Nitric Oxide Information

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Nitric Oxide metabolism:

Nitric oxide (NO) is as a major signaling molecule in neurons and in the immune system, either acting within the cell in which it is produced or by penetrating cell membranes to affect adjacent cells. Nitric oxide is generated from arginine by the action of nitric oxide synthase (NOS). NO has a half-life of only a few seconds in vivo . However, since it is soluble in both aqueous and lipid media, it readily diffuses through the cytoplasm and plasma membranes. NO has effects on neuronal transmission as well as on synaptic plasticity in the central nervous system. In the vasculature, NO reacts with iron in the active site of the enzyme guanylyl cyclase (GC), stimulating it to produce the intracellular mediator cyclic GMP (cGMP), that in turn enhances the release of neurotransmitters resulting in smooth muscle relaxation and vasodilation. NO may also be involved in the regulation of protein activity through S-nitrosylation. In the extracellular milieu, NO reacts with oxygen and water to form nitrates and nitrites. NO toxicity is linked to its ability to combine with superoxide anions (O2-) to form peroxynitrite (ONOO-), an oxidizing free radical that can cause DNA fragmentation and lipid oxidation. In the mitochondria, ONOO- acts on the respiratory chain (I-IV) complex and manganese superoxide dismutase (MnSOD), to generate superoxide anions and hydrogen peroxide (H2O2), respectively

Brown, G.C., Nitric oxide and mitochondrial respiration. Biochim. Biophys. Acta., 1411, 351-369 (1999).

Lipton, S.A., Neuronal protection and destruction by NO. Cell Death Differ., 6, 943-951 (1999).

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Nitric Oxide and IGF-1:

Nitric Oxide increases glucose transport in skeletal muscle

Evidence that nitric oxide increases glucose transport in skeletal muscle. J. Appl. Physiol. 82(1): 359-363, 1997.

These observations suggest: (a) that IGF-I increases blood flow through a nitric oxide-dependent mechanism; (b) that total blood flow does not affect the insulinlike response of muscle to IGF-I; and (c) that nitric oxide may be required for the protein synthetic (growth hormone- like) response of muscle to IGF-I.

(J. Clin. Invest. 1996. 97: 1319-1328.)

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Arginine and Nitrogen Balance:

Arginine Improves Nitrogen Balance in Healthy Men

For seven days, Beaumier et al. (1995) fed healthy young adult males energy-balanced diets characterized by either normal (56.1 mg/kg/day) or arginine-supplemented (561 mg/kg/day) status. The arginine-supplemented group experienced lost weight, which was attributed to sodium and water loss, possibly due to reduced tubular reabsorption of these two compounds. Despite the fact that the nitrogen intake was the same for both groups, the arginine-supplemented group demonstrated an increase in nitrogen retention. These data are suggestive of yet further benefits for bodybuilders increased anabolism with decreased retention of sodium and water, i.e., a more muscular physique.

Cynober et al. (1996) summarizes the clinical applications of arginine:In septic rats, arginine- enriched nutrition (either enteral or parenteral) improves nitrogen balance and total body and liver protein synthesis. In addition, arginine stimulates growth hormone and insulin secretion. The most remarkable action of arginine is certainly that exerted on cellular immunity. This action concerns thymus and extra-thymus areas. Finally, arginine favours wound healing improves host defenses in cancer and slows tumour growth. The pharmacological action of arginine probably depends upon various mechanisms: its action on immunity may be mediated by the synthesis of nitric oxide and polyamines (via ornithine synthesis). The effect on wound healing may be related to proline synthesis. The effects on nitrogen metabolism may be linked to growth hormone secretion. These observations form the rationale for the administration of arginine- enriched diets to injured patients.

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Vitamin C and Nitric Oxide:

Long-Term Vitamin C Treatment Increases Vascular Tetrahydrobiopterin Levels and Nitric Oxide Synthase Activity

Livius V. d’Uscio, Sheldon Milstien, Darcy Richardson, Leslie Smith, Zvonimir S. Katusic

From the Departments of Anesthesiology, and Molecular Pharmacology and Experimental Therapeutics (L.V.U., D.R., L.S., Z.S.K.), Mayo Clinic and Foundation, Rochester, Minn; and the National Institute of Mental Health (S.M.), NIH, Bethesda, Md.

Correspondence to Zvonimir S. Katusic, MD, PhD, Dept of Anesthesiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail katusic.zvonimir@mayo.edu

In cultured endothelial cells, the antioxidant, L-ascorbic acid (vitamin C), increases nitric oxide synthase (NOS) enzyme activity via chemical stabilization of tetrahydrobiopterin. Our objective was to determine the effect of vitamin C on NOS function and tetrahydrobiopterin metabolism in vivo. Twenty-six to twenty-eight weeks of diet supplementation with vitamin C (1%/kg chow) significantly increased circulating levels of vitamin C in wild-type (C57BL/6J) and apolipoprotein E (apoE)–deficient mice. Measurements of NOS enzymatic activity in aortas of apoE-deficient mice indicated a significant increase in total NOS activity. However, this increase was mainly due to high activity of inducible NOS, whereas eNOS activity was reduced. Significantly higher tetrahydrobiopterin levels were detected in aortas of apoE-deficient mice. Long-term treatment with vitamin C restored endothelial NOS activity in aortas of apoE-deficient mice, but did not affect activity of inducible NOS. In addition, 7,8-dihydrobiopterin levels, an oxidized form of tetrahydrobiopterin, were decreased and vascular endothelial function of aortas was significantly improved in apoE-deficient mice. Interestingly, vitamin C also increased tetrahydrobiopterin and NOS activity in aortas of C57BL/6J mice. In contrast, long-term treatment with vitamin E (2000 U/kg chow) did not affect vascular NOS activity or metabolism of tetrahydrobiopterin. In vivo, beneficial effect of vitamin C on vascular endothelial function appears to be mediated in part by protection of tetrahydrobiopterin and restoration of eNOS enzymatic activity.

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Arginine and fatloss (Arginine as a PPAR-gamma agonist):

Dietary L-arginine supplementation reduces fat mass in Zucker diabetic fatty rats.

Fu WJ, Haynes TE, Kohli R, Hu J, Shi W, Spencer TE, Carroll RJ, Meininger CJ, Wu G.

Faculty of Nutrition, Texas A&M University, College Station, TX 77843, USA.

This study was conducted to test the hypothesis that dietary supplementation of arginine, the physiologic precursor of nitric oxide (NO), reduces fat mass in the Zucker diabetic fatty (ZDF) rat, a genetically obese animal model of type-II diabetes mellitus. Male ZDF rats, 9 wk old, were pair-fed Purina 5008 diet and received drinking water containing arginine-HCl (1.51%) or alanine (2.55%, isonitrogenous control) for 10 wk. Serum concentrations of arginine and NO(x) (oxidation products of NO) were 261 and 70% higher, respectively, in arginine-supplemented rats than in control rats. The body weights of arginine-treated rats were 6, 10, and 16% lower at wk 4, 7, and 10 after the treatment initiation, respectively, compared with control rats. Arginine supplementation reduced the weight of abdominal (retroperitoneal) and epididymal adipose tissues (45 and 25%, respectively) as well as serum concentrations of glucose (25%), triglycerides (23%), FFA (27%), homocysteine (26%), dimethylarginines (18-21%), and leptin (32%). The arginine treatment enhanced NO production (71-85%), lipolysis (22-24%), and the oxidation of glucose (34-36%) and octanoate (40-43%) in abdominal and epididymal adipose tissues. Results of the microarray analysis indicated that arginine supplementation increased adipose tissue expression of key genes responsible for fatty acid and glucose oxidation: NO synthase-1 (145%), heme oxygenase-3 (789%), AMP-activated protein kinase (123%), and peroxisome proliferator-activated receptor gamma coactivator-1alpha (500%) . The induction of these genes was verified by real-time RT-PCR analysis. In sum, arginine treatment may provide a potentially novel and useful means to enhance NO synthesis and reduce fat mass in obese subjects with type-II diabetes mellitus.

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Arginine and health / safety / cholesterol / circulation:

Arginine is an amino acid and is also referred to as "L-Arginine" (the L stands for "levo" and designates the amino acid as naturally occurring and distinguishes from the D or " " synthetic amino acids.).

Claims:

Protection from heart disease
Reduces cholesterol
Lowers blood pressure
Improves poor circulation

Theory:

Arginine is a key component of the nitric oxide pathway and important cascade of reactions involved in vasodilation and related to cardiovascular function. Arginine supplements have been associated with reductions in symptoms associated with coronary artery disease and may be capable of slowing the progression of atherosclerosis

In the body, arginine serves as the substrates for the nitric oxide synthase enzyme, which catalyzes the oxidation of arginine to produce citrulline and nitric oxide (NO). In the cells that line the blood vessels (endothelium cells), nitric oxide production causes vasodilation (opening of the vessels). NO is involved in the overall regulation of systemic vascular resistance, where it inhibits the adherence of cells and foreign substances to the blood vessel walls and helps suppress the overgrowth of smooth muscle cells in the lining of the vessels.

Because humans can synthesize arginine, it has been classified as a non-essential amino acid. Recent evidence suggests that the rate of synthesis of arginine in the body is insufficient for optimal health ? a situation which would re-classify arginine as a semi-essential or conditionally essential amino acid.


Scientific Support:

In people with elevated cholesterol levels, it is common to see a reduced ability of the endothelium to produce NO and, therefore, to dilate effectively. In addition, because NO production may be limited, blood cells such as monocytes and platelets are more likely to attach themselves to the inner vessel wall and lead to blockages. Arginine supplements (8-21 grams per day) have been shown to restore endothelial vasodilation in the coronary arteries of people with high cholesterol and reduce the ability of blood cells to adhere to the vessel walls. Improvements in coronary artery blood flow and reductions in myocardial ischemia and walking pain due to claudication have been noted with arginine supplements (9-14 g/day).

Safety:

Arginine supplements have been used safely in patients with heart disease in doses up to more than 20 grams per day.

Value:

For those individuals at risk for coronary artery disease, including those who experience ischemia due to reduced blood flow and oxygen delivery, arginine supplements may be an effective strategy for improving circulation to the heart and other affected areas (such as vessels in the calves).

Dosage:

A daily arginine requirement has been calculated to be approximately 8 grams per day (based on calculations for a 70-kg person). Since the average American diet contains only about 5 grams of arginine per day, there would appear to be a deficit in intake versus requirements. Importantly, the primary dietary sources of arginine, like all amino acids, are meats and other high protein foods (nuts, eggs).

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Arginine and Androgens:

Influence of dietary arginine on the anabolic effects of androgens.

Cremades A, Ruzafa C, Monserrat F, Lopez-Contreras AJ, Penafiel R.

Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Murcia, Spain.

Feeding mice an arginine-deficient diet decreased plasma concentrations of arginine, citrulline and ornithine in the females and arginine in the males, abolishing the sexual dimorphic pattern of these amino acids found in mice fed the standard diet. In addition, the restriction of dietary arginine produced a marked decrease in body and renal weights as well as in the activity of renal ornithine decarboxylase, decreases that were gender dependent since they were observed exclusively in males. The fact that these changes were not associated with the decrease in the circulating levels of testosterone and that the dietary arginine restriction prevented the body weight gain induced by testosterone treatment of female mice fed the standard diet indicates that dietary arginine is required for the anabolic action of androgens. Moreover, under certain conditions that could compromise the renal synthesis of arginine, as in the compensatory renal hypertrophy that follows unilateral nephrectomy, the myotrophic effect of testosterone was transiently impaired. The results also revealed that arginine deficiency produced an opposite effect in the expression of IGF-I and IGF-binding protein 1 in the liver and kidney. Taken together, our results indicate that dietary arginine may be relevant to the anabolic action of testosterone, and suggest that this effect may be mediated by changes in the insulin-like growth factor system.

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Nitric Oxide (eNOS) and Erections:

How Erections Work

The penis is an organ with paired erection chambers (corpora cavernosa), which are filled with spongy erectile tissue (corporal sinusoids) composed predominantly of muscle. Erection and loss of erection are related primarily to blood flow events regulated by the relaxation and contraction, respectively, of the smooth muscle in the penile arteries and the erectile bodies themselves. Erection is a hydraulic event, regulated by hormones and nerves, which allow increased blood flow into and storage of blood within the erectile bodies leading to an increase in pressure and the development of rigidity (hardness). Penile erection is triggered by one of two main mechanisms: direct stimulation of the genitalia or through stimuli coming from the brain (fantasy, smell, etc).

Upon stimulation, chemicals are released in the brain that cause signals to pass down the spinal cord and outward through special nerves (nervi erigentes) into the penis. These nerves release another chemical (Nitric Oxide) that causes the aforementioned smooth muscle to relax and blood rushes into the erectile bodies, causing erection. Anxiety or fear can prevent the brain signals from reaching the level required to induce erection. Medical conditions can block the erection arteries or cause scarring of the spongy erection tissue and prevent proper blood flow or trapping of blood and, therefore, limit the erection. Thus, the erection mechanism is much like a tire; a firm tire is dependent upon a hose that can deliver air in adequate amounts in a speedy fashion and a valve mechanism that holds the air in place. In the penis the hose is represented by the erection arteries, which rapidly carry blood into the erectile bodies and the valve mechanism, while complicated in its structure, ensures that the blood is trapped inside the erectile bodies until ejaculation occurs or the sexual stimulus has passed.

Suggested Reading
1 Krane RJ et al: Impotence. New England Journal Of Medicine J, 321: 1648-1659, 1989
2 Giuliano FA et al.: Neural Control of Penile Erection. Urologic Clinics Of North America, 22: 747-66, 1995
3 Rajfer J et al.: Nitric oxide as a mediator of relaxation of the corpus cavernosum on response to nonadrenergic, noncholinergic neurotransmission. New England Journal Of Medicine, 326: 90-4, 1992
4 Burnett AL et al.: Nitric oxide: A physiologic mediator of penile erection. Science, 257: 401-3, 1992

Originally Posted by Arthur Burnett, M.D., associate professor of urology at Hopkins

"Once blood starts flowing into the penis, the source of nitric oxide in the blood vessels is continuously activated so that more nitric oxide is released, more tissue relaxes, more blood comes in and a sustained erection is achieved.

This cascade of events begins when erotic thoughts or physical sensations produce nitric oxide release in nerve endings in the penis. Nitric oxide is a relaxant that allows blood vessels to open up or dilate, bringing increased blood flow and swelling of tissues. The flow of blood also creates a minor stress on the blood vessel wall which activates the release of more nitric oxide. This time it is from cells in the wall of the blood vessel - the endothelial cells - rather than from nerves. Endothelial nitric oxide causes more tissue to relax and the process repeats until the penis is fully erect."

A key element in the attainment of erection is the continuous activation of the source of nitric oxide in blood vessel walls. Finding this source, a special form of the enzyme called endothelial nitric oxide synthase (eNOS), plus the discovery that the pressure of flowing blood against a vessel wall could induce it to produce nitric oxide, were critical pieces of the puzzle. These discoveries offer a fuller picture of the complex physiology of erection".

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Arginine Alpha-Ketoglutarate (AKG / AAKG):

Arginine alpha-ketoglutarate (AKG) is a salt formed by combining two molecules of the amino acid Arginine and one molecule of alpha-ketoglutarate. Because AKG seems to be involved in amino acid synthesis and protein availability, many athletes supplement with AKG as a way to increase muscle mass and strength – although the evidence for its effectiveness is this regard is quite limited.

Increases muscle size and strength
Reduces body fat
Stimulates the immune system

AKG has been used to treat patients suffering from burns, surgery, malnutrition and other trauma. Although the precise mechanism is unknown, AKG treatment decreases muscle protein catabolism (breakdown) and/or increases protein synthesis, in addition to promoting wound healing. AKG may promote the secretion of anabolic hormones such as insulin and growth hormone and increase amino acid metabolism (glutamine & arginine), which may help explain some of the clinical findings.

Scientific Support

Arginine and Arginine are precursors of nitric oxide and polyamines, respectively -metabolites which participate in a number of metabolic functions. AKG supplements have been shown to promote growth hormone and insulin secretion with anabolic effects in postoperative patients. Their intermediary metabolites (glutamine & proline) may also have beneficial effects in promoting recovery from trauma. In animal studies, AKG supplementation increases levels of arginine and glutamine in skeletal muscles and stimulates immune system function compared to animals not receiving AKG. The immunomodulatory properties found with AKG suggest that it may enhance host-defense mechanisms, particularly during injury and acute stress

AKG supplements (15 grams per day for 5 months) have been shown to improve growth rates in small children. The AKG supplements resulted in elevated concentrations of anabolic (growth) hormones and amino acid metabolites, including insulin-like growth factor 1 (IGF1), glutamine and glutamate. In another study of healthy men, AKG given at 10 grams per day resulted in a 20-30% elevation in insulin (another anabolic hormone), which were not observed with supplementation of either Arginine or alpha-ketoglutarate alone.

A test tube study found that AKG induces a significant increase in growth of human fibroblasts – cells with similarities to muscle fiber cells. This effect was dose-dependent, meaning that a more pronounced growth effect was noted with increasing levels of AKG (but not with increasing levels of Arginine or alpha-ketoglutarate alone).

In one study, the anti-catabolic effects of AKG were investigated in 14 multiple trauma patients who were highly catabolic and hyper-metabolic. One group of subjects received 20 grams of AKG per day and showed a significant increase in protein turnover as well as a an increase in blood levels of insulin, growth hormone, and free amino acids (glutamine, proline and Arginine) compared to subjects not receiving AKG supplements.


References:
1. Cochard A, Guilhermet R, Bonneau M. Plasma growth hormone (GH), insulin and amino acid responses to arginine with or without aspartic acid in pigs. Effect of the dose. Reprod Nutr Dev 1998 May-Jun;38(3):331-43.

2. Jeevanandam M, Petersen SR. Substrate fuel kinetics in enterally fed trauma patients supplemented with Arginine alpha ketoglutarate. Clin Nutr 1999 Aug;18(4):209-17.

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Arginine Ethyl Ester:

Arginine is a semi essential amino acid that is a building block of protein. Arginine is not manufactured endogenously, and exogenous consumption is required to satisfy arginine requirements.1

Arginine Ethyl Ester HCL (AEE) is an arginine amino acid with an ester attached. Esters are organic compounds that are formed by esterification - the reaction of carboxylic acid and alcohols. Arginine Ethyl Ester can not be obtained via dietary means and must be obtained via supplementation.

What does it do and what scientific studies give evidence to support this?

Arginine Ethyl Ester is a new kind of arginine. It is, technically, an arginine derivative, so the ergogenic effects will be similar to those of regular L-arginine, but the presence of an ester will make the ergogenic effects of Arginine Ethyl Ester more pronounced.

As good as regular L-arginine is, it's inherently limited. The first of its limits are its limited absorption through the intestine. Whereas Arginine Ethyl Ester can pass through the intestine largely intact, regular L-arginine is mostly degraded in the intestine, leaving only trace amounts of the ingested dose active.

Because of the rapid breakdown of L-arginine in the intestine, its effects on NO2 regulation, sexual arousal, and hemodialation are limited. This rapid breakdown also limits the ability of L-arginine to promote muscular growth via increases in exercise endurance and the delivery of nutrients to working muscle tissue via the muscle pump.

Injury healing, muscle growth and cellular function are all positively impacted by L-arginine, and currently accepted models of arginine metabolism suggest that these processes may be positively impacted by Arginine Ethyl Ester to a greater degree.

The presence of the ester not only enhances the function of arginine and overcomes its inherent limitations, but the presence of an ester and increased absorption also reduce the need for large doses, which may put less stress on the body.

The presence of an ester may also prolong the generation of nitric oxide and extend the benefits of arginine over a greater time period. This may result in greater endurance, enhanced pumps, and quicker recovery from exercise.

Who needs it and what are some symptoms of deficiency?

Everyone may benefit from arginine ethyl ester supplementation - even persons for whom past l-arginine supplementation proved ineffective.

How much should be taken? Are there any side effects?

Dosage amounts for Arginine Ethyl Ester range from one to four grams daily for maximum ergogenic effect. Arginine Ethyl Ester is best consumed in divided doses throughout the day so as to ensure sustained arginine release.

Individuals with existing heart or psychiatric conditions should consult with their physician prior to supplementing with arginine-based products.

REFERENCES

1. Alternative Medical Review. 2002, Dec;7 (6):512-22.

2. Burnett AL. Novel nitric oxide signaling mechanisms regulate the erectile response. Int J Impot Res. 2004 Jun;16 Suppl 1:S15-9.