ABSTRACT: Transcription profiling by high throughput sequencing of pancreatic islets isolated from free fatty acid receptor 3 knockout (Ffar3 KO) and wild type (Ffar3 WT) male mice
Project description:The short chain fatty acid (SCFA) receptor (free fatty acid receptor-3; FFAR3) is expressed in pancreatic beta cells; however, its role in insulin secretion is not clearly defined. Here, we examined the role of FFAR3 in insulin secretion. Using islets from global knockout FFAR3 (Ffar3-/-) mice, we explored the role of FFAR3 and ligand-induced FFAR3 signaling on glucose stimulated insulin secretion. RNA sequencing was also performed to gain greater insight into the impact of FFAR3 deletion on the islet transcriptome. First exploring insulin secretion, it was determined that Ffar3-/- islets secrete more insulin in a glucose-dependent manner as compared to wildtype (WT) islets. Next, exploring its primary endogenous ligand, propionate, and a specific agonist for FFAR3, signaling by FFAR3 inhibited glucose-dependent insulin secretion, which occurred through a Gαi/o pathway. To help understand these results, transcriptome analyses by RNA-sequencing of Ffar3-/- and WT islets observed multiple genes with well known roles in islet biology to be altered by genetic knockout of FFAR3. Our data shows that FFAR3 signaling mediates glucose stimulated insulin secretion through Gαi/o sensitive pathway. Future studies are needed to more rigorously define the role of FFAR3 by in vivo approaches. Analysis of total RNA from 3 biological replicates of pancreatic islets isolated from free fatty acid receptor 3 knockout (Ffar3 KO) and wildtype (Ffar3 WT) male mice
Project description:The short chain fatty acid (SCFA) receptor (free fatty acid receptor-3; FFAR3) is expressed in pancreatic beta cells; however, its role in insulin secretion is not clearly defined. Here, we examined the role of FFAR3 in insulin secretion. Using islets from global knockout FFAR3 (Ffar3-/-) mice, we explored the role of FFAR3 and ligand-induced FFAR3 signaling on glucose stimulated insulin secretion. RNA sequencing was also performed to gain greater insight into the impact of FFAR3 deletion on the islet transcriptome. First exploring insulin secretion, it was determined that Ffar3-/- islets secrete more insulin in a glucose-dependent manner as compared to wildtype (WT) islets. Next, exploring its primary endogenous ligand, propionate, and a specific agonist for FFAR3, signaling by FFAR3 inhibited glucose-dependent insulin secretion, which occurred through a Gαi/o pathway. To help understand these results, transcriptome analyses by RNA-sequencing of Ffar3-/- and WT islets observed multiple genes with well known roles in islet biology to be altered by genetic knockout of FFAR3. Our data shows that FFAR3 signaling mediates glucose stimulated insulin secretion through Gαi/o sensitive pathway. Future studies are needed to more rigorously define the role of FFAR3 by in vivo approaches.
Project description:UDP-sugars were identified as extracellular signaling molecules, assigning a new function to these compounds in addition to their well defined role in intracellular substrate metabolism and storage. Previously regarded as an orphan receptor, the G protein-coupled receptor (GPCR) P2Y14 (GPR105) was found to bind extracellular UDP and UDP-sugars. Little is known about the physiological functions of this GPCR. To study its physiological role we used a gene-deficient (KO) mouse strain expressing the bacterial LacZ reporter gene to monitor the physiological expression pattern of P2Y14. We found that P2Y14 is mainly expressed in pancreas and salivary glands and in subpopulations of smooth muscle cells of the gastrointestinal tract, blood vessels, lung and uterus. Among other phenotypical differences KO mice showed a significantly impaired glucose tolerance following oral and intraperitoneal glucose application. An unchanged insulin tolerance suggested altered pancreatic islet function. Transcriptome analysis of pancreatic islets showed that P2Y14 deficiency significantly changed expression of components involved in insulin secretion. Insulin secretion tests revealed a reduced insulin release from P2Y14-deficient islets highlighting P2Y14 as a new modulator of proper insulin secretion. 10 samples from pancreatic islets isolated from wildtype mice; 10 samples from pancreatic islets isolated from P2Y14-knockout mice
Project description:Sirtuins are a family of protein deacetylases, deacylases, and ADP-ribosyltransferases that regulate life span, control the onset of numerous age-associated diseases, and mediate metabolic homeostasis. We have uncovered a novel role for the mitochondrial sirtuin SIRT4 in the regulation of hepatic lipid metabolism during changes in nutrient availability. We show that SIRT4 levels decrease in the liver during fasting and that SIRT4 null mice display increased expression of hepatic peroxisome proliferator activated receptor (PPAR ) target genes associated with fatty acid catabolism. Accordingly, primary hepatocytes from SIRT4 knockout (KO) mice exhibit higher rates of fatty acid oxidation than wild-type hepatocytes, and SIRT4 overexpression decreases fatty acid oxidation rates. The enhanced fatty acid oxidation observed in SIRT4 KO hepatocytes requires functional SIRT1, demonstrating a clear cross talk between mitochondrial and nuclear sirtuins. Thus, SIRT4 is a new component of mitochondrial signaling in the liver and functions as an important regulator of lipid metabolism. SIRT4 knockout (KO) and wild-type (WT) littermates (male; n 6 per genotype; 7- to 8-month-old littermates) were sacrificed after a 16-h overnight fast. Samples were individually hybridized on Affymetrix Mouse Genome 430 2.0 GeneChips by the Biopolymers Facility (Harvard Medical School).
Project description:Irisin, released from exercised muscle, has been shown to have beneficial effects on numerous tissues but its effects on bone are unclear. We found significant sex and genotype differences in bone from wildtype (WT) mice compared to mice lacking Fndc5 (KO), with and without calcium deficiency. Despite their bone being 2 indistinguishable from WT females, KO female mice were partially protected from osteocytic osteolysis and osteoclastic bone resorption when allowed to lactate or when placed on a low-calcium diet. Male KO mice have more but weaker bone compared to WT males, and when challenged with a low-calcium diet lost more bone than WT males. To begin to understand responsible molecular mechanisms, osteocyte transcriptomics was performed. Osteocytes from WT females had greater expression of genes associated with osteocytic osteolysis and osteoclastic bone resorption compared to WT males which had greater expression of genes associated with steroid and fatty acid metabolism. Few differences were observed between female KO and WT osteocytes, but with a low calcium diet, the KO females had lower expression of genes responsible for osteocytic osteolysis and osteoclastic resorption than the WT females. Male KO osteocytes had lower expression of genes associated with steroid and fatty acid metabolism, but higher expression of genes associated with bone resorption compared to male WT. In conclusion, irisin plays a critical role in the development of the male but not the female skeleton and protects male but not female bone from calcium deficiency. We propose irisin ensures the survival of offspring by targeting the osteocyte to provide calcium in lactating females, a novel function for this myokine.
Project description:The purinergic receptor P2Y13 (P2RY13) has been shown to play a role in the uptake of holo-HDL particles in in vitro hepatocyte experiments. In order to determine the role of P2Y13 in lipoprotein metabolism in vivo, we ablated the expression of this gene in mice and found that P2Y13 knockout mice have lower plasma HDL (17%) and LDL (27%) levels as well as lower fecal concentrations of neutral sterols. In addition, significant decreases were detected in serum levels of fatty acids, glycerol and triglycerides in P2Y13 knockout mice. mRNA profiling analyses showed that ablation of P2Y13 affects hepatic gene expression in a gender-specific manner. Non-supervised agglomerative cluster analysis showed that expression changes in mice with the same genotype (KO or WT) cluster together and that distinct gene expression clusters can be observed for males and females. Subsequent gene set enrichment analysis showed increased expression of cholesterol and fatty acid biosynthesis genes, while fatty acid beta-oxidation genes were significantly decreased. Liver gene signatures also identified changes in SREBP-regulated and PPARgamma-regulated transcript levels. Differential gene expression upon P2RY13 gene ablation. Livers were isolated from male and female wildtype and P2RY13 knockout mice (6 per gender/genotype group, except for 5 per male/WT group). Isolated RNA was subjected to microarray analyses. The results of a one-way ANOVA analysis (p<0.05) showed 3471 transcripts whose relative expression changes were more than 20%.
Project description:Expression profiling of pancreatic islets in Tcf1 knock out mice. Experiment Overall Design: two biological replicates per condition; two conditions are WT and Tcf1 KO mice; platforms are Affy MG-U74A and B array
Project description:β-cell Specific Kcnj11 -/- mice and their islets exhibited a hirtherto unkown switch in the major signaling pathway of G-protein coulpled receptors from Gs to Gq, and overall enhanced Gq signaling. That the phenomeno was also observed in their isolated islets, and that the genetic manipulation of the mice was only in the pancreatic beta-cells, we reasoned that peharps knockout of Kcnj11 in beta cells could result to a general change in the expression of genes related to G-protein coupled receptor signaling. Since New-Generation Sequencing (NGS) has revolutionized cellular based pathway analysis, we extracted total RNA from WT and bKO islets, performed NGS and compared global changes in the expression of genes between WT and bKO islets.