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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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Adenosine,also known as adenine nucleoside,is an important bioactive substances. A large number of studies found that adenosine is involved in the prevention and treatment of many diseases by activating adenosine receptors. Up to now,Adenosine receptors have cloned four subtypes,such as A1,A2a,A2b and A3 and they can be combined with AD and start the downstream signal transduction mechanism,then have different effects on the body. This article will summarize the distribution and activation of adenosine A2 receptor and its role and mechanism in the prevention and treatment of disease.
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Objective To evaluate the opening level and optimal time window of the blood-brain barrier induced by adenosine A2 receptor agonist ( Lexiscan) via dynamic enhanced MRI. Methods Twen-ty New Zealand white rabbits were divided into experiment group ( group A, n=10) and control group ( group B, n=10) . Rabbits in group A were injected with Lexiscan and rabbits in group B were injected with physiological salt via ear vein, then the coronary scanning was performed. Contrast enhanced MRI was performed at different time points ( 5, 10, 15, 20 min, and then every 10 min, until 2 h) following the in-fusion of Gd-diethylene triamine pentaacetic acid (DTPA). The signal intensity (SI) of region of interest ( ROI) was measured and the percent enhancement of SI was calculated. Evens blue staining results in brain tissues were observed. Pair t test was used to analyze the data. Results The percent enhancement of SI in group A significantly increased to (40. 93±3.70)％ at 5 min, reached the maximum of (43.03±3.62)％ at 30 min, slowly decreased until 50 min, and got to a stable level at almost 80 min. At each time point, the per-cent enhancement of SI in group A was significantly higher than that in group B ( t values:6.88-20.28, all P<0. 05) . The staining was evident in group A. Conclusions Lexiscan can open blood-brain barrier tem-porarily and reversibly, and the optimal opening time window is 10-50 min post-injection.
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Vasodilator stress MPI plays an important role in the detection of abnormal myocardial perfusion.Currently as the only selective A2A adenosine receptor agonist approved by FDA,the new myocardial stress agent regadenoson has been increasingly used in vasodilator stress MPI on clinic.This review describes the pharmacologic properties and overviews the clinical data on regadenoson,especially its diagnostic efficacy,prognosis predicting value and adverse effect as a vasodilator stress agent.
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OBJECTIVE To study the therapeutic effect and the underlying mechanism of asiatico?side on bleomycin-induced rat interstitial pulmonary fibrosis(IPF). METHODS Male Sprague-Dawley (SD)rats were divided into normal control group,bleomycin 5 mg·kg-1 model group and asiaticoside 50 mg · kg-1 group. The model and asiaticoside group were administrated with bleomycin 5 mg · kg-1 to induce IPF,while the asiaticoside group was administrated with asiaticoside 50 mg·kg-1 by gastric perfusion. Hematein eosin(HE)and Masson staining were carried out to analyze the histopathological changes in the lung. Lung homogenates were used to examine hydroxyproline(HYP) content,and serum samples were used to measure the concentration of interferon-γ(IFN-γ),interleukin-4(IL-4) and tumor necrosis factor-α(TNF-α). In addition,immunohistochemical methods were used to locate lung transforming growth factor-β1(TGF-β1)and adenosine 2A receptor(A2AR)expression,and Western blotting was used to examine the expression levels of TGF-β1 and A2AR. RESULTS On the 7th,14th and 28th days,the scores of pulmonary inflammation were higher in model group than in control group (P<0.01),and the asiaticoside group showed mitigated alveolitis(P<0.01,P<0.05) compared with model group. Compared with control group,the scores of pulmonary fibrosis in model group were elevated(P<0.01),and the asiaticoside group showed reduced pulmonary fibrosis(P<0.05). On the 14th and 28th days,HYP content in the model group〔1.85±0.10,(2.48±0.18)mg·g-1〕was higher than in the control group〔0.79 ± 0.07,(0.84 ± 0.08)mg · g-1〕(P<0.01),but HYP content in the asiaticoside group〔1.32±0.131,(1.71±0.13)mg·g-1〕was lower than in the model group(P<0.05). IL-4 and TNF-αin the asiaticoside group were lower than in model group(P<0.05),but were higher in the model group than in the control group(P<0.01,P<0.05). The expression level of TGF-β1 protein in the asiaticoside group was lower than in the model group(P<0.05),but was higher in the model group than in the control group(P<0.05). The expression level of A2AR protein in the asiaticoside group was higher than in the model group(P<0.05),but was lower in the model group than in the control group(P<0.05). CONCLUSION Asiaticoside can mitigate bleomycin-induced IPF by inhibiting the expression of IL-4, TNF-αand TGF-β1,and raising the level of A2AR.
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Objective To investigate the mechanism of hypoxia regulate osteopontin (OPN) secreting by mature dendritic cells (mDCs). Methods CD14 + cells were enriched using anti-CD14 immunomagnetic beads, for inducing to mDCs, CD14 + cells were cultured with GM-CSF and IL-4 in hypoxia or normoxiain vitro. Concentration of OPN and TGF-β1 in supernatant were detected by sandwich ELISA, OPN mRNA detected by RT-PCR. Approach regulating function of A2 R in expressing of OPN by mDCs by using NECA (surrogate of adenosine), A2R agonist (CGS21680), A2R antagonist (SCH58261) and investigate role of TGF-β1 in this process by using rhTGF-β1 and anti-TGF-β1 Ab. Results Hypoxia inreased the level of OPN and OPN mRNA in mDCs, and this effect could be reversed by A2 R antagonist. Under normoxia,both NECA and A2R agonist (CGS21680) could upregulate the level of OPN and OPN mRNA in mDCs significantly, but this positive effect could be reversed by A2 R antagonist. A2 R played a role in regulating TGF-β1, and confirmed TGF-β1 involved in regulation of OPN by using rhTGF-β1 and anti-TGF-β1 Ab. Conclusion High adenosine induce the generation of TGF-β1 through the A2R on mDCs, and then TGF-β1 raise the OPN secreting by mDCs.