The adipokine lipocalin 2 is regulated by obesity and promotes insulin resistance
ABSTRACT We identified lipocalin 2 (Lcn2) as a gene induced by dexamethasone and tumor necrosis factor-alpha in cultured adipocytes. The purpose of this study was to determine how expression of Lcn2 is regulated in fat cells and to ascertain whether Lcn2 could be involved in metabolic dysregulation associated with obesity.
We examined Lcn2 expression in murine tissues and in 3T3-L1 adipocytes in the presence and absence of various stimuli. We used quantitative Western blotting to observe Lcn2 serum levels in lean and obese mouse models. To assess effects on insulin action, we used retroviral delivery of short hairpin RNA to reduce Lcn2 levels in 3T3-L1 adipocytes.
Lcn2 is highly expressed by fat cells in vivo and in vitro. Expression of Lcn2 is elevated by agents that promote insulin resistance and is reduced by thiazolidinediones. The expression of Lcn2 is induced during 3T3-L1 adipogenesis in a CCAAT/enhancer-binding protein-dependent manner. Lcn2 serum levels are elevated in multiple rodent models of obesity, and forced reduction of Lcn2 in 3T3-L1 adipocytes improves insulin action. Exogenous Lcn2 promotes insulin resistance in cultured hepatocytes.
Lcn2 is an adipokine with potential importance in insulin resistance associated with obesity.
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ABSTRACT: The aim of this study was to evaluate serum levels and urinary excretion of neutrophil-gelatinase associated lipocalin (respectively sNGAL and uNGAL) and urinary excretion of Cathepsin L (uCathL) in children with type 1 diabetes mellitus (DM1) who presented normoalbuminuria and the estimated glomerular filtration rate (eGFR) above 90 mL/min/1.73 m2. The study group consisted of 63 children with a diabetes duration of 5.16 ± 3.39 years. The degree of albuminuria was based on urine albumin-to-creatinine ratio (ACR), while eGFR was based on serum cystatin C. Glomerular hyperfiltration (GH) was defined as an eGFR value above 135 mL/min/1.73 m2. Children with DM1 showed significantly higher concentrations of uNGAL, and lower sNGAL and uCathL. Significant changes of uNGAL and uCathL levels were even found in children without GH and with optimal glycaemic control (HbA1c < 7.5%). Positive correlations between uNGAL, ACR and eGFR were shown, as well as between uCathL and eGFR. Significant changes in the concentration of markers of early kidney injury: sNGAL, uNGAL, and uCathL, can occur in children with DM1 and normoalbuminuria. The changes of uNGAL and uCathL can be even found in children without GH and with optimal glycaemic control. The earliest signs of diabetic kidney dysfunction seem to result from tubular damage. (Endokrynol Pol 2014; 65 (6): 479-484).Endokrynologia Polska 01/2014; 65(6):479-84. DOI:10.5603/EP.2014.0067 · 1.21 Impact Factor
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ABSTRACT: Obesity is associated with increased breast cancer (BrCA) incidence. Considering that inactivation of the estrogen receptor (ER)α promotes obesity and metabolic dysfunction in women and female mice, understanding the mechanisms and tissue-specific sites of ERα action to combat metabolic-related disease, including BrCA, is of clinical importance. To study the role of ERα in adipose tissue we generated fat-specific ERα knockout (FERKO) mice. Herein we show that ERα deletion increased adipocyte size, fat pad weight, and tissue expression and circulating levels of the secreted glycoprotein, lipocalin 2 (Lcn2), an adipokine previously associated with BrCA development. Chromatin immunoprecipitation and luciferase reporter studies showed that ERα binds the Lcn2 promoter to repress its expression. Since adipocytes constitute an important cell type of the breast microenvironment, we examined the impact of adipocyte ERα deletion on cancer cell behavior. Conditioned media (CM) from ERα-null adipocytes and media containing pure Lcn2 increased proliferation and migration of a sub-set of BrCA cells in culture. The proliferative and pro-migratory effects of ERα-deficient adipocyte CM on BrCA cells was reversed by Lcn2 deletion. BrCA cell responsiveness to exogenous Lcn2 was heightened in cell types where endogenous Lcn2 expression was minimal, but components of the Lcn2 signaling pathway were enriched, i.e. Lcn2-R (slc22a17) and 3-hydroxy butyrate dehydrogenase (BDH2). In breast tumor biopsies from women diagnosed with BrCA we found that BDH2 expression was positively associated with adiposity and circulating Lcn2 levels. Collectively these data suggest that reduction of ERα expression in adipose tissue promotes adiposity and is linked with the progression and severity of BrCA via increased adipocyte-specific Lcn2 production and enhanced tumor cell Lcn2 sensitivity. Copyright © 2014, The American Society for Biochemistry and Molecular Biology.Journal of Biological Chemistry 12/2014; DOI:10.1074/jbc.M114.606459 · 4.60 Impact Factor
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ABSTRACT: Lipocalin-2 (LCN2) is an acute phase protein with multiple functions that has garnered a great deal of interest over the last decade. However, its precise role in the pathophysiology of the central nervous system (CNS) remains to be outlined. Emerging evidence indicates that LCN2 is synthesized and secreted as an inducible factor from activated microglia, reactive astrocytes, neurons, and endothelial cells in response to inflammatory, infectious, or injurious insults. More recently, it has been recognized as a modulatory factor for diverse cellular phenotypes in the CNS, such as cell death, survival, morphology, migration, invasion, differentiation, and functional polarization. LCN2 induces chemokine production in the CNS in response to inflammatory challenges, and actively participates in the innate immune response, cellular influx of iron, and regulation of neuroinflammation and neurodegeneration. LCN2 also modulates several biobehavioral responses including pain hypersensitivity, cognitive functions, emotional behaviors, depression, neuronal excitability, and anxiety. This review covers recent advances in our knowledge regarding functional roles of LCN2 in the CNS, and discusses how LCN2 acts as an autocrine mediator of astrocytosis, a chemokine inducer, and a modulator of various cellular phenotypes in the CNS. We finally explore the possibilities and challenges of employing LCN2 as a signature of several CNS anomalies.KeywordsLipocalin-2Acute phase proteinNeuroinflammationMicrogliaAstrocyteCentral nervous systemChemokineFunctional polarizationBiomarkerTherapeutic targetBiobehaviorNeuroscience & Biobehavioral Reviews 12/2014; 49. DOI:10.1016/j.neubiorev.2014.12.006 · 10.28 Impact Factor