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Keto acid metabolites of branched-chain amino acids inhibit oxidative stress-induced necrosis and attenuate myocardial ischemia-reperfusion injury.

ABSTRACT: Branched chain ?-keto acids (BCKAs) are endogenous metabolites of branched-chain amino acids (BCAAs). BCAA and BCKA are significantly elevated in pathologically stressed heart and contribute to chronic pathological remodeling and dysfunction. However, their direct impact on acute cardiac injury is unknown. Here, we demonstrated that elevated BCKAs significantly attenuated ischemia-reperfusion (I/R) injury and preserved post I/R function in isolated mouse hearts. BCKAs protected cardiomyocytes from oxidative stress-induced cell death in vitro. Mechanistically, BCKA protected oxidative stress induced cell death by inhibiting necrosis without affecting apoptosis or autophagy. Furthermore, BCKAs, but not BCAAs, protected mitochondria and energy production from oxidative injury. Finally, administration of BCKAs during reperfusion was sufficient to significantly attenuate cardiac I/R injury. These findings uncover an unexpected role of BCAA metabolites in cardioprotection against acute ischemia/reperfusion injury, and demonstrate the potential use of BCKA treatment to preserve ischemic tissue during reperfusion.

SUBMITTER: Dong W

PROVIDER: S-EPMC5174097 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Keto acid metabolites of branched-chain amino acids inhibit oxidative stress-induced necrosis and attenuate myocardial ischemia-reperfusion injury.

Dong Weibing W Zhou Meiyi M Dong Mei M Pan Bangfen B Liu Yunxia Y Shao Jing J Gu Xiaoping X Huang Ying Y Li Guangping G Wang Yibin Y Sun Haipeng H

Journal of molecular and cellular cardiology 20161108

Branched chain α-keto acids (BCKAs) are endogenous metabolites of branched-chain amino acids (BCAAs). BCAA and BCKA are significantly elevated in pathologically stressed heart and contribute to chronic pathological remodeling and dysfunction. However, their direct impact on acute cardiac injury is unknown. Here, we demonstrated that elevated BCKAs significantly attenuated ischemia-reperfusion (I/R) injury and preserved post I/R function in isolated mouse hearts. BCKAs protected cardiomyocytes fr ...[more]

PMID: 27832938

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Project description:Rationale: Myocardial vulnerability to ischemia/reperfusion (I/R) injury is strictly regulated by energy substrate metabolism. Branched chain amino acids (BCAA), consisting of valine, leucine and isoleucine, are a group of essential amino acids that are highly oxidized in the heart. Elevated levels of BCAA have been implicated in the development of cardiovascular diseases; however, the role of BCAA in I/R process is not fully understood. The present study aims to determine how BCAA influence myocardial energy substrate metabolism and to further clarify the pathophysiological significance during cardiac I/R injury. Methods: Parameters of glucose and fatty acid metabolism were measured by seahorse metabolic flux analyzer in adult mouse cardiac myocytes with or without BCAA incubation. Chronic accumulation of BCAA was induced in mice receiving oral BCAA administration. A genetic mouse model with defective BCAA catabolism was also utilized. Mice were subjected to MI/R and the injury was assessed extensively at the whole-heart, cardiomyocyte, and molecular levels. Results: We confirmed that chronic accumulation of BCAA enhanced glycolysis and fatty acid oxidation (FAO) but suppressed glucose oxidation in adult mouse ventricular cardiomyocytes. Oral gavage of BCAA enhanced FAO in cardiac tissues, exacerbated lipid peroxidation toxicity and worsened myocardial vulnerability to I/R injury. Etomoxir, a specific inhibitor of FAO, rescued the deleterious effects of BCAA on I/R injury. Mechanistically, valine, leucine and their corresponding branched chain ?-keto acid (BCKA) derivatives, but not isoleucine and its BCKA derivative, transcriptionally upregulated peroxisome proliferation-activated receptor alpha (PPAR-?). BCAA/BCKA induced PPAR-? upregulation through the general control nonderepresible-2 (GCN2)/ activating transcription factor-6 (ATF6) pathway. Finally, in a genetic mouse model with BCAA catabolic defects, chronic accumulation of BCAA increased FAO in myocardial tissues and sensitized the heart to I/R injury, which could be reversed by adenovirus-mediated PPAR-? silencing. Conclusions: We identify BCAA as an important nutrition regulator of myocardial fatty acid metabolism through transcriptional upregulation of PPAR-?. Chronic accumulation of BCAA, caused by either dietary or genetic factors, renders the heart vulnerable to I/R injury via exacerbating lipid peroxidation toxicity. These data support the notion that BCAA lowering methods might be potentially effective cardioprotective strategies, especially among patients with diseases characterized by elevated levels of BCAA, such as obesity and diabetes.

Project description:ObjectivesInsulin resistance (IR) in adolescents with obesity is associated with a sex-dependent metabolic 'signature' comprising the branched-chain amino acids (BCAAs), glutamate/glutamine, C3/C5 acylcarnitines and uric acid. Here, we compared the levels of branched-chain α-keto acids (BCKAs) and glutamate/glutamine, which are the byproducts of BCAA catabolism and uric acid among adolescents with obesity prior to and following a 6-month lifestyle-intervention program.MethodsFasting plasma samples from 33 adolescents with obesity (16 males, 17 females, aged 12-18 year) were analysed by flow-injection tandem MS and LC-MS/MS. Multiple linear regression models were used to correlate changes in BCKAs, glutamate/glutamine and uric acid with changes in weight and insulin sensitivity as assessed by HOMA-IR, adiponectin and the ratio of triglyceride (TG) to HDL. In predictive models, BCKAs, glutamate/glutamine and uric acid at baseline were used as explanatory variables.ResultsBaseline BCKAs, glutamate/glutamine and uric acid were higher in males than females despite comparable BMI-metrics. Following lifestyle-intervention, α-keto-β-methylvalerate (α-KMV, a metabolic by product of isoleucine) decreased in males but not in females. The ratio of BCKA/BCAA trended lower in males. In the cohort as a whole, BCKAs correlated positively with the ratio of TG to HDL at baseline and HOMA-IR at 6-month-follow-up. Glutamate/glutamine was positively associated with HOMA-IR at baseline and 6-month-follow-up. A reduction in BCKAs was associated with an increase in adiponectin, and those with higher BCKAs at baseline had higher adiponectin levels at 6-month-follow-up. Interestingly those adolescents with higher uric acid levels at baseline had greater reduction in weight.ConclusionsBCKAs and glutamate/glutamine may serve as biomarkers of IR in adolescents with obesity, and uric acid might serve as a predictor of weight loss in response to lifestyle-intervention. Differential regulation of BCAA catabolism in adolescent males and females implicates critical roles for sex steroids in metabolic homeostasis.

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Keto acid metabolites of branched-chain amino acids inhibit oxidative stress-induced necrosis and attenuate myocardial ischemia-reperfusion injury.

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Keto acid metabolites of branched-chain amino acids inhibit oxidative stress-induced necrosis and attenuate myocardial ischemia-reperfusion injury.

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