Inflammation in obesity and diabetes: islet dysfunction and therapeutic opportunity

The processing intermediate of human amylin, pro-amylin(1-48), has in vivo and in vitro bioactivity

Amylin is released by pancreatic beta-cells in response to a meal and its major soluble mature form (37 amino acid-peptide) produces its biological effects by activating amylin receptors. Amylin is derived from larger propeptides that are processed within the synthesizing beta-cell. There are suggestions that a partially processed form, pro-amylin(1-48) is also secreted. We tested the hypothesis that pro-amylin(1-48) has biological activity and that human pro-amylin(1-48) may also form toxic pre-amyloid species. Amyloid formation, the ability to cross-seed and in vitro toxicity were similar between human pro-amylin(1-48) and amylin. Human pro-amylin(1-48) was active at amylin-responsive receptors, though its potency was reduced at rat, but not human amylin receptors. Pro-amylin(1-48) was able to promote anorexia by activating neurons of the area postrema, amylin's primary site of action, indicating that amylin can tolerate significant additions at the N-terminus without losing bioactivity. Our studies help to shed light on the possible roles of pro-amylin(1-48) which may be relevant for the development of future amylin-based drugs.

Butyrate functions as a histone deacetylase inhibitor to protect pancreatic beta cells from IL-1β-induced dysfunction

Butyrate, a gut microbial metabolite, has beneficial effects on glucose homeostasis and has become an attractive drug candidate for type 2 diabetes (T2D). Recently, we showed that butyrate protects pancreatic beta cells against cytokine-induced dysfunction. In this study, we explored the underlying mechanisms of butyrate action. Pancreatic mouse islets were exposed to a non-cytotoxic concentration of interleukin-1β (IL-1β) for 10 days to mimic low-grade inflammation in T2D. Similar to the effect of butyrate, an isoform-selective histone deacetylase 3 (HDAC3) inhibitor normalized IL-1β-reduced glucose-stimulated insulin secretion and insulin content. In contrast, free fatty acid receptor 2 and 3 (FFAR2/3) agonists failed to normalize IL-1β-induced beta cell dysfunction. Furthermore, butyrate inhibited HDAC activity and increased the acetylation of histone H3 and H4 by 3- and 10-fold, respectively. Genome-wide analysis of histone H3 lysine 27 acetylation (H3K27ac) revealed that butyrate mainly increased H3K27ac at promoter regions (74%), while H3K27ac peaks regulated by IL-1β were more equally distributed at promoters (38%), introns (23%) and intergenic regions (23%). Gene ontology analysis showed that butyrate increased IL-1β-reduced H3K27ac levels near several genes related to hormone secretion and reduced IL-1β-increased H3K27ac levels near genes associated with inflammatory responses. Butyrate alone increased H3K27ac near many genes related to MAPK signaling, hormone secretion, and differentiation, and decreased H3K27ac at genes involved in cell replication. Together, these results suggest that butyrate prevents IL-1β-induced pancreatic islet dysfunction by inhibition of HDACs resulting in changes in H3K27ac levels at genes relevant for beta cell function and inflammatory responses.

Vertical sleeve gastrectomy improves glucose-insulin homeostasis by enhancing β-cell function and survival via FGF15/19

Vertical sleeve gastrectomy (VSG) restores glucose homeostasis in obese mice and humans. In addition, the increased fibroblast growth factor (FGF)15/19 circulating level postsurgery has been implicated in this effect. However, the impact of FGF15/19 on pancreatic islets remains unclear. Using a diet-induced obese mice model, we demonstrate that VSG attenuates insulin hypersecretion in isolated pancreatic islets, likely due to morphological alterations in the endocrine pancreas such as reduction in islet, β-cell, and α-cell mass. In addition, VSG relieves gene expression of endoplasmic reticulum (ER) stress and inflammation markers in islets from obese mice. Incubation of INS-1E β-cells with serum from obese mice induced dysfunction and cell death, whereas these conditions were not induced with serum from obese mice submitted to VSG, implicating the involvement of a humoral factor. Indeed, VSG increased FGF15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E cells treated with the serum from these mice. Moreover, exposing INS-1E cells to an FGFR inhibitor abolished the effects of VSG serum on insulin secretion and cell death. Also, recombinant FGF19 prevents INS-1E cells from dysfunction and death induced by serum from obese mice. These findings indicate that the amelioration of glucose-insulin homeostasis promoted by VSG is mediated, at least in part, by FGF15/19. Therefore, approaches promoting FGF15/19 release or action may restore pancreatic islet function in obesity.NEW & NOTEWORTHY Vertical sleeve gastrectomy (VSG) decreases insulin secretion, endoplasmic reticulum (ER) stress, and inflammation in pancreatic islets from obese mice. In addition, VSG increased fibroblast growth factor (FGF)15 circulating levels in obese mice, as well as the expression of FGF receptor 1 (Fgfr1) and its coreceptor β-klotho (Klb), both in pancreatic islets from VSG mice and in INS-1E β-cells treated with the serum from these mice. Serum from operated mice protects INS-1E cells from dysfunction and apoptosis, which was mediated by FGF15/19.

Comparison of changes in adipokine and inflammatory cytokine levels in patients with newly diagnosed type 2 diabetes treated with exenatide, insulin, or pioglitazone: A post-hoc study of the CONFIDENCE trial

Background

Adipokines and inflammatory cytokines (ADICs) play important roles in type 2 diabetes mellitus (T2DM). This study aimed to compare the changes of ADIC levels (ΔADICs) in patients with newly diagnosed T2DM treated with different antihyperglycemic agents, and further investigate the impact of these changes on metabolic indices, β-cell function and insulin resistance (IR).

Methods

Four hundred and sixteen patients with newly diagnosed T2DM from 25 centers in China randomly received 48-week intervention with exenatide, insulin or pioglitazone. Anthropometric and laboratory data, indices of β-cell function and IR, and levels of AIDCs, including interleukin-1 beta (IL-1β), interferon-gamma (IFN-γ), leptin, and fibroblast growth factor 21 (FGF21) were detected at baseline and the end of the study.

Results

In total, 281 participants (68 % male, age: 50.3 ± 9.4 years) completed the study. After 48- week treatment, IL-1β and IFN-γ were significantly decreased with exenatide treatment (P < 0.001 and P = 0.001, respectively), but increased with insulin (P = 0.009 and P = 0.026, respectively). However, pioglitazone treatment had no impact on ADICs. No significant change in leptin or FGF21 was detected with any of the treatments. After adjustment for baseline values and changes of body weight, waist and HbA1c, the between-group differences were found in ΔIL-1β (exenatide vs. insulin: P = 0.048; and exenatide vs. pioglitazone: P = 0.003, respectively) and ΔIFN-γ (exenatide vs. insulin: P = 0.049; and exenatide vs. pioglitazone: P < 0.001, respectively). Multiple linear regression analysis indicated that Δweight was associated with ΔIL-1β (β = 0.753; 95 % CI, 0.137-1.369; P = 0.017). After adjusting for treatment effects, Δweight was also be correlated with ΔFGF21 (β = 1.097; 95%CI, 0.250-1.944; P = 0.012); furthermore, ΔHOMA-IR was correlated with Δleptin (β = 0.078; 95%CI, 0.008-0.147; P = 0.029) as well. However, ΔHOMA-IR was not significantly associated with ΔIL-1β after adjusting for treatment effects (P = 0.513).

Conclusion

Exenatide treatment led to significant changes of inflammatory cytokines levels (IL-1β and IFN-γ), but not adipokines (leptin and FGF21), in newly diagnosed T2DM patients. The exenatide-mediated improvement in weight and IR may be associated with a decrease in inflammatory cytokine levels.

Stem cells as a regenerative medicine approach in treatment of microvascular diabetic complications

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by high blood glucose and is associated with high morbidity and mortality among the diabetic population. Uncontrolled chronic hyperglycaemia causes increased formation and accumulation of different oxidative and nitrosative stress markers, resulting in microvascular and macrovascular complications, which might seriously affect the quality of a patient's life. Conventional treatment strategies are confined to controlling blood glucose by regulating the insulin level and are not involved in attenuating the life-threatening complications of diabetes mellitus. Thus, there is an unmet need to develop a viable treatment strategy that could target the multi-etiological factors involved in the pathogenesis of diabetic complications. Stem cell therapy, a regenerative medicine approach, has been investigated in diabetic complications owing to their unique characteristic features of self-renewal, multilineage differentiation and regeneration potential. The present review is focused on potential therapeutic applications of stem cells in the treatment of microvascular diabetic complications such as nephropathy, retinopathy, and polyneuropathy.

Construction and evaluation of a prognostic prediction model based on the mEGOS score for patients with Guillain-Barré syndrome

Background

Guillain-Barré syndrome (GBS) is an immune-mediated acute peripheral neuropathy in which up to 20% patients remain unable to walk independently after 6 months of onset. This study aimed to develop a clinical prognostic model based on the modified Erasmus GBS Outcome Score (mEGOS) for predicting the prognosis of GBS patients at 6 months of onset.

Methods

The clinical data of 201 GBS patients were retrospectively analyzed. According to the GBS disability score (GBS-DS) at 6 months of onset, patients were divided into a good prognosis group (GBS-DS <3 points) and a poor prognosis group (GBS-DS≥3 points). Univariate and multivariate analysis was used to screen out independent risk factors for poor prognosis, and a prediction model was accordingly constructed for GBS prognosis.

Results

The mEGOS score, serum albumin (ALB) and fasting plasma glucose (FPG) were independent risk factors for poor prognosis in patients with GBS, and the above risk factors were used to construct a prognostic model of mEGOS-I and a nomogram. The receiver operating characteristic (ROC) curve showed that the area under curve (AUC) of mEGOS-I at admission and at 7 days of admission to predict poor prognosis at 6 months of GBS onset was 0.891 and 0.916, respectively, with sensitivities of 82.7% and 82.6% and specificities of 86.5% and 86.6%, respectively. Decision curve analysis showed that the nomogram had a very high clinical benefit.

Conclusion

To our knowledge, this is the first report of the construction of a prognostic prediction model based on the mEGOS score, ALB, and FPG that can accurately and stably predict the prognosis of GBS patients at 6 months of onset.

Fenofibrate alleviates insulin resistance by reducing tissue inflammation in obese ovariectomized mice

BACKGROUND

Fenofibrate is a hypolipidemic peroxisome proliferator-activated receptor α (PPARα) agonist used clinically to reduce hypercholesterolemia and hypertriglyceridemia.

OBJECTIVE

We investigated the effects of fenofibrate on insulin resistance and tissue inflammation in a high-fat diet (HFD)-fed ovariectomized (OVX) C57BL/6J mice, a mouse model of obese postmenopausal women.

METHODS

Female OVX mice were randomly divided into 3 groups and received a low-fat diet, an HFD, or an HFD supplemented with 0.05% (w/w) fenofibrate for 9 weeks. Parameters of insulin resistance and tissue inflammation were measured using blood analysis, histological analysis, immunohistochemistry, and quantitative real-time polymerase chain reaction.

RESULTS

When fenofibrate was administered to HFD-fed OVX mice for 9 weeks, we observed reductions in body weight gain, adipose tissue mass, and the size of visceral adipocytes without the change of food intake. Fenofibrate improved mild hyperglycemia, severe hyperinsulinemia, and glucose tolerance in these mice. It also reduced pancreatic islet size and insulin-positive β-cell area to levels similar to those in OVX mice fed a low-fat diet. Concomitantly, administration of fenofibrate not only suppressed pancreatic lipid accumulation but also decreased CD68-positive macrophages in both the pancreas and visceral adipose tissue. Treatment with fenofibrate reduced tumor necrosis factor α (TNFα) mRNA levels in adipose tissue and lowered serum TNFα levels.

CONCLUSION

These results suggest that fenofibrate treatment attenuates insulin resistance in part by reducing tissue inflammation and TNFα expression in HFD-fed OVX 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.

Type 1 and Type 2 Diabetes Mellitus: Commonalities, Differences and the Importance of Exercise and Nutrition

Diabetes mellitus represents a group of physiological dysfunctions characterized by hyperglycaemia resulting directly from insulin resistance (in the case of type 2 diabetes mellitus-T2DM), inadequate insulin secretion/production, or excessive glucagon secretion (in type 1 diabetes mellitus-T1DM) [...].

The spatial distribution of interleukin-4 (IL-4) reference values in China based on a back propagation (BP) neural network

This study aimed to investigate the geospatial distribution of normal reference values of Interleukin 4 (IL-4) in healthy Chinese adults and to provide a basis for the development of standard references. IL-4 values of 5,221 healthy adults from 64 cities in China were collected and analyzed for a potential correlation with 24 topographical, climatic and soil factors. Seven of these factors were extracted and used to build a back propagation (BP) neural network model that was used to predict IL-4 reference values in healthy individuals from 2,317 observation sites nationwide. The predicted values were tested for normality and geographic distribution by analytic Kriging interpolation to map the geographic distribution of IL-4 reference values in healthy Chinese subjects. The results showed that IL-4 values generally decreased and then increased from the South to the North. We concluded that the BP neural network model applies to this approach, where certain geographical factors determine levels of various biochemical and immunological standards in healthy adults in regions with different topography, climate and soil indices.

Antioxidant and anti-inflammatory properties of ginsenoside Rg1 for hyperglycemia in type 2 diabetes mellitus: systematic reviews and meta-analyses of animal studies

Background: According to existing laboratory data, ginsenoside Rg1 may help cure diabetes and its complications by reducing oxidative stress (OS) and managing inflammation. However, this conclusion lacks reliability and is unclear. As a result, the purpose of this systematic review and meta-analysis was to evaluate the antioxidant and anti-inflammatory effects of ginsenoside Rg1 in the treatment of diabetes and its complications. Methods: We searched for relevant studies published through December 2022, including electronic bibliographic databases such as PubMed, EMBASE, Web of Science, CNKI, and Wanfang. The SYstematic Review Center for Laboratory Animal Experimentation Risk of Bias (SYRCLE RoB) tool was used to conduct a meta-analysis to assess the methodological quality of animal research. The meta-analysis was conducted using RevMan5.4 software, following the Cochrane Handbook for Systematic Reviews of Interventions. This study is registered in the International Systems Review Prospective Registry (PROSPERO) as CRD42023386830. Results: Eighteen eligible studies involving 401 animals were included. Ginsenoside Rg1 was significantly correlated with blood glucose (BG), insulin levels, body weight, superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels. In addition, according to subgroup analysis, the hypoglycemic, anti-inflammatory, and antioxidant effects of ginsenoside Rg1 in type 2 diabetic animals were not affected by experimental species, modeling, experimental drug dosage, or course of treatment. Conclusion: This meta-analysis presents a summary of the hypoglycemic effects of ginsenoside Rg1, which are achieved through anti-inflammatory and antioxidant mechanisms. These findings provide evidence-based support for the medical efficacy of ginsenoside Rg1. Specifically, ginsenoside Rg1 reduced MDA levels and restored SOD activity to exert its antioxidant activity. It had a positive effect on the reduction of IL-6 and TNF-α levels. However, the inclusion of studies with low methodological quality and the presence of publication bias may undermine the validity of the results. Further investigation with a more rigorous experimental design and comprehensive studies is necessary to fully understand the specific glycemic mechanisms of ginsenosides. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/, identifier https://CRD42023386830.

Geranylgeranylacetone Ameliorates Skin Inflammation by Regulating and Inducing Thioredoxin via the Thioredoxin Redox System

Geranylgeranylacetone (GGA) exerts cytoprotective activity against various toxic stressors via the thioredoxin (TRX) redox system; however, its effect on skin inflammation and molecular mechanism on inducing the TRX of GGA is still unknown. We investigated the effects of GGA in a murine irritant contact dermatitis (ICD) model induced by croton oil. Both a topical application and oral administration of GGA induced TRX production and Nrf2 activation. GGA ameliorated ear swelling, neutrophil infiltration, and inhibited the expression of TNF-α, IL-1β, GM-CSF, and 8-OHdG. GGA's cytoprotective effect was stronger orally than topically in mice. In vitro studies also showed that GGA suppressed the expression of NLRP3, TNF-α, IL-1β, and GM-CSF and scavenged ROS in PAM212 cells after phorbol myristate acetate stimulation. Moreover, GGA induced endogenous TRX production and Nrf2 nuclear translocation in PAM212 cells (dependent on the presence of ROS) and activated the PI3K-Akt signaling pathway. GGA significantly downregulated thioredoxin-interacting protein (TXNIP) levels in PAM212 cells treated with or without Nrf2 siRNA. After knocking down Nrf2 in PAM212 cells, the effect of GGA on TRX induction was significantly inhibited. This suggests that GGA suppress ICD by inducing endogenous TRX, which may be regulated by PI3K/Akt/Nrf2 mediation of the TRX redox system.

The trigger for pancreatic disease: NLRP3 inflammasome

NLRP3 inflammasome is a multiprotein complex expressed in a variety of cells to stimulate the production of inflammatory factors. Activation of NLRP3 inflammasome depends on a complex regulatory mechanism, and its pro-inflammatory function plays an important role in pancreatic diseases. In this literature review, we summarize the activation mechanism of NLRP3 and analyze its role in each of the four typical pancreatic diseases. Through this article, we provide a relatively comprehensive summary to the researchers in this field, and provide some targeted therapy routes.

Physiopathological mechanisms related to inflammation in obesity and type 2 diabetes mellitus

Overweight, obesity, and type 2 diabetes mellitus pose global health problems that are ever-increasing. A chronic low-grade inflammatory status and the presence of various pro-inflammatory markers either in circulation or within dysfunctional metabolic tissues are well established. The presence of these factors can, to some extent, predict disease development and progression. A central role is played by the presence of dysfunctional adipose tissue, liver dysfunction, and skeletal muscle dysfunction, which collectively contribute to the increased circulatory levels of proinflammatory factors. Weight loss and classical metabolic interventions achieve a decrease in many of these factors’ circulating levels, implying that a better understanding of the processes or even the modulation of inflammation may alleviate these diseases. This review suggests that inflammation plays a significant role in the development and progression of these conditions and that measuring inflammatory markers may be useful for assessing disease risk and development of future treatment methods.

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

FALCON systematically interrogates free fatty acid biology and identifies a novel mediator of lipotoxicity

Cellular exposure to free fatty acids (FFAs) is implicated in the pathogenesis of obesity-associated diseases. However, there are no scalable approaches to comprehensively assess the diverse FFAs circulating in human plasma. Furthermore, assessing how FFA-mediated processes interact with genetic risk for disease remains elusive. Here, we report the design and implementation of fatty acid library for comprehensive ontologies (FALCON), an unbiased, scalable, and multimodal interrogation of 61 structurally diverse FFAs. We identified a subset of lipotoxic monounsaturated fatty acids associated with decreased membrane fluidity. Furthermore, we prioritized genes that reflect the combined effects of harmful FFA exposure and genetic risk for type 2 diabetes (T2D). We found that c-MAF-inducing protein (CMIP) protects cells from FFA exposure by modulating Akt signaling. In sum, FALCON empowers the study of fundamental FFA biology and offers an integrative approach to identify much needed targets for diverse diseases associated with disordered FFA metabolism.

Deficiency of WTAP in islet beta cells results in beta cell failure and diabetes in mice

AIMS/HYPOTHESIS

N⁶-methyladenosine (m⁶A) mRNA methylation and m⁶A-related proteins (methyltransferase-like 3 [METTL3], methyltransferase-like 14 [METTL14] and YTH domain containing 1 [YTHDC1]) have been shown to regulate islet beta cell function and the pathogenesis of diabetes. However, whether Wilms' tumour 1-associating protein (WTAP), a key regulator of the m⁶A RNA methyltransferase complex, regulates islet beta cell failure during pathogenesis of diabetes is largely unknown. The present study aimed to investigate the role of WTAP in the regulation of islet beta cell failure and diabetes.

METHODS

Islet beta cell-specific Wtap-knockout and beta cell-specific Mettl3-overexpressing mice were generated for this study. Blood glucose, glucose tolerance, serum insulin, glucose-stimulated insulin secretion (both in vivo and in vitro), insulin levels, glucagon levels and beta cell apoptosis were examined. RNA-seq and MeRIP-seq were performed, and the data were well analysed.

RESULTS

WTAP was downregulated in islet beta cells in type 2 diabetes, due to lipotoxicity and chronic inflammation, and islet beta cell-specific deletion of Wtap (Wtap-betaKO) induced beta cell failure and diabetes. Wtap-betaKO mice showed severe hyperglycaemia (above 20 mmol/l [360 mg/dl]) from 8 weeks of age onwards. Mechanistically, WTAP deficiency decreased m⁶A mRNA modification and reduced the expression of islet beta cell-specific transcription factors and insulin secretion-related genes by reducing METTL3 protein levels. Islet beta cell-specific overexpression of Mettl3 partially reversed the abnormalities observed in Wtap-betaKO mice.

CONCLUSIONS/INTERPRETATION

WTAP plays a key role in maintaining beta cell function by regulating m⁶A mRNA modification depending on METTL3, and the downregulation of WTAP leads to beta cell failure and diabetes.

DATA AVAILABILITY

The RNA-seq and MeRIP-seq datasets generated during the current study are available in the Gene Expression Omnibus database repository ( https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE215156 ; https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE215360 ).

Pericytes modulate islet immune cells and insulin secretion through Interleukin-33 production in mice

Introduction

Immune cells were recently shown to support β-cells and insulin secretion. However, little is known about how islet immune cells are regulated to maintain glucose homeostasis. Administration of various cytokines, including Interleukin-33 (IL-33), was shown to influence β-cell function. However, the role of endogenous, locally produced IL-33 in pancreatic function remains unknown. Here, we show that IL-33, produced by pancreatic pericytes, is required for glucose homeostasis.

Methods

To characterize pancreatic IL-33 production, we employed gene expression, flow cytometry, and immunofluorescence analyses. To define the role of this cytokine, we employed transgenic mouse systems to delete the Il33 gene selectively in pancreatic pericytes, in combination with the administration of recombinant IL-33. Glucose response was measured in vivo and in vitro, and morphometric and molecular analyses were used to measure β-cell mass and gene expression. Immune cells were analyzed by flow cytometry.

Resuts

Our results show that pericytes are the primary source of IL-33 in the pancreas. Mice lacking pericytic IL-33 were glucose intolerant due to impaired insulin secretion. Selective loss of pericytic IL-33 was further associated with reduced T and dendritic cell numbers in the islets and lower retinoic acid production by islet macrophages.

Discussion

Our study demonstrates the importance of local, pericytic IL-33 production for glucose regulation. Additionally, it proposes that pericytes regulate islet immune cells to support β-cell function in an IL-33-dependent manner. Our study reveals an intricate cellular network within the islet niche.

Long-term exercise preserves pancreatic islet structure and β-cell mass through attenuation of islet inflammation and fibrosis

Islet fibrosis is associated with the disruption of islet structure and contributes to β-cell dysfunction, playing an essential role in the pathogenesis of type 2 diabetes. Physical exercise has been shown to attenuate fibrosis in various organs; however, the effect of exercise on islet fibrosis has not been defined. Male Sprague-Dawley rats were divided into four groups: normal diet sedentary [N-Sed], normal diet + exercise [N-Ex], high-fat diet sedentary [H-Sed], and high-fat diet + exercise [H-Ex]. After 60 weeks of exercise, 4452 islets from Masson-stained slides were analyzed. Exercise led to a 68% and 45% reduction in islet fibrosis in the normal and high-fat diet groups and was correlated with a lower serum blood glucose. Fibrotic islets were characterized by irregular shapes and substantial loss of β-cell mass, which were significantly reduced in the exercise groups. Remarkably, the islets from exercised rats at week 60 were morphologically comparable to those of sedentary rats at 26 weeks. In addition, the protein and RNA levels of collagen and fibronectin, and the protein levels of hydroxyproline in the islets were also attenuated by exercise. This was accompanied by a significant reduction in inflammatory markers in the circulation Interleukin-1 beta (IL-1β)] and pancreas [IL-1β, Tumor Necrosis Factor-alpha, Transforming Growth Factor-β, and Phosphorylated Nuclear Factor Kappa-B p65 subunit], lower macrophage infiltration, and stellate cell activation in the islets of exercised rats. In conclusion, we have demonstrated that long-term exercise preserves pancreatic islet structure and β-cell mass through anti-inflammatory and anti-fibrotic actions, suggesting additional rationales for the success of exercise training in the prevention and treatment of type 2 diabetes that should be further explored.

FALCON systematically interrogates free fatty acid biology and identifies a novel mediator of lipotoxicity

Cellular exposure to free fatty acids (FFA) is implicated in the pathogenesis of obesity-associated diseases. However, studies to date have assumed that a few select FFAs are representative of broad structural categories, and there are no scalable approaches to comprehensively assess the biological processes induced by exposure to diverse FFAs circulating in human plasma. Furthermore, assessing how these FFA- mediated processes interact with genetic risk for disease remains elusive. Here we report the design and implementation of FALCON (Fatty Acid Library for Comprehensive ONtologies) as an unbiased, scalable and multimodal interrogation of 61 structurally diverse FFAs. We identified a subset of lipotoxic monounsaturated fatty acids (MUFAs) with a distinct lipidomic profile associated with decreased membrane fluidity. Furthermore, we developed a new approach to prioritize genes that reflect the combined effects of exposure to harmful FFAs and genetic risk for type 2 diabetes (T2D). Importantly, we found that c-MAF inducing protein (CMIP) protects cells from exposure to FFAs by modulating Akt signaling and we validated the role of CMIP in human pancreatic beta cells. In sum, FALCON empowers the study of fundamental FFA biology and offers an integrative approach to identify much needed targets for diverse diseases associated with disordered FFA metabolism.

Highlights

FALCON (Fatty Acid Library for Comprehensive ONtologies) enables multimodal profiling of 61 free fatty acids (FFAs) to reveal 5 FFA clusters with distinct biological effectsFALCON is applicable to many and diverse cell typesA subset of monounsaturated FAs (MUFAs) equally or more toxic than canonical lipotoxic saturated FAs (SFAs) leads to decreased membrane fluidityNew approach prioritizes genes that represent the combined effects of environmental (FFA) exposure and genetic risk for diseaseC-Maf inducing protein (CMIP) is identified as a suppressor of FFA-induced lipotoxicity via Akt-mediated signaling.

The crucial role and mechanism of insulin resistance in metabolic disease

Insulin resistance (IR) plays a crucial role in the development and progression of metabolism-related diseases such as diabetes, hypertension, tumors, and nonalcoholic fatty liver disease, and provides the basis for a common understanding of these chronic diseases. In this study, we provide a systematic review of the causes, mechanisms, and treatments of IR. The pathogenesis of IR depends on genetics, obesity, age, disease, and drug effects. Mechanistically, any factor leading to abnormalities in the insulin signaling pathway leads to the development of IR in the host, including insulin receptor abnormalities, disturbances in the internal environment (regarding inflammation, hypoxia, lipotoxicity, and immunity), metabolic function of the liver and organelles, and other abnormalities. The available therapeutic strategies for IR are mainly exercise and dietary habit improvement, and chemotherapy based on biguanides and glucagon-like peptide-1, and traditional Chinese medicine treatments (e.g., herbs and acupuncture) can also be helpful. Based on the current understanding of IR mechanisms, there are still some vacancies to follow up and consider, and there is also a need to define more precise biomarkers for different chronic diseases and lifestyle interventions, and to explore natural or synthetic drugs targeting IR treatment. This could enable the treatment of patients with multiple combined metabolic diseases, with the aim of treating the disease holistically to reduce healthcare expenditures and to improve the quality of life of patients to some extent.

Downregulation of the m6A reader protein YTHDC1 leads to islet β-cell failure and diabetes

N6-methyladenosine (m⁶A) methyltransferase writer proteins (METTL3/METTL14) have been shown to regulate β-cell function and diabetes. However, whether and which m⁶A reader proteins regulate β-cell function and the pathogenesis of diabetes are largely unknown. In this study, we showed that YTHDC1 (YTH domain-containing protein 1), a key m⁶A nuclear reader protein, plays an essential role in maintaining β-cell function. YTHDC1 is downregulated in islet β cells in type 2 diabetes, which is due to lipotoxicity and chronic inflammation. β-Cell specific deletion of Ythdc1 results in β-cell failure and diabetes, which is likely due to the decreased expression of β-cell specific transcription factors and insulin secretion-related genes. Taken together, YTHDC1 is required for maintaining β-cell function, and the downregulation of YTHDC1 leads to β-cell failure and diabetes.

UPLC-ESI-QTOF-MS Profiling of Phenolic Compounds from Eriocephalus africanus: In Vitro Antioxidant, Antidiabetic, and Anti-Inflammatory Potentials

The present study investigated phenolic compounds, antioxidant, antidiabetic, and the anti-inflammatory potentials of methanolic and chloroform extracts of Eriocephalus africanus. The methanolic extract included, polyphenols (112 ± 2.81 mg gallic acid equivalent (GAE)/g), flavonols (76.12 ± 7.95 mg quercetin equivalents (QE)/g); antioxidant capacity (Ferric Reducing Antioxidant Power (FRAP) (752.64 ± 89.0 μmol of ascorbic acid equivalents (AAE) per g dry weight (µmol AAE/g), 2,2-dyphenyl-1-picrylhydrazyl (DPPH) (812.18 ± 51.12 Trolox equivalents per gram of dry mass of plant extracts (μmol TE/g), TEAC (631.63 ± 17.42 µmol TE/g)), while the chloroform extract included polyphenols (39.93 ± 1.36 mg GAE/g), flavonols (44.81 ± 3.74 mg QE/g); antioxidant capacity, DPPH (58.70 ± 5.18 µmol TE/g), TEAC (118.63 ± 3.74 µmol TE/g) and FRAP (107.10 ± 2.41 µmol AAE/g). The phytochemicals profiling performed by UPLC-ESI-QTOF-MS revealed some important polyphenols, predominantly flavonoids, that could be responsible for the antioxidant capacity and biological effects. Both extracts demonstrated a dose-dependent manner of the alpha-glucosidase inhibition with an IC₅₀ between 125 and 250 μg/mL for methanolic extract, while the chloroform extract was at 250 μg/mL. In the L6 myoblasts and C3A hepatocytes, the methanolic extract slightly increased the utilization of glucose, and both extracts exhibited a dose-dependent increase in the glucose uptake in both cell types without significantly increasing the cytotoxicity. Furthermore, both extracts exhibited an anti-inflammatory potential and the findings from the present study could serve as a baseline for further research in the development of pharmaceutical agents.

Identification of Selective BRD9 Inhibitor via Integrated Computational Approach

Bromodomain-containing protein 9 (BRD9), a member of the bromodomain and extra terminal domain (BET) protein family, works as an epigenetic reader. BRD9 has been considered an essential drug target for cancer, inflammatory diseases, and metabolic disorders. Due to its high similarity among other isoforms, no effective treatment of BRD9-associated disorders is available. For the first time, we performed a detailed comparative analysis among BRD9, BRD7, and BRD4. The results indicate that residues His42, Gly43, Ala46, Ala54, Val105, and Leu109 can confer the BRD9 isoform selectivity. The predicted crucial residues were further studied. The pharmacophore model's features were precisely mapped with some key residues including, Gly43, Phe44, Phe45, Asn100, and Tyr106, all of which play a crucial role in BRD9 inhibition. Docking-based virtual screening was utilized with the consideration of the conserved water network in the binding cavity to identify the potential inhibitors of BRD9. In this workflow, 714 compounds were shortlisted. To attain selectivity, 109 compounds were re-docked to BRD7 for negative selection. Finally, four compounds were selected for molecular dynamics studies. Our studies pave the way for the identification of new compounds and their role in causing noticeable, functional differences in isoforms and between orthologues.

Approaches to Peripheral Artery Disease in Diabetes: Are There Any Differences?

Peripheral artery disease (PAD) increases the risk of diabetes, while diabetes increases the risk of PAD, and certain symptoms in each disease increase the risk of contracting the other. This review aims to shed light on this harmful interplay between the two disorders, with an emphasis on the phenotype of a patient with both diabetes and PAD, and whether treatment should be individualized in this high-risk population. In addition, current guideline recommendations for the treatment of PAD were analyzed, in an attempt to establish the differences and evidence gaps across a population suffering from these two interconnected disorders.

The Effects of Persimmon (Diospyros kaki L.f.) Oligosaccharides on Features of the Metabolic Syndrome in Zebrafish

Metabolic syndrome has become a global health care problem since it is rapidly increasing worldwide. The search for alternative natural supplements may have potential benefits for obesity and diabetes patients. Diospyros kaki fruit extract and its oligosaccharides, including gentiobiose, melibiose, and raffinose, were examined for their anti-insulin resistance and obesity-preventing effect in zebrafish larvae. The results show that D. kaki oligosaccharides improved insulin resistance and high-fat-diet-induced obesity in zebrafish larvae, evidenced by enhanced β-cell recovery, decreased abdominal size, and reduced the lipid accumulation. The mechanism of the oligosaccharides, molecular docking, and enzyme activities of PTP1B were investigated. Three of the oligosaccharides had a binding interaction with the catalytic active sites of PTP1B, but did not show inhibitory effects in an enzyme assay. The catalytic residues of PTP1B were typically conserved and the cellular penetration of the cell membrane was necessary for the inhibitors. The results of the mechanism of action study indicate that D. kaki fruit extract and its oligosaccharides affected gene expression changes in inflammation- (TNF-α, IL-6, and IL-1β), lipogenesis- (SREBF1 and FASN), and lipid-lowering (CPT1A)-related genes. Therefore, D. kaki fruit extract and its oligosaccharides may have a great potential for applications in metabolic syndrome drug development and dietary supplements.

Kynurenine-3-monooxygenase expression is activated in the pancreatic endocrine cells by diabetes and its blockade improves glucose-stimulated insulin secretion

Type 2 diabetes is associated with an inflammatory phenotype in the pancreatic islets. We previously demonstrated that proinflammatory cytokines potently activate the tryptophan/kynurenine pathway (TKP) in INS-1 cells and in normal rat islets. Here we examined: (1) the TKP enzymes expression in the diabetic GK islets; (2) the TKP enzymes expression profiles in the GK islets before and after the onset of diabetes; (3) The glucose-stimulated insulin secretion (GSIS) in vitro in GK islets after KMO knockdown using specific morpholino-oligonucleotides against KMO or KMO blockade using the specific inhibitor Ro618048; (4) The glucose tolerance and GSIS after acute in vivo exposure to Ro618048 in GK rats. We report a remarkable induction of the kmo gene in GK islets and in human islets exposed to proinflammatory conditions. It occurred prominently in beta cells. The increased expression and activity of KMO reflected an acquired adaptation. Both KMO knockdown and specific inhibitor Ro618048 enhanced GSIS in vitro in GK islets. Moreover, acute administration of Ro618048 in vivo improved glucose tolerance, GSIS and basal blood glucose levels in GK rats. These results demonstrate that targeting islet TKP is able to correct defective GSIS. KMO inhibition could represent a potential therapeutic strategy for type 2 diabetes.

Lipoxins reduce obesity-induced adipose tissue inflammation in 3D-cultured human adipocytes and explant cultures

Adipose tissue inflammation drives obesity-related cardiometabolic diseases. Enhancing endogenous resolution mechanisms through administration of lipoxin A4, a specialized pro-resolving lipid mediator, was shown to reduce adipose inflammation and subsequently protects against obesity-induced systemic disease in mice. Here, we demonstrate that lipoxins reduce inflammation in 3D-cultured human adipocytes and adipose tissue explants from obese patients. Approximately 50% of patients responded particularly well to lipoxins by reducing inflammatory cytokines and promoting an anti-inflammatory M2 macrophage phenotype. Responding patients were characterized by elevated systemic levels of C-reactive protein, which causes inflammation in cultured human adipocytes. Responders appeared more prone to producing anti-inflammatory oxylipins and displayed elevated prostaglandin D2 levels, which has been interlinked with transcription of lipoxin-generating enzymes. Using explant cultures, this study provides the first proof-of-concept evidence supporting the therapeutic potential of lipoxins in reducing human adipose tissue inflammation. Our data further indicate that lipoxin treatment may require a tailored personalized-medicine approach.

Epigenetic Reprogramming of the Inflammatory Response in Obesity and Type 2 Diabetes

For the past several decades, the prevalence of obesity and type 2 diabetes (T2D) has continued to rise on a global level. The risk contributing to this pandemic implicates both genetic and environmental factors, which are functionally integrated by epigenetic mechanisms. While these conditions are accompanied by major abnormalities in fuel metabolism, evidence indicates that altered immune cell functions also play an important role in shaping of obesity and T2D phenotypes. Interestingly, these events have been shown to be determined by epigenetic mechanisms. Consistently, recent epigenome-wide association studies have demonstrated that immune cells from obese and T2D individuals feature specific epigenetic profiles when compared to those from healthy subjects. In this work, we have reviewed recent literature reporting epigenetic changes affecting the immune cell phenotype and function in obesity and T2D. We will further discuss therapeutic strategies targeting epigenetic marks for treating obesity and T2D-associated inflammation.

Glyoxalase 1 knockdown induces age-related β-cell dysfunction and glucose intolerance in mice

Tight control of glycemia is a major treatment goal for type 2 diabetes mellitus (T2DM). Clinical studies indicated that factors other than poor glycemic control may be important in fostering T2DM progression. Increased levels of methylglyoxal (MGO) associate with complications development, but its role in the early steps of T2DM pathogenesis has not been defined. Here, we show that MGO accumulation induces an age-dependent impairment of glucose tolerance and glucose-stimulated insulin secretion in mice knockdown for glyoxalase 1 (Glo1KD). This metabolic alteration associates with the presence of insular inflammatory infiltration (F4/80-positive staining), the islet expression of senescence markers, and higher levels of cytokines (MCP-1 and TNF-α), part of the senescence-activated secretory profile, in the pancreas from 10-month-old Glo1KD mice, compared with their WT littermates. In vitro exposure of INS832/13 β-cells to MGO confirms its casual role on β-cell dysfunction, which can be reverted by senolytic treatment. These data indicate that MGO is capable to induce early phenotypes typical of T2D progression, paving the way for novel prevention approaches to T2DM.

Dihydromyricetin-Encapsulated Liposomes Inhibit Exhaustive Exercise-Induced Liver Inflammation by Orchestrating M1/M2 Macrophage Polarization

Exhaustive exercise (EE) induced hepatic inflammatory injury has been well reported. Dihydromyricetin (DHM) has shown anti-inflammatory bioactivity and hepatoprotective effects but is limited by poor bioavailability. Here, high-bioavailability DHM-encapsulated liposomes were synthesized and explored for their therapeutic potential and regulatory mechanisms in a hepatic inflammatory injury model. The animal model was established by swimming-to-exhaustive exercise in C57BL/6 mice, and the anti-inflammatory effects were detected after administration of DHM or DHM liposome. NIR fluorescence imaging was used to assess the potential of liver targeting. The DHM liposome-induced macrophage polarization was measured by flow cytometry ex vivo. The anti-inflammatory mechanism of DHM was studied in cell line RAW264.7 in vitro. Liposome encapsulation enhanced DHM bioavailability, and DHM liposome could alleviate liver inflammation more effectively. Moreover, DHM liposome targeted hepatic macrophages and polarized macrophages into an anti-inflammatory phenotype. The SIRT3/HIF-1α signaling pathway could be the major mechanism of DHM motivated macrophage polarization. Our study indicates that DHM liposomes can alleviate liver inflammation induced by EE through sustained releasing and hepatic targeting. It is a promising option to achieve the high bioavailability of DHM. Also, this study provides new insights into the regional immune effect of DHM against inflammation.

Manno-oligosaccharides from cassia seed gum ameliorate inflammation and improve glucose metabolism in diabetic rats

Functional oligosaccharides show anti-diabetic effects through inflammation regulation with improved glucose metabolism. In this study, novel prebiotics of manno-oligosaccharides from cassia seed gum (CMOS) were incorporated into the diet of streptozotocin (STZ) plus high-fat and high-sugar diet (HFSD)-induced rats. After feeding for 8 weeks, CMOS (300-1200 mg per kg b.w. per d) significantly ameliorated the fasting blood glucose level (7.1-8.2 mmol L^-1) as compared with that of the model group (14.2 mmol L^-1), where the area under the oral glucose tolerance test curve was decreased by 20.0%-24.5%. Meanwhile, CMOS prevented STZ plus HFSD-induced damage to islet tissue with a clear and integrated morphology and reduced the glucagon/insulin area ratio (by 97.9% for 300 mg per kg b.w. per d CMOS). CMOS also reduced metabolic endotoxemia and maintained intestinal integrity with recovered mRNA expression of Zo-1 and occludin to the normal comparable level. Upon 16S rDNA sequencing, it was found that CMOS regulated the microbiota composition in the cecum with an increased relative abundance of Bifidobacteria, while that of Shigella was decreased. The molecular mechanisms involved in the anti-diabetic effects of CMOS were further studied. CMOS reduced the mRNA expression of Tlr2 and Tlr4 in the intestines of STZ plus HFSD-induced rats. Meanwhile, Nlrp3 associated inflammasome activation in the intestine and liver with glucose metabolism disorder was inhibited by CMOS, resulting in reduced interleukin-1β secretion (by 38.8-46.4% for CMOS of 300-1200 mg per kg b.w. per d) and inflammation. Furthermore, CMOS regulated the AKT/IRS/AMPK signaling pathway and improved glucose metabolism in the liver. Findings obtained here implicated that CMOS could modulate metabolic-inflammation as a functional dietary supplement.

Inhibitory Effects of Polyphenols-Rich Components From Three Edible Seaweeds on Inflammation and Colon Cancer in vitro

Polyphenols from edible seaweeds display various health benefits which have not been adequately studied. This study aimed to characterize the composition of extractable polyphenol-rich components (EPCs) and non-extractable polyphenol-rich components (NEPCs) from three edible seaweeds (i.e., Laminaria japonica, Ulva lactuca, and Porphyra tenera) and evaluate their anti-inflammatory capacities in activated macrophages and anticancer properties in colon cancer cells. Both EPCs and NEPCs from three edible seaweeds against lipopolysaccharides (LPS) stimulated nitric oxide in activated macrophages. Immunoblotting and qRT-PCR indicated that EPCs and NEPCs regulated the expression levels of proinflammatory enzymes, proinflammatory cytokines, and antioxidant enzymes in macrophages. Furthermore, EPCs and NEPCs lowered the viability of colon cancer cells, while normal colon cells were not affected. Additionally, EPCs and NEPCs induced cellular apoptosis and led to G0/G1 cell cycle arrest in HCT116 cells. Overall, these results provide a rationale for future animal and human studies designed to examine the anti-inflammatory and chemopreventive capacities of polyphenols-rich components from L. japonica, U. lactuca, and P. tenera.

NF-κB-inducing kinase (NIK) is activated in pancreatic β-cells but does not contribute to the development of diabetes

The transcription factor nuclear factor-κB (NF-κB) has a key role in the pathogenesis of diabetes and its complications. Although activation of the canonical NF-κB pathway in β-cells is generally deleterious, little is known about the role of the non-canonical NF-κB signalling and its main regulator, the NF-κB-inducing kinase (NIK), on pancreatic β-cell survival and function. Previous studies based on models of NIK overexpression in pancreatic islet cells showed that NIK induced either spontaneous β-cell death due to islet inflammation or glucose intolerance during diet-induced obesity (DIO) in mice. Therefore, NIK has been proposed as a potential target for diabetes therapy. However, no clear studies showed whether inhibition of NIK improves diabetes development. Here we show that genetic silencing of NIK in pancreatic β-cells neither modifies diabetes incidence nor inflammatory responses in a mouse model of immune-mediated diabetes. Moreover, NIK silencing in DIO mice did not influence body weight gain, nor glucose metabolism. In vitro studies corroborated the in vivo findings in terms of β-cell survival, function, and downstream gene regulation. Taken together, our data suggest that NIK activation is dispensable for the development of diabetes.

The glucose-lowering effect of low-dose diacerein and its responsiveness metabolic markers in uncontrolled diabetes

Objective

Diacerein inhibits the synthesis and activity of pro-inflammatory cytokines, decreases macrophage infiltration in adipose tissue and thus increases insulin sensitivity and signalling. We conducted this study to determine the efficacy of low-dose diacerein in improving glycaemic control in type 2 diabetes mellitus (T2DM) patients with inadequate glycaemic control and to identify the metabolic determinants for such improvement. We randomised 25 T2DM patients with poor glycaemic control, despite being treated with at least three glucose-lowering agents, to receive diacerein 50 mg once-daily (n = 18) or placebo (n = 17) for 12 weeks. Changes in glycated haemoglobin (HbA1c) were evaluated at the 4th and 12th weeks. Metabolic profiling was performed using liquid chromatography electrospray ionisation quadrupole time-of-flight mass spectrometry.

Results

HbA1c levels were significantly reduced from baseline in the diacerein group at 12 weeks (− 0.6%, p < 0.05), whereas fasting plasma glucose (FPG) levels were not significantly decreased (− 18.9 mg/dl, p = 0.06). Partial least squares-discriminant analysis demonstrated an association between the serum abundance of threo-isocitric acid (ICA) and HbA1c response in the diacerein group. After adjusting for serum high-sensitivity C-reactive protein, ICA was still significantly related to the change in HbA1c.

Retrospective trial registration Current Controlled Trials TCTR20200820004, 20 August 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05974-9.

Targeting Protein O-GlcNAcylation, a Link between Type 2 Diabetes Mellitus and Inflammatory Disease

Unresolved hyperglycaemia, a hallmark of type 2 diabetes mellitus (T2DM), is a well characterised manifestation of altered fuel homeostasis and our understanding of its role in the pathologic activation of the inflammatory system continues to grow. Metabolic disorders like T2DM trigger changes in the regulation of key cellular processes such as cell trafficking and proliferation, and manifest as chronic inflammatory disorders with severe long-term consequences. Activation of inflammatory pathways has recently emerged as a critical link between T2DM and inflammation. A substantial body of evidence has suggested that this is due in part to increased flux through the hexosamine biosynthetic pathway (HBP). The HBP, a unique nutrient-sensing metabolic pathway, produces the activated amino sugar UDP-GlcNAc which is a critical substrate for protein O-GlcNAcylation, a dynamic, reversible post-translational glycosylation of serine and threonine residues in target proteins. Protein O-GlcNAcylation impacts a range of cellular processes, including inflammation, metabolism, trafficking, and cytoskeletal organisation. As increased HBP flux culminates in increased protein O-GlcNAcylation, we propose that targeting O-GlcNAcylation may be a viable therapeutic strategy for the prevention and management of glucose-dependent pathologies with inflammatory components.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

Interorgan crosstalk in pancreatic islet function and pathology

Pancreatic β cells secrete insulin in response to glucose, a process that is regulated at multiple levels, including a network of input signals from other organ systems. Impaired islet function contributes to the pathogenesis of type 2 diabetes mellitus (T2DM), and targeting inter-organ communications, such as GLP-1 signalling, to enhance β-cell function has been proven to be a successful therapeutic strategy in the last decade. In this review, we will discuss recent advances in inter-organ communication from the metabolic, immune and neural system to pancreatic islets, their biological implication in normal pancreas endocrine function and their role in the (mal)adaptive responses of islet to nutrition-induced stress.

RHEUMATOID ARTHRITIS AS A PREDISPOSING FACTOR FOR INCREASED RISK OF DIABETES MELLITUS INCIDENCE

OBJECTIVE

The aim: Recent advances in diabetic mellitus (DM) care are focusing emphasis on comorbidities including rheumatoid arthritis (RA). The goal of this study is to determine the relationship between RA and diabetes as a risk factor.

PATIENTS AND METHODS

Materials and methods: Participants whose diagnosis of RA was confirmed by rheumatologists were recruited into a cross-sectional observational cohort using data from government and private clinics. Participants filled out detailed questionnaires. We included patients with DM and combined DM and RA who was diagnosed with both conditions by specialists between (October 2021 to April 2022) in Al Kut city, Iraq.

RESULTS

Results: Our finding shows no difference between the two groups DM and DM+RA in age, BMI, and smoking. However, the health status represented by hospitalization was more frequent in the DM+RA group. The inflammatory pathway in RA also increases the incidence of DM where we show an increase in the ESR in the DM+RA group. Interestingly Glycated hemoglobin (Hb a1c) indicator of DM was significantly increased in DM+RA compared to the DM group.

CONCLUSION

Conclusions: In conclusion, RA is linked to an increased chance of developing diabetes. This data backs up the theory that inflammatory pathways play a role in diabetes development.

Lipid-Induced Adaptations of the Pancreatic Beta-Cell to Glucotoxic Conditions Sustain Insulin Secretion

Over the last decades, lipotoxicity and glucotoxicity emerged as established mechanisms participating in the pathophysiology of obesity-related type 2 diabetes in general, and in the loss of β-cell function in particular. However, these terms hold various potential biological processes, and it is not clear what precisely they refer to and to what extent they might be clinically relevant. In this review, we discuss the basis and the last advances of research regarding the role of free fatty acids, their metabolic intracellular pathways, and receptor-mediated signaling related to glucose-stimulated insulin secretion, as well as lipid-induced β-cell dysfunction. We also describe the role of chronically elevated glucose, namely, glucotoxicity, which promotes failure and dedifferentiation of the β cell. Glucolipotoxicity combines deleterious effects of exposures to both high glucose and free fatty acids, supposedly provoking synergistic defects on the β cell. Nevertheless, recent studies have highlighted the glycerolipid/free fatty acid cycle as a protective pathway mediating active storage and recruitment of lipids. Finally, we discuss the putative correspondence of the loss of functional β cells in type 2 diabetes with a natural, although accelerated, aging process.

Terminalia catappa Extract Palliates Redox Imbalance and Inflammation in Diabetic Rats by Upregulating Nrf-2 Gene

This study aims at evaluating the ameliorative role of Terminalia catappa aqueous leaf extract (TCA) on hyperglycaemia-induced oxidative stress and inflammation in a high-fat, low dose streptozotocin-induced type 2 diabetic rat model. Experimental rats were treated orally with 400 and 800 mg/kg bw TCA daily for four weeks. Antioxidant enzyme activities, plasma glucose concentration, protein concentration, oxidative stress, and inflammation biomarkers were assayed using standard methods. Hepatic relative expressions of tumour necrosis factor-alpha (TNF-α), interleukin-six (IL-6), and nuclear factor-erythroid 2 related factor 2 (Nrf-2) were also assessed. Molecular docking and prediction of major TCA phytoconstituents' biological activity related to T2DM-induced oxidative stress were evaluated in silico. Induction of diabetes significantly (p < 0.05) reduced superoxide dismutase, glutathione-S-transferase, and peroxidase activities. Glutathione and protein stores were significantly (p < 0.05) depleted, while glucose, MDA, interleukin-six (IL-6), and tumour necrosis factor-α (TNF-α) concentrations were significantly (p < 0.05) increased. A significant (p < 0.05) upregulation of hepatic TNF-α and IL-6 expression and downregulation (p < 0.05) of Nrf-2 expression were observed during diabetes onset. TCA treatment significantly (p < 0.05) modulated systemic diabetic-induced oxidative stress and inflammation, mRNA expression dysregulation, and dysregulated macromolecule metabolism. However, only 800 mg/kg TCA treatment significantly (p < 0.05) downregulated hepatic TNF-α expression. 9-Oxabicyclo[3.3.1]nonane-2,6-diol and 1,2,3-Benzenetriol bound comparably to glibenclamide in Nrf-2, IL-6, and TNF-α binding pockets. They were predicted to be GST A and M substrate, JAK2 expression, ribulose-phosphate 3-epimerase, NADPH peroxidase, and glucose oxidase inhibitors. These results suggest that TCA ameliorates hyperglycaemia-induced oxidative stress and inflammation by activating Nrf-2 gene.

An Overview of Glycosylation and its Impact on Cardiovascular Health and Disease

The cardiovascular system is a complex and well-organized system in which glycosylation plays a vital role. The heart and vascular wall cells are constituted by an array of specific receptors; most of them are N- glycosylated and mucin-type O-glycosylated. There are also intracellular signaling pathways regulated by different post-translational modifications, including O-GlcNAcylation, which promote adequate responses to extracellular stimuli and signaling transduction. Herein, we provide an overview of N-glycosylation and O-glycosylation, including O-GlcNAcylation, and their role at different levels such as reception of signal, signal transduction, and exogenous molecules or agonists, which stimulate the heart and vascular wall cells with effects in different conditions, like the physiological status, ischemia/reperfusion, exercise, or during low-grade inflammation in diabetes and aging. Furthermore, mutations of glycosyltransferases and receptors are associated with development of cardiovascular diseases. The knowledge on glycosylation and its effects could be considered biochemical markers and might be useful as a therapeutic tool to control cardiovascular diseases.

NOX1 mediates metabolic heart disease in mice and is upregulated in monocytes of humans with diastolic dysfunction

AIMS

Microvascular inflammation plays an important role in the pathogenesis of diastolic dysfunction (DD) and metabolic heart disease. NOX1 is expressed in vascular and immune cells and has been implicated in the vascular pathology of metabolic disease. However, its contribution to metabolic heart disease is less understood.

METHODS AND RESULTS

NOX1-deficient mice (KO) and male wild-type (WT) littermates were fed a high-fat high-sucrose diet (HFHS) and injected streptozotocin (75 mg/kg i.p.) or control diet (CTD) and sodium citrate. Despite similar weight gain and increase in fasting blood glucose and insulin, only WT-HFHS but not KO-HFHS mice developed concentric cardiac hypertrophy and elevated left ventricular filling pressure. This was associated with increased endothelial adhesion molecule expression, accumulation of Mac-2-, IL-1β- and NLRP3-positive cells and nitrosative stress in WT-HFHS but not KO-HFHS hearts. Nox1 mRNA was solidly expressed in CD45+ immune cells isolated from healthy mouse hearts, but was negligible in cardiac CD31+ endothelial cells. However, in vitro, Nox1 expression increased in response to LPS in endothelial cells and contributed to LPS-induced upregulation of Icam-1. Nox1 was also upregulated in mouse bone marrow-derived macrophages in response to LPS. In peripheral monocytes from age- and sex-matched symptomatic patients with and without DD, NOX1 was significantly higher in patients with DD compared to those without DD.

CONCLUSIONS

NOX1 mediates endothelial activation and contributes to myocardial inflammation and remodeling in metabolic disease in mice. Given its high expression in monocytes of humans with DD, NOX1 may represent a potential target to mitigate heart disease associated with DD.

TRANSLATIONAL PERSPECTIVE

In their multifactorial pathogenesis, diastolic dysfunction (DD) and heart failure with preserved ejection fraction (HFpEF) still remain poorly understood. They frequently occur in patients with obesity and metabolic syndrome. Microvascular inflammation and dysfunction have recently been recognized as major driving forces. We show that genetic deletion of Nox1 prevents cardiac inflammation, remodeling and dysfunction in metabolic disease in mice and find NOX1 upregulated in peripheral monocytes of patients with DD. These findings add to our understanding how obesity, inflammation and heart disease are linked, which is a prerequisite to find therapeutic strategies beyond the control of co-morbidities in HFpEF.

Impact of Bariatric Surgery on Adipose Tissue Biology

Bariatric surgery (BS) procedures are actually the most effective intervention to help subjects with severe obesity achieve significant and sustained weight loss. White adipose tissue (WAT) is increasingly recognized as the largest endocrine organ. Unhealthy WAT expansion through adipocyte hypertrophy has pleiotropic effects on adipocyte function and promotes obesity-associated metabolic complications. WAT dysfunction in obesity encompasses an altered adipokine secretome, unresolved inflammation, dysregulated autophagy, inappropriate extracellular matrix remodeling and insufficient angiogenic potential. In the last 10 years, accumulating evidence suggests that BS can improve the WAT function beyond reducing the fat depot sizes. The causal relationships between improved WAT function and the health benefits of BS merits further investigation. This review summarizes the current knowledge on the short-, medium- and long-term outcomes of BS on the WAT composition and function.

Glucose metabolism and pyruvate carboxylase enhance glutathione synthesis and restrict oxidative stress in pancreatic islets

Glucose metabolism modulates the islet β cell responses to diabetogenic stress, including inflammation. Here, we probed the metabolic mechanisms that underlie the protective effect of glucose in inflammation by interrogating the metabolite profiles of primary islets from human donors and identified de novo glutathione synthesis as a prominent glucose-driven pro-survival pathway. We find that pyruvate carboxylase is required for glutathione synthesis in islets and promotes their antioxidant capacity to counter inflammation and nitrosative stress. Loss- and gain-of-function studies indicate that pyruvate carboxylase is necessary and sufficient to mediate the metabolic input from glucose into glutathione synthesis and the oxidative stress response. Altered redox metabolism and cellular capacity to replenish glutathione pools are relevant in multiple pathologies beyond obesity and diabetes. Our findings reveal a direct interplay between glucose metabolism and glutathione biosynthesis via pyruvate carboxylase. This metabolic axis may also have implications in other settings where sustaining glutathione is essential.

Anti-inflammatory activities of the mixture of strawberry and rice powder as materials of fermented rice cake on RAW264.7 macrophage cells and mouse models

Rice cake is a traditional food in Korea, and is made by rice alone, or with other grain powder. To improve the health benefits of fermented rice cake, the rice powder was supplemented with strawberry powder. Anti-inflammatory activities of the mixture of strawberry and rice powder were evaluated. Treatment with the mixture significantly decreased the production of nitric oxide (NO). The mixture of strawberry and rice powder in the ratio 10: 90 effectively and dose-dependently reduced the immune-associated genes iNOS, IL-1β, IL-6, COX-2, and TNF-α. Furthermore, carrageenan-injected mice were used to study the anti-inflammatory effect of the mixture. Pre-oral administration of the mixture of strawberry and rice powder at doses of 50 and 100 mg/kg BW significantly reduced paw edema induced by carrageenan. These results suggest that for fermented rice cake production and processing, the strawberry and rice powder mixture may be a potential source of anti-inflammatory activity.

Fetuin-A secretion from β-cells leads to accumulation of macrophages in islets, aggravates inflammation and impairs insulin secretion

Elevated fetuin-A levels, chemokines and islet-resident macrophages are crucial factors associated with obesity-mediated type 2 diabetes (T2D). Here, the aim of the study was to investigate the effect of MIN6 (a mouse insulinoma cell line)-derived fetuin-A (also known as AHSG) in macrophage polarization and decipher the effect of M1 type pro-inflammatory macrophages in commanding over insulin secretion. MIN6 and islet-derived fetuin-A induced expression of the M1 type macrophage markers Emr1 (also known as Adgre1), Cd68 and CD11c (Itgax) (∼1.8 fold) along with increased cytokine secretion. Interestingly, suppression of fetuin-A in MIN6 successfully reduced M1 markers by ∼1.5 fold. MIN6-derived fetuin-A also induced chemotaxis of macrophages in a Boyden chamber chemotaxis assay. Furthermore, high-fat feeding in mice showed elevated cytokine and fetuin-A content in serum and islets, and also migration and polarization of macrophages to the islets, while β-cells failed to meet the increased insulin demand. Moreover, in MIN6 culture, M1 macrophages sharply decreased insulin secretion by ∼2.8 fold. Altogether our results support an association of fetuin-A with islet inflammation and β-cell dysfunction, owing to its role as a key chemoattractant and macrophage polarizing factor.

Chemical inducer of regucalcin attenuates lipopolysaccharide-induced inflammatory responses in pancreatic MIN6 β-cells and RAW264.7 macrophages

We previously isolated derrisfolin A, a novel rotenoid derivative, from the stems of Derris  trifoliata Lour. (Leguminosae). Here, we report that derrisfolin A induces the expression of endogenous regucalcin (RGN) protein in both pancreatic MIN6 β‐cells and RAW264.7 macrophages. Induction of RGN expression by derrisfolin A or retrovirus‐mediated gene transfer in MIN6 cells and RAW264.7 macrophages significantly decreased lipopolysaccharide (LPS)‐induced mRNA expression of Nos2, Il1b, and Tnf via nuclear factor‐κB activation; reduced LPS‐induced apoptosis in MIN6 cells, accompanied by decreased production of nitric oxide, interleukin‐1β, and tumor necrosis factor‐α; and attenuated generation of LPS‐induced reactive oxygen species, malondialdehyde, and 3‐nitrotyrosine in MIN6 cells. Additionally, in co‐cultures of MIN6 cells with RAW264.7 macrophages in the presence of LPS, induction of RGN expression by derrisfolin A or retrovirus‐mediated gene transfer in RAW264.7 macrophages attenuated apoptosis and oxidative/nitrosative stress in MIN6 cells. These results suggest that the induction of RGN expression in MIN6 cells was effective in suppressing LPS‐induced inflammatory cytotoxicity and that in co‐culture conditions, the induction of RGN expression in RAW264.7 macrophages blocked LPS‐induced paracrine effects of RAW264.7 macrophages on inflammatory cytotoxicity in MIN6 cells. Our findings suggest that derrisfolin A, a chemical inducer of RGN, might be useful for developing a new drug against macrophage‐associated β‐cell inflammation in type 2 diabetes.

Butyrate Protects Pancreatic Beta Cells from Cytokine-Induced Dysfunction

Pancreatic beta cell dysfunction caused by metabolic and inflammatory stress contributes to the development of type 2 diabetes (T2D). Butyrate, produced by the gut microbiota, has shown beneficial effects on glucose metabolism in animals and humans and may directly affect beta cell function, but the mechanisms are poorly described. The aim of this study was to investigate the effect of butyrate on cytokine-induced beta cell dysfunction in vitro. Mouse islets, rat INS-1E, and human EndoC-βH1 beta cells were exposed long-term to non-cytotoxic concentrations of cytokines and/or butyrate to resemble the slow onset of inflammation in T2D. Beta cell function was assessed by glucose-stimulated insulin secretion (GSIS), gene expression by qPCR and RNA-sequencing, and proliferation by incorporation of EdU into newly synthesized DNA. Butyrate protected beta cells from cytokine-induced impairment of GSIS and insulin content in the three beta cell models. Beta cell proliferation was reduced by both cytokines and butyrate. Expressions of the beta cell specific genes Ins, MafA, and Ucn3 reduced by the cytokine IL-1β were not affected by butyrate. In contrast, butyrate upregulated the expression of secretion/transport-related genes and downregulated inflammatory genes induced by IL-1β in mouse islets. In summary, butyrate prevents pro-inflammatory cytokine-induced beta cell dysfunction.