Lipidomic analysis of human primary hepatocytes following LXR activation with GW3965 identifies AGXT2L1 as a main target associated to changes in phosphatidylethanolamine.

Liver X receptor (LXR) agonists have the potential to alleviate obesity related diseases, particularly atherosclerosis. However, LXRs are transcriptional regulators that induce de novo lipogenesis and lipid accumulation in hepatocytes which represents a serious adverse effect. In this work, we sought to characterize the LXR agonist GW3965 effects on fatty acid (FA) and phospholipid (PL) remodelling and the correlation with gene expression in order to better understand the underlying effects leading to hepatic pathology upon LXR activation.

Addition of Dexamethasone Alters the Bile Acid Composition by Inducing CYP8B1 in Primary Cultures of Human Hepatocytes.

Background: Primary human hepatocytes offer the best human in vitro model for studies on human liver cell metabolism. Investigators use a variety of different media supplements and matrix biocoatings and the type of culture system used may influence the outcome.

Objectives: To optimize in vitro conditions for primary human hepatocytes with regard to bile acid synthesis.

LXR activation by GW3965 alters fat tissue distribution and adipose tissue inflammation in ob/ob female mice.

To investigate the role of liver X receptor (LXR) in adipose tissue metabolism during obesity, ob/ob mice were treated for 5 weeks with the synthetic LXR agonist GW3965. MRI analysis revealed that pharmacological activation of LXR modified fat distribution by decreasing visceral (VS) fat and inversely increasing subcutaneous (SC) fat storage without affecting whole body fat content. This was concordant with opposite regulation by GW3965 of the lipolytic markers hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) in the two fat depots; moreover, the expression of genes involved in lipogenesis was significantly induced in SC fat.

Fasting-induced FGF21 is repressed by LXR activation via recruitment of an HDAC3 corepressor complex in mice.

The liver plays a pivotal role in the physiological adaptation to fasting and a better understanding of the metabolic adaptive responses may give hints on new therapeutic strategies to control the metabolic diseases. The liver X receptors (LXRs) are well-established regulators of lipid and glucose metabolism. More recently fibroblast growth factor 21 (FGF21) has emerged as an important regulator of energy homeostasis.

The human ADFP gene is a direct liver-X-receptor (LXR) target gene and differentially regulated by synthetic LXR ligands.

Expression of adipocyte differentiation-related protein (ADFP), residing on the surface of lipid droplets, correlates to hepatic fat storage. In the context of consequences and treatment of metabolic disorders, including hepatic steatosis, it is imperative to gain knowledge about the regulation of the human ADFP gene. The nuclear receptor liver-X-receptor (LXR) is a key regulator of hepatic fatty acid biosynthesis and cholesterol homeostasis as well as a potential drug target.

Ghrelin induces abdominal obesity via GHS-R-dependent lipid retention.

Circulating ghrelin elevates abdominal adiposity by a mechanism independent of its central orexigenic activity. In this study we tested the hypothesis that peripheral ghrelin induces a depot-specific increase in white adipose tissue (WAT) mass in vivo by GH secretagogue receptor (GHS-R(1a))-mediated lipolysis. Chronic iv infusion of acylated ghrelin increased retroperitoneal and inguinal WAT volume in rats without elevating superficial sc fat, food intake, or circulating lipids and glucose.

Effects of the synthetic liver X receptor agonist T0901317 on the growth hormone and thyroid hormone axes in male rats.

Liver X receptors (LXRs), activated by oxysterols, play an important role in the regulation of lipid and glucose metabolism, which is also markedly dependent on thyroid hormone and growth hormone (GH) status. Here, we investigated how a 1-week exposure to the synthetic LXR agonist T0901317 affected GH secretion and thyroid hormone status in male rats. While the pulse frequency of GH secretion was marginally affected there was a highly significant decrease in the triiodo-L-thyronine/thyroxine (T3/T4) ratio in plasma.

Transcriptional activity and developmental expression of liver X receptor (lxr) in zebrafish.

Mammalian liver-X-receptors (LXRs) are transcription factors activated by oxysterols. They play an essential role in lipid and glucose metabolism. We have cloned the open reading frame of zebrafish lxr and describe its genomic organization.

Physiological differences between human and rat primary hepatocytes in response to liver X receptor activation by 3-[3-[N-(2-chloro-3-trifluoromethylbenzyl)-(2,2-diphenylethyl)amino]propyloxy]phenylacetic acid hydrochloride (GW3965).

The liver is central to the maintenance of glucose and lipid homeostasis, and liver X receptors (LXRs) are key regulators of expression of the genes involved. So far, effects of activation of LXR in human hepatocytes have not been well characterized. Here we show that treatment of primary human hepatocytes with the synthetic LXR ligand 3-[3-[N-(2-chloro-3-trifluoromethylbenzyl)-(2,2-diphenylethyl)amino]propyloxy]phenylacetic acid hydrochloride (GW3965) results in reduced output of bile acids and very low density lipoprotein triglycerides and induced expression of adipose differentiation-related protein accompanied by increased lipid storage.

In vivo transfection of rat liver discloses binding sites conveying GH-dependent and female-specific gene expression.

The sexually dimorphic mode of GH secretion leads to a sex-differentiated expression of many hepatic target genes. Expression of the a1bg gene in rat liver is specifically induced by the female pattern of GH secretion. In this study, we have used the a1bg promoter in in vivo transfection experiments to investigate molecular mechanisms of GH-mediated female-specific hepatic gene regulation.

In vivo evaluation of a novel, orally bioavailable, small molecule growth hormone receptor antagonist.

IGF-I is regarded as the most sensitive marker of growth hormone (GH) secretion in both GH deficient individuals and in individuals with excessive GH production. Studies on the effect of inhibitors of GH action in normal experimental animals are difficult to evaluate due to the complex relationship and feed back mechanisms of the GH/IGF-I system and the hypothalamo-pituitary axis. To circumvent the GH/IGF-I feedback mechanisms, we have used hypophysectomized (HX) rats treated with GH to assess the potential of a new low molecular weight compound, BVT-A ((N-[5-(aminosulfonyl)-2-methylphenyl]-5-bromo-2-furamide), to act as a GH receptor antagonist in vivo.

Sex and the liver - a journey through five decades.

Metabolism of steroids and drugs in rodents is sexually differentiated. The reason for this turned out to be the sexually differentiated growth hormone (GH) secretory pattern regulating the expression of a number of hepatic cytochrome P-450 genes. Although not fully resolved, it is clear that several signaling pathways and transcription factors are involved in mediating the effects of GH.

Antisense and sense RNA probe hybridization to immobilized crude cellular lysates: a tool to screen growth hormone antagonists.

The growth-promoting effect of growth hormone (GH) is primarily mediated by insulin-like growth factor-1 (IGF-1). The liver is the main source of circulating IGF-I. The authors have used rodent primary hepatocytes for studies on pharmacological intervention of IGF-I mRNA expression.

PPARalpha activators down-regulate CYP2C7, a retinoic acid and testosterone hydroxylase.

Peroxisome proliferators (PP) are a large class of structurally diverse chemicals that mediate their effects in the liver mainly through the peroxisome proliferator-activated receptor alpha (PPARalpha). Exposure to PP results in down-regulation of CYP2C family members under control of growth hormone and sex steroids including CYP2C11 and CYP2C12. We hypothesized that PP exposure would also lead to similar changes in CYP2C7, a retinoic acid and testosterone hydroxylase.

Activation of the glucocorticoid receptor or liver X receptors interferes with growth hormone-induced akr1b7 gene expression in rat hepatocytes.

The akr1b7 gene encodes an aldo-keto reductase involved in detoxification of isocaproaldehyde, the product from side chain cleavage of cholesterol, and of 4-hydroxynonenal (4-HNE) formed by lipid peroxidation and cleavage. Here we show that the expression of akr1b7 mRNA in rat liver is sexually differentiated, expressed in females but not in males, and regulated by the sexually dimorphic secretion pattern of GH. A GH dose-dependent induction of akr1b7 was demonstrated in cultured primary rat hepatocytes, which was sensitive to cycloheximide.

Effects of gender and GH secretory pattern on sterol regulatory element-binding protein-1c and its target genes in rat liver.

We investigated whether the sexually dimorphic secretory pattern of growth hormone (GH) in the rat regulates hepatic gene expression of sterol regulatory element-binding protein-1c (SREBP-1c) and its target genes. SREBP-1c, fatty acid synthase (FAS), and glycerol-3-phosphate acyltransferase (GPAT) mRNA were more abundant in female than in male livers, whereas acetyl-CoA carboxylase-1 (ACC1) and stearoyl-CoA desaturase-1 (SCD-1) were similarly expressed in both sexes. Hypophysectomized female rats were given GH as a continuous infusion or as two daily injections for 7 days to mimic the female- and male-specific GH secretory patterns, respectively.

Pattern-dependent suppression of growth hormone (GH) pulsatility by ghrelin and GH-releasing peptide-6 in moderately GH-deficient rats.

The peptide hormone ghrelin binds to the GH secretagogue receptor (GHS-R), stimulates GH secretion, and promotes adipogenesis. However, continuous GHS infusion does not stimulate skeletal growth and is associated with desensitization to further GH secretagogue treatment. In this study, 7-d intermittent (i.

Effects of rGH and G118RrGH on the induction of CYP2C12 and IGF-I in primary rat hepatocytes.

We have investigated the induction of the CYP2C12 and IGF-I genes by rGH and a "binding site 2 mutant", G118RrGH, in primary hepatocytes derived from male and female rats. Both the basal and the induced levels of CYP2C12, but not of IGF-I, were markedly lower in male derived than in female derived hepatocytes. A lower degree of receptor occupancy appears needed to elicit the CYP2C12 than the IGF-I response in cells obtained from both gender.

Interaction between growth hormone and insulin in the regulation of lipoprotein metabolism in the rat.

The importance of insulin for the in vivo effects of growth hormone (GH) on lipid and lipoprotein metabolism was investigated by examining the effects of GH treatment of hypophysectomized (Hx) female rats with and without concomitant insulin treatment. Hypophysectomy-induced changes of HDL, apolipoprotein (apo)E, LDL, and apoB levels were normalized by GH treatment but not affected by insulin treatment. The hepatic triglyceride secretion rate was lower in Hx rats than in normal rats and increased by GH treatment.

Possible involvement of truncated signal transducer and activator of transcription-5 in the GH pattern-dependent regulation of CYP2C12 gene expression in rat liver.

The transcription factors signal transducer and activator of transcription (Stat)5a and Stat5b have been implicated in the GH regulation of CYP2C genes in rodent liver. In addition to full-length Stat5 isoforms, truncated Stat5 proteins (Stat5beta), lacking the transactivating domain, have been demonstrated. In this study we found that Stat5beta can be formed by proteolytic cleavage in rat liver nuclei and that the activity of the protease is independent of GH.

Growth hormone regulation of rat liver gene expression assessed by SSH and microarray.

The sexually dimorphic secretion of growth hormone (GH) that prevails in the rat leads to a sex-differentiated expression of GH target genes, particularly in the liver. We have used subtractive suppressive hybridization (SSH) to search for new target genes induced by the female-characteristic, near continuous, pattern of GH secretion. Microarrays and dot-blot hybridizations were used in an attempt to confirm differential ratios of expression of obtained SSH clones.