing for the role of amino acids in this process.
In such a work, human osteoblasts from both healthy and problematic bodies were treated with arginine, lysine and different combinations of them for a short testing period of a week. Alkaline phosphatase increased for all treatments and for both types of osteoblasts. Healthy body derived osteoblast had a positive reaction in terms of reducing IL-6. In the case of the osteopenic samples, only the combined treatment resulted in a measurable differentiation of IL-6 contents. Just arginine treatment initiated collagen production for the healthy samples, but not for the poor ones. Treatment with lysine resulted in no differentiation of the poor samples, but it provoked a change in growth factor in the healthy samples. Again, combined treatment led to a positive behavior for healthy samples but neutral for the poor ones.
More work is obviously required in this field. Effects of different essential amino acids on bone mass loss mechanisms should be investigated in terms of human age, current diet, and reported health issues. Such studies exist in the literature but they are based on protein effect and origin. Performing and reporting works on the specific amino acids effects on bone cell metabolism is a very promising action for the improvement of muscular skeletal diseases reduction. Such research can be undertaken at a theoretical level via powerful available computational tools and systems. Biological simulators and computational chemistry tools require much less resources in order to investigate processes involving less active compounds [amino acids]. This research topic seems ideal for application of such tools in order to investigate biological mechanisms at atomistic level. Such an approach requires just a fraction of research time and provides multiple measurable results in comparison to experimental approaches. Furthermore, it will strengthen the application of computational advances in biology.
Amino acid – specific research requires Density Functional Theory [DFT] or Ab Initio approaches for investigating the chemical and biological pathways of procedures involved. DFT however, due to the lowest scaling of computational requirements in relation to biological system size, offers a more attractive choice. DFT has been utilized in numerous relevant works providing highly accurate predictions on pathways, charge transfers, molecular transformations and other attributes of biological processes.
Using computational biology and computational chemistry tools, the effects of each specific compound and their mixtures can be monitored, investigated and explained in a revolutionary way. Work currently carried out in related fields such as protein folding reveals the true potential of such approaches. New, larger grid systems are available for worldwide cooperations that reduce the required computational times efficiently thus providing additional boost to the computational biology approach. It is expected that in the next decades, most novelties in the field will occur due to the use of such tools than to the use of traditional experimental techniques. -
Investigating the effectiveness of D- Leucine as an anti-seizure agent
One of the diseases that remains scarcely investigated in regard to potential application of amino acids as medicine is the intractable epilepsy. Amino acids seem to be promising medicines for such cases, given the other approaches that have been used so far for their treatment. Such a thought has triggered research in the field with great results.
L-Leucine and L-Lysine have been used as inhibitors of seizures in mice, with protective action exhibited only in the first case; L-Lysine failed to provide protection against induced seizure. In addition to this discovery, it was also found that D-Leucine also acted as a seizure inhibitor, probably even more efficient that L-isomer. This is especially important, since D-isomer is found in the brain, in tiny quantities. D-isomer also exhibited long term action and inhibition even after the seizure was induced. Such effects make this amino acid a potential anti seizure agent that was unknown up to now.
This fact is a great breakthrough in medicinal industry since, the anti-seizure drugs have not been significantly improved for decades. The most viable solution up to date was a high fat, low carbohydrates diet which presents difficulties in its utilization, as has been discussed by many research groups. The idea and the logic in choosing L-Leucine for testing its potential action against occurrence of seizures lie in the fact that L-Leucine is a ketogenic amino acid; its degradation produces ketonic compounds that have been utilized in the field. A reason that this investigation did not occur years ago, is partly because older works suggested that high levels of L-Leucine are correlated with increased seizures frequency and acute exposure with hypoglycemia. The actual mechanisms of action of both L- and D- isomers have yet not been proved. Continuation of this research work should aim at revealing the real biological/ chemical mechanisms behind this action so that more amino acids could be identified as potential seizure inhibitors or synergistic agents for L- and D- Leucine.
D-Leucine has a very interesting attribute; it is not included into mammalian proteins. This characteristic, along with the discovered anti-seizure action could become a part of the vegan diet debate, which is so active in our times. The specific amino acid is found in food and it accumulates in traces in the brain; vegan supporters can further continue the presented investigation to suggest more advantages of a mammalian free diet for the modern world, which meets moral requirements as well as health ones. Other such amino acids with familiar effects would strengthen this point. The structural differences between the two isomers will reveal the actual pathways of anti-seizure action. It is possible that steric hindrances between a two bodies [at least] process approach are involved and result to the D isomer effectiveness in contrast to the L isomer ineffectiveness.
This observation alone can provide information on the actual pathway on molecular level; confinement effects, steric effects, inaccessibility of spaces can be assumed and studied in turn for the seizure process. Realization of experiments and/or theoretical calculations on micro scale using the information on the D isomer effectiveness can lead to significant advances in the years to come. Nutritional supplements based on the most efficient of isomers would exhibit enhanced action that today’s formulations. -
Novel composite membranes based on amino acids for wound treatment: Present and future
Wound treatment is a significant research field for the pharmaceutical industry. Biocompatible, non toxic, porous materials with high adhesion to skin cells are required in order to create the optimum wound dressing. Skin itself exhibits self healing ability. Wound dressings act in a two way fashion; they stop loss of important liquids from the body to the environment and they inhibit pathogens entry to the body via the wound. Optimum wound dressings are highly porous and based on bio compatible polymers such as chitosan. Fibrous nanomaterial coatings offer additional advantages such as more connection points to the skin surface, minimum permeability of pathogens, and an ordered microporous three dimensional modifiable network with tailored physical, chemical and biological properties. Hydrophilicity of the manufactured membrane coatings is a requirement that is easily met either by choosing a known hydrophilic polymeric matrix or by the tailoring of the coating surface’s structure.
The combination of a polymeric matrix with a second compound leads to polymer blends and composites. The use of a polymer blend consisting of Chitosan modified with deacetylated arginine has led to the development of an excellent wound coating. Chitosan itself has been proven to improve intrusion of anti-inflammatory cells into the damaged area, via fibroblasts migration and proliferation and collagen deposition. In addition, it has been suggested that it exhibits haemostatic behavior through erythrocytes aggregation. Its antimicrobial activity can be significantly increased via the grafting of positively charged amino acids such as L-arginine and others. Positively charged L-arginine besides creating numerous positive local charges in the modified Chitosan polymeric chain, also increases the collage deposition rate as supported by research works.
Composite membranes’ attributes that affect the transportation inward and outwards the skin are selectivity and permeability which in turn depend on diffusivity and solubility of compounds in the matrix. Selectivity is a factor depending on structural and electrostatic properties of each molecule and the pore size distribution of each matrix. Permeability on the other hand depends mainly on pore size distribution and less on structural or electrostatic properties. Common issues reported with the use of a number of membranes is the accumulation of a species into a boundary layer that blocks the permeable pores and stops the entire exchange process. This phenomenon occurs due to low diffusivity of soluble species. Such issues are tangled by tailoring the pore size distributions of the 3D polymeric matrices.
The wound dressing coating based on the Chitosan/ Arginine polymer blend three dimensional fibrous structure offers great enhancement of wound healing, owing to a number of factors as discussed. Such works provide new guidelines for the design and manufacturing of wound coatings with tailored and increased properties based on combinations of properties of two or more compounds. Amino acids are a particularly important class of chemical compounds for this field due to their unique properties of easiness of insertion on polymeric backbones, biocompatibility, activity in biological processes and biodegradation. Immediate attention should be given to the construction of other amino acid based membranes as well as on the development of the presented amino acid blend with the addition of other functional amino acids. Composite formulations including more than one functional amino acid could lead to the manufacturing of revolutionary wound dressings.
The structural design of such coatings is also of greatest importance due to the permeability and selectivity characteristics that they exhibit. These properties are essential to the functionality of the membrane coating since they dictate which molecules can transport from the external environment to the damaged area, and which will be blocked. Knowledge of membrane manufacturing from other fields is extremely helpful for the design of the wound dressings. Fibrous microporous membranes are easily constructed by various techniques, with a continuously reduced cost. -
オランダ人高齢者における食事由来のアミノ酸及び高血圧リスク
背景：食事から摂取するタンパク質と高血圧症との間には逆相関があると報告されており、特定のアミノ酸に起因している可能性がある。
目的：ロッテルダム・スタディにおいて、グルタミン酸、アルギニン、システイン、リジン、チロシンの摂取は、血圧（BP）値（n=3086）や高血圧の発生率（n=1810）に関連があるか否かを調べた。
研究デザイン：年齢、性別、BMI、喫煙、アルコール摂取、教育、食事の要因で調節をおこない、アミノ酸のタンパク質総摂取量に占める割合（タンパク質中のパーセント）の四分位数を用いて血圧値を測定した。
次に、同じ交絡因子を含むコックス（Cox）比例モデルを用いて特定アミノ酸の摂取量と高血圧発症率との関連性を評価した。
結果：グルタミン酸はタンパク質摂取量に最も寄与しており（タンパク質の21％）、リジンは7％、アルギニン5％、チロシン4％、システインは1.5％であった。
チロシンの摂取量が高い程 （タンパク質のw0.3％）、2.4mm Hg低い収縮期血圧（Pトレンド=0.05）に大きな関連が見られたが、拡張期血圧（P=0.35）には相関がみられなかった。
クロスセクション解析では、他のアミノ酸には血圧値に対する大きな相関はみられなかった。
フォローアップの6 年間 （7292人）で873例に高血圧が発症した。いずれのアミノ酸にも高血圧症発症率との関係に有意な差はみられなかった（HR：0.81-1.18, Pトレンド 0.2）。
結論：本データは、母集団の血圧や高血圧のリスクを決定する上でグルタミン酸、アルギニン、リジン、チロシン、システインの摂取量（タンパク質摂取量中の割合として）が主要な役割を果たしていることを示唆している訳ではない。 -
重症疾患におけるタンパク異化作用及び栄養要求
全身タンパク質量の損失はタンパク質エネルギー栄養失調症を調べるマーカーであり、多数の合併症と相関関係を有している。
重症疾患は、主に骨格筋からの全身タンパク質量の損失が特徴である。
タンパク質の代謝回転に関する複数の研究では、タンパク質分解の増加、（程度は少ないが）全身タンパク質合成の増加、そして肝臓周囲から肝臓までのアミノ酸のフラックスの増加について述べられている。
適切な栄養摂取によりタンパク質異化作用を抑制することができる。
栄養サポートでは急性の重症疾患で生じた全身タンパク質量の損失を抑制はするが、止めることはできない。
タンパク動態に対する影響の研究については、恐らく用いる研究方法や栄養サポートが多様であるために異論も多い。
数日間のカロリーバランスの維持だけでは、臨床上の成果を明確に改善するには至らない。
それに対して、エネルギーバランスの取れたエネルギー摂取を伴う1.2－1.5g/kg（体重）・日のタンパク質の摂取により、全身タンパク質量の損失を最小限に抑えることができる。
グルタミンそして恐らくロイシンは臨床結果を改善する可能性があるが、それが全身タンパク質量やその代謝回転、またはその他のメカニズムへの影響によるものか否かについては明らかでない。
現在推奨されている事項では、最初の72－96時間は20－25kcal/kg・日を投与し、それ以降はエネルギー摂取量を目標量まで増やすこととされている。
同時に、タンパク質の摂取量は1.2-1.5 g/kg・日とする。
外傷、急性呼吸窮迫症候群（ARDS）、そして軽度の敗血症の症例に対してはアルギニン、ヌクレオチド及びオメガ-3脂肪酸を強化した経腸性免疫栄養法が示されている。
熱傷及び外傷の症例に対しては経腸性栄養剤に（ESPENガイドライン2006）、集中治療室 （ICU）の症例に対しては一般にジペプチドの形で、非経腸栄養剤にグルタミン（L-グルタミン 0.2-0.4g/kg・日）を添加するものとする（ESPENガイドライン2009）。 -
非経口栄養摂取におけるアミノ酸の構成：その根拠
レビューの目的：完全な非経口栄養液には、 9つの必須アミノ酸とさまざまな組成からなる非必須アミノ酸による混合アミノ酸が含まれている。非経口栄養アミノ酸の組成変更に関する正確な比較効果の研究は比較的少ない。
最近の知見：非経口栄養摂取において、全てのアミノ酸または特定アミノ酸の最適な摂取量を決定する上で、十分な説得力のある利用可能な二重盲検ランダム化臨床試験のデータは少ない。但し例外として、グルタミンの非経口栄養補給の効能や単回の非経口投与に関する研究は増加している。
非経口によるグルタミンの摂取は特定の患者に効果がみられるが、グルタミンの最適投与量の決定やこのアミノ酸からの効果が最も期待される患者のサブグルーブに関する追加的な研究データが必要である。いくつかの有望な研究が公表されているものの、現段階ではアルギニン、分岐鎖アミノ酸、システイン、タウリンの非経口摂取量を変更した場合の臨床効果に関して、栄養面のサポートを示唆する研究データはほとんど存在しない。
要約：非経口による栄養摂取を日常的に利用しているにもかかわらず、こうした治療が必要な成人及び小児患者において、全てのアミノ酸または特定アミノ酸の投与量を示す臨床的に有効なデータはほとんど存在しない。このことは、研究者や資金提供機関の注目を集め、アミノ酸の非経口による栄養摂取が必要な患者のサブグループに対する最適投与計画を適切に設定することが必要であることを意味している。