Teduglutide in intestinal adaptation and repair: light at the end of the tunnel

Perioperative Dietary Therapy in Inflammatory Bowel Disease

BACKGROUND AND AIMS

The incidence of inflammatory bowel disease [IBD] is rising worldwide and no cure is available. Many patients require surgery and they often present with nutritional deficiencies. Although randomised controlled trials of dietary therapy are lacking, expert IBD centres have long-established interdisciplinary care, including tailored nutritional therapy, to optimise clinical outcomes and resource utilisation. This topical review aims to share expertise and offers current practice recommendations to optimise outcomes of IBD patients who undergo surgery.

METHODS

A consensus expert panel consisting of dietitians, surgeons, and gastroenterologists, convened by the European Crohn's and Colitis Organisation, performed a systematic literature review. Nutritional evaluation and dietary needs, perioperative optimis ation, surgical complications, long-term needs, and special situations were critically appraised. Statements were developed using a Delphi methodology incorporating three successive rounds. Current practice positions were set when ≥80% of participants agreed on a recommendation.

RESULTS

A total of 26 current practice positions were formulated which address the needs of IBD patients perioperatively and in the long term following surgery. Routine screening, perioperative optimisation by oral, enteral, or parenteral nutrition, dietary fibre, and supplements were reviewed. IBD-specific situations, including management of patients with a restorative proctocolectomy, an ostomy, strictures, or short-bowel syndrome, were addressed.

CONCLUSIONS

Perioperative dietary therapy improves the outcomes of IBD patients who undergo a surgical procedure. This topical review shares interdisciplinary expertise and provides guidance to optimise the outcomes of patients with Crohn's disease and ulcerative colitis. taking advantage of contemporary nutrition science.

Emerging therapeutic targets for osteoporosis

Introduction: Osteoporosis is a chronic, skeletal disorder characterized by compromised bone strength and increased fracture risk; it affects 50% of women and 20% of men. In the past two decades, there have been substantial improvements in the pharmacotherapy of osteoporosis which have yielded potent inhibitors of bone resorption or stimulators of bone formation.Areas covered: This review discusses newly identified targets and pathways and conceptual approaches to the prevention of multiple age-related disorders. Furthermore, it summarizes existing therapeutic strategies for osteoporosis.Expert opinion: Our enhanced understanding of bone biology and the reciprocal interactions between bone and other tissues have allowed the identification of new targets that may facilitate the development of novel drugs. These drugs will hopefully achieve the uncoupling of bone formation from resorption and possibly exert a dual anabolic and antiresorptive effect on bone. Alas, limitations regarding adherence, efficacy on nonvertebral fracture prevention and the long-term adverse events still exist for currently available therapeutics. Moreover, the efficacy of most agents is limited by the tight coupling of osteoblasts and osteoclasts; hence the reduction of bone resorption invariably reduces bone formation, and vice versa. This field is very much 'a work in progress.'

Oral Bifidobacterium longum expressing GLP-2 improves nutrient assimilation and nutritional homeostasis in mice

Bifidobacterium has been developed for the oral delivery of peptides and has the added beneficial effect on our bodies through its probiotic properties. Here, we utilize Bifidobacterium as a delivery system to orally deliver Glucagon like peptide-2 (GLP-2). We constructed vector derived from pET-31b(+) to construct a Bifidobacterium longum expressing GLP-2. We then determined the bioactivity of recombinant Bifidobacterium in Caco-2 cells. Finally, we quantified newly synthesized ApoB48 and chylomicron production in mice infused with exogenous GLP-2 or Bifidobacterium expressing GLP-2. Results based on secretion of the triglyceride (TG)-rich lipoprotein (TRL)-ApoB48 and secretion of chylomicron revealed that recombinant Bifidobacterium was efficient in treating intestinal dysfunction,suggesting an alternative way to use Bifidobacterium as a delivery system to deliver GLP-2 for gastrointestinal nutrition coordination.

A DPP-IV-resistant glucagon-like peptide-2 dimer with enhanced activity against radiation-induced intestinal injury

Although radiotherapy is a highly effective treatment for abdominal or pelvic cancer patients, it can increase the incidence of severe gastrointestinal (GI) toxicity. As an intestinal growth factor, glucagon-like peptide 2 (GLP-2) has been shown to improve the preclinical models of both short bowel syndrome and inflammatory bowel disease by stimulating intestinal growth. Teduglutide ([Gly²]GLP-2), a recombinant human GLP-2 variant, has a prolonged half-life and stability as compared to the native GLP-2 peptide, but still requires daily application in the clinic. Here, we designed and prepared a new degradation-resistant GLP-2 analogue dimer, designated GLP-2②, with biotechnological techniques. The purity of GLP-2②reached 97% after ammonium sulphate precipitation and anion exchange chromatography purification, and the purification process was simple and cost-effective. We next confirmed that the GLP-2② exhibited enhanced activities compared with [Gly²]GLP-2, the long-acting, degradation-resistant analogue. Notably, GLP-2② offers a pharmacokinetic and therapeutic advantage in the treatment of radiation-induced intestinal injury over [Gly²]GLP-2. We further demonstrated that GLP-2② rapidly activates divergent intracellular signaling pathways involved in cell survival and apoptosis. Taken together, our data revealed a potential novel and safe peptide drug for limiting the adverse effect of radiotherapy on the gastrointestinal system.

Glucagonlike peptide 2 analogue teduglutide: stimulation of proliferation but reduction of differentiation in human Caco-2 intestinal epithelial cells

IMPORTANCE

Short bowel syndrome occurs when a shortened intestine cannot absorb sufficient nutrients or fluids. Teduglutide is a recombinant analogue of human glucagonlike peptide 2 that reduces dependence on parenteral nutrition in patients with short bowel syndrome by promoting enterocytic proliferation, increasing the absorptive surface area. However, enterocyte function depends not only on the number of cells that are present but also on differentiated features that facilitate nutrient absorption and digestion.

OBJECTIVE

To test the hypothesis that teduglutide impairs human intestinal epithelial differentiation.

DESIGN AND SETTING

We investigated the effects of teduglutide in the modulation of proliferation and differentiation in human Caco-2 intestinal epithelial cells at a basic science laboratory. This was an in vitro study using Caco-2 cells, a human-derived intestinal epithelial cell line commonly used to model enterocytic biology.

EXPOSURE

Cells were exposed to teduglutide or vehicle control.

MAIN OUTCOMES AND MEASURES

We analyzed the cell cycle by bromodeoxyuridine incorporation or propidium iodide staining and flow cytometry and measured cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. We used quantitative reverse transcription-polymerase chain reaction to assay the expression of the enterocytic differentiation markers villin, sucrase-isomaltase, glucose transporter 2 (GLUT2), and dipeptidyl peptidase 4 (DPP-4), as well as that of the putative differentiation signals schlafen 12 (SLFN12) and caudal-related homeobox intestine-specific transcription factor (Cdx2). Villin promoter activity was measured by a luciferase-based assay.

RESULTS

The MTS assay demonstrated that teduglutide increased cell numbers by a mean (SD) of 10% (2%) over untreated controls at a maximal 500 nM (n = 6, P < .05). Teduglutide increased bromodeoxyuridine-positive cells vs untreated controls by a mean (SD) of 19.4% (2.3%) vs 12.0% (0.8%) (n = 6, P < .05) and increased the S-phase fraction by flow cytometric analysis. Teduglutide reduced the mean (SD) expression of villin by 29% (6%), Cdx2 by 31% (10%), DPP-4 by 15% (6%), GLUT2 by 40% (11%), SLFN12 by 61% (14%), and sucrase-isomaltase by 28% (8%) (n = 6, P < .05 for all).

CONCLUSIONS AND RELEVANCE

Teduglutide increased Caco-2 proliferation but tended to inhibit intestinal epithelial differentiation. The effects of mitogenic stimulation with teduglutide in patients with short bowel syndrome might be greater if the more numerous teduglutide-treated cells could be stimulated toward a more fully differentiated phenotype.

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.

Enteral nutrients potentiate glucagon-like peptide-2 action and reduce dependence on parenteral nutrition in a rat model of human intestinal failure

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent, proglucagon-derived gut hormone that shows promise for the treatment of short bowel syndrome (SBS). Our objective was to investigate how combination GLP-2 + enteral nutrients (EN) affects intestinal adaption in a rat model that mimics severe human SBS and requires parenteral nutrition (PN). Male Sprague-Dawley rats were assigned to one of five groups and maintained with PN for 18 days: total parenteral nutrition (TPN) alone, TPN + GLP-2 (100 μg·kg(-1)·day(-1)), PN + EN + GLP-2(7 days), PN + EN + GLP-2(18 days), and a nonsurgical oral reference group. Animals underwent massive distal bowel resection followed by jejunocolic anastomosis and placement of jugular catheters. Starting on postoperative day 4, rats in the EN groups were allowed ad libitum access to EN. Groups provided PN + EN + GLP-2 had their rate of PN reduced by 0.25 ml/day starting on postoperative day 6. Groups provided PN + EN + GLP-2 demonstrated significantly greater body weight gain with similar energy intake and a safe 80% reduction in PN compared with TPN ± GLP-2. Groups provided PN + EN + GLP-2 for 7 or 18 days showed similar body weight gain, residual jejunal length, and digestive capacity. Groups provided PN + EN + GLP-2 showed increased jejunal GLP-2 receptor (GLP-2R), insulin-like growth factor-I (IGF-I), and IGF-binding protein-5 (IGFBP-5) expression. Treatment with TPN + GLP-2 demonstrated increased jejunal expression of epidermal growth factor. Cessation of GLP-2 after 7 days with continued EN sustained the majority of intestinal adaption and significantly increased expression of colonic proglucagon compared with PN + EN + GLP-2 for 18 days, and increased plasma GLP-2 concentrations compared with TPN alone. In summary, EN potentiate the intestinotrophic actions of GLP-2 by improving body weight gain allowing for a safe 80% reduction in PN with increased jejunal expression of GLP-2R, IGF-I, and IGFBP-5 following distal bowel resection in the rat.

GLP-2 receptor agonism ameliorates inflammation and gastrointestinal stasis in murine postoperative ileus

Glucagon-like peptide 2 (GLP-2) is a pleiotropic intestinotrophic hormone that we hypothesized could lessen gastrointestinal inflammation associated with postoperative ileus (POI). To test this idea, the prophylactic timing and dose of a long-acting variant of human GLP-2 linked to the Fc portion of murine immunoglobulin G (IgG) (GLP-2/IgG) was optimized in a murine model of POI. Surgically treated mice received a single dose of GLP-2/IgG, IgG isotype control, or phosphate-buffered saline 1 to 48 h before small bowel surgical manipulation. The distribution of orally fed fluorescein isothiocyanate-dextran and histological analyses of myeloperoxidase-positive immune cells were determined 24 and 48 h postoperatively. TaqMan quantitative polymerase chain reaction was used to determine early changes in mRNA expression in the muscularis or mucosa. In normal mice, prolonged exposure to GLP-2 increased upper gastrointestinal (GI) transit and mucosal weight. When administered 1 or 3 h before surgery, GLP-2/IgG reduced the leukocyte infiltrate 24 and 48 h postoperatively and improved GI transit 48 h postoperatively. Surgical manipulation rapidly increased gene expression of proinflammatory cytokines and enzymes for kinetically active mediators in the mucosa and muscularis. GLP-2/IgG2a affected the expression of genes associated with mucosal inflammation and barrier function. We conclude that prophylactic treatment with a long-acting GLP-2 agonist ameliorates inflammation and improves intestinal dysmotility associated with surgical manipulation of the bowel. The action of GLP-2 is consistent with a lessening of inflammation, leading to a more rapid recovery.

Intestinal failure: A new era in clinical management

Only 50 years ago intestinal failure was considered incompatible with life. Since then, developments in parenteral nutrition, and, more recently, small intestinal transplantation, have provided new therapeutic options with the potential to offer long-term survival with a good quality of life. Current medical and surgical strategies are aimed at enhancing intestinal adaptation, improving absorption to achieve nutritional independence, and minimizing the complications of parenteral nutrition therapy. An integrated, multidisciplinary approach to the management of patients with intestinal failure, closely linked to a transplantation program to facilitate early referral, is recognized as a key factor in optimizing patient outcomes.

Membrane-tethered ligands are effective probes for exploring class B1 G protein-coupled receptor function

Class B1 (secretin family) G protein-coupled receptors (GPCRs) modulate a wide range of physiological functions, including glucose homeostasis, feeding behavior, fat deposition, bone remodeling, and vascular contractility. Endogenous peptide ligands for these GPCRs are of intermediate length (27-44 aa) and include receptor affinity (C-terminal) as well as receptor activation (N-terminal) domains. We have developed a technology in which a peptide ligand tethered to the cell membrane selectively modulates corresponding class B1 GPCR-mediated signaling. The engineered cDNA constructs encode a single protein composed of (i) a transmembrane domain (TMD) with an intracellular C terminus, (ii) a poly(asparagine-glycine) linker extending from the TMD into the extracellular space, and (iii) a class B1 receptor ligand positioned at the N terminus. We demonstrate that membrane-tethered peptides, like corresponding soluble ligands, trigger dose-dependent receptor activation. The broad applicability of this approach is illustrated by experiments using tethered versions of 7 mammalian endogenous class B1 GPCR agonists. In parallel, we carried out mutational studies focused primarily on incretin ligands of the glucagon-like peptide-1 receptor. These experiments suggest that tethered ligand activity is conferred in large part by the N-terminal domain of the peptide hormone. Follow-up studies revealed that interconversion of tethered agonists and antagonists can be achieved with the introduction of selected point mutations. Such complementary receptor modulators provide important new tools for probing receptor structure-function relationships as well as for future studies aimed at dissecting the tissue-specific biological role of a GPCR in vivo (e.g., in the brain vs. in the periphery).

Glucagon-like peptide-2 reduces intestinal permeability but does not modify the onset of type 1 diabetes in the nonobese diabetic mouse

The development of type 1 diabetes (T1D) has been linked to environmental factors and dietary components. Increasing evidence indicates that the integrity of the gut mucosa plays a role in the development of autoimmune diseases, and evidence from both preclinical and clinical studies demonstrates that increased leakiness of the intestinal epithelium precedes the development of type 1 diabetes. However, there is limited information on modulation of gut barrier function and its relationship to diabetes development. Here we show that the nonobese diabetic (NOD) mouse, a model of T1D, exhibits enhanced intestinal transcellular permeability before the development of autoimmune diabetes. Treatment of NOD mice with a glucagon-like peptide 2 (GLP-2) analog, synthetic human [Gly(2)] glucagon-like peptide-2 (h[Gly(2)]GLP-2, increased the length and weight of the small bowel and significantly improved jejunal transepithelial resistance. However, chronic administration of once daily h[Gly(2)]GLP-2 failed to delay or reverse the onset of T1D when treatment was initiated in young, normoglycemic female NOD mice. Furthermore, h[Gly(2)]GLP-2 administration had no significant effect on lymphocyte subpopulations in NOD mice. These findings demonstrate that h[Gly(2)]GLP-2-mediated enhancement of gut barrier function in normoglycemic NOD mice disease is not sufficient to prevent or delay the development of experimental T1D.