Ghrelin's Effects on Proinflammatory Cytokine Mediated Apoptosis and Their Impact on β-Cell Functionality

Impact of chitosan administration on titanium dioxide nanoparticles induced testicular dysfunction

The potential reproductive toxic effects of oral TiO₂ NPs in adult male rats as well as the possible alleviation of chitosan administration was investigated. Animals were allocated to four groups; the first group received deionized water and was assigned as a control group. In the second group, rats received chitosan at a dose of 5 mg/kg BW/day. The third group was designed for administration of TiO₂ NPs at a dose of 150 mg/kg BW/day (1/80 LD₅₀). Rats in the fourth group received both TiO₂ NPs and chitosan. After 14 days, TiO₂ NPs induced testicular lipid peroxidation as well as oxidative stress. Nano-titanium significantly upregulated genes that encode apoptosis and inflammation in testicular tissue. Moreover, it induced histological alteration in the testicular structure with impairment in spermatogenesis via reduction of PCNA immune-staining. Chitosan administration significantly improved the activities of testicular GPx, SOD, and CAT enzymes. In addition, it significantly down-regulated the relative expressions of pro-apoptotic and pro-inflammatory testicular genes. Chitosan was able to improve the testicular architecture as well as spermatogenesis. The current study revealed the capability of chitosan to ameliorate nano-titanium induced testicular toxicity. Thus, attention should be given to the extensive consumption of nano-titanium particles.

Protective and Healing Effects of Ghrelin and Risk of Cancer in the Digestive System

Ghrelin is an endogenous ligand for the ghrelin receptor, previously known as the growth hormone secretagogue receptor. This hormone is mainly produced by endocrine cells present in the gastric mucosa. The ghrelin-producing cells are also present in other organs of the body, mainly in the digestive system, but in much smaller amount. Ghrelin exhibits a broad spectrum of physiological effects, such as stimulation of growth hormone secretion, gastric secretion, gastrointestinal motility, and food intake, as well as regulation of glucose homeostasis and bone formation, and inhibition of inflammatory processes. This review summarizes the recent findings concerning animal and human data showing protective and therapeutic effects of ghrelin in the gut, and also presents the role of growth hormone and insulin-like growth factor-1 in these effects. In addition, the current data on the possible influence of ghrelin on the carcinogenesis, its importance in predicting the risk of developing gastrointestinal malignances, as well as the potential usefulness of ghrelin in the treatment of cancer, have been presented.

IL-17A is involved in diabetic inflammatory pathogenesis by its receptor IL-17RA

IMPACT STATEMENT

The participation of interleukin (IL)-17A in diabetic pathogenesis is suggested in animal models of autoimmune diabetes and in patients with type 1 diabetes (T1D), but with some contradictory results. Particularly, evidence for a direct injury of IL-17A to pancreatic β cells is lacking. We showed that IL-17A deficiency alleviated diabetic signs including hyperglycemia, hypoinsulinemia, and inflammatory response in Ins2Akita (Akita) mice, a T1D model with spontaneous mutation in insulin 2 gene leading to β-cell apoptosis. IL-17A enhanced inflammatory reaction, oxidative stress, and cell apoptosis but attenuated insulin level in mouse insulin-producing MIN6 cells. IL-17A had also a synergistic destruction to MIN6 cells with streptozotocin (STZ), a pancreatic β-cell-specific cytotoxin. Blocking IL-17 receptor A (IL-17RA) reduced all these deleterious effects of IL-17A on MIN6 cells. The results demonstrate the role and the importance of IL-17A in T1D pathogenesis and suggest a potential therapeutic strategy for T1D targeting IL-17A and/or IL-17RA.

Boswellic extracts and 11-keto-ß-boswellic acids prevent type 1 and type 2 diabetes mellitus by suppressing the expression of proinflammatory cytokines

BACKGROUND

Type 1 diabetes is an autoimmune disease directed to the pancreatic islets where inflammation leads to the death of insulin-producing ß cells and insulin deficiency. Type 2 diabetes, which is closely related to overweight, is characterized by insulin resistance. In both cases, proinflammatory cytokines play an important role by causing insulitis and insulin resistance. The gum resin of Boswellia species and its pharmacologically active compounds, including 11-keto-ß-boswellic acids have been shown to suppress the expression of proinflammatory cytokines in various immune-competent cells.

PURPOSE

To review the present evidence of the therapeutic effects of boswellic extracts (BE) and/or 11-keto-ß-boswellic acids in the prevention/treatment of diabetes mellitus and to provide comprehensive insights into the underlying molecular mechanisms.

METHODS

This review considers all available informations from preclinical and clinical studies concerning BEs, 11-keto-ß-boswellic acids, proinflammatory cytokines and diabetes mellitus collected via electronic search (PubMed) and related publications of the author.

RESULTS

Type 1 diabetes: Studies in mice with autoimmune diabetes revealed that in the model of multiple injections of low doses of streptozotocin (MLD-STZ), an extract of the gum resin of Boswellia serrata and 11-keto-ß-boswellic acid (KBA) suppressed the increase in proinflammatory cytokines in the blood, infiltration of lymphocytes into pancreatic islets and increase in blood glucose. In a second model, i.e. the nonobese diabetic (NOD) mouse, KBA prevented the infiltration of lymphocytes into pancreatic islets. Regarding the clinical effects, a case report provided evidence that BE suppressed the blood levels of tyrosine phosphatase antibody (IA₂-A), a marker for insulitis, in a patient with late-onset autoimmune diabetes of the adult (LADA). Type 2 diabetes: In a preclinical study in rats where obesity was alimentary induced, the administration of BE significantly reduced food intake, overweight, proinflammatory cytokines such as interleukin-1ß (IL-1ß), and tumor necrosis factor-α (TNF-α) and ameliorated the parameters of glucose and lipid metabolism. Similar results were obtained in a second animal study, where type 2 diabetes was induced by a combination of a high-fat/high-fructose diet and a single dose of streptozotocin. Two clinical trials with patients with type 2 diabetes receiving the resin of Boswellia serrata demonstrated improvement in the blood glucose, HbA_1c and lipid parameters.

CONCLUSION

Preclinical and clinical data suggest that BE and/or 11-keto-ß-boswellic acids by inhibiting the expression of proinflammatory cytokines from immune-competent cells, may prevent insulitis and insulin resistance in type 1 and type 2 diabetes, respectively, and therefore may be an option in the treatment/prevention of type 1 and type 2 diabetes. It is hypothesized that molecularly, BE and 11-keto-ß-boswellic acids act via interference with the IκB kinase/Nuclear Transcription Factor-κB (IKK/NF-κB) signaling pathway through inhibition of the phosphorylation activity of IKK. However, further investigations and well-designed clinical studies are required.

Ghrelin mitigates β-cell mass loss during insulitis in an animal model of autoimmune diabetes mellitus, the BioBreeding/Worcester rat

BACKGROUND

Ghrelin is a peptide hormone with pleiotropic effects. It stimulates cell proliferation and inhibits apoptosis-mediated cell death. It prevents diabetes mellitus in several models of chemical, surgical and biological toxic insults to pancreas in both in vivo and in vitro models and promotes glucose-stimulated insulin secretion under cytotoxic conditions. It has not yet been tested in vivo in an autoimmune model of diabetes with a persistent insult to the β-cell. Given the immunomodulating effects of ghrelin and its trophic effects on β-cells, we hypothesized that ghrelin treatment during the early stages of insulitis would delay diabetes onset.

METHODS

BioBreeding/Worcester male rats received ghrelin (10 ng/kg/day) before insulitis development. Glucose metabolism was characterized by glucose and insulin tolerance tests. β-cell mass, islet area, islet number, β-cell clusters, proliferation and apoptosis and degree of insulitis were analysed by histomorphometry. A Kaplan-Meier survival curve was plotted and analysed applying the log-rank (Mantel-Cox) test.

RESULTS

Ghrelin treatment significantly reduced the probability of developing diabetes in our model (p < 0.0001). It decreased islet infiltration and partially prevented β-cell mass loss, enabling the maintenance of β-cell neogenesis and proliferation rates. Furthermore, ghrelin treatment did not induce any metabolic perturbations.

CONCLUSIONS

These findings support the hypothesis that ghrelin delays the development of autoimmune diabetes by attenuating insulitis and supporting β-cell mass.

GENERAL SIGNIFICANCE

Ghrelin promotes β-cell viability and function through diverse mechanisms that may have significant implications for diabetes prevention, therapy and also transplant success of both islets and complete pancreas. Copyright © 2016 John Wiley & Sons, Ltd.

Replicative capacity of β-cells and type 1 diabetes

Efforts to restore β-cell number or mass in type 1 diabetes (T1D) must combine an intervention to stimulate proliferation of remaining β-cells and an intervention to mitigate or control the β-cell-directed autoimmunity. This review highlights features of the β-cell, including it being part of a pancreatic islet, a mini-organ that is highly vascularized and highly innervated, and efforts to promote β-cell proliferation. In addition, the β-cell in T1D exists in a microenvironment with interactions and input from other islet cell types, extracellular matrix, vascular endothelial cells, neuronal projections, and immune cells, all of which likely influence the β-cell's capacity for replication. Physiologic β-cell proliferation occurs in human and rodents in the neonatal period and early in life, after which there is an age-dependent decline in β-cell proliferation, and also as part of the β-cell's compensatory response to the metabolic challenges of pregnancy and insulin resistance. This review reviews the molecular pathways involved in this β-cell proliferation and highlights recent work in two areas: 1) Investigators, using high-throughput screening to discover small molecules that promote human β-cell proliferation, are now focusing on the dual-specificity tyrosine-regulated kinase-1a and cell cycle-dependent kinase inhibitors CDKN2C/p18 or CDKN1A/p21as targets of compounds to stimulate adult human β-cell proliferation. 2) Local inflammation, macrophages, and the local β-cell microenvironment promote β-cell proliferation. Future efforts to harness the responsible mechanisms may lead to new approaches to promote β-cell proliferation in T1D.