Citations

Zebrafish Na+/H+exchanger 3b (zNHE3b) is highly expressed in the apical membrane of ionocytes where Na+is absorbed from ion-poor fresh water against a concentration gradient. Much in vivo data indicated that zNHE3b is involved in Na+absorption but not leakage. However, zNHE3b-mediated Na+absorption has not been thermodynamically explained, and zNHE3b activity has not been measured. To address this issue, we overexpressed zNHE3b in Xenopus oocytes and characterized its activity by electrophysiology. Exposure of zNHE3b oocytes to Na+-free media resulted in significant decrease in intracellular pH (pHi) and intracellular Na+activity ( aNai). aNaiincreased significantly when the cytoplasm was acidified by media containing CO2-HCO3−or butyrate. Activity of zNHE3b was inhibited by amiloride or 5-ethylisopropyl amiloride (EIPA). Although the activity was accompanied by a large hyperpolarization of ∼50 mV, voltage-clamp experiments showed that Na+/H+exchange activity of zNHE3b is electroneutral. Exposure of zNHE3b oocytes to medium containing NH3/NH4+resulted in significant decreases in pHiand aNaiand significant increase in intracellular NH4+activity, indicating that zNHE3b mediates the Na+/NH4+exchange. In low-Na+(0.5 mM) media, zNHE3b oocytes maintained aNaiof 1.3 mM, and Na+-influx was observed when pHiwas decreased by media containing CO2-HCO3−or butyrate. These results provide thermodynamic evidence that zNHE3b mediates Na+absorption from ion-poor fresh water by its Na+/H+and Na+/NH4+exchange activities.

Abstract Dihydropyrimidine dehydrogenase (DPD, encoded by DPYD) is the rate-limiting enzyme in the uracil catabolic pathway and has a pivotal role in the pharmacokinetics of the commonly prescribed anticancer drug 5-fluorouracil (5-FU). Deficiency of DPD, whether due to inadequate expression or deleterious variants in DPYD, has been linked to severe toxic responses to 5-FU. Little is known about the mechanisms governing DPD expression in the liver. In this report, we show increased accumulation of RNA-induced silencing complex (RISC) proteins on DPYD mRNA in cells overexpressing the highly homologous microRNAs (miRNA) miR-27a and miR-27b. These miRNAs were shown to repress DPD expression through two conserved recognition sites in DPYD. The IC50 of 5-FU for HCT116 cells overexpressing miR-27a or miR-27b was 4.4 μmol/L (both), significantly lower than that for cells expressing a nontargeting (scramble) control miRNA (14.3 μmol/L; P = 3.3 × 10−5 and P = 1.5 × 10−7, respectively). Mouse liver DPD enzyme activity was inversely correlated with expression levels of miR-27a (R2 = 0.49; P = 0.0012) and miR-27b (R2 = 0.29; P = 0.022). A common variant in the hairpin loop region of hsa-mir-27a (rs895819) was also shown to be associated with elevated expression of the miR-27a in a panel of cell lines (P = 0.029) and in a transgenic overexpression model (P = 0.0011). Furthermore, rs895819 was associated with reduced DPD enzyme activity (P = 0.028) in a cohort of 40 healthy volunteers. Taken together, these results suggest that miR-27a and miR-27b expression may be pharmacologically relevant modulators of DPD enzyme function in the liver. Furthermore, our data suggest that rs895819 may be a potential risk allele for 5-FU sensitivity. Mol Cancer Ther; 13(3); 742–51. ©2014 AACR.

Hydrophilic polymer coated introducer sheaths and medical devices are widely used in interventional cardiology. Despite the potential procedural advantages that these provide, a risk of polymer embolization has been recently reported. We describe the first reported case of hydrophilic polymer induced acute transcatheter aortic valve thrombosis. © 2014 Wiley Periodicals, Inc.

Objectives To define whether the high sensitivity cardiac troponin T (hs-cTnT) assay in patients with immunoglobulin light chain amyloidosis (AL) improves risk prediction. Background Cardiac involvement is the major cause of death in patients with AL amyloidosis. Risk stratification is facilitated by cardiac biomarkers such as cardiac troponin T (cTnT) and N-terminal pro B-type natriuretic peptide (NT-proBNP). Methods Stored serum from patients with newly diagnosed AL was used to measure hs-cTnT, cTnT, and NT-proBNP. Survival modelling was performed. Results The direct numeric result from hs-cTnT measurement cannot merely be substituted for a cTnT measurement in the Mayo AL staging system. The performance of the receiver operator curve derived an hs-cTnT cut-point of 54 ng/L which improves on the value of 35 ng/L validated with the prior iteration of the assay. An alternate staging option using hs-cTnT alone—using the two thresholds 14 ng/L and 54 ng/L—performs as well as either the original Mayo AL staging system or other systems incorporating hs-cTnT. On multivariate analysis, an hs-cTnT alone staging system was independent of period of diagnosis, type of therapy, and NT-proBNP value, the last of which dropped out of the model. Alternate models were explored, but none performed better than the original system or the new hs-cTnT system. Thus, hs-cTnT can be used alone for the staging of disease prognosis. Conclusions A survival model based on hs-cTnT improves the prognostic staging of patients with AL amyloidosis, relegating NT-proBNP to a measure of cardiac response.

Despite advances in understanding the roles of adiposity, food intake, GI and adipocyte-related hormones, inflammatory mediators, the gut–brain axis and the hypothalamic nervous system in the pathophysiology of obesity, the effects of different therapeutic interventions on those pathophysiological mechanisms are controversial. There are still no low-cost, safe, effective treatments for obesity and its complications. Currently, bariatric surgical approaches targeting the GI tract are more effective than non-surgical approaches in inducing weight reduction and resolving obesity-related comorbidities. However, current guidelines emphasise non-surgical approaches through lifestyle modification and medications to achieve slow weight loss, which is not usually sustained and may be associated with medication-related side effects. This review analyses current central, peripheral or hormonal targets to treat obesity and addresses challenges and opportunities to develop novel approaches for obesity.

AbstractMice homozygous for the targeted disruption of the glycoprotein hormone α-subunit (αGsu) display hypertrophy and hyperplasia of the anterior pituitary thyrotropes. Thyrotrope hyperplasia results in tumors in aged αGsu−/− mice. These adenomatous pituitaries can grow independently as intrascapular transplants in hypothyroid mice, suggesting that they have progressed beyond simple hyperplasia. We used magnetic resonance imaging to follow the growth and regression of thyrotrope adenomatous hyperplasia in response to thyroid hormone treatment and discovered that the tumors retain thyroid hormone responsiveness. Somatostatin (SMST) and its diverse receptors have been implicated in cell proliferation and tumorigenesis. To test the involvement of SMST receptor 2 (SMSTR2) in pituitary tumor progression and thyroid hormone responsiveness in αGsu−/− mutants, we generated Smstr2−/−, αGsu−/− mice. Smstr2−/−, αGsu−/− mice develop hyperplasia of thyrotropes, similar to αGsu−/− mutants, demonstrating that SMSTR2 is dispensable for the development of pituitary adenomatous hyperplasia. Thyrotrope hyperplasia in Smstr2−/−, αGsu−/− mice regresses in response to T4 treatment, suggesting that SMSTR2 is not required in the T4 feedback loop regulating TSH secretion.