Biodiesel Production from Transesterification with Lipase from Pseudomonas cepacia Immobilized on Modified Structured Metal Organic Materials.

This research presents the modification of MOF-199 and ZIF-8 using furfuryl alcohol (FA) as a carbon source to subsequently fix lipase from Pseudomonas cepacia and use these biocatalysts in the transesterification of African palm oil (APO). The need to overcome the disadvantages of free lipases in the biodiesel production process led to the use of metal organic framework (MOF)-type supports because they provide greater thermal stability and separation of the catalytic phase, thus improving the activity and efficiency in relation to the use of free lipase, disadvantages that could not be overcome with the use of other types of catalysts used in transesterification/esterification reactions for the production of biodiesel. The modification of MOFs ZIF-8 and MOF-199 with FA increases the pore volume which allows better immobilization of Pseudomonas cepacia lipase (PCL). The results show that these biocatalysts undergo transesterification with biodiesel yields above 90%. Additionally, studies were carried out on the effect of (1) enzyme loading, 2) enzyme immobilization time, (3) enzyme immobilization temperature, and (4) pH on the % immobilization of the enzyme and the specific activity. The results show that the highest immobilization efficiency for the FA@ZIF-8 support has a value of 91.2% when the load of this support was 3.5 mg/mg and has a specific activity of 142.5 U/g protein. The FA@MOF-199 support presented 80.3% enzyme immobilization and 125% U/g specific activity protein. We established that the specific activity increases in the period from 0.5 to 5.0 h for the systems under investigation. After this time, both the specific activity and the % efficiency of enzyme immobilization decrease. Therefore, 5.0 h (immobilization efficiency of 95 and 85% for FA@MOF-199, respectively) was chosen as the most appropriate time for PCL immobilization. Methods of adding methanol, with three and four steps, were tested, where biodiesel yields greater than 90% were obtained for the biocatalysts synthesized in this work (FA@ZIF-8-PCL and FA@MOF-199-PCL) and above 70% for free PCL, and the maximum yield was reached at a molar ratio between methanol and APO of 4:1 when using the one-step method under the same reaction conditions (as mentioned above). Only the results of FA@ZIF-8-PCL are presented here; however, it should be noted that the results for biocatalyst FA@MOF-199-PCL and lipase-free PCL presented the same behavior. The order of biocatalyst performance was FA@ZIF-8-PCL > FA@MOF-199-PCL > PCL-Free, which demonstrates that the use of FA as a modifier is a novel aspect in the conversion of palm oil into biodiesel components.

Biocatalysts Synthesized with Lipase from Pseudomonas cepacia on Glycol-Modified ZIF-8: Characterization and Utilization in the Synthesis of Green Biodiesel.

This research presents results on the production of biodiesel from the transesterification of acylglycerides present in palm oil, using the biocatalysts ZIF-8-PCL and Gly@ZIF-8-PCL synthesized by immobilization of Pseudomonas Cepacia Lipase as catalytic materials and using pure ZIF-8 and Gly@ZIF-8 (modified ZIF-8) as supports. The Gly@ZIF-8 carbonaceous material was prepared by wet impregnation of ZIF-8 with ethylene glycol as the carbon source, and then thermally modified. The calcination conditions were 900 °C for two hours with a heating rate of 7 °C/min in an inert atmosphere. A textural characterization was performed, and results showed superficial changes of materials at the microporous and mesoporous levels for the Gly@ZIF-8 material. Both the starting materials and biocatalysts were characterized by infrared spectroscopy (FTIR) and Raman spectroscopy. During the transesterification, using the two biocatalysts (ZIF-8-PCL and Gly@ZIF-8-PCL), two supernatant liquids were generated which were characterized by infrared spectroscopy (FTIR), gas chromatography coupled to mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). The results show that the two routes of synthesis of supports from ZIF-8 will be configured as effective methods for the generation of effective biocatalysts for biodiesel production.

Protection from ß-cell apoptosis by inhibition of TGF-ß/Smad3 signaling.

Prevailing insulin resistance and the resultant hyperglycemia elicits a compensatory response from pancreatic islet beta cells (ß-cells) that involves increases in ß-cell function and ß-cell mass. However, the sustained metabolic stress eventually leads to ß-cell failure characterized by severe ß-cell dysfunction and progressive loss of ß-cell mass. Whereas, ß-cell dysfunction is relatively well understood at the mechanistic level, the avenues leading to loss of ß-cell mass are less clear with reduced proliferation, dedifferentiation, and apoptosis all potential mechanisms. Butler and colleagues documented increased ß-cell apoptosis in pancreas from lean and obese human Type 2 diabetes (T2D) subjects, with no changes in rates of ß-cell replication or neogenesis, strongly suggesting a role for apoptosis in ß-cell failure. Here, we describe a permissive role for TGF-ß/Smad3 in ß-cell apoptosis. Human islets undergoing ß-cell apoptosis release increased levels of TGF-ß1 ligand and phosphorylation levels of TGF-ß's chief transcription factor, Smad3, are increased in human T2D islets suggestive of an autocrine role for TGF-ß/Smad3 signaling in ß-cell apoptosis. Smad3 phosphorylation is similarly increased in diabetic mouse islets undergoing ß-cell apoptosis. In mice, ß-cell-specific activation of Smad3 promotes apoptosis and loss of ß-cell mass in association with ß-cell dysfunction, glucose intolerance, and diabetes. In contrast, inactive Smad3 protects from apoptosis and preserves ß-cell mass while improving ß-cell function and glucose tolerance. At the molecular level, Smad3 associates with Foxo1 to propagate TGF-ß-dependent ß-cell apoptosis. Indeed, genetic or pharmacologic inhibition of TGF-ß/Smad3 signals or knocking down Foxo1 protects from ß-cell apoptosis. These findings reveal the importance of TGF-ß/Smad3 in promoting ß-cell apoptosis and demonstrate the therapeutic potential of TGF-ß/Smad3 antagonism to restore ß-cell mass lost in diabetes.

Puntualizaciones a los proyectos de estandarización del tratamiento del cáncer de la unión esofagogástrica: centralización, registros y formación / Standardizing the treatment of esophagogastric junction tumors: Centralization, registries and surgical training

No disponible

Corrigendum to "Islet ß-Cell Mass Preservation and Regeneration in Diabetes Mellitus: Four Factors with Potential Therapeutic Interest".

[This corrects the article DOI: 10.1155/2012/230870.].

LRH-1 agonism favours an immune-islet dialogue which protects against diabetes mellitus.

Type 1 diabetes mellitus (T1DM) is due to the selective destruction of islet beta cells by immune cells. Current therapies focused on repressing the immune attack or stimulating beta cell regeneration still have limited clinical efficacy. Therefore, it is timely to identify innovative targets to dampen the immune process, while promoting beta cell survival and function. Liver receptor homologue-1 (LRH-1) is a nuclear receptor that represses inflammation in digestive organs, and protects pancreatic islets against apoptosis. Here, we show that BL001, a small LRH-1 agonist, impedes hyperglycemia progression and the immune-dependent inflammation of pancreas in murine models of T1DM, and beta cell apoptosis in islets of type 2 diabetic patients, while increasing beta cell mass and insulin secretion. Thus, we suggest that LRH-1 agonism favors a dialogue between immune and islet cells, which could be druggable to protect against diabetes mellitus.

GATA6 Controls Insulin Biosynthesis and Secretion in Adult ß-Cells.

GATA4 and GATA6 play essential, but redundant, roles in pancreas formation in mice, and GATA6 mutations cause pancreatic agenesis in humans. GATA6 mutations have also recently been linked to adult-onset diabetes, with subclinical or no exocrine insufficiency, suggesting an important role for GATA6 in human ß-cell physiology. To investigate the role of GATA6 in the adult endocrine pancreas, we generated mice in which Gata6 is specifically inactivated in the pancreas. These mice develop glucose intolerance. Islets deficient in GATA6 activity display decreased insulin content and impaired insulin secretion. Gata6-deficient ß-cells exhibit ultrastructural abnormalities, including increased immature insulin granules, swollen mitochondria, and disorganized endoplasmic reticulum. We also demonstrate that Pdx1 expression in adult ß-cells depends on GATA sites in transgenic reporter mice and that loss of GATA6 greatly affects ß-cell-specific gene expression. These findings demonstrate the essential role of GATA6 in ß-cell function.

Esplenectomía parcial laparoscópica por quiste epidermoide esplénico / Laparoscopic partial splenectomy for a splenic epidermoid cyst

No disponible

Levothyroxine enhances glucose clearance and blunts the onset of experimental type 1 diabetes mellitus in mice.

BACKGROUND AND PURPOSE: Thyroid hormones induce several changes in whole body metabolism that are known to improve metabolic homeostasis. However, adverse side effects have prevented its use in the clinic. In view of the promising effects of thyroid hormones, we investigated the effects of levothyroxine supplementation on glucose homeostasis. EXPERIMENTAL APPROACH: C57BL/6 mice were treated with levothyroxine from birth to 24 weeks of age, when mice were killed. The effects of levothyroxine supplementation on metabolic health were determined. C57BL/6 mice treated with levothyroxine for 2 weeks and then challenged with streptozotocin to monitor survival. Mechanistic experiments were conducted in the pancreas, liver and skeletal muscle. RIP-B7.1 mice were treated with levothyroxine for 2 weeks and were subsequently immunized to trigger experimental autoimmune diabetes (EAD). Metabolic tests were performed. Mice were killed and metabolic tissues were extracted for immunohistological analyses. KEY RESULTS: Long-term levothyroxine supplementation enhanced glucose clearance and reduced circulating glucose in C57BL/6 mice. Levothyroxine increased simultaneously the proliferation and apoptosis of pancreatic beta cells, promoting the maintenance of a highly insulin-expressing beta cell population. Levothyroxine increased circulating insulin levels, inducing sustained activation of IRS1-AKT signalling in insulin-target tissues. Levothyroxine-treated C57BL/6 mice challenged with streptozotocin exhibited extended survival. Levothyroxine blunted the onset of EAD in RIP-B7.1 mice by inducing beta cell proliferation and preservation of insulin-expressing cells. CONCLUSIONS AND IMPLICATIONS: Interventions based on the use of thyroid hormones or thyromimetics could be explored to provide therapeutic benefit in patients with type 1 diabetes mellitus.

PAX4 preserves endoplasmic reticulum integrity preventing beta cell degeneration in a mouse model of type 1 diabetes mellitus.

AIMS/HYPOTHESIS: A strategy to enhance pancreatic islet functional beta cell mass (BCM) while restraining inflammation, through the manipulation of molecular and cellular targets, would provide a means to counteract the deteriorating glycaemic control associated with diabetes mellitus. The aims of the current study were to investigate the therapeutic potential of such a target, the islet-enriched and diabetes-linked transcription factor paired box 4 (PAX4), to restrain experimental autoimmune diabetes (EAD) in the RIP-B7.1 mouse model background and to characterise putative cellular mechanisms associated with preserved BCM. METHODS: Two groups of RIP-B7.1 mice were genetically engineered to: (1) conditionally express either PAX4 (BPTL) or its diabetes-linked mutant variant R129W (mutBPTL) using doxycycline (DOX); and (2) constitutively express luciferase in beta cells through the use of RIP. Mice were treated or not with DOX, and EAD was induced by immunisation with a murine preproinsulin II cDNA expression plasmid. The development of hyperglycaemia was monitored for up to 4 weeks following immunisation and alterations in the BCM were assessed weekly by non-invasive in vivo bioluminescence intensity (BLI). In parallel, BCM, islet cell proliferation and apoptosis were evaluated by immunocytochemistry. Alterations in PAX4- and PAX4R129W-mediated islet gene expression were investigated by microarray profiling. PAX4 preservation of endoplasmic reticulum (ER) homeostasis was assessed using thapsigargin, electron microscopy and intracellular calcium measurements. RESULTS: PAX4 overexpression blunted EAD, whereas the diabetes-linked mutant variant PAX4R129W did not convey protection. PAX4-expressing islets exhibited reduced insulitis and decreased beta cell apoptosis, correlating with diminished DNA damage and increased islet cell proliferation. Microarray profiling revealed that PAX4 but not PAX4R129W targeted expression of genes implicated in cell cycle and ER homeostasis. Consistent with the latter, islets overexpressing PAX4 were protected against thapsigargin-mediated ER-stress-related apoptosis. Luminal swelling associated with ER stress induced by thapsigargin was rescued in PAX4-overexpressing beta cells, correlating with preserved cytosolic calcium oscillations in response to glucose. In contrast, RNA interference mediated repression of PAX4-sensitised MIN6 cells to thapsigargin cell death. CONCLUSIONS/INTERPRETATION: The coordinated regulation of distinct cellular pathways particularly related to ER homeostasis by PAX4 not achieved by the mutant variant PAX4R129W alleviates beta cell degeneration and protects against diabetes mellitus. The raw data for the RNA microarray described herein are accessible in the Gene Expression Omnibus database under accession number GSE62846.

PAX4 Defines an Expandable ß-Cell Subpopulation in the Adult Pancreatic Islet.

PAX4 is a key regulator of pancreatic islet development whilst in adult acute overexpression protects ß-cells against stress-induced apoptosis and stimulates proliferation. Nonetheless, sustained PAX4 expression promotes ß-cell dedifferentiation and hyperglycemia, mimicking ß-cell failure in diabetic patients. Herein, we study mechanisms that allow stringent PAX4 regulation endowing favorable ß-cell adaptation in response to changing environment without loss of identity. To this end, PAX4 expression was monitored using a mouse bearing the enhanced green fluorescent protein (GFP) and cre recombinase construct under the control of the islet specific pax4 promoter. GFP was detected in 30% of islet cells predominantly composed of PAX4-enriched ß-cells that responded to glucose-induced insulin secretion. Lineage tracing demonstrated that all islet cells were derived from PAX4(+) progenitor cells but that GFP expression was confined to a subpopulation at birth which declined with age correlating with reduced replication. However, this GFP(+) subpopulation expanded during pregnancy, a state of active ß-cell replication. Accordingly, enhanced proliferation was exclusively detected in GFP(+) cells consistent with cell cycle genes being stimulated in PAX4-overexpressing islets. Under stress conditions, GFP(+) cells were more resistant to apoptosis than their GFP(-) counterparts. Our data suggest PAX4 defines an expandable ß-cell sub population within adult islets.

A Simple High Efficiency Intra-Islet Transduction Protocol Using Lentiviral Vectors.

Successful normalization of blood glucose in patients transplanted with pancreatic islets isolated from cadaveric donors established the proof-of-concept that Type 1 Diabetes Mellitus is a curable disease. Nonetheless, major caveats to the widespread use of this cell therapy approach have been the shortage of islets combined with the low viability and functional rates subsequent to transplantation. Gene therapy targeted to enhance survival and performance prior to transplantation could offer a feasible approach to circumvent these issues and sustain a durable functional ß-cell mass in vivo. However, efficient and safe delivery of nucleic acids to intact islet remains a challenging task. Here we describe a simple and easy-to-use lentiviral transduction protocol that allows the transduction of approximately 80 % of mouse and human islet cells while preserving islet architecture, metabolic function and glucose-dependent stimulation of insulin secretion. Our protocol will facilitate to fully determine the potential of gene expression modulation of therapeutically promising targets in entire pancreatic islets for xenotransplantation purposes.

Hepatocyte growth factor/c-Met signaling is required for ß-cell regeneration.

Hepatocyte growth factor (HGF) is a mitogen required for ß-cell replication during pregnancy. To determine whether HGF/c-Met signaling is required for ß-cell regeneration, we characterized mice with pancreatic deletion of the HGF receptor, c-Met (PancMet KO mice), in two models of reduced ß-cell mass and regeneration: multiple low-dose streptozotocin (MLDS) and partial pancreatectomy (Ppx). We also analyzed whether HGF administration could accelerate ß-cell regeneration in wild-type (WT) mice after Ppx. Mouse islets obtained 7 days post-Ppx displayed significantly increased c-Met, suggesting a potential role for HGF/c-Met in ß-cell proliferation in situations of reduced ß-cell mass. Indeed, adult PancMet KO mice displayed markedly reduced ß-cell replication compared with WT mice 7 days post-Ppx. Similarly, ß-cell proliferation was decreased in PancMet KO mice in the MLDS mouse model. The decrease in ß-cell proliferation post-Ppx correlated with a striking decrease in D-cyclin levels. Importantly, PancMet KO mice showed significantly diminished ß-cell mass, decreased glucose tolerance, and impaired insulin secretion compared with WT mice 28 days post-Ppx. Conversely, HGF administration in WT Ppx mice further accelerated ß-cell regeneration. These results indicate that HGF/c-Met signaling is critical for ß-cell proliferation in situations of diminished ß-cell mass and suggest that activation of this pathway can enhance ß-cell regeneration.

Islet ß-Cell Mass Preservation and Regeneration in Diabetes Mellitus: Four Factors with Potential Therapeutic Interest.

Islet ß-cell replacement and regeneration are two promising approaches for the treatment of Type 1 Diabetes Mellitus. Indeed, the success of islet transplantation in normalizing blood glucose in diabetic patients has provided the proof of principle that cell replacement can be employed as a safe and efficacious treatment. Nonetheless, shortage of organ donors has hampered expansion of this approach. Alternative sources of insulin-producing cells are mandatory to fill this gap. Although great advances have been achieved in generating surrogate ß-cells from stem cells, current protocols have yet to produce functionally mature insulin-secreting cells. Recently, the concept of islet regeneration in which new ß-cells are formed from either residual ß-cell proliferation or transdifferentiation of other endocrine islet cells has gained much interest as an attractive therapeutic alternative to restore ß-cell mass. Complementary approaches to cell replacement and regeneration could aim at enhancing ß-cell survival and function. Herein, we discuss the value of Hepatocyte Growth Factor (HGF), Glucose-Dependent Insulinotropic Peptide (GIP), Paired box gene 4 (Pax4) and Liver Receptor Homolog-1 (LRH-1) as key players for ß-cell replacement and regeneration therapies. These factors convey ß-cell protection and enhanced function as well as facilitating proliferation and transdifferentiation of other pancreatic cell types to ß-cells, under stressful conditions.