Dapagliflozin stimulates glucagon secretion at high glucose: experiments and mathematical simulations of human A-cells.

Glucagon is one of the main regulators of blood glucose levels and dysfunctional stimulus secretion coupling in pancreatic A-cells is believed to be an important factor during development of diabetes. However, regulation of glucagon secretion is poorly understood. Recently it has been shown that Na(+)/glucose co-transporter (SGLT) inhibitors used for the treatment of diabetes increase glucagon levels in man. Here, we show experimentally that the SGLT2 inhibitor dapagliflozin increases glucagon secretion at high glucose levels both in human and mouse islets, but has little effect at low glucose concentrations. Because glucagon secretion is regulated by electrical activity we developed a mathematical model of A-cell electrical activity based on published data from human A-cells. With operating SGLT2, simulated glucose application leads to cell depolarization and inactivation of the voltage-gated ion channels carrying the action potential, and hence to reduce action potential height. According to our model, inhibition of SGLT2 reduces glucose-induced depolarization via electrical mechanisms. We suggest that blocking SGLTs partly relieves glucose suppression of glucagon secretion by allowing full-scale action potentials to develop. Based on our simulations we propose that SGLT2 is a glucose sensor and actively contributes to regulation of glucagon levels in humans which has clinical implications

Differential cross section for neutron-proton bremsstrahlung

The neutron-proton bremsstrahlung process $(np \to np\gamma)$ is known to be sensitive to meson exchange currents in the nucleon-nucleon interaction. The triply differential cross section for this reaction has been measured for the first time at the Los Alamos Neutron Science Center, using an intense, pulsed beam of up to 700 MeV neutrons to bombard a liquid hydrogen target. Scattered neutrons were observed at six angles between 12$^\circ$ and 32$^\circ$, and the recoil protons were observed in coincidence at 12$^\circ$, 20$^\circ$, and 28$^\circ$ on the opposite side of the beam. Measurement of the neutron and proton energies at known angles allows full kinematic reconstruction of each event. The data are compared with predictions of two theoretical calculations, based on relativistic soft-photon and non-relativistic potential models.Comment: 5 pages, 3 figure

P171Elevated free fetal haemoglobin threatens vasculoprotection in the fetal circulation of preeclamptic pregnancy

Placental up-regulation of free fetal haemoglobin (fHbF) occurs in preeclamptic (PE) pregnancy. Heme oxygenase-1 (HO-1) is an important vasculoprotective enzyme in the catabolism of the associated heme porphyrin structure. We have previously shown that fHbF negatively influences the vasculoprotective capacity of the fetal circulation. Here we study fHbF levels in the fetal cord blood of pregnancies complicated by PE; a pathology associated with dysregulated fetoplacental vascular tone. We have previously shown that fHbF binds nitric oxide (NO) to elicit elevated vascular resistance in the fetoplacental circulation, using ex vivo human dual placental perfusion and in vitro placental endothelial cell shear stress studies. Furthermore, fHbF causes morphological changes to the fetoplacental endothelium. Here we hypothesise that elevated levels of fHbF in fetal plasma associated with placental pathology contribute to fetoplacental hypertension. Purpose: To evaluate and derive a robust cord blood collection and processing protocol for the accurate measurement of fetal plasma fHbF levels in normal and PE pregnancies. Methods: Fetal venous cord blood was collected by syringe and needle, or Vacutainer method into either EDTA or citrate tubes, within 10 minutes of partum. Plasma recovery occurred immediately, or after 30 minutes, prior to centrifugation at 2000g x 10 min at room temperature. Following evaluation to reduce mechanical haemolysis, newly collected normal & PE plasma (n=13 & 6, respectively) was subjected to ELISAs for HbF and HO-1. Results: Venipuncture collection of cord venous blood taken from the cord-placenta insertion point by Vacutainer system with a 21G needle, into citrate collection tubes with immediate centrifugation prevented mechanical haemolysis. There was no difference in plasma HO-1 between groups (medians = 5.9 & 5.3 ng/mL; normal & PE, respectively; Mann-Whitney). Whilst there was no difference in fHbF between groups (Mann-Whitney), variability was high in the PE group and there were some very high values for fHbF compared to the normal range, whilst fHbF values in the control group were within a tighter lower range (medians & ranges = 45.9 & 0-206 and 118.8 & 29-640 μg/mL). Conclusion: Fetal plasma HO-1 levels appear stable in preeclamptic fetal plasma, permitting fHbF to remain unchecked in some cases. High pathophysiological levels of fHbF in some cases of PE pregnancies are capable of evoking elevated vascular resistance within the fetoplacental circulation, caused by nitric oxide sequestration and disruption to the endothelium. Further evaluation is require

Recruitment, augmentation and apoptosis of rat osteoclasts in 1,25-(OH)2D3 response to short-term treatment with 1,25-dihydroxyvitamin D3in vivo

Background Although much is known about the regulation of osteoclast (OC) formation and activity, little is known about OC senescence. In particular, the fate of of OC seen after 1,25-(OH)2D3 administration in vivo is unclear. There is evidence that the normal fate of OC is to undergo apoptosis (programmed cell death). We have investigated the effect of short-term application of high dose 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on OC apoptosis in an experimental rat model. Methods OC recruitment, augmentation and apoptosis was visualised and quantitated by staining histochemically for tartrate resistant acid phosphatase (TRAP), double staining for TRAP/ED1 or TRAP/DAPI, in situ DNA fragmentation end labelling and histomorphometric analysis. Results Short-term treatment with high-dose 1,25-(OH)2D3 increased the recruitment of OC precursors in the bone marrow resulting in a short-lived increase in OC numbers. This was rapidly followed by an increase in the number of apoptotic OC and their subsequent removal. The response of OC to 1,25-(OH)2D3 treatment was dose and site dependent; higher doses producing stronger, more rapid responses and the response in the tibiae being consistently stronger and more rapid than in the vertebrae. Conclusions This study demonstrates that (1) after recruitment, OC are removed from the resorption site by apoptosis (2) the combined use of TRAP and ED1 can be used to identify OC and their precursors in vivo (3) double staining for TRAP and DAPI or in situ DNA fragmentation end labelling can be used to identify apoptotic OC in vivo

Metformin, but not rosiglitazone, attenuates the increasing plasma levels of a new cardiovascular marker, fibulin-1, in patients with type 2 diabetes

OBJECTIVE The extracellular matrix protein fibulin-1 is upregulated in the arterial wall in type 2 diabetes (T2D) and circulates in increased concentrations in diabetes. Metformin is an antidiabetic drug with beneficial cardiovascular disease effects in diabetes. We hypothesized that metformin would influence the increased level of plasma fibulin-1 in diabetes. RESEARCH DESIGN AND METHODS After a 4-week run-in period, 371 eligible patients with T2D were randomized to treatment groups in a factorial design including insulin alone (control), +metformin, +rosiglitazone, or +both metformin and rosiglitazone. Plasma fibulin-1 was analyzed at the beginning of the study and after 18 and 24 months. RESULTS Plasma fibulin-1 increased in all groups throughout the 2-year period; however, the increase was strongly attenuated among patients treated with metformin. A highly significant difference was observed when the mean change in plasma fibulin-1 was compared between metformin- and non–metformin-treated individuals both at 18 and 24 months of treatment, but rosiglitazone had no effect. Metformin and rosiglitazone alone reduced the HbA1c levels to comparable levels and in combination even further. CONCLUSIONS Metformin attenuates the increase in plasma fibulin-1 concentrations in T2D, independently of glycemic effects. Changes in fibulin-1 may reflect an important element in diabetic arteriopathy that can be influenced by metformin. </jats:sec

Synthesis and bioactivity of analogues of the marine antibiotic tropodithietic acid

Tropodithietic acid (TDA) is a structurally unique sulfur-containing antibiotic from the Roseobacter clade bacterium Phaeobacter inhibens DSM 17395 and a few other related species. We have synthesised several structural analogues of TDA and used them in bioactivity tests against Staphylococcus aureus and Vibrio anguillarum for a structure–activity relationship (SAR) study, revealing that the sulfur-free analogue of TDA, tropone-2-carboxylic acid, has an antibiotic activity that is even stronger than the bioactivity of the natural product. The synthesis of this compound and of several analogues is presented and the bioactivity of the synthetic compounds is discussed