Effects of exercise and dietary epigallocatechin gallate and β-alanine on skeletal muscle in aged mice

Impact of dietary supplementation with β-alanine on the rumen microbial crude protein supply, nutrient digestibility and nitrogen retention in beef steers elucidated through sequencing the rumen bacterial community

This study investigated the effects of β-alanine (β-Ala) on rumen fermentation, nutrient digestibility, nitrogen (N) metabolism, plasma biochemical parameters, and rumen bacterial communities in beef steers. Six steers with initial liveweight of 252.8 ± 5.2 kg and 3 treatments of supplementing with 0, 30, or 60 g β-Ala per day to basal diet were allocated in a replicated 3 × 3 Latin square design. Each experimental period was 20 d, of which the first 15 d were for adaptation and the subsequent 5 d were for sampling. The results showed that β-Ala linearly increased the ruminal concentration of microbial crude protein (MCP) (P = 0.005), but it did not affect the ruminal concentrations of ammonia N and total volatile fatty acids (P > 0.10). β-Ala also linearly increased the dry matter (DM) (P = 0.009), organic matter (OM) (P = 0.017) and crude protein (CP) (P = 0.043) digestibility, tended to decrease the acid detergent fiber digestibility (P = 0.077), but it did not affect the neutral detergent fiber digestibility (P = 0.641). β-Ala quadratically increased the relative abundance of ruminal Bacteroidota (P = 0.021) at the phylum level, and increased Prevotella (P = 0.028) and Prevotellaceae_UCG-003 (P = 0.014), and decreased the relative abundance of NK4A214_group (P = 0.009) at the genus level. Feeding steers with β-Ala linearly increased the urinary N (P = 0.006), urea excretions (P = 0.002) and the N retention (P = 0.004), but it did not affect the N utilization efficiency (P = 0.120). β-Ala quadratically increased the plasma concentration of the total antioxidant capacity (P = 0.011) and linearly increased the plasma concentration of insulin-like growth factor-1 (P < 0.001). In summary, dietary supplementation with β-Ala improved the rumen MCP supply and increased the digestibility of DM, OM, CP and the N retention. Further research is necessary to verify the ruminal degradability of β-Ala and to investigate the mechanism of the impact of absorbed β-Ala on the anti-oxidative ability in steers.

Mechanisms Underlying the Effects of the Green Tea Polyphenol EGCG in Sarcopenia Prevention and Management

Sarcopenia is prevalent among the older population and severely affects human health. Tea catechins may benefit for skeletal muscle performance and protect against secondary sarcopenia. However, the mechanisms underlying their antisarcopenic effect are still not fully understood. Despite initial successes in animal and early clinical trials regarding the safety and efficacy of (-)-epigallocatechin-3-gallate (EGCG), a major catechin of green tea, many challenges, problems, and unanswered questions remain. In this comprehensive review, we discuss the potential role and underlying mechanisms of EGCG in sarcopenia prevention and management. We thoroughly review the general biological activities and general effects of EGCG on skeletal muscle performance, EGCG's antisarcopenic mechanisms, and recent clinical evidence of the aforesaid effects and mechanisms. We also address safety issues and provide directions for future studies. The possible concerted actions of EGCG indicate the need for further studies on sarcopenia prevention and management in humans.

Accounting Gut Microbiota as the Mediator of Beneficial Effects of Dietary (Poly)phenols on Skeletal Muscle in Aging

Sarcopenia, the age-related loss of muscle mass and function increasing the risk of disability and adverse outcomes in older people, is substantially influenced by dietary habits. Several studies from animal models of aging and muscle wasting indicate that the intake of specific polyphenol compounds can be associated with myoprotective effects, and improvements in muscle strength and performance. Such findings have also been confirmed in a smaller number of human studies. However, in the gut lumen, dietary polyphenols undergo extensive biotransformation by gut microbiota into a wide range of bioactive compounds, which substantially contribute to bioactivity on skeletal muscle. Thus, the beneficial effects of polyphenols may consistently vary across individuals, depending on the composition and metabolic functionality of gut bacterial communities. The understanding of such variability has recently been improved. For example, resveratrol and urolithin interaction with the microbiota can produce different biological effects according to the microbiota metabotype. In older individuals, the gut microbiota is frequently characterized by dysbiosis, overrepresentation of opportunistic pathogens, and increased inter-individual variability, which may contribute to increasing the variability of biological actions of phenolic compounds at the skeletal muscle level. These interactions should be taken into great consideration for designing effective nutritional strategies to counteract sarcopenia.

The beneficial therapeutic effects of plant-derived natural products for the treatment of sarcopenia

Sarcopenia is an age-related muscle disorder typically associated with a poor quality of life. Its definition has evolved over time, and several underlying causes of sarcopenia in the elderly have been proposed. However, the exact mechanisms involved in sarcopenia, as well as effective treatments for this condition, are not fully understood. The purpose of this article was to conduct a comprehensive review of previous evidence regarding the definition, diagnosis, risk factors, and efficacy of plant-derived natural products for sarcopenia. The methodological approach for the current narrative review was performed using PubMed, Scopus, and Web of Science databases, as well as Google Scholar (up to March 2021) in order to satisfy our objectives. The substantial beneficial effects along with the safety of some plant-derived natural products including curcumin, resveratrol, catechin, soy protein, and ginseng on sarcopenia are reported in this review. Based on clinical studies, nutraceuticals and functional foods may have beneficial effects on physical performance, including handgrip and knee-extension strength, weight-lifting capacity, time or distance travelled before feeling fatigued, mitochondrial function, muscle fatigue, mean muscle fibre area, and total number of myonuclei. In preclinical studies, supplementation with herbs and natural bioactive compounds resulted in beneficial effects including increased plantaris mass, skeletal muscle mass and strength production, increased expression of anabolic factors myogenin, Myf5 and MyoD, enhanced mitochondrial capacity, and inhibition of muscle atrophy and sarcopenia. We found that several risk factors such as nutritional status, physical inactivity, inflammation, oxidative stress, endocrine system dysfunction, insulin resistance, history of chronic disease, mental health, and genetic factors are linked or associated with sarcopenia. The substantial beneficial effects of some nutraceuticals and functional foods on sarcopenia, including curcumin, resveratrol, catechin, soy protein, and ginseng, without any significant side effects, are reported in this review. Plant-derived natural products might have a beneficial effect on various components of sarcopenia. Nevertheless, due to limited human trials, the clinical benefits of plant-derived natural products remain inconclusive. It is suggested that comprehensive longitudinal clinical studies to better understand risk factors over time, as well as identifying a treatment strategy for sarcopenia that is based on its pathophysiology, be undertaken in future investigations.

Beneficial Effects of Flavonoids on Skeletal Muscle Health: A Systematic Review and Meta-Analysis

Skeletal muscle (SkM) is a highly dynamic tissue that responds to physiological adaptations or pathological conditions, and SkM mitochondria play a major role in bioenergetics, regulation of intracellular calcium homeostasis, pro-oxidant/antioxidant balance, and apoptosis. Flavonoids are polyphenolic compounds with the ability to modulate molecular pathways implicated in the development of mitochondrial myopathy. Therefore, it is pertinent to explore its potential application in conditions such as aging, disuse, denervation, diabetes, obesity, and cancer. To evaluate preclinical and clinical effects of flavonoids on SkM structure and function. We performed a systematic review of published studies, with no date restrictions applied, using PubMed and Scopus. The following search terms were used: "flavonoids" OR "flavanols" OR "flavones" OR "anthocyanidins" OR "flavanones" OR "flavan-3-ols" OR "catechins" OR "epicatechin" OR "(-)-epicatechin" AND "skeletal muscle." The studies included in this review were preclinical studies, clinical trials, controlled clinical trials, and randomized-controlled trials that investigated the influence of flavonoids on SkM health. Three authors, independently, assessed trials for the review. Any disagreement was resolved by consensus. The use of flavonoids could be a potential tool for the prevention of muscle loss. Their effects on metabolism and on mitochondria function suggest their use as muscle regulators.

The regulatory role of dietary factors in skeletal muscle development, regeneration and function

Skeletal muscle plays a crucial role in motor function, respiration, and whole-body energy homeostasis. How to regulate the development and function of skeletal muscle has become a hot research topic for improving lifestyle and extending life span. Numerous transcription factors and nutritional factors have been clarified are closely associated with the regulation of skeletal muscle development, regeneration and function. In this article, the roles of different dietary factors including green tea, quercetin, curcumin (CUR), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and resveratrol (RES) in regulating skeletal muscle development, muscle mass, muscle function, and muscle recovery have been summarized and discussed. We also reviewed the potential regulatory molecular mechanism of these factors. Based on the current findings, dietary factors may be used as a potential therapeutic agent to treat skeletal muscle dysfunction as well as its related diseases.

Antioxidant supplements and endurance exercise: Current evidence and mechanistic insights

Antioxidant supplements are commonly consumed by endurance athletes to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. There are numerous commercially available nutritional supplements that are targeted to athletes and health enthusiasts that allegedly possess antioxidant properties. However, most of these compounds are poorly investigated with respect to their in vivo redox activity and efficacy in humans. Therefore, this review will firstly provide a background to endurance exercise-related redox signalling and the subsequent adaptations in skeletal muscle and vascular function. The review will then discuss commonly available compounds with purported antioxidant effects for use by athletes. N-acetyl cysteine may be of benefit over the days prior to an endurance event; while chronic intake of combined 1000 mg vitamin C + vitamin E is not recommended during periods of heavy training associated with adaptations in skeletal muscle. Melatonin, vitamin E and α-lipoic acid appear effective at decreasing markers of exercise-induced oxidative stress. However, evidence on their effects on endurance performance are either lacking or not supportive. Catechins, anthocyanins, coenzyme Q10 and vitamin C may improve vascular function, however, evidence is either limited to specific sub-populations and/or does not translate to improved performance. Finally, additional research should clarify the potential benefits of curcumin in improving muscle recovery post intensive exercise; and the potential hampering effects of astaxanthin, selenium and vitamin A on skeletal muscle adaptations to endurance training. Overall, we highlight the lack of supportive evidence for most antioxidant compounds to recommend to athletes.

Catechins enhance skeletal muscle performance

Muscle-related disorders, such as sarcopenia and cachexia, caused by aging and chronic diseases can lead to the loss of muscle mass and strength to different degrees, severely affecting human health. Globally, tea is one of the three most popular beverages, and its major active ingredient catechins have been reported to delay muscular atrophy and enhance movement. However, currently, there is no systematic review to elaborate its roles and the associated mechanisms. This article reviews the (1) functions and mechanisms of catechins in the differentiation of myogenic stem cells, biogenesis of mitochondria, synthesis and degradation of proteins, regulation of glucose level, and metabolism of lipids in muscle cells; and (2) effect of catechins on the blood vessels, bones, and nerves that are closely related to the skeletal muscles. Catechins could prevent, mitigate, delay, and even treat muscle-related disorders caused by aging and diseases.

Role of exercise in age-related sarcopenia

Sarcopenia is an age-associated decline of skeletal muscle mass and function and is known to lead to frailty, cachexia, osteoporosis, metabolic syndromes, and death. Notwithstanding the increasing incidence of sarcopenia, the molecular and cellular mechanisms driving age-related sarcopenia are not completely understood. This article reviews current definitions of sarcopenia, its potential mechanisms, and effects of exercise on sarcopenia. The pathogenesis of age-related sarcopenia is multifactorial and includes myostatin, inflammatory cytokines, and mitochondria-derived problems. Especially, age-induced mitochondrial dysfunction triggers the production of reactive oxygen species (ROS) by mitochondria, impedes mitochondrial dynamics, interrupts mitophagy, and leads to mitochondria-mediated apoptosis. Aerobic exercise provides at least a partial solution to sarcopenia as it ameliorates mitochondria-derived problems, and resistance exercise strengthens muscle mass and function. Furthermore, combinations of these exercise types provide the benefits of both. Collectively, this review summarizes potential mechanisms of age-related sarcopenia and emphasizes the use of exercise as a therapeutic strategy, suggesting that combined exercise provides the most beneficial means of combating age-related sarcopenia.

Drugs of Muscle Wasting and Their Therapeutic Targets

Muscle wasting and weakness such as cachexia, atrophy, and sarcopenia are characterized by marked decreases in the protein content, myonuclear number, muscle fiber size, and muscle strength. This chapter focuses on the recent advances of pharmacological approach for attenuating muscle wasting.A myostatin-inhibiting approach is very intriguing to prevent sarcopenia but not muscular dystrophy in humans. Supplementation with ghrelin is also an important candidate to combat sarcopenia as well as cachexia. Treatment with soy isoflavone, trichostatin A (TSA), and cyclooxygenase 2 (Cox2) inhibitors seems to be effective modulators attenuating muscle wasting, although further systematic research is needed on this treatment in particular concerning side effects.

Long-term supplementation with EGCG and beta-alanine decreases mortality but does not affect cognitive or muscle function in aged mice

We have previously shown that 6weeks of a diet containing epigallocatechin gallate (EGCG) and beta-alanine (B-ALA) was not effective in improving either cognitive or muscle function in aged (18month) mice (Gibbons et al. Behav Brain Res 2014). However, diet reduced oxidative stress in the brain, and previous studies using longer-term interventions have documented beneficial effects in cognitive, but not muscle, function. Therefore, we investigated the effect of 6months of feeding on measures of cognitive and muscle function in mice. Mice (12months, N=15/group) were fed AIN-93M containing 0.15% EGCG and 0.34% B-ALA or standard AIN-93M for 6months, then underwent a battery of tests for cognitive and muscle function at 18months. Interestingly, a higher percentage of mice receiving EGCG and B-ALA (E+B, 80%) survived to study end compared to control (Ctrl, 40%) mice (p=0.02). E+B did not affect arm preference in the Y-maze test (p=0.74, novel arm) and did not alter performance in an active avoidance test (p=0.16, avoidances per 50 trials). E+B increased rotarod performance (p=0.03), did not affect grip strength (p=0.91), and decreased time to exhaustion in a treadmill fatigue test (p=0.02) compared to Ctrl. In conclusion, E+B reduced mortality, had no effect on cognitive function and variable effects on muscle function.

Dose-dependent decrease in mortality with no cognitive or muscle function improvements due to dietary EGCG supplementation in aged mice

We have previously shown that a diet containing epigallocatechin gallate (EGCG) and beta-alanine is not effective in improving either cognitive or muscle function in aged (18 month) mice (Gibbons et al., Behav. Brain Res., 2014, 272:131–140; Pence et al., Appl. Physiol. Nutr. Metab., 2016, 41(2): 181–190). However, this diet reduced oxidative stress in the brain, and previous studies using longer term interventions and other doses have documented beneficial effects in cognitive and muscle function, especially with EGCG. Here we hypothesized that a different dose of EGCG or longer feeding period would be more efficacious in improving cognition. Aged (21–25 mo) Balb/cByJ male mice underwent 63 days of feeding with EGCG at 0, 0.091, or 3.67 mg/g AIN-93M diet and were then subjected to a battery of cognitive and muscle function tests. EGCG feeding at either of the 2 doses did not alter preference for novel versus familiar arm in the Y-maze test (p = 0.29) and did not affect learning in the active avoidance test (p = 0.76). Similarly, EGCG did not affect preference for novel versus familiar mice in a social discrimination test (p = 0.17). Likewise, there was no effect of EGCG on muscle function by grip strength (p = 0.16), rotarod (p = 0.18), or treadmill test to exhaustion (p = 0.25). EGCG reduced mortality in a dose-dependent fashion (p = 0.05, log-rank test for trend), with 91% of high EGCG, 72% of low EGCG, and 55% of control mice surviving to the end of the study. In conclusion, EGCG improves survival in aged mice but does not affect cognitive or muscle function.

Voluntary running depreciates the requirement of Ca2+-stimulated cAMP signaling in synaptic potentiation and memory formation

Mental health and cognitive functions are influenced by both genetic and environmental factors. Although having active lifestyle with physical exercise improves learning and memory, how it interacts with the specific key molecular regulators of synaptic plasticity is largely unknown. Here, we examined the effects of voluntary running on long-term potentiation (LTP) and memory formation in mice lacking type 1 adenylyl cyclase (AC1), a neurospecific synaptic enzyme that contributes to Ca(2+)-stimulated cAMP production. Following 1 mo of voluntary running-wheel exercise, the impaired LTP and object recognition memory in AC1 knockout (KO) mice were significantly attenuated. Running up-regulated exon II mRNA level of BDNF (brain-derived neurotrophic factor), though it failed to increase exon I and IV mRNAs in the hippocampus of AC1 KO mice. Intrahippocampal infusion of recombinant BDNF was sufficient to rescue LTP and object recognition memory defects in AC1 KO mice. Therefore, voluntary running and exogenous BDNF application overcome the defective Ca(2+)-stimulated cAMP signaling. Our results also demonstrate that alteration in Ca(2+)-stimulated cAMP can affect the molecular outcome of physical exercise.