Involvement of the ornithine decarboxylase gene in acid stress response in probiotic Lactobacillus delbrueckii UFV H2b20.

Amino acid decarboxylation is important for the maintenance of intracellular pH under acid stress. This study aims to carry out phylogenetic and expression analysis by real-time PCR of two genes that encode proteins involved in ornithine decarboxylation in Lactobacillus delbrueckii UFV H2b20 exposed to acid stress. Sequencing and phylogeny analysis of genes encoding ornithine decarboxylase and amino acid permease in L. delbrueckii UFV H2b20 showed their high sequence identity (99%) and grouping with those of L. delbrueckii subsp. bulgaricus ATCC 11842. Exposure of L. delbrueckii UFV H2b20 cells in MRS pH 3.5 for 30 and 60 min caused a significant increase in expression of the gene encoding ornithine decarboxylase (up to 8.1 times higher when compared to the control treatment). Increased expression of the ornithine decarboxylase gene demonstrates its involvement in acid stress response in L. delbrueckii UFV H2b20, evidencing that the protein encoded by that gene could be involved in intracellular pH regulation. The results obtained show ornithine decarboxylation as a possible mechanism of adaptation to an acidic environmental condition, a desirable and necessary characteristic for probiotic cultures and certainly important to the survival and persistence of the L. delbrueckii UFV H2b20 in the human gastrointestinal tract.

Máxima velocidade aeróbia calculada pelo custo da frequência cardíaca: relação com a performance / Velocidad aeróbica máxima calculada por el costo del ritmo cardíaco: relación con el rendimiento / Maximal aerobic speed calculated by heart rate cost: relationship with performance

Objetivos. Comparar a máxima velocidade aeróbia (MVA) calculada pelo custo de oxigênio (vVO2max) e o custo da frequência cardíaca (vFCmax) com a medida direta da MVA (Vpico) e verificar a relação entre a vFCmax e a performance em provas de 10 e 15 km de corredores recreacionais de meia idade. Método. Participaram 21 corredores (idade: 30‐49 anos), subdivididos em 2 grupos a partir da idade (G1 e G2). Os participantes foram submetidos a um teste incremental contínuo máximo em laboratório para determinação do consumo máximo de oxigênio. A MVA foi determinada a partir das propostas apresentadas na literatura com base no vVO2max e no vFCmax. Além disso, foram realizadas 2 performances em pista de atletismo (10 e 15 km). Resultados. A menor diferença entre as médias observada para a Vpico foi em relação à vFCmax de Lacour et al. (0,0 km h–1; p > 0,05). A maior diferença foi em relação à vFCmax de Di Prampero (1,55 km h–1; p < 0,05). O mesmo padrão de diferenças foi observado quando analisado o G1 e G2. A vFCmax determinada a partir de 2 diferentes métodos propostos na literatura se correlacionou com as provas de 10 e 15 km (0,55 ≤ r ≤ 0,82; p < 0,05). Conclusões. A vFCmax em corredores recreacionais de meia idade tem elevada relação com as performances de 10 e 15 km e não foi diferente da Vpico (para vFCmax de Lacour et al.), apresentando resultados semelhantes aos observados pelos métodos baseados no custo de oxigênio (AU)

Objetivo: Comparar la velocidad aeróbica máxima (VAM), calculada a través del costo de oxígeno (vVO2max) y del costo de la frecuencia cardíaca (vFCmáx), con la medida directa de la VAM (Vpico) y verificar la relación entre la vFCmax y la performance de 10 e 15 km de corredores recreativos de mediana edad. Método: Participaron 21 corredores recreativos (edades: 30-49 años) subdivididos en 2 grupos por edad (G1 y G2). Los participantes se sometieron a un test incremental continuo máximo en laboratorio para la determinación del consumo máximo de oxígeno. La MVA fue determinada a través de las propuestas presentadas en la literatura basada en el vVO2max y el vFCmáx. Además, se realizaron 2 pruebas en pista de atletismo (10 e 15 km). Resultados: La menor diferencia entre las medias observadas para la Vpico fue en relación con la vFCmax de Lacour et al. (0,0 km h-1; p > 0,05). La mayor diferencia fue en relación con la vFCmax de Di Prampero (1,55 km h-1; p < 0,05). El mismo patrón de diferencias fue observado cuando se analizaron el G1 y G2. La vFCmáx determinada a través de 2 distintos métodos propuestos en la literatura se correlacionó con las pruebas de 10 y 15 km (0,55 ≤ r ≤ 0,82; p < 0,05). Conclusiones: La vFCmáx, en corredores recreativos de mediana edad, tiene alta correlación con las pruebas de 10 y 15 km y no fue diferente de la Vpico (para vFCmáx de Lacour et al.), presentando resultados similares a los observados por los métodos basados en el costo de oxígeno

Objectives. To compare maximal aerobic speed (MAS) calculated by oxygen cost (vVO2max) and heart rate cost (vHRmax) with the direct measurement of MAS (Vpeak) and to verify the relationship between vHRmax and 10‐ and 15‐km performance in middle‐age recreationally runners. Method. Twenty one recreationally runners participated in this study (age: 30 to 49 years), allocated in two groups according to age (G1 and G2). Participants were submitted to an incremental continuous test of maximal effort in laboratory to determine maximal oxygen uptake. MAS was determined according to proposes presented in literature based on vVO2max and vHRmax. Besides, it was performed two performances in field track (10 and 15 km). Results. The lowest difference between the mean values observed and Vpeak was in relation to vHRmax from Lacour et al. (0.0 km h–1; p > 0.05). The highest was in relation to vHRmax from di Prampero (1.55 km h–1; p < 0.05). The same pattern of differences was observed when G1 and G2 were analyzed. The vHRmax determined according to two different methods presented in literature showed to be correlated with 10 and 15 km performances (0.55 ≤ r ≤ 0.82; p < 0.05). Conclusions. The vHRmax in middle‐aged recreational runners has elevated correlation with 10 and 15 km performances and was not different from Vpeak (to vHRmax from Lacour et al.) showing similar results than the method based on oxygen cost (AU)