- Email: [email protected]
Indices of Insulin Suppression of Non-Esterified Fatty Acids Measured During an Oral Glucose Challenge and Their Association with the Insulin-Glucose Clamp Index and Central Adiposity
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Abstracts / Can J Diabetes 37 (2013) S13eS84
females) following HFD feeding, as well as decreased fasting insulin and leptin levels. This study demonstrates that caspase 8 plays an important role in adipose tissue regulation of whole body energy and glucose homeostasis, and disruption of adipocyte caspase 8 protects mice from obesity and diabetes.
188 Absence of the ROS Scavenger DJ-1 Paradoxically Protects Mice from Obesity and Insulin Resistance SALLY Y. SHI*, SHUN-YAN LU, THARINI SIVASUBRAMANIYAM, ERICA P. CAI, STEPHANIE A. SCHROER, RAYMOND H. KIM, TAK W. MAK, MINNA WOO Toronto, ON While excessive reactive oxygen species (ROS) have been implicated in the development of insulin resistance and type 2 diabetes, ROS generated at physiological levels play essential biological functions. DJ-1 is an evolutionarily conserved protein originally identified in the context of neuronal survival in Parkinson’s disease. It is thought to participate in the oxidative stress response by acting as a ROS scavenger or redox sensor. To investigate its role in metabolism, we employed a mouse model of chronic metabolic stress by feeding mice with a high-fat diet (HFD) for 3 months starting at 8 weeks of age. Of all the metabolic tissues examined, prolonged HFD feeding induced a 2-fold increase in DJ-1 expression in mouse skeletal muscle, particularly in females. This increase occurred in association with an expected elevation in muscle ROS levels. Consistent with its antioxidant role, whole-body DJ-1 deficiency further raised HFD-induced ROS accumulation in muscle, accompanied by enhanced activation of ROS-activated pathways including AMP-activated protein kinase (AMPK) and autophagy. In line with the implication of AMPK in cellular energy metabolism, DJ-1 knockout (KO) mice exhibited increased energy expenditure and reduced adiposity. Accordingly, DJ-1 KO mice, especially females, were protected from HFD-induced obesity, glucose intolerance and insulin resistance. This metabolically favourable phenotype was attributed to elevated muscle ROS and was abolished by the antioxidant N-acetyl-L-cysteine. Altogether, our study demonstrates a key role of DJ-1 in metabolism and identifies finetuning of ROS as a potential therapeutic strategy for type 2 diabetes.
189 Adipocyte-Specific Deletion of Janus Kinase 2 (JAK2) Leads to Increased Adiposity and Age-Related Glucose Intolerance SALLY Y. SHI*, CYNTHIA T. LUK, JARA J. BRUNT, STEPHANIE A. SCHROER, KAY-UWE WAGNER, MINNA WOO Toronto, ON; Omaha, NE Adipocytes are now recognized as active endocrine cells with indispensable physiological functions. Alterations in adipocyte development and/or function have been implicated in the pathophysiology of type 2 diabetes. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway mediates signalling by numerous cytokines and hormones that regulate adipocyte function. Several cytokines secreted by adipocytes also utilize this pathway, illustrating the physiological importance of JAK-STATs in adipocyte biology. We sought to investigate potential metabolic roles of adipose JAK2 using adipocyte-specific JAK2 knockout (F-JAK2 KO) mice generated using the Cre-loxP system with Cre expression driven by the aP2 promoter. Starting at 2 to 3 months of age, F-JAK2 KO mice on a chow diet gradually gained more body weight compared to control littermates. This was primarily due to increased adiposity, accompanied by increased leptin and decreased adiponectin levels in the circulation. To determine
the underlying basis for the increased adiposity, energy balance was assessed using indirect calorimetry. Daily food intake was not changed, whereas energy expenditure and physical activity were significantly reduced in F-JAK2 KO mice. In the perigonadal adipose tissue, an increase in expression of hormone sensitive lipase (Hsl) and a reduction in adipose triglyceride lipase (Atgl) were observed, suggesting dysregulated lipolysis. Accordingly, while glucose metabolism was normal at 2 months of age, by 5 to 6 months, FJAK2 KO mice became more glucose intolerant and insulin resistant. Thus, adipocyte JAK2 plays a critical role in metabolism and may constitute a novel therapeutic target for the treatment of obesity and type 2 diabetes.
190 Metabolic and Body Composition Responses to a Moderate Energy Restriction, Abundant Protein Diet in Type 2 Diabetic Adults AYLA COUSSA*, ERROL B. MARLISS, STEPHANIE CHEVALIER, JOSE A. MORAIS, MARIE LAMARCHE, MICHAEL TSOUKAS, REJEANNE GOUGEON Montreal, QC We reported insulin resistance of protein metabolism in hyperglycemic type 2 diabetic adults. Resulting inefficient protein utilization could be exacerbated by weight loss diets that keep protein as a fixed % of energy. Aim: We tested whether a moderately hypoenergetic, abundantprotein diet could prevent this, while preserving the glucoregulatory improvement. Methods: Diet provided 60% of energy requirements, 45% of energy as carbohydrate, 26% as protein (1.9 g/kgLBM/day) for 5 weeks in obese diabetic adults (n¼5, 52 to 64 years). Insulin sensitivity of whole-body glucose (3-3H-glucose) and protein (13C-leucine) kinetics were quantified pre- and post-diet, postabsorptive and during hyperinsulinemic (w500pM), isoglycemic (7.70.4 pre vs. 5.70.2 mM post), isoaminoacidemic clamps. Results: Weight loss was 5.30.7 kg, as fat 4.00.3 kg (both p<0.004) and LBM 1.21.0 kg (NS), and RMR/LBM maintained. The following decreased post-diet (p<0.05): postabsorptive glycemia (7.70.4 to 5.70.2 mM), insulin (10917 to 698 pM), HOMA-IR (6.21.0 to 2.90.4), A1C (7.6 to 6.6%) and antihypertensive and/or diabetes medications. Whereas glucose Ra and Rd (1.90.2 mg/ kgBW/min) did not change, MCR (Rd/glycemia) increased. Notably, protein catabolism and oxidation decreased, resulting in less negative net balance (p<0.05). Clamp glucose Ra and Rd responses did not improve, but MCR increased from 2.30.2 to 3.50.4 mL/ kg∙min (p¼0.01); protein catabolism was suppressed but synthesis not stimulated, resulting in no net anabolism improvement. Summary/Conclusions: Weight lost was fat, lean mass preserved, fasting glycemia, insulin and protein balance improved. In response to hyperinsulinemia, only MCR improved, but protein metabolism did not worsen. Thus, abundant protein appears to preserve body proteins in the face of energy deficit and insulin resistance.
191 Indices of Insulin Suppression of Non-Esterified Fatty Acids Measured During an Oral Glucose Challenge and Their Association with the Insulin-Glucose Clamp Index and Central Adiposity FOUED NAIMI, JEAN-PATRICE BAILLARGEON Sherbrooke, QC Objective: To determine the indices of insulin-induced NEFA suppressibility derived from the oral glucose tolerance test (OGTT)
Abstracts / Can J Diabetes 37 (2013) S13eS84
that are best associated with the standard measure derived from the insulin-glucose clamp and with central adiposity. Methods: Sixteen men and 10 women, aged 20 to 35 years, without any disease or family history of type 2 diabetes, underwent a 75 g OGTT and a 2-step euglycemic clamp with low- and highdose insulin infusions (10 and 40 mU/kg/min). OGTT indices of NEFA suppressibility were: area under the curve (AUC) of NEFA, AUCNEFAAUCinsulin, NEFA T50, insulin concentration at T50 (EC50) and negative slope of the log-linear portion of NEFA suppression curve corrected by AUCinsulin (NegSlopeLnNEFA/AUCIns). NEFA insulin suppression during the clamp was calculated by DNEFA/Dinsulin at low-dose insulin (from baseline¼positive results). Central adiposity was estimated mainly by the waist-to-hip ratio (WHR) and glucose insulin sensitivity, by the M/I value (clamp, high-dose insulin). Results: OGTT-derived indices of insulin-induced NEFA suppression significantly associated with clamp DNEFA/Dinsulin: AUCNEFAAUCinsulin (r¼0.54), EC50 (r¼0.50), NegSlopeLnNEFA/AUCIns (r¼e0.44) and %reductionNEFA/AUCinsulin (r¼e0.42). The only index significantly associated with WHR: AUCNEFAAUCinsulin (r¼0.55). Based on a step-wise regression analysis, the variables significantly and independently associated with WHR were: AUCNEFAAUCinsulin (p¼0.002) and AUCglucose (p¼0.01) (model R2¼0.49). Conclusions: AUCNEFAAUCinsulin may represent the best OGTTderived parameter to estimate sensitivity to insulin suppression of lipolysis because, in our sample, it was the only one significantly correlated with central adiposity. Moreover, among all metabolic parameters measured in our study, AUCNEFAAUCinsulin and AUCglucose were the two main factors independently associated with central adiposity.
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193 Erythropoietin Signalling in Adipocytes is Not Essential for Regulation of Metabolism In Vivo CYNTHIA T. LUK*, SALLY Y. SHI, DIANA CHOI, ERICA P. CAI, STEPHANIE A. SCHROER, MINNA WOO Toronto, ON Erythropoietin (EPO) has increasingly been shown to have extraerythropoietic and cytoprotective roles. Exogenous administration has recently been shown to have beneficial effects on obesity and diabetes in mouse models and we have previously shown that EPO protects against diabetes through direct effects on pancreatic b-cells. EPO can directly modulate adipogenesis and insulin signalling in 3T3-L1 adipocytes; however, its physiological role in vivo has not been identified. To study the role of erythropoietin signalling in adipocytes, we used an adipocyte protein 2 (aP2) CRE-loxP recombination system to generate adipose tissue-specific erythropoietin receptor (EpoR) knockout mice. Knockout mice did not display any differences in weight gain compared to wild-type littermate controls on either control chow diet (p¼0.65, n¼5 males; p¼0.46, n¼5 females) or high-fat diet (HFD) (p¼0.79, n¼10 males; p¼0.76, n¼10 females) up to 8 months of age. Similarly, even with HFD, disruption of EpoR did not significantly alter body composition, adipose tissue morphology or energy homeostasis, including energy expenditure, respiratory expenditure ratio or activity level. Furthermore, disruption of EPO signalling in adipocytes did not alter glucose tolerance (p0.05, n¼14) or insulin sensitivity (p0.05, n¼14) in vivo, and did not alter adipocyte inflammation or expression of genes involved in angiogenesis. In summary, we determine that adipocyte EPO signalling is not essential for maintenance of energy homeostasis or glucose metabolism. In contrast to the pharmacological effects of EPO, we demonstrate that physiological EPO signalling is not essential for adipose tissue regulation of metabolism.
192 Influence of Depot Origin on the Susceptibility of Adipose Progenitor Cells to Cell Death AMANDA BIERNACKA-LAROCQUE*, ANNEMARIE GAGNON, ALEXANDER SORISKY Ottawa, ON Nutrient excess and a sedentary lifestyle lead to an accumulation of adipose tissue (obesity) through an increase in adipocyte size (hypertrophy) and number (hyperplasia). Hypertrophic obesity results in dysfunctional adipocytes associated with adipose tissue inflammation and insulin resistance. On the other hand, hyperplastic adipose tissue expansion is linked to preservation of insulin sensitivity. Metabolically functional adipose tissue expansion via hyperplasia may require an adequate number of responsive adipose progenitor cells. Distinct adipose tissue depots vary with respect to functional responses, such as lipolysis and adipogenesis. The aim of this study was to investigate the influence of depot origin on the susceptibility of adipose progenitor cells to cell death. Using serum deprivation alone or in the presence of 25nM tumor necrosis factor (TNF) a, visceral omental (OM) versus abdominal subcutaneous (SC) adipose progenitor cells displayed a 3- and 1.7-fold increase in cell death, as assessed by by Hoechst staining, respectively (p<0.05, n¼3 or 4). Similar results were obtained when cell death rates were evaluated by cell enumeration. The ratio of OM/SC cell death in response to serum deprivation was positively correlated with body mass index (r¼0.96; p<0.01, n¼5). The depot-specific difference in apoptosis susceptibility observed was lost when a stronger apoptotic stimulus (TNFa with cycloheximide) was used. Depot-related differences in apoptotic susceptibility of adipose progenitor cells may influence regional cellular remodelling during adipose tissue expansion and alter metabolic functionality in obesity.
194 Assessing Energy Expenditure in Obese Adolescents in a Clinical Setting: Is the Handheld Indirect Calorimeter Valid and Accurate? PAULA P.W. WOO*, GAYATHRI MURTHY*, CINDY WONG, JEAN-PIERRE CHANOINE, RAJAVEL ELANGO Vancouver, BC As energy balance is dependent on caloric consumption and expenditure, providing food recommendations based on individualized energy assessment could optimize pediatric weight management. Resting energy expenditure (REE), which contributes 70% to 80% of total energy expenditure, is key to meaningful energy prescriptions. Standard open-circuit indirect calorimeter carts (VMax, VM), used as a gold standard, measure valid REE but are not easily accessible. Recently, a handheld indirect calorimeter (MedGem, MG) has become available in the pediatric outpatient clinic. Its validity, however, has never been assessed in the obese adolescent ambulatory population. Objective: To validate REE measured by MG against VM in obese adolescents and to compare measured REE with those estimated by predictive equations. Methods: Eighteen adolescents (7:11, M:F), aged 14.71.8 years, participated in the study after an overnight fast. Anthropometric measurements were performed. REE were measured with both MG (upright, 7 to 13 mins) and VM (supine, 20 to 25 mins) in random order. Results: Body mass index was 31.34.7 kg/m2. Measured average REE using MG and VM were 1608331 kcal/day (19.6 kcal/kg) and 1666335 kcal/day (20.3 kcal/kg), respectively. Data show significant correlation (R2¼0.89) between the 2 methods. Predictive equations overestimate REE by 25% of indirect calorimeters.
Abstracts / Can J Diabetes 37 (2013) S13eS84
females) following HFD feeding, as well as decreased fasting insulin and leptin levels. This study demonstrates that caspase 8 plays an important role in adipose tissue regulation of whole body energy and glucose homeostasis, and disruption of adipocyte caspase 8 protects mice from obesity and diabetes.
188 Absence of the ROS Scavenger DJ-1 Paradoxically Protects Mice from Obesity and Insulin Resistance SALLY Y. SHI*, SHUN-YAN LU, THARINI SIVASUBRAMANIYAM, ERICA P. CAI, STEPHANIE A. SCHROER, RAYMOND H. KIM, TAK W. MAK, MINNA WOO Toronto, ON While excessive reactive oxygen species (ROS) have been implicated in the development of insulin resistance and type 2 diabetes, ROS generated at physiological levels play essential biological functions. DJ-1 is an evolutionarily conserved protein originally identified in the context of neuronal survival in Parkinson’s disease. It is thought to participate in the oxidative stress response by acting as a ROS scavenger or redox sensor. To investigate its role in metabolism, we employed a mouse model of chronic metabolic stress by feeding mice with a high-fat diet (HFD) for 3 months starting at 8 weeks of age. Of all the metabolic tissues examined, prolonged HFD feeding induced a 2-fold increase in DJ-1 expression in mouse skeletal muscle, particularly in females. This increase occurred in association with an expected elevation in muscle ROS levels. Consistent with its antioxidant role, whole-body DJ-1 deficiency further raised HFD-induced ROS accumulation in muscle, accompanied by enhanced activation of ROS-activated pathways including AMP-activated protein kinase (AMPK) and autophagy. In line with the implication of AMPK in cellular energy metabolism, DJ-1 knockout (KO) mice exhibited increased energy expenditure and reduced adiposity. Accordingly, DJ-1 KO mice, especially females, were protected from HFD-induced obesity, glucose intolerance and insulin resistance. This metabolically favourable phenotype was attributed to elevated muscle ROS and was abolished by the antioxidant N-acetyl-L-cysteine. Altogether, our study demonstrates a key role of DJ-1 in metabolism and identifies finetuning of ROS as a potential therapeutic strategy for type 2 diabetes.
189 Adipocyte-Specific Deletion of Janus Kinase 2 (JAK2) Leads to Increased Adiposity and Age-Related Glucose Intolerance SALLY Y. SHI*, CYNTHIA T. LUK, JARA J. BRUNT, STEPHANIE A. SCHROER, KAY-UWE WAGNER, MINNA WOO Toronto, ON; Omaha, NE Adipocytes are now recognized as active endocrine cells with indispensable physiological functions. Alterations in adipocyte development and/or function have been implicated in the pathophysiology of type 2 diabetes. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway mediates signalling by numerous cytokines and hormones that regulate adipocyte function. Several cytokines secreted by adipocytes also utilize this pathway, illustrating the physiological importance of JAK-STATs in adipocyte biology. We sought to investigate potential metabolic roles of adipose JAK2 using adipocyte-specific JAK2 knockout (F-JAK2 KO) mice generated using the Cre-loxP system with Cre expression driven by the aP2 promoter. Starting at 2 to 3 months of age, F-JAK2 KO mice on a chow diet gradually gained more body weight compared to control littermates. This was primarily due to increased adiposity, accompanied by increased leptin and decreased adiponectin levels in the circulation. To determine
the underlying basis for the increased adiposity, energy balance was assessed using indirect calorimetry. Daily food intake was not changed, whereas energy expenditure and physical activity were significantly reduced in F-JAK2 KO mice. In the perigonadal adipose tissue, an increase in expression of hormone sensitive lipase (Hsl) and a reduction in adipose triglyceride lipase (Atgl) were observed, suggesting dysregulated lipolysis. Accordingly, while glucose metabolism was normal at 2 months of age, by 5 to 6 months, FJAK2 KO mice became more glucose intolerant and insulin resistant. Thus, adipocyte JAK2 plays a critical role in metabolism and may constitute a novel therapeutic target for the treatment of obesity and type 2 diabetes.
190 Metabolic and Body Composition Responses to a Moderate Energy Restriction, Abundant Protein Diet in Type 2 Diabetic Adults AYLA COUSSA*, ERROL B. MARLISS, STEPHANIE CHEVALIER, JOSE A. MORAIS, MARIE LAMARCHE, MICHAEL TSOUKAS, REJEANNE GOUGEON Montreal, QC We reported insulin resistance of protein metabolism in hyperglycemic type 2 diabetic adults. Resulting inefficient protein utilization could be exacerbated by weight loss diets that keep protein as a fixed % of energy. Aim: We tested whether a moderately hypoenergetic, abundantprotein diet could prevent this, while preserving the glucoregulatory improvement. Methods: Diet provided 60% of energy requirements, 45% of energy as carbohydrate, 26% as protein (1.9 g/kgLBM/day) for 5 weeks in obese diabetic adults (n¼5, 52 to 64 years). Insulin sensitivity of whole-body glucose (3-3H-glucose) and protein (13C-leucine) kinetics were quantified pre- and post-diet, postabsorptive and during hyperinsulinemic (w500pM), isoglycemic (7.70.4 pre vs. 5.70.2 mM post), isoaminoacidemic clamps. Results: Weight loss was 5.30.7 kg, as fat 4.00.3 kg (both p<0.004) and LBM 1.21.0 kg (NS), and RMR/LBM maintained. The following decreased post-diet (p<0.05): postabsorptive glycemia (7.70.4 to 5.70.2 mM), insulin (10917 to 698 pM), HOMA-IR (6.21.0 to 2.90.4), A1C (7.6 to 6.6%) and antihypertensive and/or diabetes medications. Whereas glucose Ra and Rd (1.90.2 mg/ kgBW/min) did not change, MCR (Rd/glycemia) increased. Notably, protein catabolism and oxidation decreased, resulting in less negative net balance (p<0.05). Clamp glucose Ra and Rd responses did not improve, but MCR increased from 2.30.2 to 3.50.4 mL/ kg∙min (p¼0.01); protein catabolism was suppressed but synthesis not stimulated, resulting in no net anabolism improvement. Summary/Conclusions: Weight lost was fat, lean mass preserved, fasting glycemia, insulin and protein balance improved. In response to hyperinsulinemia, only MCR improved, but protein metabolism did not worsen. Thus, abundant protein appears to preserve body proteins in the face of energy deficit and insulin resistance.
191 Indices of Insulin Suppression of Non-Esterified Fatty Acids Measured During an Oral Glucose Challenge and Their Association with the Insulin-Glucose Clamp Index and Central Adiposity FOUED NAIMI, JEAN-PATRICE BAILLARGEON Sherbrooke, QC Objective: To determine the indices of insulin-induced NEFA suppressibility derived from the oral glucose tolerance test (OGTT)
Abstracts / Can J Diabetes 37 (2013) S13eS84
that are best associated with the standard measure derived from the insulin-glucose clamp and with central adiposity. Methods: Sixteen men and 10 women, aged 20 to 35 years, without any disease or family history of type 2 diabetes, underwent a 75 g OGTT and a 2-step euglycemic clamp with low- and highdose insulin infusions (10 and 40 mU/kg/min). OGTT indices of NEFA suppressibility were: area under the curve (AUC) of NEFA, AUCNEFAAUCinsulin, NEFA T50, insulin concentration at T50 (EC50) and negative slope of the log-linear portion of NEFA suppression curve corrected by AUCinsulin (NegSlopeLnNEFA/AUCIns). NEFA insulin suppression during the clamp was calculated by DNEFA/Dinsulin at low-dose insulin (from baseline¼positive results). Central adiposity was estimated mainly by the waist-to-hip ratio (WHR) and glucose insulin sensitivity, by the M/I value (clamp, high-dose insulin). Results: OGTT-derived indices of insulin-induced NEFA suppression significantly associated with clamp DNEFA/Dinsulin: AUCNEFAAUCinsulin (r¼0.54), EC50 (r¼0.50), NegSlopeLnNEFA/AUCIns (r¼e0.44) and %reductionNEFA/AUCinsulin (r¼e0.42). The only index significantly associated with WHR: AUCNEFAAUCinsulin (r¼0.55). Based on a step-wise regression analysis, the variables significantly and independently associated with WHR were: AUCNEFAAUCinsulin (p¼0.002) and AUCglucose (p¼0.01) (model R2¼0.49). Conclusions: AUCNEFAAUCinsulin may represent the best OGTTderived parameter to estimate sensitivity to insulin suppression of lipolysis because, in our sample, it was the only one significantly correlated with central adiposity. Moreover, among all metabolic parameters measured in our study, AUCNEFAAUCinsulin and AUCglucose were the two main factors independently associated with central adiposity.
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193 Erythropoietin Signalling in Adipocytes is Not Essential for Regulation of Metabolism In Vivo CYNTHIA T. LUK*, SALLY Y. SHI, DIANA CHOI, ERICA P. CAI, STEPHANIE A. SCHROER, MINNA WOO Toronto, ON Erythropoietin (EPO) has increasingly been shown to have extraerythropoietic and cytoprotective roles. Exogenous administration has recently been shown to have beneficial effects on obesity and diabetes in mouse models and we have previously shown that EPO protects against diabetes through direct effects on pancreatic b-cells. EPO can directly modulate adipogenesis and insulin signalling in 3T3-L1 adipocytes; however, its physiological role in vivo has not been identified. To study the role of erythropoietin signalling in adipocytes, we used an adipocyte protein 2 (aP2) CRE-loxP recombination system to generate adipose tissue-specific erythropoietin receptor (EpoR) knockout mice. Knockout mice did not display any differences in weight gain compared to wild-type littermate controls on either control chow diet (p¼0.65, n¼5 males; p¼0.46, n¼5 females) or high-fat diet (HFD) (p¼0.79, n¼10 males; p¼0.76, n¼10 females) up to 8 months of age. Similarly, even with HFD, disruption of EpoR did not significantly alter body composition, adipose tissue morphology or energy homeostasis, including energy expenditure, respiratory expenditure ratio or activity level. Furthermore, disruption of EPO signalling in adipocytes did not alter glucose tolerance (p0.05, n¼14) or insulin sensitivity (p0.05, n¼14) in vivo, and did not alter adipocyte inflammation or expression of genes involved in angiogenesis. In summary, we determine that adipocyte EPO signalling is not essential for maintenance of energy homeostasis or glucose metabolism. In contrast to the pharmacological effects of EPO, we demonstrate that physiological EPO signalling is not essential for adipose tissue regulation of metabolism.
192 Influence of Depot Origin on the Susceptibility of Adipose Progenitor Cells to Cell Death AMANDA BIERNACKA-LAROCQUE*, ANNEMARIE GAGNON, ALEXANDER SORISKY Ottawa, ON Nutrient excess and a sedentary lifestyle lead to an accumulation of adipose tissue (obesity) through an increase in adipocyte size (hypertrophy) and number (hyperplasia). Hypertrophic obesity results in dysfunctional adipocytes associated with adipose tissue inflammation and insulin resistance. On the other hand, hyperplastic adipose tissue expansion is linked to preservation of insulin sensitivity. Metabolically functional adipose tissue expansion via hyperplasia may require an adequate number of responsive adipose progenitor cells. Distinct adipose tissue depots vary with respect to functional responses, such as lipolysis and adipogenesis. The aim of this study was to investigate the influence of depot origin on the susceptibility of adipose progenitor cells to cell death. Using serum deprivation alone or in the presence of 25nM tumor necrosis factor (TNF) a, visceral omental (OM) versus abdominal subcutaneous (SC) adipose progenitor cells displayed a 3- and 1.7-fold increase in cell death, as assessed by by Hoechst staining, respectively (p<0.05, n¼3 or 4). Similar results were obtained when cell death rates were evaluated by cell enumeration. The ratio of OM/SC cell death in response to serum deprivation was positively correlated with body mass index (r¼0.96; p<0.01, n¼5). The depot-specific difference in apoptosis susceptibility observed was lost when a stronger apoptotic stimulus (TNFa with cycloheximide) was used. Depot-related differences in apoptotic susceptibility of adipose progenitor cells may influence regional cellular remodelling during adipose tissue expansion and alter metabolic functionality in obesity.
194 Assessing Energy Expenditure in Obese Adolescents in a Clinical Setting: Is the Handheld Indirect Calorimeter Valid and Accurate? PAULA P.W. WOO*, GAYATHRI MURTHY*, CINDY WONG, JEAN-PIERRE CHANOINE, RAJAVEL ELANGO Vancouver, BC As energy balance is dependent on caloric consumption and expenditure, providing food recommendations based on individualized energy assessment could optimize pediatric weight management. Resting energy expenditure (REE), which contributes 70% to 80% of total energy expenditure, is key to meaningful energy prescriptions. Standard open-circuit indirect calorimeter carts (VMax, VM), used as a gold standard, measure valid REE but are not easily accessible. Recently, a handheld indirect calorimeter (MedGem, MG) has become available in the pediatric outpatient clinic. Its validity, however, has never been assessed in the obese adolescent ambulatory population. Objective: To validate REE measured by MG against VM in obese adolescents and to compare measured REE with those estimated by predictive equations. Methods: Eighteen adolescents (7:11, M:F), aged 14.71.8 years, participated in the study after an overnight fast. Anthropometric measurements were performed. REE were measured with both MG (upright, 7 to 13 mins) and VM (supine, 20 to 25 mins) in random order. Results: Body mass index was 31.34.7 kg/m2. Measured average REE using MG and VM were 1608331 kcal/day (19.6 kcal/kg) and 1666335 kcal/day (20.3 kcal/kg), respectively. Data show significant correlation (R2¼0.89) between the 2 methods. Predictive equations overestimate REE by 25% of indirect calorimeters.