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Hould, Frédéric-Simon

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Frédéric-Simon

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Université Laval. Département de chirurgie

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Voici les éléments 1 - 10 sur 13
  • PublicationAccès libre
    Methylation quantitative trait loci within the TOMM20 gene are associated with metabolic syndrome-related lipid alterations in severely obese subjects
    (BioMed Central Ltd., 2016-07-29) Toro Martin, Juan de; Guénard, Frédéric; Pérusse, Louis; Hould, Frédéric-Simon; Marceau, Picard; Vohl, Marie-Claude; Deshaies, Yves; Lebel, Stéfane; Tchernof, André
    Background : The TOMM20 gene was previously identified as differentially expressed and methylated between severely obese subjects with and without metabolic syndrome (MS). Since metabolic complications do not affect all obese patients to the same extent, the aim of this study was to identify methylation quantitative trait loci (meQTL) potentially associated with MS-related complications within the TOMM20 locus. Methods : Methylation profiling, SNP genotyping and meQTL association tests (general linear models) were performed in a population of 48 severely obese subjects. Genotyping was extended to a larger population of 1720 severely obese subjects with or without MS, where genotype- and diplotype-based association tests were assessed by logistic regression. In silico analyses were performed using TRAP. Results : Four SNPs were identified as significant meQTLs for the differentially methylated site cg16490124. Individuals carrying rare alleles of rs4567344 (A > G) (P = 4.9 × 10−2) and rs11301 (T > C) (P = 5.9 × 10−3) showed decreased methylation levels at this site, whereas those carrying rare alleles of rs4551650 (T > C) (P = 3.5 × 10−15) and rs17523127 (C > G) (P = 3.5 × 10−15) exhibited a significant increase in methylation. rs4567344 and rs11301 were associated with increased susceptibility to exhibit high plasma triglycerides (TG ≥ 1.69 mmol/L), while rare alleles of rs4551650 and rs17523127 were significantly more represented in the low plasma total-C group (total-C ≤ 6.2 mmol/L). Haplotype reconstruction with the four meQTLs (rs4567344, rs11301, rs4551650, rs17523127) led to the identification of ten different diplotypes, with H1/H2 (GCGG/ACGG) exhibiting a nearly absence of methylation at cg16490124, and showing the highest risk of elevated plasma TG levels [OR = 2.03 (1.59–3.59)], a novel association with elevated LDL-cholesterol [OR = 1.86 (1.06–3.27)] and the complete inversion of the protective effect on total-C levels [OR = 2.03 (1.59–3.59)], especially in men. In silico analyses revealed that rs17523127 overlapped the CpG site cg16490124 and encompassed the core binding sites of the transcription factors Egr 1, 2 and 3, located within the TOMM20 promoter region. Conclusion : This study demonstrates that TOMM20 SNPs associated with MS-related lipid alterations are meQTLs potentially exerting their action through a CpG methylation-dependent effect. The strength of the diplotype-based associations may denote a novel meQTL additive action and point to this locus as particularly relevant in the inter-individual variability observed in the metabolic profiles of obese subjects.
  • PublicationAccès libre
    Use of blood as a surrogate model for the assessment of visceral adipose tissue methylation profiles associated with the metabolic syndrome in men
    (Library Pub. Media, 2016-01-12) Guénard, Frédéric; Hould, Frédéric-Simon; Deshaies, Yves; Marceau, Picard; Vohl, Marie-Claude; Lebel, Stéfane; Tchernof, André
    Epigenetic mechanisms are known to be involved in tissue-specific differentiation. DNA methylation patterns have been shown to be largely conserved across tissues but with variation for specific genes. However, it is unclear whether the variability observed in the methylation profile of a metabolically active tissue is reflected in other sources such as hematopoietic tissue. This study aimed to test blood genome-wide CpG site methylation levels as a surrogate model for visceral adipose tissue (VAT) methylation and to verify whether it appropriately reflects differences in methylation levels found in VAT between men discordant for the metabolic syndrome (MetS). Tissue specimens (VAT and blood samples) were obtained from 16 severely obese individuals discordant for the MetS. CpG sites methylation levels were measured with the Infinium HumanMethylation450 BeadChip and correlations of methylation levels between VAT and blood were computed. Differences in methylation levels between individuals with and without MetS were tested in both tissues. Pathway analysis was conducted for differentially methylated CpG sites common to both tissues. High cross-tissue correlations were observed for VAT and blood (0.952±0.014) while some CpG sites had significantly different methylation levels in VAT versus blood. Differential methylation analysis between individuals with and without MetS demonstrated a higher number of differentially methylated CpG sites in VAT than in blood (11,778 vs. 881, respectively) with nearly 4% of differentially methylated sites found in VAT being also represented in blood. Common differentially methylated sites were involved in inflammatory-, lipid- and diabetes-related pathways. These results suggest that blood methylation levels of specific CpG sites may adequately reflect VAT methylation levels for some of the MetS-related genes, specifically for inflammatory, lipid and glucose metabolism genes.
  • PublicationAccès libre
    Characterization of dedifferentiating human mature adipocytes from the 6 visceral and subcutaneous fat compartments : fibroblast-activation protein 7 alpha and Dipeptidyl peptidase 4 as major components of matrix remodeling
    (Public Library of Science, 2015-03-27) Biron, Simon; Biertho, Laurent; Lescelleur, Odette; Hould, Frédéric-Simon; Marceau, Simon; Marceau, Picard; Moustarah, Fady; Lebel, Stéfane; Pelletier, Mélissa; Lessard, Julie.; Tchernof, André
    Mature adipocytes can reverse their phenotype to become fibroblast-like cells. This is achieved by ceiling culture and the resulting cells, called dedifferentiated fat (DFAT) cells, are multipotent. Beyond the potential value of these cells for regenerative medicine, the dedifferentiation process itself raises many questions about cellular plasticity and the pathways implicated in cell behavior. This work has been performed with the objective of obtaining new information on adipocyte dedifferentiation, especially pertaining to new targets that may be involved in cellular fate changes. To do so, omental and subcutaneous mature adipocytes sampled from severely obese subjects have been dedifferentiated by ceiling culture. An experimental design with various time points along the dedifferentiation process has been utilized to better understand this process. Cell size, gene and protein expression as well as cytokine secretion were investigated. Il-6, IL-8, SerpinE1 and VEGF secretion were increased during dedifferentiation, whereas MIF-1 secretion was transiently increased. A marked decrease in expression of mature adipocyte transcripts (PPARγ2, C/EBPα, LPL and Adiponectin) was detected early in the process. In addition, some matrix remodeling transcripts (FAP, DPP4, MMP1 and TGFβ1) were rapidly and strongly up-regulated. FAP and DPP4 proteins were simultaneously induced in dedifferentiating mature adipocytes supporting a potential role for these enzymes in adipose tissue remodeling and cell plasticity.
  • PublicationRestreint
    Comprehensive genetic analysis of the dipeptidyl peptidase-4 gene and cardiovascular disease risk factors in obese individuals
    (SpringerLink, 2008-08-06) Faucher, Geneviève; Hould, Frédéric-Simon; Marceau, Picard; Vohl, Marie-Claude; Lebel, Stéfane; Deshaies, Yves; Bouchard, Luigi; Tchernof, André
    The incretin system has been shown to stimulate insulin secretion in a glucose dependent manner and currently fosters considerable hope for the treatment of diabetes. Recently, we have shown that the dipeptidylpeptidase-4 (DPP4) gene, which is responsible for incretin inactivation, was overexpressed in omental adipose tissue of obese men with the metabolic syndrome, compared to men not characterized by this condition. Since the cardiovascular disease (CVD) risk profile shows substantial inter-individual variability in obesity, this study aimed at verifying whether DPP4 polymorphisms contribute to explain such a difference. In the first step of this multi-stage study, seven tagging SNPs were genotyped in a sample of 576 obese (BMI > 40 kg/m2) individuals and tested for their association with blood pressure and lipids, as well as diabetes-related phenotypes. Then, in an additional sample of 572 obese individuals (stage 2), SNPs showing trends (P < 0.10) for an association in the first sample were genotyped and reanalyzed. Logistic regressions were used to compute odds ratio for obesity-related metabolic complications. In sample 1, homozygotes for rs17848915 and rs7608798 minor alleles were at lower risk of hyperglycemia/diabetes (P = 0.002) and elevated plasma triglyceride levels (P = 0.030) respectively, whereas rs1558957 heterozygotes were at higher risk to have high plasma triglyceride (P = 0.040), HDL- (P = 0.021), LDL- (P = 0.001) and total-cholesterol (P = 0.003) levels. However, none of these associations was consistently replicated in stage 2. This first comprehensive genetic analysis does not support the notion that DPP4 polymorphisms could modulate the CVD risk profile among obese patients.
  • PublicationAccès libre
    Biliopancreatic diversion with duodenal switch in the elderly : long-term results of a matched-control study
    (Springer, 2015-07-01) Marchand, Geneviève B.; Biron, Simon; Biertho, Laurent; Lebel, Stéfane; Lescelleur, Odette; Nadeau, Mélanie; Marceau, Simon; Hould, Frédéric-Simon; Michaud, Andréanne; Tchernof, André
    Background : Biliopancreatic diversion with duodenal switch (BPD-DS) is one of the most effective surgical approaches for the treatment of severe obesity. Objective : The objective of this study is to compare perioperative complications and long-term results of open BPD-DS in elderly versus younger patients. Methods : All patients aged 60 years and above who underwent a primary open BPD-DS in our center were selected (n = 105). Patients were matched 1:1 for sex, BMI, the presence of type 2 diabetes (T2DM), and year of surgery with a group of younger patients (aged ≤55 years). Results : The mean age of the patients was 62.3 ± 2.0 vs. 40.4 ± 7.0 years (p ≤ 0.0001). Initial BMI and prevalence of T2DM were similar in both groups, at 50.9 kg/m2 and 57 %, respectively. Mean operative time (178.6 ± 46.7 vs. 162.5 ± 39.9 min, p = 0.01), hospital stay (10.2 ± 8.3 vs. 6.3 ± 1.5 days, p = 0.0001), and blood loss (593 ± 484 vs. 474 ± 241 ml, p = 0.05) were significantly higher in elderly patients. No difference in 30-day mortality rate was observed (0.9 % in each group). There was no significant difference in major complication rate (16.2 vs. 8.6 %, p = 0.09). At a mean follow-up of 7.1 ± 4.1 years, excess weight loss (67.6 ± 19.2 vs. 72.7 ± 20.7 %, p = 0.06) and BMI (32.2 ± 5.7 vs. 30.8 ± 6.6 kg/m2, p = 0.15) were not significantly different. No significant difference was observed between the two groups for the resolution of T2DM (p = 0.53) and obstructive sleep apnea (p = 0.44). Conclusions : Open BPD-DS is associated with similar long-term benefits in elderly and younger patients, in terms of weight loss and resolution or improvement of obesity-related comorbidities. Perioperative complications might be more frequent in the elderly population, but this was not associated with increased mortality.
  • PublicationRestreint
    Effects of the peroxisome proliferator-activated receptor-gamma co-activator-1 Gly482Ser variant on features of the metabolic syndrome
    (Academic Press, 2005-08-24) Hould, Frédéric-Simon; Marceau, Picard; Lebel, Stéfane; Houde, Alain; Vohl, Marie-Claude
    Factors influencing the severity of the metabolic syndrome among obese subjects or the conversion to cardiovascular disease or type 2 diabetes (T2D) remain largely unknown, but there is strong evidence for genetic susceptibilities. Peroxisome proliferator-activated receptor-γ co-activator-1 (PPARGC1) is a transcriptional co-activator of many nuclear receptors including PPAR-γ, involved in the regulation of fatty acid oxidation, skeletal muscle fiber type specificity, and gluconeogenesis. Given the critical role of PPARGC1, it becomes a promising candidate gene for the metabolic syndrome and T2D. This study aimed to investigate whether genetic variations in human PPARGC1 gene are associated with metabolic syndrome-related phenotypes and T2D among obese subjects. Molecular screening of the PPARGC1 gene in 24 morbidly obese French-Canadians revealed 13 variants. Eight genetic variations were in introns: c.55-27T > A, c.234 + 52C > A, c.553-40A > G, c.553-11T > C, c.757 + 161T > C, c.1793 + 19C > G, c.2141 + 192G > A, and c.2293+146A > G, and five were in coding regions: Thr394Thr, Asp475Asp, Gly482Ser, Thr528Thr, and Thr612Met with a relative allele frequency of 18.5, 5.2, 37.0, 42.5, and 6.8%, respectively. Thr394Thr, Asp475Asp, and Thr528Thr were in linkage disequilibrium with the Gly482Ser variant, the only non-synonymous variant with a relative allele frequency of more than 10%. Association studies were performed with the Gly482Ser variant. In non-diabetics, we compared between genotype differences in metabolic syndrome-related traits (waist girth, SBP, DBP, triglycerides, HDL-cholesterol (C), and fasting glucose levels). There was a difference in mean plasma HDL-C concentrations, the Gly/Gly group had lower concentrations than the Gly/Ser group (P < 0.05). These results suggest that the Gly482Ser polymorphism may explain some of the between-obese variance observed in metabolic syndrome-related traits.
  • PublicationAccès libre
    The rare allele of DGKZ SNP rs10838599 is associated with variability in HDL-cholesterol levels among severely obese patients
    (Open Access Text Pvt. Ltd, 2016-05-12) Guénard, Frédéric; Pérusse, Louis; Hould, Frédéric-Simon; Deshaies, Yves; Marceau, Picard; Bégin, Stéphanie; Vohl, Marie-Claude; Lebel, Stéfane; Tchernof, André
    Introduction: Diacylglycerol kinase-zeta, one of the ten isoforms of DGKs expressed in mammals is an important enzyme of lipid metabolism. It catalyzes the interconversion of diacylglycerol and phosphatidic acid, two major second messengers. Its gene DGKZ has been previously identified as being overexpressed and undermethylated in visceral adipose tissue of patients with (MetS+) versus without (MetS-) the metabolic syndrome (MetS). Objective: The aim of this study was to investigate the associations between DGKZ gene polymorphisms (SNPs) and phenotypes related to MetS (BMI, waist girth, CRP, fasting glucose, lipid profile (triglycerides, total-cholesterol, LDL-cholesterol and HDL-cholesterol (HDL-C)), resting systolic and diastolic blood pressures). Methods: The study sample included 1752 severely obese participants who underwent bariatric surgery. Associations between the five selected tSNPs of DGKZ and features of the MetS were tested. The effects of these SNPs on DGKZ methylation and expression levels were tested in subgroups of 32 and 14 obese subjects, respectively. Correlations between methylation and expression levels were also computed. Results: Homozygotes for the rare allele of rs10838599 displayed higher plasma HDL-C concentrations compared to the other genotype groups (p=0.03). For gene methylation, only a trend with the cg05412031 CpG site (p=0.09) was found for the single significantly phenotype-associated SNP. There was no significant correlation between DGKZ methylation at cg05412031 and expression levels. Conclusion: These results suggest that DGKZ SNP rs10838599 modulates plasma HDL-C levels thereby its gene contributes to the inter-individual variability observed in the cardiometabolic risk profile of patients with severe obesity.
  • PublicationAccès libre
    DUSP1 gene polymorphisms are associated with obesity-related metabolic complications among severely obese patients and impact on gene methylation and expression
    (Hindawi Publishing Corporation, 2013-08-06) Guénard, Frédéric; Pérusse, Louis; Bouchard, Luigi; Hould, Frédéric-Simon; Marceau, Picard; Vohl, Marie-Claude; Deshaies, Yves; Lebel, Stéfane; Tchernof, André
    The DUSP1 gene encodes a member of the dual-specificity phosphatase family previously identified as being differentially expressed in visceral adipose tissue (VAT) of severely obese men with versus without the metabolic syndrome. Objective. To test the association between DUSP1 polymorphisms, obesity-related metabolic complications, gene methylation, and expression levels in VAT. Methods. The DUSP1 locus and promoter region were sequenced in 25 individuals. SNPs were tested for association with obesity-related complications in a cohort of more than 1900 severely obese individuals. The impact of SNPs on methylation levels of 36 CpG sites and correlations between DNA methylation and gene expression levels in VAT were computed in a subset of 14 samples. Results. Heterozygotes for rs881150 had lower HDL-cholesterol levels (HDL-C; P = 0.01), and homozygotes for the minor allele of rs13184134 and rs7702178 had increased fasting glucose levels (P = 0.04 and 0.01, resp.). rs881150 was associated with methylation levels of CpG sites located ~1250 bp upstream the transcription start site. Methylation levels of 4 CpG sites were inversely correlated with DUSP1 gene expression. Conclusion. These results suggest that DUSP1 polymorphisms modulate plasma glucose and HDL-C levels in obese patients possibly through alterations of DNA methylation and gene expression levels.
  • PublicationRestreint
    Contribution of genetic and metabolic syndrome to omental adipose tissue PAI-1 gene mRNA and plasma levels in obesity
    (Springer Nature, 2010-02-02) Pérusse, Louis; Mauriege, Pascale; Lebel, Stéfane; Hould, Frédéric-Simon; Marceau, Picard; Vohl, Marie-Claude; Bouchard, Luigi; Bergeron, Jean
    Background Plasminogen activator inhibitor type-1 (PAI-1) has already been associated with atherosclerosis; myocardial infarction; and cardiovascular disease risk factors such as obesity, insulin resistance, and dyslipidemia. However, factors regulating PAI-1 adipose tissue (AT) gene expression and plasma levels are not yet well defined. Aim This study aims to assess the contribution of PAI-1 omental AT mRNA levels and genetic and metabolic factors to variation in plasma PAI-1 concentrations. Methods Ninety-one non-diabetic premenopausal severely obese women (body mass index, BMI >35 kg/m2) undergoing bariatric surgery were phenotyped (fasting plasma glucose, lipid-lipoprotein, and PAI-1 levels) and genotyped for four PAI-1 polymorphisms. Omental AT PAI-1 mRNA levels were determined using real-time polymerase chain reaction. Stepwise regression analysis was used to identify independent PAI-1 AT mRNA and plasma level predictors. Results Among the variables included to the stepwise regression analysis, plasma high-density lipoprotein (HDL)-cholesterol (r = 0.38; p = 0.0004) and total cholesterol (r = 0.16; p = 0.0541) levels were the only two (out of 12) independent variables retained as predictive of PAI-1 omental AT mRNA levels, whereas BMI (r = 0.35; p = 0.0039), plasma HDL-cholesterol concentrations (r = −0.31; p = 0.0375), PAI-1 omental AT mRNA levels (r = 0.19; p = 0.0532) and PAI-1-844G/A (p = 0.0023), and rs6092 (p.A15T; p = 0.0358) polymorphisms contributed independently to plasma PAI-1 concentrations. Taken together, these variables explained 17.8% and 31.0% of the variability in PAI-1 AT mRNA and plasma levels, respectively. Conclusion These results suggest that PAI-1 polymorphisms contribute significantly to PAI-1 plasma levels but do not support the notion that omental AT is one of its major source.
  • PublicationRestreint
    A polymorphism of the interferon-gamma-inducible protein 30 gene is associated with hyperglycemia in severely obese individuals
    (Springer-Verlag, 2011-01-24) Pérusse, Louis; Turcot, Valérie; Faucher, Geneviève; Hould, Frédéric-Simon; Marceau, Picard; Vohl, Marie-Claude; Deshaies, Yves; Bouchard, Luigi; Lebel, Stéfane; Tchernof, André
    A previous expression profiling of visceral adipose tissue (VAT) revealed that the immune response gene interferon-gamma-inducible protein 30 (IFI30) gene was 1.72-fold more highly expressed in non-diabetic severely obese men with the metabolic syndrome as compared to those without. Given the importance of low-grade inflammation in obesity-related metabolic complications, we hypothesized that variants in the IFI30 gene are associated with cardiovascular disease (CVD) risk factors. A detailed genetic investigation was performed at the IFI30 locus by sequencing its promoter, exons and intron-exon junction boundaries using DNA of 25 severely obese men. Among the 21 sequence-derived single-nucleotide polymorphisms (SNPs), 5 tagged SNPs (covering 100% of the common SNPs identified) were genotyped in two independent samples of severely obese patients (total n = 1,283). Using a multistage experimental design, chi-square analyses and logistic regressions were performed to compare genotype frequencies and compute odds-ratios (OR) for low and high CVD risk groups (dyslipidemia, hyperglycemia/diabetes and hypertension). A significant association was observed with the non-synonymous SNP rs11554159 (p.R76Q), where GA individuals showed lower risk (OR = 0.67; P = 0.0009) for hyperglycemia/diabetes as compared to homozygotes for the major allele (GG). No association was observed between rs11554159 and VAT IFI30 mRNA levels (P = 0.81), and the expression levels were not correlated with fasting plasma glucose levels (P = 0.31) in 112 non-diabetic severely obese women. The localization of rs11554159 near the active site of IFI30 suggests a functional effect of this SNP. This study showed a novel association between rs11554159 (p.R76Q) polymorphism at the IFI30 locus and the risk of hyperglycemia/diabetes in severely obese individuals.