RESUMO
Beta-alanine is a nonessential amino acid that is commonly used to improve exercise performance. It could influence the buffering of hydrogen ions produced during intense exercise and delay fatigue, providing a substrate for increased synthesis of intramuscular carnosine. This systematic review evaluates the effects of beta-alanine supplementation on maximal intensity exercise in trained, young, male individuals. Six databases were searched on August 10, 2023, to identify randomized, double-blinded, placebo-controlled trials investigating the effect of chronic beta-alanine supplementation in trained male individuals with an age range of 18-40 years. Studies evaluating exercise performance through maximal or supramaximal intensity efforts falling within the 0.5-10 min duration were included. A total of 18 individual studies were analyzed, employing 18 exercise test protocols and 15 outcome measures in 331 participants. A significant (p = .01) result was observed with an overall effect size of 0.39 (95% confidence interval [CI] [0.09, 0.69]), in favor of beta-alanine supplementation versus placebo. Results indicate significant effects at 4 weeks of supplementation, effect size 0.34 (95% CI [0.02, 0.67], p = .04); 4-10 min of maximal effort, effect size 0.55 (95% CI [0.07, 1.04], p = .03); and a high beta-alanine dosage of 5.6-6.4 g per day, effect size 0.35 (95% CI [0.09, 0.62], p = .009). The results provide insights into which exercise modality will benefit the most, and which dosage protocols and durations stand to provide the greatest ergogenic effects. This may be used to inform further research, and professional or recreational training design, and optimization of supplementation strategies.
RESUMO
MicroRNAs (miRNAs) and copy number variations (CNVs) represent two classes of newly discovered genomic elements that were shown to contribute to genome plasticity and evolution. Recent studies demonstrated that miRNAs and CNVs must have co-evolved and interacted in an attempt to maintain the balance of the dosage sensitive genes and at the same time increase the diversity of dosage non-sensitive genes, contributing to species evolution. It has been previously demonstrated that both the number of miRNAs that target genes found in CNV regions as well as the number of miRNA binding sites are significantly higher than those of genes found in non-CNV regions. These findings raise the possibility that miRNAs may have been created under evolutionary pressure, as a mechanism for increasing the tolerance to genome plasticity. In the current study, we aimed in exploring the differences of miRNAs-CNV functional interactions between human and seven others species. By performing in silico whole genome analysis in eight different species (human, chimpanzee, macaque, mouse, rat, chicken, dog and cow), we demonstrate that miRNAs targeting genes located within CNV regions in humans have special functional characteristics that provide an insight into the differences between humans and other species.
