Effect of taurine and caffeine on sleep-wake activity in Drosophila melanogaster

Fly into tranquility: GABA's role in Drosophila sleep

Sleep is conserved across the animal kingdom, and Drosophila melanogaster is a prime model to understand its intricate circadian and homeostatic control. GABA (gamma-aminobutyric acid), the brain's main inhibitory neurotransmitter, plays a central role in sleep. This review delves into GABA's complex mechanisms of actions within Drosophila's sleep-regulating neural networks. We discuss how GABA promotes sleep, both by inhibiting circadian arousal neurons and by being a key neurotransmitter in sleep homeostatic circuits. GABA's impact on sleep is modulated by glia through astrocytic GABA recapture and metabolism. Interestingly, GABA can be coexpressed with other neurotransmitters in sleep-regulating neurons, which likely contributes to context-based sleep plasticity.

Caffeine affects the neurobehavioral impact of sodium benzoate in adolescent rats

The continuous high intake of caffeinated products may harm CNS. Sodium benzoate (SB), broadly used for food preservation, may also have an impact. The current research studied the influence of caffeine and two doses of SB during adolescence period on behavior and brain alterations. Adolescent rats (90-120 gm) were exposed to vehicle, SB 100 and 400 mg/kg, p.o, caffeine (30 mg/kg, i.p), SB 100 or 400 + caffeine for 28 days. Locomotor performances were assessed by the open field, learning and memory were considered with novel object and y-maze, while anxiety was evaluated by light and dark as well as successive allays tests. The results showed that the motor activity of adolescent rats increased with each single treatment. Recognition memory was improved by SB100 and its combination with caffeine while working memory was reduced by SB (100 or 400) combination with caffeine compared with caffeine group. The anxiolytic effect of caffeine was reduced by SB co-treatment in either dose. Concerning biochemical study in the frontal cortex and hippocampus, oxidative biomarkers as well as Cholinesterase content were elevated due to SB400 + caffeine. Dopamine content was almost elevated by all treatments in both regions while GABA content was increased in the frontal cortex only. The obtained results pointed to histopathological changes as a result of brain oxidative stress and undesirable working memory consequences due to caffeine administration with SB, mostly the large dose. The outcomes propose new recommendations to evade the consolidation between processed nourishment and caffeinated beverages during adolescence.

Energy Drinks and Sleep among Adolescents

Many adolescents worldwide have the problem of meeting recommended nightly sleep hours. The causes of sleep disturbance are multifactorial, but interest in food’s effect on sleep has dramatically increased lately. In this study, we investigated the association between regular energy drink (ED) intake (weekly or more frequent) and sufficient sleep (SS) (≥8 h) in adolescents. Additional objectives were to examine the relationship between health-related behaviors and SS, stratified by gender. A population-based cross-sectional study was conducted during the 2019/2020 school year from 12 schools in Belgrade. There were 1287 students aged 15 to 19 who participated (37.4% male). We used a modified version of the food frequency questionnaire adapted for Serbian adolescents. Logistic regression revealed that regular ED consumption was an independent risk factor negatively related to SS in both sexes. Additionally, daily vegetable and water intake (≥2 L) showed a positive correlation with SS in boys, while in girls, the odds of realizing SS decreased with statements of sedative use. In conclusion, we show that ED intake is negatively associated with SS in both sexes; daily vegetable and water intake (≥2 L) may raise the odds of SS in boys, while sedative use may decrease the chances of SS in girls.

Microengineered devices enable long-term imaging of the ventral nerve cord in behaving adult Drosophila

The dynamics and connectivity of neural circuits continuously change on timescales ranging from milliseconds to an animal's lifetime. Therefore, to understand biological networks, minimally invasive methods are required to repeatedly record them in behaving animals. Here we describe a suite of devices that enable long-term optical recordings of the adult Drosophila melanogaster ventral nerve cord (VNC). These consist of transparent, numbered windows to replace thoracic exoskeleton, compliant implants to displace internal organs, a precision arm to assist implantation, and a hinged stage to repeatedly tether flies. To validate and illustrate our toolkit we (i) show minimal impact on animal behavior and survival, (ii) follow the degradation of chordotonal organ mechanosensory nerve terminals over weeks after leg amputation, and (iii) uncover waves of neural activity caffeine ingestion. Thus, our long-term imaging toolkit opens up the investigation of premotor and motor circuit adaptations in response to injury, drug ingestion, aging, learning, and disease.

The Regulation of Drosophila Sleep

Sleep is critical for diverse aspects of brain function in animals ranging from invertebrates to humans. Powerful genetic tools in the fruit fly Drosophila melanogaster have identified - at an unprecedented level of detail - genes and neural circuits that regulate sleep. This research has revealed that the functions and neural principles of sleep regulation are largely conserved from flies to mammals. Further, genetic approaches to studying sleep have uncovered mechanisms underlying the integration of sleep and many different biological processes, including circadian timekeeping, metabolism, social interactions, and aging. These findings show that in flies, as in mammals, sleep is not a single state, but instead consists of multiple physiological and behavioral states that change in response to the environment, and is shaped by life history. Here, we review advances in the study of sleep in Drosophila, discuss their implications for understanding the fundamental functions of sleep that are likely to be conserved among animal species, and identify important unanswered questions in the field.

Acute effect of cola and caffeine on locomotor activity in drosophila and rat

Caffeine is well known for reducing fatigue and its effect on behavior is widely studied. Usually, caffeine is not ingested in its pure form but rather in sugar-sweetened beverages such as cola. Our aim was to compare the acute effect of cola and caffeine on locomotor activity. Rats and flies ingested cola or caffeine solution for 24 hours. The open field test revealed higher locomotor activity in cola groups for both flies and rats. Surprisingly, no differences have been observed between caffeineand control group. We conclude that caffeine itself does not explain the effect of cola on locomotor activity. Effect of cola cannot be generalized and interpreted for any caffeinated drink with other contents. Rather, the observed effect on locomotor activity may be caused by interaction of caffeine with other substances present in cola.

Chronic and Acute Oral Administration of Caffeine Enhance Performance of Olfactory Learning in Crickets

Crickets were arbitrarily fed a caffeine-containing diet during their lifetime or were orally administered caffeine in solution once during the conditioning session. These chronically or acutely treated crickets were used to test whether there were positive effects of caffeine on their learning performance. The effects of chronic exposure to caffeine on crickets' growth were also examined by measuring their body weight and counting the number of adults that emerged from larvae. Chronic treatment with relatively high concentrations of caffeine (5 mg/g and 0.5 mg/g in the diet) impaired the growth of crickets. Mortality was higher with 5 mg/g caffeine, and the survivors could not attain the final molt (eclosion). Body weight gain and eclosion rate were also negatively influenced in the group fed 0.5 mg/g caffeine. The olfactory learning paradigm was used to examine the effects of chronic caffeine treatment. Of the caffeine concentrations tested (0.5 µg/g to 0.5 mg/g), significant improvement in long-term memory (LTM) formation was observed only with 50 µg/g caffeine. Acute effects on olfactory learning were examined after oral administration of 0.1 nM to 10 µM caffeine solutions during the conditioning session. Administration of caffeine ≥ 1 nM consistently resulted in a significant improvement in LTM formation. These results suggest that chronic exposure to caffeine enhances learning performance in crickets at a specific dose (50 µg/g in the diet), although it inhibits their growth at higher doses (≥ 0.5 mg/g). In contrast, acute oral administration of caffeine in naive crickets may enhance their learning performance even at a very low (nanomolar) concentration.

GABA and l-theanine mixture decreases sleep latency and improves NREM sleep

CONTEXT

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter and it is well established that activation of GABA_A receptors favours sleep. l-Theanine, a naturally occurring amino acid first discovered in green tea, is a well-known anti-anxiety supplement with proven relaxation benefits.

OBJECTIVE

This study investigated the potential synergistic sleep enhancement effect of GABA/l-theanine mixture.

MATERIALS AND METHODS

Pentobarbital-induced sleep test was applied to find proper concentration for sleep-promoting effect in ICR mice. Electroencephalogram (EEG) analysis was performed to investigate total sleeping time and sleep quality in normal SD rats and caffeine-induced awareness model. Real-time polymerase chain reaction (RT-PCR) was applied to investigate whether the sleep-promoting mechanism of GABA/l-theanine mixture involved transcriptional processes.

RESULTS

GABA/l-theanine mixture (100/20 mg/kg) showed a decrease in sleep latency (20.7 and 14.9%) and an increase in sleep duration (87.3 and 26.8%) compared to GABA or theanine alone. GABA/l-theanine mixture led to a significant increase in rapid eye movement (REM) (99.6%) and non-REM (NREM) (20.6%) compared to controls. The use of GABA/l-theanine mixture rather than GABA or l-theanine alone restored to normal levels sleep time and quality in the arousal animal model. The administration of GABA/l-theanine led to increased expression of GABA and the glutamate GluN1 receptor subunit.

CONCLUSIONS

GABA/l-theanine mixture has a positive synergistic effect on sleep quality and duration as compared to the GABA or l-theanine alone. The increase in GABA receptor and GluN1 expression is attributed to the potential neuromodulatory properties of GABA/l-theanine combination, which seems to affect sleep behaviour.

Anxiety-like behavior and whole-body cortisol responses to components of energy drinks in zebrafish (Danio rerio)

The current study investigated the independent and combined effects of caffeine and taurine on anxiety-like behavior and neuroendocrine responses in adult zebrafish (Danio rerio). Caffeine (1,3,7-trimethylpurine-2,6-dione), the world’s most commonly used psychoactive drug, acts as an adenosine receptor blocker and a mild central nervous system stimulant. However, excessive use of caffeine is associated with heightened anxiety levels. Taurine (2-aminoethanesulfonic acid), a semi-essential amino acid synthesized within the human brain, has been hypothesized to play a role in regulating anxiolytic behavior. Caffeine and taurine are two common additives in energy drinks and are often found in high concentrations in these beverages. However, few studies have investigated the interaction of these two chemicals with regards to anxiety measures. A suitable vertebrate to examine anxiety-like behavior and physiological stress responses is the zebrafish, which has shown promise due to substantial physiological and genetic homology with humans. Anxiety-like behavior in zebrafish can be determined by analyzing habituation to novelty when fish are placed into a novel tank and scototaxis (light avoidance) behavior in the light-dark test. Stress-related neuroendocrine responses can be measured in zebrafish by analyzing whole-body cortisol levels. The goal of this study was to determine if exposure to caffeine, taurine, or a combination of the two compounds altered anxiety-like behavior and whole-body cortisol levels in zebrafish relative to control. Zebrafish were individually exposed to either caffeine (100 mg/L), taurine (400 mg/L), or both for 15 min. Zebrafish in the control group were handled in the same manner but were only exposed to system tank water. After treatment, fish were transferred to the novel tank test or the light-dark test. Behavior was tracked for the first 6 min in the novel tank and 15 min in the light-tark test. Fifteen min after introduction to the behavioral task, fish were euthanized for the analysis of whole-body cortisol levels. The results demonstrate that caffeine treatment decreased the amount of exploration in the top of the novel tank and increased scototaxis behavior in the light-dark test, which supports the established anxiogenic effect of acute exposure to caffeine. Taurine alone did not alter basal levels of anxiety-like behavioral responses nor ameliorated the anxiogenic effects of caffeine on behavior when the two compounds were administered concurrently. None of the drug treatments altered basal levels of whole-body cortisol. The current results of this study suggest that, at least at this dose and time of exposure, taurine does not mitigate the anxiety-producing effects of caffeine when administered in combination, such as with energy drink consumption.

Taurine and its analogs in neurological disorders: Focus on therapeutic potential and molecular mechanisms

Taurine is a sulfur-containing amino acid and known as semi-essential in mammals and is produced chiefly by the liver and kidney. It presents in different organs, including retina, brain, heart and placenta and demonstrates extensive physiological activities within the body. In the several disease models, it attenuates inflammation- and oxidative stress-mediated injuries. Taurine also modulates ER stress, Ca2+ homeostasis and neuronal activity at the molecular level as part of its broader roles. Different cellular processes such as energy metabolism, gene expression, osmosis and quality control of protein are regulated by taurine. In addition, taurine displays potential ameliorating effects against different neurological disorders such as neurodegenerative diseases, stroke, epilepsy and diabetic neuropathy and protects against injuries and toxicities of the nervous system. Several findings demonstrate its therapeutic role against neurodevelopmental disorders, including Angelman syndrome, Fragile X syndrome, sleep-wake disorders, neural tube defects and attention-deficit hyperactivity disorder. Considering current biopharmaceutical limitations, developing novel delivery approaches and new derivatives and precursors of taurine may be an attractive option for treating neurological disorders. Herein, we present an overview on the therapeutic potential of taurine against neurological disorders and highlight clinical studies and its molecular mechanistic roles. This article also addresses the neuropharmacological potential of taurine analogs.

Consumption of Energy Drinks and Their Effects on Sleep Quality among Students at the Copperbelt University School of Medicine in Zambia

Background. Good sleep quality is cardinal to good health, and research has shown that it plays a fundamental role in immunity, learning, metabolism, and other biological functions. Energy drink consumption is a popular practice among college students in the United States. There has been little research done on the consumption of energy drinks and its effects in Zambian universities. The main objective was to determine the effects of energy drinks on sleep quality among students at the Copperbelt University School of Medicine. A self-administered questionnaire was administered to 195 undergraduate students at the Copperbelt University School of Medicine in their second- and third-year of study. Energy drink consumption and sleep quality were assessed by univariate, bivariate, and multivariate analyses. 157 students were enrolled into the study. The prevalence of energy drink consumption was 27.4% among participants. Studying for an exam was the most common reason for drinking energy drinks (83.7% of energy drink users). The majority of participants were found to be have poor sleep quality (59.6%). There was a statistically significant association between energy drink consumption and poor sleep quality (p value < 0.01). The findings of our study show that energy drink consumption is not a common practice in the Zambian university setting as the prevalence was 27.4%. Furthermore, the prevalence of poor sleep quality among Zambian university students is high and is significantly associated with energy drink consumption, and there is a need to better understand the patterns of energy drink use as well as their effects on various aspects of health including sleep quality in the Zambian setting. Further research should assess the knowledge of nonmedical students on the effects of energy drinks.

Sleep and Metabolism: Eaat-ing Your Way to ZZZs

A new study in fruit flies identifies a molecule, Eaat2, that regulates both sleep and metabolic rate. Surprisingly, Eaat2 acts in a specific glial subtype to modulate both processes, suggesting a cellular link in the brain between sleep and metabolism.

The Taurine Transporter Eaat2 Functions in Ensheathing Glia to Modulate Sleep and Metabolic Rate

Sleep is critical for many aspects of brain function and is accompanied by brain-wide changes in the physiology of neurons and synapses [1, 2]. Growing evidence suggests that glial cells contribute to diverse aspects of sleep regulation, including neuronal and metabolic homeostasis [3-5], although the molecular basis for this remains poorly understood. The fruit fly, Drosophila melanogaster, displays all the behavioral and physiological characteristics of sleep [1, 2], and genetic screening in flies has identified both conserved and novel regulators of sleep and wakefulness [2, 6, 7]. With this approach, we identified Excitatory amino acid transporter 2 (Eaat2) and found that its loss from glia, but not neurons, increases sleep. We show that Eaat2 is expressed in ensheathing glia, where Eaat2 functions during adulthood to regulate sleep. Increased sleep in Eaat2-deficient flies is accompanied by reduction of metabolic rate during sleep bouts, an indicator of deeper sleep intensity. Eaat2 is a member of the conserved EAAT family of membrane transport proteins [8], raising the possibility that it affects sleep by controlling the movement of ions and neuroactive chemical messengers to and from ensheathing glia. In vitro, Eaat2 is a transporter of taurine [9], which promotes sleep when fed to flies [10]. We find that the acute effect of taurine on sleep is abolished in Eaat2 mutant flies. Together, these findings reveal a wake-promoting role for Eaat2 in ensheathing glia through a taurine-dependent mechanism.

Impact of Sampling and Cellular Separation on Amino Acid Determinations in Drosophila Hemolymph

The fruit fly is a frequently used model system with a high degree of human disease-related genetic homology. The quantitative chemical analysis of fruit fly tissues and hemolymph uniquely brings chemical signaling and compositional information to fly experimentation. The work here explores the impact of measured chemical content of hemolymph with three aspects of sample collection and preparation. Cellular content of hemolymph was quantitated and removed to determine hemolymph composition changes for seven primary amine analytes. Hemolymph sampling methods were adapted to determine differences in primary amine composition of hemolymph collected from the head, antenna, and abdomen. Also, three types of anesthesia were employed with hemolymph collection to quantitate effects on measured amino acid content. Cell content was found to be 45.4 ± 22.1 cells/nL of hemolymph collected from both adult and larvae flies. Cell-concentrated fractions of adult, but not larvae, hemolymph were found to have higher and more variable amine content. There were amino acid content differences found between all three areas indicating a robust method to characterize chemical markers from specific regions of a fly, and these appear related to physiological activity. Methods of anesthesia have an impact on hemolymph amino acid composition related to overall physiological impact to fly including higher amino acid content variability and oxygen deprivation effects. Together, these analyses identify potential complications with Drosophila hemolymph analysis and opportunities for future studies to relate hemolymph content with model physiological activity.

Dietary Zinc Acts as a Sleep Modulator

While zinc is known to be important for many biological processes in animals at a molecular and physiological level, new evidence indicates that it may also be involved in the regulation of sleep. Recent research has concluded that zinc serum concentration varies with the amount of sleep, while orally administered zinc increases the amount and the quality of sleep in mice and humans. In this review, we provide an exhaustive study of the literature connecting zinc and sleep, and try to evaluate which molecular mechanism is likely to be involved in this phenomenon. A better understanding should provide critical information not only about the way zinc is related to sleep but also about how sleep itself works and what its real function is.

Nutrition Influences Caffeine-Mediated Sleep Loss in Drosophila

Study objectives

Plant-derived caffeine is regarded as a defensive compound produced to prevent herbivory. Caffeine is generally repellent to insects and often used to study the neurological basis for aversive responses in the model insect, Drosophila melanogaster. Caffeine is also studied for its stimulatory properties where sleep or drowsiness is suppressed across a range of species. Since limiting access to food also inhibits fly sleep-an effect known as starvation-induced sleep suppression-we tested whether aversion to caffeinated food results in reduced nutrient intake and assessed how this might influence fly studies on the stimulatory effects of caffeine.

Methods

We measured sleep and total consumption during the first 24 hours of exposure to caffeinated diets containing a range of sucrose concentrations to determine the relative influence of caffeine and nutrient ingestion on sleep. Experiments were replicated using three fly strains.

Results

Caffeine reduced total consumption and nighttime sleep, but only at intermediate sucrose concentrations. Although sleep can be modeled by an exponential dose response to nutrient intake, caffeine-mediated sleep loss cannot be explained by absolute caffeine or sucrose ingestion alone. Instead, reduced sleep strongly correlates with changes in total consumption due to caffeine. Other bitter compounds phenocopy the effect of caffeine on sleep and food intake.

Conclusions

Our results suggest that a major effect of dietary caffeine is on fly feeding behavior. Changes in feeding behavior may drive caffeine-mediated sleep loss. Future studies using psychoactive compounds should consider the potential impact of nutrition when investigating effects on sleep.

The influence of commercial energy shots on response time and power output in recreational cyclists

Background

Caffeine based energy shot products accounted for $1.3 billion in sales in 2011. Caffeine has been shown to confer numerous benefits during exercise and is oftentimes combined with ingredients such as carbohydrates and taurine in the hope of further performance improvement. The purpose of this project was to compare auditory response time, power output, and physiological responses between the ingestion of a CHO, PRO, caffeine supplement (CPC), a caffeine-taurine-niacin based supplement (CTN), and a placebo (PL) in commercially formulated products that make claims as to improving performance.

Methods

Fourteen subjects cycled an interval exercise of 70% VO₂max for 13 minutes and 90% of VO₂max for two minutes for a total of 120 minutes which was then followed by a six-minute power output (PO) task. Subjects ingested a total of 45 g CHO, 7.5 g PRO, and 375 mg caffeine for CPC while 512 mg caffeine and 1200 mg taurine were ingested for CTN throughout the exercise. The treatments were administered in a double blind, randomly assigned protocol. Response time was assessed by auditory response. Significance was set at p < 0.05.

Results

Average PO was significantly greater for CPC: 309 ± 60 W than CTN: 290 ± 57 W and PL: 282 ± 63 W. Response time was significantly faster for the CPC: 0.219 ± .049 s than CTN: 0.232 ± .060 s and PL: 0.228 ± .047 s. HR was significantly greater for CTN: 143 ± 16 bpm than CPC: 139 ± 16 bpm. RPE was significantly lower for CPC: 13.0 ± 1.7 than CTN: 13.5 ± 1.2 and PL: 13.8 ± 1.9. Blood glucose was greater for CPC: 5.5 ± 0.8 mM/L than CTN: 4.9 ± 0.7 mM/L and PL: 4.6 ± 1.1 mM/L. No significant differences were observed for RER.

Conclusions

The co-ingestion of CPC improved both cycling power output and auditory response time following 2 hours of moderate and high intensity interval cycling compared to CTN and PL. It is possible that the CPC treatment conferred not only a positive peripheral effect, but also a central effect. Even with a large caffeine dose, the combination of caffeine, taurine, niacin led to an inhibitory pattern which did not improve power output or response time performances over a PL.

The buzz on caffeine in invertebrates: effects on behavior and molecular mechanisms

A number of recent studies from as diverse fields as plant-pollinator interactions, analyses of caffeine as an environmental pollutant, and the ability of caffeine to provide protection against neurodegenerative diseases have generated interest in understanding the actions of caffeine in invertebrates. This review summarizes what is currently known about the effects of caffeine on behavior and its molecular mechanisms in invertebrates. Caffeine appears to have similar effects on locomotion and sleep in both invertebrates and mammals. Furthermore, as in mammals, caffeine appears to have complex effects on learning and memory. However, the underlying mechanisms for these effects may differ between invertebrates and vertebrates. While caffeine's ability to cause release of intracellular calcium stores via ryanodine receptors and its actions as a phosphodiesterase inhibitor have been clearly established in invertebrates, its ability to interact with invertebrate adenosine receptors remains an important open question. Initial studies in insects and mollusks suggest an interaction between caffeine and the dopamine signaling pathway; more work needs to be done to understand the mechanisms by which caffeine influences signaling via biogenic amines. As of yet, little is known about whether other actions of caffeine in vertebrates, such as its effects on GABAA and glycine receptors, are conserved. Furthermore, the pharmacokinetics of caffeine remains to be elucidated. Overall behavioral responses to caffeine appear to be conserved amongst organisms; however, we are just beginning to understand the mechanisms underlying its effects across animal phyla.