Las concentraciones de glutamina y citrulina reflejan la síntesis del óxido nítrico en el sistema nervioso humano / Glutamine and citrulline concentrations reflect nitric oxide synthesis in the human nervous system

INTRODUCCIÓN: Aunque la citrulina es producida por la sintasa del óxido nítrico (NO) al activarse el receptor glutamatérgico NMDA, nitritos y nitratos (NOx) son considerados los mejores marcadores de síntesis del NO pues citrulina es también metabolizada por otras enzimas. En este estudio se realizó un análisis de correlaciones de concentraciones de citrulina y NOx en líquido cefalorraquídeo humano para evaluar la proporción en que la citrulina refleja la síntesis del NO y la neurotransmisión glutamatérgica. MÉTODOS: Se incluyeron pacientes con trastornos neurológicos agudos a los que se realizó punción lumbar (n = 240). Se determinó la concentración de NOx y aminoácidos por HPLC. RESULTADOS: NOx no fue diferente por la presencia de infección (p = 0,110) o inflamación (p = 0,349). La regresión múltiple mostró que NOx correlacionó con glutamina (r = -0,319, p < 0,001) y citrulina (r = 0,293, p = 0,005) pero no con el cociente citrulina/arginina (r = -0,160, p = 0,173). El ANCOVA confirmó que NOx está asociado con citrulina (F = 7,6, p = 0,007) pero no con el cociente citrulina/arginina (F = 2,2; p = 0,136), ni con la infección (F = 1,8; p = 0,173) o la inflamación (F = 1,4; p = 0,227). NOx no correlacionó con arginina ni con glutamato. CONCLUSIONES: Esto sugiere que citrulina refleja parte de la síntesis del NO a pesar de la contribución de otras vías metabólicas. Además, este estudio muestra que la glutamina es un modulador importante de la actividad de la NOS, y que arginina y glutamato no correlacionan con la concentración de NOx

INTRODUCTION: Although citrulline is produced by nitric oxide (NO) synthase upon activation of the NMDA glutamate receptor, nitrite and nitrate (NOx) concentration is considered the best marker of NO synthesis, as citrulline is also metabolised by other enzymes. This study analyses the correlation between human cerebrospinal fluid NOx and citrulline concentrations in order to determine the extent to which citrulline reflects NO synthesis and glutamatergic neurotransmission. METHODS: Participants were patients with acute neurological diseases undergoing lumbar puncture (n = 240). NOx and amino acid concentrations were determined by HPLC. RESULTS: NOx concentrations did not vary significantly where infection (p = 0,110) or inflammation (p = 0,349) were present. Multiple regression analysis showed that NOx concentration was correlated with glutamine (r = -0,319, p < 0,001) and citrulline concentrations (r = 0,293, p = 0,005) but not with the citrulline/arginine ratio (r = -0,160, p = 0,173). ANCOVA confirmed that NOx concentration was correlated with citrulline concentration (F = 7,6, p = 0,007) but not with the citrulline/arginine ratio (F = 2,2, p = 0,136), or presence of infection (F=1,8, p = 0,173) or inflammation (F = 1,4, p = 0,227). No association was found between NOx and arginine or glutamate concentrations. CONCLUSION: The results suggest that CSF citrulline concentration reflects NOx synthesis to some extent, despite the contribution of other metabolic pathways. In addition, this study shows that glutamine is an important modulator of NO synthase activity, and that arginine and glutamate are not correlated with NOx

Glutamine and citrulline concentrations reflect nitric oxide synthesis in the human nervous system. / Las concentraciones de glutamina y citrulina reflejan la síntesis del óxido nítrico en el sistema nervioso humano.

INTRODUCTION: Although citrulline is produced by nitric oxide (NO) synthase upon activation of the NMDA glutamate receptor, nitrite and nitrate (NOx) concentration is considered the best marker of NO synthesis, as citrulline is also metabolised by other enzymes. This study analyses the correlation between human cerebrospinal fluid NOx and citrulline concentrations in order to determine the extent to which citrulline reflects NO synthesis and glutamatergic neurotransmission. METHODS: Participants were patients with acute neurological diseases undergoing lumbar puncture (n=240). NOx and amino acid concentrations were determined by HPLC. RESULTS: NOx concentrations did not vary significantly where infection (p=0,110) or inflammation (p=0,349) were present. Multiple regression analysis showed that NOx concentration was correlated with glutamine (r=-0,319, p<0,001) and citrulline concentrations (r=0,293, p=0,005) but not with the citrulline/arginine ratio (r=-0,160, p=0,173). ANCOVA confirmed that NOx concentration was correlated with citrulline concentration (F=7,6, p=0,007) but not with the citrulline/arginine ratio (F=2,2, p=0,136), or presence of infection (F=1,8, p=0,173) or inflammation (F=1,4, p=0,227). No association was found between NOx and arginine or glutamate concentrations. CONCLUSION: The results suggest that CSF citrulline concentration reflects NOx synthesis to some extent, despite the contribution of other metabolic pathways. In addition, this study shows that glutamine is an important modulator of NO synthase activity, and that arginine and glutamate are not correlated with NOx.

Imbalance between nitric oxide and dopamine may underly aggression in acute neurological patients.

The neurochemical basis of aggressive behavior in humans is not fully understood. In this study we explored the relationship between aggressiveness (as measured by the Overt Aggression Scale), cognitive performance (as measured by the Mini Mental State Examination), and biochemical markers of dopamine neurotransmission (homovanillic acid, HVA) and nitric oxide synthesis (nitrite plus nitrate, NO(x)) in cerebrospinal fluid from 70 patients with acute brain disorders, mainly brain infections. Aggressive behavior and cognitive performance showed an inverse correlation. NO(x)/HVA ratio was inversely correlated to aggressive behavior, and positively correlated to cognitive performance. A subanalysis with antipsychotic-naïve patients confirmed those results. The balance between nitric oxide and dopamine could be related to the cognitive control of aggressive impulse.