Ki Up Lee

Preferential Infiltration of Macrophages During Early Stages of Insulitis in Diabetes-Prone BB Rats

The subpopulation of lymphoid cells at the different stages of insulitis in BB rats was determined by immunohistochemical techniques with various monoclonal antibodies, including the recently developed OX41, which distinguishes macrophages from T-lymphocytes, OX19 for pan–T-lymphocytes, W3/25 for both helper T-lymphocytes and macrophages, OX8 for cytotoxic T-lymphocytes and natural killer cells, and OX12 for B-lymphocytes. The major population of infiltrated cells found during the early stages of insulitis appeared to be macrophages. This preceded invasion by a mixed population of cells, including both T- and B-lymphocytes and/or natural killer cells. The preferential infiltration of macrophages during the early stages of insulitis strongly suggested that there might be an initial change in the target β-cells that precedes their immune destruction, although the amplification of immune response by activated T-lymphocytes and natural killer cells at a later stage seemed to be required for the clinical expression of the disease.

Hypothalamic Angptl4/Fiaf Is a Novel Regulator of Food Intake and Body Weight

OBJECTIVE The angiopoietin-like protein 4 (Angptl4)/fasting-induced adipose factor (Fiaf) is known as a regulator of peripheral lipid and glucose metabolism. In the present study, we investigated the physiological role of Angptl4 in central regulation of body weight homeostasis. RESEARCH DESIGN AND METHODS Hypothalamic Angptl4 expression levels were measured using immunoblot assay during feeding manipulation or after administration of leptin, insulin, and nutrients. The effects of Angptl4 on food intake, body weight, and energy expenditure were determined following intracerebroventricular (ICV) administration of Angptl4 in C57BL/6 mice. Food intake, energy metabolism, and feeding responses to leptin, insulin, and nutrients were compared between Angptl4-null mice and their wild littermates. Finally, the relationship of hypothalamic AMP-activated protein kinase (AMPK) and Angptl4 was studied. RESULTS Hypothalamic Angptl4 expression levels were increased upon food intake or administration of leptin, insulin, and nutrients. Furthermore, central administration of Angptl4 suppressed food intake and body weight gain but enhanced energy expenditure. These effects were mediated via suppression of hypothalamic AMPK activities. Consistently, Angptl4-null mice displayed increased body weight and hypothalamic AMPK activity but reduced energy expenditure. Food intake following a fast was significantly greater in Angptl4-null mice, which was normalized by centrally administered Angptl4. Moreover, anorectic responses to leptin, insulin, and glucose were diminished in Angptl4-null mice. In contrast, Angptl4-null mice were resistant to diet-induced obesity, indicating obesity-promoting effects of Angptl4 under the condition of fat-enriched diet. CONCLUSIONS We have demonstrated that hypothalamic Angptl4 is regulated by physiological appetite regulators and mediates their anorexigenic effects via inhibition of hypothalamic AMPK activity. Therefore, Angptl4 appears to have an important role in central regulation of energy metabolism.

Role of hypothalamic 5′-AMP-activated protein kinase in the regulation of food intake and energy homeostasis

Although obesity is an epidemic threat to general health worldwide, an effective treatment has yet to be found. Insights into weight-regulatory pathways will accelerate the identification of new molecular targets for anti-obesity agents. 5′-AMP-activated protein kinase (AMPK) is an enzyme activated during low cellular energy charge. In peripheral tissues, the activation of AMPK influences various metabolic pathways, including glucose uptake, glycolysis, and fatty acid oxidation, all of which help to re-establish a normal cellular energy balance. AMPK is also present in the neurons of the hypothalamus, a critical center in the regulation of energy homeostasis. Recent studies from our group and others have shown that many factors (α-lipoic acid, leptin, insulin, ghrelin, glucose, 2-deoxyglucose, etc.) cause an alteration in hypothalamic AMPK activity that mediates effects on feeding behavior. Hypothalamic AMPK also appears to play a role in the central regulation of energy expenditure and peripheral glucose metabolism. These data indicate that hypothalamic AMPK is an important signaling molecule that integrates nutritional and hormonal signals and modulates feeding behavior and energy metabolism.

Background and Data Configuration Process of a Nationwide Population-Based Study Using the Korean National Health Insurance System

Background The National Health Insurance Service (NHIS) recently signed an agreement to provide limited open access to the databases within the Korean Diabetes Association for the benefit of Korean subjects with diabetes. Here, we present the history, structure, contents, and way to use data procurement in the Korean National Health Insurance (NHI) system for the benefit of Korean researchers. Methods The NHIS in Korea is a single-payer program and is mandatory for all residents in Korea. The three main healthcare programs of the NHI, Medical Aid, and long-term care insurance (LTCI) provide 100% coverage for the Korean population. The NHIS in Korea has adopted a fee-for-service system to pay health providers. Researchers can obtain health information from the four databases of the insured that contain data on health insurance claims, health check-ups and LTCI. Results Metabolic disease as chronic disease is increasing with aging society. NHIS data is based on mandatory, serial population data, so, this might show the time course of disease and predict some disease progress, and also be used in primary and secondary prevention of disease after data mining. Conclusion The NHIS database represents the entire Korean population and can be used as a population-based database. The integrated information technology of the NHIS database makes it a world-leading population-based epidemiology and disease research platform.

Overexpression of Uncoupling Protein 2 in THP1 Monocytes Inhibits β2 Integrin-Mediated Firm Adhesion and Transendothelial Migration

Objective—Uncoupling protein 2 (UCP2) belongs to the mitochondrial anion carrier family and regulates production of reactive oxygen species in macrophages. Previous studies have shown that selective genetic disruption of UCP2 in bone marrow cells results in excess accumulation of monocytes/macrophages in the vascular wall of hypercholesterolemic low-density lipoprotein receptor-deficient (LDLR−/−) mice. Here we investigated whether UCP2 regulates expression of genes involved in monocyte recruitment. Methods and Results—UCP2 overexpression in THP1 monocytes, which induced a 10-fold increase in mitochondrial UCP2 protein levels, reduced steady-state level of intracellular reactive oxygen species (ROS) and H2O2-induced ROS production. THP1 monocytes with UCP2 overexpression showed lower intracellular calcium levels and less H2O2-triggered intracellular calcium mobilization, and less protein and mRNA levels of β2 integrins, most notably CD11b. UCP2 overexpression reduced β2 integrin-mediated firm adhesion of monocytes to either tumor necrosis factor-α (TNF-α)–stimulated human aortic endothelial cell (HAEC) monolayers or to plates coated with intercellular adhesion molecule-1, not vascular cell adhesion molecule-1. UCP2 overexpression also inhibited cell spreading and actin polymerization in monocytes treated with TNF-α and monocyte chemoattractant protein-1 (MCP-1), and reduced MCP-1–induced transmigration of monocytes through HAEC monolayers. Conclusions—Mitochondrial UCP2 in circulating monocytes may prevent excessive accumulation of monocytes/macrophages in the arterial wall, thereby reducing atherosclerotic plaque formation.

NF-κB Activation in Hypothalamic Pro-opiomelanocortin Neurons Is Essential in Illness- and Leptin-induced Anorexia

Anorexia and weight loss are prevalent in infectious diseases. To investigate the molecular mechanisms underlying these phenomena, we established animal models of infection-associated anorexia by administrating bacterial and viral products, lipopolysaccharide (LPS) and human immunodeficiency virus-1 transactivator protein (Tat). In these models, we found that the nuclear factor-κB (NF-κB), a pivotal transcription factor for inflammation-related proteins, was activated in the hypothalamus. In parallel, administration of LPS and Tat increased hypothalamic pro-inflammatory cytokine production, which was abrogated by inhibition of hypothalamic NF-κB. In vitro, NF-κB activation directly stimulated the transcriptional activity of pro-opiomelanocortin (POMC), a precursor of anorexigenic melanocortin, and mediated the stimulatory effects of LPS, Tat, and pro-inflammatory cytokines on POMC transcription, implying the involvement of NF-κB in controlling feeding behavior. Consistently, hypothalamic injection of LPS and Tat caused a significant reduction in food intake and body weight, which was prevented by blockade of NF-κB and melanocortin. Furthermore, disruption of IκB kinase-β, an upstream kinase of NF-κB, in POMC neurons attenuated LPS- and Tat-induced anorexia. These findings suggest that infection-associated anorexia and weight loss are mediated via NF-κB activation in hypothalamic POMC neurons. In addition, hypothalamic NF-κB was activated by leptin, an important anorexigenic hormone, and mediates leptin-stimulated POMC transcription, indicating that hypothalamic NF-κB also serves as a downstream signaling pathway of leptin.

Protective Role of Clusterin/Apolipoprotein J Against Neointimal Hyperplasia via Antiproliferative Effect on Vascular Smooth Muscle Cells and Cytoprotective Effect on Endothelial Cells

Objective—Clusterin is induced in vascular smooth muscle cells (VSMCs) during atherosclerosis and injury-induced neointimal hyperplasia. However, its functional roles in VSMCs and endothelial cells remain controversial and elusive. This study was undertaken to clarify the role of clusterin in neointimal hyperplasia and elucidate its mechanism of action. Methods and Results—Adenovirus-mediated overexpression of clusterin (Ad-Clu) repressed TNF-&agr;–stimulated expression of MCP-1, fractalkine, ICAM-1, VCAM-1, and MMP-9, leading to inhibition of VSMC migration. Both Ad-Clu and secreted clusterin suppressed VSMC proliferation by inhibiting DNA synthesis, but not by inducing apoptosis. Ad-Clu upregulated p53 and p21cip1/waf1 but downregulated cyclins D and E, leading to suppression of pRb phosphorylation and subsequent induction of G1 arrest in VSMCs. Clusterin deficiency augmented VSMC proliferation in vitro and accelerated neointimal hyperplasia in vivo, but concomitantly impaired reendothelialization in wire-injured murine femoral arteries. Moreover, Ad-Clu significantly reduced neointimal thickening in balloon-injured rat carotid arteries. Clusterin also diminished TNF-&agr;–induced apoptosis of human umbilical vein endothelial cells and restored endothelial nitric oxide synthase expression suppressed by TNF-&agr;. Conclusion—These results suggest that upregulation of clusterin during vascular injury may be a protective response against, rather than a causative response to, the development of neointimal hyperplasia.

Hormonal activity of AIMP1/p43 for glucose homeostasis

AIMP1/p43 is known as a cytokine working in the control of angiogenesis, inflammation, and wound healing. Here we report its enrichment in pancreatic α cells and glucagon-like hormonal activity. AIMP1 is secreted from the pancreas upon glucose starvation. Exogenous infusion of AIMP1 increased plasma levels of glucose, glucagon, and fatty acid, and AIMP1-deficient mice showed reduced plasma glucose levels compared with the wild-type mice under fasting conditions. Thus, AIMP1 plays a glucagon-like role in glucose homeostasis.

Clusterin Attenuates the Development of Renal Fibrosis

Upregulation of clusterin occurs in several renal diseases and models of nephrotoxicity, but whether this promotes injury or is a protective reaction to injury is unknown. Here, in the mouse unilateral ureteral obstruction model, obstruction markedly increased the expression of clusterin, plasminogen activator inhibitor-1 (PAI-1), type I collagen, and fibronectin. Compared with wild-type mice, clusterin-deficient mice exhibited higher levels of PAI-1, type I collagen, and fibronectin and accelerated renal fibrosis in response to obstruction. In cultured rat tubular epithelium-like cells, adenovirus-mediated overexpression of clusterin inhibited the expression of TGF-β-stimulated PAI-1, type I collagen, and fibronectin. Clusterin inhibited TGF-β-stimulated Smad3 activity via inhibition of Smad3 phosphorylation and its nuclear translocation. Moreover, intrarenal delivery of adenovirus-expressing clusterin upregulated expression of clusterin in tubular epithelium-like cells and attenuated obstruction-induced renal fibrosis. In conclusion, clusterin attenuates renal fibrosis in obstructive nephropathy. These results suggest that upregulation of clusterin during renal injury is a protective response against the development of renal fibrosis.

Dissociation of diabetes and obesity in mice lacking orphan nuclear receptor small heterodimer partner.

Mixed background SHP−/− mice are resistant to diet-induced obesity due to increased energy expenditure caused by enhanced PGC-1α expression in brown adipocytes. However, congenic SHP−/− mice on the C57BL/6 background showed normal expression of PGC-1α and other genes involved in brown adipose tissue thermogenesis. Thus, we reinvestigated the impact of small heterodimer partner (SHP) deletion on diet-induced obesity and insulin resistance using congenic SHP−/− mice. Compared with their C57BL/6 wild-type counterparts, SHP−/− mice subjected to a 6 month challenge with a Western diet (WestD) were leaner but more glucose intolerant, showed hepatic insulin resistance despite decreased triglyceride accumulation and increased β-oxidation, exhibited alterations in peripheral tissue uptake of dietary lipids, maintained a higher respiratory quotient, which did not decrease even after WestD feeding, and displayed islet dysfunction. Hepatic mRNA expression analysis revealed that many genes expressed higher in SHP−/− mice fed WestD were direct peroxisome proliferator-activated receptor alpha (PPARα) targets. Indeed, transient transfection and chromatin immunoprecipitation verified that SHP strongly repressed PPARα-mediated transactivation. SHP is a pivotal metabolic sensor controlling lipid homeostasis in response to an energy-laden diet through regulating PPARα-mediated transactivation. The resultant hepatic fatty acid oxidation enhancement and dietary fat redistribution protect the mice from diet-induced obesity and hepatic steatosis but accelerate development of type 2 diabetes.