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Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis.

Kraus WE, Muoio DM, Stevens R, Craig D, Bain JR, Grass E, Haynes C, Kwee L, Qin X, Slentz DH, Krupp D, Muehlbauer M, Hauser ER, Gregory SG, Newgard CB, Shah SH - PLoS Genet. (2015)

Bottom Line: Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm.Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP.Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiology, Department of Medicine, Duke University, Durham, North Carolina, United States of America.

ABSTRACT
Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10-6-2.3x10-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

No MeSH data available.


Related in: MedlinePlus

Dicarboxylic (DC) acylcarnitines measured in HEK 293 cell lysates (A) and conditioned medium (B) after 24 h exposure to BSA alone or in complex with 500 uM fatty acids (FA, oleate:palmitate, 1:1). C) Representative Western blot analysis of the ER stress protein, BiP, in HEK 293 cells treated 24 h with 500 uM FA ± increasing doses of tunicamycin (NT; no treatment, Vehicle (DMSO), 8 ng/mL and 32 ng/mL tunicamycin). High dose tunicamycin (500 ng/mL) served as a positive control. Asterisks indicate significant difference between BSA and FA experiments (p<0.05).
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pgen.1005553.g003: Dicarboxylic (DC) acylcarnitines measured in HEK 293 cell lysates (A) and conditioned medium (B) after 24 h exposure to BSA alone or in complex with 500 uM fatty acids (FA, oleate:palmitate, 1:1). C) Representative Western blot analysis of the ER stress protein, BiP, in HEK 293 cells treated 24 h with 500 uM FA ± increasing doses of tunicamycin (NT; no treatment, Vehicle (DMSO), 8 ng/mL and 32 ng/mL tunicamycin). High dose tunicamycin (500 ng/mL) served as a positive control. Asterisks indicate significant difference between BSA and FA experiments (p<0.05).

Mentions: The above findings linking ER stress to SCDA metabolites led us to question whether nutrient-induced accumulation of dicarboxylacylcarnitines would be accompanied by ER stress in cultured cells. Exposure of human HEK293 kidney cells to 500 uM fatty acids for 24 hours (a condition designed to mimic elevated fatty acid levels observed in human obesity) increased cellular production and efflux of several long, medium and short-chain dicarboxylacylcarnitines (Fig 3A and 3B). Interestingly, fatty acid-induced production of dicarboxylacylcarnitines was accompanied by elevated expression of the molecular chaperone protein BiP (Fig 3C), a well-recognized marker of ER stress. At low doses of the ER stress agent tunicamycin (lower than required to cause cytotoxicity), fatty acid exposure also augmented BiP expression (Fig 3C). Together, these results point to an intriguing connection between cellular carbon load, dicarboxylic acylcarnitines and proteotoxicity.


Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis.

Kraus WE, Muoio DM, Stevens R, Craig D, Bain JR, Grass E, Haynes C, Kwee L, Qin X, Slentz DH, Krupp D, Muehlbauer M, Hauser ER, Gregory SG, Newgard CB, Shah SH - PLoS Genet. (2015)

Dicarboxylic (DC) acylcarnitines measured in HEK 293 cell lysates (A) and conditioned medium (B) after 24 h exposure to BSA alone or in complex with 500 uM fatty acids (FA, oleate:palmitate, 1:1). C) Representative Western blot analysis of the ER stress protein, BiP, in HEK 293 cells treated 24 h with 500 uM FA ± increasing doses of tunicamycin (NT; no treatment, Vehicle (DMSO), 8 ng/mL and 32 ng/mL tunicamycin). High dose tunicamycin (500 ng/mL) served as a positive control. Asterisks indicate significant difference between BSA and FA experiments (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4634848&req=5

pgen.1005553.g003: Dicarboxylic (DC) acylcarnitines measured in HEK 293 cell lysates (A) and conditioned medium (B) after 24 h exposure to BSA alone or in complex with 500 uM fatty acids (FA, oleate:palmitate, 1:1). C) Representative Western blot analysis of the ER stress protein, BiP, in HEK 293 cells treated 24 h with 500 uM FA ± increasing doses of tunicamycin (NT; no treatment, Vehicle (DMSO), 8 ng/mL and 32 ng/mL tunicamycin). High dose tunicamycin (500 ng/mL) served as a positive control. Asterisks indicate significant difference between BSA and FA experiments (p<0.05).
Mentions: The above findings linking ER stress to SCDA metabolites led us to question whether nutrient-induced accumulation of dicarboxylacylcarnitines would be accompanied by ER stress in cultured cells. Exposure of human HEK293 kidney cells to 500 uM fatty acids for 24 hours (a condition designed to mimic elevated fatty acid levels observed in human obesity) increased cellular production and efflux of several long, medium and short-chain dicarboxylacylcarnitines (Fig 3A and 3B). Interestingly, fatty acid-induced production of dicarboxylacylcarnitines was accompanied by elevated expression of the molecular chaperone protein BiP (Fig 3C), a well-recognized marker of ER stress. At low doses of the ER stress agent tunicamycin (lower than required to cause cytotoxicity), fatty acid exposure also augmented BiP expression (Fig 3C). Together, these results point to an intriguing connection between cellular carbon load, dicarboxylic acylcarnitines and proteotoxicity.

Bottom Line: Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm.Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP.Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiology, Department of Medicine, Duke University, Durham, North Carolina, United States of America.

ABSTRACT
Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10-6-2.3x10-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

No MeSH data available.


Related in: MedlinePlus