Updated: Sep 28, 2021
Urolithin B increases muscle protein synthesis and muscle protein breakdown. There has also been evidence of its ability to protect muscle from wasting.
It has also shown anti-aromatase and anti-oestrogen effects.
Table of Contents:
What Is Urolithin B?
It is a urolithin, a type of phenolic compound produced in the human gut after absorption of ellagitannin-containing foods such as pomegranate, strawberries, red raspberries, walnuts or oak-aged red wine.
Urolithin B is produced in the human gut after absorption of ellagitannin-containing foods such as the following.
Oak-aged red wine
It is present in the urine in the form of urolithin B glucuronide, which is a glucuronide metabolite.
There are multiple benefits of urolithin B, as shown below.
Urolithin b increases muscle protein synthesis via mediation of the AR pathway.
It also reduces muscle protein breakdown via inhibition of the ubiquitin-proteasome pathway, which is a key factor in protein degradation and muscle breakdown.
Due to these effects, urolithin B has also been hypothesised to have muscle protective effects, which has later proven to be true in animal studies.
Interestingly, urolithin B has anti-proliferative effects on breast cancer, found to be via its anti-aromatase activity and its effects on the oestrogen receptor (ER).
Urolithin B Stimulates Muscle Protein Synthesis
For the in-vivo experiments, mice were implanted with mini-osmotic pumps delivering 10 μg/day continuously of urolithin B for 28 days. (1)
Muscle atrophy was studied in mice with a sciatic nerve denervation receiving urolithin B in the same way.
Myotubes were incubated with different urolithin concentrations for 24 hours and evaluated the impact of each treatment on their size.
They was never affected in the presence of Urolithin A, whereas the low doses of Urolithin B increased the diameter of myotubes.
As a result of this research, it was shown that urolithin B promotes the development and differentiation of muscle cells by boosting protein synthesis and inhibiting the ubiquitin–proteasome pathway.
The androgen receptor is implicated in this scenario, click here to read about the importance of the AR.
Studies indicate that the androgen receptor and the mTOR pathway are in communication with one another, perhaps via AMPK.
In vivo studies have shown that urolithin B causes muscle growth in mice and that it decreases muscle atrophy when the sciatic nerve is cut in the same animals. (1)
Urolithin B Decreases Muscle Protein Breakdown
Studies suggest that the ubiquitin-proteasome pathway is a key factor in muscle protein breakdown, it is one of three key pathways in muscle breakdown. (2)
The other two major pathways are:
Muscle protein breakdown is a catabolic state in which muscle cells are broken down into their individual components, providing a source of energy.
This means that any up regulation of the protein breakdown pathways will results in the reduction in muscle mass.
Research suggest that a lower activity of the ubiquitin-proteasome system in seen in myotubes exposed to urolithin B. (3)
These results show that the faster growth of myotubes exposed to Urolithin B is due to higher protein synthesis as well as reduced activity of the ubiquitin-proteasome system (a major protein breakdown pathway), meaning reduced protein breakdown.
As protein turnover is constantly in a state of balance between protein synthesis and protein breakdown, a higher synthesis rate as well as a lower breakdown rate will increase the net protein balance of the muscles, increasing growth.
Urolithin B May Be Mediated by the Androgen Receptor (AR)
Previous studies show a link between the androgen receptor (AR) and the mTORC1 pathway which provided evidence for the anti-aromatase properties of urolithin B.
It was also hypothesised that urolithin B induces hypertrophy in myogenic cells via the activation of the AR. (4)
Therefore, in one study the AR was inactivated genetically by using a set of specific small interfering RNA (siRNAs) and also inactivated pharmacologically by using a chemical called bicalutamide. (1)
Interestingly, siRNAs completely blocked the hypertrophy induced by testosterone (and other androgens), but also urolithin B.
This provides evidence for the effects of urolithin B being mediated by the androgen receptor.
Muscle Protective Effects of Urolithin B
As urolithin B induces muscle hypertrophy via increased protein synthesis and decreased protein breakdown, it was hypothesised that it could also have a muscular protective effect during states of atrophy and catabolism.
In this study, female mice were denervated and were simultaneously implanted with a mini-osmotic pump delivering 10 μg/day of urolithin B.
The results after 7 days were compared between the groups. It was shown that urolithin B reduced muscle atrophy during denervation.
Urolithin B prevented a decrease in the cross-sectional area of the muscle fibres of denervated TIB muscles.
This data indicates that urolithin B reduces denervation-induced muscle atrophy, indicating a muscle protective effect.
However, this has only been studied in animals and needs to be replicated in humans to provide any real-world meaning.
Urolithin B has also been shown to be an inhibitor of the enzyme aromatase; therefore, preventing testosterone from being converted into oestrogen. (5)
Research has found a decreased level of aromatase in the urine of animals that had received urolithin B treatment.
Other types of urolithin also have a similar effect on aromatase.
Interestingly, this may also have the additional benefit of preventing breast cancer via interacting with the oestrogen receptor (ER). (5)
A typical dosage of urolithin B is around 150mg, in its extracted form, two times per day. Though, there has not been much research on the safety of long-term usage.
However, we don't recommend taking urolithin b due its unknown long-term safety.
Written by Billy White
Billy White is a qualified Kinesiologist and Personal Trainer. He is an aspiring bodybuilder, fitness enthusiast, and health and fitness researcher.
He has multiple years of experience within the fitness, bodybuilding and health space. He is committed to providing the highest-quality information.
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This evidence-based analysis of urolithin b features 5 references, listed below.
1. Rodriguez J, Pierre N, Naslain D, Bontemps F, Ferreira D, Priem F, Deldicque L, Francaux M. Urolithin B, a newly identified regulator of skeletal muscle mass. J Cachexia Sarcopenia Muscle. (2017, Aug) ✔
2. Stewart H. Lecker, Vered Solomon, William E. Mitch, Alfred L. Goldberg. Muscle Protein Breakdown and the Critical Role of the Ubiquitin-Proteasome Pathway in Normal and Disease States. The Journal of Nutrition. (1999, Jan)
3. Urolithin B, a newly identified regulator of skeletal muscle mass: Urolithin B as regulator of skeletal muscle mass. Scientific Figure on ResearchGate
4. Rodriguez, Julie & Pierre, Nicolas & Naslain, Damien & Bontemps, Françoise & Ferreira, Daneel & Priem, Fabian & Deldicque, Louise & Francaux, Marc. Urolithin B, a newly identified regulator of skeletal muscle mass: Urolithin B as regulator of skeletal muscle mass. Journal of Cachexia, Sarcopenia and Muscle. (2017)
5. Adams LS, Zhang Y, Seeram NP, Heber D, Chen S. Pomegranate ellagitannin-derived compounds exhibit antiproliferative and antiaromatase activity in breast cancer cells in vitro. Cancer Prev Res (Phila). (2010, Jan) ✔
✔ Citations with a tick indicate the information is from a trusted source.
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