MAFB mediates the therapeutic effect of sleeve gastrectomy for obese diabetes mellitus by activation of FXR expression

Farnesoid X receptor (FXR) and related pathways are involved in the therapeutic effect of sleeve gastrectomy for overweight or obese patients with diabetes mellitus. This study aimed to investigate the mechanism of FXR expression regulation during the surgical treatment of obese diabetes mellitus by sleeve gastrectomy. Diabetic rats were established by combined streptozotocin and high-fat diet induction. Data collection included body weight, chemical indexes of glucose and lipid metabolism, liver function, and the expression levels of musculoaponeurotic fibrosarcoma oncogene family B (MAFB), FXR, and related genes induced by sleeve gastrectomy. Chang liver cells overexpressing MAFB gene were established to confirm the expression of related genes. The binding and activation of FXR gene by MAFB were tested by Chip and luciferase reporter gene assays. Vertical sleeve gastrectomy induced significant weight loss and decreased blood glucose and lipids in diabetic rat livers, as well as decreased lipid deposition and recovered lipid function. The expression of MAFB, FXR, and FXR-regulated genes in diabetic rat livers were also restored by sleeve gastrectomy. Overexpression of MAFB in Chang liver cells led to FXR gene expression activation and the alteration of multiple FXR-regulated genes. Chip assay showed that MAFB could directly bind with FXR promoter, and the activation of FXR expression was confirmed by luciferase reporter gene analysis. The therapeutic effect of sleeve gastrectomy for overweight or obese patients with diabetes mellitus was mediated by activation of FXR expression through the binding of MAFB transcription factor.

Lung Retinoid Metabolism and Signaling in Chronic Obstructive Pulmonary Disease.

There are a number of sites that are required for the production and/or action of all-trans retinoic acid (ATRA). In particular, interruption of different components of the chain of trafficking and metabolism has been associated with cancers arising in numerous organs of the body. Preliminary work suggests that such interruptions may be a factor in lung disorders induced by the smoke exposure. The active metabolite of retinoid, ATRA offers a therapeutic strategy to protect against functional abnormality in the lung, including chronic obstructive pulmonary disease (COPD). This review deals with the lung retinoid metabolism and mediators of retinoid trafficking and signaling with special emphasis on their roles in health and disease.

Effect of Super-Oxidized Water, Sodium Hypochlorite and EDTA on Dentin Microhardness

The present study aimed to evaluate the influence of the following irrigating solutions on the microhardness of root canal dentin: 2% sodium hypochlorite (2NaOCl), 5% sodium hypochlorite (5NaOCl), super-oxidized water (400 ppm Sterilox - Sx) and 17% EDTA (E). Eighty roots from bovine incisors were randomly divided into 8 groups (n=10): 2NaOCl, 5NaOCl, Sx, and 2NaOCl + E, 5NaOCl + E, Sx + E (associated with E as final irrigant for 5 min), E solely and distilled water (dH2O) as the negative control. Root canal preparation was performed by hand instruments, using one of the irrigation protocols for 30 min. Then, 5 mm of the cervical root third were cut out from each sample and subjected to the Vickers microhardness test, at two points, one at approximately 500-1000 µm from the root canal lumen (distance 1), and the other at approximately 500-1000 µm from the external root surface (distance 2). Data were analyzed by Wilcoxon and Kruskal-Wallis tests at 5% significance level. Microhardness values at distance 1 were significantly lower than those at distance 2 for all groups, except 5NaOCl and 5NaOCl + E groups (p>0.05). EDTA showed the lowest microhardness values. However, no statistically significant difference was detected among groups at distance 1 and EDTA was significantly different only from Sx at distance 2. In conclusion, all tested solutions showed lower microhardness at the most superficial root canal dentin layer compared to the one found near the external root surface, except 5NaOCl and 5NaOCl + E; EDTA promoted lower microhardness values in comparison to Sterilox at this site.

O presente estudo teve como objetivo avaliar a influência das seguintes soluções irrigadoras na microdureza da dentina do canal radicular: hipoclorito de sódio a 2% (NaOCl2), hipoclorito de sódio a 5% (NaOCl5), água superoxidada (Sterilox(r) 400 ppm - Sx) e EDTA a 17% (E). Oitenta raízes de incisivos bovinos foram divididas aleatoriamente em 8 grupos (n=10): NaOCl2, NaOCl5, Sx e NaOCl2 + E, NaOCl5 + E, Sx + E (associados ao E como irrigante final por 5 min), E isolado e água destilada (H2Od), como controle negativo. O preparo dos canais radiculares foi realizado com instrumentos manuais, usando um dos protocolos de irrigação por 30 min. A seguir, 5 mm do terço cervical de cada amostra foram cortados perpendicularmente e submetidos ao teste de microdureza de Vickers, em dois pontos, um aproximadamente 500-1000 µm da luz do canal radicular (distância 1), e o outro aproximadamente 500-1000 µm da superfície externa da raiz (distância 2). Os dados foram analisados pelos testes de Wilcoxon e Kruskal-Wallis com um nível de significância de 5%. Os valores de microdureza na distância 1 foram significativamente menores do que na distância 2 para todos os grupos, exceto NaOCl5 e NaOCl5 +E (p>0,05). O EDTA mostrou os menores valores de microdureza. No entanto, não foi detectada diferença estatisticamente significativa entre os grupos na distância 1 e o EDTA foi significativamente diferente apenas do Sx na distância 2. Pode-se concluir que todas as soluções testadas mostraram menor microdureza na camada de dentina mais superficial do canal radicular em comparação aos valores encontrados próximo à superfície radicular externa, exceto NaOCl5 e NaOCl5 + E; o EDTA promoveu menor microdureza em comparação ao Sterilox(r) neste ponto.

The role of gut-liver axis in the pathogenesis of liver cirrhosis and portal hypertension

Because of the anatomical position and its unique vascular system, the liver is susceptible to the exposure to the microbial products from the gut. Although large amount of microbes colonize in the gut, translocation of the microbes or microbial products into the liver and systemic circulation is prevented by gut epithelial barrier function and cleansing and detoxifying functions of the liver in healthy subjects. However, when the intestinal barrier function is disrupted, large amount of bacterial products can enter into the liver and systemic circulation and induce inflammation through their receptors. Nowadays, there have been various reports suggesting the role of gut flora and bacterial translocation in the pathogenesis of chronic liver disease and portal hypertension. This review summarizes the current knowledge about bacterial translocation and its contribution to the pathogenesis of chronic liver diseases and portal hypertension.

Inhibition of cytohesin-1 by siRNA leads to reduced IGFR signaling in prostate cancer

To explore how cytohesin-1 (CYTH-1) small interfering RNA (siRNA) influences the insulin-like growth factor receptor (IGFR)-associated signal transduction in prostate cancer, we transfected human prostate cancer PC-3 cell lines with liposome-encapsulatedCYTH-1 siRNA in serum-free medium and exposed the cells to 100 nM IGF-1. The mRNA and protein levels of the signal molecules involved in the IGFR signaling pathways were determined by real-time PCR and detected by Western blotting. The relative mRNA levels of CYTH-1, c-Myc, cyclinD1 and IGF-1R (CYTH-1 siRNA group vs scrambled siRNA group) were 0.26 vs 0.97, 0.34 vs 1.06, 0.10 vs 0.95, and 0.27 vs 0.41 (P < 0.05 for all), respectively. The relative protein levels of CYTH-1, pIGF-1R, pIRS1, pAkt1, pErk1, c-Myc, and cyclinD1 (CYTH-1 siRNA group vsscrambled siRNA group) were 0.10 vs 1.00 (30 min), 0.10 vs 0.98 (30 min), 0.04 vs 0.50 (30 min), 0.10 vs 1.00 (30 min), 0.10 vs 1.00 (30 min), 0.13 vs 0.85 (5 h), and 0.08 vs 0.80 (7 h), respectively. The tyrosine kinase activity of IGF-1R was associated with CYTH-1. The proliferative activity of PC-3 cells transfected with CYTH-1 siRNA was significantly lower than that of cells transfected with scrambled siRNA at 48 h (40.5 vs87.6 percent, P < 0.05) and at 72 h (34.5 vs 93.5 percent, P < 0.05). In conclusion, the interference of siRNA with cytohesin-1 leads to reduced IGFR signaling in prostate cancer; therefore, CYTH-1 might serve as a new molecular target for the treatment of prostate cancer.

Función de los ácidos biliares en el control del metabolismo de la glucosa / Role of bile acids on glucose metabolism control

Insulin resistance is the basis of several common diseases, such as type 2 diabetes, affecting millions people worldwide and satisfactory treatments are limited. Therefore, it is important to understand the molecular mechanisms underlying this condition and to find new and more effective therapies. Bile acids may actively participate in the control of metabolism. They derive from cholesterol, and function as natural ligands of nuclear and membrane receptors, regulating gene expression and controlling their own metabolism and that of glucose, including insulin response. Moreover, bile acids have been related to endoplasmic reticulum stress, a cellular response tightly associated to insulin resistance. These features give bile acids pharmacological properties with potential therapeutic use. Herein, we discuss the physiological role of bile acids on glucose metabolism, particularly on the regulation of the insulin response.

Nuclear receptor regulation of stemness and stem cell differentiation

Stem cells include a diverse number of toti-, pluri-, and multi-potent cells that play important roles in cellular genesis and differentiation, tissue development, and organogenesis. Genetic regulation involving various transcription factors results in the self-renewal and differentiation properties of stem cells. The nuclear receptor (NR) superfamily is composed of 48 ligand-activated transcription factors involved in diverse physiological functions such as metabolism, development, and reproduction. Increasing evidence shows that certain NRs function in regulating stemness or differentiation of embryonic stem (ES) cells and tissue-specific adult stem cells. Here, we review the role of the NR superfamily in various aspects of stem cell biology, including their regulation of stemness, forward- and trans-differentiation events; reprogramming of terminally differentiated cells; and interspecies differences. These studies provide insights into the therapeutic potential of the NR superfamily in stem cell therapy and in treating stem cell-associated diseases (e.g., cancer stem cell).

Role of PXR and CAR in Cholestasis / 대한간학회지

Cholestatic liver diseases are characterized by impairments of bile flows and accumulations of biliary constituents such as bile acids and bilirubin. The changes of phase I and II metabolism and the hepatobiliary transport system minimize cholestatic liver injury. These adaptive responses are transcriptionally regulated by several nuclear receptors. Recent studies have revealed that the pregnane X receptor (PXR) and the constitutive androstane receptor (CAR) are key nuclear receptors for regulating many of the adaptive responses noted in cholestasis. PXR and CAR coordinately regulate not only bile acid metabolism and transport, but also bilirubin clearance. PXR and CAR ligands may be useful in the future for the treatment of cholestatic liver disease.

Nuevos receptores nucleares heterodiméricos: reguladores metabólicos con impacto en fisiopatología y su proyección terapéutica en dislipidemias y diabetes mellitus / New heterodimeric nuclear receptors: key metabolic regulators with relevance in the pathophysiology and therapy of dyslipidemias and diabetes mellitus

The regulation of gene expression is crucial for the normal development and the homeostatic maintenance of body tissues. Thus, its malfunction may determine a variety of human disease conditions. A growing body of evidence has shown the overwhelming relevance of a new class of gene expression regulators: the heterodimeric nuclear receptors, a family of structurally related proteins involved in multiple biological functions. In response to activating ligands, these molecules bind to specific genomic regulatory regions where they can coordinately modify the transcriptional activity of several genes involved in the main metabolic pathways of lipids and carbohydrates in cells. These functional properties have stimulated the study of the relationships between heterodimeric nuclear receptors and various disease conditions, such as dyslipidemias and diabetes mellitus. Here we review the experimental, clinical and epidemiological evidences that support the relevance of these transcriptional regulators in the pathophysiology of the most prevalent and lethal diseases in Western countries. We also explore the potential therapeutic impact of new strategies based in the pharmacological modulation of the heterodimeric nuclear receptors.

RANK, RANKL and osteoprotegerin in arthritic bone loss

Rheumatoid arthritis is characterized by the presence of inflammatory synovitis and destruction of joint cartilage and bone. Tissue proteinases released by synovia, chondrocytes and pannus can cause cartilage destruction and cytokine-activated osteoclasts have been implicated in bone erosions. Rheumatoid arthritis synovial tissues produce a variety of cytokines and growth factors that induce monocyte differentiation to osteoclasts and their proliferation, activation and longer survival in tissues. More recently, a major role in bone erosion has been attributed to the receptor activator of nuclear factor kappa B ligand (RANKL) released by activated lymphocytes and osteoblasts. In fact, osteoclasts are markedly activated after RANKL binding to the cognate RANK expressed on the surface of these cells. RANKL expression can be upregulated by bone-resorbing factors such as glucocorticoids, vitamin D3, interleukin 1 (IL-1), IL-6, IL-11, IL-17, tumor necrosis factor-alpha, prostaglandin E subscrito 2, or parathyroid hormone-related peptide. Supporting this idea, inhibition of RANKL by osteoprotegerin, a natural soluble RANKL receptor, prevents bone loss in experimental models. Tumor growth factor-ß released from bone during active bone resorption has been suggested as one feedback mechanism for upregulating osteoprotegerin and estrogen can increase its production on osteoblasts. Modulation of these systems provides the opportunity to inhibit bone loss and deformity in chronic arthritis.

Fetal growth and development: roles of fatty acid transport proteins and nuclear transcription factors in human placenta.

In the feto-placental unit, preferential transport of maternal plasma arachidonic acid (20:4n-6) and docosahexaenoic acid (22:5n-3) across the placenta is of critical importance for fetal growth and development. More than 90 per cent of the fat deposition in the fetus occurs in the last 10 weeks of pregnancy. All of the n -3 and n -6 fatty acid structures acquired by the fetus have to cross the placenta and fetal blood are enriched in long chain polyunsaturated fatty acids (LCPUFA) relative to the maternal supply. Fatty acids cross the placental microvillous and basal membranes by simple diffusion and via the action of membrane bound (FAT, FATP and p-FABPpm) and cytoplasmic fatty acid-binding proteins (FABPs). The direction and magnitude of fatty acid flux is mainly dictated by the relative abundance of available binding sites. The existence of a fatty-acid-transport system comprising multiple binding proteins in human placenta may be essential to facilitate the preferential transport of maternal plasma fatty acids in order to meet the requirements of the growing fetus. The critical importance of long-chain fatty acids in cellular homeostasis demands an efficient uptake system for these fatty acids and their metabolism in tissues. In fact, involvement of several nuclear transcription factors (PPARgamma, LXR, RXR, and SREBP-1) is critical in the expression of genes responsible for fatty acids uptake, placental trophoblast differentiation and hCG production. These indicate that these receptors are potential regulators of placental lipid transfer and homeostasis. This review discusses importance of nuclear receptors and fatty acid binding/transport proteins in placental fatty acid uptake, transport and metabolism.

Novel model of calcium and inositol 1, 4, 5-trisphosphate regulation of InsP3 receptor channel gating in native endoplasmic reticulum

The InsP3R Ca2+-release channel has biphasic dependence on cytoplasmic free Ca2+ concentration ([Ca2+]i). InsP3 activates gating primarily by reducing high [Ca2+]i inhibition. To determine whether relieving Ca2+ inhibition is sufficient for activation, we examined single-channels in low [Ca2+]i in the absence of InsP3 by patch clamping isolated Xenopus oocyte nuclei. For both endogenous Xenopus type 1 and recombinant rat type 3 InsP3R channels, spontaneous InsP3-independent activities with low open probability Po (~ 0.03) were observed in [Ca2+]i < 5 nM, whereas none were observed in 25 nM Ca2+. These results establish the half-maximal inhibitory [Ca2+]i in the absence of InsP3 and demonstrate that the channel can be active when all of its ligand-binding sites are unoccupied. In the simplest allosteric model that fits all observations in nuclear patch-clamp studies, the tetrameric channel can adopt six conformations, the equilibria among which are controlled by two inhibitory, one activating Ca2+-binding, and one InsP3-binding sites in a manner similar to the Monod-Wyman-Changeux model. InsP3 binding activates gating by affecting the relative affinity for Ca2+ of one of the inhibitory sites in different channel conformations, transforming it into an activating site. Ca2+ inhibition of InsP3-liganded channels is mediated by an InsP3-independent second inhibitory site.

Calmodulin and calcium-release channels

Calmodulin (CaM) is a ubiquitous cytosolic protein that plays a critical role in regulating cellular functions by altering the activity of a large number of ion channels. There are many examples for CaM directly mediating the feedback effects of Ca2+ on Ca2+ channels. Recently the molecular mechanisms by which CaM interacts with voltage-gated Ca2+ channels, Ca2+-activated K+ channels and ryanodine receptors have been clarified. CaM plays an important role in regulating these ion channels through lobe-specific Ca2+ detection. CaM seems to behave as a channel subunit. It binds at low [Ca2+] and undergoes conformational changes upon binding of Ca2+, leading to an interaction with another part of the channel to regulate its gating. Here we focus on the mechanism by which CaM regulates the inositol 1,4,5-trisphosphate receptor (IP3R). Although the IP3R is inhibited by CaM and by other CaM-like proteins in the presence of Ca2+, we conclude that CaM does not act as the Ca2+ sensor for IP3R function. Furthermore we discuss a novel Ca2+-induced Ca2+-release mechanism found in A7r5 (embryonic rat aorta) and 16HBE14o- (human bronchial mucosa) cells for which CaM acts as a Ca2+ sensor.

Modulation of cytosolic calcium signaling by protein kinase A-mediated phosphorylation of inositol 1, 4, 5-trisphosphate receptors

Calcium release via intracellular Ca2+ release channels is a central event underpinning the generation of numerous, often divergent physiological processes. In electrically non-excitable cells, this Ca2+ release is brought about primarily through activation of inositol 1,4,5-trisphosphate receptors and typically takes the form of calcium oscillations. It is widely believed that information is carried in the temporal and spatial characteristics of these signals. Furthermore, stimulation of individual cells with different agonists can generate Ca2+ oscillations with dramatically different spatial and temporal characteristics. Thus, mechanisms must exist for the acute regulation of Ca2+ release such that agonist-specific Ca2+ signals can be generated. One such mechanism by which Ca2+ signals can be modulated is through simultaneous activation of multiple second messenger pathways. For example, activation of both the InsP3 and cAMP pathways leads to the modulation of Ca2+ release through protein kinase A mediated phosphoregulation of the InsP3R. Indeed, each InsP3R subtype is a potential substrate for PKA, although the functional consequences of this phosphorylation are not clear. This review will focus on recent advances in our understanding of phosphoregulation of InsP3R, as well as the functional consequences of this modulation in terms of eliciting specific cellular events.

IP3 receptors and Ca2+ signals in adult skeletal muscle satellite cells in situ

In this short article we review muscle satellite cell characteristics and our studies in adult rodent muscle satellite cells in situ. Using confocal laser scanning microscopy and immunocytochemistry, a high level of IP3 receptor (IP3R) immunostaining was detected in satellite cells. These cells were identified by their peripheral position, their size, the shape of their nucleus, the paucity of the apparent cytoplasm, and the immunostaining with specific molecular markers such as a-actinin, the neural cell adhesion molecule (N-CAM) and desmin. High extracellular K+ (60 mM) induced long-lasting Ca2+ signals in satellite cells in situ. We suggest that electrical activity stimulates IP3-associated Ca2+ signals that could act in concert with signaling pathways triggered by growth factors and/or hormones.

Reverse Cholesterol Transport in Cultured Gallbladder Epithelial Cells / 대한소화기학회지

Bile is the major route of cholesterol excretion from the body. It is concentrated in the gallbladder, and often results in supersaturation of cholesterol. The high levels of cholesterol in gallbladder bile has clinical implications with respect to cholesterol gallstone formation and cholesterolosis of the gallbladder wall. Gallbladder epithelial cells (GBEC) are exposed to high cholesterol concentrations on their apical surfaces. Therefore, GBEC are uniquely positioned to play an important role in modulating biliary cholesterol concentrations. Recently, it has been documented that the key-transporter for polarized cholesterol and phospholipid efflux in GBEC is ATP-binding cassette transporter A1 (ABCA1) and Liver X receptor (LXR) and retinoid X receptor (RXR) in the nucleus of GBEC have a role that regulates ABCA1 expression. In addition, GBEC synthesize apolipoprotein A-I and E as cholesterol acceptors. These results indicate that GBEC has a perfect system for reverse cholesterol transport. We introduce the roles and mechanisms of ABCA1, scavenger receptor class B-I, LXR and RXR related to reverse cholesterol transport in GBEC with a review of our study experience and related literature.

Lipid rafts are important for the association of RANK and TRAF6

Rafts, cholesterol- and sphingolipid-rich membrane microdomains, have been shown to play an important role in immune cell activation. More recently rafts were implicated in the signal transduction by members of the TNF receptor (TNFR) family. In this study, we provide evidences that the raft microdomain has a crucial role in RANK (receptor activator of NF-kappaB) signaling. We found that the majority of the ectopically expressed RANK and substantial portion of endogenous TRAF2 and TRAF6 were detected in the low-density raft fractions. In addition, TRAF6 association with rafts was increased by RANKL stimulation. The disruption of rafts blocked the TRAF6 translocation by RANK ligand and impeded the interaction between RANK and TRAF6. Our observations demonstrate that proper RANK signaling requires the function of raft membrane microdomains.

Modulation of InsP3 receptor properties by phosphorylation: targeting of PKA to InsP3 receptors shapes oscillatory calcium signals in pancreatic acinar cells

No abstract available.

Dissecting the molecular mechanism of nuclear receptor action: transcription coactivators and corepressors

No abstract available.

Mecanismos moleculares de açäo hormonal / Molecular mechanisms of hormonal action

A característica principal dos hormônios é a sua habilidade em interagir com receptores altamente seletivos e ativar vias intracelulares do sinalizaçäo nos órgaos específicos. Após a interaçäo dos hormônios com seus receptores, uma seqüência de reaçöes pode levar ao aumento ou diminuiçäo na atividade de determinadas enzimas que, por sua vez, produzem a resposta fisiológica. Os hormônios säo bioquimicamente classificados em esteróides, peptídeos ou aminas e seus receptores diferem, basicamente, por sua localizaçäo, intra ou extracelular. No presente trabalho, o mecanismo molecular de açäo dos hormônios peptídicos (hidrofílicos) e esteróides (lipofílicos) é discutido.