49 research outputs found
Lâimpact dâune diĂšte nĂ©onatale dĂ©ficiente en nutriments essentiels Ă la dĂ©fense antioxydante sur le mĂ©tabolisme Ă©nergĂ©tique Ă long terme
Les prĂ©maturĂ©s subissent un stress oxydant qui rĂ©sulte dâune dĂ©fense antioxydante faible et/ou dâune charge oxydante. Des donnĂ©es suggĂšrent quâun stress oxydant peut affecter le mĂ©tabolisme Ă©nergĂ©tique et mener au syndrome mĂ©tabolique.
HypothÚse: Une faible défense antioxydante tÎt dans la vie est suffisante pour affecter le métabolisme énergétique à long terme.
MĂ©thodes: Quatre groupes de cobayes (n=21) ont reçu entre leurs 3e et 7e jours de vie une diĂšte standard (C-1sem, C-14sem) ou une diĂšte dĂ©ficiente (DC-1sem, DC-14sem). Ă 7 jours, les groupes C-1sem et DC-1sem ont Ă©tĂ© sacrifiĂ©s, le plasma et le foie collectĂ©s. Les groupes C-14sem et DC-14sem ont reçu la diĂšte standard jusquâĂ 14sem de vie. La glycĂ©mie et les triglycĂ©rides plasmatiques ont Ă©tĂ© mesurĂ©s Ă 1, 3, 11, et 13-14sem. La tolĂ©rance au glucose a Ă©tĂ© Ă©valuĂ©e Ă 13sem. Les antioxydants hĂ©patiques et les protĂ©ines rĂ©gulant le mĂ©tabolisme Ă©nergĂ©tique ont Ă©tĂ© analysĂ©s Ă 1 et 14sem.
RĂ©sultats: Un statut redox oxydĂ© du glutathion Ă©tait associĂ© avec la diĂšte dĂ©ficiente et Ă©tait maintenu oxydĂ© au moins jusquâĂ 14sem (p<0.01). Les faibles niveaux de triglycĂ©rides plasmatiques et de glycĂ©mies, ainsi quâune meilleure tolĂ©rance au glucose Ă 14sem (p<0.05) Ă©taient associĂ©s avec un statut redox plus oxydĂ©.
Conclusion: Le faible taux de glutathion observĂ© chez les prĂ©maturĂ©s a Ă©tĂ© reproduit dans notre modĂšle. Puisque nos donnĂ©es suggĂšrent un rĂŽle protecteur dâun redox plus oxydĂ© et que lâenvironnement redox est un important rĂ©gulateur mĂ©tabolique influençant le dĂ©veloppement, il faudrait faire attention avant dâinitier des traitements antioxydants agressifs chez les prĂ©maturĂ©s.Preterm infants are faced to oxidative stress resulting from a low antioxidant defence and/or a high oxidant load. Datas suggest that an oxidative stress may impair energy metabolism leading to metabolic syndrome development.
Hypothesis: A weak antioxidant defence early in life such as observed in preterm newborns is sufficient to impair energy metabolism later in life.
Methods: Four groups of guinea pigs (n=21) received between their 3rd and 7th days of life a control diet (C-1week, C-14weeks) or antioxidant deficient diet (DC-1week, DC-14weeks). At 7 day-old, 1week-groups were sacrificed for plasma and liver sampling whereas 14week-groups were fed with the control diet until 14 week-old. Blood glucose and plasma triacylglycerol were determined at 1, 3, 11 and 13-14 week-old. Glucose tolerance test was performed at 13 week-old. Hepatic antioxidant defences and key proteins regulating lipid and glucose metabolism were measured at 1 and 14 weeks.
Results: The oxidized redox status of glutathione associated with the neonatal deficient diet was maintained until at least 14 week-old (p<0.01). The low plasma triacylglycerol, low blood glucose and better tolerance to glucose at 14 weeks (p<0.05) were associated with an oxidized redox status.
Conclusion: The low glutathione observed in newborn preterm infants has been reproduced in our animal model. Since the oxidized redox state observed here seems to be protective against impaired energy metabolism and since the cellular redox environment is known to be an important rheostat of metabolism influencing development, it suggests being careful before adopting aggressive antioxidant treatments in preterm infants
Comparison of the dipeptidyl peptidase-4 gene methylation levels between severely obese subjects with and without the metabolic syndrome
Background : The dipeptidyl peptidase-4 (DPP4) enzyme is a novel adipokine potentially involved in the development of the metabolic syndrome (MetS). Previous observations demonstrated higher visceral adipose tissue (VAT) DPP4 gene expression in non-diabetic severely obese men with (MetS+) vs. without (MetSâ) MetS. DPP4 mRNA abundance in VAT correlated also with CpG site methylation levels (%Meth) localized within and near its exon 2 (CpG94 to CpG102) in non-diabetic severely obese women, regardless of their MetS status. The actual study tested whether DPP4 %Meth levels in VAT are different between MetSâ and MetS+ non-diabetic severely obese subjects, whether variable metabolic and plasma lipid profiles are observed between DPP4 %Meth quartiles, and whether correlation exists in DPP4 %Meth levels between VAT and white blood cells (WBCs).
Methods : DNA was extracted from the VAT of 26 men (MetSâ: n=12, MetS+: n=14) and 79 women (MetSâ: n=60; MetS+: n=19), as well as from WBCs in a sub-sample of 17 women (MetSâ: n=9; MetS+: n=8). The %Meth levels of CpG94 to CpG102 were assessed by pyrosequencing of sodium bisulfite-treated DNA. ANOVA analyses were used to compare the %Meth of CpGs between MetSâ and MetS+ groups, and to compare the metabolic phenotype and plasma lipid levels between methylation quartiles. Pearson correlation coefficient analyses were computed to test the relationship between VAT and WBCs CpG94-102 %Meth levels.
Results : No difference was observed in CpG94-102 %Meth levels between MetSâ and MetS+ subjects in VAT (P=0.67), but individuals categorized into CpG94-102 %Meth quartiles had variable plasma total-cholesterol concentrations (P=0.04). The %Meth levels of four CpGs in VAT were significantly correlated with those observed in WBCs (r=0.55â0.59, Pâ€0.03).
Conclusions : This study demonstrated that %Meth of CpGs localized within and near the exon 2 of the DPP4 gene in VAT are not associated with MetS status. The actual study also revealed an association between the %Meth of this locus with plasma total-cholesterol in severe obesity, which suggests a link between the DPP4 gene and plasma lipid levels
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Protein-coding variants implicate novel genes related to lipid homeostasis contributing to body-fat distribution.
Body-fat distribution is a risk factor for adverse cardiovascular health consequences. We analyzed the association of body-fat distribution, assessed by waist-to-hip ratio adjusted for body mass index, with 228,985 predicted coding and splice site variants available on exome arrays in up to 344,369 individuals from five major ancestries (discovery) and 132,177 European-ancestry individuals (validation). We identified 15 common (minor allele frequency, MAF â„5%) and nine low-frequency or rare (MAF <5%) coding novel variants. Pathway/gene set enrichment analyses identified lipid particle, adiponectin, abnormal white adipose tissue physiology and bone development and morphology as important contributors to fat distribution, while cross-trait associations highlight cardiometabolic traits. In functional follow-up analyses, specifically in Drosophila RNAi-knockdowns, we observed a significant increase in the total body triglyceride levels for two genes (DNAH10 and PLXND1). We implicate novel genes in fat distribution, stressing the importance of interrogating low-frequency and protein-coding variants
Rare and low-frequency coding variants alter human adult height
Height is a highly heritable, classic polygenic trait with ~700 common associated variants identified so far through genome - wide association studies . Here , we report 83 height - associated coding variants with lower minor allele frequenc ies ( range of 0.1 - 4.8% ) and effects of up to 2 16 cm /allele ( e.g. in IHH , STC2 , AR and CRISPLD2 ) , >10 times the average effect of common variants . In functional follow - up studies, rare height - increasing alleles of STC2 (+1 - 2 cm/allele) compromise d proteolytic inhibition of PAPP - A and increased cleavage of IGFBP - 4 in vitro , resulting in higher bioavailability of insulin - like growth factors . The se 83 height - associated variants overlap genes mutated in monogenic growth disorders and highlight new biological candidates ( e.g. ADAMTS3, IL11RA, NOX4 ) and pathways ( e.g . proteoglycan/ glycosaminoglycan synthesis ) involved in growth . Our results demonstrate that sufficiently large sample sizes can uncover rare and low - frequency variants of moderate to large effect associated with polygenic human phenotypes , and that these variants implicate relevant genes and pathways
Génétique et épigénétique du syndrome métabolique
L'obĂ©sitĂ© viscĂ©rale est souvent associĂ©e Ă un profil mĂ©tabolique dĂ©tĂ©riorĂ©, aussi dĂ©fini comme un syndrome mĂ©tabolique (SMet), et qui inclut une rĂ©sistance Ă l'insuline, une dyslipidĂ©mie et une hypertension. Les individus obĂšses ne sont pas tous Ă©gaux face au dĂ©veloppement du SMet et une dysfonction du tissu adipeux, de mĂȘme qu'une susceptibilitĂ© gĂ©nĂ©tique et Ă©pigĂ©nĂ©tique pourraient expliquer cette hĂ©tĂ©rogĂ©nĂ©itĂ©. Une prĂ©cĂ©dente analyse transcriptomique du tissu adipeux viscĂ©ral (TAV) a identifiĂ© plusieurs gĂšnes diffĂ©rentiellement exprimĂ©s entre des hommes avec obĂ©sitĂ© sĂ©vĂšre atteints (SMet+) ou non (SMet-) d'un SMet. Le principal objectif de cette thĂšse Ă©tait d'identifier des variations gĂ©nĂ©tiques et Ă©pigĂ©nĂ©tiques parmi des gĂšnes diffĂ©rentiel lement exprimĂ©s dans le TAV entre des hommes SMet+ et SMet- et qui sont associĂ©es Ă une variabilitĂ© de l'expression gĂ©nique et aux composantes du SMet chez des individus avec obĂ©sitĂ© sĂ©vĂšre. Des associations significatives ont Ă©tĂ© observĂ©es entre une variation gĂ©nĂ©tique des gĂšnes interferon-gamma-inducible protein 30 (IFI30) et thymic stromal lymphopoietin (TSIP) avec l'hyperglycĂ©mie / diabĂšte de type 2 et la pression artĂ©rielle, respectivement. Des niveaux plus faibles de mĂ©thylation globale de l'ADN du gĂ©nome, en quantifiant la mĂ©thylation des Ă©lĂ©ments rĂ©pĂ©titifs du gĂ©nome de type LINE-1, Ă©taient associĂ©s avec un plus grand risque de SMet. Les pourcentages de mĂ©thylation prĂšs de l'exon 2 du gĂšne dipeptidylpeptidase-4 (DPP4) Ă©taient associĂ©s avec son expression gĂ©nique dans le TAV et avec les concentrations de cholestĂ©rol-HDL, mais Ă©taient semblables entre un plus grand groupe d'individus SMet+ et SMet- dans le TAV et les globules blancs pĂ©riphĂ©riques. Finalement, une approche d'analyse in silico a Ă©tĂ© proposĂ©e afin de cibler des gĂšnes candidats de l'obĂ©sitĂ© dont l'expression serait potentiellement rĂ©gulĂ©e par la mĂ©thylation dans leur pomoteur. Cette derniĂšre Ă©tude a Ă©tĂ© effectuĂ©e lors d'un stage Ă l'Ă©tranger et l'approche proposĂ©e serait applicable dans d'autres contextes pathologiques, dont le SMet. Cette thĂšse dresse donc un aperçu des connaissances actuelles sur la gĂ©nĂ©tique et l'Ă©pigĂ©nĂ©tique du SMet et les rĂ©sultats qui y sont prĂ©sentĂ©s contribueront, Ă leur maniĂšre, Ă amĂ©liorer notre comprĂ©hension de la pathophysiologie du SMet, ainsi que la susceptibilitĂ© gĂ©nĂ©tique et Ă©pigĂ©nĂ©tique Ă dĂ©velopper des complications mĂ©taboliques en prĂ©sence d'obĂ©sitĂ©
DEPARTEMENT DES SCIENCES DES ALIMENTS ET DE NUTRITION
à la Faculté des études supérieures et postdoctorales de l'Université Laval dans le cadre du programme de doctorat en nutrition pour l'obtention du grade de Philosophiae doctor (Ph.D.