Glucolipotoxicity diminishes cardiomyocyte TFEB and inhibits lysosomal autophagy during obesity and diabetes

Trivedi, Purvi; Bartlett, Jordan; Pérez, Lester J.; Brunt, Keith R.; Légaré, France; Hassan, Ansar; Kienesberger, Petra C.; Pulinilkunnil, Thomas

doi:10.1016/j.bbalip.2016.09.004

Cited by 62 publications

(57 citation statements)

References 93 publications

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“…A key function of nutrient sensor mTOR is to maintain the available amino acid pool by regulating protein translation. Indeed during DIO, glucolipotoxicity exacerbates IR with concomitant mTOR activation in the heart and skeletal muscle (87,88). We demonstrate that the three BCKAs individually activated mTOR, with ketoleucine and ketoisoleucine exhibiting pronounced effects which are in agreement with prior studies in cultured adipocytes (26) showing increased mTORC1 activity and defective insulin pathway in response to BCKA exposure (89).…”

Section: Discussionsupporting

confidence: 90%

Silencing branched-chain ketoacid dehydrogenase or treatment with branched-chain ketoacids ex vivo inhibits muscle insulin signaling

Biswas

Dao

Mercer

et al. 2020

Preprint

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AbbreviationsAcadm, Acyl-Coenzyme A dehydrogenase, medium chain; BCAAs, branched-chain amino acids; BCKAs, branched-chain keto acids; BCATm, mitochondrial branched chain aminotransferase; BCKDH, branchedchain α-keto acid dehydrogenase; BCKDK, branched-chain keto acid dehydrogenase kinase; BT2, 3,6dichlorobenzo [b]thiophene-2-carboxylic acid; Cyclo, Cyclophilin; DIO, diet induced obesity; Glut, glucose transporter; Hadh, Hydroxyacyl-Coenzyme A dehydrogenase; HFD, high fat diet; HFHS, high fat high sucrose diet; Hmgcs1, 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 1; IR, insulin resistance; Ivd2, Isovaleryl-CoA dehydrogenase; KIC, α-ketoisocaproic acid; KLF15, Kruppel like factor-15; mTOR, mammalian target of rapamycin; Mut, methylmalonyl-Coenzyme A mutase; PDH, pyruvate dehydrogenase; PPM1K, mitochondrial-targeted protein phosphatase; Rer1, Retention in endoplasmic reticulum sorting receptor 1; Rpl41, Ribosomal protein L41; Rpl7l1, Ribosomal protein L7-like 1; T2D, type 2 diabetes 3 Abstract Branched-chain α-keto acids (BCKAs) are downstream catabolites of branched-chain amino acids (BCAAs). Mitochondrial oxidation of BCKAs is catalyzed by branched-chain ketoacid dehydrogenase (BCKDH), an enzyme sensitive to inhibitory phosphorylation by BCKD kinase (BCKDK). Emerging studies show that defective BCAA catabolism and elevated BCKAs levels correlate with glucose intolerance and cardiac dysfunction. However, if/how BCKDH and BCKDK exert control on the availability and flux of intramyocellular BCKAs and if BCKA reprograms nutrient metabolism by influencing insulin action remains unexplored. We observed altered BCAA catabolizing enzyme expression in the murine heart and skeletal muscle during physiological fasting and diet-induced obesity and after ex vivo exposure of C2C12 cells to increasing concentration of saturated fatty acid, palmitate. BCKAs per se impaired insulin-induced AKT phosphorylation and AKT activity in skeletal myotubes and cardiomyocytes. In skeletal muscle cells, mTORC1 and protein translation signaling was enhanced by BCKA with concomitant suppression of mitochondrial respiration. Lowering intracellular BCKA levels by genetic and pharmacological activation of BCKDHA enhanced insulin signaling and activated pyruvate dehydrogenase, an effector of glucose oxidation and substrate metabolism. Our findings suggest that BCKAs profoundly influence muscle insulin function, providing new insight into the molecular nexus of BCAA metabolism and signaling with cellular insulin action and respiration.

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Section: Discussionsupporting

confidence: 90%

Silencing branched-chain ketoacid dehydrogenase or treatment with branched-chain ketoacids ex vivo inhibits muscle insulin signaling

Biswas

Dao

Mercer

et al. 2020

Preprint

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“…This is directly supported by the present study and also has been implicated by several reports from the cardiac field. For instance, cardiac glucolipotoxicity in obesity and diabetes has been linked to diminished TFEB and autophagic flux in cardiomyocytes [48]. Disrupting the ALP through impairing lysosome acidification and repressing TFEB signaling was recently reported to contribute to doxorubicin cardiotoxicity [49, 50].…”

Section: Discussionmentioning

confidence: 99%

TFEB activation protects against cardiac proteotoxicity via increasing autophagic flux

Pan

Zhang

Cui

et al. 2017

Journal of Molecular and Cellular Cardiology

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Insufficient lysosomal removal of autophagic cargoes in cardiomyocytes has been suggested as a main cause for the impairment of the autophagic-lysosomal pathway (ALP) in many forms of heart disease including cardiac proteinopathy and may play an important pathogenic role; however, the molecular basis and the correcting strategy for the cardiac ALP insufficiency require further investigation. The present study was sought to determine whether myocardial expression and activity of TFEB, the recently identified ALP master regulator, are impaired in a cardiac proteinopathy mouse model and to determine the effect of genetic manipulation of TFEB expression on autophagy and proteotoxicity in a cardiomyocyte model of proteinopathy. We found that increased myocardial TFEB mRNA levels and a TFEB protein isoform switch were associated with marked decreases in the mRNA levels of representative TFEB target genes and increased mTORC1 activation, in mice with cardiac transgenic expression of a missense (R120G) mutant αB-crystallin (CryABR120G), a well-established model of cardiac proteinopathy. Using neonatal rat ventricular cardiomyocyte cultures, we demonstrated that downregulation of TFEB decreased autophagic flux in cardiomyocytes both at baseline and during CryABR120G overexpression and increased CryABR120G protein aggregates. Conversely, forced TFEB overexpression increased autophagic flux and remarkably attenuated the CryABR120G overexpression- induced accumulation of ubiquitinated proteins, caspase 3 cleavage, LDH leakage, and decreases in cell viability. Moreover, these protective effects of TFEB were dramatically diminished by inhibiting autophagy. We conclude that myocardial TFEB signaling is impaired in cardiac proteinopathy and forced TFEB overexpression protects against proteotoxicity in cardiomyocytes through improving ALP activity.

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“…Right atrial appendages (AA) and subcutaneous adipose tissue (SAT) samples were obtained from patients undergoing elective, first-time cardiac surgery at the New Brunswick Heart Centre in Saint John, NB and the Maritime Heart Centre (MHC) in Halifax, NS, as previously described 51 . Patients were classified as non-obese (N), pre-obese (P), obese class I (CI), obese class II (CII), and obese class III (CIII) based on their body mass index (BMI, 18.5–24.9 kg/m 2 for N, 25.0–29.9 kg/m 2 for P, 30.0–34.9 kg/m 2 for CI, 35.0–39.9 kg/m 2 for CII, >40.0 kg/m 2 for CIII).…”

Section: Methodsmentioning

confidence: 99%

“…(murine myoblasts, CRL-1772, ATCC) were seeded at a density of 5 × 10 5 cells in 60 mm plates and maintained in Dulbecco’s modified Eagle’s high-glucose medium (DMEM-HG, SH30243.01, Hyclone Laboratories) supplemented with 10% fetal bovine serum (FBS, 1400–500, Seradigm) for 24 h. Thereafter, C2C12 cells were differentiated in DMEM-HG supplemented with 0.2% FBS for 48 h. To induced insulin resistance, differentiated cells were incubated with DMEM-1X (11966025, Thermo Fisher Scientific) supplemented with 5 mM glucose and 0.75 mM sodium palmitate for 18 h. Palmitate-containing media was prepared as previously described 51 . Controls were cultured in the absence of palmitate.…”

Section: Methodsmentioning

confidence: 99%

Validation of optimal reference genes for quantitative real time PCR in muscle and adipose tissue for obesity and diabetes research

Pérez

Rios

Trivedi

et al. 2017

Sci Rep

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The global incidence of obesity has led to an increasing need for understanding the molecular mechanisms that drive this epidemic and its comorbidities. Quantitative real-time RT-PCR (RT-qPCR) is the most reliable and widely used method for gene expression analysis. The selection of suitable reference genes (RGs) is critical for obtaining accurate gene expression information. The current study aimed to identify optimal RGs to perform quantitative transcriptomic analysis based on RT-qPCR for obesity and diabetes research, employing in vitro and mouse models, and human tissue samples. Using the ReFinder program we evaluated the stability of a total of 15 RGs. The impact of choosing the most suitable RGs versus less suitable RGs on RT-qPCR results was assessed. Optimal RGs differed between tissue and cell type, species, and experimental conditions. By employing different sets of RGs to normalize the mRNA expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), we show that sub-optimal RGs can markedly alter the PGC1α gene expression profile. Our study demonstrates the importance of validating RGs prior to normalizing transcriptional expression levels of target genes and identifies optimal RG pairs for reliable RT-qPCR normalization in cells and in human and murine muscle and adipose tissue for obesity/diabetes research.

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Glucolipotoxicity diminishes cardiomyocyte TFEB and inhibits lysosomal autophagy during obesity and diabetes

Cited by 62 publications

References 93 publications

Silencing branched-chain ketoacid dehydrogenase or treatment with branched-chain ketoacids ex vivo inhibits muscle insulin signaling

Silencing branched-chain ketoacid dehydrogenase or treatment with branched-chain ketoacids ex vivo inhibits muscle insulin signaling

TFEB activation protects against cardiac proteotoxicity via increasing autophagic flux

Validation of optimal reference genes for quantitative real time PCR in muscle and adipose tissue for obesity and diabetes research

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