Regulatory Peptides最新文献

Specific methylation of appetite-related genes in leukocytes could serve as a useful biomarker to predict weight regain after an energy restriction program. We aimed to evaluate whether the pre-intervention DNA methylation patterns involved in the epigenetic control of appetite-regulatory genes in leukocytes are associated with the weight regain process. Eighteen men who lost ≥ 5% of body weight after an 8-week nutritional intervention were categorized as “regainers” (≥ 10% weight regain) and “non-regainers” (< 10% weight regain) 32 weeks after stopping dieting. At baseline, leukocytes were isolated and DNA was analyzed for epigenetic methylation patterns of appetite-related gene promoters by MALDI-TOF mass spectrometry. Regainers showed higher methylation levels than non-regainers in proopiomelanocortin (POMC) CpG sites + 136 bp and + 138 bp (fold change from non-regainers = 26%; p = 0.020) and lower methylation of the whole analyzed region of neuropeptide Y (NPY; fold change from non-regainers = − 22%; p = 0.033), as well as of several individual NPY-promoter CpG sites. Importantly, total baseline NPY methylation was associated with weight-loss regain (r = − 0.76; p < 0.001), baseline plasma ghrelin levels (r = 0.60; p = 0.011) and leptin/ghrelin ratio (r = − 0.52; p = 0.046). Lower methylation levels of POMC CpG sites + 136 bp and + 138 bp were associated with success in weight-loss maintenance (odds ratio = 0.042 [95% CI 0.01–0.57]; p = 0.018), whereas lower total methylation levels in NPY promoter were associated with higher risk of weight regain (odds ratio = 14.0 [95% CI 1.13–172]; p = 0.039). Therefore, the study of leukocyte methylation levels reflects a putative epigenetic regulation of NPY and POMC, which might be implicated in the weight regain process and be used as biomarkers for predicting weight regain after dieting.

Endogenous neurokinin and adrenergic mechanisms might co-participate in the pathology of acute myocardial infarction (MI). This study sought to investigate the role of endogenous neurokinin and its relationship with β₁-adrenergic mechanism in the infarction induced arrhythmias.

In 60 min of MI in rats, the contents of substance P (SP), a native agonist of neurokinin 1 receptor (NK1-R), norepinephrine (NE), NK1-R and β1-adrenergic receptor in the myocardium at risk of ischemia were examined and the ventricular arrhythmias were analyzed. The effects of pretreatment with D-SP (152 ng/kg), a specific antagonist of NK1-R, esmolol (10 mg/kg), a specific blocker of β₁-adrenergic receptor, and a combination of the two blockers were studied. The results showed that the overlaps of up-regulation of NE, SP and the increase of ventricular arrhythmias were observed. D-SP exacerbated the episodes and duration of VT & VF by 54% and 104%, respectively (all P < 0.05). Esmolol inhibited the morbidity rate, the episodes and the duration of VT & VF by 66%, 92% and 95%, respectively. Surprisingly, esmolol significantly attenuated the arrhythmogenic effect of D-SP throughout the MI, beyond the time span of esmolol action, during which a significant up-regulation of the NK1-R (by 19%, P < 0.05) was detected.

In conclusion, the findings of this study may indicate an anti-arrhythmic effect of endogenous neurokinin mechanism, through the activation of which, via up-regulation of NK1 receptor, esmolol may exert its anti-arrhythmic action at the early time of acute myocardial infarction.

The primary goal was to determine agonist-specific regulation of CRF_2(a) receptor function. Exposure of human retinoblastoma Y79 cells to selective (UCN2, UCN3 or stresscopins) and non-selective (UCN1 or sauvagine) agonists prominently desensitized CRF_2(a) receptors in a rapid, concentration-dependent manner. A considerably slower rate and smaller magnitude of desensitization developed in response to the weak agonist CRF. CRF₁ receptor desensitization stimulated by CRF, cortagine or stressin1-A had no effect on CRF_2(a) receptor cyclic AMP signaling. Conversely, desensitization of CRF_2(a) receptors by UCN2 or UCN3 did not cross-desensitize Gs-coupled CRF₁ receptor signaling. In transfected HEK293 cells, activation of CRF_2(a) receptors by UCN2, UCN3 or CRF resulted in receptor phosphorylation and internalization proportional to agonist potency. Neither protein kinase A nor casein kinases mediated CRF_2(a) receptor phosphorylation or desensitization. Exposure of HEK293 or U2OS cells to UCN2 or UCN3 (100 nM) produced strong βarrestin2 translocation and colocalization with membrane CRF_2(a) receptors while CRF (1 μM) generated only weak βarrestin2 recruitment. βarrestin2 did not internalize with the receptor, however, indicating that transient CRF_2(a) receptor–arrestin complexes dissociate at or near the cell membrane. Since deletion of the βarrestin2 gene upregulated Gs-coupled CRF_2(a) receptor signaling in MEF cells, a βarrestin2 mechanism restrains Gs-coupled CRF_2(a) receptor signaling activated by urocortins. We further conclude that the rate and extent of homologous CRF_2(a) receptor desensitization are governed by agonist-specific mechanisms affecting GRK phosphorylation, βarrestin2 recruitment, and internalization thereby producing unique signal transduction profiles that differentially affect the stress response.

Objectives

To determine the effects of lixisenatide, a new once-daily (QD) glucagon-like peptide-1 receptor agonist, on postprandial glucose (PPG) and gastric emptying, and the relationship between these effects in patients with type 2 diabetes mellitus (T2DM).

Methods

Data were obtained from a randomized, double-blind, placebo-controlled, parallel-group study with treatment duration of 28 days in patients with T2DM receiving ≤ 2 oral antidiabetic drugs. Lixisenatide was injected subcutaneously using an ascending dose range (5–20 μg) increased every fifth day in increments of 2.5 μg. Blood glucose was determined before and after three standardized meals (breakfast, lunch, and dinner). Gastric emptying of the standardized breakfast was determined by a ¹³C-octanoic acid breath test at baseline (Day−1) and at Day 28.

Results

A total of 21 and 22 patients were randomized to lixisenatide 20 μg QD and placebo, respectively. With lixisenatide 20 μg QD, there was a reduction in PPG when compared with placebo after breakfast (p < 0.0001), lunch (p < 0.001) and dinner (p < 0.05). Hence, lixisenatide 20 μg administered in the morning exhibited a pharmacodynamic effect on blood glucose throughout the day. Gastric emptying (50% emptying time) increased substantially from baseline with lixisenatide 20 μg QD, but not with placebo (change from baseline ± SD: − 24.1 ± 133.1 min for placebo and 211.5 ± 278.5 min for lixisenatide; p < 0.01). There was an inverse relationship between PPG area under the curve after breakfast and gastric emptying with lixisenatide 20 μg QD (n = 17, r² = 0.51, p < 0.05), but not with placebo.

Conclusions

In this study, lixisenatide at a dose of 20 μg QD reduced postprandial glycemic excursions in patients with T2DM, possibly as a result of sustained slowing of gastric emptying.

Angiotensin (Ang) II plays a vital role in vascular smooth muscle cell (VSMC) growth and proliferation. Angiotensin-converting enzyme 2 (ACE2) is a specific Ang II-degrading enzyme but its role in VSMC proliferation remains largely unknown. We hypothesized that ACE2 might suppress Ang II-mediated oxidative stress and VSMC proliferation. Human umbilical artery smooth muscle cells (HUASMCs) were pretreated with Ang II (100 nM) for 6 h and 24 h, respectively. Exposure to Ang II resulted in significant increases in suppressor of cytokine signaling 3 (SOCS3) expression and phosphorylation levels of JAK2, STAT3 and ERK1/2 linked with elevated superoxide production and cell proliferation in HUASMCs. These changes were strikingly prevented by administration of ERK1/2 inhibitor PD98059 (10 μM) and JAK/STAT inhibitor WP1066 (5 μM) but were largely aggravated by ACE2 inhibitor DX600 (0.5 μM). More importantly, treatment with human recombinant ACE2 (hrACE2; 1 mg/ml) dramatically prevented Ang II-mediated SOCS3 expression and the JAK2–STAT3 and ERK1/2 signaling, and resulted in attenuation of superoxide production and cell proliferation in HUASMCs. Intriguingly, downregulation of profilin-1 with profilin-1 siRNA (50 nM) was able to abolish Ang II-induced upregulations of profilin-1 expression, ERK1/2 phosphorylation and superoxide production with attenuation of VSMC proliferation. In conclusion, treatment with hrACE2 prevents Ang II-mediated activation of the JAK2/STAT3/SOCS3 and profilin-1/MAPK signaling pathways, contributing to attenuation of superoxide generation and cell proliferation in HUASMCs, suggesting a protective mechanism of ACE2 against Ang II-mediated oxidative stress and VSMC proliferation. ACE2 may represent a potential candidate to prevent and treat vascular disorders.

Colonic dysmotility occurs in diabetes and the patients exhibit diarrhea or constipation. The pathogenetic mechanisms underlying colonic dysmotility in diabetic patients remain poorly understood. The effects of β-arrestin2 on colonic contraction in diabetic rats were investigated for the first time. Male SD rats were treated with a single intraperitoneally injected dose of streptozotocin, and those displaying sustained high blood glucose were selected as diabetes mellitus models. Longitudinal muscle strips of the distal colon were prepared to monitor contraction of the colon in vitro. Expression of β-arrestin2 was investigated by Western blot analysis. Anti-β-arrestin2 antibody had no direct effect on the contraction of distal colonic strips in both normal and diabetic rats. Carbachol-induced contractions of distal colonic strips were higher in diabetic rats than in normal rats. Anti-β-arrestin2 antibody partly blocked carbachol-induced increases of distal colonic strips in diabetic rats. The expression level of β-arrestin2 protein in the colon was higher in diabetic rats than in normal rats. These results suggest that β-arrestin2 is involved in the increase of distal colonic contraction in diabetic rats.

The intestinal hormone cholecystokinin (CCK) delays gastric emptying and inhibits food intake by actions on vagal afferent neurons. Recent studies suggest plasminogen activator inhibitor (PAI)-1 suppresses the effect of CCK on food intake. In this study we asked whether PAI-1 also modulated CCK effects on gastric emptying. Five minute gastric emptying of liquid test meals was studied in conscious wild type mice (C57BL/6) and in transgenic mice over-expressing PAI-1 in gastric parietal cells (PAI-1H/Kβ mice), or null for PAI-1. The effects of exogenous PAI-1 and CCK8s on gastric emptying were studied after ip administration. Intragastric peptone delayed gastric emptying in C57BL/6 mice by a mechanism sensitive to the CCK-1 receptor antagonist lorglumide. Peptone did not delay gastric emptying in PAI-1-H/Kβ mice. Exogenous CCK delayed gastric emptying of a control test meal in C57BL/6 mice and this was attenuated by administration of PAI-1; exogenous CCK had no effect on emptying in PAI-1-H/Kβ mice. Prior administration of gastrin to increase gastric PAI-1 inhibited CCK-dependent effects on gastric emptying in C57BL/6 mice but not in PAI-1 null mice. Thus, both endogenous and exogenous PAI-1 inhibit the effects of CCK (whether exogenous or endogenous) on gastric emptying. The data are compatible with emerging evidence that gastric PAI-1 modulates vagal effects of CCK.

The aim of the present study was to determine if insulin is able to modulate the pressor response to intracerebroventricularly administered angiotensin II in insulin resistant fructose overloaded rats.

Male Sprague-Dawley rats were divided into two groups: 1) Control group (C) with tap water to drink for 6 weeks (n = 36); and 2) fructose treated (F), with fructose solution (10% w/v) to drink for 6 weeks (n = 36). On the day of the experiment, anesthetized male C and F rats were intracerebroventricularly infused with insulin (12 mU/h, n = 15) or Ringer's solution as vehicle (n = 15) for 2 h. Immediately, changes in mean arterial pressure (MAP) in response to an intracerebroventricular subpressor dose of angiotensin II (5 pmol, n = 10) or vehicle (n = 5) were measured for 10 min. Then, hypothalami were removed and Akt and ERK1/2 phosphorylation levels were determined. In a subset of C (n = 10) and F (n = 20) animals, PD98059 (p44/42 MAPK inhibitor) or vehicle was administered intracerebroventricularly at a flow rate of 5 μl/min for 1 min. Ten minutes later, insulin (12 mU/h, n = 5 for each group) or vehicle (Ringer's solution, only in the F group, n = 5) was perfused for 2 h at a flow rate of 4 μl/h, and cardiovascular parameters were measured every 15 min. Immediately, changes in MAP and HR in response to a subpressor dose of Ang II (5 pmol/2 μl) were evaluated for 10 min (n = 5 for each group). In other subset of animals (n = 6 for each group), AT1 and AT2 hypothalamic receptor levels were measured by Western blotting.

Intracerebroventricular insulin pre-treatment increased the pressor response to angiotensin II in C rats. In F rats (with or without insulin pretreatment), the pressor response to angiotensin II was higher than that in vehicle pre-treated C animals, but similar to that observed in C after insulin infusion. In C rats phospho-ERK 1/2 hypothalamic levels significantly increased after angiotensin II injection in insulin pretreated animals compared to vehicle pre-treated rats, suggesting that MAPK activation might be involved in insulin potentiation of blood pressure response to angiotensin II in the brain. Phospho-ERK 1/2 hypothalamic levels were significantly increased in vehicle treated F rats compared to C, suggesting that basal MAPK activation might play a role in the enhanced response to angiotensin II observed in these animals. Finally, in F rats, either after vehicle or insulin infusion, angiotensin II injection was associated with a similar increase in phospho-ERK 1/2 hypothalamic levels, comparable