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Genetic Deficiency for Proprotein Convertase 2 (PC2) in Mice is Protective form Age and Diet-induced Obesity.
MONTREAL 2008 ABSTRACTS
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ORAL PRESENTATIONS 45
Genetic Deficiency for Proprotein Convertase 2 (PC2) in Mice is Protective form Age and Diet-induced Obesity. Younes Anini, Janice Mayne, Francine Sirois, Jeffrey Gagnon, Andrew Chen, Nadine Kaefer, Mary-Ellen Harper, Michel Chrétien, Majambu Mbikay, Dalhousie University, Halifax, and Ottawa Health Research Institute, Ottawa. Proprotein convertase 2 (PC2) is a member of the subtilase family of proteinases. PC2 is primarily expressed in endocrine and neroendocrine tissues where it mediates the production of neuropeptides and hormones known to influence glucose and energy homeostasis. In this study, we examined the importance of PC2 in food intake, fuel preference, energy expenditure and body mass. Relative to their wild type counterparts, 16 weeks old PC2-/mice carried significantly less epididymal fat, (PC2+/+, 0.386 ± 0.102 g vs PC2-/-, 2.276 ± 0.156, P < 0.0001) with no significant difference in the lean mass (gastroc muscle). Visceral and perikidney fat mass was also significantly reduced in PC2-/-. These observation was corroborated by the reduced level of circulating leptin in PC2-/- mice. There was no significant difference between PC2+/+ and PC2-/- mice in the rate of food intake nor in the level of the orexigenic hormone ghrelin. Mice of both genotypes were subjected to either lowfat (LFD) or high-fat diet (HFD), for 10 weeks. PC2+/+ mice gained more weight under the HFD. In contrast, PC2-/- mice gained similar amount of weight under HFD and LFD. Indirect calorimetry was conducted on aged mice indicated that PC2-/mice use carbohydrates more than lipids as energy source. We have shown that PC2-deficient mice are insensitive to age and diet-induced body weight gain. These data indicate that PC2 level in endocrine tissue is a quantitative trait controlling diet-induced obesity.
47
ABSTRACT #141
46
CSEM
Evidence for Association between Measures of Insulin Secretion and Insulin Sensitivity and Type 2 Diabetes Susceptibility Variants Identified through Genome-Wide Association Studies
OBESITY STEPHANIE-MAY RUCHAT
*,1 , CATHY ELKS1, RUTH J.F LOOS1, 1 1 MARIE-CLAUDE VOHL , S.JOHN WEISNAGEL , TUOMO 1 1 1 RANKINEN , CLAUDE BOUCHARD , LOUIS PERUSSE , Department of Preventive Medicine, Laval University, Quebec, QC
Recently, several novel single nucleotide polymorphisms (SNPs) for T2DM risk have been identified by genome wide association (GWA) studies. Studying the impact of these SNPs on T2DM intermediate phenotypes is essential to clarify the physiological mechanism through which they exert their effects on the disease etiology. The objective of the present study was to test several novel diabetes susceptibility variants for association with T2DMrelated phenotypes in a well-characterized population-based sample, the Quebec Family Study (QFS). We analysed 34 SNPs in 9 T2DM genes identified through GWA studies (CDKAL1, CDKN2B, HHEX/IDE, IGF2BP2, KCNJ11, SLC30A8, TCF2, TCF7L2 and WFS1) in a maximum of 712 subjects from the QFS. The subjects underwent a 75-g oral glucose tolerance test (OGTT) and were measured for glucose, insulin and C-peptide levels. Indices of insulin sensitivity and insulin secretion were derived from fasting and OGTT measurements. We confirmed the significant association of variants in CDKAL1, CDKN2B, HHEX/IDE, KCNJ11 and TCF7L2 with insulin secretion (p<0.05 for all) and also found associations of some of these variants with glucose tolerance and insulin sensitivity-related phenotypes. IGF2BP2 and SLC30A8 SNPs were not associated with insulin secretion but were associated with glucose tolerance and/or insulin sensitivity (0.002p0.02). No association were found with TCF2 and WFS1 variants. To examine the joint effects of these variants and their contribution to the variance in T2DM intermediate 2 traits, stepwise regression models were used and the model R was computed. The variance in the phenotypes explained by specific combination of the variants ranged from 3.5% to 9.6%. In conclusion, diabetes-associated variants in CDKAL1, CDKN2B, HHEX/IDE, IGF2BP2, KCNJ11, SLC30A8 and TCF7L2 are associated with different physiological alterations leading to T2DM, such as impaired insulin secretion, insulin resistance and glucose intolerance, supporting their role in the disease aetiology. Specific combination of these variants can significantly contribute to the variation in T2DM-related traits.
ABSTRACT #19 CSEM GENETICS
48 Local Expression of B7-H4 by Transducing Recombinant Adenovirus in Islet Grafts Improves Allotransplant Outcomes. XIAOJIE WANG , JIANQIANG HAO1, DANIEL L. METZGER2, ALICE MUI1, ZILIANG AO1, C. BRUCE VERCHERE3, LIEPING CHEN4, DAWEI OU1, GARTH L. WARNOCK1, Departments of Surgery1, Paediatrics2, and Pathology and Laboratory Medicine3, University of British Columbia, Vancouver, BC, Canada, Department of Dermatology and Oncology, Johns Hopkins University Scholl of Medicine, Baltimore, MD, USA4 Allogeneic pancreatic islet transplantation has potential as a treatment option for type I diabetes. Costimulatory molecules, which play a major role in both initiation and termination of the immune response to antigens during graft rejection, may be used to inhibit allograft destruction. B7-H4 is one such member in the B7-CD28 family of costimulatory molecules which has established negative regulation of T-cell responses. To determine whether local expression of B7-H4 protein can protect islet beta cells from damage mediated by immune rejection responses in islet transplantation, we have developed a recombinant adenovirus expressing a mouse B7-H4 cDNA (Ad-B7H4). Primary islet cells were infected with Ad-B7-H4 to express B7-H4 protein in a dose-dependent fashion. Treatment of fresh isolated islets by Ad-B7-H4 infection at an optimized condition of 5 pfu for 24 h did not show inhibition of glucose-stimulated insulin secretion. To study the in vivo effects of B7-H4 overexpression on islet graft survival, 400 adenovirus-transduced islets from donor BALB/C mice were transplanted streptozotocin-diabetic C57BL/6 (B6) recipient mice. The B6 recipient group (n=12) that received Ad-B7-H4-transduced islet grafts established euglycemia for 56.5 days, compared with the recipient group (n=12) transplanted with islets infected by control adenovirus (Ad-LacZ) for 14 days (P<0.0001 by log-rank test). Splenocytes and renal lymph-node cells isolated from the B6 recipients of Ad-B7H4-transduced islets showed clear hyporesponsiveness to alloantigenic stimulation in mixed lymphocyte reaction assay, compared with the control recipients of untreated islets from BALB/c (P<0.00003) indicating the acceptance of allografts. We conclude that local over-expression of B7-H4 by Ad-B7-H4 inhibits transplant rejection to allogeneic islet grafts in vivo, suggesting translational potential for beta-cell substitution with reduced immune injury.
202 CSEM Transplantation
| 313
ORAL PRESENTATIONS 45
Genetic Deficiency for Proprotein Convertase 2 (PC2) in Mice is Protective form Age and Diet-induced Obesity. Younes Anini, Janice Mayne, Francine Sirois, Jeffrey Gagnon, Andrew Chen, Nadine Kaefer, Mary-Ellen Harper, Michel Chrétien, Majambu Mbikay, Dalhousie University, Halifax, and Ottawa Health Research Institute, Ottawa. Proprotein convertase 2 (PC2) is a member of the subtilase family of proteinases. PC2 is primarily expressed in endocrine and neroendocrine tissues where it mediates the production of neuropeptides and hormones known to influence glucose and energy homeostasis. In this study, we examined the importance of PC2 in food intake, fuel preference, energy expenditure and body mass. Relative to their wild type counterparts, 16 weeks old PC2-/mice carried significantly less epididymal fat, (PC2+/+, 0.386 ± 0.102 g vs PC2-/-, 2.276 ± 0.156, P < 0.0001) with no significant difference in the lean mass (gastroc muscle). Visceral and perikidney fat mass was also significantly reduced in PC2-/-. These observation was corroborated by the reduced level of circulating leptin in PC2-/- mice. There was no significant difference between PC2+/+ and PC2-/- mice in the rate of food intake nor in the level of the orexigenic hormone ghrelin. Mice of both genotypes were subjected to either lowfat (LFD) or high-fat diet (HFD), for 10 weeks. PC2+/+ mice gained more weight under the HFD. In contrast, PC2-/- mice gained similar amount of weight under HFD and LFD. Indirect calorimetry was conducted on aged mice indicated that PC2-/mice use carbohydrates more than lipids as energy source. We have shown that PC2-deficient mice are insensitive to age and diet-induced body weight gain. These data indicate that PC2 level in endocrine tissue is a quantitative trait controlling diet-induced obesity.
47
ABSTRACT #141
46
CSEM
Evidence for Association between Measures of Insulin Secretion and Insulin Sensitivity and Type 2 Diabetes Susceptibility Variants Identified through Genome-Wide Association Studies
OBESITY STEPHANIE-MAY RUCHAT
*,1 , CATHY ELKS1, RUTH J.F LOOS1, 1 1 MARIE-CLAUDE VOHL , S.JOHN WEISNAGEL , TUOMO 1 1 1 RANKINEN , CLAUDE BOUCHARD , LOUIS PERUSSE , Department of Preventive Medicine, Laval University, Quebec, QC
Recently, several novel single nucleotide polymorphisms (SNPs) for T2DM risk have been identified by genome wide association (GWA) studies. Studying the impact of these SNPs on T2DM intermediate phenotypes is essential to clarify the physiological mechanism through which they exert their effects on the disease etiology. The objective of the present study was to test several novel diabetes susceptibility variants for association with T2DMrelated phenotypes in a well-characterized population-based sample, the Quebec Family Study (QFS). We analysed 34 SNPs in 9 T2DM genes identified through GWA studies (CDKAL1, CDKN2B, HHEX/IDE, IGF2BP2, KCNJ11, SLC30A8, TCF2, TCF7L2 and WFS1) in a maximum of 712 subjects from the QFS. The subjects underwent a 75-g oral glucose tolerance test (OGTT) and were measured for glucose, insulin and C-peptide levels. Indices of insulin sensitivity and insulin secretion were derived from fasting and OGTT measurements. We confirmed the significant association of variants in CDKAL1, CDKN2B, HHEX/IDE, KCNJ11 and TCF7L2 with insulin secretion (p<0.05 for all) and also found associations of some of these variants with glucose tolerance and insulin sensitivity-related phenotypes. IGF2BP2 and SLC30A8 SNPs were not associated with insulin secretion but were associated with glucose tolerance and/or insulin sensitivity (0.002p0.02). No association were found with TCF2 and WFS1 variants. To examine the joint effects of these variants and their contribution to the variance in T2DM intermediate 2 traits, stepwise regression models were used and the model R was computed. The variance in the phenotypes explained by specific combination of the variants ranged from 3.5% to 9.6%. In conclusion, diabetes-associated variants in CDKAL1, CDKN2B, HHEX/IDE, IGF2BP2, KCNJ11, SLC30A8 and TCF7L2 are associated with different physiological alterations leading to T2DM, such as impaired insulin secretion, insulin resistance and glucose intolerance, supporting their role in the disease aetiology. Specific combination of these variants can significantly contribute to the variation in T2DM-related traits.
ABSTRACT #19 CSEM GENETICS
48 Local Expression of B7-H4 by Transducing Recombinant Adenovirus in Islet Grafts Improves Allotransplant Outcomes. XIAOJIE WANG , JIANQIANG HAO1, DANIEL L. METZGER2, ALICE MUI1, ZILIANG AO1, C. BRUCE VERCHERE3, LIEPING CHEN4, DAWEI OU1, GARTH L. WARNOCK1, Departments of Surgery1, Paediatrics2, and Pathology and Laboratory Medicine3, University of British Columbia, Vancouver, BC, Canada, Department of Dermatology and Oncology, Johns Hopkins University Scholl of Medicine, Baltimore, MD, USA4 Allogeneic pancreatic islet transplantation has potential as a treatment option for type I diabetes. Costimulatory molecules, which play a major role in both initiation and termination of the immune response to antigens during graft rejection, may be used to inhibit allograft destruction. B7-H4 is one such member in the B7-CD28 family of costimulatory molecules which has established negative regulation of T-cell responses. To determine whether local expression of B7-H4 protein can protect islet beta cells from damage mediated by immune rejection responses in islet transplantation, we have developed a recombinant adenovirus expressing a mouse B7-H4 cDNA (Ad-B7H4). Primary islet cells were infected with Ad-B7-H4 to express B7-H4 protein in a dose-dependent fashion. Treatment of fresh isolated islets by Ad-B7-H4 infection at an optimized condition of 5 pfu for 24 h did not show inhibition of glucose-stimulated insulin secretion. To study the in vivo effects of B7-H4 overexpression on islet graft survival, 400 adenovirus-transduced islets from donor BALB/C mice were transplanted streptozotocin-diabetic C57BL/6 (B6) recipient mice. The B6 recipient group (n=12) that received Ad-B7-H4-transduced islet grafts established euglycemia for 56.5 days, compared with the recipient group (n=12) transplanted with islets infected by control adenovirus (Ad-LacZ) for 14 days (P<0.0001 by log-rank test). Splenocytes and renal lymph-node cells isolated from the B6 recipients of Ad-B7H4-transduced islets showed clear hyporesponsiveness to alloantigenic stimulation in mixed lymphocyte reaction assay, compared with the control recipients of untreated islets from BALB/c (P<0.00003) indicating the acceptance of allografts. We conclude that local over-expression of B7-H4 by Ad-B7-H4 inhibits transplant rejection to allogeneic islet grafts in vivo, suggesting translational potential for beta-cell substitution with reduced immune injury.
202 CSEM Transplantation