Team Taurine

By Nancy Patel, Morgan Askew, & Lauren Jacobs

Introduction

Taurine (2-aminoethanesulfonic acid) is a naturally occurring amino acid involved in energy production in animal cells. It is found in high levels in chicken embryos, especially in the brain (Mierzejewska et al., 2024, p. 02). Although taurine occurs naturally, intake from energy drinks is rising among young adults and raising concerns. A 2022 rabbit study showed that taurine exposure caused ventricular arrhythmias by decreasing cardiac refractory periods needed for a steady heart rate (Ellermann et al., 2022, p. 1290). This experiment examined how different taurine levels affect developing chicken embryos through in ovo injection. Taurine concentrations are naturally highest in the brain, heart, and skeletal muscle (Costa & Peana, 2023, p. 02).

This study focuses on how the heart and brain (two systems with high taurine levels) respond to low versus high taurine exposure. Taurine has been shown to increase cardiac stroke volume and potentially lower blood pressure, affecting heart function (Bitchler et al., 2006, p. 427). We hypothesized that higher taurine concentrations would increase and destabilize heart rate, reduce brain size, and lead to more cardiovascular malformations. Heart rate and brain size were the primary measurements used to test this. The goal of this project was to better understand how taurine may influence development in human fetuses.

Methods

Chicken eggs were injected (n=10 per week) on day 3 of incubation with 0.05 mL PBS (control) or 0.05 mL PBS-taurine solutions (1 mg/L or 5 mg/L). The eggs were cleaned with ethanol, injected into the yolk sac via sterile insulin syringes, and injection sites were sealed with tape, being assigned an identification label to keep track of which treatment group they belonged to.

Experimental Design:

Eggs were randomly assigned to three groups:

Control (0 ppm)
Low-dose 91 ppm)
High-dose (5 ppm)

Eggs were then incubated for 7 days post-injection.

Embryo Assessment:

On day 10, albumin was removed from the injection site (maximum if 1ml) , and embryos were extracted, making note of any physiological changes to the heart rate and brain size based on their respected treatment group. Dissection scopes were utilized for further implication of change which provided a more deepened visualization. Mortality and fertilization were also recorded as significant data.

Data Collection & Analysis:

Standardized photography was conducted for morphometric measurements with the average brain size and heart rate being calculated amongst the three treamtents. ANOVA testing was used to compare statistical analysis between treatments amd ImageJ was used to determine the brain area (cm^2) from the visuals taken.

Results

Figure 1. Heart rate (bpm) of chicken embryos injected on day 3 across taurine concentrations. Control (0 ppm), low (1 ppm), and high (5 ppm) groups are shown. Means ± SD appear to the left of the data points.

Figure 2. Brain area (cm²) of chicken embryos across taurine concentrations. Control (0 ppm), low (1 ppm), and high (5 ppm) groups are shown. Means ± SD are displayed to the left of the data points.

A total of 69 developing chicken embryos were injected with varying doses of taurine to determine dose-dependent impacts on heart rate (beats per minute) and brain size (cm^2).

The control group (0 ppm) was noted to have the most statistical variation in heart rate range with an average heart rate being calculated at 48.8 BPM.
The low-dose treatment group (1 ppm) proved to have the smallest range, with an average heart rate calculated at 33.64 BPM.
The high-dose treatment group (5 ppm) had a statistical average heart rate of 34.4 BPM (Figure 1).

The heart rate data showed no significant difference between the three treatment groups (F = 2.6, df = 2, P = 0.09).

The brain area (in cm^2) was averaged at 1.063 for the control group, 1.218 for the low-dose treatment, and 1.303 for the high-dose treatment. (Figure 2). The brain size data suggest that there is a strong statistical difference between the three treatment groups (F = 42, df = 2, P < 0.01).

Discussion & Conclusion

This study tested whether higher taurine exposure during early chicken embryo development affects heart rate and brain growth, two systems naturally high in taurine. This is important as taurine intake from energy drinks has increased among young adults. Heart rate did not differ significantly across treatment groups (F = 2.6, p = 0.09), suggesting the doses used did not alter cardiac rhythm. However, brain size differed significantly (F = 42, p < 0.01), with the high-dose group showing the largest brain area. These results partly contradict our hypothesis, which predicted higher heart rates and smaller brains with increased taurine concentrations. Instead, they suggest early cardiac function may remain stable while brain development is more sensitive to taurine. More research is needed to understand how elevated taurine intake, such as from energy drinks, may impact human fetal development.
In present to the statistical analysis conducted, taurine exposure proved to yield a dose dependent increase to brain area, with both low and high dose treatment groups displaying significantly larger brain measurements in comparison to the statistical control group. This device aligns similarly to prior studies that identify taurine as an essential developmental neural modulator that has the ability to influence neural proliferation, osmoregulation, and antioxidant defense. (Mierzejeweska et al. (2024)) It was reported that within the parameters of the study, taurine supplementation altered embryonic growth parameters, and oxidative stress markers, proving a meaningful effect on the developmental trajectories within chick embryos. It is a supported ideal that taurine acts on early cellular processes in which contribute to the increased brain area observed within the statistical analysis conducted. In similar conjunction, a study on zebra fish noted that taurine exposure and modulated pathways and improved neural function, providing that taurine supports neural development (Fontana et al 2020))

The main strengths of this study included the easily repeatable methodology and the implementation of multiple types of controls (negative and negative-negative) to reduce confounding variables in the data. The main limitation of this study was the limited sample size of 69 total eggs. Along with the small sample size, 14 of the eggs were rotten at the time of embryo extraction. This decreased the measurable sample size down to 55 eggs. To ensure the credibility of the results of this study, further experimentation with larger sample sizes should be implemented. While we found that increased taurine concentrations resulted in increased brain sizes, this experiment did not answer whether this benefits or harms the embryos. Further research to confirm the results of this study and to expand on the physiological impacts of increased brain size further along in development (in-ovo and ex-ovo) due to taurine exposure should be studied.

References

Bichler, A., Swenson, A., & Harris, M. A. (2006). A combination of caffeine and taurine has no effect on short term memory but induces changes in heart rate and mean arterial blood pressure. Amino Acids, 31(4), 471–476. https://doi.org/10.1007/s00726-005-0302-x

Cadoni, C., & Peana, A. T. (2023). Energy drinks at adolescence: Awareness or unawareness? Frontiers in Behavioral Neuroscience, https://doi.org/10.3389/fnbeh.2023.1080963

Ellermann, C., Hakenes, T., Wolfes, J., Wegner, F. K., Willy, K., Leitz, P., Rath, B., Eckardt, L., & Frommeyer, G. (2022). Cardiovascular risk of energy drinks: Caffeine and taurine facilitate ventricular arrhythmias in a sensitive whole-heart model. Journal of cardiovascular electrophysiology, 33(6), 1290–1297. https://doi.org/10.1111/jce.15458

Łukasiewicz Mierzejewska, M., Kotuszewska, M., Puppel, K., & Madras Majewska, B. (2024). Effects of In Ovo Taurine Injection on Embryo Development, Antioxidant Status, and Bioactive Peptide Content in Chicken Embryos (Gallus gallus domesticus). International Journal of Molecular Sciences, 25(21), 11783. https://doi.org/10.3390/ijms252111783

Fontana, B. D., Stefanello, F. V., Mezzomo, N. J., Müller, T. E., Quadros, V. A., Parker, M. O., Rico, E. P., & Rosemberg, D. B. (2018). Taurine modulates acute ethanol-induced social behavioral deficits and fear responses in adult zebrafish. Journal of psychiatric research, 104, 176–182. https://doi.org/10.1016/j.jpsychires.2018.08.008

Authors

Morgan Askew

mea77037@uga.edu

Lauren Jacobs

loj57357@uga.edu

Nancy Patel

nsp73013@uga.edu

Our whole group designed the experiment. M.A., N.P., and L.J. contributed equally to the data collection efforts. N.P. organized the data, M.A. and L.J. conducted the data analysis and M.A. prepared the figures. Each group member wrote their own sections for the assignment, which were then jointly edited for the final submission.

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