Beta cell apoptosis in diabetes

Magnetic Resonance Imaging-Based Assessment of Pancreatic Fat Strongly Correlates With Histology-Based Assessment of Pancreas Composition

OBJECTIVE

The aim of the study is to assess the relationship between magnetic resonance imaging (MRI)-based estimation of pancreatic fat and histology-based measurement of pancreatic composition.

MATERIALS AND METHODS

In this retrospective study, MRI was used to noninvasively estimate pancreatic fat content in preoperative images from high-risk individuals and disease controls having normal pancreata. A deep learning algorithm was used to label 11 tissue components at micron resolution in subsequent pancreatectomy histology. A linear model was used to determine correlation between histologic tissue composition and MRI fat estimation.

RESULTS

Twenty-seven patients (mean age 64.0 ± 12.0 years [standard deviation], 15 women) were evaluated. The fat content measured by MRI ranged from 0% to 36.9%. Intrapancreatic histologic tissue fat content ranged from 0.8% to 38.3%. MRI pancreatic fat estimation positively correlated with microanatomical composition of fat (r = 0.90, 0.83 to 0.95], P < 0.001); as well as with pancreatic cancer precursor ( r = 0.65, P < 0.001); and collagen ( r = 0.46, P < 0.001) content, and negatively correlated with pancreatic acinar ( r = -0.85, P < 0.001) content.

CONCLUSIONS

Pancreatic fat content, measurable by MRI, correlates to acinar content, stromal content (fibrosis), and presence of neoplastic precursors of cancer.

Anti-Inflammatory Properties of Eugenol in Lipopolysaccharide-Induced Macrophages and Its Role in Preventing β-Cell Dedifferentiation and Loss Induced by High Glucose-High Lipid Conditions

Inflammation is a natural immune response to injury, infection, or tissue damage. It plays a crucial role in maintaining overall health and promoting healing. However, when inflammation becomes chronic and uncontrolled, it can contribute to the development of various inflammatory conditions, including type 2 diabetes. In type 2 diabetes, pancreatic β-cells have to overwork and the continuous impact of a high glucose, high lipid (HG-HL) diet contributes to their loss and dedifferentiation. This study aimed to investigate the anti-inflammatory effects of eugenol and its impact on the loss and dedifferentiation of β-cells. THP-1 macrophages were pretreated with eugenol for one hour and then exposed to lipopolysaccharide (LPS) for three hours to induce inflammation. Additionally, the second phase of NLRP3 inflammasome activation was induced by incubating the LPS-stimulated cells with adenosine triphosphate (ATP) for 30 min. The results showed that eugenol reduced the expression of proinflammatory genes, such as IL-1β, IL-6 and cyclooxygenase-2 (COX-2), potentially by inhibiting the activation of transcription factors NF-κB and TYK2. Eugenol also demonstrated inhibitory effects on the levels of NLRP3 mRNA and protein and Pannexin-1 (PANX-1) activation, eventually impacting the assembly of the NLRP3 inflammasome and the production of mature IL-1β. Additionally, eugenol reduced the elevated levels of adenosine deaminase acting on RNA 1 (ADAR1) transcript, suggesting its role in post-transcriptional mechanisms that regulate inflammatory responses. Furthermore, eugenol effectively decreased the loss of β-cells in response to HG-HL, likely by mitigating apoptosis. It also showed promise in suppressing HG-HL-induced β-cell dedifferentiation by restoring β-cell-specific biomarkers. Further research on eugenol and its mechanisms of action could lead to the development of therapeutic interventions for inflammatory disorders and the preservation of β-cell function in the context of type 2 diabetes.

IMT504 protects beta cells against apoptosis and maintains beta cell identity, without modifying proliferation

We have demonstrated that oligodeoxynucleotide IMT504 promotes significant improvement in the diabetic condition in diverse animal models. Based on these results, here we evaluated whether these effects observed in vivo could be due to direct effects on β-cells. We demonstrate by immunofluorescence that IMT504 enters the cell and locates in cytoplasm where it induces GSK-3β phosphorylation that inactivates this kinase. As GSK-3β tags Pdx1 for proteasomal degradation, by inactivating GSK-3β, IMT504 induces an increase in Pdx1 protein levels, demonstrated by Western blotting. Concomitantly, an increase in Ins2 and Pdx1 gene transcription was observed, with no significant increase in insulin content or secretion. Enhanced Pdx1 is promising since it is a key transcription factor for insulin synthesis and is also described as an essential factor for the maintenance β-cell phenotype and function. Dose-dependent inhibition of H2 O2 -induced apoptosis determined by ELISA as well as decreased expression of Bax was also observed. These results were confirmed in another β-cell line, beta-TC-6 cells, in which a cytokine mix induced apoptosis that was reversed by IMT504. In addition, an inhibitor of IMT504 entrance into cells abrogated the effect IMT504. Based on these results we conclude that the β-cell recovery observed in vivo may include direct effects of IMT504 on β-cells, by maintaining their identity/phenotype and protecting them from oxidative stress and cytokine-induced apoptosis. Thus, this work positions IMT504 as a promising option in the framework of the search of new therapies for type I diabetes treatment.

Dysfunctions, molecular mechanisms, and therapeutic strategies of pancreatic β-cells in diabetes

Pancreatic beta-cell death has been established as a critical mediator in the progression of type 1 and type 2 diabetes mellitus. Beta-cell death is associated with exacerbating hyperglycemia and insulin resistance and paves the way for the progression of DM and its complications. Apoptosis has been considered the primary mechanism of beta-cell death in diabetes. However, recent pieces of evidence have implicated the substantial involvement of several other novel modes of cell death, including autophagy, pyroptosis, necroptosis, and ferroptosis. These distinct mechanisms are characterized by their unique biochemical features and often precipitate damage through the induction of cellular stressors, including endoplasmic reticulum stress, oxidative stress, and inflammation. Experimental studies were identified from PubMed literature on different modes of beta cell death during the onset of diabetes mellitus. This review summarizes current knowledge on the crucial pathways implicated in pancreatic beta cell death. The article also focuses on applying natural compounds as potential treatment strategies in inhibiting these cell death pathways.

Inflammation versus regulation: how interferon-gamma contributes to type 1 diabetes pathogenesis

Type 1 diabetes is an autoimmune disease with onset from early childhood. The insulin-producing pancreatic beta cells are destroyed by CD8⁺ cytotoxic T cells. The disease is challenging to study mechanistically in humans because it is not possible to biopsy the pancreatic islets and the disease is most active prior to the time of clinical diagnosis. The NOD mouse model, with many similarities to, but also some significant differences from human diabetes, provides an opportunity, in a single in-bred genotype, to explore pathogenic mechanisms in molecular detail. The pleiotropic cytokine IFN-γ is believed to contribute to pathogenesis of type 1 diabetes. Evidence of IFN-γ signaling in the islets, including activation of the JAK-STAT pathway and upregulation of MHC class I, are hallmarks of the disease. IFN-γ has a proinflammatory role that is important for homing of autoreactive T cells into islets and direct recognition of beta cells by CD8⁺ T cells. We recently showed that IFN-γ also controls proliferation of autoreactive T cells. Therefore, inhibition of IFN-γ does not prevent type 1 diabetes and is unlikely to be a good therapeutic target. In this manuscript we review the contrasting roles of IFN-γ in driving inflammation and regulating the number of antigen specific CD8⁺ T cells in type 1 diabetes. We also discuss the potential to use JAK inhibitors as therapy for type 1 diabetes, to inhibit both cytokine-mediated inflammation and proliferation of T cells.

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.

Ultrasound Stimulation Potentiates Management of Diabetic Hyperglycemia

OBJECTIVE

Glucose homeostasis is the only way to manage diabetic progression as all medications used do not cure diabetes. This study was aimed at verifying the feasibility of lowering glucose with non-invasive ultrasonic stimulation.

METHODS

The ultrasonic device was homemade and controlled via a mobile application on the smartphone. Diabetes was induced in Sprague-Dawley rats through high-fat diets followed by streptozotocin injection. The treated acupoint CV12 was at the middle of the xiphoid and umbilicus of the diabetic rats. Parameters of ultrasonic stimulation were an operating frequency of 1 MHz, pulse repetition frequency of 15 Hz, duty cycle of 10% and sonication time of 30 min for a single treatment.

DISCUSSION

The diabetic rats exhibited a significant decrease of 11.5% ± 3.6% in blood glucose in 5 min of ultrasonic stimulation (p < 0.001). After the single treatment on the first day, third day and fifth day in the first week, the treated diabetic rats had a significantly small area under the curve of the glucose tolerance test (p < 0.05) compared with the untreated diabetic rats in the sixth week. Hematological analyses indicated that the serum concentrations of β-endorphin were significantly increased by 58% ± 71.9% (p < 0.05) and the insulin level was increased by 56% ± 88.2% (p = 0.15) without statistical significance after a single treatment.

CONCLUSION

Therefore, non-invasive ultrasound stimulation at an appropriate dose can produce a hypoglycemic effect and improve glucose tolerance for glucose homeostasis and may play a role as adjuvant therapy with diabetic medications in the future.

Protective Effects of Hemp (Cannabis sativa) Root Extracts against Insulin-Deficient Diabetes Mellitus In Mice

The pharmacological potential of industrial hemp (Cannabis sativa) has been widely studied. However, the majority of studies have focused on cannabidiol, isolated from the inflorescence and leaf of the plant. In the present study, we evaluated the anti-diabetic potential of hemp root water (HWE) and ethanol extracts (HEE) in streptozotocin (STZ)-induced insulin-deficient diabetic mice. The administration of HWE and HEE ameliorated hyperglycemia and improved glucose homeostasis and islet function in STZ-treated mice (p < 0.05). HWE and HEE suppressed β-cell apoptosis and cytokine-induced inflammatory signaling in the pancreas (p < 0.05). Moreover, HWE and HEE normalized insulin-signaling defects in skeletal muscles and apoptotic response in the liver and kidney induced by STZ (p < 0.05). Gas chromatography-mass spectrometry analysis of HWE and HEE showed possible active compounds which might be responsible for the observed anti-diabetic potential. These findings indicate the possible mechanisms by which hemp root extracts protect mice against insulin-deficient diabetes, and support the need for further studies geared towards the application of hemp root as a novel bioactive material.

GLUT4 degradation by GLUTFOURINH® in mice resembles moderate-obese diabetes of human with hyperglycemia and low lipid accumulation

BACKGROUNDS AND AIMS

Type 2 diabetes mellitus (T2D) is a chronic disease characterized by insulin resistance and hyperglycemia. To investigate T2D, genetic and chemical induced hyper-obese rodent models have been experimentally developed. However, establishment of moderate-obese diabetes model will confer diverse opportunities for translational studies. In this study, we found the chemical, GLUTFOURINH® (GFI), induces post-translational degradation of glucose transporter 4 (GLUT4). We aimed to establish novel diabetic model by using GFI.

METHODS AND RESULTS

Low plasma membrane GLUT4 (pmGLUT4) levels by GFI resulted in reduction of intracellular glucose uptake and TG, and increase of intracellular FFA in A204 cells. Likewise, GFI treatment decreased intracellular TG and increased intracellular FFA levels in Hep3B and 3T3-L1 cells. Mice were administered with GFI (16 mg/kg) for short-term (3-day) and long-term (28- and 31-day) to compared with vehicle injection, HFD model, and T2D model, respectively. Short-term and long-term GFI treatments induced hyperglycemia and hyperinsulinemia with low pmGLUT4 levels. Compared to HFD model, long-term GFI with HFD reduced adipose weight and intracellular TG accumulation, but increased plasma FFA. GFI treatment resulted in insulin resistance by showing low QUICKI and high HOMA-IR values, and low insulin response during insulin tolerance test. Additionally, low pmGLUT4 by GFI heightened hyperglycemia, hyperinsulinemia, and insulin resistance compared to T2D model.

CONCLUSIONS

In summary, we report GLUT4 degradation by novel chemical (GFI) induces moderate-obese diabetes representing hyperglycemia, insulin resistance and low intracellular lipid accumulation. The GLUT4 degradation by GFI has translational value for studying diseases related to moderate-obese 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.

Cannabinoids and terpenes for diabetes mellitus and its complications: from mechanisms to new therapies

The number of people diagnosed with diabetes mellitus and its complications is markedly increasing worldwide, leading to a worldwide epidemic across all age groups, from children to older adults. Diabetes is associated with premature aging. In recent years, it has been found that peripheral overactivation of the endocannabinoid system (ECS), and in particular cannabinoid receptor 1 (CB1R) signaling, plays a crucial role in the progression of insulin resistance, diabetes (especially type 2), and its aging-related comorbidities such as atherosclerosis, nephropathy, neuropathy, and retinopathy. Therefore, it is suggested that peripheral blockade of CB1R may ameliorate diabetes and diabetes-related comorbidities. The use of synthetic CB1R antagonists such as rimonabant has been prohibited because of their psychiatric side effects. In contrast, phytocannabinoids such as cannabidiol (CBD) and tetrahydrocannabivarin (THCV), produced by cannabis, exhibit antagonistic activity on CB1R signaling and do not show any adverse side effects such as psychoactive effects, depression, or anxiety, thereby serving as potential candidates for the treatment of diabetes and its complications. In addition to these phytocannabinoids, cannabis also produces a substantial number of other phytocannabinoids, terpenes, and flavonoids with therapeutic potential against insulin resistance, diabetes, and its complications. In this review, the pathogenesis of diabetes, its complications, and the potential to use cannabinoids, terpenes, and flavonoids for its treatment are discussed.

The Role of Galectin 3 in the Pathogenesis of Diabetes Mellitus: Focus on Β-Cell Function and Survival

Galectin 3 is a lectin expressed in many tissues with a significant biological role in physiological and pathological processes. Our review aims to sublimate the effects of galectin 3 on the β-cells function and survival. Data about the effect of galectin 3 on β- cells are scarce and contradictory. Several studies have shown that reduced activity of the galectin 3 gene reduces the risk of developing type 1 diabetes in an experimental model of diabetes in galectin 3 deficient mice. On the other side, in an experimental model of type 1 diabetes with mice with selectively enhanced expression of galectin 3 in β-cells, was shown that increased expression of this lectin has a protective role. Unlike type 1 diabetes where the autoimmune process plays a dominant role in pathogenesis, the pathogenesis of type 2 diabetes is multifactorial. One of the main factors which contribute to type 2 diabetes, the insulin resistance, is related to the concentration of soluble galectin 3. The effect of galectin 3 is very important for β-cell function. When a harmful factor acts on a β-cell, its intracellular concentration increases to preserve the function of β-cells and prevent their apoptosis, by blocking the internal path of apoptosis. However, excessive accumulation of galectin 3 inside the cell leads to its secretion, which encourages tissue inflammation. Based on all the above, galectin 3 has a double effect on β-cells.

The Influence of Microenvironment on Survival of Intraportal Transplanted Islets

Clinical islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still uncommon because transplanted islets are damaged by multiple challenges, including instant blood mediated inflammatory reaction (IBMIR), inflammatory cytokines, hypoxia/reperfusion injury, and immune rejection. The transplantation microenvironment plays a vital role especially in intraportal islet transplantation. The identification and targeting of pathways that function as “master regulators” during deleterious inflammatory events after transplantation, and the induction of immune tolerance, are necessary to improve the survival of transplanted islets. In this article, we attempt to provide an overview of the influence of microenvironment on the survival of transplanted islets, as well as possible therapeutic targets.

Classical and non-classical islet peptides in the control of β-cell function

The dual role of the pancreas as both an endocrine and exocrine gland is vital for food digestion and control of nutrient metabolism. The exocrine pancreas secretes enzymes into the small intestine aiding digestion of sugars and fats, whereas the endocrine pancreas secretes a cocktail of hormones into the blood, which is responsible for blood glucose control and regulation of carbohydrate, protein and fat metabolism. Classical islet hormones, insulin, glucagon, pancreatic polypeptide and somatostatin, interact in an autocrine and paracrine manner, to fine-tube the islet function and insulin secretion to the needs of the body. Recently pancreatic islets have been reported to express a number of non-classical peptide hormones involved in metabolic signalling, whose major production site was believed to reside outside pancreas, e.g. in the small intestine. We highlight the key non-classical islet peptides, and consider their involvement, together with established islet hormones, in regulation of stimulus-secretion coupling as well as proliferation, survival and transdifferentiation of β-cells. We furthermore focus on the paracrine interaction between classical and non-classical islet hormones in the maintenance of β-cell function. Understanding the functional relationships between these islet peptides might help to develop novel, more efficient treatments for diabetes and related metabolic disorders.

Angiotensin(1-7) Improves Islet Function in Diabetes Through Reducing JNK/Caspase-3 Signaling

The aim of this study is to investigate whether Angiotensin (1-7), the physiological antagonist of Angiotensin II (AngII), has antidiabetic activity and the possible mechanism. Male Wistar rats were randomly divided into 3 groups: control group fed the normal diet, DM group fed high-fat diet and injected with STZ, and Angiotensin (1-7) group receiving injection of STZ followed by Angiotensin (1-7) treatment. Serum Ang II, fasting blood glucose, insulin, HOMA-IR, and HOMA-beta were determined in control, diabetes and Angiotensin (1-7) groups. The increased AngII and insulin resistance in diabetes group were accompanied by changes in islet histopathology. However, Angiotensin (1-7) improved the islet function and histopathology in diabetes without affecting the level of AngII. Western blot confirmed that Angiotensin (1-7) decreased the cleaved caspase 3 levels in pancreas of DM. The increased expression of JNK, Bax, and Bcl2 genes under diabetic conditions were partially reversed after Angiotensin (1-7) administration in pancreas. Immunofluorescence analysis showed that p-JNK was markedly increased in islet of DM rats, which was markedly alleviated after Angiotensin (1-7) treatment. Furthermore, Angiotensin (1-7) reversed high glucose(HG) induced mitochondrial apoptosis augments. Finally, Angiotensin (1-7) attenuated the apoptosis of INS-1 cells through reducing JNK activation in diabetes, which was blocked by anisomycin (a potent agonist of JNK). Our findings provide supporting evidence that Angiotensin (1-7) improved the islet beta-cells apoptosis by JNK-mediated mitochondrial dysfunction, which might be a novel target for the treatment and prevention of beta-cells dysfunction in DM.

Inhibition of Notch activity promotes pancreatic cytokeratin 5-positive cell differentiation to beta cells and improves glucose homeostasis following acute pancreatitis

Some individuals develop prediabetes and/or diabetes following acute pancreatitis (AP). AP-induced beta-cell injury and the limited regenerative capacity of beta cells might account for pancreatic endocrine insufficiency. Previously, we found that only a few pancreatic cytokeratin 5 positive (Krt5⁺) cells differentiated into beta cells in the murine AP model, which was insufficient to maintain glucose homeostasis. Notch signaling determines pancreatic progenitor differentiation in pancreas development. This study aimed to examine whether Notch signaling inhibition could promote pancreatic Krt5⁺ cell differentiation into beta cells and improve glucose homeostasis following AP. Pancreatic tissues from patients with acute necrotizing pancreatitis (ANP) were used to evaluate beta-cell injury, Krt5⁺ cell activation and differentiation, and Notch activity. The murine AP model was induced by cerulein, and the effect of Notch inhibition on Krt5⁺ cell differentiation was evaluated both in vivo and in vitro. The results demonstrated beta-cell loss in ANP patients and AP mice. Krt5⁺ cells were activated in ANP pancreases along with persistently elevated Notch activity, which resulted in the formation of massive duct-like structures. AP mice that received Notch inhibitor showed that impaired glucose tolerance was reversed 7 and 15 days following AP, and increased numbers of newborn small islets due to increased differentiation of Krt5⁺ cells to beta cells to some extent. In addition, Krt5⁺ cells isolated from AP mice showed increased differentiation to beta cells by Notch inhibition. Collectively, these findings suggest that beta-cell loss contributes to pancreatic endocrine insufficiency following AP, and inhibition of Notch activity promotes pancreatic Krt5⁺ cell differentiation to beta cells and improves glucose homeostasis. The findings from this study may shed light on the potential treatment of prediabetes/diabetes following AP.

Sigma receptor knockdown augments dysfunction and apoptosis of beta cells induced by palmitate

Sigma-1 receptor (Sig-1R) is located in the endoplasmic reticulum (ER) and clustered on the mitochondria related endoplasmic membranes, which are involved in the regulation of nervous system disease. Here, we designed Sig-1R silence MIN6 cells and studied the influence of Sig-1R silence on beta cells. We showed Sig-1R inactivation in MIN6 cells could not only decrease cell proliferation but also inhibit cell cycle, and this inhibitory effect on cell cycle might be achieved by regulating the FoxM1/Plk1/Cenpa pathway. Moreover, Sig-1R deficiency increased MIN6 cells sensitivity to lipotoxicity, exaggerated palmitate (PA)-induced apoptosis, and impaired insulin secretion. On the other hand, ER chaperone GRP78 and ER proapoptotic molecules CHOP increased in Sig-1R knockdown MIN6 cells. The ATP level decreased and reactive oxygen species (ROS) increased in this kind of cells. Furthermore not only GRP78 and CHOP levels, but also ATP and ROS levels changed more in Sig-1R silence cells after cultured with PA. Therefore, Sig-1R deficiency exaggerated PA induced beta cells apoptosis by aggravating ER stress and mitochondrial dysfunction. Together, our study showed that Sig-1R might influence the proliferation, apoptosis, and function of beta cells.

The synergistic protection of EGCG and quercetin against streptozotocin (STZ)-induced NIT-1 pancreatic β cell damage via upregulation of BCL-2 expression by miR-16-5p

EGCG and quercetin are flavonoids which usually co-exist in edible plants and they exhibit anti-diabetes effects. This study aimed to explore the mechanisms by which quercetin and EGCG synergistically protected pancreatic β-cells from streptozotocin-induced apoptosis. EGCG, quercetin, and their combinations (both 15 μM) all reversed STZ-induced cells damage and enhanced glucose-stimulated insulin secretion, with the combination being more effective than a single compound. At the molecular level, the EGCG-quercetin combination upregulated BCL-2 expression and caused a greater reduction in miR-16-5p level than EGCG alone or quercetin alone. Overexpression of miR-16-5p could offset the down-regulated apoptotic genes caused by the synergistic action of the combination. These findings suggest that EGCG and quercetin exert synergistic anti-diabetes effect, possibly via decreasing the expression of miR-16-5p that targets directly BCL-2. This is the first report on a miRNA-based mechanism underlying the synergistic protective effect of EGCG and quercetin against pancreatic cell damage.

Molecular mechanisms of lipotoxicity-induced pancreatic β-cell dysfunction

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

ι-Carrageenan Tetrasaccharide from ι-Carrageenan Inhibits Islet β Cell Apoptosis Via the Upregulation of GLP-1 to Inhibit the Mitochondrial Apoptosis Pathway

ι-Carrageenan performs diversified biological activities but has low bioavailability. ι-Carrageenan tetrasaccharide (ιCTs), a novel marine oligosaccharide prepared by the marine enzyme Cgi82A, was investigated for its effects on insulin resistance in high-fat and high-sucrose diet mice. Oral administration of ιCTs (ιCTs-L 30.0 mg/kg·bw, ιCTs-H 90.0 mg/kg·bw) decreased fasting blood glucose by 35.1% ± 1.41 (P < 0.01) and 27.4% ± 0.420 (P < 0.05), and enhanced glucose tolerance. Besides, ιCTs-L ameliorated islet vacuolization, decreased the β cell apoptosis by 21.8% ± 0.200 (P < 0.05), and promoted insulin secretion by 5.41% ± 0.0173 (P < 0.01) through pancreatic hematoxylin and eosin (H&E) staining, TUNEL staining, and insulin-glucagon immunostaining analysis. Interestingly, ιCTs-L and ιCTs-H treatment increased the incretin GLP-1 content in serum by 22.1% ± 0.402 (P < 0.01) and 10.7% ± 0.0935 (P < 0.05) respectively, through regulating the bile acid levels, which contributed to the inhibition of β cell apoptosis. Mechanically, ιCTs upregulated the expression of the GLP-1 receptor (GLP-1R) and protein kinase A (PKA) in the GLP-1/cAMP/PKA signaling pathway, and further inhibited the expression of cytochrome C and caspase 3 in the mitochondrial apoptotic pathway. In conclusion, this study suggested that ιCTs alleviated insulin resistance by GLP-1-mediated inhibition of β cell apoptosis and proposed a new strategy for developing potential functional foods that prevent insulin resistance.

Gene Expression Profiling of Apoptotic Proteins in Circulating Peripheral Blood Mononuclear Cells in Type II Diabetes Mellitus and Modulation by Metformin

INTRODUCTION

Insulin resistance in obesity and type 2 diabetes mellitus (T2DM) is associated with cardiovascular complications such as atherosclerosis. On the other hand, the reduction of apoptosis in macrophages has been linked with accelerated atherosclerosis. Apoptosis is controlled by a different family of proteins including Bcl-2 and caspases.

METHODS

To examine apoptosis in insulin resistance, we assessed the mRNA expression by qRT-PCR of several Bcl-2 family members, as well as caspase-3, -7, -8, and -9 in peripheral blood mononuclear cells (PBMCs) isolated from lean, obese, diabetic, and diabetic on metformin individuals.

RESULTS

PBMCs of diabetic individuals exhibited reduced expression of caspase-7 and increased expression of Bcl-10, Bad, Bax, Bid, and caspase-3. T2DM on metformin group had significantly higher Bad, Bax, and caspase-7 expression.

DISCUSSION

The moderate up-regulation of pro-apoptotic Bcl-10, Bax, Bad, Bid, and the effector caspase-3 coupled with inhibition of caspase-7 in circulating PBMCs of T2DM could be the result of increased inflammation in T2DM. Metformin treatment significantly inhibited the expression of Bcl-10, Bid, and caspase-3 and upregulated Bad/Bax/caspase-7 pathway suggesting the activation of Bad/Bax/caspase-7 apoptotic pathway. Further studies are warranted to elicit the underlying apoptotic pathways of PBMCs in T2DM and following metformin treatment.

The blockade of cytoplasmic HMGB1 modulates the autophagy/apoptosis checkpoint in stressed islet beta cells

High mobility group (HMGB1) is an alarmin known to be harmful to pancreatic beta cells and associated with diabetes mellitus pathogenesis and pancreatic islet graft failure. It has been long thought that the suppression of HMGB1 molecule is beneficial to the beta cells. However, recent studies have indicated that cytoplasmic HMGB1 (cHMGB1) could function as a modulator to relieve cells from apoptotic stress by autophagy induction. Particularly, pancreatic beta cells have been known to utilize the autophagy-to-apoptosis switch when exposed to hypoxia or lipotoxicity. This study aimed to investigate the beta cells under hypoxic and lipotoxic stress while utilizing a small molecule inhibitor of HMGB1, inflachromene (ICM) which can suppress cHMGB1 accumulation. It was revealed that under cellular stress, blockade of cHMGB1 accumulation decreased the viability of islet grafts, primary islets and MIN6 cells. MIN6 cells under cHMGB1 blockade along with lipotoxic stress showed decreased autophagic flux and increased apoptosis. Moreover, cHMGB1 blockade in HFD-fed mice produced unfavorable outcomes on their glucose tolerance. In sum, these results suggested the role of cHMGB1 within beta cell autophagy/apoptosis checkpoint. Given the importance of autophagy in beta cells under apoptotic stresses, this study might provide further insights regarding HMGB1 and diabetes.

IL-17F induces inflammation, dysfunction and cell death in mouse islets

Type 17 immune responses, typified by the production of the cytokines IL-17A and IL-17F, have been implicated in the development of type 1 diabetes in animal models and human patients, however the underlying pathogenic mechanisms have not been clearly elucidated. While previous studies show that IL-17A enhances inflammatory gene expression and cell death in mouse β-cells and human islets, the function of IL-17F in pancreatic β-cells is completely untested to date. Here we show that IL-17F exhibits potent pathogenic effects in mouse β-cell lines and islets. IL-17F signals via the IL-17RA and -RC subunits in β-cells and in combination with other inflammatory cytokines induces expression of chemokine transcripts, suppresses the expression of β-cell identity genes and impairs glucose stimulated insulin secretion. Further IL-17F induces cell death in primary mouse islets. This occurs via Jnk, p38 and NF-κB dependent induction of Nos2 and is completely ablated in the presence of an inducible nitric oxide synthase (iNOS) inhibitor. Together these data indicate that IL-17F possesses similar pathogenic activities to IL-17A in mouse β-cell lines and islets and is likely to be a type 17 associated pathogenic factor in type 1 diabetes.

A direct look at the dysfunction and pathology of the β cells in human type 2 diabetes

β cells uniquely produce and secrete insulin under the control of several, integrated signals, to maintain blood glucose concentrations within a narrow physiological interval. β cell failure is key to the onset and progression of type 2 diabetes, due to impaired function and reduced mass. In this review we focus on several features of human β cell dysfunction and pathology in type 2 diabetes, as revealed by direct assessment of isolated islet traits and examination of pancreatic tissue from organ donors, surgical samples or autoptic specimens. Insulin secretion defects and pathology findings are discussed in relation to some of the major underlying mechanisms, to also provide clues for conceiving better prevention and treatment of type 2 diabetes by targeting the pancreatic β cells.

Prevention of Oxidative Stress-Induced Pancreatic Beta Cell Damage by Broussonetia Kazinoki Siebold Fruit Extract Via the ERK-Nox4 Pathway

Pancreatic beta cells are vulnerable to oxidative stress, which causes beta cell death and dysfunction in diabetes mellitus. Broussonetia kazinoki Siebold (BK) is a widely used herbal medicine, but its potential effects against beta cell death-induced diabetes have not been studied. Therefore, we investigated the protective effect of an ethanolic extract of BK fruit (BKFE) against streptozotocin (STZ)-induced toxicity in pancreatic beta cells. Intraperitoneal injection of STZ in mice induced hyperglycemia; however, oral administration of BKFE significantly decreased the blood glucose level as well as HbA1c levels. BKFE treatment improved glucose tolerance and increased body weight in diabetic mice. Moreover, BKFE treatment resulted in increased serum insulin levels and insulin expression in the pancreas as well as decreased 4-hydroxynonenal levels induced by oxidative stress. Treatment with STZ decreased cell viability of mouse insulinoma cells (MIN6), which was blocked by BKFE pretreatment. BKFE significantly inhibited apoptotic cells and decreased the expression levels of cleaved-caspase-3 and cleaved-poly (ADP-ribose) polymerase (PARP) induced by STZ treatment. Production of reactive oxygen species in STZ-treated MIN6 cells was also significantly decreased by treatment with BKFE. Erk phosphorylation and Nox4 levels increased in STZ-treated MIN6 cells and the pancreas of mice injected with STZ and this increase was inhibited by treatment with BKFE. Inhibition of Erk phosphorylation by treatment with the PD98059 inhibitor or siRNA Erk also blocked the expression of Nox4 induced by STZ treatment. In conclusion, BKFE inhibits Erk phosphorylation, which in turn prevents STZ-induced oxidative stress and beta cell apoptosis. These results suggested that BKFE can be used to prevent or treat beta cell damage in diabetes.

Ceramides and diabetes mellitus: an update on the potential molecular relationships

Recent evidence suggests that ceramides can play an important pathophysiological role in the development of diabetes. Ceramides are primarily recognized as lipid bilayer building blocks, but recent work has shown that these endogenous molecules are important intracellular signalling mediators and may exert some diabetogenic effects via molecular pathways involved in insulin resistance, β-cell apoptosis and inflammation. In the present review, we consider the available evidence on the possible roles of ceramides in diabetes mellitus and introduce eight different molecular mechanisms mediating the diabetogenic action of ceramides, categorized into those predominantly related to insulin resistance vs those mainly implicated in β-cell dysfunction. Specifically, the mechanistic evidence involves β-cell apoptosis, pancreatic inflammation, mitochondrial stress, endoplasmic reticulum stress, adipokine release, insulin receptor substrate 1 phosphorylation, oxidative stress and insulin synthesis. Collectively, the evidence suggests that therapeutic agents aimed at reducing ceramide synthesis and lowering circulating levels may be beneficial in the prevention and/or treatment of diabetes and its related complications.

Bcl-XL: A multifunctional anti-apoptotic protein

B-cell lymphoma-extra large (Bcl-X_L) is one of the anti-apoptotic proteins of the Bcl-2 family that is localized in the mitochondria. Bcl-X_L is one of the key regulators of apoptosis that can also regulate other important cellular functions. Bcl-X_L is overexpressed in many cancers, and its inhibitors have shown good therapeutic effects. Bcl-X_L interacts with Beclin 1, a key factor regulating autophagy. Bcl-X_L is essential for the survival of neurons and plays protective roles in neuronal injuries. It can promote the growth of neurons and the correct formation of neural networks, enhance synaptic plasticity, and control neurotoxicity. Bcl-X_L can also promote the transport of Ca²⁺ to mitochondria, increase the production of ATP, and improve metabolic efficiency. In addition, targeting Bcl-X_L has shown potential value in autoimmune diseases and aging. In this review, we summarize the functions of Bcl-X_L in cancer, autophagy, Ca²⁺ signaling, neuroprotection, neuronal growth and synaptic plasticity, energy metabolism, immunity, and senescence as revealed by investigations conducted in the past 10 years. Moreover, we list some inhibitors that have been developed based on the functions of Bcl-X_L.

Function of Nr4a Orphan Nuclear Receptors in Proliferation, Apoptosis and Fuel Utilization Across Tissues

The Nr4a family of nuclear hormone receptors is composed of three members-Nr4a1/Nur77, Nr4a2/Nurr1 and Nr4a3/Nor1. While currently defined as ligandless, these transcription factors have been shown to regulate varied processes across a host of tissues. Of particular interest, the Nr4a family impinge, in a tissue dependent fashion, on cellular proliferation, apoptosis and fuel utilization. The regulation of these processes occurs through both nuclear and non-genomic pathways. The purpose of this review is to provide a balanced perspective of the tissue specific and Nr4a family member specific, effects on cellular proliferation, apoptosis and fuel utilization.

β-Cell Maturation and Identity in Health and Disease

The exponential increase of patients with diabetes mellitus urges for novel therapeutic strategies to reduce the socioeconomic burden of this disease. The loss or dysfunction of insulin-producing β-cells, in patients with type 1 and type 2 diabetes respectively, put these cells at the center of the disease initiation and progression. Therefore, major efforts have been taken to restore the β-cell mass by cell-replacement or regeneration approaches. Implementing novel therapies requires deciphering the developmental mechanisms that generate β-cells and determine the acquisition of their physiological phenotype. In this review, we summarize the current understanding of the mechanisms that coordinate the postnatal maturation of β-cells and define their functional identity. Furthermore, we discuss different routes by which β-cells lose their features and functionality in type 1 and 2 diabetic conditions. We then focus on potential mechanisms to restore the functionality of those β-cell populations that have lost their functional phenotype. Finally, we discuss the recent progress and remaining challenges facing the generation of functional mature β-cells from stem cells for cell-replacement therapy for diabetes treatment.

Pathogenesis of fulminant type 1 diabetes: Genes, viruses and the immune mechanism, and usefulness of patient-derived induced pluripotent stem cells for future research

We reviewed fulminant type 1 diabetes, a recently established subtype of type 1 diabetes, from the aspects of genes, viruses, immune mechanism and usefulness of patient-derived induced pluripotent stem cells (iPSCs). In an analysis of the pancreas of patients with fulminant type 1 diabetes, viral antigens and viral receptors were expressed in β-cells, as well as macrophages and T lymphocytes surrounding the β-cells. These findings suggest that the β-cells of patients with fulminant type 1 diabetes are destroyed during an immune response against viral infection of the pancreas. Recently, fulminant type 1 diabetes was induced by treatment with anti-programmed cell death 1 antibodies, suggesting that immune regulatory mechanisms are also involved in the onset of this disease. We generated iPSCs from patients with fulminant type 1 diabetes for the first time. We also successfully differentiated patient-derived iPSCs into insulin-producing cells in vitro, and produced a disease model. The proportion of cytokine-induced apoptotic cells among insulin-positive cells was higher in the iPSCs from patients with fulminant type 1 diabetes than in iPSCs from healthy control participants. We carried out ribonucleic acid sequencing in insulin-producing cells differentiated from patient-derived iPSCs, and are now attempting to identify new biomarkers for the disease.

Amorphous solid dispersion of Berberine mitigates apoptosis via iPLA2β/Cardiolipin/Opa1 pathway in db/db mice and in Palmitate-treated MIN6 β-cells

Aims: Berberine (BBR) improves beta-cell function in Type 2 diabetes (T2D) because of its anti-apoptotic activity, and our laboratory developed a new preparation named Huang-Gui Solid Dispersion (HGSD) to improve the oral bioavailability of BBR. However, the mechanism by which BBR inhibits beta-cell apoptosis is unclear. We hypothesized that the Group VIA Ca²⁺-Independent Phospholipase A₂ (iPLA₂β)/Cardiolipin(CL)/Opa1 signaling pathway could exert a protective role in T2D by regulating beta-cell apoptosis and that HGSD could inhibit β-cell apoptosis through iPLA₂β/CL/Opa1 upregulation.

Methods: We examined how iPLA₂β and BBR regulated apoptosis and insulin secretion through CL/Opa1 in vivo and in vitro. In in vitro studies, we developed Palmitate(PA)-induced apoptotic cell death model in mouse insulinoma cells (MIN6). iPLA₂β overexpression and silencing technology were used to examine how the iPLA₂β/CL/Opa1 interaction may play an important role in BBR treatment. In in vivo studies, db/db mice were used as a diabetic animal model. The pancreatic islet function and morphology, beta-cell apoptosis and mitochondrial injury were examined to explore the effects of HGSD. The expression of iPLA₂β/CL/Opa1 was measured to explore whether the signaling pathway was damaged in T2D and was involved in HGSD treatment.

Results: The overexpression of iPLA₂β and BBR treatment significantly attenuated Palmitate- induced mitochondrial injury and apoptotic death compared with Palmitate-treated MIN6 cell. In addition, iPLA₂β silencing could simultaneously partly abolish the anti-apoptotic effect of BBR and decrease CL/Opa1 signaling in MIN6 cells. Moreover, HGSD treatment significantly decreased beta-cell apoptosis and resulted in the upregulation of iPLA₂β/CL/Opa1 compared to those of the db/db mice.

Conclusion: The results indicated that the regulation of iPLA₂β/CL/Opa1 by HGSD may prevent beta-cell apoptosis and may improve islet beta-cell function in Type 2 diabetic mice and in palmitate-treated MIN6 cells.

Ethanolic extracts of Pluchea indica (L.) leaf pretreatment attenuates cytokine-induced β-cell apoptosis in multiple low-dose streptozotocin-induced diabetic mice

Loss of β-cell mass and function is a fundamental feature of pathogenesis for type 1 and type 2 diabetes. Increasing evidence indicates that apoptosis is one of the main mechanisms of β-cell death in both types. Ethanolic extracts of Pluchea indica leaf (PILE) have been reported to possess blood glucose lowering actions in vivo. Nevertheless, further study is required to determine the underlying mechanisms. In this report, we have investigated the preventive effects of PILE on multiple low doses of streptozotocin (MLDS)-induced β-cell apoptosis. Mice were pre-treated with PILE at 50 mg/kg (PILE 50) or 100 mg/kg (PILE 100) for 2 weeks before streptozotocin (STZ) stimulation, and the treatment continued for 4 or 8 weeks. Results revealed that PILE 100 mice exhibited improved blood biochemistry, maintained a higher body weight, had decreased hyperglycemia, and restored islet architectures compared to non-treated STZ mice. Significantly, PILE 100 decreased levels of inflammatory response markers interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and interlukin1-β (IL-1β), concomitant with the inhibition of caspase-3, caspase-8, capsepase-9, phosphorylation of signal transducer and activator of transcription 1 (pSTAT1), nuclear factor-κBp65 (NF-κBp65), and inducible nitric oxide synthase (iNOS). Additionally, survival and proliferative ability of β-cells was mediated by up-regulated Bcl-2 and Ki67, respectively. These results provide strong evidence that pretreatment with PILE 100 effectively attenuated STZ-induced diabetes-related symptoms and these effects could be associated with the inhibition of cytokine-induced β-cell apoptosis.

MANF protects human pancreatic beta cells against stress-induced cell death

AIMS/HYPOTHESIS

There is a great need to identify factors that could protect pancreatic beta cells against apoptosis or stimulate their replication and thus prevent or reverse the development of diabetes. One potential candidate is mesencephalic astrocyte-derived neurotrophic factor (MANF), an endoplasmic reticulum (ER) stress inducible protein. Manf knockout mice used as a model of diabetes develop the condition because of increased apoptosis and reduced proliferation of beta cells, apparently related to ER stress. Given this novel association between MANF and beta cell death, we studied the potential of MANF to protect human beta cells against experimentally induced ER stress.

METHODS

Primary human islets were challenged with proinflammatory cytokines, with or without MANF. Cell viability was analysed and global transcriptomic analysis performed. Results were further validated using the human beta cell line EndoC-βH1.

RESULTS

There was increased expression and secretion of MANF in human beta cells in response to cytokines. Addition of recombinant human MANF reduced cytokine-induced cell death by 38% in human islets (p < 0.05). MANF knockdown in EndoC-βH1 cells led to increased ER stress after cytokine challenge. Mechanistic studies showed that the protective effect of MANF was associated with repression of the NF-κB signalling pathway and amelioration of ER stress. MANF also increased the proliferation of primary human beta cells twofold when TGF-β signalling was inhibited (p < 0.01).

CONCLUSIONS/INTERPRETATION

Our studies show that exogenous MANF protein can provide protection to human beta cells against death induced by inflammatory stress. The antiapoptotic and mitogenic properties of MANF make it a potential therapeutic agent for beta cell protection.

miR15a and miR16 in Chilean type 1 diabetes patients: possible association with apoptosis, inflammatory, or autoimmunity markers

AIM

Type 1 diabetes mellitus (T1D) is an autoimmune disease characterized by the progressive destruction of β cells, mediated by the interaction between T cells and several cytokines. The pathogenesis of T1D has established its possible relationship with miRNAs. In this study, we analyze the expression profile of miR-15a and miR-16 in peripheral blood mononuclear cells (PBMCs) and their possible association with apoptosis, inflammation, or autoimmunity markers.

PATIENTS AND METHODOLOGY

38 T1D patients and 41 control subjects were recruited. mRNAs were analyzed by means of qPCR and TaqMan probes. PBMCs were treated with different concentrations of glucose (baseline, 11 and 25 mM) with or without an inflammatory stimulus as TNF-α (10 ng/ml).

RESULTS

A decrease in the levels of the miR-15a expression in basal conditions is observed in T1D patients compared to healthy control subjects (relative units 0.5 vs. 1.8, p < 0.05). This change in miR-15a and miR-16 is not affected by the addition of TNF-α. No association is observed with inflammatory markers (IL-6, TNF-α, vCAM) or apoptosis (bcl2 expression). The relationship with immunological markers shows an interaction effect between miR16 and IA-2 (p < 0.03).

CONCLUSION

TNF-α does not affect the expression profile of miR-15a and miR16 in PBMCs. A weak correlation is observed between miR-16 and with the autoimmunity profile (IA-2 autoantibody).

Sall2 knockdown exacerbates palmitic acid induced dysfunction and apoptosis of pancreatic NIT-1 beta cells

Spalt-like (Sall) proteins are a class of transcription factors. The role of Sall2 in beta cells remain poorly understood. Here, we aimed to explore whether Sall2 involved in lipotoxicity-mediated dysfunction and apoptosis in pancreatic NIT-1 beta cells. Our results showed that high concentrations of palmitic acid (PA) led to impaired cell viability and decreased Sall2 expression in NIT-1 cells. Knocking down of Sall2 in NIT-1 cells resulted in increased sensitivity to lipotoxicity and caused higher rates of cell apoptosis following PA treatment. Additionally, Sall2 Knockdown impaired insulin synthesis and secretion in response to glucose. Further research indicated Sall2 knockdown attenuate antioxidant capacity and decreased expression level of Peroxiredoxin 2 in NIT-1 cells. These finding implicate that Sall2 may play a significant role in NIT-1 cell function and cell apoptosis under lipotoxic conditions. Therefore, the study of Sall2 in NIT-1 cells provided a new perspective for molecular mechanism of lipotoxicity mediating dysfunction and apoptosis of beta cells.

Neutralization Versus Reinforcement of Proinflammatory Cytokines to Arrest Autoimmunity in Type 1 Diabetes

As physiological pathways of intercellular communication produced by all cells, cytokines are involved in the pathogenesis of inflammatory insulitis as well as pivotal mediators of immune homeostasis. Proinflammatory cytokines including interleukins, interferons, transforming growth factor-β, tumor necrosis factor-α, and nitric oxide promote destructive insulitis in type 1 diabetes through amplification of the autoimmune reaction, direct toxicity to β-cells, and sensitization of islets to apoptosis. The concept that neutralization of cytokines may be of therapeutic benefit has been tested in few clinical studies, which fell short of inducing sustained remission or achieving disease arrest. Therapeutic failure is explained by the redundant activities of individual cytokines and their combinations, which are rather dispensable in the process of destructive insulitis because other cytolytic pathways efficiently compensate their deficiency. Proinflammatory cytokines are less redundant in regulation of the inflammatory reaction, displaying protective effects through restriction of effector cell activity, reinforcement of suppressor cell function, and participation in islet recovery from injury. Our analysis suggests that the role of cytokines in immune homeostasis overrides their contribution to β-cell death and may be used as potent immunomodulatory agents for therapeutic purposes rather than neutralized.

miR15a and miR16 in Chilean type 1 diabetes patients: possible association with apoptosis, inflammatory, or autoimmunity markers

AIM

Type 1 diabetes mellitus (T1D) is an autoimmune disease characterized by the progressive destruction of β cells, mediated by the interaction between T cells and several cytokines. The pathogenesis of T1D has established its possible relationship with miRNAs. In this study, we analyze the expression profile of miR-15a and miR-16 in peripheral blood mononuclear cells (PBMCs) and their possible association with apoptosis, inflammation, or autoimmunity markers.

PATIENTS AND METHODOLOGY

38 T1D patients and 41 control subjects were recruited. mRNAs were analyzed by means of qPCR and TaqMan probes. PBMCs were treated with different concentrations of glucose (baseline, 11 and 25 mM) with or without an inflammatory stimulus as TNF-α (10 ng/ml).

RESULTS

A decrease in the levels of the miR-15a expression in basal conditions is observed in T1D patients compared to healthy control subjects (relative units 0.5 vs. 1.8, p < 0.05). This change in miR-15a and miR-16 is not affected by the addition of TNF-α. No association is observed with inflammatory markers (IL-6, TNF-α, vCAM) or apoptosis (bcl2 expression). The relationship with immunological markers shows an interaction effect between miR16 and IA-2 (p < 0.03).

CONCLUSION

TNF-α does not affect the expression profile of miR-15a and miR16 in PBMCs. A weak correlation is observed between miR-16 and with the autoimmunity profile (IA-2 autoantibody).

Insulin-producing cells derived from 'induced pluripotent stem cells' of patients with fulminant type 1 diabetes: Vulnerability to cytokine insults and increased expression of apoptosis-related genes

AIMS/INTRODUCTION

The present study was carried out to generate induced pluripotent stem cells (iPSCs) from patients with fulminant type 1 diabetes, and evaluate the cytokine-induced apoptotic reactions of β-like insulin-producing cells differentiated from the iPSCs.

MATERIALS AND METHODS

iPSCs were generated from fibroblasts of patients with fulminant type 1 diabetes by inducing six reprogramming factors. Insulin-producing cells were differentiated from the iPSCs in vitro. The proportion of cleaved caspase-3-positive or terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling-positive cells among insulin (INS)-positive cells derived from fulminant type 1 diabetes iPSC and control human iPSC lines was evaluated under treatment with tumor necrosis factor-α, interleukin-1β and interferon-γ. Ribonucleic acid sequencing was carried out to compare gene expressions in INS-positive cells derived from fulminant type 1 diabetes iPSC and control human iPSC lines.

RESULTS

Two iPSC clones were established from each of three patients with fulminant type 1 diabetes. The differentiation of insulin-producing cells from fulminant type 1 diabetes iPSC was confirmed by immunofluorescence analysis and KCl-induced C-peptide secretion. After treatment with pro-inflammatory cytokines, these INS-positive cells showed higher expression of cleaved caspase-3 than those derived from control human iPSCs. Altered expression levels of several apoptosis-related genes were observed in INS-positive cells derived from the fulminant type 1 diabetes iPSCs by ribonucleic acid sequencing.

CONCLUSIONS

We generated iPSCs from patients with fulminant type 1 diabetes and differentiated them into insulin-producing cells. This in vitro disease model can be used to elucidate the disease mechanisms of fulminant type 1 diabetes.

Abnormalities in alternative splicing in diabetes: therapeutic targets

Diabetes mellitus (DM) is a non-communicable, metabolic disorder that affects 416 million individuals worldwide. Type 2 diabetes contributes to a vast 85-90% of the diabetes incidences while 10-15% of patients suffer from type 1 diabetes. These two predominant forms of DM cause a significant loss of functional pancreatic β-cell mass causing different degrees of insulin deficiency, most likely, due to increased β-cell apoptosis. Treatment options involve the use of insulin sensitisers, α-glucosidase inhibitors, and β-cell secretagogues which are often expensive, limited in efficacy and carry detrimental adverse effects. Cost-effective options for treatment exists in the form of herbal drugs, however, scientific validations of these widely used medicinal plants are still underway. Alternative splicing (AS) is a co-ordinated post-transcriptional process in which a single gene generates multiple mRNA transcripts which results in increased amounts of functionally different protein isoforms and in some cases aberrant splicing leads to metabolic disease. In this review, we explore the association of AS with metabolic alterations in DM and the biological significance of the abnormal splicing of some pathogenic diabetes-related genes. An understanding of the molecular mechanism behind abnormally spliced transcripts will aid in the development of new diagnostic, prognostic and therapeutic tools.

Is there a role for gut microbiota in type 1 diabetes pathogenesis?

Type 1 diabetes mellitus (T1D) is an autoimmune disease characterized by insufficient insulin production due to the destruction of insulin secreting β-cells in the Langerhans islets. A variety of factors, including chemicals, viruses, commensal bacteria and diet have been proposed to contribute to the risk of developing the disorder. In the last years, gut microbiota has been proposed as a main factor in T1D pathogenesis. Several alterations of gut microbiota composition were described both in animal model and in humans. The decrease of Firmicutes/Bacteroides ratio was the most frequent pattern described, in particular, in human studies. Furthermore, Bacteroides, Clostridium cluster XIVa, Lactobacillus, Bifidobacterium, and Prevotella relative abundances were different in healthy and affected subjects. Dysbiosis would seem to increase intestinal permeability and thus promote the development of a pro-inflammatory niche that stimulates β-cell autoimmunity in predisposed subjects. Preliminary studies on animal models were realized to investigate the role of gut microbiota modulation as therapy or prevention approach in predisposed animals: promising and stimulating results have been reported. Key message Dietary antigens and microbiota-derived products might act as triggers of T1D by causing a pro-inflammatory and metabolic dysfunctional environment.

7, 8-Dihydroxycoumarin (daphnetin) protects INS-1 pancreatic β-cells against streptozotocin-induced apoptosis

BACKGROUND AND OBJECTIVE

Daphnetin (7, 8-dihydroxycoumarin), a natural coumarin compound, is known to exhibit antioxidant and anti-inflammatrory effects. However, the underlying mechanisms of its anti-apoptotic and antidiabetic effects yet not been examined. Therefore, the present work studied the anti-apoptotic and anti-diabetic effects of daphnetin by in vitro experiments.

METHODS

The rat insulinoma (INS-1) cells were pre-treated with daphnetin at different concentrations (1, 10, 20 and 40µM) for 24h followed by exposition to streptozotocin (STZ) (3mM) for 12h. Effects of daphnetin and STZ on INS-1 cells were determined by MTT assay, glucose stimulated insulin secretion (GSIS) assay, lipid peroxidation, antioxidant status (SOD, CAT, GPx, and GST) Apoptosis staining (DAPI, Hoechst 33342, AO/EB and ROS) was performed by fluorescence microscopy, and Bcl-2, Bax and NF-κB protein expression was detected by Western blotting.

RESULTS

MTT assay indicated that the viability of INS-1 cells was significantly reduced with exposure to STZ for 12h as compared to control cells, while pre-treated with daphnetin for 24h resulted in a significant improvement of cell viability. The effects daphnetin treatment in INS-1 cells on insulin secretion was tested and results showed that the pre-treatment of daphnetin could improve GSIS. Further, daphnetin pre-treatment significantly reduced the levels of lipid peroxidation markers and also improved antioxidant enzymes' activities in STZ-induced INS-1 cells. Western blotting assay revealed that daphnetin could suppress apoptosis through up-regulation of anti-apoptotic Bcl-2 protein expression and the down-regulation of pro-apoptotic Bax and nuclear factor NF-κB protein levels.

CONCLUSION

The results showed that daphnetin might be used in treating diabetes due to its insulin stimulating property and subsequent regulation of apoptotic pathway.

Role of Ceramide in Apoptosis and Development of Insulin Resistance

This review presents data on the functional biochemistry of ceramide, one of the key sphingolipids with properties of a secondary messenger. Molecular mechanisms of the involvement of ceramide in apoptosis in pancreatic β-cells and its role in the formation of insulin resistance in pathogenesis of type 2 diabetes are reviewed. One of the main predispositions for the development of insulin resistance and diabetes is obesity, which is associated with ectopic fat deposition and significant increase in intracellular concentrations of cytotoxic ceramides. A possible approach to the restoration of tissue sensitivity to insulin in type 2 diabetes based on selective reduction of the content of cytotoxic ceramides is discussed.