Simulated Cholinergic Reinnervation of β (INS-1) Cells: Antidiabetic Utility of Heterotypic Pseudoislets Containing β Cell and Cholinergic Cell

Sonic hedgehog signalling pathway contributes in age-related disorders and Alzheimer's disease

Alzheimer's disease (AD) is caused by the aging process and manifested by cognitive deficits and progressive memory loss. During aging, several conditions, including hypertension, diabetes, and cholesterol, have been identified as potential causes of AD by affecting Sonic hedgehog (Shh) signalling. In addition to being essential for cell differentiation and proliferation, Shh signalling is involved in tissue repair and the prevention of neurodegeneration. Neurogenesis is dependent on Shh signalling; inhibition of this pathway results in neurodegeneration. Several protein-protein interactions that are involved in Shh signalling are implicated in the pathophysiology of AD like overexpression of the protein nexin-1 inhibits the Shh pathway in AD. A protein called Growth Arrest Specific-1 works with another protein called cysteine dioxygenase (CDO) to boost Shh signalling. CDO is involved in the development of the central nervous system (CNS). Shh signalling strengthened the blood brain barrier and therefore prevent the entry of amyloid beta and other toxins to the brain from periphery. Further, several traditional remedies used for AD and dementia, including Epigallocatechin gallate, yokukansan, Lycium barbarum polysaccharides, salvianolic acid, and baicalin, are known to stimulate the Shh pathway. In this review, we elaborated that the Shh signalling exerts a substantial influence on the pathogenesis of AD. In this article, we have tried to explore the various possible connections between the Shh signalling and various known pathologies of AD.

Towards a better understanding of diabetes mellitus using organoid models

Our understanding of diabetes mellitus has benefited from a combination of clinical investigations and work in model organisms and cell lines. Organoid models for a wide range of tissues are emerging as an additional tool enabling the study of diabetes mellitus. The applications for organoid models include studying human pancreatic cell development, pancreatic physiology, the response of target organs to pancreatic hormones and how glucose toxicity can affect tissues such as the blood vessels, retina, kidney and nerves. Organoids can be derived from human tissue cells or pluripotent stem cells and enable the production of human cell assemblies mimicking human organs. Many organ mimics relevant to diabetes mellitus are already available, but only a few relevant studies have been performed. We discuss the models that have been developed for the pancreas, liver, kidney, nerves and vasculature, how they complement other models, and their limitations. In addition, as diabetes mellitus is a multi-organ disease, we highlight how a merger between the organoid and bioengineering fields will provide integrative models.

Unfolding and identification of membrane proteins in situ

Single-molecule force spectroscopy (SMFS) uses the cantilever tip of an AFM to apply a force able to unfold a single protein. The obtained force-distance curve encodes the unfolding pathway, and from its analysis it is possible to characterize the folded domains. SMFS has been mostly used to study the unfolding of purified proteins, in solution or reconstituted in a lipid bilayer. Here, we describe a pipeline for analyzing membrane proteins based on SMFS, that involves the isolation of the plasma membrane of single cells and the harvesting of force-distance curves directly from it. We characterized and identified the embedded membrane proteins combining, within a Bayesian framework, the information of the shape of the obtained curves, with the information from Mass Spectrometry and proteomic databases. The pipeline was tested with purified/reconstituted proteins and applied to five cell types where we classified the unfolding of their most abundant membrane proteins. We validated our pipeline by overexpressing 4 constructs, and this allowed us to gather structural insights of the identified proteins, revealing variable elements in the loop regions. Our results set the basis for the investigation of the unfolding of membrane proteins in situ, and for performing proteomics from a membrane fragment.

Bioengineered Islet Cell Transplantation

Purpose of Review

β cell replacement via whole pancreas or islet transplantation has greatly evolved for the cure of type 1 diabetes. Both these strategies are however still affected by several limitations. Pancreas bioengineering holds the potential to overcome these hurdles aiming to repair and regenerate β cell compartment. In this review, we detail the state-of-the-art and recent progress in the bioengineering field applied to diabetes research.

Recent Findings

The primary target of pancreatic bioengineering is to manufacture a construct supporting insulin activity in vivo. Scaffold-base technique, 3D bioprinting, macro-devices, insulin-secreting organoids, and pancreas-on-chip represent the most promising technologies for pancreatic bioengineering.

Summary

There are several factors affecting the clinical application of these technologies, and studies reported so far are encouraging but need to be optimized. Nevertheless pancreas bioengineering is evolving very quickly and its combination with stem cell research developments can only accelerate this trend.

lncRNA SNHG17 is Downregulated in Gestational Diabetes Mellitus (GDM) and Has Predictive Values

AIM

Long non-coding RNA (lncRNA) SNHG17 has been shown to participate in type 2 diabetes mellitus, while its role in gestational diabetes mellitus (GDM) is unknown.

METHODS

Quantitative real-time PCR (qRT-PCR) assays were conducted to compare the differential expression of SNHG17 among 60 GDM patients and 60 healthy pregnant female controls. In addition, peripheral blood samples from 240 pregnant females were collected to evaluate the predictive value of SNHG17 for GDM patients. All females were followed-up until delivery to record the occurrence of GDM and perinatal outcomes. GDM-free curves were plotted to compare the occurrence of GDM between high- and low- SNHG17 expression groups. The diagnostic value of plasma SNHG17 for GDM was analyzed by ROC curve analysis. Moreover, the cell counting kit (CCK-8) assay was performed to evaluate the impact of SNHG17 on cell viability of INS-1, and the level of insulin secretion was detected by enzyme linked immunosorbent assay (ELISA) after overexpression or knockdown of SNHG17.

RESULTS

SNHG17 was downregulated in GDM patients compared to normal pregnant females. Low plasma expression levels of SNHG17 were closely correlated with the high incidence rate of GDM (GDM-free curve). Remarkably, plasma expression levels of SNHG17 at 4 weeks before the diagnosis of GDM (diagnosed by standard method) can be used to distinguish (ROC curve) GDM patients (diagnosed during follow-up) from normal pregnant females (GDM was not diagnosed during follow-up).

CONCLUSION

Plasma circulating SNHG17 is downregulated in GDM and has predictive values.

Recent advances in the design of implantable insulin secreting heterocellular islet organoids

Islet transplantation has proved one of the most remarkable transmissions from an experimental curiosity into a routine clinical application for the treatment of type I diabetes (T1D). Current efforts for taking this technology one-step further are now focusing on overcoming islet donor shortage, engraftment, prolonged islet availability, post-transplant vascularization, and coming up with new strategies to eliminate lifelong immunosuppression. To this end, insulin secreting 3D cell clusters composed of different types of cells, also referred as heterocellular islet organoids, spheroids, or pseudoislets, have been engineered to overcome the challenges encountered by the current islet transplantation protocols. β-cells or native islets are accompanied by helper cells, also referred to as accessory cells, to generate a cell cluster that is not only able to accurately secrete insulin in response to glucose, but also superior in terms of other key features (e.g. maintaining a vasculature, longer durability in vivo and not necessitating immunosuppression after transplantation). Over the past decade, numerous 3D cell culture techniques have been integrated to create an engineered heterocellular islet organoid that addresses current obstacles. Here, we first discuss the different cell types used to prepare heterocellular organoids for islet transplantation and their contribution to the organoids design. We then introduce various cell culture techniques that are incorporated to prepare a fully functional and insulin secreting organoids with select features. Finally, we discuss the challenges and present a future outlook for improving clinical outcomes of islet transplantation.

Amniotic Membrane Extract Protects Islets From Serum-Deprivation Induced Impairments and Improves Islet Transplantation Outcome

Islet culture prior to transplantation is a standard practice in many transplantation centers. Nevertheless, the abundant islet mass loss and function impairment during this serum-deprivation culture period restrain the success of islet transplantation. In the present study, we used a natural biomaterial derived product, amniotic membrane extract (AME), as medium supplementation of islet pretransplant cultivation to investigate its protective effect on islet survival and function and its underlying mechanisms, as well as the engraftment outcome of islets following AME treatment. Results showed that AME supplementation improved islet viability and function, and decreased islet apoptosis and islet loss during serum-deprived culture. This was associated with the increased phosphorylation of PI3K/Akt and MAPK/ERK signaling pathway. Moreover, transplantation of serum-deprivation stressed islets that were pre-treated with AME into diabetic mice revealed better blood glucose control and improved islet graft survival. In conclusion, AME could improve islet survival and function in vivo and in vitro, and was at least partially through increasing phosphorylation of PI3K/Akt and MAPK/ERK signaling pathway.

[Insulin-secreting organoids: a first step towards the bioartificial pancreas]

Pancreatic islet transplantation is a valid cure for selected type-1 diabetic patients. It offers a minimally invasive β-cell replacement approach and has proven its capacity to significantly enhance patients quality of life. However, these insulin-secreting mini-organs suffer from the loss of intrinsic vascularization and extra-cellular matrix occurring during isolation, resulting in hypoxic stress and necrosis. In addition, they have to face inflammatory and immune destruction once transplanted in the liver. Organoid generation represents a strategy to overcome these obstacles by allowing size and shape control as well as composition. It does offer the possibility to add supporting cells such as endothelial cells, in order to facilitate revascularization or cells releasing anti-inflammatory and/or immunomodulatory factors. This review describes the limitations of pancreatic islet transplantation and details the benefits offered by organoids as a cornerstone toward the generation of a bioartificial pancreas.

Generation of insulin-secreting organoids: a step toward engineering and transplanting the bioartificial pancreas

Diabetes is a major health issue of increasing prevalence. ß‐cell replacement, by pancreas or islet transplantation, is the only long‐term curative option for patients with insulin‐dependent diabetes. Despite good functional results, pancreas transplantation remains a major surgery with potentially severe complications. Islet transplantation is a minimally invasive alternative that can widen the indications in view of its lower morbidity. However, the islet isolation procedure disrupts their vasculature and connection to the surrounding extracellular matrix, exposing them to ischemia and anoikis. Implanted islets are also the target of innate and adaptive immune attacks, thus preventing robust engraftment and prolonged full function. Generation of organoids, defined as functional 3D structures assembled with cell types from different sources, is a strategy increasingly used in regenerative medicine for tissue replacement or repair, in a variety of inflammatory or degenerative disorders. Applied to ß‐cell replacement, it offers the possibility to control the size and composition of islet‐like structures (pseudo‐islets), and to include cells with anti‐inflammatory or immunomodulatory properties. In this review, we will present approaches to generate islet cell organoids and discuss how these strategies can be applied to the generation of a bioartificial pancreas for the treatment of type 1 diabetes.

Formation of βTC3 and MIN6 Pseudoislets Changes the Expression Pattern of Gpr40, Gpr55, and Gpr119 Receptors and Improves Lysophosphatidylcholines-Potentiated Glucose-Stimulated Insulin Secretion

The impaired spatial arrangement and connections between cells creating islets of Langerhans as well as altered expression of G protein-coupled receptors (GPCRs) often lead to dysfunction of insulin-secreting pancreatic β cells and can significantly contribute to the development of diabetes. Differences in glucose-stimulated insulin secretion (GSIS) are noticeable not only in diabetic individuals but also in model pancreatic β cells, e.g., βTC3 and MIN6 β cell lines with impaired and normal insulin secretion, respectively. Now, we compare the ability of GPCR agonists (lysophosphatidylcholines bearing fatty acid chains of different lengths) to potentiate GSIS in βTC3 and MIN6 β cell models, cultured as adherent monolayers and in a form of pseudoislets (PIs) with pancreatic MS1 endothelial cells. Our aim was also to investigate differences in expression of the GPCRs responsive to LPCs in these experimental systems. Aggregation of β cells into islet-like structures greatly enhanced the expression of Gpr40, Gpr55, and Gpr119 receptors. In contrast, the co-culture of βTC3 cells with endothelial cells converted the GPCR expression pattern closer to the pattern observed in MIN6 cells. Additionally, the efficiencies of various LPC species in βTC3-MS1 PIs also shifted toward the MIN6 cell model.

Phloretin Modulates Human Th17/Treg Cell Differentiation In Vitro via AMPK Signaling

Objective

We conducted studies to explore the effect of phloretin on glucose uptake, proliferation, and differentiation of human peripheral blood CD4⁺ T cells and investigated the mechanism of phloretin on inducing Th17/Treg development.

Methods

Naïve CD4⁺ T cells were purified from peripheral blood of healthy volunteers, stimulated with anti-CD3/CD28 antibodies, and polarized in vitro to generate Th17 or Treg cells. Glucose uptake, proliferation, cell cycle, protein expression (phospho-Stat3, phospho-Stat5), and Th17 and Treg cell numbers were analyzed by flow cytometry. AMP-activated protein kinase (AMPK) signaling was analyzed by western blot. Results and Discussion. Phloretin could inhibit the glucose uptake and proliferation of activated CD4⁺ T cells. The proliferation inhibition was due to the G0/G1 phase arrest. Phloretin decreased Th17 cell generation and phospho-Stat3 expression as well as increased Treg cell generation and phospho-Stat5 expression in the process of inducing Th17/Treg differentiation. The phosphorylation level of AMPK was significantly enhanced, while the phosphorylation level of mTOR was significantly decreased in activated CD4⁺ T cells under phloretin treatment. The AMPK signaling inhibitor compound C (Com C) could neutralize the effect of phloretin, while the agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) could impact the Th17/Treg balance similar to phloretin during Th17/Treg induction.

Conclusion

Our results suggest that phloretin can mediate the Th17/Treg balance by regulating metabolism via the AMPK signal pathway.

Comparative Study of Two Different Islet Transplantation Sites in Mice: Hepatic Sinus Tract vs Splenic Parenchyma

Although 90% of clinical islet transplantations are performed via the portal vein approach, it is still far from the ideal transplant site. Alternative islet transplant sites are promising to reduce the islet dose required to reverse hyperglycemia, thereby improving the efficiency of islet transplantation. The aim of this study was to compare the differences in survival and metabolic function of islet grafts transplanted into the hepatic sinus tract (HST) and the splenic parenchyma (SP). Approximately 300 syngeneic mouse islets were transplanted into the HST (n = 6) and the SP (n = 6) of recipient diabetic mice, respectively. After transplantation, the glycemic control, glucose tolerance, and morphology of islet grafts were evaluated and compared in each group. The nonfasting blood glucose of the two groups of mice receiving islet transplantation gradually decreased to the normal range and sustained for more than 100 d. There is no significant difference in the time required to restore normoglycemia (P > 0.05). The results of the glucose tolerance test showed that the SP group presented a smaller area under the curve than the HST group (P < 0.05). Histopathological results showed that islet grafts in the HST and the SP were characterized with normal islet morphology and robust insulin production. Compared with the HST, islet transplantation in the SP presents better blood glucose regulation, although there is no significant difference in the time required to restore normoglycemia.

Pentapeptide Protects INS-1 Cells From hIAPP-Mediated Apoptosis by Enhancing Autophagy Through mTOR Pathway

The human islet amyloid polypeptide (hIAPP), the major component of islet amyloid deposition, is one of the amyloidogenic peptides and has been associated with β cell loss and dysfunction in type 2 diabetes (T2D). Autophagy plays a central role in the clearance of hIAPP aggregates, thereby diminishing the hIAPP-induced cytotoxicity. Conversely, hIAPP has been reported to have interfering effects on the autophagy. The pentapeptide FLPNF developed in our previous study has been shown to have effects on the level of the downstream proteins of mTOR and autophagy–lysosome pathway. In the present study, the peptide FLPNF-mediated increase in autophagy flux and its underlying mechanisms, as well as its protecting effect on INS-1 cells, were investigated. Autophagy flux in INS-1 cells overexpressing hIAPP (hIAPP-INS-1 cells) markedly increased after exposure to peptide FLPNF for 24 h and peaked at a concentration of 200 µM. Peptide FLPNF enhanced the autophagy by inhibiting the mTORC1 activity. Flow cytometry results showed the peptide FLPNF bind to mammalian target of rapamycin (mTOR), and further molecular docking analysis revealed a direct interaction between peptide FLPNF and the FRB domain of mTOR. Meanwhile, both peptide FLPNF and rapamycin significantly decreased the hIAPP-induced apoptosis, whereas 3-MA increased the apoptosis. Furthermore, peptide FLPNF reduced the hIAPP oligomer and improved the hIAPP-INS-1 cells insulin release function at high glucose concentration. Taken together, the peptide FLPNF decreased the hIAPP oligomer via upregulating autophagy by inhibiting mTORC1 activity, thus protecting the INS-1 cells from hIAPP-induced apoptosis and improving the insulin release function of INS-1 cells.