Hepatic gene expression data from Gpr146 WT and KO male mice
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ABSTRACT: GPR146 is a susceptible gene associated with plasma cholesterol levels in humans, its physiological and molecular functions have not been fully characherized. In this study, we generated Gpr146 whole-body knockout mice and found that depletion of GPR146 led to substantilly reduced plasma total cholesterol levels. We used microarrays to detail the global programme of gene expression in liver of Gpr146 WT and KO male mice upon 6-hour refeeding after a 16-hour fast.
Project description:Both PIK3R1(Y657X) mutant and wild-type C57Bl/6J mice were maintained on chow until 16 weeks old, at which time they were fasted for 16 hours and then refed chow for 6 hours. The tissues were harvested and snap-frozen at three time points: chow diet before overnight fast (ad libitum chow, ALC), after 16 hour fast (overnight fast, ONF), and after 6 hour refeeding (refed 6 hours, RF6).
Project description:For more than a century, fasting regimens have been shown to improve health, lifespan, and tissue regeneration in diverse model organisms and humans. However, important questions remain regarding how fasting and refeeding cycles stimulate stem cell output and how this influences their role in early tumor formation. Here, we demonstrate that in the mammalian intestine, a short 24-hour fast followed by a 24-hour refeeding period (that is, post-fast refeeding) and not fasting itself elevates the stemness program and regenerative capacity of Lgr5+ intestinal stem cells (ISCs). Furthermore, loss of the tumor suppressor APC in post-fast refed ISCs significantly boosts tumor incidence in the small intestine and colon compared to those in the fasted or ad libitum fed states. Mechanistically, robust induction of insulin-PI3K-mTORC1 signaling as well as elevated intestinal polyamines level increase protein synthesis in post-fast refed ISCs to mediate these changes as inhibition of mTORC1, polyamine, or protein synthesis abrogate the regenerative or tumorigenic effects of post-fast refeeding. Thus, our data indicate that post-fast refeeding leads to a burst not only in stem cell-driven regeneration but also in tumorigenicity and that careful consideration be given to fast-refeeding cycles when planning diet-based strategies.
Project description:GATA4 is a transcription factor known for its crucial role in the development of many tissues, including liver; however, its role in adult liver metabolism is unknown. Here, using high-throughput sequencing technologies, including assay for transposase-accessible chromatin with sequencing (ATAC-Seq), we identified GATA4 as a transcriptional regulator of metabolism in liver. GATA4 expression is elevated in response to refeeding, and its occupancy is increased at enhancers of genes linked to fatty acid and lipoprotein metabolism. Knocking out GATA4 in adult liver (Gata4LKO) decreased transcriptional activity at GATA4 binding sites especially during feeding. Gata4LKO mice have reduced plasma HDL cholesterol and increased liver triglyceride levels. The expression of a panel of genes involved in cholesterol export and triglyceride hydrolysis was downregulated and the expression of those involved in lipid uptake were upregulated in Gata4LKO liver, We further demonstrate that GATA4 collaborates with LXR liver. GATA4 shares a number of binding sites and direct transcriptional targets with LXRs, and loss of GATA4 impairs the hepatic transcriptional response to LXR agonist. Collectively, these results show that hepatic GATA4 contributes to the transcriptional control of hepatic and systemic lipid homeostasis.
Project description:Temporally restricted feeding has a profound effect on the circadian clock. Fasting and feeding paradigms are known to influence hepatic transcription. This dataset shows the dynamic effects of refeeding mice after a 24hour fasting period. Mice were entrained for two weeks under ad libitum access to food. Mice were then released into constant darkness and food was withdrawn at CT4 on the first day in constant darkness. On the second day in constant darkness mice were either fed (Refed) or continously fasted (Fast) at CT4. Liver tissue was collected at the indicated timepoints. Total RNA was extracted and standard Affymetrix protocol were used for amplification, labeling and hybridization
Project description:Transitions between the fed and fasted state are common in mammals. The liver orchestrates adaptive responses to feeding/fasting by transcriptionally regulating metabolic pathways of energy usage and storage. Transcriptional and enhancer dynamics following cessation of fasting (refeeding) have not been explored. We examined the transcriptional and chromatin events occurring upon refeeding in mice, including kinetic behavior and molecular drivers. We found that the refeeding response is temporally-organized with the early response focused on ramping up protein translation while the later stages of refeeding drive a bifurcated lipid synthesis program. While both the cholesterol biosynthesis and lipogenesis pathways were inhibited during fasting, most cholesterol biosynthesis genes returned to their basal levels upon refeeding while most lipogenesis genes markedly overshoot above pre-fasting levels. Gene knockout, enhancer dynamics and ChIP-seq analyses revealed that lipogenic gene overshoot is dictated by LXRα. These findings from unbiased analyses unravel the mechanism behind the long-known phenomenon of refeeding fat overshoot.
Project description:PCSK9 promotes the lysosomal degradation of cell surface LDL receptor (LDLR). We analyzed how excess LDLR generated by PCSK9 deficiency is differently handled in male and female mice to possibly unveil the mechanism leading to the lower efficacy of PCSK9 mAb on LDL-cholesterol levels in women. Analysis of intact or ovariectomized PCSK9 knockout (KO) mice supplemented with placebo or 17β-estradiol (E2) demonstrated that female, but not male mice massively shed the soluble ectodomain of the LDLR in the plasma. Liver-specific PCSK9 KO or alirocumab-treated WT mice exhibit the same pattern. This shedding is distinct from the basal one and is inhibited by ZLDI-8, a metalloprotease inhibitor pointing at ADAM10/ADAM17. In PCSK9 KO female mice, ZLDI- 8 raises by 80 % the LDLR liver content in a few hours. This specific shedding is likely cholesterol-dependent: it is prevented in PCSK9 KO male mice that exhibit low intra-hepatic cholesterol levels without activating SREBP-2, and enhanced by mevalonate or high cholesterol feeding, or by E2 known to stimulate cholesterol synthesis via the estrogen receptor-α. Liver transcriptomics demonstrates that critically low liver cholesterol in ovariectomized female or knockout male mice also hampers the cholesterol-dependent G2/M transition of the cell cycle. Finally, higher levels of shed LDLR were measured in the plasma of women treated with PCSK9 mAb. PCSK9 knockout female mice hormonally sustain cholesterol synthesis and shed excess LDLR, seemingly like women. In contrast, male mice rely on high surface LDLR to replenish their stocks, despite 80 % lower circulating LDL.
Project description:Atherosclerosis is characterized by the pathological accumulation of cholesterol-laden macrophages in the arterial wall. Atherosclerosis is also the main underlying cause of cardiovascular diseases (CVDs), and its development is largely driven by elevated plasma cholesterol. Strong epidemiological data find an inverse association between plasma β-carotene with atherosclerosis, and we recently showed that β-carotene oxygenase 1 (BCO1) activity, responsible for β-carotene cleavage to vitamin A, is associated with reduced plasma cholesterol in humans and mice. In this study, we explore whether intact β-carotene or vitamin A affect atherosclerosis progression in the atheroprone low-density lipoprotein receptor (LDLR) - deficient mice. In comparison to control-fed Ldlr-/- mice, β-carotene-supplemented mice showed reduced atherosclerotic lesion size at the level of the aortic root and plasma cholesterol levels (P = 0.0003). These changes were absent in Ldlr-/-/Bco1-/- mice, despite accumulating β-carotene in plasma and atherosclerotic lesions. We discarded the implication of myeloid BCO1 in the development of atherosclerosis by performing bone marrow transplant experiments. Lipid production assays found that retinoic acid, the active form of vitamin A, reduced the secretion of newly synthetized triglyceride and cholesteryl ester in cell culture and mice. Overall, our findings provide insights into the role of BCO1 activity and vitamin A in atherosclerosis progression through the regulation of hepatic lipid metabolism.
Project description:If the function of the nuclear receptor PPARa is well-known during a prolongated fasting, its hepatic biological function during feeding and refeeding conditions still needs to be investigated. Moreover, in vivo data collected so far on PPARa function during fasting were obtained using the total Ppara KO transgenic mouse model. To identify genes whose expression is under the strict dependence of hepatic PPARa activity, we generated a new mouse strain of PPARa-specific deletion in hepatocyte (albumin-Cre+/- Pparaflox/flox or LKO) and we compared them to total Ppara KO (KO), wild-type (WT) and liver WT (albumin-Cre-/- Pparaflox/flox or LWT) mice under three nutritional challenges. We used microarrays to detail the global programme of gene expression in liver of Ppara LKO, LWT, Ppara KO and WT male mice fed ad libitum, fasted for 24 hours and refed. There are 52 liver samples, each from an individual mouse. The samples are from Ppara liver KO (LKO), Ppara KO (KO), wild-type (WT) and liver WT (LWT) male mice of 8 week-old from the same genetic background (C57Bl/6J) fed ad libitum, fasted for 24 hours, fasted for 24 hours and then refed 24 hours more with glucose added in water (200g/l). In fed condition (Fed), n= 3 mice for LKO, LWT genotypes, n= 5 for KO and n= 4 fot WT; in fasting condition (Fas), n=5 for LKO, LWT and WT genotypes and n= 3 for KO; in refeeding condition (Ref), n= 5 for LKO, KO and WT genotypes and n= 4 for LWT. All mice were sacrified at ZT14.
Project description:Background Small intestine and liver greatly contribute to whole body lipid, cholesterol and phospholipid metabolism but to which extent cholesterol and phospholipid handling in these tissues is affected by high fat Western-style obesogenic diets remains to be defined. We therefore quantified cholesterol and phospholipid concentrations in intestine and liver and determined fecal neutral sterol and bile acid excretion in C57Bl/6N mice fed for 12 weeks either a cholesterol-free high carbohydrate control diet or a high fat diet containing 0.03 % (w/w) cholesterol. To identify underlying mechanisms of dietary adaptation in intestine and liver, changes in gene expression were assessed by microarray and qPCR profiling, respectively. Results Animals on high fat diet showed increased plasma cholesterol levels, associated with the higher dietary cholesterol supply, yet, significantly reduced cholesterol levels were found in intestine and liver. Transcript profiling revealed evidence that expression of numerous genes involved in cholesterol synthesis and uptake via LDL, but also in phospholipid metabolism, underwent compensatory regulations in both tissues. Alterations in glycerophospholipid metabolism were confirmed at the metabolite level by phospolipid profiling via mass spectrometry. Conclusions Our findings suggest that intestine and liver react to a high dietary fat intake by an activation of de novo cholesterol synthesis and other cholesterol-saving mechanisms, as well as with major changes in phospholipid metabolism, to accommodate to the fat load. The proximal part of the intestine of mice fed either a control or a high fat diet were analyzed. 5 replicates each.
Project description:In cell models, changes in the “accessible” pool of plasma membrane (PM) cholesterol are linked with the regulation of ER sterol synthesis and metabolism by the Aster family of nonvesicular transporters. However, the relevance of such nonvesicular transport mechanisms for lipid homeostasis in vivo has not been defined. Here we reveal two physiological contexts that generate accessible PM cholesterol and engage the Aster pathway in liver: fasting and reverse cholesterol transport (RCT). During fasting, adipose tissue–derived fatty acids activate hepatocyte sphingomyelinase to liberate sequestered PM cholesterol. Aster-dependent cholesterol transport during fasting facilitates cholesteryl ester (CE) formation, cholesterol movement into bile, and VLDL production. During RCT, HDL delivers excess cholesterol to the hepatocyte PM through SR-BI. Loss of hepatic Asters impairs cholesterol movement into feces, raises plasma cholesterol levels, and causes cholesterol accumulation in peripheral tissues. These results reveal fundamental mechanisms by which Aster cholesterol flux contributes to hepatic and systemic lipid homeostasis.