In cirrhotic livers, increased resistance to portal flow, in part due to an exaggerated response to vasoconstrictors, is the primary factor in the pathophysiology of portal hypertension. Our aim was to evaluate the response of the intrahepatic circulation of cirrhotic rat livers to the I n cirrhotic livers, increased resistance to portal blood flow is the primary factor in the pathophysiology of portal hypertension. 1 This increased resistance is determined in part by the architectural distortion of the hepatic structure caused by cirrhosis. However, substantial evidence shows that a dynamic component, caused by the active contraction of vascular and extravascular contractile cells, plays a major role in further increasing intrahepatic resistance. 2 This dynamic component of hepatic vascular resistance is believed to be the consequence of an imbalance between the vasodilator/vasoconstrictor forces that regulate hepatic vascular tone. 1 In addition, the hepatic vascular resistance of cirrhotic livers exhibits a hyperresponse to several vasoconstrictors, such as endothelin 1, 3 norepinephrine, 4 or leukotriene D 4 . 5 Nitric oxide blunts the response of the hepatic vascular bed to several vasoconstrictors, 6 and its production is decreased in the cirrhotic liver. It is therefore possible that an insufficient availability of NO 7 could account for the hyperresponse to vasoconstrictors observed in cirrhotic livers.In addition, it has been shown that the activation of G protein-coupled receptors, such as those for ␣ 1 -adrenergic agonists, vasopressin, or endothelin 1, stimulates release of arachidonic acid, leading to the formation of its vasoactive-derived metabolites, including prostaglandins (PGs), thromboxanes (TXs), and leukotrienes. [8][9][10] Cyclooxygenase (COX)

We have screened a subtracted cDNA library in order to identify differentially expressed genes in omental adipose tissue of human patients with Type 2 diabetes. One clone (#1738) showed a marked reduction in omental adipose tissue from patients with Type 2 diabetes. Sequencing and BLAST analysis revealed clone #1738 was the adipocyte-specific secreted protein gene apM1 (synonyms ACRP30, AdipoQ, GBP28). Consistent with the murine orthologue, apM1 mRNA was expressed in cultured human adipocytes and not in preadipocytes. Using RT-PCR we confirmed that apM1 mRNA levels were significantly reduced in omental adipose tissue of obese patients with Type 2 diabetes compared with lean and obese normoglycemic subjects. Although less pronounced, apM1 mRNA levels were reduced in subcutaneous adipose tissue of Type 2 diabetic patients. Whereas the biological function of apM1 is presently unknown, the tissue specific expression, structural similarities to TNFα and the dysregulated expression observed in obese Type 2 diabetic patients suggest that this factor may play a role in the pathogenesis of insulin resistance and Type 2 diabetes.

Adipogenesis is regulated by a coordinated cascade of sequencespecific transcription factors and coregulators with chromatinmodifying activities that are between them responsible for the establishment of the gene expression pattern of mature adipocytes. Here we examine the histone H3 post-translational modifications occurring at the promoters of key adipogenic genes during adipocyte differentiation. We show that the promoters of apM1, glut4, gpd1, and leptin are enriched in dimethylated histone H3 Lys 4 (H3-K4) in 3T3-L1 fibroblasts, where none of these genes are yet expressed. A detailed study of the apM1 locus shows that H3-K4 dimethylation is restricted to the promoter region in undifferentiated cells and associates with RNA polymerase II (pol II) loading. The beginning of apM1 transcription at the early stages of adipogenesis coincides with promoter H3 hyperacetylation and H3-K4 trimethylation. At the coding region, H3 acetylation and dimethylation, as well as pol II binding, are found in cells at later stages of differentiation, when apM1 transcription reaches its maximal peak. This same pattern of histone modifications is detected in mouse primary preadipocytes and adipocytes but not in a related fibroblast cell line that is not committed to an adipocyte fate. Inhibition of H3-K4 methylation by treatment of 3T3-L1 cells with methylthioadenosine results in decreased apM1 gene expression as well as decreased adipogenesis. Taken together, our data indicate that H3-K4 dimethylation and pol II binding to the promoter of key adipogenic genes are distinguishing marks of cells that have undergone determination to a preadipocyte stage.The influence exerted by the post-translational modifications of histones over the regulation of gene expression has been extensively studied in the past few years. Numerous studies have shown a clear link between the pattern of histone modifications found at promoter regions and gene transcription, thus leading to the statement of the histone code hypothesis (1), which postulates that the pattern of histone post-translational modifications in a locus considerably extends the amount of information conveyed by the genomic code. Histone H3 and H4 hyperacetylation in promoter regions is closely correlated with gene activation in organisms ranging from yeast to mammals, and transcriptionally active euchromatin regions are highly enriched in acetylated histones (1-5). Unlike acetylation, histone H3 methylation can be equally associated with either transcriptional activation or repression. Methylation of the lysine residue Lys 4 of histone H3 (H3-K4) 3 correlates with activation of gene expression in most systems (2, 4 -7), whereas H3 Lys 9 (H3-K9) methylation is involved in the establishment and maintenance of silent heterochromatin regions (8). Moreover, lysine residues can be mono-, di-, or trimethylated in vivo, thus providing a further layer of complexity and exponentially increasing functional diversity (9, 10). The recent identification of LSD1, the first histone demethylase to be ch...

The increasing worldwide incidence of obesity and the limitations of current treatments raise the need for finding novel therapeutic approaches to treat this disease. The purpose of the current study was first to investigate the effects of tungstate on body weight and insulin sensitivity in a rat model of diet-induced obesity. Second, we aimed to gain insight into the molecular mechanisms underlying its action. Oral administration of tungstate significantly decreased body weight gain and adiposity without modifying caloric intake, intestinal fat absorption, or growth rate in obese rats. Moreover, the treatment ameliorated dislipemia and insulin resistance of obese rats. These effects were mediated by an increase in whole-body energy dissipation and by changes in the expression of genes involved in the oxidation of fatty acids and mitochondrial uncoupling in adipose tissue. Furthermore, treatment increased the number of small adipocytes with a concomitant induction of apoptosis. Our results indicate that tungstate treatment may provide the basis for a promising novel therapy for obesity.

Gastrin (G) and cholecystokinin (CCK) are gastrointestinal neuropeptides that are released into circulation during a meal. G is also transiently expressed during embryogenic and early ontogenic development of the pancreas and is believed to act on islet-cell development. Both peptides act on pancreatic endocrine function; however, the effects are dependent on the species and on cellular and molecular underlying mechanisms that remain poorly characterized. Since CCK-B/G subtype receptor is predominant over the CCK-A subtype in the human pancreas, we hypothesized that it could be expressed by islet cells. Here we present reverse transcription-polymerase chain reaction and immunohistochemistry data demonstrating that the CCK-B/G receptor is expressed in islet cells and that islet glucagon-producing cells are the major site of CCK-B/G receptor expression in adult and fetal pancreas. Moreover, G immunoreactivity was detected in the fetal human pancreas at embryogenic week 22. G- and CCK-stimulated glucagon are released from purified human islets. Concentration of CCK and G eliciting a half-maximal level of glucagon secretion were 13 +/- 6 and 8 +/- 5 pmol/l, respectively. Maximal glucagon secretion was achieved in the presence of 30 pmol/l peptides and was similar to that obtained in the presence of 10 mmol/l L-arginine (1.6 pmol x ml(-1) x 90 min(-1)). The nonpeptide antagonist of the CCK-B/G receptor, RPR-101048, fully inhibited CCK- and G-stimulated glucagon secretion at 100 nmol/l concentration. These data are consistent with the view that the CCK-B/G receptor is involved in glucose homeostasis in adult humans and mediates the autocrine effects of G on islet differentiation and growth in the fetal pancreas.