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Erectile Dysfunction
Published in Charles Theisler, Adjuvant Medical Care, 2023
L-Arginine: Arginine is a precursor of nitric oxide, which helps to dilate blood vessels. It is a commonly used adjuvant to regular medicines for the treatment of erectile dysfunction. In small studies, men were given 2.8–6 gm of arginine per day for several weeks.1,2,3 Forty percent of the men in one treatment group experienced improvement, compared to none in the placebo group.2 In a double-blind trial, men with erectile concerns took 5 gm of arginine per day or a placebo for six weeks.4 Nine of 29 patients (31%) taking L-arginine reported a significant subjective improvement in sexual function.3
Free Radicals and Antioxidants
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
L-arginine (L-arg), is the main precursor of nitric oxide (NO), an endogenous messenger molecule involved in a variety of endothelium-mediated physiological effects in the nervous, immune, and cardiovascular systems (88–89). L-arginine is metabolized by two major pathways under the action of two specific enzymes: nitric oxide synthase and arginase. The nitric oxide synthase (NOS) pathway converts L-arg to NO and L-citrulline by three distinct isoforms of this enzyme: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS) (26–29, 88–89). The arginase pathway catalyzes the hydrolysis of L-arg to urea and ornithine in the liver through the urea cycle with the genesis of different polyamines (putrescine, spermidine and spermine). Briefly, L-arg plays a central role in the biosynthesis of nitric oxide, creatinine, agmatine, polyamines, proline, glutamate, and so on (26–27, 88–89). Most tissues in the body must be supplied with adequate intracellular levels of L-arg from circulation for their good function. All animal and vegetable proteins from the diet can be catabolized by the body into L-amino acids, of which L-arg. L-arginine is found abundantly in meat, milk, seafood, poultry, egg, soybeans, nuts, seeds, and more (88). In contrast, cereals are comparatively devoid of L-arginine, with only 3–4% of their low protein content being L-arginine (88). About 5 g of L-arginine is ingested each day in a normal Western diet (88).
An Overview of Molecular Nutrition
Published in Nicole M. Farmer, Andres Victor Ardisson Korat, Cooking for Health and Disease Prevention, 2022
Vincent W. Li, Catherine Ward, Delaney K. Schurr
Not only are proteins used as the body’s building blocks, but they do so also because they are made of building blocks. At their most basic level, proteins are combinations of chains of 22 naturally occurring amino acids. These combinations may be long chains, branched, sheets, or helixes. If not in any of the aforementioned forms, amino acids also serve multiple functions. Certain single amino acids (aspartic acid, glutamic acid, gamma-aminobutyric acid, glycine, taurine) can function as neurotransmitters. Two amino acid combinations, called dipeptides, may function as cell-to-cell communicators. Because of these different functions for amino acids, clinically there are several uses of amino acids: for example, L-tryptophan for sleep. This clinical use also provides a basis for the role of certain amino acids naturally found at higher combinations in certain foods. For example, arginine is an amino acid with vasodilation capabilities. The Mayo Clinic recommends an arginine-rich diet for patients suffering from poor blood perfusion, such as peripheral artery disease (Mayo Clinic, 2021). Arginine-rich foods include walnuts, brazil nuts, and almonds and may thus be beneficial to this patient population.
Comprehensive analysis of metabolic changes in spontaneously hypertensive rats
Published in Clinical and Experimental Hypertension, 2023
Yanan Li, Dadi Xie, Luxi Li, Pei Jiang
Significant changes in arginine synthesis and metabolism were also detected in multiple tissues. The effects of arginine on hypertension are multifaceted. Arginine can be metabolized into various products, including NO, urea, creatine, proline, and glutamate, which affect the development of hypertension in different ways. The arginine-NO pathway plays a vital role in maintaining vascular homeostasis. NO can diffuse into vascular smooth muscle cells through the guanylate cyclase pathway, causing vasodilation (26). Studies have shown that inhibition of NO synthesis exacerbates the development of hypertension (27). In contrast, increased NO bioavailability leads to antihypertensive effects and improves target organ damage in hypertension (28). In addition, the arginine and proline metabolic pathways also exhibited abnormalities. Proline is a specific secondary amino acid that can be interconverted with glutamate. Glutamate can generate glutamic-γ-semialdehyde and be converted to ornithine, a precursor for arginine synthesis in the urea cycle (29). On the other hand, glutamic-γ-semialdehyde produces pyrroline-5-carboxylate and converts it to proline. Studies have shown that arginase can convert arginine into ornithine and urea. Increased expression of arginase can reduce NO synthesis and promote glutamate and proline production (30). Disorders of arginine biosynthesis and arginine and proline metabolism found in multiple tissues of 5-week-old SHR may affect endothelial function by decreasing NO bioactivity, which may be another critical pathway in the regulation of hypertension.
A possible ocular biomarker for response to hyperornithinemia in gyrate atrophy: the effect of pyridoxine, lysine, and arginine-restricted diet in a patient with advanced disease
Published in Ophthalmic Genetics, 2023
Mariana Matioli da Palma, Cristy Ku, Austin D. Igelman, Amanda Burr, Liliya Shevchenko Sutherland, Celide Koerner, David Valle, Mark E. Pennesi, Paul Yang
The benefit of pyridoxine supplementation and a restrictive diet can be limited due to the variable response and difficulty with long-term adherence to a strict diet, respectively (11). Arginine is a protein amino acid present in nearly all animal and plant proteins (dairy, poultry, fish, meats, eggs, grains nuts, and seeds), which makes it very difficult to restrict without advanced planning and strict discipline (14). In comparison, dietary supplementation with pyridoxine tablets is easy to do, however not all patients respond. Genotype–phenotype correlations likely explain the variable response rate (2,11). More than 60 variants have been reported in OAT gene, and the majority are missense variations according to the Human Gene Mutation Database [HGMD http://www.hgmd.cf.ac.uk/]. The missense variant p.Val332 Met was the first description of a vitamin-responsive mutation by Ramesh in 1988 (9). Other variants have been described as responsive in the literature, including p.Thr181 Met (10), p.Glu318Lys (10,11), p.Gly51Asp (11), and p.Ala226Val (17). In contrast, p.Tyr299* (18,19), p.Asn54Lys (9), and p.His319Tyr (20) have been reported to be non-responsive to pyridoxine. The present study characterizes the treatment effect of pyridoxine and an arginine-restricted diet on the retinal structure and function in a patient with gyrate atrophy due to two heterozygous pathogenic variants, p.Tyr299* and p.Ala270Pro, in OAT.
Impact of COVID 19 on erectile function
Published in The Aging Male, 2022
D. H. Adeyemi, A. F. Odetayo, M. A. Hamed, R. E. Akhigbe
Erection is an enlarged and rigid state of the penis in which one of the main regulators is nitric oxide (NO) [186]. L-arginine is the natural precursor for the synthesis of NO and its availability at the physiologic level is believed to have a positive effect on the production of NO [187]. Hence, reduced NO bioavailability that may be a consequence of a marked reduction in L-arginine has been implicated as a major cause of erectile dysfunction. In the presence of nitric oxide synthase isoforms, L-arginine is converted to NO to be released from both the cavernosal nerve ending and the endothelial cells of the artery that supplies the penis (penile artery) following the stimulation from the spinal cord [188]. Once the NO has been released, it will lead to a cascade of events that will eventually lead to the relaxation in the smooth muscle of the corpora cavernosa, veno-occlusion, and penile erection [186]. Hence, reduced arginine-dependent NO bioavailability may contribute to COVID-19-induced ED. This may involve several pathways. Reduced NO bioavailability may downregulate NO/cGMP signaling, leading to impaired relaxation of the corpus carvenosa and ED [80,86]. Also, a low level of arginine-dependent NO inhibits the vasodilator activity of NO and blood flow [78], thus impairing penile perfusion and erection. Furthermore, since arginine has been demonstrated to exert antioxidant and anti-inflammatory effects [189], a low level of arginine impairs its capacity to scavenge Ang II-induced free radical generation, leading to endothelial dysfunction [162], and ED.