Translational Medical Research Commons^™

Sphk2−/− Mice Are Protected From Obesity And Insulin Resistance, Shwetha Ravichandran, Brian S. Finlin, Philip A. Kern, Sabire Özcan

Clinical and Translational Science Faculty Publications

Sphingosine kinases phosphorylate sphingosine to sphingosine 1‑phosphate (S1P), which functions as a signaling molecule. We have previously shown that sphingosine kinase 2 (Sphk2) is important for insulin secretion. To obtain a better understanding of the role of Sphk2 in glucose and lipid metabolism, we have characterized 20- and 52-week old Sphk2^−/− mice using glucose and insulin tolerance tests and by analyzing metabolic gene expression in adipose tissue. A detailed metabolic characterization of these mice revealed that aging Sphk2^−/− mice are protected from metabolic decline and obesity compared to WT mice. Specifically, we found that 52-week old …

Efficacy Of Nutritional Interventions To Lower Circulating Ceramides In Young Adults: Fruvedomic Pilot Study, Alice T. Matthews, Oluremi A. Famodu, Melissa D. Olfert, Pamela J. Murray, Christopher F. Cuff, Marianne T. Downes, Norman J. Haughey, Sarah E. Colby, Paul D. Chantler, I. Mark Olfert, Joseph W. Mcfadden

Faculty & Staff Scholarship

The 2010 USDA Dietary Guidelines for Americans (DGA) recommends a diet largely composed of fruit and vegetables. Consuming a diet high in fruit and vegetables and low in refined carbohydrates and saturated fat may reduce an individual’s risk for type 2 diabetes, nonalcoholic fatty liver disease, low-grade chronic inflammation, and metabolic syndrome (MetS). Several recent studies have implicated the bioactive sphingolipid ceramide as an associative and causative biomarker for the development of these conditions. Considering that the intake of fruit and vegetables is frequently inadequate in young adults, we performed a pilot investigation to assess the efficacy of a free-living …

Impact Of Sleep And Circadian Disruption On Energy Balance And Diabetes: A Summary Of Workshop Discussions, Deanna M. Arble, Joseph Bass, Cecilia Diniz Behn, Matthew P. Butler, Etienne Challet, Charles Czeisler, Christopher M. Depner, Joel Elmquist, Paul Franken, Michael A. Grandner, Erin C. Hanlon, Alex C. Keene, Michael J. Joyner, Ilia Karatsoreos, Philip A. Kern, Samuel Klein, Christopher J. Morris, Allan I. Pack, Satchidananda Panda, Louis J. Ptacek, Naresh M. Punjabi, Paolo Sassone-Corsi, Frank A. Scheer, Richa Saxena, Elizabeth R. Seaquest, Matthew S. Thimgan, Eve Van Cauter, Kenneth P. Wright

Clinical and Translational Science Faculty Publications

A workshop was held at the National Institute for Diabetes and Digestive and Kidney Diseases with a focus on the impact of sleep and circadian disruption on energy balance and diabetes. The workshop identified a number of key principles for research in this area and a number of specific opportunities. Studies in this area would be facilitated by active collaboration between investigators in sleep/circadian research and investigators in metabolism/diabetes. There is a need to translate the elegant findings from basic research into improving the metabolic health of the American public. There is also a need for investigators studying the impact …

Insulin-Resistant Subjects Have Normal Angiogenic Response To Aerobic Exercise Training In Skeletal Muscle, But Not In Adipose Tissue, R. Grace Walton, Brian S. Finlin, Jyothi Mula, Douglas E. Long, Beibei Zhu, Christopher S. Fry, Philip M. Westgate, Jonah D. Lee, Tamara Bennett, Philip A. Kern, Charlotte A. Peterson

Clinical and Translational Science Faculty Publications

Reduced vessel density in adipose tissue and skeletal muscle is associated with obesity and may result in decreased perfusion, decreased oxygen consumption, and insulin resistance. In the presence of VEGFA, Angiopoietin-2 (Angpt2) and Angiopoietin-1 (Angpt1) are central determinants of angiogenesis, with greater Angpt2:Angpt1 ratios promoting angiogenesis. In skeletal muscle, exercise training stimulates angiogenesis and modulates transcription of VEGFA, Angpt1, and Angpt 2. However, it remains unknown whether exercise training stimulates vessel growth in human adipose tissue, and it remains unknown whether adipose angiogenesis is mediated by angiopoietin signaling. We sought to determine whether insulin-resistant subjects would display an impaired angiogenic …

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 …

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 …

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 …

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, …

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 …

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 …