GLP-1 playing the role of a gut regulatory compound

GLP-1 Agonists: A Practical Overview for Plastic and Reconstructive Surgeons

BACKGROUND

Glucagon-like peptide-1 (GLP-1) agonists, such as exenatide, liraglutide, dulaglutide, semaglutide, and tirzepatide, effectively manage type 2 diabetes by promoting insulin release, suppressing glucagon secretion, and enhancing glucose metabolism. They also aid weight reduction and cardiovascular health, potentially broadening their therapeutic scope. In plastic surgery, they hold promise for perioperative weight management and glycemic control, potentially impacting surgical outcomes.

METHODS

A comprehensive review was conducted to assess GLP-1 agonists' utilization in plastic surgery. We analyzed relevant studies, meta-analyses, and trials to evaluate their benefits and limitations across surgical contexts, focusing on weight reduction, glycemic control, cardiovascular risk factors, and potential complications.

RESULTS

Studies demonstrate GLP-1 agonists' versatility, spanning weight management, cardiovascular health, neurological disorders, and metabolic dysfunction-associated liver diseases. Comparative analyses highlight variations in glycemic control, weight loss, and cardiometabolic risk. Meta-analyses reveal significant reductions in hemoglobin A1C levels, especially with high-dose semaglutide (2 mg) and tirzepatide (15 mg). However, increased dosing may lead to gastrointestinal side effects and serious complications like pancreatitis and bowel obstruction. Notably, GLP-1 agonists' efficacy in weight reduction and glycemic control may impact perioperative management in plastic surgery, potentially expanding surgical candidacy for procedures like autologous flap-based breast reconstruction and influencing outcomes related to lymphedema. Concerns persist regarding venous thromboembolism and delayed gastric emptying, necessitating further investigation into bleeding and aspiration risk with anesthesia.

CONCLUSIONS

GLP-1 agonists offer advantages in perioperative weight management and glycemic control in plastic surgery patients. They may broaden surgical candidacy and mitigate lymphedema risk but require careful consideration of complications, particularly perioperative aspiration risk. Future research should focus on their specific impacts on surgical outcomes to optimize their integration into perioperative protocols effectively. Despite challenges, GLP-1 agonists promise to enhance surgical outcomes and patient care in plastic surgery.

Pain relief and pain intensity response to GLP-1 receptor agonist ROSE-010 in irritable bowel syndrome; clinical study cross-analysis with respect to patient characteristics

BACKGROUND AND AIMS

Glucagon-like peptide-1 receptor agonist ROSE-010 has been studied for management of irritable bowel syndrome (IBS). ROSE-010 showed promising effects by reducing pain during attacks of IBS. In this exploratory substudy, we cross-analyzed earlier data to identify the most suitable subpopulation for treatment with ROSE-010.

METHODS

Data comprising 166 participants (116 females, 50 males) treated by subcutaneous injection with ROSE-010 at 100 µg and 300 µg versus placebo were broken down into subpopulations with recall of historical pain intensity, pain intensity immediately before treatment, gender, age, BMI, IBS subtype as well as pain intensity and pain relief of ROSE-010 with relationship to plasma glucose using visual analogue scores. Statistical cross-analysis was performed to detect optimal responders for adequate pain relief response.

RESULTS

ROSE-010 gave dose- and time-dependent effects with maximum pain relief at 300 µg relative 100 µg and placebo at 120 min post injection. Females had greater pain relief than males; age and BMI did not affect treatment response. IBS pain relief was greatest in constipation-dominant IBS (IBS-C) and mixed IBS (IBS-M) relative diarrhea-dominant and unspecified IBS.

CONCLUSIONS

Clinical trial data indicate that female participants are more likely than males to respond to ROSE-010 100 µg and 300 µg to achieve meaningful IBS pain relief. Maximum pain relief was achieved at 120 min with the higher dose, although this was accompanied with higher rates of nausea. Improvement of IBS pain attacks was most pronounced in IBS-C and IBS-M, suggesting these subgroups to be optimal ROSE-010 responders.

The role of incretins and incretin-based drugs in autoimmune diseases

Incretin hormones, including glucagon-like peptide (GLP)-1, GLP-2 and glucose-dependent insulinotropic polypeptide (GIP), are gastrointestinal peptides secreted from enteroendocrine cells. These hormones play significant roles in many physiological processes via binding to G-protein coupled receptors (GPCRs) on different organs and tissues; one of them is the immunomodulatory effect on the immune system and its molecular components such as cytokines and chemokines. Anti-inflammatory effects of incretins and dependent molecules involving long-acting analogs and DPP4 inhibitors through regulation of T and B cell activation may attenuate autoimmune diseases caused by immune system disorders in mistakenly recognizing self as the foreign agent. In this review, we investigate incretin effects on the immune system response and the potential benefits of incretin-based therapy for treating autoimmune diseases.

GLP-1 Receptor Agonists: Beyond Their Pancreatic Effects

Glucagon like peptide-1 (GLP-1) is an incretin secretory molecule. GLP-1 receptor agonists (GLP-1RAs) are widely used in the treatment of type 2 diabetes (T2DM) due to their attributes such as body weight loss, protection of islet β cells, promotion of islet β cell proliferation and minimal side effects. Studies have found that GLP-1R is widely distributed on pancreatic and other tissues and has multiple biological effects, such as reducing neuroinflammation, promoting nerve growth, improving heart function, suppressing appetite, delaying gastric emptying, regulating blood lipid metabolism and reducing fat deposition. Moreover, GLP-1RAs have neuroprotective, anti-infectious, cardiovascular protective, and metabolic regulatory effects, exhibiting good application prospects. Growing attention has been paid to the relationship between GLP-1RAs and tumorigenesis, development and prognosis in patient with T2DM. Here, we reviewed the therapeutic effects and possible mechanisms of action of GLP-1RAs in the nervous, cardiovascular, and endocrine systems and their correlation with metabolism, tumours and other diseases.

Effects of Zuojin pill on depressive behavior and gastrointestinal function in rats with chronic unpredictable mild stress: Role of the brain-gut axis

ETHNOPHARMACOLOGICAL RELEVANCE

Zoujin pill (ZJP), a medication used to treat gastrointestinal disorders since the 15th Century in China, have been reported to exert anti-depressant effects in various models.

STUDY AIM

To assess the effects of ZJP on gastrointestinal function and depressive behavior in rats under chronic unpredictable mild stress (CUMS), and to examine the underlying mechanisms related to brain-gut axis.

METHODS

The rats suffered the stressor once daily for 5 weeks. ZJP (0.6 and 1.2 g/kg) and fluoxetine (15 mg/kg) as positive control were administered to the rats through gastric intubation once daily for 5 consecutive weeks. The anti-depression effects were compared by performing sucrose preference tests and open field tests. Gastrointestinal motility was investigated by determining the gastrointestinal transit rate and by electrogastrogram. The serum levels of the gastrointestinal hormone (GAS, MOT, VIP, SP), inflammatory cytokine (IL-1β, IL-6; , TNFα) and glucagon-like peptide-1 (GLP-1) were assayed by enzyme-linked immunosorbent assay. For monoamine neurotransmitters (NE, 5-HT, DA), the levels were determined by high-performance liquid chromatography and electrochemical detection in conjunction, which was applied on the samples taken from the hypothalamus, hippocampus, and striatum.

RESULTS

The depression-like symptoms among rats under CUMS were significantly relieved by ZJP administration (0.6 and 1.2 g/kg). Gastrointestinal motility was also improved by restoring gastric electrical rhythm and promoting gastrointestinal propulsion. The ZJP at 0.6 g/kg dosage obviously up-regulated 5-HT and DA levels in hippocampus. The ZJP at 1.2 g/kg dosage could increase 5-HT and DA levels in hypothalamus, striatum, and hippocampus, while down-regulated the NE level in hypothalamus and hippocampus. ZJP also reversed the alterations in serum gastrointestinal hormones. Furthermore, treatment with ZJP significantly reduced levels of IL-1β, IL-6 and TNF-α and increased serum GLP-1 compared with the CUMS group. Fluoxetine also exerted similar anti-depressant effects in the absence of effects on gastrointestinal motility and the levels of serum hormone, inflammatory cytokine and GLP-1.

CONCLUSION

ZJP imposed anti-depressant and gastrointestinal regulating functions in rats under CUMS, suggesting potential clinical application. .

Glucagon‑like peptide‑1 analogue exendin‑4 modulates serotonin transporter expression in intestinal epithelial cells

Serotonin-selective reuptake transporter (SERT) regulates extracellular availability of serotonin (5-hydroxytryptamine; 5-HT) and participates in the pathogenesis of functional disorders. Colonic SERT expression is decreased in colonic sensitized rats, and the glucagon-like peptide-1 analogue, exendin-4, reduces visceral hypersensitivity by decreasing 5-HT levels and increasing SERT expression. The present in vitro study aimed to further investigate the effects of exendin-4 on SERT expression, and to examine the role of GLP-1 and its receptor in the regulation of 5-HT. SERT mRNA and protein expression levels were detected by reverse transcription-quantitative PCR and western blotting. A ^[3H]−5-HT reuptake experiment was performed in IEC-6 rat intestinal epithelial cells treated with exendin-4. Effects on the adenosine cyclophosphate (AC)/PKA pathway were examined by variously treating cells with the AC activator forskolin, the protein kinase A (PKA) inhibitor H89 and the AC inhibitor SQ22536. Exendin-4 treatment upregulated SERT expression and enhanced 5-HT reuptake in IEC-6 cells. Also, PKA activity in IEC-6 cells was increased by both exendin-4 and forskolin, whereas these effects were abolished by the pre-treatment of exendin-9, which is a GLP-1R inhibitor, SQ22536 and H89. In conclusion, exendin-4 may be associated with the upregulation of SERT expression via the AC/PKA signaling pathway.

Endocrine regulation of gut function - a role for glucagon-like peptide-1 in the pathophysiology of irritable bowel syndrome

NEW FINDINGS

What is the topic of this review? Pathophysiological changes linked to irritable bowel syndrome (IBS) include stress and immune activation, changes in gastrointestinal microbial and bile acid profiles and sensitization of extrinsic and intrinsic gut neurons. This review explores the potential role for L-cells in these pathophysiological changes. What advances does it highlight? L-cells, which secrete glucagon-like peptide-1 in response to nutrients, microbial factors, bile acids and short-chain fatty acids, may sense IBS-related changes in the luminal environment. Glucagon-like peptide-1 can act as a hormone, a paracrine factor or a neuromodulatory factor and, through its actions on central or peripheral neurons, may play a role in gastrointestinal dysfunction.

ABSTRACT

The prevalent and debilitating functional bowel disorder, irritable bowel syndrome (IBS), is characterized by symptoms that include abdominal pain, bloating, diarrhoea and/or constipation. The heterogeneity of IBS underscores a complex multifactorial pathophysiology, which is not completely understood but involves dysfunction of the bi-directional signalling axis between the brain and the gut. This axis incorporates efferent and afferent branches of the autonomic nervous system, circulating endocrine hormones and immune factors, local paracrine and neurocrine factors and microbial metabolites. L-cells, which are electrically excitable biosensors embedded in the gastrointestinal epithelium, secrete glucagon-like peptide-1 (GLP-1) in response to nutrients in the small intestine. However, they appear to function in a different manner more distally in the gastrointestinal tract, where they are activated by luminal factors including short-chain fatty acids, bile acids and microbial metabolic products, all of which are altered in IBS patients. Glucagon-like peptide-1 can also interact with the hypothalamic-pituitary-adrenal stress axis and the immune system, both of which are activated in IBS. Given that a GLP-1 mimetic has been found to alleviate acute pain symptoms in IBS patients, GLP-1 might be important in the manifestation of IBS symptoms. This review assesses the current knowledge about the role of GLP-1 in IBS pathophysiology and its potential role as a signal transducer in the microbiome-gut-brain signalling axis.

Decreased glucagon-like peptide-1 correlates with abdominal pain in patients with constipation-predominant irritable bowel syndrome

BACKGROUND AND OBJECTIVE

The glucagon-like peptide-1 (GLP-1) analog, ROSE-010, plays a critical role in alleviating abdominal pain in patients with irritable bowel syndrome (IBS); however, the underling mechanism is unclear. In the present study, we determined the serum GLP-1 level in patients with constipation-predominant IBS (IBS-C). The relationship between GLP-1 and abdominal pain was investigated. In addition, the expression of the GLP-1 receptor in the colon was determined.

METHODS

Rectosigmoid biopsies were gathered from 38 patients with IBS-C who met the Rome III criteria, and 22 healthy controls. Abdominal pain was quantified by a validated questionnaire. Serum GLP-1 was measured by ELISA and correlated with abdominal pain scores. The presence of the GLP-1 receptor in the colonic mucosa was assessed by immunohistochemistry.

RESULTS

Serum GLP-1 was substantially decreased in patients with IBS-C. Decreased serum GLP-1 had a negative correlation with the abdominal pain scores. Biopsies from patients with IBS-C revealed a significant down-regulation of the GLP-1 receptor in colonic mucosa compared with control subjects.

CONCLUSIONS

Decreased serum GLP-1 correlates with abdominal pain in patients with IBS-C. Decreased expression of GLP-1 and GLP-1 receptor may be the basis for alleviation of abdominal pain in patients with IBS-C by ROSE-010.

Progress in treatment of irritable bowel syndrome

Irritable bowel syndrome is a common functional bowel disorder whose incidence has a tendency to increase year by year. At present, the pathogenesis of irritable bowel syndrome is not completely clear, and treatments are mainly symptomatic. In recent years, with the better understanding of its pathogenesis, some new drugs and treatments have been developed, such as methods of improving intestinal micro-ecology (antibiotics, fecal transplantation), mesalazine, and new drugs of improving intestinal secretion, motiligy and sensitivity, plant drugs, some of which have been applied clinically. This article will make a review of the current progress in treatment of irritable bowel syndrome.

Exogenous glucagon-like peptide 1 reduces contractions in human colon circular muscle

Glucagon-like peptide 1 (GLP1) is a naturally occurring peptide secreted by intestinal L-cells. Though its primary function is to serve as an incretin, GLP1 reduces gastrointestinal motility. However, only a handful of animal studies have specifically evaluated the influence of GLP1 on colonic motility. Consequently, the aims of this study were to investigate the effects induced by exogenous GLP1, to analyze the mechanism of action, and to verify the presence of GLP1 receptors (GLP1Rs) in human colon circular muscular strips. Organ bath technique, RT-PCR, western blotting, and immunofluorescence were used. In human colon, exogenous GLP1 reduced, in a concentration-dependent manner, the amplitude of the spontaneous contractions without affecting the frequency and the resting basal tone. This inhibitory effect was significantly reduced by exendin (9-39), a GLP1R antagonist, which per se significantly increased the spontaneous mechanical activity. Moreover, it was abolished by tetrodotoxin, a neural blocker, or Nω-nitro-l-arginine - a blocker of neuronal nitric oxide synthase (nNOS). The biomolecular analysis revealed a genic and protein expression of the GLP1R in the human colon. The double-labeling experiments with anti-neurofilament or anti-nNOS showed, for the first time, that immunoreactivity for the GLP1R was expressed in nitrergic neurons of the myenteric plexus. In conclusion, the results of this study suggest that GLP1R is expressed in the human colon and, once activated by exogenous GLP1, mediates an inhibitory effect on large intestine motility through NO neural release.

Treatment of irritable bowel syndrome: sex and gender specific aspects

Patients with functional gastrointestinal disorders constitute the majority of patients seeking healthcare for gastrointestinal symptoms in primary and secondary care. Of these disorders irritable bowel syndrome (IBS) is one of the most common and affects 10-20% in the Western world. IBS is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. Sex and gender aspects are important in understanding differences between men and women in their risk and experience of IBS. Relative to men, women are diagnosed more frequently with IBS. Female patients are more likely to be constipated, complain of abdominal distension and of certain extracolonic symptoms. Given the variability of IBS, the most successful treatment will be comprehensive, involving multiple strategies. Efficacy, safety and tolerability are important in the evaluation of IBS therapies, as patients are likely to require long-term treatment. Laxatives, antidiarrheals or antispasmodics are common in the treatment of IBS but the majority of patients receive antispasmodics followed by prokinetic agents. In treatment of IBS there appears to be a greater clinical response to serotonergic agents developed for IBS in women compared to men. There is an absence of drugs licensed specifically for the treatment of IBS. Further studies with novel agents are needed, to evaluate new approaches to IBS management including gender specific behavioral therapies and better characterization of patient subgroups with regard to drug therapy so that personalized therapy can be tested.

Role of the gut in lipid homeostasis

Intestinal lipid transport plays a central role in fat homeostasis. Here we review the pathways regulating intestinal absorption and delivery of dietary and biliary lipid substrates, principally long-chain fatty acid, cholesterol, and other sterols. We discuss the regulation and functions of CD36 in fatty acid absorption, NPC1L1 in cholesterol absorption, as well as other lipid transporters including FATP4 and SRB1. We discuss the pathways of intestinal sterol efflux via ABCG5/G8 and ABCA1 as well as the role of the small intestine in high-density lipoprotein (HDL) biogenesis and reverse cholesterol transport. We review the pathways and genetic regulation of chylomicron assembly, the role of dominant restriction points such as microsomal triglyceride transfer protein and apolipoprotein B, and the role of CD36, l-FABP, and other proteins in formation of the prechylomicron complex. We will summarize current concepts of regulated lipoprotein secretion (including HDL and chylomicron pathways) and include lessons learned from families with genetic mutations in dominant pathways (i.e., abetalipoproteinemia, chylomicron retention disease, and familial hypobetalipoproteinemia). Finally, we will provide an integrative view of intestinal lipid homeostasis through recent findings on the role of lipid flux and fatty acid signaling via diverse receptor pathways in regulating absorption and production of satiety factors.

Glucagon-like peptide-1 modulates neurally evoked mucosal chloride secretion in guinea pig small intestine in vitro

Glucagon-like peptide-1 (GLP-1) acts at the G protein-coupled receptor, GLP-1R, to stimulate secretion of insulin and to inhibit secretion of glucagon and gastric acid. Involvement in mucosal secretory physiology has received negligible attention. We aimed to study involvement of GLP-1 in mucosal chloride secretion in the small intestine. Ussing chamber methods, in concert with transmural electrical field stimulation (EFS), were used to study actions on neurogenic chloride secretion. ELISA was used to study GLP-1R effects on neural release of acetylcholine (ACh). Intramural localization of GLP-1R was assessed with immunohistochemistry. Application of GLP-1 to serosal or mucosal sides of flat-sheet preparations in Ussing chambers did not change baseline short-circuit current (I(sc)), which served as a marker for chloride secretion. Transmural EFS evoked neurally mediated biphasic increases in I(sc) that had an initial spike-like rising phase followed by a sustained plateau-like phase. Blockade of the EFS-evoked responses by tetrodotoxin indicated that the responses were neurally mediated. Application of GLP-1 reduced the EFS-evoked biphasic responses in a concentration-dependent manner. The GLP-1 receptor antagonist exendin-(9-39) suppressed this action of GLP-1. The GLP-1 inhibitory action on EFS-evoked responses persisted in the presence of nicotinic or vasoactive intestinal peptide receptor antagonists but not in the presence of a muscarinic receptor antagonist. GLP-1 significantly reduced EFS-evoked ACh release. In the submucosal plexus, GLP-1R immunoreactivity (IR) was expressed by choline acetyltransferase-IR neurons, neuropeptide Y-IR neurons, somatostatin-IR neurons, and vasoactive intestinal peptide-IR neurons. Our results suggest that GLP-1R is expressed in guinea pig submucosal neurons and that its activation leads to a decrease in neurally evoked chloride secretion by suppressing release of ACh at neuroepithelial junctions in the enteric neural networks that control secretomotor functions.

The effect of the once-daily human glucagon-like peptide 1 analog liraglutide on the pharmacokinetics of acetaminophen

INTRODUCTION

Acetaminophen is a commonly used analgesic and antipyretic drug, and is frequently used to study gastric emptying. Due to its high permeability and high solubility, acetaminophen can be used as a pharmacologic model for medications with similar characteristics. The objective of this study was to assess the effect of liraglutide on the pharmacokinetics (PK) of acetaminophen in patients with type 2 diabetes.

METHODS

This was a randomized, placebo-controlled, two-period crossover trial in which subjects with type 2 diabetes received placebo or liraglutide. After steady state PK of liraglutide 1.8 mg/ placebo were established, a single dose of acetaminophen 1 g was administered at the time of liraglutide C(max) (maximum concentration). The PK profile of acetaminophen was assessed at 18 time points during the 8-hour post-dosing period. Placebo and liraglutide were considered equivalent with respect to area under the curve (AUC)(0-∞) and AUC(0-480) min of acetaminophen if the 90% CI for the ratio was fully contained within the limits of 0.80 to 1.25.

RESULTS

All subjects (n=18; mean [SD] age 59 [7] years, body mass index [BMI] 29.7 [4.2] kg/m(2), and glycated hemoglobin [HbA(1c)] 7.8% [0.6%]) completed the study. Equivalence was demonstrated between liraglutide 1.8 mg at steady state and placebo, with respect to acetaminophen AUC(0-∞) (estimated ratio 1.04; 90% CI: 0.97, 1.10) and acetaminophen AUC(0-480) min (estimated ratio 0.95; 90% CI: 0.89, 1.01). During liraglutide, a lower C(max) was observed (estimated ratio 0.69; 90% CI: 0.56, 0.85) and the median acetaminophen t(max) occurred 15 minutes later compared with placebo.

CONCLUSION

The overall exposure of acetaminophen following a 1 g dose was comparable for subjects taking liraglutide or placebo, and the clinical impact of the lower C(max) and delay in absorption of acetaminophen was considered to be transient and small, and without clinical relevance. No adjustment for acetaminophen is recommended when used concomitantly with liraglutide.

Enteric nervous system in the small intestine: pathophysiology and clinical implications

The digestive system is endowed with its own, local nervous system, referred to as the enteric nervous system (ENS). Given the varied functions of small intestine, its ENS has developed individualized characteristics relating to motility, secretion, digestion, and inflammation. The ENS regulates the major enteric processes such as immune response, detecting nutrients, motility, microvascular circulation, intestinal barrier function, and epithelial secretion of fluids, ions, and bioactive peptides. Remarkable progress has been made in understanding the signaling pathways in this complex system and how they work. In this article, we focus on recent advances that have led to new insights into small intestinal ENS function and the development of new therapies.

Diagnosis and management of IBS

IBS is a common gastrointestinal condition characterized by chronic or recurrent abdominal pain associated with altered bowel habits. IBS is considered a functional bowel disorder (that is, not defined by structural or biochemical abnormalities) and is diagnosed using symptom-based criteria. Limited and judicious use of diagnostic testing is recommended, particularly in patients with typical symptoms of IBS without alarm signs and symptoms. Management of IBS is based on a multifactorial approach and includes establishment of an effective patient-provider relationship, education, reassurance, dietary alterations, pharmacotherapy, behavioral and psychological treatment. Patient-centered care is recommended, in which management is focused on the patient's most bothersome and impactful symptoms, their preferences and previous experiences with treatment, and addressing factors associated with the onset and exacerbation of symptoms. Pharmacotherapy is typically targeted against the predominant symptom. This Review discusses the current evidence-based recommendations for the diagnosis and management of IBS. An improved understanding of the recommended diagnostic and therapeutic approaches for IBS will lead to greater patient satisfaction, as well as reduced health-care costs.