Co-culture of clonal beta cells with GLP-1 and glucagon-secreting cell line impacts on beta cell insulin secretion, proliferation and susceptibility to cytotoxins

Dipeptidyl Peptidase (DPP)-IV Inhibitors with Antioxidant Potential Isolated from Natural Sources: A Novel Approach for the Management of Diabetes

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia that is predominantly caused by insulin resistance or impaired insulin secretion, along with disturbances in carbohydrate, fat and protein metabolism. Various therapeutic approaches have been used to treat diabetes, including improvement of insulin sensitivity, inhibition of gluconeogenesis, and decreasing glucose absorption from the intestines. Recently, a novel approach has emerged using dipeptidyl peptidase-IV (DPP-IV) inhibitors as a possible agent for the treatment of T2DM without producing any side effects, such as hypoglycemia and exhaustion of pancreatic β-cells. DPP-IV inhibitors improve hyperglycemic conditions by stabilizing the postprandial level of gut hormones such as glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptides, which function as incretins to help upregulate insulin secretion and β-cell mass. In this review, we summarized DPP-IV inhibitors and their mechanism of inhibition, activities of those isolated from various natural sources, and their capacity to overcome oxidative stress in disease conditions.

Genome Editing Human Pluripotent Stem Cells to Model β-Cell Disease and Unmask Novel Genetic Modifiers

A mechanistic understanding of the genetic basis of complex diseases such as diabetes mellitus remain elusive due in large part to the activity of genetic disease modifiers that impact the penetrance and/or presentation of disease phenotypes. In the face of such complexity, rare forms of diabetes that result from single-gene mutations (monogenic diabetes) can be used to model the contribution of individual genetic factors to pancreatic β-cell dysfunction and the breakdown of glucose homeostasis. Here we review the contribution of protein coding and non-protein coding genetic disease modifiers to the pathogenesis of diabetes subtypes, as well as how recent technological advances in the generation, differentiation, and genome editing of human pluripotent stem cells (hPSC) enable the development of cell-based disease models. Finally, we describe a disease modifier discovery platform that utilizes these technologies to identify novel genetic modifiers using induced pluripotent stem cells (iPSC) derived from patients with monogenic diabetes caused by heterozygous mutations.

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.

Kaempferol in ameliorating diabetes-induced fibrosis and renal damage: An in vitro and in vivo study in diabetic nephropathy mice model

BACKGROUND

Kaempferol is a natural polyflavonol that has gained considerable attention as antidiabetic therapeutics. Recent reports emphasize the role of hyperglycemia and RhoA/Rho Kinase activity in the pathogenesis of diabetic nephropathy (DN). This study aims to evaluate the GLP-1 and insulin release along with RhoA/Rho Kinase inhibition pertaining to the anti-fibrotic and reno-protective effects of Kaempferol in DN.

METHODS

The effect of Kaempferol on GLP-1 and insulin release along with underlying mechanisms (Ca2+ and cAMP levels) in GLUTag and MIN6 cells as well as in their co-culture has been evaluated. Further, the effect of Kaempferol on GLP-1 and insulin release was evaluated under in-vivo circumstances in the DN C57BL/6 mouse model. Histology and fibrosis specific staining was performed to study the renal injuries and fibrosis, while the expression of mRNA and protein of interest was evaluated by RT-PCR and western blot analysis.

RESULTS

Kaempferol treatment promoted the GLP-1 and insulin release, which was accompanied by increased intracellular levels of cAMP and Ca2+ in GLUTag and MIN6 cells. In agreement with in vitro studies, Kaempferol also increased the release of GLP-1 and insulin in the DN mouse model. Notably, Kaempferol showed the potential to ameliorate the histological changes as well as renal fibrosis while decreasing the expression levels of DN markers including TGF-β1, CTGF, fibronectin, collagen IV, IL-1β, RhoA, ROCK2, and p-MYPT1 in DN kidney tissues. A rise in the expression of E-cadherin and nephrin was also noted in the same study.

CONCLUSION

This study establishes that Kaempferol ameliorates renal injury and fibrosis by enhancing the release of GLP-1, insulin, and inhibition of RhoA/Rho Kinase. This study recommends Kaempferol for further clinical trials to be developed as novel therapeutics for improving the renal function in DN patients.

Dezhou donkey (Equus asinus) milk a potential treatment strategy for type 2 diabetes

ETHNOPHARMACOLOGICAL RELEVANCE

Donkey (Equus asinus) milk has become a medical and nutrient product since ancient times. In addition, donkey milk was regarded as a medicinal food and substitute product for infant formula in some ancient western countries. Chinese ancient medical books documented the medicinal value of donkey milk, using donkey milk to treat diabetes, cough and jaundice.

AIM OF THE STUDY

To investigate the donkey milk's components and anti-diabetic effect of donkey milk in vitro and in vivo and to study the molecular mechanism of donkey milk was an anti-diabetic medication.

MATERIALS AND METHODS

In this study, the gastrointestinal digested donkey milk was simulated in vitro and its products of protein digestion were analyzed by SDS-PAGE. We then performed cell viability assay, insulin secretion assay, animal experiments and ELISA assays to study the anti-diabetic effect of donkey milk in vitro and in vivo. Donkey milk's anti-diabetic molecular mechanism and specific targets were detected by using quantitative real time PCR.

RESULTS

Lysozyme (LZ) and α-lactalbumin (α-La) exhibited significantly lower digestibility and higher retention than the other components of donkey milk. In vitro, 500 μg/mL of donkey milk could improve damaged β-cells viability significantly (P < 0.0001). In vivo, the blood glucose and HOMA-IR of diabetic rats treated with donkey milk were 14.23 ± 5.18 mM and 74.94 ± 23.62, respectively, whereas the diabetic group were 22.18 ± 2.23 mM and 112.16 ± 18.44, respectively (P < 0.01). The SOD value of donkey milk group was 265.87 ± 21.29 U/L, while the SOD value of diabetic group was 193.20 ± 52.07 U/L (P < 0.05). These results indicated that the blood glucose was reduced, the ability of the body to eliminate free radicals was enhanced, antioxidant levels in the body was increased, insulin resistance was improved in type 2 diabetic rats after donkey milk powder fed for 4 weeks. Furthermore, donkey milk could treat diabetes through down-regulating phosphoenolpyruvate carboxykinase 1 (Pck1) and glucose-6-phosphatase (G6PC).

CONCLUSIONS

Donkey milk has played an important role in the treatment of type 2 diabetes, and contributed to the development of the donkey milk products.

Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) in the Brain-Adipocyte Axis

The complexity of neural circuits that control food intake and energy balance in the hypothalamic nuclei explains some of the constraints involved in the prevention and treatment of obesity. Two major neuronal populations present in the arcuate nucleus control caloric intake and energy expenditure: one population co-expresses orexigenic agouti-related peptide (AgRP) and neuropeptide Y and the other expresses the anorexigenic anorectic neuropeptides proopiomelanocortin and cocaine- and amphetamine-regulated transcript (POMC/CART). In addition to integrating signals from neurotransmitters and hormones, the hypothalamic systems that regulate energy homeostasis are affected by nutrients. Fat-rich diets, for instance, elicit hypothalamic inflammation (reactive activation and proliferation of microglia, a condition named gliosis). This process generates resistance to the anorexigenic hormones leptin and insulin, contributing to the genesis of obesity. Glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs) have increasingly been used to treat type 2 diabetes mellitus. One compound (liraglutide) was recently approved for the treatment of obesity. Although most studies suggest that GLP-1RAs promote weight loss mainly due to their inhibitory effect on food intake, other central effects that have been described for native GLP-1 and some GLP-1RAs in rodents and humans encourage future clinical trials to explore additional mechanisms that potentially underlie the beneficial effects observed with this drug class. In this article we review the most relevant data exploring the mechanisms involved in the effects of GLP-1RAs in the brain–adipocyte axis.

A Specific Gut Microbiota Dysbiosis of Type 2 Diabetic Mice Induces GLP-1 Resistance through an Enteric NO-Dependent and Gut-Brain Axis Mechanism

Glucagon-like peptide-1 (GLP-1)-based therapies control glycemia in type 2 diabetic (T2D) patients. However, in some patients the treatment must be discontinued, defining a state of GLP-1 resistance. In animal models we identified a specific set of ileum bacteria impairing the GLP-1-activated gut-brain axis for the control of insulin secretion and gastric emptying. Using prediction algorithms, we identified bacterial pathways related to amino acid metabolism and transport system modules associated to GLP-1 resistance. The conventionalization of germ-free mice demonstrated their role in enteric neuron biology and the gut-brain-periphery axis. Altogether, insulin secretion and gastric emptying require functional GLP-1 receptor and neuronal nitric oxide synthase in the enteric nervous system within a eubiotic gut microbiota environment. Our data open a novel route to improve GLP-1-based therapies.