bluuebunny/crossref_metadata_2025 huggingface dataset:
Possible Differences in the Mechanism(s) of Action of Different Glucocorticoid Hormone Compounds
Authors: LANZA L. , SCUDELETTI M. , MONACO E. , MONETTI M. , PUPPO F. , FILACI G. , INDIVERI F.
Published: February 2006

ABSTRACT: Different glucocorticoid hormones (GCH) show differences in the intensity and in the kinetics of their immunomodulating activity. The mechanism(s) of action of GCH is under investigation, but is has been noted that they exert immune activity via the genomic pathway. We have studied the effects of prednisone (PDN), deflazacort (DFC), and dexamethasone (DXM) on the production of cytokines (IL‐2, IL‐6, TNF‐α, IL‐10) by peripheral T lymphocytes, and the effects on the inhibition of NF‐kB DNA binding activity by activated Jurkat cell line. The data obtained show that the three GCH molecules exert an immunosuppression on cytokine production by T lymphocytes and a strong decrease in the nuclear translocation of NF‐kB in Jurkat cells; moreover, (a) not all the cytokines investigated were affected, and not with the same intensity, by the three GCH and (b) DXM inhibited the binding activity of NF‐kB less than that of DFC and PDN. These data are in agreement with the concept that different GCH compounds might differ in their binding and affinity properties, tissue‐specific metabolism, and interaction with transcription factor.
Expression of Chemokine Receptors in the Rat Braina
Authors: BAJETTO ADRIANA , BONAVIA RUDY , BARBERO SIMONE , FLORIO TULLIO , COSTA ALFREDO , SCHETTINI GENNARO
Published: February 2006

ABSTRACT: Human immunodeficiency virus (HIV‐1) infects the brain and causes a progressive encephalopathy in 20 to 30% of infected children and adults called AIDS dementia complex. Evidence from in vitro and in vivo studies suggests a role for the viral envelope glycoprotein gp120, as a mediator of neurotoxicity. However, the site of interaction of gp120 with neurons and astrocytes to mediate neuronal death is still unknown. Recently the chemokine receptors, CCR5 and CXCR4, have been identified as co‐receptors together with CD4 for HIV‐1 entry into the target cells, suggesting a possible role for these receptors in the pathogenesis of the HIV‐1 infection in the brain. Here we report the expression of CCR5 and CXCR4 in many different rat brain areas. We also found both receptors in cultured type I astrocytes demonstrating that glial cells may represent an important target for chemokines in vivo. Indeed, the functional capacity of CXCR4 receptor in astrocytes was demonstrated showing that SDF 1α induced an increase of intracellular calcium concentration.
Modulation by Cytokines of Glucocorticoid Action
Authors: ANGELI ALBERTO , MASERA ROSA GABRIELLA , SARTORI MARIA LUISA , FORTUNATI NICOLETTA , RACCA SILVIA , DOVIO ANDREA , STAURENGHI ANTONIO , FRAIRIA ROBERTO
Published: February 2006

ABSTRACT:Glucocorticoids (GC) are potent modulators of the inflammatory response. Their effects serve to down‐regulate the inflammatory response and are mediated by genomic pathways that follow the interaction with specific receptors (glucocorticoid receptors, GR). Interleukin (IL)‐1, IL‐2, and IL‐6 are able to increase GC secretion by enhancing synthesis and release of CRH and ACTH. Cytokine effects upon steroidogenesis also occur at the adrenal level. The role of cytokines as modulators of GR has received scarce attention. IL‐1 has been shown to up‐regulate GR mRNA expression in hypothalamic CRH secreting cells. On the other hand, macrophage migration inhibitory factor (MIF), a T‐cell product inducible by inflammatory substances including other cytokines, counterregulates GC action within the immune system. Besides immunocytes and neurons, bone cells are a sensitive target for GC and cytokines. We have found that IL‐2 and IL‐6 up‐regulate remarkably the number of GR binding sites and the expression of GR mRNA in peripheral blood mononuclear cells and in osteoblast‐like Saos‐2 cells. Available data suggest that inflammatory cytokines have both direct and indirect effects on GC action at the target level. Autocrine‐induced transcription of GR in immunocytes and/or osteoblasts could be a mechanism that restrains excess cytokine production.
IL‐15/IL‐15Rα Intracellular Trafficking in Human Cells and Protection from Apoptosisaa
Authors: PERENO RAFFAELE , GAGGERO ALESSIA , SCUDELETTI MARCO , LANZA LORELLA , MEAZZA RAFFAELLA , MISHAL ZOHAR , JASMIN CLAUDE , INDIVERI FRANCESCO , FERRINI SILVANO , AZZARONE BRUNO
Published: February 2006

ABSTRACT: IL‐15 is an immunostimulatory cytokine sharing with IL‐2 the IL‐2Rβγ complex. In vivo, IL‐15 detection in synovial fluids has been associated with the development of rheumatoid arthritis. A debate exists as to whether IL‐15 has the potential to be secreted in meaningful amounts or to act as a pericellular cytokine. Our data show (1) the presence of two IL‐15 isoforms displaying signal peptides of different length and the capacity to be secreted restricted to the isoform bearing the longer one; (2) in cells expressing the two isoforms, the existence of different nuclear localization and intracellular trafficking of IL‐15 and IL‐15Rα and (3) an intercellular microcirculation of IL‐15, not detectable with ELISA kits, but displaying a role as an anti‐apoptotic factor able to induce the deflection of the TNFR associated factor 2 (TRAF) to IL‐15Rα. Our data point to a juxtacrine mechanism of action of IL‐15 and suggest a role for IL‐15/IL‐15Rα in the regulation of apoptosis.
Melatonin Influences Interleukin‐12 and Nitric Oxide Production by Primary Cultures of Rheumatoid Synovial Macrophages and THP‐1 Cellsa
Authors: CUTOLO MAURIZIO , VILLAGGIO BARBARA , CANDIDO FEDERICA , VALENTI SANDRA , GIUSTI MASSIMO , FELLI LAMBERTO , SULLI ALBERTO , ACCARDO SILVANO
Published: February 2006

ABSTRACT: Because some of the clinical symptoms related to rheumatoid arthritis (RA) synovitis, such as joint morning stiffness and gelling, might be related to the effects exerted by the diurnal rhythmicity of the neurohormone melatonin (MLT) on synovial immune cell activation, we decided to evaluate the influence of MLT on the production of IL‐12 and nitric oxide (NO) on primary cultures of RA synovial macrophages. Synovial macrophages were also prestimulated with lipopolysaccaride (LPS). Results were compared with those obtained on cultured human myeloid monocytic cells (THP‐1). A significant increase in IL‐12 (p= 0.01) was found in media of MLT‐stimulated synovial macrophages versus RMPI‐treated synovial macrophage controls. Interestingly, a significant decrease of IL‐12 (p < 0.0001) was observed in media of synovial macrophages previously activated with LPS and then treated with MLT, when compared to synovial macrophages treated with LPS alone. A significant increase in NO levels (p= 0.01) was found in MLT‐stimulated synovial macrophages versus RMPI‐treated synovial macrophage controls. Interestingly, a nonsignificant increase of NO levels was observed in media of synovial macrophages previously activated with LPS and then treated with MLT, when compared to synovial macrophages treated with LPS alone. Finally, a significant increase in IL‐12 (p= 0.03) and NO (p= 0.002) concentrations was observed in media of MLT‐stimulated THP‐1 cells versus RMPI‐treated controls.

Our results therefore show that MLT induces IL‐12 secretion and NO production by unstimulated cultured RA synovial macrophages and human monocytic myeloid THP‐1 cells. The unexpected and opposite effects on IL‐12 and NO production in RA synovial macrophages treated with LPS may be related to dose‐dependent mechanisms exerted by MLT or to altered cell priming in RA macrophages; these are matters of our further research.

This study strongly supports the role of MLT in immune response modulation and in particular suggests a close relationship between diurnal rhythmicity of neuroendocrine pathways, cytokine and reactive oxygen intermediate production by monocyte/macrophages, and synovial arthritis symptomatology, at least in RA.
Androgens and Dry Eye in Sjögren's Syndromea
Authors: SULLIVAN DAVID A. , WICKHAM L. ALEXANDRA , ROCHA EDUARDO M. , KRENZER KATHLEEN L. , SULLIVAN BENJAMIN D. , STEAGALL REBECCA , CERMAK JENNIFER M. , DANA M. REZA , ULLMAN M. DAVID , SATO ELCIO H. , GAO JIANPING , ROCHA FLAVIO J. , ONO MASAFUMI , SILVEIRA LILIA A. , LAMBERT ROSS WILLIAM , KELLEHER ROBIN S. , TOLLS DOROTHY BAZZINOTTI , TODA IKUKO
Published: February 2006

ABSTRACT: Sjögren's syndrome is an extremely complex and currently incurable autoimmune disorder, which occurs primarily in females, and is associated with lacrimal gland inflammation, meibomian gland dysfunction, and severe dry eye. We hypothesize that androgen deficiency, which reportedly occurs in primary and secondary Sjögren's syndrome (e.g., systemic lupus erythematosus, rheumatoid arthritis), is a critical etiologic factor in the pathogenesis of dry eye syndromes. We further hypothesize that androgen treatment to the ocular surface will promote both lacrimal and meibomian gland function and alleviate both “aqueous‐deficient” and “evaporative” dry eye. Our results demonstrate that androgens regulate both lacrimal and meibomian gland function, and suggest that topical androgen administration may serve as a safe and effective therapy for the treatment of dry eye in Sjögren's syndrome.
Androgens and Ankylosing Spondylitis: A Role in the Pathogenesis?
Authors: GILTAY ERIK J. , van SCHAARDENBURG DIRKJAN , GOOREN LOUIS J. G. , POPP‐SNIJDERS CORRIE , DIJKMANS BEN A. C.
Published: February 2006

ABSTRACT: The frequency and severity of ankylosing spondylitis (AS) show a male preponderance, and androgenic steroids have been implicated in its etiology. Some reports have indicated that serum androgen levels are slightly elevated relative to estrogen levels in patients with AS as compared to controls.

In more recent studies, however, serum testosterone, 17β‐estradiol, and androstenedione levels did not significantly differ between AS patients and controls. Moreover, testosterone levels measured directly in serum can be spuriously elevated, especially in patients using phenylbutazone. Elevated serum levels of the adrenal steroids 17α‐hydroxyprogesterone and dehydroepiandrosterone (DHEA) sulfate have been found in patients with AS. These elevations might be explained by partial 11β‐ or 21‐hydroxylase deficiencies, but may also be secondary to an enhanced stress response. In vitro studies as well as studies in animals and humans indicate that DHEA enhanced, and 17β‐estradiol and progesterone inhibit, the cell‐mediated immune response, which may play a role in the pathogenesis of AS. Oral estrogen therapy in female patients and human chorionic gonadotrophin injections in male patients with AS, increased the 17β‐estradiol/testosterone ratio and resulted in a moderate clinical improvement.

In conclusion, serum testosterone levels are not elevated in patients with AS. Therefore testosterone probably has no role in the perpetuation of long‐standing AS and provides no basis for antiandrogenic treatment. Cross‐sectional case‐control studies, however, cannot clearly distinguish etiological factors from secondary disease effects, especially when blood sampling occurs many years after the onset of AS. Consequently, the role of sex steroids in the pathogenesis is still insufficiently elucidated.
Evaluation of Some Newer Matrix Metalloproteinases
Authors: MURPHY GILLIAN , KNÄUPER VERA , COWELL SUSAN , HEMBRY ROSALIND , STANTON HEATHER , BUTLER GEORGINA , FREIJE JOSÉ , PENDÁS ALBERTO M. , LÓPEZ‐OTÍN CARLOS
Published: February 2006

ABSTRACT: Recombinant protein expression techniques have been utilized to facilitate the biochemical and cell biological characterization of human matrix metalloproteinases (MMPs). The importance of the membrane type 1 MMP (MMP 14) in the regulation of pericellular proteolysis, either directly or through the activation of MMP‐2, MMP‐9, and MMP‐13 has been identified. Studies on an in vitro chondrocyte‐like cell and an in vivo cartilage repair model indicated that such MT1 MMP‐regulated activation cascades are physiologically feasible. MMP19 shows a limited sequence identity with other MMPs and may represent a novel subclass. However, analysis of the recombinant protein identified a number of biochemical properties typical of the MMP family.
The Next Generation of MMP Inhibitors: Design and Synthesis
Authors: DE BISWANATH , NATCHUS MICHAEL G. , CHENG MENYAN , PIKUL STANISLAW , ALMSTEAD NEIL G. , TAIWO YETUNDE O. , SNIDER CATHERINE E. , CHEN LONGYIN , BARNETT BOBBY , GU FEI , DOWTY MARTIN
Published: February 2006

ABSTRACT: Since their inception during the eighties, MMP inhibitors (MMPIs) have gone through several cycles of metamorphosis. The design of early MMPIs was based on the cleavage site of peptide substrates. The second generation contained a substituted succinate scaffold (e.g., marimastat) coupled to a modified amino acid residue. The lower molecular weight analogs with multiple substitution possibilities produced a series of MMP inhibitors with varying degrees of selectivity for various MMPs. The introduction of sulfonamides in the midnineties added a new dimension to this field. The simplicity of synthesis coupled with high potency (e.g., CGS‐27023A, AG‐3340) produced a number of clinical candidates. This review highlights some of the key features that contributed to the discovery of this novel series of MMP inhibitors.
Insights into MMP‐TIMP Interactions
Authors: BODE WOLFRAM , FERNANDEZ‐CATALAN CARLOS , GRAMS FRANK , GOMIS‐RÜTH FRANZ‐XAVER , NAGASE HIDEAKI , TSCHESCHE HARALD , MASKOS KLAUS
Published: February 2006

ABSTRACT: The proteolytic activity of the matrix metalloproteinases (MMPs) involved in extracellular matrix degradation must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance can result in serious diseases such as arthritis and tumor growth and metastasis. Knowledge of the tertiary structures of the proteins involved in such processes is crucial for understanding their functional properties and to interfere with associated dysfunctions. Within the last few years, several three‐dimensional structures have been determined showing the domain organization, the polypeptide fold, and the main specificity determinants of the MMPs. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure‐based design and improvement of high‐affinity ligands, which might be elaborated into drugs. Very recently, structural information also became available for some TIMP structures and MMP‐TIMP complexes, and these new data elucidated important structural features that govern the enzyme‐inhibitor interaction.
MMP‐9 Activity in Urine from Patients with Various Tumors, as Measured by a Novel MMP Activity Assay Using Modified Urokinase as a Substrate
Authors: HANEMAAIJER R. , SIER C.F. M. , VISSER H. , SCHOLTE L. , van LENT N. , HOEKMAN K. , VERHEIJEN J. H.
Published: February 2006

ABSTRACT: Matrix metalloproteinases (MMPs) play an important role in many pathologic processes, but their activities are difficult to determine since no simple specific and/or chromogenic substrate exists. We have developed a novel MMP activity assay using a modified urokinase as a substrate. Protein engineering enabled the plasmin activation site in this urokinase to be substituted by a specific activation site recognized by MMPs. In this way the MMP activity can be monitored via urokinase activity as measured by a simple chromogenic assay. The assay was made specific for MMP‐9 by a capture step using MMP‐9‐specific antibodies that do not interfere with MMP‐activity. This assay monitors the amount of active enzyme as well as the latent, but potentially active proform. Using this assay the levels of MMP‐9 were investigated in urine from patients with various kinds of carcinoma. High levels of both active and latent MMP‐9 were detected in urine from patients with carcinoma of the bladder, whereas hardly any activity was observed in urine from healthy controls. MMP‐9 in urine was present in its intact form. Surprisingly, MMP‐9 was also increased in the urine of patients with nonurogenital carcinoma. Therefore, measurement of urinary MMP‐9 activity levels may be a convenient diagnostic tool for various types of carcinoma.
Measurement of Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases in Blood and Tissues: Clinical and Experimental Applications
Authors: ZUCKER STANLEY , HYMOWITZ MICHELLE , CONNER CATHLEEN , ZARRABI HOSEIN M. , HUREWITZ ADAM N. , MATRISIAN LYNN , BOYD DOUGLAS , NICOLSON GARTH , MONTANA STEVE
Published: February 2006

ABSTRACT: The balance between production and activation of MMPs and their inhibition by TIMPs is a crucial aspect of cancer invasion and metastasis. On the basis of the concept that MMPs synthesized in tissues seep into the bloodstream, we have examined MMP levels in the plasma of patients with cancer. In colorectal, breast, prostate, and bladder cancer, most patients with aggressive disease have increased plasma levels of gelatinase B. In patients with advanced colorectal cancer, high levels of either gelatinase B or TIMP complex were associated with shortened survival. We propose that these assays may be clinically useful in characterizing metastatic potential in selected kinds of cancer. In rheumatoid arthritis and systemic lupus erythematosus (SLE), serum and plasma levels of stromelysin‐1 were ∼ 3‐5‐fold increased. Fluctuating serum stromelysin‐1 levels in SLE did not correspond with change in disease activity. In SLE, stromelysin‐1 may be a component of the chronic tissue repair process rather than being responsible for inciting tissue damage. On the basis of these observations, we conclude that measurement of plasma/serum MMP and TIMP levels may provide important data for selecting and following patients considered for treatment with drugs that interfere with MMP activity.
Preclinical and Clinical Studies of MMP Inhibitors in Cancer
Authors: DRUMMOND ALAN H. , BECKETT PAUL , BROWN PETER D. , BONE ELISABETH A. , DAVIDSON ALAN H. , GALLOWAY W. ALAN , GEARING ANDY J.H. , HUXLEY PHIL , LABER DAVID , MCCOURT MATTHEW , WHITTAKER MARK , WOOD L. MICHAEL , WRIGHT ANNETTE
Published: February 2006

ABSTRACT: The role of matrix metalloproteinases in tumor angiogenesis and growth is now well recognized for models of both human and animal cancer. Clinical studies currently under way with the prototype matrix metalloproteinase inhibitor, marimastat, will establish whether inhibitors of these enzymes are of benefit in the treatment of different types of human cancer. On chronic therapy in humans, marimastat induces a reversible tendinitis that can also be detected in certain animal species. This paper compares the ability of broad‐spectrum and various types of selective matrix metalloproteinase inhibitors to induce tendinitis and to exhibit anticancer effects in an animal cancer model. Under conditions in which both systemic exposure and inhibitor potency are controlled, selective inhibitors are less pro‐tendinitic, but are weaker anticancer agents than broad‐spectrum agents such as marimastat. The clinical relevance of these findings is discussed.
MMP‐Mediated Events in Diabetes
Authors: RYAN MARIA EMANUEL , RAMAMURTHY NUNGAVARUM S. , SORSA TIMO , GOLUB LORNE M.
Published: February 2006

ABSTRACT: Both Type I and Type II diabetes mellitus (DM) have been associated with unusually aggressive periodontitis. Accordingly, rat models of both types of DM were used to study (i) mechanisms mediating this systemic/local interaction and (ii) new pharmacologic approaches involving a series of chemically modified tetracyclines (CMTs) that have lost their antimicrobial but retained their host‐modulating (e.g., MMP‐inhibitory) properties. In vitro experiments on tissues from Type I DM rats demonstrated that several of these CMTs were better matrix metalloproteinase (MMP) inhibitors than was anti‐bacterial doxycycline (doxy), except for CMT‐5, which, unlike the other MMP inhibitors, was found not to react with zinc. Data from in vivo studies on the same rat model generally supported the relative efficacy of these compounds: the CMTs and doxy were found to inhibit MMP activity, enzyme expression, and alveolar bone loss. To examine other long‐term complications such as nephropathy and retinopathy, a Type II (ZDF) model of DM was studied. Treatment of these DM rats with CMT‐8 produced a 37% (p < 0.05), 93% (p < 0.001), and 50% (p < 0.01) reduction in the incidence of cataract development, proteinuria, and tooth loss, respectively; whereas the doxy‐treated ZDF rats showed little or no effect on these parameters. CMT treatment decreased mortality of the Type II ZDF diabetic animals, clearly indicating that CMTs, but not commercially available antibiotic tetracyclines (TCs), may have therapeutic applications for the long‐term management of diabetes.
Specialized Surface Protrusions of Invasive Cells, Invadopodia and Lamellipodia, Have Differential MT1‐MMP, MMP‐2, and TIMP‐2 Localization
Authors: CHEN WEN‐TIEN , WANG JAW‐YUAN
Published: February 2006

ABSTRACT: Surface protrusions, invadopodia, and analogous lamellipodia at the leading edge of an invasive cell, which make contact with the underlying extracellular matrix (ECM), are the main motor for cellular locomotion and invasion. Previous studies have demonstrated that invadopodia, but not lamellipodia, are sites of ECM degradation on the cell surface. Such degradative activity is in part due to the localization of latent matrix metalloproteinase‐2 (MMP‐2) and membrane type‐1 MMP (MT1‐MMP) to invadopodia, where MMP activation occurs. Although lamellipodia exhibit similar structure and mobility to invadopodia, lamellipodia, by virtue of their location at the cellular periphery, are readily accessible to the soluble tissue inhibitor of matrix metalloproteinase‐2 (TIMP‐2) and blood‐borne inhibitors. We show here that TIMP‐2 co‐localizes with MT1‐MMP and MMP‐2 at lamellipodia but not with that of invadopodia. Thus, the MMP‐TIMP localization at lamellipodia may be a key mechanism for the regulation of MMP activation on the cell surface, which in turn governs expression of the cell‐invasive phenotype.
Activation of ProMMP‐9 by a Plasmin/MMP‐3 Cascade in a Tumor Cell Model: Regulation by Tissue Inhibitors of Metalloproteinases
Authors: HAHN‐DANTONA ELIZABETH , RAMOS‐DeSIMONE NOEMI , SIPLEY JOHN , NAGASE HIDEAKI , FRENCH DEBORAH L. , QUIGLEY JAMES P.
Published: February 2006

ABSTRACT: To examine MMP‐9 activation in a cellular setting we employed cultures of human tumor cells that were induced to produce MMP‐9 over a 200‐fold concentration range (0.03 to 8.1 nM). The secreted levels of TIMPs in all the induced cultures remain relatively constant at 1‐4 nM. Quantitation of the zymogen/active enzyme status of MMP‐9 in the cultures indicates that even in the presence of potential activators, the molar ratio of endogenous MMP‐9 to TIMP dictates whether proMMP‐9 activation can progress. When the MMP‐9/TIMP ratio exceeds 1.0, MMP‐9 activation progresses, but only via an interacting protease cascade involving plasmin and stromelysin 1 (MMP‐3). Plasmin, generated by the endogenous plasminogen activator (uPA), is not an efficient activator of proMMP‐9. Plasmin, however, is very efficient at generating active MMP‐3 from exogenously added proMMP‐3. The activated MMP‐3, when its concentration exceeds that of TIMP, becomes a potent activator of proMMP‐9. Addition to the cultures of already‐activated MMP‐3 relinquishes the requirement for plasminogen and proMMP‐3 additions and results in direct activation of the endogenous proMMP‐9. The activated MMP‐9 enhances the invasive phenotype of the cultured cells as their ability to transverse basement membrane is significantly increased following zymogen activation. That this enhanced tissue remodeling capability is due to the activation of MMP‐9 is demonstrated through the use of a specific anti‐MMP‐9‐blocking monoclonal antibody.
Etiology of the Metabolic Syndrome: Potential Role of Insulin Resistance, Leptin Resistance, and Other Players
Authors: ZIMMET P. , BOYKO E. J. , COLLIER G. R. , de COURTEN M.
Published: February 2006

ABSTRACT: Obesity and Type 2 diabetes are now major public health issues in developed nations and have reached epidemic proportions in many developing nations, as well as disadvantaged groups in developed countries, e.g., Mexican‐Americans, African‐Americans, and Australian Aborigines. These groups all show hyperinsulinemia and insulin resistance, which have been demonstrated to be future predictors of Type 2 diabetes and have also been suggested as key factors in the etiology of the Metabolic Syndrome. It is now increasingly recognized that Type 2 diabetes is part of a cluster of cardiovascular disease (CVD) risk factors comprising the Metabolic Syndrome. This group is at very high risk of atherosclerosis because each of the risk factors in the Metabolic Syndrome cluster in its own right is an important CVD risk factor. They also contribute cumulatively to atherosclerosis. A key strategy in reducing macrovascular disease lies in the better understanding of the Metabolic Syndrome‐glucose intolerance, hypertension, hyperlipidemia, and central obesity. Although it has been suggested that hyperinsulinemia/insulin resistance is the central etiological factor for the Metabolic Syndrome, epidemiological data do not support the idea that this can account for all of the cluster abnormalities. We have animal and human data suggesting that hyperleptinemia rather than, or synergistically with, hyperinsulinemia may play a central role in the genesis of the CVD risk factor cluster that constitutes the syndrome. Studies in Psammomys obesus (the Israeli sand rat) suggest hyperinsulinemia/insulin resistance is an early metabolic lesion in the development of obesity and Type 2 diabetes. This animal also develops other features of the Metabolic Syndrome, making it an excellent model to investigate etiology. Psammomys, when placed on an ad libitum laboratory diet, develops hyperinsulinemia, insulin resistance, impaired glucose tolerance, diabetes, and dyslipidemia. It also develops hyperleptinemia and leptin insensitivity, and hyperleptinemia is correlated with insulin resistance independent of changes in body weight. It is likely that a similar sequence occurs in the transition from the prediabetic state to Type 2 diabetes in humans. More recently, other potential players in the etiology of the Metabolic Syndrome have been suggested including endothelial dysfunction and acetylation‐stimulating protein (ASP). It has been suggested that endothelial dysfunction may be an antecedent for both Type 2 diabetes and the Metabolic Syndrome. In addition, ASP is a serious new candidate for an important role in insulin resistance. The ASP pathway plays a critical role in fatty acid metabolism and storage, and it has been suggested that ineffective storage of fatty acids by adipocytes due to a defect in the ASP pathway may lead to insulin resistance and Type 2 diabetes.
Mechanisms of Hypertension and Kidney Disease in Obesity
Authors: HALL JOHN E. , BRANDS MICHAEL W. , HENEGAR JEFFREY R.
Published: February 2006

ABSTRACT: Abnormal kidney function is an important cause as well as a consequence of obesity. Excess renal sodium reabsorption, probably in the loop of Henle, and a hypertensive shift of pressure natriuresis play a major role in initiating increased blood pressure associated with weight gain. The mechanisms responsible for increased sodium reabsorption and altered pressure natriuresis in obesity include activation of the renin‐angiotension and sympathetic nervous systems, and physical compression of the kidneys due to accumulation of intrarenal fat and extracellular matrix. Sympathetic activation may be mediated, in part, by elevated circulating leptin and interactions with neuropeptides in the hypothalamus. Renal remodeling and extracellular matrix proliferation likely involve complex interactions between intrarenal physical forces, neurohumoral factors, and local growth factors and cytokines. Although glomerular hyperfiltration and increased arterial pressure help to compensate for increased renal tubular reabsorption in the early phases of obesity, these changes also increase glomerular capillary wall stress which, along with activation of neurohumoral systems and increased lipids and glucose intolerance, cause glomerular cell proliferation, matrix accumulation, and eventually glomerulosclerosis and loss of nephron function in the early phases of obesity. This creates a slowly developing vicious cycle that requires additional increases in arterial pressure to maintain sodium balance and therefore makes effective antihypertensive therapy more difficult. Because obesity is the main cause of Type 2 diabetes and an important cause of human essential hypertension, it seems likely that obesity is also one of the most important risk factors for end‐stage renal disease.
Chronic Angiotensin II Infusion Promotes Atherogenesis in Low Density Lipoprotein Receptor −/− Mice
Authors: DAUGHERTY ALAN , CASSIS LISA
Published: February 2006

ABSTRACT: The purpose of this study was to determine the effect of chronic angiotensin II (AngII) infusion on the severity of the atherogenic process in low density lipoprotein (LDL) receptor −/− mice with established lesions. LDL receptor −/− mice receiving a diet enriched in cholesterol, saturated fat, and cholate, were infused with saline or AngII (500 ng/kg/min) for 28 days. Systolic blood pressure increased in LDL receptor −/− mice following 7 days of AngII infusion, followed by a decline to baseline levels at 28 days, despite continued AngII infusion. Serum cholesterol was not influenced by AngII infusion in LDL receptor −/− mice; however, serum triglyceride concentrations were reduced significantly in LDL receptor −/− mice receiving AngII. The percent of intimal surface area covered by lesion was not increased in LDL receptor −/− mice receiving AngII; however, the content of cholesterol (esterified and unesterified) in lesions of the arch, thoracic, and abdominal aorta was significantly increased in those mice infused with AngII. Of note, in 20% of the LDL receptor −/− mice receiving AngII, large aneurysms were found in the abdominal aorta. Aneurysms appeared as breaks in the media and surrounding tissue of the vessel wall, encompassing amorphous and acellular masses with patches of thrombotic material. These results demonstrate that chronic infusion of AngII promotes the atherogenic processes in LDL receptor −/− mice, manifest as increases in lesion cholesterol content. Effects of AngII to promote atherogenesis were apparent at doses which did not markedly elevate systolic pressure. Importantly, infusion of AngII in LDL receptor −/− mice resulted in the development of aortic aneurysms.
Insulin Signaling and Action in Fat Cells: Associations with Insulin Resistance and Type 2 Diabetes
Authors: SMITH ULF , AXELSEN METTE , CARVALHO EUGENIA , ELIASSON BJÖRN , JANSSON PER‐ANDERS , WESSLAU CHRISTIAN
Published: February 2006

ABSTRACT: Adipose tissue only accounts for a relatively small proportion (<10%) of the peripheral glucose utilization in response to insulin. However, the fat cells may still play an important role in insulin resistance and Syndrome X through, for instance, its endocrine functions (production of leptin, TNFα, PAI‐1, etc.) and involvement in lipid metabolism (FFA release and hydrolysis of triglycerides). The fat cells are also highly sensitive to insulin and may thus be used to elucidate molecular mechanisms for insulin resistance in man. Examinations of the intracellular signaling mechanisms for insulin in fat cells from individuals with Type 2 diabetes revealed markedly lower insulin‐stimulated PI3‐kinase activity. This was due to a pronounced reduction in the cellular expression of the docking protein, IRS 1, whereas expression of IRS 2 was normal. However, IRS 2‐associated PI3‐kinase activity was only approximately one‐third of that found to be associated with IRS 1 in normal cells.

Downstream activation and serine phosphorylation of PKB/Akt by insulin were also markedly reduced in Type 2 diabetes. Furthermore, the dose‐response curve for this effect of insulin was similar to that for glucose transport in both normal and Type 2 diabetic cells. Thus, these data show that both PI3‐kinase and PKB activation by insulin are markedly reduced in Type 2 diabetes. We also examined whether an attenuated activation of PI3‐kinase by insulin can be seen in non‐diabetic insulin‐resistant states. Approximately 30% of healthy subjects with at least two first‐degree relatives with Type 2 diabetes exhibited perturbations in IRS‐1 expression and signaling. These individuals were characterized by insulin resistance as well as other markers of Syndrome X. Thus, impaired IRS‐1 expression and downstream signaling events in fat cells in response to insulin are associated with insulin resistance and Syndrome X.
Molecular Mechanism of Metabolic Syndrome X: Contribution of Adipocytokines · Adipocyte‐derived Bioactive Substances
Authors: MATSUZAWA YUJI , FUNAHASHI TOHRU , NAKAMURA TADASHI
Published: February 2006

ABSTRACT: Syndrome X is a clinical syndrome in which multiple risks cluster in an individual, and it is a common basis of vascular disease in the industrial countries. The molecular basis of Syndrome X, however, has not been elucidated. We have analyzed body fat distribution using CT scan and have shown that people who have accumulated intra‐abdominal visceral fat frequently have multiple risks and vascular diseases. Thus, “visceral fat syndrome” is a clinical entity compatible with Syndrome X. To clarify the molecular mechanism of the disorders in visceral fat syndrome, we analyzed the expressed genes in adipose tissue by a large‐scale random sequencing. Unexpectedly, visceral fat expressed a variety of the genes for secretory proteins including various bioactive substances; we designated them adipocytokines. One of them, plasminogen activator inhibitor‐1, was overproduced in accumulated visceral fat and might contribute to the development of vascular disease. We have also cloned a novel adipose‐specific gene named adiponectin. Adiponectin is a collagen‐like plasma protein which has an inhibitory effect on proliferation of vascular smooth muscle cells; its plasma levels are paradoxically decreased in obesity. Adipocytokines may play important roles in the development of the disorders in Syndrome X.
On the Control of Lipolysis in Adipocytes
Authors: LONDOS CONSTANTINE , BRASAEMLE DAWN L. , SCHULTZ CHARLES J. , ADLER‐WAILES DIANE C. , LEVIN DANIEL M. , KIMMEL ALAN R. , RONDINONE CRISTINA M.
Published: February 2006

ABSTRACT: The lipolytic reaction in adipocytes is one of the most important reactions in the management of bodily energy reserves, and dysregulation of this reaction may contribute to the symptoms of Type 2 diabetes mellitus. Yet, progress on resolving the molecular details of this reaction has been relatively slow. However, recent developments at the molecular level begin to paint a clearer picture of lipolysis and point to a number of unanswered questions. While HSL has long been known to be the rate‐limiting enzyme of lipolysis, the mechanism by which HSL attacks the droplet lipids is not yet firmly established. Certainly, the immunocytochemical evidence showing the movement of HSL to the lipid droplet upon stimulation leaves little doubt that this translocation is a key aspect of the lipolytic reaction, but whether or not HSL phosphorylation contributes to the translocation, and at which site(s), is as yet unresolved. It will be important to establish whether there is an activation step in addition to the translocation reaction. The participation of perilipin A is indicated by the findings that this protein can protect neutral lipids within droplets from hydrolysis, but active participation in the lipolytic reaction is yet to be proved. Again, it will be important to determine whether mutations of serine residues of PKA phosphorylation sites of perilipins prevent lipolysis, and whether such modifications abolish the physical changes in the droplet surfaces that accompany lipolysis.
Signaling Pathways Mediating Insulin‐Stimulated Glucose Transport
Authors: SUMMERS SCOTT A. , YIN VIRAVUTH P. , WHITEMAN EILEEN L. , GARZA LUIS A. , CHO HAN , TUTTLE ROBYN L. , BIRNBAUM MORRIS J.
Published: February 2006

ABSTRACT: A major action of insulin is to accelerate the rate of uptake of sugar into muscle and adipose cells following a meal. The biochemical mechanism by which this is accomplished has been a subject of intense experimentation, although elucidation of the pathways has remained elusive. In recent years, numerous signaling molecules and cascades modulated by insulin have been identified, although few have been definitively established as important to the metabolic actions of the hormone. An exception to this is the lipid kinase phosphatidylinositide 3′‐kinase, which, under many conditions, appears absolutely required for insulin to stimulate hexose uptake into adipocytes. Akt/PKB, a serine/threonine protein kinase activated by insulin in a phosphatidylinositide 3′‐kinase‐dependent manner, has been implicated as a critical mediator of insulin's actions on metabolism and cell survival. Nonetheless, Akt/PKB's role in many insulin effects, particularly accelerated glucose transport, remains controversial. Interestingly, soluble analogues of ceramide antagonize both insulin's activation of Akt/PKB as well as its stimulation of glucose transport, consistent with a causal relationship between the two.
Neuroendocrine Regulation of Nutrient Partitioning
Authors: ROHNER‐JEANRENAUD FRANÇOISE
Published: February 2006

ABSTRACT: Leptin is a satiety factor which acts within the hypothalamus to decrease the levels of several neuropeptides stimulating food intake (among them, neuropeptide Y [NPY]), while increasing those that inhibit food intake. These effects of leptin bring about decreased body weight. In vivo, leptin potentiates basal and insulin‐stimulated glucose utilization, presumably its oxidation, and decreases fat storage. Leptin increases sympathetic‐mediated energy dissipation, and the expression of uncoupling proteins‐1, ‐2, and ‐3. In peripheral tissues (muscles, adipose, others), leptin decreases triglyceride content by increasing fatty acid oxidation, decreasing the activity/expression of esterification and lipogenic enzymes, and favoring lipolysis. It decreases the lipogenic activity of insulin. Ultimately, leptin depletes fat stores and promotes leanness. NPY, taken as one example of what an orexigenic agent may produce, increases food intake and body weight. It favors fat storage in adipose tissue by stimulating lipogenic activity. It decreases glucose utilization by muscles, making more glucose carbon available for lipogenesis. Effects of NPY result from vagus nerve‐mediated hyperinsulinemia and overactivity of the hypothalamo‐pituitary‐adrenal axis. Thus, NPY favors fat stores, and ultimately obesity.

Glucocorticoids are necessary for NPY effects to occur, because central administration of the neuropeptide in adrenalectomized animals is ineffective. Glucocorticoids also have genuine effects when administered centrally to normal rats. They increase the hypothalamic content of NPY and decrease that of CRH. This double neuropeptidic change stimulates food intake, insulin output, adipose tissue storage ability, decreases the expression of uncoupling proteins‐1 and ‐3, and increases body weight. Body weight homeostasis appears to require a finely tuned regulation of both leptin and glucocorticoids, with their respective opposite effects.
Molecular Pathology in the Obese Spontaneous Hypertensive Koletsky Rat: A Model of Syndrome X
Authors: ERNSBERGER PAUL , KOLETSKY RICHARD J. , FRIEDMAN JACOB E.
Published: February 2006

ABSTRACT: The SHROB rat is a unique strain with genetic obesity, hypertriglyceridemia, hyperinsulinemia, renal disease with proteinuria, and genetically determined hypertension, characteristics paralleling human Syndrome X. The obese phenotype results from a single homozygous recessive trait, designated faK, and is allelic with the Zucker fatty trait (fa), but of distinct origin. The faK mutation is a premature stop codon in the extracellular domain of the leptin receptor, resulting in a natural receptor knockout. The SHROB are glucose intolerant compared to heterozygous or wild‐type SHR, but retain fasting euglycemia even on a high sucrose diet, suggesting that diabetes requires polygenic interaction with additional modifier genes. Insulin‐stimulated phosphorylation of tyrosine residues on the insulin receptor and on the associated docking protein IRS‐1 are reduced in skeletal muscle and liver compared to SHR, due mainly to diminished expression of insulin receptor and IRS‐1 proteins. Despite multiple metabolic derangements and severe insulin resistance, hypertension is not exacerbated in SHROB compared to SHR. Thus, insulin resistance and hypertension are independent in this model. Increased activity of the sympathetic nervous system may be a common factor leading by separate pathways to hypertension and to insulin resistance. We studied the chronic effects of sympathetic inhibition with moxonidine on glucose metabolism in SHROB. Moxoni‐dine (8 mg/kg/day), a selective I1‐imidazoline receptor agonist, not only reduced blood pressure but also ameliorated glucose intolerance. Moxonidine reduced fasting insulin by 47% and plasma free fatty acids by 30%. Moxonidine enhanced expression and insulin‐stimulated phosphorylation of IRS‐1 in skeletal muscle by 74 and 27%, respectively. Thus, central sympatholytic therapy not only counters hypertension but also insulin resistance, glucose tolerance, and hyperlipidemia in the SHROB model of Syndrome X.
Hypothalamic Origin of the Metabolic Syndrome X
Authors: BJÖRNTORP PER , ROSMOND ROLAND
Published: February 2006

ABSTRACT:The conspicuous similarities between Cushing's syndrome and the Metabolic Syndrome X open up the possibility that hypercortisolemia is involved also in the latter. Salivary cortisol is possible to measure during undisturbed conditions including perceived stressful events during everyday life. Such measurements clearly show that normally regulated cortisol secretion is associated with excellent health in anthropometric, metabolic, and hemodynamic variables. Upon perceived stress cortisol secretion is increased and followed by the Metabolic Syndrome X (insulin resistance, abdominal obesity, elevated lipids, and blood pressure). In a minor part of the population a defect, “burned‐out” cortisol secretion, occurs with decreased sex steroid and growth hormone secretions, and strong, consistent associations with the Metabolic Syndrome X. Psychosocial and socioeconomic handicaps with tendencies to abuse and depressive‐anxious mood changes are consistently associated. The feedback control of cortisol secretion by central glucocorticoid receptors (GR) is blunted, and the function of the GR is abnormal. This corresponds to a polymorphism early in the GR gene locus, which is also associated with abdominal obesity and insulin resistance and is found in 14% of the Swedish male population.

We suggest that the Metabolic Syndrome X is due to a discretely elevated cortisol secretion, discoverable during reactions to perceived stress in everyday life. This is based on environmental factors and expressed with different impact depending on genetic susceptibility.
Neurological Changes Induced by Stress in Streptozotocin Diabetic Rats
Authors: REAGAN LAWRENCE P. , MAGARIÑOS ANA MARIA , McEWEN BRUCE S.
Published: February 2006

ABSTRACT:Previous studies from our laboratory demonstrated that chronic stress produces molecular, morphological, and ultrastructural changes in the rat hippocampus that are accompanied by cognitive deficits. Glucocorticoid impairment of glucose utilization is proposed as a causative factor involved in stress‐induced changes. Current studies have examined the neurological changes induced by stress in rats with a preexisting strain upon their homeostatic load‐namely, in streptozotocin (stz)‐diabetic rats. Administration of stz (70 mg/kg, iv) produced diabetic symptoms such as weight loss, polyuria, polydipsia, hyperglycemia, and neuroendocrine dysfunction. Morphological analysis of hippocampal neurons revealed that diabetes alone produced dendritic atrophy of CA3 pyramidal neurons, an effect potentiated by 7 days of restraint stress. Analysis of genes critical to neuronal homeostasis revealed that glucose transporter 3 (GLUT3) mRNA and protein levels were specifically increased in the hippocampus of diabetic rats, while stress had no effect upon GLUT3 expression. Insulin‐like growth factor (IGF) receptor expression was also increased in the hippocampus of diabetic rats subjected to stress. In spite of the activation of these adaptive mechanisms, diabetic rats subjected to stress also had signs of neuronal damage and oxidative damage. Collectively, these results suggest that the hippocampus of diabetic rats is extremely susceptible to additional stressful events, which in turn can lead to irreversible hippocampal damage.
Functional Brain Imaging in the Resting State and during Activation in Alzheimer's Disease: Implications for Disease Mechanisms Involving Oxidative Phosphorylation
Authors: RAPOPORT STANLEY I.
Published: February 2006

ABSTRACT:In vivobrain imaging of patients with Alzheimer's disease (AD) using positron emission tomography (PET) demonstrates progressive reductions in resting‐state brain glucose metabolism and blood flow in relation to dementia severity, more so in association than primary cortical regions. During cognitive or psychophysical stimulation, blood flow and metabolism in the affected regions can increase to the same extent in mildly demented AD patients as in age‐matched controls, suggesting that energy delivery is not rate limiting. Activation declines with dementia severity, and is markedly reduced in severely demented patients. These results suggest that there is an initial “normal” functionally‐responsive stage in AD, followed by a late less responsive stage. Studies of biopsied and postmortem brain indicate that the initial stage is accompanied by selective and potentially reversible down‐regulation of the brain enzymes, including cytochrome oxidase, which mediate mitochondrial oxidative‐phosphorylation.
Use of Cytoplasmic Hybrid Cell Lines for Elucidating the Role of Mitochondrial Dysfunction in Alzheimer's Disease and Parkinson's Disease
Authors: GHOSH SOUMITRA S. , SWERDLOW RUSSELL H. , MILLER SCOTT W. , SHEEMAN BRINA , PARKER W. DAVIS , DAVIS ROBERT E.
Published: February 2006

ABSTRACT: There is substantial evidence of mitochondrial defects in neurodegenerative disorders such as Alzheimer's and Parkinson's diseases (AD and PD). We have probed the molecular implications of mitochondrial dysfunction in these diseases by transferring mitochondria from platelets obtained from disease and control donors into mitochondrial DNA‐depleted recipient neuron‐based cells (ρ0 cells). This process creates cytoplasmic hybrid (cybrid) cells where the mitochondrial DNA (mtDNA) from the donor is expressed in the nuclear and cellular background of the host ρ0 cell. Differences in phenotype between disease and control groups can thus be attributed to the exogenous mitochondria and mtDNA. Key methodological issues relating to this approach were addressed by demonstrating that recipient ρ0 cells have < 1 mtDNA copy/cell, and that exclusive repopulation with donor mtDNA occurs in cybrid cells. Further, we describe that sampling of heterogeneous cell populations is a valid approach for cybrid analysis. Our studies show that the focal respiratory chain defects reported in platelets of AD and PD cybrids can be recapitulated in AD and PD cybrids. In addition, both AD and PD cybrids display increased oxidative stress and perturbations in calcium homeostasis. These data suggest that the transfer of a mtDNA defect from disease donor platelets is the likely cause of the cybrid biochemical phenotype, and highlight the potential value of these cell lines as cellular disease models.