Caffeine induces neurobehavioral effects through modulating neurotransmitters

Antidepressant effects of SY-2476: A caffeine derivative's role in A1/A2A gene expression modulation in corticosterone-induced depressed rats

Depression is a pervasive mood disorder that continues to challenge researchers and clinicians worldwide. Caffeine and its derivatives have been studied for their neuroprotective and antidepressant effect. Current study aimed to explore the potential antidepressant effect of a caffeine derivative, Sy-2476 [4-(1, 3, 7-trimethyl-2, 6-dioxo-2, 3, 6, 7-tetrahydro-1H-purin-8-yl) benzo nitrile], in corticosterone-induced rat model of depression. Depression-like behaviour in rats was induced by administering 20 mg/kg hydrocortisone s.c for 21 days. Behavioural studies evaluated the potential antidepressant effect of caffeine derivative Sy-2476, its effect on cortisol levels, modulation of A1/A2A receptors mRNA expression and antioxidant assays. Treatment of rats with Sy-2476 exhibited robust antidepressant-like effects in corticosterone-exposed rats by increasing sucrose preference (p = 0.0002) while reducing immobility time (p = 0.0118) in the forced swim test. Sy-2476 also reduced lipid peroxidation and increased the level of antioxidant enzymes, including glutathione, catalase, and superoxide dismutase. Moreover, Sy-2476 significantly lowered cortisol levels (p = 0.0019) and up-regulated mRNA expression of A1 (p = 0.0001) and A2A receptors (p = 0.0016) compared to the corticosterone-only treated group. In conclusion, Sy-2476 showed an antidepressant effect primarily by suppressing serum cortisol levels, modulating the expression of adenosine receptors, and exhibiting antioxidant properties.

Caffeine's Neuroprotective Effect on Memory Impairment: Suppression of Adenosine A2A Receptor and Enhancement of Tyrosine Hydroxylase in Dopaminergic Neurons Under Hypobaric Hypoxia Conditions

AIMS

Chronic hypobaric hypoxia frequently results in memory deficits, with severe cases showing marked alterations in dopamine levels and its metabolites. This research explores caffeine's modulation of the adenosine A2A receptor (A2AR) and its regulatory effects on tyrosine hydroxylase (TH), aiming to restore dopamine homeostasis and mitigate memory impairments associated with hypoxia. The goal is to identify novel preventive strategies against cognitive decline induced by hypoxia.

METHODS

Network pharmacological analysis was employed to predict the interactions between caffeine, cognitive function, and hypobaric hypoxia-related disorders. The novel object recognition and Y-maze tests were utilized to assess caffeine's impact on memory deficits under hypobaric hypoxia conditions in male mice. LC-MS/MS analysis was subsequently conducted to examine the variations in dopamine and its metabolites within the midbrain. Molecular docking further confirmed the binding affinities between A2AR and caffeine, as well as TH and caffeine. Additionally, immunofluorescence and protein-protein docking were employed to elucidate the interaction between A2AR and TH.

RESULTS

The findings highlight the pivotal role of adenosine receptors and dopamine-related pathways in the interplay between caffeine, cognition, and hypobaric hypoxia-related disorders. Behavioral tests demonstrated that caffeine effectively alleviated memory impairments caused by chronic hypobaric hypoxia. LC-MS/MS results revealed significant differences in dopamine, metanephrine, and 3-hydroxyanthranilic acid levels following caffeine treatment for hypoxia-induced cognitive deficits. Molecular docking confirmed the high affinity between A2AR and caffeine, as well as TH and caffeine, while immunofluorescence and protein-protein docking provided insights into the A2AR-TH interaction and its modulation during hypobaric hypoxia.

CONCLUSIONS

Caffeine exhibits potent neuroprotective effects against chronic high-altitude-induced cognitive impairments, potentially through its action on A2AR, leading to enhanced TH expression and subsequent release of dopamine and its related neurotransmitters.

Muscle contraction time after caffeine intake is faster after 30 minutes than after 60 minutes

BACKGROUND

This study aimed to determine the optimal time point, either 30 or 60 minutes, at which muscle reactivity to caffeine administration is highest. Unlike previous studies that focused on the nervous system response, we employed tensiomyography (TMG) to directly assess the effects of caffeine on muscle fibers.

METHODS

TMG measurements were performed on the gastrocnemius medialis muscle of 42 male athletes who regularly consumed caffeine. Participants received a dose of 6 mg/kg body weight and TMG measurements were taken prior to caffeine intake, as well as 30 and 60 minutes afterward.

RESULTS

Analysis of TMG parameters including time to contraction (Tc), time delay (Td), and maximal displacement (Dm) revealed that muscles exhibited faster contractions and greater stiffness at the 30-minute mark compared to both pre-caffeine intake and the 60-minute time point. Time exerted a significant main effect on Tc (F(2, 246) = 12.09, p < .001, ή2p = 0.09), Td (F(2, 246) = 3.39, p = .035, ή2p = 0.03), and Dm (F(2, 246) = 6.83, p = .001, ή2p = 0.05), while no significant effect of body side was observed.

CONCLUSIONS

The findings indicate that muscle contraction time (Tc) and delay time (Td) are influenced by the time elapsed since caffeine ingestion, with the fastest responses occurring after 30 minutes. Additionally, a systemic effect of caffeine was observed, as there were no discernible differences in measurements between the two sides of the body. TMG proves to be an effective noninvasive method for assessing muscle responses following caffeine administration.

Genetic susceptibility to caffeine intake and metabolism: a systematic review

BACKGROUND

Coffee and tea consumption account for most caffeine intake and 2-3 billion cups are taken daily around the world. Caffeine dependence is a widespread but under recognized problem.

OBJECTIVES

To conduct a systematic review on the genetic susceptibility factors affecting caffeine metabolism and caffeine reward and their association with caffeine intake.

METHODOLOGY

We conducted PubMed and Embase searches using the terms "caffeine", "reward", "gene", "polymorphism", "addiction", "dependence" and "habit" from inception till 2024. The demographics, genetic and clinical data from included studies were extracted and analyzed. Only case-control studies on habitual caffeine drinkers with at least 100 in each arm were included.

RESULTS

A total of 2552 studies were screened and 26 studies involving 1,851,428 individuals were included. Several genes that were involved with caffeine metabolism such as CYP1A2, ADORA2A, AHR, POR, ABCG2, CYP2A6, PDSS2 and HECTD4 rs2074356 (A allele specific to East Asians and monomorphic in Europeans, Africans and Americans) were associated with habitual caffeine consumption with effect size difference of 3% to 32% in number of cups of caffeinated drink per day per effect allele. In addition, ALDH2 was linked to the Japanese population. Genes associated with caffeine reward included BDNF, SLC6A4, GCKR, MLXIPL and dopaminergic genes such as DRD2 and DAT1 which had around 2-5% effect size difference in number of cups of caffeinated drink for each allele per day.

CONCLUSION

Several genes that were involved in caffeine metabolism and reward were associated with up to 30% effect size difference in number of cups of caffeinated drink per day, and some associations were specific to certain ethnicities. Identification of at-risk caffeine dependence individuals can lead to early diagnosis and stratification of at-risk vulnerable individuals such as pregnant women and children, and can potentially lead to development of drug targets for dependence to caffeine.

Stress-Relieving Effects of Green Tea Depend on the Ratio of Its Special Ingredients and the Infusion Conditions

Theanine, an amino acid unique to tea leaves, has been reported to exhibit stress-relieving effects. However, the stress-relieving effects of theanine (T) are greatly inhibited by caffeine (C) and epigallocatechin gallate (E), the main components of green tea, while being enhanced by arginine (A). Animal and clinical studies using matcha tea have shown that it can alleviate stress if the molar ratio of C and E against T and A (CE/TA) is less than 2. In general, the CE/TA ratio in tea leaves is reflected by the CE/TA ratio in the infused solution; however, it is not clear what infusion conditions would be expected to ensure a stress-relieving effect. In this study, to examine the stress-relieving effect of green-tea-infused solutions, the CE/TA ratio was measured under different infusion conditions. Furthermore, a study using a model solution consisting of C, E, T, and A revealed that a CE/TA ratio of at least less than 2 and a T content greater than 0.23 mM were required for stress reduction. Based on these results, we identified tea leaves and their infusion conditions that can be expected to reduce stress.

Caffeine intake during lactation has a sex-dependent effect on the hippocampal excitatory/inhibitory balance and pups' behavior

During early life, disruptions in glutamatergic and GABAergic synapse development in the hippocampus may contribute to several neurodevelopmental disorders, including cognitive deficits and psychiatric disorders. Caffeine is the most consumed psychoactive drug in the world, and previous work from our group has shown that caffeine disrupts visual system connections at different stages of development. This work aimed to investigate the effects of caffeine consumption during lactation in the glutamatergic and GABAergic synaptic markers in the hippocampus and on the behavior of rat offspring. We found that maternal caffeine intake significantly reduced GluN1 subunits of the NMDA receptor, increased the GluA1/GluA2 ratio of AMPA receptor in the dorsal hippocampus, and decreased GAD content in female pups' ventral hippocampus. On the other hand, an increase in GluN1/GluN2b subunits, a decrease in GAD content in the dorsal hippocampus, and a reduction of the GluA1 content in the ventral hippocampus were observed in male pups. In addition, changes in the behavior of the offspring submitted to indirect caffeine consumption were also sex-dependent, with females developing anxiety-like behavior and males showing anxiety-like behavior and hyper-locomotion. These results highlight that maternal caffeine intake promotes changes in the hippocampal excitatory and inhibitory balance and offspring behavior in a sex-dependent manner, suggesting that the population should be alerted to reduced caffeine consumption by breastfeeding mothers.

Adenosinergic system and nucleoside transporters in attention deficit hyperactivity disorder: Current findings

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with high heterogeneity that can affect individuals of any age. It is characterized by three main symptoms: inattention, hyperactivity, and impulsivity. These neurobehavioral alterations and neurochemical and pharmacological findings are mainly attributed to unbalanced catecholaminergic signaling, especially involving dopaminergic pathways within prefrontal and striatal areas. Dopamine receptors and transporters are not solely implicated in this imbalance, as evidence indicates that the dopaminergic signaling is modulated by adenosine activity. To this extent, alterations in adenosinergic signaling are probably involved in ADHD. Here, we review the current knowledge about adenosine's role in the modulation of chemical, behavioral and cognitive parameters of ADHD, especially regarding dopaminergic signaling. Current literature usually links adenosine receptors signaling to the dopaminergic imbalance found in ADHD, but there is evidence that equilibrative nucleoside transporters (ENTs) could also be implicated as players in dopaminergic signaling alterations seen in ADHD, since their involvement in other neurobehavioral impairments.

Stress-relieving properties of a polyherbal blend with Syzygium aromaticum L. and Coffea canephora Pierre ex A. Froehner: A review and bibliometric analysis

OBJECTIVE

Syzygium aromaticum and Coffea canephora are acknowledged for their outstanding antioxidant, anti-inflammatory, and nerve-stimulant properties, showcasing potential in brain protection. Therefore, this study aims to quantitatively review existing literature and assess the potential of using it to formulate a herbal tea blend for managing stress and anxiety.

METHODS

Data was retrieved from the Scopus database, and a bibliometric analysis was performed using VOSviewer software.

RESULTS

Following a screening process, a total of 121 articles were identified, with S. aromaticum yielding a higher number compared to C. canephora. A detailed exploration of each plant revealed active components such as eugenol, β-caryophyllene, α-humulene, caffeine, mangiferin, and chlorogenic acids, each exhibiting stimulatory effects alongside antioxidant and anti-inflammatory properties. The neuroprotective effects were attributed to the reduction of oxidative stress and inflammation, coupled with the stimulation of neurotransmitters and hormones like dopamine, serotonin, cortisol, and adrenaline.

CONCLUSIONS

The review showed that these plants positively affect mood and cognition by influencing the brain's pleasure system. This suggests the need for further research to combine these plant extracts for developing 'Tenang tea', a potential herbal blend for managing stress and anxiety.

Chronic administration of caffeine, modafinil, AVL-3288 and CX516 induces time-dependent complex effects on cognition and mood in an animal model of sleep deprivation

OBJECTIVE

Caffeine and modafinil are used to reverse effects of sleep deprivation. Nicotinic alpha-7 receptor and AMPA receptor positive allosteric modulators (PAM) are also potential substances in this context. Our objective is to evaluate the effects of caffeine, modafinil, AVL-3288 (nicotinic alpha-7 PAM) and CX516 (AMPA receptor PAM) on cognition and mood in a model of sleep deprivation.

METHOD

Modified multiple platform model is used to sleep-deprive mice for 24 days, for 8 h/day. Vehicle, Modafinil (40 mg/kg), Caffeine (5 mg/kg), CX516 (10 mg/kg), and AVL3288 (1 mg/kg) were administered intraperitoneally daily. A cognitive test battery was applied every six days for four times. The battery that included elevated plus maze, novel object recognition, and sucrose preference tests was administered on consecutive days.

RESULTS

Sleep deprivation decreased novel object recognition skill, but no significant difference was found in anxiety and depressive mood. Caffeine administration decreased anxiety-like behavior in short term, but this effect disappeared in chronic administration. Caffeine administration increased memory performance in chronic period. AVL group showed better memory performance in short term, but this effect disappeared in the rest of experiment. Although, in the modafinil group, no significant change in mood and memory was observed, anhedonia was observed in the chronic period in vehicle, caffeine and modafinil groups, but not in AVL-3288 and CX-516 groups.

CONCLUSION

Caffeine has anxiolytic effect in acute administration. The improvement of memory in chronic period may be associated with the neuroprotective effects of caffeine. AVL-3288 had a short-term positive effect on memory, but tolerance to these effects developed over time. Furthermore, no anhedonia was observed in AVL-3288 and CX516 groups in contrast to vehicle, caffeine and modafinil groups. This indicates that AVL-3288 and CX516 may show protective effect against depression.

Biomarkers of Parkinson's Disease: From Basic Research to Clinical Practice

Parkinson's disease (PD) is a common neurodegenerative disease characterized pathologically by dopaminergic neuron loss and the formation of Lewy bodies, which are enriched with aggregated α-synuclein (α-syn). PD currently has no cure, but therapeutic strategies are available to alleviate symptoms. Early diagnosis can greatly improve therapeutic interventions, but the clinical diagnosis of PD remains challenging and depends mainly on clinical features and imaging tests. Efficient and specific biomarkers are crucial for the diagnosis, monitoring, and evaluation of PD. Here, we reviewed the biomarkers of PD in different tissues and biofluids, along with the current clinical biochemical detection methods. We found that the sensitivity and specificity of single biomarkers are limited, and selecting appropriate indicators for combined detection can improve the diagnostic accuracy of PD.

Molecular targets of caffeine in the central nervous system

Caffeine is an alkaloid obtained from plants and is one of the most consumptive drug in the form of chocolate, coffee and beverages. The potential impact of caffeine within CNS can be easily understood by mechanism of action-antagonism of adenosine receptor, calcium influx, inhibits phosphodiesterases. Adenosine a neuromodulator for adenosine receptors, which are abundantly expressed within the central nervous system. Caffeine antagonized the adenosine receptor, hence stimulate expression of dopamine. It plays pivotal role in many metabolic pathways within the brain and nervous system, it reduced the amyloid-β-peptide (Aβ) accumulation, downregulation of tau protein phosphorylation, stimulate cholinergic neurons and inhibits the acetylcholinestrase (AChE). It also possess antioxidant and antiapoptotic activity. Caffeine act as nutraceutical product, improves mental health. It contains antioxidants, vitamins, minerals and dietary supplements, by reducing the risk factor of several neurodegenerations including Alzheimer's disease, migraine, gallstone, cancer, Huntington's disease and sclerosis. This act as a stimulant and have capability to increase the effectiveness of certain pain killer. Beside positive affects, over-consumption of caffeine leads to negative impact: change in sleep pattern, hallucinations, high blood pressure, mineral loss and even heartburn. This chapter highlights pros and cons of caffeine consumption.

Coffee Bean and Its Chemical Constituent Caffeine and Chlorogenic Acid as Promising Chemoprevention Agents: Updated Biological Studies against Cancer Cells

Cancer is a complicated and ever-evolving disease that remains a significant global cause of disease and mortality. Its complexity, which is evident at the genetic and phenotypic levels, contributes to its diversity and resistance to treatment. Numerous scientific investigations on human and animal models demonstrate the potential of phytochemicals in cancer prevention. Coffee has been shown to possess potent anti-carcinogenic properties, and studies have documented the consumption of coffee as a beverage reduces the risk of cancer occurrence. The major secondary metabolites of coffee, named caffeine and chlorogenic acid, have been linked to anti-inflammatory and antineoplastic effects through various signaling. In light of this, this review article provides a comprehensive analysis based on studies in anticancer effects of coffee, chlorogenic acid, and caffeine published between 2010 and 2023, sourced from Scopus, Pubmed, and Google Scholar databases. We summarize recent advances and scientific evidence on the association of phytochemicals found in coffee with a special emphasis on their biological activities against cancer and their molecular mechanism deemed potential to be used as a novel therapeutic target for cancer prevention and therapy.

Coffee and mental disorders: How caffeine affects anxiety and depression

Caffeine, the main psychoactive component in coffee, has garnered significant attention for its potential impact on the most prevalent mental health conditions like anxiety and depression. This chapter comprehensively examines the neurobiological effects of caffeine, its influence on anxiety and depression, and relevant clinical studies. Caffeine exerts its psychostimulant effects primarily through antagonizing adenosine receptors, modulating neurotransmitter systems, and influencing intracellular calcium signaling in the brain. Caffeine exhibits dose-dependent effects. While moderate caffeine consumption is safe in healthy adults and may offer benefits for mental health, excessive intake is linked to adverse effects on neurological and psychiatric health and can aggravate symptoms, highlighting the importance of adjusting consumption patterns. High caffeine intake correlates with elevated anxiety levels, especially in individuals predisposed to anxiety disorders. However, the relationship between caffeine consumption and the risk of depression is intricate, with some studies suggesting a potential protective effect of moderate intake, while others find no significant association. Individual variations in caffeine metabolism, sensitivity, and genetic factors considerably impact responses to caffeine. The chapter also explores the therapeutic potential of caffeine as an adjunct treatment and outlines challenges and future research directions in elucidating caffeine's multifaceted role in mental health.

Evaluation of the responsiveness pattern to caffeine through a smart data-driven ECG non-linear multi-band analysis

This study aimed to explore more efficient ways of administering caffeine to the body by investigating the impact of caffeine on the modulation of the nervous system's activity through the analysis of electrocardiographic signals (ECG). An ECG non-linear multi-band analysis using Discrete Wavelet Transform (DWT) was employed to extract various features from healthy individuals exposed to different caffeine consumption methods: expresso coffee (EC), decaffeinated coffee (ED), Caffeine Oral Films (OF_caffeine), and placebo OF (OF_placebo). Non-linear feature distributions representing every ECG minute time series have been selected by PCA with different variance percentages to serve as inputs for 23 machine learning models in a leave-one-out cross-validation process for analyzing the behavior differences between ED/EC and OF_placebo/OF_caffeine groups, respectively, over time. The study generated 50-point accuracy curves per model, representing the discrimination power between groups throughout the 50 min. The best model accuracies for ED/EC varied between 30 and 70 %, (using the decision tree classifier) and OF_placebo/OF_caffeine ranged from 62 to 84 % (using Fine Gaussian). Notably, caffeine delivery through OFs demonstrated effective capacity compared to its placebo counterpart, as evidenced by significant differences in accuracy curves between OF_placebo/OF_caffeine. Caffeine delivery via OFs also exhibited rapid dissolution efficiency and controlled release rate over time, distinguishing it from EC. The study supports the potential of caffeine delivery through Caffeine OFs as a superior technology compared to traditional methods by means of ECG analysis. It highlights the efficiency of OFs in controlling the release of caffeine and underscores their promise for future caffeine delivery systems.

Defining a vitamin A5/X specific deficiency - vitamin A5/X as a critical dietary factor for mental health

A healthy and balanced diet is an important factor to assure a good functioning of the central and peripheral nervous system. Retinoid X receptor (RXR)-mediated signaling was identified as an important mechanism of transmitting major diet-dependent physiological and nutritional signaling such as the control of myelination and dopamine signalling. Recently, vitamin A5/X, mainly present in vegetables as provitamin A5/X, was identified as a new concept of a vitamin which functions as the nutritional precursor for enabling RXR-mediated signaling. The active form of vitamin A5/X, 9-cis-13,14-dehydroretinoic acid (9CDHRA), induces RXR-activation, thereby acting as the central switch for enabling various heterodimer-RXR-signaling cascades involving various partner heterodimers like the fatty acid and eicosanoid receptors/peroxisome proliferator-activated receptors (PPARs), the cholesterol receptors/liver X receptors (LXRs), the vitamin D receptor (VDR), and the vitamin A(1) receptors/retinoic acid receptors (RARs). Thus, nutritional supply of vitamin A5/X might be a general nutritional-dependent switch for enabling this large cascade of hormonal signaling pathways and thus appears important to guarantee an overall organism homeostasis. RXR-mediated signaling was shown to be dependent on vitamin A5/X with direct effects for beneficial physiological and neuro-protective functions mediated systemically or directly in the brain. In summary, through control of dopamine signaling, amyloid β-clearance, neuro-protection and neuro-inflammation, the vitamin A5/X - RXR - RAR - vitamin A(1)-signaling might be "one of" or even "the" critical factor(s) necessary for good mental health, healthy brain aging, as well as for preventing drug addiction and prevention of a large array of nervous system diseases. Likewise, vitamin A5/X - RXR - non-RAR-dependent signaling relevant for myelination/re-myelination and phagocytosis/brain cleanup will contribute to such regulations too. In this review we discuss the basic scientific background, logical connections and nutritional/pharmacological expert recommendations for the nervous system especially considering the ageing brain.

Timing Matters: Time of Day Impacts the Ergogenic Effects of Caffeine-A Narrative Review

Caffeine has attracted significant attention from researchers in the sports field due to its well-documented ergogenic effects across various athletic disciplines. As research on caffeine continues to progress, there has been a growing emphasis on evaluating caffeine dosage and administration methods. However, investigations into the optimal timing of caffeine intake remain limited. Therefore, this narrative review aimed to assess the ergogenic effects of caffeine administration at different times during the morning (06:00 to 10:00) and evening (16:00 to 21:00). The review findings suggest that circadian rhythms play a substantial role in influencing sports performance, potentially contributing to a decline in morning performance. Caffeine administration has demonstrated effectiveness in mitigating this phenomenon, resulting in ergogenic effects and performance enhancement, even comparable to nighttime levels. While the specific mechanisms by which caffeine regulates circadian rhythms and influences sports performance remain unclear, this review also explores the mechanisms underlying caffeine's ergogenic effects, including the adenosine receptor blockade, increased muscle calcium release, and modulation of catecholamines. Additionally, the narrative review underscores caffeine's indirect impact on circadian rhythms by enhancing responsiveness to light-induced phase shifts. Although the precise mechanisms through which caffeine improves morning performance declines via circadian rhythm regulation necessitate further investigations, it is noteworthy that the timing of caffeine administration significantly affects its ergogenic effects during exercise. This emphasizes the importance of considering caffeine intake timing in future research endeavors to optimize its ergogenic potential and elucidate its mechanisms.

Using caffeine as a chemical means to induce flow states

Flow is an intrinsically rewarding state characterised by positive affect and total task absorption. Because cognitive and physical performance are optimal in flow, chemical means to facilitate this state are appealing. Caffeine, a non-selective adenosine receptor antagonist, has been emphasized as a potential flow-inducer. Thus, we review the psychological and biological effects of caffeine that, conceptually, enhance flow. Caffeine may facilitate flow through various effects, including: i) upregulation of dopamine D1/D2 receptor affinity in reward-associated brain areas, leading to greater energetic arousal and 'wanting'; ii) protection of dopaminergic neurons; iii) increases in norepinephrine release and alertness, which offset sleep-deprivation and hypoarousal; iv) heightening of parasympathetic high frequency heart rate variability, resulting in improved cortical stress appraisal, v) modification of striatal endocannabinoid-CB1 receptor-signalling, leading to enhanced stress tolerance; and vi) changes in brain network activity in favour of executive function and flow. We also discuss the application of caffeine to treat attention deficit hyperactivity disorder and caveats. We hope to inspire studies assessing the use of caffeine to induce flow.

Bioactive compounds in coffee and their role in lowering the risk of major public health consequences: A review

This article addresses the bioactive components in coffee aroma, their metabolism, and the mechanism of action in lowering the risk of various potential health problems. The main bioactive components involved in the perceived aroma of coffee and its related health benefits are caffeine, chlorogenic acid (CGA), trigonelline, diterpenes, and melanoids. These compounds are involved in various physiological activities. Caffeine has been shown to have anticancer properties, as well as the ability to prevent the onset and progression of hepatocellular carcinoma and to be anti-inflammatory. CGA exhibits antioxidant action and is implicated in gut health, neurodegenerative disease protection, type 2 diabetes, and cardiovascular disease prevention. Furthermore, together with diterpenes, CGA has been linked to anticancer activity. Trigonelline, on the other side, has been found to lower oxidative stress by increasing antioxidant enzyme activity and scavenging reactive oxygen species. It also prevents the formation of kidney stones. Diterpenes and melanoids possess anti-inflammatory and antioxidant properties, respectively. Consuming three to four cups of filtered coffee per day, depending on an individual's physiological condition and health status, has been linked to a lower risk of several degenerative diseases. Despite their health benefits, excessive coffee intake above the recommended daily dosage, calcium and vitamin D deficiency, and unfiltered coffee consumption all increase the risk of potential health concerns. In conclusion, moderate coffee consumption lowers the risk of different noncommunicable diseases.

Naringin corrects renal failure related to Lesch-Nyhan disease in a rat model via NOS-cAMP-PKA and BDNF/TrkB pathways

This study explored the effect of naringin (NAR) on HGPRT1 deficiency and hyperuricemia through NOS-cAMP-PKA and BDNF/TrkB signaling pathways induced by caffeine (CAF) and KBrO3 in a rat model. Sixty-three adult male albino rats were randomly assigned into nine (n = 7) groups. Group I: control animals, Group II was treated with 100 mg/kg KBrO3 , Group III was treated with 250 mg/kg CAF, Group IV was treated with 100 mg/kg KBrO3  + 250 mg/kg CAF, Group V was administered with 100 mg/kg KBrO3  + 100 mg/kg haloperidol, Group VI was administered with 100 mg/kg KBrO3  + 50 mg/kg NAR, Group VII was administered with 500 mg/kg CAF + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO3  + 250 mg/kg CAF + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The exposure of rats to KBrO3 and CAF for 21 days induced renal dysfunction linked with Lesch-Nyhan disease. NAR obliterated renal dysfunction linked with Lesch-Nyhan disease by decreasing uric acid, renal malondialdehyde level, inhibiting the activities of arginase, and phosphodiesterase-51 (PDE-51) with corresponding upregulation of brain derived-neurotrophic factor and its receptor (BDNF-TrkB), Bcl11b, HGPRT1, and DARPP-32. Additionally, renal failure related to Lesch-Nyhan disease was remarkably corrected by NAR as shown by the reduced activities of AChE and enzymes of ATP hydrolysis (ATPase, AMPase, and ADA) with affiliated increase in the NO level. This study therefore validates NAR as nontoxic and effective chemotherapy against kidney-related Lesch-Nyhan disease by mitigating effects of toxic food additives and enzymes of ATP-hydrolysis via NOS-cAMP-PKA and BDNF/TrkB signaling pathways.

Current therapeutic targets and multifaceted physiological impacts of caffeine

Caffeine, which shares consubstantial structural similarity with purine adenosine, has been demonstrated as a nonselective adenosine receptor antagonist for eliciting most of the biological functions at physiologically relevant dosages. Accumulating evidence supports caffeine's beneficial effects against different disorders, such as total cardiovascular diseases and type 2 diabetes. Conversely, paradoxical effects are also linked to caffeine ingestion in humans including hypertension-hypotension and tachycardia-bradycardia. These observations suggest the association of caffeine action with its ingested concentration and/or concurrent interaction with preferential molecular targets to direct explicit events in the human body. Thus, a coherent analysis of the functional targets of caffeine, relevant to normal physiology, and disease pathophysiology, is required to understand the pharmacology of caffeine. This review provides a broad overview of the experimentally validated targets of caffeine, particularly those of therapeutic interest, and the impacts of caffeine on organ-specific physiology and pathophysiology. Overall, the available empirical and epidemiological evidence supports the dose-dependent functional activities of caffeine and advocates for further studies to get insights into the caffeine-induced changes under specific conditions, such as asthma, DNA repair, and cancer, in view of its therapeutic applications.

Does the timing of intake matter? Association between caffeine intake and depression: Evidence from the National Health and Nutrition Examination Survey

BACKGROUND

Recent research suggests that caffeine intake is associated with a reduced risk of depression. However, the relationship between caffeine intake during different periods of the day and depression is still unclear.

METHODS

This cross-sectional study analyzed noninstitutionalized adults from the National Health and Nutrition Examination Survey, with a weighted representation of approximately 218 million US adults. Covariate-adjusted sample-weighted regressions were used to examine associations between caffeine intake and depression in different periods.

RESULTS

Caffeine intake during non-early morning periods (outside of 5:00-8:00 AM) is associated with a high prevalence of depression (unadjusted OR: 1.08, 95%CI: 1.05-1.11; adjusted OR: 1.03, 95 % CI: 1.00-1.06). Participants who consumed caffeine in the early morning (5:00-8:00 AM) had a lower prevalence of depression compared to participants who did not consume caffeine in the early morning (unadjusted OR: 0.75, 95%CI: 0.67-0.85; adjusted OR: 0.86, 95 % CI: 0.75-0.99).

LIMITATIONS

Cross-sectional study could not determine the temporal association; patients with depression in this study were not clinically diagnosed with Major Depressive Disorder.

CONCLUSIONS

Among US adults, early morning caffeine consumers had a lower prevalence of depression than non-consumers; caffeine intake during non-early morning periods is associated with a high prevalence of depression. Our results may suggest the importance of caffeine intake time for depression.

Coffee and tea intake with long-term risk of irritable bowel syndrome: a large-scale prospective cohort study

BACKGROUND

To investigate prospective association of coffee and tea intake with incident irritable bowel syndrome (IBS) in a long-term cohort.

METHODS

Participants free of IBS, coeliac disease, inflammatory bowel disease and any cancer at baseline from UK Biobank were included. Coffee and tea intake was measured separately via baseline touchscreen questionnaire, with four categories for each intake (0, 0.5-1, 2-3 and ≥4 cups/day). Primary outcome was incident IBS. Cox proportional hazard model was used to estimate associated risk.

RESULTS

Among 425 387 participants, 83 955(19.7%) and 186 887(43.9%) consumed ≥4 cups/day of coffee and tea at baseline, respectively. During median 12.4-year follow-up, incident IBS was identified in 7736 participants. Compared with no coffee intake, consumption of 0.5-1, 2-3 and ≥4 cups/day was associated with lower IBS risk [hazard ratio (HR)=0.93, 95% CI: 0.87-0.99; 0.91, 0.85-0.97; 0.81, 0.76-0.88; Ptrend < 0.001]. Specifically, decreased risk was evident in individuals who consumed instant (HR = 0.83, 0.78-0.88) or ground coffee (HR = 0.82, 0.76-0.88) compared with no coffee drink. Regarding tea intake, protective association was only found in individuals who consumed 0.5-1 cup/day (HR = 0.87, 0.80-0.95), whereas no significant association was detected in those who consumed 2-3 (HR = 0.94, 0.88-1.01) or ≥4 cups/day (HR = 0.95, 0.89-1.02) compared with no-tea intake (Ptrend = 0.848).

CONCLUSIONS

Higher intake of coffee, particularly instant and ground coffee, is associated with lower risk of incident IBS, with significant dose-response relationship. Moderate-tea intake (0.5-1 cup/day) is associated with lower IBS risk.

Soft Drinks and Symptoms of Depression and Anxiety in Overweight Subjects: A Longitudinal Analysis of an European Cohort

BACKGROUND

Studies about the association of carbonated/soft drinks, coffee, and tea with depression and anxiety are scarce and inconclusive and little is known about this association in European adults. Our aim was to examine the association between the consumption of these beverages and depressive and anxiety symptom severity.

METHODS

A total of 941 European overweight adults (mean age, 46.8 years) with subsyndromal depression that participated in the MooDFOOD depression prevention randomized controlled trial (Clinical Trials.gov identifier: NCT2529423; date of the study: from 2014 to 2018) were analyzed. Depressive and anxiety symptom severity and beverage consumption were assessed using multilevel mixed-effects ordinal logistic regression models for each beverage consumption (carbonated/soft drink with sugar, carbonated/soft drink with non-nutritive sweeteners, coffee, and tea) with the three repeated measures of follow-up (baseline and 6 and 12 months). A case report form for participants' sociodemographic and clinical characteristics, the Food Frequency Questionnaire, the Patient Health Questionnaire-9, the Generalized Anxiety Disorder 7-Item Scale, the MINI International Neuropsychiatric Interview 5.0, the Short Questionnaire to Assess Health-Enhancing Psychical Activity, and the Alcohol Use Disorders Identification Test were the research tools used.

RESULTS

Daily consumption of carbonated/soft drinks with sugar was associated with a higher level of anxiety. Trends towards significance were found for associations between both daily consumption of carbonated/soft drinks with sugar and non-nutritive sweeteners and a higher level of depression. No relationship was found between coffee and tea consumption and the level of depression and anxiety.

CONCLUSIONS

The high and regular consumption of carbonated/soft drink with sugar (amount of consumption: ≥1 unit (200 mL)/day) tended to be associated with higher level of anxiety in a multicountry sample of overweight subjects with subsyndromal depressive symptoms. It is important to point out that further research in this area is essential to provide valuable information about the intake patterns of non-alcoholic beverages and their relationship with affective disorders in the European adult population.

Gender Differences in the Frequency of Positive and Negative Effects after Acute Caffeine Consumption

Gender-specific caffeine-related adverse effects should be thoroughly investigated. Sixty-five adult participants were included in the study, 30 men and 35 women (age, 22.5 ± 2.8; body weight, 71.7 ± 16.2 kg; BMI, 23.6 ± 4.4). The participants who were classified as low and moderate caffeine users received 3 mg/kg, and high caffeine users received 6 mg/kg of caffeine in one dose. One hour after ingestion of caffeine and within twenty-four hours, the participants completed a side effect questionnaire. Effects after the ingestion of CAF were divided into two subgroups: negative (muscle soreness, increased urine output, tachycardia and palpitations, anxiety or nervousness, headache, gastrointestinal problems, and insomnia) and positive (perception improvement; increased vigor/activeness). Caffeine ingestion resulted in a statistically significant association between gender and negative effects one hour after ingestion (p = 0.049). Gender and positive effects one hour after ingestion (p = 0.005), and between gender and positive effects within 24 h after ingestion (p = 0.047). There were significant associations between gender and perception improvement (p = 0.032) and gender and increased vigor/activeness (p = 0.009) one hour after ingestion. Nearly 30% of men and 54% of women reported negative effects. At the same time, 20% of women and more than 50% of men reported positive effects. Gender is an important factor in the negative and positive effects of caffeine consumption.

Tryptophan and Substance Abuse: Mechanisms and Impact

Addiction, the continuous misuse of addictive material, causes long-term dysfunction in the neurological system. It substantially affects the control strength of reward, memory, and motivation. Addictive substances (alcohol, marijuana, caffeine, heroin, methamphetamine (METH), and nicotine) are highly active central nervous stimulants. Addiction leads to severe health issues, including cardiovascular diseases, serious infections, and pulmonary/dental diseases. Drug dependence may result in unfavorable cognitive impairments that can continue during abstinence and negatively influence recovery performance. Although addiction is a critical global health challenge with numerous consequences and complications, currently, there are no efficient options for treating drug addiction, particularly METH. Currently, novel treatment approaches such as psychological contingency management, cognitive behavioral therapy, and motivational enhancement strategies are of great interest. Herein, we evaluate the devastating impacts of different addictive substances/drugs on users' mental health and the role of tryptophan in alleviating unfavorable side effects. The tryptophan metabolites in the mammalian brain and their potential to treat compulsive abuse of addictive substances are investigated by assessing the functional effects of addictive substances on tryptophan. Future perspectives on developing promising modalities to treat addiction and the role of tryptophan and its metabolites to alleviate drug dependency are discussed.

Combined Exposure to Chronic Sleep Deprivation and Caffeine Potentiates Behavioural Deficits by Altering Neurochemical Profile and Synaptophysin Expression in Long-Evans Rats

Using the Unpredictable Chronic Sleep Deprivation (UCSD) paradigm we developed, the combined effects of chronic sleep deprivation and high caffeine intake on prefrontal cortical synaptophysin expression, neurochemical profiles, and behavioural outcomes in Long-Evans rats were evaluated. The combination of chronic sleep deprivation and high-dose caffeine treatment produced varying degrees of behavioural impairments, depletion of antioxidants, serotonin, and an upregulation of acetylcholinesterase (AChE) activity in the prefrontal cortex. An immunohistochemical assessment revealed a reduction in synaptophysin protein expression in the prefrontal cortex following exposure to high-dose caffeine and chronic sleep deprivation. Overall, our findings support the advocacy for adequate sleep for optimal mental performance as a high intake of caffeine to attenuate the effects of sleep deprivation that may alter the neurochemical profile and synaptic plasticity in the prefrontal cortex, significantly increasing the risk of neuropsychiatric/degenerative disorders.

Disorders of Hippocampus Facilitated by Hypertension in Purine Metabolism Deficiency is Repressed by Naringin, a Bi-flavonoid in a Rat Model via NOS/cAMP/PKA and DARPP-32, BDNF/TrkB Pathways

Individuals who are hypertensive have a higher tendency of predisposition to other genetic diseases including purine metabolism deficiency. Therefore, the search for nontoxic and effective chemo protective agents to abrogate hypertension-mediated genetic disease is vital. This study therefore investigated the repressive effect of naringin (NAR) against disorder of hippocampus facilitated by hypertension in purine metabolism deficiency. Male albino rats randomly assigned into nine groups (n = 7) were treated for 35 days. Group I: control animals, Group II was treated with 100 mg/kg KBrO₃, Group III was treated with 250 mg/kg caffeine, and Group IV was treated with 100 mg/kg KBrO₃ + 250 mg/kg caffeine. Group V was administered with 100 mg/kg KBrO₃ + 100 mg/kg haloperidol. Group VI was administered with 100 mg/kg KBrO₃ + 50 mg/kg NAR. Group VII was administered with 250 mg/kg caffeine + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO₃ + 250 mg/kg caffeine + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The sub-acute exposure to KBrO₃ and CAF induced hypertension and mediated impairment in the hippocampus cells. This was apparent by the increase in PDE-5¹, arginase, and enzymes of ATP hydrolysis (ATPase and AMPase) with a simultaneous increase in cholinergic (AChE and BuChE) and adenosinergic (ADA) enzymes. The hypertensive-mediated hippocampal impairment was associated to alteration of NO and AC signaling coupled with lower expression of brain-derived neurotrophic factor and its receptor (BDNF-TrkB), down regulation of Bcl11b and DARPP-32 which are neurodevelopmental proteins, and hypoxanthine accumulation. However, these features of CAF-mediated hippocampal damage in KBrO₃-induced hypertensive rats were repressed by post-treatment with NAR via production of neuro-inflammatory mediators, attenuation of biochemical alterations, stabilizing neurotransmitter enzymes, regulating NOS/cAMP/PKA and DARPP-32, BDNF/TrkB signaling, and restoring hippocampal tissues.

Caffeine for intestinal transit after laparoscopic colectomy: randomized clinical trial (CaCo trial)

BACKGROUND

Coffee has been suggested to help postoperative gastrointestinal motility but the mechanism is not known. This trial assessed whether caffeine shortened time to bowel activity after laparoscopic colectomy.

METHODS

This was a single-centre, randomized, double-blinded, placebo-controlled superiority trial (October 2015 to August 2020). Patients aged at least 18 years undergoing elective laparoscopic colectomy were assigned randomly to receive 100 mg or 200 mg caffeine, or a placebo (250 mg corn starch) three times a day orally. The primary endpoint was the time to first bowel movement. Secondary endpoints included colonic transit time, time to tolerance of solid food, duration of hospital stay, and perioperative morbidity.

RESULTS

Sixty patients were assigned randomly to either the 200-mg caffeine group (20 patients), the 100-mg caffeine group (20) or the placebo group (20). In the intention-to-treat analysis, the mean(s.d.) time to first bowel movement was 67.9(19.2) h in the 200-mg caffeine group, 68.2(32.2) h in the 100-mg caffeine group, and 67.3(22.7) h in the placebo group (P = 0.887). The per-protocol analysis and measurement of colonic transit time confirmed no measurable difference with caffeine.

CONCLUSION

Caffeine was not associated with reduced time to first bowel movement.

REGISTRATION NUMBER

NCT02510911 (http://www.clinicaltrials.gov).

Neurohormetic phytochemicals in the pathogenesis of neurodegenerative diseases

The world population is progressively ageing, assuming an enormous social and health challenge. As the world ages, neurodegenerative diseases are on the rise. Regarding the progressive nature of these diseases, none of the neurodegenerative diseases are curable at date, and the existing treatments can only help relieve the symptoms or slow the progression. Recently, hormesis has increased attention in the treatment of age-related neurodegenerative diseases. The concept of hormesis refers to a biphasic dose-response phenomenon, where low levels of the drug or stress exert protective of beneficial effects and high doses deleterious or toxic effects. Neurohormesis, as the adaptive aspect of hormetic dose responses in neurons, has been shown to slow the onset of neurodegenerative diseases and reduce the damages caused by aging, stroke, and traumatic brain injury. Hormesis was also observed to modulate anxiety, stress, pain, and the severity of seizure. Thus, neurohormesis can be considered as a potentially innovative approach in the treatment of neurodegenerative and other neurologic disorders. Herbal medicinal products and supplements are often considered health resources with many applications. The hormesis phenomenon in medicinal plants is valuable and several studies have shown that hormetic mechanisms of bioactive compounds can prevent or ameliorate the neurodegenerative pathogenesis in animal models of Alzheimer’s and Parkinson’s diseases. Moreover, the hormesis activity of phytochemicals has been evaluated in other neurological disorders such as Autism and Huntington’s disease. In this review, the neurohormetic dose–response concept and the possible underlying neuroprotection mechanisms are discussed. Different neurohormetic phytochemicals used for the better management of neurodegenerative diseases, the rationale for using them, and the key findings of their studies are also reviewed.

Assessment of caffeine neurotoxicity using novel biomarkers of neural function in SH-SY5Y cells - Is there a need for environmental concern?

Worldwide usage of caffeine results in its constant release into the aquatic environment and growing concerns related to associated risks. We assessed (neuro)toxicity of environmentally relevant concentrations of caffeine, using novel biomarkers of neural function in SH-SY5Y cells and markers of general toxicity also in HepG2 cells. The RQ-PCR analyses showed that caffeine disturbs the expression of genes encoding several key elements of neurotransmitter pathways, with the most prominent responses observed for serotonin receptor 3A, dopamine receptor D2, monoamine oxidase B and GABA-transaminase. Expression of genes encoding synaptotagmin 10 involved in exocytosis of neurotransmitters and ATPase Na⁺/K⁺ transporting subunit alpha 3 was also disturbed. Caffeine stimulated the activity of monoamine oxidase, while cytotoxicity and effects on mitochondrial membrane potential were not observed. Our study points out the new possible molecular targets of caffeine and suggests that the raising concerns related to its growing environmental presence are justified.

Improvement of Depressed Mood with Green Tea Intake

Being in a prolonged depressed state increases the risk of developing depression. To investigate whether green tea intake is effective in improving depression-like moods, we used an experimental animal model of depression with lipopolysaccharide (LPS) and clarified the effects of green tea on the biological stress response and inflammation in the brain. Regarding the stress reduction effect of green tea, we found that the sum of caffeine (C) and epigallocatechin gallate (E) relative to the sum of theanine (T) and arginine (A), the major components of green tea, or the CE/TA ratio, is important. The results showed that depression-like behavior, adrenal hypertrophy as a typical stress response, and brain inflammation were suppressed in mice fed green tea components with CE/TA ratios of 2 to 8. In addition, the expression of Npas4, which is reduced in anxiety and depression, was maintained at the same level as controls in mice that consumed green tea with a CE/TA ratio of 4. In clinical human trials, the consumption of green tea with CE/TA ratios of 3.9 and 4.7 reduced susceptibility to subjective depression. These results suggest that the daily consumption of green tea with a CE/TA ratio of 4–5 is beneficial to improving depressed mood.

Chronic caffeine consumption improves the acute REM sleep deprivation-induced spatial memory impairment while altering NMDA receptor subunit expression in male rats

Caffeine is a psychostimulant substance that is mostly used to prevent fatigue, increase alertness, and ameliorate sleep loss situations. In this study, we aimed to investigate the effect of chronic caffeine consumption on learning and memory functions and related genes in REM (rapid-eye-movement) sleep-deprived rats. During the neonatal period [postnatal day (PND) 28] Wistar albino male rats (n=32) were randomly assigned into four groups: control (C), caffeine application (Cf), acute REM sleep-deprivation (RD), and caffeine application+acute RD (Cf+RD). The 48 hours of RD was executed when caffeine administration was completed. The learning and memory performance was evaluated by the Morris Water Maze Test (MWMT). Following this, the rats were decapitated to isolate hippocampus tissues. In MWMT, time spent in the targeted quadrant decreased significantly in the RD group compared to the C and Cf+RD group. NR2A expression level increased in the RD group compared to C, Cf, and Cf+RD groups (p<0.05). NR2B expression level increased in RD and Cf +RD groups compared to C and Cf groups (p<0.05). BDNF and c-Fos expression levels did not differ significantly between the groups. RD impaired hippocampal spatial memory performance in the MWMT test. Our results indicated that chronic caffeine consumption has a therapeutic effect on spatial memory deterioration impairment caused by RD. Furthermore, it seems that the effect of caffeine RD on the hippocampus may be mediated by NR2A.

Is Stress Taking the Pleasure out of Food?—A Characterization of the Food Pleasure Profiles, Appetite, and Eating Behaviors of People with Chronic Stress

Psychological stressors frequently occur in modern society, and are associated with general anhedonic traits (inability to experience pleasure) and altered eating behavior. As eating behavior is largely motivated by a desire for pleasure, the Food Pleasure Scale (FPS) was introduced as a new research tool for investigating aspects of pleasure from food-related experiences. Thereby, insights on whether some aspects of pleasure are more affected by stress than others can be investigated, and can help explain why changes in eating behavior are seen when under the influence of stress. A consumer survey including n = 190 Danish consumers all with moderate or high levels of perceived stress was conducted to explore the perception of pleasure from food, general appetite, meal patterns, as well as specific food preferences. The study showed that the majority found pleasure in the sensory modalities of food, as well as in the ‘comforting’ aspects of food pleasure. Furthermore, the moderately stressed respondents had fewer main meals and more post-dinner snacks and night meals, as compared to before falling ill, whereas the highly stressed group showed signs of anhedonic traits and losing appetite altogether. The present study contributes to our understanding of how a common condition, such as chronic stress, can affect individual, as well as public, health.

Divergent Effects of the Nonselective Adenosine Receptor Antagonist Caffeine in Pre-Manifest and Motor-Manifest Huntington's Disease

There is a controversy about potentially positive or negative effects of caffeine consumption on onset and disease progression of neurodegenerative diseases such as Huntington’s Disease (HD). On the molecular level, the psychoactive drug caffeine targets in particular adenosine receptors (AR) as a nonselective antagonist. The aim of this study was to evaluate clinical effects of caffeine consumption in patients suffering from premanifest and motor-manifest HD. Data of the global observational study ENROLL-HD were used, in order to analyze the course of HD regarding symptoms onset, motor, functional, cognitive and psychiatric parameters, using cross-sectional and longitudinal data of up to three years. We split premanifest and manifest participants into two subgroups: consumers of >3 cups of caffeine (coffee, cola or black tea) per day (>375 mL) vs. subjects without caffeine consumption. Data were analyzed using ANCOVA-analyses for cross-sectional and repeated measures analysis of variance for longitudinal parameters in IBM SPSS Statistics V.28. Within n = 21,045 participants, we identified n = 1901 premanifest and n = 4072 manifest HD patients consuming >3 cups of caffeine/day vs. n = 841 premanifest and n = 2243 manifest subjects without consumption. Manifest HD patients consuming >3 cups exhibited a significantly better performance in a series of neuropsychological tests. They also showed at the median a later onset of symptoms (all p < 0.001), and, during follow-up, less motor, functional and cognitive impairments in the majority of tests (all p < 0.050). In contrast, there were no beneficial caffeine-related effects on neuropsychological performance in premanifest HD mutation carriers. They showed even worse cognitive performances in stroop color naming (SCNT) and stroop color reading (SWRT) tests (all p < 0.050) and revealed more anxiety, depression and irritability subscores in comparison to premanifest participants without caffeine consumption. Similarly, higher self-reported anxiety and irritability were observed in genotype negative/control group high dose caffeine drinkers, associated with a slightly better performance in some cognitive tasks (all p < 0.050). The analysis of the impact of caffeine consumption in the largest real-world cohort of HD mutation carriers revealed beneficial effects on neuropsychological performance as well as manifestation and course of disease in manifest HD patients while premanifest HD mutation carrier showed no neuropsychological improvements, but worse cognitive performances in some tasks and exhibited more severe signs of psychiatric impairment. Our data point to state-related psychomotor-stimulant effects of caffeine in HD that might be related to regulatory effects at cerebral adenosine receptors. Further studies are required to validate findings, exclude potential other unknown biasing factors such as physical activity, pharmacological interventions, gender differences or chronic habitual influences and test for dosage related effects.

Neurotransmitters-Key Factors in Neurological and Neurodegenerative Disorders of the Central Nervous System

Neurotransmitters are molecules that amplify, transmit, and convert signals in cells, having an essential role in information transmission throughout the nervous system. Hundreds of such chemicals have been discovered in the last century, continuing to be identified and studied concerning their action on brain health. These substances have been observed to influence numerous functions, including emotions, thoughts, memories, learning, and movements. Thus, disturbances in neurotransmitters' homeostasis started being correlated with a plethora of neurological and neurodegenerative disorders. In this respect, the present paper aims to describe the most important neurotransmitters, broadly classified into canonical (e.g., amino acids, monoamines, acetylcholine, purines, soluble gases, neuropeptides) and noncanonical neurotransmitters (e.g., exosomes, steroids, D-aspartic acid), and explain their link with some of the most relevant neurological conditions. Moreover, a brief overview of the recently developed neurotransmitters' detection methods is offered, followed by several considerations on the modulation of these substances towards restoring homeostasis.

Characterization of electrocorticographic, electromyographic and electrocardiographic recordings after the use of caffeine in Wistar rats

Objective:

To describe electrocorticographic, electromyographic and electrocardiographic profiles to report the electrophysiological effects of caffeine in Wistar rats.

Methods:

Male adult Wistar rats weighing 230g to 250g were used. Rats were allocated to one of two groups, as follows: Group 1, Control, intraperitoneal injection of 0.9% saline solution (n=27); and Group 2, treated with intraperitoneal injection of caffeine (50mg/kg; n=27). The rats were submitted to electrocorticographic, electromyographic and electrocardiographic assessment.

Results:

Brain oscillations (delta, theta, alpha, beta and gamma) in the frequency range up to 40Hz varied after caffeine administration to rats. Powers in delta and theta oscillations ranges were preponderant. The contractile force of the skeletal striated and cardiac muscles increased. Electrocardiogram analysis revealed shorter RR, QRS and QT intervals under the effect of caffeine.

Conclusion:

In the central nervous system, there was an increase in the delta, theta and alpha amplitude spectrum, which are related to memory encoding and enhanced learning. With regard to skeletal muscle, increased contraction of the gastrocnemius muscle was demonstrated, a clear indication of how caffeine can be used to enhance performance of some physical activities. Electrocardiographic changes observed after caffeine administration are primarily related to increased heart rate and energy consumption.

Caffeine: cardiorespiratory effects and tissue protection in animal models

The aim of this review is to analyze the cardiorespiratory and tissue-protective effects of caffeine in animal models. Peer-reviewed literature published between 1975 and 2021 was retrieved from CAB Abstracts, PubMed, ISI Web of Knowledge, and Scopus. Extracted data were analyzed to address the mechanism of action of caffeine on cardiorespiratory parameters (heart rate and rhythm), vasopressor effects, and some indices of respiratory function; we close this review by discussing the current debate on the research carried out on the effects of caffeine on tissue protection. Adenosine acts through specific receptors and is a negative inotropic and chronotropic agent. Blockage of its cardiac receptors can cause tachycardia (with arrhythmogenic potential) due to the intense activity of β1 receptors. In terms of tissue protection, caffeine inhibits hyperoxia-induced pulmonary inflammation by decreasing proinflammatory cytokine expression in animal models. The protection that caffeine provides to tissues is not limited to the CNS, as studies have demonstrated that it generates attenuation of inflammatory effects in pulmonary tissue. It inhibits the effects of some pro-inflammatory cytokines and prevents functional and structural changes.

Estrous cycle modulates the anxiogenic effects of caffeine in the elevated plus maze and light/dark box in female rats

Caffeine is a commonly used stimulant of the central nervous system that reduces fatigue, increases alertness, and exerts positive effects on emotion through actions on various brain structures. High doses of caffeine can cause headaches, heart palpitations, hyperactivity, and anxiety symptoms. Consequently, reducing the consumption of stimulant substances, such as sugar and caffeine, is proposed to ameliorate symptoms of premenstrual syndrome in women. The administration of steroid hormones has been suggested to modulate the effects of caffeine, but unknown is whether endogenous hormone variations during the estrous cycle modulate the pharmacological effects of caffeine. The present study evaluated the effects of caffeine (10, 20, and 40 mg/kg) during metestrus-diestrus and proestrus-estrus of the ovarian cycle in rats on anxiety-like behavior using the elevated plus maze and light/dark box. During metestrus-diestrus, all doses of caffeine increased anxiety-like behavior, indicated by the main variables in both behavioral tests (i.e., higher Anxiety Index and lower percent time spent on the open arms in the elevated plus maze and less time spent in the light compartment in the light/dark box). During proestrus-estrus, only 20 and 40 mg/kg caffeine increased these parameters of anxiety-like behavior, albeit only slightly. In conclusion, caffeine increased anxiety-like behaviors in metestrus-diestrus, with an attenuation of these effects of lower doses of caffeine in proestrus-estrus. These effects that were observed in metestrus-diestrus and proestrus-estrus may be associated with low and high concentrations of steroid hormones, respectively, that naturally occur during these phases of the ovarian cycle.

Melatonin Regulates the Neurotransmitter Secretion Disorder Induced by Caffeine Through the Microbiota-Gut-Brain Axis in Zebrafish (Danio rerio)

Melatonin has been widely used as a “probiotic agent” capable of producing strong neurotransmitter secretion regulatory effects, and the microbiota-gut-brain axis-related studies have also highlighted the role of the gut microbiota in neuromodulation. In the present study, a zebrafish neural hyperactivity model was established using caffeine induction to explore the regulatory effects of melatonin and probiotic on neurotransmitter secretion disorder in zebrafish. Disorders of brain neurotransmitter secretion (dopamine, γ-aminobutyric acid, and 5-hydroxytryptamine) caused by caffeine were improved after interference treatment with melatonin or probiotic. Shotgun metagenomic sequencing demonstrated that the melatonin-treated zebrafish gradually restored their normal intestinal microbiota and metabolic pathways. Germ-free (GF) zebrafish were used to verify the essential role of intestinal microbes in the regulation of neurotransmitter secretion. The results of the neurotransmitter and short-chain fatty acid determination revealed that the effect on the zebrafish in the GF group could not achieve that on the zebrafish in the melatonin group after adding the same dose of melatonin. The present research revealed the potential mode of action of melatonin through the microbiota-gut-brain axis to regulate the disruption of neurotransmitter secretion, supporting the future development of psychotropic drugs targeting the intestinal microbiota.

The Aging GABAergic System and Its Nutritional Support

Aging is associated with a decline in hormones and an associated decline in GABAergic function and calcium and ion current dysregulation. Neurosteroid hormones act as direct calcium channel blockers, or they can act indirectly on calcium channels through their interaction with GABA receptors. The calcium channel dysfunction associated with hormone loss further leads to an excitatory cell state, which can ultimately lead to cell death. The calcium theory of aging posits that cellular mechanisms, which maintain the homeostasis of cytosol Ca2+ concentration, play a key role in brain aging and that sustained changes in Ca2+ homeostasis provide the final common pathway for age-associated brain changes. There is a link between hormone loss and calcium dysregulation. Loss of calcium regulation associated with aging can lead to an excitatory cell state, primarily in the mitochondria and nerve cells, which can ultimately lead to cell death if not kept in check. A decline in GABAergic function can also be specifically tied to declines in progesterone, allopregnanolone, and DHEA levels associated with aging. This decline in GABAergic function associated with hormone loss ultimately affects GABAergic inhibition or excitement and calcium regulation throughout the body. In addition, declines in GABAergic function can also be tied to vitamin status and to toxic chemicals in the food supply. The decline in GABAergic function associated with aging has an effect on just about every body organ system. Nutritional support of the GABAergic system with supportive foods, vitamins, and GABA or similar GABA receptor ligands may address some of the GABAergic dysfunction associated with aging.

Caffeine-Induced Effects on Human Skeletal Muscle Contraction Time and Maximal Displacement Measured by Tensiomyography

Studies on muscle activation time in sport after caffeine supplementation confirmed the effectiveness of caffeine. The novel approach was to determine whether a dose of 9 mg/kg/ body mass (b.m.) of caffeine affects the changes of contraction time and the displacement of electrically stimulated muscle (gastrocnemius medialis) in professional athletes who regularly consume products rich in caffeine and do not comply with the caffeine discontinuation period requirements. The study included 40 professional male handball players (age = 23.13 ± 3.51, b.m. = 93.51 ± 15.70 kg, height 191 ± 7.72, BMI = 25.89 ± 3.10). The analysis showed that in the experimental group the values of examined parameters were significantly reduced (p ≤ 0.001) (contraction time: before = 20.60 ± 2.58 ms/ after = 18.43 ± 3.05 ms; maximal displacement: before = 2.32 ± 0.80 mm/after = 1.69 ± 0.51 mm). No significant changes were found in the placebo group. The main achievement of this research was to demonstrate that caffeine at a dose of 9 mg/kg in professional athletes who regularly consume products rich in caffeine has a direct positive effect on the mechanical activity of skeletal muscle stimulated by an electric pulse.

Potential of Caffeine in Alzheimer's Disease-A Review of Experimental Studies

Alzheimer's disease (AD) is the most common type of dementia leading to progressive memory loss and cognitive impairment. Considering that pharmacological treatment options for AD are few and not satisfactory, increasing attention is being paid to dietary components that may affect the development of the disease. Such a dietary component may be caffeine contained in coffee, tea or energy drinks. Although epidemiological data suggest that caffeine intake may counteract the development of cognitive impairment, results of those studies are not conclusive. The aim of the present study is to review the existing experimental studies on the efficacy of caffeine against AD and AD-related cognitive impairment, focusing on the proposed protective mechanisms of action. In conclusion, the reports of studies on experimental AD models generally supported the notion that caffeine may exert some beneficial effects in AD. However, further studies are necessary to elucidate the role of caffeine in the effects of its sources on cognition and possibly AD risk.

Effects of Coffee and Its Components on the Gastrointestinal Tract and the Brain-Gut Axis

Coffee is one of the most popular beverages consumed worldwide. Roasted coffee is a complex mixture of thousands of bioactive compounds, and some of them have numerous potential health-promoting properties that have been extensively studied in the cardiovascular and central nervous systems, with relatively much less attention given to other body systems, such as the gastrointestinal tract and its particular connection with the brain, known as the brain–gut axis. This narrative review provides an overview of the effect of coffee brew; its by-products; and its components on the gastrointestinal mucosa (mainly involved in permeability, secretion, and proliferation), the neural and non-neural components of the gut wall responsible for its motor function, and the brain–gut axis. Despite in vitro, in vivo, and epidemiological studies having shown that coffee may exert multiple effects on the digestive tract, including antioxidant, anti-inflammatory, and antiproliferative effects on the mucosa, and pro-motility effects on the external muscle layers, much is still surprisingly unknown. Further studies are needed to understand the mechanisms of action of certain health-promoting properties of coffee on the gastrointestinal tract and to transfer this knowledge to the industry to develop functional foods to improve the gastrointestinal and brain–gut axis health.

GABA-enriched teas as neuro-nutraceuticals

Teas enriched in GABA are consumed for their beneficial effects on blood pressure, stress and anxiety. These effects may involve actions of GABA on the central and peripheral nervous systems. The anaerobic procedures for the production of GABA-enriched teas increase GABA levels by 10-20 times. They also significantly alter the levels of other constituents that may interact with the actions of GABA. These include epigallocatechin gallate, caffeine and theanine. The possible interactions of these active constituents make the understanding of the effects of GABA-enriched teas complex. More data is needed to establish where and how GABA is acting following consumption of GABA-enriched teas. While there is considerable evidence that such GABA is acting on GABA receptors in the periphery, there is rather less evidence that is acting directly in the brain. Certainly, there is more to the action of GABA-enriched teas than GABA itself.

Effects of Caffeine on Event-Related Potentials and Neuropsychological Indices After Sleep Deprivation

Objective: Caffeine is a central nervous system stimulant that can effectively alleviate brain fatigue and low cognitive efficiency induced by total sleep deprivation (TSD). Recent studies have demonstrated that caffeine can improve subjective attention and objective behavioral metrics, such as arousal level, reaction time, and memory efficiency. However, only a few studies have examined the electrophysiological changes caused by the caffeine in humans following sleep disturbance. In this study, an event-related potential (ERP) technique was employed to measure the behavioral, cognitive, and electrophysiological changes produced by caffeine administration after TSD.

Methods: Sixteen healthy subjects within-subject design performed a visual Go/No-Go task with simultaneous electroencephalogram recording. Behavioral and ERP data were evaluated after 36 h of TSD, and the effects of ingestion of either 400 mg of caffeine or placebo were compared in a double-blind randomized design.

Results: Compared with placebo administration, the Go hit rates were significantly enhanced in the caffeine condition. A simple effect analysis revealed that, compared with baseline, the Go-P2 amplitude was significantly enhanced after TSD in the caffeine consumption condition. A significant main effect of the drug was found on No-Go-P2, No-Go-N2 amplitude, and Go-P2 latency before and after TSD.

Conclusion: Our findings indicate that caffeine administration has acute effects on improving the efficiency of individual automatic reactions and early cognitive processes. Caffeine was related to the preservation of an individual’s arousal level and accelerated response-related decisions, while subjects’ higher-level recognition had limited improvement with prolonged awareness.