Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we will assume that you are happy to receive all cookies and you will not see this message again. Click 'Find out more' for information on how to change your cookie settings.
  • Recent advances in image-based stem-cell labeling and tracking, and scaffold-based organ development in cardiovascular disease

    17 October 2018

    © 2014 Bentham Science Publishers. Myocardial infarction (MI)and heart failure (HF)are leading causes of mortality and morbidity in the Western World. Therapeutic approaches using interventional cardiology and bioengineering techniques have thus far focused on either salvaging viable tissue post-infarction or preserving cardiac function in the failing myocardium. Regenerative medicine on the other hand, attempts to renew damaged tissue and enhance cardiac functional performance. Tremendous advances have been made in this field since the introduction and ethical approval for use of stem-cells (SC)and relevant technologies in pre-clinical and clinical practice. While study outcomes are still ambivalent on the potential translational impact of SCs, renewed hope has arisen since the introduction of induced pluripotent stem-cells (iPS)and the prospect of intact organ development and transplantation. The aim of this work is to review recent discoveries and the patent landscape employing stem-cell engineering, labeling and image-based monitoring strategies, their use in bioreactors and constructions of enriched bio-artificial membranes, as well as the potential role in artificial organ development and transplantation, with relevance to anticipated impact in pre-clinical screening and widespread clinical use.

  • Systemic Administration of Glibenclamide Fails to Achieve Therapeutic Levels in the Brain and Cerebrospinal Fluid of Rodents.

    17 October 2018

    Activating mutations in the Kir6.2 (KCNJ11) subunit of the ATP-sensitive potassium channel cause neonatal diabetes (ND). Patients with severe mutations also suffer from neurological complications. Glibenclamide blocks the open KATP channels and is the treatment of choice for ND. However, although glibenclamide successfully restores normoglycaemia, it has a far more limited effect on the neurological problems. To assess the extent to which glibenclamide crosses the blood-brain barrier (BBB) in vivo, we quantified glibenclamide concentrations in plasma, cerebrospinal fluid (CSF), and brain tissue of rats, control mice, and mice expressing a human neonatal diabetes mutation (Kir6.2-V59M) selectively in neurones (nV59M mice). As only small sample volumes can be obtained from rodents, we developed a highly sensitive method of analysis, using liquid chromatography tandem mass spectrometry acquisition with pseudo-selected reaction monitoring, achieving a quantification limit of 10ng/ml (20nM) glibenclamide in a 30μl sample. Glibenclamide was not detectable in the CSF or brain of rats after implantation with subcutaneous glibenclamide pellets, despite high plasma concentrations. Further, one hour after a suprapharmacological glibenclamide dose was administered directly into the lateral ventricle of the brain, the plasma concentration was twice that of the CSF. This suggests the drug is rapidly exported from the CSF. Elacridar, an inhibitor of P-glycoprotein and breast cancer resistance protein (major multidrug resistance transporters at the BBB), did not affect glibenclamide levels in CSF and brain tissue. We also identified a reduced sensitivity to volatile anaesthetics in nV59M mice and showed this was not reversed by systemic delivery of glibenclamide. Our results therefore suggest that little glibenclamide reaches the central nervous system when given systemically, that glibenclamide is rapidly removed across the BBB when given intracranioventricularly, and that any glibenclamide that does enter (and is below our detection limit) is insufficient to influence neuronal function as assessed by anaesthesia sensitivity.

  • Pharmacological inhibition of FTO.

    17 October 2018

    In 2007, a genome wide association study identified a SNP in intron one of the gene encoding human FTO that was associated with increased body mass index. Homozygous risk allele carriers are on average three kg heavier than those homozygous for the protective allele. FTO is a DNA/RNA demethylase, however, how this function affects body weight, if at all, is unknown. Here we aimed to pharmacologically inhibit FTO to examine the effect of its demethylase function in vitro and in vivo as a first step in evaluating the therapeutic potential of FTO. We showed that IOX3, a known inhibitor of the HIF prolyl hydroxylases, decreased protein expression of FTO (in C2C12 cells) and reduced maximal respiration rate in vitro. However, FTO protein levels were not significantly altered by treatment of mice with IOX3 at 60 mg/kg every two days. This treatment did not affect body weight, or RER, but did significantly reduce bone mineral density and content and alter adipose tissue distribution. Future compounds designed to selectively inhibit FTO's demethylase activity could be therapeutically useful for the treatment of obesity.

  • Reversible changes in pancreatic islet structure and function produced by elevated blood glucose.

    17 October 2018

    Diabetes is characterized by hyperglycaemia due to impaired insulin secretion and aberrant glucagon secretion resulting from changes in pancreatic islet cell function and/or mass. The extent to which hyperglycaemia per se underlies these alterations remains poorly understood. Here we show that β-cell-specific expression of a human activating KATP channel mutation in adult mice leads to rapid diabetes and marked alterations in islet morphology, ultrastructure and gene expression. Chronic hyperglycaemia is associated with a dramatic reduction in insulin-positive cells and an increase in glucagon-positive cells in islets, without alterations in cell turnover. Furthermore, some β-cells begin expressing glucagon, whilst retaining many β-cell characteristics. Hyperglycaemia, rather than KATP channel activation, underlies these changes, as they are prevented by insulin therapy and fully reversed by sulphonylureas. Our data suggest that many changes in islet structure and function associated with diabetes are attributable to hyperglycaemia alone and are reversed when blood glucose is normalized.

  • Fetal macrosomia and neonatal hyperinsulinemic hypoglycemia associated with transplacental transfer of sulfonylurea in a mother with KCNJ11-related neonatal diabetes.

    17 October 2018

    OBJECTIVE: Sulfonylureas (SUs) are effective at controlling glycemia in permanent neonatal diabetes mellitus (PNDM) caused by KCNJ11 (Kir6.2) mutations. RESEARCH DESIGN AND METHODS: We report the case of a woman with PNDM who continued high doses of glibenclamide (85 mg/day) during her pregnancy. The baby was born preterm, and presented with macrosomia and severe hyperinsulinemic hypoglycemia requiring high-rate intravenous glucose infusion. RESULTS: Postnatal genetic testing excluded a KCNJ11 mutation in the baby. Glibenclamide was detected in both the baby's blood and the maternal milk. CONCLUSIONS: We hypothesize that high doses of glibenclamide in the mother led to transplacental passage of the drug and overstimulation of fetal β-cells, which resulted in severe hyperinsulinemic hypoglycemia in the neonate (who did not carry the mutation) and contributed to fetal macrosomia. We suggest that glibenclamide (and other SUs) should be avoided in mothers with PNDM if the baby does not carry the mutation or if prenatal screening has not been performed, while glibenclamide may be beneficial when the fetus is a PNDM carrier.

  • A mutation causing increased KATP channel activity leads to reduced anxiety in mice.

    17 October 2018

    Activating mutations in the Kir6.2 (KCNJ11) subunit of the ATP-sensitive potassium channel cause neonatal diabetes. Many patients also suffer from neurological complications. By using mice carrying a human Kir6.2 mutation (Val(59) to Met(59); nV59M mice) targeted to neurones, we show that these mutations also result in altered anxiety behaviour. The light/dark box, successive alleys and elevated plus maze tasks revealed that nV59M mice have reduced anxiety related responses. Additionally, nV59M mice displayed enhanced basal locomotor activity and exploratory behaviour, as assessed by the low anxiety open-field test. These findings, in combination with previously reported hyperactivity of nV59M mice, appear to correlate with the increased impulsivity and inattentiveness reported in iDEND/DEND patients.

  • Type 2 diabetes and congenital hyperinsulinism cause DNA double-strand breaks and p53 activity in β cells.

    17 October 2018

    β cell failure in type 2 diabetes (T2D) is associated with hyperglycemia, but the mechanisms are not fully understood. Congenital hyperinsulinism caused by glucokinase mutations (GCK-CHI) is associated with β cell replication and apoptosis. Here, we show that genetic activation of β cell glucokinase, initially triggering replication, causes apoptosis associated with DNA double-strand breaks and activation of the tumor suppressor p53. ATP-sensitive potassium channels (KATP channels) and calcineurin mediate this toxic effect. Toxicity of long-term glucokinase overactivity was confirmed by finding late-onset diabetes in older members of a GCK-CHI family. Glucagon-like peptide-1 (GLP-1) mimetic treatment or p53 deletion rescues β cells from glucokinase-induced death, but only GLP-1 analog rescues β cell function. DNA damage and p53 activity in T2D suggest shared mechanisms of β cell failure in hyperglycemia and CHI. Our results reveal membrane depolarization via KATP channels, calcineurin signaling, DNA breaks, and p53 as determinants of β cell glucotoxicity and suggest pharmacological approaches to enhance β cell survival in diabetes.

  • ATP-sensitive potassium channels in health and disease

    17 October 2018

    Since their discovery over 20 years ago, it has been recognized that adenosine triphosphate-sensitive potassium (KATP) channels play a critical role in insulin secretion. When these channels are open, insulin secretion is inhibited, and when they are shut, secretion is initiated. Consequently drugs, mutations, or changes in beta-cell metabolism that open KATP channels decrease insulin secretion and may cause diabetes, whereas those manipulations that close KATP channels have the opposite effect, increasing insulin secretion and hypoglycemia. This chapter reviews our current knowledge of the pancreatic beta-cell KATP channel, and discusses new data on its structure, structure-function relationships, and role in disease. © 2008 Springer.