The breast cancer resistance protein (BCRPABCG2) is a member of the ATP-binding cassette family of drug transporters and confers resistance to various anticancer drugs. We show here that mice lacking Bcrp1Abcg2 become extremely sensitive to the dietary chlorophyll-breakdown product pheophorbide a, resulting in severe, sometimes lethal phototoxic lesions on light-exposed skin. Pheophorbide a occurs in various plant-derived foods and food supplements. Bcrp1 transports pheophorbide a and is highly efficient in limiting its uptake from ingested food. Bcrp1(-/-) mice also displayed a previously unknown type of protoporphyria. Erythrocyte levels of the heme precursor and phototoxin protoporphyrin IX, which is structurally related to pheophorbide a, were increased 10-fold. Transplantation with wild-type bone marrow cured the protoporphyria and reduced the phototoxin sensitivity of Bcrp1(-/-) mice. These results indicate that humans or animals with low or absent BCRP activity may be at increased risk for developing protoporphyria and diet-dependent phototoxicity and provide a striking illustration of the importance of drug transporters in protection from toxicity of normal food constituents.

The oxysterol-activated liver X receptor (LXR) provides a link between sterol and fatty acid metabolism; activation of LXR induces transcription of lipogenic genes. This study shows that induction of the lipogenic genes Srebp-1c, Fas, and Acc1 upon administration of the synthetic LXR agonist T0901317 to C57BL/6J mice (10 mg/kg/day, 4 days) is associated with massive hepatic steatosis along the entire liver lobule and a 2.5-fold increase in very low density lipoprotein-triglyceride (VLDL-TG) secretion. The increased VLDL-TG secretion was fully accounted for by formation of larger (129 ؎ 9 nm versus 94 ؎ 12 nm, a 2.5-fold increase of particle volume) TG-rich particles. Stimulation of VLDL-TG secretion did not lead to elevated plasma TG levels in C57BL/6J mice, indicating efficient particle metabolism and clearance. However, T0901317 treatment did lead to severe hypertriglyceridemia in mouse models of defective TG-rich lipoprotein clearance, i.e. APOE*3-Leiden transgenic mice (3.2-fold increase) and apoE؊/؊ LDLr؊/؊ double knockouts (12-fold increase). Incubation of rat hepatoma McA-RH7777 cells with T0901317 also resulted in intracellular TG accumulation and enhanced TG secretion. We conclude that, in addition to raising high density lipoprotein cholesterol concentrations, pharmacological LXR activation in mice leads to development of hepatic steatosis and secretion of atherogenic, large TG-rich VLDL particles.

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The ATP-binding cassette transporter ABCA1 is essential for high density lipoprotein (HDL) formation and considered rate-controlling for reverse cholesterol transport. Expression of the Abca1 gene is under control of the liver X receptor (LXR). We have evaluated effects of LXR activation by the synthetic agonist T0901317 on hepatic and intestinal cholesterol metabolism in C57BL/6J and DBA/1 wild-type mice and in ABCA1-deficient DBA/1 mice. In wild-type mice, T0901317 increased expression of Abca1 in liver and intestine, which was associated with a ϳ60% rise in HDL. Biliary cholesterol excretion rose 2.7-fold upon treatment, and fecal neutral sterol output was increased by 150 -300%. Plasma cholesterol levels also increased in treated Abca1 ؊/؊ mice (؉120%), but exclusively in very low density lipoproteinsized fractions. Despite the absence of HDL, hepatobiliary cholesterol output was stimulated upon LXR activation in Abca1 ؊/؊ mice, leading to a 250% increase in the biliary cholesterol/phospholipid ratio. Most importantly, fecal neutral sterol loss was induced to a similar extent (؉300%) by the LXR agonist in DBA/1 wild-type and Abca1 ؊/؊ mice. Expression of Abcg5 and Abcg8, recently implicated in biliary excretion of cholesterol and its intestinal absorption, was induced in T0901317-treated mice. Thus, activation of LXR in mice leads to enhanced hepatobiliary cholesterol secretion and fecal neutral sterol loss independent of (ABCA1-mediated) elevation of HDL and the presence of ABCA1 in liver and intestine. Reverse cholesterol transport (RCT)1 or centripetal cholesterol flux is a key process in maintenance of whole body cholesterol homeostasis (1-6). RCT involves efflux of excess cholesterol from peripheral cells toward nascent high density lipoprotein (HDL) and its transport to the liver, followed by hepatic uptake mediated by scavenger receptor class B type I (SR-BI), biliary secretion in the form of cholesterol or bile salt, and finally disposal into feces. HDL-mediated RCT is generally assumed to underlie the well known epidemiological relationship between high HDL cholesterol levels and low risk for development of atherosclerosis.Efflux of cholesterol from peripheral cells, including macrophages in the vessel wall, is now known to be mediated in part by the ATP-binding cassette transporter ABCA1 (7-10). Abca1 mRNA is widely distributed throughout the body, with high expression levels in macrophages, hepatocytes, and enterocytes (11,12). This distribution pattern has recently been confirmed for the ABCA1 protein (13). The role of ABCA1 in hepatocytes is currently unknown, but may involve formation of pre-␤-HDL particles (14). In the intestine, ABCA1 has been suggested to be involved in cholesterol efflux from enterocytes into the lumen, thereby regulating the efficiency of intestinal cholesterol absorption (15, 16).HDL is considered a major source for bile-destined cholesterol and phospholipid (17,18). Yet, we have recently demonstrated that, despite the absence of HDL, hepatobiliary cholesterol flux and fe...

Obesity and type 2 diabetes have a heritable component that is not attributable to genetic factors. Instead, epigenetic mechanisms may play a role. We have developed a mouse model of intrauterine growth restriction (IUGR) by in utero malnutrition. IUGR mice developed obesity and glucose intolerance with aging. Strikingly, offspring of IUGR male mice also developed glucose intolerance. Here, we show that in utero malnutrition of F1 males influenced the expression of lipogenic genes in livers of F2 mice, partly due to altered expression of Lxra. In turn, Lxra expression is attributed to altered DNA methylation of its 5' UTR region. We found the same epigenetic signature in the sperm of their progenitors, F1 males. Our data indicate that in utero malnutrition results in epigenetic modifications in germ cells (F1) that are subsequently transmitted and maintained in somatic cells of the F2, thereby influencing health and disease risk of the offspring.

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About 24 intrinsic neurosecretory neurons within the pericardial organs (POs) of the crab Carcinus maenas produce a novel crustacean hyperglycaemic hormone (CHH)-like peptide (PO-CHH) and two CHH-precursor-related peptides (PO-CPRP I and II) as identified immunochemically and by peptide chemistry. Edman sequencing and MS revealed PO-CHH as a 73 amino acid peptide (8630 Da) with a free C-terminus. PO-CHH and sinus gland CHH (SG-CHH) share an identical N-terminal sequence, positions 1-40, but the remaining sequence, positions 41-73 or 41-72, differs considerably. PO-CHH may have different precursors, as cDNA cloning of PO-derived mRNAs has revealed several similar forms, one exactly encoding the peptide. All PO-CHH cDNAs contain a nucleotide stretch coding for the SG-CHH(41-76) sequence in the 3'-untranslated region (UTR). Cloning of crab testis genomic DNA revealed at least four CHH genes, the structure of which suggest that PO-CHH and SG-CHH arise by alternative splicing of precursors and possibly post-transcriptional modification of PO-CHH. The genes encode four exons, separated by three variable introns, encoding part of a signal peptide (exon I), the remaining signal peptide residues, a CPRP, the PO-CHH(1-40)/SG-CHH(1-40) sequences (exon II), the remaining PO-CHH residues (exon III) and the remaining SG-CHH residues and a 3'-UTR (exon IV). Precursor and gene structures are more closely related to those encoding related insect ion-transport peptides than to penaeid shrimp CHH genes. PO-CHH neither exhibits hyperglycaemic activity in vivo, nor does it inhibit Y-organ ecdysteroid synthesis in vitro. From the morphology of the neurons it seems likely that novel functions remain to be discovered.

van Straten EME, Bloks VW, Huijkman NCA, Baller JFW, van Meer H, Lü tjohann D, Kuipers F, Plö sch T. The liver X-receptor gene promoter is hypermethylated in a mouse model of prenatal protein restriction. Am J Physiol Regul Integr Comp Physiol 298: R275-R282, 2010. First published November 4, 2009 doi:10.1152/ajpregu.00413.2009.-Prenatal nutrition as influenced by the nutritional status of the mother has been identified as a determinant of adult disease. Feeding low-protein diets during pregnancy in rodents is a well-established model to induce programming events in offspring. We hypothesized that protein restriction would influence fetal lipid metabolism by inducing epigenetic adaptations. Pregnant C57BL/6J mice were exposed to a protein-restriction protocol (9% vs. 18% casein). Shortly before birth, dams and fetuses were killed. To identify putative epigenetic changes, CG-dinucleotiderich region in the promoter of a gene (CpG island) methylation microarrays were performed on DNA isolated from fetal livers. Two hundred four gene promoter regions were differentially methylated upon protein restriction. The liver X-receptor (Lxr) alpha promoter was hypermethylated in protein-restricted pups. Lxr alpha is a nuclear receptor critically involved in control of cholesterol and fatty acid metabolism. The mRNA level of Lxra was reduced by 32% in fetal liver upon maternal protein restriction, whereas expression of the Lxr target genes Abcg5/Abcg8 was reduced by 56% and 51%, respectively, measured by real-time quantitative PCR. The same effect, although less pronounced, was observed in the fetal intestine. In vitro methylation of a mouse Lxra-promoter/luciferase expression cassette resulted in a 24-fold transcriptional repression. Our study demonstrates that, in mice, protein restriction during pregnancy interferes with DNA methylation in fetal liver. Lxra is a target of differential methylation, and Lxra transcription is dependent on DNA methylation. It is tempting to speculate that perinatal nutrition may influence adult lipid metabolism by DNA methylation, which may contribute to the epidemiological relation between perinatal/neonatal nutrition and adult disease.programming; epigenetics; CpG island methylation microarray AN OVERWHELMING BODY OF EVIDENCE links fetal (mal)nutrition to the development of chronic diseases at adult age [developmental origins of health and disease hypothesis (4, 5)]. Epidemiological data show that children small for gestational age, who were undernourished during intrauterine development, have a higher risk of developing cardiovascular diseases or the metabolic syndrome in adulthood (3). In humans, fetal malnutrition is related to external factors (starvation, malnutrition, drug consumption of the mother) or to internal factors, such as placental dysfunction leading to reduced routing of nutrients to the fetus (32).Knowledge of underlying mechanisms of metabolic programming may help to design strategies to halt the current epidemic in metabolic diseases. For this purpose, several animal mo...