Activation of Immune T Cells Leads to Behavioral Changes

Activation of Immune T Cells Leads to Behavioral Changes

Summary: A new Nature Immunology study reveals immune cells alter the body’s metabolism when activated, leading to changes in behavior.

Source: RIKEN.

Scientists from the RIKEN Center for Integrative Medical Sciences in Japan and collaborators have found that T cells — immune cells that help to protect the body from infections and cancer — change the body’s metabolism when they are activated, and that this activation actually leads to changes in behavior.

It is currently known that individual T cells change their metabolism to meet their energy needs after being activated, but the systemic metabolic effect of sustained activation of the immune system has remained unexplored. To understand the systemic effects, the group looked at T cell activation in mice designed to lack a surface receptor called PD-1, which is necessary for inhibiting the activity of T cells. T cells remain activated in mice without the receptor, similar to those in the immune systems of people with certain types of autoimmune disease. In these mice, they found that amino acids–molecules that are used to build proteins–were depleted in the blood, and that they were increased in the T cells themselves, implicating the T cells in the change.

The team tracked and imaged amino acids in many organs, and found that the depletion of amino acids from the blood was taking place due to the accumulation of amino acids in activated T cells in the lymph nodes, showing that strong or long lasting immune responses can cause metabolic changes elsewhere in the body.

The remaining question was whether this depletion of amino acids was actually having any systemic effect. By analyzing the biochemistry of the brain, they found that the systemic decrease in the amino acids tryptophan and tyrosine in blood led to lower amounts available in the brain, limiting production of the neurotransmitters serotonin and dopamine. These neurotransmitters affect emotions, motivation and fear–for example, serotonin is often a target of drugs that combat depression. The researchers found that their depletion in mice without PD-1 resulted in behavioral changes dominated by anxiety and exacerbated fear responses, which could be remedied by providing a diet rich in an essential amino acid.

This research, which was published in Nature Immunology, required teamwork and collaboration to link diverse fields of biology: immunology, neuroscience and behavior, using cutting edge metabolite measurements and imaging methods. “Together these data indicate that excessive activation of T cells causes a systemic metabolomic shift with consequences that extend beyond the immune system” says Michio Miyajima, one of the four first co-authors of this study.

t cell

According to Sidonia Fagarasan, the leader of the group, “We were fascinated to see that this happens-as it revealed the power of the immune system to influence many aspects of the body’s physiology besides infection and immunity. It will be interesting in the future to investigate whether the trigger of fear and anxiety by T cell activation is merely a side effect of the process, or whether there is an evolutionary benefit of this adaptation. We would also like to further investigate these changes, as the blockade of PD-1 is being investigated as an anti-cancer therapy, and it is important to understand if this could have behavioral changes such as increases in anxiety.”

ABOUT THIS NEUROSCIENCE RESEARCH ARTICLE

Funding: This research was supported by the Japan Agency for Medical Research and Development-Core Research for Evolutional Science and Technology (14532135 to S.F.), Japan Agency for Medical Research and Development (145208 and 16770835 to T.H.) and the Cell Science Foundation (K.C). The work was done by RIKEN in collaboration with Keio University, Kyoto University, and other institutions.

Source: Jens Wilkinson – RIKEN
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public doamin.
Original Research: Abstract for “Metabolic shift induced by systemic activation of T cells in PD-1-deficient mice perturbs brain monoamines and emotional behavior” by Michio Miyajima, Baihao Zhang, Yuki Sugiura, Kazuhiro Sonomura, Matteo M Guerrini, Yumi Tsutsui, Mikako Maruya, Alexis Vogelzang, Kenji Chamoto, Kurara Honda, Takatoshi Hikida, Satomi Ito, Hongyan Qin, Rikako Sanuki, Keiichiro Suzuki, Takahisa Furukawa, Yasushi Ishihama, Fumihiko Matsuda, Makoto Suematsu, Tasuku Honjo & Sidonia Fagarasan in Nature Immunology. Published online October 23 2017 doi:10.1038/ni.3867

CITE THIS NEUROSCIENCENEWS.COM ARTICLE
RIKEN “Activation of Immune T Cells Leads to Behavioral Changes.” NeuroscienceNews. NeuroscienceNews, 23 October 2017.
<http://neurosciencenews.com/t-cell-behavioral-changes-7792/&gt;.

Abstract

Metabolic shift induced by systemic activation of T cells in PD-1-deficient mice perturbs brain monoamines and emotional behavior

T cells reorganize their metabolic profiles after being activated, but the systemic metabolic effect of sustained activation of the immune system has remained unexplored. Here we report that augmented T cell responses in Pdcd1−/− mice, which lack the inhibitory receptor PD-1, induced a metabolic serum signature characterized by depletion of amino acids. We found that the depletion of amino acids in serum was due to the accumulation of amino acids in activated Pdcd1−/− T cells in the lymph nodes. A systemic decrease in tryptophan and tyrosine led to substantial deficiency in the neurotransmitters serotonin and dopamine in the brain, which resulted in behavioral changes dominated by anxiety-like behavior and exacerbated fear responses. Together these data indicate that excessive activation of T cells causes a systemic metabolomic shift with consequences that extend beyond the immune system.

“Metabolic shift induced by systemic activation of T cells in PD-1-deficient mice perturbs brain monoamines and emotional behavior” by Michio Miyajima, Baihao Zhang, Yuki Sugiura, Kazuhiro Sonomura, Matteo M Guerrini, Yumi Tsutsui, Mikako Maruya, Alexis Vogelzang, Kenji Chamoto, Kurara Honda, Takatoshi Hikida, Satomi Ito, Hongyan Qin, Rikako Sanuki, Keiichiro Suzuki, Takahisa Furukawa, Yasushi Ishihama, Fumihiko Matsuda, Makoto Suematsu, Tasuku Honjo & Sidonia Fagarasan in Nature Immunology. Published online October 23 2017 doi:10.1038/ni.3867

Tryptophan – Niacin – NAD = Anti-aging

tryp foodtryptryptophan and niacin

Chocolate, oats, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, almonds, sunflower seeds, pumpkin seeds, buckwheat, spirulina, bananas, and peanuts.

Tryptophan

For many organisms (including humans), tryptophan is needed to prevent illness or death, but cannot be synthesized by the organism and must be ingested; in short, it is an essential amino acid. Amino acids, including tryptophan, act as building blocks in protein biosynthesis, and proteins are required to sustain life. In addition, tryptophan functions as a biochemical precursor for the following compounds (see also figure to the right):

  • Serotonin (a neurotransmitter), synthesized via tryptophan hydroxylase.[9][10] Serotonin, in turn, can be converted to melatonin (a neurohormone), via N-acetyltransferase and 5-hydroxyindole-O-methyltransferase activities.[11]
  • Niacin, also known as vitamin B3, is synthesized from tryptophan via kynurenine and quinolinic acids as key biosynthetic intermediates.[12]
  • Auxins (a class of phytohormones) are synthesized from tryptophan.[13]
  • The disorder fructose malabsorption causes improper absorption of tryptophan in the intestine, reduced levels of tryptophan in the blood,[14] and depression.[15] Some studies did not find reduced tryptophan in cases of lactose maldigestion.[14]
  • Niacin and its derivative nicotinamide are dietary precursors of nicotinamide adenine dinucleotide (NAD), which can be phosphorylated (NADP) and reduced (NADH and NADPH). NAD functions in oxidation-reduction (redox) reactions and non-redox reactions. (More information)
  • Pellagra is the disease of severe niacin deficiency. It is characterized by symptoms affecting the skin, the digestive system, and the nervous system and can lead to death if left untreated. (More information)
  • Dietary tryptophan can be converted to niacin, although the efficiency of conversion is low in humans and affected by deficiencies in other nutrients. (More information)
  • Causes of niacin deficiency include inadequate oral intake, poor bioavailability from unlimed grains, defective tryptophan absorption, metabolic disorders, and the long-term use of chemotherapeutic treatments. (More information)
  • The requirements for niacin are based on the urinary excretion of niacin metabolites. (More information)
  • NAD is the sole substrate for PARP enzymes involved in DNA repair activity in response to DNA strand breaks; thus, NAD is critical for genome stability. Several studies, mostly using in vitro and animal models, suggest a possible role for niacin in cancer prevention. Nevertheless, large studies are needed to investigate the association between niacin deficiency and cancer risk in human populations. (More information)
  • Despite promising initial results, nicotinamide administration has failed to prevent or delay the onset of type 1 diabetes in high-risk relatives of type 1 diabetics. Future research might explore the use of nicotinamide in combined therapy and evaluate activators of NAD-dependent enzymes. (More information)
  • At pharmacologic doses, niacin, but not nicotinamide, improves the lipid profile and reduces coronary events and total mortality in patients at high risk for coronary heart disease. Several clinical trials have explored the cardiovascular benefit of niacin in combination with other lipid-lowering medications. (More information)
  • Elevated tryptophan breakdown and niacin deficiency have been reported in HIV-positive people. This population is also at high risk for cardiovascular disease, and current data show that they could benefit from niacin supplementation. (More information)
  • The tolerable upper intake level (UL) for niacin is based on skin flushing, niacin’s most prominent side effect. A new drug, laropiprant, has been developed to reduce skin flushing. Adverse effects have also been reported with pharmacologic doses of niacin administrated alone or in combination with other lipid-lowering medications. (More information)
  • Niacin is a water-soluble vitamin, which is also known as nicotinic acid or vitamin B3. Nicotinamide is the derivative of niacin and used by the body to form the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). The chemical structures of the various forms of niacin are shown (Figure 1). None of the forms are related to the nicotine found in tobacco, although their names are similar (1).

Function

  • Oxidation-reduction (redox) reactions
  • Living organisms derive most of their energy from oxidation-reduction (redox) reactions, which are processes involving the transfer of electrons. Over 400 enzymes require the niacin coenzymes, NAD and NADP, mainly to accept or donate electrons for redox reactions (2). NAD functions most often in energy-producing reactions involving the degradation (catabolism) of carbohydrates, fats, proteins, and alcohol. NADP functions more often in biosynthetic (anabolic) reactions, such as in the synthesis of all macromolecules, including fatty acids and cholesterol (1, 3).

Non-redox reactions

  • The niacin coenzyme, NAD, is the substrate (reactant) for at least four classes of enzymes that separate the nicotinamide moiety from NAD and transfer ADP-ribose to acceptors.
  • Mono-ADP-ribosyltransferase enzymes were first discovered in certain bacteria, where they mediate the action of toxins, such as cholera and diptheria. In mammalian cells, these enzymes transfer an ADP-ribose residue from NAD to a specific amino acid of a target protein, with the creation of an ADP-ribosylated protein and the release of nicotinamide. Mono ADP-ribosylation reactions reversibly modify the activity of acceptor proteins, such as G-proteins that bind guanosine-5′-triphosphate (GTP) and act as intermediaries in a number of cell-signaling pathways (4).
  • Poly-ADP-ribose polymerases (PARPs) are enzymes that catalyze the transfer of polymers of ADP-ribose from NAD to acceptor proteins. PARPs appear to function in DNA repair and stress responses, cell signaling, transcription, regulation, apoptosis, chromatin structure, and cell differentiation, suggesting a role for NAD in cancer prevention (3). At least six different PARPs have been identified, and although their functions are not yet fully understood, their existence indicates a potential for considerable consumption of NAD (5, 6).
  • A new nomenclature has been proposed for enzymes catalyzing ADP-ribosylation: The PARP family was renamed ARTD, while ARTC designates the mono ADP-ribosyltransferase family (6).
  • ADP-ribosylcyclases catalyze the formation of cyclic ADP-ribose from ADP-ribose. Cyclic ADP-ribose works within cells to provoke the release of calcium ions from internal storage sites and probably also plays a role in cell signaling (1).
  • Sirtuins are a class of NAD-dependent deacetylase enzymes that remove acetyl groups from the acetylated lysine residues of target proteins. During the deacetylation process, an ADP-ribose is added to the acetyl group to produce O-acetyl-ADP-ribose. Both acetylation and ADP-ribosylation are known post-translational modifications that affect protein activities. The initial interest in sirtuins followed the discovery that their activation could mimic calorie restriction, which has been shown to increase lifespan in lower organisms. Such a role in mammals is controversial, although sirtuins are energy-sensing regulators involved in signaling pathways that could play important roles in delaying the onset of age-related diseases (e.g., cardiovascular disease, cancer, dementia, arthritis). To date, the spectrum of their biological functions include gene silencing, DNA damage repair, cell cycle regulation, and cell differentiation (7).

Summary

  • Niacin and its derivative nicotinamide are dietary precursors of nicotinamide adenine dinucleotide (NAD), which can be phosphorylated (NADP) and reduced (NADH and NADPH). NAD functions in oxidation-reduction (redox) reactions and non-redox reactions. (More information)
  • Pellagra is the disease of severe niacin deficiency. It is characterized by symptoms affecting the skin, the digestive system, and the nervous system and can lead to death if left untreated. (More information)
  • Dietary tryptophan can be converted to niacin, although the efficiency of conversion is low in humans and affected by deficiencies in other nutrients. (More information)
  • Causes of niacin deficiency include inadequate oral intake, poor bioavailability from unlimed grains, defective tryptophan absorption, metabolic disorders, and the long-term use of chemotherapeutic treatments. (More information)
  • The requirements for niacin are based on the urinary excretion of niacin metabolites. (More information)
  • NAD is the sole substrate for PARP enzymes involved in DNA repair activity in response to DNA strand breaks; thus, NAD is critical for genome stability. Several studies, mostly using in vitro and animal models, suggest a possible role for niacin in cancer prevention. Nevertheless, large studies are needed to investigate the association between niacin deficiency and cancer risk in human populations. (More information)
  • Despite promising initial results, nicotinamide administration has failed to prevent or delay the onset of type 1 diabetes in high-risk relatives of type 1 diabetics. Future research might explore the use of nicotinamide in combined therapy and evaluate activators of NAD-dependent enzymes. (More information)
  • At pharmacologic doses, niacin, but not nicotinamide, improves the lipid profile and reduces coronary events and total mortality in patients at high risk for coronary heart disease. Several clinical trials have explored the cardiovascular benefit of niacin in combination with other lipid-lowering medications. (More information)
  • Elevated tryptophan breakdown and niacin deficiency have been reported in HIV-positive people. This population is also at high risk for cardiovascular disease, and current data show that they could benefit from niacin supplementation. (More information)
  • The tolerable upper intake level (UL) for niacin is based on skin flushing, niacin’s most prominent side effect. A new drug, laropiprant, has been developed to reduce skin flushing. Adverse effects have also been reported with pharmacologic doses of niacin administrated alone or in combination with other lipid-lowering medications. (More information)
  • Niacin is a water-soluble vitamin, which is also known as nicotinic acid or vitamin B3. Nicotinamide is the derivative of niacin and used by the body to form the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). The chemical structures of the various forms of niacin are shown (Figure 1). None of the forms are related to the nicotine found in tobacco, although their names are similar (1).
  • Figure 1. Chemical Structures of Niacin and Related Compounds. Niacin is also known as nicotinic acid or vitamin B3. nicotinamide is the derivative of niacin that is used to form the coenzymes NAD and NADP.

Function

  • Oxidation-reduction (redox) reactions
  • Living organisms derive most of their energy from oxidation-reduction (redox) reactions, which are processes involving the transfer of electrons. Over 400 enzymes require the niacin coenzymes, NAD and NADP, mainly to accept or donate electrons for redox reactions (2). NAD functions most often in energy-producing reactions involving the degradation (catabolism) of carbohydrates, fats, proteins, and alcohol. NADP functions more often in biosynthetic (anabolic) reactions, such as in the synthesis of all macromolecules, including fatty acids and cholesterol (1, 3).

Non-redox reactions

  • The niacin coenzyme, NAD, is the substrate (reactant) for at least four classes of enzymes that separate the nicotinamide moiety from NAD and transfer ADP-ribose to acceptors.
  • Mono-ADP-ribosyltransferase enzymes were first discovered in certain bacteria, where they mediate the action of toxins, such as cholera and diptheria. In mammalian cells, these enzymes transfer an ADP-ribose residue from NAD to a specific amino acid of a target protein, with the creation of an ADP-ribosylated protein and the release of nicotinamide. Mono ADP-ribosylation reactions reversibly modify the activity of acceptor proteins, such as G-proteins that bind guanosine-5′-triphosphate (GTP) and act as intermediaries in a number of cell-signaling pathways (4).
  • Poly-ADP-ribose polymerases (PARPs) are enzymes that catalyze the transfer of polymers of ADP-ribose from NAD to acceptor proteins. PARPs appear to function in DNA repair and stress responses, cell signaling, transcription, regulation, apoptosis, chromatin structure, and cell differentiation, suggesting a role for NAD in cancer prevention (3). At least six different PARPs have been identified, and although their functions are not yet fully understood, their existence indicates a potential for considerable consumption of NAD (5, 6).
  • A new nomenclature has been proposed for enzymes catalyzing ADP-ribosylation: The PARP family was renamed ARTD, while ARTC designates the mono ADP-ribosyltransferase family (6).
  • ADP-ribosylcyclases catalyze the formation of cyclic ADP-ribose from ADP-ribose. Cyclic ADP-ribose works within cells to provoke the release of calcium ions from internal storage sites and probably also plays a role in cell signaling (1).
  • Sirtuins are a class of NAD-dependent deacetylase enzymes that remove acetyl groups from the acetylated lysine residues of target proteins. During the deacetylation process, an ADP-ribose is added to the acetyl group to produce O-acetyl-ADP-ribose. Both acetylation and ADP-ribosylation are known post-translational modifications that affect protein activities. The initial interest in sirtuins followed the discovery that their activation could mimic calorie restriction, which has been shown to increase lifespan in lower organisms. Such a role in mammals is controversial, although sirtuins are energy-sensing regulators involved in signaling pathways that could play important roles in delaying the onset of age-related diseases (e.g., cardiovascular disease, cancer, dementia, arthritis). To date, the spectrum of their biological functions include gene silencing, DNA damage repair, cell cycle regulation, and cell differentiation (7).

Deficiency: Pellagra

  • The late stage of severe niacin deficiency is known as pellagra. Early records of pellagra followed the widespread cultivation of corn in Europe in the 1700s (1). The disease is generally associated with poorer social classes whose chief dietary staple consisted of cereals like corn or sorghum. Pellagra was also common in the southern United States during the early 1900s where income was low and corn products were a major dietary staple (8).
  • Interestingly, pellagra was not known in Mexico, where corn was also an important dietary staple and much of the population was also poor. In fact, corn contains appreciable amounts of niacin, but it is present in a bound form that is not nutritionally available to humans. The traditional preparation of corn tortillas in Mexico involves soaking the corn in a lime (calcium oxide) solution, prior to cooking. Heating the corn in an alkaline solution results in the release of bound niacin, increasing its bioavailability (9).
  • The most common symptoms of niacin deficiency involve the skin, the digestive system, and the nervous system (3). The symptoms of pellagra are commonly referred to as the three D’s: dermatitis, diarrhea, and dementia. A fourth D, death, occurs if pellagra is left untreated (10). In the skin, a thick, scaly, darkly pigmented rash develops symmetrically in areas exposed to sunlight. In fact, the word “pellagra” comes from “pelle agra,” the Italian phrase for rough or raw skin. Symptoms related to the digestive system include inflammation of the mouth and tongue (“bright red tongue”), vomiting, constipation, abdominal pain, and ultimately, diarrhea.
  • Gastrointestinal disorders and diarrhea contribute to the ongoing malnourishment of the subjects. Neurologic symptoms include headache, apathy, fatigue, depression, disorientation, and memory loss and are more consistent with delirium than with the historically described dementia (11). Disease presentations vary in appearance since the classic triad rarely presents in its entirety. The absence of dermatitis, for example, is known as pellagra sine pellagra.

Treatment of pellagra

  • To treat pellagra, the World Health Organization (WHO) recommends administering nicotinamide to avoid the flushing commonly caused by niacin (see Safety). Treatment guidelines suggest using 300 mg nicotinamide per day orally in divided doses, or 100 mg per day parenterally in divided doses, for three to four weeks (12, 13). Because patients with pellagra often display additional vitamin deficiencies, administration of a vitamin B-complex preparation is advised.

Tryptophan metabolism

  • In addition to its synthesis from dietary niacin, NAD can be synthesized from the dietary amino acid tryptophan via the kynurenine pathway (see Figure 2 below). The relative ability to make this conversion varies greatly from mice to humans. The first step is catalyzed by the extrahepatic enzyme indoleamine 2,3-dioxygenase (IDO), which is responsible for the oxidative cleavage of tryptophan. The chronic stimulation of tryptophan oxidation, mediated by an increased activity of IDO and/or inadequate niacin levels, is observed in a number of diseases, including human immunodeficiency virus (HIV) infection (see HIV/AIDS). In healthy individuals, less than 2% of dietary tryptophan is converted to NAD by this tryptophan oxidation pathway (14).
  • Tryptophan metabolism plays an essential regulatory role by mediating immunological tolerance of the fetus during pregnancy (15). It is now understood that tryptophan oxidation in the placenta drives a physiologic tryptophan depletion that impairs the function of nearby maternal T-lymphocytes and prevents the rejection of the fetus. However, the synthesis of niacin from tryptophan is a fairly inefficient pathway that depends on enzymes requiring vitamin B6 and riboflavin, as well as an enzyme containing heme (iron). On average, 1 milligram (mg) of niacin can be synthesized from the ingestion of 60 mg of tryptophan. The term “niacin equivalent” (NE) is used to describe the contribution to dietary intake of all the forms of niacin that are available to the body.
  • Thus, 60 mg of tryptophan are considered to be 1 mg NE. However, studies of pellagra in the southern US during the early twentieth century indicated that the diets of many individuals who suffered from pellagra contained enough NE to prevent pellagra (10), challenging the idea that 60 mg of dietary tryptophan are equivalent to 1 mg of niacin. In particular, one study in young men found that the tryptophan content of the diet had no effect on the decrease in red blood cell niacin content that resulted from low dietary niacin (16).

Causes of niacin deficiency

  • Niacin deficiency or pellagra may result from inadequate dietary intake of niacin and/or tryptophan. As mentioned above, other nutrient deficiencies may also contribute to the development of niacin deficiency. Niacin deficiency, often associated with malnutrition, is observed in the homeless population, in individuals suffering from anorexia nervosa or obesity, and in consumers of diets high in maize and poor in animal proteins (17-20).
  • Patients with Hartnup’s disease, a hereditary disorder resulting in defective tryptophan absorption, have developed pellagra (3). Other malabsorptive states that can lead to pellagra include Crohn’s disease and megaduodenum (21, 22). Carcinoid syndrome, a condition of increased secretion of serotonin and other catecholamines by carcinoid tumors, may also result in pellagra due to increased utilization of dietary tryptophan for serotonin rather than niacin synthesis. Further, prolonged treatment with the anti-tuberculosis drug Isoniazid has resulted in niacin deficiency (23).
  • Other pharmaceutical agents, including the immunosuppressive drugs Azathioprine and 6-Mercaptopurine, the anti-cancer drug 5-Fluorouracil, and Carbidopa, a drug given to people with Parkinson’s disease, are known to increase the reliance on dietary niacin by interfering with the tryptophan-kinurenine-niacin pathway. Finally, other populations at risk for niacin deficiency include dialysis patients, cancer patients (13, 24), individuals suffering from chronic alcoholism (11), and people with HIV (see HIV/AIDS).

Disease Prevention: Cancer

  • Studies of cultured cells (in vitro) provide evidence that NAD content influences mechanisms that maintain genomic stability. Loss of genomic stability, characterized by a high rate of damage to DNA and chromosomes, is a hallmark of cancer (28). The current understanding is that the pool of NAD is decreased during niacin deficiency and that it affects the activity of NAD-consuming enzymes rather than redox and metabolic functions (29). Among NAD-dependent reactions, poly ADP-ribosylations catalyzed by PARP enzymes are critical for the cellular response to DNA injury. After DNA damage, PARPs are activated.
  • The subsequent poly ADP-ribosylations of a number of signaling and structural molecules by PARPs were shown to facilitate DNA repair at DNA strand breaks. Cellular depletion of NAD has been found to decrease levels of the tumor suppressor protein p53, a target for poly ADP-ribosylation, in human breast, skin, and lung cells (27). The expression of p53 was also altered by niacin deficiency in rat bone marrow cells (30). Impairment of DNA repair caused by niacin deficiency could lead to genomic instability and drive tumor development in rat models (31, 32).
  • Both PARPs and sirtuins have been recently involved in the maintenance of heterochromatin, a chromosomal domain associated with genome stability, as well as in transcriptional gene silencing, telomere integrity, and chromosome segregation during cell division (33, 34). Neither the cellular NAD content nor the dietary intake of NAD precursors (niacin and tryptophan) necessary for optimizing protective responses following DNA damage has been determined, but both are likely to be higher than that required for the prevention of pellagra.

Bone marrow

  • Cancer patients often suffer from bone marrow suppression following chemotherapy, given that bone marrow is one of the most proliferative tissues in the body and thus a primary target for chemotherapeutic agents. Niacin deficiency was found to decrease bone marrow NAD and poly-ADP-ribose levels and increase the risk of chemically induced leukemia in rats (35). Conversely, a pharmacologic dose of niacin was able to increase NAD and poly ADP-ribose in bone marrow and decrease the development of leukemia in rats (36).
  • It has been suggested that niacin deficiency often observed in cancer patients could sensitize bone marrow tissue to the suppressive effect of chemotherapy. However, little is known regarding cellular NAD levels and the prevention of DNA damage or cancer in humans. One study in two healthy individuals involved elevating NAD levels in blood lymphocytes by supplementation with 100 mg/day niacin for eight weeks.
  • Compared to non-supplemented individuals, the supplemented individuals had reduced DNA strand breaks in lymphocytes exposed to free radicals in a test tube assay (37). However, niacin supplementation of up to 100 mg/day in 21 healthy smokers failed to provide any evidence of a decrease in cigarette smoke-induced genetic damage in blood lymphocytes compared to placebo (38).
  • More recently, the frequency of chromosome translocation was used to evaluate DNA damage in peripheral blood lymphocytes of 82 pilots chronically exposed to ionizing radiation, a known human carcinogen. In this observational study, the rate of chromosome aberrations was significantly lower in subjects with high (28.4 mg/day) compared to low (20.5 mg/day) dietary niacin intake (39).

Upper digestive tract

  • Generally, relationships between dietary factors and cancer are established first in epidemiological studies and followed up by basic cancer research at the cellular level. In the case of niacin, research on biochemical and cellular aspects of DNA repair has stimulated an interest in the relationship between niacin intake and cancer risk in human populations (40). A large case-control study found increased consumption of niacin, along with antioxidant nutrients, to be associated with decreased incidence of oral (mouth), pharyngeal (throat), and esophageal cancers in northern Italy and Switzerland (41, 42). An increase in daily niacin intake of 6.2 mg was associated with about a 40% decrease in cases of cancers of the mouth and throat, while a 5.2 mg increase in daily niacin intake was associated with a similar decrease in cases of esophageal cancer.

Skin

  • Niacin deficiency can lead to severe sunlight sensitivity in exposed skin. Given the implication of NAD-dependent enzymes in DNA repair, there has been some interest in the effect of niacin on skin health. In vitro and animal experiments have helped gather information, but human data on niacin/NAD status and skin cancer are severely limited. One study reported that niacin supplementation decreased the risk of ultraviolet light (UV)-induced skin cancers in mice, despite the fact that mice convert tryptophan to NAD more efficiently than rats and humans and thus do not get severely deficient (43).
  • Hyper-proliferation and impaired differentiation of skin cells can alter the integrity of the skin barrier and increase the occurrence of pre-malignant and malignant skin conditions. A protective effect of niacin was suggested by topical application of myristyl nicotinate, a niacin derivative, which successfully increased the expression of epidermal differentiation markers in subjects with photodamaged skin (44). The activation of the “niacin receptors,” GPR109A and GPR109B, by pharmacologic doses of niacin could be involved in improving skin barrier function. Conversely, differentiation defects in skin cancer cells were linked to the abnormal cellular localization of defective “niacin receptors” (45).
  • Nicotinamide restriction with subsequent depletion of cellular NAD was shown to increase oxidative stress-induced DNA damage in a precancerous skin cell model, implying a protective role of NAD-dependent pathways in cancer (46). Altered NAD availability also affects sirtuin expression and activity in UV-exposed human skin cells. Along with PARPs, NAD-consuming sirtuins could play an important role in the cellular response to photodamage and skin homeostasis (47).

Type 1 diabetes mellitus

  • Type 1 (insulin-dependent) diabetes mellitus in children is known to result from the autoimmune destruction of insulin-secreting β-cells in the pancreas. Prior to the onset of symptomatic diabetes, specific antibodies, including islet cell antibodies (ICA), can be detected in the blood of high-risk individuals. The ability to detect individuals at high risk for the development of IDDM led to the enrollment of high-risk siblings of children with IDDM into trials designed to prevent its onset. Evidence from in vitro and animal research indicates that high levels of nicotinamide protect β-cells from damage by toxic chemicals, inflammatory white blood cells, and reactive oxygen species. Pharmacologic doses of nicotinamide (up to 3 grams/day) were first used to protect β-cells in patients shortly after the onset of IDDM.
  • An analysis of 10 published trials (5 placebo-controlled) found evidence of improved β-cell function after one year of treatment with nicotinamide, but the analysis failed to find any clinical evidence of improved glycemic (blood glucose) control (48). However, high doses of nicotinamide could decrease insulin sensitivity in high-risk relatives of IDDM patients (49), which might explain the finding of improved β-cell function without concomitant improvement in glycemic control.

http://lpi.oregonstate.edu/mic/vitamins/niacin

https://en.wikipedia.org/wiki/Tryptophan

https://www.technologyreview.com/s/534636/the-anti-aging-pill/

Click to access bogan08.pdf

For energy metabolism, consume protein- rich foods (6 functional amino acids); brain uses 20% of the energy from food

Energy MetabolismOf the 20 amino acids required for protein synthesis, six of them (arginine, cysteine, glutamine, leucine, proline, and tryptophan), collectively known as the functional amino acids, regulate key metabolic pathways involved in cellular growth, and development, as well as other important biological processes such as immunity and reproduction.

Note:
Intense exercise decreases the plasma glutamine concentration and this may be related to immunosuppression.
Several researches found the efficacy of L-arginine and nitric oxide on penile erection, fixing erectile dysfunction.

For example, leucine activates mTOR signaling and increases protein synthesis, leading to lymphocyte proliferation. Therefore, a lack of leucine can compromise immune function. Metabolic pathways interrelated with the biosynthesis and degradation of these amino acids include vitamin and cofactor biosynthesis (such as SAM or S-Adenosyl Methionine) as well as neurotransmitter metabolism (such as glutamate).

Leucine food sources Leucine content (grams/ 100 gram food)
Soybeans, mature seeds, raw 2.97
lentils, raw 2.03
cowpea, catjang, mature seeds, raw 1.83
Beef, round, top round, separable lean and fat, trimmed to 1/8″ fat, select, raw 1.76
Beef, top sirloin, separable lean only, trimmed to 1/8″ fat, choice, raw 1.74
Peanuts, all types, raw 1.67
Salami, Italian, pork 1.63
Fish, salmon, pink, raw
1.62
Crustaceans, shrimp, mixed species, raw 1.61
Chicken, broilers or fryers, thigh, meat only, raw 1.48
Nuts, almonds 1.47
Egg, yolk, raw, fresh 1.40
Chickpeas (garbanzo beans, bengal gram), mature seeds, raw 1.37
Seeds, sesame butter, tahini, from raw and stone ground kernels 1.36
Chicken, broilers or fryers, wing, meat and skin, raw 1.29
flax seed, raw
1.24
Nuts, walnuts, english 1.17
Egg, whole, raw, fresh 1.09
Egg, white, raw, fresh 1.02
Sausage, Italian, pork, raw 0.96
Milk, sheep, fluid 0.59
Pork, fresh, separable fat, raw 0.40
Hummus 0.35
Milk, goat, fluid 0.31
Milk, whole, 3.25% milkfat 0.27
Soy milk, fluid 0.24
asparagus 0.13
Snap beans, green, raw 0.11
Milk, human, mature, fluid 0.10

Amino Acid L-Arginine, Nitric Oxide, and Erectile Dysfunction
Last Updated on Thursday, 05 April 2012 15:20
According to the National Health Institute (NIH) Consensus Development Panel on Impotence, erectile dysfunction (ED) is defined as the persistent inability to achieve and/or maintain an erection sufficient for satisfactory sexual performance.
Causes of erectile dysfunction may be psychological and physiological factors (neurogenic, vascular, endocrine causes). It may also be a side effect of drugs and a symptom of health complications such as diabetes.
Penile erection occurs as a result of increased blood inflow to the penis, engorgement with blood, and decreased outflow of blood from the penis. Primarily, this process is mediated by nitric oxide, which is a neurotransmitter and vasodilator. Nitric oxide is synthesized from L-arginine.

Several researches on the efficacy of L-arginine and nitric oxide on penile erection, fixing erectile dysfunction, have reported positive effects of both chemicals in stimulating and maintaining erection. For example, a study reported that 80 % of men (out of 40, age group 25 – 45) with erectile dysfunction treated with L-arginine (dosage: 1.7 g/ day) and Pycnogenol, an extract from French maritime pine bark (Pinus pinaster), (dosage: 80 mg/day) recovered from their erectile dysfunction after one month of treatment. Pycnogenol, also an antioxidant, stimulates synthesis of nitric oxide from L-arginine. The researchers reported that there was no side effect associated with the supplements.

In another double-blind, placebo-controlled, clinical research on the effect and safety of the combination of 6 g of L-arginine glutamate and 6 mg of yohimbine hydrochloride with that of 6 mg of yohimbine hydrochloride alone and that of placebo alone, for the treatment of erectile dysfunction (ED), it was reported that combined oral administration of the L-arginine glutamate ( 6 g) and yohimbine (6 mg) was effective in improving erectile function in patients with mild to moderate erectile dysfunction (ED).

Herbs and sexuality:
Yohimbe: health benefits and side effects
Ginseng: health benefits and side effects
Ginkgo Biloba: health benefits and side effects

Erectile dysfunction related articles:
What is erectile dysfunction? How does erection occur?
What are the causes of erectile dysfunction?
What are the treatments for erectile dysfunction?

References:

Stanislavov, R. and Nikolova. 2003. Treatment of Erectile Dysfunction with Pycnogenol and L-arginine. Journal of Sex and Marital Therapy, 29(3): 207 – 213.

Basu, A. and Ryder, R. E. J. 2004. New Treatment Options for Erectile Dysfunction in Patients with Diabetes Mellitus. Drugs, 64(23): 2667 – 2688.

Toda, N. Ayajiki, K. Okamura, T. 2005. Nitric Oxide and Penile Erectile Function. Pharmacology and Therapeutics, 106: 233 – 266.

Lebret, T., Hervéa, J. M., Gornyb, P., Worcelc, M. and Botto, H. 2002. Efficacy and Safety of a Novel Combination of L-Arginine Glutamate and Yohimbine Hydrochloride: A New Oral Therapy for Erectile Dysfunction. European Urology 41(6): 608-613.

Functions of non-essential amino acids

The following list includse the 12 non-essential amino acids. Included is a some of the functions and benefits and side effects (if any) of the amino acids.

Alanine: Removes toxic substances released from breakdown of muscle protein during intensive exercise. Side effects: Excessive alanine level in the body is associated with chronic fatigue.
Cysteine: Component of protein type abundant in nails, skin and hair. It acts as antioxidant (free radical scavenger), and has synergetic effect when taken with other antioxidants such as vitamin E and selenium.
Cystine: The same as cysteine, it aids in removal of toxins and formation of skin.
Glutamine: Promotes healthy brain function. It is also necessary for the synthesis of RNA and DNA molecules.
Glutathione: Is antioxidant and has anti-aging effect. It is useful in removal of toxins.
Glycine: Component of skin and is beneficial for wound healing. It acts as neurotransmitter. The side effect of high level glycine in the body is that it may cause fatigue.
Histidine: Important for the synthesis of red and white blood cells. It is a precursor for histamine which is good for sexual arousal. Improve blood flow. Side effects of high dosage of histidine include stress and anxiety.
Serine: Constituent of brain proteins and aids in the synthesis of immune system proteins. It is also good for muscle growth.
Taurine: Necessary for proper brain function and synthesis of amino acids. It is important in the assimilation of mineral nutrients such as magnesium, calcium and potassium.
Threonine: Balances protein level in the body. It promotes immune system. It is also beneficial for the synthesis of tooth enamel and collagen.
Asparagine: It helps promote equilibrium in the central nervous system—aids in balancing state of emotion.
Apartic acid: Enhances stamina, aids in removal of toxins and ammonia from the body, and beneficial in the synthesis of proteins involved in the immune system.
Proline: plays role in intracellular signalling.
L-arginine: plays role in blood vessel relaxation, stimulating and maintaining erection in men, production of ejaculate, and removal of excess ammonia from the body.

A list of sample of high or low protein food sources is below:
Protein food source Estimated protein content
½ cup tofu
14 g
½ cup legumes 7 g
2 ounce lean meat, fish, poultry 14 g
1-2 ounces of nuts 14 g
1 slice of bread 3 g
1 cup raw vegetables 2 g

Maintenance of Immunity
It is generally believed that moderate exercise enhances immunocompetence and is effective for the prevention of inflammatory diseases, infection, and cancer, while excessive physical activity leads to immunosuppression and an increase of inflammatory and allergic disorders.

Susceptibility to infections following excessive physical activity is ascribed to an increase in the production of immunosuppressive factors such as adrenocortical hormones and anti-inflammatory cytokines, leading to a decrease in the number and activity of circulating natural killer cells and T cells as well as a lower IgA concentration in the saliva.
Therefore, athletes performing high-intensity training are exposed to the risk of impaired immunocompetence. Intake of carbohydrates during prolonged exercise at submaximal intensity attenuates the increase of plasma cortisol and cytokine levels after exercise, which could lead to the inhibition of immunosuppression.
Vitamin C and vitamin E have actions that promote immunity, and are essential for T cell differentiation and for maintenance of T cell function.
However, there is limited evidence about the effects of vitamins supplementation on immune function in relation to exercise.
Glutamine is an important energy source for lymphocytes, macrophages, and neutrophils, and is also an essential amino acid for the differentiation and growth of these cells.
Intense exercise decreases the plasma glutamine concentration and this may be related to immunosuppression.
Castell et al. reported that athletes who ingested glutamine had a lower infection rate after a marathon compared with the placebo group. They also demonstrated that intake of glutamine resulted in an increase of the T-helper/T-suppressor cell ratio.
Furthermore, glutamine enhances the activity of intestinal enterobacteria and inhibits the production of cytokines involved in inflammation or immunosuppression.
Conclusion
Due to a social background that includes changes of dietary habits, an aging population, and increased medical costs, people have shown a growing interest in health and have come to expect complex and diverse actions of foods.
In recent years, various food factors that fulfill such requirements have been evaluated scientifically to determine whether they are any physiological effects like prevention of diseases.

In the sports market, a variety of functional foods are available, but among these functional foods, some have not clearly demonstrated any efficacy and others are advertised with inappropriate and exaggerated claims, so consumers are often confused. Some of the food components described in this article should be studied further because of differing views with regard to their efficacy in different reports.

Furthermore, the effectiveness of the components may differ according to gender, between individuals, and with the mode of ingestion, so that the optimum method of intake the quantity and quality of foods to be ingested, and the timing of their intake need to be established in accordance with the purpose of using each food or food component, after understanding the physiological changes by exercise.

In the future, guidelines for the use and evaluation system of sports functional foods should be established with backing by clear scientific evidence related to the individual foods.
Wataru Aoi1 ,2 , Yuji Naito3 and Toshikazu Yoshikawa2 ,3
1Research Center for Sports Medicine, Doshisha University, Kyoto 602-8580, Japan
2Department of Inflammation and Immunology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan
3Department of Medical Proteomics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan

Nutrition Journal 2006, 5:15 doi:10.1186/1475-2891-5-15