Gluconeogenetic Genes Research Articles

FX5 as a non-steroidal GR antagonist improved glucose homeostasis in type 2 diabetic mice via GR/HNF4α/miR-122-5p pathway

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by glucose metabolic disorders, and gluconeogenesis inhibiting is a promisingly therapeutic strategy for T2DM. Glucocorticoid receptor (GR) is tightly implicated in the regulation of gluconeogenesis, although the underlying mechanism remains obscure. Here, we discovered that small molecule, 5-chloro-N-[4-chloro-3-(trifluoromethyl)phenyl]thiophene-2-sulfonamide (FX5) as a new non-steroidal GR antagonist efficiently ameliorated glucose homeostasis in db/db and HFD/STZ-induced T2DM mice. The mechanism underlying the suppression of FX5 against gluconeogenesis was highly investigated. FX5 suppressed gluconeogenetic genes G6Pase and PEPCK in mouse primary hepatocytes and liver tissues of T2DM mice. Results of mammalian one-hybrid and transactivation as well as nuclear translocation assays totally evaluated the antagonistic features of FX5 against GR. Moreover, siRNA and overexpression related assays verified that FX5 alleviated gluconeogenesis either directly by antagonizing GR or indirectly through GR/HNF4α/miR122-5p signaling pathway. Our work has presented a new mode for GR antagonist in the regulation of gluconeogenesis, which is expected to highlight the potential of FX5 in the treatment of T2DM.

Berberine Attenuates Hyperglycemia by Inhibiting the Hepatic Glucagon Pathway in Diabetic Mice.

Dysregulated glucagon drives hyperfunction in hepatic glucose output, which is the main cause of persistent hyperglycemia in type 2 diabetes. Berberine (Zhang et al., 2010) has been used as a hypoglycemic agent, yet the mechanism by which BBR inhibits hepatic gluconeogenesis remains incompletely understood. In this study, we treated diabetic mice with BBR, tested blood glucose levels, and then performed insulin, glucose lactate, and glucagon tolerance tests. Intracellular cAMP levels in hepatocytes were determined by ELISA, hepatic gluconeogenetic genes were assayed by RT-qPCR, and the phosphorylation of CREB, which is the transcriptional factor controlling the expression of gluconeogenetic genes, was detected by western blot. BBR reduced blood glucose levels, improved insulin and glucose tolerance, and suppressed lactate- and glucagon-induced hepatic gluconeogenesis in ob/ob and STZ-induced diabetic mice. Importantly, BBR blunted glucagon-induced glucose production and gluconeogenic gene expression in hepatocytes, presumably through reducing cAMP, which resulted in the phosphorylation of CREB. By utilizing a cAMP analogue, adenylate cyclase (AC), to activate cAMP synthetase, and an inhibitor of the cAMP degradative enzyme, phosphodiesterase (PDE), we revealed that BBR accelerates intracellular cAMP degradation. BBR reduces the intracellular cAMP level by activating PDE, thus blocking activation of downstream CREB and eventually downregulating gluconeogenic genes to restrain hepatic glucose production.

The tacrolimus-induced glucose homeostasis imbalance in terms of the liver: From bench to bedside.

Tacrolimus (TAC), the mainstay of maintenance immunosuppressive agents, plays a crucial role in new-onset diabetes after transplant (NODAT). Previous studies investigating the diabetogenic effects of TAC have focused on the β cells of islets. In this study, we found that TAC contributed to NODAT through directly affecting hepatic metabolic homeostasis. In mice, TAC-induced hypoglycemia rather than hyperglycemia during starvation via suppressing gluconeogenetic genes, suggesting the limitation of fasting blood glucose in the diagnosis of NODAT. In addition, TAC caused hepatic insulin resistance and triglyceride accumulation through insulin receptor substrate (IRS)2/AKT and sterol regulatory element binding protein (SREBP1) signaling, respectively. Furthermore, we found a pivotal role of CREB-regulated transcription coactivator 2 (CRTC2) in TAC-induced metabolic disorders. The restoration of hepatic CRTC2 alleviated the metabolic disorders through its downstream molecules (eg, PCK1, IRS2, and SREBP1). Consistent with the findings from bench, low CRTC2 expression in graft hepatocytes was an independent risk factor for NODAT (odds ratio=2.692, P=.023, n=135). Integrating grafts' CRTC2 score into the clinical model could significantly increase the predictive capacity (areas under the receiver operating characteristic curve: 0.71 vs 0.79, P=.048). Taken together, in addition to its impact on pancreatic cells, TAC induces "hematogenous diabetes" via CRTC2 signaling. Liver-targeted management may be of help to prevent or heal TAC-associated diabetes.

Impact of Proinflammatory Cytokines on the Virulence of Uropathogenic Escherichia coli.

The effect of a urinary tract infection on the host is a well-studied research field. However, how the host immune response affects uropathogenic Escherichia coli (CFT073) virulence is less studied. The aim of the present study was to investigate the impact of proinflammatory cytokine exposure on the virulence of uropathogenic Escherichia coli. We found that all tested proinflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8 and IFN-γ) induced an increased CFT073 growth. We also found that biofilm formation and hemolytic activity was reduced in the presence of all proinflammatory cytokines. However, a reduction in siderophore release was only observed in the presence of IL-1β, IL-6 and IL-8. Real time-qPCR showed that all proinflammatory cytokines except TNF-α significantly increased genes associated with the iron acquisition system in CFT073. We also found that the proinflammatory cytokines induced significant changes in type-1 fimbriae, P-fimbriae and gluconeogenetic genes. Furthermore, we also showed, using a Caenorhabditis elegans (C. elegans) killing assay that all cytokines decreased the survival of C. elegans worms significantly. Taken together, our findings show that proinflammatory cytokines have the ability to alter the virulence traits of UPEC.

Candida albicans Dispersed Cells Are Developmentally Distinct from Biofilm and Planktonic Cells.

ABSTRACTCandida albicans surface-attached biofilms such as those formed on intravenous catheters with direct access to the bloodstream often serve as a nidus for continuous release of cells capable of initiating new infectious foci. We previously reported that cells dispersed from a biofilm are yeast cells that originate from the top-most hyphal layers of the biofilm. Compared to their planktonic counterparts, these biofilm dispersal yeast cells displayed enhanced virulence-associated characteristics and drug resistance. However, little is known about their molecular properties. To address that issue, in this study we aimed to define the molecular characteristics of these biofilm dispersal cells. We found that the inducer of dispersal, PES1, genetically interacts with the repressor of filamentation, NRG1, in a manner consistent with the definition of dispersed cells as yeast cells. Further, using a flow biofilm model, we performed comprehensive comparative RNA sequencing on freshly dispersed cells in order to identify unique transcriptomic characteristics. Gene expression analysis demonstrated that dispersed cells largely inherit a biofilm-like mRNA profile. Strikingly, however, dispersed cells seemed transcriptionally reprogrammed to acquire nutrients such as zinc and amino acids and to metabolize alternative carbon sources, while their biofilm-associated parent cells did not induce the same high-affinity transporters or express gluconeogenetic genes, despite exposure to the same nutritional signals. Collectively, the findings from this study characterize cell dispersal as an intrinsic step of biofilm development which generates propagules more adept at colonizing distant host sites. This developmental step anticipates the need for virulence-associated gene expression before the cells experience the associated external signals.

Effects of Multi-Electrode Renal Denervation on Insulin Sensitivity and Glucose Metabolism in a Canine Model of Type 2 Diabetes Mellitus

PurposeTo evaluate the effects of multi-electrode catheter-based renal denervation (RDN) on insulin sensitivity and glucose metabolism in a type 2 diabetes mellitus (T2DM) canine model. Materials and MethodsThirty-three dogs were divided equally into 3 groups: bilateral renal denervation (BRDN) group, left renal denervation (LRDN) group, and sham operation (SHAM) group. Body weight and blood biochemistry were measured at baseline, 20 weeks, and 32 weeks, and renal angiography and computerized tomographic (CT) angiography were determined before the procedure and 1 month, 2 months, and 3 months after the procedure. Western blot was used to identify the activities of gluconeogenic enzymes and insulin-signaling proteins. ResultsFasting plasma glucose (9.64 ± 1.57 mmol/L vs 5.12 ± 1.08 mmol/L; P < .0001), fasting insulin (16.19 ± 1.43 mIU/mL vs 5.07 ± 1.13 mIU/mL; P < .0001), and homeostasis-model assessment of insulin resistance (HOMA-IR; 6.95 ± 1.33 vs 1.15 ± 0.33; P < .0001) in the BRDN group had significantly decreased at the 3-month follow-up compared with the SHAM group. Western blot analyses showed that RDN suppressed the gluconeogenetic genes, modulated insulin action, and activated insulin receptors–AKT signaling cascade in the liver. CT angiography and histopathologic analyses did not show any dissection, aneurysm, thrombus, or rupture in any of the renal arteries. ConclusionsThese findings identified that multi-electrode catheter-based RDN could effectively decrease gluconeogenesis and glycogenolysis, resulting in improvements in insulin sensitivity and glucose metabolism in a T2DM canine model.

3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145) ameliorated dexamethasone induced hepatic gluconeogenesis through activation of Akt/FoxO1 pathway

3-(2-amino-ethyl)-5-[3-(4-butoxyl-phenyl)-propylidene]-thiazolidine-2,4-dione (K145) is identified as a selective SphK2 inhibitor. It was previously reported as an anti-tumor agent, in this study we demonstrated that K145 was able to regulate hepatic gluconeogenesis and improve glucose intolerance in mice. C57BL/6 mice treated with dexamethasone injection were used as experimental animals, which exhibited impaired glucose tolerance and increased gluconeogenetic enzymes. After K145 treatment, we found that the impairment of glucose tolerance and gluconeogenetic genes mRNA expression were improved. Besides, both in vivo and in votro studies suggested that K145 stimulated insulin dependent Akt phosphorylation and subsequently activates FoxO1 phosphorylation therefore inhibited gluconeogenetic genes expression including PEPCK and G6pase. Our study figures out a potential extent increase the value of developing K145 as therapeutic candidate for diabetes.

Dissociation of Intestinal and Hepatic Activities of FXR and LXRα Supports Metabolic Effects of Terminal Ileum Interposition in Rodents

The farnesoid X receptor (FXR) and the liver x receptors (LXRs) are bile acid–activated receptors that are highly expressed in the enterohepatic tissues. The mechanisms that support the beneficial effects of bariatric surgery are only partially defined. We have investigated the effects of ileal interposition (IT), a surgical relocation of the distal ileum into the proximal jejunum, on FXR and LXRs in rats. Seven months after surgery, blood concentrations of total bile acids, taurocholic acid, an FXR ligand, and taurohyocholic acid, an LXRα ligand, were significantly increased by IT (P < 0.05). In contrast, liver and intestinal concentrations of conjugated and nonconjugated bile acids were decreased (P < 0.05). These changes were associated with a robust induction of FXR and FXR-regulated genes in the intestine, including Fgf15, a negative regulator of bile acid synthesis. IT repressed the liver expression of glucose-6-phosphatase (G6PC) and phosphoenolpyruvate carboxykinase (Pepck), two gluconeogenetic genes, along with the expression of LXRα and its target genes sterol regulatory element-binding protein (Srebp) 1c and fatty acid synthase (Fas) in the liver. Treating IT rats with chenodeoxycholic acid ameliorated insulin signaling in the liver. Whether confirmed in human settings, these results support the association of pharmacological therapies with bariatric surgeries to exploit the selective activation of intestinal nuclear receptors.

Maf1, repressor of tRNA transcription, is involved in the control of gluconeogenetic genes in Saccharomyces cerevisiae

Maf1 is a negative regulator of RNA polymerase III (Pol III) in yeast. Maf1-depleted cells manifest elevated tRNA transcription and inability to grow on non-fermentable carbon source, such as glycerol. Using genomic microarray approach, we examined the effect of Maf1 deletion on expression of Pol II-transcribed genes in yeast grown in medium containing glycerol. We found that transcription of FBP1 and PCK1, two major genes controlling gluconeogenesis, was decreased in maf1Δ cells.FBP1 is located on chromosome XII in close proximity to a tRNA-Lys gene. Accordingly we hypothesized that decreased FBP1 mRNA level could be due to the effect of Maf1 on tgm silencing (tRNA gene mediated silencing). Two approaches were used to verify this hypothesis. First, we inactivated tRNA-Lys gene on chromosome XII by inserting a deletion cassette in a control wild type strain and in maf1Δ mutant. Second, we introduced a point mutation in the promoter of the tRNA-Lys gene cloned with the adjacent FBP1 in a plasmid and expressed in fbp1Δ or fbp1Δ maf1Δ cells. The levels of FBP1 mRNA were determined by RT-qPCR in each strain. Although the inactivation of the chromosomal tRNA-Lys gene increased expression of the neighboring FBP1, the mutation preventing transcription of the plasmid-born tRNA-Lys gene had no significant effect on FBP1 transcription. Taken together, those results do not support the concept of tgm silencing of FBP1. Other possible mechanisms are discussed.

Interaction of Constitutive Photomorphogenesis 1 Protein with Protein-Tyrosine Phosphatase 1B Suppresses Protein-Tyrosine Phosphatase 1B Activity and Enhances Insulin Signaling

Recent studies reveal that COP1 suppresses the expression of gluconeogenetic genes and prohibits hepatic glucose production. To get more insight into COP1 in hepatic cells, we examined the impact of COP1 on insulin-responsive genes and insulin signaling. We found that COP1 increased the responsiveness of insulin-modulated genes to insulin in that it promoted the expression of insulin-induced genes and inhibited that of insulin-suppressed genes and that COP1 enhanced insulin signaling as it promoted phosphorylation of Akt and ERK as well as tyrosine phosphorylation of IRβ induced by insulin. To delineate the mechanism under which COP1 modulates insulin signaling, we examined the possibility that COP1 modulates the activity of PTP1B, the major insulin receptor tyrosine phosphatase. The results indicated that COP1 physically interacted with PTP1B and suppressed PTP1B phosphatase activity as well as the association of PTP1B with IRβ. We suggest that COP1 is a positive regulator of hepatic insulin signaling.

TrmB an archael transcriptional regulator

In Pyrococcus furiosus two binding protein–dependent, substrate–specific ABC transporters could be identified, one of it being a trehalose/maltose (TM)–transporter, which is responsible for the uptake of trehalose and maltose. By binding to the respective operator sites TrmB prevents the further binding of transcription factors and subsequent RNA polymerase recruitment, which leads to an inhibition of transcription. With the aid of in vitro transcription assays using purified components of P. furiosus it could be shown that TrmB–mediated inhibition of transcription on both promoters is released by specific carbohydrates with maltose and trehalose being inducers for the TM operon, and maltodextrins as well as sucrose releasing inhibition on the MD promoter.TrmBL1 is homologue to TrmB and is involved in the regulation of genes encoding glycolytic and gluconeogenetic enzymes, respectively, where it recognizes a conserved sequence motif called TGM. It inhibits transcription of glycolytic genes with maltose, maltotriose and fructose as inducers (3). On the other hand TrmBL1 activates the expression of gluconeogenetic genes as well. Since the TGM is not present in the promoter region of the TrmBL1 gene, the TGM is not essential for TrmBL1 target recognition (3).Both TrmB and TrmBL1 share the unique property of recognizing different DNA sequences on different promoters and showing distinctive, promoter–dependent sugar specificity.In vitro transcription assays, EMSA and DNaseI footprinting experiments proved that TrmB and TrmBL1 have at least two different HTH motifs and recognize their respective target promoters with different helices within their N–terminal DNA binding domains.

Social Isolation Affects the Development of Obesity and Type 2 Diabetes in Mice

Social isolation is associated with increased risks of mortality and morbidity. In this study, we show that chronic individual housing accelerated body weight gain and adiposity in KK mice but not C57BL6J mice, and fully developed diabetes in KKA(y) mice. Individually housed KK and KKA(y) mice increased body weight gain over the initial 2 wk without increased daily average food consumption compared with group-housed animals. The individually housed KK and KKA(y) mice then gradually increased food consumption for the next 1 wk. The chronic social isolation-induced obesity (SIO) was associated with hyperleptinemia and lower plasma corticosterone and active ghrelin levels but not hyperinsulinemia. Elevated plasma leptin in the SIO suppressed expression of 5-HT2C receptor in white adipose tissue. The SIO was also associated with decreased expression of beta3-adrenergic receptors in white adipose tissue and hypothalamic leptin receptor, which might be secondary to the enhanced adiposity. Interestingly, social isolation acutely reduced food consumption and body weight gain compared with group-housed obese db/db mice with leptin receptor deficiency. Social isolation-induced hyperglycemia in KKA(y) mice was associated with increased expression of hepatic gluconeogenetic genes independent of insulin. These findings suggest that social isolation promotes obesity due to primary decreased energy expenditure and secondary increased food consumption, which are independent of the disturbed leptin signaling, in KK mice, and develops into insulin-independent diabetes associated with increased expression of hepatic gluconeogenetic genes in KKA(y) mice. Thus, social isolation can be included in the environmental factors that contribute to the development of obesity and type 2 diabetes.

Xanthohumol, the chalcone from beer hops ( Humulus lupulus L.), is the ligand for farnesoid X receptor and ameliorates lipid and glucose metabolism in KK- Ay mice

We have examined the modulating action of xanthohumol (XN) on the farnesoid X receptor (FXR) in vitro and in vivo. In the transient transfection assay, XN dose-dependently increased the BSEP promoter-driven luciferase activity. XN-fed KK- A y mice exhibited lowered levels of plasma glucose, plasma, and hepatic triglyceride. They also showed decreased amounts of water intake, lowered weights of white adipose tissue, and exhibited increased levels of plasma adiponectin, indicating that XN attenuated diabetes in KK- A y mice. The hepatic gene expression of XN-fed mice showed lowered levels of SREBP-1c including its targets involved in fatty acid synthesis and lowered levels of gluconeogenetic genes. However, the expression of cholesterol 7-hydroxylase (CYP7A1) was significantly induced in the liver of XN-fed mice. From the present results, it is suggested that XN acts on FXR through a selective bile acid receptor modulator (SBARM) like guggulsterone or polyunsaturated fatty acids, which have previously been reported as SBARMs.

Nitrogen regulation in Sinorhizobium meliloti probed with whole genome arrays

Using whole genome arrays, we systematically investigated nitrogen regulation in the plant symbiotic bacterium Sinorhizobium meliloti. The use of glutamate instead of ammonium as a nitrogen source induced nitrogen catabolic genes independently of the carbon source, including two glutamine synthetase genes, various aminoacid transporters and the glnKamtB operon. These responses depended on both the ntrC and glnB nitrogen regulators. Glutamate repressible genes included glutamate synthase and a H +-translocating pyrophosphate synthase. The smc01041- ntrBC operon was negatively autoregulated in a glnB-dependent fashion, indicating an involvement of phosphorylated NtrC. In addition to the nitrogen response, glutamate remodelled expression of carbon metabolism by inhibiting expression of the Entner–Doudoroff and pentose phosphate pathways, and by stimulating gluconeogenetic genes independently of ntrC.