Let7b-5p inhibits insulin secretion and decreases pancreatic ß-cell mass in mice.

MicroRNAs are crucial regulators for the development, mass and function of pancreatic ß-cells. MiRNA dysregulation is associated with ß-cell dysfunction and development of diabetes. The members of let7 family are important players in regulating cellular growth and metabolism. In this study we investigated the functional role of let7b-5p in the mouse pancreatic ß-cells. We generated pancreatic ß-cell-specific let7b-5p transgenic mouse model and analyzed the glucose metabolic phenotype, ß-cells mass and insulin secretion in vivo. Luciferase reporter assay, immunofluorescence staining and western blot were carried out to study the target genes of let7b-5p in ß-cells. Let7b-5p overexpression impaired the insulin production and secretion of ß-cells and resulted impaired glucose tolerance in mice. The overexpressed let7b-5p inhibited pancreatic ß-cell proliferation and decreased the expression of cyclin D1 and cyclin D2. Our findings demonstrated that let7b-5p was critical in regulating the proliferation and insulin secretion of pancreatic ß-cells.

Altered Inflammatory Pathway but Unaffected Liver Fibrosis in Mouse Models of Nonalcoholic Steatohepatitis Involving Interleukin-1 Receptor-Associated Kinase 1 Knockout.

BACKGROUND Interleukin-1 receptor-associated kinases (IRAKs) are crucial mediators in the signaling pathways of Toll-like receptors (TLRs)/IL1Rs. Targeting the IRAK4/IRAK1/TRAF6 axis and its associated pathway has therapeutic benefits in liver fibrosis. However, the function of IRAK1 itself in the development of liver fibrosis remains unknown. MATERIAL AND METHODS Irak1 global knockout (KO) mice were generated to study the functional role of Irak1 in liver fibrosis. Male Irak1 knockout and control mice were challenged with chronic carbon tetrachloride (CCl4) or fed a methionine- and choline-deficient diet (MCDD) to generate models of nonalcoholic steatohepatitis (NASH). Liver inflammation and collagen deposition were assessed by histological examination, quantitative real-time PCR (qRT-PCR), and western blotting of hepatic tissues. RESULTS The mRNA expression of the downstream inflammatory gene Il1b was significantly lower in Irak1-KO than in control mice. Irak1 ablation had little effect on inflammatory cell infiltration into livers of mice with NASH. Collagen deposition and the expression of genes related to fibrogenesis were similar in the livers of Irak1-KO and control mice exposed to CCl4 and MCDD. The loss of Irak1 did not affect lipid or glucose metabolism in these experimental models of steatohepatitis. CONCLUSIONS Irak1 knockout reduced the expression of inflammatory genes but had no effect on hepatic fibrogenesis. The Irak1-related pathway may regulate liver fibrosis via other pathways or be compensated for by other factors.

YY1 deficiency in ß-cells leads to mitochondrial dysfunction and diabetes in mice.

BACKGROUND: The transcription factor YY1 is an important regulator for metabolic homeostasis. Activating mutations in YY1 lead to tumorigenesis of pancreatic ß-cells, however, the physiological functions of YY1 in ß-cells are still unknown. Here, we investigated the effects of YY1 ablation on insulin secretion and glucose metabolism. METHODS: We established two models of ß-cell-specific YY1 knockout mice. The glucose metabolic phenotypes, ß-cell mass and ß-cell functions were analyzed in the mouse models. Transmission electron microscopy was used to detect the ultrastructure of ß-cells. The flow cytometry analysis, measurement of OCR and ROS were performed to investigate the mitochondrial function. Histological analysis, quantitative PCR and ChIP were performed to analyze the target genes of YY1 in ß-cells. RESULTS: Our results showed that loss of YY1 resulted in reduction of insulin production, ß-cell mass and glucose tolerance in mice. Ablation of YY1 led to defective ATP production and mitochondrial ROS accumulation in pancreatic ß-cells. The inactivation of YY1 impaired the activity of mitochondrial oxidative phosphorylation, induced mitochondrial dysfunction and diabetes in mouse models. CONCLUSION: Our findings demonstrate that the transcriptional activity of YY1 is essential for the maintenance of mitochondrial functions and insulin secretion in ß-cells.

MiR-221/222 Inhibit Insulin Production of Pancreatic ß-Cells in Mice.

Microribonucleic acids (miRNAs) are essential for the regulation of development, proliferation, and functions of pancreatic ß-cells. The conserved miR-221/222 cluster is an important regulator in multiple cellular processes. Here we investigated the functional role of miR-221/222 in the regulation of ß-cell proliferation and functions in transgenic mouse models. We generated 2 pancreatic ß-cell-specific-miR-221/222 transgenic mouse models on a C57BL/6J background. The glucose metabolic phenotypes, ß-cell mass, and ß-cell functions were analyzed in the mouse models. Adenovirus-mediated overexpression of miR-221/222 was performed on ß-cells and mouse insulinoma 6 (MIN6) cells to explore the effect and mechanisms of miR-221/222 on ß-cell proliferation and functions. Luciferase reporter assay, histological analysis, and quantitative polymerase chain reaction (PCR) were carried out to study the direct target genes of miR-221/222 in ß-cells. The expression of miR-221/222 was significantly upregulated in ß-cells from the high-fat diet (HFD)-fed mice and db/db mice. Overexpression of miR-221/222 impaired the insulin production and secretion of ß-cells and resulted in glucose intolerance in vivo. The ß-cell mass and proliferation were increased by miR-221/222 expression via Cdkn1b and Cdkn1c. MiR-221/222 repressed insulin transcription activity through targeting Nfatc3 and lead to reduction of insulin in ß-cells. Our findings demonstrate that miR-221/222 are important regulators of ß-cell proliferation and insulin production. The expression of miR-221/222 in ß-cells could regulate glucose metabolism in physiological and pathological processes.

Targeting hepatic miR-221/222 for therapeutic intervention of nonalcoholic steatohepatitis in mice.

BACKGROUND: Effective targeting therapies for common chronic liver disease nonalcoholic steatohepatitis (NASH) are in urgent need. MicroRNA-targeted therapeutics would be potentially an effective treatment strategy of hepatic diseases. Here we investigated the functional role of miR-221/222 and the therapeutic effects of antimiRs-221/222 in NASH mouse models. METHODS: We generated the miR-221/222flox/flox mice on a C57BL/6 J background and the hepatic miR-221/222 knockout (miR-221/222-LKO) mice. The mice were challenged with the methionine and choline deficient diet (MCDD) or chronic carbon tetrachloride (CCl4) treatment to generate experimental steatohepatitis models. Adenovirus-mediated re-expression of miR-221/222 was performed on the MCDD-fed miR-221/222-LKO mice. The MCDD and control diet-fed mice were treated with locked nucleic acid (LNA)-based antimiRs of miR-221/222 to evaluate the therapeutic effects. Histological analysis, RNA-seq, quantitative PCR and Western blot of liver tissues were carried out to study the hepatic lipid accumulation, inflammation and collagen deposition in mouse models. FINDINGS: Hepatic deletion of miR-221/222 resulted in significant reduction of liver fibrosis, lipid deposition and inflammatory infiltration in the MCDD-fed and CCl4-treated mouse models. The hepatic steatosis and fibrosis were dramatically aggravated by miR-221/222 re-expression in MCDD-fed miR-221/222-LKO mice. AntimiRs of miR-221/222 could effectively reduce the MCDD-mediated hepatic steatosis and fibrosis. Systematically mechanistic study revealed that hepatic miR-221/222 controlled the expression of target gene Timp3 and promoted the progression of NASH. INTERPRETATION: Our findings demonstrate that miR-221/222 are crucial for the regulation of lipid metabolism, inflammation and fibrosis in the liver. LNA-antimiRs targeted miR-221/222 could reduce steatohepatitis with prominent antifibrotic effect in NASH mice. FUND: This work is supported by the Natural Science Foundation of China (81530020, 81390352 to Dr. Ning and 81522032 to Dr. Cao and 81670793 to Dr. Jiang); National Key Research and Development Program (No. 2016YFC0905001 and 2017YFC0909703 to Dr. Cao); the Shanghai Rising-Star Program (15QA1402900 to Dr. Cao); Shanghai Municipal Education Commission-Gaofeng Clinical Medicine Grant (20171905 to Dr. Jiang).

Resistance to high-fat diet-induced obesity in male heterozygous Pprc1 knockout mice.

Peroxisome proliferator-activated receptor gamma, co-activator-related 1 (Pprc1) is the third member of the Pgc1 family. Other than the well-characterized Pgc1a and Pgc1b that act as regulators of mitochondrial biogenesis and oxidative metabolism, the function of Pprc1 in vivo is rarely reported, due to embryonic lethality of whole-body Pprc1 knockout mice. To investigate the biological and physiological function of Pprc1 in metabolic processes, male Pprc1(+/-) mice fed with a high fat diet (HFD) showed resistance to diet-induced obesity with a decrease of adipose tissue in Pprc1(+/-) mice, which was a result of elevated energy expenditure. In skeletal muscle of Pprc1(+/-) mice, Pprc1 level showed haplo-insufficiency with down-regulation of Pgc1b and Pgc1a, whereas in adipose tissue, Pprc1 expression remained normal, with significant compensatory increase of other Pgc1 family members to induce an up-regulation of respiratory chain genes. Taken together, as the first report on the metabolic roles of Pprc1 in vivo, these results indicated an elevated basal metabolic rate and lipid metabolic alteration of male Pprc1(+/-) mice on HFD, suggesting the significant role of Pprc1 in controlling mitochondrial gene expression and energy metabolic processes, synergistically with Pgc1a and Pgc1b.

miR-144/451 Promote Cell Proliferation via Targeting PTEN/AKT Pathway in Insulinomas.

Insulinoma is the main type of functional pancreatic neuroendocrine tumors. The functional microRNAs (miRNAs) regulating tumor growth and progression in insulinomas are still unknown. We conducted the miRNA expression profile analysis using miRNA quantitative RT-PCR array and identified 114 differentially expressed miRNAs in human insulinomas compared with normal pancreatic islets. Forty-one differentially expressed miRNAs belonged to 7 miRNA families, and 28 miRNAs in 3 of the families localized in the epigenetically regulated imprinted chromosome 14q32 region. We validated the most significant differentially expressed miRNA cluster miR-144/451 in another 8 human normal islet samples and 25 insulinomas. Our data showed that the overexpression of miR-144/451 in mouse pancreatic ß-cells promoted cell proliferation by targeting the ß-cell regulator phosphatase and tensin homolog deleted on chromosome ten/v-akt murine thymoma viral oncogene homolog pathway and cyclin-dependent kinase inhibitor 2D. Our findings highlight the importance of functional miRNAs in insulinomas.

Generation and Characterization of Transgenic Mice Expressing Mouse Ins1 Promoter for Pancreatic ß-Cell-Specific Gene Overexpression and Knockout.

The technologies for pancreatic ß-cell-specific gene overexpression or knockout are fundamental for investigations of functional genes in vivo. Here we generated the Ins1-Cre-Dsred and Ins1-rtTA mouse models, which expressed the Cre recombinase or reverse tetracycline regulatable transactivator (rtTA) without hGH minigene under the control of mouse Ins1 promoter. Our data showed that the Cre-mediated recombination and rtTA-mediated activation could be efficiently detected at embryonic day 13.5 when these models were crossed with the reporter mice (ROSA(mT/mG) or tetO-HIST1H2BJ/GFP). The Cre and rtTA expression was restricted to ß-cells without leakage in the brain and other tissues. Moreover, both the transgenic lines showed normal glucose tolerance and insulin secretion. These results suggested that the Ins1-Cre-Dsred and Ins1-rtTA mice could be used to knock out or overexpress target genes in embryos and adults to facilitate ß-cell researches.

Whole exome sequencing of insulinoma reveals recurrent T372R mutations in YY1.

Functional pancreatic neuroendocrine tumours (PNETs) are mainly represented by insulinoma, which secrete insulin independent of glucose and cause hypoglycaemia. The major genetic alterations in sporadic insulinomas are still unknown. Here we identify recurrent somatic T372R mutations in YY1 by whole exome sequencing of 10 sporadic insulinomas. Further screening in 103 additional insulinomas reveals this hotspot mutation in 30% (34/113) of all tumours. T372R mutation alters the expression of YY1 target genes in insulinomas. Clinically, the T372R mutation is associated with the later onset of tumours. Genotyping of YY1, a target of mTOR inhibitors, may contribute to medical treatment of insulinomas. Our findings highlight the importance of YY1 in pancreatic ß-cells and may provide therapeutic targets for PNETs.

Peri-implantation lethality in mice lacking the PGC-1-related coactivator protein.

BACKGROUND: Members of the PPARγ coactivator-1 (PGC-1) family are central transcriptional coactivators that regulate cell metabolic processes ranging from mitochondrial biogenesis to oxidative respiration. PGC-1-related coactivator (PPRC1 or PRC), initially identified as a member of the PGC-1 family, is believed to regulate mitochondria biogenesis, respiration pathways, and cell proliferation. However, its physiological role is not clearly understood. Here, we investigate the biological functions of PPRC1 in vivo using PPRC1 deficient mice generated by gene targeting. RESULTS: Homozygous deficient PPRC1 mice failed to form egg cylinders and died after implantation but before embryonic day 6.5, whereas mice heterozygous for PPRC1 were viable, fertile and indistinguishable from their wild-type littermates. Furthermore, PPRC1 mRNA was expressed at the embryonic stage before implantation and was rapidly up-regulated during the first day of embryoid body formation. The PPRC1 mRNA was then subsequently down-regulated, although its precise function at this stage of development was unclear. CONCLUSIONS: This is the first study to suggest a nonredundant role for PPRC1 in mouse early embryonic development.

Effects of salvianolic acid B on proliferation, neurite outgrowth and differentiation of neural stem cells derived from the cerebral cortex of embryonic mice.

Salvianolic acid B is isolated from Salvia miltiorrhiza, the root of which is widely used as a traditional Chinese medicine to treat stroke. However, little is known about how salvianolic acid B influences growth characteristics of neural stem cells (NSCs). The purpose of the present study was to evaluate the effects of salvianolic acid B on proliferation, neurite outgrowth and differentiation of NSCs derived from the cerebral cortex of embryonic mice using MTT, flow cytometry, immunofluorescence and RT-PCR. It was found that 20 microg mL(-1) and 40 microg mL(-1) salvianolic acid B had similar effects on proliferation of NSCs, and a suitable concentration of salvianolic acid B increased the number of NSCs and their derivative neurospheres. The growth-promoting activity of salvianolic acid B was dependent on and associated with an accumulation in the G2/S-phase cell population. Salvianolic acid B also promoted the neurite outgrowth of NSCs and their differentiation into neurons. The mRNA for tau, GFAP and nestin were present in differentiating neurospheres induced by salvianolic acid B. However, high-level expression of tau mRNA and low-level expression of GFAP mRNA was detected in differentiated cells, in contrast to the control conditions. This collective evidence indicates that exogenous salvianolic acid B is capable of promoting proliferation of neurospheres and differentiation towards the neuronal lineage in vitro and may act in the proliferation of NSCs and may promote NSC differentiation into neuronal cells.

[Distribution of neuronal nitric oxide synthase-immunopositive neurons in rat corpus striatum and their ultrastructures].

OBJECTIVE: To observe the distribution of neuronal nitric oxide synthase (nNOS)-immunopositive neurons in rat corpus striatum and their ultrastructural features. METHODS: Brain tissue specimens were obtained from normal SD rats, in which nNOS-immunopositive neurons were visualized by ABC immunocytochemistry and observed under immunoelectron microscope with pre-embedding staining. RESULTS: Under light microscope, nNOS-immunopositive neurons appeared brown with distinct profiles of the cell body and processes. These neurons, mostly medium-sized and small cells, were located mainly in the lateral region of the corpus striatum. Only a few immunopositive neurons were detected in the medial region of the corpus striatum. Immunohistochemistry and transmission electron microscopy identified the nNOS-immunopositive neurons as interneurons possessing large nuclei with small amount of cytoplasma. The immunopositive granules were visualized as black plaques, and the larger ones distributed mainly in the cell bodies, some with monolayer membrane encapsulation. The small granules did not have the encapsulation, scattering in perinuclear regions and under the cell membrane, but not in the cell body. The immunopositive granules were also found in the axons and dendrites, but not in the vesicles of the synapses. In addition, many immunopositive terminals were found close to the blood vessels. CONCLUSIONS: nNOS-immunopositive neurons in rat corpus striatum are mainly medium-sized and small cells as is typical of the interneurons. The immunopositive granules locate in the cytoplasma, axons and dendrites, and larger granules have membrane coating while small ones do not, possibly in relation to their functions.