In a study published recently in the Journal of the International Society of Sports Nutrition (JISSN), researchers from several institutions in Japan investigated whether aronia berry supplementation could stimulate skeletal muscle formation in rats following the stimulus of resistance exercise. The researchers’ hypothesis rested on the reported functions of one of the constituents of aronia—ursolic acid.
Expected effects of ursolic acid
Ursolic acid is a constituent of many fruits and vegetables such as apples and is particularly prevalent in aronia berries (Aronia melanocarpa, or black chokecherry), a member of the Rosacea family of shrubs native to eastern North America. Ursolic acid has been shown to stimulate muscle growth in mice, and was identified in a 2011 paper in the journal Cell Metabolism as a potential defense against muscle atrophy in humans.
The researchers in the present study used Sprague Dawley rats divided into two groups, one receiving a standard feed mix with the other receiving a chow supplemented with aronia berry extract at a dose of 3 g/kg of AME and 115 mg/kg of ursolic acid. The rats were kept on the diet for seven days.
The rats’ right gastrocnemius muscles (the animals’ calf muscle, essentially) were exercised isometrically (5 sets of ten 3-s contractions, with a 7-s interval between contractions and 3-min rest intervals between sets), with the corresponding muscle serving as an internal control. The researchers measured mTORC1 activity, which is a key signally pathway in the response of skeletal muscle to an exercise stimulus. An acute bout of resistance exercise increases mTORC1 activity and rates of protein synthesis/breakdown, causing skeletal muscle hypertrophy.
After a seven days of acclimatization, seven days of selective feeding and a bout of resistance exercise, the rats were sacrificed and chemical assays and muscle dissections performed. The researchers found the expected uptick in mTORC1 activity. But there was no effect on MPS or muscle protein breakdown.
Data on inflammation, less on MPS effects
There has been significant interest in aronia berry supplementation with regard to its effects on sports performance. But most of those studies have centered on its role in regulating oxidative stress such as this one from 2005, and another, more recent study published in JISSN in 2014. More data is needed to flesh out the story of aronia’s potential effects on muscle growth, the authors of the present study said.
“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,” they concluded.
Source: Journal of the International Society of Sports Nutrition
16, Article number: 60 (2019)
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
Authors: Makanae Y, Ato S, Kito K, Fujita S
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