Ghrelin suppresses glucose-stimulated insulin secretion and deteriorates glucose tolerance in healthy humans

Systematic Review: Does Exercise Training Influence Ghrelin Levels?

Ghrelin, a gastric-derived peptide, regulates appetite, food intake, and energy homeostasis. Body weight plays a crucial role in modulating circulating ghrelin levels. Since exercise training is one of the most valuable tools for controlling body weight, it is relevant to consider whether exercise can influence total ghrelin secretion. This study aims to perform a systematic review of the effect of acute/chronic exercise on plasma ghrelin levels. An extensive literature search was carried out on various databases, including PubMed, ScienceDirect, and Google Scholar. The search was conducted using English keywords such as acute-exercise, transient-exercise, exercise, chronic-exercise, training, physical-activity, physical-training, exercise training, and total-ghrelin, ghrelin, appetite-related-peptides, gastrointestinal-peptides, gastrointestinal-hormones, and appetite-regulating-hormone. Initially, 2104 studies were identified. After evaluating study quality, data from 61 relevant studies were extracted for inclusion in this review. Most studies indicated that short-term acute aerobic exercise did not affect total ghrelin levels regardless of exercise intensity, characteristics, or growth hormone (GH) secretion. However, long and very-long aerobic/chronic exercise increased total ghrelin levels, mainly in overweight/obese individuals. Acute/chronic exercise may differentially influence total ghrelin secretion. Short-term acute aerobic exercise induces stable plasma ghrelin concentrations, independent of GH secretion. Long-term aerobic training increased its levels mainly in overweight/obese individuals through body composition and oxidative stress reduction. Additionally, total ghrelin secretion is more sensitive to exercise/training duration than exercise/training intensity.

Effects of exogenous ghrelin treatment on oxidative stress, inflammation and histological parameters in a fat-fed streptozotocin rat model

In this study, the anti-inflammatory, antioxidative, and protective effects of ghrelin were investigated in a fat-fed streptozotocin (STZ) rat model and compared with metformin, diabetes and the healthy control groups. Histopathological evaluations were performed on H&E-stained pancreas and brain sections. Biochemical parameters were investigated by enzyme-linked immunosorbent assay. Blood glucose levels were significantly decreased with ghrelin or metformin treatments than the diabetes group. STZ administration increased brain, renal and pancreatic IL-1β, TNF-α and MDA while decreasing GPX, CAT, SOD, and NGF levels. Ghrelin increased renal GPX, CAT, NGF pancreatic GPX, SOD, CAT, NGF and brain SOD, NGF while it decreased renal, pancreatic and brain IL-1β, TNF-α and MDA levels. Ghrelin reduced neuronal loss and degeneration in the cerebral cortex and hippocampus and greatly ameliorated diabetes-related damage in pancreas. In conclusion, the data suggested that ghrelin is an effective candidate as a protectant for reducing the adverse effects of diabetes.

Gut-pancreas axis in the control of insulin secretion in streptozotocin-resistant rats

The Spontaneously Running Tokushima Shikoku (SPORTS) rat is characterized by hyperactive behavior but is also a potential model for studies of the role of the gut-pancreas axis in the regulation of insulin secretion. We here explored the role of ghrelin, a hormone associated with appetite regulation, in insulin dynamics within the context of streptozotocin (STZ) resistance in SPORTS rats. Comprehensive analyses-including histological examinations, gene expression profiling, and assessment of metabolic parameters-revealed that SPORTS rats are resistant to STZ-induced pancreatic injury and that, in addition to low circulating ghrelin levels, they manifest increased circulating levels of active glucagon-like peptide-1 (GLP-1) and upregulated expression of Pdx1 in the pancreas. Ghrelin administration attenuated the STZ resistance of these rats, with suppression of GLP-1 and downregulation of Pdx1 expression being implicated in this effect. Our results highlight the complex interplay among ghrelin, GLP-1, and insulin dynamics, and they suggest potential new therapeutic targets for diabetes.

Relationship between ghrelin and thyroid disease: a meta-analysis

Background

Previous studies have identified a close relationship between ghrelin levels and thyroid disease. Ghrelin levels were lower in patients with hyperthyroidism compared with healthy individuals, and increased after treatment. However, other studies have reported inconsistent results. As such, the association between ghrelin and thyroid disease remains controversial.

Methods

A literature search of the Web of Science, Wiley Online Library, Embase, and PubMed databases was performed. The title or abstract search term "thyroid" was used in combination with "ghrelin". Meta-analysis results are reported as standardized mean difference with corresponding 95% confidence interval (CI).

Results

Twenty-three studies were included in this meta-analysis. Ghrelin levels in patients with hyperthyroidism were significantly lower than those in healthy individuals (SMD: -1.03, 95% CI [-1.75, 0.32]), but significantly higher after effective treatment (SMD: 0.77, 95% CI [0.03, 1.51]). Ghrelin levels were higher, but not significantly, in patients with hypothyroidism compared with healthy controls (SMD: 0.48, 95% CI [-0.13, 1.08]).

Conclusions

This systematic review is the first to evaluate the relationship between ghrelin and thyroid disease. Determining the role of ghrelin in thyroid disease will significantly contribute to understand of symptom or pathomechanism.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024591501.

Effects of Weight Loss on Endothelium and Vascular Homeostasis: Impact on Cardiovascular Risk

Available knowledge shows that obesity is associated with an impaired endothelial function and an increase in cardiovascular risk, but the mechanisms of this association are not yet fully understood. Adipose tissue dysfunction, adipocytokines production, along with systemic inflammation and associated comorbidities (e.g., diabetes and hypertension), are regarded as the primary physiological and pathological factors. Various strategies are now available for the control of excess body weight. Dietary regimens alone, or in association with bariatric surgery when indicated, are now widely used. Of particular interest is the understanding of the effect of these interventions on endothelial homeostasis in relation to cardiovascular health. Substantial weight loss resulting from both diet and bariatric surgery decreases circulating biomarkers and improves endothelial function. Extensive clinical trials and meta-analyses show that bariatric surgery (particularly gastric bypass) has more substantial and long-lasting effect on weight loss and glucose regulation, as well as on distinct circulating biomarkers of cardiovascular risk. This review summarizes the current understanding of the distinct effects of diet-induced and surgery-induced weight loss on endothelial function, focusing on the key mechanisms involved in these effects.

Effect of ghrelin on glucose tolerance, gut hormones, appetite, and food intake after sleeve gastrectomy

Ghrelin is an appetite-stimulating hormone secreted from the gastric mucosa in the fasting state, and secretion decreases in response to food intake. After sleeve gastrectomy (SG), plasma concentrations of ghrelin decrease markedly. Whether this affects appetite and glucose tolerance postoperatively is unknown. We investigated the effects of ghrelin infusion on appetite and glucose tolerance in individuals with obesity before and 3 mo after SG. Twelve participants scheduled for SG were included. Before and 3 mo after surgery, a mixed-meal test followed by an ad libitum meal test was performed with concomitant infusions of acyl-ghrelin (1 pmol/kg/min) or placebo. Infusions began 60 min before meal intake to reach a steady state before the mixed-meal and were continued throughout the study day. Two additional experimental days with 0.25 pmol/kg/min and 10 pmol/kg/min of acyl-ghrelin infusions were conducted 3 mo after surgery. Both before and after SG, postprandial glucose concentrations increased dose dependently during ghrelin infusions compared with placebo. Ghrelin infusions inhibited basal and postprandial insulin secretion rates, resulting in lowered measures of β-cell function, but no effect on insulin sensitivity was seen. Ad libitum meal intake was unaffected by the administration of ghrelin. In conclusion, ghrelin infusion increases postprandial plasma glucose concentrations and impairs β-cell function before and after SG but has no effect on ad libitum meal intake. We speculate that the lower concentration of ghrelin after SG may impact glucose metabolism following this procedure.NEW & NOTEWORTHY Ghrelin's effect on glucose tolerance and food intake following sleeve gastrectomy (SG) was evaluated. Acyl-ghrelin was infused during a mixed-meal and ad libitum meals before and 3 mo after surgery. Postprandial glucose concentrations increased during ghrelin infusions, both before and after surgery, while insulin production was inhibited. However, ad libitum meal intake did not differ during ghrelin administration compared with placebo. The decreased ghrelin concentration following SG may contribute to the glycemic control after surgery.

Intestinal expression profiles and hepatic expression of LEAP2, ghrelin and their common receptor, GHSR, in humans

Liver-expressed antimicrobial peptide 2 (LEAP2) and ghrelin have reciprocal effects on their common receptor, the growth hormone secretagogue receptor (GHSR). Ghrelin is considered a gastric hormone and LEAP2 a liver-derived hormone and both have been proposed to be involved in the pathophysiology of obesity and type 2 diabetes (T2D). We investigated the mRNA expression of LEAP2, ghrelin and GHSR along the intestinal tract of individuals with and without TD2, and in the liver of men with and without obesity. Mucosal biopsies retrieved with 30-cm intervals throughout the small intestine and from 7 well-defined locations along the large intestine from 12 individuals with T2D and 12 healthy controls together with liver biopsies from 15 men with obesity and 15 lean men were subjected to bulk transcriptomics analysis. Both in individuals with and without T2D, mRNA expression of LEAP2 increased through the small intestine until dropping at the ileocecal valve, with little LEAP2 mRNA expression in the large intestine. Pronounced LEAP2 expression was observed in the liver of men with and without obesity. Robust ghrelin mRNA expression was observed in the duodenum of individuals with and without T2D, gradually decreasing along the small intestine with little expression in the large intestine. Ghrelin mRNA expression was not detected in the liver biopsies, and GHSR mRNA expression was not. In conclusion, we provide unique mRNA expression profiles of LEAP2, ghrelin and GHSR along the human intestinal tract showing no T2D-associated changes, and in the liver showing no differences between men with and without obesity.

Regulation of peripheral tissue substrate metabolism by the gut-derived hormone ghrelin

Ghrelin increases in the circulation prior to entrained mealtimes, with the acylated (AG) form functioning to stimulate food intake and growth hormone release. Acutely, AG induces whole-body insulin resistance, potentially to maintain glycemia between meals. Alternatively, chronic administration of both AG and the unacylated isoform of ghrelin (unAG) is associated with improved skeletal muscle insulin sensitivity as well as reduced intramuscular lipids and inflammation. This may be due to effects on lipid metabolism, with ghrelin promoting storage of fat in adipose and liver while stimulating oxidation in skeletal muscle, preventing ectopic lipid accumulation. This is of specific relevance in the handling of meal-derived lipids, as ghrelin rises preprandially with effects persisting for 2-3 h following exposure in skeletal muscle, coinciding with elevated plasma FFAs. We hypothesize that ghrelin acts as a preparatory signal for incoming lipids, as well as a regulatory hormone for their use and storage. The effects of ghrelin on skeletal muscle are lost with high fat diet feeding and physical inactivity, potentially being implicated in the pathogenesis of metabolic disease. This review summarizes the metabolic effects of both ghrelin isoforms on peripheral tissues including the pancreas, adipose, liver, and skeletal muscle. Additionally, we speculate on the physiological relevance of these effects in vivo and suggest that ghrelin may be a key regulatory hormone for nutrient handling in the postprandial state.

Early chronotype favors appetite and reduced later day caloric intake among adults with obesity

Late chronotype (LC) is related to obesity and altered food intake throughout the day. But whether appetite perception and gut hormones differ among chronotypes is unclear. Thus, we examined if early chronotype (EC) have different appetite responses in relation to food intake than LC. Adults with obesity were categorized using the Morningness-Eveningness Questionnaire (MEQ) as either EC (n = 21, 18F, MEQ = 63.9 ± 1.0, 53.7 ± 1.2 yr, 36.2 ± 1.1 kg/m2) and LC (n = 28, 24F, MEQ = 47.2 ± 1.5, 55.7 ± 1.4 yr, 37.1 ± 1.0 kg/m2). Visual analog scales were used during a 120 min 75 g oral glucose tolerance test (OGTT) at 30 min intervals to assess appetite perception, as well as glucose, insulin, GLP-1 (glucagon-like polypeptide-1), GIP (glucose-dependent insulinotrophic peptide), PYY (protein tyrosine tyrosine), and acylated ghrelin. Dietary intake (food logs), resting metabolic rate (RMR; indirect calorimetry), aerobic fitness (maximal oxygen consumption (VO2max)), and body composition dual-energy X-ray absorptiometry (DXA) were also assessed. Age, body composition, RMR, and fasting appetite were similar between groups. However, EC had higher satisfaction and fullness as well as reduced desires for sweet, salty, savory, and fatty foods during the OGTT (P <0.05). Only GIP tAUC0-120 min was elevated in EC versus LC (p = 0.01). Daily dietary intake was similar between groups, but EC ate fewer carbohydrates (p = 0.05) and more protein (p = 0.01) at lunch. Further, EC had lower caloric (p = 0.03), protein (p = 0.03) and fat (p = 0.04) intake during afternoon snacking compared to LC. Dietary fat was lower, and carbohydrates was higher, in EC than LC (p = 0.05) at dinner. Low glucose and high insulin as well as GLP-1 tAUC60-120 min related to desires for sweet foods (p < 0.05). Taken together, EC had more favorable appetite and lower caloric intake later in the day compared with LC.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.

Inhibition of ghrelin activity by the receptor antagonist [D-Lys3]-GHRP-6 enhances hepatic fatty acid oxidation and gluconeogenesis in a growing pig model

Despite its central role in regulating energy intake and metabolism, ghrelin is little understood when it comes to its effects on hepatic lipid and glucose metabolism. Growing pigs were intravenously injected with ghrelin receptor antagonist [D-Lys3]-GHRP-6 (DLys; 6 mg/kg body weight) for seven days to determine whether ghrelin plays a role in glucose and lipid metabolism. DLys treatment significantly reduced body weight gain and adipose histopathology found that DLys treatment dramatically reduced adipocyte size. DLys treatment significantly increased serum NEFA and insulin levels, hepatic glucose level and HOMA-IR, and significantly decreased serum TBA level of growing pigs after fasting. Moreover, DLys treatment changed the dynamics of serum metabolic parameters, including glucose, NEFA, TBA, insulin, GH, leptin, and cortisol. Liver transcriptome showed that DLys treatment affected the metabolism-related pathways. Compared with the control group, adipose tissue lipolysis (the adipose triglyceride lipase level was significantly increased), hepatic gluconeogenesis (the G6PC protein level was significantly increased) and fatty acid oxidation (the CPT1A protein level was significantly increased) were promoted in the DLys group. DLys treatment expanded degrees of oxidative phosphorylation in the liver, coming about in a higher NAD+ /NADH proportion and enactment of the SIRT1 signaling pathway. Additionally, the liver protein levels of the DLys group were significantly higher than those of the control group for GHSR, PPAR alpha, and PGC-1. To summarize, inhibition of ghrelin activity can significantly affect metabolism and alter energy levels by enhancing fat mobilization, hepatic fatty acid oxidation and gluconeogenesis without affecting fatty acid uptake and synthesis in the liver.

Desacyl-ghrelin, not just an inactive form of ghrelin?-A review of current knowledge on the biological actions of desacyl-ghrelin

Desacyl-ghrelin is a form of ghrelin which lacks acyl-modification of the third serine residue of ghrelin. Originally, desacyl-ghrelin was considered to be just an inactive form of ghrelin. More recently, however, it has been suggested to have various biological activities, including control of food intake, growth hormone, glucose metabolism, and gastric movement, and is involved in cell survival. In this review, we summarize the current knowledge of the biological actions of desacyl-ghrelin and the proposed mechanisms by which it exerts the effects.

State of art on the mechanisms of laparoscopic sleeve gastrectomy in treating type 2 diabetes mellitus

Obesity and type-2 diabetes mellitus (T2DM) are metabolic disorders. Obesity increases the risk of T2DM, and as obesity is becoming increasingly common, more individuals suffer from T2DM, which poses a considerable burden on health systems. Traditionally, pharmaceutical therapy together with lifestyle changes is used to treat obesity and T2DM to decrease the incidence of comorbidities and all-cause mortality and to increase life expectancy. Bariatric surgery is increasingly replacing other forms of treatment of morbid obesity, especially in patients with refractory obesity, owing to its many benefits including good long-term outcomes and almost no weight regain. The bariatric surgery options have markedly changed recently, and laparoscopic sleeve gastrectomy (LSG) is gradually gaining popularity. LSG has become an effective and safe treatment for type-2 diabetes and morbid obesity, with a high cost-benefit ratio. Here, we review the me-chanism associated with LSG treatment of T2DM, and we discuss clinical studies and animal experiments with regard to gastrointestinal hormones, gut microbiota, bile acids, and adipokines to clarify current treatment modalities for patients with obesity and T2DM.

Postprandial effect of gastrointestinal hormones and gastric activity in patients with irritable bowel syndrome

Altered gut regulation, including motor and secretory mechanisms, is characteristic of irritable bowel syndrome (IBS). The severity of postprandial symptoms in IBS patients is associated with discomfort and pain; gas-related symptoms such as bloating and abdominal distension; and abnormal colonic motility. The aim of this study was to assess the postprandial response, i.e., gut peptide secretion and gastric myoelectric activity, in patients with constipation-predominant IBS. The study was conducted on 42 IBS patients (14 males, 28 females, mean age 45.1 ± 15.3 years) and 42 healthy participants (16 males, 26 females, mean age 41.1 ± 8.7 years). The study assessed plasma gut peptide levels (gastrin, CCK-Cholecystokinin, VIP-Vasoactive Intestinal Peptide, ghrelin, insulin) and gastric myoelectric activity obtained from electrogastrography (EGG) in the preprandial and postprandial period (meal-oral nutritional supplement 300 kcal/300 ml). Mean preprandial gastrin and insulin levels were significantly elevated in IBS patients compared to the control group (gastrin: 72.27 ± 26.89 vs. 12.27 ± 4.91 pg/ml; p < 0.00001 and insulin: 15.31 ± 12.92 vs. 8.04 ± 3.21 IU/ml; p = 0.0001), while VIP and ghrelin levels were decreased in IBS patients (VIP: 6.69 ± 4.68 vs. 27.26 ± 21.51 ng/ml; p = 0.0001 and ghrelin: 176.01 ± 88.47 vs. 250.24 ± 84.55 pg/ml; p < 0.0001). A nonsignificant change in the CCK level was observed. IBS patients showed significant changes in postprandial hormone levels compared to the preprandial state-specifically, there were increases in gastrin (p = 0.000), CCK (p < 0.0001), VIP (p < 0.0001), ghrelin (p = 0.000) and insulin (p < 0.0001). Patients with IBS showed reduced preprandial and postprandial normogastria (59.8 ± 22.0 vs. 66.3 ± 20.2%) compared to control values (83.19 ± 16.7%; p < 0.0001 vs. 86.1 ± 9.4%; p < 0.0001). In response to the meal, we did not observe an increase in the percentage of normogastria or the average percentage slow-wave coupling (APSWC) in IBS patients. The postprandial to preprandial power ratio (PR) indicates alterations in gastric contractions; in controls, PR = 2.7, whereas in IBS patients, PR = 1.7, which was significantly lower (p = 0.00009). This ratio reflects a decrease in gastric contractility. Disturbances in the postprandial concentration of gut peptides (gastrin, insulin and ghrelin) in plasma may contribute to abnormal gastric function and consequently intestinal motility, which are manifested in the intensification of clinical symptoms, such as visceral hypersensitivity or irregular bowel movements in IBS patients.

Ghrelin does not impact the blunted counterregulatory response to recurrent hypoglycemia in mice

Introduction

Recurrent episodes of insulin-induced hypoglycemia in patients with diabetes mellitus can result in hypoglycemia-associated autonomic failure (HAAF), which is characterized by a compromised response to hypoglycemia by counterregulatory hormones (counterregulatory response; CRR) and hypoglycemia unawareness. HAAF is a leading cause of morbidity in diabetes and often hinders optimal regulation of blood glucose levels. Yet, the molecular pathways underlying HAAF remain incompletely described. We previously reported that in mice, ghrelin is permissive for the usual CRR to insulin-induced hypoglycemia. Here, we tested the hypothesis that attenuated release of ghrelin both results from HAAF and contributes to HAAF.

Methods

C57BL/6N mice, ghrelin-knockout (KO) + control mice, and GhIRKO (ghrelin cell-selective insulin receptor knockout) + control mice were randomized to one of three treatment groups: a "Euglycemia" group was injected with saline and remained euglycemic; a 1X hypoglycemia ("1X Hypo") group underwent a single episode of insulin-induced hypoglycemia; a recurrent hypoglycemia ("Recurrent Hypo") group underwent repeated episodes of insulin-induced hypoglycemia over five successive days.

Results

Recurrent hypoglycemia exaggerated the reduction in blood glucose (by ~30%) and attenuated the elevations in plasma levels of the CRR hormones glucagon (by 64.5%) and epinephrine (by 52.9%) in C57BL/6N mice compared to a single hypoglycemic episode. Yet, plasma ghrelin was equivalently reduced in "1X Hypo" and "Recurrent Hypo" C57BL/6N mice. Ghrelin-KO mice exhibited neither exaggerated hypoglycemia in response to recurrent hypoglycemia, nor any additional attenuation in CRR hormone levels compared to wild-type littermates. Also, in response to recurrent hypoglycemia, GhIRKO mice exhibited nearly identical blood glucose and plasma CRR hormone levels as littermates with intact insulin receptor expression (floxed-IR mice), despite higher plasma ghrelin in GhIRKO mice.

Conclusions

These data suggest that the usual reduction of plasma ghrelin due to insulin-induced hypoglycemia is unaltered by recurrent hypoglycemia and that ghrelin does not impact blood glucose or the blunted CRR hormone responses during recurrent hypoglycemia.

The role of the gastric fundus in glycemic control

PURPOSE

Ghrelin, one of the most studied gut hormones, is mainly produced by the gastric fundus. Abundant evidence exists from preclinical and clinical studies underlining its contribution to glucose regulation. In the following narrative review, the role of the gastric fundus in glucose regulation is summarized and we investigate whether its resection enhances glycemic control.

METHODS

An electronic search was conducted in the PubMed® database and in Google Scholar® using a combination of medical subject headings (MeSH). We examined types of metabolic surgery, including, in particular, gastric fundus resection, either as part of laparoscopic sleeve gastrectomy (LSG) or modified laparoscopic gastric bypass with fundus resection (LRYGBP + FR), and the contribution of ghrelin reduction to glucose regulation.

RESULTS

Fourteen human studies were judged to be eligible and included in this narrative review. Reduction of ghrelin levels after fundus resection might be related to early glycemic improvement before significant weight loss is achieved. Long-term data regarding the role of ghrelin reduction in glucose homeostasis are sparse.

CONCLUSION

The exact role of ghrelin in achieving glycemic control is still ambiguous. Data from human studies reveal a potential contribution of ghrelin reduction to early glycemic improvement, although further well-designed studies are needed.

Ghrelin and glucagon-like peptide-1 according to body adiposity and glucose homeostasis

Objective

We investigated the biological behavior of ghrelin and glucagon-like peptide-1 (GLP-1) after a standard liquid meal according to body adiposity and glucose homeostasis.

Subjects and methods

This cross-sectional study included 41 individuals (92.7% women; aged 38.3 ± 7.8 years; BMI 32.2 ± 5.5 kg/m2) allocated into three groups according to body adiposity and glucose homeostasis, as follows: normoglycemic eutrophic controls (CON, n = 11), normoglycemic with obesity (NOB, n = 15), and dysglycemic with obesity (DOB, n = 15). They were tested at fasting and 30 and 60 min after the ingestion of a standard liquid meal in which we measured active ghrelin, active GLP-1, insulin, and plasma glucose levels.

Results

As expected, DOB exhibited the worst metabolic status (glucose, insulin, HOMA-IR, HbA1c) and an inflammatory status (TNF-α) at fasting, besides a more significant increase in glucose than postprandial NOB (p ≤ 0.05). At fasting, no differences between groups were detected in lipid profile, ghrelin, and GLP-1 (p ≥ 0.06). After the standard meal, all groups exhibited a reduction in ghrelin levels between fasting vs. 60 min (p ≤ 0.02). Additionally, we noticed that GLP-1 and insulin increased equally in all groups after the standard meal (fasting vs. 30 and 60 min). Although glucose levels increased in all groups after meal intake, these changes were significantly more significant in DOB vs. CON and NOB at 30 and 60 min post-meal (p ≤ 0.05).

Conclusion

Time course of ghrelin and GLP-1 levels during the postprandial period was not influenced by body adiposity or glucose homeostasis. Similar behaviors occurred in controls and patients with obesity, independently of glucose homeostasis.

A rising tide lifts all MBOATs: recent progress in structural and functional understanding of membrane bound O-acyltransferases

Acylation modifications play a central role in biological and physiological processes. Across a range of biomolecules from phospholipids to triglycerides to proteins, introduction of a hydrophobic acyl chain can dramatically alter the biological function and cellular localization of these substrates. Amongst the enzymes catalyzing these modifications, the membrane bound O-acyltransferase (MBOAT) family occupies an intriguing position as the combined substrate selectivities of the various family members span all three classes of these biomolecules. MBOAT-dependent substrates are linked to a wide range of health conditions including metabolic disease, cancer, and neurodegenerative disease. Like many integral membrane proteins, these enzymes have presented challenges to investigation due to their intractability to solubilization and purification. However, over the last several years new solubilization approaches coupled with computational modeling, crystallography, and cryoelectron microscopy have brought an explosion of structural information for multiple MBOAT family members. These studies enable comparison of MBOAT structure and function across members catalyzing modifications of all three substrate classes, revealing both conserved features amongst all MBOATs and distinct architectural features that correlate with different acylation substrates ranging from lipids to proteins. We discuss the methods that led to this renaissance of MBOAT structural investigations, our new understanding of MBOAT structure and implications for catalytic function, and the potential impact of these studies for development of new therapeutics targeting MBOAT-dependent physiological processes.

Ghrelin intronic lncRNAs, lnc-GHRL-3:2 and lnc-GHRL-3:3, as novel biomarkers in type 2 diabetes mellitus

BACKGROUND

We aim to identify circulating lncRNAs located in the region of the ghrelin (GHRL) gene that play a role in the development of T2DM.

METHODS

Bioinformatic tool was used to identify candidates GHRL-lncRNAs. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to compare the expression levels of selected lncRNAs on diabetic patients and non-diabetic controls.Receiver operating characteristic (ROC) curve analysis was performed to evaluate the discriminatory power of selected GHRL-lncRNAs.

RESULTS

The bioinformatic analysis predicted three antisense and eight sense-intronic GHRL- lncRNAs. Two differentially expressed GHRL-lncRNAs were detected in diabetic patients. The expression levels of lnc-GHRL-3:2, lnc-GHRL-3:3, and the GHRL mRNA were significantly (p ≤ .0001) lower in the diabetic patients. ROC analysis showed that the area under the curve (AUC) value was 0.93 for lnc-GHRL-3:2 and 0.90 for lnc-GHRL-3:3.

CONCLUSION

lnc-GHRL-3:2 and lnc-GHRL-3:3 are novel biomarkers and might play a regulatory role in T2DM pathogenesis.

Ghrelin receptor signaling in health and disease: a biased view

As allosteric complexes, G-protein-coupled receptors (GPCRs) respond to extracellular stimuli and pleiotropically couple to intracellular transducers to elicit signaling pathway-dependent effects in a process known as biased signaling or functional selectivity. One such GPCR, the ghrelin receptor (GHSR1a), has a crucial role in restoring and maintaining metabolic homeostasis during disrupted energy balance. Thus, pharmacological modulation of GHSR1a bias could offer a promising strategy to treat several metabolism-based disorders. Here, we summarize current evidence supporting GHSR1a functional selectivity in vivo and highlight recent structural data. We propose that precise determinations of GHSR1a molecular pharmacology and pathway-specific physiological effects will enable discovery of GHSR1a drugs with tailored signaling profiles, thereby providing safer and more effective treatments for metabolic diseases.

Novel Approaches to the Management of Diabetes Mellitus in Patients with Coronary Artery Disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in individuals with diabetes mellitus (DM). Although benefit has been attributed to the strict control of hyperglycemia with traditional antidiabetic treatments, novel antidiabetic medications have demonstrated cardiovascular (CV) safety and benefits by reducing major adverse cardiac events, improving heart failure (HF), and decreasing CVD-related mortality. Emerging data underline the interrelation between diabetes, as a metabolic disorder, and inflammation, endothelial dysfunction, and oxidative stress in the pathogenesis of microvascular and macrovascular complications. Conventional glucose-lowering medications demonstrate controversial CV effects. Dipeptidyl peptidase- 4 inhibitors have not only failed to prove to be beneficial in patients with coronary artery disease, but also their safety is questionable for the treatment of patients with CVD. However, metformin, as the first-line option for type 2 DM (T2DM), shows CVD protective properties for DM-induced atherosclerotic and macrovascular complications. Thiazolidinedione and sulfonylureas have questionable effects, as evidence from large studies shows a reduction in the risk of CV events and deaths, but with an increased rate of hospitalization for HF. Moreover, several studies have revealed that insulin monotherapy for T2DM treatment increases the risk of major CV events and deaths from HF, when compared to metformin, although it may reduce the risk of myocardial infarction. Finally, this review aimed to summarize the mechanisms of action of novel antidiabetic drugs acting as glucagon-like peptide-1 receptor agonists and sodium-glucose co-transporter-2 inhibitors that show favorable effects on blood pressure, lipid levels, and inflammation, leading to reduced CVD risk in T2DM patients.

The Interplay between Ghrelin and Microglia in Neuroinflammation: Implications for Obesity and Neurodegenerative Diseases

Numerous studies have shown that microglia are capable of producing a wide range of chemokines to promote inflammatory processes within the central nervous system (CNS). These cells share many phenotypical and functional characteristics with macrophages, suggesting that microglia participate in innate immune responses in the brain. Neuroinflammation induces neurometabolic alterations and increases in energy consumption. Microglia may constitute an important therapeutic target in neuroinflammation. Recent research has attempted to clarify the role of Ghre signaling in microglia on the regulation of energy balance, obesity, neuroinflammation and the occurrence of neurodegenerative diseases. These studies strongly suggest that Ghre modulates microglia activity and thus affects the pathophysiology of neurodegenerative diseases. This review aims to summarize what is known from the current literature on the way in which Ghre modulates microglial activity during neuroinflammation and their impact on neurometabolic alterations in neurodegenerative diseases. Understanding the role of Ghre in microglial activation/inhibition regulation could provide promising strategies for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

Role of brain-gut-muscle axis in human health and energy homeostasis

The interrelationship between brain, gut and skeletal muscle plays a key role in energy homeostasis of the body, and is becoming a hot topic of research. Intestinal microbial metabolites, such as short-chain fatty acids (SCFAs), bile acids (BAs) and tryptophan metabolites, communicate with the central nervous system (CNS) by binding to their receptors. In fact, there is a cross-talk between the CNS and the gut. The CNS, under the stimulation of pressure, will also affect the stability of the intestinal system, including the local intestinal transport, secretion and permeability of the intestinal system. After the gastrointestinal tract collects information about food absorption, it sends signals to the central system through vagus nerve and other channels to stimulate the secretion of brain-gut peptide and produce feeding behavior, which is also an important part of maintaining energy homeostasis. Skeletal muscle has receptors for SCFAs and BAs. Therefore, intestinal microbiota can participate in skeletal muscle energy metabolism and muscle fiber conversion through their metabolites. Skeletal muscles can also communicate with the gut system during exercise. Under the stimulation of exercise, myokines secreted by skeletal muscle causes the secretion of intestinal hormones, and these hormones can act on the central system and affect food intake. The idea of the brain-gut-muscle axis is gradually being confirmed, and at present it is important for regulating energy homeostasis, which also seems to be relevant to human health. This article focuses on the interaction of intestinal microbiota, central nervous, skeletal muscle energy metabolism, and feeding behavior regulation, which will provide new insight into the diagnostic and treatment strategies for obesity, diabetes, and other metabolic diseases.

Circadian rhythms and pancreas physiology: A review

Type 2 diabetes mellitus, obesity and metabolic syndrome are becoming more prevalent worldwide and will present an increasingly challenging burden on healthcare systems. These interlinked metabolic abnormalities predispose affected individuals to a plethora of complications and comorbidities. Furthermore, diabetes is estimated by the World Health Organization to have caused 1.5 million deaths in 2019, with this figure projected to rise in coming years. This highlights the need for further research into the management of metabolic diseases and their complications. Studies on circadian rhythms, referring to physiological and behavioral changes which repeat approximately every 24 hours, may provide important insight into managing metabolic disease. Epidemiological studies show that populations who are at risk of circadian disruption such as night shift workers and regular long-haul flyers are also at an elevated risk of metabolic abnormalities such as insulin resistance and obesity. Aberrant expression of circadian genes appears to contribute to the dysregulation of metabolic functions such as insulin secretion, glucose homeostasis and energy expenditure. The potential clinical implications of these findings have been highlighted in animal studies and pilot studies in humans giving rise to the development of circadian interventions strategies including chronotherapy (time-specific therapy), time-restricted feeding, and circadian molecule stabilizers/analogues. Research into these areas will provide insights into the future of circadian medicine in metabolic diseases. In this review, we discuss the physiology of metabolism and the role of circadian timing in regulating these metabolic functions. Also, we review the clinical aspects of circadian physiology and the impact that ongoing and future research may have on the management of metabolic disease.

Overcoming the Limitations of Stem Cell-Derived Beta Cells

Great advances in type 1 diabetes (T1D) and type 2 diabetes (T2D) treatment have been made to this day. However, modern diabetes therapy based on insulin injections and cadaveric islets transplantation has many disadvantages. That is why researchers are developing new methods to regenerate the pancreatic hormone-producing cells in vitro. The most promising approach is the generation of stem cell-derived beta cells that could provide an unlimited source of insulin-secreting cells. Recent studies provide methods to produce beta-like cell clusters that display glucose-stimulated insulin secretion—one of the key characteristics of the beta cell. However, in comparison with native beta cells, stem cell-derived beta cells do not undergo full functional maturation. In this paper we review the development and current state of various protocols, consider advantages, and propose ways to improve them. We examine molecular pathways, epigenetic modifications, intracellular components, and the microenvironment as a possible leverage to promote beta cell functional maturation. A possibility to create islet organoids from stem cell-derived components, as well as their encapsulation and further transplantation, is also examined. We try to combine modern research on beta cells and their crosstalk to create a holistic overview of developing insulin-secreting systems.

Targeting appetite and satiety in diabetes and obesity, via G protein-coupled receptors

Type 2 diabetes and obesity have reached pandemic proportions throughout the world, so much so that the World Health Organisation coined the term "Globesity" to help encapsulate the magnitude of the problem. G protein-coupled receptors (GPCRs) are highly tractable drug targets due to their wide involvement in all aspects of physiology and pathophysiology, indeed, GPCRs are the targets of approximately 30% of the currently approved drugs. GPCRs are also broadly involved in key physiologies that underlie type 2 diabetes and obesity including feeding reward, appetite and satiety, regulation of blood glucose levels, energy homeostasis and adipose function. Despite this, only two GPCRs are the target of approved pharmaceuticals for treatment of type 2 diabetes and obesity. In this review we discuss the role of these, and select other candidate GPCRs, involved in various facets of type 2 diabetic or obese pathophysiology, how they might be targeted and the potential reasons why pharmaceuticals against these targets have not progressed to clinical use. Finally, we provide a perspective on the current development pipeline of anti-obesity drugs that target GPCRs.

Serum ghrelin is positively associated with physiological anxiety but negatively associated with pathological anxiety in humans: Data from a large community-based study

The orexigenic hormone ghrelin is being increasingly recognized as a stress hormone being involved in anxiety regulation. In animals, ghrelin effects on, and responses to acute stress differed from those in chronic stress, an animal model for anxiety and depression. In humans, elevated ghrelin levels were reported in pathological anxiety (e.g. panic disorder). However, no reports exist on physiological anxiety in mentally healthy subjects. In addition, reports on generalized anxiety symptoms, both in mentally healthy subjects (e.g. worrying) or in adult patients, are lacking. Total serum ghrelin was determined in 1666 subjects of a population-based cross-sectional study ('LIFE'). The 7-item Generalized Anxiety Disorder Scale (GAD-7), detecting also other anxiety disorders, was administered. For multiple linear regression analyses, 1091 subjects were finally included. Serum ghrelin and GAD-7 scores were positively but not significantly associated in the total group (ß=0.00025, standardized β = 0.039, 95%CI: -0.00006;0.0006;p = 0.144), in subjects with no more than mild anxiety, there was a significant positive association (GAD-7 ≤9: n = 1061, 97.25%, β = 0.00032; standardized β = 0.060; 95%CI: 0.000023;0.00062;p = 0.036). In contrast, there was a negative association in subjects with anxiety symptoms above the GAD-7 cut-off (GAD-7 ≥10: n = 30, 2.75%, ß=-0.003, standardized β = -0.462; 95% CI:-0.006;0.0001;p = 0.045). Ghrelin levels were only numerically (p = 0.23) higher in subjects with clinically relevant anxiety symptoms (963.5 ± 399.6 pg/ml; mean±SD) than in those without (901.0 ± 416.4 pg/ml). In conclusion, the positive association between ghrelin and no more than mild anxiety is an initial indication for a role for ghrelin in the regulation of physiological anxiety in humans. This association and the opposed association in pathological anxiety resemble findings in animals showing diverging ghrelin effects in acute and chronic stress.

Influence of food images with different macronutrient compositions on serum ghrelin levels: Analysis in healthy males

Objective

Serum concentrations of the orexigenic hormone ghrelin fluctuate in anticipation of food intake. Moreover, presentation of food images causes an increase in serum ghrelin levels. Thus, the visual system may have a quantifiable role in the development of hunger via the endocrine system. The influence of macronutrient visualization on ghrelin has not yet been investigated.

Methods

In four separate sessions, ghrelin concentrations, insulin, and glucose levels were compared before and after the presentation of different pictures to 14 male participants. Pictures included neutral, non‐food‐related items or isocaloric dishes whose macronutrient composition corresponded predominately to protein/fat, simple carbohydrates, or complex carbohydrates.

Results

While pre/post ghrelin concentrations numerically increased in all sessions, significant increases were only observed following neutral and protein/fat pictures. The differences were not significant between food groups and compared to neutral images. Insulin levels decreased in all groups, but no significant differences were observed between sessions. The glucose concentrations were within the euglycemic range.

Conclusion

The results did not reproduce the induction of ghrelin secretion in different food images. Therefore, it is unclear whether the visual perception of food influences ghrelin secretion or whether separation into macronutrients changes the hormone response. Further research is required to differentiate the interactions of sensory‐specific satiety.

Enteroendocrine Cell Formation Is an Early Event in Pancreatic Tumorigenesis

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a 5-year survival rate of only 11%, due, in part, to late diagnosis, making the need to understand early events in tumorigenesis critical. Acinar-to-ductal metaplasia (ADM), when not resolved, is a PDAC precursor. Recently, we showed that ADM is constituted by a heterogenous population of cells, including hormone-producing enteroendocrine cells (EECs: gamma, delta, epsilon, and enterochromaffin cells). In this study, we employed histopathological techniques to identify and quantify the abundance of EEC subtypes throughout pancreatic tumorigenesis in mouse models and human disease. We found that EECs are most abundant in ADM and significantly decrease with lesion progression. Co-immunofluorescence identifies distinct lineages and bihormonal populations. Evaluation of EEC abundance in mice lacking Pou2f3 demonstrates that the tuft cell master regulator transcription factor is not required for EEC formation. We compared these data to human neoplasia and PDAC and observed similar trends. Lastly, we confirm that EECs are a normal cellular compartment within the murine and human pancreatic ductal trees. Altogether, these data identify EECs as a cellular compartment of the normal pancreas, which expands early in tumorigenesis and is largely lost with disease progression.

Do patients with Prader-Willi syndrome have favorable glucose metabolism?

Background

In recent years, more studies have observed that patients with Prader–Willi syndrome have lower insulin levels and lower insulin resistance than body mass index-matched controls, which may suggest protected glucose metabolism.

Method

The PubMed and Web of Science online databases were searched to identify relevant studies published in the English language using the terms “Prader–Willi syndrome” with “glucose”, “insulin”, “diabetes mellitus”, “fat”, “adipo*”, “ghrelin”, “oxytocin”, “irisin” or “autonomic nervous system”.

Results

The prevalence of impaired glucose intolerance, type 2 diabetes mellitus and some other obesity-associated complications in patients with Prader–Willi syndrome tends to be lower when compared to that in general obesity, which is consistent with the hypothetically protected glucose metabolism. Factors including adipose tissue, adiponectin, ghrelin, oxytocin, irisin, growth hormone and the autonomic nervous system possibly modulate insulin sensitivity in patients with Prader–Willi syndrome.

Conclusion

Although lower insulin levels, lower IR and protected glucose metabolism are widely reported in PWS patients, the causes are still mysterious. Based on existing knowledge, we cannot determine which factor is of utmost importance and what are the underlying mechanisms, and further research is in urgent need.

Ghrelin Represses Thymic Stromal Lymphopoietin Gene Expression through Activation of Glucocorticoid Receptor and Protein Kinase C Delta in Inflamed Skin Keratinocytes

Ghrelin, a peptide hormone secreted from enteroendocrine cells of the gastrointestinal tract, has anti-inflammatory activity in skin diseases, including dermatitis and psoriasis. However, the molecular mechanism underlying the beneficial effect of ghrelin on skin inflammation is not clear. In this study, we found that ghrelin alleviates atopic dermatitis (AD)-phenotypes through suppression of thymic stromal lymphopoietin (TSLP) gene activation. Knockdown or antagonist treatment of growth hormone secretagogue receptor 1a (GHSR1a), the receptor for ghrelin, suppressed ghrelin-induced alleviation of AD-like phenotypes and suppression of TSLP gene activation. We further found that ghrelin induces activation of the glucocorticoid receptor (GR), leading to the binding of GR with histone deacetylase 3 (HDAC3) and nuclear receptor corepressor (NCoR) NCoR corepressor to negative glucocorticoid response element (nGRE) on the TSLP gene promoter. In addition, ghrelin-induced protein kinase C δ (PKCδ)-mediated phosphorylation of p300 at serine 89 (S89), which decreased the acetylation and DNA binding activity of nuclear factor- κB (NF-κB) p65 to the TSLP gene promoter. Knockdown of PKCδ abolished ghrelin-induced suppression of TSLP gene activation. Our study suggests that ghrelin may help to reduce skin inflammation through GR and PKCδ-p300-NF-κB-mediated suppression of TSLP gene activation.

Ghrelin and Cancer: Examining the Roles of the Ghrelin Axis in Tumor Growth and Progression

Ghrelin, a hormone produced and secreted from the stomach, is prim arily known as an appetite stimulant. Recently, it has emerged as a potential regulator/biomarker of cancer progression. Inconsistent results on this subject make this body of literature difficult to interpret. Here, we attempt to identify commonalities in the relationships between ghrelin and various cancers, and summarize important considerations for future research. The main players in the ghrelin family axis are unacylated ghrelin (UAG), acylated ghrelin (AG), the enzyme ghrelin O-acyltransferase (GOAT), and the growth hormone secretagogue receptor (GHSR). GOAT is responsible for the acylation of ghrelin, after which ghrelin can bind to the functional ghrelin receptor GHSR-1a to initiate the activation cascade. Splice variants of ghrelin also exist, with the most prominent being In1-ghrelin. In this review, we focus primarily on the potential of In1-ghrelin as a biomarker for cancer progression, the unique characteristics of UAG and AG, the importance of the two known receptor variants GHSR-1a and 1b, as well as the possible mechanisms through which the ghrelin axis acts. Further understanding of the role of the ghrelin axis in tumor cell proliferation could lead to the development of novel therapeutic approaches for various cancers.

Peptides in the regulation of glucagon secretion

Glucose homeostasis is maintained by the glucoregulatory hormones, glucagon, insulin and somatostatin, secreted from the islets of Langerhans. Glucagon is the body's most important anti-hypoglycemic hormone, mobilizing glucose from glycogen stores in the liver in response to fasting, thus maintaining plasma glucose levels within healthy limits. Glucagon secretion is regulated by both circulating nutrients, hormones and neuronal inputs. Hormones that may regulate glucagon secretion include locally produced insulin and somatostatin, but also urocortin-3, amylin and pancreatic polypeptide, and from outside the pancreas glucagon-like peptide-1 and 2, peptide tyrosine tyrosine and oxyntomodulin, glucose-dependent insulinotropic polypeptide, neurotensin and ghrelin, as well as the hypothalamic hormones arginine-vasopressin and oxytocin, and calcitonin from the thyroid. Each of these hormones have distinct effects, ranging from regulating blood glucose, to regulating appetite, stomach emptying rate and intestinal motility, which makes them interesting targets for treating metabolic diseases. Awareness regarding the potential effects of the hormones on glucagon secretion is important since secretory abnormalities could manifest as hyperglycemia or even lethal hypoglycemia. Here, we review the effects of each individual hormone on glucagon secretion, their interplay, and how treatments aimed at modulating the plasma levels of these hormones may also influence glucagon secretion and glycemic control.

Status of ghrelin as an islet hormone and paracrine/autocrine regulator of insulin secretion

Ghrelin is expressed in the pancreatic islet cells as well as the stomach. In the perfused pancreas and isolated islets, GHS-R antagonism, ghrelin immunoneutralization and ghrelin-knockout (Ghr-KO) all increase glucose-induced insulin release. Thus, pharmacological, immunological and genetic blockades of ghrelin in the pancreatic islets all markedly augment glucose-induced insulin release, showing that islet-derived ghrelin physiologically restricts insulin release in rodents. In this review, we focus on the current understanding of the following key questions: 1) from which islet cells ghrelin is released, 2) on which islet cells ghrelin acts, and 3) mechanisms by which the islet-derived ghrelin inhibits insulin secretion.

The emerging role of heterodimerisation and interacting proteins in ghrelin receptor function

Ghrelin is a peptide hormone secreted primarily by the stomach that acts upon the growth hormone secretagogue receptor (GHSR1), a G protein-coupled receptor whose functions include growth hormone secretion, appetite regulation, energy expenditure, regulation of adiposity, and insulin release. Following the discovery that GHSR1a stimulates food intake, receptor antagonists were developed as potential therapies to regulate appetite. However, despite reductions in signalling, the desired effects on appetite were absent. Studies in the past 15 years have demonstrated GHSR1a can interact with other transmembrane proteins, either by direct binding (i.e. heteromerisation) or via signalling cross-talk. These interactions have various effects on GHSR1a signalling including preferential coupling to one pathway (i.e. biased signalling), coupling to a unique G protein (G protein switching), suppression of GHSR1a signalling, and enhancement of signalling by both receptors. While many of these interactions have been shown in cells overexpressing the proteins of interest and remain to be verified in tissues, substantial evidence exists showing that GHSR1a and the dopamine receptor D1 (DRD1) form heteromers, which promote synaptic plasticity and formation of hippocampal memory. Additionally, a reduction in GHSR1a-DRD1 complexes in favour of establishment of GHSR1a-Aβ complexes correlates with Alzheimer's disease, indicating that GHSR1a heteromers may have pathological functions. Herein, we summarise the evidence published to date describing interactions between GHSR1a and transmembrane proteins, discuss the experimental strengths and limitations of these studies, describe the physiological evidence for each interaction, and address their potential as novel drug targets for appetite regulation, Alzheimer's disease, insulin secretion, and inflammation.

Acute Effects of Sleeve Gastrectomy on Glucose Variability, Glucose Metabolism, and Ghrelin Response

PURPOSE

This study aims to examine the changes of glucose metabolism, glucose variability (GV), and ghrelin secretion within 1 week following SG in Chinese patients with obesity.

MATERIALS AND METHODS

Forty-nine patients with obesity (15 with type 2 diabetes) were enrolled to undergo SG. Within 1 week before and after surgery, liquid meal tests were performed in all subjects, and continuous glucose monitoring (CGM) was performed in diabetic patients. Blood samples were collected at 0, 15, 30, 45, 60, 120, and 180 min for glucose, C-peptide, insulin, and ghrelin analysis in liquid meal test. Mean amplitude of glucose excursions (MAGE), standard deviations (SD), and percent time-in-range (%TIR) determined by CGM were analyzed.

RESULTS

Both in diabetic and non-diabetic groups, significant decrease was observed in glucose, insulin, C-peptide, and ghrelin. Homeostasis model assessment-insulin resistance and liver fat content was decreased. In diabetic group, MAGE and SD were decreased significantly, and the percent time-in-range was higher. The decrease in blood glucose was positively correlated with the decrease in ghrelin concentration in non-diabetic group.

CONCLUSION

Within 1 week after SG, both glucose metabolism and glucose variability were improved significantly. Suppression of ghrelin secretion postoperatively might be a driver of this early improved glycemia homeostasis.

Progress in treatment of type 2 diabetes by bariatric surgery

The incidence of type 2 diabetes (T2D) is increasing at an alarming rate worldwide. Bariatric surgical procedures, such as the vertical sleeve gastrectomy and Roux-en-Y gastric bypass, are the most efficient approaches to obtain substantial and durable remission of T2D. The benefits of bariatric surgery are realized through the consequent increased satiety and alterations in gastrointestinal hormones, bile acids, and the intestinal microbiota. A comprehensive understanding of the mechanisms by which various bariatric surgical procedures exert their benefits on T2D could contribute to the design of better non-surgical treatments for T2D. In this review, we describe the classification and evolution of bariatric surgery and explore the multiple mechanisms underlying the effect of bariatric surgery on insulin resistance. Based upon our summarization of the current knowledge on the underlying mechanisms, we speculate that the gut might act as a new target for improving T2D. Our ultimate goal with this review is to provide a better understanding of T2D pathophysiology in order to support development of T2D treatments that are less invasive and more scalable.

Ghrelin Response to Acute and Chronic Exercise: Insights and Implications from a Systematic Review of the Literature

BACKGROUND

Ghrelin is a peptide hormone predominantly produced by the stomach. It exerts a wide range of functions including stimulating growth hormone release and regulating appetite, food intake, and glucose and lipid metabolism. Since physical exercise affects all these aspects, a particular interest is accorded to the relationship between ghrelin and exercise. This systematic review aimed to summarize the current available data on the topic for a better understanding of the relationship.

METHODS

An extensive computerized search was performed in the PubMed and SPORTDiscus databases for retrieving relevant articles. The search contained the following keywords: ghrelin, appetite-related peptides, gastrointestinal peptides, gastrointestinal hormones, exercise, acute exercise, chronic exercise, training, and physical activity. Studies investigating the effects of acute/chronic exercise on circulating forms of ghrelin were included.

RESULTS

The initial search identified 840 articles. After screening, 80 articles were included. Despite a heterogeneity of studies and a variability of the findings, the review suggests that acute exercise suppresses acyl ghrelin production regardless of the participants and the exercise characteristics. Long- and very long-term exercise training programs mostly resulted in increased total and des-acyl ghrelin production. The increase is more noticeable in overweight/obese individuals, and is most likely due to weight loss resulting from the training program.

CONCLUSION

The review suggests that exercise may impact ghrelin production. While the precise mechanisms are unclear, the effects are likely due to blood flow redistribution and weight loss for acute and chronic exercise, respectively. These changes are expected to be metabolically beneficial. Further research is needed for a better understanding of the relationship between ghrelin and exercise.

Ghrelin octanoylation by ghrelin O-acyltransferase: protein acylation impacting metabolic and neuroendocrine signalling

The acylated peptide hormone ghrelin impacts a wide range of physiological processes but is most well known for controlling hunger and metabolic regulation. Ghrelin requires a unique posttranslational modification, serine octanoylation, to bind and activate signalling through its cognate GHS-R1a receptor. Ghrelin acylation is catalysed by ghrelin O-acyltransferase (GOAT), a member of the membrane-bound O-acyltransferase (MBOAT) enzyme family. The ghrelin/GOAT/GHS-R1a system is defined by multiple unique aspects within both protein biochemistry and endocrinology. Ghrelin serves as the only substrate for GOAT within the human proteome and, among the multiple hormones involved in energy homeostasis and metabolism such as insulin and leptin, acts as the only known hormone in circulation that directly stimulates appetite and hunger signalling. Advances in GOAT enzymology, structural modelling and inhibitor development have revolutionized our understanding of this enzyme and offered new tools for investigating ghrelin signalling at the molecular and organismal levels. In this review, we briefly summarize the current state of knowledge regarding ghrelin signalling and ghrelin/GOAT enzymology, discuss the GOAT structural model in the context of recently reported MBOAT enzyme superfamily member structures, and highlight the growing complement of GOAT inhibitors that offer options for both ghrelin signalling studies and therapeutic applications.

Obesity-induced changes in human islet G protein-coupled receptor expression: Implications for metabolic regulation

G protein-coupled receptors (GPCRs) are a large family of cell surface receptors that are the targets for many different classes of pharmacotherapy. The islets of Langerhans are central to appropriate glucose homeostasis through their secretion of insulin, and islet function can be modified by ligands acting at the large number of GPCRs that islets express. The human islet GPCRome is not a static entity, but one that is altered under pathophysiological conditions and, in this review, we have compared expression of GPCR mRNAs in human islets obtained from normal weight range donors, and those with a weight range classified as obese. We have also considered the likely outcomes on islet function that the altered GPCR expression status confers and the possible impact that adipokines, secreted from expanded fat depots, could have at those GPCRs showing altered expression in obesity.

Novel therapies with precision mechanisms for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is one of the greatest health crises of our time and its prevalence is projected to increase by >50% globally by 2045. Currently, 10 classes of drugs are approved by the US Food and Drug Administration for the treatment of T2DM. Drugs in development for T2DM must show meaningful reductions in glycaemic parameters as well as cardiovascular safety. Results from an increasing number of cardiovascular outcome trials using modern T2DM therapeutics have shown a reduced risk of atherosclerotic cardiovascular disease, congestive heart failure and chronic kidney disease. Hence, guidelines have become increasingly evidence based and more patient centred, focusing on reaching individualized glycaemic goals while optimizing safety, non-glycaemic benefits and the prevention of complications. The bar has been raised for novel therapies under development for T2DM as they are now expected to achieve these aims and possibly even treat concurrent comorbidities. Indeed, the pharmaceutical pipeline for T2DM is fertile. Drugs that augment insulin sensitivity, stimulate insulin secretion or the incretin axis, or suppress hepatic glucose production are active in more than 7,000 global trials using new mechanisms of action. Our collective goal of being able to truly personalize medicine for T2DM has never been closer at hand.

Secondary analysis of gut hormone data from children with and without in utero exposure to gestational diabetes: Differences in the associations among ghrelin, GLP-1, and insulin secretion

BACKGROUND

Intrauterine exposure to gestational diabetes mellitus (GDM) increases risk for type 2 diabetes (T2D). Ghrelin and GLP-1 have opposite functions in nutritional homeostasis and are associated with insulin secretion, but it is not known if individuals exposed to GDM exhibit dysregulation in these associations.

OBJECTIVE

Test the hypothesis that children exposed to GDM in utero will exhibit dysregulation among ghrelin, GLP-1, and C-peptide (reflecting insulin secretion).

METHODS

Data from N = 43 children aged 5 to 10 years were included in this secondary analysis of ghrelin, GLP-1, and C-peptide response to a liquid meal test. Repeated measures mixed model analyses were used to measure associations among hormones.

RESULTS

The association of ghrelin and GLP-1 was moderated by GDM group (P < .01), such that ghrelin was inversely associated with GLP-1 in children without GDM exposure, but not for those exposed to GDM. GLP-1 was positively associated with C-peptide in both groups, but the association was stronger in those exposed to GDM (estimate = 1.06 vs 1.01).

CONCLUSIONS

Differences in the associations among ghrelin, GLP-1, and C-peptide displayed here suggest novel lines of research about whether the regulation of gut hormones and insulin secretion contribute to obesity and risk for T2D in children exposed to GDM.

The Gut-Brain Axis and Its Role in Controlling Eating Behavior in Intestinal Inflammation

Malnutrition represents a major problem in the clinical management of the inflammatory bowel disease (IBD). Presently, our understanding of the cross-link between eating behavior and intestinal inflammation is still in its infancy. Crohn's disease patients with active disease exhibit strong hedonic desires for food and emotional eating patterns possibly to ameliorate feelings of low mood, anxiety, and depression. Impulsivity traits seen in IBD patients may predispose them to palatable food intake as an immediate reward rather than concerns for future health. The upregulation of enteroendocrine cells (EEC) peptide response to food intake has been described in ileal inflammation, which may lead to alterations in gut-brain signaling with implications for appetite and eating behavior. In summary, a complex interplay of gut peptides, psychological, cognitive factors, disease-related symptoms, and inflammatory burden may ultimately govern eating behavior in intestinal inflammation.

The regulation of gastric ghrelin secretion

Ghrelin is a gastric hormone with multiple physiological functions, including the stimulation of food intake and adiposity. It is well established that circulating ghrelin levels are closely associated with feeding patterns, rising strongly before a meal and lowering upon food intake. However, the mechanisms underlying the modulation of ghrelin secretion are not fully understood. The purpose of this review is to discuss current knowledge on the circadian oscillation of circulating ghrelin levels, the neural mechanisms stimulating fasting ghrelin levels and peripheral mechanisms modulating postprandial ghrelin levels. Furthermore, the therapeutic potential of targeting the ghrelin pathway is discussed in the context of the treatment of various metabolic disorders, including obesity, type 2 diabetes, diabetic gastroparesis and Prader-Willi syndrome. Moreover, eating disorders including anorexia nervosa, bulimia nervosa and binge-eating disorder are also discussed.

Do Gut Hormones Contribute to Weight Loss and Glycaemic Outcomes after Bariatric Surgery?

Bariatric surgery is an effective intervention for management of obesity through treating dysregulated appetite and achieving long-term weight loss maintenance. Moreover, significant changes in glucose homeostasis are observed after bariatric surgery including, in some cases, type 2 diabetes remission from the early postoperative period and postprandial hypoglycaemia. Levels of a number of gut hormones are dramatically increased from the early period after Roux-en-Y gastric bypass and sleeve gastrectomy—the two most commonly performed bariatric procedures—and they have been suggested as important mediators of the observed changes in eating behaviour and glucose homeostasis postoperatively. In this review, we summarise the current evidence from human studies on the alterations of gut hormones after bariatric surgery and their impact on clinical outcomes postoperatively. Studies which assess the role of gut hormones after bariatric surgery on food intake, hunger, satiety and glucose homeostasis through octreotide use (a non-specific inhibitor of gut hormone secretion) as well as with exendin 9–39 (a specific glucagon-like peptide-1 receptor antagonist) are reviewed. The potential use of gut hormones as biomarkers of successful outcomes of bariatric surgery is also evaluated.

An overview of obesity mechanisms in humans: Endocrine regulation of food intake, eating behaviour and common determinants of body weight

Obesity is one of the biggest health challenges of the 21st century, already affecting close to 700 million people worldwide, debilitating and shortening lives and costing billions of pounds in healthcare costs and loss of workability. Body weight homeostasis relies on complex biological mechanisms and the development of obesity occurs on a background of genetic susceptibility and an environment promoting increased caloric intake and reduced physical activity. The pathophysiology of common obesity links neuro-endocrine and metabolic disturbances with behavioural changes, genetics, epigenetics and cultural habits. Also, specific causes of obesity exist, including monogenetic diseases and iatrogenic causes. In this review, we provide an overview of obesity mechanisms in humans with a focus on energy homeostasis, endocrine regulation of food intake and eating behavior, as well as the most common specific causes of obesity.

Acyl-Ghrelin Influences Pancreatic β-Cell Function by Interference with KATP Channels

The aim for this study was to elucidate how the hypothalamic hunger-inducing hormone acyl-ghrelin (AG), which is also produced in the pancreas, affects β-cell function, with particular attention to the role of ATP-sensitive K⁺ (K_ATP) channels and the exact site of action of the hormone. AG hyperpolarized the membrane potential and decreased cytoplasmic calcium concentration [Ca²⁺]_c and glucose-stimulated insulin secretion (GSIS). These effects were abolished in β-cells from SUR1-knockout (KO) mice. AG increased K_ATP current but only in a configuration with intact metabolism. Unacylated ghrelin counteracted the effects of AG. The influence of AG on membrane potential and GSIS could only be averted in the combined presence of a ghrelin receptor (GHSR1a) antagonist and an inverse agonist. The inhibition of GSIS by AG could be prevented by dibutyryl cyclic-cAMP or 3-isobutyl-1-methylxanthine and the somatostatin (SST) receptor 2-5 antagonist H6056. These data indicate that AG indirectly opens K_ATP channels probably by interference with the cAMP/cAMP-dependent protein kinase pathway, resulting in a decrease of [Ca²⁺]_c and GSIS. The experiments with SUR1-KO β-cells point to a direct effect of AG on β-cells and not, as earlier suggested, to an exclusive effect by AG-induced SST release from δ-cells. Nevertheless, SST receptors may be involved in the effect of AG, possibly by heteromerization of AG and SST receptors.

[Body composition, mineral metabolism, and endocrine function of adipose tissue: influence of a nutritional supplement of propolis]

Introduction

Introduction: propolis and its components influence lipid metabolism; however, its effect on body composition and mineral metabolism remains unknown. Objectives: to determine the effect of natural propolis supplementation on body composition, mineral metabolism, and the endocrine function of adipose tissue. Material and methods: twenty albino male Wistar rats (8 weeks old) were divided into two groups of 10 animals each. The rats were fed two different types of diet for 90 days: a standard diet for the control group (group C) and the same standard diet + 2 % propolis (group P). Thyroid hormones, ghrelin, leptin, adiponectin and insulin, non-esterified fatty acids (NEFA) in plasma, body composition (lean mass, fat mass and body water), and mineral deposition in target organs (spleen, brain, heart, lungs, testicles, kidneys and femur) were assessed. Results: thyroid stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) did not show any differences after supplementation with propolis, while ghrelin and adiponectin decreased (p < 0.01 and p < 0.05, respectively) and insulin (p < 0.01), leptin (p < 0.05) and NEFA (p < 0.05) increased when 2 % propolis was supplied, while weight and body fat were reduced (p < 0.05) and lean mass increased. Lastly, the propolis supplement improves calcium deposition in the spleen, lungs, testes, and femur (p < 0.05). Conclusion: propolis supplementation of the diet (2 %) causes a decrease in the secretion of ghrelin and adiponectin, increasing the release of non-esterified fatty acids and the rate of insulin secretion. In addition, propolis supplementation induces an improvement in calcium deposition in target organs without affecting the rest of minerals, which improves body composition by inducing a reduction in weight and visceral adipose tissue, and improvement in lean mass.