Unknown,Transcriptomics,Genomics,Proteomics

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Comparison of hepatic gene expression in response to fasting or 2 week high fat diet

ABSTRACT: The metabolic syndrome represents a cluster of well-documented risk factors for the development of type 2 diabetes and cardiovascular disease. Next to visceral obesity, dyslipidemia and insulin resistance, excessive triglyceride accumulation in the liver has been implicated to play a role in the development of the metabolic syndrome. To investigate the underlying molecular changes leading to hepatic steatosis we performed microarray analysis on livers of mice either fasted over night or fed a high fat diet for 2 Weeks. We analysed 7 500 genes and subsequently performed a pathway analysis to identify changes in hepatic genes in both models. Fasting induced a high number of differentially expressed hepatic genes, resulting in an change towards an energy saving phenotype. In contrast only a small number of genes were differentially expressed after high fat diet. Fasting promoted gluconeogenesis and b-oxidation, strongly suppressed cholesterol synthesis and activated pathways to preserve hepatic function. High fat diet induced steatosis was accompanied by the activation of the stearoyl-CoA desaturase and the lipogenic transcription factor Srebp-1c, both implicated in the development of hepatic insulin resistance. These changes reflect the activation of different gene expression programs in response to plasma lipid overload. Keywords: Diet intervention Two conditions, fasting and high fat diet. 5 biological replicates for comparison of high fat diet versus fasting and controls versus high fat diet, 4 biological replicates for the comparison of controls versus fasting. All biological replicates are performed as technical replicates in the form of a dye-swap. Total number of arrays hybridises is therefore 28.

ORGANISM(S): Mus musculus

SUBMITTER: Anja Schiel

PROVIDER: E-GEOD-8576 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Hepatic fat accumulation has been widely associated with diabetes and hepatocellular carcinoma (HCC). Here, we aim to characterize the metabolic response that high fat availability elicits in livers prior to development of these diseases. We find that, after a short term on high fat diet, otherwise healthy mice show elevated hepatic glucose metabolization, activated glucose uptake, glycolysis and glucose contribution to serine as well as elevated pyruvate carboxylase activity compared to control diet mice. To understand other changes in the liver tissue after high fat diet exposure, we conducted untargeted transcriptomics and proteomics. This glucose phenotype occurred independent from transcriptional or proteomic programming, which identified increased peroxisomal and lipid metabolism pathways. Interestingly, we observe that high fat diet fed mice exhibit an increased lactate production when challenged with glucose. This trait seems to find a parallel in a human cohort, where we observe a correlation between waist circumference and lactate secretion after an oral glucose bolus across healthy individuals. In an in vitro model of hepatoma cells, we found physiologically relevant palmitate exposure stimulated production of reactive oxygen species (ROS) and glucose uptake, a similar glycolytic phenotype to the in vivo study. This effect is inhibited upon interference with peroxisomal lipid metabolism and ROS production. Furthermore, we find that with exposure to an HCC-inducing hepatic carcinogen, continuation of high fat diet enhances the formation of HCC (100% with resectable tumors) as compared to control (50% with resectable tumors) in mice. However, regardless of the dietary background, all murine tumors showed similar alterations in glucose metabolism compared to those identified in fat exposed non-transformed mouse livers. Further, the presence of tumors in high fat diet exposed mice normalized glucose tolerance. Lipidomics analysis of tumor tissue and liver tissue from high fat diet exposed mice identified tumor tissue enrichment of diacylglycerol (DG) and phosphatidylcholine (PC) species. Some of these species were also increased in high fat diet liver tissue compared to control diet liver tissue. These findings suggest that fat can induce similar metabolic changes in non-transformed liver cells than found in HCC, and that peroxisomal metabolism of lipids may be a factor in driving a glycolytic metabolism In conclusion, we show that normal, non-transformed livers respond to fat by inducing glucose metabolism.

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Comparison of hepatic gene expression in response to fasting or 2 week high fat diet

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