Viruses as a potential environmental trigger of type 1 diabetes mellitus (Review).

The etiopathogenesis of type 1 diabetes mellitus (T1DM) is a complex multifactorial process that involves an intricate network of genetic, epigenetic, immunological, and environmental factors. Despite the advances in recent years, some aspects of the mechanisms involved in triggering the disease are still unclear. Infections with certain viruses have been suggested as possible environmental triggers for the autoimmune process that leads to selective and progressive destruction of pancreatic ß-cells and insufficiency of insulin production, which is its hallmark. In this review, advances in knowledge and evidence that suggest the participation of certain viruses in the mechanisms of disease initiation and progression are described. It has been accepted that environmental factors, including viruses, can initiate and possibly sustain, accelerate, or slow down the autoimmune process and consequently damage insulin-producing pancreatic ß-cells. Although the role of these agents, especially human enteroviruses, has been exhaustively studied as the most likely triggers of the activation of autoimmunity that destroys pancreatic islets and leads to T1DM, certain doubts remain. Clinical epidemiological and experimental studies in humans and animals provide consistent and increasing evidence that persistent viral infections, especially with human enteroviruses and rotavirus infections, are associated with an increased risk of the disease in individuals genetically predisposed to autoimmunity.

Mesenchymal Stem Cell Therapy for Treating the Underlying Causes of Diabetes Mellitus and Its Consequences.

Diabetes mellitus (DM) is a multifaceted pathological condition, which at present is being considered an epidemic disease keeping the rampant rate of its increase in almost all population groups of the world in consideration. Out of the two types of DM described, T1D is characterized as an autoimmune condition that leads to the destruction of pancreatic ß-cells by macrophages and T-cells, thereby, adversely affecting the production of insulin. On the other hand, T2D, often caused by insulin resistance, is commonly related to unhealthy habits, and therefore, it can be prevented in most cases. In both of the conditions, high levels of proinflammatory cytokines like IL-6, TNF-α, and INF-Æ´, lead to chronic inflammation, and elevated oxidative stress resulting in apoptosis and destruction of tissues. Although several treatments are available to treat the symptoms, the underlying causes are not well addressed. One of the most promising approaches to tackle the ill effects and the primary causes of DM is mesenchymal stem cell (MSC) therapy. The use of MSC therapy, because of the immunomodulatory and regenerative properties recorded in this type of cells in a number of experiments carried out in animal models and clinical trials of the disease, has reported positive outcomes. This review covers the principal mechanisms of action induced during MSC therapy in reference to the described pathophysiological pathways of both T1D and T2D. In addition, how this therapeutic intervention can counteract the ill effects of this condition leading to the promotion of tissue regeneration has been covered.

IMT504 protects beta cells against apoptosis and maintains beta cell identity, without modifying proliferation.

We have demonstrated that oligodeoxynucleotide IMT504 promotes significant improvement in the diabetic condition in diverse animal models. Based on these results, here we evaluated whether these effects observed in vivo could be due to direct effects on ß-cells. We demonstrate by immunofluorescence that IMT504 enters the cell and locates in cytoplasm where it induces GSK-3ß phosphorylation that inactivates this kinase. As GSK-3ß tags Pdx1 for proteasomal degradation, by inactivating GSK-3ß, IMT504 induces an increase in Pdx1 protein levels, demonstrated by Western blotting. Concomitantly, an increase in Ins2 and Pdx1 gene transcription was observed, with no significant increase in insulin content or secretion. Enhanced Pdx1 is promising since it is a key transcription factor for insulin synthesis and is also described as an essential factor for the maintenance ß-cell phenotype and function. Dose-dependent inhibition of H2 O2 -induced apoptosis determined by ELISA as well as decreased expression of Bax was also observed. These results were confirmed in another ß-cell line, beta-TC-6 cells, in which a cytokine mix induced apoptosis that was reversed by IMT504. In addition, an inhibitor of IMT504 entrance into cells abrogated the effect IMT504. Based on these results we conclude that the ß-cell recovery observed in vivo may include direct effects of IMT504 on ß-cells, by maintaining their identity/phenotype and protecting them from oxidative stress and cytokine-induced apoptosis. Thus, this work positions IMT504 as a promising option in the framework of the search of new therapies for type I diabetes treatment.

Pre-treatment with IL-6 potentiates ß-cell death induced by pro-inflammatory cytokines.

BACKGROUND: Type I Diabetes mellitus (T1D) is characterized by a specific destruction of ß-cells by the immune system. During this process pro-inflammatory cytokines are released in the pancreatic islets and contribute for ß-cells demise. Cytokine-induced iNOS activation, via NF-κB, is implicated in induction of ß-cells death, which includes ER stress activation. Physical exercise has been used as an adjunct for better glycemic control in patients with T1D, since it is able to increase glucose uptake independent of insulin. Recently, it was observed that the release of IL-6 by skeletal muscle, during physical exercise, could prevent ß-cells death induced by pro-inflammatory cytokines. However, the molecular mechanisms involved in this beneficial effect on ß-cells are not yet completely elucidated. Our aim was to evaluate the effect of IL-6 on ß-cells exposed to pro-inflammatory cytokines. RESULTS: Pre-treatment with IL-6 sensitized INS-1E cells to cytokine-induced cell death, increasing cytokine-induced iNOS and Caspase-3 expression. Under these conditions, however, there was a decrease in cytokines-induced p-eIF2-α but not p-IRE1expression, proteins related to ER stress. To address if this prevention of adequate UPR response is involved in the increase in ß-cells death markers induced by IL-6 pre-treatment, we used a chemical chaperone (TUDCA), which improves ER folding capacity. Use of TUDCA increased cytokines-induced Caspase-3 expression and Bax/Bcl-2 ratio in the presence of IL-6 pre-treatment. However, there is no modulation of p-eIF2-α expression by TUDCA in this condition, with increase of CHOP expression. CONCLUSION: Treatment with IL-6 alone is not beneficial for ß-cells, leading to increased cell death markers and impaired UPR activation. In addition, TUDCA has not been able to restore ER homeostasis or improve ß-cells viability under this condition, suggesting that other mechanisms may be involved.

LDL Promotes Disorders in ß-Cell Cholesterol Metabolism, Implications on Insulin Cellular Communication Mediated by EVs.

Dyslipidemia is described as a hallmark of metabolic syndrome, promoting a stage of metabolic inflammation (metainflammation) that could lead to misbalances in energetic metabolism, contributing to insulin resistance, and modifying intracellular cholesterol pathways and the renin-angiotensin system (RAS) in pancreatic islets. Low-density lipoprotein (LDL) hypercholesterolemia could disrupt the tissue communication between Langerhans ß-cells and hepatocytes, wherein extracellular vesicles (EVs) are secreted by ß-cells, and exposition to LDL can impair these phenomena. ß-cells activate compensatory mechanisms to maintain insulin and metabolic homeostasis; therefore, the work aimed to characterize the impact of LDL on ß-cell cholesterol metabolism and the implication on insulin secretion, connected with the regulation of cellular communication mediated by EVs on hepatocytes. Our results suggest that ß-cells can endocytose LDL, promoting an increase in de novo cholesterol synthesis targets. Notably, LDL treatment increased mRNA levels and insulin secretion; this hyperinsulinism condition was associated with the transcription factor PDX-1. However, a compensatory response that maintains basal levels of intracellular calcium was described, mediated by the overexpression of calcium targets PMCA1/4, SERCA2, and NCX1, together with the upregulation of the unfolded protein response (UPR) through the activation of IRE1 and PERK arms to maintain protein homeostasis. The LDL treatment induced metainflammation by IL-6, NF-κB, and COX-2 overexpression. Furthermore, LDL endocytosis triggered an imbalance of the RAS components. LDL treatment increased the intracellular levels of cholesterol on lipid droplets; the adaptive ß-cell response was portrayed by the overexpression of cholesterol transporters ABCA1 and ABCG1. Therefore, lipotoxicity and hyperinsulinism induced by LDL were regulated by the natural compound auraptene, a geranyloxyn coumarin modulator of cholesterol-esterification by ACAT1 enzyme inhibition. EVs isolated from ß-cells impaired insulin signaling via mTOR/p70S6Kα in hepatocytes, a phenomenon regulated by auraptene. Our results show that LDL overload plays a novel role in hyperinsulinism, mechanisms associated with a dysregulation of intracellular cholesterol, lipotoxicity, and the adaptive UPR, which may be regulated by coumarin-auraptene; these conditions explain the affectations that occur during the initial stages of insulin resistance.

Islet amyloid toxicity: From genesis to counteracting mechanisms.

Islet amyloid polypeptide (IAPP or amylin) is a hormone co-secreted with insulin by pancreatic ß-cells and is the major component of islet amyloid. Islet amyloid is found in the pancreas of patients with type 2 diabetes (T2D) and may be involved in ß-cell dysfunction and death, observed in this disease. Thus, investigating the aspects related to amyloid formation is relevant to the development of strategies towards ß-cell protection. In this sense, IAPP misprocessing, IAPP overproduction, and disturbances in intra- and extracellular environments seem to be decisive for IAPP to form islet amyloid. Islet amyloid toxicity in ß-cells may be triggered in intra- and/or extracellular sites by membrane damage, endoplasmic reticulum stress, autophagy disruption, mitochondrial dysfunction, inflammation, and apoptosis. Importantly, different approaches have been suggested to prevent islet amyloid cytotoxicity, from inhibition of IAPP aggregation to attenuation of cell death mechanisms. Such approaches have improved ß-cell function and prevented the development of hyperglycemia in animals. Therefore, counteracting islet amyloid may be a promising therapy for T2D treatment.

The influence of high-density lipoprotein (HDL) and HDL subfractions on insulin secretion and cholesterol efflux in pancreatic derived ß-cells.

BACKGROUND: High-density lipoprotein (HDL) is considered a complex plasma-circulating particle with subfractions that vary in function, size, and chemical composition. We sought to test the effects of HDL, and HDL subfractions on insulin secretion and cholesterol efflux in the ß-cell line MIN-6. METHODS: We used total HDL and HDL subfractions 2a, 2b, 3a, 3b, and 3c, isolated from human plasma, to test insulin secretion under different glucose concentrations as well as insulin content and cholesterol efflux in the insulinoma MIN-6 cell line. RESULTS: Incubation of MIN-6 cells with low glucose and total HDL increased insulin release two-fold. Meanwhile, when high glucose and HDL were used, insulin release increased more than five times. HDL subfractions 2a, 2b, 3a, 3b, and 3c elicited higher insulin secretion and cholesterol efflux than their respective controls, at both low and high glucose concentrations. The insulin content of the MIN-6 cells incubated with low glucose and any of the five HDL subclasses had a modest reduction compared with their controls. However, there were no statistically significant differences between each HDL subfraction on their capacity of eliciting insulin secretion, insulin content, or cholesterol efflux. CONCLUSIONS: HDL can trigger insulin secretion under low, normal, and high glucose conditions. We found that all HDL subfractions exhibit very similar capacity to increase insulin secretion and cholesterol efflux. This is the first report demonstrating that HDL subfractions act both as insulin secretagogues (under low glucose) and insulin secretion enhancers (under high glucose) in the MIN-6 cell line.

Amyloidogenesis of feline amylin and plasma levels in cats with diabetes mellitus or pancreatitis.

Amylin is a pancreatic hormone cosecreted along with insulin and involved in pancreatic amyloidosis and ß-cell apoptosis in diabetic cats and humans. Amylin is usually elevated in early stages of type 2 diabetes but recently was found to be increased in acute and chronic pancreatitis in humans. Currently, there are little data about feline amylin propensity to fibrillate and no information on circulating levels of this hormone during feline pancreatitis. We compared 4 amylin analogues and found cat amylin to be more prone to amyloid fibrillation than human amylin, the triple-proline analogue pramlintide and rat amylin. We also measured plasma amylin levels in healthy lean cats, diabetic cats, and cats with pancreatitis. Plasma amylin was higher in diabetic cats compared with healthy lean cats (P < 0.001). Interestingly, amylin levels during pancreatitis were higher than those of both lean cats (P < 0.0001) and diabetic cats without pancreatitis (P < 0.005). These data support evidence of feline amylin being more prone to aggregation than human amylin in vitro, which may influence diabetes mellitus progression and ß-cell failure in vivo. Furthermore, our data show an increase in amylin levels during feline pancreatitis and the need for future research on the role of this hormone in the pathogenesis of pancreatic inflammation associated to feline diabetes mellitus.

Diabetes Mellitus Is a Chronic Disease that Can Benefit from Therapy with Induced Pluripotent Stem Cells.

Diabetes mellitus (DM) is one of the main causes of morbidity and mortality, with an increasing incidence worldwide. The impact of DM on public health in developing countries has triggered alarm due to the exaggerated costs of the treatment and monitoring of patients with this disease. Considerable efforts have been made to try to prevent the onset and reduce the complications of DM. However, because insulin-producing pancreatic ß-cells progressively deteriorate, many people must receive insulin through subcutaneous injection. Additionally, current therapies do not have consistent results regarding the prevention of chronic complications. Leveraging the approval of real-time continuous glucose monitors and sophisticated algorithms that partially automate insulin infusion pumps has improved glycemic control, decreasing the burden of diabetes management. However, these advances are facing physiologic barriers. New findings in molecular and cellular biology have produced an extraordinary advancement in tissue development for the treatment of DM. Obtaining pancreatic ß-cells from somatic cells is a great resource that currently exists for patients with DM. Although this therapeutic option has great prospects for patients, some challenges remain for this therapeutic plan to be used clinically. The purpose of this review is to describe the new techniques in cell biology and regenerative medicine as possible treatments for DM. In particular, this review highlights the origin of induced pluripotent cells (iPSCs) and how they have begun to emerge as a regenerative treatment that may mitigate the pathology of this disease.

Chronic activation of GPR40 does not negatively impact upon BRIN-BD11 pancreatic ß-cell physiology and function.

BACKGROUND: Free fatty acids (FFAs) are known for their dual effects on insulin secretion and pancreatic ß-cell survival. Short-term exposure to FFAs, such as palmitate, increases insulin secretion. On the contrary, long-term exposure to saturated FFAs results in decreased insulin secretion, as well as triggering oxidative stress and endoplasmic reticulum (ER) stress, culminating in cell death. The effects of FFAs can be mediated either via their intracellular oxidation and consequent effects on cellular metabolism or via activation of the membrane receptor GPR40. Both pathways are likely to be activated upon both short- and long-term exposure to FFAs. However, the precise role of GPR40 in ß-cell physiology, especially upon chronic exposure to FFAs, remains unclear. METHODS: We used the GPR40 agonist (GW9508) and antagonist (GW1100) to investigate the impact of chronically modulating GPR40 activity on BRIN-BD11 pancreatic ß-cells physiology and function. RESULTS: We observed that chronic activation of GPR40 did not lead to increased apoptosis, and both proliferation and glucose-induced calcium entry were unchanged compared to control conditions. We also observed no increase in H2O2 or superoxide levels and no increase in the ER stress markers p-eIF2α, CHOP and BIP. As expected, palmitate led to increased H2O2 levels, decreased cell viability and proliferation, as well as decreased metabolism and calcium entry. These changes were not counteracted by the co-treatment of palmitate-exposed cells with the GPR40 antagonist GW1100. CONCLUSIONS: Chronic activation of GPR40 using GW9508 does not negatively impact upon BRIN-BD11 pancreatic ß-cells physiology and function. The GPR40 antagonist GW1100 does not protect against the deleterious effects of chronic palmitate exposure. We conclude that GPR40 is probably not involved in mediating the toxicity associated with chronic palmitate exposure.

Palmitic acid-induced lipotoxicity promotes a novel interplay between Akt-mTOR, IRS-1, and FFAR1 signaling in pancreatic ß-cells.

BACKGROUND: Free fatty acid receptor 1 (FFAR1) is G-protein coupled receptor predominantly expressed in pancreatic ß-cells that is activated by a variety of free fatty acids (FFAs). Once activated, it promotes glucose-stimulated insulin secretion (GSIS). However, increased levels of FFAs lead to lipotoxicity, inducing loss of ß-cell function. FFAR1 plays a key role in the development of type 2 diabetes (T2D), and previous studies have indicated the importance of developing anti-diabetic therapies against FFAR1, although its role in the regulation of ß-cell function remains unclear. The present study investigated the role of FFAR1 under lipotoxic conditions using palmitic acid (PA). The rat insulinoma 1 clone 832/13 (INS-1 832/13) cell line was used as a model as it physiologically resembles native pancreatic ß-cells. Key players of the insulin signaling pathway, such as mTOR, Akt, IRS-1, and the insulin receptor (INSR1ß), were selected as candidates to be analyzed under lipotoxic conditions. RESULTS: We revealed that PA-induced lipotoxicity affected GSIS in INS-1 cells and negatively modulated the activity of both IRS-1 and Akt. Reduced phosphorylation of both IRS-1 S636/639 and Akt S473 was observed, in addition to decreased expression of both INSR1ß and FFAR1. Moreover, transient knockdown of FFAR1 led to a reduction in IRS-1 mRNA expression and an increase in INSR1ß mRNA. Finally, PA affected localization of FFAR1 from the cytoplasm to the perinucleus. CONCLUSIONS: In conclusion, our study suggests a novel regulatory involvement of FFAR1 in crosstalk with mTOR-Akt and IRS-1 signaling in ß-cells under lipotoxic conditions.

Fatty Acid and Lipopolysaccharide Effect on Beta Cells Proteostasis and its Impact on Insulin Secretion.

Metabolic overload by saturated fatty acids (SFA), which comprises ß-cell function, and impaired glucose-stimulated insulin secretion are frequently observed in patients suffering from obesity and type 2 diabetes mellitus. The increase of intracellular Ca2+ triggers insulin granule release, therefore several mechanisms regulate Ca2+ efflux within the ß-cells, among others, the plasma membrane Ca2+-ATPase (PMCA). In this work, we describe that lipotoxicity mediated mainly by the saturated palmitic acid (PA) (16C) is associated with loss of protein homeostasis (proteostasis) and potentially cell viability, a phenomenon that was induced to a lesser extent by stearic (18C), myristic (14C) and lauric (12C) acids. PA was localized on endoplasmic reticulum, activating arms of the unfolded protein response (UPR), as also promoted by lipopolysaccharides (LPS)-endotoxins. In particular, our findings demonstrate an alteration in PMCA1/4 expression caused by PA and LPS which trigger the UPR, affecting not only insulin release and contributing to ß-cell mass reduction, but also increasing reactive nitrogen species. Nonetheless, stearic acid (SA) did not show these effects. Remarkably, the proteolytic degradation of PMCA1/4 prompted by PA and LPS was avoided by the action of monounsaturated fatty acids such as oleic and palmitoleic acid. Oleic acid recovered cell viability after treatment with PA/LPS and, more interestingly, relieved endoplasmic reticulum (ER) stress. While palmitoleic acid improved the insulin release, this fatty acid seems to have more relevant effects upon the expression of regulatory pumps of intracellular Ca2+. Therefore, chain length and unsaturation of fatty acids are determinant cues in proteostasis of ß-cells and, consequently, on the regulation of calcium and insulin secretion.

Effects of islet neogenesis associated protein depend on vascular endothelial growth factor gene expression modulated by hypoxia-inducible factor 1-alpha.

BACKGROUND: Pharmacology has provided efficient tools to improve insulin effect/secretion but the decrease in ß-cell mass remains elusive. INGAP-PP could provide a therapeutic alternative to meet that challenge. AIM: To further understand the mechanism that links INGAP-PP effects upon ß-cell mass and function with islet angiogenesis. METHODOLOGY: Normal male Wistar rats were divided into 2 groups and injected with a single dose of 100 mg/Kg suramin or saline. Both groups were divided into 2 subgroups that received daily doses of 2 mg/kg INGAP-PP or saline for ten days. Plasma glucose, triacylglycerol, TBARS, and insulin levels were measured. Pancreas immunomorphometric analyses were also performed. Pancreatic islets were isolated to measure glucose-stimulated insulin secretion (GSIS). Specific islet mRNA levels were studied by qRT-PCR. Statistical analysis was done using ANOVA. RESULTS: No differences were recorded in body weight, food intake, or any other plasma parameter measured in all groups. Islets from INGAP-PP-treated rats significantly increased GSIS, ß-cell mass, and mRNA levels of Bcl-2, Ngn-3, VEGF-A, VEGF-R2, CD31, Ang1 and Ang2, Laminin ß-1, and Integrin ß-1, and decreased mRNA levels of Caspase-8, Bad, and Bax. Islets from suramin-treated rats showed significant opposite effects, but INGAPP-PP administration rescued most of the suramin effects in animals treated with both compounds. CONCLUSION: Our results reinforce the concept that INGAP-PP enhances insulin secretion and ß-cell mass, acting through PI3K/Akt/mTOR pathways and simultaneously activating angiogenesis through HIF-1α-mediated VEGF-A secretion. Therefore, INGAP-PP might be a suitable antidiabetic agent able to overcome two major alterations present in T2D.

Palmitic acid-induced lipotoxicity promotes a novel interplay between Akt-mTOR, IRS-1, and FFAR1 signaling in pancreatic ß-cells

BACKGROUND: Free fatty acid receptor 1 (FFAR1) is G-protein coupled receptor predominantly expressed in pancreatic ß-cells that is activated by a variety of free fatty acids (FFAs). Once activated, it promotes glucose-stimulated insulin secretion (GSIS). However, increased levels of FFAs lead to lipotoxicity, inducing loss of ß-cell function. FFAR1 plays a key role in the development of type 2 diabetes (T2D), and previous studies have indicated the importance of developing anti-diabetic therapies against FFAR1, although its role in the regulation of ß-cell function remains unclear. The present study investigated the role of FFAR1 under lipotoxic conditions using palmitic acid (PA). The rat insulinoma 1 clone 832/13 (INS-1 832/13) cell line was used as a model as it physiologically resembles native pancreatic ß-cells. Key players of the insulin signaling pathway, such as mTOR, Akt, IRS-1, and the insulin receptor (INSR1ß), were selected as candidates to be analyzed under lipotoxic conditions. RESULTS: We revealed that PA-induced lipotoxicity affected GSIS in INS-1 cells and negatively modulated the activity of both IRS-1 and Akt. Reduced phosphorylation of both IRS-1 S636/639 and Akt S473 was observed, in addition to decreased expression of both INSR1ß and FFAR1. Moreover, transient knockdown of FFAR1 led to a reduction in IRS-1 mRNA expression and an increase in INSR1ß; mRNA. Finally, PA affected localization of FFAR1 from the cytoplasm to the perinucleus. CONCLUSIONS: In conclusion, our study suggests a novel regulatory involvement of FFAR1 in crosstalk with mTOR-Akt and IRS-1 signaling in ß-cells under lipotoxic conditions.

Pancreatic ß-Cells and Type 2 Diabetes Development.

Diabetes mellitus (DM) is a group of metabolic disorders characterized by hyperglycemia. In particular, type 2 diabetes (T2D) represents one of the main causes of death in the world, and those suffering from it have a lower quality of life. Although there are multiple hypotheses about the pathophysiological mechanisms that lead to the development of T2D, the effects of this pathology on pancreatic ß-cells are often ignored. We now know that in addition to genetic defects, ß-cell organellar dysfunction participates in the earliest stages of the disease; other factors also contribute to this dysfunction, such as excessive production of reactive oxygen species and a decrease in cellular volume and mass. These features usually result from increased apoptosis, which is not adequately compensated for by the characteristic regeneration mechanisms of these cells. In this study, we specifically examine the genetic, epigenetic and metabolic defects that contribute to ß-cell dysfunction and lead to the establishment of T2D, particularly the dysregulated insulin synthesis and secretion in these cells.

Polygodial, a sesquiterpene isolated from Drimys brasiliensis (Winteraceae), triggers glucocorticoid-like effects on pancreatic ß-cells.

Despite its common use, the synthetic glucocorticoid dexamethasone can cause several adverse effects, such as diabetes and insulin-related metabolic impairment. Thus, research on molecules that could provide the same anti-inflammatory response with milder side effects is constant. In this work the anti-inflammatory activity of the natural sesquiterpene polygodial, extracted from the endemic Brazilian plant Drimys brasiliensis Miers (Winteraceae), was investigated. Employing a pancreatic ß-cell model (INS 1E), the effect of polygodial on signaling pathways is similar to that caused by dexamethasone - both increased MKP1 and decreased ERK1/2 expression in a dose-response and time-dependent manner. Relating to such finding, nuclear translocation of the glucocorticoid receptor was also discovered to be induced by the sesquiterpene. Molecular modeling results indicated that polygodial was capable of docking to the glucocorticoid receptor, but presented preference for the Arg611 binding site rather than Thr739 when set to bind freely inside the pocket. At last, fragmentation of DNA was verified as consequence of sesquiterpene-induced cell death. Altogether, our results suggest that, like dexamethasone, polygodial interacts the glucocorticoid receptor ligand binding domain but create fewer ligand-protein interactions at the site, yielding a weaker effector response. Such property provides an advantage when regarding the adverse effects resulting from stronger affinity ligands of the glucocorticoid receptor, such as in the case of the current standard dexamethasone-based treatment. This aspect, also, turns polygodial an interesting hit compound to the development of new drugs based on its backbone structure providing less harmful anti-inflammatory treatments.

Protective Action of Carica papaya on ß-Cells in Streptozotocin-Induced Diabetic Rats.

The aim of the present study was to investigate the effect of C. papaya L. leaf extract (CPLE) on pancreatic islets in streptozotocin (STZ)-induced diabetic rats, as well as on cultured normal pancreatic cells with STZ in the medium. CPLE (3-125 mg/Kg) was administered orally for 20 days, while a group of diabetic rats received 5 IU/Kg/day of insulin. At the end of the treatment the rats were sacrificed. Blood was obtained to assess glucose and insulin levels. The pancreas was dissected to evaluate ß cells by immunohistochemistry. In addition, normal pancreatic cells were cultured in a medium that included CPLE (3-12 mg). One half of the cultured cells received simultaneously CPLE and STZ (6 mg), while the other half received CPLE and five days later the STZ. After three days of incubation, insulin was assayed in the incubation medium. The CPLE administered to diabetic rats improved the fasting glycemia and preserved the number and structure of pancreatic islets. However, when CPLE was added to pancreatic cells in culture along with STZ, the insulin concentration was higher in comparison with the cells that only received STZ. In conclusion, the CPLE preserves the integrity of pancreatic islets, improves the basal insulin secretion and protects cultured cells from the adverse effects of STZ.