Unknown,Transcriptomics,Genomics,Proteomics

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Role of transcriptional regulators IFRD1 and IFRD2 in intestinal lipid absorption and obesity

ABSTRACT: Because of the epidemic rise of obesity worldwide, the identification of novel target genes for pharmacological treatment of obesity and related disorders is becoming of high importance. IFRD1 and IFRD2 are members of a novel transcriptional regulators family. Intestinal over-expression of mouse homologue of IFRD1 promoted intestinal triglyceride uptake and induced whole body adiposity in mice. To further elucidate the role of IFRD1 and IFRD2 in vivo, we generated mice lacking both mouse homologues of IFRD1 (TIS7) and IFRD2 (SKMc15) genes. Here, we report that mice deficient in TIS7 and SKMc15 genes, despite normal calorie intake had severely reduced amount of adipose tissue, were resistant to diet-induced obesity and displayed high glucose tolerance. Lower dietary fat entry into the circulation suggested that this phenotype resulted from impaired intestinal lipid transport. We identified down-regulation of CD36, a fatty acid transporter, both on RNA and protein levels. Reporter assays indicated that TIS7 and SKMc15 transcriptionally regulated CD36 expression and CD36 overexpression partially restored fatty acid uptake in vitro. Hence, our study suggested that TIS7 and SKMc15 play an important role in the regulation of the lipid metabolism and might represent a novel strategy for treatment of disorders caused by excess fat intake. To determine whether decreased intestinal lipid absorption might be caused by changes in expression of lipid processing and transport molecules, we performed Affymetrix microarray analyses of total RNA samples isolated from the jejunum of HFD-fed WT type and dKO animals. The moderated t-test was used to calculate p-values for significance of differential gene expression between 3 dKO and 3 wild type mice. These raw p-values were adjusted for multiple hypothesis testing using the method from Benjamini and Hochberg for a strong control of the false discovery rate (FDR) and genes with thus adjusted p-values < 0.05 were considered significant. Age-matched (7-10 week old) male wild type and TIS7 (Ifrd1) SKMc15 (Ifrd2) double knock out mice (C57Bl6 background) were caged individually and maintained from 3 weeks up to 8 weeks on a synthetic high saturated fat (HFD) diet (Ssniff). Small intestines (jejunum) were harvested for total RNA isolation. RNAs from 3 WT and 3 dKO mice were subjected to Affymetrix based whole genome gene expression analysis (Mouse 430.2 GeneChip).

ORGANISM(S): Mus musculus

SUBMITTER: Johannes Rainer

PROVIDER: E-GEOD-27019 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Because of the epidemic rise of obesity worldwide, the identification of novel target genes for pharmacological treatment of obesity and related disorders is becoming of high importance. IFRD1 and IFRD2 are members of a novel transcriptional regulators family. Intestinal over-expression of mouse homologue of IFRD1 promoted intestinal triglyceride uptake and induced whole body adiposity in mice. To further elucidate the role of IFRD1 and IFRD2 in vivo, we generated mice lacking both mouse homologues of IFRD1 (TIS7) and IFRD2 (SKMc15) genes. Here, we report that mice deficient in TIS7 and SKMc15 genes, despite normal calorie intake had severely reduced amount of adipose tissue, were resistant to diet-induced obesity and displayed high glucose tolerance. Lower dietary fat entry into the circulation suggested that this phenotype resulted from impaired intestinal lipid transport. We identified down-regulation of CD36, a fatty acid transporter, both on RNA and protein levels. Reporter assays indicated that TIS7 and SKMc15 transcriptionally regulated CD36 expression and CD36 overexpression partially restored fatty acid uptake in vitro. Hence, our study suggested that TIS7 and SKMc15 play an important role in the regulation of the lipid metabolism and might represent a novel strategy for treatment of disorders caused by excess fat intake. To determine whether decreased intestinal lipid absorption might be caused by changes in expression of lipid processing and transport molecules, we performed Affymetrix microarray analyses of total RNA samples isolated from the jejunum of HFD-fed WT type and dKO animals. The moderated t-test was used to calculate p-values for significance of differential gene expression between 3 dKO and 3 wild type mice. These raw p-values were adjusted for multiple hypothesis testing using the method from Benjamini and Hochberg for a strong control of the false discovery rate (FDR) and genes with thus adjusted p-values < 0.05 were considered significant.

Project description:Chronic stress leads post-traumatic stress disorder (PTSD) and to metabolic complications, including fatty liver. It is feasible, that stress immediately initiates molecular mechanisms to alter energy metabolism and glucose homeostasis which interfere with hepatic lipid accumulation after stress recovery. We aim to elucidate these molecular mechanisms of long term stress effects on metabolism and focus on physiological adaptation and the role of FGF21, which is protective in hepatic lipid accumulation. Methods FGF21 knockout and control mice were exposed to chronic variable stress (Cvs) and recovered for 3 months to simulate PTSD. We determined in vivo and ex vivo energy metabolism, mitochondrial function by extracellular flux analysis, alterations in DNA modifying enzymes and gene regulation immediately after stress and after the recovery period to determine long term alterations. Results Chronic stress leads to reduced insulin sensitivity and hepatic lipid accumulation with increased fatty acid uptake (FAU), stress-induced lipolysis, and reduction in NAD+/NAD ratio and Sirt activity. Immediately after stress, PPARa and SREBP-1 target genes are differentially regulated and are involved in the development of stress-induced fatty liver. After recovery, insulin sensitivity increases but insulin-induced de novo lipogenesis (DNL) is reduced and FAU is increased. HDAC and MT activity are suppressed, whereas HAT activity increases, linking metabolic adjustments to transcriptional regulators. Thus, key metabolic genes are differentially regulated and secreted proteins indicate the activation of liver disease by Cvs only in FGF21WT. GR binding to the Cd36 promoter is altered. After stress recovery, serum FGF21 is increased and protects against lipid accumulation. FGF21 interacts by attenuating DNL, increasing FAU and HAT activity, and balancing mitochondrial activity. Higher long-term stress-induced activation and binding of GR to the FGF21 promoter may contribute to the prolonged FGF21 release. Conclusions We show that previous stress exposure determines predisposition to fatty liver disease is regulated by FGF21. Immediately after Cvs, altered gene regulation and activity of DNA-modifying enzymes determine the metabolic late effects seen in PTSD. FGF21 functions after chronic stress exposure i) to protect against hepatic lipid accumulation, ii) to maintain mitochondrial capacity, and iii) to mediate in the modulation of DNA-modifying enzymes. These findings highlight the protective role of FGF21 even in stress-induced hepatic lipid accumulation.

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Role of transcriptional regulators IFRD1 and IFRD2 in intestinal lipid absorption and obesity

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