Translational Medical Research Commons^™

Matrix Metalloproteinase-9 Is Increased In Obese Subjects And Decreases In Response To Pioglitazone, Resat Unal, Aiwei Yao-Borengasser, Vijayalakshmi Varma, Neda Rasouli, Craig Labbate, Philip A. Kern, Gouri Ranganathan

Clinical and Translational Science Faculty Publications

Context: The study investigated the regulation of matrix metalloproteinases (MMP)-9 in obesity-associated insulin resistance in humans.

Objectives: The objectives of the investigation were to study MMP-9 regulation by insulin resistance and pioglitazone treatment in impaired glucose tolerant subjects using adipose tissue biopsies and study the mechanism of MMP-9 regulation by pioglitazone in adipocyte cultures.

Research Design: 86 nondiabetic, weight-stable subjects between 21 and 66 yr of age were recruited in a university hospital research center setting. All subjects underwent a sc adipose tissue incisional biopsy from the lower abdominal wall and insulin sensitivity testing using a frequently sampled iv glucose …

The Impact Of Exercise Training Compared To Caloric Restriction On Hepatic And Peripheral Insulin Resistance In Obesity, Robert H. Coker, Rick H. Williams, Sophie E. Yeo, Patrick M. Kortebein, Don L. Bodenner, Philip A. Kern, William J. Evans

Clinical and Translational Science Faculty Publications

Context: It has been difficult to distinguish the independent effects of caloric restriction versus exercise training on insulin resistance.

Objective: Utilizing metabolic feeding and supervised exercise training, we examined the influence of caloric restriction vs. exercise training with and without weight loss on hepatic and peripheral insulin resistance.

Design, Participants, and Intervention: Thirty-four obese, older subjects were randomized to: caloric restriction with weight loss (CR), exercise training with weight loss (EWL), exercise training without weight loss (EX), or controls. Based on an equivalent caloric deficit in EWL and CR, we induced matched weight loss. Subjects in the EX group received …

Endoplasmic Reticulum Stress Markers Are Associated With Obesity In Nondiabetic Subjects, Neeraj K. Sharma, Swapan K. Das, Ashis K. Mondal, Oksana Hackney, Winston S. Chu, Philip A. Kern, Neda Rasouli, Horace J. Spencer, Aiwei Yao-Borengasser, Steven C. Elbein

Clinical and Translational Science Faculty Publications

Objective: Adipocyte and hepatocyte endoplasmic reticulum (ER) stress response is activated in dietary and genetic models of obesity in mice. We hypothesized that ER stress was also activated and associated with reduced insulin sensitivity (S_I) in human obesity.

Research Design and Methods: We recruited 78 healthy, nondiabetic individuals over a spectrum of body mass index (BMI) who underwent oral and iv glucose tolerance tests, and fasting sc adipose and muscle biopsies. We tested expression of 18 genes and levels of total and phosphorylated eukaryotic initiation factor 2α, c-jun, and c-Jun N-terminal kinase 1 in adipose tissue. We compared …

Stearoyl-Coenzyme A Desaturase 1 Gene Expression Increases After Pioglitazone Treatment And Is Associated With Peroxisomal Proliferator-Activated Receptor-Γ Responsiveness, Aiwei Yao-Borengasser, Negah Rassouli, Vijayalakshmi Varma, Angela M. Bodles, Neda Rasouli, Resat Unal, Bounleut Phanavanh, Gouri Ranganathan, Robert E. Mcgehee Jr., Philip A. Kern

Clinical and Translational Science Faculty Publications

Context and Objective: Stearoyl-coenzyme A desaturase (SCD1) is the rate-limiting enzyme that converts palmitoyl- and stearoyl-coenzyme A to palmitoleoyl- and oleoyl-cownzyme A, respectively. SCD-deficient mice are protected from obesity, and the ob/ob mouse has high levels of SCD. This study was designed to better characterize SCD1 gene and protein expression in humans with varying insulin sensitivity.

Design, Participants, and Setting: In a university hospital clinical research center setting, SCD1 gene expression was measured in sc adipose and vastus lateralis muscle of 86 nondiabetic subjects; 10 wk of pioglitazone (45 mg daily) and metformin (1000 mg twice daily) treatment were assessed …

Thrombospondin-1 Is An Adipokine Associated With Obesity, Adipose Inflammation, And Insulin Resistance, Vijayalakshmi Varma, Aiwei Yao-Borengasser, Angela M. Bodles, Neda Rasouli, Bounleut Phanavanh, Greg T. Nolen, Emily M. Kern, Radhakrishnan Nagarajan, Horace J. Spencer, Mi-Jeong Lee, Susan K. Fried, Charlotte A. Peterson, Philip A. Kern

Clinical and Translational Science Faculty Publications

OBJECTIVE-We examined the relationship between the expression of thrombospondin (TSP)1, an antiangiogenic factor and regulator of transforming growth factor-β activity, obesity, adipose inflammation, and insulin resistance.

RESEARCH DESIGN AND METHODS-TSP1 gene expression was quantified in subcutaneous adipose tissue (SAT) of 86 nondiabetic subjects covering a wide range of BMI and insulin sensitivity, from visceral adipose (VAT) and SAT from 14 surgical patients and from 38 subjects with impaired glucose tolerance randomized to receive either pioglitazone or metformin for 10 weeks. An adipocyte culture system was also used to assess the effects of pioglitazone and coculture with macrophages on …

Retinol Binding Protein 4 Expression In Humans: Relationship To Insulin Resistance, Inflammation, And Response To Pioglitazone, Aiwei Yao-Borengasser, Vijayalakshmi Varma, Angela M. Bodles, Neda Rasouli, Bounleut Phanavanh, Mi-Jeong Lee, Tasha Starks, Leslie M. Kern, Horace J. Spencer Iii, Amir Adel Rashidi, Robert E. Mcgehee Jr., Susan K. Fried, Philip A. Kern

Clinical and Translational Science Faculty Publications

Context: Retinol binding protein 4 (RBP4) was recently found to be expressed and secreted by adipose tissue, and was strongly associated with insulin resistance.

Objective: The aim was to determine the relationship between RBP4 and obesity, insulin resistance, and other markers of insulin resistance in humans.

Design and Patients: RBP4 mRNA levels in adipose tissue and muscle of nondiabetic human subjects with either normal or impaired glucose tolerance (IGT) were studied, along with plasma RBP4. RBP4 gene expression was also measured in adipose tissue fractions, and from visceral and sc adipose tissue (SAT) from surgical patients.

Setting: The study was …

Human Visfatin Expression: Relationship To Insulin Sensitivity, Intramyocellular Lipids, And Inflammation, Vijayalakshmi Varma, Aiwei Yao-Borengasser, Neda Rasouli, Angela M. Bodles, Bounleut Phanavanh, Mi-Jeong Lee, Tasha Starks, Leslie M. Kern, Horace J. Spencer Iii, Robert E. Mcgehee Jr., Susan K. Fried, Philip A. Kern

Clinical and Translational Science Faculty Publications

Context: Visfatin (VF) is a recently described adipokine preferentially secreted by visceral adipose tissue (VAT) with insulin mimetic properties.

Objective: The aim of this study was to examine the association of VF with insulin sensitivity, intramyocellular lipids (IMCL), and inflammation in humans.

Design and Patients: VF mRNA was examined in paired samples of VAT and abdominal sc adipose tissue (SAT) obtained from subjects undergoing surgery. Plasma VF and VF mRNA was also examined in SAT and muscle tissue, obtained by biopsy from well-characterized subjects with normal or impaired glucose tolerance, with a wide range in body mass index (BMI) and …

Oxpat/Pat-1 Is A Ppar-Induced Lipid Droplet Protein That Promotes Fatty Acid Utilization, Nathan E. Wolins, Benjamin K. Quaynor, James R. Skinner, Anatoly Tzekov, Michelle A. Croce, Matthew C. Gropler, Vijayalakshmi Varma, Aiwei Yao-Borengasser, Neda Rasouli, Philip A. Kern, Brian N. Finck, Perry E. Bickel

Clinical and Translational Science Faculty Publications

Lipid droplet proteins of the PAT (perilipin, adipophilin, and TIP47) family regulate cellular neutral lipid stores. We have studied a new member of this family, PAT-1, and found that it is expressed in highly oxidative tissues. We refer to this protein as "OXPAT." Physiologic lipid loading of mouse liver by fasting enriches OXPAT in the lipid droplet tissue fraction. OXPAT resides on lipid droplets with the PAT protein adipophilin in primary cardiomyocytes. Ectopic expression of OXPAT promotes fatty acid-induced triacylglycerol accumulation, long-chain fatty acid oxidation, and mRNAs associated with oxidative metabolism. Consistent with these observations, OXPAT is induced in mouse …

The Lipogenic Enzymes Dgat1, Fas, And Lpl In Adipose Tissue: Effects Of Obesity, Insulin Resistance, And Tzd Treatment, Gouri Ranganathan, Resat Unal, Irina D. Pokrovskaya, Aiwei Yao-Borengasser, Bounleut Phanavanh, Beata Lecka-Czernik, Neda Rasouli, Philip A. Kern

Clinical and Translational Science Faculty Publications

Acyl-coenzyme A:diacylglycerol transferase (DGAT), fatty acid synthetase (FAS), and LPL are three enzymes important in adipose tissue triglyceride accumulation. To study the relationship of DGAT1, FAS, and LPL with insulin, we examined adipose mRNA expression of these genes in subjects with a wide range of insulin sensitivity (S_I). DGAT1 and FAS (but not LPL) expression were strongly correlated with S_I. In addition, the expression of DGAT1 and FAS (but not LPL) were higher in normal glucose-tolerant subjects compared with subjects with impaired glucose tolerance (IGT) (P < 0.005). To study the effects of insulin sensitizers, subjects with IGT were treated with pioglitazone or metformin for 10 weeks, and lipogenic enzymes were measured in adipose tissue. After pioglitazone treatment, DGAT1 expression was increased by 33 ± 10% (P < 0.05) and FAS expression increased by 63 ± 8% (P < 0.05); however, LPL expression was not altered. DGAT1, FAS, and LPL mRNA expression were not significantly changed after metformin treatment. The treatment of mice with rosiglitazone also resulted in an increase in adipose expression of DGAT1 by 2- to 3-fold, as did the treatment of 3T3 F442A adipocytes in vitro with thiazolidinediones. These data support a more global concept suggesting that adipose lipid storage functions to prevent peripheral lipotoxicity.

Lipin Expression Is Attenuated In Adipose Tissue Of Insulin-Resistant Human Subjects And Increases With Peroxisome Proliferator-Activated Receptor Γ Activation, Aiwei Yao-Borengasser, Neda Rasouli, Vijayalakshmi Varma, Lesliie M. Miles, Bounleut Phanavanh, Tasha Starks, Jack Phan, Horace J. Spencer Iii, Robert E. Mcgehee Jr., Karen Reue, Philip A. Kern

Clinical and Translational Science Faculty Publications

Lipin-α and -β are the alternatively spliced gene products of the Lpin1 gene, whose product lipin is required for adipocyte differentiation. Lipin deficiency causes lipodystrophy, fatty liver, and insulin resistance in mice, whereas adipose tissue lipin overexpression results in increased adiposity but improved insulin sensitivity. To assess lipin expression and its relation to insulin resistance in humans, we examined lipin-α and -β mRNA levels in subjects with normal or impaired glucose tolerance. We found higher expression levels of both lipin isoforms in lean, insulin-sensitive subjects. When compared with normal glucose-tolerant subjects, individuals with impaired glucose tolerance were more insulin resistant, …

Pioglitazone Induces Apoptosis Of Macrophages In Human Adipose Tissue, Angela M. Bodles, Vijayalakshmi Varma, Aiwei Yao-Borengasser, Bounleut Phanavanh, Charlotte A. Peterson, Robert E. Mcgehee Jr., Neda Rasouli, Martin Wabitsch, Philip A. Kern

Clinical and Translational Science Faculty Publications

Metabolic syndrome and type 2 diabetes mellitus are associated with an increased number of macrophage cells that infiltrate white adipose tissue (WAT). Previously, we demonstrated that the treatment of subjects with impaired glucose tolerance (IGT) with the peroxisome proliferator-activated receptor γ (PPARγ) agonist pioglitazone resulted in a decrease in macrophage number in adipose tissue. Here, adipose tissue samples from IGT subjects treated with pioglitazone were examined for apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. TUNEL-positive cells were identified, and there was a significant 42% increase in TUNEL-positive cells following pioglitazone treatment. Overlay experiments with anti-CD68 antibody …

Expression Of Cd68 And Macrophage Chemoattractant Protein-1 Genes In Human Adipose And Muscle Tissues: Association With Cytokine Expression, Insulin Resistance, And Reduction By Pioglitazone, Gina B. Di Gregorio, Aiwei Yao-Borengasser, Neda Rasouli, Vijayalakshmi Varma, Tong Lu, Leslie M. Milrd, Gouri Ranganathan, Charlotte A. Peterson, Robert E. Mcgehee Jr., Philip A. Kern

Clinical and Translational Science Faculty Publications

To examine the role of adipose-resident macrophages in insulin resistance, we examined the gene expression of CD68, a macrophage marker, along with macrophage chemoattractant protein-1 (MCP-1) in human subcutaneous adipose tissue using real-time RT-PCR. Both CD68 and MCP-1 mRNAs were expressed in human adipose tissue, primarily in the stromal vascular fraction. When measured in the adipose tissue from subjects with normal glucose tolerance, covering a wide range of BMI (21-51 kg/m²) and insulin sensitivity (S_I) (0.6-8.0 × 10^-4 min^-1 · μU^-1 · ml^-1), CD68 mRNA abundance, which correlated with the number …

Divergent Effects Of Peroxisome Proliferator-Activated Receptor Γ Agonists And Tumor Necrosis Factor Α On Adipocyte Apoe Expression, Lili Yue, Neda Rasouli, Gouri Ranganathan, Philip A. Kern, Theodore Mazzone

Clinical and Translational Science Faculty Publications

ApoE is expressed in multiple mammalian cell types in which it supports cellular differentiated function. In this report we demonstrate that apoE expression in adipocytes is regulated by factors involved in modulating systemic insulin sensitivity. Systemic treatment with pioglitazone increased systemic insulin sensitivity and increased apoE mRNA levels in adipose tissue by 2-3-fold. Treatment of cultured 3T3-L1 adipocytes with ciglitazone increased apoE mRNA levels by 2-4-fold in a dose-dependent manner and increased apoE secretion from cells. Conversely, treatment of adipocytes with tumor necrosis factor (TNF) α reduced apoE mRNA levels and apoE secretion by 60%. Neither insulin nor a peroxisome …

Insulin Sensitivity Following Agent Orange Exposure In Vietnam Veterans With High Blood Levels Of 2,3,7,8-Tetrachlorodibenzo-P-Dioxin, Philip A. Kern, Sufyan Said, William G. Jackson Jr., Joel E. Michalek

Clinical and Translational Science Faculty Publications

Our objective was to determine whether insulin sensitivity was related to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Vietnam veterans exposed to Agent Orange. Air Force veterans of Operation Ranch Hand, the unit responsible for spraying Agent Orange and other herbicides in Vietnam from 1962 to 1971, and comparison veterans who did not spray herbicides were included. We measured insulin sensitivity (S_I) using a frequently sampled iv glucose tolerance test in a matched study of 29 matched pairs of veterans and a quantitative insulin sensitivity check index (QUICKI) based on fasting glucose and insulin in 71 matched pairs. No group differences were …

Transgenic Mice Expressing Lipoprotein Lipase In Adipose Tissue: Absence Of The Proximal 3′-Untranslated Region Causes Translational Upregulation, Lori L. Hensley, Gouri Ranganathan, Elke M. Wagner, Brian D. Wells, Joseph C. Daniel, Diane Vu, Clay F. Semenkovich, Rudolf Zechner, Philip A. Kern

Clinical and Translational Science Faculty Publications

Lipoprotein lipase (LPL) is a key enzyme in lipoprotein and adipocyte metabolism. Defects in LPL can lead to hypertriglyceridemia and the subsequent development of atherosclerosis. The mechanisms of regulation of this enzyme are complex and may occur at multiple levels of gene expression. Because the 3′-untranslated region (UTR) is involved in LPL translational regulation, transgenic mice were generated with adipose tissue expression of an LPL construct either with or without the proximal 3′-UTR and driven by the aP2 promoter. Both transgenic mouse colonies were viable and expressed the transgene, resulting in a 2-fold increase in LPL activity in white adipose …

Adiponectin Expression From Human Adipose Tissue: Relation To Obesity, Insulin Resistance, And Tumor Necrosis Factor-Α Expression, Philip A. Kern, Gina B. Di Gregorio, Tong Lu, Negah Rassouli, Gouri Ranganathan

Clinical and Translational Science Faculty Publications

Adiponectin is a 29-kDa adipocyte protein that has been linked to the insulin resistance of obesity and lipodystrophy. To better understand the regulation of adiponectin expression, we measured plasma adiponectin and adipose tissue adiponectin mRNA levels in nondiabetic subjects with varying degrees of obesity and insulin resistance. Plasma adiponectin and adiponectin mRNA levels were highly correlated with each other (r = 0.80, P < 0.001), and obese subjects expressed significantly lower levels of adiponectin. However, a significant sex difference in adiponectin expression was observed, especially in relatively lean subjects. When men and women with a BMI2were compared, women had a twofold higher percent body fat, yet their plasma adiponectin levels were 65% higher (8.6 ± 1.1 and 14.2 ± 1.6 μg/ml in men and women, respectively; P < 0.02). Plasma adiponectin had a strong association with insulin sensitivity index (S_I) (r = 0.67, P < 0.0001, n = 51) that was not affected by sex, but no relation with insulin secretion. To separate the effects of obesity (BMI) from S_I, subjects who were discordant for S_I were matched for BMI, age, and sex. Using this approach, insulin-sensitive subjects demonstrated a twofold higher plasma level of …

The Translational Regulation Of Lipoprotein Lipase By Epinephrine Involves An Rna Binding Complex Including The Catalytic Subunit Of Protein Kinase A, Gouri Ranganathan, Dan Phan, Irina D. Pokrovskaya, Joan E. Mcewen, Chunling Li, Philip A. Kern

Clinical and Translational Science Faculty Publications

The balance of lipid flux in adipocytes is controlled by the opposing actions of lipolysis and lipogenesis, which are controlled primarily by hormone-sensitive lipase and lipoprotein lipase (LPL), respectively. Catecholamines stimulate adipocyte lipolysis through reversible phosphorylation of hormone-sensitive lipase, and simultaneously inhibit LPL activity. However, LPL regulation is complex and previous studies have described translational regulation of LPL in response to catecholamines because of an RNA-binding protein that interacts with the 3′-untranslated region of LPL mRNA. In this study, we identified several protein components of an LPL RNA binding complex. Using an LPL RNA affinity column, we identified two of …

Regulation Of Lipoprotein Lipase By Protein Kinase Cα In 3t3-F442a Adipocytes, Gouri Ranganathan, Wei Song, Nicholas Dean, Brett Monia, Steven W. Barger, Philip A. Kern

Clinical and Translational Science Faculty Publications

Lipoprotein lipase (LPL) is an important enzyme in adipocyte and lipid metabolism with complex cellular regulation. Previous studies demonstrated an inhibition of LPL activity and synthesis following depletion of protein kinase C (PKC) isoforms with long term treatment of 3T3-F442A adipocytes with 12-O-tetradecanoylphorbol-13-acetate. To identify the specific PKC isoforms involved, we treated cells with antisense oligonucleotides that block expression of specific PKC isoforms. An antisense oligonucleotide to PKCα inhibited LPL activity by 78 ± 8%, whereas antisense oligonucleotides directed against PKCδ or PKCε had no effect on LPL activity. The change in LPL activity was maximal at 72 …

The Hiv Protease Inhibitor Saquinavir Impairs Lipid Metabolism And Glucose Transport In Cultured Adipocytes, S. Ranganathan, Philip A. Kern

Clinical and Translational Science Faculty Publications

Treatment of HIV infection using protease inhibitors is frequently associated with lipodystrophy and impaired lipid and glucose metabolism. We examined the effect of saquinavir, one of the protease inhibitors, on lipid metabolism and glucose transport in cultured adipocytes. Saquinavir inhibited lipoprotein lipase (LPL) activity in 3T3-F442A and 3T3-L1 adipocytes. The inhibition of LPL was 81% at a concentration of 20 μg/ml. Another closely related drug, indinavir, had a small inhibitory effect. Saquinavir also inhibited the biosynthesis of lipids from [¹⁴C]-acetate. Saquinavir increased the lipolysis. Saquinavir had no significant effect on the cellular protein synthesis or protein content. Saquinavir …

The Translational Regulation Of Lipoprotein Lipase In Diabetic Rats Involves The 3′-Untranslated Region Of The Lipoprotein Lipase Mrna, Gouri Ranganathan, Chunling Li, Philip A. Kern

Clinical and Translational Science Faculty Publications

Adipose tissue lipoprotein lipase (LPL) activity is decreased in patients with poorly controlled diabetes, and this contributes to the dyslipidemia of diabetes. To study the mechanism of this decrease in LPL, we studied adipose tissue LPL expression in male rats with streptozotocin-induced diabetes. Heparin releasable and extractable LPL activity in the epididymal fat decreased by 75-80% in the diabetic group and treatment of the rats with insulin prior to sacrifice reversed this effect. Northern blot analysis indicated no corresponding change in LPL mRNA levels. However, LPL synthetic rate, measured using [³⁵S]methionine pulse labeling, was decreased by 75% in …

Exposure To 2,3,7,8-Tetrachlorodibenzo-P-Dioxin (Tcdd) Is Associated With Hyperinsulinemia And Insulin Resistance, Morris Cranmer, Shirley Louie, Richard H. Kennedy, Philip A. Kern, Vivian A. Fonseca

Clinical and Translational Science Faculty Publications

High exposures of Vietnam veterans to 2,3,7,8-Tetrachlorodibenzo-p- dioxin, a dioxin contained in the herbicide mixture Agent Orange, have previously been demonstrated to be associated with an increased prevalence of diabetes and hyperinsulinemia in non-diabetic subjects. Sixty-nine persons were identified who were in good health and had normal glucose levels during glucose tolerance testing. These subjects lived within 25 miles of the Vertac/Hercules Superfund site located in Jacksonville, Arkansas. The blood sera lipid concentrations of TCDD for the 69 subjects ranged between 2 and 94 ppt. When subjects with blood sera lipid TCDD levels in the top 10% (TCDD > 15 ppt, …

Role Of Protein Kinase C In The Translational Regulation Of Lipoprotein Lipase In Adipocytes, Gouri Ranganathan, Rami Kaakaji, Philip A. Kern

Clinical and Translational Science Faculty Publications

The hypertriglyceridemia of diabetes is accompanied by decreased lipoprotein lipase (LPL) activity in adipocytes. Although the mechanism for decreased LPL is not known, elevated glucose is known to increase diacylglycerol, which activates protein kinase C (PKC). To determine whether PKC is involved in the regulation of LPL, we studied the effect of 12-O-tetradecanoyl phorbol 13-acetate (TPA) on adipocytes. LPL activity was inhibited when TPA was added to cultures of 3T3-F442A and rat primary adipocytes. The inhibitory effect of TPA on LPL activity was observed after 6 h of treatment, and was observed at a concentration of 6 nM. …

Thiazolidinediones Inhibit Lipoprotein Lipase Activity In Adipocytes, Subramanian Ranganathan, Philip A. Kern

Clinical and Translational Science Faculty Publications

The thiazolidinediones troglitazone and BRL 49653 improve insulin sensitivity in humans and animals with insulin resistance. Adipose tissue lipoprotein lipase is an insulin-sensitive enzyme. We examined the effects of thiazolidinediones on lipoprotein lipase expression in adipocytes. When added to 3T3-F442A, 3T3-L1, and rat adipocytes in culture, troglitazone and BRL 49653 inhibited lipoprotein lipase activity. This inhibition was observed at concentrations as low as 0.1 μM and within 2 h after addition of the drug. Lipoprotein lipase activity was inhibited in differentiated adipocytes as well as the differentiating cells. Despite this decrease in enzyme activity, these drugs increased mRNA levels in …

Lack Of Effect Of Leptin On Glucose Transport, Lipoprotein Lipase, And Insulin Action In Adipose And Muscle Cells, Subramanian Ranganathan, Theodore P. Ciaraldi, Robert R. Henry, Sunder Mudaliar, Philip A. Kern

Clinical and Translational Science Faculty Publications

The effect of leptin on glucose transport, lipogenesis, and lipoprotein lipase activity was studied in cultured rat adipocytes and 3T3-L1 adipocytes. Leptin had no effect on basal and insulin stimulated glucose transport in isolated adipocytes from the rat and the genetically obese mouse. The incorporation of glucose into lipids was also unaffected. Lipoprotein lipase (LPL) activity remained unchanged in response to leptin in these cells, as well as in minced adipose tissue. Leptin also had no effect on both basal and insulin-stimulated glucose transport in cultured rat and human skeletal muscle cells. These studies showed that leptin had no effect …

Effects Of Tumor Necrosis Factor-Α On Glucose Metabolism In Cultured Human Muscle Cells From Nondiabetic And Type 2 Diabetic Subjects, Theodore P. Ciaraldi, Leslie Carter, Sunder Mudaliar, Philip A. Kern, Robert R. Henry

Clinical and Translational Science Faculty Publications

The effects of tumor necrosis factor-a (TNFα) on glucose uptake and glycogen synthase (GS) activity were studied in human skeletal muscle cell cultures from nondiabetic and type 2 diabetic subjects. In nondiabetic muscle cells, acute (90-Min) exposure to TNFα (5 ng/ml) stimulated glucose uptake (73 ± 14% increase) to a greater extent than insulin (37 ± 4%; P < 0.02). The acute uptake response to TNFα in diabetic cells (51 ± 6% increase) was also greater than that to insulin (31 ± 3%; P < 0.05). Prolonged (24-h) exposure of nondiabetic muscle cells to TNFα resulted in a further stimulation of uptake (152 ± 31%; P < 0.05), whereas the increase in cells from type 2 diabetics was not significant compared with that in cells receiving acute treatment. After TNFα treatment, the level of glucose transporter-1 protein was elevated in nondiabetic (4.6-fold increase) and type 2 (1.7-fold) cells. Acute TNFα treatment had no effect on the fractional velocity of GS in either nondiabetic or type 2 cells. Prolonged exposure reduced the GS fractional velocity in both nondiabetic and diabetic cells. In summary, both acute and prolonged treatment with TNFα up-regulate glucose uptake activity in cultured human muscle cells, but reduce GS activity. Increased skeletal muscle glucose uptake in conditions of TNFα excess may serve as a compensatory mechanism in the insulin resistance of type 2 diabetes.

Potential Role Of Tnfα And Lipoprotein Lipase As Candidate Genes For Obesity, Philip A. Kern

Clinical and Translational Science Faculty Publications

To maintain body weight, metabolic efficiency was promoted during evolution; two candidate genes for body weight regulation are lipoprotein lipase (LPL) and tumor necrosis factor-α [TNFα). Human fat cells do not synthesize lipid, but rely on LPL-mediated plasma triglyceride hydrolysis. Adipose LPL is elevated in obesity. Following weight loss, LPL is elevated further, suggesting attempts to maintain lipid stores during fasting and to replenish lipid stores during refeeding. Muscle LPL is regulated inversely to adipose LPL. Thus, an increased adipose/muscle LPL ratio would partition dietary lipid into adipose tissue and would explain some of the variability in weight gain when …

Translational Regulation Of Lipoprotein Lipase By Epinephrine Involves A Trans-Acting Binding Protein Interacting With The 3′ Untranslated Region, Gouri Ranganathan, Diane Vu, Philip A. Kern

Clinical and Translational Science Faculty Publications

To better characterize the translational regulation of lipoprotein lipase (LPL) by epinephrine, cytoplasmic extracts were prepared from 3T3-L1 adipocytes, 3T3-F442A adipocytes, and other nonadipocyte cell lines (C2 cells, 3T3 fibroblasts, and Chinese hamster ovary cells). After treatment with epinephrine, cell extracts from the adipocytes inhibited LPL translation in an in vitro translation assay, whereas extracts from the C2 cells and 3T3 fibroblasts did not affect LPL translation. To identify the region on the LPL mRNA that controlled translation, in vitro translation was carried out using constructs containing different LPL sequences. Specific deletion of the first 50 (1601-1650) nucleotides of the …

1,25-Dihydroxyvitamin D Induces Lipoprotein Lipase Expression In 3t3-L1 Cells In Association With Adipocyte Differentiation, Diane Vu, John M. Ong, Thomas L. Clemens, Philip A. Kern

Clinical and Translational Science Faculty Publications

1,25-dihydroxyvitamin D₃ [1,25-(OH)₂D₃] is known to modulate the development of hone and other mesenchymal cell types. Since osteoblasts and adipocytes are thought to arise in bone marrow from a common progenitor, this work examined the effects of 1,25-(OH)₂D₃ on adipocyte development, and in particular on the expression of lipoprotein lipase (LPL), which is an early marker for the differentiated adipocyte. 3T3-L1 preadipocytes were cultured in the presence of 1.25-(OH)₂D₃ (10^-9 to 10^-7 M) for up to 7 days. LPL activity was measured in the medium and cell …

Tissue-Specific Expression Of Human Lipoprotein Lipase: Effect Of The 3′-Untranslated Region On Translation, Gouri Ranganathan, John M. Ong, Ada Yukht, Mehrnoosh Saghizadeh, Rosa B. Simsolo, Andrea Pauer, Philip A. Kern

Clinical and Translational Science Faculty Publications

Lipoprotein lipase (LPL) is a central enzyme in lipoprotein metabolism and is expressed predominantly in adipose tissue and muscle. In these tissues, the regulation of LPL is complex and often opposite in response to the same physiologic stimulus. In addition, much regulation of LPL occurs post-transcriptionally. The human LPL cDNA is characterized by a long 3′-untranslated region, which has two polyadenylation signals. In this report, human adipose tissue expressed two LPL mRNA species (3.2 and 3.6 kb) due to an apparent random choice of sites for mRNA polyadenylation, whereas human skeletal and heart muscle expressed predominantly the longer 3.6-kb mRNA …