Type 2 diabetes-a matter of beta-cell life and death?

Waist-to-hip ratio better reflect beta-cell function and predicts diabetes risk in adult with overweight or obesity

OBJECTIVE

Controversy remains as to which obesity measures better predict type 2 diabetes (T2D) risk in overweight or obese individuals. The objective of this study is to determine which commonly used obesity measures better reflect beta cell function and predict T2D risk in participants with overweight or obesity and to validate the findings using prospective cohort data.

PATIENTS AND METHODS

Cross-sectional data from the Obesity Clinic of the Xiangya Hospital of the Central South University and prospective cohort from UK Biobank. BMI, waist circumference (WC), waist-to-hip ratio (WHpR), and waist-to-height ratio (WHtR) were measured. Primary outcomes included beta cell function indices in the cross-sectional study and the occurrence of diabetes obtained from UK Biobank data.

RESULTS

One thousand four hundred and ninety-seven participants with overweight or obesity (median age 29 years, 41% males) and 322,023 UK Biobank participants without diabetes at baseline (mean age 56.83 years, 50.4% males) were studied. WHpR had a stronger association with beta cell function and central body fat distribution than the other three obesity measures irrespective of glucometabolic states. WHpR associated positively with diabetes risk in participants using the hazard ratio scale (HR per SD increase of WHpR, 2.311, 95% CI 2.250-2.374).

CONCLUSIONS

WHpR is a superior index in reflecting central body obesity, estimating beta cell function, and predicting T2D risk in people with overweight or obesity compared to BMI, WC, and WHtR.

Disordered regions in the IRE1α ER lumenal domain mediate its stress-induced clustering

Conserved signaling cascades monitor protein-folding homeostasis to ensure proper cellular function. One of the evolutionary conserved key players is IRE1, which maintains endoplasmic reticulum (ER) homeostasis through the unfolded protein response (UPR). Upon accumulation of misfolded proteins in the ER, IRE1 forms clusters on the ER membrane to initiate UPR signaling. What regulates IRE1 cluster formation is not fully understood. Here, we show that the ER lumenal domain (LD) of human IRE1α forms biomolecular condensates in vitro. IRE1α LD condensates were stabilized both by binding to unfolded polypeptides as well as by tethering to model membranes, suggesting their role in assembling IRE1α into signaling-competent stable clusters. Molecular dynamics simulations indicated that weak multivalent interactions drive IRE1α LD clustering. Mutagenesis experiments identified disordered regions in IRE1α LD to control its clustering in vitro and in cells. Importantly, dysregulated clustering of IRE1α mutants led to defects in IRE1α signaling. Our results revealed that disordered regions in IRE1α LD control its clustering and suggest their role as a common strategy in regulating protein assembly on membranes.

Implications of endoplasmic reticulum stress and beta-cell loss in immunodeficient diabetic NRG-Akita mice for understanding monogenic diabetes

BACKGROUND

Immunodeficient mice models have become increasingly important as in vivo models engrafted with human cells or tissues for research. The NOD-Rag1 null Ins2 Akita Il2r null (NRG-Akita) mice is a model combined with immunodeficient NRG and monogenic diabetes Akita mice that develop spontaneous hyperglycemia with progressive loss of pancreatic insulin-producing beta-cells with age. This model is one of the monogenic diabetic models, which has been providing a powerful platform for transplantation experiments of stem cells-generated human β-cells. This research aimed to provide insights into the mechanisms underlying this monogenic diabetes, which remains incompletely understood.

METHODS

Histological and immunofluorescence analyses were conducted on endocrine pancreatic islets to compare NRG wild-type (Wt) controls with NRG-Akita mice. Our investigation focused on assessing the expression of endocrine hormones, transcription factors, proliferation, ER stress, and apoptosis.

RESULTS

Histological analyses on NRG-Akita mice revealed smaller islets at 6-weeks-old, due to fewer β-cells in the islets, compared to NRG-Wt controls, which further progressed with age. The proliferation rate decreased, and apoptosis was abundant in β-cells in NRG-Akita mice. Interestingly, our mechanistic analyses revealed that β-cells in NRG-Akita mice progressively accumulated the endoplasmic reticulum (ER) stresses, leading to a decreased expression of pivotal β-cell transcriptional factor PDX1.

CONCLUSIONS

Altogether, our mechanistic insight into β-cell loss in this model could shed light on essential links between ER stress, proliferation, and cell identity, which might open the door to new therapeutic strategies for various diseases since ER stress is one of the most common features not only in diabetes but also in other degenerative diseases.

Research advances in understanding crosstalk between organs and pancreatic β-cell dysfunction

Obesity has increased dramatically worldwide. Being overweight or obese can lead to various conditions, including dyslipidaemia, hypertension, glucose intolerance and metabolic syndrome (MetS), which may further lead to type 2 diabetes mellitus (T2DM). Previous studies have identified a link between β-cell dysfunction and the severity of MetS, with multiple organs and tissues affected. Identifying the associations between pancreatic β-cell dysfunction and organs is critical. Research has focused on the interaction between the liver, gut and pancreatic β-cells. However, the mechanisms and related core targets are still not perfectly elucidated. The aims of this review were to summarize the mechanisms of β-cell dysfunction and to explore the potential pathogenic pathways and targets that connect the liver, gut, adipose tissue, muscle, and brain to pancreatic β-cell dysfunction.

S100A8/A9-activated IFNγ+ NK cells trigger β-cell necroptosis in hepatitis B virus-associated liver cirrhosis

BACKGROUND AND AIMS

Hepatitis B virus (HBV)-associated liver cirrhosis (LC), a common condition with high incidence and mortality rates, is often associated with diabetes mellitus (DM). However, the molecular mechanisms underlying impaired glucose regulation during HBV-associated LC remain unclear.

METHODS

Data from 63 patients with LC and 62 patients with LC-associated DM were analysed. Co-culture of NK cells and islet β cell lines were used to study the glucose regulation mechanism. A mouse model of LC was used to verify the effect of S100A8/A9 on the glucose regulation.

RESULTS

Higher levels of interferon (IFN)-γ derived from natural killer (NK) cells and lower levels of insulin emerged in the peripheral blood of patients with both LC and DM compared with those from patients with LC only. IFN-γ derived from NK cells facilitated β cell necroptosis and impaired insulin production. Furthermore, S100A8/A9 elevation in patients with both LC and DM was found to upregulate IFN-γ production in NK cells. Consistently, in the mouse model for LC, mice treated with carbon tetrachloride (CCL4) and S100A8/A9 exhibited increased blood glucose, impaired insulin production, increased IFN-γ, and increased β cells necroptosis compared with those treated with CCL4. Mechanistically, S100A8/A9 activated the p38 MAPK pathway to increase IFN-γ production in NK cells. These effects were diminished after blocking RAGE.

CONCLUSION

Together, the data indicate that IFN-γ produced by NK cells induces β cell necroptosis via the S100A8/A9-RAGE-p38 MAPK axis in patients with LC and DM. Reduced levels of S100A8/A9, NK cells, and IFN-γ could be valuable for the treatment of LC with DM. Accumulation of S100A8/A9 in patients with LC may indicate the emergence of DM.

The anterior chamber of the eye technology and its anatomical, optical, and immunological bases

The anterior chamber of the eye (ACE) is distinct in its anatomy, optics, and immunology. This guarantees that the eye perceives visual information in the context of physiology even when encountering adverse incidents like inflammation. In addition, this endows the ACE with the special nursery bed iris enriched in vasculatures and nerves. The ACE constitutes a confined space enclosing an oxygen/nutrient-rich, immune-privileged, and less stressful milieu as well as an optically transparent medium. Therefore, aside from visual perception, the ACE unexpectedly serves as an excellent transplantation site for different body parts and a unique platform for noninvasive, longitudinal, and intravital microimaging of different grafts. On the basis of these merits, the ACE technology has evolved from the prototypical through the conventional to the advanced version. Studies using this technology as a versatile biomedical research platform have led to a diverse range of basic knowledge and in-depth understanding of a variety of cells, tissues, and organs as well as artificial biomaterials, pharmaceuticals, and abiotic substances. Remarkably, the technology turns in vivo dynamic imaging of the morphological characteristics, organotypic features, developmental fates, and specific functions of intracameral grafts into reality under physiological and pathological conditions. Here we review the anatomical, optical, and immunological bases as well as technical details of the ACE technology. Moreover, we discuss major achievements obtained and potential prospective avenues for this technology.

The Regulation of Metabolic Homeostasis by Incretins and the Metabolic Hormones Produced by Pancreatic Islets

In healthy humans, the complex biochemical interplay between organs maintains metabolic homeostasis and pathological alterations in this process result in impaired metabolic homeostasis, causing metabolic diseases such as diabetes and obesity, which are major global healthcare burdens. The great advancements made during the last century in understanding both metabolic disease phenotypes and the regulation of metabolic homeostasis in healthy individuals have yielded new therapeutic options for diseases like type 2 diabetes (T2D). However, it is unlikely that highly desirable more efficacious treatments will be developed for metabolic disorders until the complex systemic regulation of metabolic homeostasis becomes more intricately understood. Hormones produced by pancreatic islet beta-cells (insulin) and alpha-cells (glucagon) are pivotal for maintaining metabolic homeostasis; the activity of insulin and glucagon are reciprocally correlated to achieve strict control of glucose levels (normoglycaemia). Metabolic hormones produced by other pancreatic islet cells and incretins produced by the gut are also crucial for maintaining metabolic homeostasis. Recent studies highlighted the incomplete understanding of metabolic hormonal synergism and, therefore, further elucidation of this will likely lead to more efficacious treatments for diseases such as T2D. The objective of this review is to summarise the systemic actions of the incretins and the metabolic hormones produced by the pancreatic islets and their interactions with their respective receptors.

Insulin reduces endoplasmic reticulum stress-induced apoptosis by decreasing mitochondrial hyperpolarization and caspase-12 in INS-1 pancreatic β-cells

Pancreatic β-cell mass is a critical determinant of insulin secretion. Severe endoplasmic reticulum (ER) stress causes β-cell apoptosis; however, the mechanisms of progression and suppression are not yet fully understood. Here, we report that the autocrine/paracrine function of insulin reduces ER stress-induced β-cell apoptosis. Insulin reduced the ER-stress inducer tunicamycin- and thapsigargin-induced cell viability loss due to apoptosis in INS-1 β-cells. Moreover, the effect of insulin was greater than that of insulin-like growth factor-1 at physiologically relevant concentrations. Insulin did not attenuate the ER stress-induced increase in unfolded protein response genes. ER stress did not induce cytochrome c release from mitochondria. Mitochondrial hyperpolarization was induced by ER stress and prevented by insulin. The protonophore/mitochondrial oxidative phosphorylation uncoupler, but not the antioxidants N-acetylcysteine and α-tocopherol, exhibited potential cytoprotection during ER stress. Both procaspase-12 and cleaved caspase-12 levels increased under ER stress. The caspase-12 inhibitor Z-ATAD-FMK decreased ER stress-induced apoptosis. Caspase-12 overexpression reduced cell viability, which was diminished in the presence of insulin. Insulin decreased caspase-12 levels at the post-translational stages. These results demonstrate that insulin protects against ER stress-induced β-cell apoptosis in this cell line. Furthermore, mitochondrial hyperpolarization and increased caspase-12 levels are involved in ER stress-induced and insulin-suppressed β-cell apoptosis.

GRP94 is an IGF-1R chaperone and regulates beta cell death in diabetes

High workload-induced cellular stress can cause pancreatic islet β cell death and dysfunction, or β cell failure, a hallmark of type 2 diabetes mellitus. Thus, activation of molecular chaperones and other stress-response genes prevents β cell failure. To this end, we have shown that deletion of the glucose-regulated protein 94 (GRP94) in Pdx1+ pancreatic progenitor cells led to pancreas hypoplasia and reduced β cell mass during pancreas development in mice. Here, we show that GRP94 was involved in β cell adaption and compensation (or failure) in islets from leptin receptor-deficient (db/db) mice in an age-dependent manner. GRP94-deficient cells were more susceptible to cell death induced by various diabetogenic stress conditions. We also identified a new client of GRP94, insulin-like growth factor-1 receptor (IGF-1R), a critical factor for β cell survival and function that may mediate the effect of GRP94 in the pathogenesis of diabetes. This study has identified essential functions of GRP94 in β cell failure related to diabetes.

Burdock miR8175 in diet improves insulin resistance induced by obesity in mice through food absorption

The incidence of type 2 diabetes mellitus (T2DM) induced by obesity is rapidly increasing. Although there are many synthetic drugs for treating T2DM, they have various side effects. Here, we report that miR8175, a plant miRNA from burdock root, has effective antidiabetic activity. After administration of burdock decoction or synthetic miR8175 by gavage, both burdock decoction and miR8175 can significantly improve the impaired glucose metabolism of diabetic mice induced by a high-fat diet (HFD). Our results demonstrate that burdock decoction and miR8175 enhance the insulin sensitivity of the hepatic insulin signaling pathway by targeting Ptprf and Ptp1b, which may be the reason for the improvement in metabolism. This study provides a theoretical basis for the main active component and molecular mechanism of burdock to improve insulin resistance. And the study also suggests that plant miRNA may be an indispensable nutrient for maintaining human health.

Mechanisms and risk factors of metabolic syndrome in children and adolescents

Metabolic syndrome (MetS) is a complex disorder characterized by abdominal obesity, elevated blood pressure, hyperlipidemia, and elevated fasting blood glucose levels. The diagnostic criteria for MetS in adults are well-established, but there is currently no consensus on the definition in children and adolescents. The etiology of MetS is believed to involve a complex interplay between genetic predisposition and environmental factors. While genetic predisposition explains only a small part of MetS pathogenesis, modifiable environmental risk factors play a significant role. Factors such as maternal weight during pregnancy, children's lifestyle, sedentariness, high-fat diet, fructose and branched-chain amino acid consumption, vitamin D deficiency, and sleep disturbances contribute to the development of MetS. Early identification and treatment of MetS in children and adolescents is crucial to prevent the development of chronic diseases later in life. In this review we discuss the latest research on factors contributing to the pathogenesis of MetS in children, focusing on non-modifiable and modifiable risk factors, including genetics, dysbiosis and chronic low-grade inflammation.

Novel lipid mediator 7S,14R-docosahexaenoic acid: biogenesis and harnessing mesenchymal stem cells to ameliorate diabetic mellitus and retinal pericyte loss

Introduction: Stem cells can be used to treat diabetic mellitus and complications. ω3-docosahexaenoic acid (DHA) derived lipid mediators are inflammation-resolving and protective. This study found novel DHA-derived 7S,14R-dihydroxy-4Z,8E,10Z,12E,16Z,19Z-docosahexaenoic acid (7S,14R-diHDHA), a maresin-1 stereoisomer biosynthesized by leukocytes and related enzymes. Moreover, 7S,14R-diHDHA can enhance mesenchymal stem cell (MSC) functions in the amelioration of diabetic mellitus and retinal pericyte loss in diabetic db/db mice. Methods: MSCs treated with 7S,14R-diHDHA were delivered into db/db mice i.v. every 5 days for 35 days. Results: Blood glucose levels in diabetic mice were lowered by 7S,14R-diHDHA-treated MSCs compared to control and untreated MSC groups, accompanied by improved glucose tolerance and higher blood insulin levels. 7S,14R-diHDHA-treated MSCs increased insulin+ β-cell ratio and decreased glucogan+ α-cell ratio in islets, as well as reduced macrophages in pancreas. 7S,14R-diHDHA induced MSC functions in promoting MIN6 β-cell viability and insulin secretion. 7S,14R-diHDHA induced MSC paracrine functions by increasing the generation of hepatocyte growth factor and vascular endothelial growth factor. Furthermore, 7S,14R-diHDHA enhanced MSC functions to ameliorate diabetes-caused pericyte loss in diabetic retinopathy by increasing their density in retina in db/db mice. Discussion: Our findings provide a novel strategy for improving therapy for diabetes and diabetic retinopathy using 7S,14R-diHDHA-primed MSCs.

The effects of EGCG supplementation on pancreatic islet α and β cells distribution in adult male mice

Tea and tea products are widely used as the most popular beverage in the world. EGCG is the most abundant bioactive tea polyphenol in green tea, which has positive effects on the prevention and treatment of diabetes. However, the impact of EGCG exposure on glucose homeostasis and islets in adult mice have not been reported. In this study, we studied glucose homeostasis and the morphological and molecular changes of pancreatic islet α and β cells in adult male mice after 60 d of exposure to 1 and 10 mg/kg/day EGCG by drinking water. Glucose homeostasis was not affected in both EGCG groups. The expression of pancreatic duodenal homebox1 (Pdx1) in β cells was upregulated, which might be related to increased insulin level, β cell mass and β cell proliferation in 10 mg/kg/day EGCG group. The expression of aristaless-related homeobox (Arx) in α cells did not change significantly, which corresponded with the unchanged α-cell mass. The significant reduction of musculoaponeurotic fibrosarcoma oncogene homolog B (MafB) positive α-cells might be associated with decreased glucagon level in both EGCG groups. These results suggest that EGCG supplementation dose-dependent increases β cell mass of adult mice and affects the levels of serum insulin and glucagon. Our results show that regular tea drinking in healthy people may have the possibility of preventing diabetes.

Research Progress on the Effect and Mechanism of Tea Products with Different Fermentation Degrees in Regulating Type 2 Diabetes Mellitus

A popular non-alcoholic beverage worldwide, tea can regulate blood glucose levels, lipid levels, and blood pressure, and may even prevent type 2 diabetes mellitus (T2DM). Different tea fermentation levels impact these effects. Tea products with different fermentation degrees containing different functional ingredients can lower post-meal blood glucose levels and may prevent T2DM. There are seven critical factors that shed light on how teas with different fermentation levels affect blood glucose regulation in humans. These factors include the inhibition of digestive enzymes, enhancement of cellular glucose uptake, suppression of gluconeogenesis-related enzymes, reduction in the formation of advanced glycation end products (AGEs), inhibition of dipeptidyl peptidase-4 (DPP-4) activity, modulation of gut flora, and the alleviation of inflammation associated with oxidative stress. Fermented teas can be used to lower post-meal blood glucose levels and can help consumers make more informed tea selections.

Phogrin Regulates High-Fat Diet-Induced Compensatory Pancreatic β-Cell Growth by Switching Binding Partners

The receptor protein tyrosine phosphatase phogrin primarily localizes to hormone secretory granules in neuroendocrine cells. Concurrent with glucose-stimulated insulin secretion, phogrin translocates to pancreatic β-cell plasma membranes, where it interacts with insulin receptors (IRs) to stabilize insulin receptor substrate 2 (IRS2) that, in turn, contributes to glucose-responsive β-cell growth. Pancreatic β-cell development was not altered in β-cell-specific, phogrin-deficient mice, but the thymidine incorporation rate decreased in phogrin-deficient islets with a moderate reduction in IRS2 protein expression. In this study, we analyzed the β-cell response to high-fat diet stress and found that the compensatory expansion in β-cell mass was significantly suppressed in phogrin-deficient mice. Phogrin-IR interactions occurred only in high-fat diet murine islets and proliferating β-cell lines, whereas they were inhibited by the intercellular binding of surface phogrin under confluent cell culture conditions. Thus, phogrin could regulate glucose-stimulated compensatory β-cell growth by changing its binding partner from another β-cell phogrin to IR in the same β-cells.

Insulin Resistance, Obesity, and Lipotoxicity

Lipotoxicity, originally used to describe the destructive effects of excess fat accumulation on glucose metabolism, causes functional impairments in several metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas, and muscle. Ectopic lipid accumulation in the kidneys, liver, and heart has important clinical counterparts like diabetic nephropathy in type 2 diabetes mellitus, obesity-related glomerulopathy, nonalcoholic fatty liver disease, and cardiomyopathy. Insulin resistance due to lipotoxicity indirectly lead to reproductive system disorders, like polycystic ovary syndrome. Lipotoxicity has roles in insulin resistance and pancreatic beta-cell dysfunction. Increased circulating levels of lipids and the metabolic alterations in fatty acid utilization and intracellular signaling have been related to insulin resistance in muscle and liver. Different pathways, like novel protein kinase c pathways and the JNK-1 pathway, are involved as the mechanisms of how lipotoxicity leads to insulin resistance in nonadipose tissue organs, such as liver and muscle. Mitochondrial dysfunction plays a role in the pathogenesis of insulin resistance. Endoplasmic reticulum stress, through mainly increased oxidative stress, also plays an important role in the etiology of insulin resistance, especially seen in non-alcoholic fatty liver disease. Visceral adiposity and insulin resistance both increase the cardiometabolic risk, and lipotoxicity seems to play a crucial role in the pathophysiology of these associations.

The spontaneous-diabetes rat: a model of noninsulin dependent diabetes mellitus by Yoshio Goto and Masaei Kakizaki (1981)

Y. Goto and M. Kakizaki produced a rat model of non-insulin dependent diabetes mellitus (NIDDM) by repetitive selective breeding of rats with slightly impaired glucose tolerance. In contrast to most obese diabetes models, which were genetically modified animals created by inducing a gene mutation, this rat was a unique model because it was a spontaneous diabetes model created by selective breeding. Furthermore, when it became clear that this rat was a non-obese diabetic model that exhibited hyperglycemia due to a decrease in insulin secretion capacity, it was recognized as a valuable model for elucidating non-obese, hypoinsulinemic diabetes commonly seen in East Asians. Diabetes is becoming an important health problem worldwide, especially in the East Asian region, thus Goto-Kakizaki (GK) rats are becoming increasingly important as a model of non-insulin dependent diabetes mellitus.

Obesity under the moonlight of c-MYC

The moonlighting protein c-Myc is a master regulator of multiple biological processes including cell proliferation, differentiation, angiogenesis, apoptosis and metabolism. It is constitutively and aberrantly expressed in more than 70% of human cancers. Overwhelming evidence suggests that c-Myc dysregulation is involved in several inflammatory, autoimmune, metabolic and other non-cancerous diseases. In this review, we addressed the role of c-Myc in obesity. Obesity is a systemic disease, accompanied by multi-organ dysfunction apart from white adipose tissue (WAT), such as the liver, the pancreas, and the intestine. c-Myc plays a big diversity of functions regulating cellular proliferation, the maturation of progenitor cells, fatty acids (FAs) metabolism, and extracellular matrix (ECM) remodeling. Moreover, c-Myc drives the expression of a wide range of metabolic genes, modulates the inflammatory response, induces insulin resistance (IR), and contributes to the regulation of intestinal dysbiosis. Altogether, c-Myc is an interesting diagnostic tool and/or therapeutic target in order to mitigate obesity and its consequences.

Beta-cell compensation and gestational diabetes

Gestational diabetes mellitus (GDM) is characterized by glucose intolerance in pregnant women without a previous diagnosis of diabetes. While the etiology of GDM remains elusive, the close association of GDM with increased maternal adiposity and advanced gestational age implicates insulin resistance as a culpable factor for the pathogenesis of GDM. Pregnancy is accompanied by the physiological induction of insulin resistance in the mother secondary to maternal weight gain. This effect serves to spare blood glucose for the fetus. To overcome insulin resistance, maternal β-cells are conditioned to release more insulin into the blood. Such an adaptive response, termed β-cell compensation, is essential for maintaining normal maternal metabolism. β-cell compensation culminates in the expansion of β-cell mass and augmentation of β-cell function, accounting for increased insulin synthesis and secretion. As a result, a vast majority of mothers are protected from developing GDM during pregnancy. In at-risk pregnant women, β-cells fail to compensate for maternal insulin resistance, contributing to insulin insufficiency and GDM. However, gestational β-cell compensation ensues in early pregnancy, prior to the establishment of insulin resistance in late pregnancy. How β-cells compensate for pregnancy and what causes β-cell failure in GDM are subjects of investigation. In this mini-review, we will provide clinical and preclinical evidence that β-cell compensation is pivotal for overriding maternal insulin resistance to protect against GDM. We will highlight key molecules whose functions are critical for integrating gestational hormones to β-cell compensation for pregnancy. We will provide mechanistic insights into β-cell decompensation in the etiology of GDM.

Irisin suppresses pancreatic β cell pyroptosis in T2DM by inhibiting the NLRP3-GSDMD pathway and activating the Nrf2-TrX/TXNIP signaling axis

BACKGROUND

Irisin plays a key role in metabolic diseases, including type 2 diabetes mellitus (T2DM). However, the mechanism underlying the link between irisin and the development of T2DM, particularly in pancreatic islet β-cells, remains unknown.

METHODS

In vitro, Min6 cells were treated with high glucose (HG) to generate T2DM cell models. GSDMD-N staining, Western blotting assays, and ELISA were performed to measure the expression levels of GSDMD, caspase 1, IL-1β, and IL-18. Next, the NLRP3 stimulator, ATP, was used to assess the effect of irisin on NLRP3 inflammasome. To evaluate the function of the Nrf2-TrX/TXNIP signaling axis, the Nrf2 inhibitor ML385 was used. For in vivo assessment, we first established T2DM model mice. Then, hematoxylin and eosin (H&E) staining was performed to observe the islet morphology, and the immunofluorescence technique was used to examine the mass of α and β cells. To confirm the role of the Nrf2-TrX/TXNIP signaling axis, ML385 was injected into the mice. Immunofluorescence of Nrf2, caspase 1, and GSDMD was detected in the islet cells of the model mice to verify the results.

RESULTS

We found that irisin treatment significantly decreased the expression of GSDMD-N (P31) and cleaved caspase-1 (p20), decreased caspase1 activity, and inhibited the secretion of IL-1β and IL-18 in HG-treated Min6 cells. We also found that irisin inhibited oxidative stress and NLRP3 expression by activating the Nrf2-TrX/TXNIP signaling axis. Additionally, in the T2DM model mice, irisin enhanced the function of islet cells, decreased insulin resistance, and preserved the morphology of pancreatic islets.

CONCLUSION

We showed in this study that irisin can be used for treating pyroptosis in HG-induced islet β-cells and T2DM model mice. We also found that irisin inhibits pyroptosis and oxidative stress by inhibiting the NLRP3-GSDMD pathway and activating the Nrf2-TrX/TXNIP signaling axis.

A data-driven computational model for obesity-driven diabetes onset and remission through weight loss

Obesity is a major risk factor for the development of type 2 diabetes (T2D), where a sustained weight loss may result in T2D remission in individuals with obesity. To design effective and feasible intervention strategies to prevent or reverse T2D, it is imperative to study the progression of T2D and remission together. Unfortunately, this is not possible through experimental and observational studies. To address this issue, we introduce a data-driven computational model and use human data to investigate the progression of T2D with obesity and remission through weight loss on the same timeline. We identify thresholds for the emergence of T2D and necessary conditions for remission. We explain why remission is only possible within a window of opportunity and the way that window depends on the progression history of T2D, individual's metabolic state, and calorie restrictions. These findings can help to optimize therapeutic intervention strategies for T2D prevention or treatment.

Partners in diabetes epidemic: A global perspective

There is a recent increase in the worldwide prevalence of both obesity and diabetes. In this review we assessed insulin signaling, genetics, environment, lipid metabolism dysfunction and mitochondria as the major determinants in diabetes and to identify the potential mechanism of gut microbiota in diabetes diseases. We searched relevant articles, which have key information from laboratory experiments, epidemiological evidence, clinical trials, experimental models, meta-analysis and review articles, in PubMed, MEDLINE, EMBASE, Google scholars and Cochrane Controlled Trial Database. We selected 144 full-length articles that met our inclusion and exclusion criteria for complete assessment. We have briefly discussed these associations, challenges, and the need for further research to manage and treat diabetes more efficiently. Diabetes involves the complex network of physiological dysfunction that can be attributed to insulin signaling, genetics, environment, obesity, mitochondria and stress. In recent years, there are intriguing findings regarding gut microbiome as the important regulator of diabetes. Valid approaches are necessary for speeding medical advances but we should find a solution sooner given the burden of the metabolic disorder - What we need is a collaborative venture that may involve laboratories both in academia and industries for the scientific progress and its application for the diabetes control.

The protective role of shenqi compound in type 2 diabetes: A comprehensive investigation of pancreatic β-cell function and mass

Type 2 diabetes (T2D) is a prevalent metabolic disorder characterized by impaired insulin secretion and insulin resistance, resulting in elevated blood glucose levels. The dysfunction and loss of pancreatic β-cells, responsible for producing insulin, contribute to the development of T2D. Traditional Chinese medicine (TCM) has emerged as a potential source of innovative therapeutic interventions. However, limited research exists on Chinese herbal formulations specifically targeting the protection of pancreatic β-cell function and mass. One such formulation is the Shenqi compound (SQC), widely used in China and consisting of Panax Ginseng, Astragali Radix, Rhizoma Dioscoreae, Corni Fructus, Rehmanniae Radix, Salviae Miltiorrhizae Radix et Rhizoma, Radix Trichosanthis, and Rhei Radix et Rhizoma. Understanding the mechanisms underlying the therapeutic effects of SQC is crucial for developing novel treatment strategies for T2D. This study aims to comprehensively investigate the scientific evidence supporting the role of SQC in alleviating T2D by targeting the protection of pancreatic β-cell function and mass. Spontaneously diabetic GK rats were used as the animal model, receiving SQC (14.4 g/kg/d) for 8 weeks. The results demonstrate multiple beneficial effects of SQC, including significant control of blood glucose levels (P < 0.05), inhibition of insulin resistance (measured by Western Blot), reduction of hyperinsulinemia (P < 0.05), attenuation of oxidative stress (P < 0.05), suppression of inflammation (P < 0.05), protection against islet hypertrophy and beta cell proliferation (evaluated through pathological staining), and inhibition of β-cell apoptosis and senescence (also assessed through pathological staining). These findings indicate the promotion of β-cell survival and function. In vitro experiments using isolated islets further support these results, revealing improvements in insulin secretion (P < 0.05) and β-cell function following SQC therapy (P < 0.05). This represents a significant breakthrough in addressing β-cell dysfunction and preserving mass within the context of TCM. Overall, SQC shows promise as a natural therapeutic approach for T2D, with potential benefits in preserving pancreatic β-cell function and mass. This enhances the practical applicability and significance of the research by bridging the gap between experimental findings and clinical practice, thereby providing important clinical value in TCM treatment of T2D. Further research is necessary to elucidate its precise mechanisms of action and optimize its clinical application.

Glycerol contributes to tuberculosis susceptibility in male mice with type 2 diabetes

Diabetes mellitus increases risk for tuberculosis disease and adverse outcomes. Most people with both conditions have type 2 diabetes, but it is unknown if type 1 and type 2 diabetes have identical effects on tuberculosis susceptibility. Here we show that male mice receiving a high-fat diet and streptozotocin to model type 2 diabetes, have higher mortality, more lung pathology, and higher bacterial burden following Mycobacterium tuberculosis infection compared to mice treated with streptozotocin or high-fat diet alone. Type 2 diabetes model mice have elevated plasma glycerol, which is a preferred carbon source for M. tuberculosis. Infection studies with glycerol kinase mutant M. tuberculosis reveal that glycerol utilization contributes to the susceptibility of the type 2 diabetes mice. Hyperglycemia impairs protective immunity against M. tuberculosis in both forms of diabetes, but our data show that elevated glycerol contributes to an additional adverse effect uniquely relevant to type 2 diabetes.

Comprehensive Search for GPCR Compounds which Can Enhance MafA and/or PDX-1 Expression Levels Using a Small Molecule Compound Library

It has been shown that chronic hyperglycemia gradually decreases insulin biosynthesis and secretion which is accompanied by reduced expression of very important insulin gene transcription factors MafA and PDX-1. Such phenomena are well known as β-cell glucose toxicity. It has been shown that the downregulation of MafA and/or PDX-1 expression considerably explains the molecular mechanism for glucose toxicity. However, it remained unknown which molecules can enhance MafA and/or PDX-1 expression levels. In this study, we comprehensively searched for G protein-coupled receptor (GPCR) compounds which can enhance MafA and/or PDX-1 expression levels using a small molecule compound library in pancreatic β-cell line MIN6 cells and islets isolated from nondiabetic C57BL/6 J mice and obese type 2 diabetic C57BL/KsJ-db/db mice. We found that fulvestrant and dexmedetomidine hydrochloride increased MafA, PDX-1, or insulin expression levels in MIN6 cells. We confirmed that fulvestrant and dexmedetomidine hydrochloride increased MafA, PDX-1, or insulin expression levels in islets from nondiabetic mice as well. Furthermore, these reagents more clearly enhanced MafA, PDX-1, or insulin expression levels in islets from obese type 2 diabetic db/db mice in which MafA and PDX-1 expression levels are reduced due to glucose toxicity. In conclusion, fulvestrant and dexmedetomidine hydrochloride increased MafA, PDX-1, or insulin expression levels in MIN6 cells and islets from nondiabetic mice and obese type 2 diabetic db/db mice. To the best of our knowledge, this is the first report showing some molecule which can enhance MafA and/or PDX-1 expression levels. Therefore, although further extensive study is necessary, we think that the information in this study could be, at least in part, useful at some point such as in the development of new antidiabetes medicine based on the molecular mechanism of β-cell glucose toxicity in the future.

Restoration of PITPNA in Type 2 diabetic human islets reverses pancreatic beta-cell dysfunction

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre, Pitpnaflox/flox mice leads to hyperglycemia resulting from decreasing glucose-stimulated insulin secretion (GSIS) and reducing pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirms its role in PtdIns-4-P synthesis and leads to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reverses these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D.

A highly sensitive strategy for monitoring real-time proliferation of targeted cell types in vivo

Cell proliferation processes play pivotal roles in timely adaptation to many biological situations. Herein, we establish a highly sensitive and simple strategy by which time-series showing the proliferation of a targeted cell type can be quantitatively monitored in vivo in the same individuals. We generate mice expressing a secreted type of luciferase only in cells producing Cre under the control of the Ki67 promoter. Crossing these with tissue-specific Cre-expressing mice allows us to monitor the proliferation time course of pancreatic β-cells, which are few in number and weakly proliferative, by measuring plasma luciferase activity. Physiological time courses, during obesity development, pregnancy and juvenile growth, as well as diurnal variation, of β-cell proliferation, are clearly detected. Moreover, this strategy can be utilized for highly sensitive ex vivo screening for proliferative factors for targeted cells. Thus, these technologies may contribute to advancements in broad areas of biological and medical research.

The hippo kinases MST1/2 in cardiovascular and metabolic diseases: A promising therapeutic target option for pharmacotherapy

Cardiovascular diseases (CVDs) and metabolic disorders are major components of noncommunicable diseases, causing an enormous health and economic burden worldwide. There are common risk factors and developmental mechanisms among them, indicating the far-reaching significance in exploring the corresponding therapeutic targets. MST1/2 kinases are well-established proapoptotic effectors that also bidirectionally regulate autophagic activity. Recent studies have demonstrated that MST1/2 influence the outcome of cardiovascular and metabolic diseases by regulating immune inflammation. In addition, drug development against them is in full swing. In this review, we mainly describe the roles and mechanisms of MST1/2 in apoptosis and autophagy in cardiovascular and metabolic events as well as emphasis on the existing evidence for their involvement in immune inflammation. Moreover, we summarize the latest progress of pharmacotherapy targeting MST1/2 and propose a new mode of drug combination therapy, which may be beneficial to seek more effective strategies to prevent and treat CVDs and metabolic disorders.

Discovery of IHMT-MST1-39 as a novel MST1 kinase inhibitor and AMPK activator for the treatment of diabetes mellitus

Insulin-producing pancreatic β cell death is the fundamental cause of type 1 diabetes (T1D) and a contributing factor to type 2 diabetes (T2D). Moreover, metabolic disorder is another hallmark of T2D. Mammalian sterile 20-like kinase 1 (MST1) contributes to the progression of diabetes mellitus through apoptosis induction and acceleration of pancreatic β cell dysfunction. AMP-activated protein kinase (AMPK) is an energy sensing kinase and its activation has been suggested as a treatment option for metabolic diseases. Thus, pharmacological inhibition of MST1 and activation of AMPK simultaneously represents a promising approach for diabetes therapy. Here, we discovered a novel selective MST1 kinase inhibitor IHMT-MST1-39, which exhibits anti-apoptosis efficacy and improves the survival of pancreatic β cells under diabetogenic conditions, as well as primary pancreatic islets in an ex vivo disease model. Mechanistically, IHMT-MST1-39 activated AMPK signaling pathway in hepatocytes in vitro, combination of IHMT-MST1-39 and metformin synergistically prevented hyperglycemia and significantly ameliorated glucose tolerance and insulin resistance in diabetic mice. Taken together, IHMT-MST1-39 is a promising anti-diabetic candidate as a single agent or in combination therapy for both T1D and T2D.

Venom Peptides, Polyphenols and Alkaloids: Are They the Next Antidiabetics That Will Preserve β-Cell Mass and Function in Type 2 Diabetes?

Improvement of insulin secretion by pancreatic β-cells and preservation of their mass are the current challenges that future antidiabetic drugs should meet for achieving efficient and long-term glycemic control in patients with type 2 diabetes (T2D). The successful development of glucagon-like peptide 1 (GLP-1) analogues, derived from the saliva of a lizard from the Helodermatidae family, has provided the proof of concept that antidiabetic drugs directly targeting pancreatic β-cells can emerge from venomous animals. The literature reporting on the antidiabetic effects of medicinal plants suggests that they contain some promising active substances such as polyphenols and alkaloids, which could be active as insulin secretagogues and β-cell protectors. In this review, we discuss the potential of several polyphenols, alkaloids and venom peptides from snake, frogs, scorpions and cone snails. These molecules could contribute to the development of new efficient antidiabetic medicines targeting β-cells, which would tackle the progression of the disease.

Adult exposure of atrazine alone or in combination with carbohydrate diet hastens the onset/progression of type 2 diabetes in Drosophila

AIM

The combined impact of traditional and non-traditional risk factors of type 2 diabetes (T2D) on the development and progression of insulin resistance and associated complications is poorly understood. Therefore, we assessed the effect of moderately rich sugar diet coupled with environmental chemical exposure on the development and progression of T2D using Drosophila as a model organism.

MAIN METHODS

We reared newly eclosed Drosophila males on a diet containing atrazine (20 μg/ml; non-traditional risk factor) and/or moderately high sucrose (0.5 M/1 M; to mimic binge eating, Traditional risk factor) for 20-30 days. Subsequently, we assessed diabetic parameters, oxidative stress parameters and also the abundance of advanced glycation end products (AGEs) along with their receptor (RAGE) in these flies. For diabetic cardiomyopathy, we examined the pericardin (tissue fibrosis marker) level in Drosophila heart.

KEY FINDINGS

Flies reared on 20 μg/ml atrazine alone showed T2D hallmarks at 30 days. In contrast, flies reared on 0.5 M sucrose+ 20 μg/ml atrazine showed insulin resistance characterized by hyperglycemia and increased Drosophila insulin-like peptides along with reduced insulin signaling at 20 days, similar to those reared on high sucrose diet. In addition, both groups had high levels of oxidative stress and showed starvation response (converting triglycerides into fatty acids). Alarmingly, flies fed with sucrose+atrazine for 20 and 30 days had elevated pericardin in heart tissues, indicating early onset of diabetic complications such as cardiomyopathy.

SIGNIFICANCE

Lifestyle-chemical exposure synergistically impairs glucose metabolism, affects organisms' redox state and leads to the early onset of T2D and associated complications like cardiomyopathy.

Evaluation of miRNA-143 and miRNA-145 Expression and Their Association with Vitamin-D Status Among Obese and Non-Obese Type-2 Diabetic Patients

Objective

Growing epidemics of type-2 diabetes mellitus (T2DM) and obesity have become a serious health concern. Since miRNAs and vitamin levels affect the development and progression of numerous pathogenic diseases, including diabetes, the present study aimed to evaluate miRNA-143 and miRNA-145 expression and vitamin-D status among obese and non-obese T2DM patients.

Methods

The study included 100 clinically confirmed newly diagnosed obese and non-obese T2DM cases and 100 healthy subjects. Total RNA was extracted from collected blood samples and 100 ng of RNA was used for cDNA synthesis, then TaqMan assay was performed to evaluate the miRNA-143 and miRNA-145 relative expression.

Results

T2DM cases with hypertension (4.08 fold, p=0.01; 5.36 fold, p=0.009), fatigue (5.07 fold, p=0.04; 5.32 fold, p=0.03) and blurred vision (5.15 fold, p=0.01) showed higher miRNA-143 and miRNA-145 relative expression compared with their counterparts, respectively. A positive correlation was observed between miRNA-143 and miRNA-145 expression and decreased vitamin-D status in T2DM had significant association with impaired blood glucose fasting (p=0.001) and HDL level (p<0.0001). Obese T2DM cases showed higher miRNA-143 and miRNA-145 expression compared with their counterparts. Vitamin-D deficient T2DM cases had higher miRNA-143 and miRNA-145 expression (5.69 fold, 5.91 fold) compared with insufficient (4.27 fold, p=0.03; 4.61 fold, p=0.03) and sufficient (4.08 fold, p=0.002; 4.29 fold, p=0.003). ROC curve for miRNA-143 and miRNA-145 between obese T2DM vs non-obese T2DM cases, at best possible cutoff value of 4.39 fold, 4.0 fold showed increased miRNA-143 and miRNA-145 expression, the sensitivity and specificity were 85%, 88% and 61%, 53% respectively (AUC=0.83, p<0.0001; AUC=0.81, p<0.0001).

Conclusion

Higher miRNA-143 and miRNA-145 expression could be a predictive indicator for obese T2DM cases, decreased status of vitamin-D was also significantly associated with impaired fasting blood sugar and HDL level, therefore it is important to evaluate the vitamin-D status among T2DM cases for better clinical outcome during the intervention.

Effects of altitude on meat quality difference and its relationship with HIF-1α during postmortem maturation of beef

This study investigated the differences in meat quality during postmortem aging of yak meat from different altitudes as well as the relationship between the release of hypoxic factor HIF-1α and meat quality. The results showed that the HIF-1α increased with altitude but during aging process, there was an initial increase before a subsequent decrease (p < .05). Moreover, significant increases were showed in glycolytic potential, a* value, pH, HIF-1α mRNA expression, HIF-1α protein expression and shear force with altitude (p < .05). Additionally, the b* value, L* value, water holding power and MFI decreased significantly (p < .05). HIF-1α was shown, by PLS-DA method analysis, to be the main protein marker for differences in the quality during aging time of meat from three altitude groups. HIF-1α protein expression was high correlated with glycolytic potential, pH value, meat color, tenderness and water holding capacity during postmortem aging. The results demonstrated that HIF-1α is a novel marker protein that influences meat quality in yak from different altitudes and that HIF-1α-mediated glycolytic pathway was key to the meat quality during postmortem aging. PRACTICAL APPLICATIONS: Yak meat has the advantages of high protein, low fat, good amino acid and fatty acid composition, so the nutritional value of yak meat is in line with the current best-selling beef with less fat in domestic and foreign markets. But consumers often think that the meat tenderness of yak meat is worse than that of beef and improving the quality of yak meat was worthy of attention specifically. This study investigated the differences in meat quality during postmortem aging of yak meat at different altitudes and the relationship between hypoxic factor HIF-1α release and meat quality.

In vivo and in vitro binding of [125 I]I-R-(+)-TISCH: A dopamine D1 receptor ligand for studying pancreatic β-cell mass

Diabetes mellitus (DM) and insulinoma are mainly affected by the status of pancreatic β-cell mass (BCM). Development of imaging agents for BCM allows to study pancreatic β cells and the relationship between β cells and DM or insulinoma. In this study, we investigated the density of dopamine D₁ receptor on the β cells and measured BCM by statistical image processing. The pancreatic uptakes of [¹²⁵ I]I-R-(+)-7-chloro-8-hydroxy-1-(3'-iodopheny1)-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine ([¹²⁵ I]I-R-(+)-TISCH), dopamine D₁ receptor tracer, in normal and diabetic rats displayed significant differences at 30 min (1.11 ± 0.08% ID/g vs. 0.63 ± 0.09% ID/g, p < 0.0001). In the presence of SCH23390, the pancreatic uptake of [¹²⁵ I]I-R-(+)-TISCH at 30 min in normal rats was lower (1.01 ± 0.04% ID/g, p < 0.05). Although the blocking was not complete, [¹²⁵ I]I-R-(+)-TISCH showed specific binding signals to the pancreas. Furthermore, the uptakes of [¹²⁵ I]I-R-(+)-TISCH in INS-1 cells were reduced in the presence of SCH23390 at different concentrations. [¹²⁵ I]I-R-(+)-TISCH displayed a respectable uptake in insulinoma. Overall, [¹²⁵ I]I-R-(+)-TISCH provided specific binding signals to pancreatic β cells. Although the specific signal may not be sufficient for imaging in vivo, the dopamine D₁ receptor can still be considered as a potential target for studying BCM. Further investigation will be required to optimize the ligand.

Insulin expression in β cells is reduced within islets before islet loss in diabetic cats

OBJECTIVES

Diabetes mellitus is a common condition that requires intensive treatment and markedly impacts the welfare of affected cats. The aim of this study was to identify diabetes mellitus-associated perturbations in the feline pancreatic islet microenvironment. The utility of "clear, unobstructed brain/body imaging cocktails and computational analysis" (CUBIC) for three-dimensional pancreatic analysis was investigated.

METHODS

Formalin-fixed paraffin-embedded tissues from cats with diabetes mellitus, or control cats without pancreatic pathology, were retrospectively identified. Immunohistochemistry for synaptophysin and ionised calcium binding adaptor molecule 1, and immunofluorescence for insulin and synaptophysin, were used to assess changes in islets. An image analysis pipeline was developed to analyse images acquired from two-dimensional immunofluorescence. CUBIC was used to optically clear selected pancreas samples before immunofluorescence and deep three-dimensional confocal microscopy.

RESULTS

Diabetic cats have a significant reduction in synaptophysin-positive islet area. Whilst islets from diabetic patients have similar numbers of β cells to islets from control cats, significantly lower intensity of insulin expression can be observed in the former. CUBIC facilitates clear visualisation of pancreatic islets in three dimensions.

CLINICAL SIGNIFICANCE

The data presented support the theory that there is a decrease in function of β cells before their destruction, suggesting a potentially significant step in the pathogenesis of feline diabetes mellitus. In parallel, we demonstrate CUBIC as a valuable new tool to visualise the shape of feline pancreatic islets and to interrogate pathology occurring in the islets of diabetic pets.

Role of AMPK in Myocardial Ischemia-Reperfusion Injury-Induced Cell Death in the Presence and Absence of Diabetes

Recent studies indicate cell death is the hallmark of cardiac pathology in myocardial infarction and diabetes. The AMP-activated protein kinase (AMPK) signalling pathway is considered a putative salvaging phenomenon, plays a decisive role in almost all cellular, metabolic, and survival functions, and therefore entails precise regulation of its activity. AMPK regulates various programmed cell death depending on the stimuli and context, including autophagy, apoptosis, necroptosis, and ferroptosis. There is substantial evidence suggesting that AMPK is down-regulated in cardiac tissues of animals and humans with type 2 diabetes or metabolic syndrome compared to non-diabetic control and that stimulation of AMPK (physiological or pharmacological) can ameliorate diabetes-associated cardiovascular complications, such as myocardial ischemia-reperfusion injury. Furthermore, AMPK is an exciting therapeutic target for developing novel drug candidates to treat cell death in diabetes-associated myocardial ischemia-reperfusion injury. Therefore, in this review, we summarized how AMPK regulates autophagic, apoptotic, necroptotic, and ferroptosis pathways in the context of myocardial ischemia-reperfusion injury in the presence and absence of diabetes.

Cardiovascular protection by SGLT2 inhibitors - Do anti-inflammatory mechanisms play a role?

BACKGROUND

Metabolic syndrome and related metabolic disturbances represent a state of low-grade inflammation, which accelerates insulin resistance, type 2 diabetes (T2D) and cardiovascular disease (CVD) progression. Among antidiabetic medications, sodium glucose co-transporter (SGLT) 2 inhibitors are the only agents which showed remarkable reductions in heart failure (HF) hospitalizations and major cardiovascular endpoints (MACE) as well as renal endpoints regardless of diabetes status in large randomized clinical outcome trials (RCTs). Although the exact mechanisms underlying these benefits are yet to be established, growing evidence suggests that modulating inflammation by SGLT2 inhibitors may play a key role.

SCOPE OF REVIEW

In this manuscript, we summarize the current knowledge on anti-inflammatory effects of SGLT2 inhibitors as one of the mechanisms potentially mediating their cardiovascular (CV) benefits. We introduce the different metabolic and systemic actions mediated by these agents which could mitigate inflammation, and further present the signalling pathways potentially responsible for their proposed direct anti-inflammatory effects. We also discuss controversies surrounding some of these mechanisms.

MAJOR CONCLUSIONS

SGLT2 inhibitors are promising anti-inflammatory agents by acting either indirectly via improving metabolism and reducing stress conditions or via direct modulation of inflammatory signalling pathways. These effects were achieved, to a great extent, in a glucose-independent manner which established their clinical use in HF patients with and without diabetes.

β-cell dynamics in type 2 diabetes and in dietary and exercise interventions

Pancreatic β-cell dysfunction and insulin resistance are two of the major causes of type 2 diabetes (T2D). Recent clinical and experimental studies have suggested that the functional capacity of β-cells, particularly in the first phase of insulin secretion, is a primary contributor to the progression of T2D and its associated complications. Pancreatic β-cells undergo dynamic compensation and decompensation processes during the development of T2D, in which metabolic stresses such as endoplasmic reticulum stress, oxidative stress, and inflammatory signals are key regulators of β-cell dynamics. Dietary and exercise interventions have been shown to be effective approaches for the treatment of obesity and T2D, especially in the early stages. Whilst the targeted tissues and underlying mechanisms of dietary and exercise interventions remain somewhat vague, accumulating evidence has implicated the improvement of β-cell functional capacity. In this review, we summarize recent advances in the understanding of the dynamic adaptations of β-cell function in T2D progression and clarify the effects and mechanisms of dietary and exercise interventions on β-cell dysfunction in T2D. This review provides molecular insights into the therapeutic effects of dietary and exercise interventions on T2D, and more importantly, it paves the way for future research on the related underlying mechanisms for developing precision prevention and treatment of T2D.

Immunomodulator FTY720 improves glucose homeostasis and diabetic complications by rejuvenation of β-cell function in nonhuman primate model of diabetes

Inadequate β‐cell mass is essential for the pathogenesis of type 2 diabetes (T2D). Previous report showed that an immunomodulator FTY720, a sphingosine 1‐phosphate (S1P) receptor modulator, sustainably normalized hyperglycemia by stimulating β‐cell in vivo regeneration in db/db mice. We further examined the effects of FTY720 on glucose homeostasis and diabetic complications in a translational nonhuman primate (NHP) model of spontaneously developed diabetes. The male diabetic cynomolgus macaques of 18–19 year old were randomly divided into Vehicle (Purified water, n = 5) and FTY720 (5 mg/kg, n = 7) groups with oral gavage once daily for 10 weeks followed by 10 weeks drug free period. Compared with the Vehicle group, FTY720 effectively lowered HbA1c, blood concentrations of fasting glucose (FBG) and insulin, hence, decreased homeostatic model assessment of insulin resistance (HOMA‐IR); ameliorated glucose intolerance and restored glucose‐stimulated insulin release, indicating rejuvenation of β‐cell function in diabetic NHPs. Importantly, after withdrawal of FTY720, FBG, and HbA1c remained at low level in the drug free period. Echocardiography revealed that FTY720 significantly reduced proteinuria and improved cardiac left ventricular systolic function measured by increased ejection fraction and fractional shortening in the diabetic NHPs. Finally, flow cytometry analysis (FACS) detected that FTY720 significantly reduced CD4 + and CD8 + T lymphocytes as well as increased DC cells in the circulation. Immunomodulator FTY720 improves glucose homeostasis via rejuvenation of β‐cell function, which can be mediated by suppression of cytotoxic CD8 + T lymphocytes to β‐cells, thus, may be a novel immunotherapy to reverse T2D progression and ameliorate the diabetic complications.

Protective Role of Mitochondrial Uncoupling Proteins against Age-Related Oxidative Stress in Type 2 Diabetes Mellitus

The accumulation of oxidative damage to DNA and other biomolecules plays an important role in the etiology of aging and age-related diseases such as type 2 diabetes mellitus (T2D), atherosclerosis, and neurodegenerative disorders. Mitochondrial DNA (mtDNA) is especially sensitive to oxidative stress. Mitochondrial dysfunction resulting from the accumulation of mtDNA damage impairs normal cellular function and leads to a bioenergetic crisis that accelerates aging and associated diseases. Age-related mitochondrial dysfunction decreases ATP production, which directly affects insulin secretion by pancreatic beta cells and triggers the gradual development of the chronic metabolic dysfunction that characterizes T2D. At the same time, decreased glucose oxidation in skeletal muscle due to mitochondrial damage leads to prolonged postprandial blood glucose rise, which further worsens glucose homeostasis. ROS are not only highly reactive by-products of mitochondrial respiration capable of oxidizing DNA, proteins, and lipids but can also function as signaling and effector molecules in cell membranes mediating signal transduction and inflammation. Mitochondrial uncoupling proteins (UCPs) located in the inner mitochondrial membrane of various tissues can be activated by ROS to protect cells from mitochondrial damage. Mitochondrial UCPs facilitate the reflux of protons from the mitochondrial intermembrane space into the matrix, thereby dissipating the proton gradient required for oxidative phosphorylation. There are five known isoforms (UCP1-UCP5) of mitochondrial UCPs. UCP1 can indirectly reduce ROS formation by increasing glutathione levels, thermogenesis, and energy expenditure. In contrast, UCP2 and UCP3 regulate fatty acid metabolism and insulin secretion by beta cells and modulate insulin sensitivity. Understanding the functions of UCPs may play a critical role in developing pharmacological strategies to combat T2D. This review summarizes the current knowledge on the protective role of various UCP homologs against age-related oxidative stress in T2D.

The effects of metformin monotherapy and combination of metformin and glibenclamide therapy on the expression of RAGE, Sirt1, and Nrf2 genes in peripheral blood mononuclear cells of type 2 diabetic patients

Purpose

Although metformin is the first-line treatment of type 2 diabetes mellitus (T2DM), a few studies have evaluated the benefits of monotherapies (metformin) versus combination therapy (metformin and glibenclamide) for treatment of T2DM patients. The present study aimed to evaluate the effect of monotherapy with metformin compared to combination therapy with metformin and glibenclamide on the expression of RAGE, Nrf 2, and Sirt1genes.

Methods

EightyT2DM patients and 40 healthy individuals participated in this case-control study. The patients in the treatment group were divided into two groups who received either metformin alone (n = 40) or metformin in combination with glibenclamide (n = 40). FBS, HbA1c, and fructosamine were measured. The expression of RAGE, Nrf 2, and Sirt 1 genes in PBMC of all subjects were assessed using real-time PCR.

Results

RAGE gene expression in both treatment groups was significantly lower than the control (P < 0.05). RAGE gene expression was significantly reduced in the combination of metformin and glibenclamide treated group compared to metformin group (P < 0.05). Additionally, the expression of Sirt 1 and Nrf 2 genes in both treatment groups was higher than that of the control group (P < 0.05). The expression of Sirt 1 and Nrf 2 genes in metformin and glibenclamide treated group were higher than the metformin group (P < 0.05).

Conclusion

Combination therapy (metformin and glibenclamide) showed stronger effect on repression of the RAGE gene and activation of Nrf 2 and Sirt 1 genes compared to monotherapy (metformin); therefore, it can be concluded that combination therapy may have more protective effects on the T2DM patients. No significant correlation was observed between HbA1c and RAGE, Sirt 1, and Nrf 2 genes expression.

Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes

The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.

Using adipose-derived mesenchymal stem cells to fight the metabolic complications of obesity: Where do we stand?

Obesity is a critical risk factor for the development of metabolic diseases, and its prevalence is increasing worldwide. Stem cell-based therapies have become a promising tool for therapeutic intervention. Among them are adipose-derived mesenchymal stem cells (ADMSCs), secreting numerous bioactive molecules, like growth factors, cytokines, and chemokines. Their unique features, including immunosuppressive and immunomodulatory properties, make them an ideal candidates for clinical applications. Numerous experimental studies have shown that ADMSCs can improve pancreatic islet cell viability and function, ameliorate hyperglycemia, improve insulin sensitivity, restore liver function, counteract dyslipidemia, lower pro-inflammatory cytokines, and reduce oxidative stress in the animal models. These results prompted scientists to use ADMSCs clinically. However, up to date, there have been few clinical studies or ongoing trails using ADMSCs to treat metabolic disorders such as type 2 diabetes mellitus (T2DM) or liver cirrhosis. Most human studies have implemented autologous ADMSCs with minimal risk of cellular rejection. Because the functionality of ADMSCs is significantly reduced in subjects with obesity and/or metabolic syndrome, their efficacy is questioned. ADMSCs transplantation may offer a potential therapeutic approach for the treatment of metabolic complications of obesity, but randomized controlled trials are required to establish their safety and efficacy in humans prior to routine clinical use.

TXNIP: A Double-Edged Sword in Disease and Therapeutic Outlook

Thioredoxin-interacting protein (TXNIP) was originally named vitamin D₃ upregulated protein-1 (VDUP1) because of its ability to bind to thioredoxin (TRX) and inhibit TRX function and expression. TXNIP is an alpha-arrestin protein that is essential for redox homeostasis in the human body. TXNIP may act as a double-edged sword in the cell. The balance of TXNIP is crucial. A study has shown that TXNIP can travel between diverse intracellular locations and bind to different proteins to play different roles under oxidative stress. The primary function of TXNIP is to induce apoptosis or pyroptosis under oxidative stress. TXNIP also inhibits proliferation and migration in cancer cells, although TXNIP levels decrease, and function diminishes in various cancers. In this review, we summarized the main structure, binding proteins, pathways, and the role of TXNIP in diseases, aiming to explore the double-edged sword role of TXNIP, and expect it to be helpful for future treatment using TXNIP as a therapeutic target.

Long-Term Diabetes Improvement After Duodenal Exclusion in Zucker Diabetic Fatty Rats Is Associated with Prevention of Strain-Specific Pancreatic Remodeling and Increased Beta Cell Proliferation

Background

Response to metabolic surgery is heterogeneous and the metabolic states that underpin weight loss and metabolic improvement are still unclear. In this study, we investigate parameters of post-bariatric fasting glucoregulation and leverage artificial intelligence-assisted whole-slide image analyses to characterize associated immunohistologic features of the pancreas.

Materials and Methods

We performed either loop duodeno-jejunostomy (DJOS) with exclusion of 1/3 of total intestinal length, loop duodeno-ileostomy with exclusion of 2/3 of total intestinal length (DiOS), or a sham operation on 8-week-old male obese ZDF rats. Six months post-operative, we measured blood metabolites and hormones. Subsequently, pancreatic and intestinal tissue was removed, formalin fixed, and paraffin embedded. Immunohistologic (IHC) analyses included proliferating cell nuclear antigen (PCNA) to visualize the proliferation fraction and pancreatic and duodenal homeobox 1 (PDX 1) as a measure of pancreatic cell differentiation. For IHC quantification, all slides were digitalized and analyzed using QuPath. All analyzed slides were reviewed by two independent pathologists for correctness.

Results

DJOS and DiOS were associated with preserved fasting insulin production compared to sham. Histopathologic evaluation showed significantly higher numbers of beta cells and specifically of clustered cell organization in DJOS and DiOS compared to sham. Cell proliferation (PCNA) was significantly elevated in DJOS and DiOS compared to sham.

Conclusion

In this interventional model of bariatric surgery in severe genetic diabetes, we demonstrate post-operative histologic and immunohistologic features of the pancreas associated with improved fasting glucose homeostasis.

Graphical abstract

Cellular Senescence in Diabetes Mellitus: Distinct Senotherapeutic Strategies for Adipose Tissue and Pancreatic β Cells

Increased insulin resistance and impaired insulin secretion are significant characteristics manifested by patients with type 2 diabetes mellitus (T2DM). The degree and extent of these two features in T2DM vary among races and individuals. Insulin resistance is accelerated by obesity and is accompanied by accumulation of dysfunctional adipose tissues. In addition, dysfunction of pancreatic β-cells impairs insulin secretion. T2DM is significantly affected by aging, as the β-cell mass diminishes with age. Moreover, both obesity and hyperglycemia-related metabolic changes in developing diabetes are associated with accumulation of senescent cells in multiple organs, that is, organismal aging. Cellular senescence is defined as a state of irreversible cell cycle arrest with concomitant functional decline. It is caused by telomere shortening or senescence-inducing stress. Senescent cells secrete proinflammatory cytokines and chemokines, which is designated as the senescence-associated secretory phenotype (SASP), and this has a negative impact on adipose tissues and pancreatic β-cells. Recent advances in aging research have suggested that senolysis, the removal of senescent cells, can be a promising therapeutic approach to prevent or improve aging-related diseases, including diabetes. The attenuation of a SASP may be beneficial, although the pathophysiological involvement of cellular senescence in diabetes is not fully understood. In the clinical application of senotherapy, tissue-context-dependent senescent cells are increasingly being recognized as an issue to be solved. Recent studies have observed highly heterogenic and complex senescent cell populations that serve distinct roles among tissues, various stages of disease, and different ages. For example, in high-fat-diet induced diabetes with obesity, mouse adipose tissues display accumulation of p21Cip1-highly-expressing (p21high) cells in the early stage, followed by increases in both p21high and p16INK4a-highly-expressing (p16high) cells in the late stage. Interestingly, elimination of p21high cells in visceral adipose tissue can prevent or improve insulin resistance in mice with obesity, while p16high cell clearance is less effective in alleviating insulin resistance. Importantly, in immune-deficient mice transplanted with fat from obese patients, dasatinib plus quercetin, a senolytic cocktail that reduces the number of both p21high and p16high cells, improves both glucose tolerance and insulin resistance. On the other hand, in pancreatic β cells, p16high cells become increasingly predominant with age and development of diabetes. Consistently, elimination of p16high cells in mice improves both glucose tolerance and glucose-induced insulin secretion. Moreover, a senolytic compound, the anti-Bcl-2 inhibitor ABT263 reduces p16INK4a expression in islets and restores glucose tolerance in mice when combined with insulin receptor antagonist S961 treatment. In addition, efficacy of senotherapy in targeting mouse pancreatic β cells has been validated not only in T2DM, but also in type 1 diabetes mellitus. Indeed, in non-obese diabetic mice, treatment with anti-Bcl-2 inhibitors, such as ABT199, eliminates senescent pancreatic β cells, resulting in prevention of diabetes mellitus. These findings clearly indicate that features of diabetes are partly determined by which or where senescent cells reside in vivo, as adipose tissues and pancreatic β cells are responsible for insulin resistance and insulin secretion, respectively. In this review, we summarize recent advances in understanding cellular senescence in adipose tissues and pancreatic β cells in diabetes. We review the different potential molecular targets and distinctive senotherapeutic strategies in adipose tissues and pancreatic β cells. We propose the novel concept of a dual-target tailored approach in senotherapy against diabetes.

Carnosic Acid Protects INS-1 β-Cells against Streptozotocin-Induced Damage by Inhibiting Apoptosis and Improving Insulin Secretion and Glucose Uptake

Carnosic acid (CA), a natural polyphenolic diterpene derived from Rosmarinus officinalis, has been proven to possess a broad spectrum of medicinal properties. Nevertheless, no studies on its impact on pancreatic β-cells have been conducted to date. Herein, clonal rat INS-1 (832/13) cells were pretreated with CA for 24 h and then incubated with streptozotocin (STZ) for 3 h. Several functional experiments were performed to determine the effect of CA on STZ-induced pancreatic β-cell damage, including cell viability assay, apoptosis analysis, and measurement of the level of insulin secretion, glucose uptake, malondialdehyde (MDA), reactive oxygen species (ROS), and proteins expression. STZ treatment decreased cell survival, insulin secretion, glucose uptake, and increased apoptosis, MDA, and ROS production in INS-1 cells. Furthermore, protein expression/phosphorylation analysis showed significant down-regulation in insulin, PDX-1, PI3K, AKT/p-AKT, and Bcl₂. On the other hand, expression of BAX and BAD and cleaved PARP were significantly increased. Interestingly, preincubation with CA reversed the adverse impact of STZ at the cellular and protein expression levels. In conclusion, the data indicate that CA protects β-cells against STZ-induced damage, presumably through its modulatory effect on the different pathways, including the Pi3K/AKT/PDX-1/insulin pathway and mitochondria-mediated apoptosis.

Green Silver Nanoparticles Synthesized from Taverniera couneifolia Elicits Effective Anti-Diabetic Effect in Alloxan-Induced Diabetic Wistar Rats

Background: Using a variety of chemical compounds and biomolecules, researchers have been working on new antidiabetic drugs for many years. Anti-diabetic research is increasingly using nanomaterials because of their unique qualities, such as their tiny size, biocompatibility, and ability to penetrate cell membranes for drug delivery. Using extract of T. couneifolia coated with silver nanoparticles as a model for diabetes mellitus research was one of the goals of this work. Methods: Uv-Vis spectroscopy was used to measure the TAgNPs surface plasmon resonance. FTIR spectroscopy confirmed the attached functional groups, XRD analysis confirmed the size and crystallinity, scanning electron microscopy revealed that the majority of the particles were spherical, and EDX performed the elemental analysis. For 21 days, alloxan-induced diabetic Wistar rats (N = 25, n = 5/group) were administered 10 mg/kg body weight of photosynthesized AgNPs as a standard animal model, while those in the untreated normal control group C, received distilled water as a control, diabetics who were treated with 0.5 mg/kg of body weight of glibenclamide, 10 mg/kg of methanolic T. couneifolia extract, and diabetics who were given 10 mg/kg of body weight of synthetic AgNPs derived from T. couneifolia in the DAgNPs group. At the conclusion of the treatment, lipid, liver and kidney profiles were re-examined to determine whether or not the treatment had been effective (day 21). Oral glucose doses of 2 g/kg of body weight were administered to each group, and blood glucose levels were measured at various intervals (day 21). Fasting glucose levels were measured using a glucometer. Each animal's urine was tested for leukocytes, nitrites, and bilirubin using lab-made prepared assay kits. One-way ANOVA and Dunnett's test were used for statistical analysis. Results: The surface plasmon resonance effect was examined with UV-vis, it showed a sharp peak at 412 nm. X-ray diffraction measurements indicated that the produced nanoparticles were between 15 to 31.44 nm in size. Alloxan-induced diabetic rats were fed AgNPs derived from phytosynthesized AgNPs, compared to diabetic control rats, diabetic rats treated with AgNPs showed a considerable improvement in their dyslipidemia status. Over the course of the days, it also lowered blood glucose levels. A reduction in blood glucose levels, a rise in body weight, and significant improvements in the lipid, liver, and renal profiles were also seen. Conclusions: The present findings revealed that plant mediated silver nanoparticles significantly improved the alloxan induced diabetic changes in various treated rats and might be used for the treatment of diabetes.