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Emile Levy - One of the best experts on this subject based on the ideXlab platform.
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Chylomicron Retention Disease: genetics, biochemistry, and clinical spectrum.
Current opinion in lipidology, 2019Co-Authors: Emile Levy, Pierre Poinsot, Schohraya SpahisAbstract:Purpose of reviewChylomicron Retention Disease (CRD) is an autosomic recessive disorder, in which intestinal fat malabsorption is the main cause of diverse severe manifestations. The specific molecular defect was identified in 2003 and consists of mutations in the SAR1B or SARA2 gene encoding for in
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Ernest G Seidman, Emile LevyAbstract:Background—Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the...
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Ernest Seidman, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Emile LevyAbstract:Background-Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the critical proteins governing Chylomicron secretion by the small intestine, and its mutations lead to Chylomicron Retention Disease, despite the presence of Sar1A paralog. Objective-The central aim of this work is to examine the cause-effect relationship between Sar1B expression and Chylomicron output and to determine whether Sar1B is obligatory for normal high-density lipoprotein biogenesis. Approach and Results-The SAR1B gene was totally silenced in Caco-2/15 cells using the zinc finger nuclease technique. SAR1B deletion resulted in significantly decreased secretion of triglycerides (approximate to 40%), apolipoprotein B-48 (approximate to 57%), and Chylomicron (approximate to 34.5%). The absence of expected Chylomicron production collapse may be because of the compensatory SAR1A elevation observed in our experiments. Therefore, a double knockout of SAR1A and SAR1B was engineered in Caco-2/15 cells, which led to almost complete inhibition of triglycerides, apolipoprotein B-48, and Chylomicron output. Further experiments with labeled cholesterol revealed the downregulation of high-density lipoprotein biogenesis in cells deficient in SAR1B or with the double knockout of the 2 SAR1 paralogs. Similarly, there was a fall in the movement of labeled cholesterol from cells to basolateral medium containing apolipoprotein A-I, thereby limiting newly synthesized high-density lipoprotein in genetically modified cells. The decreased cholesterol efflux was associated with impaired expression of ABCA1 (ATP-binding cassette subfamily A member 1). Conclusions-These findings demonstrate that the deletion of the 2 SAR1 isoforms is required to fully eliminate the secretion of Chylomicron in vitro. They also underscore the limited high-density lipoprotein production by the intestinal cells in response to SAR1 knockout. Visual Overview-An online visual overview is available for this article.
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Establishment of reference values of α-tocopherol in plasma, red blood cells and adipose tissue in healthy children to improve the management of Chylomicron Retention Disease, a rare genetic hypocholesterolemia
Orphanet journal of rare diseases, 2016Co-Authors: Charlotte Cuerq, Emile Levy, Lioara Restier, Emilie Blond, Jocelyne Drai, Mathilde Di Filippo, Marie-caroline Michalski, Adeline Roux, Sybil Charrière, Alain LachauxAbstract:Chylomicron Retention Disease (CMRD), a rare genetic hypocholesterolemia, results in neuro-ophtalmologic damages, which can be prevented by high doses of vitamin E during infancy. In these patients, plasma vitamin E concentration is significantly reduced due to defects of Chylomicron secretion. Vitamin E in adipose tissue (AT) and red blood cells (RBC) have been proposed as potential relevant biomarkers of vitamin E status but no reference values in children are available. The objectives were (i) to establish age-reference intervals in healthy children for α-tocopherol in plasma, red blood cells (RBC) and adipose tissue (AT) and (ii) to determine the variations of α-tocopherol in patients with CMRD after oral treatment with vitamin E. This prospective study included 166 healthy children (1 month - 18 years) and 4 patients with CMRD. Blood and AT were collected in healthy children during a scheduled surgery and in patients before and after a 4-month treatment with α-tocopherol acetate. The reference ranges for α-tocopherol were 11.9 - 30 μmol/L in plasma, 2.0 - 7.8 μmol/L packed cells in RBC and 60 - 573 nmol/g in AT. α-tocopherol levels in plasma correlated with those of RBC (r = 0.31; p
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Establishment of reference values of α-tocopherol in plasma, red blood cells and adipose tissue in healthy children to improve the management of Chylomicron Retention Disease, a rare genetic hypocholesterolemia
Orphanet Journal of Rare Diseases, 2016Co-Authors: Charlotte Cuerq, Emile Levy, Lioara Restier, Emilie Blond, Jocelyne Drai, Mathilde Di Filippo, Marie-caroline Michalski, Adeline Roux, Sybil Charrière, Alain LachauxAbstract:Background Chylomicron Retention Disease (CMRD), a rare genetic hypocholesterolemia, results in neuro-ophtalmologic damages, which can be prevented by high doses of vitamin E during infancy. In these patients, plasma vitamin E concentration is significantly reduced due to defects of Chylomicron secretion. Vitamin E in adipose tissue (AT) and red blood cells (RBC) have been proposed as potential relevant biomarkers of vitamin E status but no reference values in children are available. The objectives were (i) to establish age-reference intervals in healthy children for α-tocopherol in plasma, red blood cells (RBC) and adipose tissue (AT) and (ii) to determine the variations of α-tocopherol in patients with CMRD after oral treatment with vitamin E. Methods This prospective study included 166 healthy children (1 month - 18 years) and 4 patients with CMRD. Blood and AT were collected in healthy children during a scheduled surgery and in patients before and after a 4-month treatment with α-tocopherol acetate. Results The reference ranges for α-tocopherol were 11.9 - 30 μmol/L in plasma, 2.0 - 7.8 μmol/L packed cells in RBC and 60 - 573 nmol/g in AT. α-tocopherol levels in plasma correlated with those of RBC ( r = 0.31; p
Noël Peretti - One of the best experts on this subject based on the ideXlab platform.
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Ernest G Seidman, Emile LevyAbstract:Background—Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the...
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Ernest Seidman, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Emile LevyAbstract:Background-Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the critical proteins governing Chylomicron secretion by the small intestine, and its mutations lead to Chylomicron Retention Disease, despite the presence of Sar1A paralog. Objective-The central aim of this work is to examine the cause-effect relationship between Sar1B expression and Chylomicron output and to determine whether Sar1B is obligatory for normal high-density lipoprotein biogenesis. Approach and Results-The SAR1B gene was totally silenced in Caco-2/15 cells using the zinc finger nuclease technique. SAR1B deletion resulted in significantly decreased secretion of triglycerides (approximate to 40%), apolipoprotein B-48 (approximate to 57%), and Chylomicron (approximate to 34.5%). The absence of expected Chylomicron production collapse may be because of the compensatory SAR1A elevation observed in our experiments. Therefore, a double knockout of SAR1A and SAR1B was engineered in Caco-2/15 cells, which led to almost complete inhibition of triglycerides, apolipoprotein B-48, and Chylomicron output. Further experiments with labeled cholesterol revealed the downregulation of high-density lipoprotein biogenesis in cells deficient in SAR1B or with the double knockout of the 2 SAR1 paralogs. Similarly, there was a fall in the movement of labeled cholesterol from cells to basolateral medium containing apolipoprotein A-I, thereby limiting newly synthesized high-density lipoprotein in genetically modified cells. The decreased cholesterol efflux was associated with impaired expression of ABCA1 (ATP-binding cassette subfamily A member 1). Conclusions-These findings demonstrate that the deletion of the 2 SAR1 isoforms is required to fully eliminate the secretion of Chylomicron in vitro. They also underscore the limited high-density lipoprotein production by the intestinal cells in response to SAR1 knockout. Visual Overview-An online visual overview is available for this article.
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REVIEW Open Access
2013Co-Authors: Noël Peretti, Agnes Sassolas, Mathilde Charcosset, Justine Castagnetti, Sylvie Labarge, Claude C Roy, Colette Desl, Laurence Pugnet-chardon, Lise Bouthillier, Alain LachauxAbstract:Guidelines for the diagnosis and management of Chylomicron Retention Disease based on a review of the literature and the experience of two center
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Anderson’s Disease/Chylomicron Retention Disease and Mutations in the SAR1B Gene
Mutations in Human Genetic Disease, 2012Co-Authors: Agnes Sassolas, Lawrence P. Aggerbeck, Noël Peretti, M. Di Filippo, Marie-elisabeth Samson-boumaAbstract:Anderson’s Disease (AD)/Chylomicron Retention Disease (CMRD) (OMIM #607689) is a rare autosomal recessively inherited lipid malabsorption syndrome characterized by hypocholesterolemia associated with failure to thrive, diarrhea, steatorrhea and abdominal distension that presents most frequently in young infants. Charlotte Anderson first published a description of the disorder in 1961 [1] based upon observations of a young girl of seven months of age who manifested a characteristic macroscopic and microscopic appearance of the intestinal mucosa which was filled with fat. Forty two years later, in 2003, Jones and colleagues [2], in 8 families, identified mutations in the SAR1B gene, which encodes for the intracellular trafficking protein SAR1b, and proposed that this was the molecular defect in the disorder. The Disease is very rare. From the first clinical description of the Disease up to the identification of the causal gene, only 39 patients from 24 families were described in the literature [3-21]. From 2003 to the present, 23 new patients from 14 additional families have been identified. In all, 16 different mutations in the SAR1B gene now have been described in 34 patients from 21 families [2, 22-27]. Here, we provide an overview of this Disease, including the description of 4 new patients from 3 new families (one new mutation), and we describe the predicted molecular impact on the SAR1b protein of novel or previously-described mutations in the SAR1B gene.
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anderson s Disease Chylomicron Retention Disease and mutations in the sar1b gene
2012Co-Authors: Agnes Sassolas, Lawrence P. Aggerbeck, Noël Peretti, M. Di Filippo, Marie Elisabeth SamsonboumaAbstract:Anderson’s Disease (AD)/Chylomicron Retention Disease (CMRD) (OMIM #607689) is a rare autosomal recessively inherited lipid malabsorption syndrome characterized by hypocholesterolemia associated with failure to thrive, diarrhea, steatorrhea and abdominal distension that presents most frequently in young infants. Charlotte Anderson first published a description of the disorder in 1961 [1] based upon observations of a young girl of seven months of age who manifested a characteristic macroscopic and microscopic appearance of the intestinal mucosa which was filled with fat. Forty two years later, in 2003, Jones and colleagues [2], in 8 families, identified mutations in the SAR1B gene, which encodes for the intracellular trafficking protein SAR1b, and proposed that this was the molecular defect in the disorder. The Disease is very rare. From the first clinical description of the Disease up to the identification of the causal gene, only 39 patients from 24 families were described in the literature [3-21]. From 2003 to the present, 23 new patients from 14 additional families have been identified. In all, 16 different mutations in the SAR1B gene now have been described in 34 patients from 21 families [2, 22-27]. Here, we provide an overview of this Disease, including the description of 4 new patients from 3 new families (one new mutation), and we describe the predicted molecular impact on the SAR1b protein of novel or previously-described mutations in the SAR1B gene.
Lawrence P. Aggerbeck - One of the best experts on this subject based on the ideXlab platform.
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Anderson’s Disease/Chylomicron Retention Disease and Mutations in the SAR1B Gene
Mutations in Human Genetic Disease, 2012Co-Authors: Agnes Sassolas, Lawrence P. Aggerbeck, Noël Peretti, M. Di Filippo, Marie-elisabeth Samson-boumaAbstract:Anderson’s Disease (AD)/Chylomicron Retention Disease (CMRD) (OMIM #607689) is a rare autosomal recessively inherited lipid malabsorption syndrome characterized by hypocholesterolemia associated with failure to thrive, diarrhea, steatorrhea and abdominal distension that presents most frequently in young infants. Charlotte Anderson first published a description of the disorder in 1961 [1] based upon observations of a young girl of seven months of age who manifested a characteristic macroscopic and microscopic appearance of the intestinal mucosa which was filled with fat. Forty two years later, in 2003, Jones and colleagues [2], in 8 families, identified mutations in the SAR1B gene, which encodes for the intracellular trafficking protein SAR1b, and proposed that this was the molecular defect in the disorder. The Disease is very rare. From the first clinical description of the Disease up to the identification of the causal gene, only 39 patients from 24 families were described in the literature [3-21]. From 2003 to the present, 23 new patients from 14 additional families have been identified. In all, 16 different mutations in the SAR1B gene now have been described in 34 patients from 21 families [2, 22-27]. Here, we provide an overview of this Disease, including the description of 4 new patients from 3 new families (one new mutation), and we describe the predicted molecular impact on the SAR1b protein of novel or previously-described mutations in the SAR1B gene.
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anderson s Disease Chylomicron Retention Disease and mutations in the sar1b gene
2012Co-Authors: Agnes Sassolas, Lawrence P. Aggerbeck, Noël Peretti, M. Di Filippo, Marie Elisabeth SamsonboumaAbstract:Anderson’s Disease (AD)/Chylomicron Retention Disease (CMRD) (OMIM #607689) is a rare autosomal recessively inherited lipid malabsorption syndrome characterized by hypocholesterolemia associated with failure to thrive, diarrhea, steatorrhea and abdominal distension that presents most frequently in young infants. Charlotte Anderson first published a description of the disorder in 1961 [1] based upon observations of a young girl of seven months of age who manifested a characteristic macroscopic and microscopic appearance of the intestinal mucosa which was filled with fat. Forty two years later, in 2003, Jones and colleagues [2], in 8 families, identified mutations in the SAR1B gene, which encodes for the intracellular trafficking protein SAR1b, and proposed that this was the molecular defect in the disorder. The Disease is very rare. From the first clinical description of the Disease up to the identification of the causal gene, only 39 patients from 24 families were described in the literature [3-21]. From 2003 to the present, 23 new patients from 14 additional families have been identified. In all, 16 different mutations in the SAR1B gene now have been described in 34 patients from 21 families [2, 22-27]. Here, we provide an overview of this Disease, including the description of 4 new patients from 3 new families (one new mutation), and we describe the predicted molecular impact on the SAR1b protein of novel or previously-described mutations in the SAR1B gene.
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anderson s Disease Chylomicron Retention Disease in a japanese patient with uniparental disomy 7 and a normal sar1b gene protein coding sequence
Orphanet Journal of Rare Diseases, 2011Co-Authors: Tomoo Okada, Michio Miyashita, Junji Fukuhara, Marie Elisabeth Samsonbouma, Masahiko Sugitani, Takahiro Ueno, Lawrence P. AggerbeckAbstract:Background Anderson's Disease (AD)/Chylomicron Retention Disease (CMRD) is a rare hereditary hypocholesterolemic disorder characterized by a malabsorption syndrome with steatorrhea, failure to thrive and the absence of Chylomicrons and apolipoprotein B48 post-prandially. All patients studied to date exhibit a mutation in the SAR1B gene, which codes for an essential component of the vesicular coat protein complex II (COPII) necessary for endoplasmic reticulum to Golgi transport. We describe here a patient with AD/CMRD, a normal SAR1B gene protein coding sequence and maternal uniparental disomy of chromosome 7 (matUPD7).
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Anderson's Disease/Chylomicron Retention Disease in a Japanese patient with uniparental disomy 7 and a normal SAR1B gene protein coding sequence
Orphanet journal of rare diseases, 2011Co-Authors: Tomoo Okada, Michio Miyashita, Junji Fukuhara, Masahiko Sugitani, Takahiro Ueno, Marie-elisabeth Samson-bouma, Lawrence P. AggerbeckAbstract:Background Anderson's Disease (AD)/Chylomicron Retention Disease (CMRD) is a rare hereditary hypocholesterolemic disorder characterized by a malabsorption syndrome with steatorrhea, failure to thrive and the absence of Chylomicrons and apolipoprotein B48 post-prandially. All patients studied to date exhibit a mutation in the SAR1B gene, which codes for an essential component of the vesicular coat protein complex II (COPII) necessary for endoplasmic reticulum to Golgi transport. We describe here a patient with AD/CMRD, a normal SAR1B gene protein coding sequence and maternal uniparental disomy of chromosome 7 (matUPD7).
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Anderson's Disease/Chylomicron Retention Disease in a Japanese patient with uniparental disomy 7 and a normal SAR1B gene protein coding sequence.
Orphanet Journal of Rare Diseases, 2011Co-Authors: Tomoo Okada, Michio Miyashita, Junji Fukuhara, Masahiko Sugitani, Takahiro Ueno, Marie-elisabeth Samson-bouma, Lawrence P. AggerbeckAbstract:UNLABELLED: ABSTRACT: BACKGROUND: Anderson's Disease (AD)/Chylomicron Retention Disease (CMRD) is a rare hereditary hypocholesterolemic disorder characterized by a malabsorption syndrome with steatorrhea, failure to thrive and the absence of Chylomicrons and apolipoprotein B48 post-prandially. All patients studied to date exhibit a mutation in the SAR1B gene, which codes for an essential component of the vesicular coat protein complex II (COPII) necessary for endoplasmic reticulum to Golgi transport. We describe here a patient with AD/CMRD, a normal SAR1B gene protein coding sequence and maternal uniparental disomy of chromosome 7 (matUPD7). METHODS AND RESULTS: The patient, one of two siblings of a Japanese family, had diarrhea and steatorrhea beginning at five months of age. There was a white duodenal mucosa upon endoscopy. Light and electron microscopy showed that the intestinal villi were normal but that they had lipid laden enterocytes containing accumulations of lipid droplets in the cytoplasm and lipoprotein-size particles in membrane bound structures. Although there were decreased amounts in plasma of total- and low-density lipoprotein cholesterol, apolipoproteins AI and B and vitamin E levels, the triglycerides were normal, typical of AD/CMRD. The presence of low density lipoproteins and apolipoprotein B in the plasma, although in decreased amounts, ruled out abetalipoproteinemia. The parents were asymptomatic with normal plasma cholesterol levels suggesting a recessive disorder and ruling out familial hypobetalipoproteinemia. Sequencing of genomic DNA showed that the 8 exons of the SAR1B gene were normal. Whole genome SNP analysis and karyotyping revealed matUPD7 with a normal karyotype. In contrast to other cases of AD/CMRD which have shown catch-up growth following vitamin supplementation and a fat restricted diet, our patient exhibits continued growth delay and other aspects of the matUPD7 and Silver-Russell Syndrome phenotypes. CONCLUSIONS: This patient with AD/CMRD has a normal SAR1B gene protein coding sequence which suggests that factors other than the SAR1B protein may be crucial for Chylomicron secretion. Further, this patient exhibits matUPD7 with regions of homozygosity which might be useful for elucidating the molecular basis of the defect(s) in this individual. The results provide novel insights into the relation between phenotype and genotype in these Diseases and for the mechanisms of secretion in the intestine.
A Bagala - One of the best experts on this subject based on the ideXlab platform.
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vitamin e deficiency due to Chylomicron Retention Disease in marinesco sjogren syndrome
Annals of Neurology, 2000Co-Authors: Umberto Aguglia, Ferdinanda Annesi, A A Pasqua, Francesca Cavalcanti, L Crescibene, Grazia Annesi, Gianandrea Pasquinelli, Antonio Gambardella, Patrizia Spadafora, A BagalaAbstract:We report on 2 brothers (aged 19 and 12 years) with Marinesco-Sjogren syndrome who also had very low serum vitamin E concentrations with an absence of postprandial Chylomicrons. The molecular study ruled out ataxia with isolated vitamin E deficiency, abetalipoproteinemia, and hypobetalipoproteinemia. The electron microscopy of the intestinal mucosa was consistent with a Chylomicron Retention Disease. We speculate that both Chylomicron Retention Disease and Marinesco-Sjogren syndrome are related to defects in a gene crucial for the assembly or secretion of the Chylomicron particles, leading to very low serum levels of vitamin E. Ann Neurol 2000;47:260–264
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vitamin e deficiency due to Chylomicron Retention Disease in marinesco sjogren syndrome
Annals of Neurology, 2000Co-Authors: Umberto Aguglia, Ferdinanda Annesi, A A Pasqua, Francesca Cavalcanti, L Crescibene, Grazia Annesi, Gianandrea Pasquinelli, Antonio Gambardella, Patrizia Spadafora, A BagalaAbstract:We report on 2 brothers (aged 19 and 12 years) with Marinesco-Sjogren syndrome who also had very low serum vitamin E concentrations with an absence of postprandial Chylomicrons. The molecular study ruled out ataxia with isolated vitamin E deficiency, abetalipoproteinemia, and hypobetalipoproteinemia. The electron microscopy of the intestinal mucosa was consistent with a Chylomicron Retention Disease. We speculate that both Chylomicron Retention Disease and Marinesco-Sjogren syndrome are related to defects in a gene crucial for the assembly or secretion of the Chylomicron particles, leading to very low serum levels of vitamin E.
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Vitamin E deficiency due to Chylomicron Retention Disease in Marinesco‐Sjögren syndrome
Annals of neurology, 2000Co-Authors: Umberto Aguglia, Ferdinanda Annesi, A A Pasqua, Francesca Cavalcanti, L Crescibene, Grazia Annesi, Gianandrea Pasquinelli, Antonio Gambardella, Patrizia Spadafora, A BagalaAbstract:We report on 2 brothers (aged 19 and 12 years) with Marinesco-Sjogren syndrome who also had very low serum vitamin E concentrations with an absence of postprandial Chylomicrons. The molecular study ruled out ataxia with isolated vitamin E deficiency, abetalipoproteinemia, and hypobetalipoproteinemia. The electron microscopy of the intestinal mucosa was consistent with a Chylomicron Retention Disease. We speculate that both Chylomicron Retention Disease and Marinesco-Sjogren syndrome are related to defects in a gene crucial for the assembly or secretion of the Chylomicron particles, leading to very low serum levels of vitamin E.
Schohraya Spahis - One of the best experts on this subject based on the ideXlab platform.
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Chylomicron Retention Disease: genetics, biochemistry, and clinical spectrum.
Current opinion in lipidology, 2019Co-Authors: Emile Levy, Pierre Poinsot, Schohraya SpahisAbstract:Purpose of reviewChylomicron Retention Disease (CRD) is an autosomic recessive disorder, in which intestinal fat malabsorption is the main cause of diverse severe manifestations. The specific molecular defect was identified in 2003 and consists of mutations in the SAR1B or SARA2 gene encoding for in
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Ernest G Seidman, Emile LevyAbstract:Background—Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the...
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Understanding Chylomicron Retention Disease Through Sar1b Gtpase Gene DisruptionHighlights: Insight From Cell Culture
Arteriosclerosis Thrombosis and Vascular Biology, 2017Co-Authors: Alain Théophile Sané, Schohraya Spahis, Edgard Delvin, Ernest Seidman, Noël Peretti, Marie Laure Kleme, Colette Deslandres, Carole Garofalo, Emile LevyAbstract:Background-Understanding the specific mechanisms of rare autosomal disorders has greatly expanded insights into the complex processes regulating intestinal fat transport. Sar1B GTPase is one of the critical proteins governing Chylomicron secretion by the small intestine, and its mutations lead to Chylomicron Retention Disease, despite the presence of Sar1A paralog. Objective-The central aim of this work is to examine the cause-effect relationship between Sar1B expression and Chylomicron output and to determine whether Sar1B is obligatory for normal high-density lipoprotein biogenesis. Approach and Results-The SAR1B gene was totally silenced in Caco-2/15 cells using the zinc finger nuclease technique. SAR1B deletion resulted in significantly decreased secretion of triglycerides (approximate to 40%), apolipoprotein B-48 (approximate to 57%), and Chylomicron (approximate to 34.5%). The absence of expected Chylomicron production collapse may be because of the compensatory SAR1A elevation observed in our experiments. Therefore, a double knockout of SAR1A and SAR1B was engineered in Caco-2/15 cells, which led to almost complete inhibition of triglycerides, apolipoprotein B-48, and Chylomicron output. Further experiments with labeled cholesterol revealed the downregulation of high-density lipoprotein biogenesis in cells deficient in SAR1B or with the double knockout of the 2 SAR1 paralogs. Similarly, there was a fall in the movement of labeled cholesterol from cells to basolateral medium containing apolipoprotein A-I, thereby limiting newly synthesized high-density lipoprotein in genetically modified cells. The decreased cholesterol efflux was associated with impaired expression of ABCA1 (ATP-binding cassette subfamily A member 1). Conclusions-These findings demonstrate that the deletion of the 2 SAR1 isoforms is required to fully eliminate the secretion of Chylomicron in vitro. They also underscore the limited high-density lipoprotein production by the intestinal cells in response to SAR1 knockout. Visual Overview-An online visual overview is available for this article.
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Tissue Distribution and Regulation of the Small Sar1b GTPase in Mice
Cellular physiology and biochemistry : international journal of experimental cellular physiology biochemistry and pharmacology, 2014Co-Authors: Valerie Marcil, Schohraya Spahis, Alain Théophile Sané, Ernest G Seidman, Daniel Sinnett, Rocio Sanchez, Emile LevyAbstract:Background/Aims: Sar1b GTPase (Sar1b) represents an obligatory component of COPII vesicles that bud from the endoplasmic reticulum to transport proteins to the Golgi apparatus. Its genetic mutations lead to a severe disorder known as Chylomicron Retention Disease. Despite growing knowledge on Sar1b, little is known about it tissue distribution and regulation, which constitute the aims of the present study. We aimed to determine the Sar1b tissue distribution and modulation by a high-fat diet and gene forcing using transgenic mice in comparison to wild-type mice. Methods: The expression pattern of Sar1b was studied in different organs of wild-type and Sar1b transgenic mice by qRT-PCR and Western blot. The effect of transgenesis and insulin resistance induced by a 12-week high-fat diet on Sar1b gene expression was also assessed by qRT-PCR. Results: Evaluation of Sar1b mRNA revealed the skeletal muscle as the tissue with the highest Sar1b expression, followed by the heart and liver, the organs composing the digestive tract, the brain and finally the lung and the adipose tissue. Sar1b protein expression levels follow a similar pattern among the organs, except for its lower expression in the heart. While the high-fat diet did not exert any significant alterations, Sar1b transgenic mice displayed higher gene expression in the liver, ileum, jejunum, proximal and distal colon compared to wild-type mice. Conclusion: Our study supports the importance of Sar1b in organs involved in lipid transport and/or calcium trafficking such as the liver, intestine, skeletal muscle and heart.
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sar1b transgenic male mice are more susceptible to high fat diet induced obesity insulin insensitivity and intestinal Chylomicron overproduction
Journal of Nutritional Biochemistry, 2014Co-Authors: Emile Levy, Schohraya Spahis, Carole Garofalo, Valerie Marcil, Alain Montoudis, Daniel Sinnet, Rocio Sanchez, N Peretti, Jeanfrancois BeaulieuAbstract:In the intracellular secretory network, nascent proteins are shuttled from the endoplasmic reticulum to the Golgi by transport vesicles requiring Sar1b, a small GTPase. Mutations in this key enzyme impair intestinal lipid transport and cause Chylomicron Retention Disease. The main aim of this study was to assess whether Sar1b overexpression under a hypercaloric diet accelerated lipid production and Chylomicron (CM) secretion, thereby inducing cardiometabolic abnormalities. To this end, we generated transgenic mice overexpressing human Sar1b (Sar1b+/+) using pBROAD3-mcs that features the ubiquitous mouse ROSA26 promoter. In response to a high-fat diet (HFD), Sar1b+/+ mice displayed significantly increased body weight and adiposity compared with Sar1b+/+ mice under the same regimen or with wild-type (WT) mice exposed to chow diet or HFD. Furthermore, Sar1b+/+ mice were prone to liver steatosis as revealed by significantly elevated hepatic triglycerides (TG) and cholesterol in comparison with WT animals. They also exhibited augmented levels of plasma TG along with alterations in fatty acid composition. Concomitantly, they showed susceptibility to develop insulin insensitivity and they responded abnormally to oral glucose tolerance test. Finally, Sar1b+/+ mice that have been treated with Triton WR-1330 (to inhibit TG catabolism) and orotic acid (to block secretion of very low-density lipoprotein by the liver) responded more efficiently to fat meal tests as reflected by the rise in plasma TG and CM concentrations, indicating exaggerated intestinal fat absorption. These results suggest that Sar1b+/+ under HFD can elicit cardiometabolic traits as revealed by incremental weight gain, fat deposition, dyslipidemia, hepatic steatosis, insulin insensitivity and intestinal fat absorption.