ABSTRACT
Abstract Background: Studies have persuasively demonstrated that citrulline has a key role in the arginine-nitric oxide system, increasing nitric oxide bioavailability, an important mediator of peripheral vasodilation. Objective: To analyze the inter-individual post-exercise hypotension responsiveness following acute citrulline supplementation in hypertensives. Methods: Forty hypertensives were randomly assigned to one of the four experimental groups (control-placebo, control-citrulline, exercise-placebo, and exercise-citrulline). They ingested placebo or citrulline malate [CM] (6 grams). During the exercise session, individuals performed 40 minutes of walking/running on a treadmill at 60-70% of HR reserve. For the control session, the individuals remained seated at rest for 40 minutes. Office blood pressure (BP) was taken every 10 minutes until completing 60 minutes after the experimental session. The ambulatory BP device was programmed to take the readings every 20 minutes (awake time) and every 30 minutes (sleep time) over the course of 24 hours of monitoring. Statistical significance was defined as p < 0.05. Results: Unlike the other experimental groups, there were no "non-responders" in the exercise/citrulline (EC) for "awake" (systolic and diastolic BP) and "24 hours" (diastolic BP). The effect sizes were more consistent in the EC for systolic and diastolic ambulatorial BP response. The effects were "large" (> 0.8) for "awake", "asleep", and "24 hours" only in the EC for diastolic BP. Conclusion: CM supplementation can increase the post-exercise hypotensive effects in hypertensives. In addition, the prevalence of non-responders is lower when associated with aerobic exercise and CM supplementation.
Resumo Fundamento: Estudos demonstraram de maneira persuasiva que a citrulina tem um papel fundamental no sistema arginina-óxido nítrico, aumentando a biodisponibilidade do óxido nítrico, um importante mediador da vasodilatação periférica. Objetivo: Analisar a responsividade interindividual da hipotensão pós-exercício após suplementação aguda com citrulina em hipertensos. Métodos: Quarenta hipertensos foram aleatoriamente designados para um dos quatro grupos experimentais (controle-placebo, controle-citrulina, exercício-placebo e exercício-citrulina). Eles ingeriram placebo ou citrulina malato [CM] (6 gramas). Durante a sessão de exercício, os indivíduos realizaram 40 minutos de caminhada/corrida em esteira a 60-70% da FC de reserva. Para a sessão de controle, os indivíduos permaneceram sentados em repouso por 40 minutos. A medida da pressão arterial (PA) no consultório foi realizada a cada 10 minutos até completar 60 minutos após a sessão experimental. O dispositivo ambulatorial de PA foi programado para fazer as leituras a cada 20 minutos (tempo de vigília) e a cada 30 minutos (tempo de sono) ao longo de 24 horas de monitoramento. A significância estatística foi definida como p < 0,05. Resultados: Diferentemente de outros grupos experimentais, não houve "não respondedores" no exercício/citrulina (EC) para "acordado" (PA sistólica e diastólica) e "24 horas" (PA diastólica). Os tamanhos de efeito foram mais consistentes no EC para a resposta sistólica e diastólica da PA ambulatorial. Os efeitos foram "grandes" (> 0,8) para "acordado", "dormindo", e para "24 horas" apenas no EC para a PA diastólica. Conclusão: A suplementação com CM pode aumentar os efeitos hipotensivos pós-exercício em hipertensos. Além disso, a prevalência de "não respondedores" é menor quando associada ao exercício aeróbico e à suplementação com CM.
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Aged , Aged, 80 and over , Vasodilator Agents/pharmacology , Blood Pressure/drug effects , Exercise/physiology , Citrulline/analogs & derivatives , Post-Exercise Hypotension/physiopathology , Hypertension/physiopathology , Malates/pharmacology , Arginine/metabolism , Reference Values , Time Factors , Placebo Effect , Anthropometry , Double-Blind Method , Analysis of Variance , Treatment Outcome , Citrulline/pharmacology , Statistics, Nonparametric , Exercise Test , Hypertension/therapy , Nitric Oxide/metabolismABSTRACT
Maize phosphoenolpyruvate carboxylase (PEPC) was rapidly and completely inactivated by very low concentrations of trypsin at 37 degrees C. PEP+Mg2+ and several other effectors of PEP carboxylase offered substantial protection against trypsin inactivation. Inactivation resulted from a fairly specific cleavage of 20 kDa peptide from the enzyme subunit. Limited proteolysis under catalytic condition (in presence of PEP, Mg2+ and HCO3) although yielded a truncated subunit of 90 kDa, did not affect the catalytic function appreciably but desensitized the enzyme to the effectors like glucose-6-phosphate glycine and malate. However, under non-catalytic condition, only malate sensitivity was appreciably affected. Significant protection of the enzyme activity against trypsin during catalytic phase could be either due to a conformational change induced on substrate binding. Several lines of evidence indicate that the inactivation caused by a cleavage at a highly conserved C-terminal end of the subunit.