Short-term administration of glucagon-like peptide-2. Effects on bone mineral density and markers of bone turnover in short-bowel patients with no colon

Effect of gut hormones on bone metabolism and their possible mechanisms in the treatment of osteoporosis

Bone is a highly dynamic organ that changes with the daily circadian rhythm. During the day, bone resorption is suppressed due to eating, while it increases at night. This circadian rhythm of the skeleton is regulated by gut hormones. Until now, gut hormones that have been found to affect skeletal homeostasis include glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2), glucose-dependent insulinotropic polypeptide (GIP), and peptide YY (PYY), which exerts its effects by binding to its cognate receptors (GLP-1R, GLP-2R, GIPR, and Y1R). Several studies have shown that GLP-1, GLP-2, and GIP all inhibit bone resorption, while GIP also promotes bone formation. Notably, PYY has a strong bone resorption-promoting effect. In addition, gut microbiota (GM) plays an important role in maintaining bone homeostasis. This review outlines the roles of GLP-1, GLP-2, GIP, and PYY in bone metabolism and discusses the roles of gut hormones and the GM in regulating bone homeostasis and their potential mechanisms.

Efficacy and safety of glucagon-like peptide 2 in patients with short bowel syndrome: A systematic review and network meta-analysis

BACKGROUND

Glucagon-like peptide 2 (GLP-2) is a highly conserved enteroendocrine hormone that seems to be a regulator promoting intestinal adaptation. This study aimed to summarize the evidence on the efficacy and safety of exogenous GLP-2 in patients with short bowel syndrome (SBS).

METHODS

A database search was performed on PubMed, Web of Science Core Collection, Scopus, Ovid, and the Cochrane Central Register of Controlled Trials in November 2022. Clinical trials on the effect of GLP-2 on patients with SBS were included. The Cochrane Risk of Bias 2 and Risk Of Bias In Non-randomized Studies - of Interventions tools for quality assessment of randomized and nonrandomized trials were used. The extracted data were analyzed qualitatively and quantitatively using a network meta-analysis model.

RESULTS

This study included 23 clinical trials with 843 patients. The patients' ages ranged from 4.0 to 62.4 years. The treatment doses were 0.1, 0.05, and 0.025 mg/kg/day for teduglutide; 5 and 10 mg/week for apraglutide, and 0.1, 1, and 10 mg/day for glepaglutide. The treatment duration ranged from 1 to 32 weeks. Regarding citrulline level, 0.1 mg/kg/day of teduglutide had the highest mean difference (MD; 14.77; 95% CI, 10.20-19.33), followed by 0.05 mg/kg/day (13.04; 95% CI, 9.79-16.2) and 0.025 mg/kg/day (7.84; 95% CI, 2.42-13.26) of teduglutide. In addition, the effect estimate showed significant differences between all teduglutide dose groups and the control group. Different doses of glepaglutide were analyzed to assess the effect on alkaline phosphatase (ALP) levels, in which 0.1 mg/day of glepaglutide showed a significantly higher MD (20.71; 95% CI, 2.62-38.80) than 1 mg/day (the reference) and 10 mg/day (8.45; 95% CI, -10.72 to 27.62) of glepaglutide. However, 0.1 vs 10 mg of glepaglutide has an MD of -14.57 (95% CI, -437.24 to 148.11) for the indirect estimate, whereas 10 mg of glepaglutide has an MD of 8.45 (95% CI, -10.72 to 27.62) for the network estimate. Regarding safety outcomes, there was no significant difference among all teduglutide and apraglutide dose groups compared with the control group. Catheter-related bloodstream infection was the most common adverse event reported with the use of apraglutide, teduglutide, and glepaglutide.

CONCLUSION

Despite the small number of patients in the included studies and variable follow-up duration, GLP-2 seems to be safe and effective in patients with SBS. GLP-2 showed a positive effect on increasing plasma citrulline level and decreasing ALP level.

Gut-Derived Peptide Hormone Analogues and Potential Treatment of Bone Disorders in Obesity and Diabetes Mellitus

Obesity and diabetes mellitus are prevalent metabolic disorders that have a detrimental impact on overall health. In this regard, there is now a clear link between these metabolic disorders and compromised bone health. Interestingly, both obesity and diabetes lead to elevated risk of bone fracture which is independent of effects on bone mineral density (BMD). In this regard, gastrointestinal (GIT)-derived peptide hormones and their related long-acting analogues, some of which are already clinically approved for diabetes and/or obesity, also seem to possess positive effects on bone remodelling and microarchitecture to reduce bone fracture risk. Specifically, the incretin peptides, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), as well as glucagon-like peptide-2 (GLP-2), exert key direct and/or indirect benefits on bone metabolism. This review aims to provide an initial appraisal of the relationship between obesity, diabetes and bone, with a focus on the positive impact of these GIT-derived peptide hormones for bone health in obesity/diabetes. Brief discussion of related peptides such as parathyroid hormone, leptin, calcitonin and growth hormone is also included. Taken together, drugs engineered to promote GIP, GLP-1 and GLP-2 receptor signalling may have potential to offer therapeutic promise for improving bone health in obesity and diabetes.

Long-acting agonists of human and rodent GLP-2 receptors for studies of the physiology and pharmacological potential of the GLP-2 system

BACKGROUND AND PURPOSE

Glucagon-like peptide-2 (GLP-2) is secreted postprandially from enteroendocrine Lcells and has anabolic action on gut and bone. Short-acting teduglutide is the only approved GLP-2 analog for the treatment of short-bowel syndrome (SBS). To improve the therapeutic effect, we created a series of lipidated GLP-2R agonists.

EXPERIMENTAL APPROACH

Six GLP-2 analogs were studied in vitro for cAMP accumulation, β-arrestin 1 and 2 recruitment, affinity, and internalization. The trophic actions on intestine and bone were examined in vivo in rodents.

KEY RESULTS

Lipidations at lysines introduced at position 12, 16, and 20 of hGLP-2(1-33) were well-tolerated with less than 2.2-fold impaired potency and full efficacy at the hGLP-2R in cAMP accumulation. In contrast, N- and C-terminal (His1 and Lys30) lipidations impaired potency by 4.2- and 45-fold and lowered efficacy to 77% and 85% of hGLP-2, respectively. All variants were similarly active on the rat and mouse GLP-2Rs and the three most active variants displayed increased selectivity for hGLP-2R over hGLP-1R activation, compared to native hGLP-2. Impact on arrestin recruitment and receptor internalization followed that of Gαs-coupling, except for lipidation in position 20, where internalization was more impaired, suggesting desensitization protection. A highly active variant (C16 at position 20) with low internalization and a half-life of 9.5 h in rats showed improved gut and bone tropism with increased weight of small intestine in mice and decreased CTX levels in rats.

CONCLUSION AND IMPLICATION

We present novel hGLP-2 agonists suitable for in vivo studies of the GLP-2 system to uncover its pharmacological potential.

The Gut-Bone Axis in Diabetes

PURPOSE OF REVIEW

To describe recent advances in the understanding of how gut-derived hormones regulate bone homeostasis in humans with emphasis on pathophysiological and therapeutic perspectives in diabetes.

RECENT FINDINGS

The gut-derived incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is important for postprandial suppression of bone resorption. The other incretin hormone, glucagon-like peptide 1 (GLP-1), as well as the intestinotrophic glucagon-like peptide 2 (GLP-2) has been shown to suppress bone resorption in pharmacological concentrations, but the role of the endogenous hormones in bone homeostasis is uncertain. For ambiguous reasons, both patients with type 1 and type 2 diabetes have increased fracture risk. In diabetes, the suppressive effect of endogenous GIP on bone resorption seems preserved, while the effect of GLP-2 remains unexplored both pharmacologically and physiologically. GLP-1 receptor agonists, used for the treatment of type 2 diabetes and obesity, may reduce bone loss, but results are inconsistent. GIP is an important physiological suppressor of postprandial bone resorption, while GLP-1 and GLP-2 may also exert bone-preserving effects when used pharmacologically. A better understanding of the actions of these gut hormones on bone homeostasis in patients with diabetes may lead to new strategies for the prevention and treatment of skeletal frailty related to diabetes.

The Multiple Biological Functions of Dipeptidyl Peptidase-4 in Bone Metabolism

Dipeptidyl peptidase-4 (DPP4) is a ubiquitously occurring protease involved in various physiological and pathological processes ranging from glucose homeostasis, immunoregulation, inflammation to tumorigenesis. Recently, the benefits of DPP4 inhibitors as novel hypoglycemic agents on bone metabolism have attracted extensive attraction in many studies, indicating that DPP4 inhibitors may regulate bone homeostasis. The effects of DPP4 on bone metabolism are still unclear. This paper thoroughly reviews the potential mechanisms of DPP4 for interaction with adipokines, bone cells, bone immune cells, and cytokines in skeleton system. This literature review shows that the increased DPP4 activity may indirectly promote bone resorption and inhibit bone formation, increasing the risk of osteoporosis. Thus, bone metabolic balance can be improved by decreasing DPP4 activities. The substantial evidence collected and analyzed in this review supports this implication.

An overview of the current management of short-bowel syndrome in pediatric patients

Short-bowel syndrome (SBS) is defined as a state of malabsorption after resection or loss of a major portion of the bowel due to congenital or acquired factors. This article presents an overview on the recent management of pediatric SBS. The pediatric SBS population is very heterogeneous. The incidence of SBS is estimated to be 24.5 per 100,000 live births. The nutritional, medical, and surgical therapies available require a comprehensive evaluation. Thus, multidisciplinary intestinal rehabilitation programs (IRPs) are necessary for the management of these complex patients. The key points of focus in IRP management are hepato-protective strategies to minimize intestinal failure-associated liver disease; the aggressive prevention of catheter-related bloodstream infections; strategic nutritional supply to optimize the absorption of enteral calories; and the management and prevention of small bowel bacterial overgrowth, nephrocalcinosis, and metabolic bone disease. As the survival rate of children with SBS currently exceeds 90%, the application of small bowel transplantation has been evolving. The introduction of innovative treatments, such as combined therapy of intestinotrophic hormones, including glucagon-like peptide-2, may lead to further improvements in patients' quality of life.

G-CSF partially mediates effects of sleeve gastrectomy on the bone marrow niche

Bariatric surgeries are integral to the management of obesity and its metabolic complications. However, these surgeries cause bone loss and increase fracture risk through poorly understood mechanisms. In a mouse model, vertical sleeve gastrectomy (VSG) caused trabecular and cortical bone loss that was independent of sex, body weight, and diet, and this loss was characterized by impaired osteoid mineralization and bone formation. VSG had a profound effect on the bone marrow niche, with rapid loss of marrow adipose tissue, and expansion of myeloid cellularity, leading to increased circulating neutrophils. Following VSG, circulating granulocyte-colony stimulating factor (G-CSF) was increased in mice, and was transiently elevated in a longitudinal study of humans. Elevation of G-CSF was found to recapitulate many effects of VSG on bone and the marrow niche. In addition to stimulatory effects of G-CSF on myelopoiesis, endogenous G-CSF suppressed development of marrow adipocytes and hindered accrual of peak cortical and trabecular bone. Effects of VSG on induction of neutrophils and depletion of marrow adiposity were reduced in mice deficient for G-CSF; however, bone mass was not influenced. Although not a primary mechanism for bone loss with VSG, G-CSF plays an intermediary role for effects of VSG on the bone marrow niche.

Gut Hormones and Their Effect on Bone Metabolism. Potential Drug Therapies in Future Osteoporosis Treatment

Bone homeostasis displays a circadian rhythm with increased resorption during the night time as compared to day time, a difference that seems-at least partly-to be caused by food intake during the day. Thus, ingestion of a meal results in a decrease in bone resorption, but people suffering from short bowel syndrome lack this response. Gut hormones, released in response to a meal, contribute to this link between the gut and bone metabolism. The responsible hormones appear to include glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), known as incretin hormones due to their role in regulating glucose homeostasis by enhancing insulin release in response to food intake. They interact with their cognate receptors (GIPR and GLP-1R), which are both members of the class B G protein-coupled receptors (GPCRs), and already recognized as targets for treatment of metabolic diseases, such as type 2 diabetes mellitus (T2DM) and obesity. Glucagon-like peptide-2 (GLP-2), secreted concomitantly with GLP-1, acting via another class B receptor (GLP-2R), is also part of this gut-bone axis. Several studies, including human studies, have indicated that these three hormones inhibit bone resorption and, moreover, that GIP increases bone formation. Another hormone, peptide YY (PYY), is also secreted from the enteroendocrine L-cells (together with GLP-1 and GLP-2), and acts mainly via interaction with the class A GPCR NPY-R2. PYY is best known for its effect on appetite regulation, but recent studies have also shown an effect of PYY on bone metabolism. The aim of this review is to summarize the current knowledge of the actions of GIP, GLP-1, GLP-2, and PYY on bone metabolism, and to discuss future therapies targeting these receptors for the treatment of osteoporosis.

Dipeptidyl Peptidase-4 Inhibitor, Vildagliptin, Improves Trabecular Bone Mineral Density and Microstructure in Obese, Insulin-Resistant, Pre-diabetic Rats

OBJECTIVE

Obese insulin resistance and type 2 diabetes mellitus profoundly impair bone mechanical properties and bone quality. However, because several antidiabetes drugs, especially thiazolidinediones, further aggravate bone loss in individuals with diabetes, diabetic osteopathy should not be treated by using simply any glucose-lowering agents. Recently, incretins have been reported to affect osteoblast function positively. The present study aimed to investigate the effects of vildagliptin, an inhibitor of dipeptidyl peptidase-4, on bone of rats with high-fat-diet-induced prediabetes.

METHODS

Male rats were fed a high-fat diet for 12 weeks to induce obese insulin resistance and then treated with vildagliptin for 4 weeks. The effects of the drug on bone were determined by microcomputed tomography and bone histomorphometry.

RESULTS

Vildagliptin markedly improved insulin resistance in these obese insulin-resistant rats. It also significantly increased volumetric bone mineral density. Specifically, vildagliptin-treated obese insulin-resistant rats exhibited higher trabecular volumetric bone mineral density than vehicle-treated obese insulin-resistant rats, whereas cortical volumetric bone mineral density, cortical thickness and area were not changed. Bone histomorphometric analysis in a trabecular-rich area (i.e. tibial metaphysis) revealed greater trabecular bone volume and number and less trabecular separation without change in trabecular thickness, osteocyte lacunar area or cortical thickness in the vildagliptin-treated group.

CONCLUSIONS

Vildagliptin had a beneficial effect on the bone of obese insulin-resistant rats with prediabetes, particularly at the trabecular site. Such benefit probably results from enhanced bone formation rather than from suppressed bone resorption.

Effect of Dipeptidyl Peptidase-4 Inhibitors on Bone Metabolism and the Possible Underlying Mechanisms

Diabetes mellitus has been demonstrated to be closely associated with osteoporosis. Accordingly, hypoglycemic therapy is considered effective in treating metabolic bone disease. Recently, the effects of dipeptidyl peptidase-4 (DPP-4) inhibitors, a new type of antidiabetic drug, on bone metabolism have been widely studied. This review mainly describes the effects of DPP-4 inhibitors on bone metabolism, including their effects on bone mineral density, bone quality, and fracture risk. In addition, the potential underlying mechanisms are discussed. Based on the current progress in this research field, DPP-4 inhibitors have been proved to reduce fracture risk. In addition, sitagliptin, a strong and highly selective DPP-4 inhibitor, showed its beneficial effects on bone metabolism by improving bone mineral density, bone quality, and bone markers. With regard to the potential underlying mechanisms, DPP-4 inhibitors may promote bone formation and reduce bone resorption through DPP-4 substrates and DPP-4-related energy metabolism. Vitamin D and other related signaling pathways also play a role in affecting bone metabolism. Although these assumptions are controversial, they provide a translational pharmacology approach for the clinical use of DPP-4 inhibitors in the treatment of metabolic diseases. Prior to the use of these drugs in clinic, further studies should be conducted to determine the appropriate type of DPP-4 inhibitor, the people who would benefit the most from this therapy, appropriate dose and duration, and the effects of the treatment.

Growth Hormone Favorably Affects Bone Turnover and Bone Mineral Density in Patients With Short Bowel Syndrome Undergoing Intestinal Rehabilitation

BACKGROUND

Patients with short bowel syndrome (SBS) have a high prevalence of metabolic bone disease due to nutrient malabsorption and potential effects of parenteral nutrition (PN). Human growth hormone (hGH) has been shown in some studies to have anabolic effects on bone, but hGH effects on bone in patients with SBS are unknown.

METHODS

Adults with PN-dependent SBS underwent a 7-day period of baseline studies while receiving usual oral diet and PN and then began receiving modified diets designed to improve nutrient absorption and daily oral calcium/vitamin D supplements (1500 mg elemental calcium and 600 IU vitamin D, respectively). Subjects were randomized to receive in a double-blind manner either subcutaneous (sc) saline placebo as the control or hGH (0.1 mg/kg/d for 3 weeks, then 0.1 mg/kg 3 days a week for 8 subsequent weeks). Open-label hGH was given from week 13 to week 24 in subjects who required PN after completion of the 12-week double-blind phase. Markers of bone turnover (serum osteocalcin and urinary N-telopeptide [NTX]), vitamin D nutriture (serum calcium, 25-hydroxyvitamin D [25-OH D] and parathyroid hormone [PTH] concentrations), and intestinal calcium absorption were measured at baseline and at weeks 4 and 12. Dual x-ray absorptiometry (DXA) of the hip and spine was performed to determine bone mineral density (BMD) at baseline and weeks 12 and 24.

RESULTS

The majority of subjects in each group exhibited evidence of vitamin D deficiency at baseline (25-OH D levels<30 ng/mL; 78% and 79% of control and hGH-treated subjects, respectively). Subjects treated with hGH demonstrated a significant increase from baseline in serum osteocalcin levels at 12 weeks (+62%; p<.05). The levels of NTX were increased over time in the hGH-treated group; however, this did not reach statistical significance. Both NTX and osteocalcin remained unchanged in control subjects. BMD of the spine and total hip was unchanged in subjects treated with placebo or hGH at 24 weeks. However, femoral neck BMD was slightly but significantly decreased in the placebo group at this time point but remained unchanged from baseline in the hGH-treated subjects.

CONCLUSIONS

hGH therapy significantly increased markers of bone turnover during the initial 3 months of therapy and stabilized femoral neck bone mass over a 6-month period in patients with severe SBS undergoing intestinal rehabilitation.

Intestinal Incretins and the Regulation of Bone Physiology

Although originally identified as modulators of nutrient absorption, the gut hormones gastric inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon-like peptide-2 (GLP-2) have also been found to play an important role in the regulation of bone turnover. These "incretin" hormones promote bone anabolism by stimulating osteoblast differentiation as well as increasing osteoblast longevity. In addition, GIP and perhaps GLP-2 attenuate the activity of osteoclastic cells, leading to a net increase in bone deposition and ultimately increasing bone mass. Studies have demonstrated that these hormones are important for bone mineralization and overall bone quality and function evolutionarily as important nutritional links signaling nutrient availability for skeletal anabolic functions. Accordingly, these entero-osseous hormones (EOH) have therapeutic potential for the management of osteoporosis. Although this chapter primarily focuses on skeletal effects of these incretin hormones, the GIP, GLP-1, and GLP-2 receptors are actually widely expressed throughout the body. Therefore, we will also briefly discuss these extraosseous receptors/effects and how they may indirectly impact the skeleton.

Boning up on DPP4, DPP4 substrates, and DPP4-adipokine interactions: Logical reasoning and known facts about bone related effects of DPP4 inhibitors

Dipeptidyl peptidase 4 (DPP4) is a conserved exopeptidase with an important function in protein regulation. The activity of DPP4, an enzyme which can either be anchored to the plasma membrane or circulate free in the extracellular compartment, affects the glucose metabolism, cellular signaling, migration and differentiation, oxidative stress and the immune system. DPP4 is also expressed on the surface of osteoblasts, osteoclasts and osteocytes, and was found to play a role in collagen metabolism. Many substrates of DPP4 have an established role in bone metabolism, among which are incretins, gastrointestinal peptides and neuropeptides. In general, their effects favor bone formation, but some effects are complex and have not been completely elucidated. DPP4 and some of its substrates are known to interact with adipokines, playing an essential role in the energy metabolism. The prolongation of the half-life of incretins through DPP4 inhibition led to the development of these inhibitors to improve glucose tolerance in diabetes. Current literature indicates that the inhibition of DPP4 activity might also result in a beneficial effect on the bone metabolism, but the long-term effect of DPP4 inhibition on fracture outcome has not been entirely established. Diabetic as well as postmenopausal osteoporosis is associated with an increased activity of DPP4, as well as a shift in the expression levels of DPP4 substrates, their receptors, and adipokines. The interactions between these factors and their relationship in bone metabolism are therefore an interesting field of study.

Management and Complications of Short Bowel Syndrome: an Updated Review

Short bowel syndrome (SBS) is defined as loss of bowel mass from surgical resection, congenital defects, or disease. Intestinal failure (IF) includes the subset of SBS unable to meet nutrition needs with enteral supplements and requires parenteral nutrition (PN). The parenteral treatment of SBS is now a half-century old. Recent pharmacologic treatment (GLP-2 analogues) has begun to make a significant impact in the care and ultimate management of these patients such that the possibility of reducing PN requirements in formerly PN-dependent patients is a now a real possibility. Finally, newer understanding and possible treatment for some of the complications related to IF have more recently evolved and will be an emphasis of this report. This review will focus on developments over the last 10 years with the goal of updating the reader to new advances in our understanding of the care and feeding of the SBS patient.

Pediatric intestinal failure: Predictors of metabolic bone disease

PURPOSE

The purpose of this study was to identify risk factors for the development of metabolic bone disease (MBD) in pediatric intestinal failure (IF).

METHODS

A retrospective single-center study of 36 pediatric IF patients who were screened for MBD was performed. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA). Simple regression analysis was initially performed to screen predictors, followed by multivariate step-wise linear regression analysis to identify risk factors of MBD.

RESULTS

Mean lumbar spine BMD Z-score was -1.16 ± 1.32, and 50.0% of patients had a BMD Z-score less than -1.0. Deficiency of 25-hydroxyvitamin-D (25-OHD <30 ng/ml) was present in the 63.8% of patients, while 25.0% had hyperparathyroidism (intact parathyroid hormone (PTH)>55 pg/ml). Seven patients (19.4%) had bone pain, of which 4 (11.1%) suffered a pathologic fracture. Using multivariate analysis, parenteral nutrition (PN) duration predicted decreased BMD (B=-0.132, p=0.006). Serum 25-OHD nonsignificantly correlated with BMD Z-score (B=0.024, p=0.092). Interestingly, repeat DXA after increasing vitamin D supplementation showed no improvement in BMD Z-score (-1.18 ± 1.49 vs -1.36 ± 1.47, p=0.199).

CONCLUSIONS

Pediatric IF is associated with a significant risk of MBD, which is predicted by the duration of PN-dependence. These findings underscore the importance of BMD monitoring. Better therapies for treating IF-associated MBD are needed.

The pharmacologic treatment of short bowel syndrome: new tricks and novel agents

Short bowel syndrome (SBS) is a manifestation of massive resection of the intestines resulting in severe fluid, electrolyte, and vitamin/mineral deficiencies. Diet and parenteral nutrition play a large role in the management of SBS; however, pharmacologic options are becoming more readily available. These pharmacologic agents focus on reducing secretions and stimulating intestinal adaptation. The choice of medication is highly dependent on the patient's symptoms, remaining anatomy, and risk versus benefit profile for each agent. This article focuses on common and novel pharmacologic medications used in SBS, including expert advice on their indications and use.

Stem cells and biopharmaceuticals: vital roles in the growth of tissue-engineered small intestine

Tissue engineering currently constitutes a complex, multidisciplinary field exploring ideal sources of cells in combination with scaffolds or delivery systems in order to form a new, functional organ to replace native organ lack or loss. Short bowel syndrome (SBS) is a life-threatening condition with high morbidity and mortality rates in children. Current therapeutic strategies consist of costly and risky allotransplants that demand lifelong immunosuppression. A promising alternative is the implantation of autologous organoid units (OU) to create a tissue-engineered small intestine (TESI). This strategy is proven to be stem cell and mesenchyme dependent. Intestinal stem cells (ISCs) are located at the base of the crypt and are responsible for repopulating the cycling mucosa up to the villus tip. The stem cell niche governs the biology of ISCs and, together with the rest of the epithelium, communicates with the underlying mesenchyme to sustain intestinal homeostasis. Biopharmaceuticals are broadly used in the clinic to activate or enhance known signaling pathways and may greatly contribute to the development of a full-thickness intestine by increasing mucosal surface area, improving blood supply, and determining stem cell fate. This review will focus on tissue engineering as a means of building the new small intestine, highlighting the importance of stem cells and recombinant peptide growth factors as biopharmaceuticals.

Physiology and pharmacology of the enteroendocrine hormone glucagon-like peptide-2

Glucagon-like peptide-2 (GLP-2) is a 33-amino-acid proglucagon-derived peptide secreted from enteroendocrine L cells. GLP-2 circulates at low basal levels in the fasting period, and plasma levels rise rapidly after food ingestion. Renal clearance and enzymatic inactivation control the elimination of bioactive GLP-2. GLP-2 increases mesenteric blood flow and activates proabsorptive pathways in the gut, facilitating nutrient absorption. GLP-2 also enhances gut barrier function and induces proliferative and cytoprotective pathways in the small bowel. The actions of GLP-2 are transduced via a single G protein-coupled receptor (GLP-2R), expressed predominantly within the gastrointestinal tract. Disruption of GLP-2R signaling increases susceptibility to gut injury and impairs the adaptive mucosal response to refeeding. Sustained augmentation of GLP-2R signaling reduces the requirement for parenteral nutrition in human subjects with short-bowel syndrome. Hence GLP-2 integrates nutrient-derived signals to optimize mucosal integrity and energy absorption.

Review article: the management of long-term parenteral nutrition

BACKGROUND

Home parenteral nutrition (HPN) is currently the management of choice for patients with chronic intestinal failure.

AIM

To summarise the major issues in delivering long-term parenteral nutrition (>3 months) and assess outcome as per complications, mortality and quality of life. To assess the evidence for the therapeutic use of trophic factors such as teduglutide and to review evolving therapeutic options in the treatment of chronic intestinal failure.

METHODS

A literature search using PubMed and MEDLINE databases was performed.

RESULTS

Safe delivery of HPN relies upon individualised formulations of parenteral nutrition administered via carefully maintained central venous catheters by trained patients or carers, supported by a skilled multidisciplinary team. Early diagnosis and treatment of complications including catheter-associated blood stream infection (reported incidence 0.14-0.83 episodes/patient-year on HPN) and central venous thrombosis (reported incidence 0.03 episodes/patient-year) is important to minimise mortality and morbidity. There is a significant variation in the reported incidence of both hepatobiliary complications (19-75%) and advanced liver disease (0-50%). Five-year survival rates in large centres are reported between 60% and 78% with survival primarily related to underlying diagnosis. Long-term survival remains higher on HPN than with intestinal transplantation. The role of intestinal lengthening procedures is yet to be validated in adults.

CONCLUSIONS

Home parenteral nutrition delivered by skilled nutrition teams has low incidences of catheter-related complications. Most deaths relate to the underlying disease. Therapies such as teduglutide and small bowel transplantation appear promising, but home parenteral nutrition appears likely to remain the bedrock of management in the near term.

What the future holds for gliptins

Gliptins have revolutionised the treatment of Type 2 Diabetes Mellitus, addressing the hyperglycemia through its effects on the alpha and beta cells of the pancreas. In this article,we review the extra-glycemic effects of gliptins on central nervous system, cardiovascular biology and the bone health and concerns regarding pancreatitis and pancreatic cancer.

Short bowel syndrome in children: current and potential therapies

Short bowel syndrome (SBS) reflects a state of malabsorption that occurs due to loss of a significant portion of the small bowel. The pathophysiology of SBS is determined largely by the process of adaptation, which is the innate attempt by the remnant portions of the intestine to increase fluid and nutrient reabsorption. In recent years, emphasis has been placed on intestinal rehabilitation with multidisciplinary teams as a comprehensive approach to the management of patients with SBS. In our institution, the multidisciplinary team members include pediatric gastroenterologists, pediatric surgeons, pediatric dieticians, physical therapists, occupational therapists, neonatologists (especially for patients still under their care), transplant surgeons, transplant coordinators and social workers. Parenteral nutrition plays a significant role in the management of SBS, but its use is associated with many potential complications, including cholestatic liver disease. Fish oil-based lipid emulsions have shown promise in their ability to reverse and also prevent the development of cholestasis in these patients. Clinical trials have shown that growth factors and other trophic hormones facilitate the process of adaptation. The most significant impact has been shown with the use of glucagon-like peptide-2 and its analog (teduglutide). Surgical interventions remain an important part of the management of SBS to facilitate adaptation and treat complications. Intestinal transplantation is a last resort option when the process of adaptation is unsuccessful. This review article is intended to provide an overview of the conventional and emerging therapies for pediatric SBS.

Ghrelin is an Osteoblast Mitogen and Increases Osteoclastic Bone Resorption In Vitro

Ghrelin is released in response to fasting, such that circulating levels are highest immediately prior to meals. Bone turnover is acutely responsive to the fed state, with increased bone resorption during fasting and suppression during feeding. The current study investigated the hypothesis that ghrelin regulates the activity of bone cells. Ghrelin increased the bone-resorbing activity of rat osteoclasts, but did not alter osteoclast differentiation in a murine bone marrow assay nor bone resorption in ex vivo calvarial cultures. Ghrelin showed mitogenic activity in osteoblasts, with a strong effect in human cells and a weaker effect in rat osteoblasts. The expression of the human ghrelin receptor, GHSR, varied among individuals and was detectable in 25–30% of bone marrow and osteoblast samples. However, the rodent Ghsr expression was undetectable in bone cells and cell lines from rat and mouse. These data suggest that elevated levels of ghrelin may contribute to the higher levels of bone turnover that occurs in the fasted state.

Emerging treatment options for short bowel syndrome: potential role of teduglutide

INTRODUCTION

Current medical management of short bowel syndrome (SBS) involves the use of lifelong parenteral nutrition (PN). Glucagon-like peptide-2 (GLP-2), an important intestinotrophic growth factor has been shown to increase intestinal absorption in SBS through augmentation of post-resection intestinal adaptation. This may lead to the reduction of PN dependence in patients with SBS.

AREAS COVERED IN REVIEW

Advancing research of GLP-2 physiology has spurred the growing understanding of the diverse effects of GLP-2. The development of the degradation resistant GLP-2 analog, teduglutide (Gattex(TM), NPS Pharmaceuticals, Bedminster, NJ), has allowed its exploration as a therapeutic agent in a variety of clinical settings. Recent multicenter, placebo-controlled studies of GLP-2 in SBS patients demonstrate meaningful reductions in PN requirements with good safety profiles. The reparative and immunomodulatory effects of teduglutide may also be beneficial in patients with inflammatory bowel disease (IBD). Safety concerns about possible carcinogenic properties during long-term use require ongoing evaluation.

SUMMARY

GLP-2 appears to offer a novel adjuvant treatment modality for SBS. Promise for its use in other clinical settings like IBD has been shown in small pilot studies.

Receptors and effects of gut hormones in three osteoblastic cell lines

Background

In recent years the interest on the relationship of gut hormones to bone processes has increased and represents one of the most interesting aspects in skeletal research. The proportion of bone mass to soft tissue is a relationship that seems to be controlled by delicate and subtle regulations that imply "cross-talks" between the nutrient intake and tissues like fat. Thus, recognition of the mechanisms that integrate a gastrointestinal-fat-bone axis and its application to several aspects of human health is vital for improving treatments related to bone diseases. This work analysed the effects of gut hormones in cell cultures of three osteoblastic cell lines which represent different stages in osteoblastic development. Also, this is the first time that there is a report on the direct effects of glucagon-like peptide 2, and obestatin on osteoblast-like cells.

Methods

mRNA expression levels of five gut hormone receptors (glucose-dependent insulinotropic peptide [GIP], glucagon-like peptide 1 [GLP-1], glucagon-like peptide 2 [GLP-2], ghrelin [GHR] and obestatin [OB]) were analysed in three osteoblastic cell lines (Saos-2, TE-85 and MG-63) showing different stages of osteoblast development using reverse transcription and real time polymerase chain reaction. The responses to the gut peptides were studied using assays for cell viability, and biochemical bone markers: alkaline phosphatase (ALP), procollagen type 1 amino-terminal propeptides (P1NP), and osteocalcin production.

Results

The gut hormone receptor mRNA displayed the highest levels for GIP in Saos-2 and the lowest levels in MG-63, whereas GHR and GPR39 (the putative obestatin receptor) expression was higher in TE-85 and MG-63 and lower in Saos-2. GLP-1 and GLP-2 were expressed only in MG-63 and TE-85. Treatment of gut hormones to cell lines showed differential responses: higher levels in cell viability in Saos-2 after GIP, in TE-85 and MG-63 after GLP-1, GLP-2, ghrelin and obestatin. ALP showed higher levels in Saos-2 after GIP, GHR and OB and in TE-85 after GHR. P1NP showed higher levels after GIP and OB in Saos-2. Decreased levels of P1NP were observed in TE-85 and MG-63 after GLP-1, GLP-2 and OB. MG-63 showed opposite responses in osteocalcin levels after GLP-2.

Conclusions

These results suggest that osteoblast activity modulation varies according to different development stage under different nutrition related-peptides.

Obesity, diabetes mellitus and last but not least, osteoporosis

Knowledge about the influence of bone on intermediary metabolism corresponds to a developing area that has gained prominence. The old concept of bone and adipose tissues as inert metabolic tissues, with minor contributions to metabolic adaptations has been reconsidered in light of findings that bone is involved in the development of insulin sensitivity. Similarly adipose tissue exerts important influences on bone mass development and maintenance. Moreover, the use of drugs in the treatment of metabolic disorders such as diabetes mellitus can impact bone metabolism. These networks linking osteoporosis to obesity and diabetes mellitus have reinvigorated investigations in the pathophysiology of osteoporosis. The present review examines this aspect and calls attention to health care providers and potential treatments of skeletal disorder.

Differential effects of PPAR-{gamma} activation versus chemical or genetic reduction of DPP-4 activity on bone quality in mice

Patients with type 2 diabetes mellitus have an increased risk of fracture that can be further exacerbated by thiazolidinediones. A new class of antidiabetic agents control glucose through reduction of dipeptidyl peptidase-4 (DPP-4) activity; however the importance of DPP-4 for the control of bone quality has not been extensively characterized. We compared the effects of the thiazolidinedione pioglitazone and the DPP-4 inhibitor sitagliptin on bone quality in high-fat diet (HFD)-fed wild-type mice. In complementary studies, we examined bone quality in Dpp4(+/+) vs. Dpp4(-/-) mice. Pioglitazone produced yellow bones with greater bone marrow adiposity and significantly reduced vertebral bone mechanics in male, female, and ovariectomized (OVX) HFD fed female mice. Pioglitazone negatively affected vertebral volumetric bone mineral density, trabecular architecture, and mineral apposition rate in male mice. Sitagliptin treatment of HFD-fed wild-type mice significantly improved vertebral volumetric bone mineral density and trabecular architecture in female mice, but these improvements were lost in females after OVX. Genetic inactivation of Dpp4 did not produce a major bone phenotype in male and female Dpp4(-/-) mice; however, OVX Dpp4(-/-) mice exhibited significantly reduced femoral size and mechanics. These findings delineate the skeletal consequences of pharmacological and genetic reduction of DPP-4 activity and reveal significant differences in the effects of pioglitazone vs. sitagliptin vs. genetic Dpp4 inactivation on bone mechanics in mice.

The effect of glucagon-like peptide 2 injection on performance, small intestinal morphology, and nutrient transporter expression of stressed broiler chickens

An experiment was conducted to determine the effect of injecting glucagon-like peptide 2 (GLP-2) on the small intestinal weight, morphology, and nutrient transporter expression in pharmacologically stressed broiler chickens. A total of 144 seven-day-old birds were fed either a basal diet (CTRL) or a basal diet plus 30 mg of corticosterone (CORT)/kg of diet for a total of 14 d. Half of the birds from each group were injected daily with GLP-2 (6.7 nmol/kg of BW) or saline for 14 d. The average final BW, ADG, ADFI, and the ratio of feed intake to weight gain (F:G) was recorded over 21 d for the 4 groups of 36 birds, namely CTRL + saline, CTRL + GLP-2, CORT + saline, and CORT + GLP-2. In addition, the absolute and relative small intestinal weight, villus height (VH), and crypt depth (CD) of the duodenum and jejunum, as well as the abundance of sodium and glucose co-transporter 1 (SGLT-1), vitamin D-dependent calcium-binding protein-28,000 molecular weight (CaBP-D28k), and peptide transporter 1 (PepT-1) mRNA in the duodenum and of liver fatty acid-binding protein (L-FABP) mRNA in the jejunum. The total DNA, RNA, and protein content in small intestinal mucosa were also determined. The results showed that CORT administration significantly lowered average final BW, ADG, ADFI, absolute small intestinal weight, VH, and CD of duodenum and jejunum (P < 0.05) while increasing the relative small intestinal weight, F:G, relative abundance of SGLT-1, CaBP-D28k, PepT-1, and L-FABP mRNA (P < 0.05). Glucagon-like peptide 2 injection increased the average final BW, ADG, VH, and CD in duodenum and jejunum and relative abundance of SGLT-1, CaBP-28k, PepT1, and PepT1 mRNA of broiler chickens, respectively (P < 0.05), and decreased F:G (P < 0.05). In chickens fed basal diet plus CORT, injecting GLP-2 decreased F:G (P < 0.05); increased VH and CD of duodenum and CD of jejunum; and increased relative abundance of SGLT-1, CaBP-D28k, PepT-1, and L-FABP mRNA, RNA, and total protein content in small intestine compared with the injection of saline (P < 0.05). In birds fed the basal diet, GLP-2 injection decreased F:G (P < 0.05) and increased final BW, ADG, small bowel weight, CD of jejunum, and relative abundance of CaBP-D28k and PepT-1 mRNA compared with injecting saline (P < 0.05). In conclusion, GLP-2 injection reversed the negative effect of stress on the weight and morphology and the absorptive function of small bowel of broiler chickens. Glucagon-like peptide 2 injection also had a positive effect on the growth performance of healthy broiler chickens.

Reduced amylin levels are associated with low bone mineral density in women with anorexia nervosa

CONTEXT

Anorexia nervosa, characterized by extreme low body weight due to reduced nutrient intake, is associated with severe bone loss. Peptide hormones, including amylin, GIP, and GLP2, are released immediately after nutrient intake and may be involved in the regulation of bone turnover.

OBJECTIVE

To investigate fasting levels of amylin, GIP, and GLP2 and their relationships with bone mineral density (BMD) in women with anorexia nervosa compared to healthy controls.

DESIGN

Cross-sectional.

SETTING

Clinical Research Center.

STUDY PARTICIPANTS

15 women with anorexia nervosa and 16 healthy controls.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Fasting serum amylin, GIP, and GLP2, and BMD.

RESULTS

Women with anorexia nervosa had significantly lower fasting serum amylin and GIP levels than healthy controls. Fasting serum GLP2 levels were not significantly different between groups. Fasting amylin levels were positively associated with BMD and Z-score at the PA spine, total hip, and femoral neck. Fasting amylin levels were also positively associated with weight and percent fat; after controlling for these variables, amylin was still a significant predictor of BMD and Z-score at the femoral neck and of Z-score at the total hip. In the anorexia nervosa group, there was a trend toward an inverse association between amylin and C-terminal telopeptide (CTX) levels (R=-0.47, p=0.08). GIP and GLP2 levels did not predict BMD at any site.

CONCLUSION

Decreased secretion of amylin may be a mechanism through which reduced nutrient intake adversely affects BMD in anorexia nervosa.

Growth factors: possible roles for clinical management of the short bowel syndrome

The structural and functional changes during intestinal adaptation are necessary to compensate for the sudden loss of digestive and absorptive capacity after massive intestinal resection. When the adaptive response is inadequate, short bowel syndrome (SBS) ensues and patients are left with the requirement for parenteral nutrition and its associated morbidities. Several hormones have been studied as potential enhancers of the adaptation process. The effects of growth hormone, insulin-like growth factor-1, epidermal growth factor, and glucagon-like peptide 2 on adaptation have been studied extensively in animal models. In addition, growth hormone and glucagon-like peptide 2 have shown promise for the treatment of SBS in clinical trials in human beings. Several lesser studied hormones, including leptin, corticosteroids, thyroxine, testosterone, and estradiol, are also discussed.

Short bowel syndrome: the role of GLP-2 on improving outcome

PURPOSE OF REVIEW

The medical management of short bowel syndrome frequently requires lifelong parenteral nutrition. Methods of increasing intestinal absorption and reducing parenteral nutrition dependence, by improving postresection intestinal adaptation, are increasingly being explored. Glucagon-like peptide-2 (GLP-2) is an important intestinotrophic growth factor and mediator of intestinal adaptation. This review summarizes our current understanding of GLP-2 physiology and provides an update on clinical trials in short bowel syndrome and related conditions.

RECENT FINDINGS

There is growing understanding how the effects of GLP-2 are mediated by downstream effectors such as insulin-like growth factor-1. In the treatment of short bowel syndrome, GLP-2 and the long-acting GLP-2 analogue teduglutide (Gattex) are effective in improving fluid absorption. A recent multicentre, placebo-controlled study demonstrates that this can translate into meaningful reductions in parenteral nutrition requirements. Treatment dose and timing of treatment initiation might influence the mucosal growth response. Most of the small intestine has to be preserved to facilitate the previously documented benefits of GLP-2 on bone metabolism. Therapeutic uses of GLP-2 in other gastrointestinal conditions are being explored. GLP-2 treatment appears well tolerated, although concerns about the long-term use of this growth-promoting agent remain.

SUMMARY

GLP-2 therapy holds promise as an adjuvant treatment modality for short bowel syndrome and other gastrointestinal disorders.

Short bowel patients treated for two years with glucagon-like Peptide 2: effects on intestinal morphology and absorption, renal function, bone and body composition, and muscle function

BACKGROUND AND AIMS

In a short-term study, Glucagon-like peptide 2 (GLP-2) has been shown to improve intestinal absorption in short bowel syndrome (SBS) patients. This study describes longitudinal changes in relation to GLP-2 treatment for two years.

METHODS

GLP-2, 400 micrograms, s.c.,TID, were offered, to eleven SBS patients keeping parenteral support constant. 72-hour nutritional balance studies were performed at baseline, weeks 13, 26, 52 during two years intermitted by an 8-week washout period. In addition, mucosal morphometrics, renal function (by creatinine clearance), body composition and bone mineral density (by DEXA), biochemical markers of bone turnover (by s-CTX and osteocalcin, PTH and vitamin D), and muscle function (NMR, lungfunction, exercise test) were measured.

RESULTS

GLP-2 compliance was >93%. Three of eleven patients did not complete the study. In the remaining 8 patients, GLP-2 significantly reduced the fecal wet weight from approximately 3.0 to approximately 2.0 kg/day. This was accompanied by a decline in the oral wet weight intake, maintaining intestinal wet weight absorption and urinary weight constant. Renal function improved. No significant changes were demonstrated in energy intake or absorption, and GLP-2 did not significantly affect mucosal morphology, body composition, bone mineral density or muscle function.

CONCLUSIONS

GLP-2 treatment reduces fecal weight by approximately 1000 g/d and enables SBS patients to maintain their intestinal fluid and electrolyte absorption at lower oral intakes. This was accompanied by a 28% improvement in creatinine clearance.

Relationships of acylated and des-acyl ghrelin levels to bone mineralization in obese children and adolescents

AIMS

Bodyweight is a significant predictor of bone mass. Hormonal factors are thought to play a role in the mechanisms controlling the association of body weight and fat mass with bone mass. Very recently, the orexigenic hormone ghrelin has also been implicated in bone metabolism. In this study we examined the associations of circulating acylated and des-acyl ghrelin concentrations with measures of bone in a group of obese children and adolescents as well as in a group of healthy control children. We also determined whether the associations were independent of body composition, chronological age, gender, Tanner stage, and leptin, glucose, insulin and insulin-like growth factor (IGF)-1 levels.

METHODS

We performed a prospective cross-sectional study of 100 obese children [age, 8.9 (8.3 to 9.4); BMI-Standard Deviation Score (SDS), 2.2 (2.0 to 2.3)], and 100 age-matched lean healthy subjects. Fasting insulin, leptin, IGF-1, acylated and total ghrelin were measured by radioimmunoassay. Des-acyl ghrelin values were calculated as total ghrelin minus acylated ghrelin. Whole body (WB) and lumbar spine (LS) BMD, and BMC as well as body composition were assessed by DXA (Hologic QDR-4500W). LS volumetric BMD (BMAD) was estimated using the formula of Katzman (BMC/area(1.5)), while WB BMC data were expressed as BMC/height.

RESULTS

Backward linear regression analysis was performed for individual groups, with age, gender, Tanner stage, weight, height, body composition (lean and fat mass), acylated ghrelin, des-acyl ghrelin, leptin, glucose, insulin, and IGF-1, entered into the model. In healthy children, acylated ghrelin was a significant and independent negative predictor of WB BMD, and WB BMC/height, while lean mass was positively associated significantly with these bone measures. In contrast, in obese children, a positive significant association was observed between des-acyl ghrelin and WB BMD as well as WB BMC/height, along with lean mass, and to a lesser degree, with fat mass. Acylated as well as des-acyl ghrelin were not significant predictors of LS BMD and LS BMAD in obese as well as control children.

CONCLUSIONS

The results of this investigation indicate that the influence of the two distinct isoforms of ghrelin on BMD is mediated by specific body composition parameters in obese and control healthy children.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

Effects of treatment with glucagon-like peptide-2 on bone resorption in colectomized patients with distal ileostomy or jejunostomy and short-bowel syndrome

OBJECTIVE

The gut hormone GLP-2 (glucagon-like peptide-2) seems to be involved in the circadian pattern of bone resorption, whereas parathyroid hormone (PTH) is an established key hormone in bone turnover. Endogenous GLP-2 secretion is lacking in colectomized patients with short-bowel syndrome (SBS) and they have reduced bone mineral density (BMD). The aim of the study was to investigate the anti-resorptive effect (assessed by s-CTX) of 14 days of GLP-2 treatment in these patients and to determine whether 56 days of treatment would improve BMD. PTH secretion in response to GLP-2 was also investigated in colectomized SBS patients and colectomized controls (with ileostomy).

MATERIAL AND METHODS

Eight SBS patients and 13 patients with ileostomy were treated with subcutaneous injections of 1600 microg GLP-2 at bedtime for 56 and 14 consecutive days, respectively. BMD was determined at days 1 and 56 in SBS patients. On days 1 and 14, measurements of CTX, P1NP and PTH were taken 4 h after the GLP-2 injection.

RESULTS

Patients with ileostomy showed a significant reduction in bone resorption after GLP-2 injections at days 1 and 14. In contrast, there was no change in s-CTX after 1 and 14 days in the SBS patients, and after 56 days of GLP-2 treatment there was no improvement in BMD. A significant reduction in PTH secretion in response to GLP-2 was observed only in patients with ileostomy.

CONCLUSIONS

The decreased bone resorption in response to GLP-2 injections cannot be elicited in SBS patients and therefore precludes treatment of their osteopenia with GLP-2. The anti-resorptive response to GLP-2 seems to require an intact small intestine and may involve suppression of PTH secretion.

Reduction in bone resorption by exogenous glucagon-like peptide-2 administration requires an intact gastrointestinal tract

OBJECTIVE

Biochemical markers for bone resorption (s-CTX) are reduced by food intake, whereas markers for bone formation seem to be unaffected by meal status. Glucagon-like peptide-2 (GLP-2) is a peptide secreted from endocrine L cells in the intestinal mucosa in relation to food-intake. Subcutaneous GLP-2 treatment has been shown to reduce bone resorption in postmenopausal women. The objective of this study was to investigate the ability of exogenous GLP-2 to reduce bone resorption in patients with jejunostomy or ileostomy and to elucidate whether an intact gastrointestinal tract and the ability to secrete GLP-2 are required for meal-induced inhibition of bone resorption.

MATERIAL AND METHODS

Fifteen control subjects, 13 colectomized patients with an ileostomy and 12 colectomized patients with a jejunostomy (remnant small bowel 89 +/- 53 cm) were given: a) a subcutaneous injection of 1600 microg GLP-2, b) placebo and c) 3.8 MJ of a breakfast meal. Blood was sampled for measurements of s-CTX, s-osteocalcin and GLP-2 for 4 h after each intervention.

RESULTS

After the GLP-2 injection, only control subjects showed a significant reduction in s-CTX (24% +/- 13%, p = 0.05, 120 min) compared with baseline values. Patients with an ileostomy had a preserved endogenous postprandial GLP-2 secretion, which was absent in patients with a jejunostomy. Consumption of a meal reduced s-CTX in all groups but significantly less so in the jejunostomy group.

CONCLUSIONS

Reductions in bone resorption by exogenous GLP-2 require an intact gastrointestinal tract. The decreased meal-induced inhibition of bone resorption in the jejunostomy patients, who lack a GLP-2 response, supports the view that GLP-2 plays a role in postprandial reduction in bone resorption.

Relationships between fat and bone

Body weight impacts both bone turnover and bone density, making it, therefore, an important risk factor for vertebral and hip fractures and ranking it alongside age in importance. The effect of body weight is probably contributed to by both fat mass and lean mass, though in postmenopausal women, fat mass has been more consistently demonstrated to be important. A number of mechanisms for the fat-bone relationship exist and include the effect of soft tissue mass on skeletal loading, the association of fat mass with the secretion of bone active hormones from the pancreatic beta cell (including insulin, amylin, and preptin), and the secretion of bone active hormones (e.g., estrogens and leptin) from the adipocyte. These factors alone probably do not fully explain the observed clinical associations, and study of the actions on bone of novel hormones related to nutrition is an important area of further research. An understanding of this aspect of bone biology may open the way for new treatments of osteoporosis. More immediately, the role of weight maintenance in the prevention of osteoporosis is an important public health message that needs to be more widely appreciated.

GLP-2 administration results in increased proliferation but paradoxically an adverse outcome in a juvenile piglet model of short bowel syndrome

OBJECTIVE

The objective of the present study was to examine the effect of glucagon-like peptide-2 (GLP-2) administration in a piglet, juvenile model of short bowel syndrome.

MATERIALS AND METHODS

Four-week-old piglets underwent either a sham operation or 75% small bowel resection. Postoperatively, piglets received either polymeric infant formula diet or the diet and subcutaneous human recombinant GLP-2 (1600 microg/day for 7 days, 800 microg/day thereafter). Food intake was monitored throughout the experiment, and stool and serum samples obtained fortnightly. After the piglets were killed, tissues were obtained from the duodenum, jejunum, ileum, and terminal ileum, and used for morphological and functional analysis.

RESULTS

Treatment with GLP-2 resulted in significantly increased numbers of proliferating and apoptotic cells in the ileum of sham and small bowel resection piglets (P < 0.05). GLP-2 administration resulted in decreased weight gain, serum albumin, and disaccharidases in both sham and small bowel resection piglets (P < 0.001 compared with polymeric infant formula diet alone).

CONCLUSIONS

This is the first study to our knowledge to examine the effect of GLP-2 administration in a juvenile short bowel syndrome model. Contrary to adult rodent studies, administration of GLP-2 resulted in adverse outcomes including reduced ability to gain weight; decreased serum albumin, tissue maltase, and sucrase; and villous atrophy. We anticipate this information will have important implications for future paediatric clinical trials.

Complications of parenteral nutrition

Parenteral nutrition plays a vital role for patients with intestinal failure and those who are unable to maintain oral or enteral nutrition alone. Parenteral nutrition has been shown to improve clinical outcome in patients with malnutrition and intestinal tract dysfunction. The use of parenteral nutrition is not without risk of serious complications. Parenteral nutrition complications can be divided into mechanical related to vascular access, septic, and metabolic. This article provides a review on the short- and long-term complications of parenteral nutrition and their management.

Review article: glucagon-like peptide 2--current applications and future directions

BACKGROUND

Glucagon-like peptide 2 (GLP-2) is an important peptide growth factor secreted from the human intestine. The trophic properties of GLP-2 are very specific to the gut where it is pivotal in the regulation of mucosal morphology, function and integrity.

AIMS

This review details the current understanding of the molecular biology of GLP-2, its mechanisms of action and physiological properties. A major focus is the discussion of recent clinical data evaluating the use of GLP-2 as a therapeutic agent.

METHODS

Relevant articles were identified using Medline searches and from the reference lists of key papers.

RESULTS AND CONCLUSIONS

In the treatment of short bowel syndrome, GLP-2 has been shown to be highly effective in improving fluid absorption. In Crohn's disease, GLP-2 is superior to placebo in the induction of remission. Early data also suggest that the effects of GLP-2 on bone metabolism can provide a new treatment approach for patients with osteoporosis. In the future, the positive effects of GLP-2 on intestinal barrier function, splanchnic perfusion and mucosal healing could be utilized to expand its therapeutic application to other causes of intestinal injury. However, important safety aspects need to be considered when using this potent growth-promoting agent for a long term.

Skeletal muscle mass, fat mass, and hip bone mineral density in elderly women with hip fracture

Soft tissue body composition strongly affects bone health. Our aim was to investigate the relationship between both skeletal muscle mass (SMM) and fat mass (FM) and femoral bone mineral density (BMD) in a sample of elderly women with hip fracture. We assessed 293 of 325 hip fracture women admitted consecutively to a rehabilitation hospital. Soft tissue body composition and BMD were assessed by dual-energy X-ray absorptiometry (DXA), 23.2 +/- 7.7 (mean +/- SD) days after fracture occurrence. BMD was measured at four sites (neck, total femur, trochanter, intertrochanteric area) in the unfractured femur. Appendicular lean mass (aLM) was calculated as the sum of LM in arms and legs. We used two approaches to adjust aLM for body size: aLM divided by height squared (aLM/ht(2)), and aLM adjusted for height and FM (residuals). Both FM and aLM were significantly correlated with femoral BMD. However, the correlation coefficients for aLM were lower than for FM; they further decreased after adjustment for height squared, and were no longer significant after correction for both height and FM (residuals). When FM, aLM/ht(2), age, and time spent between fracture occurrence and DXA assessment were included together as the independent variables in a regression model, FM was the only independent variable significantly associated with BMD. The coefficients of partial correlation ranged from 0.414 to 0.647 depending on the femoral region of BMD assessment (P < 0.001). FM, but not SMM emerged as a pivotal determinant of BMD in our sample of hip fracture women.

Glucagon-like Peptide-2

Multiple peptide hormones produced within the gastrointestinal system aid in the regulation of energy homeostasis and metabolism. Among these is the intestinotrophic peptide glucagon-like peptide-2 (GLP-2), which is released following food intake and plays a significant role in the adaptive regulation of bowel mass and mucosal integrity. The discovery of GLP-2's potent growth-promoting and cytoprotective effects in the gastrointestinal (GI) tract stimulated interest in its use as a therapeutic agent for the treatment of GI diseases involving malabsorption, inflammation, and/or mucosal damage. Current research has focused on determining the physiological mechanisms contributing to the effects of GLP-2 and factors regulating its biological mechanisms of action. This chapter provides an overview of the biology of GLP-2 with a focus on the most recent findings on the role of this peptide hormone in the normal and diseased GI tract.

Necrotizing enterocolitis increases the bone resorption in premature infants

BACKGROUND

Necrotizing enterocolitis is a common neonatal gastrointestinal disease that affects approximately 10% of premature infants less than 1500 g. The average mortality is 20-40% and survivors may present with diarrhea or malabsorption, intestinal strictures and fistulas, feeding abnormalities and failure to thrive. It is not clear whether the higher incidence of this gastrointestinal disease in premature infants contributes to the risk of osteopenia of prematurity.

AIM

To examine bone turnover state in premature infants who had a necrotizing enterocolitis attack during postnatal period.

STUDY DESIGN AND SUBJECTS

We examine the bone turnover markers in infants with necrotizing enterocolitis and compare them with infants with sepsis. Forty-one premature infants participated in the study and were divided into three groups. In group I, there were 14 premature infants who developed necrotizing enterocolitis with negative blood culture during their hospitalization. In group II, there were 12 premature infants who developed sepsis during their hospitalization. Age-matched 15 premature infants who were given parenteral nutrition served as control group (group III). Blood samples and 6-h urine samples were obtained for bone turnover markers and calcium, phosphorous, creatinine and 25-hydroxy vitamin D between the day 20 and 25. Bone osteoblastic activity was assessed by measurement of serum osteocalcin. Bone resorption was assessed by measurement of serum levels of beta-CrossLaps and urinary deoxypyridinoline.

RESULTS

There were no significant differences in bone osteoblastic activity among the groups, but bone resorption markers were significantly higher in infants with necrotizing enterocolitis compared to other groups (p < 0.016).

CONCLUSION

Necrotizing enterocolitis increases the bone resorption in premature infants. It may be related with reduced glucagon like peptide-2 levels, a new intestinal hormone that is primary secreted from distal small intestine.

New growth factor therapies aimed at improving intestinal adaptation in short bowel syndrome

Short bowel syndrome (SBS) is used to describe a condition of malabsorption and malnutrition resulting from the loss of absorptive area following massive small bowel resection. The key to improved clinical outcome after massive small bowel resection is the ability of the residual bowel to adapt. Although still in experimental stages, a major goal in the management of SBS may be the augmented use of growth factors to promote increased adaptation. A number of growth factors have been implicated in promoting the adaptation process. The best-described growth factors are reviewed: glucagon-like peptide-2 (GLP-2), epidermal growth factor (EGF), and growth hormone (GH). This article reviews the ability of recombinant GLP-2, EGF and GH to modulate structural and functional aspects of intestinal adaptation following small bowel resection. Although these growth factors have shown promise, small sample size, inconsistent measurement parameters and uncontrolled study designs have hampered the acquisition of strong data advocating the use of growth factor treatment for SBS. Multicenter trials using well-defined outcome measures to assess clinical efficacy are needed to direct the clinical indications, timing and duration of therapy and assess potential risks associated with growth factor therapies.