Unacylated Ghrelin Rapidly Modulates Lipogenic and Insulin Signaling Pathway Gene Expression in Metabolically Active Tissues of GHSR Deleted Mice

Background: There is increasing evidence that unacylated ghrelin (UAG) improves insulin sensitivity and glucose homeostasis; however, the mechanism for this activity is not fully understood since a UAG receptor has not been discovered. Methodology/Principal Findings: To assess potential mechanisms of UAG action in vivo, we examined rapid effects of UAG on genome-wide expression patterns in fat, muscle and liver of growth hormone secretagogue receptor (GHSR)-ablated mice using microarrays. Expression data were analyzed using Ingenuity Pathways Analysis and Gene Set Enrichment Analysis. Regulation of subsets of these genes was verified by quantitative PCR in an independent experiment. UAG acutely regulated clusters of genes involved in glucose and lipid metabolism in all three tissues, consistent with enhancement of insulin sensitivity. Conclusions/Significance: Fat, muscle and liver are central to the control of lipid and glucose homeostasis. UAG rapidly modulates the expression of metabolically important genes in these tissues in GHSR-deleted mice indicating a direct, GHSRindependent, action of UAG to improve insulin sensitivity and metabolic profile

Role of the fibrinolytic and matrix metalloproteinase systems in adipogenesis

Overgewicht en zwaarlijvigheid (obesitas) worden een steeds groter probleem in onze Westerse samenleving en gaan gepaard met een verhoogd risico op levensbedreigende aandoeningen. Bij de ontwikkeling van obesitas zijn zowel adipogenetische (vetcel vorming) als angiogenetische (bloedvat vorming) processen betrokken waarbij een hermodelering van de extracellulaire matrix nodig is.Het doel van dit project was de studie van de rol in deze processen van twee proteolytische systemen, namelijk het fibrinolytisch (plasminogeen/plasmine) en matrix metalloproteïnase (MMP) systeem. Hierbij werd vooral aandacht besteed aan de fysiologische inhibitoren van beide systemen, namelijk plasminogeen activator inhibitoren (PAI-1 en PAI-2) en weefsel inhibitor van MMPs-1 (TIMP-1). De voornaamste doelstellingen van dit project waren: de rol van beide proteolytische systemen bestuderen in de vroege stadia van adipogenese en in de ontwikkeling van vetweefsel bij nutritioneel geïnduceerde obesitas bij de muis. In het eerste hoofdstuk van de resultaten beschrijven we de zoektocht naar de rol van murien PAI-1 (mPAI-1) in in vitro en in vivo adipogenese. We hebben, in vitro, geen functionele rol kunnen aantonen daar: 1) de differentiatie van muriene embryonale stam (ES) cellen al dan niet met PAI-1 overexpressie geen verschil vertoonde; 2) de mate van differentiatie tot adipocyten van primaire muriene embryonale fibroblasten afgeleid van wild-type (WT) of PAI-1 deficiënte muizen niet significant verschillend bleek; 3) differentiatie van 3T3-F442A preadipocyten niet veranderd was na behandeling met een mPAI-1 neutraliserend monoclonaal antilichaam (H4B3); 4) differentiatie van dezelfde cellen niet beïnvloed werd door stabiele overexpressie van mPAI-1. In vivo hebben we een concentratie afhankelijk effect van PAI-1 op bloedvatvorming en vetweefselontwikkeling vastgesteld, hetgeen bleek uit: 1) neutralisatie van PAI-1 in een model van de novo adipogenese waarbij 3T3-F442A preadipocyten onderhuids geinjecteerd werden in de rug van naakte Balb/c muizen (die vervolgens gedurende 4 weken een vetrijk dieet kregen) resulteerde in kleinere vetcellen; 2) vetweefselontwikkeling was vergelijkbaar na injectie van matrigel en fibroblast groeifactor in WT en PAI-1 deficiënte muizen; 3) locale overexpressie van PAI-1 in een gelijkaardig model van de novo adipogenese resulteerde in grotere vetkussentjes en 4) systemische overexpressie van PAI-1 in dergelijk de novo adipogenese model was geassocieerd met kleinere bloedvaten in het vetweefsel. Vervolgens werd de rol van PAI-2 in adipogenese bestudeerd. PAI-2 bleek tot expressie te komen tijdens in vitro differentiatie van preadipocyten en in vivo in zowel subcutaan als gonadaal vetweefsel. PAI-2 deficiënte muizen op vetrijk dieet ontwikkelden minder vetweefsel en kleinere vetcellen dan wild-type controles, via een mechanisme onafhankelijk van de antifibrinolytische activiteit van PAI-2.Tenslotte werd de rol van TIMP-1 in adipogenese zowel in vitro als in vivo bestudeerd. In vitro leverde de zoektocht naar de rol van TIMP-1 bij adipocyt differentiatie tegenstrijdige resultaten op daar: 1) de mate van differentiatie tot adipocyten van primaire muriene embryonale fibroblasten afgeleid van TIMP-1 deficiënte muizen, lager bleek in vergelijking met WT fibroblasten; 2) differentiatie van 3T3-F442A preadipocyten met overexpressie van humaan TIMP-1 (hTIMP-1) trager verliep, maar vergelijkbaar was met controle cellen. In vivo was het effect van locale en systemische expressie van hTIMP-1 tijdens de novo adipogenese verschillend, met een beduidend effect op angiogenese, daar: 1) locale expressie resulteerde in grotere bloedvaten en 2) systemische overexpressie resulteerde in vetkussentjes met grotere vetcellen en een kleinere bloedvat densiteit.Uit deze studies kunnen we dus besluiten dat het effect van deze protease inhibitoren op in vitro differentiatie van preadipocyten naar mature adipocyten niet in alle condities overeenstemt met de effecten op vetweefselvorming in vivo. De in vivo effecten blijken afhankelijk van zowel concentratie als verdeling in plaats en tijd.status: publishe

CD36 deficiency blunts effects of diet on regulatory T cells in murine gonadal adipose tissue and mesenteric lymph nodes

The effect of cluster of differentiation (CD)36 on regulatory T cells (Treg) was investigated in gonadal (GN) adipose tissues and mesenteric lymph nodes (MLN) of wild-type (WT) and CD36 deficient (CD36−/−) mice kept on standard fat (SFD, lean) or on high fat diet (HFD, obese). GN adipose tissue mass was smaller, but MLN size larger for obese CD36−/− versus obese WT mice. Overall, the reduction of Treg cells in GN adipose tissue and MLN after a HFD is much more prominent in WT than CD36−/− mice. Moreover, CD36−/− mice may be protected against obesity-related chronic inflammation.publisher: Elsevier articletitle: CD36 deficiency blunts effects of diet on regulatory T cells in murine gonadal adipose tissue and mesenteric lymph nodes journaltitle: Cellular Immunology articlelink: http://dx.doi.org/10.1016/j.cellimm.2015.08.006 content_type: article copyright: Copyright © 2015 Elsevier Inc. All rights reserved.status: publishe

The Anti-Adipogenic Potential of COUP-TFII Is Mediated by Downregulation of the Notch Target Gene Hey1

BACKGROUND: Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) belongs to the steroid/thyroid hormone receptor superfamily and may contribute to the pathogenesis of obesity. It has not conclusively been established, however, whether its role is pro- or anti-adipogenic. METHODS AND RESULTS: Gene silencing of Coup-tfII in 3T3-F442A preadipocytes resulted in enhanced differentiation into mature adipocytes. This was associated with upregulation of the Notch signaling target gene Hey1. A functional role of Hey1 was confirmed by gene silencing in 3T3-F442A preadipocytes, resulting in impaired differentiation. In vivo, de novo fat pad formation in NUDE mice was significantly stimulated following injection of preadipocytes with Coup-tfII gene silencing, but impaired with Hey1 gene silencing. Moreover, expression of Coup-tfII was lower and that of Hey1 higher in isolated adipocytes of obese as compared to lean adipose tissue. CONCLUSIONS: These in vitro and in vivo data support an anti-adipogenic role of COUP-TFII via downregulating the Notch signaling target gene Hey1.status: publishe

MicroRNAs regulated by adiponectin as novel targets for controlling adipose tissue inflammation.

A low-grade proinflammatory state contributes to the metabolic syndrome (MS). Adiponectin (ApN), which is reduced in the MS, has emerged as a master regulator of inflammation/immunity. We wanted to identify whether microRNAs (miRNAs) may mediate the antiinflammatory action of ApN on adipose tissue (AT). miRNA expression profiling was performed in mice overexpressing ApN specifically in AT and in wild-type controls. The role of specific miRNAs was analyzed by gain- or loss-of function approaches in 3T3-F442A (pre)-adipocytes and in de novo AT formed from engineered 3T3-F442A preadipocytes transplanted in nude mice. miRNA expression was compared in the omental AT of lean and obese subjects. The expression of miR532-5p and miR1983 was down-regulated, whereas that of miR883b-5p and miR1934 was up-regulated in AT of mice overexpressing ApN specifically in AT. We focused on miR883b-5p identified by computational analysis as being involved in inflammatory pathways. miR883b-5p overexpression down-regulated the lipopolysaccharide-binding protein (LBP) in 3T3-F442A cells, whereas miR883b-5p blockade had reverse effects. LBP aids in lipopolysaccharide binding to Toll-like receptor-4. miR883b-5p blockade also abolished the protective effects of ApN on proinflammatory adipokine induction. These data were recapitulated in the de novo AT in which miR883b-5p silencing induced LBP production and tissue inflammation. Eventually miR883b-5p expression was down-regulated in AT of obese subjects. We identified several novel miRNAs that are regulated by ApN in AT in vivo. miR883b-5p, which is up-regulated by ApN represses LBP and Toll-like receptor-4 signaling, acting therefore as a major mediator of the antiinflammatory action of ApN. These novel miRNAs may open new therapeutic perspectives for the MS

ADAMTS13 deficiency in mice does not affect adipose tissue development

BACKGROUND: BMI and ADAMTS13 levels are positively correlated in man. Development of obesity is associated with angiogenesis and inflammation, and increased ADAMTS13 synthesis in the liver. METHODS: Male wild-type (WT) and ADAMTS13 deficient (Adamts13-/-) mice were kept on normal chow (SFD) or high fat diet (HFD) for 15 weeks. RESULTS: HFD feeding of WT mice resulted in significantly enhanced levels of ADAMTS13 antigen and activity as compared to SFD feeding. ADAMTS13 deficiency had no significant effect on body weight gain, subcutaneous (SC) or gonadal (GN) adipose tissue mass, or on adipocyte size. In GN fat of obese (HFD) Adamts13-/- mice, adipocyte density was higher and blood vessel density lower as compared to obese WT mice. No marked effects of genotype were observed on mRNA expression of adipogenic, endothelial, inflammatory or oxidative stress markers in adipose tissue. Analysis of metabolic parameters and of glucose and insulin tolerance did not reveal significant differences between both obese genotypes, except for higher adiponectin and cholesterol levels in obese Adamts13-/- as compared to WT mice. CONCLUSION: Our data do not support a functional role of ADAMTS13 in adiposity nor in associated angiogenesis or inflammation in mice. GENERAL SIGNIFICANCE: ADAMTS13 deficiency may cause thrombotic thrombocytopenic purpura (TTP). Obesity, which is associated with enhanced ADAMTS13 levels is nevertheless considered to be an independent risk factor for TTP. To resolve this apparent contradiction, we show that ADAMTS13 does not directly promote development of adipose tissue in a mouse model.publisher: Elsevier articletitle: ADAMTS13 deficiency in mice does not affect adipose tissue development journaltitle: Biochimica et Biophysica Acta (BBA) - General Subjects articlelink: http://dx.doi.org/10.1016/j.bbagen.2015.03.008 content_type: article copyright: Copyright © 2015 Elsevier B.V. All rights reserved.status: publishe

Gelatinase A (MMP-2) promotes murine adipogenesis

status: publishe