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Guénard, Frédéric

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Université Laval. Institut sur la nutrition et les aliments fonctionnels
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Voici les éléments 1 - 10 sur 17
  • Publication
    Accès libre
    Bariatric surgery induces hypomethylation of genes related to type 2 diabetes and insulin resistance
    (MedCrave Group, 2017-04-21) Guénard, Frédéric; Toro Martin, Juan de; Marceau, Picard; Deshaies, Yves; Vohl, Marie-Claude; Tchernof, André
    Biliopancreatic diversion with duodenal switch (BPD-DS) is a surgical intervention known to induce substantial weight loss and significant long-lasting metabolic improvements including a decrease in insulin resistance (IR) and resolution of type 2diabetes(T2D). The specific mechanisms by which metabolic improvements occur after BPD-DS are still not fully elucidated and the impact of BPD-DS on gene methylation profiles has not been studied. To gain understanding of epigenetic factors that may predispose to metabolic improvements after weight loss surgery, we characterized the methylation signature of genes associated to T2D and IR after BPD-DS. Most of the genes involved in T2D and IR pathways exhibited significant differences in methylation levels after BPD-DS compared to a pre-surgery control group. The majority of these loci were significantly hypomethylated, suggesting an effect of bariatric surgery on the epigenetic signature of genes encoding proteins involved in glucose homeostasis.
  • Publication
    Accès libre
    Differential methylation of inflammatory and insulinotropic genes after metabolic surgery in women
    (iMed Pub LLC, 2015-10-03) Guénard, Frédéric; Marceau, Picard; Cianflone, Katherine M.; Deshaies, Yves; Vohl, Marie-Claude; Tchernof, André; Kral, John G.
    Context: Biliopancreatic diversion with duodenal switch (BPD-DS), a metabolic bariatric operation, induces durable loss of excess weight and reduced cardiometabolic risk. Altered epigenetic marks are mechanistically associated with environment-driven phenotypic variations. Objective: The current study aimed to compare gene methylation levels before and after BPD-DS to identify epigenetic marks potentially linked to metabolic improvements induced by BPD-DS. Design and patients: Metabolic risk factors and gene methylation levels of 20 women studied mean 12 years (range 4-22) after BPD-DS were compared to those of 20 severely obese surgical candidates as controls, matched for pre-surgical age, body mass index and dyslipidemia and hypertension prevalences. Whole-genome blood DNA methylation analysis enabled between-group differential methylation analyses. We calculated correlations between methylation levels of the most differentially methylated CpG sites and plasma glucose and insulin levels and HOMA-IR. Results: Differential methylation analysis identified 15,343 genes demonstrating at least one differentially methylated CpG site (p<1.43x10-7). Diabetic and inflammation/immune functions were among the most overrepresented from the 200 genes exhibiting the largest group differences in methylation levels. CpG sites methylation levels of genes related to insulin action correlated significantly with fasting insulin levels and homeostatic model of insulin resistance (p≤0.002 for all). Conclusion: These findings suggest that differential methylation levels in obese controls versus treated women may partially explain the durable metabolic improvements after BPD-DS.
  • Publication
    Differential methylation in visceral adipose tissue of obese men discordant for metabolic disturbances
    (American Physiological Society, 2014-03-15) Guénard, Frédéric; Biron, Simon; Biertho, Laurent; Pérusse, Louis; Lescelleur, Odette; Vohl, Marie-Claude; Deshaies, Yves; Marceau, Simon; Tchernof, André
    Obesity is associated with an increased risk of Type 2 diabetes and cardiovascular diseases (CVD). The severely obese population is heterogeneous regarding CVD risk profile. Our objective was to identify metabolic pathways potentially associated with development of metabolic syndrome (MetS) through an analysis of overrepresented pathways from differentially methylated genes between severely obese men with (MetS+) and without (MetS-) the MetS. Genome-wide quantitative DNA methylation analysis in VAT of severely obese men was carried out using the Infinium HumanMethylation450 BeadChip. Differences in methylation levels between MetS+ (n = 7) and MetS- (n = 7) groups were tested. Overrepresented pathways from the list of differentially methylated genes were identified and visualized with the Ingenuity Pathway Analysis system. Differential methylation analysis between MetS+ and MetS- groups identified 8,578 methylation probes (3,258 annotated genes) with significant differences in methylation levels (false discovery rate-corrected DiffScore ≥ |13| ∼ P ≤ 0.05). Pathway analysis from differentially methylated genes identified 41 overrepresented (P ≤ 0.05) pathways. The most overrepresented pathways were related to structural components of the cell membrane, inflammation and immunity and cell cycle regulation. This study provides potential targets associated with adipose tissue dysfunction and development of the MetS.
  • Publication
    Accès libre
    Body mass index is associated with epigenetic age acceleration in the visceral adipose tissue of subjects with severe obesity
    (Springer, 2019-12-02) Guénard, Frédéric; Toro Martin, Juan de; Hould, Frédéric-Simon; Vohl, Marie-Claude; Lebel, Stéfane; Tchernof, André; Julien, François; Marceau, Simon
    Background There is solid evidence that obesity induces the acceleration of liver epigenetic aging. However, unlike easily accessible blood or subcutaneous adipose tissue, little is known about the impact of obesity on epigenetic aging of metabolically active visceral adipose tissue (VAT). Herein, we aimed to test whether obesity accelerates VAT epigenetic aging in subjects with severe obesity. Results A significant and positive correlation between chronological age and epigenetic age, estimated with a reduced version of the Horvath’s epigenetic clock, was found in both blood (r = 0.78, p = 9.4 × 10−12) and VAT (r = 0.80, p = 1.1 × 10−12). Epigenetic age acceleration, defined as the residual resulting from regressing epigenetic age on chronological age, was significantly correlated with body mass index (BMI) in VAT (r = 0.29, p = 0.037). Multivariate linear regression analysis showed that, after adjusting for chronological age, sex and metabolic syndrome status, BMI remained significantly associated with epigenetic age acceleration in VAT (beta = 0.15, p = 0.035), equivalent to 2.3 years for each 10 BMI units. Binomial logistic regression showed that BMI-adjusted epigenetic age acceleration in VAT was significantly associated with a higher loss of excess body weight following biliopancreatic diversion with duodenal switch surgery (odds ratio = 1.21; 95% CI = 1.04–1.48; p = 0.03). Conclusions Epigenetic age acceleration increases with BMI in VAT, but not in blood, as previously reported in liver. These results suggest that obesity is associated with epigenetic age acceleration of metabolically active tissues. Further studies that deepen the physiological relevance of VAT epigenetic aging will help to better understand the onset of metabolic syndrome and weight loss dynamics following bariatric surgery.
  • Publication
    Accès libre
    Characterization of functional methylomes by next-generation capture sequencing identifies novel disease-associated variants
    (Nature Publishing Group, 2015-02-28) Allum, Fiona; Guénard, Frédéric; Shao, Xiaojian; Vohl, Marie-Claude; Lessard, Julie.; Simon, Marie-Michelle; Tchernof, André; Busche, Stephan; Caron, Maxime; Lambourn, John; Tandre, Karolina; Hedman, Asa K.; Kwan, Tony; Ge, Bing; Rönnblom, Lars; McCarthy, Mark I.; Deloukas, Panos; Richmond, Todd; Burgess, Daniel; Spector, T. D. (Timothy David); Marceau, Simon; Lathrop, Mark; Pastinen, Tomi; Grundberg, Elin
    Most genome-wide methylation studies (EWAS) of multifactorial disease traits use targetedarrays or enrichment methodologies preferentially covering CpG-dense regions, tocharacterize sufficiently large samples. To overcome this limitation, we present here a newcustomizable, cost-effective approach, methylC-capture sequencing (MCC-Seq), forsequencing functional methylomes, while simultaneously providing genetic variationinformation. To illustrate MCC-Seq, we use whole-genome bisulfite sequencing on adiposetissue (AT) samples and public databases to design AT-specific panels. We establish itsefficiency for high-density interrogation of methylome variability by systematic comparisonswith other approaches and demonstrate its applicability by identifying novel methylationvariation within enhancers strongly correlated to plasma triglyceride and HDL-cholesterol,including atCD36. Our more comprehensive AT panel assesses tissue methylation andgenotypes in parallel atB4 andB3 M sites, respectively. Our study demonstrates thatMCC-Seq provides comparable accuracy to alternative approaches but enables more efficientcataloguing of functional and disease-relevant epigenetic and genetic variants for large-scale EWAS.
  • Publication
    Accès libre
    Methylation and expression of immune and inflammatory genes in the offspring of bariatric bypass surgery patients.
    (Hindawi, 2013-06-11) Guénard, Frédéric; Marceau, Picard; Cianflone, Katherine M.; Vohl, Marie-Claude; Kral, John G.; Deshaies, Yves; Tchernof, André
    Background. Maternal obesity, excess weight gain and overnutrition during pregnancy increase risks of obesity, type 2 diabetes mellitus, and cardiovascular disease in the offspring. Maternal biliopancreatic diversion is an effective treatment for severe obesity and is beneficial for offspring born after maternal surgery (AMS). These offspring exhibit lower severe obesity prevalence and improved cardiometabolic risk factors including inflammatory marker compared to siblings born before maternal surgery (BMS). Objective. To assess relationships between maternal bariatric surgery and the methylation/expression of genes involved in the immune and inflammatory pathways. Methods. A differential gene methylation analysis was conducted in a sibling cohort of 25 BMS and 25 AMS offspring from 20 mothers. Following differential gene expression analysis (23 BMS and 23 AMS), pathway analysis was conducted. Correlations between gene methylation/expression and circulating inflammatory markers were computed. Results. Five immune and inflammatory pathways with significant overrepresentation of both differential gene methylation and expression were identified. In the IL-8 pathway, gene methylation correlated with both gene expression and plasma C-reactive protein levels. Conclusion. These results suggest that improvements in cardiometabolic risk markers in AMS compared to BMS offspring may be mediated through differential methylation of genes involved in immune and inflammatory pathways.
  • Publication
    Accès libre
    Remodeling adipose tissue through in silico modulation of fat storage for the prevention of type 2 diabetes
    (BioMed Central, 2017-06-12) Chénard, Thierry; Guénard, Frédéric; Vohl, Marie-Claude; Tchernof, André; Carpentier, André; Najmanovich, Rafaël
    Background: Type 2 diabetes is one of the leading non-infectious diseases worldwide and closely relates to excess adipose tissue accumulation as seen in obesity. Specifically, hypertrophic expansion of adipose tissues is related to increased cardiometabolic risk leading to type 2 diabetes. Studying mechanisms underlying adipocyte hypertrophy could lead to the identification of potential targets for the treatment of these conditions. Results: We present iTC1390adip, a highly curated metabolic network of the human adipocyte presenting various improvements over the previously published iAdipocytes1809. iTC1390adip contains 1390 genes, 4519 reactions and 3664 metabolites. We validated the network obtaining 92.6% accuracy by comparing experimental gene essentiality in various cell lines to our predictions of biomass production. Using flux balance analysis under various test conditions, we predict the effect of gene deletion on both lipid droplet and biomass production, resulting in the identification of 27 genes that could reduce adipocyte hypertrophy. We also used expression data from visceral and subcutaneous adipose tissues to compare the effect of single gene deletions between adipocytes from each compartment. Conclusions: We generated a highly curated metabolic network of the human adipose tissue and used it to identify potential targets for adipose tissue metabolic dysfunction leading to the development of type 2 diabetes
  • Publication
    Accès 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.
  • Publication
    Accès libre
    Temporal changes in gene expression profile during mature adipocyte dedifferentiation
    (Hindawi Publishing Corporation, 2017-03-19) Guénard, Frédéric; Biron, Simon; Lapointe, Marc-André; Vohl, Marie-Claude; Côté, Julie Anne; Lessard, Julie.; Tchernof, André
    Objective. To characterize changes in gene expression profile during human mature adipocyte dedifferentiation in ceiling culture. Methods. Subcutaneous (SC) and omental (OM) adipose tissue samples were obtained from 4 participants paired for age and BMI. Isolated adipocytes were dedifferentiated in ceiling culture. Gene expression analysis at days 0, 4, 7, and 12 of the cultures was performed using Affymetrix Human Gene 2.0 STvi arrays. Hierarchical clustering according to similarity of expression changes was used to identify overrepresented functions. Results. Four clusters gathered genes with similar expression between day 4 to day 7 but decreasing expression from day 7 to day 12. Most of these genes coded for proteins involved in adipocyte functions (LIPE, PLIN1, DGAT2, PNPLA2, ADIPOQ, CEBPA, LPL, FABP4, SCD, INSR, and LEP). Expression of several genes coding for proteins implicated in cellular proliferation and growth or cell cycle increased significantly from day 7 to day 12 (WNT5A, KITLG, and FGF5). Genes coding for extracellular matrix proteins were differentially expressed between days 0, 4, 7, and 12 (COL1A1, COL1A2, and COL6A3, MMP1, and TGFB1). Conclusion. Dedifferentiation is associated with downregulation of transcripts encoding proteins involved in mature adipocyte functions and upregulation of genes involved in matrix remodeling, cellular development, and cell cycle.
  • Publication
    Polygenic risk score for predicting weight loss after bariatric surgery
    (American Society for Clinical Investigation, 2018-09-06) Guénard, Frédéric; Toro Martin, Juan de; Pérusse, Louis; Marceau, Simon; Vohl, Marie-Claude; Tchernof, André
    BACKGROUND. The extent of weight loss among patients undergoing bariatric surgery is highly variable. Herein, we tested the contribution of genetic background to such interindividual variability after biliopancreatic diversion with duodenal switch. METHODS. Percentage of excess body weight loss (%EBWL) was monitored in 865 patients over a period of 48 months after bariatric surgery, and 2 polygenic risk scores were constructed with 186 and 11 (PRS₁₈₆ and PRS₁₁) single nucleotide polymorphisms previously associated with BMI. RESULTS. The accuracy of the %EBWL logistic prediction model — including initial BMI, age, sex, and surgery modality, and assessed as the area under the receiver operating characteristics (ROC) curve adjusted for optimism ((AUCadj= 0.867) — significantly increased after the inclusion of PRS186 (ΔAUCadj = 0.021; 95% CI of the difference (95% CIdiff) = 0.0046–0.038) but not PRS11 (ΔAUCadj= 0.008; 95% CIdiff= –0.003–0.019). The overall fit of the longitudinal linear mixed model for %EBWL showed a significant increase after addition of PRS₁₈₆ (–2 log-likelihood = 12.3; P = 0.002) and PRS11 (–2 log-likelihood = 9.9; P = 0.007). A significant interaction with postsurgery time was found for PRS₁₈₆ (β = –0.003; P = 0.008) and PRS₁₁ (β = –0.008; P = 0.03). The inclusion of PRS₁₈₆ and PRS₁₁ into the model improved the cost-effectiveness of bariatric surgery by reducing the percentage of false negatives from 20.4% to 10.9% and 10.2%, respectively. CONCLUSION. These results revealed that genetic background has a significant impact on weight loss after biliopancreatic diversion with duodenal switch. Likewise, the improvement in weight loss prediction after addition of polygenic risk scores is cost-effective, suggesting that genetic testing could potentially be used in the presurgical assessment of patients with severe obesity.