bluuebunny/crossref_metadata_2025_split huggingface dataset:
Endothelial Nitric Oxide Synthase (eNOS) Knockout Mice Have Defective Mitochondrial β-Oxidation
Authors: Gouill Eric Le , Jimenez Maria , Binnert Christophe , Jayet Pierre-Yves , Thalmann Sebastien , Nicod Pascal , Scherrer Urs , Vollenweider Peter 
Published: September 2007

OBJECTIVE— Recent observations indicate that the delivery of nitric oxide by endothelial nitric oxide synthase (eNOS) is not only critical for metabolic homeostasis, but could also be important for mitochondrial biogenesis, a key organelle for free fatty acid (FFA) oxidation and energy production. Because mice deficient for the gene of eNOS (eNOS−/−) have increased triglycerides and FFA levels, in addition to hypertension and insulin resistance, we hypothesized that these knockout mice may have decreased energy expenditure and defective β-oxidation.
RESEARCH DESIGN AND METHODS— Several markers of mitochondrial activity were assessed in C57BL/6J wild-type or eNOS−/− mice including the energy expenditure and oxygen consumption by indirect calorimetry, in vitro β-oxidation in isolated mitochondria from skeletal muscle, and expression of genes involved in fatty acid oxidation.
RESULTS— eNOS−/− mice had markedly lower energy expenditure (−10%, P &lt; 0.05) and oxygen consumption (−15%, P &lt; 0.05) than control mice. This was associated with a roughly 30% decrease of the mitochondria content (P &lt; 0.05) and, most importantly, with mitochondrial dysfunction, as evidenced by a markedly lower β-oxidation of subsarcolemmal mitochondria in skeletal muscle (−30%, P &lt; 0.05). Finally, impaired mitochondrial β-oxidation was associated with a significant increase of the intramyocellular lipid content (30%, P &lt; 0.05) in gastrocnemius muscle.
CONCLUSIONS— These data indicate that elevated FFA and triglyceride in eNOS−/− mice result in defective mitochondrial β-oxidation in muscle cells.
Decreased l-Type Ca2+ Current in Cardiac Myocytes of Type 1 Diabetic Akita Mice Due to Reduced Phosphatidylinositol 3-Kinase Signaling
Authors: Lu Zhongju , Jiang Ya-Ping , Xu Xin-Hua , Ballou Lisa M. , Cohen Ira S. , Lin Richard Z. 
Published: September 2007

OBJECTIVE—Contraction of cardiac myocytes is initiated by Ca2+ entry through the voltage-dependent l-type Ca2+ channel (LTCC). Previous studies have shown that phosphatidylinositol (PI) 3-kinase signaling modulates LTCC function. Because PI 3-kinases are key mediators of insulin action, we investigated whether LTCC function is affected in diabetic animals due to reduced PI 3-kinase signaling.
RESEARCH DESIGN AND METHODS—We used whole-cell patch clamping and biochemical assays to compare cardiac LTCC function and PI 3-kinase signaling in insulin-deficient diabetic mice heterozygous for the Ins2Akita mutation versus nondiabetic littermates.
RESULTS—Diabetic mice had a cardiac contractility defect, reduced PI 3-kinase signaling in the heart, and decreased l-type Ca2+ current (ICa,L) density in myocytes compared with control nondiabetic littermates. The lower ICa,L density in myocytes from diabetic mice is due at least in part to reduced cell surface expression of the LTCC. ICa,L density in myocytes from diabetic mice was increased to control levels by insulin treatment or intracellular infusion of PI 3,4,5-trisphosphate [PI(3,4,5)P3]. This stimulatory effect was blocked by taxol, suggesting that PI(3,4,5)P3 stimulates microtubule-dependent trafficking of the LTCC to the cell surface. The voltage dependence of steady-state activation and inactivation of ICa,L was also shifted to more positive potentials in myocytes from diabetic versus nondiabetic animals. PI(3,4,5)P3 infusion eliminated only the difference in voltage dependence of steady-state inactivation of ICa,L.
CONCLUSIONS—Decreased PI 3-kinase signaling in myocytes from type 1 diabetic mice leads to reduced Ca2+ entry through the LTCC, which might contribute to the negative effect of diabetes on cardiac contractility.
PTEN Expression Contributes to the Regulation of Muscle Protein Degradation in Diabetes
Authors: Hu Zhaoyong , Lee In Hee , Wang Xiaonan , Sheng Hongmiao , Zhang Liping , Du Jie , Mitch William E. 
Published: September 2007

OBJECTIVE—Conditions accelerating muscle proteolysis are frequently associated with defective phosphatidylinositol 3-kinase (PI3K)/Akt signaling and reduced PI3K-generated phosphatidylinositol 3,4,5-triphosphate (PIP3). We evaluated the control of muscle protein synthesis and degradation in mouse models of type 1 and 2 diabetes to determine whether defects besides PI3K/Akt activities affect muscle metabolism.
RESEARCH DESIGN AND METHODS—We evaluated the expression and activity of PTEN, the phosphatase converting PIP3 to inactive phosphatidylinositol 4,5-bisphosphate, and studied how PTEN influences muscle protein in diabetic wild-type mice and in mice with partial deficiency of PTEN+/−.
RESULTS—In acutely diabetic mice, muscle PTEN expression was decreased. It was increased by chronic diabetes or insulin resistance. In cultured C2C12 myotubes, acute suppression of PI3K activity led to decreased PTEN expression, while palmitic acid increased PTEN in myotubes in a p38-dependent fashion. To examine whether PTEN affects muscle protein turnover, we studied primary myotubes cultures from wild-type and PTEN+/− mice. The proteolysis induced by serum deprivation was suppressed in PTEN+/− cells. Moreover, the sizes of muscle fibers in PTEN+/− and wild-type mice were similar, but the increase in muscle proteolysis caused by acute diabetes was significantly suppressed by PTEN+/−. This antiproteolytic response involved higher PIP3 and p-Akt levels and a decrease in caspase-3–mediated actin cleavage and activation of the ubiquitin-proteasome system as signified by reduced induction of atrogin-1/MAFbx or MurF1 (muscle-specific RING finger protein 1).
CONCLUSIONS—Changes in PTEN expression participate in the regulation of muscle proteolytic pathways. A decrease in PTEN could be a compensatory mechanism to prevent muscle protein losses.
Deficiency of Cbl-b Gene Enhances Infiltration and Activation of Macrophages in Adipose Tissue and Causes Peripheral Insulin Resistance in Mice
Authors: Hirasaka Katsuya , Kohno Shohei , Goto Jumpei , Furochi Harumi , Mawatari Kazuaki , Harada Nagakatsu , Hosaka Toshio , Nakaya Yutaka , Ishidoh Kazumi , Obata Toshiyuki , Ebina Yousuke , Gu Hua , Takeda Shin'ichi , Kishi Kyoichi , Nikawa Takeshi 
Published: September 2007

OBJECTIVE—c-Cbl plays an important role in whole-body fuel homeostasis by regulating insulin action. In the present study, we examined the role of Cbl-b, another member of the Cbl family, in insulin action.
RESEARCH DESIGN AND METHODS—C57BL/6 (Cbl-b+/+) or Cbl-b-deficient (Cbl-b−/−) mice were subjected to insulin and glucose tolerance tests and a hyperinsulinemic-euglycemic clamp test. Infiltration of macrophages into white adipose tissue (WAT) was assessed by immunohistochemistry and flow cytometry. We examined macrophage activation using co-cultures of 3T3-L1 adipocytes and peritoneal macrophages.
RESULTS—Elderly Cbl-b−/− mice developed glucose intolerance and peripheral insulin resistance; serum insulin concentrations after a glucose challenge were always higher in elderly Cbl-b−/− mice than age-matched Cbl-b+/+ mice. Deficiency of the Cbl-b gene significantly decreased the uptake of 2-deoxyglucose into WAT and glucose infusion rate, whereas fatty liver was apparent in elderly Cbl-b−/− mice. Cbl-b deficiency was associated with infiltration of macrophages into the WAT and expression of cytokines, such as tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein (MCP)-1. Co-culture of Cbl-b−/− macrophages with 3T3-L1 adipocytes induced leptin expression and dephosphorylation of insulin receptor substrate 1, leading to impaired glucose uptake in adipocytes. Furthermore, Vav1, a key factor in macrophage activation, was highly phosphorylated in peritoneal Cbl-b−/− macrophages compared with Cbl-b+/+ macrophages. Treatment with a neutralizing anti–MCP-1 antibody improved peripheral insulin resistance and macrophage infiltration into WAT in elderly Cbl-b−/− mice.
CONCLUSIONS—Cbl-b is a negative regulator of macrophage infiltration and activation, and macrophage activation by Cbl-b deficiency contributes to the peripheral insulin resistance and glucose intolerance via cytokines secreted from macrophages.
The Peroxisome Proliferator–Activated Receptor-γ Agonist Pioglitazone Increases Number and Function of Endothelial Progenitor Cells in Patients With Coronary Artery Disease and Normal Glucose Tolerance
Authors: Werner Christian , Kamani Christel Hermann , Gensch Christoph , Böhm Michael , Laufs Ulrich 
Published: September 2007

OBJECTIVE—Peroxisome proliferator–activated receptor-γ (PPARγ) agonists (thiazolidinediones [TZDs]) are used for the treatment of diabetes. Bone marrow–derived endothelial progenitor cells (EPCs) improve vascular function and predict cardiovascular risk. The effect of pioglitazone therapy on EPCs was examined.
RESEARCH DESIGN AND METHODS AND RESULTS—We performed a prospective, randomized, double-blind study on patients with documented stable coronary artery disease and normal glucose tolerance. Of 54 patients with normal fasting glucose levels, 18 showed impaired glucose tolerance and 36 patients with normal glucose tolerance were randomized to 30-day treatment with pioglitazone (45 mg) or placebo in addition to optimal medical therapy. All patients in the TZD group showed an increase of adiponectin levels as an indicator of compliance (11.4 ± 1.1 to 36.8 ± 2.1 μg/ml; P &lt; 0.001). TZD, but not placebo, decreased mean high-sensitivity C-reactive protein to 43 ± 19% (P &lt; 0.05). Pioglitazone increased CD34+/kinase insert domain receptor+ EPCs to 142 ± 9% and cultured 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine–labeled acetylated LDL+/lectin+ EPCs to 180 ± 3% (P &lt; 0.05). EPC numbers were not changed in the placebo group. TZD increased the SDF-1–induced migratory capacity to 146 ± 9% per EPC number (P &lt; 0.05) and upregulated the clonogenic potential of EPCs, increasing the colony-forming units to 172 ± 12% (P &lt; 0.001). In cultured human EPCs, TZD increased EPC numbers and migration and reduced NADPH-oxidase activity. The TZD effect was reversed by the PPARγ antagonist GW9662 and mimicked by treatment with adiponectin.
CONCLUSIONS—The PPARγ agonist pioglitazone increases the number and function of EPCs in patients with coronary artery disease. The effect represents a potential regenerative mechanism in atherosclerosis and is observed in normoglycemic individuals with stable coronary artery disease.
The Role of Melanocortin 3 Receptor Gene in Childhood Obesity
Authors: Seng Lee Yung , Kok Seng Poh Larry , Lay Kee Kek Betty , Yin Loke Kah 
Published: September 2007

OBJECTIVE—Melanocortin 3 receptor (MC3R) plays a critical role in weight regulation of rodents, but its role in humans remains unclear. The objective of this study was to identify genetic variants of the MC3R gene and determine its association with childhood obesity.
RESEARCH DESIGN AND METHODS—We screened 201 obese children for MC3R gene mutations with anthropometric measurements, blood tests, feeding behavior, and body composition assessment. We identified three novel heterozygous mutations (Ile183Asn, Ala70Thr, and Met134Ile) in three unrelated subjects, which were not found in 188 control subjects, and two common polymorphisms Thr6Lys and Val81Ile.
RESULTS—In vitro functional studies of the resultant mutant receptors revealed impaired signaling activity but normal ligand binding and cell surface expression. The heterozygotes demonstrated higher leptin levels and adiposity and less hunger compared with obese control subjects, reminiscent of the MC3R knockout mice. Family studies showed that these mutations may be associated with childhood or early-onset obesity. The common variants Thr6Lys and Val81Ile were in complete linkage disequilibrium, and in vitro studies revealed reduced signaling activity compared with wild-type MC3R. Obese subjects with the 6Lys/81Ile haplotype had significantly higher leptin levels, percentage body fat, and insulin sensitivity, and the causative role of the 6Lys/81Ile variants is supported by the presence of an additive effect in which heterozygotes had an intermediate phenotype compared with homozygotes.
CONCLUSIONS— MC3R mutations may not result in autosomal dominant forms of obesity but may contribute as a predisposing factor to childhood obesity and exert an effect on the human phenotype. Our report supports the role of MC3R in human weight regulation.
Evidence for a Role of Superoxide Generation in Glucose-Induced β-Cell Dysfunction In Vivo
Authors: Tang Christine , Han Ping , Oprescu Andrei I. , Lee Simon C. , Gyulkhandanyan Armen V. , Chan Gary N.Y. , Wheeler Michael B. , Giacca Adria 
Published: September 2007

OBJECTIVE— Prolonged elevation of glucose can adversely affect β-cell function. In vitro studies have linked glucose-induced β-cell dysfunction to oxidative stress; however, whether oxidative stress plays a role in vivo is unclear. Therefore, our objective was to investigate the role of oxidative stress in an in vivo model of glucose-induced β-cell dysfunction.
RESEARCH DESIGN AND METHODS— Wistar rats were infused intravenously with glucose for 48 h to achieve 20 mmol/l hyperglycemia with/without co-infusion of one of the following antioxidants: taurine (2-amino ethanesulfonic acid) (TAU), an aldehyde scavenger; N-acetylcysteine (NAC), a precursor of glutathione; or tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (TPO), a superoxide dismutase mimetic. This was followed by islet isolation or hyperglycemic clamp.
RESULTS— A 48-h glucose infusion decreased glucose-stimulated insulin secretion (GSIS) and elevated reactive oxygen species (ROS), total superoxide, and mitochondrial superoxide in freshly isolated islets. TPO prevented the increase in total and mitochondrial superoxide and the β-cell dysfunction induced by high glucose. However, TAU and NAC, despite completely normalizing H2DCF-DA (dihydro-dichlorofluorescein diacetate)-measured ROS, did not prevent the increase in superoxide and the decrease in β-cell function induced by high glucose. TPO but not TAU also prevented β-cell dysfunction induced by less extreme hyperglycemia (15 mmol/l) for a longer period of time (96 h). To further investigate whether TPO is effective in vivo, a hyperglycemic clamp was performed. Similar to the findings in isolated islets, prolonged glucose elevation (20 mmol/l for 48 h) decreased β-cell function as assessed by the disposition index (insulin secretion adjusted for insulin sensitivity), and co-infusion of TPO with glucose completely restored β-cell function.
CONCLUSIONS— These findings implicate superoxide generation in β-cell dysfunction induced by prolonged hyperglycemia.
In Vivo Cytotoxicity of Insulin-Specific CD8+ T-Cells in HLA-A*0201 Transgenic NOD Mice
Authors: Jarchum Irene , Baker Jason C. , Yamada Tatsuya , Takaki Toshiyuki , Marron Michele P. , Serreze David V. , DiLorenzo Teresa P. 
Published: September 2007

OBJECTIVE—CD8+ T-cells specific for islet antigens are essential for the development of type 1 diabetes in the NOD mouse model of the disease. Such T-cells can also be detected in the blood of type 1 diabetic patients, suggesting their importance in the pathogenesis of the human disease as well. The development of peptide-based therapeutic reagents that target islet-reactive CD8+ T-cells will require the identification of disease-relevant epitopes.RESEARCH DESIGN AND METHODS—We used islet-infiltrating CD8+ T-cells from HLA-A*0201 transgenic NOD mice in an interferon-γ enzyme-linked immunospot assay to identify autoantigenic peptides targeted during the spontaneous development of disease. We concentrated on insulin (Ins), which is a key target of the autoimmune response in NOD mice and patients alike.RESULTS—We found that HLA-A*0201-restricted T-cells isolated from the islets of the transgenic mice were specific for Ins1 L3–11, Ins1 B5–14, and Ins1/2 A2–10. Insulin-reactive T-cells were present in the islets of mice as young as 5 weeks of age, suggesting an important function for these specificities early in the pathogenic process. Although there was individual variation in peptide reactivity, Ins1 B5–14 and Ins1/2 A2–10 were the immunodominant epitopes. Notably, in vivo cytotoxicity to cells bearing these peptides was observed, further confirming them as important targets of the pathogenic process.CONCLUSIONS—The human versions of B5–14 and A2–10, differing from the murine peptides by only a single residue, represent excellent candidates to explore as CD8+ T-cell targets in HLA-A*0201–positive type 1 diabetic patients.
Mice Heterozygous for Tumor Necrosis Factor-α Converting Enzyme Are Protected From Obesity-Induced Insulin Resistance and Diabetes
Authors: Serino Matteo , Menghini Rossella , Fiorentino Loredana , Amoruso Roberta , Mauriello Alessandro , Lauro Davide , Sbraccia Paolo , Hribal Marta L. , Lauro Renato , Federici Massimo 
Published: September 2007

OBJECTIVE—Tumor necrosis factor (TNF)-α is known to affect insulin sensitivity, glucose, and lipid metabolism through alternative and redundant mechanisms at both translational and post-translational levels. TNF-α exerts its paracrine effects once the membrane-anchored form is shed and released from the cell membrane. TNF-α cleavage is regulated by TNF-α converting enzyme (TACE), which regulates the function of several transmembrane proteins, such as interleukin-6 receptor and epidermal growth factor receptor ligands. The role of TACE in high-fat diet (HFD)-induced obesity and its metabolic complications is unknown.
RESEARCH DESIGN AND METHODS—To gain insights into the role of TACE in metabolic disorders, we used Tace+/− mice fed a standard or high-fat diet for 16 weeks.
RESULTS—We observed that Tace+/− mice are relatively protected from obesity and insulin resistance compared with wild-type littermates. When fed an HFD, wild-type mice exhibited visceral obesity, increased free fatty acid and monocyte chemoattractant protein (MCP)1 levels, hypoadiponectinemia, glucose intolerance, and insulin resistance compared with Tace+/− mice. Interestingly, Tace+/− mice exhibited increased uncoupling protein-1 and GLUT4 expression in white adipose tissue.
CONCLUSIONS—Our results suggest that modulation of TACE activity is a new pathway to be investigated for development of agents acting against obesity and its metabolic complications.
Evidence for Vasculoprotective Effects of ETB Receptors in Resistance Artery Remodeling in Diabetes
Authors: Sachidanandam Kamakshi , Portik-Dobos Vera , Harris Alex K. , Hutchinson Jim R. , Muller Erin , Johnson Maribeth H. , Ergul Adviye 
Published: September 2007

OBJECTIVE—Vascular remodeling, characterized by extracellular matrix deposition and increased media-to-lumen (M/l) ratio, contributes to the development of microvascular complications in diabetes. Matrix metalloproteinases (MMPs) play an important role in the regulation of extracellular matrix (ECM) turnover and vascular remodeling. Vasoactive factor endothelin (ET)-1 not only causes potent vasoconstriction but also exerts profibrotic and proliferative effects that change vessel architecture, which makes it a likely candidate for a key role in vascular complications of diabetes. Thus, this study investigated the regulation of MMP activity of resistance arteries under mild-to-moderate diabetes conditions, as seen in type 2 diabetes, and the relative role of ET receptors in this process.
RESEARCH DESIGN AND METHODS—Vessel structure, MMP activity, and ECM proteins were assessed in control Wistar and diabetic Goto-Kakizaki (GK) rats treated with vehicle, ETA receptor antagonist atrasentan (5 mg · kg−1 · day−1), or ETB receptor antagonist A-192621 (15 mg · kg−1 · day−1) for 4 weeks.
RESULTS—M/l ratio was increased in diabetes. Atrasentan prevented this increase, whereas A-192621 caused further thickening of the medial layer. Increased MMP-2 activity in diabetes was prevented by atrasentan treatment. Collagenase activity was significantly decreased in diabetes, and while ETA antagonism improved enzyme activity, ETB blockade further reduced collagenase levels. Accordingly, collagen deposition was augmented in GK rats, which was reversed by atrasentan but exacerbated with A-192621.
CONCLUSIONS—ET-1 contributes to the remodeling of mesenteric resistance arteries in diabetes via activation of ETA receptors, and ETB receptors provide vasculoprotective effects.
Serum Cystatin C Predicts Progression of Subclinical Coronary Atherosclerosis in Individuals With Type 1 Diabetes
Authors: Maahs David M. , Ogden Lorraine G. , Kretowski Adam , Snell-Bergeon Janet K. , Kinney Gregory L. , Berl Tomas , Rewers Marian 
Published: September 2007

OBJECTIVE—Renal function is an important determinant of coronary atherosclerosis, and serum cystatin C is a novel accurate measure of glomerular filtration rate (GFR) and a predictor of cardiovascular events and mortality. We hypothesized that in individuals with type 1 diabetes, cystatin C would 1) predict progression of subclinical coronary atherosclerosis (SCA) and 2) be a stronger predictor of SCA than serum creatinine, GFR (estimated by the Cockcroft-Gault [GFRCG] and Modification of Diet in Renal Disease [GFRMDRD] formulas), and albumin excretion rate.RESEARCH DESIGN AND METHODS—Coronary artery calcification was measured twice, using Imatron C-150 Ultrafast CT, over a 2.5 ± 0.4-year interval in 509 adults with type 1 diabetes (42% male, age 36 ± 9 years, duration 23 ± 9 years). SCA progression (n = 131) was defined as a &gt;2.5 increase in square root calcium volume score or development of clinical coronary artery disease. Predictors of SCA progression were examined in a model selected by stepwise logistic regression and an a priori–determined model. Next, each measure of renal function was inserted into the stepwise model, one at a time, and Akaike information criterion was used to compare the fit of the competing models.RESULTS—The stepwise model included cystatin C (odds ratio 1.44, 95% CI 1.00–2.18, P = 0.048), age, baseline coronary artery calcification, sex, diabetes duration, systolic blood pressure, and HDL. The stepwise model had a better fit than any of the competing models with serum creatinine, GFRCG, GFRMDRD, or albumin excretion rate replacing cystatin C.CONCLUSIONS—In individuals with type 1 diabetes, cystatin C modestly predicts SCA.