The sulfonylurea drug, glimepiride, stimulates glucose transport, glucose transporter translocation, and dephosphorylation in insulin-resistant rat adipocytes in vitro

Müller, Günter; Wied, Susanne

doi:10.2337/diabetes.42.12.1852

Cited by 54 publications

(69 citation statements)

References 21 publications

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“…To assess insulin sensitivity after primary culture, washed adipocytes were incubated with insulin (0.02-50 nM human insulin, Hoechst AG) prior to assaying lipogenesis, glucose transport, glycogen synthase activity, PKA activity, and lipolysis. Loss of cells due to incubation and washing was identical among control and leptin-treated cell groups (26).…”

mentioning

confidence: 82%

“…Glucose transport was assayed as uptake of the non-metabolizable and radiolabeled glucose analogue, 2-deoxy-D- [2,6-3 H]glucose (45 Ci/ mmol, Amersham-Buchler) according to previously published procedures (26). 50 l of adipocytes in KRH, preincubated in the absence or presence of insulin for 20 min at 37°C, were incubated with 50 l of KRH containing deoxy [ 3 H]glucose (0.5 Ci, 0.2 mM) for 5 min at 25°C.…”

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confidence: 99%

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Leptin Impairs Metabolic Actions of Insulin in Isolated Rat Adipocytes

Müller¹,

Ertl²,

Gerl³

et al. 1997

Journal of Biological Chemistry

408

273

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Leptin is an adipocyte hormone involved in the regulation of energy homeostasis. Generally accepted biological effects of leptin are inhibition of food intake and stimulation of metabolic rate in ob/ob mice that are defective in the leptin gene. In contrast to these centrally mediated effects of leptin, we are reporting here on leptin effects on isolated rat adipocytes. Leptin impairs several metabolic actions of insulin, i.e. stimulation of glucose transport, glycogen synthase, lipogenesis, inhibition of isoproterenol-induced lipolysis, and protein kinase A activation, as well as stimulation of protein synthesis. Insulin effects were reduced by leptin (2 nM) with a half-life of about 8 h. At low leptin concentrations (<1 nM), the insulin sensitivity was reduced leading to a shift to the right in the dose-response curve. At higher concentrations the responsiveness was diminished, resulting in nearly complete inhibition of insulin effects at >30 nM leptin. The IC 50 value of leptin was 3.1 ؎ 1 nM after 15 h of preincubation of adipocytes in primary culture. The natural splice variant des-Gln 49 -leptin exhibited a significantly lower potency. Adipocytes regained full insulin sensitivity within a few hours after leptin removal. The stimulation of glucose transport by vanadate was not affected by leptin. These data show specific and potent impairment of insulin action by leptin in the physiological concentration range of both leptin and insulin, which may be related to the pathophysiology of insulin resistance in both non-insulin-dependent diabetes mellitus and obesity.

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confidence: 82%

mentioning

confidence: 99%

Leptin Impairs Metabolic Actions of Insulin in Isolated Rat Adipocytes

Müller¹,

Ertl²,

Gerl³

et al. 1997

Journal of Biological Chemistry

408

273

View full text Add to dashboard Cite

show abstract

“…A large number of studies during the past three decades have demonstrated multiple effects of sulphonylurea drugs on isolated normal and insulinresistant rat [12,[37][38][39][40][41][42][43] and mouse 3T3 adipocytes [44][45][46], cultured myocytes [47][48][49][50][51], isolated rat diaphragms [52] and perfused rat hind limbs [53] (for a review see Ref. [54]).…”

Section: Discussionmentioning

confidence: 99%

“…The plasma membrane and LDM fractions were subjected to SDS-PAGE (25#g protein/lane) and electrophoretically transferred onto nitrocellulose filters [28]. Incubations of the filters with primary and secondary antibodies (nSI-anti-rabbit IgG from goat), autoradiography and quantitative evaluation of the immunoreactive material by densitometry were carried out as described previously [12].…”

Section: Isolation and Incubation Of Rat Adipocytes Preparation Of Hmentioning

confidence: 99%

Stimulation of glucose utilization in 3T3 adipocytes and rat diaphragm in vitro by the sulphonylureas, glimepiride and glibenclamide, is correlated with modulations of the cAMP regulatory cascade

Müller

Wied

Wetekam

et al. 1994

Biochemical Pharmacology

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Abstract--The long-term hypoglycemic activity of sulphonylurea drugs has been attributed, in part at least, to the stimulation of glucose utilization in extra-pancreatic tissues. The novel sulphonylurea, glimepiride, gives rise to a longer lasting reduction in the blood sugar level in dogs and rabbits compared to glibenclamide (Geisen K, Drug Res 38: 1120-1130). This cannot be explained adequately by elevated plasma insulin levels. This study investigated whether this prolonged hypoglycemic phase was based on the drug's abilities to stimulate glucose utilization and affect the underlying regulatory mechanisms in insulin-sensitive cells in vitro. It was found that in the absence of added insulin, glimepiride and glibenclamide (1-50/iM) stimulated lipogenesis (3T3 adipocytes) and glycogenesis (isolated rat diaphragm) -4.5-and 2.5-fold, respectively, and reduced the isoproterenol-stimulated lipolysis (rat adipocytes) up to 40-60%. The increased glucose utilization was correlated with a 3-4-fold higher 2-deoxyglucose transport rate and amount of GLUT4 at the plasma membrane, as well as with increased activities of key metabolic enzymes (glycerol-3-phosphate acyltransferase, glycogen synthase) within the same concentration range. Furthermore, the low K,, cAMP-specific phosphodiesterase was activated 1.8-fold, whereas the cytosolic cAMP level and protein kinase A activity ratios were significantly lowered after incubation of isoproterenol-stimulated rat adipocytes with the sulphonylureas. In many of the aspects studied the novel sulphonylurea, glimepiride, exhibited slightly lower EDs0-values than glibenclamide. This study demonstrates correlations existing between druginduced stimulation of glucose transport/metabolism and cAMP degradation/protein kinase A inhibition as well as between the relative efficiencies of,glimepiride and glibenclamide in inducing these extrapancreatic processes. Therefore, it is suggested that the stimulation of glucose utilization by sulphonylureas is mediated by a decrease of cAMP-dependent phosphorylation of GLUT4 and glucose metabolizing enzymes. The therapeutic relevance of extra-pancreatic effects of sulphonylureas, in general, and of the differences between glimepiride and glibenclamide as observed in vitro in this work, in particular, remain to be elucidated.

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“…The homogenate was centrifuged (12000g, 15 min, 4 "C). Plasma membranes were prepared according to published procedures (McKeel & Jarett, 1970;Karnieli et al, 198 1;Muller & Wied, 1993) with the following modifications: The pellet was suspended in 15 mL of homogenization buffer and recentrifuged (1 OOOg, 10 min). Aliquots (7.5 mL) of the supernatant were supplemented with 32 mL of Percoll medium containing 0.25 M sucrose and 20 mM Tris-HC1 (pH 7.4) and centrifuged (48000g, 20 min, 4 "C).…”

Section: Muller Et Almentioning

confidence: 99%

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

Müller

Wetekam²,

Jung³

et al. 1994

Biochemistry

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CAMP-binding ectoprotein (Gcel ) and lipoprotein lipase (LPL) are anchored to plasma membranes of rat adipocytes by glycosylphosphatidylinositol (GPI) moieties as demonstrated by cleavage by bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), reactivity with anti-crossreacting determinant antibodies (anti-CRD), and metabolic labeling with radiolabeled palmitic acid and myoinositol. Quantitative release from the membrane of LPL and Gcel requires both lipolytic removal of their GPI anchors and the presence of either 2 M NaCl or 1 mM inositol 1,2-cyclic monophosphate or inositol 1 -monophosphate. PI-PLC-cleaved and released LPL or Gcel reassociates with isolated plasma membranes of rat adipocytes and, less efficiently, with membranes of 3T3 fibroblasts. The specificity of the reassociation is demonstrated (i) by its inhibition after pretreatment of the membranes with trypsin, (ii) by its competition with inositol 1,2-cyclic monophosphate and inositol 1-monophosphate in a concentration-dependent manner, and (iii) by the limited number of binding sites. Enzymic or chemical removal as well as masking with anti-CRD antibodies of the terminal inositol (cyclic) monophosphate moiety of hydrophilic Gcel and LPL significantly impairs the reassociation. These data suggest that in rat adipocytes GPI-proteins are not readily released from the cell surface upon lipolytic cleavage, but remain associated through a receptor which specifically recognizes the terminal inositol (cyclic) monophosphate epitope of the (G)PI-PLCcleaved GPI moiety. This interaction may have implications for the regulated membrane release of GPIproteins and for their possible internalization.GPI-proteins,' a subclass of ectoproteins in both lower and higher eucaryotes, are anchored to the outer leaflet of the plasma membrane by covalently attached GPI glycolipids which are characterized by a high degree of structural conservation from yeast to man. Their linear core structure is built from phosphatidylinositol bound via nonacetylated glucosamine to three mannose residues. The nonreducing end is linked to ethanolamine via a phosphodiester bridge. From this conserved core glycan various carbohydrate and/ or phosphoethanolamine residues may branch off [for a review see Ferguson and Williams (1988), Low (1989), and McConville and Ferguson (1993l. During the biosynthesis of GPI-proteins, the amino group of ethanolamine of the complete preformed GPI structure is coupled in a pseudo transpeptidation reaction to the carboxy terminus of the mature fully translated polypeptide chain, thereby replacing a transmembrane domain present in the protein precursor [for a review see Doering et al. (1990) and Thomas et al. (1990)l.Despite the lack of a cytoplasmic domain someGPI-proteins seem to have important roles in transmembrane signaling

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The sulfonylurea drug, glimepiride, stimulates glucose transport, glucose transporter translocation, and dephosphorylation in insulin-resistant rat adipocytes in vitro

Cited by 54 publications

References 21 publications

Leptin Impairs Metabolic Actions of Insulin in Isolated Rat Adipocytes

Leptin Impairs Metabolic Actions of Insulin in Isolated Rat Adipocytes

Stimulation of glucose utilization in 3T3 adipocytes and rat diaphragm in vitro by the sulphonylureas, glimepiride and glibenclamide, is correlated with modulations of the cAMP regulatory cascade

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

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