Interleukin-6 amplifies glucagon secretion: coordinated control via the brain and pancreas

Single and consecutive 10-day remote ischemic preconditioning modify physical performance, post-exercise exerkine levels, and inflammation

Purpose

Remote ischemic preconditioning (RIPC) is a method of protection against induced ischemia reperfusion injury, and an increasing number of studies showed some of its inconclusive ergogenic effects in sports. RIPC involves short cycles of cuff inflation followed by its deflation which may affect many body systems. While most of the studies focus on single RIPC effects, there is insufficient data regarding training-like repeated RIPC interventions. Thus, in this study, we analyzed the effect of a single- and consecutive 10-day RIPC procedure on a single leg, focusing on the exerkine levels and changes in inflammation markers following the Wingate Anaerobic Test (WAnT).

Methods

Two single-blinded, sham-controlled protocols were designed to evaluate the 1) single (crossover study) and 2) consecutive 10-day (parallel study) RIPC effects on the WAnT performance and exercise-induced lactate, glucose, exerkine, and inflammation markers (BDNF; IL-6; IL-10; IL-15; LIF; oncostatin M). In each protocol, 37 physically active men (19.98 ± 1.17 years) were randomly assigned into two groups according to a particular study design.

Results

An increase in participants' mean (4.81%, p < 0.05) and peak power (6.25%, p < 0.05) during the WAnT was observed only after the consecutive 10-day RIPC. Similarly, a significant 15.5% (p < 0.05) decrease in the IL-6 concentration 120 min after the WAnT was observed only in the consecutive 10-day RIPC protocol, as well as a 12.2% (p < 0.01) increase in oncostatin M 60 min after the WAnT.

Conclusion

The results demonstrate the efficacy of the consecutive 10-day RIPC procedure in modulating exercise performance and post-exercise inflammation markers.

The immunology of sickness metabolism

Everyone knows that an infection can make you feel sick. Although we perceive infection-induced changes in metabolism as a pathology, they are a part of a carefully regulated process that depends on tissue-specific interactions between the immune system and organs involved in the regulation of systemic homeostasis. Immune-mediated changes in homeostatic parameters lead to altered production and uptake of nutrients in circulation, which modifies the metabolic rate of key organs. This is what we experience as being sick. The purpose of sickness metabolism is to generate a metabolic environment in which the body is optimally able to fight infection while denying vital nutrients for the replication of pathogens. Sickness metabolism depends on tissue-specific immune cells, which mediate responses tailored to the nature and magnitude of the threat. As an infection increases in severity, so do the number and type of immune cells involved and the level to which organs are affected, which dictates the degree to which we feel sick. Interestingly, many alterations associated with metabolic disease appear to overlap with immune-mediated changes observed following infection. Targeting processes involving tissue-specific interactions between activated immune cells and metabolic organs therefore holds great potential for treating both people with severe infection and those with metabolic disease. In this review, we will discuss how the immune system communicates in situ with organs involved in the regulation of homeostasis and how this communication is impacted by infection.

Intravenous lipopolysaccharide challenge in early- versus mid-lactation dairy cattle. II: The production and metabolic responses

Most immunometabolic research uses mid-lactation (ML) cows. Cows in early lactation (EL) are in a presumed state of immune suppression/dysregulation and less is known about how they respond to a pathogen. Study objectives were to compare the production and metabolic responses to i.v. LPS and to differentiate between the direct effects of immune activation and the indirect effects of illness-induced hypophagia in EL and ML cows. Cows in EL (n = 11; 20 ± 2 DIM) and ML (n = 12; 131 ± 31 DIM) were enrolled in a 2 × 2 factorial design containing 2 experimental periods (P). During P1 (3 d), cows were fed ad libitum and baseline data were collected. At the initiation of P2 (3 d), cows were randomly assigned to 1 of 2 treatments by lactation stage (LS): (1) EL (EL-LPS; n = 6) or ML (ML-LPS; n = 6) cows administered i.v. a single bolus of 0.09 µg LPS/kg of BW; Escherichia coli O55:B5 or (2) pair-fed (PF) EL (EL-PF; n = 5) or ML (ML-PF; n = 6) cows administered i.v. saline. Administering LPS decreased DMI and this was more severe in EL-LPS than ML-LPS cows (34% and 11% relative to baseline, respectively). By design, P2 DMI patterns were similar in the PF groups compared with their LPS counterparts. Milk yield decreased following LPS (42% on d 1 relative to P1) and despite an exacerbated decrease in EL-LPS cows on d 1 (25% relative to ML-LPS), remained similar between LS from d 2 to 3. The EL-LPS cows had increased milk fat content, but no difference in protein and lactose percentages compared with ML-LPS cows. Further, cumulative ECM yield was increased (21%) in EL-LPS compared with ML-LPS cows. During P2, EL-LPS cows had a more intense increase in MUN and BUN than ML-LPS and EL-PF cows. Administering LPS did not cause hypoglycemia in either EL-LPS or ML-LPS cows, but glucose was increased (33%) in EL-LPS compared with EL-PF. Hyperinsulinemia occurred after LPS, and insulin was further increased in ML-LPS than EL-LPS cows (2.2-fold at 12 h peak). During P2, circulating glucagon increased only in EL-LPS cows (64% relative to all other groups). Both EL groups had increased NEFA at 3 and 6 h after LPS from baseline (56%), but NEFA in EL-LPS cows gradually returned to baseline thereafter and were reduced relative to EL-PF until 36 h (50% from 12 to 24 h). Alterations in BHB did not differ between ML groups, but EL-LPS had reduced BHB compared with EL-PF from 24 to 72 h (51%). Results indicate that there are distinct LS differences in the anorexic and metabolic responses to immune activation. Collectively, EL cows are more sensitive to the catabolic effects of LPS than ML cows, but these exacerbated metabolic responses appear coordinated to fuel an augmented immune system while simultaneously supporting milk synthesis.

Blocking IL-6 signaling improves glucose tolerance via SLC39A5-mediated suppression of glucagon secretion

BACKGROUND AND AIMS

Hyperinsulinemia, hyperglucagonemia, and low-grade inflammation are frequently presented in obesity and type 2 diabetes (T2D). The pathogenic regulation between hyperinsulinemia/insulin resistance (IR) and low-grade inflammation is well documented in the development of diabetes. However, the cross-talk of hyperglucagonemia with low-grade inflammation during diabetes progression is poorly understood. In this study, we investigated the regulatory role of proinflammatory cytokine interleukin-6 (IL-6) on glucagon secretion.

METHODS

The correlations between inflammatory cytokines and glucagon or insulin were analyzed in rhesus monkeys and humans. IL-6 signaling was blocked by IL-6 receptor-neutralizing antibody tocilizumab in obese or T2D rhesus monkeys, glucose tolerance was evaluated by intravenous glucose tolerance test (IVGTT). Glucagon and insulin secretion were measured in isolated islets from wild-type mouse, primary pancreatic α-cells and non-α-cells sorted from GluCre-ROSA26EYFP (GYY) mice, in which the enhanced yellow fluorescent protein (EYFP) was expressed under the proglucagon promoter, by fluorescence-activated cell sorting (FACS). Particularly, glucagon secretion in α-TC1 cells treated with IL-6 was measured, and RNA sequencing was used to screen the mediator underlying IL-6-induced glucagon secretion. SLC39A5 was knocking-down or overexpressed in α-TC1 cells to determine its impact in glucagon secretion and cytosolic zinc density. Dual luciferase and chromatin Immunoprecipitation were applied to analyze the signal transducer and activator of transcription 3 (STAT3) in the regulation of SLC39A5 transcription.

RESULTS

Plasma IL-6 correlate positively with plasma glucagon levels, but not insulin, in rhesus monkeys and humans. Tocilizumab treatment reduced plasma glucagon, blood glucose and HbA1c in spontaneously obese or T2D rhesus monkeys. Tocilizumab treatment also decreased glucagon levels during IVGTT, and improved glucose tolerance. Moreover, IL-6 significantly increased glucagon secretion in isolated islets, primary pancreatic α-cells and α-TC1 cells. Mechanistically, we found that IL-6-activated STAT3 downregulated the zinc transporter SLC39A5, which in turn reduced cytosolic zinc concentration and ATP-sensitive potassium channel activity and augmented glucagon secretion.

CONCLUSIONS

This study demonstrates that IL-6 increases glucagon secretion via the downregulation of zinc transporter SLC39A5. This result revealed the molecular mechanism underlying the pathogenesis of hyperglucagonemia and a previously unidentified function of IL-6 in the pathophysiology of T2D, providing a potential new therapeutic strategy of targeting IL-6/glucagon to preventing or treating T2D.

Pregnancy induces pancreatic insulin secretion in women with long-standing type 1 diabetes

INTRODUCTION

Pregnancy entails both pancreatic adaptations with increasing β-cell mass and immunological alterations in healthy women. In this study, we have examined the effects of pregnancy on β-cell function and immunological processes in long-standing type 1 diabetes (L-T1D).

RESEARCH DESIGN AND METHODS

Fasting and stimulated C-peptide were measured after an oral glucose tolerance test in pregnant women with L-T1D (n=17) during the first trimester, third trimester, and 5-8 weeks post partum. Two 92-plex Olink panels were used to measure proteins in plasma. Non-pregnant women with L-T1D (n=30) were included for comparison.

RESULTS

Fasting C-peptide was detected to a higher degree in women with L-T1D during gestation and after parturition (first trimester: 64.7%, third trimester: 76.5%, and post partum: 64.7% vs 26.7% in non-pregnant women). Also, total insulin secretion and peak C-peptide increased during pregnancy. The plasma protein levels in pregnant women with L-T1D was dynamic, but few analytes were functionally related. Specifically, peripheral levels of prolactin (PRL), prokineticin (PROK)-1, and glucagon (GCG) were elevated during gestation whereas levels of proteins related to leukocyte migration (CCL11), T cell activation (CD28), and antigen presentation (such as CD83) were reduced.

CONCLUSIONS

In summary, we have found that some C-peptide secretion, that is, an indirect measurement of endogenous insulin production, is regained in women with L-T1D during pregnancy, which might be attributed to elevated peripheral levels of PRL, PROK-1, or GCG.

Improvement of liver metabolic activity in people with advanced HIV after antiretroviral therapy initiation

OBJECTIVE

Evaluating hepatic metabolic changes in people with HIV (PWH) with advanced disease, before and after antiretroviral therapy (ART) initiation, using [ 18 F]-fluorodeoxyglucose (FDG) PET-computed tomography (PET/CT). FDG PET/CT noninvasively quantifies glucose metabolism in organs.

DESIGN/METHODS

Forty-eight viremic PWH (CD4 + cell counts <100 cells/μl) underwent FDG PET/CT at baseline and approximately 6 weeks after ART initiation (short-term). Twenty-seven PWH participants underwent follow-up scans 2 years after treatment (long-term). FDG PET/CT scans from 20 healthy controls were used for comparison. Liver FDG uptake was quantified from the PET/CT scans. Imaging findings as well as clinical, laboratory, and immune markers were compared longitudinally and cross-sectionally to healthy controls.

RESULTS

Liver FDG uptake was lower at baseline and short-term in PWH compared with controls ( P  < 0.0001). At the long-term scan, liver FDG uptake of PWH increased relative to baseline and short-term ( P  = 0.0083 and 0.0052) but remained lower than controls' values ( P  = 0.004). Changes in FDG uptake correlated negatively with levels of glucagon, myeloperoxidase, sCD14, and MCP-1 and positively with markers of recovery (BMI, albumin, and CD4 + cell counts) ( P  < 0.01). In multivariable analyses of PWH values across timepoints, BMI and glucagon were the best set of predictors for liver FDG uptake ( P  < 0.0001).

CONCLUSION

Using FDG PET/CT, we found decreased liver glucose metabolism in PWH that could reflect hepatocytes/lymphocytes/myeloid cell loss and metabolic dysfunction because of inflammation. Although long-term ART seems to reverse many hepatic abnormalities, residual liver injury may still exist within 2 years of treatment initiation, especially in PWH who present with low nadir CD4 + cell counts.

Choice of Lipid Emulsion Determines Inflammation of the Gut-Liver Axis, Incretin Profile, and Insulin Signaling in a Murine Model of Total Parenteral Nutrition

SCOPE

The aim of this study is to test whether the choice of the lipid emulsion in total parenteral nutrition (TPN), that is, n-3 fatty acid-based Omegaven versus n-6 fatty acid-based Intralipid, determines inflammation in the liver, the incretin profile, and insulin resistance.

METHODS AND RESULTS

Jugular vein catheters (JVC) are placed in C57BL/6 mice and used for TPN for 7 days. Mice are randomized into a saline group (saline infusion with oral chow), an Intralipid group (IL-TPN, no chow), an Omegaven group (OV-TPN, no chow), or a chow only group (without JVC). Both TPN elicite higher abundance of lipopolysaccharide binding protein in the liver, but only IL-TPN increases interleukin-6 and interferon-γ, while OV-TPN reduces interleukin-4, monocyte chemoattractant protein-1, and interleukin-1α. Insulin plasma concentrations are higher in both TPN, while glucagon and glucagon-like peptide-1 (GLP-1) were higher in IL-TPN. Gluconeogenesis is increased in IL-TPN and the nuclear profile of key metabolic transcription factors shows a liver-protective phenotype in OV-TPN. OV-TPN increases insulin sensitivity in the liver and skeletal muscle.

CONCLUSION

OV-TPN as opposed to IL-TPN mitigates inflammation in the liver and reduces the negative metabolic effects of hyperinsulinemia and hyperglucagonemia by "re-sensitizing" the liver and skeletal muscle to insulin.

Hyperglycemia, inflammatory response and infarct size in obstructive acute myocardial infarction and MINOCA

BACKGROUND

Hyperglycemia has been associated with increased inflammatory indexes and larger infarct sizes in patients with obstructive acute myocardial infarction (obs-AMI). In contrast, no studies have explored these correlations in non-obstructive acute myocardial infarction (MINOCA). We investigated the relationship between hyperglycemia, inflammation and infarct size in a cohort of AMI patients that included MINOCA.

METHODS

Patients with AMI undergoing coronary angiography between 2016 and 2020 were enrolled. The following inflammatory markers were evaluated: C-reactive protein, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and neutrophil-to-platelet ratio (NPR). Myocardial infarct size was measured by peak high sensitivity troponin I (Hs-TnI) levels, left-ventricular-end-diastolic-volume (LVEDV) and left ventricular ejection fraction (LVEF).

RESULTS

The final study population consisted of 2450 patients with obs-AMI and 239 with MINOCA. Hyperglycemia was more prevalent among obs-AMI cases. In all hyperglycemic patients-obs-AMI and MINOCA-NLR, NPR, and LPR were markedly altered. Hyperglycemic obs-AMI subjects exhibited a higher Hs-TnI (p < 0.001), a larger LVEDV (p = 0.003) and a lower LVEF (p < 0.001) compared to normoglycemic ones. Conversely, MINOCA patients showed a trivial myocardial damage, irrespective of admission glucose levels.

CONCLUSIONS

Our data confirm the association of hyperglycemic obs-AMI with elevated inflammatory markers and larger infarct sizes. MINOCA patients exhibited modest myocardial damage, regardless of admission glucose levels.

Extracellular ATP Increases Glucose Metabolism in Skeletal Muscle Cells in a P2 Receptor Dependent Manner but Does Not Contribute to Palmitate-Induced Insulin Resistance

Saturated fatty acids such as palmitate contribute to the development of Type 2 Diabetes by reducing insulin sensitivity, increasing inflammation and potentially contributing to anabolic resistance. We hypothesized that palmitate-induced ATP release from skeletal muscle cells may increase inflammatory cytokine production and contribute to insulin/anabolic resistance in an autocrine/paracrine manner. In C2C12 myotubes differentiated at physiological glucose concentrations (5.5 mM), palmitate treatment (16 h) at concentrations greater than 250 μM increased release of ATP and inflammatory cytokines IL-6 and MIF, significantly blunted insulin and amino acid-induced signaling and reduced mitochondrial function. In contrast to our hypothesis, degradation of extracellular ATP using apyrase, did not alter palmitate-induced insulin resistance nor alter release of cytokines. Moreover, treatment with ATPγS (16 h), a non-hydrolysable ATP analog, in the absence of palmitate, did not diminish insulin sensitivity. Acute treatment with ATPγS produced insulin mimetic roles; increased phosphorylation of PKB (aka AKT), S6K1 and ERK and enhanced GLUT4-mediated glucose uptake in the absence of exogenous insulin. The increases in PKB and S6K1 phosphorylation were completely prevented by pre-incubation with broad spectrum purinergic receptor (P2R) blockers PPADs and suramin but not by P2 × 4 or P2 × 7 blockers 5-BDBD or A-438079, respectively. Moreover, ATPγS increased IL-6 yet decreased MIF release, similar to the cytokine profile produced by exercise. Acute and chronic treatment with ATPγS increased glycolytic rate in a manner that was differentially inhibited by PPADs and suramin, suggesting heterogeneous P2R activation in the control of cellular metabolism. In summary, our data suggest that the palmitate-induced increase in ATP does not contribute to insulin/anabolic resistance in a cell autonomous manner.

Human immune cell mobilization during exercise: effect of IL-6 receptor blockade

NEW FINDINGS

What is the central question of this study? Does blockade of the IL-6 receptor by tocilizumab inhibit immune cell mobilization to the blood stream in humans during an acute bout of exercise? What is the main finding and its importance? Blockade of IL-6 receptor signalling by tocilizumab attenuates mobilization of NK cells and dendritic cells to the blood stream during exercise. This implies an inhibitory effect of tocilizumab on the innate immune response to physical stress, which could be considered in clinical settings.

ABSTRACT

Immune cells are recruited from their storage organs and the endothelial walls to the blood stream in response to physiological stress. This is essential for the recognition and clearing of infected, transformed or damaged cells. One of the most potent stimuli to recruit immune cells to the circulation is exercise. Accordingly, exercise has proven beneficial in disease settings, such as cancer and diabetes. Interleukin-6 (IL-6) is released from contracting skeletal muscle in response to exercise, and rodent studies have established a link between exercise-induced IL-6 and recruitment of natural killer (NK) cells. Whether exercise-induced IL-6 is involved in regulating NK cell mobilization in humans is unclear. This study explored the effect of IL-6 receptor blockade on immune cell mobilization during an acute bout of exercise in humans. In a randomized, placebo-controlled clinical study, abdominally obese humans receiving placebo infusions or tocilizumab infusions performed an acute bout of exercise before and after the intervention. Immune cell recruitment was measured by flow cytometry. IL-6 receptor blockade attenuated the increase of NK cells by 53% (mean difference -0.49 (95% CI: -0.89 to -0.08) × 10⁹ cells L^-1 , P < 0.001) and dendritic cells by 66% (mean difference -0.14 (95% CI: -0.28 to 0.010) × 10⁹ cells L^-1 , P < 0.001) induced by an acute bout of exercises. No changes were observed for T cells, monocytes and neutrophils. Treatments which interact with the exercise-mediated immune surveillance provide relevant clinical information in pursuing the 'exercise as medicine' concept.

The cytokine alterations/abnormalities and oxidative damage in the pancreas during hypertension development

The aim of the present study was to compare the content of cytokines, chemokines, and oxidative stress markers in the pancreas of spontaneously hypertensive rats (SHRs) and Wistar Kyoto Rats (WKYs) serving as controls. Enzyme-like immunosorbent assay (ELISA) and biochemical methods were used to measure pancreatic levels of interleukin-1ß, interleukin-6, tumor necrosis factor α, transforming growth factor β, RANES, monocyte chemoattractant protein 1, interferon gamma-induced protein 10, malondialdehyde, and sulfhydryl groups. The results showed that the pancreatic concentrations of all studied cytokines and chemokines did not differ between 5-week-old SHRs and WKYs, except RANTES which was significantly reduced in juvenile SHRs. In 10-week-old animals, except interleukin-1ß, the levels of all these proteins were significantly reduced in SHRs. The pancreatic levels of malondialdehyde were significantly reduced in 5-week-old SHRs and significantly elevated in 10-week-old SHRs while the contents of sulfhydryl groups were similar in both rat strains at any age studied. In conclusion, these data provide evidence that in maturating SHRs, the pancreatic levels of cytokines and chemokines are significantly reduced, while malondialdehyde significantly elevated. This suggests that in the pancreas of mature SHRs, the inflammation process is suppressed but there is ongoing oxidative damage.

Rapid changes in the microvascular circulation of skeletal muscle impair insulin delivery during sepsis

Sepsis costs the healthcare system $23 billion annually and has a mortality rate between 10 and 40%. An early indication of sepsis is the onset of hyperglycemia, which is the result of sepsis-induced insulin resistance in skeletal muscle. Previous investigations have focused on events in the myocyte (e.g., insulin signaling and glucose transport and subsequent metabolism) as the causes for this insulin-resistant state. However, the delivery of insulin to the skeletal muscle is also an important determinant of insulin action. Skeletal muscle microvascular blood flow, which delivers the insulin to the muscle, is known to be decreased during sepsis. Here we test whether the reduced capillary blood flow to skeletal muscle belies the sepsis-induced insulin resistance by reducing insulin delivery to the myocyte. We hypothesize that decreased capillary flow and consequent decrease in insulin delivery is an early event that precedes gross cardiovascular alterations seen with sepsis. This hypothesis was examined in mice treated with either lipopolysaccharide (LPS) or polymicrobial sepsis followed by intravital microscopy of the skeletal muscle microcirculation. We calculated insulin delivery to the myocyte using two independent methods and found that LPS and sepsis rapidly reduce insulin delivery to the skeletal muscle by ~50%; this was driven by decreases in capillary flow velocity and the number of perfused capillaries. Furthermore, the changes in skeletal muscle microcirculation occur before changes in both cardiac output and arterial blood pressure. These data suggest that a rapid reduction in skeletal muscle insulin delivery contributes to the induction of insulin resistance during sepsis.

How Does Inflammation-Induced Hyperglycemia Cause Mitochondrial Dysfunction in Immune Cells?

Inflammatory mediators have an established role in inducing insulin resistance and promoting hyperglycemia. In turn, hyperglycemia has been argued to drive immune cell dysfunction as a result of mitochondrial dysfunction. Here, the authors review the evidence challenging this view. First, it is pointed out that inflammatory mediators are known to induce altered mitochondrial function. In this regard, critical care patients suffer both an elevated inflammatory tone as well as hyperglycemia, rendering it difficult to distinguish between the effects of inflammation and hyperglycemia. Second, emerging evidence indicates that a decrease in mitochondrial respiration and an increase in reactive oxygen species (ROS) production are not necessarily manifestations of pathology, but adaptations taking shape as the mitochondria is abdicating its adenosine triphosphate (ATP)-producing function (which is taken over by glycolysis) and instead becomes "retooled" for an immunological role. Collectively, these observations challenge the commonly held belief that acute hyperglycemia induces mitochondrial damage leading to immune cell dysfunction.

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.

Hyperglycaemia in critically ill patients: the immune system's sweet tooth

There is an ongoing debate regarding the efficacy of glycaemic control in critically ill patients. Here we briefly highlight the key function of elevated glucose in critically ill patients, namely, to enable elevation of aerobic glycolysis in rapidly dividing cells. In particular, aerobic glycolysis provides metabolic intermediates necessary for expansion of biomass in immune cells and promotion of tissue repair. Furthermore, we emphasise that insulin may inhibit autophagy, a cell survival process used in the bulk degradation of cellular debris and damaged organelles. These observations provide a rational basis for tolerating elevated glucose levels in certain critically ill patients.

Assessment of the link between in utero exposure to 2-aminoanthracene (2AA) and type-1 diabetes (T1D)

BACKGROUND

A recent diabetes report revealed an increased incidence in diabetes including type 1-diabetes (T1D). The increase in the numbers of T1D incidences are thought to be related to environmental reasons such as the exposure to environmental chemicals including arylamine 2-aminoanthracene (2AA). T1D is an autoimmune disease of the pancreatic islet in which insulin-producing beta cells are destroyed by auto-reactive T-cells and monocytic cells.

METHODS

The purpose of this study is to examine the extent to which 2AA exposure contributes to T1D. Three groups of pregnant Sprague Dawley dams ingested various concentrations of dietary 2AA from gestation through the postnatal period. A select number of cytokines and adipokines previously noted to play a significant role in inflammatory response were analyzed in the pancreas of the pups for alteration. The anatomy of the pancreas was also evaluated to determine any histological changes.

RESULTS

Results showed over-expression of pro-inflammatory protein IL-6. Up-regulation of humoral genes IL-7 and IL-21 were also noted. Pathologic characterization showed no significant changes. Moreover, serum total protein was significantly reduced in exposed groups. Elevated serum glucose concentration seems to correspond to slightly lower insulin levels in serum. Cumulative neonatal weight gain analysis showed no major alterations between the control and gestationally-exposed rats.

CONCLUSION

It appears that systemic effects of 2AA ingestion were mild in the neonates. Further assessments of pups who lived longer than two weeks could be a useful way to measure the progression and possibly further support our hypothesis that 2AA can lead to systemic effects that are indicative of inducing T1D.

Glucagon in artificial pancreas systems: Potential benefits and safety profile of future chronic use

The role of glucagon in the pathophysiology of diabetes has long been recognized, although its approved clinical use has so far been limited to the emergency treatment of severe hypoglycaemia. A novel use of glucagon as intermittent mini-boluses is proposed in the dual-hormone version (insulin and glucagon) of the external artificial pancreas. Short-term studies suggest that the incorporation of glucagon into artificial pancreas systems has the potential to further decrease hypoglycaemic risk and improve overall glucose control; however, the potential long-term safety and benefits also need to be investigated given the recognized systemic effects of glucagon. In the present report, we review the available animal and human data on the physiological functions of glucagon, as well as its pharmacological use, according to dosing and duration (acute and chronic). Along with its main role in hepatic glucose metabolism, glucagon affects the cardiovascular, renal, pulmonary and gastrointestinal systems. It has a potential role in weight reduction through its central satiety function and its role in increasing energy expenditure. Most of the pharmacological studies investigating the effects of glucagon have used doses exceeding 1 mg, in contrast to the mini-boluses used in the artificial pancreas. The available data are reassuring but comprehensive human studies using small but chronic glucagon doses that are close to the physiological ranges are lacking. We propose a list of variables that could be monitored during long-term trials of the artificial pancreas. Such trials should address the questions about the risk-benefit ratio of chronic glucagon use.

A Metabolomic Approach (1H HRMAS NMR Spectroscopy) Supported by Histology to Study Early Post-transplantation Responses in Islet-transplanted Livers

Intrahepatic transplantation of islets requires a lot of islets because more than 50% of the graft is lost during the 24 hours following transplantation. We analyzed, in a rat model, early post-transplantation inflammation using systemic inflammatory markers, or directly in islet-transplanted livers by immunohistochemistry. 1H HRMAS NMR was employed to investigate metabolic responses associated with the transplantation. Inflammatory markers (Interleukin-6, α2-macroglobulin) are not suitable to follow islet reactions as they are not islet specific. To study islet specific inflammatory events, immunohistochemistry was performed on sections of islet transplanted livers for thrombin (indicator of the instant blood-mediated inflammatory reaction (IBMIR)) and granulocytes and macrophages. We observed a specific correlation between IBMIR and granulocyte and macrophage infiltration after 12 h. In parallel, we identified a metabolic response associated with transplantation: after 12 h, glucose, alanine, aspartate, glutamate and glutathione were significantly increased. An increase of glucose is a marker of tissue degradation, and could be explained by immune cell infiltration. Alanine, aspartate and glutamate are inter-connected in a common metabolic pathway known to be activated during hypoxia. An increase of glutathione revealed the presence of antioxidant protection. In this study, IBMIR visualization combined with 1H HRMAS NMR facilitated the characterization of cellular and molecular pathways recruited following islet transplantation.

The Cardiovascular Biology of Glucagon-like Peptide-1

Glucagon-like peptide-1, produced predominantly in enteroendocrine cells, controls glucose metabolism and energy homeostasis through regulation of islet hormone secretion, gastrointestinal motility, and food intake, enabling development of GLP-1 receptor (GLP-1R) agonists for the treatment of diabetes and obesity. GLP-1 also acts on the immune system to suppress inflammation, and GLP-1R signaling in multiple tissues impacts cardiovascular function in health and disease. Here we review how GLP-1 and clinically approved GLP-1R agonists engage mechanisms that influence the risk of developing cardiovascular disease. We discuss how GLP-1R agonists modify inflammation, cardiovascular physiology, and pathophysiology in normal and diabetic animals through direct and indirect mechanisms and review human studies illustrating mechanisms linking GLP-1R signaling to modification of the cardiovascular complications of diabetes. The risks and benefits of GLP-1R agonists are updated in light of recent data suggesting that GLP-1R agonists favorably modify outcomes in diabetic subjects at high risk for cardiovascular events.

Glucagon orchestrates stress-induced hyperglycaemia

Hyperglycaemia is commonly observed on admission and during hospitalization for medical illness, traumatic injury, burn and surgical intervention. This transient hyperglycaemia is referred to as stress-induced hyperglycaemia (SIH) and frequently occurs in individuals without a history of diabetes. SIH has many of the same underlying hormonal disturbances as diabetes mellitus, specifically absolute or relative insulin deficiency and glucagon excess. SIH has the added features of elevated blood levels of catecholamines and cortisol, which are not typically present in people with diabetes who are not acutely ill. The seriousness of SIH is highlighted by its greater morbidity and mortality rates compared with those of hospitalized patients with normal glucose levels, and this increased risk is particularly high in those without pre-existing diabetes. Insulin is the treatment standard for SIH, but new therapies that reduce glucose variability and hypoglycaemia are desired. In the present review, we focus on the key role of glucagon in SIH and discuss the potential use of glucagon receptor blockers and glucagon-like peptide-1 receptor agonists in SIH to achieve target glucose control.

Exercise and the Regulation of Hepatic Metabolism

The accelerated metabolic demands of the working muscle cannot be met without a robust response from the liver. If not for the hepatic response, sustained exercise would be impossible. The liver stores, releases, and recycles potential energy. Exercise would result in hypoglycemia if it were not for the accelerated release of energy as glucose. The energetic demands on the liver are largely met by increased oxidation of fatty acids mobilized from adipose tissue. Adaptations immediately following exercise facilitate the replenishment of glycogen stores. Pancreatic glucagon and insulin responses orchestrate the hepatic response during and immediately following exercise. Like skeletal muscle and other physiological systems, liver adapts to repeated demands of exercise by increasing its capacity to produce energy by oxidizing fat. The ability of regular physical activity to increase fat oxidation is protective and can reverse fatty liver disease. Engaging in regular physical exercise has broad ranging positive health implications including those that improve the metabolic health of the liver.