Induction of oxidative stress, suppression of glucose-induced insulin release, ATP production, glucokinase activity, and histomorphometric changes in pancreatic islets of hypothyroid rat

Preventive Effect of Molecular Iodine in Pancreatic Disorders from Hypothyroid Rabbits

Pancreatic alterations such as inflammation and insulin resistance accompany hypothyroidism. Molecular iodine (I2) exerts antioxidant and differentiation actions in several tissues, and the pancreas is an iodine-uptake tissue. We analyzed the effect of two oral I2 doses on pancreatic disorders in a model of hypothyroidism for 30 days. Adult female rabbits were divided into the following groups: control, moderate oral dose of I2 (0.2 mg/kg, M-I2), high oral dose of I2 (2.0 mg/kg, H-I2), oral dose of methimazole (MMI; 10 mg/kg), MMI + M-I2,, and MMI + H-I2. Moderate or high I2 supplementation did not modify circulating metabolites or pancreatic morphology. The MMI group showed reductions of circulating thyroxine (T4) and triiodothyronine (T3), moderate glucose increments, and significant increases in cholesterol and low-density lipoproteins. Acinar fibrosis, high insulin content, lipoperoxidation, and overexpression of GLUT4 were observed in the pancreas of this group. M-I2 supplementation normalized the T4 and cholesterol, but T3 remained low. Pancreatic alterations were prevented, and nuclear factor erythroid-2-related factor-2 (Nrf2), antioxidant enzymes, and peroxisome proliferator-activated receptor gamma (PPARG) maintained their basal values. In MMI + H-I2, hypothyroidism was avoided, but pancreatic alterations and low PPARG expression remained. In conclusion, M-I2 supplementation reestablishes thyronine synthesis and diminishes pancreatic alterations, possibly related to Nrf2 and PPARG activation.

Immunomodulatory potential of human clonal mesenchymal stem cells and their extracellular vesicle subpopulations in an inflammatory-mediated diabetic Rhesus monkey model

AIMS

This study aimed to investigate the therapeutic potential of a homogenous clonal population of mesenchymal stem cells (cMSC) and their extracellular vesicles (cMSC-EV) subpopulations on isolated rat islets in vitro and in inflammatory-mediated type 1 diabetes (T1D) non-human primate models.

MAIN METHODS

EV subpopulations were isolated from human bone marrow-derived cMSC supernatant by low- and high-speed ultracentrifuge (EV-20K and EV-U110K) and sucrose density gradient (EV-S110K). The EVs were characterized generally and for the level of albumin, acetylcholinesterase (AChE) activity, co-isolate apoptotic markers, and expression of CD63+/annexin V+. Rat islet-derived single cells (iSCs) proliferation was measured using a Ki-67 proliferation assay. Diabetes was induced by multiple low-dose administrations of streptozotocin in rhesus monkeys. The diabetic monkeys were divided into three groups: the cMSC group, received two injections of 1.5 × 106 cMSC/kg body weight; the EV group received two injections of EVs isolated from 1.5 × 106 cMSC/kg, and the vehicle group received phosphate-buffered saline.

KEY FINDINGS

EV-S110K showed higher AChE activity, lower expression of CD63+/annexin V+, and lower apoptotic co-isolates. EV-S110K induced β-cell proliferation in vitro in a dose-dependent manner. The administration of EV-S110K and/or cMSC in diabetic monkeys demonstrated no significant changes in general diabetic indices and β-cell mass in the pancreas of the monkeys. Both treatments demonstrated a lowering trend in blood glucose levels and reduced pro-inflammatory cytokines. In contrast, regulatory T cells and anti-inflammatory cytokines were increased.

SIGNIFICANCE

cMSC and cMSC-EV provided initial evidence to attenuate clinical symptoms in inflammatory-mediated T1D non-human primates through immunomodulation.

Comparison of antithyroid effects and hepatic complications of methimazole with catechin and its nanoencapsulation form in adult male rats

OBJECTIVES

Methimazole is an antithyroid drug and is used clinically in hyperthyroidism. Liver dysfunction is one of the side effects of methimazole. Catechins are natural flavonoids and have antioxidant, antithyroid, and liver protection effects. Despite the wide range of biological properties of catechins, their effective use is limited due to poor water solubility, low stability, and low bioavailability. Catechin niosomal nanoencapsulation improves the properties of catechin and increases its antioxidant activities.

METHODS

Niosomal vesicles were synthesized by the Thin Film Hydration method and their physicochemical characteristics, morphology, and percentage of trapped catechin in them were determined by dynamic light scattering (DLS), transmission electron microscopy (TEM), and spectrophotometry, respectively. In this study, 32 adult male rats were divided into 4 groups: control, 50 mg/kg methimazole, 100 mg/kg catechin, and 100 mg/kg nanocapsule niosomal form of catechin. The drugs were administered orally and the duration of treatment was 8 weeks. Then, the serum concentration of thyroid hormones and thyroid stimulating hormone (TSH) by enzyme-linked immunosorbent assay (ELISA) method, and serum liver function tests were performed using an autoanalyzer. The activities of hepatic oxidative enzymes were measured spectrophotometrically.

RESULTS

Our study showed that the percentage of catechin encapsulation in the niosome was calculated to be 51%. A significant difference was observed in the catechin and encapsulated catechin treatment groups compared to the methimazole group (p <0.0001). In all three treatment groups of methimazole, catechin, and niosomal nanocapsule catechin, serum levels of TT3, TT4, FT3, FT4, body weight and daily consumption of water and food were significantly reduced compared to the control group (p <0.0001).

CONCLUSIONS

The antithyroid effects of catechin and its encapsulated form were comparable to methimazole. Also, the encapsulation improved the hepatoprotective effects of catechin.

Interplay between Fatty Acid Binding Protein 4, Fetuin-A, Retinol Binding Protein 4 and Thyroid Function in Metabolic Dysregulation

Signalling between the tissues integrating synthesis, transformation and utilization of energy substrates and their regulatory hormonal axes play a substantial role in the development of metabolic disorders. Interactions between cytokines, particularly liver derived hepatokines and adipokines, secreted from adipose tissue, constitute one of major areas of current research devoted to metabolic dysregulation. The thyroid exerts crucial influence on the maintenance of basal metabolic rate, thermogenesis, carbohydrate and lipid metabolism, while its dysfunction promotes the development of metabolic disorders. In this review, we discuss the interplay between three adipokines: fatty acid binding protein type 4, fetuin-A, retinol binding protein type 4 and thyroid hormones, that shed a new light onto mechanisms underlying atherosclerosis, cardiovascular complications, obesity, insulin resistance and diabetes accompanying thyroid dysfunction. Furthermore, we summarize clinical findings on those cytokines in the course of thyroid disorders.

Cotransplant With Pancreatic Islet Homogenate Improved Survival and Long-Term Efficacy of Islet Transplant in Streptozotocin-Diabetic Rats

OBJECTIVES

Pancreatic islet transplant is suggested as a promising treatment option in diabetes, but the number of viable and functional islets and the long-term efficacy of transplanted islets have not been satisfactory. Islet isolation leads to destruction of the extracellular matrix and loss of trophic support of islets, which reduces their survival and function. Reconstruction of islet microenvironment with biomaterials may preserve islet survival and graft efficacy. Accordingly, we investigated the effects of pancreatic islet homogenate on islet quality and graft outcomes in diabetic rats.

MATERIALS AND METHODS

Islets were isolated from the pancreas of Sprague Dawley rats and were cultured with or without pancreatic islet homogenate. Before transplant, viability, insulin content, and insulin released from cultured islets were assessed. Islets were then transplanted into subcapsular space of diabetic rat kidney. Transplant outcomes were evaluated by plasma glucose and insulin levels, glucose tolerance tests, and stress oxidative markers.

RESULTS

Viability and insulin release in the pancreatic islet homogenate-treated islets were significantly higher than that in the control islets. After transplant of islets, recipient rats with pancreatic islet homogenate showed significant decreases in blood glucose and malondialdehyde levels and increases in superoxide dismutase activity and plasma insulin levels.

CONCLUSIONS

Islet treatment with pancreatic islet homogenate could improve islet survival and transplant function and outcomes. Oxidative stress reduction might be a secondary beneficial effect of improved quality of treated islets.

Combined therapy of mesenchymal stem cells with a GLP-1 receptor agonist, liraglutide, on an inflammatory-mediated diabetic non-human primate model

AIMS

Immunomodulation concurrent with the promotion of β-cell function is a strategy used to develop innovative therapies for type 1 diabetes (T1D). Here, we assessed the therapeutic potential of co-administration of human clonal mesenchymal stem (stromal) cells (hBM-cMSCs) and liraglutide as a glucagon-like peptide-1 agonist in a non-human primate model with streptozotocin (STZ)-induced diabetes.

MAIN METHODS

Diabetes was induced through intravenous (i.v.) multiple low-dose (MLD) infusions of STZ at a dose of 30 mg/kg body weight (b.w.) for five consecutive days, followed by two booster injections of 35 mg/kg on days 12 and 19. After 90 days, the diabetic animals were randomly allocated to two groups: The combination therapy group (n = 4) received injections of 1.5 × 10⁶ hBM-cMSCs/kg b.w. through celiac artery by angiography on days 91 and 105 and daily subcutaneous injections of liraglutide (up to 1.8 mg/day) until day 160 while vehicle group received phosphate-buffered saline. The monkeys were assessed for functional, immunological, and histological analysis.

KEY FINDINGS

The combined treatment group had continued reduction in FBG levels up to day 160, which was accompanied by increased b.w., C-peptide, and β-cell function, and decreased HbA1c and fructosamine levels compared to vehicle group. The combined treatment increased Tregs, IL-4, IL-10, and TGF-β1 and decreased IL-6 and IL-1β. Stereological analysis of the pancreatic tissue exhibited more total volume of insulin-secreting islets in the combined treatment group compared to vehicle group.

SIGNIFICANCE

Our findings demonstrated this combined treatment impaired the clinical symptoms of diabetes in this animal model through immunomodulation and β-cell preservation.

Thymoquinone Preserves Pancreatic Islets Structure Through Upregulation of Pancreatic β-Catenin in Hypothyroid Rats

BACKGROUND

Altered status of thyroid hormones, which have a key role in regulating metabolism, was reported to affect glucose homeostasis and insulin secretion.

OBJECTIVE

This study was designed to assess the impact of propylthiouracil (PTU)-induced hypothyroidism on the pancreatic islet cells and the efficacy of thymoquinone (TQ) in alleviating this impact and explore the mechanism behind it alleviating oxidative stress and affecting β-catenin expression.

MATERIALS AND METHODS

PTU (6 mg/kg/body weight) was used to induce hypothyroidism in Wistar rats. Four groups of rats (n=6 each) were utilized in this study. Untreated hypothyroid and TQ-treated hypothyroid groups (50 mg/kg/body weight for 4 weeks) were included. Thyroid functions, antioxidant profile and pancreatic β-catenin and IL-10 mRNA were measured. Histopathological and immunohistochemical assessment of the pancreas was performed.

RESULTS

PTU administration induced a hypothyroid status that was associated with a marked disturbed oxidant/antioxidant status and a significant hyperglycemia (p<0:001), hypoinsulinemia (p=0.01) and decreased HOMA-β-cell (p<0.001). Islet cells of hypothyroid pancreas showed many degenerative changes with increased apoptosis, reduced insulin β-catenin immunoexpression. Administration of TQ alleviated these effects on the thyroid function, antioxidants, structure of pancreatic islet cells. Up-regulation of β-catenin, IL-10 and CAT gene expression in pancreatic islets after treatment with TQ supported its antioxidant and preserving β-cell function and viability mechanistic action.

CONCLUSION

TQ alleviated PTU-induced hypothyroidism changes in insulin homeostasis and pancreatic β cells mostly through its antioxidant effect as well as up-regulation of pancreatic β-catenin expression.

Gestational hypothyroidism elicits more pronounced lipid dysregulation in mice than pre-pregnant hypothyroidism

Thyroid hormone is crucial for regulating lipid and glucose metabolism, which plays essential role in maintaining the health of pregnant women and their offspring. However, the current literature is just focusing on the development of offspring born to the untreated mothers with hypothyroidism, rather than mothers themselves. Additionally, the interaction between hypothyroidism and pregnancy, and its impact on the women's health are still elusive. Therefore, this study was designed to compare the metabolic differences in dams with hypothyroidism starting before pregnancy and after pregnancy. Pre-pregnant hypothyroidism was generated in 5-week-old female C57/BL/6J mice using iodine-deficient diet containing 0.15% propylthiouracil for 4 weeks, and the hypothyroidism was maintained until delivery. Gestational hypothyroidism was induced in dams after mating, using the same diet intervention until delivery. Compared with normal control, gestational hypothyroidism exhibited more prominent increase than pre-pregnant hypothyroidism in plasma total cholesterol and low-density lipoprotein cholesterol, and caused hepatic triglycerides accumulation. Similarly, more significant elevations of protein expressions of SREBP1c and p-ACL, while more dramatic inhibition of CPT1A and LDL-R levels were also observed in murine livers with gestational hypothyroidism than those with pre-pregnant hypothyroidism. Moreover, the murine hepatic levels of total cholesterol and gluconeogenesis were dramatically and equally enhanced in two hypothyroid groups, while plasma triglycerides and protein expressions of p-AKT, p-FoxO1 and APOC3 were reduced substantially in two hypothyroid groups. Taken together, our current study illuminated that gestational hypothyroidism may elicit more pronounced lipid dysregulation in dams than dose the pre-pregnant hypothyroidism.

Improving effect of combined inorganic nitrate and nitric oxide synthase inhibitor on pancreatic oxidative stress and impaired insulin secretion in streptozotocin induced-diabetic rats

Purpose

The aim of this study was to evaluate the effect of dietary nitrate on secretory function of pancreatic islet and oxidative stress status in streptozotocin (STZ) induced type 1 diabetes in absence or presence of nitric oxide synthase inhibitor (L-NAME).

Methods

Fifty adult male sprague-dawly rats were divided into 5 groups: controls (C), diabetes (D), diabetes+nitrate (DN), diabetes +L-NAME (D + Ln), and diabetes+nitrate+L-NAME (DN + Ln) for 45 days. The concentrations of sodium nitrate and L-NAME were respectively 80 mg/L in drinking water and 5 mg/kg intraperitoneally. Body weight gain, plasma levels of glucose and insulin, islet insulin secretion and content, lipid peroxidation and antioxidant status in the pancreas of rats were determined.

Results

Compared to control group, the body weight gain and plasma insulin level were significantly decreased and plasma glucose and pancreatic NO and MDA concentrations and antioxidant enzymes activities were significantly increased in the STZ diabetic rats. In the diabetic rats, nitrate alone significantly reduced plasma glucose and increased pancreatic SOD and GPx activity. Reduced plasma glucose, pancreatic MDA and NO concentrations and increased plasma insulin level and pancreatic islet insulin secretion were observed in D + Ln and DN + Ln groups. Antioxidant enzymes activities were increased in diabetic rats which received combination of nitrate and L-NAME.

Conclusions

Our results showed that nitrate without effect on pancreatic islet insulin content and secretion decreased the blood glucose and slightly moderate oxidative stress and its effects in the presence of L-NAME on glucose hemostasis and pancreatic insulin secretion higher than those of nitrate alone.

Effects of platelet-rich plasma on the pancreatic islet survival and function, islet transplantation outcome and pancreatic pdx1 and insulin gene expression in streptozotocin-induced diabetic rats

Platelet-rich plasma (PRP) is a therapeutic option in different fields based on its growth factors. We investigated influence of PRP on islet survival, function, transplantation outcomes, and pancreatic genes expression in diabetic rats. In vitro: pancreatic isolated islets were incubated with/without PRP then viability, insulin secretion, and content were assessed. In vivo: Series 1 were designed to determine whether islet treatment with PRP improves transplantation outcome in diabetic rats by evaluating plasma glucose and insulin concentrations and oxidative parameters. Series 2, effects of PRP subcutaneous injection were evaluated on pancreatic genes expression and glucose tolerance test in diabetic rats. PRP enhanced viability and secretary function of islet. Reduced glucose and malondialdehyde levels as well as increased insulin levels, superoxide dismutase activity, and expressions of pdx1 and insulin were observed in diabetic rats. PRP treatment has positive effects on islet viability, function, transplantation outcome, and pancreatic genes expression in diabetic rats.

Platelet-rich plasma improves impaired glucose hemostasis, disrupted insulin secretion, and pancreatic oxidative stress in streptozotocin-induced diabetic rat

Our study aimed to investigate the effects of platelet-rich plasma (PRP) on impaired glucose homeostasis, disrupted islet insulin secretion, and pancreatic oxidative status in streptozotocin (STZ)-diabetic rats. A total of 64 Sprague-Dawley male were randomized to four groups including controls, diabetes, control-PRP, and diabetes-PRP. The rats received the PRP (0.5 ml/kg, SC injection) twice weekly for 4 weeks. Plasma glucose and insulin levels, pancreatic oxidative stress markers and islet insulin secretion and content were measured. Compared with the control group, in the diabetic group, increased plasma glucose and malondialdehyde (MDA) levels and decreased plasma insulin level, islet insulin secretion, pancreatic superoxide dismutase (SOD), and catalase activities were observed. PRP treatment significantly reduced plasma glucose and MDA levels and enhanced plasma insulin, antioxidant enzyme activity, islet insulin secretion, and content in the diabetic rats. These findings showed that PRP can improve pancreatic islet insulin secretion, pancreatic oxidative stress and regulate plasma insulin and glucose levels in diabetic rats.

Contribution of Oxidative Stress and Impaired Biogenesis of Pancreatic β-Cells to Type 2 Diabetes

Significance: Type 2 diabetes development involves multiple changes in β-cells, related to the oxidative stress and impaired redox signaling, beginning frequently by sustained overfeeding due to the resulting lipotoxicity and glucotoxicity. Uncovering relationships among the dysregulated metabolism, impaired β-cell "well-being," biogenesis, or cross talk with peripheral insulin resistance is required for elucidation of type 2 diabetes etiology. Recent Advances: It has been recognized that the oxidative stress, lipotoxicity, and glucotoxicity cannot be separated from numerous other cell pathology events, such as the attempted compensation of β-cell for the increased insulin demand and dynamics of β-cell biogenesis and its "reversal" at dedifferentiation, that is, from the concomitantly decreasing islet β-cell mass (also due to transdifferentiation) and low-grade islet or systemic inflammation. Critical Issues: At prediabetes, the compensation responses of β-cells, attempting to delay the pathology progression-when exaggerated-set a new state, in which a self-checking redox signaling related to the expression of Ins gene expression is impaired. The resulting altered redox signaling, diminished insulin secretion responses to various secretagogues including glucose, may lead to excretion of cytokines or chemokines by β-cells or excretion of endosomes. They could substantiate putative stress signals to the periphery. Subsequent changes and lasting glucolipotoxicity promote islet inflammatory responses and further pathology spiral. Future Directions: Should bring an understanding of the β-cell self-checking and related redox signaling, including the putative stress signal to periphery. Strategies to cure or prevent type 2 diabetes could be based on the substitution of the "wrong" signal by the "correct" self-checking signal.

Amla (Emblica officinalis) improves hepatic and renal oxidative stress and the inflammatory response in hypothyroid female wistar rats fed with a high-fat diet

BACKGROUND

We investigated the protective effects of amla (Emblica officinalis) on the pathogenesis of oxidative stress (OS) and inflammatory response in hypothyroid rats fed with a high-fat diet (HFD) as an experimental model of hypothyroidism (HT) with obesity.

METHODS

A total of 80 female wistar rats (5-months-old) were divided into eight different groups. Propylthiouracil (PTU) and HFD were used to induce the experimental HT and obesity, respectively. The euthyroid and hypothyroid rats were fed either normal chow or HFD with and without amla extract (AE, 100 mg/kg bw/day) for 6 weeks. The blood and tissues, liver and kidney OS and inflammatory parameters were studied using appropriate biochemical and molecular techniques.

RESULTS

PTU and HFD per se caused OS and inflammatory response as evidenced by increased plasma MDA, TNF-α, CRP and GPx in association with decreased levels of TAS and reduced glutathione (GSH). The proteomic analysis revealed that the expressions of pERK, pP38, TNF-α, IL6, COX2 and NOX-4 were up-regulated in the liver and kidney of these rats. In addition, all these metabolic derangements were further augmented when HT was followed by the addition of HFD. This suggested that there was a synergism between HT and the intake of HFD on the development of OS and inflammatory response.

CONCLUSIONS

The treatment with amla fruit extract significantly restored the redox imbalance and inflammatory signaling and ameliorated OS and inflammatory response, suggesting the use of this natural compound as an alternative remedy or adjuvant for the management of metabolic complications concomitant with HT.

The Roles of Thyroid and Thyroid Hormone in Pancreas: Physiology and Pathology

It is widely accepted that thyroid hormones (THs), secreted from the thyroid, play important roles in energy metabolism. It is also known that THs also alter the functioning of other endocrine glands; however, their effects on pancreatic function have not yet been reviewed. One of the main functions of the pancreas is insulin secretion, which is altered in diabetes. Diabetes, therefore, could be related to thyroid dysfunction. Earlier research on this subject focused on TH regulation of pancreas function (such as insulin secretion) or on insulin function through TH-mediated increase of energy metabolism. Afterwards, epidemiological investigations and animal test research found a link between autoimmune diseases, thyroid dysfunction, and pancreas pathology; however, the underlying mechanisms remain unknown. Furthermore, recent studies have shown that THs also play important roles in pancreas development and on islet pathology, both in diabetes and in pancreatic cancer. Therefore, an overview of the effects of thyroid and THs on pancreas physiology and pathology is presented. The topics contained in this review include a summary of the relationship between autoimmune thyroid dysfunction and autoimmune pancreas lesions and the effects of THs on pancreas development and pancreas pathology (diabetes and pancreatic cancer).