Caffeine enhances sustained attention among adolescents

Dual effect of the herbal matcha green tea (Camellia sinensis L. kuntze) supplement in EA.hy926 endothelial cells and Artemia salina

ETHNOPHARMACOLOGICAL RELEVANCE

Matcha green tea (Camellia sinensis) based-supplements have been widely used since they present a greater content of phenolic compounds than traditional green tea, which is popularly used in the treatment of diabetes. However, there are few studies on the effectiveness and safety of matcha supplements.

AIM OF THE STUDY

This work aimed to evaluate the efficacy and safety of this supplement in endothelial cells (EA.hy926) in the hyperglycemic model and in vivo Artemia salina.

MATERIALS AND METHODS

To assess the effect of Matcha herbal supplement (MHS), EA. hy926 endothelial cells were treated with 20 μg/mL of MHS for 24 h, in a hyperglycemic medium with 35 mM glucose. After treatment, cells were trypsinized and centrifuged at 4 °C and 47×g for 5 min. The pellet was used to determine the reaction products to thiobarbituric acid and the levels of nitric oxide. Electron transport chain activity and ATP levels were also evaluated. Intracellular pH, apoptosis, and mitochondrial membrane depolarization were evaluated by flow cytometry. MHS chemical characterization was performed by HPLC-UV and total phenolic content analysis. The evaluation of the antioxidant capacity of MHS was performed by 2,2-diphenyl-1-picrylhydrazyl radical scavenger assay. To determine the in vivo acute toxicity of MHS, an A. salina assay was conducted, using 0,2 mL of different concentrations of MHS (10, 50, 100, 250, 500, 750 and 1000 μg/mL). The LD₅₀ values were obtained by interpolation of 50% (y = 50) of the dead individuals in the trend curves.

RESULTS

Our data showed that MHS was able to avoid oxidative and nitrosative stress induced by hyperglycemia, demonstrating important antioxidant activity. However, it was observed that MHS reduced up to 90% the activity of the four-electron transport complexes, reducing the ATP production of the endothelial cells. In the toxicity assay performed in Artemia salina, MHS showed mild toxicity (LD₅₀ = 0,4 mg/mL). The major compounds found in MHS were epigallocatechin gallate, epicatechin, rutin, kaempferol, and quercetin.

CONCLUSIONS

This data draws attention to the fact that supplements with high content of phenolic compounds, capable of avoiding oxidative and nitrosative stress can have a dual effect and, simultaneously to antioxidant activity, can induce toxicity in different cell types.

Effect of caffeine on resting-state alpha activity across the human menstrual cycle

RATIONALE

Caffeine is the most consumed stimulant worldwide, and there is great interest in understanding its neurophysiological effects. Resting-state electroencephalography (EEG) studies suggest that caffeine enhances arousal, which suppresses the spectral power of alpha frequencies associated with reduced alertness. However, it is unclear whether caffeine's neurophysiological effects vary across the human menstrual cycle.

OBJECTIVE

The objective of our study was to test whether caffeine's effect on EEG activity differs across the human menstrual cycle.

METHODS

Fifty-six female participants were randomly assigned to complete the experiment while in either their menstrual (n = 21), follicular (n = 19), or luteal (n = 16) phase. Each participant completed two study sessions in the same menstrual phase, approximately 1 month apart, during which they were administered either a caffeine pill (200 mg, oral) or a placebo pill in a counterbalanced order using a randomized double-blinded procedure. We measured their eyes-closed resting-state EEG approximately 30 min after pill administration and conducted a spectral power analysis at different frequency bands.

RESULTS

Caffeine reduced EEG power in the alpha₁ frequency band (8-10 Hz), but only for participants who self-reported higher weekly caffeine consumption. Importantly, caffeine's effects did not differ by menstrual phase.

CONCLUSIONS

We conclude that when studying caffeine's effects on resting-state EEG, participants' baseline caffeine consumption is more influential than their menstrual cycle phase. This study has important implications for the inclusion of menstruating individuals in neurophysiological studies of caffeine.

Identifying Factors Influencing Attention in Adolescents with a Co-Created Questionnaire: A Citizen Science Approach with Secondary Students in Barcelona, Spain

Studies on factors that can influence attention in healthy adolescents are recent and focus on recurrent topics. Students' contribution to public health research often revolves around collecting data but rarely around creating data collection instruments. The ATENC!Ó project reunited secondary students and scientists to create a questionnaire including factors that students thought could affect their attention. We conducted a cross-sectional study to assess whether the factors included in this questionnaire had an effect on attention in adolescents. A total of 1667 students (13-16 years old) from 28 schools in Barcelona performed a validated attention test and answered the questionnaire. The response speed consistency (attentiveness), expressed as hit reaction time standard error (HRT-SE, in ms), was used as the primary outcome. Analyses were conducted using conditional linear regression with school as strata, adjusted for sociodemographic characteristics and further stratified by gender and maternal social class. Some factors showed a negative influence on attention, including taking medication and not reading regularly. We found a significant 14.3% (95% confidence interval: 3.4%, 25.3%) higher median of HRT-SE (increase inattentiveness) among students who reported not having a good relationship with classmates. Students' input into research is relevant for advancing the knowledge production in public health.

Preliminary Evaluations of Habituation of Operant Responding for Sensory Stimuli in Humans

Research suggests that repetitive reinforcers wane in their ability to maintain operant behavior in a manner consistent with habituation. Weaker reinforcers, including sensory stimuli common in human work, may be most impacted by repetition. The present research examined within-session operant responding patterns for visual stimuli in humans from two experiments assessing multiple characteristics of habituation. In Experiment 1, declines in reinforced responding were assessed and stimulus specificity was evaluated to test habituation's contribution to these declines. Seventy-three participants completed two visits, both including a reinforcement paradigm using pictures. With repetition, operant responding declined. The stimulus specificity manipulation did not enhance responding, suggesting that habituation did not contribute to response declines. Several methodological concerns may have contributed to the absence of a stimulus specificity effect. Experiment 2 assessed a separate habituation characteristic, rate of stimulation, to address these methodological concerns and further evaluate habituation. Twenty-eight participants completed the reinforcement paradigm over three visits. Decline in responding was partially supported, but the rate of stimulation did not alter declines. In sum, habituation's contribution to within-session declines for sensory reinforcers was not evident in either experiment. These results suggest that assessment of habituation of sensory reinforcers in humans may require parametric evaluation.