Peptides (v.67, #C)

Peptidic tools applied to redirect alternative splicing events by Martínez-Montiel Nancy; Rosas-Murrieta Nora; Martínez-Contreras Rebeca (1-11).
Peptides are versatile and attractive biomolecules that can be applied to modulate genetic mechanisms like alternative splicing. In this process, a single transcript yields different mature RNAs leading to the production of protein isoforms with diverse or even antagonistic functions. During splicing events, errors can be caused either by mutations present in the genome or by defects or imbalances in regulatory protein factors. In any case, defects in alternative splicing have been related to several genetic diseases including muscular dystrophy, Alzheimer's disease and cancer from almost every origin. One of the most effective approaches to redirect alternative splicing events has been to attach cell-penetrating peptides to oligonucleotides that can modulate a single splicing event and restore correct gene expression. Here, we summarize how natural existing and bioengineered peptides have been applied over the last few years to regulate alternative splicing and genetic expression. Under different genetic and cellular backgrounds, peptides have been shown to function as potent vehicles for splice correction, and their therapeutic benefits have reached clinical trials and patenting stages, emphasizing the use of regulatory peptides as an exciting therapeutic tool for the treatment of different genetic diseases.
Keywords: Splicing; mRNA; Mutations; Cell-penetrating peptide; Peptide nucleic acid;

Densities of rectal peptide YY and somatostatin cells as biomarkers for the diagnosis of irritable bowel syndrome by Magdy El-Salhy; Jan Gunnar Hatlebakk; Odd Helge Gilja; Trygve Hausken (12-19).
Irritable bowel syndrome (IBS) is a common chronic disorder. IBS diagnosis is a diagnosis of exclusion since there are no blood tests, radiological or endoscopic examinations for this disorder. Although several attempts have been made to develop a symptoms-based diagnosis, such systems are not widely used in clinics. Several tests and examinations measuring pathological findings in IBS have been considered for the diagnosis of IBS, but none of them has proved useful as a biomarker. Abnormalities in the cell densities of rectal peptide YY (PYY) and somatostatin cells have been reported in IBS patients. The aim of the present study was to determine the utility of these abnormalities as biomarkers for the diagnosis of IBS. Patients with IBS established according to Rome III criteria (n  = 101) were included in this study (71 females and 30 males with a mean age of 35 years; range 18–61 years), and 62 healthy subjects (38 females and 24 males with a mean age of 41 years; range 18–65 years) were recruited as controls. Both the patients and controls underwent colonoscopy during which rectal biopsy samples were taken. The tissue samples were immunostained for PYY and somatostatin, and the number of stained cells was quantified relative to both the area of epithelial cells and per microscopic field. The density of PYY cells was significantly lower in IBS patients than in the healthy controls (P  < 0.0001); receiver operator characteristic (ROC) analysis revealed an area under the ROC curve (AUC) of 0.99. The somatostatin cell density in IBS patients was higher than in the controls (P  < 0.0001); ROC analysis revealed an AUC of 0.86. The densities of the rectal PYY and somatostatin cells appear to be clinically effective biomarkers for IBS. Furthermore, measurement of these parameters is inexpensive, rapid and does not require considerable experience or sophisticated equipment.
Keywords: Biomarkers; Diagnosis; Irritable bowel syndrome; Immunohistochemistry; PYY; Somatostatin;

The glucagon-like peptide 2 receptor is expressed in enteric neurons and not in the epithelium of the intestine by Jens Pedersen; Nis B. Pedersen; Sophie W. Brix; Kaare Villum Grunddal; Mette M. Rosenkilde; Bolette Hartmann; Cathrine Ørskov; Steen S. Poulsen; Jens J. Holst (20-28).
Glucagon-like peptide 2 (GLP-2) is a potent intestinotrophic growth factor with therapeutic potential in the treatment of intestinal deficiencies. It has recently been approved for the treatment of short bowel syndrome. The effects of GLP-2 are mediated by specific binding of the hormone to the GLP-2 receptor (GLP-2R) which was cloned in 1999. However, consensus about the exact receptor localization in the intestine has never been established.By physical, chemical and enzymatic tissue fragmentation, we were able to divide rat jejunum into different compartments consisting of: (1) epithelium alone, (2) mucosa with lamina propria and epithelium, (3) the external muscle coat including myenteric plexus, (4) a compartment enriched for the myenteric plexus and (5) intestine without epithelium. Expression of Glp2r; chromogranin A; tubulin, beta 3; actin, gamma 2, smooth muscle, enteric and glial fibrillary acidic protein in these isolated tissue fractions was quantified with qRT-PCR. Expression of the Glp2r was confined to compartments containing enteric neurons and receptor expression was absent in the epithelium.Our findings provide evidence for the expression of the GLP-2R in intestinal compartments rich in enteric neurons and, importantly they exclude significant expression in the epithelium of rat jejunal mucosa.
Keywords: Intestinotrophic; GLP-2; GLP-2R; RT-PCR; Enteric neurons;

It is now well established that peptides that were first identified on the basis of their ability to inhibit growth of bacteria and fungi are multifunctional and so are more informatively described as host-defense peptides. In some cases, their role in protecting the organism against pathogenic microorganisms, although of importance, may be secondary. A previous article in the journal (Peptides 2014; 57:67–77) assessed the potential of peptides present in the skin secretions of frogs for development into anticancer, antiviral, immunomodulatory and antidiabetic drugs. This review aims to extend the scope of this earlier article by focusing upon therapeutic applications of host-defense peptides present in skin secretions and/or skin extracts of species belonging to other vertebrate classes (Agnatha, Elasmobranchii, Teleostei, Reptilia, and Mammalia as represented by the human) that supplement their potential role as anti-infectives for use against multidrug-resistant microorganisms.
Keywords: Skin peptides; Antimicrobial; Anticancer; Antiviral; Immunomodulatory;

Effect of enalapril maleate on ghrelin levels in metabolic syndrome in rats by Bilge Aygen; Mehmet Kucuksu; Suleyman Aydin; Ibrahim Hanifi Ozercan (39-44).
We have explored how enalapril affects ghrelin levels in serum and renal tissues of rats with fructose-induced MetS, using 5-week-old Wistar albino male rats weighing 220 ± 20 g. They divided into 5 groups: (i) control (CT), no fructose supplement fed on standard rat pellet and tap water for 60 days, (ii) metabolic syndrome (MetS) fed with 10% fructose for 60 days, (iii) rats after metabolic syndrome developed treated with enalapril over 30 days (MetS + E30), (iv) rats in which only enalapril was administered for 60 days (E60), and (v) MetS-treated with enalapril for 60 days (MetS + E60). Enalapril maleate was given at 20 mg/kg per day by gavage. Fasting serum insulin, uric acid, triglyceride, low-density lipoprotein cholesterol and total cholesterol levels were significantly higher, and the amount of high density lipoprotein cholesterol, and acylated and desacyl ghrelin levels was significantly lower in the MetS groups. Ghrelins were significantly lower in all 3 groups, which were administered enalapril than that of MetS and the control group. Immunohistochemical staining showed that the density of ghrelin was parallel to the serum levels of the peptide. Ghrelin immunoreactivity in the kidneys was of moderate density in the distal and collecting tubules, mild density in the proximal tubule and glomeruli, whereas the density decreased in the MetS group and other enalapril-treated groups. In conclusion, ghrelin levels in MetS groups were significantly lower than control group, and thus Enalapril treatment improves components of MetS and has direct effects on serum ghrelin levels that are independent of MetS.
Keywords: Metabolic syndrome; Ghrelin; Enalapril;

GRPR-selective PET imaging of prostate cancer using [18F]-lanthionine-bombesin analogs by G. Carlucci; A. Kuipers; H.J.K. Ananias; D. de Paula Faria; R.A.J.O. Dierckx; W. Helfrich; R. Rink; G.N. Moll; I.J. de Jong; P.H. Elsinga (45-54).
The gastrin-releasing peptide receptor (GRPR) is overexpressed in a variety of human malignancies, including prostate cancer. Bombesin (BBN) is a 14 amino acids peptide that selectively binds to GRPR. In this study, we developed two novel Al18F-labeled lanthionine-stabilized BBN analogs, designated Al18F-NOTA-4,7-lanthionine-BBN and Al18F-NOTA-2,6-lanthionine-BBN, for positron emission tomography (PET) imaging of GRPR expression using xenograft prostate cancer models. (Methyl)lanthionine-stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN analogs were conjugated with a NOTA chelator and radiolabeled with Al18F using the aluminum fluoride strategy. Al18F-NOTA-4,7-lanthionine-BBN and Al18F-NOTA-2,6-lanthionine-BBN was labeled with Al18F with good radiochemical yield and specific activity > 30 GBq/μmol for both radiotracers. The log  D values measured for Al18F-NOTA-4,7-lanthionine-BBN and Al18F-NOTA-2,6-lanthionine-BBN were −2.14 ± 0.14 and −2.34 ± 0.15, respectively. In athymic nude PC-3 xenografts, at 120 min post injection (p.i.), the uptake of Al18F-NOTA-4,7-lanthionine-BBN and Al18F-NOTA-2,6-lanthionine-BBN in prostate cancer (PC-3) mouse models was 0.82 ± 0.23% ID/g and 1.40 ± 0.81% ID/g, respectively. An excess of unlabeled ɛ-aminocaproic acid-BBN(7–14) (300-fold) was co-injected to assess GRPR binding specificity. Tumor uptake of Al18F-NOTA-4,7-lanthionine-BBN and Al18F-NOTA-2,6-lanthionine-BBN in PC-3 tumors was evaluated by microPET (μPET) imaging at 30, 60 and 120 min p.i. Blocking studies showed decreased uptake in PC-3 bearing mice. Stabilized 4,7-lanthionine-BBN and 2,6-lanthionine-BBN peptides were rapidly and successfully labeled with 18F. Both tracers may have potential for GRPR-positive tumor imaging.
Keywords: GRPR; Bombesin; Al18F; PC-3; PET; Stability;

Cannabinoid receptor 1 and acute resistance exercise – In vivo and in vitro studies in human skeletal muscle by Satu Pekkala; Petri Wiklund; Juha J. Hulmi; Eija Pöllänen; Varpu Marjomäki; Eveliina Munukka; Philippe Pierre; Vincent Mouly; Antti Mero; Markku Alén; Sulin Cheng (55-63).
This study aimed to determine whether Cannabinoid receptor 1 (CB1) is involved in mammalian target of rapamycin (mTOR) signaling and skeletal muscle protein synthesis.This study used human vastus lateralis skeletal muscle biopsies obtained before and after a resistance exercise (RE) bout in young men (n  = 18). The signaling mechanisms were studied in vitro in human myotubes. Protein expression was determined by Western blot and confocal microscopy, and gene expression by quantitative PCR. Protein synthesis was measured in vitro using puromycin-based SuNSET technique.In human skeletal muscle, an anabolic stimulus in the form of RE down-regulated CB1 expression. The negative change in CB1 expression was associated with increased phosphorylation of mTOR signaling proteins. In vitro, CB1 antagonist AM251 induced phosphorylation of mTOR downstream targets, ribosomal protein S6 kinase (S6K1), S6 and eukaryotic initiation factor 4E binding protein (4E-BP1) in human myotubes. These effects were ERK1/2-dependent and insensitive to mTOR inhibitor, rapamycin. Compared to AM251 treatment alone, inhibition of ERK1/2 by UO126 in the presence of AM251 decreased phosphorylation of S6K1, S6 and and 4E-BP1 at Thr37/46. AM251 increased protein synthesis in cultured human myotubes, which was not rapamycin-sensitive but was ERK1/2-dependent.Our results indicate that RE down-regulates CB1 expression. Inhibition of CB1 signaling increases skeletal muscle anabolic signaling down-stream of mTOR and protein synthesis through ERK1/2. Our study may provide base for the development of CB1-blocking drugs to treat or prevent muscle wasting.
Keywords: Cannabinoid receptor 1; mTOR signaling; Protein synthesis; Resistance exercise; Skeletal muscle;

Elastin peptides, also known as elastin-derived peptides or elastokines, are soluble polypeptides in blood and tissue. The blood levels of elastin peptides are usually low but can increase during cardiovascular diseases, such as atherosclerosis, aortic aneurysm and diabetes with vascular complications. Generally, elastin peptides are derived from the degradation of insoluble elastic polymers. The biological activities of elastin peptides are bidirectional, e.g., a pro-inflammatory effect on monocyte migration induction vs. a protective effect on vasodilation promotion. However, recent in vivo studies have demonstrated that elastin peptides promote the formation of atherosclerotic plaques in hypercholesterolemic mice and induce hyperglycemia and elevations in plasma lipid levels in fasted mice. More important, the detrimental effects induced by elastin peptides can be largely inhibited by genetic or pharmacological blockade of the elastin receptor complex or by neutralization of an antibody against elastin peptides. These studies indicate new therapeutic strategies for the treatment of cardiovascular diseases by targeting elastin peptide metabolism. Therefore, the goal of this review is to summarize current knowledge about elastin peptides relevant to cardiovascular pathologies to further delineate their potential application in cardiovascular disease.
Keywords: Elastin; Peptide; Cardiovascular diseases;

Glucagon was discovered in 1922 as a hyperglycemic factor in the pancreas. During its early history up to 1970, glucagon was shown to increase circulating glucose through stimulating glycogenolysis in the liver. It was also shown to be a constituent of islet non-β cells and to signal through G protein coupled receptors and cyclic AMP. Furthermore, its chemical characteristics, including amino acid sequence, and its processing from the preproglucagon gene had been established. During the modern research during the last 40 years, glucagon has been established as a key hormone in the regulation of glucose homeostasis, including a key role for the glucose counterregulation to hypoglycemia and for development of type 2 diabetes, and today glucagon is a potential target for treatment of the disease. Glucagon has also been shown to be a key factor beyond glucose control and involved in many processes. For the coming, future research, studies will be focused on α-cell biology beyond glucagon, hyperglucagonemia in other conditions than diabetes, its involvement in the regulation of body weight and energy expenditure and the potential of glucagon as a target for other diseases than type 2 diabetes, such as type 1 diabetes and obesity. This review summarizes the more than 90 years history of this important hormone as well as discusses potential future research regarding glucagon.
Keywords: Glucagon; Glucose; Diabetes; History;