ABSTRACT
ABSTRACT The purpose of this review was to examine in the current literature the advances made in terms of the effects of caffeine supplementation on maximum strength and its associated mechanisms since the publication of two important papers in 2010. Searches were carried out in the PubMed, Medline, Scielo and Web of Science databases for articles published after 2010. Sixteen studies were included based on inclusion and exclusion criteria. Five studies did not report changes in maximal voluntary strength (31.3%). Four of them used isometric muscle contractions, although this may not be a key factor because five other studies also used isometric contractions and reported ergogenic effects. Furthermore, these four studies evaluated small muscle groups and volunteers were not accustomed to consuming caffeine. Caffeine produced ergogenic effects in eleven of the sixteen studies analyzed (68.8%). None of the doses were clearly related to ergogenic effects; however, a dose of at least 3 mg/kg of caffeine is probably necessary. Caffeine ergogenicity was affected by various factors. There was a lack of standardized protocols and controls for intervening factors (e.g., circadian cycles and nutritional states), which could affect results. An ideal caffeine supplementation protocol that is useful for future research, athletes, and physical activity practitioners, has yet to be defined. A small advance made since 2010 involved a possible lack of gender difference; it would appear that caffeine supplementation affects men and women equally. Level of Evidence I; Systematic Review of Level I Studies.
RESUMO O objetivo desta revisão foi examinar na literatura atual os avanços feitos com relação aos efeitos da suplementação de cafeína sobre a força máxima e seus mecanismos associados a partir de 2010, ano em foram publicados dois importantes artigos. As buscas foram realizadas nas bases de dados PubMed, Medline, Scielo e Web of Science procurando-se artigos publicados após 2010. Dezesseis estudos foram incluídos com base nos critérios de inclusão e exclusão. Cinco estudos não relataram alterações da força voluntária máxima (31,3%). Quatro deles usaram contrações musculares isométricas, embora isso possa não ser um fator chave, porque outros cinco estudos também usaram contrações isométricas e relataram efeitos ergogênicos. Além disso, esses quatro estudos avaliaram pequenos grupos musculares e os voluntários não eram habituados à cafeína. A cafeína produziu efeitos ergogênicos em 11 dos 16 estudos analisados (68,8%). Nenhuma dose foi claramente relacionada com efeitos ergogênicos; contudo, há indícios da necessidade de uma dose de pelo menos 3 mg/kg de cafeína. A ergogenicidade da cafeína foi afetada por vários fatores. Havia uma falta de protocolos padronizados e controle de fatores intervenientes (por exemplo, ciclo circadiano e estado nutricional) que poderiam afetar os resultados. Ainda é preciso definir um protocolo ideal de suplementação de cafeína que seja útil para futuras pesquisas, atletas e praticantes de atividade física. Um pequeno avanço feito desde 2010 envolveu a possível falta de diferença de gênero - parece que a suplementação de cafeína afeta homens e mulheres igualmente. Nível de Evidência I; Revisão Sistemática de Estudos de Nível I.
RESUMEN El objetivo de esta revisión fue examinar en la literatura actuallos avances hechos con respecto a los efectos del suplemento de cafeína sobre la fuerza máxima y sus mecanismos asociados desde 2010, año en que se publicaron dos artículos importantes. Las búsquedas se realizaron en las bases de datos PubMed, Medline, Scielo y Web of Science, por artículos publicados después de 2010. Se incluyeron 16 estudios basados en los criterios de inclusión y exclusión. Cinco estudios no reportaron cambios de la fuerza voluntaria máxima (31,3%). Cuatro de ellos usaron contracciones musculares isométricas, aunque esto puede no ser un factor clave, porque otros cinco estudios también utilizaron contracciones isométricas y reportaron efectos ergogénicos. Además, estos cuatro estudios evaluaron grupos musculares pequeños y los voluntarios no tenían el hábito de consumo de cafeína. La cafeína produjo efectos ergogénicos en 11 de los 16 estudios analizados (68,8%). Ninguna dosis fue claramente relacionada con efectos ergogénicos, sin embargo, hay indicios de la necesidad de una dosis de al menos 3 mg/kg de cafeína. La ergogenicidad de la cafeína se vio afectada por varios factores. Hubo una falta de protocolos y controles estandarizados de factores intervinientes (por ejemplo, ciclo circadiano y estado nutricional) que podrían afectar los resultados. Todavía es necesario definir un protocolo ideal de suplemento de cafeína que sea útil para futuras investigaciones, atletas y practicantes de actividad física. Un pequeño avance hecho desde 2010 involucró la posible falta de diferencia de género - parece que el suplemento de cafeína afecta a hombres y mujeres igualmente. Nivel de Evidencia I; Revisión sistemática de estudios de Nivel I.
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Objective To study the effect of cefetamet hydrochloride injection on the activity of 3 kinds of cytochrome P450 (CYP450) isoforms (CYP1A2, CYP3A4 and CYP2E1) in rat liver microsomes. Methods The SD rats were randomly divided into two groups: control group and cefetamet hydrochloride (CH) group, with each group containing 3 male rats and 3 female rats. The CH group was injected with cefetamet hydrochloride into the tail vein at 50 mg/(kg • d), twice a day for 7 days. A HPLC method was used for simultaneous determination of the production of metabolites and the degradation of the prototype probe substrates of 3 kinds of CYP450 isoforms, so as to evaluate the activity of hepatic CYP450. The analytical column was Diamonsil C18 column (150 mm X 4. 6 mm, 5 Fm), with the flow rate being 1. 0 mL/min. The mobile phase consisted of methanol (0. 1% formic acid) (A)-water (0. 1% formic acid)(B), 0-5 min; 18%A, 5-10 min; 18%-60%A, 10-15 min: 60%A and detected at 247 nm for determination of CYP1A2 activities; methanol (A)-water (0. 02% formic acid)(B), 0-11 min: 40%-60%A and detected at 223 nm for determination of CYP3A4 activities; and methanol (A)-water, 0-10 min: 37%-75%A and detected at 287 nm for determination of CYP2E1 activities. Results Probe substrates and their metabolites showed good linearity within the determining range (r≥0. 999 7). The precision of the method was 0. 05). Conclusion CH injection can significantly induce hepatic microsome CYP3A4 expression in SD rats, but has no induction or inhibition effect on CYP1A2 and CYP2E1, indicating that potential drug-drug interaction might occur when CH injection is coadministered with drugs metabolized by CYP3A4.
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Objective To investigate cytochrome P450 1A2~* 1C gene polymorphism in Dai and Han nationality volunteers from Dehong autonomous prefecture in Yunnan province. Methods One hundred and seventeen Dai and 112 Han nationality volunteers from Dehong autonomous prefecture in Yunnan province were enrolled in this study. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed in genotyping analysis. Results There were 45 wild-type homozygotes (G/G), 63 heterozygotes (G/A) and 9 homozygotes among 117 Dai nationality volunteers, while 63 wild-type homozygotes (G/G), 44 heterozygotes (G/A) and 5 homozygots among 112 Han nationality volunteers. There was significant difference in the incidences of the genotypes between the two populations (P<0.05). The distribution of the genotypes of either population was in Hardy-Weinberg equilibrium. The frequency of the allele A in the 1ocus-2964 of CYP1 A2 was 35% (95% CI30%-40%) and 24% (95% CI 20%-30%) respectively in Dai and Han nationality volunteers. There was significant difference in the frequency between two populations (P<0.05). There was also significant difference in the frequency between Dai nationality volunteers and the populations of other regions. Conclusion CYP1A2~*1C gene polymorphism is one of factors of producing individual and racial variation in pharmacology in Dai and Han people from Dehong autonomous prefecture in Yunnan province.