Day 10: Aronia effects on rat skeletal muscle
ARTICLE TITLE: mTORC1 as a Regulator of Mitochondrial Functions and a Therapeutic Target in Cancer
Karen Griselda de la Cruz López et al. Front. Oncol., 13 December 2019 (click on image for link to article)
mTORC1 is the mammalian target of rapamycin complex 1 and is a master regulator of multiple processes related to growth, stress response, and metabolism of cells, switching on and off important genes in response to stimuli
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Dietary Aronia melanocarpa extract enhances mTORC1 signaling, but has no effect on protein synthesis and protein breakdown-related signaling, in response to resistance exercise in rat skeletal muscle
Yuhei Makanae, Satoru Ato, Kohei Kido & Satoshi Fujita. Journal of the International Society of Sports Nutrition volume 16, Article number: 60 (2019)
Researchers focused on ursolic acid, one component of aronia berries. They supplemented rat diets with enough aronia berry extra to reach the goal of 115 mg ursolic acid per kg of body weight every day for 7 days. CONTROL mice ate the same food (chow), but did not get any aronia extract in their diets.
At the end of supplementation for one week, rats did one session of isometric resistance exercise on the right leg and the other leg was a control (did nothing).
THE EXERCISE: “The right gastrocnemius muscle was isometrically exercised (5 sets of ten 3-s contractions, with a 7-s interval between contractions and 3-min rest intervals between sets), while the left gastrocnemius muscle served as a control.”
Researchers measured many aspects of skeletal muscle molecular signals. Their take-home is quoted from their conclusion: “AME [aronia extract], which is rich in ursolic acid, enhanced mTORC1 activation in response to resistance exercise. On the other hand, AME did not affect MPS [muscle protein synthesis] and accelerate muscle protein degradation or otherwise have a negative effect on protein metabolism. As mTORC1 activation after resistance exercise is necessary for muscle hypertrophy, our present data showed the potential of AME for enhancing muscle hypertrophy induced by chronic resistance training. However, to establish practical nutritional strategies involving AME, further studies are needed to clarify how AME enhances mTORC1 activity and the effect of the combination of AME and chronic resistance exercise on muscle hypertrophy in humans.”
This article has a lot to unpack and look to Day 11, tomorrow for a detailed discussion of this article.
Some considerations:
1. aronia extract did impact pathways and processes that are responsible for skeletal muscle protein synthesis and control of degradation, but not in a way that suggests that this regime affected the rat skeletal muscle in a way that translates to increases in sport performance
2. the exercise that was considered resistance exercise was one bout of isometric contracts after a whole week of supplementation - testing true effects of response to resistance training might require more real-world-applicable training programs, even for rats
3. this study points to many directions for future research and represents a great in-depth look at skeletal muscle responses to aronia
