Energy drinks have turn out to be extremely popular amongst young people and athletes due to their purported performance-enhancing capabilities. Nonetheless, despite marketing a big selection of such drinks, often as weight-reduction plan supplements, there may be little data on how these affect the differentiation of muscle fibers. A brand new study published within the journal Scientific Reports explores murine myoblast response to eight different energy drinks when it comes to enhanced or reduced muscle repair processes.

Study: Effects of energy drinks on myogenic differentiation of murine C2C12 myoblasts. Image Credit: HandmadePictures / Shutterstock

Introduction

Since its first entry into the US market in 1997, aggressive marketing strategies targeting athletes and youth have significantly increased the consumption of energy drinks. Because of this, the worldwide energy drink market is anticipated to grow exponentially from $53.01 billion in 2018 to $86.01 billion in 2026.

These beverages are consumed mainly by young men between 18 and 34 years. Available data shows that one in three adolescents repeatedly ingest these drinks, mainly because of intensive marketing campaigns targeting young people and athletes.

These beverages are unregulated by the US Food and Drug Administration (FDA). Nonetheless, the ingredients in these drinks, including caffeine, sugar, multiple stimulants like taurine, L-carnitine, yerba mate, and ginseng, in addition to some vitamins, could increase the danger of multiple diseases affecting the cardiovascular, renal, digestive, and nervous systems, along with dental damage.

Caffeine, which acts via adenosine receptors, stimulates the central and peripheral nervous system, and in excessive amounts, it will probably trigger sleep disruption, anxiety, jitteriness, and even digestive disorders. Taurine is believed to advertise cognitive functions and regulate voluntary muscle function, and maybe reduce oxidative damage in muscle cells following strenuous exercise.

Glucuronolactone is touted to extend mental performance, but with little evidence to back it. Sugar can also be present in large amounts.

Nonetheless, taurine and glucuronolactone may affect the nervous system adversely. Excessive sugar is understood to cause irregular heartbeat and blood pressure and promote obesity.

“It is a growing public health concern because energy drink consumption has been related to fatal outcomes related to the cardiovascular system equivalent to myocardial infarctions, cardiomyopathies, and sudden cardiac death.”

Aside from these effects, nothing is understood about how energy drinks affect muscle recovery after injury, which may be very common during eccentric muscle contraction.

Myogenesis, also often known as myogenic differentiation, is the term used to explain the arrest of cell division amongst myoblasts, which then fuse to turn out to be syncytial myotubes with enhanced muscle-specific gene transcription.

This happens during each embryonic and adult life. Within the latter stage, it occurs as satellite cells turn out to be energetic when skeletal muscle strength is to be maintained or damage is to be repaired. These are Pax7-expressing stem cells.

Myogenesis involves an intricate network of regulatory aspects, resulting in the activation, migration, division, and differentiation of satellite cells into latest myotubes, thus restoring the damaged muscle fibers to a healthy state.

The present study focuses on the impact of energy drinks on myogenesis in teenagers and athletes. The researchers tested two products each from 4 major energy drink brands, namely, RedBull, Monster, Rockstar, and Celsius.

What did the study show?

They exposed differentiating myoblasts in vitro to every of the eight chosen products after a four-day initial period without such exposure. The researchers used an array of dilutions to detect cytotoxicity in addition to other effects on myogenesis.

Typically, the beverages weren’t cytotoxic at 1:5 and 1:50 dilutions in growth medium, but each Celsius brands (Live Fit and Heat) produced cell death at the previous level. With Live Fit, 14% of the cells died, rising to double the proportion with Heat.

With dilutions in differentiation medium, the story took a unique turn. Many of the drinks didn’t produce cell death at 1:50 dilutions, but at 1:5, there was a profound effect, with 20-30% of the cells displaying cytotoxicity. Only RedBull Zero didn’t show this dramatic shift with dilution.

Further tests of the effect of every drink on myogenic differentiation were carried out at these two dilutions. In comparison with controls, all of the drinks produced a dose-dependent inhibition of myogenesis.

With the 2 Celsius drinks, this was almost total, demonstrated by the virtual absence of MHC+ nuclei (a marker of myocyte differentiation) at !:5 dilution. At 1:50, nevertheless, their effect was much weaker.

Cell viability was thus affected by energy drinks in vitro, but different with the sort of medium. The increased cytotoxicity with Celsius drinks might be because of the doubled caffeine concentrations in comparison with the opposite beverages since caffeine is strongly cytotoxic.

Actually, caffeine has earlier been shown to inhibit myogenesis and to disrupt differentiated myotube function.

Six of the drinks at this dilution also suppressed myotube formation, as shown by the sharply decreased fusion index. The 2 exceptions were the RedBull drinks, perhaps due to their two-fold higher vitamin B6 content. This vitamin is significant to myogenesis.

Many of the drinks didn’t induce myotube atrophy at 1:5 dilution, but Celsius Live Fit reduced the myotube diameter significantly.

As expected, the expression of the regulatory protein MyoG, and differentiation marker MCK, involved on this process, were also reduced for many of the drinks. Rockstar Sugar-Free had a lower inhibitory effect in comparison with Rockstar at each dilutions.

What are the implications?

More research data indicates the association of energy drinks with sudden serious cardiovascular events, including heart attacks, cardiac arrhythmias, and sudden death. As well as, neurological symptoms, including hallucinations, panic attacks, arrhythmias, and seizures, amongst many others, have ceaselessly been reported.

Yet much stays to be known about energy drinks and their long-term consequences on health. This in vitro study paves the best way for further comparative studies.  

“These results indicate that each one energy drinks have an inhibitory effect on C2C12 myogenic differentiation with some variation between the beverages.”

Further research is required to discover the source of those variations because the eight drinks used here had different formulas.

This data could help support the necessity for energy drink regulation by the FDA, given the aggressive marketing of those beverages to young people and athletes.