Interleukin-6 enhances insulin secretion by increasing glucagon-like peptide-1 secretion from L cells and alpha cells

Fibroblast Growth Factor Binding Protein 3 (FGFBP3) impacts carbohydrate and lipid metabolism

Secreted FGF binding proteins (FGFBP) mobilize locally-acting paracrine FGFs from their extracellular storage. Here, we report that FGFBP3 (BP3) modulates fat and glucose metabolism in mouse models of metabolic syndrome. BP3 knockout mice exhibited altered lipid metabolism pathways with reduced hepatic and serum triglycerides. In obese mice the expression of exogenous BP3 reduced hyperglycemia, hepatosteatosis and weight gain, blunted de novo lipogenesis in liver and adipose tissues, increased circulating adiponectin and decreased NEFA. The BP3 protein interacts with endocrine FGFs through its C-terminus and thus enhances their signaling. We propose that BP3 may constitute a new therapeutic to reverse the pathology associated with metabolic syndrome that includes nonalcoholic fatty liver disease and type 2 diabetes mellitus.

Acute long-distance trail running increases serum IL-6, IL-15, and Hsp72 levels

Interleukin-6 (IL-6), IL-15, and heat shock protein 72 (Hsp72) are molecules that have significant metabolic effects on glucose and fat metabolism and a cell's stress response. The aim of this study is to determine serum levels of these molecules in runners after a long-distance trail run. Serum IL-15 levels after such endurance events have not been investigated yet. Blood samples were collected from 37 athletes (11 female, 26 male) before and after a 35-km trail run, with a total climb of 940 m. Serum was obtained from the samples, and IL-6, IL-15, and Hsp72 levels were measured from using the sandwich ELISA method. The athletes completed the race in 308.3 ± 37.4 min on average. After the race, the mean serum IL-6, IL-15, and Hsp72 concentrations increased 13.2-fold, 2.22-fold, and 1.6-fold, respectively (p < 0.001, p < 0.001, and p = 0.039, respectively). This is the first study to demonstrate the increase in serum IL-15 levels following an acute endurance exercise. In addition to IL-15, we report that IL-6 and soluble Hsp72 levels also increased significantly following a 35-km trail run. Since these molecules are involved in regulating glucose and fat metabolism, significant increases of IL-6, IL-15, and soluble Hsp72 may have health benefits that may be associated with long-distance trail runs, which are becoming more popular worldwide.

Evidence for acute contraction-induced myokine secretion by C2C12 myotubes

Skeletal muscle is considered a secretory organ that produces bioactive proteins known as myokines, which are released in response to various stimuli. However, no experimental evidence exists regarding the mechanism by which acute muscle contraction regulates myokine secretion. Here, we present evidence that acute contractions induced myokine secretion from C2C12 myotubes. Changes in the cell culture medium unexpectedly triggered the release of large amounts of proteins from the myotubes, and these proteins obscured the contraction-induced myokine secretion. Once protein release was abolished, the secretion of interleukin-6 (IL-6), the best-known regulatory myokine, increased in response to a 1-hour contraction evoked by electrical stimulation. Using this experimental condition, intracellular calcium flux, rather than the contraction itself, triggered contraction-induced IL-6 secretion. This is the first report to show an evidence for acute contraction-induced myokine secretion by skeletal muscle cells.

[Do Myokines Have Potential as Exercise Mimetics?]

　Exercise is generally considered to have health benefits for the body, although its beneficial mechanisms have not been fully elucidated. Recent progressive research suggests that myokines, bioactive substances secreted from skeletal muscle, play an important role in mediating the benefits of exercise. There are three types of myokines in terms of the muscular secretion mechanism: those in which the secretion is promoted by stimulation, such as irisin, interleukin (IL)-6, and IL-15; those whose secretion is constitutive, such as thioredoxin, glutaredoxin, and peroxiredoxin; and those whose secretion is suppressed by stimulation, such as by a macrophage migration inhibitory factor. Although dozens of myokines have been reported, their physiological roles are not well understood. Therefore, there currently exists no advanced drug discovery research specifically targeting myokines, with the exception of Myostatin. Myostatin was discovered as a negative regulator of muscle growth. Myostatin is secreted from muscle cells as a myokine; it signals via an activin type IIB receptor in an autocrine manner, and regulates gene expressions involved in myogenesis. Given the studies to date that have been conducted on the utilization of myostatin inhibitors for the treatment of muscle weakness, including cachexia and sarcopenia, other myokines may also be new potential drug targets.

Targeting the Incretin/Glucagon System With Triagonists to Treat Diabetes

Glucagonlike peptide 1 (GLP-1) receptor agonists have been efficacious for the treatment of type 2 diabetes due to their ability to reduce weight and attenuate hyperglycemia. However, the activity of glucagonlike peptide 1 receptor-directed strategies is submaximal, and the only potent, sustainable treatment of metabolic dysfunction is bariatric surgery, necessitating the development of unique therapeutics. GLP-1 is structurally related to glucagon and glucose-dependent insulinotropic peptide (GIP), allowing for the development of intermixed, unimolecular peptides with activity at each of their respective receptors. In this review, we discuss the range of tissue targets and added benefits afforded by the inclusion of each of GIP and glucagon. We discuss considerations for the development of sequence-intermixed dual agonists and triagonists, highlighting the importance of evaluating balanced signaling at the targeted receptors. Several multireceptor agonist peptides have been developed and evaluated, and the key preclinical and clinical findings are reviewed in detail. The biological activity of these multireceptor agonists are founded in the success of GLP-1-directed strategies; by including GIP and glucagon components, these multireceptor agonists are thought to enhance GLP-1's activities by broadening the tissue targets and synergizing at tissues that express multiple receptors, such at the brain and pancreatic islet β cells. The development and utility of balanced, unimolecular multireceptor agonists provide both a useful tool for querying the actions of incretins and glucagon during metabolic disease and a unique drug class to treat type 2 diabetes with unprecedented efficacy.

TLR4 triggered complex inflammation in human pancreatic islets

Type 2 Diabetes (T2D) is strongly associated with obesity and inflammation. Toll-like receptor-4 (TLR-4) is the major pro-inflammatory pathway with its ligands and downstream products increased systemically in T2D and in at-risk individuals. Detailed mechanisms of the complex proinflammatory response in pancreatic islets remain unknown. In isolated human islets LPS induced IL-1β, IL-6, IL-8 and TNF production in a TLR4-dependent manner and severely impaired β-cell survival and function. IL-6 antagonism improved β-cell function. IL-8, which was identified specifically in α-cells, initiated monocyte migration, a process fully blocked by IL-8 neutralization. The TLR4 response was potentiated in obese donors; with higher IL-1β, IL-6 and IL-8 expression than in non-obese donors. TLR4 activation leads to a complex multi-cellular inflammatory response in human islets, which involves β-cell failure, cytokine production and macrophage recruitment to islets. In obesity, the amplified TLR4 response may potentiate β-cell damage and accelerate diabetes progression.

DPP-4 is expressed in human pancreatic beta cells and its direct inhibition improves beta cell function and survival in type 2 diabetes

It has been reported that the incretin system, including regulated GLP-1 secretion and locally expressed DPP-4, is present in pancreatic islets. In this study we comprehensively evaluated the expression and role of DPP-4 in islet alpha and beta cells from non-diabetic (ND) and type 2 diabetic (T2D) individuals, including the effects of its inhibition on beta cell function and survival. Isolated islets were prepared from 25 ND and 18 T2D organ donors; studies were also performed with the human insulin-producing EndoC-βH1 cells. Morphological (including confocal microscopy), ultrastructural (electron microscopy, EM), functional (glucose-stimulated insulin secretion), survival (EM and nuclear dyes) and molecular (RNAseq, qPCR and western blot) studies were performed under several different experimental conditions. DPP-4 co-localized with glucagon and was also expressed in human islet insulin-containing cells. Furthermore, DPP-4 was expressed in EndoC-βH1 cells. The proportions of DPP-4 positive alpha and beta cells and DPP-4 gene expression were significantly lower in T2D islets. A DPP-4 inhibitor protected ND human beta cells and EndoC-βH1 cells against cytokine-induced toxicity, which was at least in part independent from GLP1 and associated with reduced NFKB1 expression. Finally, DPP-4 inhibition augmented glucose-stimulated insulin secretion, reduced apoptosis and improved ultrastructure in T2D beta cells. These results demonstrate the presence of DPP-4 in human islet alpha and beta cells, with reduced expression in T2D islets, and show that DPP-4 inhibition has beneficial effects on human ND and T2D beta cells. This suggests that DPP-4, besides playing a role in incretin effects, directly affects beta cell function and survival.

Time zones of pancreatic islet metabolism

Most living beings possess an intrinsic system of circadian oscillators, allowing anticipation of the Earth's rotation around its own axis. The mammalian circadian timing system orchestrates nearly all aspects of physiology and behaviour. Together with systemic signals originating from the central clock that resides in the hypothalamic suprachiasmatic nucleus, peripheral oscillators orchestrate tissue-specific fluctuations in gene transcription and translation, and posttranslational modifications, driving overt rhythms in physiology and behaviour. There is accumulating evidence of a reciprocal connection between the circadian oscillator and most aspects of physiology and metabolism, in particular as the circadian system plays a critical role in orchestrating body glucose homeostasis. Recent reports imply that circadian clocks operative in the endocrine pancreas regulate insulin secretion, and that islet clock perturbation in rodents leads to the development of overt type 2 diabetes. While whole islet clocks have been extensively studied during the last years, the heterogeneity of islet cell oscillators and the interplay between α- and β-cellular clocks for orchestrating glucagon and insulin secretion have only recently gained attention. Here, we review recent findings on the molecular makeup of the circadian clocks operative in pancreatic islet cells in rodents and in humans, and focus on the physiologically relevant synchronizers that are resetting these time-keepers. Moreover, the implication of islet clock functional outputs in the temporal coordination of metabolism in health and disease will be highlighted.

Low serum creatinine predicts risk for type 2 diabetes

AIMS

As an insulin target tissue, skeletal muscle is inversely related to type 2 diabetes mellitus (T2DM). Serum creatinine originates mainly from creatine in muscle and is considered as a reliable surrogate marker for muscle mass in apparently healthy subjects. It is therefore hypothesized that low serum creatinine could effectively predict increased risk of T2DM. Yet information is scarce regarding the longitudinal relationship between serum creatinine and T2DM. This study aims to investigate this relation in a large general population of both men and women.

METHODS

A prospective cohort study (n = 57 587; follow-up range: 1-9 years, mean: 3.57 years, 95% confidence interval: 3.55-3.58 years) was conducted in a general population sample from Tianjin, China. Multivariable Cox proportional hazards regression models were used to assess the relationship between baseline serum creatinine and the risk of developing T2DM (as defined by the American Diabetes Association criteria).

RESULTS

During the follow-up period, 2017 subjects developed T2DM. The multivariate-adjusted hazard ratios (95% confidence interval) for T2DM incidence across quintiles of serum creatinine were 1.00 (reference), 0.86 (0.75, 0.99), 0.82 (0.72, 0.94), 0.85 (0.74, 0.97), and 0.77 (0.67, 0.89; P for trend <.01). Similar results were observed in both sexes (interaction P = .56).

CONCLUSIONS

These findings indicate that serum creatinine concentration is inversely related to incident T2DM in both men and women. Measuring serum creatinine may assist in the early detection of individuals at high risk of developing T2DM.

Regulation of Energy Expenditure and Brown/Beige Thermogenic Activity by Interleukins: New Roles for Old Actors

Obesity rates and the burden of metabolic associated diseases are escalating worldwide Energy burning brown and inducible beige adipocytes in human adipose tissues (ATs) have attracted considerable attention due to their therapeutic potential to counteract the deleterious metabolic effects of nutritional overload and overweight. Recent research has highlighted the relevance of resident and recruited ATs immune cell populations and their signalling mediators, cytokines, as modulators of the thermogenic activity of brown and beige ATs. In this review, we first provide an overview of the developmental, cellular and functional heterogeneity of the AT organ, as well as reported molecular switches of its heat-producing machinery. We also discuss the key contribution of various interleukins signalling pathways to energy and metabolic homeostasis and their roles in the biogenesis and function of brown and beige adipocytes. Besides local actions, attention is also drawn to their influence in the central nervous system (CNS) networks governing energy expenditure.

Induction of Growth Differentiation Factor 15 in Skeletal Muscle of Old Taurine Transporter Knockout Mouse

It has been identified that skeletal muscle is an endocrine tissue. Since skeletal muscle aging affects not only to muscle strength and function but to systemic aging and lifespan, myokines secreted from skeletal muscle may be crucial factors for intertissue communication during aging. In the present study, we investigated the expression of myokines associated with skeletal muscle aging in taurine transporter knockout (TauTKO) mice, which exhibit the accelerated skeletal muscle aging. Among transforming growth factor (TGF)-beta family genes, only growth and differentiation factor 15 (GDF15) was markedly higher (>3-fold) in skeletal muscle of old TauTKO mice compared with that of either young TauTKO mice or old wild-type mice. Circulating levels of GDF15 were also elevated in old TauTKO mice. An elevation in circulating GDF15 was also observed in very old (30-month-old) wild-type mice, while skeletal GDF15 levels were normal. The treatment of cultured mouse C2C12 myotubular cells with aging-related factors that mediate cellular stresses, such as oxidative stress (hydrogen peroxide) and endoplasmic reticulum stress (tunicamycin and thapsigargin), leads to an increase in GDF15 secretion. In conclusion, GDF15 is a myokine secreted by aging-related stress and may control aging phenotype.

Endocrine Crosstalk Between Skeletal Muscle and the Brain

Skeletal muscle is an essential regulator of energy homeostasis and a potent coordinator of exercise-induced adaptations in other organs including the liver, fat or the brain. Skeletal muscle-initiated crosstalk with other tissues is accomplished though the secretion of myokines, protein hormones which can exert autocrine, paracrine and long-distance endocrine effects. In addition, the enhanced release or uptake of metabolites from and into contracting muscle cells, respectively, likewise can act as a powerful mediator of tissue interactions, in particular in regard to the central nervous system. The present review will discuss the current stage of knowledge regarding how exercise and the muscle secretome improve a broad range of brain functions related to vascularization, neuroplasticity, memory, sleep and mood. Even though the molecular and cellular mechanisms underlying the communication between muscle and brain is still poorly understood, physical activity represents one of the most effective strategies to reduce the prevalence and incidence of depression, cognitive, metabolic or degenerative neuronal disorders, and thus warrants further study.

Identification of therapeutic effect of glucagon-like peptide 1 in the treatment of STZ-induced diabetes mellitus in rats by restoring the balance of intestinal flora

OBJECTIVE

The objective of this study was to identify the therapeutic effect and the underlying mechanism of glucagon-like peptide 1 (GLP-1) in the treatment of STZ-induced diabetes mellitus (DM).

METHODS

Mice were treated with STZ to establish an animal model of DM, which was further treated with a GLP-1 receptor agonist. Subsequently, the status of glucose, insulin, nitric oxide, inflammatory and oxidative factors was evaluated and compared among Sham, STZ, and STZ + GLP-1 groups. In addition, the intestinal flora spectrum in each group was also evaluated.

RESULTS

In this study, it was found that the administration of STZ increased the level of glucose and glycosylated hemoglobin but reduced the level of insulin. It was also found that the levels of inflammation and oxidative stress in STZ-induced DM were both enhanced, as evidenced by a decreased level of catalase, superoxide dismutase, glutathione peroxidase, as well as increased levels of malonyldialdehyde, interleukin-1β (IL-1β), and IL-6. Meanwhile, the expression of nitric oxide, a factor associated with both oxidative stress and inflammation, was also suppressed in STZ-induced DM. More importantly, the imbalance of intestinal flora was observed in STZ-induced DM, as shown by a decreased level of both total bacteria and that of some strains including Clostridium, Bacteroides, Lactobacilli, and Bifidobacteria.

CONCLUSION

In summary, the findings of this study confirmed the antihyperglycemic effect of GLP-1 and demonstrated that the therapeutic effect of GLP-1 in the treatment of STZ-induced DM was mediated, at least partially, by its ability to restore the balance of intestinal flora.

Interleukin-6 Reduces β-Cell Oxidative Stress by Linking Autophagy With the Antioxidant Response

Production of reactive oxygen species (ROS) is a key instigator of β-cell dysfunction in diabetes. The pleiotropic cytokine interleukin 6 (IL-6) has previously been linked to β-cell autophagy but has not been studied in the context of β-cell antioxidant response. We used a combination of animal models of diabetes and analysis of cultured human islets and rodent β-cells to study how IL-6 influences antioxidant response. We show that IL-6 couples autophagy to antioxidant response and thereby reduces ROS in β-cells and human islets. β-Cell-specific loss of IL-6 signaling in vivo renders mice more susceptible to oxidative damage and cell death through the selective β-cell toxins streptozotocin and alloxan. IL-6-driven ROS reduction is associated with an increase in the master antioxidant factor NRF2, which rapidly translocates to the mitochondria to decrease mitochondrial activity and stimulate mitophagy. IL-6 also initiates a robust transient decrease in cellular cAMP levels, likely contributing to the stimulation of mitophagy to mitigate ROS. Our findings suggest that coupling autophagy to antioxidant response in β-cells leads to stress adaptation that can reduce cellular apoptosis. These findings have implications for β-cell survival under diabetogenic conditions and present novel targets for therapeutic intervention.

The Use of Complementary and Alternative Medicine in Patients With Inflammatory Bowel Disease

Complementary and alternative medicine (CAM) includes products or medical practices that encompass herbal and dietary supplements, probiotics, traditional Chinese medicines, and a variety of mind-body techniques. The use of CAM in patients with inflammatory bowel disease (IBD) is increasing as patients seek ways beyond conventional therapy to treat their chronic illnesses. The literature behind CAM therapies and their application, efficacy, and safety is limited when compared to studies of conventional, allopathic therapies. Thus, gastroenterologists are often ill equipped to engage with their patients in informed and meaningful discussions about the role of CAM in IBD. The aims of this article are to provide a comprehensive summary and discussion of various CAM modalities and to appraise the evidence for their use.

Probing the Effect of Physiological Concentrations of IL-6 on Insulin Secretion by INS-1 832/3 Insulinoma Cells under Diabetic-Like Conditions

Exercise improves insulin secretion by pancreatic beta cells (β-cells) in patients with type 2 diabetes, but molecular mechanisms of this effect are yet to be determined. Given that contracting skeletal muscle causes a spike in circulating interleukin-6 (IL-6) levels during exercise, muscle-derived IL-6 is a possible endocrine signal associated with skeletal muscle to β-cell crosstalk. Evidence to support a role of IL-6 in regulating the health and function of β-cells is currently inconsistent and studies investigating the role of IL-6 on the function of β-cells exposed to type 2 diabetic-like conditions are limited and often confounded by supraphysiological IL-6 concentrations. The purpose of this study is to explore the extent by which an exercise-relevant concentration of IL-6 influences the function of pancreatic β-cells exposed to type 2 diabetic-like conditions. Using insulin-secreting INS-1 832/3 cells as an experimental β-cell model, we show that 1-h IL-6 (10 pg/mL) has no effect on insulin secretion under normal conditions and does not restore the loss of insulin secretion caused by elevated glucose ± palmitate or IL-1β. Moreover, treatment of INS-1 832/3 cells to medium collected from C2C12 myotubes conditioned with electrical pulse stimulation does not alter insulin secretion despite significant increases in IL-6. Since insulin secretory defects caused by diabetic-like conditions are neither improved nor worsened by exposure to physiological IL-6 levels, we conclude that the beneficial effect of exercise on β-cell function is unlikely to be driven by muscle-derived IL-6.

Of Mice Not Men? Actions of Interleukin-6 on Glucose Tolerance

In mice, interleukin-6 (IL-6) improves glucose tolerance via stimulation of glucagon-like peptide 1 (GLP-1) secretion. In this issue of Cell Metabolism, Lang Lehrskov et al. (2018) demonstrate that IL-6 infusion has GLP-1-dependent and -independent actions with opposing effects on glucose tolerance, resulting in an overall improvement in healthy male volunteers but no improvement in male patients with diabetes.

Interleukin-6 Delays Gastric Emptying in Humans with Direct Effects on Glycemic Control

Gastric emptying is a critical regulator of postprandial glucose and delayed gastric emptying is an important mechanism of improved glycemic control achieved by short-acting glucagon-like peptide-1 (GLP-1) analogs in clinical practice. Here we report on a novel regulatory mechanism of gastric emptying in humans. We show that increasing interleukin (IL)-6 concentrations delays gastric emptying leading to reduced postprandial glycemia. IL-6 furthermore reduces insulin secretion in a GLP-1-dependent manner while effects on gastric emptying are GLP-1 independent. Inhibitory effects of IL-6 on gastric emptying were confirmed following exercise-induced increases in IL-6. Importantly, gastric- and insulin-reducing effects were maintained in individuals with type 2 diabetes. These data have clinical implications with respect to the use of IL-6 inhibition in autoimmune/inflammatory disease, and identify a novel target that could be exploited pharmacologically to delay gastric emptying and spare insulin, which may be beneficial for the beta cell in type 2 diabetes.

Loss of P2X7 receptor function dampens whole body energy expenditure and fatty acid oxidation

The established role of ATP-responsive P2X7 receptor in inflammatory, neurodegenerative, and immune diseases is now expanding to include several aspects of metabolic dysregulation. Indeed, P2X7 receptors are involved in β cell function, insulin secretion, and liability to diabetes, and loss of P2X7 function may increase the risk of hepatic steatosis and disrupt adipogenesis. Recently, body weight gain, abnormal lipid accumulation, adipocyte hyperplasia, increased fat mass, and ectopic fat distribution have been found in P2X7 KO mice. Here, we hypothesized that such clinical picture of dysregulated lipid metabolism might be the result of altered in vivo energy metabolism. By indirect calorimetry, we assessed 24 h of energy expenditure (EE) and respiratory exchange ratio (RER) as quotient of carbohydrate to fat oxidation in P2X7 KO mice. Moreover, we assessed the same parameters in aged-matched WT counterparts that underwent a 7-day treatment with the P2X7 antagonist A804598. We found that loss of P2X7 function elicits a severe decrease of EE that was less pronounced in A804598-treated mice. In parallel, P2X7KO mice show a drastic increase of RER, thus indicating the occurrence of a greater ratio of carbohydrate to fat oxidation. Decreased EE and fat oxidation is predictive of body weight gain, which was here confirmed. Taken together, our data provide evidence that P2X7 loss of function produces defective energy homeostasis that, together with disrupted adipogenesis, might help to explain accumulation of adipose tissue and contribute to disclose the potential role of P2X7 in metabolic diseases.

The role of exercise combined with tocilizumab in visceral and epicardial adipose tissue and gastric emptying rate in abdominally obese participants: protocol for a randomised controlled trial

BACKGROUND

Exercise reduces the amount of visceral adipose tissue (VAT) and the risk of cardiometabolic diseases. The underlying mechanisms responsible for these exercise-induced adaptations are unclear, but they may involve lipolytic actions of interleukin-6 (IL-6). Contracting skeletal muscles secrete IL-6, leading to increased circulating IL-6 levels in response to exercise. The aim of this study is to investigate whether IL-6 is involved in mediating the effects of exercise on visceral and epicardial adipose tissue volume and glycaemic control.

METHODS/DESIGN

Seventy-five physically inactive males and females aged > 18 years with a waist-to-height ratio > 0.5 and/or waist circumference ≥ 88 cm (females) or ≥ 102 cm (males) are being recruited to participate in a 12-week intervention study. Participants are randomly allocated to one of five groups (1:1:1:1:1). Two groups consist of supervised endurance exercise training combined with the IL-6 blocker tocilizumab (ET) or saline used as placebo (EP), two groups consist of no exercise combined with tocilizumab (NT) or placebo (NP), and one group consists of resistance exercise and placebo (RP). Although the study is an exploratory trial, the primary outcome is change in VAT volume from before to after intervention, with secondary outcomes being changes in (1) epicardial adipose tissue, (2) pericardial adipose tissue and (3) gastric emptying. Depots of adipose tissue are quantitated by magnetic resonance imaging Gastric emptying and glucose metabolism are assessed using mixed-meal tolerance tests.

DISCUSSION

Understanding the role of IL-6 in mediating the effects of exercise on visceral and epicardial adipose tissue and glycaemic control may lead to novel therapeutic approaches in the prevention of cardiometabolic diseases.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02901496 . Registered on 1 August 2016 and posted retrospectively on 15 September 2016.

β-Cell Autophagy in Diabetes Pathogenesis

Nearly 100 years have passed since Frederick Banting and Charles Best first discovered and purified insulin. Their discovery and subsequent improvements revolutionized the treatment of diabetes, and the field continues to move at an ever-faster pace with respect to unique treatments for both type 1 and type 2 diabetes. Despite these advances, we still do not fully understand how apoptosis of the insulin-producing β-cells is triggered, presenting a challenge in the development of preventative measures. In recent years, the process of autophagy has generated substantial interest in this realm due to discoveries highlighting its clear role in the maintenance of cellular homeostasis. As a result, the number of studies focused on islet and β-cell autophagy has increased substantially in recent years. In this review, we will discuss what is currently known regarding the role of β-cell autophagy in type 1 and type 2 diabetes pathogenesis, with an emphasis on new and exciting developments over the past 5 years. Further, we will discuss how these discoveries might be translated into unique treatments in the coming years.

Incidence and Predictors of Hypoglycemia 1 Year After Laparoscopic Sleeve Gastrectomy

INTRODUCTION

Hypoglycemia is a known adverse event following gastric bypass. The incidence of hypoglycemia after laparoscopic sleeve gastrectomy (LSG) is still under investigation. The aim of our study was to verify the presence of oral glucose tolerance test (OGTT)-related hypoglycemia after LSG and to identify any baseline predictors of its occurrence.

METHODS

We analyzed 197 consecutive non-diabetic morbid obese patients that underwent LSG. All patients were studied before and 12 months after LSG. Evaluation included anthropometric parameters, 3-h OGTT for blood glucose (BG), insulin and c-peptide, lipid profile, interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), highly sensitive C-reactive protein (hsCRP), and leptin. Hypoglycemia was defined as BG ≤ 2.7 mmol/l.

RESULTS

After surgery, 180 patients completed the OGTT. Eleven patients did not complete the test for gastric intolerance, and in six patients, the test was stopped earlier for the onset of severe symptomatic hypoglycemia. Of the patients, 61/186 (32.8%) had at least one OGTT-related hypoglycemia. The highest frequency of hypoglycemic events occurred 150' after glucose load (20.2%). At baseline, patients with hypoglycemic events after surgery (Hypo) were younger (40 ± 11 vs 46 ± 10 years; p < 0.001), less obese (BMI 46 ± 5.7 vs 48.4 ± 7.9 kg/m²; p < 0.05), and had a worse lipid profile as compared to patients without hypoglycemic events (N-Hypo). Moreover, after LSG, Hypo patients compared with N-Hypo presented a higher weight loss (%EBMIL 80 ± 20 vs 62 ± 21%; p < 0.001). Low age, low fasting glucose, and high triglyceride levels before LSG were independent predictors of hypoglycemia development after surgery (r ² = 0.131).

CONCLUSION

These findings confirm the high incidence of post-prandial hypoglycemia 1 year after LSG. Hypoglycemia is more frequent in younger patients with lower fasting glucose and higher triglyceride levels before surgery.

Exercise Increases Insulin Sensitivity and Skeletal Muscle AMPK Expression in Systemic Lupus Erythematosus: A Randomized Controlled Trial

Systemic lupus erythematosus (SLE) patients may show increased insulin resistance (IR) when compared with their healthy peers. Exercise training has been shown to improve insulin sensitivity in other insulin-resistant populations, but it has never been tested in SLE. Therefore, the aim of the present study was to assess the efficacy of a moderate-intensity exercise training program on insulin sensitivity and potential underlying mechanisms in SLE patients with mild/inactive disease. A 12-week, randomized controlled trial was conducted. Nineteen SLE patients were randomly assigned into two groups: trained (SLE-TR, n = 9) and non-trained (SLE-NT, n = 10). Before and after 12 weeks of the exercise training program, patients underwent a meal test (MT), from which surrogates of insulin sensitivity and beta-cell function were determined. Muscle biopsies were performed after the MT for the assessment of total and membrane GLUT4 and proteins related to insulin signaling [Akt and AMP-activated protein kinase (AMPK)]. SLE-TR showed, when compared with SLE-NT, significant decreases in fasting insulin [−39 vs. +14%, p = 0.009, effect size (ES) = −1.0] and in the insulin response to MT (−23 vs. +21%, p = 0.007, ES = −1.1), homeostasis model assessment IR (−30 vs. +15%, p = 0.005, ES = −1.1), a tendency toward decreased proinsulin response to MT (−19 vs. +6%, p = 0.07, ES = −0.9) and increased glucagon response to MT (+3 vs. −3%, p = 0.09, ES = 0.6), and significant increases in the Matsuda index (+66 vs. −31%, p = 0.004, ES = 0.9) and fasting glucagon (+4 vs. −8%, p = 0.03, ES = 0.7). No significant differences between SLT-TR and SLT-NT were observed in fasting glucose, glucose response to MT, and insulinogenic index (all p > 0.05). SLE-TR showed a significant increase in AMPK Thr 172 phosphorylation when compared to SLE-NT (+73 vs. −12%, p = 0.014, ES = 1.3), whereas no significant differences between groups were observed in Akt Ser 473 phosphorylation, total and membrane GLUT4 expression, and GLUT4 translocation (all p > 0.05). In conclusion, a 12-week moderate-intensity aerobic exercise training program improved insulin sensitivity in SLE patients with mild/inactive disease. This effect appears to be partially mediated by the increased insulin-stimulated skeletal muscle AMPK phosphorylation.

COMPARISON OF THE LEVELS OF C-REACTIVE PROTEIN, GLP-1 AND GLP-2 AMONG INDIVIDUALS WITH DIABETES, MORBID OBESITY AND HEALTHY CONTROLS: AN EXPLORATORY STUDY

BACKGROUND

The glucagon-like peptides 1 and 2 (GLP-1/GLP-2) are gut hormones that may directly affect the glucose homeostasis and their activity seems to be significantly affected by chronic inflammation.

OBJECTIVE

To evaluate the postprandial levels of glucagon-like peptides 1 and 2 (GLP-1/GLP-2), C-reactive protein (CRP), and the postprandial glucose and insulin levels among individuals with obesity, type 2 diabetes, and healthy controls.

METHODS

An exploratory cross-sectional study, which involved individuals awaiting for bariatric/metabolic surgery and healthy controls. Postprandial levels of GLP-1, GLP-2, glucose, and insulin were obtained after a standard meal tolerance test. Inflammation was assessed by means of CRP.

RESULTS

There were 30 individuals enrolled in the study, divided into three groups: non-diabetic with morbid obesity (NDO; n=11 individuals), diabetic with mild obesity (T2D; n=12 individuals), and healthy controls (C; n=7 individuals). The mean CRP levels were significantly higher in the NDO group (6.6±4.7 mg/dL) than in the T2D (3.3±2.2 mg/dL) and C groups (2.5±3.2 mg/dL) (P=0.038). The GLP-1 levels following standard meal tolerance test and the area under the curve of GLP-1 did not differ among the three groups. The GLP-2 levels were significantly lower in the NDO and T2D than in the C group following standard meal tolerance test at all the times evaluated. The area under the curve of the GLP-2 was significantly lower in the NDO and T2D groups than in the C group (P=0.05 and P=0.01, respectively).

CONCLUSION

GLP-2 levels were impaired in the individuals with obesity and diabetes. This mechanism seems to be enrolled in preventing the worsening of the glucose homeostasis in these individuals.

LRH-1 agonism favours an immune-islet dialogue which protects against diabetes mellitus

Type 1 diabetes mellitus (T1DM) is due to the selective destruction of islet beta cells by immune cells. Current therapies focused on repressing the immune attack or stimulating beta cell regeneration still have limited clinical efficacy. Therefore, it is timely to identify innovative targets to dampen the immune process, while promoting beta cell survival and function. Liver receptor homologue-1 (LRH-1) is a nuclear receptor that represses inflammation in digestive organs, and protects pancreatic islets against apoptosis. Here, we show that BL001, a small LRH-1 agonist, impedes hyperglycemia progression and the immune-dependent inflammation of pancreas in murine models of T1DM, and beta cell apoptosis in islets of type 2 diabetic patients, while increasing beta cell mass and insulin secretion. Thus, we suggest that LRH-1 agonism favors a dialogue between immune and islet cells, which could be druggable to protect against diabetes mellitus.

Type 1 diabetes mellitus (T1DM) is characterized by beta cell loss because of an autoimmune attack. Here the authors show that an agonist for LRH-1/NR5A2, a nuclear receptor known to be protective against beta cell apoptosis, inhibits immune-mediated inflammation and hyperglycemia in T1DM mouse models.

An ALPHA7 Nicotinic Acetylcholine Receptor Agonist (GTS-21) Promotes C2C12 Myonuclear Accretion in Association with Release of Interleukin-6 (IL-6) and Improves Survival in Burned Mice

The role of interleukin-6 (IL-6) in physiological processes and disease is poorly understood. The hypothesis tested in this study was that selective alpha7 acetylcholine receptor (α7AChR) agonist, GTS-21, releases IL-6 in association with myonuclear accretion and enhances insulin signaling in muscle cells, and improves survival of burn injured (BI) mice. The in vitro effects of GTS-21 were determined in C2C12 myoblasts and 7-day differentiated myotubes (myotubes). The in vivo effects of GTS-21 were tested in BI wild-type (WT) and IL-6 knockout (IL6KO) mice. GTS-21 dose-dependently (0 μM, 100 μM, and 200 μM) significantly increased IL-6 levels in myoblasts and myotubes at 6 and 9 h. GTS-21-induced IL-6 release in myotubes was attenuated by methyllycaconitine (α7AChR antagonist), and by Stat-3 or Stat-5 inhibitors. GTS-21 increased MyoD and Pax7 protein expression, myonuclear accretion, and insulin-induced phosphorylation of Akt, GSK-3β, and Glut4 in myotubes. The glucose levels of burned IL6KO mice receiving GTS-21 decreased significantly compared with sham-burn IL6KO mice. Superimposition of BI on IL6KO mice caused 100% mortality; GTS-21 reduced mortality to 75% in the IL6KO mice. The 75% mortality in burned WT mice was reduced to 0% with GTS-21. The in vitro findings suggest that GTS-21-induced IL-6 release from muscle is mediated via α7AChRs upstream of Stat-3 and -5 pathways and is associated with myonuclear accretion, possibly via MyoD and Pax7 expression. GTS-21 in vivo improves survival in burned WT mice and IL6KO mice, suggesting a potential therapeutic application of α7AChR agonists in the treatment of BI.

Mechanisms of Action and Therapeutic Application of Glucagon-like Peptide-1

Glucagon-like peptide-1 (GLP-1) released from gut enteroendocrine cells controls meal-related glycemic excursions through augmentation of insulin and inhibition of glucagon secretion. GLP-1 also inhibits gastric emptying and food intake, actions maximizing nutrient absorption while limiting weight gain. Here I review the circuits engaged by endogenous versus pharmacological GLP-1 action, highlighting key GLP-1 receptor (GLP-1R)-positive cell types and pathways transducing metabolic and non-glycemic GLP-1 signals. The role(s) of GLP-1 in the benefits and side effects associated with bariatric surgery are discussed and actions of GLP-1 controlling islet function, appetite, inflammation, and cardiovascular pathophysiology are highlighted. Refinement of the risk-versus-benefit profile of GLP-1-based therapies for the treatment of diabetes and obesity has stimulated development of orally bioavailable agonists, allosteric modulators, and unimolecular multi-agonists, all targeting the GLP-1R. This review highlights established and emerging concepts, unanswered questions, and future challenges for development and optimization of GLP-1R agonists in the treatment of metabolic disease.

Do skeletal muscle-secreted factors influence the function of pancreatic β-cells?

Skeletal muscle is an endocrine organ that secretes a variety of compounds including proteins (myokines), metabolites, microRNAs (miRNAs), and exosomes, many of which are regulated by exercise and play important roles in endocrine signaling. Interorgan communication via muscle-secreted factors therefore provides a novel area for investigation and implicates the importance of skeletal muscle in the pathophysiology of metabolic diseases such as type 2 diabetes (T2D). Given that underlying molecular mechanisms of T2D are subject of ongoing research, in light of new evidence it is probable that interorgan cross-talk between skeletal muscle and pancreatic β-cells plays an important part. To date, the number of studies published in this field provide the basis of this review. Specifically, we discuss current experimental evidence in support for a role of skeletal muscle to β-cell cross-talk, paying particular attention to muscle-secreted factors including myokines, metabolites, miRNAs, and factors contained within exosomes that influence the function and/or the survival of β-cells in health and disease. In reviewing this evidence, we provide an update on the list of known muscle-secreted factors that have potential to influence the function and/or survival of β-cells under normal and diabetic conditions. We also report limitations of current cross-talk methods and discuss future directions in this growing field.

Exercise has the guts: How physical activity may positively modulate gut microbiota in chronic and immune-based diseases

Limited animal and human research findings suggests that exercise might have a beneficial role for health gut. Cardiorespiratory fitness correlates with health-associated gut parameters such as taxonomic diversity and richness. Physical exercise may augment intestinal microbial diversity through several mechanisms including promotion of an anti-inflammatory state. Disease-associated microbial functions were linked to distinct taxa in previous studies of familial type 1 diabetes mellitus (T1D). An integrated multi-approach in the study of T1D, including physical exercise, is advocated. The present review explores how exercise might modulate gut microbiota and microbiome characteristics in chronic and immune-based diseases, given the demonstrated relationship between gut function and human health.

Signalling from the periphery to the brain that regulates energy homeostasis

The CNS regulates body weight; however, we still lack a clear understanding of what drives decisions about when, how much and what to eat. A vast array of peripheral signals provides information to the CNS regarding fluctuations in energy status. The CNS then integrates this information to influence acute feeding behaviour and long-term energy homeostasis. Previous paradigms have delegated the control of long-term energy homeostasis to the hypothalamus and short-term changes in feeding behaviour to the hindbrain. However, recent studies have identified target hindbrain neurocircuitry that integrates the orchestration of individual bouts of ingestion with the long-term regulation of energy balance.

Gut as an emerging organ for the treatment of diabetes: focus on mechanism of action of bariatric and endoscopic interventions

Increasing worldwide prevalence of type 2 diabetes mellitus and its accompanying pathologies such as obesity, arterial hypertension and dyslipidemia represents one of the most important challenges of current medicine. Despite intensive efforts, high percentage of patients with type 2 diabetes does not achieve treatment goals and struggle with increasing body weight and poor glucose control. While novel classes of antidiabetic medications such as incretin-based therapies and gliflozins have some favorable characteristics compared to older antidiabetics, the only therapeutic option shown to substantially modify the progression of diabetes or to achieve its remission is bariatric surgery. Its efficacy in the treatment of diabetes is well established, but the exact underlying modes of action are still only partially described. They include restriction of food amount, enhanced passage of chymus into distal part of small intestine with subsequent modification of gastrointestinal hormones and bile acids secretion, neural mechanisms, changes in gut microbiota and many other possible mechanisms underscoring the importance of the gut in the regulation of glucose metabolism. In addition to bariatric surgery, less-invasive endoscopic methods based on the principles of bariatric surgery were introduced and showed promising results. This review highlights the role of the intestine in the regulation of glucose homeostasis focusing on the mechanisms of action of bariatric and especially endoscopic methods of the treatment of diabetes. A better understanding of these mechanisms may lead to less invasive endoscopic treatments of diabetes and obesity that may complement and widen current therapeutic options.

IL-6 signalling pathways and the development of type 2 diabetes

Interleukin 6 (IL-6), a multifunctional cytokine, has been implicated in the pathophysiology of type 2 diabetes (T2D). The elevated circulating level of IL-6 is an independent predictor of T2D and is considered to be involved in the development of inflammation, insulin resistance and β-cell dysfunction. On the other hand, an increasing number of evidence suggests that IL-6 has an anti-inflammatory role and improves glucose metabolism. The complex signal transduction mechanism of IL-6 may help explain the pleiotropic nature of the cytokine. IL-6 acts via two distinct signalling pathways called classic signalling and trans-signalling. While both signalling modes lead to activation of the same receptor subunit, their final biological effects are completely different. The aim of this review is to summarize our current knowledge about the role of IL-6 in the development of T2D. We will also discuss the importance of specific blockade of IL-6 trans-signalling rather than inhibiting both signalling pathways as a therapeutic strategy for the treatment of T2D and its associated macrovascular complications.

Pancreatic Pericytes Support β-Cell Function in a Tcf7l2-Dependent Manner

Polymorphism in TCF7L2, a component of the canonical Wnt signaling pathway, has a strong association with β-cell dysfunction and type 2 diabetes through a mechanism that has yet to be defined. β-Cells rely on cells in their microenvironment, including pericytes, for their proper function. Here, we show that Tcf7l2 activity in pancreatic pericytes is required for β-cell function. Transgenic mice in which Tcf7l2 was selectively inactivated in their pancreatic pericytes exhibited impaired glucose tolerance due to compromised β-cell function and glucose-stimulated insulin secretion. Inactivation of pericytic Tcf7l2 was associated with impaired expression of genes required for β-cell function and maturity in isolated islets. In addition, we identified Tcf7l2-dependent pericytic expression of secreted factors shown to promote β-cell function, including bone morphogenetic protein 4 (BMP4). Finally, we show that exogenous BMP4 is sufficient to rescue the impaired glucose-stimulated insulin secretion of transgenic mice, pointing to a potential mechanism through which pericytic Tcf7l2 activity affects β-cells. To conclude, we suggest that pancreatic pericytes produce secreted factors, including BMP4, in a Tcf7l2-dependent manner to support β-cell function. Our findings thus propose a potential cellular mechanism through which abnormal TCF7L2 activity predisposes individuals to diabetes and implicates abnormalities in the islet microenvironment in this disease.

GPR142 prompts glucagon-like Peptide-1 release from islets to improve β cell function

Objective

GPR142 agonists are being pursued as novel diabetes therapies by virtue of their insulin secretagogue effects. But it is undetermined whether GPR142's functions in pancreatic islets are limited to regulating insulin secretion. The current study expands research on its action.

Methods and Results

We demonstrated by in situ hybridization and immunostaining that GPR142 is expressed not only in β cells but also in a subset of α cells. Stimulation of GPR142 by a selective agonist increased glucagon secretion in both human and mouse islets. More importantly, the GPR142 agonist also potentiated glucagon-like peptide-1 (GLP-1) production and its release from islets through a mechanism that involves upregulation of prohormone convertase 1/3 expression. Strikingly, stimulation of insulin secretion and increase in insulin content via GPR142 engagement requires intact GLP-1 receptor signaling. Furthermore, GPR142 agonist increased β cell proliferation and protected both mouse and human islets against stress-induced apoptosis.

Conclusions

Collectively, we provide here evidence that local GLP-1 release from α cells defines GPR142's beneficial effects on improving β cell function and mass, and we propose that GPR142 agonism may have translatable and durable efficacy for the treatment of type 2 diabetes.

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GPR142 is expressed in both α cells and β cells in pancreatic islets.

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Stimulation of GPR142 by a selective agonist increases glucagon secretion.

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GPR142 agonism promotes glucagon-like peptide-1 release from islets by upregulating prohormone convertase 1/3.

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Increases in insulin secretion and content via GPR142 engagement require intact GLP-1 receptor signaling.

"Living High-Training Low" improved weight loss and glucagon-like peptide-1 level in a 4-week weight loss program in adolescents with obesity: A pilot study

BACKGROUND

"Living High-Training Low" (LHTL) is effective for the improvement of athletic ability; however, little is known about the effect of LHTL on obese individuals. The present study determined whether LHTL would have favorable influence on body composition, rebalance the appetite hormones, and explore the underlying mechanism.

METHODS

Adolescents with obesity [body mass index (BMI) >30 kg/m] were randomly assigned to "Living Low-Training Low" (LLTL, n = 19) group that slept in a normobaric normoxia condition and the LHTL (n = 16) group slept in a normobaric hypoxia room (14.7% PO2 ∼2700 m). Both groups underwent the same aerobic exercise training program. Morphological, blood lipids, and appetite hormones were measured and assessed.

RESULTS

After the intervention, the body composition improved in both groups, whereas reductions in body weight (BW), BMI, and lean body mass increased significantly in the LHTL group (all, P < .05). In the LLTL group, cholecystokinin (CCK) decreased remarkably (P < .05) and CCK changes were positively associated with changes in BW (r = 0.585, P = .011) and BMI (r = 0.587, P = .010). However, in the LHTL group, changes in plasma glucagon-like peptide-1 (GLP-1) and interleukin-6 (IL-6) levels, positively correlated with each other (r = 0.708, P = .015) but negatively with BW changes (r = -0.608, P = .027 and r = -0.518, P = .048, respectively).

CONCLUSION

The results indicated that LHTL could induce more weight loss safely and efficiently as compared to LLTL and increase the plasma GLP-1 levels that may be mediated by IL-6 to rebalance the appetite. Thus, an efficient method to treat obesity and prevent weight regain by appetite rebalance in hypoxia condition was established.

A Single Bout of Electroacupuncture Remodels Epigenetic and Transcriptional Changes in Adipose Tissue in Polycystic Ovary Syndrome

A single bout of electroacupuncture results in muscle contractions and increased whole body glucose uptake in women with polycystic ovary syndrome (PCOS). Women with PCOS have transcriptional and epigenetic alterations in the adipose tissue and we hypothesized that electroacupuncture induces epigenetic and transcriptional changes to restore metabolic alterations. Twenty-one women with PCOS received a single bout of electroacupuncture, which increased the whole body glucose uptake. In subcutaneous adipose tissue biopsies, we identified treatment-induced expression changes of 2369 genes (Q < 0.05) and DNA methylation changes of 7055 individual genes (Q = 0.11). The largest increase in expression was observed for FOSB (2405%), and the largest decrease for LOC100128899 (54%). The most enriched pathways included Acute phase response signaling and LXR/RXR activation. The DNA methylation changes ranged from 1-16%, and 407 methylation sites correlated with gene expression. Among genes known to be differentially expressed in PCOS, electroacupuncture reversed the expression of 80 genes, including PPARγ and ADIPOR2. Changes in the expression of Nr4a2 and Junb are reversed by adrenergic blockers in rats demonstrating that changes in gene expression, in part, is due to activation of the sympathetic nervous system. In conclusion, low-frequency electroacupuncture with muscle contractions remodels epigenetic and transcriptional changes that elicit metabolic improvement.

Exercise Protects Against Olanzapine-Induced Hyperglycemia in Male C57BL/6J Mice

Olanzapine is a widely prescribed antipsychotic drug. While effective in reducing psychoses, treatment with olanzapine causes rapid increases in blood glucose. We wanted to determine if a single bout of exercise, immediately prior to treatment, would attenuate the olanzapine-induced rise in blood glucose and if this occurred in an IL-6 dependent manner. We found that exhaustive, but not moderate exercise, immediately prior to treatment, prevented olanzapine-induced hyperglycemia and this occurred in parallel with increases in serum IL-6. To determine if IL-6 was involved in the mechanisms through which exhaustive exercise protected against olanzapine-induced hyperglycemia several additional experiments were completed. Treatment with IL-6 (3 ng/g bw, IP) alone did not protect against olanzapine-induced increases in blood glucose. The protective effects of exhaustive exercise against olanzapine-induced increases in blood glucose were intact in whole body IL-6 knockout mice. Similarly, treating mice with an IL-6 neutralizing antibody prior to exhaustive exercise did not negate the protective effect of exercise against olanzapine-induced hyperglycemia. Our findings provide evidence that a single bout of exhaustive exercise protects against acute olanzapine-induced hyperglycemia and that IL-6 is neither sufficient, nor required for exercise to protect against increases in blood glucose with olanzapine treatment.

An Integrated View of Immunometabolism

The worldwide obesity epidemic has emerged as a major cause of insulin resistance and Type 2 diabetes. Chronic tissue inflammation is a well-recognized feature of obesity, and the field of immunometabolism has witnessed many advances in recent years. Here, we review the major features of our current understanding with respect to chronic obesity-related inflammation in metabolic tissues and focus on how these inflammatory changes affect insulin sensitivity, insulin secretion, food intake, and glucose homeostasis. There is a growing appreciation of the varied and sometimes integrated crosstalk between cells within a tissue (intraorgan) and tissues within an organism (interorgan) that supports inflammation in the context of metabolic dysregulation. Understanding these pathways and modes of communication has implications for translational studies. We also briefly summarize the state of this field with respect to potential current and developing therapeutics.

IL-6-Type Cytokine Signaling in Adipocytes Induces Intestinal GLP-1 Secretion

We recently showed that interleukin (IL)-6-type cytokine signaling in adipocytes induces free fatty acid release from visceral adipocytes, thereby promoting obesity-induced hepatic insulin resistance and steatosis. In addition, IL-6-type cytokines may increase the release of leptin from adipocytes and by those means induce glucagon-like peptide 1 (GLP-1) secretion. We thus hypothesized that IL-6-type cytokine signaling in adipocytes may regulate insulin secretion. To this end, mice with adipocyte-specific knockout of gp130, the signal transducer protein of IL-6, were fed a high-fat diet for 12 weeks. Compared with control littermates, knockout mice showed impaired glucose tolerance and circulating leptin, GLP-1, and insulin levels were reduced. In line, leptin release from isolated adipocytes was reduced, and intestinal proprotein convertase subtilisin/kexin type 1 (Pcsk1) expression, the gene encoding PC1/3, which controls GLP-1 production, was decreased in knockout mice. Importantly, treatment with the GLP-1 receptor antagonist exendin 9-39 abolished the observed difference in glucose tolerance between control and knockout mice. Ex vivo, supernatant collected from isolated adipocytes of gp130 knockout mice blunted Pcsk1 expression and GLP-1 release from GLUTag cells. In contrast, glucose- and GLP-1-stimulated insulin secretion was not affected in islets of knockout mice. In conclusion, adipocyte-specific IL-6 signaling induces intestinal GLP-1 release to enhance insulin secretion, thereby counteracting insulin resistance in obesity.

Mouse pancreatic islet macrophages use locally released ATP to monitor beta cell activity

AIMS/HYPOTHESIS

Tissue-resident macrophages sense the microenvironment and respond by producing signals that act locally to maintain a stable tissue state. It is now known that pancreatic islets contain their own unique resident macrophages, which have been shown to promote proliferation of the insulin-secreting beta cell. However, it is unclear how beta cells communicate with islet-resident macrophages. Here we hypothesised that islet macrophages sense changes in islet activity by detecting signals derived from beta cells.

METHODS

To investigate how islet-resident macrophages respond to cues from the microenvironment, we generated mice expressing a genetically encoded Ca2+ indicator in myeloid cells. We produced living pancreatic slices from these mice and used them to monitor macrophage responses to stimulation of acinar, neural and endocrine cells.

RESULTS

Islet-resident macrophages expressed functional purinergic receptors, making them exquisite sensors of interstitial ATP levels. Indeed, islet-resident macrophages responded selectively to ATP released locally from beta cells that were physiologically activated with high levels of glucose. Because ATP is co-released with insulin and is exclusively secreted by beta cells, the activation of purinergic receptors on resident macrophages facilitates their awareness of beta cell secretory activity.

CONCLUSIONS/INTERPRETATION

Our results indicate that islet macrophages detect ATP as a proxy signal for the activation state of beta cells. Sensing beta cell activity may allow macrophages to adjust the secretion of factors to promote a stable islet composition and size.

Enteroendocrine cells-sensory sentinels of the intestinal environment and orchestrators of mucosal immunity

The intestinal epithelium must balance efficient absorption of nutrients with partitioning commensals and pathogens from the bodies' largest immune system. If this crucial barrier fails, inappropriate immune responses can result in inflammatory bowel disease or chronic infection. Enteroendocrine cells represent 1% of this epithelium and have classically been studied for their detection of nutrients and release of peptide hormones to mediate digestion. Intriguingly, enteroendocrine cells are the key sensors of microbial metabolites, can release cytokines in response to pathogen associated molecules and peptide hormone receptors are expressed on numerous intestinal immune cells; thus enteroendocrine cells are uniquely equipped to be crucial and novel orchestrators of intestinal inflammation. In this review, we introduce enteroendocrine chemosensory roles, summarize studies correlating enteroendocrine perturbations with intestinal inflammation and describe the mechanistic interactions by which enteroendocrine and mucosal immune cells interact during disease; highlighting this immunoendocrine axis as a key aspect of innate immunity.

Dissecting the Physiology and Pathophysiology of Glucagon-Like Peptide-1

An aging world population exposed to a sedentary life style is currently plagued by chronic metabolic diseases, such as type-2 diabetes, that are spreading worldwide at an unprecedented rate. One of the most promising pharmacological approaches for the management of type 2 diabetes takes advantage of the peptide hormone glucagon-like peptide-1 (GLP-1) under the form of protease resistant mimetics, and DPP-IV inhibitors. Despite the improved quality of life, long-term treatments with these new classes of drugs are riddled with serious and life-threatening side-effects, with no overall cure of the disease. New evidence is shedding more light over the complex physiology of GLP-1 in health and metabolic diseases. Herein, we discuss the most recent advancements in the biology of gut receptors known to induce the secretion of GLP-1, to bridge the multiple gaps into our understanding of its physiology and pathology.

Macrophage polarization and meta-inflammation

Chronic overnutrition and obesity induces low-grade inflammation throughout the body. Termed "meta-inflammation," this chronic state of inflammation is mediated by macrophages located within the colon, liver, muscle, and adipose tissue. A sentinel orchestrator of immune activity and homeostasis, macrophages adopt variable states of activation as a function of time and environmental cues. Meta-inflammation phenotypically skews these polarization states and has been linked to numerous metabolic disorders. The past decade has revealed several key regulators of macrophage polarization, including the signal transducer and activator of transcription family, the peroxisome proliferator-activated receptor gamma, the CCAAT-enhancer-binding proteins (C/EBP) family, and the interferon regulatory factors. Recent studies have also suggested that microRNAs and long noncoding RNA influence macrophage polarization. The pathogenic alteration of macrophage polarization in meta-inflammation is regulated by both extracellular and intracellular cues, resulting in distinct secretome profiles. Meta-inflammation-altered macrophage polarization has been linked to insulin insensitivity, atherosclerosis, inflammatory bowel disease, cancer, and autoimmunity. Thus, further mechanistic exploration into the skewing of macrophage polarization promises to have profound impacts on improving global health.

Effects of walking in water on gut hormone concentrations and appetite: comparison with walking on land

The effects of water exercise on gut hormone concentrations and appetite currently remain unclear. The aim of the present study was to investigate the effects of treadmill walking in water on gut hormone concentrations and appetite. Thirteen men (mean ± s.d. age: 21.6 ± 2.2 years, body mass index: 22.7 ± 2.8 kg/m², peak oxygen uptake (VO_2peak): 49.8 ± 7.8 mL/kg per min) participated in the walking in water and on land challenge. During the study period, ratings of subjective feelings of hunger, fullness, satiety and motivation to eat were reported on a 100-mm visual analog scale. A test meal was presented after walking, and energy intake (EI) was calculated. Blood samples were obtained during both trials to measure glucagon-like peptide-1 (GLP-1), peptide YY (PYY) and acylated ghrelin (AG) concentrations. Hunger scores (How hungry do you feel?) were significantly lower during the water trial than during the land trial (P < 0.05). No significant differences were observed in EI between water and land trials. GLP-1 concentrations were significantly higher in the water trial than in the land trial (P < 0.05). No significant differences were observed in PYY concentrations between water and land trials. AG concentrations were significantly lower in the water trial than in the land trial (P < 0.01). In conclusion, changes in gut hormone concentrations during walking in water contribute to the exercise-induced suppression of appetite and provide novel information on the influence of walking in water on the acute regulation of appetite.

Exercise in patients with inflammatory bowel diseases: current perspectives

Inflammatory bowel diseases (IBDs), including both Crohn's disease (CD) and ulcerative colitis (UC), are chronic autoimmune diseases. Both CD and UC have relapsing and remitting courses. Although effective medical treatments exist for these chronic conditions, some patients do not respond to these traditional therapies. Patients are often left frustrated with incomplete resolution of symptoms and seek alternative or complementary forms of therapy. Patients often search for modifiable factors that could improve their symptoms or help them to maintain periods of remission. In this review, we examine both the published evidence on the benefits of exercise clinically and the pathophysiological changes associated with exercise. We then describe data on exercise patterns in patients with IBDs, potential barriers to exercise in IBDs, and the role of exercise in the development and course of IBDs. While some data support physical activity as having a protective role in the development of IBDs, the findings have not been robust. Importantly, studies of exercise in patients with mild-to-moderate IBD activity show no danger of disease or symptom exacerbation. Exercise has theoretical benefits on the immune response, and the limited available data suggest that exercise may improve disease activity, quality of life, bone mineral density, and fatigue levels in patients with IBDs. Overall, exercise is safe and probably beneficial in patients with IBDs. Evidence supporting specific exercise recommendations, including aspects such as duration and heart rate targets, is needed in order to better counsel patients with IBDs.