The dopamine receptor D2 agonist bromocriptine inhibits glucose-stimulated insulin secretion by direct activation of the α2-adrenergic receptors in beta cells

Treatment with the dopamine receptor D2 (DRD2) agonist bromocriptine improves metabolic features in obese patients with type 2 diabetes by a still unknown mechanism. In the present study, we investigated the acute effect of bromocriptine and its underlying mechanism(s) on insulin secretion both in vivo and in vitro. For this purpose, C57Bl6/J mice were subjected to an intraperitoneal glucose tolerance test (ipGTT) and a hyperglycemic (HG) clamp 60 min after a single injection of bromocriptine or placebo. The effects of bromocriptine on glucose-stimulated insulin secretion (GSIS), cell membrane potential and intracellular cAMP levels were also determined in INS-1E beta cells. We report here that bromocriptine increased glucose levels during ipGTT in vivo, an effect associated with a dose-dependent decrease in GSIS. During the HG clamp, bromocriptine reduced both first-phase and second-phase insulin response. This inhibitory effect was also observed in INS-1E beta cells, in which therapeutic concentrations of bromocriptine (0.5-50 nM) decreased GSIS. Mechanistically, neither cellular energy state nor cell membrane depolarization was affected by bromocriptine whereas intracellular cAMP levels were significantly reduced, suggesting involvement of G-protein-coupled receptors. Surprisingly, the DRD2 antagonist domperidone did not counteract the effect of bromocriptine on GSIS, whereas yohimbine, an antagonist of the α2-adrenergic receptors, completely abolished bromocriptine-induced inhibition of GSIS. In conclusion, acute administration of bromocriptine inhibits GSIS by a DRD2-independent mechanism involving direct activation of the pancreatic α2-adrenergic receptors. We suggest that treatment with bromocriptine promotes beta cells rest, thereby preventing long-lasting hypersecretion of insulin and subsequent beta cell failure.     

Distinct immunomodulation by autoimmunogenic xenobiotics in susceptible and resistant mice.

HgCl(2) and diphenylhydantoin (DPH) are prototype chemicals associated with diverse (auto)immune effects in genetically susceptible individuals. Both chemicals activate T cells, and the balance of Th1 versus Th2 activation may influence the clinical outcome of exposure. It is unknown which chemically created neoantigens are responsible for Th activation. We therefore investigated the effect of DPH and HgCl(2) on specific responses to TNP-ovalbumin, in mouse strains with varying sensitivity for the adverse effects. HgCl(2) was found to enhance Th2-driven antibody responses in susceptible B10.s, but protective type 1 responses in resistant B10.d2 mice. This was chemical-specific, as DPH enhanced type 2 responses in both strains. DBA/2 mice were relatively unresponsive to HgCl(2), whereas DPH stimulated type 1 responses in these mice. Interestingly, prior exposure to HgCl(2), but not DPH, facilitated IC deposition in B10.s mice only. Thus, we demonstrate that, depending on MHC-II and background genes, HgCl(2) and DPH preferentially adjuvate type 1 or type 2 responses. In case of HgCl(2), the type of response corresponds with susceptibility to antibody-mediated autoimmunity induced by this chemical. In addition, we demonstrate that, within one strain, different autoimmunogenic chemicals can enhance distinct responses to the same antigen.     

Superselective transcatheter arterial embolization in patients with acute peripancreatic bleeding complications: review of 44 cases

Purpose

To evaluate the efficacy of superselective transcatheter arterial embolization (TAE) in the treatment of acute peripancreatic bleeding complications.

Methods

During a 9-year period, 44 patients with acute bleeding of the peripancreatic arteries underwent TAE in our institution. Thirty-eight patients were treated using microcatheters and 6 patients with a diagnostic catheter. Embolic agents included coils (n = 38), polyvinyl alcohol (PVA) particles (n = 2), isobutyl cyanoacrylate (n = 2), coils plus PVA particles (n = 1), and coils plus isobutyl cyanoacrylate (n = 1). Outcome measures included technical success, clinical success, and the rate of complications.

Results

Identified bleeding sources included gastroduodenal artery (n = 14), splenic artery (n = 9), pancreaticoduodenal artery (n = 6), common hepatic artery (n = 5), superior mesenteric artery branches (n = 4), proper hepatic artery (n = 3), and dorsal/transverse pancreatic artery (n = 3). Technical success with effective control of active bleeding was achieved in 41/44 patients (93 %). Clinical success attributed to TAE alone was documented in 40/44 patients (91 %). The rate of major complications was 2 % including death in one patient.

Conclusions

Superselective TAE allows effective, minimally invasive control of acute peripancreatic bleeding complications with a low rate of therapeutically relevant complications.

     

Another 'soberade' on the market: does Outox keep its promise?

OBJECTIVE: Several products are being widely promoted for reduction of the concentration of alcohol in the human body. One of these preparations, the fructose soft drink Outox, claims to noticeably increase the alcohol elimination rate (beta 60). Theories to explain this 'fructose effect' are based on the assumption that NAD+, the coenzyme for alcohol dehydrogenase, is regenerated faster in the presence of fructose. METHOD: A randomized double-blind, placebo-controlled cross-over study was performed with 30 volunteers in two drinking sessions each. Under strictly identical conditions, the same amount of alcohol was consumed, followed by the consumption of either 250 ml Outox or 250 ml placebo. Periodical measurements of blood (BAC), breath (BrAC) and urine alcohol concentration (UAC) were performed. RESULTS: Analyses revealed a significant difference (P<0.0001) between the mean alcohol levels of the Outox and the placebo drinking sessions. The overall mean BAC difference was 0.077 g/l (BAC 0.748 g/l without vs 0.671 g/l with Outox), equivalent to 10.3%. The mean BrAC difference was 0.045 mg/l (BrAC 0.314 mg/l without vs 0.269 mg/l with Outox), equivalent to 14.3%. Differences were lower for women than for men. A significant difference between the alcohol elimination rates (beta 60) was not found. CONCLUSIONS: The results show that the soft drink Outox may decrease the alcohol concentration by about 10%. However, BAC and BrAC differences are rather a consequence of slower gastric absorption of alcohol, because Outox does not increase the alcohol elimination rate. Our study demonstrates that the claim of Outox or other fructose drinks to work as a 'soberade' cannot be proven from a scientific point of view. It should be the task of physicians to warn potential consumers, especially in connection with drinking and driving.     

Microglia replenished OHSC: A culture system to study in vivo like adult microglia

Recent data suggest that ramified microglia fulfil various tasks in the brain. However, to investigate this unique cell type cultured primary microglia are only a poor model. We here describe a method to deplete and repopulate organotypic hippocampal slice cultures (OHSC) with ramified microglia isolated from adult mouse brain creating microglia‐replenished OHSC (Mrep‐OHSC). Replenished microglia integrate into the tissue and ramify to a degree indistinguishable from their counterparts in the mouse brain. Moreover, wild‐type slices replenished with microglia from TNFα‐deficient animals provide similar results as OHSC prepared from microglia‐specific TNFα‐knockout mice (CX3CR1^cre/TNFα^fl/fl). Furthermore, this study demonstrates that replenished microglia in OHSC maintain original functions and properties acquired in vivo. Microglia from ERCC1^Δ/ko mice, a mouse model of accelerated aging, maintain enhanced Mac2 expression and their activated phenotype after replenishment to wild‐type OHSC tissue. Thus, the present study demonstrates that Mrep‐OHSC are a unique tool to construct chimeric brain slices allowing studying the function of different phenotypes of in vivo like microglia in a tissue culture setting. GLIA 2016 GLIA 2016;64:1285–1297     

Characterization of neuromuscular synapse function abnormalities in multiple Duchenne muscular dystrophy mouse models

Duchenne muscular dystrophy (DMD) is an X‐linked myopathy caused by dystrophin deficiency. Dystrophin is present intracellularly at the sarcolemma, connecting actin to the dystrophin‐associated glycoprotein complex. Interestingly, it is enriched postsynaptically at the neuromuscular junction (NMJ), but its synaptic function is largely unknown. Utrophin, a dystrophin homologue, is also concentrated at the NMJ, and upregulated in DMD. It is possible that the absence of dystrophin at NMJs in DMD causes neuromuscular transmission defects that aggravate muscle weakness. We studied NMJ function in mdx mice (lacking dystrophin) and wild type mice. In addition, mdx/utrn^+/? and mdx/utrn^?/? mice (lacking utrophin) were used to investigate influences of utrophin levels. The three Duchenne mouse models showed muscle weakness when comparatively tested in vivo, with mdx/utrn^?/? mice being weakest. Ex vivo muscle contraction and electrophysiological studies showed a reduced safety factor of neuromuscular transmission in all models. NMJs had ~ 40% smaller miniature endplate potential amplitudes compared with wild type, indicating postsynaptic sensitivity loss for the neurotransmitter acetylcholine. However, nerve stimulation‐evoked endplate potential amplitudes were unchanged. Consequently, quantal content (i.e. the number of acetylcholine quanta released per nerve impulse) was considerably increased. Such a homeostatic compensatory increase in neurotransmitter release is also found at NMJs in myasthenia gravis, where autoantibodies reduce acetylcholine receptors. However, high‐rate nerve stimulation induced exaggerated endplate potential rundown. Study of NMJ morphology showed that fragmentation of acetylcholine receptor clusters occurred in all models, being most severe in mdx/utrn^?/? mice. Overall, we showed mild ‘myasthenia‐like’ neuromuscular synaptic dysfunction in several Duchenne mouse models, which possibly affects muscle weakness and degeneration.     

Endocrinologic response to vasopressin infusion in advanced vasodilatory shock

OBJECTIVES: To evaluate the endocrinologic response to a combined arginine vasopressin and norepinephrine (AVP/NE) infusion in advanced vasodilatory shock, and to examine the relationship between baseline plasma AVP concentrations and the hemodynamic response to AVP. DESIGN: Preliminary, prospective, randomized, controlled clinical study. SETTING: Twenty-three-bed general and surgical intensive care unit. PATIENTS: Thirty-eight patients with advanced vasodilatory shock. Hemodynamic and laboratory data of 34 patients have already been presented in a recently published prospective, randomized, controlled study. INTERVENTIONS: Continuous AVP (4 units/hr) and NE infusion in study patients; NE infusion only in control patients. MEASUREMENTS AND MAIN RESULTS: At baseline, 24 hrs, and 48 hrs after randomization, plasma concentrations of AVP, adrenocorticotropic hormone, cortisol, renin, angiotensin II, aldosterone, prolactin, endothelin I, and atrial natriuretic factor were determined. Hemodynamic variables were recorded at baseline and 1, 12, and 24 hrs after randomization. Linear mixed effects models were used to test for differences between groups. The relationship between AVP plasma concentrations and hemodynamic response to AVP was analyzed using linear regression analyses. AVP/NE patients exhibited significantly higher AVP (p <.001) and prolactin (p <.001) plasma concentrations during the study period; there were no significant differences in plasma concentrations of other hormones. No significant correlation was detected between plasma AVP concentrations and the increase in mean arterial pressure after 1 hr (Pearson's correlation coefficient =.134, p =.584) and after 24 hrs (Pearson's correlation coefficient = -.198, p =.417). There were further no correlations between AVP plasma concentrations and the 24-hr response to AVP therapy in heart rate (Pearson's correlation coefficient = -.065, p =.791), stroke volume index (Pearson's correlation coefficient = -.106, p =.687), and NE requirements (Pearson's correlation coefficient =.04, p =.869). CONCLUSIONS: The preliminary results of this study indicate that a combined AVP and NE infusion increases prolactin plasma concentrations in advanced vasodilatory shock. Hemodynamic effects of AVP infusion are independent of baseline plasma AVP concentrations.