Exercise is necessary for muscle growth, but what genetic factors contribute to building new muscle mass? Scientists have found that an ancient virus embedded in our genomes may be involved in aiding muscle repair.
Image from Rex Fit (https://www.rex.fit/post/the-science-behind-optimizing-gym-workouts)
With the winter months upon us, it’s bulking season for many avid gym-goers: time to pack on the muscle. But this time around, there’s no need to go looking for a new protein powder or fad diet supplement; instead, you can build your gains with just your genes. Well, technically your genes.
Almost 8% of the human genome is composed of elements that aren’t actually human in origin; instead, they’re remnants of past viral infections in our human ancestors. Unlike other viruses like the seasonal flu that only infect the somatic, or body, cells, these ancient viruses were able to insert themselves into the human germline – the DNA that is passed down through human generations. But these viral elements aren’t merely sitting inert in our genes. Because the infections occurred so long ago in the timeframe of human existence, humans have evolved alongside these viruses and can now use the viral genes for our own good. It’s important to note that these viruses have undergone multiple mutational and translocation events, meaning none of them are intact enough to produce bonafide viruses. At most, some of the viruses can produce one functional protein. The most well known example is the protein Syncytin-1 which is encoded by the ERVW-1 gene. This protein was originally the envelope protein of an ancient virus, but it now serves to help form the placenta during pregnancy. More recently, this endogenous retrovirus protein has been shown to build muscle by helping muscle cells to fuse together.
More tenuously, endogenous retrovirus expression has also been associated with autoimmune diseases like multiple sclerosis, amyotrophic lateral sclerosis (ALS), and rheumatoid arthritis; as well as psychiatric conditions like schizophrenia and bipolar disorder. The expression of endogenous retroviruses hasn’t been shown to cause these conditions, but the expression of these retroviruses and presence of these diseases both share chronic levels of inflammation.
In a similar vein, acute exercise induces an inflammatory response in the body. This inflammatory response is ultimately responsible for muscle growth and repair by inducing muscle cells to expand. As past research has linked endogenous retrovirus expression to inflammatory conditions, the current study wanted to ask: what is the relationship between a single bout of strength training exercise, inflammation, and endogenous retrovirus expression in humans?
The study consisted of two cohorts: individuals who regularly perform strength training, and individuals who do not. The levels of inflammatory markers and ERVW expression in these populations were measured before and after a single strength training session. This training session included a warm up on the treadmill followed by three sets of eight to ten reps of strength exercises that focused on the arm and leg muscle groups. The results showed that both groups exhibited a baseline level of ERVW expression but only the trained individuals had a significant increase in ERVW expression after exercise. The control group, on the other hand, saw an overall decrease in ERVW expression following exercise. Additionally, both groups had an increase in the expression of TNFa, a pro-inflammatory cytokine, and IL-10, an anti-inflammatory cytokine, following exercise, confirming the inflammatory nature of strength training.
From these results, the authors hypothesize that individuals that regularly train their muscles have also trained their bodies to increase the expression of ERVW. This increase in ERVW expression may potentially enhance muscle repair and muscle growth. However, the authors note that the interplay of ERVW expression, inflammation, and muscle growth is complicated and requires further studies to understand exactly how they all fit together. Not to mention that there are multiple other endogenous retroviruses that may be expressed under exercise conditions and contribute to inflammation, and muscle repair and growth.
The main takeaway from this paper is that consistent strength training is necessary to condition the body for muscle growth. While the endogenous retroviruses present in our genes may play a role in enhancing muscle repair and growth, they aren’t the main drivers of muscle growth. Whether you’re an avid gym-goer or just starting out, you’ll need to rely on more than just your genetics to build your biceps.
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Edited by JP Flores and Jayati Sharma
GeneBites 
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