Vasodilator effect of glucagon: receptorial crosstalk among glucagon, GLP-1, and receptor for glucagon and GLP-1

Glucagon is known for its insulin-antagonist effect in the blood glucose homeostasis, while it also reduces vascular resistance. The mechanism of the vasoactive effect of glucagon has not been studied before; thereby we aimed to investigate the mediators involved in the vasodilatation induced by glucagon. The vasoactive effect of glucagon, insulin, and glucagon-like peptide-1 was studied on isolated rat thoracic aortic rings using a wire myograph. To investigate the mechanism of the vasodilatation caused by glucagon, we determined the role of the receptor for glucagon and the receptor for GLP-1, and studied also the effect of various inhibitors of gasotransmitters, inhibitors of reactive oxygen species formation, NADPH oxidase, prostaglandin synthesis, protein kinases, potassium channels, and an inhibitor of the Na(+)/Ca(2+)-exchanger. Glucagon causes dose-dependent relaxation in the rat thoracic aorta, which is as potent as that of insulin but greater than that of GLP-1 (7-36) amide. Vasodilatation by GLP-1 is partially mediated by the glucagon receptor. The vasodilatation due to glucagon evokes via the glucagon-receptor, but also via the receptor for GLP-1, and it is endothelium-independent. Contribution of gasotransmitters, prostaglandins, the NADPH oxidase enzyme, free radicals, potassium channels, and the Na(+)/Ca(2+)-exchanger is also significant. Glucagon causes dose-dependent relaxation of rat thoracic aorta in vitro, via the receptor for glucagon and the receptor for GLP-1, while the vasodilatation evoked by GLP-1 also evolves partially via the receptor for glucagon, thereby, a possible crosstalk between the 2 hormones and receptors could occur

Attenuation of Skeletal Muscle and Renal Injury to the Lower Limb following Ischemia-Reperfusion Using mPTP Inhibitor NIM-811.

INTRODUCTION: Operation on the infrarenal aorta and large arteries of the lower extremities may cause rhabdomyolysis of the skeletal muscle, which in turn may induce remote kidney injury. NIM-811 (N-metyl-4-isoleucine-cyclosporine) is a mitochondria specific drug, which can prevent ischemic-reperfusion (IR) injury, by inhibiting mitochondrial permeability transition pores (mPTP). OBJECTIVES: Our aim was to reduce damages in the skeletal muscle and the kidney after IR of the lower limb with NIM-811. MATERIALS AND METHODS: Wistar rats underwent 180 minutes of bilateral lower limb ischemia and 240 minutes of reperfusion. Four animal groups were formed called Sham (receiving vehicle and sham surgery), NIM-Sham (receiving NIM-811 and sham surgery), IR (receiving vehicle and surgery), and NIM-IR (receiving NIM-811 and surgery). Serum, urine and histological samples were taken at the end of reperfusion. NADH-tetrazolium staining, muscle Wet/Dry (W/D) ratio calculations, laser Doppler-flowmetry (LDF) and mean arterial pressure (MAP) monitoring were performed. Renal peroxynitrite concentration, serum TNF-alpha and IL-6 levels were measured. RESULTS: Less significant histopathological changes were observable in the NIM-IR group as compared with the IR group. Serum K+ and necroenzyme levels were significantly lower in the NIM-IR group than in the IR group (LDH: p<0.001; CK: p<0.001; K+: p = 0.017). Muscle mitochondrial viability proved to be significantly higher (p = 0.001) and renal function parameters were significantly better (creatinine: p = 0.016; FENa: p<0.001) in the NIM-IR group in comparison to the IR group. Serum TNF-alpha and IL-6 levels were significantly lower (TNF-alpha: p = 0.003, IL-6: p = 0.040) as well as W/D ratio and peroxynitrite concentration were significantly lower (p = 0.014; p<0.001) in the NIM-IR group than in the IR group. CONCLUSION: NIM-811 could have the potential of reducing rhabdomyolysis and impairment of the kidney after lower limb IR injury

Density of Common Complex Ocular Traits in the Aging Eye: Analysis of Secondary Traits in Genome-Wide Association Studies

Genetic association studies are identifying genetic risks for common complex ocular traits such as age-related macular degeneration (AMD). The subjects used for discovery of these loci have been largely from clinic-based, case-control studies. Typically, only the primary phenotype (e.g., AMD) being studied is systematically documented and other complex traits (e.g., affecting the eye) are largely ignored. The purpose of this study was to characterize these other or secondary complex ocular traits present in the cases and controls of clinic-based studies being used for genetic study of AMD. The records of 100 consecutive new patients (of any diagnosis) age 60 or older for which all traits affecting the eye had been recorded systematically were reviewed. The average patient had 3.5 distinct diagnoses. A subset of 10 complex traits was selected for further study because they were common and could be reliably diagnosed. The density of these 10 complex ocular traits increased by 0.017 log-traits/year (P = 0.03), ranging from a predicted 2.74 at age 60 to 4.45 at age 90. Trait-trait association was observed only between AMD and primary vitreomacular traction (P = 0.0009). Only 1% of subjects age 60 or older had no common complex traits affecting the eye. Extrapolations suggested that a study of 2000 similar subjects would have sufficient power to detect genetic association with an odds ratio of 2.0 or less for 4 of these 10 traits. In conclusion, the high prevalence of complex traits affecting the aging eye and the inherent biases in referral patterns leads to the potential for confounding by undocumented secondary traits within case-control studies. In addition to the primary trait, other common ocular phenotypes should be systematically documented in genetic association studies so that adjustments for potential trait-trait associations and other bias can be made and genetic risk variants identified in secondary analyses

Complex vasoactivity of liraglutide. Contribution of three gasotransmitters

Background: Incretine hormone glucagon-like peptide-1 (GLP-1) causes dose-dependent relaxation of the thoracic aorta of rats and other arteries via nitric oxide (NO), cAMP and ATP-sensitive potassium channels, however, through a mechanism not thoroughly described. Hereby we aimed to determine the mediators involved in the vasoactive effect of liraglutide. Methods: Isolated rat aortic rings and segments of the femoral artery were mounted in a wire myograph to study the vasoactive effect of liraglutide. Vessels were preincubated either with inhibitors of gasotransmitter-, prostaglandin- or reactive oxygen species-formation, or with inhibitors of protein kinases, potassium channels or the Na(+)/Ca(2+)-exchanger. Results: According to our findings, liraglutide activates endothelial cells and vascular smooth muscle cells leading to the production of NO, carbon monoxide, hydrogen sulphide, superoxide anion, and hydrogen peroxide. Increased production of such relaxing factors promotes the activation of protein kinase– A and –G, resulting in the activation of potassium channels (ATP-sensitive-, voltage-gated-, large-conductance-calcium activated), which profoundly contributes to the activation of the Na(+)/Ca(2+)-exchanger, thereby leading to calcium efflux and smooth muscle relaxation and vasorelaxation. Conclusions: We reveal the contribution of all gasotransmitters in the vasorelaxation induced by liraglutide. We provide ex vivo evidence that liraglutide is capable of causing vasodilatation in the central and peripherial vessels, thereby supporting the clinical observation that it lowers blood pressure

Cigarette smoke elicits relaxation of renal arteries

Epidemiological studies suggest that cigarette smoking - probably by eliciting hyperperfusion - increases glomerular filtration rate; thus, we hypothesized that cigarette smoke affects the vasomotor tone of renal arteries

Primary and secondary clarithromycin resistance in Helicobacter pylori and mathematical modeling of the role of macrolides

Clarithromycin is a macrolide antibiotic widely used for eradication of Helicobacter pylori infection, and thus resistance to this antibiotic is a major cause of treatment failure. Here, we present the results of a retrospective observational study of clarithromycin resistance (Cla-res) in 4744 H. pylori-infected patients from Central Hungary. We use immunohistochemistry and fluorescence in situ hybridization on fixed gastric tissue samples to determine H. pylori infection and to infer Cla-res status, respectively. We correlate this information with macrolide dispensing data for the same patients (available through a prescription database) and develop a mathematical model of the population dynamics of Cla-res H. pylori infections. Cla-res is found in 5.5% of macrolide-naive patients (primary Cla-res), with no significant sex difference. The model predicts that this primary Cla-res originates from transmission of resistant bacteria in 98.7% of cases, and derives from spontaneous mutations in the other 1.3%. We find an age-dependent preponderance of female patients among secondary (macrolide-exposed) clarithromycin-resistant infections, predominantly associated with prior use of macrolides for non-eradication purposes. Our results shed light into the sources of primary resistant cases, and indicate that the growth rate of Cla-res prevalence would likely decrease if macrolides were no longer used for purposes other than H. pylori eradication