Circulating levels of IL-1B+IL-6 cause ER stress and dysfunction in islets from prediabetic male mice

β-cell neogenesis: A rising star to rescue diabetes mellitus

BACKGROUND

Diabetes Mellitus (DM), a chronic metabolic disease characterized by elevated blood glucose, is caused by various degrees of insulin resistance and dysfunctional insulin secretion, resulting in hyperglycemia. The loss and failure of functional β-cells are key mechanisms resulting in type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

AIM OF REVIEW

Elucidating the underlying mechanisms of β-cell failure, and exploring approaches for β-cell neogenesis to reverse β-cell dysfunction may provide novel strategies for DM therapy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Emerging studies reveal that genetic susceptibility, endoplasmic reticulum (ER) stress, oxidative stress, islet inflammation, and protein modification linked to multiple signaling pathways contribute to DM pathogenesis. Over the past few years, replenishing functional β-cell by β-cell neogenesis to restore the number and function of pancreatic β-cells has remarkably exhibited a promising therapeutic approach for DM therapy. In this review, we provide a comprehensive overview of the underlying mechanisms of β-cell failure in DM, highlight the effective approaches for β-cell neogenesis, as well as discuss the current clinical and preclinical agents research advances of β-cell neogenesis. Insights into the challenges of translating β-cell neogenesis into clinical application for DM treatment are also offered.

Neuroinflammation induced by amyloid-forming pancreatic amylin: Rationale for a mechanistic hypothesis

Amylin is a systemic neuroendocrine hormone co-expressed and co-secreted with insulin by pancreatic β-cells. In persons with thype-2 diabetes, amylin forms pancreatic amyloid triggering inflammasome and interleukin-1β signaling and inducing β-cell apoptosis. Here, we summarize recent progress in understanding the potential link between amyloid-forming pancreatic amylin and Alzheimer's disease (AD). Clinical data describing amylin pathology in AD alongside mechanistic studies in animals are reviewed. Data from multiple research teams indicate higher amylin concentrations are associated with increased frequency of cognitive impairment and amylin co-aggregates with β-amyloid in AD-type dementia. Evidence from rodent models further suggests cerebrovascular amylin accumulation as a causative factor underlying neurological deficits. Analysis of relevant literature suggests that modulating the amylin-interleukin-1β pathway may provide an approach for counteracting neuroinflammation in AD.

Increased Pretransplant Inflammatory Biomarkers Predict Death With Function After Kidney Transplantation

BACKGROUND

Chronic systemic inflammation is associated with mortality in patients with chronic kidney disease, cardiovascular disease, and diabetes. The goal of this study was to examine the relationship between pretransplant inflammatory biomarkers (growth differentiation factor-15 [GDF-15], interleukin-6 [IL-6], soluble tumor necrosis factor receptor-1, monokine induced by gamma interferon/chemokine [C-X-C motif] ligand 9 [MIG/CXCL9], monocyte chemoattractant protein-1, soluble FAS, tumor necrosis factor-α, interleukin-15, and interleukin-1β) and death with function (DWF) after kidney transplantation (KT).

METHODS

We retrospectively measured inflammatory biomarker levels in serum collected up to 1 y before KT (time from blood draw to KT was 130 ± 110 d) in recipients transplanted between January 2006 and December 2018. Kaplan-Meier estimation, Cox regression, and Gradient Boosting Machine modeling were used to examine the relationship between inflammatory biomarkers and DWF.

RESULTS

Our cohort consisted of 1595 KT recipients, of whom 62.9% were male and 83.2% were non-Hispanic White. Over a mean follow-up of 7.4 ± 3.9 y, 21.2% of patients (n = 338) experienced DWF. Patients with the highest quartile levels of GDF-15 (>4766 pg/mL), IL-6 (>6.11 pg/mL), and MIG/CXCL9 (> 5835 pg/mL) had increased rates of DWF, and each predicted mortality independently of the others. When adjusted for clinical factors (age, diabetes, etc), the highest quartile levels of GDF-15 and IL-6 remained independently associated with DWF. Adding inflammatory markers to a clinical Cox model improved the C-statistic for DWF from 0.727 to 0.762 using a Gradient Boosting Machine modeling approach.

CONCLUSIONS

These findings suggest that pre-KT serum concentrations of GDF-15, IL-6, and MIG/CXCL9 may help to risk stratify and manage patients undergoing KT and suggests that chronic inflammation may play a role in mortality in KT recipients.

Endoplasmic reticulum stress in pancreatic β-cell dysfunction: The potential therapeutic role of dietary flavonoids

Diabetes mellitus (DM) is a global health burden that is characterized by the loss or dysfunction of pancreatic β-cells. In pancreatic β-cells, endoplasmic reticulum (ER) stress is a fact of life that contributes to β-cell loss or dysfunction. Despite recent advances in research, the existing treatment approaches such as lifestyle modification and use of conventional therapeutics could not prevent the loss or dysfunction of pancreatic β-cells to abrogate the disease progression. Therefore, targeting ER stress and the consequent unfolded protein response (UPR) in pancreatic β-cells may be a potential therapeutic strategy for diabetes treatment. Dietary phytochemicals have therapeutic applications in human health owing to their broad spectrum of biochemical and pharmacological activities. Flavonoids, which are commonly obtained from fruits and vegetables worldwide, have shown promising prospects in alleviating ER stress. Dietary flavonoids including quercetin, kaempferol, myricetin, isorhamnetin, fisetin, icariin, apigenin, apigetrin, vitexin, baicalein, baicalin, nobiletin hesperidin, naringenin, epigallocatechin 3-O-gallate hesperidin (EGCG), tectorigenin, liquiritigenin, and acacetin have shown inhibitory effects on ER stress in pancreatic β-cells. Dietary flavonoids modulate ER stress signaling components, chaperone proteins, transcription factors, oxidative stress, autophagy, apoptosis, and inflammatory responses to exert their pharmacological effects on pancreatic β-cells ER stress. This review focuses on the role of dietary flavonoids as potential therapeutic adjuvants in preserving pancreatic β-cells from ER stress. Highlights of the underlying mechanisms of action are also presented as well as possible strategies for clinical translation in the management of DM.

GHSR Deletion in β-Cells of Male Mice: Ineffective in Obesity, but Effective in Protecting against Streptozotocin-Induced β-Cell Injury in Aging

Insulin secretion from pancreatic β cells is a key pillar of glucose homeostasis, which is impaired under obesity and aging. Growth hormone secretagogue receptor (GHSR) is the receptor of nutrient-sensing hormone ghrelin. Previously, we showed that β-cell GHSR regulated glucose-stimulated insulin secretion (GSIS) in young mice. In the current study, we further investigated the effects of GHSR on insulin secretion in male mice under diet-induced obesity (DIO) and streptozotocin (STZ)-induced β-cell injury in aging. β-cell-specific-Ghsr-deficient (Ghsr-βKO) mice exhibited no glycemic phenotype under DIO but showed significantly improved ex vivo GSIS in aging. We also detected reduced insulin sensitivity and impaired insulin secretion during aging both in vivo and ex vivo. Accordingly, there were age-related alterations in expression of glucose transporter, insulin signaling pathway, and inflammatory genes. To further determine whether GHSR deficiency affected β-cell susceptibility to acute injury, young, middle-aged, and old Ghsr-βKO mice were subjected to STZ. We found that middle-aged and old Ghsr-βKO mice were protected from STZ-induced hyperglycemia and impaired insulin secretion, correlated with increased expression of insulin signaling regulators but decreased pro-inflammatory cytokines in pancreatic islets. Collectively, our findings indicate that β-cell GHSR has a major impact on insulin secretion in aging but not obesity, and GHSR deficiency protects against STZ-induced β-cell injury in aging.

Central regulation of stress-evoked peripheral immune responses

Stress-linked psychiatric disorders, including anxiety and major depressive disorder, are associated with systemic inflammation. Recent studies have reported stress-induced alterations in haematopoiesis that result in monocytosis, neutrophilia, lymphocytopenia and, consequently, in the upregulation of pro-inflammatory processes in immunologically relevant peripheral tissues. There is now evidence that this peripheral inflammation contributes to the development of psychiatric symptoms as well as to common co-morbidities of psychiatric disorders such as metabolic syndrome and immunosuppression. Here, we review the specific brain and spinal regions, and the neuronal populations within them, that respond to stress and transmit signals to peripheral tissues via the autonomic nervous system or neuroendocrine pathways to influence immunological function. We comprehensively summarize studies that have employed retrograde tracing to define neurocircuits linking the brain to the bone marrow, spleen, gut, adipose tissue and liver. Moreover, we highlight studies that have used chemogenetic or optogenetic manipulation or intracerebroventricular administration of peptide hormones to control somatic immune responses. Collectively, this growing body of literature illustrates potential mechanisms through which stress signals are conveyed from the CNS to immune cells to regulate stress-relevant behaviours and comorbid pathophysiology.

Immune checkpoint blockade therapy mitigates systemic inflammation and affects cellular FLIP-expressing monocytic myeloid-derived suppressor cells in non-progressor non-small cell lung cancer patients

Cancer cells favor the generation of myeloid cells with immunosuppressive and inflammatory features, including myeloid-derived suppressor cells (MDSCs), which support tumor progression. The anti-apoptotic molecule, cellular FLICE (FADD-like interleukin-1β-converting enzyme)-inhibitory protein (c-FLIP), which acts as an important modulator of caspase-8, is required for the development and function of monocytic (M)-MDSCs. Here, we assessed the effect of immune checkpoint inhibitor (ICI) therapy on systemic immunological landscape, including FLIP-expressing MDSCs, in non-small cell lung cancer (NSCLC) patients. Longitudinal changes in peripheral immunological parameters were correlated with patients' outcome. In detail, 34 NSCLC patients were enrolled and classified as progressors (P) or non-progressors (NP), according to the RECIST evaluation. We demonstrated a reduction in pro-inflammatory cytokines such as IL-8, IL-6, and IL-1β in only NP patients after ICI treatment. Moreover, using t-distributed stochastic neighbor embedding (t-SNE) and cluster analysis, we characterized in NP patients a significant increase in the amount of lymphocytes and a slight contraction of myeloid cells such as neutrophils and monocytes. Despite this moderate ICI-associated alteration in myeloid cells, we identified a distinctive reduction of c-FLIP expression in M-MDSCs from NP patients concurrently with the first clinical evaluation (T1), even though NP and P patients showed the same level of expression at baseline (T0). In agreement with the c-FLIP expression, monocytes isolated from both P and NP patients displayed similar immunosuppressive functions at T0; however, this pro-tumor activity was negatively influenced at T1 in the NP patient cohort exclusively. Hence, ICI therapy can mitigate systemic inflammation and impair MDSC-dependent immunosuppression.

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.

Signaling pathways and intervention for therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents one of the fastest growing epidemic metabolic disorders worldwide and is a strong contributor for a broad range of comorbidities, including vascular, visual, neurological, kidney, and liver diseases. Moreover, recent data suggest a mutual interplay between T2DM and Corona Virus Disease 2019 (COVID-19). T2DM is characterized by insulin resistance (IR) and pancreatic β cell dysfunction. Pioneering discoveries throughout the past few decades have established notable links between signaling pathways and T2DM pathogenesis and therapy. Importantly, a number of signaling pathways substantially control the advancement of core pathological changes in T2DM, including IR and β cell dysfunction, as well as additional pathogenic disturbances. Accordingly, an improved understanding of these signaling pathways sheds light on tractable targets and strategies for developing and repurposing critical therapies to treat T2DM and its complications. In this review, we provide a brief overview of the history of T2DM and signaling pathways, and offer a systematic update on the role and mechanism of key signaling pathways underlying the onset, development, and progression of T2DM. In this content, we also summarize current therapeutic drugs/agents associated with signaling pathways for the treatment of T2DM and its complications, and discuss some implications and directions to the future of this field.

Mechanisms of obesity- and diabetes mellitus-related pancreatic carcinogenesis: a comprehensive and systematic review

Research on obesity- and diabetes mellitus (DM)-related carcinogenesis has expanded exponentially since these two diseases were recognized as important risk factors for cancers. The growing interest in this area is prominently actuated by the increasing obesity and DM prevalence, which is partially responsible for the slight but constant increase in pancreatic cancer (PC) occurrence. PC is a highly lethal malignancy characterized by its insidious symptoms, delayed diagnosis, and devastating prognosis. The intricate process of obesity and DM promoting pancreatic carcinogenesis involves their local impact on the pancreas and concurrent whole-body systemic changes that are suitable for cancer initiation. The main mechanisms involved in this process include the excessive accumulation of various nutrients and metabolites promoting carcinogenesis directly while also aggravating mutagenic and carcinogenic metabolic disorders by affecting multiple pathways. Detrimental alterations in gastrointestinal and sex hormone levels and microbiome dysfunction further compromise immunometabolic regulation and contribute to the establishment of an immunosuppressive tumor microenvironment (TME) for carcinogenesis, which can be exacerbated by several crucial pathophysiological processes and TME components, such as autophagy, endoplasmic reticulum stress, oxidative stress, epithelial-mesenchymal transition, and exosome secretion. This review provides a comprehensive and critical analysis of the immunometabolic mechanisms of obesity- and DM-related pancreatic carcinogenesis and dissects how metabolic disorders impair anticancer immunity and influence pathophysiological processes to favor cancer initiation.

Glucagon induces the hepatic expression of inflammatory markers in vitro and in vivo

Glucagon exerts multiple hepatic actions, including stimulation of glycogenolysis/gluconeogenesis. The liver plays a crucial role in chronic inflammation by synthesizing proinflammatory molecules, which are thought to contribute to insulin resistance and hyperglycaemia. Whether glucagon affects hepatic expression of proinflammatory cytokines and acute-phase reactants is unknown. Herein, we report a positive relationship between fasting glucagon levels and circulating interleukin (IL)-1β (r = 0.252, p = .042), IL-6 (r = 0.230, p = .026), fibrinogen (r = 0.193, p = .031), complement component 3 (r = 0.227, p = .024) and high sensitivity C-reactive protein (r = 0.230, p = .012) in individuals without diabetes. In CD1 mice, 4-week continuous treatment with glucagon induced a significant increase in circulating IL-1β (p = .02), and IL-6 (p = .001), which was countered by the contingent administration of the glucagon receptor antagonist, GRA-II. Consistent with these results, we detected a significant increase in the hepatic activation of inflammatory pathways, such as expression of NLRP3 (p < .02), and the phosphorylation of nuclear factor kappaB (NF-κB; p < .02) and STAT3 (p < .01). In HepG2 cells, we found that glucagon dose-dependently stimulated the expression of IL-1β (p < .002), IL-6 (p < .002), fibrinogen (p < .01), complement component 3 (p < .01) and C-reactive protein (p < .01), stimulated the activation of NLRP3 inflammasome (p < .01) and caspase-1 (p < .05), induced the phosphorylation of TRAF2 (p < .01), NF-κB (p < .01) and STAT3 (p < .01). Preincubating cells with GRA-II inhibited the ability of glucagon to induce an inflammatory response. Using HepaRG cells, we confirmed the dose-dependent ability of glucagon to stimulate the expression of NLRP3, the phosphorylation of NF-κB and STAT3, in the absence of GRA-II. These results suggest that glucagon has proinflammatory effects that may participate in the pathogenesis of hyperglycaemia and unfavourable cardiometabolic risk profile.

Effect of a diet based on the dietary guidelines for americans on inflammation markers in women at risk for cardiometabolic disease: results of a randomized, controlled trial

OBJECTIVE

To evaluate the effect of a diet pattern based on Dietary Guidelines for Americans (DGA), in a controlled feeding setting, on plasma markers of inflammation and on cytokine production by peripheral blood mononuclear cells (PBMC).

DESIGN

Women (n = 44) with one or more risk factors of metabolic syndrome (and BMI: 25.2-39.8 kg/m²) completed an 8-wk controlled feeding study. They were randomized to either a group following a diet based on DGA 2010 (DGA), or a group given a 'typical American diet' (TAD), based largely on a Western diet pattern. By design, women maintained their body weight. Fasting plasma and PBMC were collected at wk. 0 (baseline) and at wk. 8 (post-intervention). Sixteen plasma markers of inflammation and eight PBMC cytokines were measured at both time points, to evaluate if the diet had a significant effect on concentrations of these inflammatory markers. Data were analyzed using ANCOVA, followed by multiple-comparison adjustment using Benjamini-Hochberg method.

RESULTS

Significant changes observed in Serum Amyloid A (SAA) and Matrix Metalloproteinase 3 (MMP3) in plasma did not retain significance upon multiple comparison adjustment. SAA: p = 0.044, adj p = 0.450; DGA mean change [95% CI] = - 12.6[- 32.3 to 7.04]; TAD mean change [95% CI] = - 2.24 [- 9.99 to 5.51]. MMP3: p = 0.014, adj p = 0.35; DGA mean change [95% CI] = 2.72[- 4.16 to 9.59]; TAD mean change [95% CI] = - 0.98[- 16.7 to 14.7]). Other inflammation markers were not differently altered by DGA relative to TAD. Effect size of change (Cohens d) indicated a large/medium-large effect of intervention on MMP3 and CRP, and medium effect on IL-6.

CONCLUSIONS

No statistically significant changes were observed in the immune markers examined in this study. The biological roles and magnitude of the non-significant differences seen with two variables, CRP and MMP3, suggest that they be examined in future studies.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT02298725.

Association between Parkinson's Disease and Diabetes Mellitus: From Epidemiology, Pathophysiology and Prevention to Treatment

Diabetes mellitus (DM) and Parkinson's disease (PD) are both age-related diseases of global concern being among the most common chronic metabolic and neurodegenerative diseases, respectively. While both diseases can be genetically inherited, environmental factors play a vital role in their pathogenesis. Moreover, DM and PD have common underlying molecular mechanisms, such as misfolded protein aggregation, mitochondrial dysfunction, oxidative stress, chronic inflammation, and microbial dysbiosis. Recently, epidemiological and experimental studies have reported that DM affects the incidence and progression of PD. Moreover, certain antidiabetic drugs have been proven to decrease the risk of PD and delay its progression. In this review, we elucidate the epidemiological and pathophysiological association between DM and PD and summarize the antidiabetic drugs used in animal models and clinical trials of PD, which may provide reference for the clinical translation of antidiabetic drugs in PD treatment.

The fates of different types of adipose tissue after transplantation in mice

Fat grafting is one of the most commonly applied procedure for soft-tissue repair. However, it remains unclear whether the type of adipose tissue would have any effects on fat graft survival. The present study aimed to determine fates of fat grafting of three different types of fat tissue. In this study, mice were randomly divided into three groups, white adipose tissue (WAT) group, beige adipose tissue (beige AT) group and brown adipose tissue (BAT) group. Before transplantation, donor mice were injected with rosiglitazone or phosphate-buffered saline (PBS). The WAT and BAT were obtained from PBS-treated mice while beige AT was obtained from the rosiglitazone-treated mice. Three types of fat tissue (150 mg each) were transplanted in three groups, respectively, and harvested at 2, 4 or 12 weeks. The BAT and beige AT contained smaller adipocytes and expressed higher level of uncoupling protein-1 gene. The retention rate of the transplanted fat was significantly higher for beige than for white fat, but was significantly lower for brown than for white fat. Transplanted brown fat was characterized by upregulated inflammation and high endoplasmic reticulum stress. By contrast, fat grafts in beige AT group showed the best adipogenic capacity, moderate inflammation level and superior angiongenesis. In vitro, under hypoxic condition, fewer apoptotic cells were found in beige adipocyte group than that in brown and white adipocyte group. Conditioned medium from brown adipocytes induced M1 polarization of RAW 264.7 macrophages while that from beige adipocytes effectively promoted M2 polarization. Therefore, we suggest that beige AT provides a new potential choice for fat grafting because of low inflammation and superior survival but BAT might not be ideal for fat grafting due to its poor survival.

Modulation of Gap Junction Coupling Within the Islet of Langerhans During the Development of Type 1 Diabetes

In type 1 diabetes (T1D), islet dysfunction occurs prior to diabetes onset. Pro-inflammatory cytokines can disrupt insulin secretion and Ca²⁺ homeostasis. Connexin36 (Cx36) gap junctions electrically couple β-cells to coordinate glucose-stimulated Ca²⁺ and insulin secretion. Cx36 gap junction coupling can also protect against cytokine-induced apoptosis. Our goal was to determine how islet gap junction coupling and Ca²⁺ dynamics are altered in mouse models of T1D prior to diabetes. Glucose tolerance was assessed in NOD and immunodeficient NOD-RAG1KO mice at 6-12 weeks age. Glucose-stimulated insulin secretion, Ca²⁺ dynamics, and gap junction coupling were measured in islets isolated at each age. Gap junction coupling was also measured in islets from mice that underwent transfer of diabetogenic splenocytes and from chromograninA knockout NOD mice. Cell death was measured in islets isolated from wild-type, Cx36 knockout or Cx36 over-expression mice, each treated with a cocktail of pro-inflammatory cytokines and K_ATP or SERCA activators/inhibitors. NOD mice over-expressing Cx36 were also monitored for diabetes development, and islets assessed for insulitis and apoptosis. NOD and NOD-RAG1KO controls showed similar glucose tolerance at all ages. Ca²⁺ dynamics and gap junction coupling were disrupted in islets of NOD mice at 9 weeks, compared to controls. Transfer of diabetogenic splenocytes also decreased gap junction coupling. Islets from chromograninA knockout mice displayed normal coupling. Overexpression of Cx36 protected islets from cytokine-induced apoptosis. A knockout of Cx36 amplified cytokine-induced apoptosis, which was reversed by K_ATP activation or SERCA activation. Cx36 overexpression in NOD mice delayed diabetes development compared to NOD controls. However, apoptosis and insulitis were not improved. Decreases in islet gap junction coupling occur prior to T1D onset. Such decreases alter islet susceptibility to apoptosis due to altered Ca²⁺. Future studies will determine if increasing Cx36 gap junction coupling in combination with restoring Ca²⁺ homeostasis protects against islet decline in T1D.

Factors That Contribute to hIAPP Amyloidosis in Type 2 Diabetes Mellitus

Cases of Type 2 Diabetes Mellitus (T2DM) are increasing at an alarming rate due to the rise in obesity, sedentary lifestyles, glucose-rich diets and other factors. Numerous studies have increasingly illustrated the pivotal role that human islet amyloid polypeptide (hIAPP) plays in the pathology of T2DM through damage and subsequent loss of pancreatic β-cell mass. HIAPP can misfold and form amyloid fibrils which are preceded by pre-fibrillar oligomers and monomers, all of which have been linked, to a certain extent, to β-cell cytotoxicity through a range of proposed mechanisms. This review provides an up-to-date summary of recent progress in the field, highlighting factors that contribute to hIAPP misfolding and aggregation such as hIAPP protein concentration, cell stress, molecular chaperones, the immune system response and cross-seeding with other amyloidogenic proteins. Understanding the structure of hIAPP and how these factors affect amyloid formation will help us better understand how hIAPP misfolds and aggregates and, importantly, help identify potential therapeutic targets for inhibiting amyloidosis so alternate and more effective treatments for T2DM can be developed.

No increase in inflammation in late-life major depression screened to exclude physical illness

Depression is a common and debilitating disorder in the elderly. Late-life depression (LLD) has been associated with inflammation and elevated levels of proinflammatory cytokines including interleukin (IL)-1β, tumor necrosis factor-alpha, and IL-6, but often depressed individuals have comorbid medical conditions that are associated with immune dysregulation. To determine whether depression has an association with inflammation independent of medical illness, 1120 adults were screened to identify individuals who had clinically significant depression but not medical conditions associated with systemic inflammation. In total, 66 patients with LLD screened to exclude medical conditions associated with inflammation were studied in detail along with 26 age-matched controls (HC). At baseline, circulating cytokines were low and similar in LLD and HC individuals. Furthermore, cytokines did not change significantly after treatment with either an antidepressant (escitalopram 20 mg/day) or an antidepressant plus a COX-2 inhibitor or placebo, even though depression scores improved in the non-placebo treatment arms. An analysis of cerebrospinal fluid in a subset of individuals for IL-1β using an ultrasensitive digital enzyme-linked immunosorbent assay revealed low levels in both LLD and HC at baseline. Our results indicate that depression by itself does not result in systemic or intrathecal elevations in cytokines and that celecoxib does not appear to have an adjunctive antidepressant role in older patients who do not have medical reasons for having inflammation. The negative finding for increased inflammation and the lack of a treatment effect for celecoxib in this carefully screened depressed population taken together with multiple positive results for inflammation in previous studies that did not screen out physical illness support a precision medicine approach to the treatment of depression that takes the medical causes for inflammation into account.

Association between Maternal Periodontitis and Development of Systematic Diseases in Offspring

Periodontal disease (PD) is one of the most common oral conditions affecting both youths and adults. There are some research works suggesting a high incidence of PD in pregnant women. As an inflammatory disease of bacterial origin, PD may result in the activation of the pathways affecting the course and the pregnancy outcome. The authors, based on the literature review, try to answer the PICO question: Does maternal periodontitis (exposure) influence the incidence of complications rates in pregnancy and the development of systemic diseases in childhood and adult offspring (outcome) in the humans of any race (population) compared to the offspring of mothers with healthy periodontium (comparison)? The authors try to describe the molecular pathways and mechanisms of these interdependencies. There is some evidence that maternal periodontitis may affect the pregnancy course and outcome, resulting in preeclampsia, preterm delivery, vulvovaginitis and low birth weight. It can be suggested that maternal periodontitis may affect offspring epigenome and result in some health consequences in their adult life.

IL-6/STAT3 Induced Neuron Apoptosis in Hypoxia by Downregulating ATF6 Expression

Background: Neuron apoptosis, regulated by endoplasmic reticulum (ER) stress in the hippocampus, is an essential factor influencing the cognitive impairment induced by hypobaric hypoxia. Hypoxia mainly changes the activating transcription factor (ATF6) pathway of ER stress. However, the role of ATF6 in neuron survival, apoptosis, and upstream regulation is still controversial. Methods: We established a hypobaric hypoxia-induced C57BL/6 murine model and cell lines exposed to 1% hypoxia, including PC12 and HT22. First, we tested the expressions of interleukin 6 (IL-6), IL-1β, and IL-10 in C57BL/6 mice's hippocampus under hypoxia using enzyme-linked immunosorbent assay (ELISA). We determined the signal transducer and activator of transcription 3 (STAT3) phosphorylation at tyrosine (Tyr)705 by western blot and the expression of ATF6, 78-kDa glucose-regulated protein (GRP78), and C/-EBP homologous protein (CHOP) related to ER stress by immunofluorescence (IF), western blot, and qRT-PCR; they were then verified on the cell model. Additionally, IL-6 (40 ng/mL) and STAT3 siRNA were used to treat the PC12 cells for 48 and 4 h to activate or silence STAT3, respectively. Subsequently, the cells of siRNA group were exposed to 1% hypoxia for 48 h. Furthermore, the ATF6 and CHOP expressions were detected with western blot and qRT-PCR. Finally, we examined the binding of STAT3 to the ATF6 promoter by chromatin immunoprecipitation (ChIP)-seq. Results: The results showed that IL-6 increased, IL-10 decreased in the hypoxia group, and IL-1β showed no difference between the hypoxia and the normoxia groups. Neuron apoptosis was significantly elevated by exposure to hypoxia for 48h in PC12 cells. The hypobaric hypoxia-induced ER stress proteins, ATF6, GRP78, and CHOP, and the p-STAT3 (Tyr705) expressions increased both in in vivo and in vitro. Besides, STAT3 silencing significantly promoted the ATF6 expression and inhibited CHOP, while STAT3 activation downregulated the expression of ATF6 and upregulated CHOP in PC12 cells. The ChIP-seq assay demonstrated that p-STAT3 (Tyr705) protein could bind to the ATF6 promoter region in HT22 cells. Conclusion: Phosphorylation of STAT3 at the Tyr705 site contributes to hypoxia-induced neuron apoptosis by downregulating ATF6, which might explain the inflammatory reaction and apoptosis of the hippocampal neurons induced by ER stress.

Chronic tissue inflammation and metabolic disease

In this review, Lee and Olefsky discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes.

Obesity is the most common cause of insulin resistance, and the current obesity epidemic is driving a parallel rise in the incidence of T2DM. It is now widely recognized that chronic, subacute tissue inflammation is a major etiologic component of the pathogenesis of insulin resistance and metabolic dysfunction in obesity. Here, we summarize recent advances in our understanding of immunometabolism. We discuss the characteristics of chronic inflammation in the major metabolic tissues and how obesity triggers these events, including a focus on the role of adipose tissue hypoxia and macrophage-derived exosomes. Last, we also review current and potential new therapeutic strategies based on immunomodulation.

Synchrotron fluorescence imaging of individual mouse beta-cells reveals changes in zinc, calcium, and iron in a model of low-grade inflammation

Pancreatic beta-cells synthesize and secrete insulin maintaining an organism's energy homeostasis. In humans, beta-cell dysfunction and death contribute to the pathogenesis of type 2 diabetes (T2D). Although the causes of beta-cell dysfunction are complex, obesity-induced low-grade systemic inflammation plays a role. For example, obese individuals exhibiting increased levels of proinflammatory cytokines IL-6 and IL-1beta have a higher risk of beta-cell dysfunction and T2D. Interestingly, obesity-induced inflammation changes the expression of several cellular metal regulating genes, prompting this study to examine changes in the beta-cell metallome after exposure to proinflammatory-cytokines. Primary mouse beta-cells were exposed to a combination of IL-6 and IL-1beta for 48 hours, were chemically fixed and imaged by synchrotron X-ray fluorescent microscopy. Quantitative analysis showed a surprising 2.4-fold decrease in the mean total cellular content of zinc from 158 ± 57.7 femtograms (fg) to 65.7 ± 29.7 fg; calcium decreased from 216 ± 67.4 to 154.3 ± 68.7 fg (control vs. cytokines, respectively). The mean total cellular iron content slightly increased from 30.4 ± 12.2 to 47.2 ± 36.4 fg after cytokine treatment; a sub-population of cells (38%) exhibited larger increases of iron density. Changes in the subcellular distributions of zinc and calcium were observed after cytokine exposure. Beta-cells contained numerous iron puncta that accumulated still more iron after exposure to cytokines. These findings provide evidence that exposure to low levels of cytokines is sufficient to cause changes in the total cellular content and/or subcellular distribution of several metals known to be critical for normal beta-cell function.

Improvement of Cognitive Function and Interleukin 1 Beta Serum Concentrations Following Cardiac Pacemaker Implantation in Patients with Symptomatic Bradycardia

Background and aim: Bradyarrhythmias cause a low cerebral blood flow with secondary neuronal ischemia and cognitive dysfunction. This study aims to assess the effect of cardiac pacemaker implantation (PI) on the cognitive function and inflammatory markers (TNF alpha, IL1β). Material and method: We conducted a prospective observational study on a number of 31 patients with symptomatic bradyarrhythmias. We performed the cognitive function assessment by two tests (Mini-Mental State Examination and Trail Making Test A), cardiac output assessment (echocardiographic), and determination of IL 1β and TNF alpha serum concentrations before pacemaker implantation and after an average period of 42 days from pacemaker implantation.Results: After pacemaker implantation we observed an increase in the cardiac index by 0.71 L/min/m² (p < 0.001) and a better scoring in cognitive performance; the mean MMSE score increased by two points (p < 0.001), and Trail Making Test A had an improvement of 16 s (p < 0.001). Regarding the inflammatory markers, a significant decrease in IL-1β with 8.6 pg/mL (p = 0.049) after pacemaker implantation was observed. Additionally, we found statistically significant correlations between IL1β and TNF alpha (positive correlation, p = 0.005), between the MMSE and cardiac index (p < 0.001), between the Trail Making Test and cardiac index (p = 0.001), and between the MMSE and Trail Making Test (p = 0.003). Conclusions: Our findings suggest that cardiac pacemaker implantation was associated with improved cognitive function—possibly related to an increased cardiac output and with adecreased serum IL1β concentration in subjects with symptomatic bradycardia.

Therapeutic opportunities for pancreatic β-cell ER stress in diabetes mellitus

Diabetes mellitus is characterized by the failure of insulin-secreting pancreatic β-cells (or β-cell death) due to either autoimmunity (type 1 diabetes mellitus) or failure to compensate for insulin resistance (type 2 diabetes mellitus; T2DM). In addition, mutations of critical genes cause monogenic diabetes. The endoplasmic reticulum (ER) is the primary site for proinsulin folding; therefore, ER proteostasis is crucial for both β-cell function and survival under physiological and pathophysiological challenges. Importantly, the ER is also the major intracellular Ca²⁺ storage organelle, generating Ca²⁺ signals that contribute to insulin secretion. ER stress is associated with the pathogenesis of diabetes mellitus. In this Review, we summarize the mutations in monogenic diabetes that play causal roles in promoting ER stress in β-cells. Furthermore, we discuss the possible mechanisms responsible for ER proteostasis imbalance with a focus on T2DM, in which both genetics and environment are considered important in promoting ER stress in β-cells. We also suggest that controlled insulin secretion from β-cells might reduce the progression of a key aspect of the metabolic syndrome, namely nonalcoholic fatty liver disease. Finally, we evaluate potential therapeutic approaches to treat T2DM, including the optimization and protection of functional β-cell mass in individuals with T2DM.

Effects of calcium‑permeable ion channels on various digestive diseases in the regulation of autophagy (Review)

Autophagy is a process of degradation and catabolism in cells. By removing damaged or dysfunctional organelles, autophagy interacts with the ubiquitin‑proteasome degradation system to jointly regulate cell function and energy homeostasis. Since autophagy plays a key role in physiology, disorders of the autophagy mechanism are associated with various diseases. Therefore, thorough understanding of the autophagy regulatory mechanism are crucially important in the diagnosis and treatment of diseases. To date, ion channels may affect the development and treatment of diseases by regulating autophagy, especially calcium‑permeable ion channels, in the process of digestive system diseases. However, the mechanism by which calcium ions and their channels regulate autophagy is still poorly understood, thus emphasizing the need for further research in this field. The present review intends to discuss the association, mechanism and application of calcium ions, their channels and autophagy in the occurrence and development of digestive system diseases.

The Capacity to Secrete Insulin Is Dose-Dependent to Extremely High Glucose Concentrations: A Key Role for Adenylyl Cyclase

Insulin secretion is widely thought to be maximally stimulated in glucose concentrations of 16.7-to-30 mM (300-to-540 mg/dL). However, insulin secretion is seldom tested in hyperglycemia exceeding these levels despite the Guinness World Record being 147.6 mM (2656 mg/dL). We investigated how islets respond to 1-h exposure to glucose approaching this record. Insulin secretion from human islets at 12 mM glucose intervals dose-dependently increased until at least 72 mM glucose. Murine islets in 84 mM glucose secreted nearly double the insulin as in 24 mM (p < 0.001). Intracellular calcium was maximally stimulated in 24 mM glucose despite a further doubling of insulin secretion in higher glucose, implying that insulin secretion above 24 mM occurs through amplifying pathway(s). Increased osmolarity of 425-mOsm had no effect on insulin secretion (1-h exposure) or viability (48-h exposure) in murine islets. Murine islets in 24 mM glucose treated with a glucokinase activator secreted as much insulin as islets in 84 mM glucose, indicating that glycolytic capacity exists above 24 mM. Using an incretin mimetic and an adenylyl cyclase activator in 24 mM glucose enhanced insulin secretion above that observed in 84 mM glucose while adenylyl cyclase inhibitor reduced stimulatory effects. These results highlight the underestimated ability of islets to secrete insulin proportionally to extreme hyperglycemia through adenylyl cyclase activity.

Hybrid labeling system for dSTORM imaging of endoplasmic reticulum for uncovering ultrastructural transformations under stress conditions

The endoplasmic reticulum (ER) transforms its morphology to fit versatile cellular functions especially under stress conditions. Since various ER stresses are critical pathophysiological factors, the precise observations of ER can provide insights into disease diagnoses and biological researches. Live-cell super-resolution imaging is highly expected for uncovering microstructures of ER. However, to achieve this, there remains a big challenge in how to efficiently label ER with advanced fluorophores. Herein, we report a new SNAP-tag fluorescent probe, namely, CLP-TMR, for specific and high-density labeling of the newly constructed dual ER-signal (targeting and retention) peptides fused-SNAP proteins. This hybrid labeling system integrating chemical probes with genetically encoded techniques enables molecular position reconstructions of ER morphologies through direct stochastic optical reconstruction microscopy (dSTORM) imaging. The super-resolution imaging reveals several never-known ultrastructural changes responding to different ER stresses, i.e. the formation of peripheral ER sheets to restore the immunogenicity, and the long flattened ER tubules under inflammation.

A Combination of Atorvastatin and Aspirin Enhances the Pro-Regenerative Interactions of Marrow Stromal Cells and Stroke-Derived Monocytes In Vitro

Background and Purpose: Marrow stromal cells (MSCs) are being tested in clinical trials for stroke patients. MSCs appear to promote recovery through secretomes that promote modulation of immune cells, including myeloid phagocytes. Many stroke patients have comorbidities such as metabolic syndrome, hypertension, hypercholesterolemia, and diabetes for which they are prescribed medications that might affect the function of MSCs and monocytes (Mo) when they are administered in stroke patients. We studied the effects of the two most commonly prescribed stroke medications, statin and statin plus aspirin, on the secretomes of MSCs and their modulation of Mo derived from stroke patients.

Methods: Human MSCs, Mo and their co-cultures were exposed to atorvastatin or atorvastatin plus aspirin followed by secretome analysis at 24 h. Monocytes were isolated from healthy controls as well as stroke patients with NIHSS ranging from 11 to 20. Secretome composition was measured using multiplex immunoassay. We used MTT assay to measure proliferation of monocytes. The mixed model was used to analyze experimental data. p-values less than 0.05 were considered significant.

Results: Atorvastatin and aspirin combination increased the release of IL-1RA from stroke Mo. In MSCs, atorvastatin and aspirin combination reduced the release of pro-inflammatory cytokines such as IL-6, IL-8, MCP-1 and IFN-γ. Atorvastatin alone reduced the release of IL-6, IL-8 and MCP-1 from co-cultures of stroke monocytes and MSCs. Combination of atorvastatin and aspirin had additive effect on reducing the secretion of IL-6 from co-cultures of stroke Mo and MSCs.

Conclusion: Atorvastatin, alone and in combination with aspirin can promote anti-inflammatory effect by modulating the secretome profile of Mo and MSCs. Our results suggest that stroke trials involving the use of intravenous MSCs should consider the effect of aspirin and atorvastatin, both of which are administered to the majority of hospitalized ischemic stroke patients.

Attenuating the Effects of Novel COVID-19 (SARS-CoV-2) Infection-Induced Cytokine Storm and the Implications

The COVID-19 pandemic constitutes an arduous global health challenge, and the increasing number of fatalities calls for the speedy pursuit of a remedy. This review emphasizes the changing aspects of the COVID-19 disease, featuring the cytokine storm's pathological processes. Furthermore, we briefly reviewed potential therapeutic agents that may modulate and alleviate cytokine storms. The literature exploration was made using PubMed, Embase, MEDLINE, Google scholar, and China National Knowledge Infrastructure databases to retrieve the most recent literature on the etiology, diagnostic markers, and the possible prophylactic and therapeutic options for the management of cytokine storm in patients hospitalized with COVID-19 disease. The causative agent, severe acute respiratory coronavirus-2 (SARS-CoV-2), continually threatens the efficiency of the immune system of the infected individuals. As the first responder, the innate immune system provides primary protection against COVID-19, affecting the disease's progression, clinical outcome, and prognosis. Evidence suggests that the fatalities associated with COVID-19 are primarily due to hyper-inflammation and an aberrant immune function. Accordingly, the magnitude of the release of pro-inflammatory cytokines such as interleukin (IL)-1, (IL-6), and tumor necrosis alpha (TNF-α) significantly differentiate between mild and severe cases of COVID-19. The early prediction of a cytokine storm is made possible by several serum chemistry and hematological markers. The prompt use of these markers for diagnosis and the aggressive prevention and management of a cytokine release syndrome is critical in determining the level of morbidity and fatality associated with COVID-19. The prophylaxis and the rapid treatment of cytokine storm by clinicians will significantly enhance the fight against the dreaded COVID-19 disease.

Molecular mechanisms of lipotoxicity-induced pancreatic β-cell dysfunction

Type 2 diabetes (T2D), a heterogeneous disorder derived from metabolic dysfunctions, leads to a glucose overflow in the circulation due to both defective insulin secretion and peripheral insulin resistance. One of the critical risk factor for T2D is obesity, which represents a global epidemic that has nearly tripled since 1975. Obesity is characterized by chronically elevated free fatty acid (FFA) levels, which cause deleterious effects on glucose homeostasis referred to as lipotoxicity. Here, we review the physiological FFA roles onto glucose-stimulated insulin secretion (GSIS) and the pathological ones affecting many steps of the mechanisms and modulation of GSIS. We also describe in vitro and in vivo experimental evidences addressing lipotoxicity in β-cells and the role of saturation and chain length of FFA on the potency of GSIS stimulation. The molecular mechanisms underpinning lipotoxic-β-cell dysfunction are also reviewed. Among them, endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, inflammation, impaired autophagy and β-cell dedifferentiation. Finally therapeutic strategies for the β-cells dysfunctions such as the use of metformin, glucagon-like peptide 1, thiazolidinediones, anti-inflammatory drugs, chemical chaperones and weight are discussed.

A Practical Guide to Rodent Islet Isolation and Assessment Revisited

Insufficient insulin secretion is a key component of both type 1 and type 2 diabetes. Since insulin is released by the islets of Langerhans, obtaining viable and functional islets is critical for research and transplantation. The effective and efficient isolation of these small islands of endocrine cells from the sea of exocrine tissue that is the rest of the pancreas is not necessarily simple or quick. Choosing and administering the digestive enzyme, separation of the islets from acinar tissue, and culture of islets are all things that must be considered. The purpose of this review is to provide a history of the development of islet isolation procedures and to serve as a practical guide to rodent islet research for newcomers to islet biology. We discuss key elements of mouse islet isolation including choosing collagenase, the digestion process, purification of islets using a density gradient, and islet culture conditions. In addition, this paper reviews techniques for assessing islet viability and function such as visual assessment, glucose-stimulated insulin secretion and intracellular calcium measurements. A detailed protocol is provided that describes a common method our laboratory uses to obtain viable and functional mouse islets for in vitro study. This review thus provides a strong foundation for successful procurement and purification of high-quality mouse islets for research purposes.

Postnatal maturation of calcium signaling in islets of Langerhans from neonatal mice

Pancreatic islet cells develop mature physiological responses to glucose and other fuels postnatally. In this study, we used fluorescence imaging techniques to measure changes in intracellular calcium ([Ca²⁺]_i) to compare islets isolated from mice on postnatal days 0, 4, and 12 with islets from adult CD-1 mice. In addition, we used publicly available RNA-sequencing data to compare expression levels of key genes in β-cell physiology with [Ca²⁺]_i data across these ages. We show that islets isolated from mice on postnatal day 0 displayed elevated [Ca²⁺]_i in basal glucose (≤4 mM) but lower [Ca²⁺]_i responses to stimulation by 12-20 mM glucose compared to adult. Neonatal islets displayed more adult-like [Ca²⁺]_i in basal glucose by day 4 but continued to show lower [Ca²⁺]_i responses to 16 and 20 mM glucose stimulation up to at least day 12. A right shift in glucose sensing (EC₅₀) correlated with lower fragment-per-kilobase-of-transcript-per-million-reads-mapped (FPKM) of Slc2a2 (glut2) and Actn3 and increased FPKM for Galk1 and Nupr1. Differences in [Ca²⁺]_i responses to additional stimuli were also observed. Calcium levels in the endoplasmic reticulum were elevated on day 0 but became adult-like by day 4, which corresponded with reduced expression in Atp2a2 (SERCA2) and novel K+-channel Ktd17, increased expression of Pml, Wfs1, Thada, and Herpud1, and basal [Ca²⁺]_i maturing to adult levels. Ion-channel activity also matured rapidly, but RNA sequencing data mining did not yield strong leads. In conclusion, the maturation of islet [Ca²⁺]_i signaling is complex and multifaceted; several possible gene targets were identified that may participate in this process.

Single-Cell Transcriptional Profiling of Mouse Islets Following Short-Term Obesogenic Dietary Intervention

Obesity is closely associated with adipose tissue inflammation and insulin resistance. Dysglycemia and type 2 diabetes results when islet β cells fail to maintain appropriate insulin secretion in the face of insulin resistance. To clarify the early transcriptional events leading to β-cell failure in the setting of obesity, we fed male C57BL/6J mice an obesogenic, high-fat diet (60% kcal from fat) or a control diet (10% kcal from fat) for one week, and islets from these mice (from four high-fat- and three control-fed mice) were subjected to single-cell RNA sequencing (sc-RNAseq) analysis. Islet endocrine cell types (α cells, β cells, δ cells, PP cells) and other resident cell types (macrophages, T cells) were annotated by transcript profiles and visualized using Uniform Manifold Approximation and Projection for Dimension Reduction (UMAP) plots. UMAP analysis revealed distinct cell clusters (11 for β cells, 5 for α cells, 3 for δ cells, PP cells, ductal cells, endothelial cells), emphasizing the heterogeneity of cell populations in the islet. Collectively, the clusters containing the majority of β cells showed the fewest gene expression changes, whereas clusters harboring the minority of β cells showed the most changes. We identified that distinct β-cell clusters downregulate genes associated with the endoplasmic reticulum stress response and upregulate genes associated with insulin secretion, whereas others upregulate genes that impair insulin secretion, cell proliferation, and cell survival. Moreover, all β-cell clusters negatively regulate genes associated with immune response activation. Glucagon-producing α cells exhibited patterns similar to β cells but, again, in clusters containing the minority of α cells. Our data indicate that an early transcriptional response in islets to an obesogenic diet reflects an attempt by distinct populations of β cells to augment or impair cellular function and/or reduce inflammatory responses as possible harbingers of ensuing insulin resistance.

Good Cop, Bad Cop: The Opposing Effects of Macrophage Activation State on Maintaining or Damaging Functional β-Cell Mass

Loss of functional β-cell mass is a hallmark of Type 1 and Type 2 Diabetes. Macrophages play an integral role in the maintenance or destruction of pancreatic β-cells. The effect of the macrophage β-cell interaction is dependent on the activation state of the macrophage. Macrophages can be activated across a spectrum, from pro-inflammatory to anti-inflammatory and tissue remodeling. The factors secreted by these differentially activated macrophages and their effect on β-cells define the effect on functional β-cell mass. In this review, the spectrum of macrophage activation is discussed, as are the positive and negative effects on β-cell survival, expansion, and function as well as the defined factors released from macrophages that impinge on functional β-cell mass.

Crosstalk between endoplasmic reticulum stress and oxidative stress: Focus on protein disulfide isomerase and endoplasmic reticulum oxidase 1

Cellular stress and inflammation, establishing as disease pathology, have reached great heights in the last few decades. Stress conditions such as hyperglycemia, hyperlipidemia and lipoproteins are known to disturb proteostasis resulting in the accumulation of unfolded or misfolded proteins, alteration in calcium homeostasis culminating in unfolded protein response. Protein disulfide isomerase and endoplasmic reticulum oxidase-1 are the key players in protein folding. The protein folding process assisted by endoplasmic reticulum oxidase-1 results in the production of reactive oxygen species in the lumen of the endoplasmic reticulum. Production of reactive oxygen species beyond the quenching capacity of the antioxidant systems perturbs ER homeostasis. Endoplasmic reticulum stress also induces the production of cytokines leading to inflammatory responses. This has been proven to be the major causative factor for various pathophysiological states compared to other cellular triggers in diseases, which further manifests to increased oxidative stress, mitochondrial dysfunction, and altered inflammatory responses, deleterious to cellular physiology and homeostasis. Numerous studies have drawn correlations between the progression of several diseases in association with endoplasmic reticulum stress, redox protein folding, oxidative stress and inflammatory responses. This review aims to provide an insight into the role of protein disulfide isomerase and endoplasmic reticulum oxidase-1 in endoplasmic reticulum stress, unfolded protein response, mitochondrial dysfunction, and inflammatory responses, which exacerbate the progression of various diseases.

Low concentration IL-1β promotes islet amyloid formation by increasing hIAPP release from humanised mouse islets in vitro

AIMS/HYPOTHESIS

Aggregation of the beta cell secretory product human islet amyloid polypeptide (hIAPP) results in islet amyloid deposition, a pathological feature of type 2 diabetes. Amyloid formation is associated with increased levels of islet IL-1β as well as beta cell dysfunction and death, but the mechanisms that promote amyloid deposition in situ remain unclear. We hypothesised that physiologically relevant concentrations of IL-1β stimulate beta cell islet amyloid polypeptide (IAPP) release and promote amyloid formation.

METHODS

We used a humanised mouse model of endogenous beta cell hIAPP expression to examine whether low (pg/ml) concentrations of IL-1β promote islet amyloid formation in vitro. Amyloid-forming islets were cultured for 48 h in the presence or absence of IL-1β with or without an IL-1β neutralising antibody. Islet morphology was assessed by immunohistochemistry and islet mRNA expression, hormone content and release were also quantified. Cell-free thioflavin T assays were used to monitor hIAPP aggregation kinetics in the presence and absence of IL-1β.

RESULTS

Treatment with a low concentration of IL-1β (4 pg/ml) for 48 h increased islet amyloid prevalence (93.52 ± 3.89% vs 43.83 ± 9.67% amyloid-containing islets) and amyloid severity (4.45 ± 0.82% vs 2.16 ± 0.50% amyloid area/islet area) in hIAPP-expressing mouse islets in vitro. This effect of IL-1β was reduced when hIAPP-expressing islets were co-treated with an IL-1β neutralising antibody. Cell-free hIAPP aggregation assays showed no effect of IL-1β on hIAPP aggregation in vitro. Low concentration IL-1β did not increase markers of the unfolded protein response (Atf4, Ddit3) or alter proIAPP processing enzyme gene expression (Pcsk1, Pcsk2, Cpe) in hIAPP-expressing islets. However, release of IAPP and insulin were increased over 48 h in IL-1β-treated vs control islets (IAPP 0.409 ± 0.082 vs 0.165 ± 0.051 pmol/5 islets; insulin 87.5 ± 8.81 vs 48.3 ± 17.3 pmol/5 islets), and this effect was blocked by co-treatment with IL-1β neutralising antibody.

CONCLUSIONS/INTERPRETATION

Under amyloidogenic conditions, physiologically relevant levels of IL-1β promote islet amyloid formation by increasing beta cell release of IAPP. Neutralisation of this effect of IL-1β may decrease the deleterious effects of islet amyloid formation on beta cell function and survival.

Mitochondria and T2D: Role of Autophagy, ER Stress, and Inflammasome

Type 2 diabetes (T2D) is one of the main current threats to human health. Both T2D and its numerous clinical complications are related to mitochondrial dysfunction and oxidative stress. Over the past decade, great progress has been made in extending our knowledge about the signaling events regulated by mitochondria. However, the links among mitochondrial impairment, oxidative stress, autophagy, endoplasmic reticulum (ER) stress, and activation of the inflammasome still need to be clarified. In light of this deficit, we aim to provide a review of the existing literature concerning the complicated crosstalk between mitochondrial impairment, autophagy, ER stress, and the inflammasome in the molecular pathogenesis of T2D.

Reflections on undergraduate research mentoring

Recruiting talented high school and college students to consider a career in the biomedical or biophysical sciences is important, yet often difficult. Encouraging students in regions like Appalachia adds additional challenges due to socioeconomic hurdles and misperceptions. This brief report contains the reflections of a research mentor engaging with students as a high school physics teacher, a principal investigator at research-intensive university, and as a principal investigator at a predominantly undergraduate-focused research university, as well as the viewpoint of a former undergraduate student in the mentor's lab. Different hurdles stand in the way of success at each level. A key issue at the high school level is engaging students in 'real science', the discovery of new knowledge and ideas. With undergraduate students at a larger research institution, a key issue is for the student to have opportunities to engage in meaningful scientific research. At a smaller and more rural research institution, especially in Appalachia, many students have socioeconomic concerns and misconceptions of what scientific careers entail. Regardless of background and environment, there are certain students who thrive on the scientific curiosity to discover new things. All they need is that opportunity to engage in meaningful scientific discovery to become interested in a scientific career.

Icariin protects neurons from endoplasmic reticulum stress-induced apoptosis after OGD/R injury via suppressing IRE1α-XBP1 signaling pathway

Icariin (ICA), a flavonol glycoside isolated from Epimedium, has been considered as a potential alternative therapy for ischemic stroke. However, the protective mechanisms of ICA on cerebral ischemia-reperfusion (I/R) are not fully illuminated yet. The effects of ICA on ER stress and inflammatory response which were involved in the pathological process of cerebral I/R were investigated in vitro. Microglia and neurons were subjected to OGD/R. ICA was administrated to microglia 1 h before OGD and maintained 2 h throughout OGD. At 24 h after reoxygenation, the protein expression of IL-1 β, IL-6, TNF-α in the supernatant of microglia was measured using ELISA assay; neuronal apoptosis was assessed by TUNEL staining; and cell viability was detected using CKK-8 assay; the expression of IRE1α, XBP1u, XBP1s, and cleaved caspase-3 in neurons was examined by western blotting and qRT-PCR; the expression of p-IRE1α in neurons was detected by western blotting. We found that OGD/R induced the expression of IL-1 β, IL-6, TNF-α in the supernatant of microglia; OGD/R and these proinflammatory cytokines promoted the mRNA as well as protein expression of XBP1u, XBP1s and cleaved caspase-3, increased the ratio of p-IRE1α/IRE1α, as well as apoptosis, and decreased cell viability in primary cortical neurons, while ICA reversed the levels of the above factors. IRE1 overexpression enhanced ER stress as well as apoptosis, and impaired the protective effects of ICA. These results suggested that ICA can inhibit apoptosis in neurons after OGD/R through IRE1/XBP1 signaling pathway beside its anti-inflammatory effect.

ER Stress Regulates Immunosuppressive Function of Myeloid Derived Suppressor Cells in Leprosy that Can Be Overcome in the Presence of IFN-γ

Myeloid derived suppressor cells (MDSCs) are a population of immature myeloid cells that suppress adaptive immune function, yet the factors that regulate their suppressive function in patients with infection remain unclear. We studied MDSCs in patients with leprosy, a disease caused by Mycobacterium leprae, where clinical manifestations present on a spectrum that correlate with immunity to the pathogen. We found that HLA-DR^-CD33⁺CD15⁺ MDSCs were increased in blood from patients with disseminated/progressive lepromatous leprosy and possessed T cell-suppressive activity as compared with self-limiting tuberculoid leprosy. Mechanistically, we found ER stress played a critical role in regulating the T cell suppressive activity in these MDSCs. Furthermore, ER stress augmented IL-10 production, contributing to MDSC activity, whereas IFN-γ allowed T cells to overcome MDSC suppressive activity. These studies highlight a regulatory mechanism that links ER stress to IL-10 in mediating MDSC suppressive function in human infectious disease.

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Cells with an MDSC phenotype are increased in blood and skin of patients with leprosy

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Only MDSCs from patients with leprosy with disseminated infection suppress T cell function

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MDSC function is dependent on increased ER stress and IL-10 production

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MDSC function can be reversed in the presence of IFN-γ

Inhibition of protein disulfide isomerase has neuroprotective effects in a mouse model of experimental autoimmune encephalomyelitis

Endoplasmic reticulum (ER) stress is strictly linked to neuroinflammation and involves in the development of neurodegenerative disorders. Protein disulfide isomerase (PDI) is an enzyme that catalyzes formation and isomerization of disulfide bonds and also acts as a chaperone that survives the cells against cell death by removal of misfolded proteins. Our previous work revealed that PDI is explicitly upregulated in response to myelin oligodendrocyte glycoprotein (MOG)-induced ER stress in the brain of experimental autoimmune encephalomyelitis (EAE) mice. The significance of overexpression of PDI in the apoptosis of neural cells prompted us to study the effect of CCF642, efficient inhibitor of PDI, in the recovery of EAE clinical symptoms. Using this in vivo model, we characterized the ability of CCF642 to decrease the expression of ER stress markers and neuroinflammation in the hippocampus of EAE mice. Our observations suggested that CCF642 administration attenuates EAE clinical symptomsand the expression of ER stress-related proteins. Further, it suppressed the inflammatory infiltration of CD4 + T cells and the activation of hippocampus-resident microglia and Th17 cells. We reported here that the inhibition of PDI protected EAE mice against neuronal apoptosis induced by prolonged ER stress and resulted in neuroprotection.

Inhibition of the endoplasmic reticulum (ER) stress-associated IRE-1/XBP-1 pathway alleviates acute lung injury via modulation of macrophage activation

Background

Both endoplasmic reticulum (ER) stress and macrophage diversity contribute to inflammatory processes in lung injury. However, the interaction between ER stress and macrophage M1/M2 imbalance in lung inflammation remains unclear. The present study, thus, aimed to evaluate the role of ER stress-mediated macrophage phenotype changes in lipopolysaccharide (LPS)-induced acute lung injury (ALI).

Methods

Lung inflammation and injury were examined in a murine model of LPS-induced ALI with or without ER stress inhibitors. Alveolar macrophage (AM) polarization was determined by flow cytometry. Bone marrow-derived macrophages (BMDMs) were treated with either an ER stress inducer, inhibitor, or an IRE-1 endonuclease inhibitor before being polarized to an M1 and M2 phenotype. The macrophage polarization status was examined via RT-PCR and flow cytometry.

Results

Our results indicated that ER stress and IRE-1/XBP-1 signaling are activated in LPS-induced ALI. Furthermore, we observed that AM polarizes to an inflammatory phenotype upon exposure to LPS in the induction phase and an anti-inflammatory phenotype in the resolution phase of lung inflammation. Inhibition of ER stress attenuated the pathophysiological features of LPS-induced lung inflammation/injury, as evidenced by a decrease in bronchoalveolar lavage (BAL) protein levels, the number of inflammatory cells, and the expression level of inflammatory mediators. In addition, the ER stress inducer promoted M1 polarization and the switch from M2 to M1 in BMDMs, whereas inhibition of ER stress and XBP-1 splicing suppressed M1 but did not promote M2, both in vivo and in vitro.

Conclusions

Our results demonstrated that inhibition of the ER stress-associated IRE-1/XBP-1 signaling pathway suppresses M1 polarization and ameliorates LPS-induced lung injury. This indicates that the interaction between ER stress and macrophage polarization might be a novel therapeutic target for endotoxin-induced lung inflammatory disorders.

ABCA12 regulates insulin secretion from β-cells

Dysregulation of lipid homeostasis is intimately associated with defects in insulin secretion, a key feature of type 2 diabetes. Here, we explore the role of the putative lipid transporter ABCA12 in regulating insulin secretion from β-cells. Mice with β-cell-specific deletion of Abca12 display impaired glucose-stimulated insulin secretion and eventual islet inflammation and β-cell death. ABCA12's action in the pancreas is independent of changes in the abundance of two other cholesterol transporters, ABCA1 and ABCG1, or of changes in cellular cholesterol or ceramide content. Instead, loss of ABCA12 results in defects in the genesis and fusion of insulin secretory granules and increases in the abundance of lipid rafts at the cell membrane. These changes are associated with dysregulation of the small GTPase CDC42 and with decreased actin polymerisation. Our findings establish a new, pleiotropic role for ABCA12 in regulating pancreatic lipid homeostasis and insulin secretion.

Reducing Glucokinase Activity to Enhance Insulin Secretion: A Counterintuitive Theory to Preserve Cellular Function and Glucose Homeostasis

Pancreatic beta-cells are the only cells in the body that can synthesize and secrete insulin. Through the process of glucose-stimulated insulin secretion, beta-cells release insulin into circulation, stimulating GLUT4-dependent glucose uptake into peripheral tissue. Insulin is normally secreted in pulses that promote signaling at the liver. Long before type 2 diabetes is diagnosed, beta-cells become oversensitive to glucose, causing impaired pulsatility and overstimulation in fasting levels of glucose. The resulting hypersecretion of insulin can cause poor insulin signaling and clearance at the liver, leading to hyperinsulinemia and insulin resistance. Continued overactivity can eventually lead to beta-cell exhaustion and failure at which point type 2 diabetes begins. To prevent or reverse the negative effects of overstimulation, beta-cell activity can be reduced. Clinical studies have revealed the potential of beta-cell rest to reverse new cases of diabetes, but treatments lack durable benefits. In this perspective, we propose an intervention that reduces overactive glucokinase activity in the beta-cell. Glucokinase is known as the glucose sensor of the beta-cell due to its high control over insulin secretion. Therefore, glycolytic overactivity may be responsible for hyperinsulinemia early in the disease and can be reduced to restore normal stimulus-secretion coupling. We have previously reported that reducing glucokinase activity in prediabetic mouse islets can restore pulsatility and enhance insulin secretion. Building on this counterintuitive finding, we review the importance of pulsatile insulin secretion and highlight how normalizing glucose sensing in the beta cell during prediabetic hyperinsulinemia may restore pulsatility and improve glucose homeostasis.

Sicyos angulatus Prevents High-Fat Diet-Induced Obesity and Insulin Resistance in Mice

Obesity is a medical condition in which excess body fat has accumulated to a serious extent. It is a chronic disease that can lead to dyslipidemia, insulin resistance, and type 2 diabetes. In the present study, we investigated the anti-obesity effects of Sicyos angulatus (SA) extract on a high-fat diet (HFD)-induced C57BL/6J obese mice. The mice were divided into vehicle and three SA groups (25, 50, and 100 mg/kg body weight). The mice were fed a HFD with or without SA for 12 weeks. The oral administration of SA reduced body and adipose tissue weight in HFD-fed mice compared to those in the vehicle group (p<0.05). Adipocyte size and inflammation significantly decreased in the SA-administered groups in a dose-dependent manner. In particular, adipocytes larger than 5000 µm² were remarkably reduced by around 50% in the SA-treated groups (p<0.05). In addition, SA contributes towards reducing insulin resistance (measured as the HOMA-IR index) and glucose intolerance in HFD-induced obese mice (p<0.05; Vehicle 21.5±3.1 vs. SA100 4.7±0.4). These beneficial effects of SA on obesity may be linked to the suppression of lipogenesis and stimulating energy metabolism in white adipose tissue and muscle. In white adipose tissue and muscle, the administration of SA activated AMPK pathway, leading to the inhibition of the development of pathophysiological conditions associated with obesity, including lipogenesis and inflammation. These findings suggest that SA may prevent obesity through inhibiting fat accumulation in HFD-induced obese mice. Therefore, SA is able to exert metabolic benefits in the prevention of obesity and insulin resistance.

Molecular Modelling of Islet β-Cell Adaptation to Inflammation in Pregnancy and Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM), a metabolic disease that develops with the increase in insulin resistance during late pregnancy, is currently one of the most common complications affecting pregnancy. The polygenic nature of GDM, together with the interplay between different genetic variants with nutritional and environmental factors has hindered the full understanding of the etiology of this disease. However, an important genetic overlap has been found with type 2 diabetes mellitus (T2DM) and, as in the case of T2DM, most of the identified loci are associated with β-cell function. Early detection of GDM and adequate interventions to control the maternal glycemia are necessary to avoid the adverse outcomes for both the mother and the offspring. The in utero exposure to the diabetic milieu predispose these children for future diseases, among them T2DM, originating a vicious circle implicated in the increased prevalence of both GDM and T2DM. The involvement of inflammatory processes in the development of GDM highlights the importance of pancreatic β-cell factors able to favor the adaptation processes required during gestation, concomitantly with the protection of the islets from an inflammatory milieu. In this regard, two members of the Pax family of transcription factors, PAX4 and PAX8, together with the chromatin remodeler factor HMG20A, have gained great relevance due to their involvement in β-cell mass adaptation together with their anti-inflammatory properties. Mutations in these factors have been associated with GDM, highlighting these as novel candidates for genetic screening analysis in the identification of women at risk of developing GDM.

Aggregated and Hyperstable Damage-Associated Molecular Patterns Are Released During ER Stress to Modulate Immune Function

Chronic ER stress occurs when protein misfolding in the Endoplasmic reticulum (ER) lumen remains unresolved despite activation of the unfolded protein response. We have shown that traumatic injury such as a severe burn leads to chronic ER stress in vivo leading to systemic inflammation which can last for more than a year. The mechanisms linking chronic ER stress to systemic inflammatory responses are not clear. Here we show that induction of chronic ER stress leads to the release of known and novel damage-associated molecular patterns (DAMPs). The secreted DAMPs are aggregated and markedly protease resistant. ER stress-derived DAMPs activate dendritic cells (DCs) which are then capable of polarizing naïve T cells. Our findings indicate that induction of chronic ER stress may lead to the release of hyperstable DAMPs into the circulation resulting in persistent systemic inflammation and adverse outcomes.

Intact pancreatic islets and dispersed beta-cells both generate intracellular calcium oscillations but differ in their responsiveness to glucose

Pancreatic islets produce pulses of insulin and other hormones that maintain normal glucose homeostasis. These micro-organs possess exquisite glucose-sensing capabilities, allowing for precise changes in pulsatile insulin secretion in response to small changes in glucose. When communication among these cells is disrupted, precision glucose sensing falters. We measured intracellular calcium patterns in 6-mM-steps between 0 and 16 mM glucose, and also more finely in 2-mM-steps from 8 to 12 mM glucose, to compare glucose sensing systematically among intact islets and dispersed islet cells derived from the same mouse pancreas in vitro. The calcium activity of intact islets was uniformly low (quiescent) below 4 mM glucose and active above 8 mM glucose, whereas dispersed beta-cells displayed a broader activation range (2-to-10 mM). Intact islets exhibited calcium oscillations with 2-to-5-min periods, yet beta-cells exhibited longer 7-10 min periods. In every case, intact islets showed changes in activity with each 6-mM-glucose step, whereas dispersed islet cells displayed a continuum of calcium responses ranging from islet-like patterns to stable oscillations unaffected by changes in glucose concentration. These differences were also observed for 2-mM-glucose steps. Despite the diversity of dispersed beta-cell responses to glucose, the sum of all activity produced a glucose dose-response curve that was surprisingly similar to the curve for intact islets, arguing against the importance of "hub cells" for function. Beta-cells thus retain many of the features of islets, but some are more islet-like than others. Determining the molecular underpinnings of these variations could be valuable for future studies of stem-cell-derived beta-cell therapies.

Could the high consumption of high glycaemic index carbohydrates and sugars, associated with the nutritional transition to the Western type of diet, be the common cause of the obesity epidemic and the worldwide increasing incidences of Type 1 and Type 2 diabetes?

The globally increasing incidences of Type 1 diabetes (T1DM) and Type 2 diabetes (T2DM) can have a common background. If challenged by the contemporary high level of nutritional glucose stimulation, the β-cells in genetically predisposed individuals are at risk for damage which can lead to the diseases. The fat to carbohydrate dietary shift can also contribute to the associated obesity epidemic.

Inflammation and pancreatic cancer: An updated review

Pancreatic cancer is a devastating disease with poor prognosis in the modern era. Inflammatory processes have emerged as key mediators of pancreatic cancer development and progression. Recently, studies have been carried out to investigate the underlying mechanisms that contribute to tumorigenesis induced by inflammation. In this review, the role of inflammation in the initiation and progression of pancreatic cancer is discussed.

Optical tools for understanding the complexity of β-cell signalling and insulin release

Following stimulation, pancreatic β-cells must orchestrate a plethora of signalling events to ensure the appropriate release of insulin and maintenance of normal glucose homeostasis. Failure at any point in this cascade leads to impaired insulin secretion, elevated blood levels of glucose and eventually type 2 diabetes mellitus. Likewise, β-cell replacement or regeneration strategies for the treatment of both type 1 and type 2 diabetes mellitus might fail if the correct cell signalling phenotype cannot be faithfully recreated. However, current understanding of β-cell function is complicated because of the highly dynamic nature of their intracellular and intercellular signalling as well as insulin release itself. β-Cells must precisely integrate multiple signals stemming from multiple cues, often with differing intensities, frequencies and cellular and subcellular localizations, before converging these signals onto insulin exocytosis. In this respect, optical approaches with high resolution in space and time are extremely useful for properly deciphering the complexity of β-cell signalling. An increased understanding of β-cell signalling might identify new mechanisms underlying insulin release, with relevance for future drug therapy and de novo stem cell engineering of functional islets.