Glucagon-like peptide-1 (GLP-1) increases in plasma and colon tissue prior to estrus and circulating levels change with increasing age in reproductively competent Wistar rats

There is a well-documented association between cyclic changes to food intake and the changing ovarian hormone levels of the reproductive cycle in female mammals. Limited research on appetite-controlling gastrointestinal peptides has taken place in females, simply because regular reproductive changes in steroid hormones present additional experimental factors to account for. This study focussed directly on the roles that gastrointestinal-secreted peptides may have in these reported, naturally occurring, changes to food intake during the rodent estrous cycle and aimed to determine whether peripheral changes occurred in the anorexigenic (appetite-reducing) hormones peptide-YY (PYY) and glucagon-like peptide-1 (GLP-1) in female Wistar rats (32–44 weeks of age). Total forms of each peptide were measured in matched fed and fasted plasma and descending colon tissue samples for each animal during the dark (feeding) phase. PYY concentrations did not significantly change between defined cycle stages, in either plasma or tissue samples. GLP-1 concentrations in fed plasma and descending colon tissue were significantly increased during proestrus, just prior to a significant reduction in fasted stomach contents at estrus, suggesting increased satiety and reduced food intake at this stage of the cycle. Increased proestrus GLP-1 concentrations could contribute to the reported reduction in food intake during estrus and may also have biological importance in providing the optimal nutritional and metabolic environment for gametes at the potential point of conception. Additional analysis of the findings demonstrated significant interactions of ovarian cycle stage and fed/fasted status with age on GLP-1, but not PYY plasma concentrations. Slightly older females had reduced fed plasma GLP-1 suggesting that a relaxation of regulatory control of this incretin hormone may also take place with increasing age in reproductively competent females.     

促胰岛素释放肽和GLP-1类似物研究进展

近年来,从细菌、真菌等低等生物和爬行类、哺乳类等高等动物的体内,都发现存在着结构和功能相关、相似的促胰岛素释放肽或GLP-1类似物.目前国内外研究都在密切关注胰高血糖素样肽-1(glucagonl-ikepeptide-1,G LP-1)和G LP-1类似物等胰高血糖素家族肽,对其进行基因工程高效表达或通过组合化学方法修饰、改造,从而设计治疗Ⅱ型糖尿病的多肽类药物.但是,从天然生物体内,尤其是最近从两栖类动物皮肤分泌液中和响尾蛇毒素中发现了大量能稳定促进胰岛素释放的生物活性肽,却还没有受到足够的重视,它们将很可能为筛选和开发出安全、高效、半衰期长的治疗Ⅱ型糖尿病新药物提供全新的思路和广阔的前景.     

Preparation and anti-osteoporotic activities in vivo of phosphorylated peptides from Antarctic krill (Euphausia superba)

Antarctic krill (Euphausia superba) protein serves as a novel sustainable protein source for human. Krill protein isolate was phosphorylated by the dry-heating method with sodium pyrophosphate. Phosphorylated peptides from Antarctic krill (PP-AKP) were obtained from phosphorylated protein through tryptic hydrolysis. Two types of phosphate bonds were introduced by phosphorylation, i.e. PO and PO bonds. The anti-osteoporotic activities of PP-AKP at two doses (400 and 800 mg/kg body weight) were investigated with an osteoporotic rat model, which was established with bilateral ovariectomy surgery. Different doses of PP-AKP were given intraperitoneal injections to rats once a day with alendronate as a positive control. Phosphorylated peptides from Antarctic krill dose-dependently preserved bone mineral density in osteoporotic rats by increasing the degree of bone mineralization. Both trabecular and cortical bone strength in osteoporotic rats was significantly improved with PP-AKP treatment. The mechanism by which PP-AKP augmented bone mineral density and bone strength was relation to the reduction in osteoclast-mediated bone remodeling, as was supported by the decrease in bone resorption markers. Phosphorylated peptides from Antarctic krill could be developed as functional food or nutritional supplements.     

Use of biochemical markers to monitor changes in bone turnover in cynomolgus monkeys

The ovariectomized old cynomolgus monkey is a recognized model of human osteoporosis, and the same species can be used for the assessment of the efficacy and potential toxicity of agents intended to prevent or treat osteoporosis. Several assays have been developed that can measure the same biochemical markers of bone turnover as are used in human patients for the diagnosis and treatment follow-up of bone-related diseases, including osteoporosis. The aim of the present study was to describe the results obtained with these assays in normal control monkeys, their variations with age and sex, and their sensitivity in monitoring the bone turnover induced by ovariectomy in old skeletally mature cynomolgus monkeys. Seven old cynomolgus monkeys were bilaterally ovariectomized and 13 age-matched monkeys were sham-operated. Bone mineral density and biochemical markers were measured before and at regular intervals after surgery for up to 20 months. Total alkaline phosphatase (total ALP), bone-specific alkaline phosphatase isoenzyme (bone ALP) and osteocalcin (OC) were highly correlated to the decrease in bone mineral density (BMD) induced by ovariectomy. Deoxypyridinoline (DPD) measured by enzyme-linked immunoassay was insensitive to the bone resorption induced by ovariectomy, but cross-linked N-telopeptide (NTX-I) was higher in ovariectomized monkeys than in control monkeys. These results demonstrate that reliable biochemical parameters are available to adequately monitor and provide insight into osteoclastic bone resorption and osteoblastic bone formation, the two components of bone turnover in this animal model, and can thus be used to assess the efficacy and toxicity of potential therapeutic agents.     

Lamprey proglucagon and the origin of glucagon-like peptides.

We characterized two proglucagon cDNAs from the intestine of the sea lamprey Petromyzon marinus. As in other vertebrates, sea lamprey proglucagon genes encode three glucagon-like sequences, glucagon, and glucagon-like peptides 1 and 2 (GLP-1 and GLP-2). This observation indicates that all three glucagon-like sequences encoded by the proglucagon gene originated prior to the divergence of jawed and jawless vertebrates. Estimates of the rates of evolution for the glucagon-like sequences suggest that glucagon originated first, about 1 billion years ago, while GLP-1 and GLP-2 diverged from each other about 700 MYA. The two sea lamprey intestinal proglucagon cDNAs have differing coding potential. Proglucagon I cDNA encodes the previously characterized glucagon and the glucagon-like peptide GLP-1, while proglucagon II cDNA encodes a predicted GLP-2 and, possibly, a glucagon. The existence of two proglucagon cDNAs which differ with regard to their potential to encode glucagon-like peptides suggests that the lamprey may use differential gene expression as a third mechanism, in addition to alternative proteolytic processing and mRNA splicing, to regulate the production of proglucagon-derived peptides.     

Design of a long acting peptide functioning as both a glucagon-like peptide-1 receptor agonist and a glucagon receptor antagonist

The closely related peptides glucagon-like peptide (GLP-1) and glucagon have opposing effects on blood glucose. GLP-1 induces glucose-dependent insulin secretion in the pancreas, whereas glucagon stimulates gluconeogenesis and glycogenolysis in the liver. The identification of a hybrid peptide acting as both a GLP-1 agonist and a glucagon antagonist would provide a novel approach for the treatment of type 2 diabetes. Toward this end a series of hybrid peptides made up of glucagon and either GLP-1 or exendin-4, a GLP-1 agonist, was engineered. Several peptides that bind to both the GLP-1 and glucagon receptors were identified. The presence of glucagon sequence at the N terminus removed the dipeptidylpeptidase IV cleavage site and increased plasma stability compared with GLP-1. Targeted mutations were incorporated into the optimal dual-receptor binding peptide to identify a peptide with the highly novel property of functioning as both a GLP-1 receptor agonist and a glucagon receptor antagonist. To overcome the short half-life of this mutant peptide in vivo, while retaining dual GLP-1 agonist and glucagon antagonist activities, site-specific attachment of long chained polyethylene glycol (PEGylation) was pursued. PEGylation at the C terminus retained the in vitro activities of the peptide while dramatically prolonging the duration of action in vivo. Thus, we have generated a novel dual-acting peptide with potential for development as a therapeutic for type 2 diabetes.     

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure–activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999–2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.     

Enteral bile acid treatment improves parenteral nutrition-related liver disease and intestinal mucosal atrophy in neonatal pigs

Total parenteral nutrition (TPN) is essential for patients with impaired gut function but leads to parenteral nutrition-associated liver disease (PNALD). TPN disrupts the normal enterohepatic circulation of bile acids, and we hypothesized that it would decrease intestinal expression of the newly described metabolic hormone fibroblast growth factor-19 (FGF19) and also glucagon-like peptides-1 and -2 (GLP-1 and GLP-2). We tested the effects of restoring bile acids by treating a neonatal piglet PNALD model with chenodeoxycholic acid (CDCA). Neonatal pigs received enteral feeding (EN), TPN, or TPN + CDCA for 14 days, and responses were assessed by serum markers, histology, and levels of key regulatory peptides. Cholestasis and steatosis were demonstrated in the TPN group relative to EN controls by elevated levels of serum total and direct bilirubin and also bile acids and liver triglyceride (TG) content. CDCA treatment improved direct bilirubin levels by almost fourfold compared with the TPN group and also normalized serum bile acids and liver TG. FGF19, GLP-1, and GLP-2 were decreased in plasma of the TPN group compared with the EN group but were all induced by CDCA treatment. Intestinal mucosal growth marked by weight and villus/crypt ratio was significantly reduced in the TPN group compared with the EN group, and CDCA treatment increased both parameters. These results suggest that decreased circulating FGF19 during TPN may contribute to PNALD. Moreover, we show that enteral CDCA not only resolves PNALD but acts as a potent intestinal trophic agent and secretagogue for GLP-2.     

Exendin-4 exerts osteogenic actions in insulin-resistant and type 2 diabetic states

Poor control of glucose homeostasis accounts for diabetes-related bone loss. Incretins – GLP-1 and GIP – have been proposed to affect bone turnover. GLP-1, apart from its anti-diabetic and other actions, has shown to exert a bone anabolic effect in streptozotocin-induced type 2 diabetic (T2D) and fructose-induced insulin-resistant (IR) rats. Exendin-4 (Ex-4), a peptide of non-mammalian nature, is sharing with GLP-1 part of its structural sequence, and also several glucoregulatory effects in mammals in an even more efficient manner. We have explored the effect of continuous administration (3 days by osmotic pump) of Ex-4 or saline (control) on bone turnover factors and bone structure in T2D and IR rats, compared to N, and the possible interaction of Ex-4 with the Wnt signalling pathway. Blood was taken before and after treatment for plasma measurements; tibiae and femurs were collected for gene expression of bone markers (RT-PCR) and structure (µCT) analysis; we also measured the mRNA levels of LRP5 – an activator of the Wnt pathway – and those of DKK1 and sclerostin (SOST) — both blockers of LRP5 activity. Compared to N-control, plasma glucose and insulin were respectively higher and lower in T2D; osteocalcin (OC) and tartrate-resistant alkaline phosphatase 5b (TRAP5b) were lower; after Ex-4, these turnover markers were further reduced in T2D and IR, while TRAP5b increased in N. Bone OC, osteoprogeterin (OPG) and receptor activator of NF-kB ligand (RANKL) mRNA were lower in T2D and IR; Ex-4 increased OC in all groups and OPG in N and IR, reduced RANKL in N and T2D but increased it in IR; the LRP5/DKK1 and LRP5/SOST mRNA ratios were similarly decreased in T2D, but in IR, the latter ratio was reduced while the former was increased; after Ex-4, both ratios augmented in N, and that of LRP5/DKK1 tended to normalize in T2D and IR. In conclusion, Ex-4 exerts osteogenis effects in T2D and IR models, and interacts with the Wnt pathway to promote bone formation.     

Glucagon-like peptides 1 and 2 in health and disease: A review

The gut derived peptides, glucagon-like peptides 1 and 2 (GLP-1 and GLP-2), are secreted following nutrient ingestion. GLP-1 and another gut peptide, glucose-dependent insulinotropic polypeptide (GIP) are collectively referred to as ‘incretin’ hormones, and play an important role in glucose homeostasis. Incretin secretion shares a complex interdependent relationship with both postprandial glycemia and the rate of gastric emptying. GLP-1 based therapies are now well established in the management of type 2 diabetes, while recent literature has suggested potential applications to treat obesity and protect against cardiovascular and neurological disease. The mechanism of action of GLP-2 is not well understood, but it shows promise as an intestinotropic agent.     

Structural Characterization by Affinity Cross-Linking of Glucagon-Like Peptide-1(7–36)Amide Receptor in Rat Brain

Abstract: Specific binding of glucagon-like peptide (GLP)-1(7–36)amide was detected in several rat brain areas, with the highest values being found in hypothalamic nuclei and the nucleus of the solitary tract. In hypothalamus and brainstem homogenate binding of ¹²⁵I-GLP-1(7–36)amide was time, temperature, and protein content dependent and was inhibited by unlabeled proglucagon-derived peptides. The rank order of potency was GLP-1(7–36)amide ? GLP-1(1–36)amide > GLP-1(1–37) ? GLP-2 > glucagon. Scatchard analysis of the steady-state binding data was consistent with the presence of both high- and low-affinity binding sites in hypothalamus and brainstem. Brain ¹²⁵I-GLP-1(7–36)amide-binding protein complexes were covalently cross-linked using disuccinimidyl suberate and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A single radiolabeled band of M_r 56,000 identified in both hypothalamus and brainstem homogenates was unaffected by reducing agents. An excess of unlabeled GLP-1(7–36)amide abolished the band labeling, whereas glucagon had no effect. Other unlabeled GLPs inhibited M_r 56,000 complex labeling with the following order of potency: GLP-1(1–36)amide > GLP-1(1–37) > GLP-2. The binding of ¹²⁵I-GLP-1(7–36)amide and the intensity of the cross-linked band were similarly inhibited in a dose-response manner by increasing concentrations of unlabeled GLP-1(7–36)amide. Covalent M_r 56,000 ¹²⁵I-GLP-1(7–36)amide-binding protein complexes solubilized by Triton X-100 were adsorbed onto wheat germ agglutinin. Our results suggest that the GLP-1(7–36)amide receptor in rat brain is a glycoprotein with a single binding subunit that has a greater molecular weight but binding features and ligand specificity similar to those of its peripheral tissue counterparts.     

Biological activities of glucagon-like peptide-1 analogues in vitro and in vivo

Studies support a role for glucagon-like peptide 1 (GLP-1) as a potential treatment for diabetes. However, since GLP-1 is rapidly degraded in the circulation by cleavage at Ala(2), its clinical application is limited. Hence, understanding the structure-activity of GLP-1 may lead to the development of more stable and potent analogues. In this study, we investigated GLP-1 analogues including those with N-, C-, and midchain modifications and a series of secretin-class chimeric peptides. Peptides were analyzed in CHO cells expressing the hGLP-1 receptor (R7 cells), and in vivo oral glucose tolerance tests (OGTTs) were performed after injection of the peptides in normal and diabetic (db/db) mice. [D-Ala(2)]GLP-1 and [Gly(2)]GLP-1 showed normal or relatively lower receptor binding and cAMP activation but exerted markedly enhanced abilities to reduce the glycemic response to an OGTT in vivo. Improved biological effectiveness of [D-Ala(2)]GLP-1 was also observed in diabetic db/db mice. Similarly, improved biological activity of acetyl- and hexenoic-His(1)-GLP-1, glucagon((1-5)-, glucagon((1-10))-, PACAP(1-5)-, VIP(1-5)-, and secretin((1-10))-GLP-1 was observed, despite normal or lower receptor binding and activation in vitro. [Ala(8/11/12/16)] substitutions also increased biological activity in vivo over wtGLP-1, while C-terminal truncation of 4-12 amino acids abolished receptor binding and biological activity. All other modified peptides examined showed normal or decreased activity in vitro and in vivo. These results indicate that specific N- and midchain modifications to GLP-1 can increase its potency in vivo. Specifically, linkage of acyl-chains to the alpha-amino group of His(1) and replacement of Ala(2) result in significantly increased biological effects of GLP-1 in vivo, likely due to decreased degradation rather than enhanced receptor interactions. Replacement of certain residues in the midchain of GLP-1 also augment biological activity.     

The biology of incretin hormones

Gut peptides, exemplified by glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted in a nutrient-dependent manner and stimulate glucose-dependent insulin secretion. Both GIP and GLP-1 also promote β cell proliferation and inhibit apoptosis, leading to expansion of β cell mass. GLP-1, but not GIP, controls glycemia via additional actions on glucose sensors, inhibition of gastric emptying, food intake and glucagon secretion. Furthermore, GLP-1, unlike GIP, potently stimulates insulin secretion and reduces blood glucose in human subjects with type 2 diabetes. This article summarizes current concepts of incretin action and highlights the potential therapeutic utility of GLP-1 receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors for the treatment of type 2 diabetes.     

Microbiome of prebiotic-treated mice reveals novel targets involved in host response during obesity

The gut microbiota is involved in metabolic and immune disorders associated with obesity and type 2 diabetes. We previously demonstrated that prebiotic treatment may significantly improve host health by modulating bacterial species related to the improvement of gut endocrine, barrier and immune functions. An analysis of the gut metagenome is needed to determine which bacterial functions and taxa are responsible for beneficial microbiota–host interactions upon nutritional intervention. We subjected mice to prebiotic (Pre) treatment under physiological (control diet: CT) and pathological conditions (high-fat diet: HFD) for 8 weeks and investigated the production of intestinal antimicrobial peptides and the gut microbiome. HFD feeding significantly decreased the expression of regenerating islet-derived 3-gamma (Reg3g) and phospholipase A2 group-II (PLA2g2) in the jejunum. Prebiotic treatment increased Reg3g expression (by ∼50-fold) and improved intestinal homeostasis as suggested by the increase in the expression of intectin, a key protein involved in intestinal epithelial cell turnover. Deep metagenomic sequencing analysis revealed that HFD and prebiotic treatment significantly affected the gut microbiome at different taxonomic levels. Functional analyses based on the occurrence of clusters of orthologous groups (COGs) of proteins also revealed distinct profiles for the HFD, Pre, HFD-Pre and CT groups. Finally, the gut microbiota modulations induced by prebiotics counteracted HFD-induced inflammation and related metabolic disorders. Thus, we identified novel putative taxa and metabolic functions that may contribute to the development of or protection against the metabolic alterations observed during HFD feeding and HFD-Pre feeding.     

Using evolutionary information and ancestral sequences to understand the sequence-function relationship in GLP-1 agonists

Glucagon-like peptide-1 (GLP-1) is an incretin hormone with therapeutic potential for type 2 diabetes. A variety of GLP-1 sequences are known from amphibian species, and some of these have been tested here and found to be able to bind and activate the human GLP-1 receptor. While little difference was observed for the in vitro potency for the human GLP-1 receptor, larger differences were found in the enzymatic stability of these peptides. Two peptides showed increased enzymatic stability, and they group together phylogenetically, though they originate from Amphibia and Reptilia. We have used ancestral sequence reconstruction to analyze the evolution of these GLP-1 molecules, including the synthesis of new peptides. We find that the increased stability could not be observed in the resurrected peptides from the common ancestor of frogs, even though they maintain the ability to activate the human GLP-1 receptor. Another method, using residue mapping on evolutionary branches yielded peptides that had maintained potency towards the receptor and also showed increased stability. This represents a new approach using evolutionary data in protein engineering.     

In depth analysis of the N-terminal bioactive domain of gastric inhibitory polypeptide

Gastric inhibitory polypeptide/glucose-dependent insulinotropic polypeptide (GIP) is an important gastrointestinal regulator of insulin release and glucose homeostasis following a meal. Strategies have been undertaken to delineate the bioactive domains of GIP with the intention of developing small molecular weight GIP mimetics. The molecular cloning of receptors for GIP and the related hormone GLP-1 (glucagon-like peptide-1) has allowed examination of the characteristics of incretin analogs in transfected cell models. The current report examines the N-terminal bioactive domain of GIP residing in residues 1-14 by alanine scanning mutagenesis and N-terminal substitution/modification. Further studies examined peptide chimeras of GIP and GLP-1 designed to localize bioactive determinants of the two hormones. The alanine scan of the GIP(1-14) sequence established that the peptide was extremely sensitive to structural perturbations. Only replacement of amino acids 2 and 13 with those found in glucagon failed to dramatically reduce receptor binding and activation. Of four GIP(1-14) peptides modified by the introduction of DP IV-resistant groups, a peptide with a reduced bond between Ala2 and Glu3 demonstrated improved receptor potency compared to native GIP(1-14). The peptide chimera studies supported recent results on the importance of a mid-region helix for bioactivity of GIP, and confirmed existence of two separable regions with independent intrinsic receptor binding and activation properties. Furthermore, peptide chimeras showed that binding of GLP-1 also involves both N- and C-terminal domains, but that it apparently contains only a single bioactive domain in its N-terminus. Together, these results should facilitate development of incretin based therapies using rational drug design for potential treatment of diabetes.     

Glucagon-like peptides: regulators of cell proliferation,differentiation, and apoptosis

Peptide hormones are secreted from endocrine cells and neurons and exert their actions through activation of G protein-coupled receptors to regulate a diverse number of physiological systems including control of energy homeostasis, gastrointestinal motility, neuroendocrine circuits, and hormone secretion. The glucagon-like peptides, GLP-1 and GLP-2 are prototype peptide hormones released from gut endocrine cells in response to nutrient ingestion that regulate not only energy absorption and disposal, but also cell proliferation and survival. GLP-1 expands islet mass by stimulating pancreatic beta-cell proliferation and induction of islet neogenesis. GLP-1 also promotes cell differentiation, from exocrine cells or immature islet progenitors, toward a more differentiated beta-cell phenotype. GLP-2 stimulates cell proliferation in the gastrointestinal mucosa, leading to expansion of the normal mucosal epithelium, or attenuation of intestinal injury in experimental models of intestinal disease. Both GLP-1 and GLP-2 exert antiapoptotic actions in vivo, resulting in preservation of beta-cell mass and gut epithelium, respectively. Furthermore, GLP-1 and GLP-2 promote direct resistance to apoptosis in cells expressing GLP-1 or GLP-2 receptors. Moreover, an increasing number of structurally related peptide hormones and neuropeptides exert cytoprotective effects through G protein-coupled receptor activation in diverse cell types. Hence, peptide hormones, as exemplified by GLP-1 and GLP-2, may prove to be useful adjunctive tools for enhancement of cell differentiation, tissue regeneration, and cytoprotection for the treatment of human disease.     

Osteoblasts participate in the innate immunity of the bone by producing human beta defensin-3

Gram-positive bacterial bone infections are an important cause of morbidity particularly in immunocompromised patients. Antimicrobial peptides (AP) are effectors of the innate immune system and directly kill microorganisms in the first hours after microbial infection. The aim of the present investigation was to study the expression and regulation of gram-positive specialized human β-defensin-3 (HBD-3) in bone. Samples of healthy and osteomyelitic human bone were assessed for the expression of HBD-3. Using primary and immortalized osteoblasts (SAOS-2 cells), release and regulation of HBD-3 was evaluated after exposure to Staphylococcus aureus supernatant and/or corticosteroids using PCR, immunohistochemistry, Western blot and ELISA. To determine the role of toll-like-receptors-2 and -4 (TLR-2/-4), shRNA was used to downregulate TLRs. An osteomyelitis mouse model was created performed to investigate the release of murine β-defensins using immunohistochemistry and RT-PCR. Cultured osteoblasts and human bone produce HBD-3 under standard conditions. The release increases within hours of bacterial supernatant exposure in cultured osteoblasts. This observation was not made in chronically infected bone samples. The shRNA-technology revealed the necessity of TLR-2 and -4 in HBD-3 induction in osteoblasts. Blocking protein synthesis with cycloheximide showed that the rapid release of HBD-3 is not dependent on a translational de novo synthesis and is not affected by glucocorticoids. The murine osteomyelitis model confirmed the in vivo release uptake of mouse β-defensins-4 (MBD-4) in bone. This report shows the bacterial induction of HBD-3 via TLR-2 and -4 in osteoblasts and suggests a central role of antimicrobial peptides in the prevention of bacterial bone infection. The rapid and effective induction of HBD-3 in osteoblasts incubated with conditioned media from bacteria is more likely a result of a rapid secretion of preformed HBD-3 by osteoblasts rather than a result of enhanced biosynthesis. The increased incidence of gram-positive bacterial bone infection in patients with regular intake of glucocorticoids does not seem to be caused by a deranged HBD-3 release in osteoblasts. The experiments comply with current German law.     

Jejunal linoleic acid infusions require GLP-1 receptor signaling to inhibit food intake: implications for the effectiveness of Roux-en-Y gastric bypass

Roux-en-Y gastric bypass surgery results in sustained decreases in food intake and weight loss. A key component is likely the direct delivery of nutrients to the jejunum and resulting changes in levels of gut peptide secretion. Prior work modeling this aspect of the surgery has shown that small-volume, prolonged jejunal infusions of linoleic acid (LA) produce sustained decreases in food intake and weight loss. LA infusions also significantly elevate plasma glucagon-like peptide-1 (GLP-1) levels. To assess a role for the increased circulating GLP-1 in the feeding suppression, we examined the effect of prolonged peripheral minipump administration of the GLP-1 receptor antagonist exendin 9-39 (Ex 9) on the feeding suppression produced by jejunal LA. Using a 2 × 2 design, we infused either saline or LA in the jejunum (7 h/day, 11.4 kcal) for 5 days with a subset of animals from each group receiving either saline or Ex 9 (25 pmol·kg(-1)·min(-1)) continuously via a minipump. The antagonist alone had no effect on food intake. LA reduced daily food intake greatly in excess of the kilocalories infused. Ex 9 completely blocked the feeding suppression produced by the jejunal LA infusion. Ex 9 also attenuated the increase in plasma GLP-1 induced by jejunal LA infusions. These data demonstrate that endogenous GLP-1 receptor signaling is necessary for the reduction in food intake produced by jejunal LA infusions. Whether increased secretion of additional gut peptides is also necessary for such suppressions remains to be determined.