To improve the power of mediation in high-throughput studies, here we introduce High-throughput m... more To improve the power of mediation in high-throughput studies, here we introduce High-throughput mediation analysis (Hitman), which accounts for direction of mediation and applies empirical Bayesian linear modeling. We apply Hitman in a retrospective, exploratory analysis of the SLIMM-T2D clinical trial in which participants with type 2 diabetes were randomized to Roux-en-Y gastric bypass (RYGB) or nonsurgical diabetes/weight management, and fasting plasma proteome and metabolome were assayed up to 3 years. RYGB caused greater improvement in HbA1c, which was mediated by growth hormone receptor (GHR). GHR’s mediation is more significant than clinical mediators, including BMI. GHR decreases at 3 months postoperatively alongside increased insulin-like growth factor binding proteins IGFBP1/BP2; plasma GH increased at 1 year. Experimental validation indicates (1) hepatic GHR expression decreases in post-bariatric rats; (2) GHR knockdown in primary hepatocytes decreases gluconeogenic gene ...
Objective To identify metabolite patterns associated with childhood obesity, and to examine their... more Objective To identify metabolite patterns associated with childhood obesity, and to examine their relations with cardiometabolic risk biomarkers. Methods We quantified 350 metabolites in serum of 262 children 7-10 y with an untargeted mass spectrophotometry approach. Using principal component analysis, we characterized 18 metabolite patterns. Next, we compared factor scores for each pattern between obese (BMI 蠅 95 %tile; n = 84) and lean children (BMI < 85 %tile; n = 150) to identify patterns related to obesity. Using multivariable linear regression we examined relations of the metabolite factor scores with ln transformed HOMA-IR, leptin, adiponectin, triglycerides, CRP, and IL-6. Results Approximately half (50.6%) of the sample were boys; 58.9% were white. Compared to lean children, obese children had higher factor scores for a branched chain amino acid (BCAA) and an androstene steroid (AS) pattern. After adjustment for age, sex, and race, every 1 unit increment in the BCAA score corresponded to 7% (1%, ...
Abstract Current therapies for post-bariatric hypoglycemia (PBH) are incompletely effective. We p... more Abstract Current therapies for post-bariatric hypoglycemia (PBH) are incompletely effective. We previously reported feasibility of an open-loop glucagon system for this challenging syndrome. In this study, patients with PBH were enrolled in a double-masked, placebo-controlled, crossover trial to determine the efficacy of a closed-loop mini-dose glucagon delivery system to reduce severe hypoglycemia after a mixed meal. A novel hypoglycemia detection & mitigation algorithm was embedded in the Artificial Pancreas System connected to a continuous glucose monitor (CGM, Dexcom) driving a patch infusion pump (Insulet) filled with study drug (Xeris liquid glucagon or vehicle). After screening and enrollment, CGM were placed; participants returned after an overnight fast for the 1st of 2 study visits. A liquid mixed meal (Ensure Compact: 64 g CHO, 18 g protein, 236 mL) was consumed, and sensor/plasma glucose were measured serially. The system autonomously delivered up to 2 doses of study drug (300/150 mcg of glucagon or equal volume vehicle) if triggered by the hypoglycemia mitigation algorithm. If plasma glucose fell to <55 mg/dL or neuroglycopenia occurred, rescue IV dextrose was given per protocol. During a 2nd study visit, the protocol was repeated, with pump filled with the other study drug. Twelve participants (11F/1M, age 52+2, postoperative duration 8+1 years, mean+SEM) completed all study visits. In an additional 3 participants, the mixed meal did not trigger either alarm or hypoglycemia, so study drug was not administered, and a second visit was not conducted. For the 12 participants receiving glucagon vs. vehicle during 2 study visits, predictive hypoglycemia alerts prompted automated drug delivery at mean 94+6 vs. 89+5 (p=0.41) minutes post meal, when sensor glucose was 114+7 vs. 121+5 mg/dL (p=0.39). Four participants did not require rescue during either visit; 1 participant required rescue during both visits. Seven participants required rescue glucose after vehicle but not after glucagon (p=0.0082). Similarly, 5 participants had severe hypoglycemia (plasma glucose <55 mg/dL) after vehicle but not after glucagon (p=0.03). Nadir plasma glucose was higher in study visits with glucagon vs. vehicle delivery (67.4±2.7 vs. 58.5±1.9 mg/dL, p=0.004). Glucagon levels were not elevated at time of alert (14.6±1.4 pg/mL) but rose after glucagon delivery (1231±187 vs. vehicle 16 ±1.4 pg/mL at 30 minutes, p = 0.001). No rebound hyperglycemia occurred. Emesis occurred before study drug delivery in 2 visits. Transient pain at infusion site was reported during both glucagon (n=11 of 12) and vehicle (n=10 of 12) study visits. No other adverse advents were observed. Our data demonstrate that a CGM-guided glucagon closed-loop system can detect imminent hypoglycemia and deliver mini-dose glucagon, yielding improvements in post-meal glucose and reducing severe hypoglycemia in patients with PBH.
Liver-specific disruption of the type 2 deiodinase gene (Alb-D2KO) results in resistance to both ... more Liver-specific disruption of the type 2 deiodinase gene (Alb-D2KO) results in resistance to both diet-induced obesity and liver steatosis in mice. Here, we report that this is explained by an ∼60% reduction in liver zinc-finger protein-125 (Zfp125) expression. Zfp125 is a Foxo1-inducible transcriptional repressor that causes lipid accumulation in the AML12 mouse hepatic cell line and liver steatosis in mice by reducing liver secretion of triglycerides and hepatocyte efflux of cholesterol. Zfp125 acts by repressing 18 genes involved in lipoprotein structure, lipid binding, and transport. The ApoE promoter contains a functional Zfp125-binding element that is also present in 17 other lipid-related genes repressed by Zfp125. While liver-specific knockdown of Zfp125 causes an "Alb-D2KO-like" metabolic phenotype, liver-specific normalization of Zfp125 expression in Alb-D2KO mice rescues the phenotype, restoring normal susceptibility to diet-induced obesity, liver steatosis, and ...
Proceedings of the National Academy of Sciences of the United States of America, 2016
Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophys... more Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophysiology of human disease, because these cells can be differentiated into multiple cell types in vitro and used to generate patient- and tissue-specific disease models. Given the critical role for skeletal muscle insulin resistance in whole-body glucose metabolism and type 2 diabetes, we have created a novel cellular model of human muscle insulin resistance by differentiating iPS cells from individuals with mutations in the insulin receptor (IR-Mut) into functional myotubes and characterizing their response to insulin in comparison with controls. Morphologically, IR-Mut cells differentiated normally, but had delayed expression of some muscle differentiation-related genes. Most importantly, whereas control iPS-derived myotubes exhibited in vitro responses similar to primary differentiated human myoblasts, IR-Mut myotubes demonstrated severe impairment in insulin signaling and insulin-stimul...
Hypoglycemia is increasingly recognized as a complication of bariatric surgery. Typically, hypogl... more Hypoglycemia is increasingly recognized as a complication of bariatric surgery. Typically, hypoglycemia does not appear immediately postoperatively, but rather more than 1 year later, and usually occurs 1-3 h after meals. While rare, insulinoma has been reported after bariatric surgery. Clinical factors which should raise suspicion for insulinoma and the need for comprehensive clinical and biochemical evaluation include hypoglycemia occurring in the fasting state, predating bariatric surgery, and/or worsening immediately postoperatively, and lack of response to conservative therapy. Localization and successful resection of insulinoma can be achieved using novel endoscopic ultrasound and surgical approaches. In summary, hypoglycemia presenting shortly after gastric bypass or with a dominant fasting pattern should be fully evaluated to exclude insulinoma. Additionally, evaluation prior to gastric bypass should include screening for history of hypoglycemia symptoms.
The Journal of clinical endocrinology and metabolism, Jan 21, 2015
Increased circulating free fatty acids (FFA) have been proposed to contribute to insulin resistan... more Increased circulating free fatty acids (FFA) have been proposed to contribute to insulin resistance in obesity. Short-term studies have investigated the effects of acipimox, an inhibitor of hormone sensitive lipase, on glucose homeostasis, but longer term studies have not been performed. To test the hypothesis that long term treatment with acipimox would reduce FFA and improve insulin sensitivity among nondiabetic, insulin resistant obese subjects. At an academic medical center, 39 obese men and women were randomized to acipimox 250 mg thrice-daily vs. identical placebo for six months. plasma lipids, insulin sensitivity, adiponectin, and mitochondrial function via assessment of the rate of post-exercise phosphocreatine recovery (PCr) on (31)P-magnetic resonance spectroscopy as well as muscle mitochondrial density and relevant muscle gene expression Results: Fasting glucose decreased significantly in acipimox-treated individuals (effect size -6mg/dL, p=0.02), in parallel with trends ...
Advances in Molecular and Cellular Endocrinology, 2006
ABSTRACT The PGC-1 family of coactivator genes has emerged as attractive candidates for type 2 di... more ABSTRACT The PGC-1 family of coactivator genes has emerged as attractive candidates for type 2 diabetes (T2DM) diabetes for several reasons: (1) they play a central role in regulating expression of genes critical for maintenance of metabolic homeostasis and oxidative metabolism in key target tissues, and (2) expression of PGC-1 and mitochondrial oxidative genes is reduced in skeletal muscle and adipose tissue from humans with diabetes and “prediabetes.” In turn, this expression phenotype may be linked to both primary sequence alterations and environmental risk factors for diabetes, including overnutrition, obesity, and inactivity. We postulate that in genetically susceptible individuals, the development of obesity and decreased aerobic capacity due to inactivity may act in concert to reduce PGC-1 expression, contributing to impaired oxidative metabolism and accumulation of lipid in key insulin target tissues, thus increasing diabetes risk. In this chapter, we review the data supporting a potential role for PGC-1 family members as integrators between genetic and environmental risk factors at a molecular level and thus contributors to pathogenesis of T2DM.
Donohue syndrome (DS) is characterized by severe insulin resistance due to mutations in the insul... more Donohue syndrome (DS) is characterized by severe insulin resistance due to mutations in the insulin receptor (INSR) gene. To identify molecular defects contributing to metabolic dysregulation in DS in the undifferentiated state, we generated mesenchymal progenitor cells (MPC) from induced pluripotent stem cells (iPS) derived from a 4-week-old female with DS and a healthy newborn male (control). INSR mRNA and protein were significantly reduced in DS MPC (for β-subunit, 64% and 89% reduction, respectively, p<0.05), but IGF1R mRNA and protein did not differ vs. Insulin-stimulated phosphorylation of INSR or the downstream substrates IRS-1 and AKT did not differ, but ERK phosphorylation tended to be reduced in DS (32% decrease, p=0.07). By contrast, IGF-1 and insulin-stimulated IGF1R phosphorylation were increased in DS (IGF-1: 8.5 vs. 4.5-fold increase, INS: 11 vs. 6-fold, p<0.05). DS MPC tended to have higher oxygen consumption in both the basal state (87% higher, p=0.09) and in ...
To improve the power of mediation in high-throughput studies, here we introduce High-throughput m... more To improve the power of mediation in high-throughput studies, here we introduce High-throughput mediation analysis (Hitman), which accounts for direction of mediation and applies empirical Bayesian linear modeling. We apply Hitman in a retrospective, exploratory analysis of the SLIMM-T2D clinical trial in which participants with type 2 diabetes were randomized to Roux-en-Y gastric bypass (RYGB) or nonsurgical diabetes/weight management, and fasting plasma proteome and metabolome were assayed up to 3 years. RYGB caused greater improvement in HbA1c, which was mediated by growth hormone receptor (GHR). GHR’s mediation is more significant than clinical mediators, including BMI. GHR decreases at 3 months postoperatively alongside increased insulin-like growth factor binding proteins IGFBP1/BP2; plasma GH increased at 1 year. Experimental validation indicates (1) hepatic GHR expression decreases in post-bariatric rats; (2) GHR knockdown in primary hepatocytes decreases gluconeogenic gene ...
Objective To identify metabolite patterns associated with childhood obesity, and to examine their... more Objective To identify metabolite patterns associated with childhood obesity, and to examine their relations with cardiometabolic risk biomarkers. Methods We quantified 350 metabolites in serum of 262 children 7-10 y with an untargeted mass spectrophotometry approach. Using principal component analysis, we characterized 18 metabolite patterns. Next, we compared factor scores for each pattern between obese (BMI 蠅 95 %tile; n = 84) and lean children (BMI < 85 %tile; n = 150) to identify patterns related to obesity. Using multivariable linear regression we examined relations of the metabolite factor scores with ln transformed HOMA-IR, leptin, adiponectin, triglycerides, CRP, and IL-6. Results Approximately half (50.6%) of the sample were boys; 58.9% were white. Compared to lean children, obese children had higher factor scores for a branched chain amino acid (BCAA) and an androstene steroid (AS) pattern. After adjustment for age, sex, and race, every 1 unit increment in the BCAA score corresponded to 7% (1%, ...
Abstract Current therapies for post-bariatric hypoglycemia (PBH) are incompletely effective. We p... more Abstract Current therapies for post-bariatric hypoglycemia (PBH) are incompletely effective. We previously reported feasibility of an open-loop glucagon system for this challenging syndrome. In this study, patients with PBH were enrolled in a double-masked, placebo-controlled, crossover trial to determine the efficacy of a closed-loop mini-dose glucagon delivery system to reduce severe hypoglycemia after a mixed meal. A novel hypoglycemia detection & mitigation algorithm was embedded in the Artificial Pancreas System connected to a continuous glucose monitor (CGM, Dexcom) driving a patch infusion pump (Insulet) filled with study drug (Xeris liquid glucagon or vehicle). After screening and enrollment, CGM were placed; participants returned after an overnight fast for the 1st of 2 study visits. A liquid mixed meal (Ensure Compact: 64 g CHO, 18 g protein, 236 mL) was consumed, and sensor/plasma glucose were measured serially. The system autonomously delivered up to 2 doses of study drug (300/150 mcg of glucagon or equal volume vehicle) if triggered by the hypoglycemia mitigation algorithm. If plasma glucose fell to <55 mg/dL or neuroglycopenia occurred, rescue IV dextrose was given per protocol. During a 2nd study visit, the protocol was repeated, with pump filled with the other study drug. Twelve participants (11F/1M, age 52+2, postoperative duration 8+1 years, mean+SEM) completed all study visits. In an additional 3 participants, the mixed meal did not trigger either alarm or hypoglycemia, so study drug was not administered, and a second visit was not conducted. For the 12 participants receiving glucagon vs. vehicle during 2 study visits, predictive hypoglycemia alerts prompted automated drug delivery at mean 94+6 vs. 89+5 (p=0.41) minutes post meal, when sensor glucose was 114+7 vs. 121+5 mg/dL (p=0.39). Four participants did not require rescue during either visit; 1 participant required rescue during both visits. Seven participants required rescue glucose after vehicle but not after glucagon (p=0.0082). Similarly, 5 participants had severe hypoglycemia (plasma glucose <55 mg/dL) after vehicle but not after glucagon (p=0.03). Nadir plasma glucose was higher in study visits with glucagon vs. vehicle delivery (67.4±2.7 vs. 58.5±1.9 mg/dL, p=0.004). Glucagon levels were not elevated at time of alert (14.6±1.4 pg/mL) but rose after glucagon delivery (1231±187 vs. vehicle 16 ±1.4 pg/mL at 30 minutes, p = 0.001). No rebound hyperglycemia occurred. Emesis occurred before study drug delivery in 2 visits. Transient pain at infusion site was reported during both glucagon (n=11 of 12) and vehicle (n=10 of 12) study visits. No other adverse advents were observed. Our data demonstrate that a CGM-guided glucagon closed-loop system can detect imminent hypoglycemia and deliver mini-dose glucagon, yielding improvements in post-meal glucose and reducing severe hypoglycemia in patients with PBH.
Liver-specific disruption of the type 2 deiodinase gene (Alb-D2KO) results in resistance to both ... more Liver-specific disruption of the type 2 deiodinase gene (Alb-D2KO) results in resistance to both diet-induced obesity and liver steatosis in mice. Here, we report that this is explained by an ∼60% reduction in liver zinc-finger protein-125 (Zfp125) expression. Zfp125 is a Foxo1-inducible transcriptional repressor that causes lipid accumulation in the AML12 mouse hepatic cell line and liver steatosis in mice by reducing liver secretion of triglycerides and hepatocyte efflux of cholesterol. Zfp125 acts by repressing 18 genes involved in lipoprotein structure, lipid binding, and transport. The ApoE promoter contains a functional Zfp125-binding element that is also present in 17 other lipid-related genes repressed by Zfp125. While liver-specific knockdown of Zfp125 causes an "Alb-D2KO-like" metabolic phenotype, liver-specific normalization of Zfp125 expression in Alb-D2KO mice rescues the phenotype, restoring normal susceptibility to diet-induced obesity, liver steatosis, and ...
Proceedings of the National Academy of Sciences of the United States of America, 2016
Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophys... more Induced pluripotent stem cells (iPS cells) represent a unique tool for the study of the pathophysiology of human disease, because these cells can be differentiated into multiple cell types in vitro and used to generate patient- and tissue-specific disease models. Given the critical role for skeletal muscle insulin resistance in whole-body glucose metabolism and type 2 diabetes, we have created a novel cellular model of human muscle insulin resistance by differentiating iPS cells from individuals with mutations in the insulin receptor (IR-Mut) into functional myotubes and characterizing their response to insulin in comparison with controls. Morphologically, IR-Mut cells differentiated normally, but had delayed expression of some muscle differentiation-related genes. Most importantly, whereas control iPS-derived myotubes exhibited in vitro responses similar to primary differentiated human myoblasts, IR-Mut myotubes demonstrated severe impairment in insulin signaling and insulin-stimul...
Hypoglycemia is increasingly recognized as a complication of bariatric surgery. Typically, hypogl... more Hypoglycemia is increasingly recognized as a complication of bariatric surgery. Typically, hypoglycemia does not appear immediately postoperatively, but rather more than 1 year later, and usually occurs 1-3 h after meals. While rare, insulinoma has been reported after bariatric surgery. Clinical factors which should raise suspicion for insulinoma and the need for comprehensive clinical and biochemical evaluation include hypoglycemia occurring in the fasting state, predating bariatric surgery, and/or worsening immediately postoperatively, and lack of response to conservative therapy. Localization and successful resection of insulinoma can be achieved using novel endoscopic ultrasound and surgical approaches. In summary, hypoglycemia presenting shortly after gastric bypass or with a dominant fasting pattern should be fully evaluated to exclude insulinoma. Additionally, evaluation prior to gastric bypass should include screening for history of hypoglycemia symptoms.
The Journal of clinical endocrinology and metabolism, Jan 21, 2015
Increased circulating free fatty acids (FFA) have been proposed to contribute to insulin resistan... more Increased circulating free fatty acids (FFA) have been proposed to contribute to insulin resistance in obesity. Short-term studies have investigated the effects of acipimox, an inhibitor of hormone sensitive lipase, on glucose homeostasis, but longer term studies have not been performed. To test the hypothesis that long term treatment with acipimox would reduce FFA and improve insulin sensitivity among nondiabetic, insulin resistant obese subjects. At an academic medical center, 39 obese men and women were randomized to acipimox 250 mg thrice-daily vs. identical placebo for six months. plasma lipids, insulin sensitivity, adiponectin, and mitochondrial function via assessment of the rate of post-exercise phosphocreatine recovery (PCr) on (31)P-magnetic resonance spectroscopy as well as muscle mitochondrial density and relevant muscle gene expression Results: Fasting glucose decreased significantly in acipimox-treated individuals (effect size -6mg/dL, p=0.02), in parallel with trends ...
Advances in Molecular and Cellular Endocrinology, 2006
ABSTRACT The PGC-1 family of coactivator genes has emerged as attractive candidates for type 2 di... more ABSTRACT The PGC-1 family of coactivator genes has emerged as attractive candidates for type 2 diabetes (T2DM) diabetes for several reasons: (1) they play a central role in regulating expression of genes critical for maintenance of metabolic homeostasis and oxidative metabolism in key target tissues, and (2) expression of PGC-1 and mitochondrial oxidative genes is reduced in skeletal muscle and adipose tissue from humans with diabetes and “prediabetes.” In turn, this expression phenotype may be linked to both primary sequence alterations and environmental risk factors for diabetes, including overnutrition, obesity, and inactivity. We postulate that in genetically susceptible individuals, the development of obesity and decreased aerobic capacity due to inactivity may act in concert to reduce PGC-1 expression, contributing to impaired oxidative metabolism and accumulation of lipid in key insulin target tissues, thus increasing diabetes risk. In this chapter, we review the data supporting a potential role for PGC-1 family members as integrators between genetic and environmental risk factors at a molecular level and thus contributors to pathogenesis of T2DM.
Donohue syndrome (DS) is characterized by severe insulin resistance due to mutations in the insul... more Donohue syndrome (DS) is characterized by severe insulin resistance due to mutations in the insulin receptor (INSR) gene. To identify molecular defects contributing to metabolic dysregulation in DS in the undifferentiated state, we generated mesenchymal progenitor cells (MPC) from induced pluripotent stem cells (iPS) derived from a 4-week-old female with DS and a healthy newborn male (control). INSR mRNA and protein were significantly reduced in DS MPC (for β-subunit, 64% and 89% reduction, respectively, p<0.05), but IGF1R mRNA and protein did not differ vs. Insulin-stimulated phosphorylation of INSR or the downstream substrates IRS-1 and AKT did not differ, but ERK phosphorylation tended to be reduced in DS (32% decrease, p=0.07). By contrast, IGF-1 and insulin-stimulated IGF1R phosphorylation were increased in DS (IGF-1: 8.5 vs. 4.5-fold increase, INS: 11 vs. 6-fold, p<0.05). DS MPC tended to have higher oxygen consumption in both the basal state (87% higher, p=0.09) and in ...
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Papers by Mary Patti