- Transcriptional profiling of PPAR α. - and CREB3L3. - regulation of hepatoproliferative and metabolic functions of PPAR α. - Background: Peroxisome Proliferator-Activated receptor α (PPAR α ) and cAMP-Responsive Element Binding Protein 3-Like 3 (CREB3L3) are transcription factors involved in the regulation of lipid metabolism in the liver. - A small number of genes, including Fgf21 and Mfsd2a, were under dual control of PPAR α and CREB3L3. - Firstly, it reduced expression of PPAR α and its target genes involved in fatty acid oxidation and ketogenesis. - The liver plays a critical role in the metabolic response to changes in the diet. - transcription factor that is involved in the adaptive response to changes in nutrient supply is PPARα [1, 2].. - Growing evidence implicates CREB3L3 in the regulation of glucose and lipid metabolism in the liver [14]. - Both PPARα and CREB3L3 are activated in the liver by fasting and play important roles in the utilization of fatty acids for energy in the fasted state . - Second, there is strong evidence that PPARα and CREB3L3 cooperate in the regulation of certain genes such as Fgf21, encoding Fibro- blast Growth Factor 21. - Specifically, PPARα and CREB3L3 physically interact to form a complex that binds to an in- tegrated CRE-PPAR-responsive element-binding motif in the Fgf21 gene promoter [22]. - More recently, it was shown that during fasting, PPARα and CREB3L3 also cooperate in the stimulation of hepatic glu- coneogenesis by targeting genes such as Pck1, encoding Phosphoenolpyruvate Carboxykinase 1 [16]. - Effect of PPAR α and/or CREB3L3 ablation on fasting plasma metabolites. - To study the potential interaction between PPARα and CREB3L3 in metabolic regulation in the fasted state, we first performed basic metabolic measurements in wild-type, PPARα. - Plasma triglyceride levels were markedly elevated in the CREB3L3. - but not in the PPARα. - 1b and c), suggesting a dominant effect of PPARα ablation. - mice compared with wild-type mice and were highest in the combined PPARα/CREB3L3. - These data in- dicate the pronounced impact of PPARα and CREB3L3 deficiency on metabolic regulation during fasting.. - Effects of PPAR α and CREB3L3 ablation on hepatic gene expression in the fasted state are largely independent To study the potential interaction between PPARα and CREB3L3 in hepatic gene regulation in the fasted state, whole genome expression analysis was performed on liver samples of the four groups of mice after 16 h of fasting. - To study the magnitude of the effect of PPARα and CREB3L3 ablation on liver gene expression, we. - Analysis of the number of significantly changed genes showed that in the fasted state, loss of PPARα altered the expression of 1097 genes, of which 553 genes were upregulated and 544 genes were downregulated (Fig. - The fact that the number of significantly changed genes in the combined PPARα/CREB3L3. - mice exceeds the sum of significantly changed genes in the PPARα. - mice suggests a modest synergistic effect of PPARα and CREB3L3 deficiency on hepatic gene regula- tion, dominated by PPARα.. - To study the potential similarity between the effect of PPARα and CREB3L3 deficiency on liver gene expression, we performed principle component analysis. - 3b) confirmed that, in general, the effects of PPARα and CREB3L3. - 1 Effect of single and combined PPAR α and CREB3L3 deficiency on metabolic parameters. - Pound sign indicates significant effect of PPAR α deficiency in wild-type mice (red vs.. - To exam- ine whether any of these 34 genes may be directly regulated by PPARα, we determined the effect of the PPARα agonist Wy-14,643 on gene expression in the liver (Fig. - To further explore the differential impact of PPARα and CREB3L3 deficiency on hepatic gene expression, the top 40 most significantly downregulated genes in each condition (PPARα. - The top 40 list of most significantly downregu- lated genes in the CREB3L3. - A relatively large portion of the genes downregulated in the CREB3L3. - mice were also downregulated in the PPARα. - mice and, especially, in the combined PPARα/CREB3L3. - For PPARα, only a very small portion of the genes downregulated in the PPARα−/−. - mice were also downregulated in the CREB3L3. - For nearly all genes shown, the downregulation in the PPARα. - mice was copied in the combined PPARα/CREB3L3. - genes in the PPARα/CREB3L3. - At the pathway level, minimal overlap was observed between the effect of PPARα and CREB3L3 deficiency (Fig. - 2 Largely independent effect of PPAR α and CREB3L3 deficiency on hepatic gene expression in the fasted state. - The region in the heatmap that is suggestive of synergistic regulation by PPAR α and CREB3L3 deficiency is indicated by a grey arrow. - Consistent with the notion that the effects of com- bined PPARα/CREB3L3 deficiency are largely taken up by PPARα deficiency, the far majority of genesets down- regulated in the combined PPARα/CREB3L3. - downregulated genesets in the combined PPARα/. - mice were very similar in the single PPARα. - 3 Limited overlap in effects of PPAR α and CREB3L3 deficiency on hepatic gene expression in the fasted state. - mice in the fasted state (IBMT P-value<. - which had similar enrichment scores in the combined PPARα/CREB3L3. - 4 PPAR α and CREB3L3 mostly regulate distinct genes in liver in the fasted state. - (right panel) in the form a heatmap, using the mean expression of each group. - Overall, the above analyses indicate that the effects of PPARα and CREB3L3 deficiency on hepatic gene expres- sion during fasting are very distinct. - Effect of PPAR α and/or CREB3L3 deficiency on plasma metabolites during ketogenic diet. - To further explore the cooperativity between PPARα and CREB3L3 in hepatic gene regulation, we compared the effect of PPARα and CREB3L3 deficiency under the condition of a ketogenic diet. - Pound sign indicates significant effect of PPAR α deficiency in wild-type mice (red vs. - 6 PPAR α and CREB3L3 regulate distinct pathways in the liver in the fasted state. - a Top 10 downregulated genesets in liver of PPAR α. - Four days of ketogenic diet induced pronounced weight loss in all groups, which was most pronounced in the PPARα. - Interest- ingly, compared to the wild-type mice, the liver to body weight ratio was modestly increased in the PPARα−/−. - mice, yet was highest in the CREB3L3. - These parameters were also increased in the PPARα−/−. - and nearly 99% decreased in the PPARα/CREB3L3−/−. - To study the magnitude of the effect of PPARα and CREB3L3 deficiency during ketogenic diet on liver gene expression, we performed Volcano plot analysis (Fig. - In contrast to what was observed in the fasted state, the effects of CREB3L3 deficiency during ketogenic diet were more pronounced as compared to PPARα defi- ciency. - Strikingly, the effect of combined deficiency of PPARα and CREB3L3 on hepatic gene expression was less pronounced as compared to deficiency of only CREB3L3. - Combined loss of PPARα and CREB3L3 altered the expression of 3707 genes, of which 1996 genes were upregulated and 1711 genes. - 7 Effect of single and combined PPAR α and CREB3L3 deficiency on metabolic parameters. - These observations indicate that deficiency of PPARα mitigates the effect of CREB3L3 deficiency on hepatic gene expression.. - These data thus show that deficiency of CREB3L3 has no effect on hepatic gene expression in the absence of PPARα, indicating that the major liver phenotype triggered by CREB3L3 deficiency during ketogenic diet is dependent on PPARα.. - Scatter plot analysis confirmed that the effects of PPARα and CREB3L3 deficiency on hepatic gene expres- sion are very dissimilar, whereas the effect of PPARα deficiency and combined PPARα/CREB3L3 deficiency are similar (Additional file 1: Figure S2A). - Enrichment scores for these latter genesets were similar in the PPARα. - In line with these data, the PPARα mRNA expression level was markedly reduced in the CREB3L3. - En- richment scores for these genesets were much lower in the PPARα. - mice, indicat- ing the selective induction of cell cycle/mitosis-related genes in the CREB3L3. - A heatmap of the most enriched genes within the geneset Cell.Cycle.Mi- totic demonstrates the pronounced upregulation of cell cycle genes in the CREB3L3. - Consistent with the upregulation of cell cycle upon CREB3L3 deficiency, many of the most highly induced genes in the CREB3L3. - Again, the upregulation of these genes was almost completely abolished in the PPARα. - Strikingly, most of these genes are also highly upregulated in the CREB3L3. - Under conditions of overnight fasting, the effect of PPARα deficiency and CREB3L3 deficiency on hepatic gene expression are largely independent, and only show a very limited degree of synergism. - A small number of genes is under dual control of PPARα and CREB3L3, including Fgf21 and Mfsd2a. - Our data do not support a strong co-dependence of PPARα and CREB3L3 in hep- atic gene regulation during fasting. - 9 CREB3L3 deficiency during ketogenic diet leads to downregulation of PPAR α targets. - In addition, we show that deficiency of CREB3L3 has virtually no effect on hepatic gene expression in the absence of PPARα, indicating that the major liver phenotype triggered by CREB3L3 deficiency during ketogenic diet is dependent on PPARα. - On the one hand, CREB3L3 deficiency leads to reduced expression of PPARα and PPARα target genes involved in fatty acid oxidation and ketogenesis. - On the other hand, CREB3L3 deficiency leads to the marked activa- tion of the hepatoproliferative effect of PPARα. - Overall, our data suggest that CREB3L3 deficiency during keto- genic diet uncouples the mitogenic and lipid metabolic effects of PPARα in the liver.. - Our data indicate that the roles of PPARα and CREB3L3 in the fasted state are very distinct, showing minimal overlap in target gene regulation (Fig. - In contrast, Nakagawa and col- leagues observed that CREB3L3 deficiency in the fasted state reduced expression of many genes involved in fatty acid oxidation, showing synergy with PPARα [25]. - in the fasted state in PPARα. - a The cartoon illustrates the distinct roles of CREB3L3 and PPAR α in the regulation of hepatic lipid metabolism during fasting. - mice in the fasted state are in blue (IBMT P-value<. - mice in the fasted state are in red. - Accordingly, these data suggest that the elevated hepatic triglycerides in the PPARα. - We find that PPARα and CREB3L3 regulate distinct genes in the liver during fasting, with the exception of a limited number of common targets such as Fgf21. - Our data underscore the distinct func- tions of PPARα and CREB3L3 in the regulation of hepatic gene expression.. - Statistical analysis of the transcriptomics data was performed as described in the previous paragraph.. - mice in the fasted state. - Similar effects of PPAR α and combined PPAR α /CREB3L3 ablation on hepatic gene expression. - A critical role for the peroxisome proliferator-activated receptor alpha (PPARalpha) in the cellular fasting response: the PPARalpha-null mouse as a model of fatty acid oxidation disorders
Xem thử không khả dụng, vui lòng xem tại trang nguồn hoặc xem
Tóm tắt