PubMed · 8878156
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C Williams. Fatigue during prolonged exercise.. https://doi.org/10.1016/s0899-9007(97)85093-9
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BACKGROUND: Ischemic heart disease (IHD) is the leading cause of morbidity and mortality. Branched-chain amino acids (BCAAs) are associated with higher IHD risk, but the underlying biological pathways remain unclear. OBJECTIVES: This study aims to explore these pathways using 2-step proteome-wide Mendelian randomization. METHODS: We examined the associations between genetic proxies for BCAAs and 2922 proteins in the United Kingdom Biobank Pharma Proteomics Project, supplemented by a meta-analysis with data from deCODE to identify proteins associated with BCAAs. Next, we tested their effects on IHD risk using Coronary Artery Disease Genome-wide Replication and Meta-analysis plus Coronary Artery Disease Genetics Consortium (122,733 cases and 424,528 controls) and replicated in FinnGen (31,640 cases and 187,152 controls). We conducted sensitivity analyses using genetic instruments from deCODE. Proteins associated with IHD risk and, in a consistent direction, with genetically predicted BCAAs were considered potential mediators. RESULTS: Genetic proxies for BCAAs were associated with 40 proteins. Among these, 6 proteins showed consistent evidence of mediation, including complement C1s subcomponent, coagulation factor II, granulin, proprotein convertase subtilisin/kexin type 9, sex hormone-binding globulin, and V-set and transmembrane domain-containing protein 2-like. These proteins are involved in inflammation, coagulation, lipid metabolism, and cellular stress response. All associations were robust across different analytical methods and replicated in independent datasets. Mediation analysis showed that these proteins accounted for 6.5% to 32.1% of the association between BCAAs and IHD risk. CONCLUSIONS: This study identified 6 proteins that potentially link BCAAs to IHD, implicating pathways related to inflammation, coagulation, lipid metabolism, and cellular stress responses. To our knowledge, these findings provide novel mechanistic insights into the BCAA-IHD relationship and highlight potential protein targets for future prevention and intervention strategies.
Complementation of an E. coli mutant auxotrophic for the branched-chain amino acids (BCAA)--valine, leucine, and isoleucine--by the ilvG gene ( slr2088) of the cyanobacterium Synechocystis PCC6803 indicates that this gene encodes an active alpha-acetohydroxy acid synthase. Differences of response of the recombinants to the addition of the essential amino acids suggested a lower specificity for the initial reaction of the valine/leucine chain than for the isoleucine one. Inactivation of ilvG in Synechocystis led to a leaky phenotype, suggesting a capacity to compensate the auxotrophies by other processes. This observation is discussed in view of the general difficulty of obtaining auxotrophs in cyanobacteria.
Maple syrup urine disease (MSUD) is an inborn error of metabolism stemming from a deficiency in 2-ketoacid dehydrogenase and resulting in the systemic accumulation of branched chain amino acids (BCAAs). Affected children may suffer profound developmental and cognitive impairment from exposure to high levels of BCAA and their associated neurotoxic metabolites. Endogenous renal clearance of BCAA is limited and several therapeutic modalities including intensive nutritional regimens, exchange transfusions, peritoneal dialysis, and continuous hemofiltration have been utilized in neonates with MSUD, all of which have had varying success in reducing systemic BCAA levels. In this report, a symptomatic 7-day-old 3-kg neonate with MSUD underwent treatment with a combination of early hemodialysis and aggressive enteral feedings of a metabolically appropriate formula. This approach results in a 75% reduction of systemic toxin levels within 3 h. When compared to other reported modalities of therapy for symptomatic neonates with MSUD, this approach appears to be most efficacious. Moreover, by minimizing the amount of time that an affected neonate is exposed to neurotoxic levels of BCAAs, long-term developmental and cognitive capabilities may be preserved.