Short-Term Supplementation of Sodium Nitrate vs. Sodium Chloride Increases Homoarginine Synthesis in Young Men Independent of Exercise

The aim of the study was to investigate the effects of short-term oral administration of inorganic nitrate (NaNO<sub<3</sub<; <i<n</i< = 8) or placebo (NaCl; <i<n</i< = 9) (each 0.1 mmol/kg body weight/d for 9 days) on plasma amino acids, creatinine, and oxidative...
Ausführliche Beschreibung

The aim of the study was to investigate the effects of short-term oral administration of inorganic nitrate (NaNO<sub<3</sub<; <i<n</i< = 8) or placebo (NaCl; <i<n</i< = 9) (each 0.1 mmol/kg body weight/d for 9 days) on plasma amino acids, creatinine, and oxidative stress in healthy young men. At baseline, the plasma concentrations of amino acids did not differ between the groups. At the end of the study, the plasma concentrations of homoarginine (hArg; by 24%, <i<p</i< = 0.0001), citrulline and ornithine (Cit/Orn; by 16%, <i<p</i< = 0.015), and glutamine/glutamate (Gln/Glu; by 6%, <i<p</i< = 0.0003) were higher in the NaNO<sub<3</sub< group compared to the NaCl group. The plasma concentrations of sarcosine (Sarc; by 28%, <i<p</i< < 0.0001), tyrosine (by 14%, <i<p</i< = 0.0051), phenylalanine (by 8%, <i<p</i< = 0.0026), and tryptophan (by 8%, <i<p</i< = 0.0047) were lower in the NaNO<sub<3</sub< group compared to the NaCl group. These results suggest that nitrate administration affects amino-acid metabolism. The arginine/glycine amidinotransferase (AGAT) catalyzes two reactions: (1) the formation of <span style="font-variant: small-caps;"<l</span<-homoarginine (hArg) and <span style="font-variant: small-caps;"<l</span<-ornithine (Orn) from <span style="font-variant: small-caps;"<l</span<-arginine (Arg) and <span style="font-variant: small-caps;"<l</span<-lysine (Lys): Arg + Lys <−< hArg + Orn, with equilibrium constant <i<K</i<<sub<harg</sub<; (2) the formation of guanidinoacetate (GAA) and Orn from Arg and glycine (Gly): Arg + Gly <−< GAA + Orn, with equilibrium constant <i<K</i<<sub<gaa</sub<. The plasma <i<K</i<<sub<gaa</sub</<i<K</i<<sub<hArg</sub< ratio was lower in the NaNO<sub<3</sub< group compared to the NaCl group (1.57 vs. 2.02, <i<p</i< = 0.0034). Our study suggests that supplementation of inorganic nitrate increases the AGAT-catalyzed synthesis of hArg and decreases the <i<N</i<-methyltransferase-catalyzed synthesis of GAA, the precursor of creatine. To our knowledge, this is the first study to demonstrate elevation of hArg synthesis by inorganic nitrate supplementation. Remarkably, an increase of 24% corresponds to the synthesis capacity of one kidney in healthy humans. Differences in the association between plasma concentrations of amino acids in the NaNO<sub<3</sub< and NaCl groups suggest changes in amino-acid homeostasis. Plasma concentrations of the oxidative stress marker malondialdehyde (MDA) did not change after supplementation of NaNO<sub<3</sub< or NaCl over the whole exercise time range. Plasma nitrite concentration turned out to be a more discriminant marker of NaNO<sub<3</sub< ingestion than plasma nitrate (area under the receiver operating characteristic curve: 0.951 vs. 0.866, <i<p</i< < 0.0001 each). Ausführliche Beschreibung

Autor*in:	Dimitrios Tsikas [verfasserIn] Norbert Maassen [verfasserIn] Antonie Thorns [verfasserIn] Armin Finkel [verfasserIn] Moritz Lützow [verfasserIn] Magdalena Aleksandra Röhrig [verfasserIn] Larissa Sarah Blau [verfasserIn] Laurianne Dimina [verfasserIn] François Mariotti [verfasserIn] Bibiana Beckmann [verfasserIn] Vladimir Shushakov [verfasserIn] Mirja Jantz [verfasserIn]

Format:	E-Artikel
Sprache:	Englisch

Erschienen:	2022

Schlagwörter:	amino acids guanidinoacetate homoarginine inorganic nitrate malondialdehyde oxidative stress

Übergeordnetes Werk:	In: International Journal of Molecular Sciences - MDPI AG, 2003, 23(2022), 18, p 10649
Übergeordnetes Werk:	volume:23 ; year:2022 ; number:18, p 10649

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DOI / URN:	10.3390/ijms231810649

Katalog-ID:	DOAJ084819243