Coronary vascular effects of vasoactive intestinal peptide in the isolated perfused rat heart

The VIP/VPAC1R Pathway Regulates Energy and Glucose Homeostasis by Modulating GLP-1, Glucagon, Leptin and PYY Levels in Mice

Simple Summary

The current study is the first complete characterization of the phenotypic, metabolic, calorimetric, and homeostatic effects of VPAC1R in a null murine model. To evaluate the role of VPAC1R on body phenotype, feeding behavior, glucose/energy homeostasis, metabolic rate and plasma hormones, a long-term study was conducted in VPAC1R^−/− and WT mice. The outcome data document that VPAC1R^−/− mice have altered metabolism and insulin intolerance, with significant increase of feeding bouts, reduction of total energy expenditure and respiratory gases during both the dark and light cycle, together with elevated fasting levels of GLP-1 and PYY, and higher postprandial levels of GLP-1, glucagon leptin and PYY. These findings suggests that VPAC1R controls glucose homeostasis and energy balance by regulating plasma metabolic hormones.

Abstract

Vasoactive Intestinal Peptide binds with high affinity to VPAC1R and VPAC2R, thus regulating key physiologic functions. Previously, we documented in VIP^−/− mice a leaner body phenotype and altered metabolic hormones. Past reports described in VPAC2^−/− mice impaired circadian rhythm, reduced food intake, and altered metabolism. To better define the effects of VPAC1R on body phenotype, energy/glucose homeostasis, and metabolism, we conducted a 12-week study in a VPAC1R null model. Our results reveal that VPAC1^−/− mice experienced significant metabolic alterations during the dark cycle with greater numbers of feeding bouts (p = 0.009), lower Total Energy Expenditure (p = 0.025), VO₂ (p = 0.029), and VCO₂ (p = 0.016); as well as during the light cycle with lower Total Energy Expenditure (p = 0.04), VO₂ (p = 0.044), and VCO₂ (p = 0.029). Furthermore, VPAC1^−/− mice had significantly higher levels of GLP-1 and PYY during fasting, and higher levels of GLP-1, glucagon leptin and PYY during postprandial conditions. In addition, VPAC1^−/− mice had lower levels of glucose at 60′ and 120′, as assessed by insulin tolerance test. In conclusion, this study supports a key role for VPAC1R in the regulation of body glucose/energy homeostasis and metabolism.

The Role of Clinical Proteomics, Lipidomics, and Genomics in the Diagnosis of Alzheimer's Disease

The early diagnosis of Alzheimer’s disease (AD) has become important to the reversal and treatment of neurodegeneration, which may be relevant to premature brain aging that is associated with chronic disease progression. Clinical proteomics allows the detection of various proteins in fluids such as the urine, plasma, and cerebrospinal fluid for the diagnosis of AD. Interest in lipidomics has accelerated with plasma testing for various lipid biomarkers that may with clinical proteomics provide a more reproducible diagnosis for early brain aging that is connected to other chronic diseases. The combination of proteomics with lipidomics may decrease the biological variability between studies and provide reproducible results that detect a community’s susceptibility to AD. The diagnosis of chronic disease associated with AD that now involves genomics may provide increased sensitivity to avoid inadvertent errors related to plasma versus cerebrospinal fluid testing by proteomics and lipidomics that identify new disease biomarkers in body fluids, cells, and tissues. The diagnosis of AD by various plasma biomarkers with clinical proteomics may now require the involvement of lipidomics and genomics to provide interpretation of proteomic results from various laboratories around the world.

Device-based autonomic modulation in arrhythmia patients: the role of vagal nerve stimulation

OPINION STATEMENT

Vagal nerve stimulation (VNS) has shown promise as an adjunctive therapy for management of cardiac arrhythmias by targeting the cardiac parasympathetic nervous system. VNS has been evaluated in the setting of ischemia-driven ventricular arrhythmias and atrial arrhythmias, as well as a treatment option for heart failure. As better understanding of the complexities of the cardiac autonomic nervous system is obtained, vagal nerve stimulation will likely become a powerful tool in the current cardiovascular therapeutic armamentarium.

Major differences in gene expression in human coronary smooth muscle cells after nebivolol or metoprolol treatment

OBJECTIVE

Vascular smooth muscle cells play a pivotal role in all stages of atherogenesis. Targeting their inflammatory and proliferative qualities might therefore inhibit the progression of atherosclerosis. This study aimed to characterize and compare the effects of the beta-receptor antagonists nebivolol and metoprolol on gene expression in human coronary artery smooth muscle cells (hcaSMC).

METHODS AND RESULTS

hcaSMC were incubated with nebivolol or metoprolol (10(-5) mol/l) for 72 h. The downregulated genes are involved in inflammatory processes, oxidative stress and smooth muscle cell proliferation: i.e. downregulated were by nebivolol: interleukin-1alpha, cyclooxygenase-2, tumor-necrosis-factor (TNF)-alpha-induced protein 6, PDGF-A, growth-related oncogenes 2 and 3. Metoprolol increased the expression of interleukin-1alpha, cyclooxygenase-1, TNF-alpha-induced protein 3, heme oxygenase 1 and granulocyte/macrophage-colony-stimulating factor. In addition downregulated was monocyte chemoattractant protein 1 (MCP-1) mRNA by nebivolol. Nebivolol (10(-5) mol/l) reduced the amount of basal NF-kappaB after 48 and 52 h but not metoprolol. In the culture supernatants, MCP-1 concentrations were reduced by nebivolol.

CONCLUSIONS

Nebivolol induced changes in the expression of inflammatory mediators in hcaSMC. These results add to data that suggest specific anti-inflammatory qualities of a beta-blocker of the third generation in comparison to metoprolol.

Mechanisms of vasoactive intestinal peptide-elicited coronary vasodilation in the isolated perfused rat heart

The present study investigated the potential role of vasoactive intestinal peptide (VIP) receptors, VPAC1 and VPAC2, in VIP-elicited coronary vasodilation of the isolated perfused rat heart. Additional studies determined the role of ATP-sensitive (K(ATP)) and voltage-gated K(+) (K(V)) channels in the VIP-elicited coronary vasodilation. Both the selective VPAC1 agonist, K15,R16,L27VIPl-7GRF8-27, and the selective VPAC2 agonist, RO25-1553, decreased coronary vascular resistance (CVR) in a dose-dependent manner, with EC(50) values of 1.67x10(-9)M and 7.11x10(-9)M, respectively (VPAC1 vs VPAC2 agonist, P<0.05). K15,R16,L27VIP1-7GRF8-27 and RO25-1553 maximally reduced CVR by -42+/-4% and -39+/-6% at 1x10(-8) and 3x10(-8)M, respectively. VIP at 1x10(-10)M decreased CVR by -14+/-2% in the absence (vehicle), by -11+/-3% in the presence of the nonselective VIP receptor antagonist VIP10-28 (1x10(-7)M; P>0.05 vs. vehicle) and by only -4+/-2% in the presence of the selective VPAC2 receptor antagonist PACAP6-38 (1x10(-7)M; P<0.05 vs. vehicle). In additional studies, VIP at 1x10(-10)M decreased CVR by -22+/-1% in the absence (control) and by only -10+/-2% in the presence of the nonselective K(+) channel blocker tetrabutylammonium (3x10(-4)M; P<0.05 vs. control). VIP reduced CVR by -4+/-1% in the presence of the K(ATP) channel blocker glibenclamide (3x10(-6)M; P<0.05 vs control) and by -28+/-2% in the presence of the K(V) channel blocker 4-aminopyridine (3x10(-4)M; P>0.05 vs control). Thus, selective VPAC1 and VPAC2 receptor activation in the coronary circulation produces vasodilation and the VIP-elicited coronary vasodilation involves activation of VPAC2 receptors and K(ATP) but not K(V) channels. In addition, VIP10-28 does not effectively block coronary vascular VIP receptors.

An Investigation into the Presence of a Vagal Tachycardia and the Effect of Vasoactive Intestinal Polypeptide on Rat Heart Rate in vitro

The presence of the vagal tachycardia and the effect of vasoactive intestinal polypeptide in the isolated innervated rat atrium were investigated. The right vagus, or cardiac branch, were stimulated at 4, 8, 16 and 32 Hz, pulse duration 1 ms, 20 V, 30 s before atropine and for 1 min after atropine (3 micromol/l), experiments were carried out in the presence of atenolol (4 micromol/l). No significant vagal tachycardia was observed in the presence of atropine, the greatest increase in heart rate was at 16 Hz which was 3+/-1 beats/min (n = 12 rats) (p = 0.052). Baseline heart rates for the control, 226+/-11 beats/min (n = 12 rats) and atropine experiments, 210+/-8 beats/min (n = 12 rats), were not significantly different (p = 0.24). VIP (0.06, 0.12, 0.24 micromol/l) caused a maximum increase of 27+/-13 beats/min (n = 5 rats) after 6 micromol/l VIP which was not significant, two higher concentrations of VIP failed to increase heart rate further. These results show that the vagal tachycardia is not present and that VIP does not cause a significant tachycardia in the rat.