Comparison of gas chromatography-mass spectrometry and gas chromatography-combustion-isotope ratio mass spectrometry analysis for in vivo estimates of metabolic fluxes.

Gas chromatography-mass spectrometry (GC-MS) was compared with gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for measurements of cholesterol (13)C enrichment after infusion of labeled precursor ([(13)C1,2]acetate). Paired results were significantly correlated, although GC-MS was less accurate than GC-C-IRMS for higher enrichments. Nevertheless, only GC-MS was able to provide information on isotopologue distribution, bringing new insights to lipid metabolism. Therefore, we assessed the isotopologue distribution of cholesterol in humans and dogs known to present contrasted cholesterol metabolic pathways. The labeled tracer incorporation was different in both species, highlighting the subsidiarity of GC-MS and GC-C-IRMS to analyze in vivo stable isotope studies.

Sex-Specific Associations of Genetically Predicted Circulating Lp(a) (Lipoprotein(a)) and Hepatic LPA Gene Expression Levels With Cardiovascular Outcomes: Mendelian Randomization and Observational Analyses.

BACKGROUND: Elevated Lp(a) (Lipoprotein(a)) levels are associated with coronary artery disease (CAD), ischemic stroke (IS), and calcific aortic valve stenosis (CAVS). Studies investigating the association between Lp(a) levels and these diseases in women have yielded inconsistent results. METHODS: To investigate the association of Lp(a) with sex-specific cardiovascular outcomes, we determined the association between genetically predicted Lp(a) levels (using 27 single nucleotide polymorphisms at the LPA locus) and hepatic LPA expression (using 80 single nucleotide polymorphisms at the LPA locus associated with LPA mRNA expression in liver samples from the Genotype-Tissue Expression dataset) on CAD, IS, and CAVS using individual participant data from the UK Biobank: 408 403 participants of European ancestry (37 102, 4283, and 2574 with prevalent CAD, IS, and CAVS, respectively). The long-term association between Lp(a) levels and incident CAD, IS, and CAVS was also investigated in European Prospective Investigation into Cancer and Nutrition-Norfolk: 18 721 participants (3964, 846, and 424 with incident CAD, IS, and CAVS, respectively). RESULTS: Genetically predicted plasma Lp(a) levels were positively and similarly associated with prevalent and incident CAD and CAVS in men and women. Genetically predicted plasma Lp(a) levels were associated with prevalent and incident IS when we studied men and women pooled together, and in men only. Genetically predicted LPA expression levels were associated with prevalent CAD and CAVS in men and women but not with IS. CONCLUSIONS: Genetically predicted blood Lp(a) and hepatic LPA gene expression as well as serum Lp(a) levels predict the risk of CAD and CAVS in men and in women. Whether RNA interference therapies aiming at lowering Lp(a) levels could be useful in reducing cardiovascular disease risk in both men and women with high Lp(a) levels needs to be determined in large-scale cardiovascular outcomes trials.

Lipoprotein Proteomics and Aortic Valve Transcriptomics Identify Biological Pathways Linking Lipoprotein(a) Levels to Aortic Stenosis.

Lipoprotein(a) (Lp(a)) is one of the most important risk factors for the development of calcific aortic valve stenosis (CAVS). However, the mechanisms through which Lp(a) causes CAVS are currently unknown. Our objectives were to characterize the Lp(a) proteome and to identify proteins that may be differentially associated with Lp(a) in patients with versus without CAVS. Our second objective was to identify genes that may be differentially regulated by exposure to high versus low Lp(a) levels in explanted aortic valves from patients with CAVS. We isolated Lp(a) from the blood of 21 patients with CAVS and 22 volunteers and performed untargeted label-free analysis of the Lp(a) proteome. We also investigated the transcriptomic signature of calcified aortic valves from patients who underwent aortic valve replacement with high versus low Lp(a) levels (n = 118). Proteins involved in the protein activation cascade, platelet degranulation, leukocyte migration, and response to wounding may be associated with Lp(a) depending on CAVS status. The transcriptomic analysis identified genes involved in cardiac aging, chondrocyte development, and inflammation as potentially influenced by Lp(a). Our multi-omic analyses identified biological pathways through which Lp(a) may cause CAVS, as well as key molecular events that could be triggered by Lp(a) in CAVS development.

A Comparative Analysis of the Lipoprotein(a) and Low-Density Lipoprotein Proteomic Profiles Combining Mass Spectrometry and Mendelian Randomization.

BACKGROUND: Lipoprotein(a) (Lp[a]), which consists of a low-density lipoprotein (LDL) bound to apolipoprotein(a), is one of the strongest genetic risk factors for atherosclerotic cardiovascular diseases. Few studies have performed hypothesis-free direct comparisons of the Lp(a) and the LDL proteomes. Our objectives were to compare the Lp(a) and the LDL proteomic profiles and to evaluate the effect of lifelong exposure to elevated Lp(a) or LDL cholesterol levels on the plasma proteomic profile. METHODS: We performed a label-free analysis of the Lp(a) and LDL proteomic profiles of healthy volunteers in a discovery (n = 6) and a replication (n = 9) phase. We performed inverse variance weighted Mendelian randomization to document the effect of lifelong exposure to elevated Lp(a) or LDL cholesterol levels on the plasma proteomic profile of participants of the INTERVAL study. RESULTS: We identified 15 proteins that were more abundant on Lp(a) compared with LDL (serping1, pi16, itih1, itih2, itih3, pon1, podxl, cd44, cp, ptprg, vtn, pcsk9, igfals, vcam1, and ttr). We found no proteins that were more abundant on LDL compared with Lp(a). After correction for multiple testing, lifelong exposure to elevated LDL cholesterol levels was associated with the variation of 18 plasma proteins whereas Lp(a) did not appear to influence the plasma proteome. CONCLUSIONS: Results of this study highlight marked differences in the proteome of Lp(a) and LDL as well as in the effect of lifelong exposure to elevated LDL cholesterol or Lp(a) on the plasma proteomic profile.

CONTEXTE: La lipoprotéine(a) (Lp[a]), qui est constituée d'une lipoprotéine de basse densité (LDL) liée à une apolipoprotéine(a), est l'un des plus importants facteurs de risque génétiques de survenue d'une maladie cardiovasculaire athéroscléreuse. Peu d'études comparatives directes sans hypothèse ont porté sur le protéome de la Lp(a) et celui des LDL. Nos objectifs étaient de comparer les profils protéomiques de la Lp(a) et des LDL et d'évaluer l'effet d'une exposition à vie à un taux élevé de Lp(a) ou de cholestérol LDL sur le profil protéomique plasmatique. MÉTHODOLOGIE: Nous avons réalisé une analyse sans marquage des profils protéomiques de la Lp(a) et des LDL chez des volontaires en bonne santé dans le cadre d'une phase de découverte (n = 6) et d'une phase de réplication (n = 9). Pour rendre compte de l'effet d'une exposition à vie à un taux élevé de Lp(a) ou de cholestérol des LDL sur le profil protéomique plasmatique des participants de l'étude INTERVAL, nous avons utilisé une analyse de randomisation Mendélienne avec pondération par l'inverse de la variance. RÉSULTATS: Nous avons relevé 15 protéines associées en plus grande abondance à la Lp(a) qu'aux LDL (serping1, pi16, itih1, itih2, itih3, pon1, podxl, cd44, cp, ptprg, vtn, pcsk9, igfals, vcam1 et ttr). Nous n'avons noté aucune protéine associée en plus grande abondance aux LDL qu'à la Lp(a). Après correction pour tenir compte de la multiplicité des tests, l'exposition à vie à un taux élevé de cholestérol LDL a été associée à la variation de 18 protéines plasmatiques, tandis que le taux de Lp(a) ne semblait pas influencer le protéome plasmatique. CONCLUSIONS: Les résultats de notre étude font ressortir les différences marquées entre le protéome de la Lp(a) et celui des LDL, ainsi qu'entre l'effet sur le profil protéomique plasmatique de l'exposition à vie à un taux élevé de cholestérol LDL et celui de l'exposition à vie à un taux élevé de Lp(a).

Interaction of Autotaxin With Lipoprotein(a) in Patients With Calcific Aortic Valve Stenosis.

Our objectives were to determine whether autotaxin (ATX) is transported by lipoprotein(a) [Lp(a)] in human plasma and if could be used as a biomarker of calcific aortic valve stenosis (CAVS). We first found that ATX activity was higher in Lp(a) compared to low-density lipoprotein fractions in isolated fractions of 10 healthy participants. We developed a specific assay to measure ATX-Lp(a) in 88 patients with CAVS and 144 controls without CAVS. In a multivariable model corrected for CAVS risk factors, ATX-Lp(a) was associated with CAVS (p = 0.003). We concluded that ATX is preferentially transported by Lp(a) and might represent a novel biomarker for CAVS.

Lipoprotein(a), Oxidized Phospholipids, and Aortic Valve Microcalcification Assessed by 18F-Sodium Fluoride Positron Emission Tomography and Computed Tomography.

BACKGROUND: Lipoprotein(a) (Lp[a]) is the preferential lipoprotein carrier of oxidized phospholipids (OxPLs) and a well-established genetic risk factor for calcific aortic valve stenosis (CAVS). Whether Lp(a) predicts aortic valve microcalcification in individuals without CAVS is unknown. Our objective was to estimate the prevalence of elevated Lp(a) and OxPL levels in patients with CAVS and to determine if individuals with elevated Lp(a) but without CAVS have higher aortic valve microcalcification. METHODS: We recruited 214 patients with CAVS from Montreal and 174 patients with CAVS and 108 controls from Québec City, Canada. In a second group of individuals with high (≥75 nmol/L, n = 27) or low (<75 nmol/L, n = 28) Lp(a) levels, 18F-sodium fluoride positron emission tomography/computed tomography was performed to determine the difference in mean tissue-to-background ratio (TBR) of the aortic valve. RESULTS: Patients with CAVS had 62.0% higher Lp(a) (median = 28.7, interquartile range [8.2-116.6] vs 10.9 [3.6-28.8] nmol/L, P < 0.0001), 50% higher OxPL-apolipoprotein-B (2.2 [1.3-6.0] vs 1.1 [0.7-2.6] nmol/L, P < 0.0001), and 69.9% higher OxPL-apolipoprotein(a) (7.3 [1.8-28.4] vs 2.2 [0.8-8.4] nmol/L, P < 0.0001) levels compared with individuals without CAVS (all P < 0.0001). Individuals without CAVS but elevated Lp(a) had 40% higher mean TBR compared with individuals with low Lp(a) levels (mean TBR = 1.25 ± 0.23 vs 1.15 ± 0.11, P = 0.02). CONCLUSIONS: Elevated Lp(a) and OxPL levels are associated with prevalent CAVS in patients studied in an echocardiography laboratory setting. In individuals with elevated Lp(a), evidence of aortic valve microcalcification by 18F-sodium fluoride positron emission tomography/computed tomography is present before the development of clinically manifested CAVS.

CONTEXTE: La lipoprotéine(a) (Lp[a]), la principale lipoprotéine assurant le transport des phospholipides oxydés (PLOx), est un facteur de risque génétique bien établi de la sténose aortique calcifiante (SAC). On ignore si la présence de Lp(a) est un facteur prédictif de la microcalcification de la valve aortique chez les individus non atteints de SAC. Notre objectif était d'estimer la prévalence de taux élevés de Lp(a) et de PLOx chez des patients atteints de SAC et de déterminer si la microcalcification de la valve aortique est plus marquée chez les individus affichant des taux élevés de Lp(a) en l'absence de SAC. MÉTHODOLOGIE: Nous avons recruté 214 patients atteints de SAC à Montréal et 174 patients atteints de SAC et 108 patients témoins à Québec (Canada). Dans un second groupe de patients présentant des taux de Lp(a) élevés (≥ 75 nmol/l, n = 27) ou faibles (< 75 nmol/l, n = 28), une tomographie par émission de positons au fluorure de sodium marqué au 18F a été réalisée en vue de comparer la valeur moyenne du rapport signal/bruit (RSB) de la valve aortique. RÉSULTATS: Les patients atteints de SAC présentaient des taux de Lp(a) plus élevés de 62,0 % (médiane = 28,7, intervalle interquartile [de 8,2 à 116,6] vs 10,9 [de 3,6 à 28,8] nmol/l, p < 0,0001), des taux de OxPL-apolipoprotéine-B plus élevés de 50 % (2,2 [de 1,3 à 6,0] vs 1,1 [de 0,7 à 2,6] nmol/l, p < 0,0001) et des taux de PLOx-apolipoprotéine(a) plus élevés de 69,9 % (7,3 [de 1,8 à 28,4] vs 2,2 [de 0,8 à 8,4] nmol/l, p < 0,0001) comparativement aux patients non atteints de SAC (toutes les valeurs p < 0,0001). Les patients non atteints de SAC mais présentant des taux élevés de Lp(a) avaient un RSB moyen supérieur de 40 % à celui des individus affichant un faible taux de Lp(a) (RSB moyen = 1,25 ± 0,23 vs 1,15 ± 0,11, p = 0,02). CONCLUSIONS: Des taux élevés de Lp(a) et de PLOx sont associés à la prévalence de la SAC chez des patients étudiés par échocardiographie. Chez les individus présentant un taux élevé de Lp(a), les signes d'une microcalcification de la valve aortique, décelés par tomographie par émission de positons au fluorure de sodium marqué au 18F /tomodensitométrie sont présents avant l'apparition des manifestations cliniques de la SAC.

Acute and chronic effect of bariatric surgery on circulating autotaxin levels.

Autotaxin (ATX), an adipose tissue-derived lysophospholipase, has been involved in the pathophysiology of cardiometabolic diseases. The impact of bariatric surgery on circulating ATX levels is unknown. We examined the short- (24 h, 5 days) and longer-term (6 and 12 months) impact of bariatric surgery; as well as the short-term effect of caloric restriction (CR) on plasma ATX levels in patients with severe obesity. We measured ATX levels in 69 men and women (mean age: 41 ± 11 years, body mass index: 49.8 ± 7.1 kg/m2 ), before and after biliopancreatic diversion with duodenal switch surgery (BPD-DS) as well as in a control group (patients with severe obesity without surgery; n = 34). We also measured ATX levels in seven patients with severe obesity and type 2 diabetes who underwent a 3-day CR protocol before their BPD-DS. At baseline, ATX levels were positively associated with body mass index, fat mass, insulin resistance (HOMA-IR) as well as insulin and leptin levels and negatively with fat-free mass. ATX concentrations decreased 26.2% at 24 h after BPD-DS (342.9 ± 152.3 pg/mL to 253.2 ± 68.9 pg/mL, P < 0.0001) and by 16.4% at 12 months after BPD-DS (342.9 ± 152.3 pg/mL to 286.8 ± 182.6 pg/mL, P = 0.04). ATX concentrations were unchanged during follow-up in the control group (P = 0.4), and not influenced by short-term CR. In patients with severe obesity, bariatric surgery induced a rapid and sustained decrease in plasma ATX levels. Acute changes in ATX may not be explained by bariatric surgery-induced CR.