Arginina

[Eagle]

Qualche curiosità su questo aminoacido.

Curr Opin Clin Nutr Metab Care. 2008 Jan;11(1):50-4.
Growth hormone, arginine and exercise.
Kanaley JA.
Department of Exercise Science, Syracuse University, Syracuse, New York, USA. jakanale@syr.edu

PURPOSE OF REVIEW: To describe the effect of an acute bout of exercise on growth hormone responses and to discuss the effect of L-arginine supplementation on growth hormone responses.

RECENT FINDINGS: Recent studies have shown that resting growth hormone responses increase with oral ingestion of L-arginine and the dose range is 5-9 g of arginine. Within this range there is a dose-dependent increase and higher doses are not well tolerated. Most studies using oral arginine have shown that arginine alone increases the resting growth hormone levels at least 100%, while exercise can increase growth hormone levels by 300-500%. The combination of oral arginine plus exercise attenuates the growth hormone response, however, and only increases growth hormone levels by around 200% compared to resting levels.

SUMMARY: Exercise is a very potent stimulator of growth hormone release and there is considerable research documenting the dramatic growth hormone rise. At rest oral L-arginine ingestion will enhance the growth hormone response and the combination of arginine plus exercise increases growth hormone, but this increase may be less than seen with exercise alone. This diminished response is seen in both in both younger and older individuals.

[Eagle]

Postepy Hig Med Dosw (Online). 2006;60:483-9.

Arginine as a crucial amino acid in carcinogenesis and tumor growth

Graboń W.
Katedra i Zakład Biochemii Akademii Medycznej w Warszawie, Poland. wojtekgrabon@interia.pl

Arginine, a cationic semi-essential amino acid, is involved in numerous pathways of human metabolism. It serves as a precursor for the biosynthesis of proteins and also of ornithine, polyamines, nitric oxide, proline, glutamate, glutamine, creatine, agmatine and dimethylarginines. Arginine is conditionally essential amino acid as it is necessary under phase of growth (in children) and in adults under some pathological conditions, as well as during recovery after catabolic diseases. There is a growing interest in the role of arginine in cancerogenesis, since this amino acid has turned out to be absolutely essential for growth of neoplastic cells. It also plays a crucial role in biosynthetic pathways that significantly influence carcinogenesis and tumor biology. They include synthesis of polyamines and nitric oxide, important molecules, which may be synthesized solely from arginine. These findings have resulted in first clinical trials on arginine deprivation in therapy of some arginine-dependent (auxotrophic) tumors. The present article is focused on recently recognised role of arginine in tumor development, including processes associated with carcinogenesis, such as apoptosis and angiogenesis.

[Eagle]

Regul Toxicol Pharmacol. 2008 Jan 26 [Epub ahead of print]

Risk assessment for the amino acids taurine, l-glutamine and l-arginine.
Shao A, Hathcock JN.
Council for Responsible Nutrition, 1828 L Street, NW, Suite 900, Washington, DC 20036-5114, USA.

Taurine, glutamine and arginine are examples of amino acids which have become increasingly popular as ingredients in dietary supplements and functional foods and beverages. Animal and human clinical research suggests that oral supplementation of these amino acids provides additional health and/or performance benefits beyond those observed from normal intake of dietary protein.

The increased consumer awareness and use of these amino acids as ingredients in dietary supplements and functional foods warrant a comprehensive review of their safety through quantitative risk assessment, and identification of a potential safe upper level of intake. The absence of a systematic pattern of adverse effects in humans in response to orally administered taurine (Tau), l-glutamine (Gln) and l-arginine (Arg) precluded the selection of a no observed adverse effect level (NOAEL) or lowest observed adverse effect level (LOAEL).

Therefore, by definition, the usual approach to risk assessment for identification of a tolerable upper level of intake (UL) could not be used. Instead, the newer method described as the Observed Safe Level (OSL) or Highest Observed Intake (HOI) was utilized.

The OSL risk assessments indicate that based on the available published human clinical trial data, the evidence for the absence of adverse effects is strong for Tau at supplemental intakes up to 3g/d, Gln at intakes up to 14g/d and Arg at intakes up to 20g/d, and these levels are identified as the respective OSLs for normal healthy adults.

Although much higher levels of each of these amino acids have been tested without adverse effects and may be safe, the data for intakes above these levels are not sufficient for a confident conclusion of long-term safety, and therefore these values are not selected as the OSLs.

[richard]

Mi permetto un commento a questi post, anche per renderli più accessibili a chi non avesse sufficiente dimestichezza con l'inglese.



Il primo è una review:

Kanaley J. A., Growth hormone, arginine and exercise, Curr Opin Clin Nutr Metab Care, 11(1):50 (2008).

e ha come scopo quello di descrivere l'effetto di uno stimolo acuto da esercizio sulla risposta del gh e di discutere come questa risposta sia condizionata da supplementazione di L-arginina. L'oggetto di analisi è, nello specifico, la risposta del gh a riposo. E' stato rilevato che sia stimolo fisico che supplementazione, considerati separatamente, aumentano tale risposta, ma essa è inferiore nel caso di concomitanza di esercizio e supplementazione rispetto al caso di solo esercizio.

E' da notare, comunque, che la risposta macroscopica sulla composizione corporea (che realmente ci interessa) e sullo sviluppo delle capacità motorie necessarie a questo scopo non è riconducibile esclusivamente alla concentrazione ematica del gh.
Qualsiasi azione ormonale va sempre e comunque inserita nel complesso della articolata rete endocrina a cui appartiene e non separata da questo contesto.


Anche il secondo riferimento è una review:

Wojciech Grabon, Arginine as a crucial amino acid in carcinogenesis and tumor growth, Postȩpy higieny i medycyny doświadczalnej (Online), 60:483 (2006).

anche se la rivista di pubblicazione non ha, a mio avviso, la risonanza internazionale di altre.
Scopo di questa review è quello di analizzare il ruolo di questo aminoacido nella formazione e nello sviluppo di un tumore. Vengono quindi presi in considerazione i pathway biologici che, a tal proposito, principalmente coinvolgono tale sostanza.

A mio avviso questo riferimento è ad elevato rischio fraintendimento (ed è, forse, "fuori tema"): è bene sottolineare/ribadire che esso non tratta del grado di cancerogeneità dell'aminoacido, ma del ruolo che esso assume nel metabolismo di un tumore.


Infine, l'ultimo riferimento:

Shao A. and Hathcock J. N., Risk assessment for the amino acids taurine, l-glutamine and l-arginine, Regulatory Toxicology and Pharmacology, in press (2008)

pone l'attenzione sui dosaggi giornalieri per tali aminoacidi, con particolare attenzione e scrupolo sui possibili effetti a lungo termine. E' infatti riconosciuto dagli autori che livelli anche notevolmente superiori a quelli indicati sono stati testati senza effetti avversi sulla salute nel breve e nel medio termine.

[LARRY SCOTT]

interessante, grazie sia ad Aquila che Richard

[richard]

interessante, grazie sia ad Aquila che Richard

[Eagle]

Non ho mai trovato niente di "sostanzioso" a proposito dell'integrazione con arginina in chi pratica bb.

Mi accontento di piccoli indizi e suggerimenti ...

Med Sci Sports Exerc. 2003 Aug;35(8):1309-15.

L-arginine ingestion after rest and exercise: effects on glucose disposal.

Robinson TM, Sewell DA, Greenhaff PL.
School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom. t.m.robinson@sheffield.ac.uk
PURPOSE: There is considerable interest, both in health and disease, in enhancing postexercise glucose uptake and glycogen resynthesis in skeletal muscle. The amino acid, arginine, is known to stimulate insulin release and enhance glucose-stimulated insulin release. METHODS: The present investigation examined whether an oral dose of L-arginine (10 g), when given with 70 g carbohydrate (CHO, in the form of simple sugars) improved factors associated with glucose disposal in previously exercised and nonexercised healthy males. The effects of different modes of activity (resistance or cycling exercise) upon these factors were also examined. RESULTS: Whole-blood glucose and serum insulin concentrations after L-arginine + CHO ingestion were not significantly different from the placebo condition (glycine + CHO ingestion) in all experimental treatments (nonexercised, resistance exercise, and cycling exercise). Similarly, CHO oxidation, forearm blood flow, blood pressure, and heart rate during the postingestion period were unaffected by L-arginine + CHO consumption in all three experimental treatments. CONCLUSION: A 10-g oral dose of L-arginine was found to have no effect on blood glucose disposal in human subjects after oral CHO ingestion, either when rested or after different modes of exercise known to differentially affect glucose disposal. These results suggest that the addition of L-arginine to a CHO beverage would not augment postexercise CHO replenishment in healthy human subjects.

[Eagle]

Questo ad esempio è molto interessante, ma sono donne, obese, non atlete ...

Potete anche aprire il full text, e stamparlo in pdf.

Am J Physiol Endocrinol Metab. 2006 Nov;291(5):E906-12. Epub 2006 Jun 13.

Beneficial effects of a long-term oral L-arginine treatment added to a hypocaloric diet and exercise training program in obese, insulin-resistant type 2 diabetic patients.

Lucotti P, Setola E, Monti LD, Galluccio E, Costa S, Sandoli EP, Fermo I, Rabaiotti G, Gatti R, Piatti P.
Diabetology, Endocrinology and Metabolic Disease Unit, Fondazione Centro San Raffaele del Monte Tabor, Milan, Italy.
Because chronic L-arginine supplementation improves insulin sensitivity and endothelial function in nonobese type 2 diabetic patients, the aim of this study was to evaluate the effects of a long-term oral L-arginine therapy on adipose fat mass (FM) and muscle free-fat mass (FFM) distribution, daily glucose levels, insulin sensitivity, endothelial function, oxidative stress, and adipokine release in obese type 2 diabetic patients with insulin resistance who were treated with a combined period of hypocaloric diet and exercise training. Thirty-three type 2 diabetic patients participated in a hypocaloric diet plus an exercise training program for 21 days. Furthermore, they were divided into two groups in randomized order: the first group was also treated with L-arginine (8.3 g/day), and the second group was treated with placebo. Although in the placebo group body weight, waist circumference, daily glucose profiles, fructosamine, insulin, and homeostasis model assessment index significantly decreased, L-arginine supplementation further decreased FM (P < 0.05) and waist circumference (P < 0.0001), preserving FFM (P < 0.03), and improved mean daily glucose profiles (P < 0.0001) and fructosamine (P < 0.03). Moreover, change in area under the curve of cGMP (second messenger of nitric oxide; P < 0.001), superoxide dismutase (index of antioxidant capacity; P < 0.01), and adiponectin levels (P < 0.02) increased, whereas basal endothelin-1 levels (P < 0.01) and leptin-to-adiponectin ratio (P < 0.05) decreased in the L-arginine group. Long-term oral L-arginine treatment resulted in an additive effect compared with a diet and exercise training program alone on glucose metabolism and insulin sensitivity. Furthermore, it improved endothelial function, oxidative stress, and adipokine release in obese type 2 diabetic patients with insulin resistance.