Targeting the pancreatic β-cell to treat diabetes

Advances in drug discovery for human beta cell regeneration

The numbers of insulin-secreting pancreatic beta cells are reduced in people with type 1 and type 2 diabetes. Driving beta cell regeneration in the pancreases of people with diabetes would be an attractive approach to reversing diabetes. While adult human beta cells have long been believed to be terminally differentiated and, therefore, irreversibly quiescent, it has become clear over recent years that this is not true. More specifically, both candidate and unbiased high-throughput screen approaches have revealed several classes of molecules that are clearly able to induce human beta cell proliferation. Here, we review recent approaches and accomplishments in human beta cell regenerative drug discovery. We also list the challenges that this rapidly moving field must confront to translate beta cell regenerative therapy from the laboratory to the clinic.

Egr-1 transactivates WNT5A gene expression to inhibit glucose-induced β-cell proliferation

Selective β-cell loss is a characteristic of type 2 diabetes mellitus (T2DM). Inhibition of glucose-stimulated β-cell proliferation is one of the in vivo results of the lipotoxicity of saturated fatty acids (SFAs). However, the mechanism by which lipotoxicity inhibits β-cell proliferation is still unclear. In this study, we found palmitate, a saturated fatty acid, inhibited the β-cell proliferation induced by high glucose through the induction of Wnt5a expression in vitro and in vivo. We also found that Wnt5a was both sufficient and necessary for inhibition of β-cell proliferation. Additionally, Egr-1, but not NF-κB, FOXO1, Smad2, Smad3, SP1 or SP3 mediated the expression of Wnt5a. Deletion and site-directed mutagenesis of the WNT5A promoter revealed that activation of WNT5A gene transcription depends primarily on a putative Egr-binding sequence between nucleotides -52 to -44, upstream of the transcription start site. Furthermore, Egr-1 bound directly to this sequence in response to palmitate treatment, both in vitro and in vivo. Moreover, after mice islets were treated with Egr inhibitors, the expression of Wnt5a decreased significantly and the glucose-induced β-cell proliferation inhibited by palmitate was resumed. These findings establish Wnt5a as an Egr-1 target gene in β-cells, uncovering a novel Egr-1/Wnt5a pathway by which saturated free fatty acids block glucose-induced β-cell proliferation. Our study lends support for the potential of Egr-1 inhibitors or Wnt5a antibodies as therapeutics for the treatment of T2DM.

Absence of cannabinoid 1 receptor in beta cells protects against high-fat/high-sugar diet-induced beta cell dysfunction and inflammation in murine islets

AIMS/HYPOTHESIS

The cannabinoid 1 receptor (CB1R) regulates insulin sensitivity and glucose metabolism in peripheral tissues. CB1R is expressed on pancreatic beta cells and is coupled to the G protein Gαi, suggesting a negative regulation of endogenous signalling in the beta cell. Deciphering the exact function of CB1R in beta cells has been confounded by the expression of this receptor on multiple tissues involved in regulating metabolism. Thus, in models of global genetic or pharmacological CB1R blockade, it is difficult to distinguish the indirect effects of improved insulin sensitivity in peripheral tissues from the direct effects of inhibiting CB1R in beta cells per se. To assess the direct contribution of beta cell CB1R to metabolism, we designed a mouse model that allows us to determine the role of CB1R specifically in beta cells in the context of whole-body metabolism.

METHODS

We generated a beta cell specific Cnr1 (CB1R) knockout mouse (β-CB1R^-/-) to study the long-term consequences of CB1R ablation on beta cell function in adult mice. We measured beta cell function, proliferation and viability in these mice in response to a high-fat/high-sugar diet and induction of acute insulin resistance with the insulin receptor antagonist S961.

RESULTS

β-CB1R^-/- mice had increased fasting (153 ± 23% increase at 10 weeks of age) and stimulated insulin secretion and increased intra-islet cAMP levels (217 ± 33% increase at 10 weeks of age), resulting in primary hyperinsulinaemia, as well as increased beta cell viability, proliferation and islet area (1.9-fold increase at 10 weeks of age). Hyperinsulinaemia led to insulin resistance, which was aggravated by a high-fat/high-sugar diet and weight gain, although beta cells maintained their insulin secretory capacity in response to glucose. Strikingly, islets from β-CB1R^-/- mice were protected from diet-induced inflammation. Mechanistically, we show that this is a consequence of curtailment of oxidative stress and reduced activation of the NLRP3 inflammasome in beta cells.

CONCLUSIONS/INTERPRETATION

Our data demonstrate CB1R to be a negative regulator of beta cell function and a mediator of islet inflammation under conditions of metabolic stress. Our findings point to beta cell CB1R as a therapeutic target, and broaden its potential to include anti-inflammatory effects in both major forms of diabetes.

DATA AVAILABILITY

Microarray data have been deposited at GEO (GSE102027).

Alpha-Mangostin Improves Insulin Secretion and Protects INS-1 Cells from Streptozotocin-Induced Damage

Alpha (α)-mangostin, a yellow crystalline powder with a xanthone core structure, is isolated from mangosteen (Garcinia mangostana), which is a tropical fruit of great nutritional value. The aim of the present study was to investigate the anti-diabetic effects of α-mangostin and to elucidate the molecular mechanisms underlying its effect on pancreatic beta (β)-cell dysfunction. To assess the effects of α-mangostin on insulin production, rat pancreatic INS-1 cells were treated with non-toxic doses of α-mangostin (1⁻10 μM) and its impact on insulin signaling was examined by Western blotting. In addition, the protective effect of α-mangostin against pancreatic β-cell apoptosis was verified by using the β-cell toxin streptozotocin (STZ). Our results showed that α-mangostin stimulated insulin secretion in INS-1 cells by activating insulin receptor (IR) and pancreatic and duodenal homeobox 1 (Pdx1) followed by phosphorylation of phospho-phosphatidylinositol-3 kinase (PI3K), Akt, and extracellular signal regulated kinase (ERK) signaling cascades, whereas it inhibited the phosphorylation of insulin receptor substrate (IRS-1) (Ser1101). Moreover, α-mangostin was found to restore the STZ-induced decrease in INS-1 cell viability in a dose-dependent manner. In addition, treatment of INS-1 cells with 50 μM STZ resulted in an increase in intracellular reactive oxygen species (ROS) levels, which was represented by the fluorescence intensity of 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). This oxidative stress was decreased by co-treatment with 5 μM α-mangostin. Similarly, marked increases in the phosphorylation of P38, c-Jun N-terminal kinase (JNK), and cleavage of caspase-3 by STZ were decreased significantly by co-treatment with 5 μM α-mangostin. These results suggest that α-mangostin is capable of improving insulin secretion in pancreatic β-cells and protecting cells from apoptotic damage.

Homogeneous Time-resolved Förster Resonance Energy Transfer-based Assay for Detection of Insulin Secretion

The detection of insulin secretion is critical for elucidating mechanisms of regulated secretion as well as in studies of metabolism. Though numerous insulin assays have existed for decades, the recent advent of homogeneous time-resolved Förster Resonance Energy Transfer (HTRF) technology has significantly simplified these measurements. This is a rapid, cost-effective, reproducible, and robust optical assay reliant upon antibodies conjugated to bright fluorophores with long lasting emission which facilitates time-resolved Förster Resonance Energy Transfer. Moreover, HTRF insulin detection is amenable for the development of high-throughput screening assays. Here we use HTRF to detect insulin secretion in INS-1E cells, a rat insulinoma-derived cell line. This allows us to estimate basal levels of insulin and their changes in response to glucose stimulation. In addition, we use this insulin detection system to confirm the role of dopamine as a negative regulator of glucose-stimulated insulin secretion (GSIS). In a similar manner, other dopamine D2-like receptor agonists, quinpirole, and bromocriptine, reduce GSIS in a concentration-dependent manner. Our results highlight the utility of the HTRF insulin assay format in determining the role of numerous drugs in GSIS and their pharmacological profiles.

An overview of type 2 diabetes and importance of vitamin D3-vitamin D receptor interaction in pancreatic β-cells

One significant health issue that plagues contemporary society is that of Type 2 diabetes (T2D). This disease is characterised by higher-than-average blood glucose levels as a result of a combination of insulin resistance and insufficient insulin secretions from the β-cells of pancreatic islets of Langerhans. Previous developmental research into the pancreas has identified how early precursor genes of pancreatic β-cells, such as Cpal, Ngn3, NeuroD, Ptf1a, and cMyc, play an essential role in the differentiation of these cells. Furthermore, β-cell molecular characterization has also revealed the specific role of β-cell-markers, such as Glut2, MafA, Ins1, Ins2, and Pdx1 in insulin expression. The expression of these genes appears to be suppressed in the T2D β-cells, along with the reappearance of the early endocrine marker genes. Glucose transporters transport glucose into β-cells, thereby controlling insulin release during hyperglycaemia. This stimulates glycolysis through rises in intracellular calcium (a process enhanced by vitamin D) (Norman et al., 1980), activating 2 of 4 proteinases. The rise in calcium activates half of pancreatic β-cell proinsulinases, thus releasing free insulin from granules. The synthesis of ATP from glucose by glycolysis, Krebs cycle and oxidative phosphorylation plays a role in insulin release. Some studies have found that the β-cells contain high levels of the vitamin D receptor; however, the role that this plays in maintaining the maturity of the β-cells remains unknown. Further research is required to develop a more in-depth understanding of the role VDR plays in β-cell function and the processes by which the beta cell function is preserved.

In type 2 diabetes induced by cigarette smoking, activation of p38 MAPK is involved in pancreatic β-cell apoptosis

Type 2 diabetes (T2D) is a chronic disease caused by pancreatic β-cell dysfunction and insulin resistance. Exposure to smoke is a risk factor for diabetes; however, its mechanisms are unclear. In an epidemiological study, we determined the relationship between cigarette smoking and β-cell function. T2D patients had a history of heavier smoking than people without T2D, and heavy smokers had more abnormal glucose metabolism. For various smoking populations, there was a dose-effect relationship between decreases of homeostatic model assessment (HOMA)-β levels or the increases of HOMA-insulin resistance (IR) levels and amount of smoking (pack-years), which indicated that smoking induced β-cell dysfunction. For MIN6 cells, cigarette smoke extract (CSE) decreased insulin secretion and content; enhanced apoptosis, as illustrated by decreases of BCL-2 levels, increases of BAX and cleaved caspase-3 levels, and an increased apoptotic index; and activated the p38 MAPK pathway. For MIN6 cells, inhibition of p-p38 MAPK by SB203580 prevented enhanced apoptosis and the dysfunction of insulin secretion induced by CSE. In sum, activation of p38 MAPK is involved in the apoptosis of pancreatic β-cells induced by cigarette smoking, which is a possible mechanism for induction of T2D by cigarette smoke.

Effect of γ-Aminobutyric Acid-Chitosan Nanoparticles on Glucose Homeostasis in Mice

Diabetes mellitus is the most common endocrine disease worldwide; hyperglycemia is a hallmark of this disease. To alleviate the pain caused by diabetes, developing and utilizing effective diabetic drugs to maintain or recover the function of the residual β-cells is an attractive therapeutic approach. γ-aminobutyric acid (GABA) has been shown to have such effects, but it is easy to have reduced GABA activity under physiological conditions. In the present study, GABA-chitosan nanoparticles (GABA-CS NPs) were prepared, and glucose homeostasis, pancreatic β-cell protection, and anti-inflammatory effects of GABA-CS NPs were investigated in vivo. The results showed that blood glucose levels and IL-1β levels in the GABA-CS NP-administered group were both significantly lower, whereas the PDX1 expression was significantly higher than that of the impaired group (p < 0.01). This indicates that GABA-CS NPs can efficiently maintain glucose homeostasis, protect β-cells, and inhibit inflammation. These nanoparticles have the potential to be applied for future diabetes theranostics.

Loss of Deubiquitinase USP1 Blocks Pancreatic β-Cell Apoptosis by Inhibiting DNA Damage Response

Impaired pancreatic β-cell survival contributes to the reduced β-cell mass in diabetes, but underlying regulatory mechanisms and key players in this process remain incompletely understood. Here, we identified the deubiquitinase ubiquitin-specific protease 1 (USP1) as an important player in the regulation of β-cell apoptosis under diabetic conditions. Genetic silencing and pharmacological suppression of USP1 blocked β-cell death in several experimental models of diabetes in vitro and ex vivo without compromising insulin content and secretion and without impairing β-cell maturation/identity genes in human islets. Our further analyses showed that USP1 inhibition attenuated DNA damage response (DDR) signals, which were highly elevated in diabetic β-cells, suggesting a USP1-dependent regulation of DDR in stressed β-cells. Our findings highlight a novel function of USP1 in the control of β-cell survival, and its inhibition may have a potential therapeutic relevance for the suppression of β-cell death in diabetes.

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Genetic and chemical inhibition of USP1 promoted β-cell survival

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USP1 inhibitors blocked β-cell death in human islets without affecting β-cell function

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USP1 inhibition reduced DDR signals in stressed β-cells

PPARβ/δ: A Key Therapeutic Target in Metabolic Disorders

Research in recent years on peroxisome proliferator-activated receptor (PPAR)β/δ indicates that it plays a key role in the maintenance of energy homeostasis, both at the cellular level and within the organism as a whole. PPARβ/δ activation might help prevent the development of metabolic disorders, including obesity, dyslipidaemia, type 2 diabetes mellitus and non-alcoholic fatty liver disease. This review highlights research findings on the PPARβ/δ regulation of energy metabolism and the development of diseases related to altered cellular and body metabolism. It also describes the potential of the pharmacological activation of PPARβ/δ as a treatment for human metabolic disorders.

The discovery of novel HDAC3 inhibitors via virtual screening and in vitro bioassay

Histone deacetylase 3 (HDAC3) is a potential target for the treatment of human diseases such as cancers, diabetes, chronic inflammation and neurodegenerative diseases. Previously, we proposed a virtual screening (VS) pipeline named “Hypo1_FRED_SAHA-3” for the discovery of HDAC3 inhibitors (HDAC3Is) and had thoroughly validated it by theoretical calculations. In this study, we attempted to explore its practical utility in a large-scale VS campaign. To this end, we used the VS pipeline to hierarchically screen the Specs chemical library. In order to facilitate compound cherry-picking, we then developed a knowledge-based pose filter (PF) by using our in-house quantitative structure activity relationship- (QSAR-) modelling approach and coupled it with FRED and Autodock Vina. Afterward, we purchased and tested 11 diverse compounds for their HDAC3 inhibitory activity in vitro. The bioassay has identified compound 2 (Specs ID: AN-979/41971160) as a HDAC3I (IC₅₀ = 6.1 μM), which proved the efficacy of our workflow. As a medicinal chemistry study, we performed a follow-up substructure search and identified two more hit compounds of the same chemical type, i.e. 2–1 (AQ-390/42122119, IC₅₀ = 1.3 μM) and 2–2 (AN-329/43450111, IC₅₀ = 12.5 μM). Based on the chemical structures and activities, we have demonstrated the essential role of the capping group in maintaining the activity for this class of HDAC3Is. In addition, we tested the hit compounds for their in vitro activities on other HDACs, including HDAC1, HDAC2, HDAC8, HDAC4 and HDAC6. We have identified these compounds are HDAC1/2/3 selective inhibitors, of which compound 2 show the best selectivity profile. Taken together, the present study is an experimental validation and an update to our earlier VS strategy. The identified hits could be used as starting structures for the development of highly potent and selective HDAC3Is.

Naringin Protects Pancreatic β-Cells Against Oxidative Stress-Induced Apoptosis by Inhibiting Both Intrinsic and Extrinsic Pathways in Insulin-Deficient Diabetic Mice

SCOPE

Oxidative stress has been suggested to play a central role in the pathogenesis of diabetes, as well as other metabolic disorders. Naringin, a major flavanone glycoside in citrus species, has been shown to display strong antioxidant potential in in vitro and in vivo models of oxidative stress; however, the underlying protective mechanisms in diabetes are unclear.

METHODS AND RESULTS

To study the protective effects and molecular mechanisms of naringin in preventing islet dysfunction and diabetes, we examined glucose homeostasis, β-cell apoptosis, and inflammatory response in insulin-deficient diabetic mice exposed to acute oxidative stress with streptozotocin (STZ). Naringin dose-dependently ameliorated hyperglycemia and islet dysfunction in insulin-deficient diabetic mice. Naringin counteracted STZ-induced β-cell apoptosis by inhibiting both the intrinsic (mitochondria-mediated) and extrinsic (death receptor-mediated) pathways. Furthermore, these protective effects were associated with suppression of DNA damage response and nuclear factor-kappa B- and mitogen-activated protein kinase-mediated signaling pathways, as well as reduction of reactive oxygen species accumulation and pro-inflammatory cytokine production in the pancreas.

CONCLUSION

Taken together, our study provides insights into the underlying mechanisms through which naringin protects the pancreatic β-cells against oxidative stress-induced apoptosis.

The Hippo Signaling Pathway in Pancreatic β-Cells: Functions and Regulations

Hippo signaling is an evolutionarily conserved pathway that critically regulates development and homeostasis of various tissues in response to a wide range of extracellular and intracellular signals. As an emerging important player in many diseases, the Hippo pathway is also involved in the pathophysiology of diabetes on the level of the pancreatic islets. Multiple lines of evidence uncover the importance of Hippo signaling in pancreas development as well as in the regulation of β-cell survival, proliferation, and regeneration. Hippo therefore represents a potential target for therapeutic agents designed to improve β-cell function and survival in diabetes. In this review, we summarize recent data on the regulation of the Hippo signaling pathway in the pancreas/in pancreatic islets, its functions on β-cell homeostasis in physiology and pathophysiology, and its contribution toward diabetes progression. The current knowledge related to general mechanisms of action and the possibility of exploiting the Hippo pathway for therapeutic approaches to block β-cell failure in diabetes is highlighted.

Microphysiological Analysis Platform of Pancreatic Islet β-Cell Spheroids

The hallmarks of diabetics are insufficient secretion of insulin and dysregulation of glucagon. It is critical to understand release mechanisms of insulin, glucagon, and other hormones from the islets of Langerhans. In spite of remarkable advancements in diabetes research and practice, robust and reproducible models that can measure pancreatic β-cell function are lacking. Here, a microphysiological analysis platform (MAP) that allows the uniform 3D spheroid formation of pancreatic β-cell islets, large-scale morphological phenotyping, and gene expression mapping of chronic glycemia and lipidemia development is reported. The MAP enables the scaffold-free formation of densely packed β-cell spheroids (i.e., multiple array of 110 bioreactors) surrounded with a perfusion flow network inspired by physiologically relevant microenvironment. The MAP permits dynamic perturbations on the β-cell spheroids and the precise controls of glycemia and lipidemia, which allow us to confirm that cellular apoptosis in the β-cell spheroid under hyperglycemia and hyperlipidemia is mostly dependent to a reactive oxygen species-induced caspase-mediated pathway. The β-cells' MAP might provide a potential new map in the pathophysiological mechanisms of β cells.

The Arg-Phe-amide peptide 26RFa/glutamine RF-amide peptide and its receptor: IUPHAR Review 24

The RFamide neuropeptide 26RFa was first isolated from the brain of the European green frog on the basis of cross-reactivity with antibodies raised against bovine neuropeptide FF (NPFF). 26RFa and its N-terminally extended form glutamine RF-amide peptide (QRFP) have been identified as cognate ligands of the former orphan receptor GPR103, now renamed glutamine RF-amide peptide receptor (QRFP receptor). The 26RFa/QRFP precursor has been characterized in various mammalian and non-mammalian species. In the brain of mammals, including humans, 26RFa/QRFP mRNA is almost exclusively expressed in hypothalamic nuclei. The 26RFa/QRFP transcript is also present in various organs especially in endocrine glands. While humans express only one QRFP receptor, two isoforms are present in rodents. The QRFP receptor genes are widely expressed in the CNS and in peripheral tissues, notably in bone, heart, kidney, pancreas and testis. Structure-activity relationship studies have led to the identification of low MW peptidergic agonists and antagonists of QRFP receptor. Concurrently, several selective non-peptidic antagonists have been designed from high-throughput screening hit optimization. Consistent with the widespread distribution of QRFP receptor mRNA and 26RFa binding sites, 26RFa/QRFP exerts a large range of biological activities, notably in the control of energy homeostasis, bone formation and nociception that are mediated by QRFP receptor or NPFF2. The present report reviews the current knowledge concerning the 26RFa/QRFP-QRFP receptor system and discusses the potential use of selective QRFP receptor ligands for therapeutic applications.

Ultrastructural alterations of pancreatic beta cells in human diabetes mellitus

BACKGROUND

Both types of diabetes are characterized by beta-cell failure and death, leading to insulin insufficiency. Very limited information is currently available about the ultrastructural alterations of beta cells in human diabetes. Our aim was to provide a comprehensive ultrastructural analysis of human pancreatic islets in type 1 (T1D) and type 2 (T2D) diabetic patients.

METHODS

We performed a morphometric electron microscopy evaluation of beta cells obtained from the pancreas of 8 nondiabetic (ND), 5 T1D, and 8 T2D organ donors.

RESULTS

A lower amount of beta cells was found in both T1D and T2D than in ND islets, whereas alpha cells were increased only in T2D. An increased number of bi-hormonal cells (showing both insulin and glucagon granules in their cytoplasm) were found in T1D. Insulin granules were less represented in T2D than in ND beta cells, whereas no significant changes were found in T1D. Volume density of the endoplasmic reticulum was increased in T2D and unchanged in T1D; mitochondria number and volume were significantly higher in T2D than in ND beta cells, whereas no significant differences were found in T1D. In both T1D and T2D, more beta cells showed signs of apoptosis than in ND.

CONCLUSIONS

Our results show that in each type of diabetes, beta cells exhibit specific ultrastructural alterations, whose better understanding might improve therapeutic strategies.

Cell membrane-derived nanoparticles: emerging clinical opportunities for targeted drug delivery

Biofunctionalization of nanoparticles (NPs) is an essential component in targeted drug delivery. However, current nanotechnology remains inadequate to imitate complex intercellular interactions existing in physiological conditions in human bodies. Emerging concepts have been explored to utilize human cells to generate cell membrane-formed NPs because cells retain inherent abilities to interact with human tissues compared with synthetic nanomaterials. Neutrophils, red blood cells (RBCs), platelets and monocytes have been employed to form therapeutic NPs to treat vascular disease and cancer, and these novel drug delivery platforms show the translation potential to improve patient quality of life. In this review, we will discuss the concept of cell membrane-formed NPs, the molecular mechanisms of their disease targeting and the potential of personalized nanomedicine.

Chemokine CCL2-CCR2 Signaling Induces Neuronal Cell Death via STAT3 Activation and IL-1β Production after Status Epilepticus

Elevated levels of chemokine C-C motif ligand 2 (CCL2) and its receptor CCR2 have been reported in patients with temporal lobe epilepsy and in experimental seizures. However, the functional significance and molecular mechanism underlying CCL2-CCR2 signaling in epileptic brain remains largely unknown. In this study, we found that the upregulated CCL2 was mainly expressed in hippocampal neurons and activated microglia from mice 1 d after kainic acid (KA)-induced seizures. Taking advantage of CX3CR1^GFP/+:CCR2^RFP/+ double-transgenic mice, we demonstrated that CCL2-CCR2 signaling has a role in resident microglial activation and blood-derived monocyte infiltration. Moreover, seizure-induced degeneration of neurons in the hippocampal CA3 region was attenuated in mice lacking CCL2 or CCR2. We further showed that CCR2 activation induced STAT3 (signal transducer and activator of transcription 3) phosphorylation and IL-1β production, which are critical for promoting neuronal cell death after status epilepticus. Consistently, pharmacological inhibition of STAT3 by WP1066 reduced seizure-induced IL-1β production and subsequent neuronal death. Two weeks after KA-induced seizures, CCR2 deficiency not only reduced neuronal loss, but also attenuated seizure-induced behavioral impairments, including anxiety, memory decline, and recurrent seizure severity. Together, we demonstrated that CCL2-CCR2 signaling contributes to neurodegeneration via STAT3 activation and IL-1β production after status epilepticus, providing potential therapeutic targets for the treatment of epilepsy.SIGNIFICANCE STATEMENT Epilepsy is a global concern and epileptic seizures occur in many neurological conditions. Neuroinflammation associated with microglial activation and monocyte infiltration are characteristic of epileptic brains. However, molecular mechanisms underlying neuroinflammation in neuronal death following epilepsy remain to be elucidated. Here we demonstrate that CCL2-CCR2 signaling is required for monocyte infiltration, which in turn contributes to kainic acid (KA)-induced neuronal cell death. The downstream of CCR2 activation involves STAT3 (signal transducer and activator of transcription 3) phosphorylation and IL-1β production. Two weeks after KA-induced seizures, CCR2 deficiency not only reduced neuronal loss, but also attenuated seizure-induced behavioral impairments, including anxiety, memory decline, and recurrent seizure severity. The current study provides a novel insight on the function and mechanisms of CCL2-CCR2 signaling in KA-induced neurodegeneration and behavioral deficits.

Discovery of a Benzamide Derivative That Protects Pancreatic β-Cells against Endoplasmic Reticulum Stress

Endoplasmic reticulum (ER) stress-mediated pancreatic insulin-producing β-cell dysfunction and death are critical elements in the onset and progression of both type 1 and type 2 diabetes. Here, through cell-based high throughput screening we identified benzamide derivatives as a novel class of β-cell protective agents against ER stress-induced dysfunction and death. Through structure-activity relationship optimization, a 3-(N-piperidinyl)methylbenzamide derivative 13d markedly protects β-cells against ER stress-induced dysfunction and death with near 100% maximum rescue activity and an EC₅₀ of 0.032 μM. Compound 13d alleviates ER stress in β-cells by suppressing ER stress-mediated activation of all three branches of unfolded protein response (UPR) and apoptotic genes. Finally, we show that 13d significantly lowers blood glucose levels and increases concomitant β-cell survival and number in a streptozotocin-induced diabetic mouse model. Identification of β-cell-protective small molecules against ER stress provides a new promising modality for the treatment of diabetes.

miR‑433 protects pancreatic β cell growth in high‑glucose conditions

Pancreatic β cell dysfunction is a key characteristic in the pathogenesis of diabetes mellitus (DM). MicroRNAs (miRNAs) have been identified to serve a role in DM pathogenesis, but how specific miRNAs regulate glucose-stimulated β cell functions remain unclear. The present study aimed to explore the effects of miR-433 on cell growth under high-glucose culture conditions and to determine the possible mechanisms involved. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis was performed to detect the expression levels of miRNAs in Min-6 pancreatic β cells cultured in high-glucose medium, which revealed that miR-433 was significantly downregulated. Results from in vitro Cell Counting Kit-8, colony formation and flow cytometry analyses indicated that overexpression of miR-433 may enhance cell viability and proliferation by promoting cell cycle progression and suppressing apoptosis. Furthermore, bioinformatics prediction and luciferase analysis demonstrated that miR-433 was able to inhibit the expression of cyclooxygenase 2 (COX2) through targeting its 3′-UTR. Moreover, knockdown of COX2 expression alleviated the inhibition of cell growth induced by high glucose, similar to overexpression of miR-433. In conclusion, the present results suggested that miR-433 may protect pancreatic β cells cultured in high glucose, which suggests that miR-433 may have beneficial effects in preventing and treating DM.

GDF11 Attenuates Development of Type 2 Diabetes via Improvement of Islet β-Cell Function and Survival

Growth differentiation factor 11 (GDF11) has been implicated in the regulation of islet development and a variety of aging conditions, but little is known about the physiological functions of GDF11 in adult pancreatic islets. Here, we showed that systematic replenishment of GDF11 not only preserved insulin secretion but also improved the survival and morphology of β-cells and improved glucose metabolism in both nongenetic and genetic mouse models of type 2 diabetes (T2D). Conversely, anti-GDF11 monoclonal antibody treatment caused β-cell failure and lethal T2D. In vitro treatment of isolated murine islets and MIN6 cells with recombinant GDF11 attenuated glucotoxicity-induced β-cell dysfunction and apoptosis. Mechanistically, the GDF11-mediated protective effects could be attributed to the activation of transforming growth factor-β/Smad2 and phosphatidylinositol-4,5-bisphosphate 3-kinase-AKT-FoxO1 signaling. These findings suggest that GDF11 repletion may improve β-cell function and mass and thus may lead to a new therapeutic approach for T2D.

Neurotrophin Signaling Is Required for Glucose-Induced Insulin Secretion

Insulin secretion by pancreatic islet β cells is critical for glucose homeostasis, and a blunted β cell secretory response is an early deficit in type 2 diabetes. Here, we uncover a regulatory mechanism by which glucose recruits vascular-derived neurotrophins to control insulin secretion. Nerve growth factor (NGF), a classical trophic factor for nerve cells, is expressed in pancreatic vasculature while its TrkA receptor is localized to islet β cells. High glucose rapidly enhances NGF secretion and increases TrkA phosphorylation in mouse and human islets. Tissue-specific deletion of NGF or TrkA, or acute disruption of TrkA signaling, impairs glucose tolerance and insulin secretion in mice. We show that internalized TrkA receptors promote insulin granule exocytosis via F-actin reorganization. Furthermore, NGF treatment augments glucose-induced insulin secretion in human islets. These findings reveal a non-neuronal role for neurotrophins and identify a new regulatory pathway in insulin secretion that can be targeted to ameliorate β cell dysfunction.

Design, synthesis, and biological evaluation of aryl N-methoxyamide derivatives as GPR119 agonists

A series of N-methoxyamide derivatives was identified and evaluated as GPR119 agonists. Several N-methoxyamides with thienopyrimidine and pyridine scaffolds showed potent GPR119 agonistic activities. Among them, compound 9c displayed good in vitro activity and potency. Moreover, compound 9c lowered glucose excursion in mice in an oral glucose tolerance test and increased GLP-1 secretion in intestinal cells.

A Narrative Review of Potential Future Antidiabetic Drugs: Should We Expect More?

Prevalence of diabetes mellitus, a chronic metabolic disease characterized by hyperglycemia, is growing worldwide. The majority of the cases belong to type 2 diabetes mellitus (T2DM). Globally, India ranks second in terms of diabetes prevalence among adults. Currently available classes of therapeutic agents are used alone or in combinations but seldom achieve treatment targets. Diverse pathophysiology and the need of therapeutic agents with more favourable pharmacokinetic-pharmacodynamics profile make newer drug discoveries in the field of T2DM essential. A large number of molecules, some with novel mechanisms, are in pipeline. The essence of this review is to track and discuss these potential agents, based on their developmental stages, especially those in phase 3 or phase 2. Unique molecules are being developed for existing drug classes like insulins, DPP-4 inhibitors, GLP-1 analogues; and under newer classes like dual/pan PPAR agonists, dual SGLT1/SGLT2 inhibitors, glimins, anti-inflammatory agents, glucokinase activators, G-protein coupled receptor agonists, hybrid peptide agonists, apical sodium-dependent bile acid transporter (ASBT) inhibitors, glucagon receptor antagonists etc. The heterogeneous clinical presentation and therapeutic outcomes in phenotypically similar patients is a clue to think beyond the standard treatment strategy.

Changes in pancreatic histology, insulin secretion and oxidative status in diabetic rats following treatment with Ficus deltoidea and vitexin

BACKGROUND

The potential application of Ficus deltoidea and vitexin for the management of symptomatologies associated with diabetes mellitus (DM) has gained much attention. However, less firm evidence comes from data to augment our understanding of the role of F. deltoidea and vitexin in protecting pancreatic β-cells. The aim of this study was to assess histological and oxidative stress changes in the pancreas of streptozotocin (STZ)-induced diabetic rats following F. deltoidea extract and vitexin treatment.

METHODS

F. deltoidea and vitexin was administrated orally to six-weeks STZ-induced diabetic rats over 8 weeks period. The glucose and insulin tolerances were assessed by intraperitoneal glucose (2 g/kg) tolerance test (IPGTT) and intraperitoneal insulin (0.65 U/kg) tolerance test (IPITT), respectively. Subsequently, insulin resistance was assessed by homeostasis assessment model of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and the insulin/triglyceride-derived McAuley index. The histological changes in the pancreas were then observed by hematoxylin-eosin (H&E) staining. Further, the pattern of fatty acid composition and infrared (IR) spectra of the serum and pancreas were monitored by gas chromatography (GC) method and Fourier Transform Infrared (FT-IR) spectroscopy.

RESULTS

F. deltoidea and vitexin increased pancreatic antioxidant enzymes and promoted islet regeneration. However, a significant increase in insulin secretion was observed only in rats treated with F. deltoidea. More importantly, reduction of fasting blood glucose is consistent with reduced FT-IR peaks at 1200-1000 cm^-1.

CONCLUSIONS

These results accentuate that F. deltoidea and vitexin could be a potential agent to attenuate pancreatic oxidative damage and advocate their therapeutic potential for treating DM.

Edible Plants and Their Influence on the Gut Microbiome and Acne

Acne vulgaris affects most people at some point in their lives. Due to unclear etiology, likely with multiple factors, targeted and low-risk treatments have yet to be developed. In this review, we explore the multiple causes of acne and how plant-based foods and supplements can control these. The proposed causative factors include insulin resistance, sex hormone imbalances, inflammation and microbial dysbiosis. There is an emerging body of work on the human gut microbiome and how it mediates feedback between the foods we eat and our bodies. The gut microbiome is also an important mediator of inflammation in the gut and systemically. A low-glycemic load diet, one rich in plant fibers and low in processed foods, has been linked to an improvement in acne, possibly through gut changes or attenuation of insulin levels. Though there is much interest in the human microbiome, there is much more unknown, especially along the gut-skin axis. Collectively, the evidence suggests that approaches such as plant-based foods and supplements may be a viable alternative to the current first line standard of care for moderate acne, which typically includes antibiotics. Though patient compliance with major dietary changes is likely much lower than with medications, it is a treatment avenue that warrants further study and development.

Sibling method increases risk assessment estimates for type 1 diabetes

We presented a risk assessment model to distinguish between type 1 diabetes (T1D) affected and unaffected siblings using only three single nucleotide polymorphism (SNP) genotypes. In addition we calculated the heritability from genome-wide identity-by-descent (IBD) sharing between full siblings. We analyzed 1,253 pairs of affected individuals and their unaffected siblings (750 pairs from a discovery set and 503 pairs from a validation set) from the T1D Genetics Consortium (T1DGC), applying a logistic regression to analyze the area under the receiver operator characteristic (ROC) curve (AUC). To calculate the heritability of T1D we used the Haseman-Elston regression analysis of the squared difference between the phenotypes of the pairs of siblings on the estimate of their genome-wide IBD proportion. The model with only 3 SNPs achieving an AUC of 0.75 in both datasets outperformed the model using the presence of the high-risk DR3/4 HLA genotype, namely AUC of 0.60. The heritability on the liability scale of T1D was approximately from 0.53 to 0.92, close to the results obtained from twin studies, ranging from 0.4 to 0.88.

Role of sodium glucose cotransporter-2 inhibitors in type I diabetes mellitus

The burden of diabetes mellitus (DM) in general has been extensively increasing over the past few years. Selective sodium glucose cotransporter-2 (SGLT2) inhibitors were extensively studied in type 2 DM and found to have sustained urinary glucose loss, improvement of glycemic control, in addition to their proven metabolic effects on weight, blood pressure, and cardiovascular benefits. Type 1 DM (T1D) patients clearly depend on insulin therapy, which till today fails to achieve the optimal glycemic control and metabolic targets that are needed to prevent risk of complications. New therapies are obviously needed as an adjunct to insulin therapy in order to try to achieve optimal control in T1D. Many oral diabetic medications have been tried in T1D patients as an adjunct to insulin treatment and have shown conflicting results. Adjunctive use of SGLT2 inhibitors in addition to insulin therapies in T1D was found to have the potential to improve glycemic control along with decrease in the insulin doses, as has been shown in certain animal and short-term human studies. Furthermore, larger well-randomized studies are needed to better evaluate their efficacy and safety in patients with T1D. Euglycemic diabetic ketoacidosis incidences were found to be increased among users of SGLT2 inhibitors, although the incidence remains very low. Recent beneficial effects of ketone body production and this shift in fuel energetics have been suggested based on the findings of protective cardiovascular benefits associated with one of the SGLT2 inhibitors.

Compound 19e, a Novel Glucokinase Activator, Protects against Cytokine-Induced Beta-Cell Apoptosis in INS-1 Cells

Previously, compound 19e, a novel heteroaryl-containing benzamide derivative, was identified as a potent glucokinase activator (GKA) and showed a glucose-lowering effect in diabetic mice. In this study, the anti-apoptotic actions of 19e were evaluated in INS-1 pancreatic beta-cells co-treated with TNF-α and IL-1β to induce cell death. Compound 19e protected INS-1 cells from cytokine-induced cell death, and the effect was similar to treatment with another GKA or exendin-4. Compound 19e reduced annexin-V stained cells and the expression of cleaved caspase-3 and poly (ADP-ribose) polymerase protein, as well as upregulated the expression of B-cell lymphoma-2 protein. Compound 19e inhibited apoptotic signaling via induction of the ATP content, and the effect was correlated with the downregulation of nuclear factor-κB p65 and inducible nitric oxide synthase. Further, 19e increased NAD-dependent protein deacetylase sirtuin-1 (SIRT1) deacetylase activity, and the anti-apoptotic effect of 19e was attenuated by SIRT1 inhibitor or SIRT1 siRNA treatment. Our results demonstrate that the novel GKA, 19e, prevents cytokine-induced beta-cell apoptosis via SIRT1 activation and has potential as a therapeutic drug for the preservation of pancreatic beta-cells.

Differential dose-dependent effects of zinc oxide nanoparticles on oxidative stress-mediated pancreatic β-cell death

AIM

To study the effects of zinc oxide nanoparticles (ZON) on oxidative stress-mediated pancreatic β-cell death.

METHODS

Cellular uptake of ZON, effects on antioxidant factors and apoptosis were studied.

RESULTS

ZON get internalized by endocytosis and increase intracellular zinc ion levels. ZON treatment (30 and 100 μg/ml) to RIN5f cells resulted in cytotoxicity, oxidative stress and apoptosis. ZON (1, 3, 10 μg/ml, subcytotoxic concentrations) increased super oxide dismutase activity and levels of reduced glutathione in RIN5f cells. Furthermore, ZON (subcytotoxic concentrations) protected RIN5f cells from H₂O₂-induced oxidative stress as evidenced by reduced reactive oxygen species levels; increased super oxide dismutase activity and glutathione levels; and reduced apoptotic death.

CONCLUSION

ZON (subcytotoxic concentrations) protect pancreatic β cells from oxidative-stress-mediated cell death.

Exendin-4 promotes pancreatic β-cell proliferation via inhibiting the expression of Wnt5a

Exendin-4, a glucagon-like peptide-1 receptor agonist, is currently regarded as an effective therapeutic strategy for type-2 diabetes. Previous studies indicated that exendin-4 promoted β cell proliferation. However, the underlying mechanisms remain largely unknown. Recently it was reported that exendin-4 promoted pancreatic β cell proliferation by regulating the expression level of Wnt4. The present study was designed to investigate whether other Wnt isoforms take part in accommodation of β-cell proliferation. We found that exendin-4 promotes the proliferation and suppresses the expression of Wnt5a in INS-1 cell line and C57Bl/6 mouse pancreatic β-cells. Further mechanistic study demonstrated that exendin-4 promoted INS-1 cell proliferation partly through down-regulating the expression of Wnt5a. Furthermore, Wnt5a could induce the activation of calmodulin-dependent protein kinase II in INS-1 cells, thereby decreasing the cellular stable β-catenin and its nuclear translocation, and finally reduce the expression of cyclin D1. In addition, we also found that both of the receptors (Frz-2 and Ror-2) mediated the effect of Wnt5a on β cell line INS-1 proliferation. Taken together, this study suggests that Wnt5a plays a critical role in exendin-4-induced β-cell proliferation, indicating that Wnt5a might be a novel regulator in counterbalance of β cell mass.

Mimicking Neuroligin-2 Functions in β-Cells by Functionalized Nanoparticles as a Novel Approach for Antidiabetic Therapy

Both pancreatic β-cell membranes and presynaptic active zones of neurons include in their structures similar protein complexes, which are responsible for mediating the secretion of bioactive molecules. In addition, these membrane-anchored proteins regulate interactions between neurons and guide the formation and maturation of synapses. These proteins include the neuroligins (e.g., NL-2) and their binding partners, the neurexins. The insulin secretion and maturation of β-cells is known to depend on their 3-dimensional (3D) arrangement. It was also reported that both insulin secretion and the proliferation rates of β-cells increase when cells are cocultured with clusters of NL-2. Use of full-length NL-2 or even its exocellular domain as potential β-cell functional enhancers is limited by the biostability and bioavailability issues common to all protein-based therapeutics. Thus, based on molecular modeling approaches, a short peptide with the potential ability to bind neurexins was derived from the NL-2 sequence. Here, we show that the NL-2-derived peptide conjugates onto innovative functional maghemite (γ-Fe2O3)-based nanoscale composite particles enhance β-cell functions in terms of glucose-stimulated insulin secretion and protect them under stress conditions. Recruiting the β-cells' "neuron-like" secretory machinery as a target for diabetes treatment use has never been reported before. Such nanoscale composites might therefore provide a unique starting point for designing a novel class of antidiabetic therapeutic agents that possess a unique mechanism of action.

A Thoroughly Validated Virtual Screening Strategy for Discovery of Novel HDAC3 Inhibitors

Histone deacetylase 3 (HDAC3) has been recently identified as a potential target for the treatment of cancer and other diseases, such as chronic inflammation, neurodegenerative diseases, and diabetes. Virtual screening (VS) is currently a routine technique for hit identification, but its success depends on rational development of VS strategies. To facilitate this process, we applied our previously released benchmarking dataset, i.e., MUBD-HDAC3 to the evaluation of structure-based VS (SBVS) and ligand-based VS (LBVS) combinatorial approaches. We have identified FRED (Chemgauss4) docking against a structural model of HDAC3, i.e., SAHA-3 generated by a computationally inexpensive “flexible docking”, as the best SBVS approach and a common feature pharmacophore model, i.e., Hypo1 generated by Catalyst/HipHop as the optimal model for LBVS. We then developed a pipeline that was composed of Hypo1, FRED (Chemgauss4), and SAHA-3 sequentially, and demonstrated that it was superior to other combinations in terms of ligand enrichment. In summary, we present the first highly-validated, rationally-designed VS strategy specific to HDAC3 inhibitor discovery. The constructed pipeline is publicly accessible for the scientific community to identify novel HDAC3 inhibitors in a time-efficient and cost-effective way.

Epigenetic control of β-cell function and failure

Type 2 diabetes is a highly heritable disease, but only ∼15% of this heritability can be explained by known genetic variant loci. In fact, body mass index is more predictive of diabetes than any of the common risk alleles identified by genome-wide association studies. This discrepancy may be explained by epigenetic inheritance, whereby changes in gene regulation can be passed along to offspring. Epigenetic changes throughout an organism's lifetime, based on environmental factors such as chemical exposures, diet, physical activity, and age, can also affect gene expression and susceptibility to diabetes. Recently, novel genome-wide assays of epigenetic marks have resulted in a greater understanding of how genetics, epigenetics, and the environment interact in the development and inheritance of diabetes.

Role of Melatonin, Galanin, and RFamide Neuropeptides QRFP26 and QRFP43 in the Neuroendocrine Control of Pancreatic β-Cell Function

Glucose homeostasis is finely regulated by a number of hormones and peptides released mainly from the brain, gastrointestinal tract, and muscle, regulating pancreatic secretion through cellular receptors and their signal transduction cascades. The endocrine function of the pancreas is controlled by islets within the exocrine pancreatic tissue that release hormones like insulin, glucagon, somatostatin, pancreatic polypeptide, and ghrelin. Moreover, both exocrine and endocrine pancreatic functions are regulated by a variety of hormonal and neural mechanisms, such as ghrelin, glucagon-like peptide, glucose-dependent insulinotropic polypeptide, or the inhibitory peptide somatostatin. In this review, we describe the role of neurohormones that have been less characterized compared to others, on the regulation of insulin secretion. In particular, we will focus on melatonin, galanin, and RFamide neuropeptides QRFP26 and QRFP43, which display either insulinotropic or insulinostatic effects. In fact, in addition to other hormones, amino acids, cytokines, and a variety of proteins, brain-derived hormones are now considered as key regulators of glucose homeostasis, representing potential therapeutic targets for the treatment of diabetes and obesity.

The Nrf2/Keap1/ARE Pathway and Oxidative Stress as a Therapeutic Target in Type II Diabetes Mellitus

Despite improvements in awareness and treatment of type II diabetes mellitus (TIIDM), this disease remains a major source of morbidity and mortality worldwide, and prevalence continues to rise. Oxidative damage caused by free radicals has long been known to contribute to the pathogenesis and progression of TIIDM and its complications. Only recently, however, has the role of the Nrf2/Keap1/ARE master antioxidant pathway in diabetic dysfunction begun to be elucidated. There is accumulating evidence that this pathway is implicated in diabetic damage to the pancreas, heart, and skin, among other cell types and tissues. Animal studies and clinical trials have shown promising results suggesting that activation of this pathway can delay or reverse some of these impairments in TIIDM. In this review, we outline the role of oxidative damage and the Nrf2/Keap1/ARE pathway in TIIDM, focusing on current and future efforts to utilize this relationship as a therapeutic target for prevention, prognosis, and treatment of TIID.

Untargeted serum metabolomics reveals Fu-Zhu-Jiang-Tang tablet and its optimal combination improve an impaired glucose and lipid metabolism in type II diabetic rats

Fu-Zhu-Jiang-Tang tablet, a six-herb preparation, was proved to show beneficial effects on type II diabetes patients in clinical. This study aims to optimize the component proportion of the six-herb preparation and explore the serum metabolic signatures of type II diabetes rats after treatment with Fu-Zhu-Jiang-Tang tablet and its optimal combination. The component proportion of the preparation was optimized using uniform experimental design and machine learning techniques. Untargeted GC-MS metabolomic experiments were carried out with serum samples from model group and treatment groups. Data were normalized, multivariate and univariate statistical analysis performed and metabolites of interest putatively identified. 23 metabolites were significantly changed by Fu-Zhu-Jiang-Tang tablet treatment and the majority of these were decreased, including various carbohydrates (glucose, mannose, fructose, allose and gluconic acid), unsaturated fatty acids (palmitic acid, 9-octadecenoic acid, oleic acid, arachidonic acid), alanine, valine, propanoic acid, 3-hydroxybutyrate, along with pyrimidine and cholesterol. Increased concentrations of oxalic acid, leucine, glycine, serine, threonine, proline, lysine and citrate were observed. In the optimal combination-fed group, 21 metabolites were significantly affected and strikingly, the magnitudes of changes here were generally much greater than that of Fu-Zhu-Jiang-Tang tablet treated rats. 18 metabolites affected in both groups included various carbohydrates (mannose, glucose, allose, fructose and gluconic acid), unsaturated fatty acids (palmitic acid, 9-octadecenoic acid, oleic acid and arachidonic acid), short-chain fatty acids (oxalic acid, 3-hydroxybutyrate), and amino acids (alanine, valine, leucine, glycine, proline and lysine), as well as pyrimidine. Metabolites exclusively affected in optimal combination treated rat included succinic acid, cysteine and phenylalanine, whilst four metabolites (propanoic acid, citrate, serine and threonine) were only altered in Fu-Zhu-Jiang-Tang tablet treated rat. Our investigation demonstrated Fu-Zhu-Jiang-Tang tablet and its optimal combination treatments were able to ameliorate impaired glucose and lipid metabolism, down- regulate the high level of glucose to a lower level and reverse abnormal levels of metabolites in serum of type II diabetes rats. However, the optimal combination treatment was able to maximize the magnitudes of changes in some metabolites. These findings may be helpful in clarifying the anti-diabetic mechanism of FZJT tablet and its optimal combination.

Proproliferative and antiapoptotic action of exogenously introduced YAP in pancreatic cells

Loss of functional pancreatic β cells is a hallmark of both type 1 and 2 diabetes. Identifying the pathways that promote β cell proliferation and/or block β cell apoptosis is a potential strategy for diabetes therapy. The transcriptional coactivator Yes-associated protein (YAP), a major downstream effector of the Hippo signaling pathway, is a key regulator of organ size and tissue homeostasis by modulating cell proliferation and apoptosis. YAP is not expressed in mature primary human and mouse β cells. We aimed to identify whether reexpression of a constitutively active form of YAP promotes β cell proliferation/survival. Overexpression of YAP remarkably induced β cell proliferation in isolated human islets, while β cell function and functional identity genes were fully preserved. The transcription factor forkhead box M1 (FOXM1) was upregulated upon YAP overexpression and necessary for YAP-dependent β cell proliferation. YAP overexpression protected β cells from apoptosis triggered by multiple diabetic conditions. The small redox proteins thioredoxin-1 and thioredoxin-2 (Trx1/2) were upregulated by YAP; disruption of the Trx system revealed that Trx1/2 was required for the antiapoptotic action of YAP in insulin-producing β cells. Our data show the robust proproliferative and antiapoptotic function of YAP in pancreatic β cells. YAP reconstitution may represent a disease-modifying approach to restore a functional β cell mass in diabetes.

Circulating betatrophin in healthy control and type 2 diabetic subjects and its association with metabolic parameters

AIMS

Betatrophin, a newly identified liver and adipose tissue-derived hormone, has been suggested as an inducer of β-cell proliferation in mice. However, the physiological role of betatrophin remains poorly understood in humans. Hence, the aim of this study was to investigate circulating betatrophin concentrations in normal and type 2 diabetes mellitus (T2DM) Saudi subjects and its association with various metabolic parameters.

METHODS

In this cross-sectional study, 200 Saudi adults (81 healthy non-T2DM controls, age: 41.43±8.35 [mean±SD]; BMI: 31.58±5.49 and 119 T2DM subjects, age: 48.78±11.76years; BMI: 30.25±4.83kg/m(2)) were studied. Anthropometric and fasting serum biochemical data were collected. Circulating betatrophin was measured using an enzyme-linked immunosorbent assay (ELISA) based kit.

RESULTS

We observed significantly higher levels of betatrophin in T2DM subjects compared to healthy controls (882.19±329.06 vs 657.14±261.04pg/ml, p<0.001). Furthermore, in T2DM subjects, betatrophin level was positively associated with blood pressure and serum fasting glucose (p<0.05).

CONCLUSIONS

Our results suggest that circulating betatrophin is significantly elevated in subjects with T2DM compared to healthy controls. Increase in the level of betatrophin in T2DM subjects might be a compensatory mechanism for enhanced insulin demand in T2DM condition.

Discovery, Synthesis, and Evaluation of 2,4-Diaminoquinazolines as a Novel Class of Pancreatic β-Cell-Protective Agents against Endoplasmic Reticulum (ER) Stress

Pancreatic insulin-producing β-cell dysfunction and death plays central roles in the onset and progression of both type 1 and type 2 diabetes. Current antidiabetic drugs cannot halt the ongoing progression of β-cell dysfunction and death. In diabetes, a major cause for the decline in β-cell function and survival is endoplasmic reticulum (ER) stress. Here, we identified quinazoline derivatives as a novel class of β-cell protective agents against ER stress-induced dysfunction and death. A series of quinazoline derivatives were synthesized from dichloroquiazoline utilizing a sequence of nucleophilic reactions. Through SAR optimization, 2,4-diaminoquinazoline compound 9c markedly protects β-cells against ER stress-induced dysfunction and death with 80% maximum rescue activity and an EC50 value of 0.56 μM. Importantly, 9c restores the ER stress-impaired glucose-stimulated insulin secretion response and survival in primary human islet β-cells. We showed that 9c protects β-cells by alleviating ER stress through the suppression of the induction of key genes of the unfolded protein response and apoptosis.

β-cell replacement sources for type 1 diabetes: a focus on pancreatic ductal cells

Thorough research on the capacity of human islet transplantation to cure type 1 diabetes led to the achievement of 3- to 5-year-long insulin independence in nearly half of transplanted patients. Yet, translation of this technique to clinical routine is limited by organ shortage and the need for long-term immunosuppression, restricting its use to adults with unstable disease. The production of new bona fide β cells in vitro was thus investigated and finally achieved with human pluripotent stem cells (PSCs). Besides ethical concerns about the use of human embryos, studies are now evaluating the possibility of circumventing the spontaneous tumor formation associated with transplantation of PSCs. These issues fueled the search for cell candidates for β-cell engineering with safe profiles for clinical translation. In vivo studies revealed the regeneration capacity of the exocrine pancreas after injury that depends at least partially on facultative progenitors in the ductal compartment. These stimulated subpopulations of pancreatic ductal cells (PDCs) underwent β-cell transdifferentiation through reactivation of embryonic signaling pathways. In vitro models for expansion and differentiation of purified PDCs toward insulin-producing cells were described using cocktails of growth factors, extracellular-matrix proteins and transcription factor overexpression. In this review, we will describe the latest findings in pancreatic β-cell mass regeneration due to adult ductal progenitor cells. We will further describe recent advances in human PDC transdifferentiation to insulin-producing cells with potential for clinical translational studies.

Transcriptome landmarks of the functional maturity of rat beta-cells, from lactation to adulthood

Research on the postnatal development of pancreatic beta-cells has become an important subject in recent years. Understanding the mechanisms that govern beta-cell postnatal maturation could bring new opportunities to therapeutic approaches for diabetes. The weaning period consists of a critical postnatal window for structural and physiologic maturation of rat beta-cells. To investigate transcriptome changes involved in the maturation of beta-cells neighboring this period, we performed microarray analysis in fluorescence-activated cell-sorted (FACS) beta-cell-enriched populations. Our results showed a variety of gene sets including those involved in the integration of metabolism, modulation of electrical activity, and regulation of the cell cycle that play important roles in the maturation process. These observations were validated using reverse hemolytic plaque assay, electrophysiological recordings, and flow cytometry analysis. Moreover, we suggest some unexplored pathways such as sphingolipid metabolism, insulin-vesicle trafficking, regulation of transcription/transduction by miRNA-30, trafficking proteins, and cell cycle proteins that could play important roles in the process mentioned above for further investigation.