Effect of Ursolic Acid on Insulin Resistance and Hyperinsulinemia in Rats with Diet-Induced Obesity: Role of Adipokines Expression

Excess of visceral adipose tissue (VAT) characteristic of obesity leads to a proinflammatory state disrupting the insulin signaling pathway, triggering insulin resistance (IR) and inflammation, the main processes contributing to obesity comorbidities. Ursolic acid (UA), a pentacyclic triterpenoid occurring in a variety of plant foods, exhibits anti-inflammatory properties. The aim of this study was to evaluate UA effects on IR, hyperinsulinemia, and inflammation in experimental diet-induced obesity. Forty male Wistar rats were randomly assigned to eight groups (n = 5). One group was used for time 0. Three groups were labeled as OBE (control): receiving high-fat diet (HFD; fat content 45.24% of energy) during 3, 6, or 9 weeks; three groups UA-PREV: exposed to simultaneous HFD and UA during 3, 6, or 9 weeks to evaluate UA preventive effects; one group UA-REV: receiving HFD for 6 weeks, followed by simultaneous HFD and UA for three additional weeks to analyze UA reversal effects. Measurements were performed after 3, 6, or 9 weeks of treatment. Adiposity was calculated by weighing VAT after sacrifice. Serum markers were quantified through colorimetric and enzyme-linked immunosorbent assay methods. VAT adipokines RNAm expression was evaluated by quantitative reverse transcriptase-polymerase chain reaction. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests. UA significantly decreased adiposity, IR, hyperinsulinemia, triacylglycerides, and cholesterol levels, and also VAT mRNA expression of MCP-1 (monocyte chemoattractant protein-1), IL (interleukin)-1β and IL-6, concomitantly increasing adiponectin levels. UA metabolic effects demonstrated in this study support its potential therapeutic utility to improve IR, hyperinsulinemia, and inflammation observed in obesity and diabetes.

Insulin glargine affects the expression of Igf-1r, Insr, and Igf-1 genes in colon and liver of diabetic rats

Objective(s):

The mitogenic effect of the analogous insulin glargine is currently under debate since several clinical studies have raised the possibility that insulin glargine treatment has a carcinogenic potential in different tissues. This study aimed to evaluate the Igf-1r, Insr, and Igf-1 gene expression in colon and liver of streptozotocin-induced diabetic rats in response to insulin glargine, neutral protamine Hagedorn (NPH) insulin, and metformin treatments.

Materials and Methods:

Male Wistar rats were induced during one week with streptozotocin to develop Type 2 Diabetes (T2D) and then randomly distributed into four groups. T2D rats included in the first group received insulin glargine, the second group received NPH insulin, the third group received metformin; finally, untreated T2D rats were included as the control group. All groups were treated for seven days; after the treatment, tissue samples of liver and colon were obtained. Quantitative PCR (qPCR) was performed to analyze the Igf-1r, Insr and Igf-1 gene expression in each tissue sample.

Results:

The liver tissue showed overexpression of the Insr and Igf-1r genes (P>0.001) in rats treated with insulin glargine in comparison with the control group. Similar results were observed for the Insr gene (P>0.011) in colonic tissue of rats treated with insulin glargine.

Conclusion:

These observations demonstrate that insulin glargine promote an excess of insulin and IGF-1 receptors in STZ-induced diabetic rats, which could overstimulate the mitogenic signaling pathways.

Lupinus albus Conglutin Gamma Modifies the Gene Expressions of Enzymes Involved in Glucose Hepatic Production In Vivo

Lupinus albus seeds contain conglutin gamma (Cγ) protein, which exerts a hypoglycemic effect and positively modifies proteins involved in glucose homeostasis. Cγ could potentially be used to manage patients with impaired glucose metabolism, but there remains a need to evaluate its effects on hepatic glucose production. The present study aimed to analyze G6pc, Fbp1, and Pck1 gene expressions in two experimental animal models of impaired glucose metabolism. We also evaluated hepatic and renal tissue integrity following Cγ treatment. To generate an insulin resistance model, male Wistar rats were provided 30% sucrose solution ad libitum for 20 weeks. To generate a type 2 diabetes model (STZ), five-day-old rats were intraperitoneally injected with streptozotocin (150 mg/kg). Each animal model was randomized into three subgroups that received the following oral treatments daily for one week: 0.9% w/v NaCl (vehicle; IR-Ctrl and STZ-Ctrl); metformin 300 mg/kg (IR-Met and STZ-Met); and Cγ 150 mg/kg (IR-Cγ and STZ-Cγ). Biochemical parameters were assessed pre- and post-treatment using colorimetric or enzymatic methods. We also performed histological analysis of hepatic and renal tissue. G6pc, Fbp1, and Pck1 gene expressions were quantified using real-time PCR. No histological changes were observed in any group. Post-treatment G6pc gene expression was decreased in the IR-Cγ and STZ-Cγ groups. Post-treatment Fbp1 and Pck1 gene expressions were reduced in the IR-Cγ group but increased in STZ-Cγ animals. Overall, these findings suggest that Cγ is involved in reducing hepatic glucose production, mainly through G6pc inhibition in impaired glucose metabolism disorders.

Administration of Lupinus albus gamma conglutin (Cγ) to n5 STZ rats augmented Ins-1 gene expression and pancreatic insulin content

Several studies support the health-promoting benefits of lupins, particularly lupin proteins. It has been demonstrated that Lupinus albus gamma conglutin (Cγ) protein lowered blood glucose levels; thus, Cγ showed promise as a new anti-diabetic compound for type 2 diabetes (T2D) treatment. The aim of this study was to evaluate the effect of Cγ on Ins-1 gene expression and on pancreatic insulin content in streptozotocin-mediated diabetic rats. Cγ was isolated from Lupinus albus seeds. Its identification was confirmed with polyacrylamide gel electrophoresis under native and denaturing conditions. We used streptozotocin (STZ) to induce T2D on the 5th day of life of newborn male Wistar rats (n5-STZ). After 20 weeks post-induction, these animals (glycemia > 200 mg/dL) were randomly assigned to three groups that received the following one-week treatments: vehicle, 0.90% w/v NaCl (n5 STZ-Ctrl); glibenclamide, 10 mg/kg (n5 STZ-Glib); or Cγ, 120 mg/kg (n5 STZ-Cγ). Glucose and insulin levels were measured before and after treatment. Ins-1 gene expression was quantified using real time polymerase chain reaction and the pancreatic insulin content was evaluated with immunohistochemistry. Post-treatment, the n5 STZ-Cγ and n5 STZ-Glib groups showed reductions in glucose, increments in serum insulin, and increases in Ins-1 gene expression and beta cell insulin content compared to the n5 STZ-Ctrl group. The results showed that Cγ had beneficial effects on Ins-1 gene expression and pancreatic insulin content. These biological effects of Cγ strengthen its promising potential as a nutraceutical and/or new agent for controlling hyperglycemia.

Increased expression of the prolactin receptor is associated with malignant laryngeal tumors

The altered expression of the prolactin receptor (PRLR) has been associated with the development of various types of cancer, particularly breast, prostate and endometrial cancer. However, in laryngeal tumors, the expression of PRLR has not yet been documented. The aim of this study was to determine the expression and localization of PRLR in laryngeal cancer (LC) in comparison with recurrent respiratory papillomatosis (RRP). PRLR expression was analyzed in 48 paraffin-embedded tissues (18 RRP and 30 laryngeal cancer tissues) by immunoperoxidase staining. Furthermore, PRLR expression was evaluated in ten samples from each group by Western blot analysis and quantitative real-time PCR. PRLR was observed in all laryngeal tumors at different intensities. PRLR overexpression was significantly associated (P<0.005) with LC. The staining pattern was homogeneous, mainly cytoplasmic, and confined to the tumor area. We found increased expression of different isoforms in LC in comparison with RRP. Our results suggest a possible role of PRL/PRLR in the development of LC. PRLR may be useful as a target for further investigations in laryngeal tissues.

Role of hydrogen peroxide and oxidative stress in healing responses

Oxidative stress is a host defense mechanism whose involvement in maintaining homeostasis and/or inducing disease has been widely investigated over the past decade. Various reactive oxygen species (ROS) have been defined and the enzymes involved in generating and/or eliminating them have been widely studied. In this review we briefly discuss general mechanisms of oxidative stress and the oxidative stress response of the host. We focus primarily on hydrogen peroxide and summarize the systems involved in its formation and elimination. We describe mechanisms whereby hydrogen peroxide and other ROS can modify protein conformation and, thus, alter protein function, and describe a group of transcription factors whose biological activity is modulated by the redox state of cells. These basic aspects of oxidative stress are followed by a discussion of mechanisms whereby hydrogen peroxide and other ROS can modulate some physiological and pathological processes, with special emphasis on wound healing and scarring of the liver.

Tumor necrosis factor alpha down-regulates expression of the alpha1(I) collagen gene in rat hepatic stellate cells through a p20C/EBPbeta- and C/EBPdelta-dependent mechanism

Tumor necrosis factor alpha (TNF-alpha) is one of the key cytokines of the acute phase response and of many inflammatory processes. This cytokine has several antifibrogenic actions and down-regulates the expression of the type I collagen genes and induces the expression of metalloproteinases. Because TNF-alpha directly antagonizes some fibrogenic actions of transforming growth factor beta(1) (TGF-beta(1)), we considered it important to map the cis-acting regulatory element of the alpha1(I) collagen (col1a1) promoter involved in TNF-alpha responsiveness in hepatic stellate cells (HSC), to investigate the transcription factors that bind to it, and to establish possible mechanisms by which TNF-alpha down-regulates its expression. In this article, we show the presence of a functional TNF-alpha-responsive element (TaRE) in the -378 to -345 region of the col1a1 promoter. This element colocalizes with a previously reported TGF-beta(1)-responsive element. We further demonstrate that TNF-alpha induces nuclear translocation and binding of transcriptional complexes containing p20C/EBPbeta, p35C/EBPbeta, and C/EBPdelta to this sequence of the promoter. Transient overexpression of C/EBPdelta or p20C/EBPbeta, the natural dominant negative form of C/EBPbeta in HSC, down-regulated activity of a CAT reporter vector driven by -412 to +110 of the col1a1 promoter. Taken together, these data suggest that the -378 to -340 region of the col1a1 promoter is the site of convergence of different stimuli that ultimately modulate col1a1 gene transcription.

H(2)O(2) is an important mediator of physiological and pathological healing responses

BACKGROUND

TGF-beta1 is a pleiotropic cytokine that plays a key role in wound healing and organ fibrosis. We have recently demonstrated that, in part, some fibrogenic actions of TGF-beta1 are mediated via formation of H(2)O(2). We have also demonstrated that TGF-beta1 plays a key role in the accelerated healing response induced by a peptidoglycan derived from some strains of Staphylococcus aureus (SaPG).

METHODS

To investigate further the role of H(2)O(2) in healing responses, we implemented and improved a method to measure this reactive oxygen species. Using this method, we quantified the production of H(2)O(2) by cultured hepatic stellate cells-the main cells involved in type I collagen production in the liver-and by saline- and SaPG-inoculated polyvinyl alcohol sponges that had been surgically subcutaneously implanted in the dorsum of rats.

RESULTS

We show that cultured hepatic stellate cells produce significant amounts of H(2)O(2). We show also that H(2)O(2) formation by saline- and SAPG-inoculated sponges is more intense during the early inflammatory phase of the healing response and precedes collagen deposition. Moreover, the production of H(2)O(2) is much higher in SaPG-inoculated sponges than in those inoculated with saline solution.

CONCLUSIONS

Based on these findings, and on the fact that H(2)O(2) is produced during TGF-beta-induced upregulation of the alpha1(I) procollagen gene, we conclude that H(2)O(2) is one of the mediators of healing responses.

Hydrogen peroxide: a link between acetaldehyde-elicited alpha1(I) collagen gene up-regulation and oxidative stress in mouse hepatic stellate cells

Ethanol induces liver fibrosis by several means that include, among others, the direct fibrogenic actions of acetaldehyde and the induction of an oxidative stress response. However, the mechanisms responsible for these activities, and the possible connections between oxidative stress and acetaldehyde-induced fibrosis are not well understood. In this communication we investigated the molecular mechanisms whereby acetaldehyde induces mouse alpha1(I) procollagen (col1a1) gene expression in cultured hepatic stellate cells. Transfection assays using reporter plasmids driven by different segments of the col1a1 promoter localized an acetaldehyde-responsive element (AcRE) between nucleotides -370 and -345. We also show that acetaldehyde enhances binding of a CCAAT/enhancer binding protein-beta (C/EBPbeta)-containing complex to this element, and that this effect is due, at least in part, to an increase in the concentration of nuclear p35C/EBPbeta protein. Although this element overlaps to a previously described transforming growth factor beta1 (TGF-beta1)-responsive element, the stimulatory effect of acetaldehyde is not mediated through this cytokine, because addition of neutralizing anti-TGF-beta1 antibodies does not prevent acetaldehyde-elicited col1a1 up-regulation. On the other hand, this effect is blocked by the addition of catalase, an H(2)O(2) scavenger. Moreover, this ethanol metabolite stimulates production of H(2)O(2) in stellate cells. Thus, these results suggest that acetaldehyde-induced col1a1 up-regulation is mediated, at least in part, through H(2)O(2). Altogether, these data suggest that the -370 to -344 region of the col1a1 gene is a point of convergence of the action of numerous extracellular stimuli that ultimately leads to col1a1 up-regulation. In addition, we have established a direct connection between oxidative stress and enhanced col1a1 expression induced by acetaldehyde.

Transforming growth factor beta1 induces the expression of alpha1(I) procollagen mRNA by a hydrogen peroxide-C/EBPbeta-dependent mechanism in rat hepatic stellate cells

Oxidative stress plays a key role in liver fibrosis. Both inflammatory cells and activated Kupffer cells produce H2O2, an oxidant involved in the activation of hepatic stellate cells (HSC). Increased production of reactive oxygen intermediates (ROIs) in fibrotic livers is associated in part with the up-regulation of transforming growth factor beta (TGF-beta), and this cytokine enhances collagen production by cultured HSC. However, the possible link between oxidative stress and the molecular mechanisms by which TGF-beta induces collagen gene expression in HSC remains to be elucidated. To address this question, we investigated whether H2O2 is a mediator of TGF-beta-elicited alpha1(I) collagen gene (col1a1) up-regulation. We demonstrated that TGF-beta induces the accumulation of H2O2, and that this oxidant is, in turn, directly involved in up-regulating the expression of the col1a1 gene. While the addition of H2O2 to HSC induced the expression of alpha1(I) procollagen mRNA, catalase, an H2O2 enzyme scavenger, abrogated TGF-beta-mediated col1a1 gene up-regulation. We transfected HSC with chimeric plasmids driven by different segments of the mouse col1a1 promoter and mapped a cis-acting element (-370 to -344) essential for TGF-beta responsiveness. We further showed that TGF-beta induced the activation and binding of a C/EBPbeta-containing transcriptional complex to this sequence, an effect that was also mimicked by the addition of H2O2. Taken together, these data demonstrate a direct connection between TGF-beta-mediated accumulation of H2O2 and the up-regulation of col1a1 gene in HSC.