Association of Genetically Predicted BCAA Levels with Muscle Fiber Size in Athletes Consuming Protein

Genomic predictors of physical activity and athletic performance

Physical activity and athletic performance are complex phenotypes influenced by environmental and genetic factors. Recent advances in lifestyle and behavioral genomics led to the discovery of dozens of DNA polymorphisms (variants) associated with physical activity and allowed to use them as genetic instruments in Mendelian randomization studies for identifying the causal links between physical activity and health outcomes. On the other hand, exercise and sports genomics studies are focused on the search for genetic variants associated with athlete status, sports injuries and individual responses to training and supplement use. In this review, the findings of studies investigating genetic markers and their associations with physical activity and athlete status are reported. As of the end of September 2023, a total of 149 variants have been associated with various physical activity traits (of which 42 variants are genome-wide significant) and 253 variants have been linked to athlete status (115 endurance-related, 96 power-related, and 42 strength-related).

Genes and Athletic Performance: The 2023 Update

Phenotypes of athletic performance and exercise capacity are complex traits influenced by both genetic and environmental factors. This update on the panel of genetic markers (DNA polymorphisms) associated with athlete status summarises recent advances in sports genomics research, including findings from candidate gene and genome-wide association (GWAS) studies, meta-analyses, and findings involving larger-scale initiatives such as the UK Biobank. As of the end of May 2023, a total of 251 DNA polymorphisms have been associated with athlete status, of which 128 genetic markers were positively associated with athlete status in at least two studies (41 endurance-related, 45 power-related, and 42 strength-related). The most promising genetic markers include the AMPD1 rs17602729 C, CDKN1A rs236448 A, HFE rs1799945 G, MYBPC3 rs1052373 G, NFIA-AS2 rs1572312 C, PPARA rs4253778 G, and PPARGC1A rs8192678 G alleles for endurance; ACTN3 rs1815739 C, AMPD1 rs17602729 C, CDKN1A rs236448 C, CPNE5 rs3213537 G, GALNTL6 rs558129 T, IGF2 rs680 G, IGSF3 rs699785 A, NOS3 rs2070744 T, and TRHR rs7832552 T alleles for power; and ACTN3 rs1815739 C, AR ≥21 CAG repeats, LRPPRC rs10186876 A, MMS22L rs9320823 T, PHACTR1 rs6905419 C, and PPARG rs1801282 G alleles for strength. It should be appreciated, however, that elite performance still cannot be predicted well using only genetic testing.

PPM1K defects cause mild maple syrup urine disease: The second case in the literature

Maple syrup urine disease (MSUD) is an inborn error of metabolism caused by the insufficient catabolism of branched-chain amino acids. BCKDHA, BCKDHB, DBT, and DLD encode the subunits of the branched-chain α-ketoacid dehydrogenase complex, which is responsible for the catabolism of these amino acids. Biallelic pathogenic variants in BCKDHA, BCKDHB, or DBT are characteristic of MSUD. In addition, a patient with a PPM1K defect was previously reported. PPM1K dephosphorylates and activates the enzyme complex. We report a patient with MSUD with mild findings and elevated BCAA levels carrying a novel homozygous start-loss variant in PPM1K. Our study offers further evidence that PPM1K variants cause mild MSUD.

The ADORA2A TT Genotype Is Associated with Anti-Inflammatory Effects of Caffeine in Response to Resistance Exercise and Habitual Coffee Intake

Caffeine is an adenosine A2A receptor (ADORA2A) antagonist with ergogenic and anti-inflammatory effects. Previous studies have reported that the ADORA2A gene regulates glutamate metabolism and immune responses, with the ADORA2A rs5751876 TT genotype (with high sensitivity to caffeine) showing larger ergogenic effect following caffeine ingestion. We therefore hypothesized that the TT genotype would be associated with greater anti-inflammatory effects of caffeine in response to exercise, and with higher coffee intake in physically active individuals. The aim of the present study was twofold: (1) to investigate the association of the ADORA2A variant with the anti-inflammatory effects of caffeine in response to intense resistance exercise (RE), and (2) to analyze the association of the rs5751876 with coffee intake in physically active individuals (n = 134). Fifteen resistance-trained athletes participated in a randomized, double-blind, placebo-controlled cross-over study, where they consumed 6 mg/kg of caffeine or placebo one hour prior to performing an RE protocol. Blood samples were taken immediately from the arterial vein before, immediately after, and 15 min after RE for the analysis of inflammatory markers myeloperoxidase (MPO) and acetylcholinesterase (AChE). We found that the ADORA2A TT genotype carriers experienced lower exercise-induced inflammatory responses (p < 0.05 for AchE) when compared to the C allele carriers (i.e., CC/CT) one hour following the ingestion of caffeine. Furthermore, the ADORA2A TT genotype was positively associated with coffee intake (p = 0.0143; irrespective of CYP1A2 rs762551 polymorphism). In conclusion, we found that the ADORA2A gene polymorphism is associated with anti-inflammatory effects of caffeine in response to resistance exercise, as well as with habitual coffee intake in physically active individuals.

Identification and Characterization of Genomic Predictors of Sarcopenia and Sarcopenic Obesity Using UK Biobank Data

The substantial decline in skeletal muscle mass, strength, and gait speed is a sign of severe sarcopenia, which may partly depend on genetic risk factors. So far, hundreds of genome-wide significant single nucleotide polymorphisms (SNPs) associated with handgrip strength, lean mass and walking pace have been identified in the UK Biobank cohort; however, their pleiotropic effects on all three phenotypes have not been investigated. By combining summary statistics of genome-wide association studies (GWAS) of handgrip strength, lean mass and walking pace, we have identified 78 independent SNPs (from 73 loci) associated with all three traits with consistent effect directions. Of the 78 SNPs, 55 polymorphisms were also associated with body fat percentage and 25 polymorphisms with type 2 diabetes (T2D), indicating that sarcopenia, obesity and T2D share many common risk alleles. Follow-up bioinformatic analysis revealed that sarcopenia risk alleles were associated with tiredness, falls in the last year, neuroticism, alcohol intake frequency, smoking, time spent watching television, higher salt, white bread, and processed meat intake; whereas protective alleles were positively associated with bone mineral density, serum testosterone, IGF1, and 25-hydroxyvitamin D levels, height, intelligence, cognitive performance, educational attainment, income, physical activity, ground coffee drinking and healthier diet (muesli, cereal, wholemeal or wholegrain bread, potassium, magnesium, cheese, oily fish, protein, water, fruit, and vegetable intake). Furthermore, the literature data suggest that single-bout resistance exercise may induce significant changes in the expression of 26 of the 73 implicated genes in m. vastus lateralis, which may partly explain beneficial effects of strength training in the prevention and treatment of sarcopenia. In conclusion, we have identified and characterized 78 SNPs associated with sarcopenia and 55 SNPs with sarcopenic obesity in European-ancestry individuals from the UK Biobank.