The identification of selective glucocorticoid receptor (GR) modifiers, which separate transactivation and transrepression properties, represents an important research goal for steroid pharmacology. Although the gene-activating properties of GR are mainly associated with undesirable side effects, its negative interference with the activity of transcription factors, such as NF-B, greatly contributes to its antiinflammatory and immune-suppressive capacities. In the present study, we found that Compound A (CpdA), a plant-derived phenyl aziridine precursor, although not belonging to the steroidal class of GR-binding ligands, does mediate geneinhibitory effects by activating GR. We demonstrate that CpdA exerts an antiinflammatory potential by down-modulating TNFinduced proinflammatory gene expression, such as IL-6 and Eselectin, but, interestingly, does not at all enhance glucocorticoid response element-driven genes or induce GR binding to glucocorticoid response element-dependent genes in vivo. We further show that the specific gene-repressive effect of CpdA depends on the presence of functional GR, displaying a differential phosphorylation status with CpdA as compared with dexamethasone treatment. The antiinflammatory mechanism involves both a reduction of the in vivo DNA-binding activity of p65 as well as an interference with the transactivation potential of NF-B. Finally, we present evidence that CpdA is as effective as dexamethasone in counteracting acute inflammation in vivo and does not cause a hyperglycemic side effect. Taken together, this compound may be a lead compound of a class of antiinflammatory agents with fully dissociated properties and might thus hold great potential for therapeutic use.cytokine ͉ glucocorticoid receptor ͉ inflammation ͉ NF-B

The peroxisome proliferator-activated receptor-␣ (PPAR␣) controls gene expression in response to a diverse class of compounds collectively referred to as peroxisome proliferators. Whereas most known peroxisome proliferators are of exogenous origin and include hypolipidemic drugs and other industrial chemicals, several endogenous PPAR␣ activators have been identified such as fatty acids and steroids. The latter finding and the fact that PPAR␣ modulates target genes encoding enzymes involved in lipid metabolism suggest a role for PPAR␣ in lipid metabolism. This was investigated in the PPAR␣-deficient mouse model. Basal levels of total serum cholesterol, high density lipoprotein cholesterol, hepatic apolipoprotein A-I mRNA, and serum apolipoprotein A-I in PPAR␣-deficient mice are significantly higher compared with wild-type controls. Treatment with the fibrate Wy 14,643 decreased apoA-I serum levels and hepatic mRNA levels in wild-type mice, whereas no effect was detected in the PPAR␣-deficient mice. Administration of the fibrate Wy 14,643 to wild-type mice results in marked depression of hepatic apolipoprotein C-III mRNA and serum triglycerides compared with untreated controls. In contrast, PPAR␣-deficient mice were unaffected by Wy 14,643 treatment. These studies demonstrate that PPAR␣ modulates basal levels of serum cholesterol, in particular high density lipoprotein cholesterol, and establish that fibrate-induced modulation in hepatic apolipoprotein A-I, C-III mRNA, and serum triglycerides observed in wild-type mice is mediated by PPAR␣.

Bile acids (BA) are signalling molecules which activate the transmembrane receptor TGR5 and the nuclear receptor FXR. BA sequestrants (BAS) complex BA in the intestinal lumen and decrease intestinal FXR activity. The BAS-BA complex also induces Glucagon-Like Peptide-1 (GLP-1) production by L-cells which potentiates β-cell glucose-induced insulin secretion. Whether FXR is expressed in L-cells and controls GLP-1 production is unknown. Here we show that FXR activation in L-cells decreases proglucagon expression by interfering with the glucose-responsive factor Carbohydrate-Responsive Element Binding Protein (ChREBP) and GLP-1 secretion by inhibiting glycolysis. In vivo, FXR-deficiency increases GLP-1 gene expression and secretion in response to glucose hence improving glucose metabolism. Moreover, treatment of ob/ob mice with the BAS colesevelam increases intestinal proglucagon gene expression and improves glycemia in a FXR-dependent manner. These findings identify the FXR/GLP-1 pathway as a new mechanism of BA control of glucose metabolism and a pharmacological target for type 2 diabetes.

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Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors, which heterodimerize with the retinoid X receptor and bind to peroxisome proliferator response elements in the promoters of regulated genes. Despite the wealth of information available on the function of PPARK K and PPARQ Q, relatively little is known about the most widely expressed PPAR subtype, PPARN N. Here we show that treatment of insulin resistant db/db mice with the PPARN N agonist L-165 041, at doses that had no effect on either glucose or triglycerides, raised total plasma cholesterol concentrations. The increased cholesterol was primarily associated with high density lipoprotein (HDL) particles, as shown by fast protein liquid chromatography analysis. These data were corroborated by the chemical analysis of the lipoproteins isolated by ultracentrifugation, demonstrating that treatment with L-165 041 produced an increase in circulating HDL without major changes in very low or low density lipoproteins. White adipose tissue lipoprotein lipase activity was reduced following treatment with the PPARN N ligand, but was increased by a PPARQ Q agonist. These data suggest both that PPARN N is involved in the regulation of cholesterol metabolism in db/db mice and that PPARN N ligands could potentially have therapeutic value. z 2000 Federation of European Biochemical Societies.

The liver plays a central role in the control of blood glucose homeostasis by maintaining a balance between glucose production and utilization. The farnesoid X receptor (FXR) is a bile acid-activated nuclear receptor. Hepatic FXR expression is regulated by glucose and insulin. Here we identify a role for FXR in the control of hepatic carbohydrate metabolism. When submitted to a controlled fasting-refeeding schedule, FXR ؊/؊ mice displayed an accelerated response to high carbohydrate refeeding with an accelerated induction of glycolytic and lipogenic genes and a more pronounced repression of gluconeogenic genes. Plasma insulin and glucose levels were lower in FXR ؊/؊ mice upon refeeding the highcarbohydrate diet. These alterations were paralleled by decreased hepatic glycogen content. Hepatic insulin sensitivity was unchanged in FXR ؊/؊ mice. Treatment of isolated primary hepatocytes with a synthetic FXR agonist attenuated glucose-induced mRNA expression as well as promoter activity of L-type pyruvate kinase, acetyl-CoA carboxylase 1, and Spot14. Moreover, activated FXR interfered negatively with the carbohydrate response elements regions. These results identify a novel role for FXR as a modulator of hepatic carbohydrate metabolism.The liver plays a major role in maintaining plasma glucose homeostasis by controlling a delicate balance between hepatic glucose uptake/utilization and hepatic glucose production. In the fed state, the liver stores energy from glucose by synthesizing glycogen and fat. Conversely, when plasma glucose concentrations decrease during fasting, the liver produces glucose by the glycogenolytic and gluconeogenic pathways. This fasting-refeeding transition involves a highly coordinated adaptation of the expression of genes encoding key metabolic enzymes that is orchestrated by hormones and nutrients.In the fed state, insulin and glucose act in concert to promote

is the chair of the scientific advisory board of Xenon Genetics Inc. Nonstandard abbreviations used: HDL cholesterol (HDL-C); adenosine triphosphate-binding cassette transporter A1 (ABCA1); bacterial artificial chromosome (BAC); oil red O (ORO); acyl-CoA:cholesterol O-acyltransferase (ACAT); coronary artery disease (CAD). Online first publication increased deposition of cholesteryl esters in several tissues and cells, most notably in macrophages (13). A 50% reduction in ABCA1 activity is associated with a significant decrease in plasma HDL-C levels (14-16). To study the role of ABCA1 in HDL metabolism and atherosclerosis, we have developed human ABCA1 overexpressing bacterial artificial chromosome (BAC) transgenic mice that show increased total plasma cholesterol and HDL-C levels and increased ApoA-I and ApoA-II levels (17), associated with increased cholesterol efflux from macrophages. We hypothesized that increasing ABCA1 activity would be associated with reduced atherosclerotic lesion formation. ApoE-/mice have been used extensively to study atherogenesis. These mice spontaneously develop severe atherosclerosis, with complex lesions that include a fibrous cap in mice as young as 15 weeks of age. Because of its validation and acceptance as a model to study factors influencing atherogenesis, we chose to test the effect of ABCA1 overexpression on atherosclerosis development, macrophage cholesterol efflux, and HDL composition in this model.

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