Browsing by Author "Pereira, Maria João"
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- Cyclosporine A and tacrolimus reduce the amount of GLUT4 at the cell-surface in human adipocytes: increased endocytosis as a potential mechanism for the diabetogenic effects of immunosuppressive agentsPublication . Pereira, Maria João; Aureliano, M.; Palming, Jenny; Rizell, Magnus; Carvalho, Eugénia; Svensson, Maria K.; Eriksson, Jan W.Context:Immunosuppressive agentes are associated with profound metabolic side effects including new-onset diabetes and dyslipidemia after organ transplantation. Objective: Toi nvestigated the effects of the cyclosporine A(CsA)or tacrolimus ong lucose uptake and insulin signalling in human adipocytes and their impact on the regulation of celular trafficking of the glucose transporter 4 (GLUT4). Design:Human isolated adipocytes were incubated with therapeutic concentrations of either CsA or tacrolimus, and glucose uptake and expression of insulin signaling proteins were assessed. Furthermore,we studied effects of CsA and tacrolimus on the regulation of celular trafficking of the GLUT4 in differentiated human pre-adipocytes and L6 cells. Results:CsA and tacrolimus had a concentration-dependent inhibitory effect on basal and insulin stimulated 14C-glucose uptake in adipocytes. Although phosphorylation at Tyr1146 of insulin receptor (IR) was inhibited by tacrolimus, the phosphorylation and/or protein levels of the insulin signalling proteinsIRS1/2,p85-PI3K,PKB,AS160 and mTORC1,as well as GLUT4 and GLUT1,were unchanged by CsA or tacrolimus. Furthermore, CsA and tacrolimus reduced the GLUT4 amount localized at the cell surfasse of differentiated human pre-adipocytes and L6 cells in the presence of insulin.This occurred by na increased rate of GLUT4 endocytosis,with no change in the exocytosis rate. Conclusions: These results suggest that therapeutic concentrations of CsA and tacrolimus can inhibit glucose uptake independente of insulin signalling by removing GLUT4 from the cell surface via na increased rate of endocytosis.Such mechanisms can contribute to the development of insulin resistance and diabetes associated with immunosuppressive therapy.In addition,they may provide novel pharmacological approaches for treatment of diabetes.
- Effects of decavanadate and insulin enhancing vanadium compounds on glucose uptake in isolated rat adipocytesPublication . Pereira, Maria João; Carvalho, Eugénia; Eriksson, Jan W.; Crans, Debbie C.; Aureliano, M.The effects of different vanadium compounds namely pyridine-2,6-dicarboxylatedioxovanadium(V) (V5-dipic), bis(maltolato) oxovanadium(IV) (BMOV) and amavadine, and oligovanadates namely metavanadate and decavanadate were analysed on basal and insulin stimulated glucose uptake in rat adipocytes. Decavanadate (50 lM), manifest a higher increases (6-fold) on glucose uptake compared with basal, followed by BMOV (1 mM) and metavanadate (1 mM) solutions (3-fold) whereas V5 dipic and amavadine had no effect. Decavanadate (100 lM) also shows the highest insulin like activity when compared with the others compounds studied. In the presence of insulin (10 nM), only decavanadate increases (50%) the glucose uptake when compared with insulin stimulated glucose uptake whereas BMOV and metavanadate, had no effect and V5 dipic and amavadine prevent the stimulation to about half of the basal value. Decavanadate is also able to reduce or eradicate the suppressor effect caused by dexamethasone on glucose uptake at the level of the adipocytes. Altogether, vanadium compounds and oligovanadates with several structures and coordination spheres reveal different effects on glucose uptake in rat primary adipocytes.
- mTOR inhibition with rapamycin cause impaired insulin signalling and glucose uptake in human subcutaneous and omental adipocytesPublication . Pereira, Maria João; Palming, Jenny; Rizell, Magnus; Aureliano, M.; Carvalho, Eugénia; Svensson, Maria K.; Eriksson, Jan W.Rapamycin is an immunosuppressive agent used after organ transplantation, but its molecular effects on glucose metabolism needs further evaluation. We explored rapamycin effects on glucose uptake and insulin signalling proteins in adipocytes obtained via subcutaneous (n = 62) and omental (n = 10) fat biopsies in human donors. At therapeutic concentration (0.01 lM) rapamycin reduced basal and insulin-stimulated glucose uptake by 20–30%, after short-term (15 min) or long-term (20 h) culture of subcutaneous (n = 23 and n = 10) and omental adipocytes (n = 6 and n = 7). Rapamycin reduced PKB Ser473 and AS160 Thr642 phosphorylation, and IRS2 protein levels in subcutaneous adipocytes. Additionally, it reduced mTOR–raptor, mTOR–rictor and mTOR–Sin1 interactions, suggesting decreased mTORC1 and mTORC2 formation. Rapamycin also reduced IR Tyr1146 and IRS1 Ser307/Ser616/Ser636 phosphorylation, whereas no effects were observed on the insulin stimulated IRS1–Tyr and TSC2 Thr1462 phosphorylation. This is the first study to show that rapamycin reduces glucose uptake in human adipocytes through impaired insulin signalling and this may contribute to the development of insulin resistance associated with rapamycin therapy.
- The immunosuppressive agents rapamycin, cyclosporin A and tacrolimus increase lipolysis, inhibit lipid storage and alter expression of genes involved in lipid metabolism in human adipose tissuePublication . Pereira, Maria João; Palming, Jenny; Rizell, Magnus; Aureliano, M.; Carvalho, Eugénia; Svensson, Maria K.; Eriksson, Jan W.Cyclosporin A (CsA), tacrolimus and rapamycin are immunosuppressive agents (IAs) associated with insulin resistance and dyslipidemia, although their molecular effects on lipid metabolism in adipose tissue are unknown. We explored IAs effects on lipolysis, lipid storage and expression of genes involved on lipid metabolism in isolated human adipocytes and/or adipose tissue obtained via subcutaneous and omental fat biopsies. CsA, tacrolimus and rapamycin increased isoproterenol-stimulated lipolysis and inhibited lipid storage by 20–35% and enhanced isoproterenol-stimulated hormone-sensitive lipase Ser552 phosphorylation. Rapamycin also increased basal lipolysis ( 20%) and impaired insulin’s antilipolytic effect. Rapamycin, down-regulated the gene expression of perilipin, sterol regulatory element-binding protein 1 (SREBP1) and lipin 1, while tacrolimus down-regulated CD36 and aP2 gene expression. All three IAs increased IL-6 gene expression and secretion, but not expression and secretion of TNF-a or adiponectin. These findings suggest that CsA, tacrolimus and rapamycin enhance lipolysis, inhibit lipid storage and expression of lipogenic genes in adipose tissue, which may contribute to the development of dyslipidemia and insulin resistance associated with immunosuppressive therapy.